Clinical Micro Exam Flash Card Format.txt

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Clinical Micro Exam Flash Card Format.txt
2012-10-25 21:06:54
Clinical Micro Exam

Clinical Micro Exam 1
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  1. Haemophilus
    • • Small G- coccobacilli, normal flora
    • • Require X, V factors from blood
  2. H. influenzae- 6 types
    • • Type B is most virulent
    • • Misnamed because first isolated during influenza outbreak
    • • Respiratory transmission, asymptomatic with exception of Type B
    • •Pathogenicity
    • o       Meningitis- primarily in children
    • o       Severe sequelae (abnormal condition following or related to a previous disease) including                deafness, mental retardation, seizures
    • • Diagnosis
    • o       Chocolate blood agar, need both X and V, use satellite system with S. aureus
    • • Prevention
    • o       Hib is type B capsule conjugate vaccine
    • o       Dramatic reduction in childhood incidence
    • o       Vaccine is needed to prevent severe sequelae in children
  3. H. ducreyi
    • • Causes sexually transmitted disease called chancroid
    • • Characterized by soft, ragged, painful lesion on genitals
  4. Gardnerella (Haemophilus) vaginalis
    • • Part of normal flora
    • • Can cause infection, usually mixed with anaerobes
    • • Diagnosis is recognition of clue cells- epithelial cells covered with coccobacilli
  5. Bordetella pertussis
    • •       Small G- coccobacilli
    • •       Virulent strains have capsule
    • •       Also fastidious requiring blood agar
    • •       Does not require X and V factor
    • • Virulence factors
    • o       Pertussis toxin- increase cAMP, increase insulin
    • o       Filamentous hemagglutinin (FHA)- attach bacteria to host cell
    • o       Extracellular adenylate cyclase- inhibits phagocytosis
    • o       Endotoxin
    • o       Non virulent strain (phase IV) can mutate to virulent strain (phase I) via phase shift by way of       transposon insertion
    • Epidemiology
    • o       Worldwide
    • o       Primarily disease of childhood
    • o       Droplet transmission
    • o       Was most common disease of childhood in U.S., often fatal
    • o       Vaccine decreased # of cases, but on the rise again
    • • Pathogenicity
    • o   Catarrhal stage
    • ♣       Sneezing
    • ♣       Coughing
    • o   Paroxysmal stage
    • ♣       Violent cough
    • ♣       Inspiratory “whoop”
    • ♣       Increased mucus production
    • ♣       Can be fatal
    • • Treatment and prevention
    • o       Antibiotics useless in severe cases
    • o       Pertussis vaccine introduced in 1940s, associated with adverse side-effects
    • o       Whole cell vaccine
    • ♣       Killed B. pertussis cells
    • ♣       Intense side effects, vomiting, fever, rarely brain infection
    • o       Acellular vaccine
    • ♣       Isolated virulence factors (either pertussis toxin, or FHA)
    • ♣       Reduced side effects, but also reduced efficacy
  6. Brucella
    • • Non-motile, G- coccobacilli
    • • All species have capsule, different antigens
    • • Epidemiology
    • o Zoonosis
    • ♣ True zoonosis, no human to human transmission
    • ♣ Goats, sheep, cattle
    • ♣ Transmitted via milk
    • ♣ Brucella can directly penetrate skin
    • • Pathogenicity
    • o Invades lymphatic system, carried to various organ systems
    • o Multiplies in phagocytes
    • o Lesions in various organs
    • o Effect on animal is female animal will often spontaneously abort fetus, not human
    • o Symptoms include
    • ♣ Undulating (variable) fever
    • ♣ Intense back pain, headache
    • ♣ Weakness malaise
    • ♣ These last from months to years
    • o Treatment
    • ♣ Immunize animals
    • ♣ Pasteurize milk
    • ♣ Antibiotics
  7. Francisella tularensis
    • • Pleomorphic (rods, cocci) G-
    • • Produce capsules
    • • Type A and Type B strains
    • • Epidemiology
    • o Disease in mammals, fish, birds, inverts. Especially common in rabbits
    • o Vectors are ticks and deer flies
    • o Transmitted by direct contact with sick animal or by vector bite
    • • Types of tularemia
    • o Ulceroglandular
    • ♣ Lesion at entry point- develops into open ulcer
    • ♣ Lymph nodes swell
