L2 - Staph vs Strep Flashcards
There are three Staphylococcus Species.
What are they?
Staph Aureus
Staph Epidermidis
Staph Saprophyticus
Are all 3 staph species gram-positive?
yes, gram +
Staph Epidermidis
what kind of pathogen is this?
opportunistic
nosocomial infections
Staph Saprophyticus
what kind of pathogen is this?
UTIs in women
There are three Streptococcus species, what are they?
Staph Pyogenes Staph Pneumoniae Group B streptococci ( S. agalactiae)
Are all the strep species gram +?
YES!
Staphylococci occur in what kind of way?
Single and in pairs, mostly in clusters!
Staphylococci. Are the Catalase + or Catalase -?
Catalase +
Streptococci occur in what kind of way?
pairs, short and long chains!
Streptococci. Catalase + or Catalase -?
Catalase -
How to differentiate between the 3 Staph species?
if they have coagulase activity.
Which Staph specie is + for Coagulase activity?
Staph Aureus
Which staph species are Coagulase -?
Staph. Epidermidis Staph Saprophyticus
Coagulase?
ability to coagulate plasma. Fibrinogen to fibrin ( insoluble)
Virulence Factors in Staph Aureus
Hemolysins Leukocidin Protein A Coagulase
Staph Aureus Invasive disease traits:
Alpha & leukocidin lyse cells by disrupting cell membrane integertiy- result in the tissue destruction and abcess formation seen with invasive staphlococcal disease. Protein A- binds Fc of IgG molecule ( prevents phagocytosis) Teichoic Acids- binds fibronectin on mucosal surfaces
Staph Toxins
Alpha Toxin - Lyses cells by forming pores in epithelium Enterotoxins - food poisoning toxic shock syndrome toxin 1 - causes hypotensive shock, rash, and cytokine elaboration Exofoliative toxin -staphylococcus scalding skin syndrome (SSSS) Panton-Valentine Leukocidin PVL - necrotic lesions involving skin and mucosa
PVL and Staph Aureus
-PVL and SA infections are associated with higher incidence of sepsis, high fever, leukopenia, hemoptysis, pleural effusion, and mortality. -Severe soft tissue and bone infection -necrotizing pneumonia -pvl genes are being found in increasing prevalence in community acquired MRSA
MRSA creates ?
PVL
Clinical Syndromes of Staph Aureus
Skin infections - folliculitis -furuncles (boils) -wounds -impetigo
Clinical syndromes of Staph Aureus
-Bacteremia -Endocarditis -Pneumonia -Osteomyelitis -Septic Arthritis
Staph Aureus Virulence Factors
Toxin-mediated disease - exfoliatin- toxin that causes sloughing of the outermost layer of the skin (SSSS) -TSST-1* - toxin which causes the hypotension, rash, desqamation and production of cytokines (TSS) Enterotoxins- acid and heat resistant toxins causes food poisoning occurs 1-8 hours after toxin ingestion. *super antigen
Epidemioglogy of Staph Aurus
-Can be carried on skin, urogenital tract -resist drying spread by contact or formites ( towels)
Laboratory Diagnosis of Staphylocci
direct gram stain and culture culture on BAP ( blood agar plate) or mannitol salt sugar usually strong BETA hemolytic ( staph aureus) non hemolytic ( staph epidermidis) Catalase test + Coagulase + Gram +
Staph infections- treatment
Oxacillin, cephalosporin, or vancomycin (MRSA) drainage of lesions plasmid encoded beta-lacatamases common
Streptococcus pyogenes, which lancefield group? Hemolytic ?
Beta-Hemolytic. Lancefield group A.