Micro 2nd SCT 1st semester
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Mention 5 diseases that can be caused by Staphylococcus aureus!
Impetigo, furunculus, pneumonia, osteomyelitis, food poisoning etc.
Mention 2 toxin-mediated staphylococcal diseases!
toxic shock syndrome (TSS), scalded skin syndrome, food poisoning
Mention 3 toxic products produced by Staphylococcus aureus!
TSST (toxic shock syndrome toxin), enterotoxin, exfoliatin, leukocidins, hemolysins
Which is the most virulent species of Staphylococcus?
Which enzymatic virulence factor is characteristic exclusively for Staphylococcus aureus?
How can we identify the source of infection in a staphylococcal food poisoning?
by phage typing
Which antibacterial drug is the first choice in serious infections caused by methycillin resistant Staphylococcus aureus (MRSA) strains?
glycopeptides (vancomycin, teicoplanin)
In which disease is Staphylococcus saprophyticus considered an obligate pathogen!
cystitis in young women
Which cell constituents determine the group-specific, and the type specific antigens of Streptococcus pyogenes, respectively?
- group specific: C- polysaccharide
- type specific: M protein
Mention 3 enzymes produced by Streptococcus pyogenes that enhance the spread of the bacterial infection in the body!
Streptokinase (fibrinolysin), hyaluronidase, streptodornase (DNAse)
List 3 diseases caused by Streptococcus pyogenes in the skin or in subcutaneous tissues!
impetigo (pyoderma), cellulitis, erysipelas, fasciitis, myositis
Mention a toxin-mediated streptococcal disease, specify the name of the toxin and its mechanism of action!
Scarlet fever - erythrogenic toxin – superantigen causing capillary destruction
Mention 2 poststreptococcal diseases!
Glomerulonephritis, rheumatic fever, erythema nodosum, chorea minor.
Which product of Streptococcus pyogenes has a major pathogenic role in poststreptococcal diseases?
M protein: may induce hypersensitivity reactions
How long does immunity against scarlet fever exist? Which immune effector mechanism is involved?
Life-long immunity. Antitoxic antibodies are involved.
What is the drug of first choice in Streptococcus pyogenes infection?
What is the patomechanism of post-streptococcal rheumatic fever?
type II hypersensitivity (cytotoxic antibodies)
What is the patomechanism of post-streptococcal glomerulonephritis?
type III hypersensitivity (immune complexes)
Which Streptococcus species plays major role in the meningitis of newborn babies?
Group B Streptococcus (S. agalactiae)
What is (are) the major causative agent(s) for subacute bacterial endocarditis?
What are the characteristics of Enterococci that can be used in their identification?
D group polysaccharide antigen; tolerance to bile and hydrolysis of esculin (BEAmedium: bile esculin agar); growth in the presence of 6,5 % NaCl
What are the specific morphologic features of Streptococcus pneumoniae?
Gram positive diplococcus, lancet shape, capsule.
Mention 3 diseases that can be caused by Streptococcus pneumoniae!
Pneumonia, meningitis, sinusitis, otitis media, sepsis, (ulcus serpens corneae)
What fast diagnostic procedure can be used in acute Neisseria gonorrhoeae infection?
Demonstration of bacteria (intracellular in PMNs) from urethral discharge by Gramor methylene blue stain; PCR amplification of bacterial DNA
What kind of immunity develops after Neisseria gonorrhoeae infection
Partial immunity of short duration; no protection from reinfection
Specify at least 2 of the most important manifestations of disseminated gonorrhoeal infections!
arthritis, skin eruptions, (endocarditis, meningitis)
What is the major manifestation of Neisseria gonorrhoeae infection in newborns?How can it be prevented?
Blenorrhoea (ophtalmia) neonatorum, silver acetate eye drops or erythromycinointment
Mention at least 3 major virulence factors of Neisseria gonorrhoeae!
pilus, outer membrane proteins, LOS (lipooligosaccharide), IgA protease
Mention at least 2 major virulence factors of Neisseria meningitidis!
polysaccharide capsule, LPS, IgA protease
What is the site of entry of Neisseria meningitidis infection? Which diseases are caused by this bacterium?
The site of entry is the nasopharynx (transmitted by airborne droplets).Meningococcemia (characterized by skin lesions), and acute (purulent) bacterial meningitis.