    • ♣ Bacteria carried in lymph to other organs- lesions form
    • o Pneumonic tularemia
    • ♣ Respiratory droplet from infected animal
    • ♣ Lung infection
    • ♣ High mortality rate
    • o Oculoglandular tularemia
    • ♣ Infection of eyes
    • o Typhoidal tularemia
    • ♣ Hard to identify
    • ♣ GI symptoms
    • ♣ Systemic infection
    • ♣ Highest mortality rate
  8. Mycobacterium
    • • Lipid content of cell wall up to 40%
    • • Acid fast staining
    • • 70 + species, most are non-pathogenic
  9. Mycobacterium tuberculosis
    • • Discovered as cause of tuberculosis by Robert Koch
    • • No capsule
    • • Aerobic
    • • Very resistant to drying and chemicals due to high lipid content cell wall
    • • Very slow growing
    • Cell wall chemistry
    • o Mycosides = glycolipids found ONLY in acid fast bacteria that are composed of a mycolic acid and a large fatty acid, bound to a carbohydrate attached to the peptidoglycan layer
    • o Cord factor = a mycoside formed by the union of 2 mycolic acids with a disaccharide. Only in virulent strains
    • o Sulfatides = mycosides that resemble cord factor with sulfates attached to the disaccharide
    • o Wax D = complicated mycoside that acts as an adjuvant that activates delayed hypersensitivity reaction in the host
  10. Tuberculosis
    • o Mostly human disease
    • o Droplet transmission
    • o Contaminated objects can transmit bacteria due to ability to reduce drying and chemicals
    • o Bacteria are inhaled, penetrate macrophages, travel to lymph nodes, multiply in macrophages
    • o Activated macrophages attack bacteria, lung tissue becomes damaged and local necrosis of lung tissue occurs
    • o The foci of the infection is called the Ghon complex and the necrosed tissue is called caseous necrosis
    • o The entire structure is called a granuloma or a tubercle
    • o Within the tubercle bacteria are kept at bay, but remain viable
    • o Most adult cases of TB occur after the bacteria have been dormant for some time
    • o The infection can occur in any of the organ systems “seeded” during the primary infection
    • o The temporary weakening of the immune system causes reactivation- many AIDS patients develop TB in this way
    • o Miliary TB- tiny millet-seed sized tubercles (granulomas) are disseminated all over the body in blood. The kidneys, liver, lungs and other organs are filled with tubercles
    • o Mycobacteria induce the delayed hypersensitivity immune response
    • o Antibodies are NOT produced, not humoral immune response
    • Diagnosis of TB
    • o Tuberculin Mantoux Test = tests skin sensitivity to TB antigens
    • o If patient has been infected with M. tuberculosis experience T cell accumulation at site of injection creating a palpable induration (24-48hrs.)
    • o PPD is purified protein derivative used now instead of killed Mycobacterium cells
    • o Interpretation of PPD test = 15 mm or more = Strongly positive
    • o Problems with skin test
    • ♣ May indicate previous infection with an atypical mycobacteria
    • ♣ May indicate BCG vaccination
    • ♣ Induration fails to occur in advanced TB
    • o Lab diagnosis
    • ♣ Isolation of tubercle bacilli using selective media
    • ♣ Acid fast stain
    • ♣ M. tuberculosis require niacin (nicotinic acid) and accumulate nicotinic acid that can be assayed
  11. Atypical mycobacteria (non-tuberculosis)
    • o Found in many places in the environment: tap water, fresh and ocean water, milk, bird droppings, soil, and house dust
    • o M. avium intracellulare (MAI or MAC)
    • ♣ Closely related to M. tuberculosis
    • ♣ Usually infects birds (can infect other animals)
    • ♣ Major cause of bacterial infection in HIV patients
  12. Mycobacterium leprae
    • o The microbe responsible for leprosy was not identified until 1874 by Dr. Hansen also called Hansen’s disease
    • o Acid fast rod shaped bacteria
    • o CanNOT be grown in laboratory culture because intracellular
    • o Transmission = M. leprae is not highly infectious. Direct contact
    • o Lepromatous leprosy
    • ♣ Defective cellular immunity
    • ♣ Infects every body organ, but the primarily the skin, nose, testes and nerves
    • ♣ Large numbers of bacteria present
