Enterotoxigenicity of Multidrug Resistant Staphylococcus aureus Isolated from Dry Catfish Sold in Some Open Markets in Zaria - Nigeria

Aim: The aim of this study was to determine the enterotoxigenic potential of MDR S. aureus isolated from dry catfish sold in some open markets in Zaria, Nigeria.

Place and Duration of Study: Department of Pharmaceutical Microbiology, Ahmadu Bello University, Zaria and Central Laboratory, City Campus of the Usman Danfodio University, Sokoto, Nigeria, from December 2017 to March 2019.

Methodology: We collected five, each of multidrug resistant and susceptible S. aureus isolates from the Pharmaceutical Microbiology Laboratory of the Ahmadu Bello University, Zaria and confirmed them as S. aureus. Cell concentrates were harvested from 24 hours old Luria and Bertani (LB) pure broth culture of S. aureus isolates by centrifugation at 4°C, 8000 rpm (6800 × g) in a micro-centrifuge for two minutes at room temperature. We used ZymoBIOMICS™ DNA Miniprep Kits to extract the genomic DNA from the harvested cells. We used PCR to amplify the 16S RNA, mecA and the enterotoxin genes after an external optimization of the reaction to ensure a better amplification. Finally, we used exactly two percent agarose gel to resolve the PCR genomic DNA fragments with their primers.

Results: The results of the PCR and gel electrophoresis indicated that all the ten (10) strains of S. aureus tested for 16S rDNA gene where positive for the gene whereas only two strains (20%) out of the ten (10) were positive for mecA gene. Among the ten (10) strains of S. aureus, tested, four (40%) strains were positive for two or more staphylococcal enterotoxin genes. All but one phenotypic multidrug resistant isolates carried genes for enterotoxins whereas, phenotypically drug susceptible isolates showed no band for enterotoxins.

Conclusion: This study showed that enterotoxin genes were common amongst the antibiotics resistant strains, which indicated a possibility of a relationship between antibiotics resistance and enterotoxogenicity.