Gram-positive cocci Flashcards by alex speers

What lab findings are useful to help diagnose Strep. pneumoniae?

spinal tap cloudy w/ increase in PMNs and low glucose

lancet-shaped gram+ cocci

alpha-hemolytic on blood agar

inhibited by optochin

older cells may appear gram-

lysed by bile

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Identify the major virulence/toxicity factor associated with Staph. saprophyticus.

novobiocin resistant

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How is Strep. agalactiae (group B strep) transmitted?

during childbirth from mother to infant

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Identify the major virulence/toxicity factor associated with Strep. viridans.

destran biofilm-mediated adhesion to teeth and heart valves

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What is the morphology of Group D Strep./Enterococcus?

cocci

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Name some pyogenic manifestations of Strep. pyogenes.

pharyngitis, cellulitis, impetigo

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When do you test for bacitracin sensitivity or resisitance?

to distinguish beta-hemolytic strep.

bacitracin-sensitive suggests GABHS (strep. pyogenes)

bacitracin-resistant suggests GBBHS (strep. agalactiae)

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What organisms are beta hemolytic?

Staph. aureus, Strep. pyogenes, Strep. agalactiae, Lysteria monocytogenes

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Identify the major virulence/toxicity factors associated with Strep. pyogenes (GABHS).

erythrogenic toxin may lead to scarlet fever which can progress to rheumatic fever

hyaluronic acid capsule in non-immunogenic, inhibiting phagoctyic uptake

M-protein is antiphagocytic

M12 strains associated with acute glomerulonephritis

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Staph. aureus is catalase __ and coagulase __.

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Viridans strep are catalase __ and optochin __.

sensitive

resistant

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How does Strep. agalactiae gram stain?

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T/F: enterococci (group D strep.) are penicillin G sensitive and show variable hemolysis

F - they are resistant but do have variable hemolysis

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What is the “most common” associated with Strep. agalactiae?

neonatal sepsis and meningitis

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What are catalase and coagulase tests used for?

Catalase is used to distinguish staph (+) from strep (-)

Coagulase is used to distinguish S. aureus (+) from S. epidermis and S. saprophyticus (-)

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How does Strep. pneumoniae gram stain?

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What is the morphology of Strep. pneumoniae?

cocci

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What lab findings are useful to help diagnose Staph. saprophyticus?

+ growth on blood agar

+ catalase

+ gamma hemolysis

+ novobiocin resistance

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Strep. pyogenes is catalase __ and bacitracin __.

negative

sensitive

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What is the second leading cause of UTIs in sexually active women?

Staph. saprophyticus

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What are the clinical manifestations of Strep. pneumoniae?

pneumonia, meningitis, bacteremia, OM, sinusitis

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What lab findings are useful to help diagnose Staph. epidermidis?

gram + cocci arranged in clusters

catalase +

coagulase -

no hemolysis

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What is the “most common” associated with Strep. pneumoniae?

bacterial pneumonia in adults

meningitis

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What lab findings are useful to help diagnose Strep. pyogenes?

beta hemolysis +

susceptible to bacitracin

rapid antigen strep test

gram + cocci in chains

catalase -

ASO titer for rheumatic fever

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Does Staph. aureus gram stain positive or negative?

Staph. aureus: TSST is a superantigen that binds to __ and __ receptors. This causes __ of T cells, leading to toxic shock syndrome.

MHC II T-cell receptors polyclonal activation of T-cells

What is the major reservoir for Strep. agalactiae?

normal flora of female genital tract

What is the morphology of Strep. pyogenes?

cocci in chains or pairs

Name some key lab findings that are useful to help diagnose Staph. aureus.

gram+ yellow, grape-like clusters on blood agar beta-hemolytic catalase + coagulase + salt tolerant ferments mannitol

Identify the major virulence/toxicity factors associated with Strep. agalactiae.

penicillin resistant encapsulated beta-hemolysin CAMP factor

List the SSx of rheumatic fever.

polyarthritis, erythema marginatum, chorea, carditis, subQ nodules

Identify the major virulence/toxicity factor associated with Strep. pneumoniae.

can make over 85 antigenically distinct capsular polysaccharides, which can interfere with phagocytosis.

Identify four major virulence/toxicity factors associated with Staph. aureus.

protein A inhibits phagocytosis, binds Fc portion of antibody enterotoxins A-E are heat stable TSST-1 causes TSS coagulases convert fibrinogen to a fibrin clot exfoliatins cause scalded skin syndrome

What is the morphology of Staph. epidermidis?

cocci

Strep. pneumococci are catalase __ and optochin __.

- sensitive

What are the "most commons" associated with Strep. pyogenes?

pharyngitis cellulitis erysipelas in children

What are the clinical manifestations of Strep. agalactiae?

acute lower UTI (uncommon) neonatal pneumonia sepsis meningitis

What is the morphology of Staph. saprophyticus?

cocci

What are the clinical manifestations of Staph. saprophyticus?

