Microbiology and Pathology 1-61.txt

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  1. Hepititis E is transmitted via which route?

    - Oral-anal
    - Skin
    - Blood borne
    - Respiratory droplets
    • Oral-anal
    • Oral-anal: Hepititis A and Hepititis E, HSV-1 (oral)
    • Respiratory droplets: Inluenza, respiratory syncytial virus, measles (rubeola), mumps, rubella, adenovirus, rhinovirus, cytomegalovirus, Epstein-Barr
    • Blood-borne: Hep. B, C, D, HIV (with genital)
    • HSV-2: genital
  2. Rotavirus belongs to the:

    - Picornavirus family
    - Reovirus family
    - Togavirus family
    - Paramyxovirus family
    • Reovirus family, non-enveloped and have an icosahedral capsid composed of an outer and inner protein shell with double-stranded RNA.
    • ** The virion contains an RNA-dependent RNA polymerase, which is required because human cells lack this enzyme and therefore cannot synthesize mRNA from an RNA template (they replicate in the cytoplasm).
    • Rotaviruses (also called gastroenteritis virus type B): are the most common cause of gastroenteritis in children (2 and under). It is spread via the decal-ral route.
    • Coltivirus (tick fever virus): causes colorado tick fever.
    • ***Viral gastroenteritis is not caused by influenza.
    • *** Concern in infants because of dehydration
    • RNA non-enveloped virus families: Picornavirus (poliovirus, coxsackie A & B viruses, rhinovirus, Hep A virus), Reovirus (Rotaviruses and coltivurus) and Calciviruses
  3. Which of the following is a paramyxovirus that causes many respiratory infections in epidemics each winter. It is common cause of bronchitis in infants, which is complicated by pneumonia in approximately 10% of the cases?

    - Influenza
    - Rubella
    - Coxsackievirus
    - Respiratory syncytial virus (RSV)
    • Respiratory syncytial virus (RSV)
    • This is the only member of the paramyxovirus family (which includes measles, mumps and parainfluenza viruses) that lacks the envelope glycoproteins.
    • RSV commonly causes respiratory tract infections ranging from the common cold to pneumonia and bronchitis.
    • *** NO vaccine is available for RSV
    • Parainfluenza viruses cause croup and pneumonia in children and a disease resembling the common cold in adults.
    • Interstitial pulmonary inflammation is most characteristic of viral pneumonia
    • Paramyxoviruses contain an RNA-dependent RNA polymerase, and resemble orthomyxoviruses except they are usually larger in size with different surface proteins.
  4. The cytopathic effect is a single mechanism of infection.

    It is not useful in diagnostic virology.

    Which statement is true and or false?
    • Both statements are false
    • The hallmark of viral infection of the cell is the cytopathic effect (CPE). This change starts with alterations of the cell morphology accompanied by marked derangement of cell function and culminates in the lysis and death of cells.
    • Not all viruses cause CPE; some can replicate while causing little morphologic or functional change in the cell, like.... Necrosis, hypertrophy, giant cell formation, hypoplasia, metaplasia, lysis, membrane fusion, apoptosis, inclusion bodies, altered membrane permeability
    • These cytologic changes provide useful presumptive evidence for the diagnosis of the virus.
    • *** Viruses use specific cell surface receptors to bind and subsequently gain entry to the host cells. The identification of these receptors explains the cellular tropism of viruses.
  5. All of the following are included in the family of herpesviruses EXCEPT one.

    - Varicella-Zoster virus (VZV)
    - Epstein-Barr virus (EBV)
    - Cytomegalovirus (CMV)
    - Coxsackievirus (A & B)
    • Coxsackievirus (A & B), these are in the piconavirus family.
    • All hespesviruses are morphologically identical, they replicate in the nucleus of the cell and are the only viruses to obtain their virion envelopes by budding from the host nuclear or Golgi membrane, not the host plasma membrane.
    • The hallmark of all herpesvirus infections is the ability of the viruses to establish latent (or silent) infections that then persist for the life of the individual. HSV-1 commonly remains latent in the trigeminal ganglion. HSV-2 most commonly remains latent in the sacral ganglia. VZV most commonly remains latent in the nuclei of the cells in the endothelium of the arterial wall and in the T lymphocytes. EBV remains latent in resting memory B lymphocytes.
    • Certain herpesviruses have oncogenic potential in humans. The Epstein-barr virus is associated with Burkitt's lymphoma and nasopharyngeal carcinomaHuman herpesvirus type 8 (Kaposi's sarcoma- associated herpesvirus) is strongly associated with the classical and AIDS-related Karposi's sarcoma)
    • DNA enveloped viruses: herpesvirus, poxvirus and hepadnavirus
  6. Prions are the most recently recognized and the simplest infectious agents, consisting of a single protein molecule

    Prions contain no nucleic acid and therefore no genetic information
    • Both statements are true
    • Prions are infectious protein particles, cause slow diseases such as Creutzfeldt-Jakob disease, a severe degenerative brain disease caused by the ingestion of beef from cows infected with mad cow disease.
    • Prions do not illicit inflammatory or antibody responses.
    • Viroids consist solely of a single molecule of circular RNA with no protein coat or envelop, they infect only plants.
    • Virions contain either single or double stranded DNA or RNA (never both) that is encased in a protein coat called a capsid. The combination is called a nucleocapsid
  7. Herpes simplex virus type 2 is only transmitted from parent to child BECAUSE it is transmitted most often through salivary exchange.

