Antibiotic Resistance Indices of Methicillin-Resistant Staphylococcus aureus isolates at a Tertiary Healthcare Facility in Calabar, Nigeria.

Abstract

Staphylococcus aureus is a common nosocomial and community acquired pathogen associated with remarkable antibiotic resistance, high morbidity and prolonged hospitalization. This study investigated the prevalence and antibiotic- resistance patterns of methicillin-resistant S. aureus (MRSA) isolated from clinical specimens in University of Calabar Teaching Hospital (UCTH), Calabar, Nigeria. A total of 98 isolates of S. aureus were collected from UCTH Microbiology Laboratory, identified by conventional bacteriological methods, and subjected to MRSA screening and antibiotics susceptibility testing using Kirby-Bauer disc- diffusion method. Multiple antibiotics resistance (MAR) index of each isolate was evaluated. The prevalence of MRSA was 53.1%, with the highest proportion of the pathogen (34.6%) obtained from urine specimens. The MRSA strains showed 96.2% susceptibility to amoxicillin-clavulanate, but exhibited high resistance to kanamycin (88.5%), erythromycin (80.7%) and gentamicin (69.2%), while 10 (19.2%) showed complete resistance to vancomycin and 30 (57.7%) were multidrug resistant strains. The MAR indices were greater than 0.2 for 92.3% of the isolates. The high MAR values of the isolates may suggest indiscriminate use of antibiotics, with likelihood for treatment failures and escalation of drug resistance in the population. Antibacterial interventions based on antibiotics susceptibility tests reports would likely enhance good clinical outcomes and prevent further escalation of drug-resistant strains in the population. The high activity of amoxicillin-clavulanate against the MRSA strains may suggest a predominance of beta- lactamase producing staphylococcal strains in this study setting, making a case for further studies to determine the drug resistance determinants of the pathogen in the population.