What kinds of prophylactic measurements are available against Neisseria meningitidis infections?
- Chemoprophylaxis: rifampin or ciprofloxacin.
- Vaccination: capsular polysaccharide (types A, C, Y and W135). No vaccine against type B!
Which rapid diagnostic methods can be used in the presumptive diagnosis of purulent bacterial meningitis?
- Gram or methylene blue stain of CSF sediment.
- Demonstration of bacterial capsular antigens by latex agglutination (from CSF).
Which capsular serotype is included in the vaccine against Haemophilus influenzae?
Which are the portals of entry of Bacillus anthracis?
Skin, lungs, gastrointestinal tract
Mention 3 important bacteria involved in nosocomial (hospital-acquired) infections!
Staphylococcus aureus, Enterococcus faecalis, Pseudomonas aeruginosa, Escherichiacoli
Mention four E. coli pathogenetic groups involved in enteric diseases!
- Enteropathogenic E. coli (EPEC)
- Enterotoxic E. coli (ETEC)
- Enteroinvasive E. coli (EIEC)
- Enterohemorrhagic E. coli (EHEC)
- Enteroaggregative E. coli (EAggEC)
What are the most important extraintestinal infections caused by E. coli? Mention at least 3 of them!
urinary tract infections, neonatal meningitis, nosocomial wound infections
The most frequent causative agent of urinary tract infections is:
Which 2 diseases are caused by E. coli O157:H7?
hemorrhagic colitis +/- HUS (hemolytic uraemic syndrome)
What is the reservoir of Salmonella typhi?
humans (with disease, or healthy carriers)
Which bacteria cause most frequently typhoid fever and enteric fever, respectively?
- Salmonella typhi (typhoid)
- Salmonella paratyphi A, B, C (enteric fever)
When typhoid fever is suspected, what kinds of clinical samples should be used to isolate the causative agent in the first 2 weeks of the disease?
Blood, (bone marrow)
What is the route of infection in Salmonella gastroenteritis?
Ingestion of contaminated food (such as eggs, cream, mayonnaise, creamed foods, etc.)containing a sufficient number of Salmonella.
Which antibacterial drugs should be administered in gastroenteritis caused by Salmonella?
Antibiotics are not usually necessary unless the infection is generalised. In case of extraintestinal infection (very young, very old or immunosuppressed patients):ampicillin, gentamicin, trimethoprim/sulfamethoxazole, or ciprofloxacin.
List the 4 Shigella species causing human disease!
Shigella dysenteriae, S. flexneri, S. boydii, S. sonnei
Mention 2 bacterial species belonging to different genera that cause bacillary dysentery
Shigella dysenteriae, (Shigella flexneri, Shigella boydii, Shigella sonnei), enteroinvasive E. coli (EIEC)
Mention 3 bacterial species belonging to different genera that cause enteritis or enterocolitis!
Campylobacter jejuni, Escherichia coli, Salmonella enteritidis, Shigella, Yersinia enterocolitica
Mention 2 bacteria causing intestinal infections which have animal reservoirs
Salmonella (not Typhi and Paratyphi!), Campylobacter jejuni, Yersinia enterocolitica, Listeria monocytogenes, E. coli O157
What are the modes of transmission for the 2 different epidemiologic forms of plague?
- - Bubonic plague is transmitted by the bite of infected rat fleas from rats to humans.
- - Primary pneumonic plague spreads directly from human to human via respiratory droplets.
What are the possible portals of entry of Francisella tularensis? Specify at least 4!
tick bite, mucous membranes, skin abrasions, resp. tract, gastroint. tract
How do humans acquire brucellosis? Where do the bacteria replicate in the human body?
Via contaminated milk products or through skin abrasions (contact with animals).Organisms spread to the mononuclear phagocytes of the reticuloendothelial system(lymph nodes, liver, spleen, bone marrow).
What are the reservoirs of the different Brucella species, respectively?
- B. abortus: cattle
- B. melitensis: goat, sheep
- B. suis: swine
What is the mechanism of action of cholera toxin?
Cholera toxin activates the adenylate cyclase enzyme in cells of the intestinal mucosa leading to increased levels of intracellular cAMP, and the secretion of large amount of water, Na+, K+, Cl-, and HCO3- into the lumen of the small intestine.