    - Both statement and reason are correct and related
    - Both statement and reason are correct, but not related
    - The statement is correct, but the reason is not
    - The statement is not correct, but the reason is correct
    - Neither the statement, nor the reason are correct
    • Neither the statement, nor the reason are correct
    • HSV-2 is spread through sexual contact, although it can be spread from mother to infant during childbirth. HSV-1 causes labial lesions.
    • HSV 1 and 2 cause manifestations of recurrent infection in otherwise healthy people.
    • Primary herpetic gingivostomatitis: cause by HSV-1 through oral secretions, usually in children under 10, symptoms are mild cold sores
    • Acute herpetic gingivostomatitis: Infection caused by acute symptoms, fever, cervical lympth-adenopathy, fiery-red gingival tissue, yellowish painful uclers on the free and attached mucosa.
    • Adult recurrence (herpes labialis, cold sore): seen on the vermillion border of the lips or even herpetic conjunctivitis, remains latent in the trigeminal ganglia.
    • HERPETIC WHITLOW is on FINGER! comes from HSV1 and HSV2 with direct contact.
  8. None of the following herpesvirus infections can be treated prophylactically by a vaccine EXCEPT one:

    - HSV - 1 
    - HSV - 2
    - Varicella-Zoster virus
    - Epstein-Barr virus
    - Cytomegalovirus
    • Varicella-Zoster virus, produces varicella (chickenpox) and herpes zoster (shingles). The virus remains latent in the dorsal root and cranial nerve ganglia. Reactivation of infection then results in shingles.
    • An effective live attenuated varicella vaccine is routine in the US children.
    • *** HSV-1 infects ABOVE the waist  (eye and mouth) and HSV-2 BELOW the waist (genital lesions). NOTE: Oral-gential sex can lead to HSV1 below the waist and HSV2 above the waist.
  9. A bacteriophage with the ability to form a stable, nondisruptive relationship within a bacterium is called a:

    - Virulent phage
    - Plasmid
    - Temperate phage
    - Phage T4
    • Temperate phage, in contrast to a virulent phage that kills the host, the temperate phage replicates and incorporates is genome in the bacterial chromosome.
    • *** Bacteriophage is a virus that can replicate only within specific host bacterial cells.
    • A lysogenic bacterium is one that contains a temperate bacteriophage
    • Lysogenic conversion: the alteration of a bacterium to a virulent strain by the transfer of DNA temperate bacteriophage. The classic example of this conversion is in the alteration of Corynebacterium diphtheriae to a virulent strain. The presence of this temperate phage renders the bacterium pathogenic (without the phage it would not be harmful).
    • Note: the Integrated viral DNA is called a prophage
    • Enterobacteria phage T4 is a phage that infects the E. coli bacteria
    • Plasmids are extrachromosomal, double-stranded, circular DNA molecules that are capable of replicating independently of the bacterial chromosome.
  10. Which of the following is NOT a component of a bacteriophage?

    - Telomere
    - Lipid
    - Double-stranded RNA
    - Single-stranded RNA
    - Protein
    • Telomere
    • A bacteriophage is a very delicate virus which may attack and destroy bacteria cells under certain conditions. Some may contain lipids.
    • Bacteriophage infection follows one of two courses: Lysis (virulent, kills the host) or Lysogeny (temperate, integrates).
    • Transduction: the transfer of DNA from a donor cell to a recipient cell with the DNA packages within a bacteriophage.
  11. Retroviruses contain an RNA genome and a reverse transcriptase.

    A provirus is formed as viral RNA is directly incorporated into the host DNA.

    Which statement is true and or false?
    • First statement is true, second is false
    • Retroviruses contain 2 identical, single-stranded, positive-sense RNA molecules and RNA-directed DNA polymerase (reverse transcriptase). Once infected, this reverse transcriptase uses the viral RNA as a template to create viral DNA, which is then incorporated into the host DNA to form a provirus.
    • Remember: Retroviruses are distinguished from other RNA viruses by their ability to replicate through a DNA intermediate using an enzyme reverse transcriptase.
    • Human Lymphotrophic retrovirsues:
    • Lentivirus: HIV-1 and HIV-2 (both cause AIDS)
    • Oncovirus: HTLV-1 (causes adult T cell leukemia) and HTLV-2 which causes myelopathy
    • For RNA viruses: Transcription occurs in the cytoplasm except for retroviruses and influenza viruses, and involves an RNA-dependent RNA polymerase, except for retroviruses that use reverse transcriptase.
    • For DNA viruses: Transcription occurs in the nucleus (except for poxviruses) and involves a host-cell DNA dependent RNA polymerase.
  12. The hallmark of all herpesvirus infections is the ability of the viruses to establish latent infections that then persist for the life of the individual. Following primary infection, EBV remains latent within:

    - Resting memory B lymphocytes
    - Salivary glands
    - T lymphocytes
    - Dorsal root and cranial nerve ganglia
    • Resting memory B lymphocytes, REMEMBER Epstein-Barr= B LYMPHOCYTES
    • CyTomegalovirus = T lymphocytes
    • HSV-1 = trigeminal ganglia
    • HSV-2 = sacral ganglia
    • Varicella-Zoster = dorsal root and cranial nerve ganglia (CHICKENPOX, SHINGLES)
  13. All of the following are RNA enveloped viruses EXCEPT one:

    - Rubella virus
    - Influenzae virsuses A, B and C
    - Rotavirus
    - Measles virus
    • Rotavirus, along with Reovirus ARE NOT ENVELOPED
    • Other non-enveloped viruses: HPV, Adenovirus, Hepevirus (hepatitis E), Polio, coxsackie, Dep. A, Rhinovirus, Enterovirus
  14. Human adenoviruses are unlikely to target the central nervous system BECAUSE the adenoviruses prefer epithelial cells for replication.

    - Both statement and reason are correct and related
    - Both statement and reason are correct, but not related
    - The statement is correct, but the reason is not
    - The statement is not correct, but the reason is correct
    - Neither the statement, nor the reason are correct
    • Both statement and reason are correct and related
    • Adenoviruses are naked (non-enveloped), double stranded linear DNA genome. Frequently cause subclinical infections. Transmitted through droplets of respiratory secretions. 
    • Causes: conjunctivitis, gastrointestinal disease, pharyngitis, UTI, respiratory illness (in children).
  15. Which of the following is widely regarded as the smallest RNA virus?

    - Rubella virus
    - Poliovirus
    - Coxsackie virus
    - Rabies virus
    • Poliovirus
    • Picornaviruses (pico=small) are a large family of small RNA viruses, which includes enteroviruses, rhinoviruses and Hep-A.
    • The term Entero refers to the enteric means of spreading (fecal-oral route), include poliovirus types 1-3, coxsackie A and B, echoviruses and enteroviruses 68-71.
    • Poliovirus: the causing agent of Poliomyelitis, replicated in the motor neurons of the anterior horn of the spinal cord; ths the dead of these cells causes paralysis. 
    • Initial symptoms include: headache, vomiting, constipation and sore throat. paralysis may follow.
    • There are 2 vaccines: Salk (intravenously) and Sabin (orally)
  16. Which of the following is the largest and most complex DNA virus?

