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Flashcards in Unit 3: Cocci Deck (29)
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When bacteria are plated onto blood agar, how do alpha, beta, and gamma colonies appear?

alpha - dark green (incomplete blood lysis)beta - clear colony (complete lysis)gamma - no change (non-hemolytic)


How do you tell if a bacteria is catalase positive?

Drop hydrogen peroxide and fizzing will occur


Lancefield typing is based on what bacterial feature?

carbohydrate composition of bacterial cell walls


When bacterial growth is inhibited by bacitracin antibiotic (Bacitracin Testing), what does it indicate?

The culture is streptococcus pyogenes (Group A is bacitracin sensitive!)


Describe what a positive CAMP test indicates

Group B strep


What cocci are gram positive and which are gram negative?

Gram positive: staphylococcus and streptococcus
Grame negative: Neisseria


How do you differentiate staphylococcus from streptococcus if they're both gram positive?

Staphylococcus is catalase positive
Streptococcus is catalase negative


What are the 3 kinds of Staph? How do you differentiate the 3?

Staph aureus, staph epidermis, s. saprophyticus

S. aureus is coagulase positive, create gold colonies, beta hemolytic and susceptible to bacteriophages whereas the other 2 are coagulase negative and non hemolytic (gamma).


What are the two alpha hemolytic streptococcus

strep pneumoniae and strep viridans


What are the two beta hemolytic streptococcus

strep pyogenes (group A)
strep agalactiae (group B)


What differentiates Streptococcus group A from Group B?

Strep Group A (pyogenes) is bacitracin sensitive
Strep Group B (agalactiae) is bacitracin resistant


What are the gamma hemolytic streptococcus

Strep fecalis (enterococcus fecalis / Group D) Peptostreptococcus


What differentiates N. meningitides from N. gonorrhoeae?

N. meningitides has CAPSULE, ferments MALTOSE on chocolate agar

N. gonorrhoeae has NO CAPSULE, NO MALTOSE

They do share these characteristics: gram negative, diplococci, oxidase positive


What shape does streptococci take on under microscope?

Chain of circles


What shape does staphylococcus take on?

clusters of circles


How does neisseria appear under microscope?



What bacteria has pili, releases several pyrogenic toxins, has streptolysin O (very antigenic), is penicillin and erythromycin sensitive. Located in pharynx and skin?

Group A Streptococci Strep pyogenes


This bacteria is bacitracin resistant, has a capsule, located in genital tract and transmitted at birth. What is it and what should be given to a pregnant woman during delivery to prevent infection?

Group B Strep (strep agalactiae)

Must give penicillin 18 hours after rupture of membranes if labor hasn't started to prevent ascending infection of uterus


This is a gram positive, alpha hemolytic diplococci that has a polysaccharide capsule, usually resides in the throat and is becoming more penicillin resistant

Strep pneumonia


This resides in the normal flora of the colon, causes abdominal abscesses, UTIs, endocarditis, and is sometimes penicillin resistant (use aminoglycosides)

Enterococcus fecalis
Streptococcus fecalis


This resides in the mouth and female genital tract, has extracellular polysaccharides, and alpha hemolytic and gram positive

Strep viridans


Found in mouth flora, respiratory tract, female genital tract and bowel. Found in abcesses with complex mix of organisms (not the primary pathogen). Non hemolytic



What do you use to treat MRSA?



Found in the nose and skin. Transmitted by direct contact or indirect fomite contact. Has a Protein a, Capsule and several toxins. Resistant to penicillin and methicillin

Staph aureus


Normally found in skin and mucous membrane, but attaches to nylon and plastic, infecting IVs, and antibiotics don't eliminate the infection. Catalase positive and coagulase negative.

Staph epidermis


Usually causes UTIs, catalase positive, coagulase negative, nonhemolytic

Staph saprophyticus


There exists a vaccine and can be treated with penicillin. Carried in respiratory tract. Endotoxin in membrane and has capsule

Neisseria meningitides


Has no capsule, has a pili, found inside neutrophils , sexual or neonatal transmission. Treated with ceftriaxone and doxycycline (penicillin resistant)

N. gonorrhoeae


If someone has a lesion that is sterile when swabbed, has rheumatic fever, chorea, or nephritis, what type of bacterial infection might they have had and recovered from prior to these new conditions?

Streptococcal infection