Molecular characterisation of methicillin-resistant staphylococcus aureus isolated at the Univeristy Teaching Hospital, Lusaka

Abstract

Methicillin-resistant Staphylococcus aureus is one of the major causes of nosocomial infections worldwide. It is endemic in hospitals and prevalent in the community and amongst livestock. Morbidity and mortality amongst patients with Methicillin-resistant Staphylococcus aureus infections are high due to resistance to many antibiotics. In Zambia, there has been an increase in the number of cases of Methicillin-resistant Staphylococcus aureus, from 23% in 2003 to 30.7% in 2010, but its molecular characteristics were unknown. In addition, its antibiotic resistance patterns are not clearly defined. Therefore, the objective of this study was to characterise Methicillin-resistant Staphylococcus aureus isolated from the University Teaching Hospital in Lusaka, Zambia, using molecular tools. The antimicrobial susceptibility pattern of the Methicillin-resistant Staphylococcus aureus was also determined. This was a laboratory-based cross-sectional study. Ninety-five clinical isolates of Staphylococcus aureus, collected between June 2009 and December 2012 at the University Teaching Hospital in Lusaka, Zambia, were analysed by SCCmec and spa typing. Antibiotic susceptibility testing was performed using the Kirby-Bauer disc diffusion method. The results demonstrated that, of the 95 S. aureus isolates, 43% were Methicillin-resistant Staphylococcus aureus strains. Antibiotic resistance to common anti-staphylococcal drugs ranged from 68% to 100%. Multi-drug resistance rates ranged from 17.5 % to 35%. The most prevalent SCCmec types were SCCmec type IV (63%) and SCCmec type III (14.6%). Five spa types, which included a novel type, were detected and the most prevalent spa type was t064 (13%). The prevalence of multidrug resistant Methicillin-resistant Staphylococcus aureus was found to be high and has continued to increase. The high prevalence of SCCmec type IV and spa type t064 suggests that the strains circulating are hospital-acquired and that there may be high genetic exchange amongst the bacterial strains. Regular surveillance and screening is recommended for infection control and treatment guidance.