Micro - Clinical Bacteriology (Gram - Basics) Flashcards Preview

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Flashcards in Micro - Clinical Bacteriology (Gram - Basics) Deck (15):

What color is a gram negative stain? What are the morphology categories of gram negative bacteria?

Pink; (1) Comma-shaped (oxidase +) (2) Diplococci (3) "Coccoid" rods (4) Rods


What are the oxidase positive, comma-shaped gram negative bacteria? How can you differentiate them?

(1) Camplyobacter jejuni - Grows in 42C (2) Vibrio cholerae - Grows in alkaline media (3) Helicobacter pylori - Produces urease


What are the gram negative diplococci? How can you differentiate them?

(1) Neisseria meningitidis - Maltose fermenter (2) Neisseria gonorrhoeae - Maltose nonfermenter


What are the gram negative "coccoid" rods? Which of these are the most important pathogens to know?

(1) Haemophilus influenzae - IMPORTANT PATHOGEN (2) Bordetella pertussis - IMPORTANT PATHOGEN (3) Brucella (4) Pasteurella


What kind of bacteria is Haemophilus influenzae? What are its growth requirements?

Gram negative "coccoid" rod; Factors V and X


What kind of bacteria is Pasteurella? With what kind of exposure is it associated?

Gram negative "coccoid" rod; Animal bites


What kind of bacteria is Brucella? What disease does it cause?

Gram negative "coccoid" rod; Brucellosis


What are the steps involved in differentiating gram negative rods?

(1) Lactose: Lactose fermenter versus Lactose nonfermenter (2) For Lactose fermenters: Fast fermenter versus Slow fermenter (3) For Lactose nonfermenters: Oxidase negative versus Oxidase positive


What are the gram negative rod lactose fermenters? Divide them into fast versus slow fermenters.

LACTOSE FERMENTERS - FAST: (1) Klebsiella (2) E. coli (3) Enterobacter, SLOW: Citrobacter, Serratia, Others


What are the gram negative rod lactose nonfermenters? Divide them into oxidase negative versus positive.

LACTOSE NON-FERMENTERS - OXIDASE (-): (1) Shigella (2) Salmonella (3) Proteus (4) Yersinia; OXIDASE (+): (1) Pseudomonas


How do lactose-fermenting enteric bacteria appear on MacConkey's agar? What are examples of such bacteria?

Pink; (1) Citrobacter (2) Klebsiella (3) E. Coli (4) Enterobacter (5) Serratia; Think: "Lactose is KEE (fast fermenters), test with maConKEE'S agar (slow and fast fermenters)"


In terms of lactose fermentation, what enzyme does E. Coli produce? What role does this enzyme play?

Beta-galactosidase; Lactose --> Glucose + Galactose


How do lactose fermenters grow on EMB agar? More particularly, how does E. Coli grown on EMB agar?

Purple/black colonies; Purple colonies with green sheen


To what antibiotics do the gram-negative outer membrane layer inhibit entry?

Penicillin G and vancomycin


To what penicillins are gram negative bacilli resistant versus susceptible?

Resistant to Penicillin G but may be susceptible to penicillin derivatives such as ampicillin and amoxicillin

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