Medical Microbiology Gram Positive Cocci

Front 1

 Gram positive
 Facultative anaerobes
 grape like-clusters
 catalase positive
 Major components of normal flora
 skin
 nose

Back 1

STAPHYLOCOCCI

Hint 1

catalase positive

Front 2

(i) One of commonest opportunistic infections:

• pneumonia
• osteomyelitis
• septic arthritis
• bacteremia: toxic shock syndrome
• endocarditis
• abscesses/boils
• other skin infections: folliculitis, scalded skin syndrome

Back 2

Staphylococcus aureus

Hint 2

scalded skin syndrome

Front 3

 Enterotoxin……Superantigen
 Toxic shock syndrome toxin (TSST)
 Exfoliatin………Scalded-skin
 Alpha toxins……necrosis
 Leucocidins…….Kill leukocytes

Back 3

Lytic exotoxins:

Staphylococcus aureus

Hint 3

Superantigen

Front 4

 food contaminated from humans
 enterotoxin

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

Back 4

Staphylococcus aureus

Food poisoning

Hint 4

enterotoxin

Front 5

 vomiting is more prominent than diarrhea

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

Back 5

Staphylococcus aureus

Food poisoning

Hint 5

vomiting is more prominent than diarrhea

Front 6

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

Back 6

Staphylococcus aureus: Enterotoxin

Hint 6

watery nonbloody diarrhea.

Front 7

 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.

Back 7

Staphylococcus aureus:

Toxic shock syndrome toxin (TSST):

Toxic shock
Nasal packing

Hint 7

(TSST)

Front 8

 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).

Back 8

Staphylococcus aureus:

Toxic shock syndrome

Hint 8

diffuse, macular, sunburn-like rash

Front 9

 babies
 scalded skin syndrome
* exfoliatin

Back 9

S. aureus

Hint 9

exfoliatin

Front 10

 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.

Back 10

Staphylococcus Protein A

Hint 10

opsonization and phagocytosis of the organisms are reduced.

Front 11

 tissue-degrading enzymes

– lipase
– hyaluronidase

Back 11

Staphylococcus Spread

Hint 11

hyaluronidase

Front 12

– sheep blood agar
• ß hemolytic

• mannitol fermentation

• Golden pigmented (aureus)

• coagulase-positive

• catalase-positive

Back 12

Staphylococcus aureus: Identification

Hint 12

ß hemolytic

Front 13

 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.

Back 13

S. aureus produces catalase and coagulase

Hint 13

degrades H2O2

Front 14

• major component skin flora

• opportunistic infections
– less common than S.aureus

• nosocomial infections
– heart valves

Back 14

Staphylococcus epidermidis

Hint 14

major component skin flora

Front 15

 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 _______.

Back 15

Staphylococcus epidermidis: glycocalyx

Hint 15

catheters

Front 16

• Non-hemolytic

– sheep blood agar

• Does not ferment mannitol

• Non-pigmented

Back 16

• sensitive to novobiocin

Identification: Staphylococcus epidermidis

Front 17

• non hemolytic
• urinary tract infections
• coagulase-negative
- not differentiated from S. epidermidis
• resistant to novobiocin

Back 17

Staphylococcus saprophyticus

Front 18

 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.

Back 18

S. saprophyticus:

Urinary Tract Infection

Front 19

 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

Back 19

Antibiotic therapy: S.aureus

Front 20

 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 _________.

Back 20

Antibiotic therapy

S.aureus

Vancomycin

Gentamicin


Vancomycin

Front 21

 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

Back 21

Drugs under investigation:

Front 22

Fluids

-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.

Back 22

The treatment of toxic shock syndrome involves correction of the shock using: