Methicillin-Resistant <i>Staphylococcus aureus</i> May Also Be Resistant to Clindamycin and Vancomycin

Abstract

Objectives: Methicillin-resistant Staphylococcus aureus (MRSA) is a global superbug widely distributed in hospitals, communities and livestock settings. This study investigated the presence and molecular characterization of MRSA co-resistance to clindamycin and vancomycin in the southeastern region of Nigeria. The susceptibility of these organisms to other selected antibiotics was also investigated. Method: Biological samples were obtained from consenting patients from three establishments in Enugu, Nigeria and cultured for isolation and purification. The pure isolates were subjected to antimicrobial susceptibility profiling using conventional antibiotics. The genomic DNAs of the pure isolates were isolated using the Promega genomic DNA purification kit while the antibiotic resistance genes (mecA) genes were identified using a multiplex polymerase chain reaction. Also, the minimum inhibitory concentration of the clindamycin and vancomycin antibiotics was determined as well as their combined activity on the MRSA isolates. Results: A large proportion (71%) of the MRSA isolates was from urine samples and then from the High Vaginal Swab (19%). All the isolates were resistant to cloxacillin while 95% were resistant to ciprofloxacin. MRSA isolates demonstrated resistance to clindamycin (with MIC of 23.44 - 250 μg/ml) and to vancomycin (with MIC of 62.5 - 250 μg/ml). The isolated MRSA also demonstrated multidrug-resistant traits. The combined effects of vancomycin and clindamycin against different species of MRSA exhibited additive, antagonistic and indifferent effects and none had a synergistic effect. Multiplex Polymerase Chain Reaction revealed that the majority of the strains were positive for the 162-bp internal fragment of the mecA gene of MRSA and basically displayed SCCmec type III, indicating that they were multidrug-resistant and hospital-acquired. Conclusion: Clindamycin and vancomycin-resistant MRSA infections are also within the Eastern region of Nigeria as found in other countries of the world. This superbug, therefore, may require drastic and urgent measures to curtail its spread and attendant healthcare challenges like outbreaks of infections. In addition, strict adherence to antibiotic policy and continuous surveillance is highly advocated.