Molecular Detection of Methicillin-Resistant Staphylococcus aureus from Wound Infections and Its Susceptibility to Aqueous and Methanolic Extracts of Hymenocardia acida and Khaya grandifoliola

Abstract

Methicillin-resistant Staphylococcus aureus (MRSA) is a leading cause of antimicrobial-resistant wound infection worldwide, and the search for alternative antibacterial agents has drawn renewed attention to medicinal plants. This study evaluated the antibacterial activity of aqueous and methanolic extracts of Hymenocardia acida stem bark and Khaya grandifoliola leaf against PCR-confirmed MRSA isolated from wound infections among patients in Ilorin, Nigeria. Staphylococcus aureus was isolated and identified by standard microbiological methods from wound swabs (n=198) of patients attending selected hospitals in Ilorin. Methicillin resistance was screened phenotypically by the cefoxitin disc diffusion method and confirmed genotypically by PCR amplification of species-specific nuc gene and the resistance-associated mec gene. Antibacterial activity of the plant extracts was assessed against the MRSA isolates using the agar well diffusion method, with vancomycin (30 µg) as positive control. Of 31 Staphylococcus aureus isolates recovered, 23 (74.2%) were phenotypically methicillin-resistant, of which 10 (43.5%) were confirmed genotypically as MRSA (nuc+/mec+). The aqueous extract of Khaya grandifoliola produced the widest mean zone of inhibition (18.6±1.5 mm), exceeding the vancomycin control (16 mm), while its methanolic extract produced a mean zone of 15.9±1.7 mm. The aqueous extract of Hymenocardia acida showed no inhibitory activity against any isolate, whereas its methanolic extract produced a mean zone of 11.6±1.1 mm. These findings demonstrate that PCR-confirmed MRSA wound isolates were more susceptible to extracts of Khaya grandifoliola than to Hymenocardia acida, and support further investigation of Khaya grandifoliola as a potential source of plant-derived antibacterial agents against MRSA.