Staphylococcus

path micro exam 2

what is the general gram staining for staph?

gram positive cocci clusters

what is the result for catalase test, in staph?

catalase positive

which species can ferment mannitol?

S. aureus

coagulase is present in ONLY which species?

s. aurues

which species has yellow colonies on blood agar?

s. aureus

which species is the MAIN pathogen?

s. aureus

which species colonizes the urinary tract?

saprophyticus

what are the virulence factors (vf) for s. aureus? (5)

• teichoic acid

• protein a

• peptidoglycan

• capsule

• slime layer

how is teichoic acid a vf?

aids in adherence (from cell wall to host cells mem)

how is protein A a vf?

disrupts opsonization/phagocytosis, binding to IgG complement site which prevents complement system activation

how is peptidoglycan and capsule a vf?

inhibits PHAGOCYTOSIS

how is the slime layer/biofilm a vf?

adherence to tissues and foreign bodies

what are the type of toxins that s. aureus can make?(4)

• cytotoxins

• exfoliative toxins

• enterotoxin

• toxic shock syndrome toxin - 1 (TSST)

what are the exfoliative toxins (A and B)? and what do they do?

serine proteases, destroy intracellular bridges in the stratum granulosum epidermis (skin sloughing)

enterotoxin ___ is mostly associated with ____ ____ ____

A, food poisoning intoxication

what food is s. aureus mostly found?

ham, processed meats; potato salad, ice cream

what requirements does TSST require for expression?

neutral pH and elevated oxygen concentrations

what are two forms of coagulase in S. aureus? and what do they do?

• bound - convert fibrinogen to insoluble fibrin

• free - coagulase-reacting factor; forms staphylothrombin and catalyzes conversion to fibrin

how does coagulase play a role in disease?

• forms fribin layer around staph. protecting from phagocytosis

• can lead to blood clots

what other enzymes in s. aureus?

• hyaluronidase

• fibrinolysin

• lipases

• nuclease

what are the disease caused by S. aureus? (~7)

• staphylococcal scalded skin syndrome (SSSS)

• staphylococcal food poisoning

• toxic shock syndrome

• cutaneous infections

• osteomyelitis/septic arthritis

• pneumonia/empyema

• bacteremia/endocarditis

how are food contaminated with s. aureus?

human carrier

what are some cutaneous infections?

• impetigo - superficial infection

• folliculitis - infection in hair follicules

• furuncles / boils - extension of folliculitis

• carbuncles - furuncles extending deeper in subcutaneous tissue

what is usually seen in SSSS?

• cutaneous blisters w/ clear fluid — desquamation of epithelium

• no scarring

• usually in neonates

what is seen in bullous impetigo?

• localized form of SSSS, but sloughing

• in young children

• high communicable

what is necrotizing pneumonia usually from?

MRSA - methicillin-resistant Staphylococcus aureus

what is MRSA?

staph that resists many common antibiotics like penicillin and methicillin

what is bacteremia?

bacterial spread into blood

what is osteomyelitis?

abscesses of the bone

how can one get abscesses in the bone?

• hematogenous (bacteremia)

• secondary infection from trauma or overlying staph infection

bacteremia can lead to dissemination to other site and can cause what?

• endocarditis

• pneumonia

• osteomyelitis

• septic arthritis

in endocarditis, there is peripheral evidence of what?

embolization (blood clots from bacteria)

who is at risk for TSS?

menstruating women

how to determine MSSA vs MRSA?

PCR

what type of testing should be done on S. aureus? and why?

susceptibility testing, due to resistance to many beta-lactams

what type of pathogen is S. epidermidis? and how?

opportunistic, associated with indwelling catheters and prosthetic heart valves

which species is part of the normal flora on the skin?

Staph epi

what are some risk factors for S. aureus? (3)

presence of foreign bodies

previous surgical procedure

suppression of normal flora by antibiotics

who is sus. for SSSS?

infants

how is sus. for cutaneous infections?

young children w/ poor hygiene

who is sus. for bacteremia, endocarditis, meningitis?

ppl w/ intravascular catheters

who is sus. for pneumonia?

ppl w/ compromised pulmonary function or preceding viral infection