DNA microarray analysis of Staphylococcus aureus from Nigeria and South Africa

Staphylococcus aureus is an important human pathogen with an arsenal of virulence factors and a propensity to acquire antibiotic resistance genes. The understanding of the global epidemiology of S. aureus through the use of various typing methods is important in the detection and tracking of novel and epidemic clones in countries and regions. However, detailed information on antibiotic resistance and virulence genes of S. aureus, and its population structure is still limited in Africa. In this study, S. aureus isolates collected in South Africa (n=38) and Nigeria (n=2) from 2001-2004 were characterized using DNA microarray. The combination of spa typing and DNA microarray classified the isolates into seven spa types and three clonal complexes (CCs) i.e. t064-CC8 (n=17), t037-CC8 (n=8), t1257-CC8 (n=6), t045-CC5 (n=5), t951-CC8 (n=1), t2723-CC88 (n=1), t6238-CC8 (n=1), and untypeable-CC8 (n=1). There was excellent agreement (only two discordant results) between antibiotic susceptibility testing and the detection of the corresponding resistance genes by DNA microarray. Antibiotic and virulence gene markers were associated with specific clones. The detection of the collagen-binding adhesion (cna) gene was unique for t037-CC8-MRSA, the enterotoxin gene cluster (egc) and staphylococcal complement inhibitor (scn) gene for t045-CC5-MRSA, and the combination of genes encoding enterotoxin (entA, entB, entK, entQ) were noted with most of the CC8 isolates. The t045-CC5-MRSA clone was positive for the mercury resistance (mer) operon. DNA microarray assay provides information on antibiotic resistance and virulence gene determinants and can be a useful tool to identify gene markers of specific S. aureus clones in Africa.