What is the principle of the treatment for cholera?
Rapid intravenous or oral replacement of the lost fluid and ions. (Administration of isotonic maintenance solution should continue until the diarrhea ceases.) In severe cases:administration of tetracycline (in addition to rehydration).
Mention 4 diseases caused by Haemophilus influenzae!
- purulent meningitis
- epiglottitis (obstructive laryngitis)
- otitis media and sinusitis
- (cellulitis, arthritis)
Which disease is caused by Haemophilus ducreyi?
Chancroid (soft chancre or ulcus molle)
What can serve as source of infections caused by Pseudomonas aeruginosa?
Pseudomonas species are normally present in the environment and can be isolated from the skin, throat, and stool of some healthy persons. They often colonize hospital food,sinks, taps, mops, and respiratory equipment.
Mention 4 diseases that are frequently caused by Pseudomonas aeruginosa!
- urinary tract infections
- wound infections (burns)
- pneumonia, sepsis (immunosupression)
- otitis externa
Mention at least 3 drugs which may be effective to treat infections caused by Pseudomonas aeruginosa!
certain penicillins: piperacillin/tazobactam combination
a 3rd generation cephalosporin: ceftazidim
a 4th generation cephalosporin: cefepime
certain aminoglycosides: gentamycin, tobramycin, amikacin
carbapenems: imipenem, meropenem
Which 2 diseases are caused by Legionella pneumophila?
- - legionellosis, legionnairs’ disease (atypical pneumonia)
- - Pontiac fever (mild, flu like illness without pneumonia)
List 3 important virulence factors of Bordetella pertussis!
- filamentous hemagglutinin, pertussis toxin,
- adenylate-cyclase toxin, trachealcytotoxin
Mention 3 bacterium species causing food poisoning!
Staphylococcus aureus, Bacillus cereus, Clostridium perfringens, Clostridiumbotulinum, Vibrio parahaemolyticus, (Salmonella serotypes causing enterocolitis)
Which bacterium has the highest germ number in the colon?
Mention 4 bacterial genera that are obligate anaerobes!
Clostridium, Bacteroides, Prevotella, Porphyromonas, Fusobacterium, Actinomyces,Bifidobacterium, Peptostreptococcus, Propionibacterium
Which is the most important gas gangrene Clostridium? What is its main virulence factor?
- Clostridium perfringens
- alpha-toxin (lecithinase)
Mention 3 Clostridium species causing gas gangrene! How are they acquired?
- Clostridium perfringens, C. novyi, C. septicum, C. histolyticum, C. tertium, C.bifermentans, C. sporogenes
- The site of infection is usually a wound that comes into contact with Clostridium spores that germinate in an anaerobic environment.
How can be tetanus prevented in patients who have wounds possibly contaminated with C.tetani spores?
Wound should be cleaned and debrided; tetanus toxoid booster injection given;tetanus immunoglobulin (TETIG) in previously unvaccinated patients and in case of heavy contamination of wound; penicillin may be added prophylactically
What are the main symptoms of tetanus infection? Specify at least 3!
Spastic paralysis: muscle spasms; lockjaw(trismus), rhisus sardonicus (grimace of theface), opisthotonus (spasm of the back); respiratory paralysis
What is the mechanism of action of the botulinus toxin?
Blocks release of acetylcholine in peripheral nerve synapses;
What are the main symptoms of botulism? Specify at least 3!
flaccid paralysis: diplopia (double vision), dysphagia (difficulty to swallow),dysphonia (hoarseness), respiratory paralysis
What kind of therapy is used to treat botulism?
Treatment: respiratory support + trivalent antitoxin
Explain whether or not antibiotic treatment is useful in botulism!
Not, because antibiotics are not effective against preformed toxins.
What diseases may be associated with Helicobacter pylori? Specify at least 3!
Gastritis, peptic and duodenal ulcers, gastric carcinoma, MALT lymphoma
What is the most important virulence factor of Corynebacterium diphtheriae?
What is the mechanism of action of the diphtheria toxin
Inhibits protein synthesis. Inhibits peptide elongation in eukaryotic ribosomes by ADP ribosylation of EF-2 (elongation factor-2)
How long does immunity against diphtheria exist? Which immune effector mechanism is involved?
Antitoxic antibodies, long lasting immunity
Which assays should be done in the lab in order to prove diphtheria?
