Detection of antimicrobial resistance and virulence genes in staphylococcus aureus isolated from clinical samples at the university teaching hospitals, Lusaka, Zambia

The pathogenicity of Staphylococcus aureus (S. aureus) is attributed to development of antimicrobial resistance and production of many virulence factors. Several genes are implicated in resistance to antimicrobials and virulence factors. This study was aimed at investigating the presence of selected antimicrobial resistance and virulence genes in S. aureus isolated from clinical samples at the University Teaching Hospitals in Lusaka, Zambia. This was a cross-sectional study involving forty-three (43) S. aureus isolates. Species identification gene (nuc), antimicrobial resistance genes (ermA, ermB, ermC, mecA, tetK tetL, tetM, and tetO) and virulence genes (spa, pvl, sea, seb, sec, sed, and see) were detected using Polymerase Chain Reaction. The nuc gene was detected in all the 43 isolates thereby confirming them as S. aureus. Of the 43 isolates, 14 (32.6%) were from blood samples while 29 (67.4%) were from skin and soft tissue samples. Five (11.6%) S. aureus isolates harboured the mecA gene (MRSA). Nine (20.9%) isolates tested positive for ermC gene while none were positive for neither ermA nor ermB. The tetK and tetL genes were detected in 3 (7.0%) and 1 (2.3%) isolates, respectively. None of the isolates tested positive for tetM, and tetO genes. One spa type t015 was detected in two isolates whereas the spa types for five isolates were unknown. Five (11.6%) isolates tested positive for sec enterotoxin gene. None of the 43 isolates possessed any of the sea, seb, sed and see enterotoxin genes as well as the pvl gene. Two (22.2%) of ermC positive isolates harboured enterotoxin sec gene. This study adds to existing knowledge by giving insight into the presence of mecA gene (MRSA) among S. aureus isolates as well as noting the presence of one MRSA strain that harboured both tet (tetK) and macrolide resistance (ermC) genes which poses a significant therapeutic challenge in disease management of staphylococcal infections in resource limited countries like Zambia. Furthermore, the carriage of staphylococcal enterotoxin S. aureus strains suggests a high potential of staphylococcal food poisoning at the largest referral hospital. This study has demonstrated the need to develop an efficient control programme to curb the transmission and spread of antimicrobial resistant particularly multi-antimicrobial resistant and food toxin producing S. aureus strains at the largest referral hospital