Staph Flashcards
factors to consider in determination of a pathogen
Type of patient (normal v. predisposed/compromised patient)
mode of infection (community v. nosocomial)
geographic distribution and/or work environment
Compromising/Predisposing factors for patients
(1) Surgery or trauma
(2) Immunoincompetence or Immunosuppression – e.g. cancer or AIDS patient
(3) Diabetic
(4) Alcoholism or drug use
(5) Pregnancy
With only rare exception, all members of a genus will exhibit the same ____ morphology. Occasionally a species may exhibit a slightly different arrangement of cells (e.g. pairs vs. chains), but nothing very significant.
Gram stain
Gram-positive ____ in clusters
Staphylococcus aureus
cocci
Large, yellowish ____ hemolytic colonies
Staphylococcus aureus
beta
Invasive tissue infections – causes about ____ of invasive tissue infections (along w/ GAS)
(Staphylococcus aureus)
90%
Pus- producing = Abscess forming
Staphylococcus aureus
Pyogenic
infection of the hair follicle
Staphylococcus aureus
Folliculitis
Staphylococcus aureus
deep seated infections (subcutaneous tissue involved) in and around the hair follicle
Furuncles (boils)
Staphylococcus aureus
similar to folliculitis/boils in skin or tissues but spreads beneath the skin
Cellulitis
Staphylococcus aureus
superficial skin infection characterized by small “blisters”/pustules followed by a thin crust over the area
Impetigo
Staphylococcus aureus
Tissue damage due to numerous invasive ____. Some invasive infections can be very severe.
(Staphylococcus aureus)
enzymes and toxins
Food poisoning due to ingestion of pre-formed heat-stable ____ (an exotoxin that affects the intestinal tract) (types A, B, C, etc, e.g. “SEB”)
(Staphylococcus aureus)
enterotoxin
Certain strains of bacteria produce enterotoxin when growing at 28C or higher for ____ hours
(Staphylococcus aureus)
2 to 4
Commonly affected foods are cooked or processed meat (especially ham), salads, and cream-filled desserts
(Staphylococcus aureus)
(Staphylococcus aureus)
Bacterial growth on food produces no change in ___
Staphylococcus aureus
flavor or odor
Clinical symptoms: nausea, vomiting, abdominal cramps, and watery diarrhea within ____; lasts from a few to about 24 hours
(Staphylococcus aureus… food poisoning)
1 to 6 hours
____ enables the Staph A microbe to invade (under proper conditions) the lipid “plug” that surrounds the hair shaft, potentially leading to folliculits
Lipase (invasive enzyme)
and Coagulase protects the bacteria
Coagulase and ______ are an interplay of protection and expansion
(enzymes of Staph)
Fibrinolysin/streptokinase
(coagulase establishes a protective fibrin clot, fibrinolysin breaks this clot down so that the microbial colony can expand)
Protective fibrin “walls” can often prevent ___ from reaching the infected site/microbial site
(Staphylococcus aureus)
abx
Certain strains produce Toxic Shock Syndrome Toxins (TSST) (plasmid mediated) - toxin probably causes massive and unregulated stimulation of the ___ system
(Staphylococcus aureus)
immune
Produces acute illness with high fever, diffuse rash, hypotension, and skin desquamation (1-2 weeks after onset), plus several other features
(Staphylococcus aureus)
Toxic shock syndrome
Infection associated with use of highly absorbent tampons (about 75% of cases) (absorption of fluids causes change of microbial growth environment resulting in change of host-microbe dynamics) or with focal or surgical wound infections in men or non-menstruating women
(Staphylococcus aureus)
Toxic shock syndrome
Tests for toxin usually not performed in routine microbiology labs
(Staphylococcus aureus)
Toxic shock syndrome
Certain strains produce exfoliatin toxins – destructive to epithelial cells
Scalded skin syndrome
Initially a localized red rash, often following conjunctivitis or upper respiratory tract infection
Followed by large flaccid bullae which rupture and sheets of epidermis peel off to reveal moist, red, “scalded” dermis
Scalded skin syndrome
Bacteria are not recovered from the ____; only from the initial infection
(Scalded skin syndrome)
bullae
bloodstream infection resulting from deep, poorly draining infections which invade the bloodstream and spread to numerous body sites – typically life-threatening unless rapidly treated with effective antimicrobics
Septicemia/bacteremia
Staph A infections of the joint/bone are common after?
device implantation or trauma
osteomyelitis & septic arthritis
Though rare, this infection can follow a viral respiratory infection or affect those with altered immune systems…
pneumonia/lower respiratory & lung abscess infections (less than 2%)
Toxins and invasive enzymes?
Coagulase
Lipase
Fibrinolysin Proteases (several varieties)
Staph’s other virulence factors?
besides toxins and enzymes
(2) Adhesive Matrix Molecules – produce biofilms
(3) Quorum-sensing regulators
(4) Superantigens (toxins) – enhance effects of toxins
(5) Pathogenicity of various strains is largely due to genes carried on plasmids and lysogenized viral genes
Most Staph A are resistant to?
Beta lactams
due to beta-lactamase enzymes coded by genes carried on plasmids
Resistant to all beta-lactam antibiotics due to mutated penicillin-binding proteins
Methicillin Resistant Staphylococcus aureus (MRSA) (about 30%, percentage increasing)
Staph A is developing resistance to?
Vancomycin
strains that are resistant to an exceptionally large number of antimicrobic types – Very problematic and serious infections
Multiply Drug Resistant (MDR)
Lab considerations for Staph A?
culture/biochemical ID (coagulase positive?)
Antigenic ID/confirmation of the lab culture
Antimicrobic susceptibility test needed (beta lactamase, MRSA, MDR)
Predominant normal flora of the skin
Staphylococcus epidermidis
The most common coagulase negative staphylococcus (CNS)
Staphylococcus epidermidis
Causes bloodstream infections (bacteremia) and endocarditis (infection of interior heart tissue) in seriously ill patients (e.g. indwelling central line) – 2nd most frequently recovered pathogen from blood culture
Staphylococcus epidermidis
Causes wound/incision infections infrequently
Staphylococcus epidermidis
Another coagulase negative Staph
Staphylococcus saprophyticus
CNS spp?
S. saprophyticus
S. epidermidis
Second most frequent cause of UTIs in women of child bearing age?
Staphylococcus saprophyticus
