Phenotypic and genotypic detection of antimicrobial-resistant bacterial pathogens from patients with infectious keratitis in selected hospitals in Ilorin, Nigeria

*1Oladejo, O. J., 2Oladejo, J. M., 3Aina, A., 4Oladejo, P., 4Odetoyin, B., 2Oluwaloniola, V., and 2Tangkat, T.

1Department of Ophthalmology, LAUTECH Teaching Hospital, Ogbomoso, Nigeria

2Department of Microbiology and Parasitology, University of Ilorin Teaching Hospital, Ilorin, Nigeria

3Deparrment of Ophthalmology, Bowen University Teaching Hospital, Ogbomoso, Nigeria

4Department of Microbiology, College of Health Sciences, Obafemi Awolowo University, Ile-Ife, Nigeria *Correspondence to:

Background: Infectious keratitis is a major cause of global blindness. Standard management approaches typically involve the collection of corneal cultures and initiation of broad-spectrum antimicrobials. However, conventional microbiological techniques, based on direct visualization or cultures of microorganisms, are limited by poor sensitivity and the prolonged time required to produce actionable results. Molecular methods based on nucleic acid amplification technique aim to circumvent the challenges of culture for hours or days. The objectives of this study are to detect the bacteria agents of infectious keratitis in Ilorin, Nigeria, using phenotypic and molecular methods, and to determine their resistance profiles to selected antimicrobials.

Methodology: This was a cross-sectional study of selected patients with clinical features of infectious keratitis attending the ophthalmology clinics of the University of Ilorin Teaching Hospital, Sobi specialist eye hospital, and the Civil Service clinic, in Ilorin, Kwara State, Nigeria, from July 2015 to July 2018. Corneal scraping samples were collected from the patients for conventional and molecular microbiological assessments. Antibiotic susceptibility testing to selected antibiotics was determined on each bacterial isolate by the Kirby-Bauer disc diffusion method. Methicillin-resistance among Staphylococcus aureus and extended spectrum beta-lactamases (ESBLs) among Gram-negative bacilli isolates, were detected by both phenotypic and genotypic testings. Data were analyzed by the Statistical Package for the Social Sciences (SPSS) version 20.0.

Results: A total of 81 patients with infectious keratitis were selected, with 59 (72.8%) males and 22 (27.2%) females. A total of 79 corneal scrapings yielded microbial isolates with 66 bacteria and 13 fungi. Out of the 66 bacterial isolates, Gram-positive bacteria (GPB) accounted for 28 (42.4%), with S. aureus 14 (21.2%) and coagulase negative staphylococci 10 (15.2%), while Gram-negative bacteria (GNB) accounted for 38 (57.6%). The most resistant isolates to the selected antibiotics are S. aureus (50.0%, 7/14), Escherichia coli (50.0%, 1/2), Klebsiella pneumoniae (25.0%, 1/4) and Pseudomonas aeruginosa (25.0%, 1/4). ESBL genes were harbored by 7 isolates of K. pneumoniae, Klebsiella oxytoca, E. coli, and Citrobacter freundii. Three of these harbored 3 ESBL (blaCTX-M, blaSHV, blaTEM) genes each while 4 harbored 2 ESBL (blaCTX-M, blaTEM) genes each. Two (14.3%) of the 14 S. aureus isolates harbored mecA gene (MRSA).

Conclusion: Staphylococcus aureus was the predominant bacterial pathogen of infectious keratitis in Ilorin, Nigeria, a few of which harbored mecA gene. Staphylococcus, Klebsiella and other GNB were resistant to the commonly used antibiotics tested in the study.

Keywords: infectious keratitis, antimicrobial resistance, ESBL, MRSA

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Phenotypic and genotypic detection of antimicrobial-resistant bacterial pathogens from patients with infectious keratitis in selected hospitals in Ilorin, Nigeria