    • ♣ Most peripheral nerves are thickened causing loss of sensation. Inability to feel leads to repetitive trauma and infection and ultimately tissue is eventually reabsorbed
    • o Tuberculoid leprosy
    • ♣ Less severe, patients can mount a cell-mediated response
    • ♣ Skin damage is not as excessive and disease is milder and sometimes self-limiting
    • ♣ Nerve involvement is common, but in loss of sensation in patches
    • o Diagnosis
    • ♣ Unable to grow M. leprae in laboratory culture, must grow in mouse food pads, armadillos
    • o Treatment
    • ♣ Dapsone + other drugs
  13. Actinomycetes
    • • Bacteria that act like fungi
    • • Two actinomycetes cause human disease
    • o Actinomyces – normal flora, can cause abscess
    • o Nocardia – not normal flora, TB like illness
  14. Spirochetes –
    3 genera Treponema, Borrelia, Leptospira
  15. Treponema pallidum - Syphilis
    • • Unique characteristic = 6 thin endoflagella called axial filaments. Lie between outer membrane and peptidoglycan layer
    • • Transmission is by contact with mucous membranes, sexually transmitted, also blood enters the body by penetrating mucous membranes
    • • Primary syphilis- lesion is a chancre = hard, painless ulcer on genitals/oral surfaces
    • • Secondary Syphilis- systemic, widespread rash on soles of feet and palms, swollen lymph nodes, loss of hair in patches. This part of the disease is why syphilis is called “the great imitator” symptoms are not definitive. Another characteristic of secondary is condylomata lata = mucous membrane lesions
    • • Easy to identify treponemes in primary and secondary syphilis, lesions are swarming with bacteria
    • • Latent syphilis- symptoms have resolved, may relapse periodically into secondary symptoms or remain in latent phase for life or progress to tertiary
    • • Tertiary syphilis-
    • o gummas are destructive lesions- necrosis of tissue
    • o cardiovascular symptoms = cardiovascular syphilis
    • o neurological symptoms = neurosyphilis
    • o Tabes dorsalis = degeneration of the posterior columns of the spinal cord and the dorsal roots, ataxia, sensory difficulty, Charcot’s joint - destructive joint disease caused by diminished proprioceptive sensation
    • o General paresis (of the insane)- paralytic dementia
    • • Congenital syphilis - infection of the fetus via placenta
    • o T. pallidum does not cross and damage fetus until the fourth month of gestation, if treated prior child born free of syphilis
    • o Congenital syphilis outcomes
    • ♣ High mortality rate (stillbirth, spontaneous abortion)
    • ♣ Infant has secondary syphilis
    • ♣ Infant is healthy, develops disease years later
    • ♣ Infant is free of disease
    • o Pathology
    • ♣ Blueberry muffin rash
    • ♣ Hutchison triad = 1. impaired vision 2. notched teeth 3. impaired hearing
    • • Serological Tests for Syphilis (STS)
    • o Nonspecific treponemal tests- testing for antibodies resulting from infection
    • o Specific treponemal tests- specifically testing for Treponema organism
    • • Treatment
    • o T. pallidum is easily killed by heat, drying
    • o Administer penicillin (dose and specific derivative depend on stage)
    • o Jarisch Herxheimer reaction = acute worsening of symptoms after beginning antibiotics
  16. Other treponemes
    • • T. pertenue = yaws- identical to T. pallidum
    • • T. vincentii = trench mouth
  17. Borrelia
    • Large spirochete
  18. Borrelia recurrentis
    • • Relapsing fever – transmitted by body lice
    • o Lesions on internal organs
    • o High fever 4-5 days
    • o Fever disappears and returns repeatedly
  19. Borrelia burgdorferi
    • • Lyme disease – transmitted by deer ticks in the nymph stage
    • o Primary Stage - skin lesion “bulls eye” or target shaped
    • o Secondary stage- erythema chronicum migrans (ECM)- appears at the site of the infecting tick bite rash that spreads
    • o Tertiary stage
    • ♣ Meningoencephalitis
    • ♣ Myocarditis
    • ♣ Musculoskeletal pain
    • ♣ Chronic arthritis
    • o Diagnosis
    • ♣ Spirochete is difficult to find and cultivate in laboratory
    • ♣ Clinical signs and history
  20. Leptospira
    • • Fine, coiled spirochete, hooked on each end
    • • Bacteria penetrate mucous membranes and invade blood and eventually various organs
    • • Some strains cause Weil’s disease or infectious jaundice
