staphylococci Flashcards
common isolates in clinical micro
gram-pos cocci
catalase-producing, gram-pos cocci
staphylococcus
catalas-producing, coagulase-negative, gram-pos cocci; staphylococci resembles this
micrococci
nonmotile, non-spore forming, aerobic/facultatively anaerobic; appear cream-colored, white or rarely light gold, “butterfly-looking”
staphylococci
coagulas-producing staphylococci
s. aureus
s.intermedius
s.delphini
s.lutrae
some strains of s.hyicus
causes bacterial cell to agglutinate to plasma
clumping factor
toxin-induced diseases associated with s.aureus
food poisoning
scalded skin syndrome
toxic shock syndrome
known to cause varous health care-acquired or nosocomial infections
s. epidermidis
associated mainly with urinary tract infections
s. saprophyticus
CoNS occasionally recovered in wounds, septicemia, uti, native valve infections
s. haemolyticus
also CoNS, but can occasionally be confused with s.aureus if performing only a traditional slide coag; catheter-related bacteremia & endocarditis
s. lugdunensis
important cause of nosocomial infections
s.aureus
numerous virulence factor of s.aureus
enterotoxins
cytolytic toxins
cellular components such as protein A
heat-stable entotoxins that cause various symptoms, including diarrhea and vomitting
staphylococcal enterotoxins
enterotoxins associated with tss
B,C and sometime G and I
food poisoning
A,B and D
also known as epidermolytic toxin; causes epidermal layer of the skin to slough off and is known to cause staphylococcal sss, sometimes referred to as ritter disease; implicated in bullous impetigo
exfoliative toxin
in addition to lysing erythrocytes, can damage platelets and macrophages and cause severe tissue damage
a-hemolysin
acts on sphingomyelin in the plasma membrane of erythrocytes and called the “hot-cold” lysin
b-hemolysin
enzymes produced by staphylococci
coagulase, protease, hyaluronidase, lipase
this enzyme hydrolyzes hyaluronic acid present in the intracellular ground substance that makes up connective tissues, permitting spread of bacteria during infection
hyaluronidase
produced by both coagulase-pos and CoNS
lipase
primary reservoir for staphylococci is the
human naris
colonization also occuring in the
axillae, vagina, pharynx, other skin surfaces
transmission of s.aureus may occur by
direct contact with unwashed, contaminated hands and by contact with inanimate objects (fomites)
some skin infections caused by s.aureus are
folliculitis, furuncles, carbuncles, bullous impetigo
mild inflammation of a hair follicle or oil gland; the infected area is raised and red
folliculitis
can be an extension of folliculitis, are large, raised, superficial abscesses
furuncles (boils)
occur when larger, more invasive lesions develop from multiple furuncles, can progress into deeper tissues
carbuncles
in contrast to furuncles, patients w/ carbuncles often present with
fever and chills, indicating systemic spread of the bacteria
highly contagious infection that is easily spread by direct contact, fomites, or autoinoculation
bullousimpetigo
bullous exfoliative dermatitis that occurs primarily in newborns and previously healthy young children
scalded skin syndrome
rare but potentially fatal, multisystem disease characterized by a sudden onset of fever, chills, vomiting, diarrhea, muscle aches and rash, which can progress to hypotension and shock; associated with the use of highly absorbent tampons
toxic shock syndrome
a clinical manif with multiple causes; it is most commonly drug induced, but some cases have been linked to infections and vaccines
toxic epidermal necrolysis
type of intoxication resulting from ingestion of a toxin formed outside the body
food poisoning
foods that often incriminated in staphylococcal food poisoning include
salads, especially salads containing mayonnaise and eggs; meat or meat products; poultry; egg products; bakery products with cream fillings; sandwich fillings; and dairy products
known to occur secondary to influenza virus infection
staphylococcal pneumonia
leading to secondary pneumonia and endocarditis has been observed among intravenous drug users
staphylococcal bacteremia
occurs as a manifestation secondary to bacteremia
staphylococcal osteomyelitis
caused by s.aureus in children, especially with trauma to the extremities, and can occur in patients with a history of rheumatoid arthritis or intravenous drug abuse
septic arthritis
infections caused by s.epidermidis are
hospital-acquired
predisposing factors are instrumentation procedures in s.epidermidis
catheterization, medical implantation, and immunosuppressive therapy
bacterial factor involved in adherence of s.epidermidis, which provides a protective advantage agains host defenses
poly-y-DL-glutamic acid
associated with UTIs in young women
s. saprophyticus
another CoNS, altho can give a positive clumping factor, but has a negative tube coagulase reaction; more virulent and can mimic s.aureus infections
s.lugdunensis
CoNS less commonly seen but opportunistic pathogens
s.warneri, s.capitis, s.simulans, s.hominis, s.schleiferi
commonly isolated CoNS; has been reported in wounds, bacteremia, endocarditis, UTIs
s.haemolyticus
staphylococcie produce
round, smooth, white, creamy colonies on SBA after 18-24 hours of incu
modifies oxidase test that can be used to rapidly differentiate stapth form micrococci
microdase disk
important marker for s.aureus
clumping factor, formerly referred to as cell-bound coagulase, causes agglutination in human, rabbit, or pig plasma
if no clot appears in tube method of coagulase, it should be
left at room temp and checked the following day; fibrinolysin activity is enhanced at 37 degrees
voges-proskauer test
s.aureus (pos)
s,.intermedius (neg)
resistant to novobiocin
s.saprophyticus
rapid agglutination test kits for differentiating s.aureus from cons
BBL staphyloslide, staphaurex, BACTiStaph
clsi do not require routine antimicrobial susceptibility testing of s.saprophyticus from urine
becoz isolates typically are sensitive to agents commonly used to treat UTIs
require treatment with penicillinase-resistant penicillins, such as nafcillin or oxacillin
penicillin-resistant strains
third type of MRSA
health care-associated community-onset methicillin-resistant staphylococcus aureus
control of MRSA requires
strict adherence to infection control practices, including barrier protection, contact isolation, and handwashing compliance
treatment of choice for MRSA
vancomycin
used for detection of methicillin resistance for staph species in the past
oxacillin
better inducer of mecA-mediated resistance
cefoxitin
growth of the resistant subpopulation is enhanced at
neutral pH, sodiumchloride conc. of 2%-4%, cooler incubation temp (30-32 degrees C), prolonged incubation (up to 48hrs)
can be used to screen for MRSA
oxacillin-salt agar plate
a macrolide, is frequently used in staphylococcal skin infections
clindamycin