    - Poxvirus family
    - Herpesvirus family
    - Papovirus family
    - Parvovirus family
    • Poxvirus family, have 3 viruses of medical importance. Smallpox virus (Variola virus), vaccinia virus and molluscum contagious virus (MCV). They are the largest and most complex viruses known.
    • These viruses multiply in the cytoplasm of host cells, usually associated with skin rashes.
    • Most important poxvirus is Smallpox (variola), it is an acute, highly infectious, often fatal disease characterized by high fever, prostration, and a vesicular, pustular rash. (has been eradicated by global vaccination)
    • Poxviruses are the only DNA viruses that replicate in the cytoplasm.
  17. All of the following are members of the Picornaviridae family EXCEPT:

    - Poliovirus
    - Coxsackie virus
    - Enterovirus
    - Hepadnavirus
    - Hepatitis A virus
    - Rhinovirus
    • Hepadnavirus
    • Picornaviruses (pico=small), large family of small RNA viruses, which include enterovirus, rhinovirus and Hepatitis A which infect humans.
    • Enterovirus include poliovirus types 1-3, coxsackie A and B, echoviruses and enteroviruses 68-71
    • The Picornaviruses are non-enveloped, and are composed of a single-stranded positive RNA genome with an icosahedral capsid, they are incapable of causing cell transformation.
    • Coxsackie viruses:
    • Group A virus: cause herpangina and hand-foot-mouth disease. Vesicular lesions accompany fever, sore throat and pain on swallowing. Location of oral lesions distinguishes these two diseases from one another. Herpangina appears on throat, palate or tongue. Oral lesions of hand-foot-mouth disease appear on buccal mucosa and gingiva.
    • Group B (for body) virus: fever and chest pain with headache, fatigue and aching muscle lasting 4-5 days.
    • Rhinovirus: main cause of the common cold with other 100 serologic types, no vaccine possible.
    • Echoviruses: aseptic meningitis, encephalitis, paralysis, rash, fever, acute upper respiratory tract infections, neonatal infections, myocarditis.
  18. Epstein-Barr virus is the causative agent for all of the following EXCEPT one:

    - Kaposi's sarcoma
    - Infectious mononucleosis
    - Nasopharyngeal carcinoma
    - Burkitt's lymphoma
    - Oral hairy leukoplakia
    • Kaposi's sarcoma
    • Epstein-Barr causes infectious mononucleosis and has been associated with subsequent development of two forms of cancer: Burkitt's lymphoma and nasopharyngeal carcinoma.
    • EBV is also associated with oral hairy leukoplakia.
    • IgM heterophile antibodies identified by a heterophile test and appear in more than 80% of the patient with infectious mononucleosis, it is highly diagnostic of disease.
    • Rubella (german measles): enveloped RNA virus, spread via droplets. Causes flat, pink, spots on face and body with rash)
    • Measles (rubeola): is characterized by formation of Koplik's spots in the oral cavity, small, blueish-white lesions surrounded by red ring that cannot be wiped off, around molars.
    • Mumps: can cause enlargement of parotid gland, deafness and orchitis (big testis, in males).
    • MMR vaccine (measles, mumps and rubella): given to children around 1 year of age.
  19. HIV1 and the related virus HIV2 are further classified as lentiviruses BECAUSE of their slowly progressive clinical effects.

    - Both statement and reason are correct and related
    - Both statement and reason are correct, but not related
    - The statement is correct, but the reason is not
    - The statement is not correct, but the reason is correct
    - Neither the statement, nor the reason are correct
    • - Both statement and reason are correct and related
    • - Transmission of HIV occurs primarily through sexual contact and transfer of infected blood. Virus infects and kills helper (CD4) T-cells resulting in the depression of both humoral and cell-mediated immunity. Travels throughout the body in macrophages, which are the first cells infected by HIV. Induces CPE (cytopathic effect) called giant-cell (syncytial) formation
    • - Important: rapid formation of new strains of HIV is primarily the result of frequent errors introduced by viral reverse transcriptase
    • - Acute HIV-1 primary infection can present as a mononucleosis-like syndrome with fever, fatigue, sore throat and skin rash
    • - HIV lyses the host cells, RNA tumor viruses invade but don't posses cytolytic activity.
    • - HTLV-1 and 2 are also retroviruses that are further classified as Oncoviruses
  20. All of the following viruses have negative polarity or contain negative sense RNA EXCEPT one?

    - Orthomyxoviruses
    - Paramyxoviruses
    - Rhabdoviruses
    - Retroviruses
    • Retroviruses, have positive polarity. in other words they posses positive sense RNA molecules (RNA with the same base sequence as the mRNA). Positive polarity has the SAME SEQUENCE on the complementary RNA.
    • RNA with negative polarity has a base sequence that is complementary to the mRNA.
    • The term negative or positive polarity only applies to RNA viruses not DNA
  21. A mother takes her child to the primary care physician. The child has a recent history of malaise and fever, and now presents with a widespread rash on his trunk and face. The mother states that the child has received a vaccinia vaccine. This child has most likely been infected with.

    - Variola
    - Varicella-Zoster
    - Cytomegalovirus
    - Herpes simplex type 1
    • Varicella-Zoster
    • VZV produces Varicella (chickenpox) and herpes Zoster (shingles)
    • In 90% of children under 9 years of age, get the Chickenpox with local lesions (vesicles) that become encrusted and fall off after a week. Administration of aspirin is contraindicated because it can cause "Reye's syndrome", which can cause encephalitis and liver impairment.
    • Shingles: result of reactivation of a latent varicella-zoster virus that remained in the body since chickenpox, Characterized by painful vesicles on the skin along a dermatome, common in immunocompromised individuals.
    • Adenosine arabinoside (vidarabine): suppresses the synthesis of varicella-zoster and herpes simplex virus.
  22. Influenza viruses have all of the following features EXCEPT?

