EFFECTIVENESS OF DIFFERENT SELECTIVE MEDIA FOR THE CULTURE OF Staphylococcus aureus.

    ABSTRACT

This present study was aimed to determine the efficacy of different culture media for Isolation and identification Staphylococcus aureus (S. aureus) present in smoked fish sold within different locations in the markets in Benin City, Nigeria. A total of Fifty (50) samples of smoked fish were collected in markets, located in Benin City, and packaged in sterile polythene bags and transported to the University of Benin Microbiology Laboratory for analysis. The samples were processed for bacteriological analysis within 1-5 hours of collection. Out of these fifty samples of isolated bacteria from the smoked fish, only twenty samples were confirmed to have Staphylococci species particularly Staphyloccocus aureus  and was cultured on a selective media such as Mannitol salt agar (MSA), Vogel-Johnson agar (VJA) and Oxacillin resistant screening agar base (ORSAB).  Out of 20 S. aureus  isolates,  only 17 (85%) grew on Mannitol salt agar plates, while the remaining three (3) were not actually Staphylococcus aureus because the bacteria does not have the ability to ferment the sugar, mannitol. Similarly, out of 20 samples, only  16 (80%) grew on Vogel-Johnson agar plates with no growth on the other four streaked area of the agar plate, this indicates that Vogel-Johnson agar is favourable for the isolation and identification  of Staphyloccocus aureus. Oxacillin resistance exhibited by Methicillin Resistant Staphyloccocus aureus (MRSA) on ORSAB was observed by growth of white colonies on the blue agar medium. The frequency of isolation and identification of  S. aureus on each selective media indicates that Oxacillin resistant screening agar base is effective for culturing Staphyloccocus aureus especially MRSA. The use of selective media only such as MSA, VJA, and ORSAB for preliminary identification of Staphyloccocus species is not totally reliable as other organisms may show similar characteristics with typical Staphyloccocus colony on this media.  Further test should be carried out for confirmation of   Staphylococcus aureus  and not any other organism.