Staph Flashcards
Staphylococcus aureus, morphology?
Gram-positive cocci in clusters
Large, large yellowish beta hemolytic colonies
- Invasive tissue infections
- Food poisoning
- Toxic shock syndrome
- Scalded skin syndrome
- Septicemia/bactermia
- Bone and Joint infections
- Pneumonia / Lower respiratory and lung abscess infections
Staphylococcus Auereus
(1) Several toxins & invasive enzymes, including coagulase, fibrinolysin, lipase, and a variety of proteases.
(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.
Staphylococcus Auereus
Staphylococcus aureus, resistance to antimicrobics?
Beta-lactamase (penicillinase) (85% of strains)
MRSA
Vancomycin
Multiple Drug Resistance (MDR)
Staphylococcus aureus, invasive tissue infections?
causes 90% of invasive tissue infections
Pyogenic=pus producing
Folliculitis
Furuncles
Cellulitis
Impetigo
Abscess (post surgery)
Tissue damage due to invasive enzymes and toxins, can be very sever.
Staphylococcus aureus, food poisoning due to?
symptoms?
time frame?
ingestion of pre-formed, heat stable enterotoxin in gut (exotoxin secreted by cell affects intestinal tract)
(a) Certain strains of bacteria produce enterotoxin when growing at 28C or higher for 2
to 4 hours
(b) Commonly affected foods are cooked or processed meat (especially ham), salads,
and cream-filled desserts
(c) Bacterial growth on food produces no change in flavor or odor
(d) Clinical symptoms: nausea, vomiting, abdominal cramps, and watery diarrhea
within 1 to 6 hours; lasts from a few to about 24 hours
Staphylococcus aureus, toxic shock syndrome produces? and association with? tested in routine lab?
Certain strains produce Toxic Shock Syndrome Toxins (TSST) (plasmid mediated) - toxin probably causes massive and unregulated stimulation of the immune system
(b) Produces acute illness with high fever, diffuse rash, hypotension, and skin
desquamation (1-2 weeks after onset), plus several other features
(c) 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
(d) Tests for toxin usually not performed in routine microbiology labs
Scalded skin syndrome, cause? in age?
Causes Toxic Epidermal Necrolysis (TEN) in children under 5 yr
i. Initially a localized red rash, often following conjunctivitis or upper respiratory
tract infection
ii. Followed by large flaccid bullae which rupture and sheets of epidermis peel off
to reveal moist, red, “scalded” dermis
Staph A, septicemia/bactermia?
- 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
Staph A, laboratory diagnosis?
Culture and biochemical identification - coagulase positive
Antimicrobic susceptibility test needed (Beta-lactamase, MRSA, MDR)
Staphylococcus epidermidis, predominant flora where?
normal flora of the skin
Staphylococcus epidermidis, most common?
Coagulase negative staphylococcus (CNS)
Staphylococcus epidermidis, causes?
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
d. Causes wound/incision infections infrequently
Staphylococcus saprophyticus, causes?
UTI in women of child bearing age, 2nd most frequent cause
Staphylococcus saprophyticus is one of the?
coagulase negative staphylococci (CNS)