    - Single stranded DNA
    - Hemagglutinin
    - Neuraminidase
    - Genetic reassortment
    - Lipoprotein coat
    • Single stranded DNA
    • Influenza viruses are the only members of the orthomyxovirus family. Composed of a unique segmented, negative, single-stranded, RNA genome.
    • Influenza A: responsible for pandemics and epidemics
    • Influenza B: often causes smaller, localized outbreaks, camps or schools
    • Influenza C: rarely produces disease in humans
    • The ability of influenza virus to cause epidemics is dependent on the antigenic changes in the hemagglutinin and neuraminidase.
    • Reye's syndrome includes vomiting, lethargy, and may result in coma. It is rare but 40% of cases are fatal. Follows certain infections like influenza and chickenpox. Aspirin is contraindicated, ibuprofen and Acetaminophen are not associated.
  23. Which of the following are the most important cause of the common cold and upper respiratory tract infections?

    - Paramyxoviruses
    - Coronaviruses
    - Rhinoviruses
    - Orthomyxoviruses
    • Rhinoviruses, more than 100 serological types, they are members of the picornavirus family. 
    • Other agents likely to cause symptoms of common cold are, enteroviruses, coronaviruses, adenoviruses and parainfluenza virus.
    • Mumps: is caused by an RNA paramyxovirus and is transmitted via respiratory droplets. Two complications are orchitis (painful swelling of the testicles) and deafness
    • Measles (rubeola): caused by rubeola virus (RNA paramyxovirus). Characterized by skin rash with Koplik's spots, Transmitted via respiratory droplets.
    • German measles (rubella): caused by rubella virus (RNA virus). Transmitted via respiratory droplets. lymphoadenopathy followed by rash on entire body.
  24. Which growth curve describes the lytic reproduction cycle that releases a large number of phage simultaneously?

    - One-step growth curve
    - Two-step growth curve
    - Three-step growth curve
    - Four-step growth curve
    • One-step growth curve
    • A typical one-step growth analysis can be divided into several phases:
    • 1. Adsorption of the virus
    • 2. Eclipse phase: this lasts for 10-12 hours
    • 3. Synthetic phase. Starts 12 hours post-infection, time during which new virus particles are assembled.
    • 4. Latent period: During this period, no extracellular virus can be detected.
  25. Orthomyxoviruses and Paramyxoviruses share the following characteristics EXCEPT one.

    - Spherical shape
    - Single-stranded RNA
    - Segmented RNA
    - Hemagglutinin
    - Negative-sense RNA
    • Segmented RNA
    • Both paramyxoviruses and orthomyxoviruses are enveloped, negative, single-stranded RNA viruses.
    • Orthomyxoviruses - Influenca viruses A, B and C
    • Paramyxoviruses - measles, mumps, respiratory syncytial
  26. Respiratory syncytial virus (RSV) is the most common causative pathogen of lower respiratory tract infections in young children. Which is the second most common?

    - Coxsackie virus
    - Adenoviruses
    - Parafinfluenza virus
    - Orthomyxoviruses
    • Parafinfluenza virus
    • Viruses that cause respiratory disease in children:
    • Respiratory Syncytial virus (RSV)
    • Parainfluenza viruses 1-4
    • Rhino viruses
    • Adenoviruses
    • Common viral causes of pharyngitis:
    • Coxsackievirus A
    • Adenovirus
    • Orthomyxooviruses (influenzas)
    • Epstein-barr
    • Causes of viral gastroenteritis:
    • Rotavirus
    • Norovirus
    • Adenovirus
    • Viruses that cross the placenta:
    • Rubella
    • herpes
    • HIV
    • Cytomegalovirus
    • Common cold:
    • Rhinoviruses
    • Coxsackieviruses
    • Coronavirus
    • Adenovirus
    • Common pediatric viral disease with rash:
    • Measles
    • Rubella
    • Roseola (HHV 6)
    • Erythema infectosium
    • Aseptic meningitis:
    • Coxsackieviruses
    • Echoviruses
    • Mumps virus
    • ** Reoviruses are the only RNA viruses that are double stranded
    • ** Rotaviruses are the most common cause of infectious diarrhea in infants and young children
    • *** Most common arbovirus is Dengue fever
    • *** CMV is the most common viral cause of mental retardation in the U.S.
  27. Which family comprises two genera: the rubiviruses, which include rubella virus, and the alphavirus, which include some of the arthropod-borne viruses?

    - Picornavirus
    - Reovirus
    - Flavivirus
    - Calcivirus
    - Togavirus
    • Togavirus
    • Rubella virus has the same structural properties and mode of replication as the other togaviruses, however, unlike other togaviruses, rubella is a respiratory virus and does not cause readily detectable cytopathologic effects.
    • Rubella (german measles) is one of the five classic childhood exanthems (produce rash), along with measles, roseola, fifth disease and chickenpox.
    • Rubella during pregnancy can cause stillbirth, spontaneous abortion and other anomalities associated with congenitcal rubella syndrome, classical tirad is cataracts, heart defects and deafness.
    • Rubella is a spherical, enveloped RNA virus with hemagglutinin-containing surface projections.
    • Vaccinated with the MMR vaccine a year after birth, then reinforced before entering school.
  28. All of the following are characteristics of Staphylococcus aureus except one?

    - Coagulase-negative
    - Gram-positive
    - Causes infective endocarditis
    - Possesses surface protein A
    - Causes toxic shock syndrome
    • Coagulase-negative, S. aureus is coagulase positive whereas other Staphylococci are coagulase negative.
    • S. aureus cannot invade through intact skin or mucous membranes and infection usually begins with traumatic inoculation of the organism.
    • S. aureus contains ribitol phosphate teichoic acid.
      S. aureus are gram-positive cocci that resemble clusters of grapes, cause skin lesions boils, carbuncles, impetigo, scalded skin syndrome, abcesses, sepsis, pneumonia, endocarditis, toxic shock syndrome TSS)
  29. M protein is the major type-specific protein associated with the virulent strains of:

    - S. aureus
    - Clostridium botulinum
    - Streptococcus pyogenes
    - Corybacterium diphtheriae
    • Streptococcus pyogenes: (M protein), 4 streptococcal pyrogenic exotoxins, lysis of white and red blood cells, cleaves DNA, resistance to phagocytosis, Streptococcal toxic shock syndrome, rapidly destroys tissue.
    • Staphylococcus aureus: (A protein), 8 enterotoxins, Food poisoning, scalded skin syndrome, toxic shock syndrome.
    • Clostridium botulinum: Botulin neurotoxin, is the most potent toxin known to man (muscle and nerve paralysis)
    • Clostridium tetani: Neurotoxin: tetanus toxin, interferes with motor neurons, Tetanus (lockjaw)
  30. Which of the following is the predominant type of bacteria on the skin?

