EVALUATION OF ANTIBIOTICS AND NON-ANTIBIOTICS COMBINATION AGAINST MULTIPLE ANTIBIOTIC RESISTANCE STRAINS OF STAPHYLOCOCCUS AUREUS
Abstract
The global rise in antibiotic-resistant pathogens, particularly Staphylococcus aureus, has intensified the search for innovative treatment strategies as conventional monotherapies continue to fail. This study investigates the antibacterial efficacy of selected antibiotics gentamicin, streptomycin, ciprofloxacin, and ceftriaxone and their combination with nonantibiotic agents, promethazine and metoclopramide, against multidrug-resistant strains of S. aureus. Clinical isolates were obtained through a mixed culture from a nasal isolate from researchers at the Nigerian Institute of Medical Research, Lagos, and traced back to rural populations in Kano State. These samples were cultured, and microbial suspensions were standardized to a 0.5 McFarland turbidity standard to ensure uniform microbial load across all sensitivity tests. Following rigorous morphological, Gram staining, and biochemical characterization, the confirmed S. aureus isolates were subjected to antibiotic susceptibility testing using the agar well diffusion method, with concentration ranges from 0.1, 10, 20, 50, 100, 200, 500, 750, 1000 to 5000 μg/mL over 24- and 48-hour incubation periods. Results showed complete resistance to all individual antibiotics tested, highlighting the alarming presence of "super microbes" bacterial strains with extensive resistance mechanisms that render standard antibiotics ineffective. Furthermore, none of the antibiotic–non-antibiotic combinations demonstrated any synergistic or inhibitory effects, despite prior evidence suggesting potential synergy between repurposed drugs and antimicrobial agents. These findings emphasize the urgent need for molecular surveillance and more strategic drug pairing based on genetic resistance profiling. The failure of both mono- and combination therapies observed in this study underscores the resilience of multidrug-resistant S. aureus in Nigeria and calls for intensified research into mechanism-based therapeutic innovations to outpace evolving microbial threats.
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