Molecular detection of virulence and resistance markers in Escherichia coli and Staphylococcus aureus isolated from Nigerian currency

Potentially pathogenic bacteria are routinely linked with different currencies worldwide. Not much focus has been on the actual pathogenic potential of these bacteria. This is essential as the risk would depend on whether the bacteria associated with the currency is a commensal or pathogen. This study was therefore aimed at exploring the virulence potential of Escherichia coli and Staphylococcus aureus isolated from specific Nigerian currency denominations. Presumptive E. coli and S. aureus isolates were obtained from the samples and their identities confirmed genotypically. A total of seven virulence and resistance genes were tested for (aggR, eae, ast, van, cat, pvl, icaA). Three of these were E. coli virulence genes (aggR, eae, ast), two S. aureus virulence (pvl, icaA) and two S. aureus resistance (van, cat). Sixty presumptive E. coli and S. aureus (30 each) were isolated and purified. Of these, 9 (30%) were confirmed as E. coli following genotypic identification and 7 (23%) as S. aureus. An assessment of the virulence potential of E. coli showed 100% detection of the ast gene, 55.6% detection of aggR and 44.4% detection of eae. For S. aureus, a much lower frequency of test genes was found with rates of 41.7%, 16.7%, 16.7% and 8.3% for pvl, icaA, van and cat respectively. This study therefore reports a low frequency of S. aureus virulence genes. The E. coli strains however, rather than being innocuous carry virulence factors. Furthermore, some of these have a known association with mobile genetic elements and hence a capacity to transform harmless commensal strains to pathogens.