    - Lactobacilli
    - Lactic acid bacteria
    - Neisseria
    - Staphylococci
    • Staphylococci
    • Teeth and mucous membrane: Streptococci, lactobacilli
    • Nares: staphylococci
    • Vagina: lactic acid bacteria
  31. On blood agar plates, beta-hemolytic streptococci:

    - Cause complete lysis of red blood cells
    - Cause incomplete lysis of red blood cells
    - Cause no hemolysis of red blood cells
    • Cause complete lysis of red blood cells
    • Streptococcus are gram-positive cocci typically arranged in pairs. Most species are facultative anaerobes. Unlike staphylococcal species, streptococci are catalase-negative.
    • Alpha = Almost
    • Beta = Best
    • Gamma = garbage
    • The group A strains are pathogenic for humans, more than 90% of disease is caused by group A beta-hemolytic streo --- S. pyogenes.
    • Streptococcal pyrogenic exotoxin A, is a superantigen produced by Streptococcus pyogenes and is associated with severe infections and high mortality rate.
    • Oral streptococci are usually alpha-hemolytic (S. vidrians, S. mutans, S. sanguis and S. salivarius) These are most common causing subacute endocarditis.
  32. Endotoxins are part of the outer membrane of the cell wall of:

    - Gram-positive bacteria only
    - Gram-negative bacteria only
    - Both gram-positive and gram-negative bacteria
    - Neither gram-positive nor gram-negative, they are a component of viruses
    • Gram-negative bacteria only
    • The biological activity of endotoxin is associated with the lipopolysaccharide (LPS). Toxicity is associated with the lipid component (Lipid A) and immunogenicity is associated with the polysaccharide components. Cell wall antigens (O antigens) of gram-negative bacteria are components of LPS. LPS elicits a variety of inflammatory responses. It activates complement by the alternative (properdin) pathway.
    • Endotoxin = gram-negative (Listeria monocytogenes is the only gram positive with endotoxin)
    • Exotoxin = gram-positive and gram negative
  33. A missense mutation is a genetic mutation in which nucleotides are either inserted or deleted from a DNA sequence.

    - Translation of mRNA derived from this mutated gene results in a protein with incorrect amino acid sequence.

    - Which statement is true and or false?
    • First statement is false, second is true
    • Point mutations:
    • Silent mutation: no detectable change at the level of the protein synthesized. If A and T are changed for C and G for example the same amino acid will be produced
    • Missense mutation: the change in DNA base sequence results in a change in the mRNA that translated into a difference in the amino acid added to the growing polypeptide chain (ex. valine replaces glutamate causing sickle cell anemia)
    • Nonsense mutation: Results in a stop codon that translates into premature chain termination, Protein function is profoundly affected.
    • Transverse mutation: A purine is replaced with a pyrimidine
    • Transition mutation: A purine is replaced with another purine, or pyrimidine with another pyrimidine.
    • Frameshift mutation: mutation that inserts or deletes a number of nucleotides not divisible by three and disrupts the reading frame.
  34. Which of the following is essential to the function of the outer membrane of gram-negative bacteria?

    - Protein
    - P antigen receptors
    - Coagulase
    - LPS
    • - LPS
    • - The function of the outer membrane of gram-negative bacteria is to act as a protective permeability barrier. The outer membrane is impermeable to large molecules and hydrophobic compounds from the environment. LPS is essential to the function of the outer membrane.
    • - ** Endotoxins are not secreted by bacterial cells. The bacterial cell must die and the outer membrane broken for the endotoxin to be released into the bloodstream.
    • - Endotoxins are highly potent lipopolysaccharides released from the cell walls of gram-negative bacteria. Minute amounts cause inflammation and resorption.
    • - Free endotoxin is present in dental plaque and in inflamed gingiva. The most likely source of bacteria found in diseased periodontal tissue is the subgingival plaque.
    • - Most exotoxins are proteinaceous in nature, while endotoxins are lipopolysaccharide complexes composed of lipid A core polysaccharide and an "O" antigenic side chain.
    • - Endotoxin can activate the complement system via the alternative pathway.

  35. Detection of protein A can be used as a specific identification test for:

    - Streptococcus pyrogenes
    - Neisseria gonorrhoeae 
    - Salmonella
    - Staphylococcus aureus
    • Staphylococcus aureus, major cause of nosocomial infections. Causes food poisoning by releasing enterotoxins into food and TSS by release of superantigens into blood stream.
    • The surface of most S. aureus strains (but not the coagulase-negative staphylococci) is coated with protein A, it has an affinity for the Fc receptor of IgG.
    • Salmonella is a gram-negative facultative rod-shaped bacterium, in the same proteobacterial family as Escherichia coli, the family Enterobacteriaceae "enteric" bacteria. It causes Salmonellosis; enteric fever, invasion of the bacteria in the bloodstream, and acute gastroenteritis, food borne infection intoxication. 
    • Streptococci are aerobic to facultatively anaerobic gram-positive cocci that grow in chains or pairs in culture. They are the most numerous in the oral cavity. S. mutans (caries), S. pneumoniae (pneumonia), S. pyogenes (rheumatic fever), and S. vidrians (heart valve infection).
    • Staphylokinase (produced by S. aureus), Streptokinase (produced by hemolytic streptococci) and Urokinase are enzymes that cleave plasminogen which causes the liquefaction of fibrin (used for removal of blood clots)
  36. Neuraminidase is produced by intestinal pathogens such as:

    - Vibrio cholerae and shigella dysenteriae
    - Streptococci and Staphylococci
    - Clostridium histolyticum and Clostridium perfringens
    - Bacillus anthracis and Bordetella pertussis
    • Vibrio cholerae and shigella dysenteriae
    • Vibrio Cholerae is facultative gram-negative Bacilli with endo and exotoxins.
    • Shigella are facultative gram-negative cause enterocolitis and bloody diarrhea
  37. Mycobacterium species, along with members of a related genus Nocardia, are classifed as:

    - Coagulase-positive bacteria
    - Collagenase-positive bacteria
    - Acid-fast bacteria
    - Phospholipase-positive bacteria
    • Acid-fast bacteria
    • Mycobacterium tuberculosis is not classified as either gram-positive or gram-negative because it does not have the same chemical characteristics of either although they do contain peptidoglycan in their cell wall.
    • Myco. tuberculosis is a faily large non-notile, rod shaped, acid-fast, niacin producing bacterium. It doesn't produce neither exotoxins nor endotoxins. It is an obligate aerobe, this is why M. TB. complexes are found on the upper lobes of the lungs.  It is a facultative intracellular parasite, usually of macrophages, and has a slow generation time of 15-20 hours.
    • Acid-fast staining is one of the methods used to diagnose active tuberculosis. They resist decolorization and appear red against a blue background. Acid-fast is attributed to the presence of lipids and waxes (mycolic acids) in the cell wall of certain bacteria.
    • The PPD classic skin test is used for testing for tuberculosis.
  38. In addition to peptidoglycan, the acid-fast cell wall of Mycobacterium contains a large amount of glycolipids, especially ______ that make up approximately 60% of the acid-fast cell wall.

