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22 Cards in this Set

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 Gram positive
 Facultative anaerobes
 grape like-clusters
 catalase positive
 Major components of normal flora
 skin
 nose
catalase positive
(i) One of commonest opportunistic infections:

• pneumonia
• osteomyelitis
• septic arthritis
• bacteremia: toxic shock syndrome
• endocarditis
• abscesses/boils
• other skin infections: folliculitis, scalded skin syndrome
Staphylococcus aureus
scalded skin syndrome
 Enterotoxin……Superantigen
 Toxic shock syndrome toxin (TSST)
 Exfoliatin………Scalded-skin
 Alpha toxins……necrosis
 Leucocidins…….Kill leukocytes
Lytic exotoxins:

Staphylococcus aureus
 food contaminated from humans
 enterotoxin

 onset and recovery both occur within few hours
 Vomiting
 nausea
 diarrhea
 abdominal pain
Staphylococcus aureus

Food poisoning
 vomiting is more prominent than diarrhea

 ingestion of enterotoxin, which is preformed in foods and hence has a short incubation period (1-8 hours).
Staphylococcus aureus

Food poisoning
vomiting is more prominent than diarrhea
Causes vomiting and watery nonbloody diarrhea.
-It acts as a superantigen within the gastrointestinal tract

-It stimulate the release of large amounts of interleukin-1 (IL-1) from macrophages

-It stimulate the release of large amounts of interleukin-2 (IL-2) from helper T cells
Staphylococcus aureus: Enterotoxin
watery nonbloody diarrhea.
 Causes ____ especially in tampon-using menstruating women or in individuals with wound infections.

 Toxic shock also occurs in patients with ____ used to stop bleeding from the nose.
Staphylococcus aureus:

Toxic shock syndrome toxin (TSST):

Toxic shock
Nasal packing
 fever, hypotension

 diffuse, macular, sunburn-like rash

 Vomiting, diarrhea and desquamation

 three or more of the following organs: liver, kidney, GI tract, central nervous system, muscle, or blood can be infected.

 can lead to adult respiratory distress syndrome (ARDS).
Staphylococcus aureus:

Toxic shock syndrome
diffuse, macular, sunburn-like rash
 babies
 scalded skin syndrome
* exfoliatin
S. aureus
 It is the major protein in the cell wall.

 It binds to the Fc portion of IgG at the complement-binding site,

 Preventing the activation of complement.

 No C3b is produced

 The opsonization and phagocytosis of the organisms are reduced.
Staphylococcus Protein A
opsonization and phagocytosis of the organisms are reduced.
 tissue-degrading enzymes

– lipase
– hyaluronidase
Staphylococcus Spread
– sheep blood agar
• ß hemolytic

• mannitol fermentation

• Golden pigmented (aureus)

• coagulase-positive

• catalase-positive
Staphylococcus aureus: Identification
ß hemolytic
 All staphylococci produce catalase, catalase degrades H2O2 into O2 and H2O. H2O2 degradation limits the ability of neutrophils to kill

 Coagulase, by clotting plasma, serves to wall off the infected site, thereby retarding the migration of neutrophils into the site. Only in S. aureus.
S. aureus produces catalase and coagulase
degrades H2O2
• major component skin flora

• opportunistic infections
– less common than S.aureus

• nosocomial infections
– heart valves
Staphylococcus epidermidis
major component skin flora
 normal human flora on the skin and mucous membranes

 cause infections of intravenous catheters and prosthetic implants, eg, heart valves, vascular grafts, and joints.

 major cause of sepsis in neonates and of peritonitis in patients with renal failure who are undergoing peritoneal dialysis through an indwelling catheter.

 Strains of S. epidermidis that produce a _______ are more likely to adhere to prosthetic implant materials and therefore are more likely to infect these implants than strains that do not produce a _______.
Staphylococcus epidermidis: glycocalyx
• Non-hemolytic

– sheep blood agar

• Does not ferment mannitol

• Non-pigmented
• sensitive to novobiocin

Identification: Staphylococcus epidermidis
• non hemolytic
• urinary tract infections
• coagulase-negative
- not differentiated from S. epidermidis
• resistant to novobiocin
Staphylococcus saprophyticus
 Causes urinary tract infections, particularly in sexually active young women.

 Most women with this infection have had sexual intercourse within the previous 24 hours.

 Second to E coli as a cause of community-acquired urinary tract infections in young women.
S. saprophyticus:

Urinary Tract Infection
 90% or more of S. _____ strains are resistant to penicillin G.
 Most strains produce b-lactamase.

 Such organisms can be treated with b-lactamase-resistant penicillins, eg, nafcillin, methicillin or cloxacillin
Antibiotic therapy: S.aureus
 Approximately 20% of S. ______ strains are "methicillin-resistant" (MRSA) or "nafcillin-resistant" (NRSA) by virtue of altered penicillin-binding proteins.

 The drug of choice for these staphylococci is ________, to which ________ is sometimes added to _________.
Antibiotic therapy




 Strains of S aureus with intermediate resistance and with complete resistance to vancomycin (so-called VISA strains) have been isolated from patients.

 These strains are typically methicillin/nafcillin-resistant as well, which makes them very difficult to treat.

 Synercid, has been shown to be effective, but Synercid is available only as an investigational drug at this time
Drugs under investigation:

-Administration of a b-lactamase resistant
penicillin such as nafcillin

-Removal of the tampon or debridement of the
infected site as needed.

- Pooled serum globulins, which contain antibodies against TSST, may be useful.
The treatment of toxic shock syndrome involves correction of the shock using: