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 agar (MSA), 5% horse blood agar (HBA), and phenolphthalein phosphate agar (PPA), to detect and recover S. aureus and methicillinresistant 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 agar 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 agar may be an alternative plate medium for large hospitals that perform extensive screening for the detection and isolation of S. aureus.

Incidence of Virulent factors in Staphylococci isolated from clinical and foods specimens in Egypt

“…Swabs of clinical specimens were directly streaked on agar surface of specific media plates, meanwhile 10g of food samples were homogenized and suspended in 90ml sterile peptone water and incubated at 37 o C for 3h. Further on, loopful inocula of prepared food samples were streaked on surface of agar specific media; Baird Parker agar (Baird-Parker et al, 1969) and Mannitol salt agar (Merlino et al, 1996). Plates were incubated at 37 o C for 24h.…”

Evaluation of CHROMagar Staph. aureus, a New Chromogenic Medium, for Isolation and Presumptive Identification of Staphylococcus aureus from Human Clinical Specimens

“…They can be supplemented with antibiotics in order to detect methicillin-resistant S. aureus (MRSA) isolates (13,18). However, the average sensitivity and specificity of mannitol-salt agar (10,12,15) do not qualify it for use for early isolation and presumptive identification of S. aureus in all clinical specimens, although supplementation with egg yolk was shown to be of clinical interest (15). There is still a need for more specific media that would retain the sensitivity of blood agar and allow single-step isolation and presumptive identification of S. aureus.…”

Evaluation of Mannitol Salt Agar for Detection of Oxacillin Resistance in Staphylococcus aureus by Disk Diffusion and Agar Screening

“…MSA was first investigated as a medium for susceptibility testing in 1985 (12). Its value as a screening medium for MRSA has been investigated in several studies (13,16). It has been further evaluated as a primary isolation medium for recovery of MRSA when containing 6 g of oxacillin per ml (28).…”