    - Beta-lactamases
    - Lipopolysaccharides
    - Teichoic acids
    - Mycolic acids
    • Mycolic acids
    • Mycobacteria are surrounded by a waxlike lipid coat of mycolic acid. The coat is responsible for virulence and antiphagocytic.
    • Functions of the acid-fast cell wall components:
    • 1. The peptidoglycan prevents osmotic lysis
    • 2. The mycolic acids and other glycolipids also impede the entry of chemicals causing the organism to grow slowly and be more resistant to chemical agents and lysosomal components of phagocytes than most bacteria.
    • 3. The surface proteins in the acid-fast cel wall, depending on the strain and species, carry out a variety of activities; functioning as enzymes, serving as adhesins.
    • 4. The periplasm contains enzymes for nutrient breakdown as well as periplasmic binding proteins to facilitate the transfer of nutrients across the cytoplasmic membrane.
    • Isoniazid inhibits mycolic acid biosynthesis and is an efficient antimycobacterial agent.
    • A tubercle or Ghon focus is a rounded nodule produced by TB infection, It is the primary lung lesion of pulmonary TB.
  39. A major factor in the cariogenicity of S. mutans is the ability to adhere to the tooth surface. This attachment is achieved largely in part due to the presence of an extracelullar glycocalyx, or:

    - Cytoplasmic membrane
    - Capsule
    - Pellice
    - Plasma membrane
    • Capsule
    • The Capsule is a gelatinous coat which surrounds the cell wall of a certain bacteria and is especially important in protecting these cells against phagocytosis by eukaryotic cells. It also mediates adherence of cells to surfaces and for identification purposes
    • These antiphagocytic polysaccharide capsules surrounding the cells of strains of streptococcus pneumoniae, for, example permit the bacteria to evade the normal defense mechanisms of the host.
    • Cell membrane (cytoplasmic membrane): is a selectively permeable membrane that is involved in energy transformations. It is bordered externally by cell wall in most bacteria.
    • Cell wall: surrounds the plasma membrane and serves to protect the cell from changes in osmotic pressure. Then it also anchors the flagella, maintains the cell shape and control the transport of molecules into and out of the cell.
    • Plasma membrane: dynamic, selectively permeable membrane enclosing the cytoplasm. located between the cell wall and the cytoplasm, regulates movement of substances.
  40. Teichoic acids are unique to the:

    - Gram-positive bacterial cell wall
    - Gram-negative bacterial cell wall
    - Gram-positive and gram-negative bacterial cell wall
    - Mycoplasma family of bacteria
    • Gram-positive bacterial cell wall:
    • Thick
    • Thick murein layer (makes up 90% of the cell wall)
    • Teichoic acids, polysaccharides that serve as attachment sites from bacteriophages.
    • Gram-negative bacterial cell wall:
    • Thin (10 nanometers)
    • More complex than the gram-positive
    • Thin Murein about (10% of the cell wall)
    • Lipoproteins are an integral part of the cell wall
    • Lipopolysaccharide layers (LPS or endotoxin)
    • Phospholipids
    • Proteins
    • ***The proteins, LPS and phospholipids make up the cell envelope of the gram-negative bacterial cell wall. This outer membrane protects the cell from antibiotics (penicillin) and enzymes (lysozyme)
  41. Lactic acid bateria are:

    - Gram-negative, strictly aerobic, non-spore forming cocci
    - Gram negative, facultatively anaerobic, spore forming rods
    Gram-positive, facultatively anaerobic or strictly anaerobic, non-spore forming rods
    - Gram-positive, strictly aerobic, spore-forming filaments.
    • Gram-positive, facultatively anaerobic or strictly anaerobic, non-spore forming rods
    • Most species of this non-sporeforming bacterium ferment glucose into lactate, hence the name Lactobacillus. They are in low numbers in the oral cavity but are linked to dental caries. (Lactobacillus casei)
    • Lactobacillus acidophilus is added to commercial milk products to assist lactose intolerant people in digesting.
    • Lactic acid bacteria include Lactobacillus and Streptococcus. These bacteria use lactid acid fermentation pathway in which pyruvate is reduced to lactic acid. These bacteria can tolerate acid environments and form acids (aciduric and acidogenic)
    • Lactobacillus is generally harmless to humans.
  42. The two organisms most commonly associated with the etiology of localized aggressive periodontitis are Capnocytophaga ochraceus and:

    - Actinobacillus actinomycetemcomitans (Aa)
    - Wolinella recta
    - Porphyromonas gingivalis
    - Actinomyces israelii
    • Actinobacillus actinomycetemcomitans (Aa)
    • Aggressive periodontitis occurs in two forms:
    • Generalized form: Prevotella intermedia and Eikenella corrodens predominate. Occurs between the ages of 12-25. Rapid, severe periodontal destruction.
    • Localized form: Gram-negative anaerobes Actinobacillus Actinomycetemcomitans (Aa) and Capnocytophaga species (ochraceus) predominate. Rapid, severe attachment loss around the incisors and first molars. Absence of plaque.
    • Aa and Capnocytophaga species (C. Ochraceus) are associated with periodontitis in juvenile diabetes.
  43. Streptococcus mutans grows optimally at a pH well below 7.0. From this statement, it can be reasoned that streptococcus mutans is:

    - Acidophilic
    - Acidogenic
    - Aciduric
    - Alkaphilic
    - Neutrophilic
    • Acidophilic
    • Aciduric means that the bacteria is capable of or can tolerate living under acid conditions. Acidogenic means that the bacteria can produce relatively high concentrations of acid.
    • Streptococci are the primary acidogenic microorganisms in the oral cavity. Lactic acid is the main cause of enamel decalcification.
  44. E. Coli is in the bacterial family Enterobacteriaceae. All of the following are characteristics of the family EXCEPT:

    - Capnophilic
    - Facultative aerobes
    - Gram-negative
    - Rod shaped
    - Flagellated
    • Capnophilic
    • E. Coli and its relatives are known as "enteric bacteria", because they live in the intestinal tract of humans and other animals. Best known as Salmonella and Shigella (cause of dysentery or bloody diarrhea)
    • Capnophilic require carbon dioxide for growth (Capnocytophaga ochraceus, found in aggressive periodontitis)
  45. Which of the following is NOT a characteristic of Streptococcus pyogenes?

