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Staphylococcus aureus

staphylococcus aureus on agar plate

Staphylococcus aureus on Columbia agar with 5% defibrinated sheep blood (Bio-Rad™). Individual colonies on agar are round, convex, and 1-4 mm in diameter with a sharp border. On blood agar plates, colonies of Staphylococcus aureus are frequently surrounded by zones of clear beta-hemolysis. The golden appearance of colonies of some strains is the etymological root of the bacteria's name; aureus meaning "golden" in Latin.
Methicillin-resistant strains of Staphylococcus aureus (i.e. MRSA) often have only weak or no beta-hemolysis and special cultivation media with oxacillin, mannitol and NaCl for their isolation are used. MRSA is able to grow on this media and produce colonies of certain color, depending on used pH indicator (in this picture pink).

Staphylococcus aureus may occur as a commensal on human skin; it also occurs in the nose frequently (in about a third of the population) and throat less commonly. The occurrence of S. aureus under these circumstances does not always indicate infection and therefore does not always require treatment (indeed, treatment may be ineffective and re-colonisation may occur). It can survive on domesticated animals such as dogs, cats and horses. S. aureus can infect other tissues when barriers have been breached (e.g., skin or mucosal lining). This leads to furuncles (boils) and carbuncles (a collection of furuncles). In infants S. aureus infection can cause a severe disease Staphylococcal scalded skin syndrome (SSSS). S. aureus infections can be spread through contact with pus from an infected wound, skin-to-skin contact with an infected person by producing hyaluronidase that destroy tissues, and contact with objects such as towels, sheets, clothing, or athletic equipment used by an infected person. Deeply penetrating S. aureus infections can be severe. Prosthetic joints put a person at particular risk for septic arthritis, and staphylococcal endocarditis (infection of the heart valves) and pneumonia, which may be rapidly spread.

Abbreviated from Wikipedia.

description image
GRAM-POSITIVE COCCI
NONMOTILE
NONSPOREFORMING
CATALASE: POSITIVE
OXIDASE: NEGATIVE
FACULTATIVELY ANAEROBIC

BASIC TESTS
FOR IDENTIFICATION

production of coagulase
(free coagulase)
presence of clumping factor
(cell-bound coagulase)
sodium chloride tolerance
(7.5%)
mannitol fermentation

ANTIBIOTIC
TREATMENT

Should be always guided by
in vitro susceptibility
tests!!

Selection of appropriate antibiotics depends on diagnosis!!

gram positive cocci drawing IF SUSCEPTIBLE:

Penicillins

ampicillin/sulbactam
amoxicillin/clavulanate
oxacillin
nafcillin

Cephalosporins

cefazolin
ceftriaxone

Macrolides

Clindamycin


ALTERNATIVES:

Trimethoprim-Sulfome-
thoxazole(TMP-SMX)
vancomycin

MRSA

vancomycin
teicoplanin
linezolid
quinupristin/dalfopristin
TMP-SMX
rifampicin
list of anntibiotics
 

COLONY MORPHOLOGY

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staphylococcus aureus staphylococcus aureus staphylococcus aureus staphylococcus aureus
staphylococcus aureus staphylococcus aureus staphylococcus aureus staphylococcus aureus
staphylococcus aureus staphylococcus aureus staphylococcus aureus staphylococcus aureus
staphylococcus aureus staphylococcus aureus staphylococcus aureus staphylococcus aureus
staphylococcus aureus staphylococcus aureus staphylococcus aureus staphylococcus aureus
staphylococcus aureus staphylococcus aureus staphylococcus aureus staphylococcus aureus
staphylococcus aureus staphylococcus aureus,escherichia coli    
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Staphylococcus sp.

Staphylococcus aureus

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