Tests
1st tests to order
CBC
Test
Leukocytosis with a left shift points to likelihood of infection.
Result
elevated WBC count
blood culture
urine culture
Test
Performed for patients with evidence of urinary tract infection.
Result
positive for MRSA
tissue culture
Test
Debrided tissue collected in patients who have evidence of tissue involvement.
Result
positive for MRSA
sputum culture
Test
Performed for patients with productive cough and possible pulmonary infection.
Result
positive for MRSA
echocardiogram
Test
Indicated in patients with a new murmur, positive blood cultures, signs of bacterial seeding such as Roth spots and Janeway lesions, or congestive heart failure.
Result
endocarditis: vegetations or ring abscess
CXR
Test
Confirmation of MRSA is usually based on sputum culture results or blood culture if the patient has MRSA bacteremia from pneumonia.
Result
pneumonia: evidence of consolidation or effusion; endocarditis: may have evidence of septic emboli or congestive cardiac failure
arthrocentesis fluid culture
Test
Should be considered in patients with evidence of joint effusion, pain, or warmth.
Result
positive for MRSA
indwelling vascular catheter tip culture
Test
Considered in patients who have indwelling vascular catheters with evidence of infection.
This includes people on dialysis, or with chronic indwelling central or peripheral venous lines.
Result
positive for MRSA
Tests to consider
polymerase chain reaction (PCR)
Test
PCR from fluid or tissue culture samples is an additional test that can be used to detect the mecA gene, which mediates oxacillin resistance.[2][22]
Methicillin resistance is mediated by penicillin-binding protein 2a that is encoded by the mecA gene.[17]
This allows growth of an organism in the presence of beta-lactam antibiotics.
Result
detects the mecA gene
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