    - group A streptococcus
    - Gram-negative
    - Nonmotile
    - Catalase-negative
    • Gram-negative
    • Streptococcus is a diverse collection of gram-positive cocci. typically arranged in pairs of chains. Most species are facultative anaerobes, and grow only in an atmosphere enhanced with carbon dioxide (capnophilic growth). Carbohydrates are fermented, resulting in the production of lactic acid.
    • Unlike Staphylococcus, streptococci are catalase-negative
    • Streptococcus pyogenes (group A streptococcus) is one of the most frequent pathogens of humans. Most common cause of bacterial pharyngitis.
  46. Phagocytosis is mediated by:

    - B lymphocytes and plasma cells
    - B lymphocytes and T lymphocytes
    - Macrophages and polymorphonuclear leukocytes
    - Kupfer cells and T lymphocytes
    • Macrophages and polymorphonuclear leukocytes
    • Fixed Phagocytes: do not circulate, fixed macrophages and cells of the reticuloendothelial system
    • Free phagocytes: circulate in the bloodstream, include leukocytes and the free macrophages
  47. Which of the following is the process in which DNA is transferred from a bacterial donor cell to a recipient cell by cell-to-cell contact?

    - Translation
    - Transduction
    - Transcription
    - Conjugation
    • Conjugation
    • A form of sexual reproduction in which the greatest amount of genetic information (as DNA) is transferred from one like bacterium to another through direct contact. The contact is established through the presence of a pilli
    • The ability to transfer DNA by conjugation is dependent on the presence of cytoplasmic entity termed the fertility factor, or F.
    • Can result in the passage of genes for antibiotic resistance.
    • Transfer of DNA within the bacterial cell wall occurs via transposons, which are portions of DNA that move from one site on the chromosome to another (or to a plasmid)
    • F+ is the donor cell
    • F- is the recipient cell
  48. Transcription occurs in the :

    - Cytoplasm of prokaryotes, while it occurs in the nucleus of eukaryotes
    - Cytoplasm of eukaryotes, while it occurs in the nucleus or prokaryotes
    - Nucleus of both prokaryotes and eukaryotes
    - Cytoplasm of both prokaryotes and eukaryotes
    • Cytoplasm of prokaryotes, while it occurs in the nucleus of eukaryotes
    • Transcription is the transfer of the genetic information from the archival copy of DNA to the short-lived messenger RNA. The enzyme RNA polymerase binds to a particular region of the DNA and starts to make a strand of MRNA with a base sequence complementary to the DNA template.
    • Translation: the process wherein information in the form of nitrogenous bases along an mRNA is translated into the amino acid sequence of a protein
    • Transduction: is the transfer of DNA via phage particle. Does not require cell-to-cell contact.
    • Reverse transcription: is the formation of DNA from an RNA template. Usually done by retroviruses with a single stranded, positive sense RNA genome.
  49. The attachment of microbes and other foreign cells to phagocytes by antibody molecules such as IgG and complement proteins such as C3b is called:

    - Conjugation
    - Transformation
    - Opsonization
    - Adhesion
    • Opsonization, or enhanced attachment, refers to the antibody molecules IgG (or IgM) and the complement proteins C3b and C4b attaching antigens to phagocytes. This results in a much more efficient phagocytosis. 
    • Opsonization is especially important against microorganisms with antiphagocytic structures such as capsules since opsonizing antibodies made against the capsule are able to stick capsules to phagocytes.
    • The two major opsonins are IgG and C3b.
  50. Exotoxin A is responsible for Streptococcal toxic shock syndrome.

    Exotoxin B rapidly destroys tissue

    M protein has a resistance to phagocytosis

    Which ones are true or false
    • They are all true
    • Streptokinase A and B, dissolves fibrin in blood clots
    • Streptolysin O and S, is responsible for lysis of red and white blood cells.
    • 4 streptococcal pyrogenic exotoxins, are responsible for many  of the clinical manifestations of severe streptococcal diseases.
  51. Spirochetes are a principal etiologic factor in necrotizing ulcerative gingivitis.

    Prevotella intermedia is the most common spirochete found in patients with this disease

    - Which statement is true and or false?
    • First statement is true, second is false
    • ANUG is an acute recurring gingival infection of complex etiology, necrosis of papillae, spontaneous bleeding and pain. The two principal bacteria associated with ANUG are Prevotella intermedia and Spirochetes.
    • IgG is the immunoglobulin that is found in the highest concentration in serum samples from patients with periodontal disease.
    • Predominant subgingival bacteria associated with gingival health: Streptococcus mitis and sanguis, Actinomyces viscosus and naeslundii, Rothia dentocariosus, Staphylococcus epidermidis, small spirochetes
  52. All of the following are eukaryotes EXCEPT one:

    - Fungi
    - Plants
    - Protozoa
    - Bacteria
    • Bacteria
    • ** All living things can be classified under being Eukaryotes (protozoa, fungi, plants, animals, humans) or prokaryotes (bacteria, rickettsia, chlamydia and mycoplasma).
    • Prokaryotes do not contain organelles
    • Eukaryotic cells contain sterols in the cell membrane while no prokaryotes except Mycoplasmas have sterols in its membrane.
    • Eukaryotes do not contain peptidoglycan, while most prokaryotes (except for mycoplasmas) have a rigid cell wall that contains peptidoglycan.
  53. In terms of extracting chemical energy, aerobic respiration is more efficient than fermentation BECAUSE aerobic respiration utilizes metabolically derived organic acids as terminal electron receptors. 

