The use of Lipovitellin mannitol salt agar supplemented with Oxacillin for direct detection of methicillin resistant staphylococcus aureus from clinical specimens(Thai)

Abstract

The aim of this study was to evaluate the use of Lipovitellin mannitol salt agar (LMS) and LMS supplemented with oxacillin 6 µ g/ml (LMS-OX) for their ability to directly isolate, recover and presumptively identify of Staphylococcus aureus and methicillin resistant S. aureus (MRSA) from clinical specimens. We compared the use of LMS and LMS-OX with the conventional media, blood agar, to detect and recover S. aureus and MRSA from 1,926 samples of clinical specimens including pus, sputum and blood samples. Three hundred and eighty seven isolates of S. aureus and 203 isolates of MRSA were more significantly recovered from LMS and LMS-OX than from routine culture using blood agar plate which recovered only 231S. aureus and 130 MRSA, (P < 0.05). LMS-OX gave a 99.01 % (201/203 isolates) correlation with the detection of PBP2a by slide latex agglutination for identification of MRSA. The advantage of using LMS and LMS-OX as primary culture medium are ease and rapid recognition of typical colonies of S. aureus and MRSA which produced yellow colonies with opaque zone, from clinical specimens, especially from those with heavy contamination with bacterial flora such as sputum. These will shorten the time for the detection of S. aureus and MRSA for 1-2 days. Therefore, these media may be the alternative plating medium for the detection and isolation of S. aureus and MRSA in routine clinical laboratories with a large number of specimens and for screening carriers in large populations.