Vancomycin Resistance in Staphylococcus aureus and Enterococcus Species isolated at the University Teaching Hospitals, Lusaka, Zambia: Should We Be Worried?

Background: Staphylococcus aureus and Enterococcus species cause invasive infections such as bacteremia and infective endocarditis. Despite vancomycin being the drug of choice for drug-resistant infections caused by these species, few studies have been conducted to ascertain vancomycin resistance in the African setting. This is crucial given the rising resistance in these organisms. This study aimed to isolate S. aureus and Enterococcus species and determine their susceptibility to vancomycin and other antibiotics at the University Teaching Hospitals in Lusaka, Zambia. Methods: This was a cross-sectional study in which S. aureus and Enterococcus spp isolates from the skin, soft tissue and bloodstream infections were included. Standard microbiological and Kirby-Baur (disc diffusion and E-strips) methods were used to identify and determine the susceptibility of the organisms, respectively. Results: From 59 S. aureus isolates, 37 were from the skin and soft tissue and 22 from blood culture. Twenty-six (44.1%) of these were Methicillin-resistant S. aureus. Thirty-nine Enterococcus were isolated from blood cultures only. Of the S. aureus (16) and Enterococcus (14) isolates tested with vancomycin E-strips, none were vancomycin-resistant. However, 12.5% S. aureus and 14.3% Enterococcus showed intermediate vancomycin susceptibility. S. aureus were resistant to penicillin (93.2%), erythromycin (52.5%) and tetracycline (50.8%). Enterococcus showed resistance to penicillin (83%) and tetracycline (84.6%). Conclusions: There was no vancomycin resistance among S. aureus and Enterococcus, implying vancomycin is still a viable treatment option for invasive infections. Given the intermediate vancomycin susceptibility, treatment guided by minimum inhibitory concentration results, continued surveillance and prudent use are key.