Methicillin resistant staphylococcus aureus laboratory findings: Difference between revisions
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Culture of the bacteria is the gold standard test for the diagnosis of MRSA infections. Samples used for culture include [[blood]], [[urine]], [[synovial fluid]], [[sputum]], [[pus]] from [[abscesses]] and [[boils]]. | Culture of the bacteria is the gold standard test for the diagnosis of MRSA infections. Samples used for culture include [[blood]], [[urine]], [[synovial fluid]], [[sputum]], [[pus]] from [[abscesses]] and [[boils]]. | ||
[[Mannitol Salt Agar]] is used for culture , which is a selective medium (encourages the growth of a group of certain bacteria while inhibiting the growth of others) with 7–9% [[Sodium chloride|NaCl]] that allows ''S. aureus'' to grow producing yellow-colored colonies as a result of salt utilization and subsequent drop in the medium's [[pH]]. | [[Mannitol Salt Agar]] is used for culture , which is a selective medium (encourages the growth of a group of certain bacteria while inhibiting the growth of others) with 7–9% [[Sodium chloride|NaCl]] that allows ''S. aureus'' to grow producing yellow-colored colonies as a result of salt utilization and subsequent drop in the medium's [[pH]]. | ||
Furthermore, for differentiation on the species level, [[catalase]] (positive for all species), [[coagulase]] (fibrin clot formation), [[DNAse]] (zone of clearance on nutrient agar), [[lipase]] (a yellow color and rancid odor smell), and [[phosphatase]] (a pink color) tests are all done. For staphylococcal food poisoning, phage typing can be performed to determine if the staphylococci recovered from the food to determine the source of infection. | |||
==References== | ==References== | ||
Revision as of 20:46, 14 August 2012
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Methicillin resistant staphylococcus aureus infections Microchapters |
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Overview
Laboratory Findings
- Complete blood count and differential count - low red cell count, leukocytosis, thrombocytopenia
- Grams staining - gram positive cocci are seen.
- C reactive protein - elevated
- ESR - elevated
- Aspiration of joint fluid for:
- Cell count
- Grams stain
- Cultures
- Liver function tests - elevated transaminases may be seen (e.g toxic shock syndrome)
- Serum creatinine - elevated
Cultures
Culture of the bacteria is the gold standard test for the diagnosis of MRSA infections. Samples used for culture include blood, urine, synovial fluid, sputum, pus from abscesses and boils. Mannitol Salt Agar is used for culture , which is a selective medium (encourages the growth of a group of certain bacteria while inhibiting the growth of others) with 7–9% NaCl that allows S. aureus to grow producing yellow-colored colonies as a result of salt utilization and subsequent drop in the medium's pH.
Furthermore, for differentiation on the species level, catalase (positive for all species), coagulase (fibrin clot formation), DNAse (zone of clearance on nutrient agar), lipase (a yellow color and rancid odor smell), and phosphatase (a pink color) tests are all done. For staphylococcal food poisoning, phage typing can be performed to determine if the staphylococci recovered from the food to determine the source of infection.