    Is the statement or/and the reason correct?
    • The statement is correct, but the reason is NOT.
    • Respiration defers to the method of obtaining metabolic energy that involves an oxidative phosphorylation. It involves the formation of ATP during electron transfer. Respiration is MUCH MORE efficient than fermentation.
    • Aerobic respiration involved a cell membrane respiratory (electron transport) chain. The electron transport chain is present in the inner mitochondrial membrane and is the final common pathway by which electrons derived from different fuels of the body flow to oxygen, it has four stages:
    • 1. Glycolysis
    • 2. Formation of acetyl Coenzyme A
    • 3. Citric acid cycle
    • 4. Electron transport chain
  54. Generally speaking, bacteria associated with periodontal health are characterized as:

    - Gram-negative, motile, aerobes
    - Gram-negative, nonmotile, anaerobes
    - Gram-positive, nonmotile, facultative anaerobes
    - Gram-positive, motile, aerobes
    • Gram-positive, nonmotile, facultative anaerobes
    • Periodontal health is characterized by gram-positive bacteria such as Streptococcus sanguis, streptococcus mitis, actinomyces viscosus, Actinomyces maeslundii and a few gram-negative species such as Veillonella parvula and Capnocytophaga ochracea.
    • In periodontal disease, the bacterial balance shifts over to gram-negative, motile, strictly anaerobic bacteria. Inflammatory disease and injury cannot develop without these bacteria.
    • Bacteria most implicated in periodontal disease and bone loss are the following:
    • Actinobacillus actinomycetemcomitans (Aa): associated with aggressive periodontal disease and localized aggressive periodontitis.
    • Porphyromonas gingivalis: associated with chronic and aggressive periodontitis.
    • Tanerella forsythensus: strongly linked to periodontal disease
    • Treponema denticola, sokranskii: associated with deep pockets, chronic periodontitis and ANUG
    • Prevotella intermedia: associated with deep pockets, chronic periodontitis and ANUG
  55. Anaerobic bacteria produce superoxide dismutase and catalase enzymes.

    Most bacteria, grow in either the presence or the absence of oxygen.

    Which statement is true and or false?
    • First statement is false, second one is true
    • Aerobic bacteria produce superoxide dismutase and catalase enzymes which can detoxify hydrogen peroxide and superoxide radicals that are the toxic byproducts of aerobic metabolism.
    • Most bacteria grow in the presence or the absence of oxygen, these are called facultative anaerobes.
    • Bacteria that can rely entirely on inorganic chemicals for their energy and source of carbon (CO2) are referred to as autographs, whereas many bacteria and animal cells that require organic carbon sources are known as heterotrophs.
  56. Some gram-positive, but never gram-negative, bacteria, such as members of the genera Bacillus and Clostridium, are spore formers.

    - The spore contains a complete copy of the chromosome, the bare minimum concentration of essential proteins and ribosomes, and a high concentration of calcium bound to dipicolinic acid.

    Which statement is true and or false?
    • Both statements are true
    • Spores are NEVER GRAM-NEGATIVE, they are bacterias like Bacillus and Clostridium. The spore is a vegetative state or dormant state.
    • The spore contains a complete copy of the chromosome, the bare minimum concentration of essential proteins and ribosomes, and a high concentration of calcium bound to dipicolinic acid.
    • To destroy the bacteria it must be autoclaved at 121C for 20 minutes.
    • Spores are a means of asexual reproduction
  57. One of the most common forms of "traveler's diarrhea" is caused by an enterotoxin produced by:

    - Bacteroides
    - Escherichia coli
    - Neisseria
    - Eikenella
    • Escherichia coli, produces an enterotoxin that causes traveler's diarrhea.
    • This enterotoxin can be detected using an ELISA (enzyme linked immunosorbent assay) assay.
    • ELISA has proven very useful in the scrutiny of serum for the presence of antibodies to HIV.
    • S. aureus and Vibrio cholerae also produce enterotoxins that can be detected using the ELISA assay.
    • Bacterial toxins are the most potent poisons known, and their potency is paralleled by their efficiency as antigens.
  58. DNA in the bacterial cell is generally confined to the:

    - Ribosomes
    - Inclusions
    - Capsule
    - Nucleoid
    • Nucleoid, a central region in the bacterial cell.
    • Ribosomes: site of translation
    • Inclusions: Storage of reserves of nutrients
    • Capsule: layer of polysaccharides, attachment to surfaces, protection against phagocytosis.
    • Cell envelope: is a descriptive term for the several layers of material that envelope or enclose the protoplasm of the cell. The cell protoplasm (cytoplasm) is surrounded by the plasma membrane, a cell wall and a capsule. The cell wall itself is a layered structure in gram-negative bacteria. All cells have a plasma membrane, which is the essential and definitive characteristic of a "cell".
  59. Genetic information is exchanged between bacteria in three ways: conjugation, transduction and transformation. Which process is depicted below?

    Image Upload
    • Transformation, is the most primitive of mechanisms for gene transfer among bacteria. There is no requirement for cell-to-cell contact. Transformation involves the DNA being taken up by the recipient cell (through dodnor lysis or lab extraction) and changes its phenotype.
    • Transduction: is the transfer of genetic material from one bacterial cell to another by viral infection.
  60. Which of the following opportunistically infects its host and utilizes Exotoxin A?

    - Neisseria gonorrhoeae
    - Helicobacter pylori
    - Pseudomonas aeruginosa
    - Staphylococcus aureus
    • Pseudomonas aeruginosa, are opportunistic pathogens, cause UTI, RTI, dermatitis, bone and joint infections.
    • Pseudomonas species are usually motile, straight or slightly curved, gram-negative, aerobic rods typically arranged in pairs. Most straights are obligate aerobe. The presence of cytochrome oxidase in Pseudomonas species is used to differentiate them from the Enterobacteriaceae.
    • Exotoxin A: believed to be one of the most important virulence factors produced by pathogenic strains of P. aeruginosa. 
    • P. aeruginosa is inherently resistant to many antibiotics. Only a few antibiotics are effective against them including fluoroquinolones, gentamicin and imipenem.
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Microbiology and Pathology 1-61.txt
2015-08-13 19:50:20
Microbiology Pathology

Microbiology and Pathology
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