Application of lipovitellin-salt-mannitol agar for screening, isolation, and presumptive identification of Staphylococcus aureus in a teaching hospital

Abstract

Lipovitellin-salt-mannitol (LSM) plate medium was examined for its ability to directly isolate, recover, and presumptively identify Staphylococcus aureus from 418 clinical specimens. The criteria for medium evaluation included colony morphology reactions, selectivity, and ease of isolation. For 298 specimens used for screening, LSM agar medium was compared with the other conventional media used, mannitol salt afar (MSA), 5% horse blood afar (HBA), and phenolphthalein phosphate afar (PPA), to detect and recover S. aureus and methicillin-resistant S. aureus. The results indicated that LSM agar is more effective than MSA, HBA, or PPA for the recovery and isolation of S. aureus and methicillin-resistant S. aureus. On a replicator multipoint inoculation system, we compared the reactions on LSM agar, MSA, and DNase afar of 227 different strains of staphylococci, which included 178 different strains of S. aureus and 49 different strains of coagulase-negative staphylococci isolated from clinical specimens. By using both the lipovitellin precipitation activity and mannitol fermentation characteristics, LSM agar gave a 100% correlation in presumptively identifying S. aureus. LSM afar may be an alternative plate medium for large hospitals that perform extensive screening for the detection and isolation of S. aureus.