Epidemiological and Genomic Patterns of Methicillin-Resistant Staphylococcus Aureus Isolates Obtained from Patients Seeking Treatment in Nakuru County Referral and Teaching Hospital, Kenya

Abstract

Staphylococcus aureus is a pathogenic bacterium that can evolve rapidly to methicillin-resistant Staphylococcus aureus (MRSA). Methicillin-Resistant Staphylococcus aureus is a global health concern that is associated with significant morbidity and mortality. Several factors have been associated with MRSA which include antibiotic use, prolonged hospitalization and surgical intervention among others. The objective of this study was to determine epidemiological and genomic patterns observed from MRSA isolates obtained from patients seeking treatment in Nakuru County Referral and Teaching Hospital. This was a cross-sectional study with a laboratory experimental component conducted over six months in Nakuru County Referral and Teaching Hospital, Microbiology Laboratory. This study used routinely collected laboratory samples such as blood, urine, pus and CSF of patients seeking treatment in the hospital. The samples were selected using systematic random sampling until the 354-sample size was achieved. In addition, the demographic and clinical factors were collected from laboratory records while patient level factors were collected from the hospital records. Microbiology samples for culture and sensitivity received from inpatient and outpatient were included in the study. Methicillin Resistant S. aureus isolates were identified phenotypically and the MRSA strains were confirmed using Whole Genome Sequencing. This data was then analyzed using IBM SPSS software Version 23. The association between independent variables and the S. aureus and MRSA were tested using Chisquare test for categorical variables and Fishers exact test as an alternative in case of small values. Mann Whitney U test was used to compare median ages. Statistical significance was interpreted at 5% level (p< 0.05). The study identified a prevalence of 7.1% for Staphylococcus aureus and 2.3% for MRSA among the sampled patients, with the highest prevalence of 28.6% observed in the burns unit. MRSA isolates exhibited significant resistance to penicillin G, erythromycin, and clindamycin, with resistance rates of 64% for these antibiotics. Despite this high resistance, MRSA isolates were highly susceptible to Cefoxitin (68%), Doripenem (56%) and Sulfamethoxazole (68%). Molecular typing revealed the dominance of clonal complexes CC8 and CC15, with ST152 being the most prevalent strain. A significant proportion (52%) of the isolates harbored virulence genes such as lukF-PV and lukS-PV, which are associated with severe infections. Key patientlevel risk factors identified included prolonged hospital stays and antibiotic use, which significantly increased the risk of MRSA infections. The study highlights critical epidemiological and genomic characteristics of MRSA at Nakuru County Teaching and Referral Hospital. These findings emphasize the need for continuous MRSA surveillance, stringent infection control practices, and routine antibiotic susceptibility testing to guide effective treatment. Understanding the genetic characteristics and virulence factors of MRSA isolates can aid in predicting clinical behavior and developing targeted interventions for managing and preventing MRSA infections. The recommendations from this study emphasize the critical need for robust infection control measures, regular surveillance of MRSA prevalence and resistance patterns, and prudent use of antibiotics to combat the spread of resistant strains. Enhancing laboratory capabilities, educating healthcare workers, and fostering interdisciplinary collaboration are vital steps in managing MRSA. Further research and public health initiatives are essential to raise awareness and develop effective preventive measures. Findings from this study was disseminated to the hospital's Medical Superintendent and healthcare workers, aiding in the proper management and prevention of MRSA infections.