Smears of the throat swab should be stained with methylene blue or Neisser stain;bacteria are cultured on Löffler’s or tellurite (Clauberg) medium; toxin production must be demonstrated by agar precipitation ( ELEK-test)
What feature of Mycobacteria make them acid fast?
The cell envelope contains a high amount (60 – 70 %) of complex lipids: mycolic acid,cord factor. Once the cells are stained (by carbol-fuchsin) they resist decolorisation by acid-ethanol.
Mention 2 atypical Mycobacterium species!
M. kansasii, M. marinum, M. avium-intracellulare complex, M. fortuitum-chelonei complex
How can one demonstrate the presence of Mycobacterium tuberculosis in clinical samples?
- Acid-fast staining (Ziehl-Neelsen)
- Culture on selective media (Löwenstein-Jensen agar, liquid BACTEC medium)
- PCR amplification of bacterial DNA
Why is multi-drug therapy used for tuberculosis?
To prevent the overgrowth of drug-resistant mutants during the long treatment period (if bacteria resistant to one drug emerge, they are most probably inhibited by the other drugs).
What is the main immune defense mechanism against Mycobacterium tuberculosis?
Mention 3 antituberculotic drugs that are of first choice against Mycobacterium tuberculosis!
isoniazid (INH), pyrazinamid, rifampin, (ethambutol, streptomycin)
What disease is caused by Mycobacterium avium-intracellulare? What patients are characteristically susceptible to infection?
It causes TB, especially in immunosuppressed patients (such as AIDS patients).
What is the reservoir of Mycobacterium tuberculosis?
What is the reservoir of atypical Mycobacteria?
environment (soil, water)
What are the 2 distinct forms of leprosy?
Tuberculoid, lepromatous forms
Mention 3 Gram-negative bacteria belonging to different genera causing zoonosis!
Brucella, Francisella tularensis, Yersinia pestis, Pasteurella
Mention 2 Gram-positive bacteria belonging to different genera causing zoonosis!
Listeria monocytogenes, Bacillus anthracis, Erysipelothrix rhusiopathiae
Mention 3 bacterial species belonging to different genera that are frequent causes of urinary tract infections!
E. coli, Klebsiella, Proteus, Pseudomonas aeruginosa, Enterococcus faecalis
Mention one aerobic and one anaerobic bacterium of the normal flora of the skin!
- aerobic: Staphylococcus epidermidis
- anaerobic: Propionobacterium acnes
Give two genuses for each category of bacteria!
Gram positive aerobic: Staphylococcus, Streptococcus, Bacillus, Corynebacterium,…Gram positive anaerobic: Clostridium, Actinomyces, Propionibacterium, Lactobacillus
Give two genuses for each category of bacteria!
- Gram negativ aerobic: Vibrio, Neisseria, Haemophilus…
- Gram negativ anaerobic: Bacteroides, Prevotella, Porphyromonas, Veillonella…
Give 2 genuses for each category of bacteria!
- Gram positive coccus: Staphylococcus, Streptococcus
- Gram negative coccus: Neisseria, Veillonella
- Gram positive rod: Clostridium, Bacillus
Give 2 genuses for each category of bacteria!
- Gram negative rod: E. coli, Salmonella, Shigella
- Spirochetes: Treponema, Borrelia, Leptospira
Describe the color and the shape of Clostridia in a Gram stained smear of gas gangrene exudate!
Gram positive (dark blue) rod (it usually does not form spores in vivo)
Mention 2 antibiotics which can be used in the empirical treatment against Gram negative obligate anaerobic bacteria!
Metronidazol, amoxicillin + clavulanic acid, imipenem
Which 3 bacterial species are the most important causative agents of neonatal (< 1 month of age) meningitis?
Streptococcus agalactiae, E. coli, Listeria monocytogenes
Which 3 bacterial species are the most important causative agents of meningitis among babies (> 1 month of age) and children?
Neisseria meningitidis, Haemophilus influenzae, Streptococcus pneumoniae
What is the causative agent of febris undulans (undulant fever)?
What is the precise definition of bacterial food poisoning?
Acute disease, usually with vomiting and diarrhea, caused by preformed toxins produced by bacteria contaminating the food. The period between consumption of food and the appearance of symptoms is short (< 4-6 hours).
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