  21. Mycoplasma
    • • Lack a cell wall, very pleomorphic
    • • Tiniest free living organisms capable of self replication
    • • Require cholesterol for growth
    • • Fried egg colonies on agar
  22. Mycoplasma pneumonia
    • Mild, self-limited bronchitis and pneumonia called primary atypical pneumonitis (PAP) or walking pneumonia
  23. Ureaplasma urealyticum
    • • T-strain Mycoplasma (T=tiny)
    • • Produce tiny colonies
    • • Ureaplasma found in urine producing urease to break down urea
    • • Sexually transmitted
  24. Rickettsiae
    • • Obligate intracellular parasites- needs cell for rare materials to synthesize ATP
    • • Very small Gram negative coccobacilli
    • • Can be grown in the laboratory in chick embryo yolk sacs
    • • Some Rickettsiae share antigens with Proteus strains
    • • Historically - Weil-Felix test – mix serum with Proteus to check for agglutination
    • • IFA – indirect fluorescent antibody testing currently used for diagnosis
  25. Group I = Typhus (Type of Rickettsial disease)
    • •Epidemic typhus = Rickettsia prowazeki = vectored by lice
    • o Bacteremia
    • o High fever
    • o Macular rash (not on soles or palms)
    • o Brill-Zinsser Disease- NOT treated with antibiotics retain R. prowazeki in a latent state, occasionally breaks out of latent state to cause Brill-Zinsser disease, milder form of epidemic typhus
    • •Endemic typhus = Rickettsia typhi = vectored by flea
    • o Similar to epidemic typhus, but not as severe and only occurs sporadically
    • •Scrub typhus = Orientia tsutsugamushi = vectored by larva of mites (chiggers which live in soil)
    • o Scab forms at initial bite site, followed by maculopapular rash
  26. Group II = Spotted fevers (Type of Rickettsial disease)
    • • Rocky Mountain Spotted Fever = Rickettsia rickettsii = vectored by spotted wood tick
    • o Maculopapular rash- with discolored spots from small hemorrhages, rash seen first on palms, soles of feet and wrists. Then spreads over body
    • • Rickettsialpox = Rickettsia akari = vectored by mites
    • o Initial bump at bite, turns into vesicle
    • o Vesicles spread over body (similar to chickenpox)
    • • Trench fever = Rickettsia quintana = vectored by body lice Pediculus humanus
    • o Fever can reach 105°F (40.5°C) and stays high for five to six days at a time. The temperature then drops, and stays down for several days, usually recurring in five- to six-day cycles
    • • Q fever = Coxiella burnetii – NO arthropod vector
    • o Unusual because has an endospore form
    • o C. burnetii lives in ticks and cattle
    • o Endospore survives in tick, cattle feces
    • o NO skin rash- develop atypical pneumonia
  27. Chlamydia
    • • Obligate intracellular parasites- can’t synthesize ATP
    • • Considered Gram negative because stain pink, but doesn’t have peptidoglycan layer, but muramic acid
    • • Life cycle =
    • o Elementary body (EB) is infective,
    • o EB enters columnar epithelial cell via endocytosis
    • o EB transforms inside cell to larger reticulate body
    • o Reticulate body in cell divides and new elementary bodies are released
  28. Chlamydia trachomatis
    • • Cause of trachoma – the leading cause of preventable blindness in the world
    • o chronic conjunctivitis transmitted by direct contact
    • o only in humans
    • • Genital transmission – cause of non-gonococcal urethritis (NGU) – infection of urethra contracted sexually
    • o NGU is the most commonly caused by C. trachomatis
    • o Many patients are asymptomatic, nearly all females
    • o Frequently spreads from cervix to uterus, fallopian tubes, ovaries….called PID (pelvic inflammatory disease
    • • Lymphogranuloma venereum - STI caused by C. trachomatis
  29. Chlamydia psittaci
    • • Causes psittacosis (parrot fever) – pneumonia like
    • • Humans inhale C. psittaci from feathers or feces
  30. Legionella pneumophila
    • • Aerobic Gram negative microbe famous for causing an outbreak of pneumonia at an American Legion convention in 1976 in Philadelphia
    • • Facultative intracellular parasite
    • • L. pneumophila is ubiquitous in natural and artificial water environments
    • • Aerosolized contaminated water is inhaled resulting in infection
    • • No person to person transmission