UTIs, esp. in young sexually active women Sx: dysuria, hematuria, frequent urination, burning urination and urgency

What lab findings are useful to help diagnose Strep. viridans?

alpha-hemolytic resistant to optochin gram+ cocci in chains bile resistant

Staph. aureus: What is the function of protein A?

virulence factor - binds to Fc-IgG and inhibits complement fixation and phagocytosis

How is Strep. pneumoniae transmitted?

respiratory drops

Does Staph. aureus ferment lactose?

T/F: S. aurues causes skin disease and organ abscesses, but not pneumonia

F - causes all 3

How does Staph. saprophyticus gram stain?

What are the pyogenic, immunologic and toxigenic clinical manifestations of Strep. pyogenes?

pyogenic (pharyngitis, impetigo, cellulitis, erysipelas) immunogenic (glomerulonephritis, erythema nodosum, rheumatic fever, rheumatic heart disease) toxigenic (scarlet fever, purperal fever)

Identify the major virulence/toxicity factors associated with Staph. epidermidis.

highly antibiotic resistant can form biofilm and adhere to surfaces like catheters

What is the major reservoir for Strep. pneumoniae?

human upper respiratory tract

How does Strep. viridans gram stain?

What are the clinical manifestations of Staph. epidermidis?

prosthetic, surgical and wound infections (nosocomial) especially in the immunocompromised patient inflammation at site of infection, fever, fatigue

How does Staph. epidermidis gram stain?

Viridans strep are __ hemolytic

alpha

Identify relevant epidemiology and risk factors associated with Staph. aureus.

surgery or any break in the skin severe neutropenia IV drug abuse chronic granulomatous disease

How is Staph. aureus transmitted?

hands and sneezing surgical wounds contaminated foods, esp. home canned meats, potato salad

Name three toxins of S. aureus and a syndrome caused by each.

TSST-1 (TSS) exofoliative toxin (scalded skin syndrome) enterotoxins (rapid onset food poisoning)

How does group D Strep/enterococcus gram stain?

What lab findings are useful to help diagnose Strep. agalactiae?

catalase - beta-hemolytic on blood agar bacitraicin resistant CAMP+ (indicates group B) hydrolyzes hippurate

What organisms are alpha-hemolytic?

strep. pneumoniae | strep. viridans

T/F: S. aureus causes acute bacterial endocarditis.

Strep agalactiae is catalase __ and bacitracin __.

- resistant

What are the clinical manifestations of group D strep/enterococcus?

URI (rare, but severe in immunocompromised, esp. following GI surgery) sepsis dt contaminated needle use (rare).

How does Staph. aureus cause toxic shock syndrome?

The toxin is a superantigen that binds to MHC II protein and T-cell receptors and induces IL-1 and IL-2, causing TSS

T/F: S. aureus food poisoning is due to bacterial infiltration of the intestinal wall.

F, dt ingestion of preformed enterotoxin

What are the clinical manifestations of Strep. viridans?

opportunistic infections of heart valves, blood, skin or wounds Strep. mutans causes dental caries.

Identify relevant epidemiology and risk factors associated with Strep. pneumoniae.

individuals with depressed cough reflex or damaged mucociliary elevator pulmonary circulation problems splenectomy head trauma alcoholism sickle cell anemia

What is the morphology of Strep. viridans?

cocci

How is Strep. pyogenes transmitted?

respiratory droplets direct contact with skin direct contact with objects.

How is Strep. viridans transmitted?

usually already present in host dental work may expose organism to heart valves which, if damaged, may become infected

What lab findings are useful to help diagnose group D strep/enterococcus?

mostly alpha- or non-hemolytic resistant to bile salts

Name the bacteria that produces a yellow pigment.

S. aureus

What is the morphology of Staph. aureus?

cocci

Which are not toxigenic manifestations of Strep. pyogenes: scarlet fever, rheumatic fever, TSS, acute glomerulonephritis.

rheumatic fever and acute glomerulonephritis are immune-mediated manifestations

How do you differentiate Strep. viridans from Strep. pneumoniae in the lab?

both are alpha-hemolytic, but viridans strep is resistant to optochin

What is the major reservoir for Strep. pyogenes?

human throat and skin

Name nine clinical manifestations of Staph. aureus.

impetigo gastroenteritis infective endocarditis abscesses and mastitis TSS pneumonia surgical infections osteomyelitis

One hour after eating custard at a picnic, the whole family vomits. After 10 hours all are better. Organism?

S. aureus (produces preformed enterotoxin)

Does Strep. pyogenes gram stain positive or negative?

What is the morphology of Strep. agalactiae?

cocci