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25 Cards in this Set
- Front
- Back
Name the three ways in which GPB are categorized |
Gram stain morphology (branching or nonbranching)
Formation of spores
catalase reaction |
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Name the catalase positive, spore forming GPB species |
Bacillus cereus Bacillus anthracis |
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Characteristics of (most) Bacillus species? |
Large rods motile hemolytic catalase + |
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Characteristics of Bacillus anthracis? |
non hemolytic non motile square-ended rods in singles or chains ("bamboo") stiff consistency on blood agar |
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Describe types of anthrax caused by B. anthracis |
Cutaneous - spore penetrates skin, causes ulceration ("black eschar"), 20% mortality rate
Pulmonary - "Woolsorter's Disease", inhalation of spores, 80-90% mortality rate if not treated early
Gastrointestinal - ingestion of spores, most patients die from toxemia and sepsis |
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Clinical significance of B. cereus? |
Leads to food poisoning via emetic or enterotoxin
Enterotoxin - watery diarrhea 8-16 hours after ingestion of contaminated food, recovery w/in 24 hours of onset
Emetic toxin - Vomiting 0.5 - 6 hours after ingestion (usually rice), recovering 9 hours after onset |
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Laboratory identification of B. cereus? |
Because B. cereus is part of normal stool flora positive identification must be confirmed from contaminated food source, not patient stool sample |
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Name the catalase positive, non spore forming GPB species |
Listeria sp. Corynebacterium sp.
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Name the catalase negative, non spore forming GPB species |
Erysipelothrix Lactobacilli sp. Gardnerella sp. Arcanobacterium sp. |
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Name the catalase positive, branching aerobic Actinomycetes GPB species |
Nocardia sp. Streptomyces sp. Rhodococcus
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Biochemical characteristics of Listeria species? |
catalase + tumbling motility on wet mount Umbrella shaped motility in semisolid media CAMP + (shovel or wedge shape) |
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Colony morphology of Listeria monocytogenes? |
small, grey colonies narrow beta hemolysis grows best at room temp, can grow at refrigerated temps |
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Infections caused by Listeria monocytogenes? |
Pregnant females can pass on organism to fetus (usually results in stillbirth, if fetus is born alive there is a 50% mortality rate)
Neonatal Listeriosis - newborns contract organism in utero (early onset) which often leads to sepsis OR during vaginal birth (late onset) which often leads to meningitis
Invasive Listeriosis - bacteremia and meningitis in immunocompromised hosts
Gastroenteritis - in healthy individuals due to food contamination (often meat and dairy products) |
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Significance of Lactobacillus? |
Normal flora of mouth, GI tract, female genital tract
Plays important role in maintaining homeostasis of female genital tract (keeps pH acidic, releases hydrogen peroxide which is poisonous to other bacteria)
Absence of Lactobacillus is major factor in developing bacterial vaginosis |
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Morphology and characteristics of Nocardia species? |
slow aerobic growth (3-30 days) chalky, matte, velvety appearance will grow on blood agar, mycology media, and LJ partially acid fast + Lysozyme resistance + grows in soil, water, decaying matter |
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characteristics of N. brasiliensis infections? |
Causes cutaneous infections, usually a result of traumatic injury
3 types of cutaneous infections: 1) mycetoma - chronic, localized, painless, subcutaneous, swelling, presence of granules 2) Lymphocutaneous - infection spreads to lymphnodes 3) superficial skin infections - cellulitis and abscesses |
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characteristics of N. asteroides infections? |
Pulmonary infections in immunocompromised patients
abscesses form in lungs can disseminate to other parts of body |
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Differentiation of N. braziliensis and N. asteroides? |
N. braziliensis = positive for casein and tyrosine hydrolysis N. asteroides = negative for casein and tyrosine hydrolysis |
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Which species of GPB is partially acid fast positive? |
Nocardia sp (use this test to differentiate from Streptomyces sp) |
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Colony morphology of Arcanobacterium sp? |
Narrow beta hemolysis may pit the agar or form black dot under colony
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Differentiation of A. haemolyticum and A. pyogenes? |
A. haemolyticum is reverse CAMP + A. pyogenes is reverse CAMP - |
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How do you identify Corynebacterium diphtheriae? |
Initial ID done with Loeffler's media (blue staining granules) or CTBA (brown halo around colonies)
Definitive ID requires demonstration of toxin production by the isolate with the Elek test |
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Typical gram stain morphology of Corynebacterium species? |
Gram positive rods club-shaped ("coryneform") pleomorphic palisading May stain irregularly |
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What are clue cells and with which bacterial species might you see them? |
Clue cells are epithelial cells covered in bacteria. Often observed with Gardnerella vaginalis infections. |
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Differentiation of Corynebacterium species on blood agar? |
C. diphtheriae - small, beta hemolytic C. jekeium - small, non hemolytic C. urealyticum - pinpoint, non hemolytic |