The Prevalence and Molecular Biology of Staphylococcus aureus Isolated from Healthy and Diseased Equine Eyes in Egypt

Hussam M M Ibrahim,Helmy K Elnafarawy,Mohamed A Youssef,Amin Tahoun,Hanem El-Sharkawy,Ahmed M El-Shehawi,Sabry El-Khodery,Mohammed Alorabi,Amira M Rizk

doi:10.3390/antibiotics11020221

Hussam M M Ibrahim, Helmy K Elnafarawy + Show 7 more

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https://doi.org/10.3390/antibiotics11020221

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Abstract

This work aimed to characterize S. aureus isolates from the eyes of healthy and clinically affected equines in the Kafrelsheikh Governorate, Egypt. A total of 110 animals were examined for the presence of S. aureus, which was isolated from 33 animals with ophthalmic lesions and 77 healthy animals. We also investigated the antimicrobial resistance profile, oxacillin resistance mechanism, and the major virulence factors implicated in many studies of the ocular pathology of pathogenic S. aureus. The association between S. aureus eye infections and potential risk factors was also investigated. The frequency of S. aureus isolates from clinically affected equine eyes was significantly higher than in clinically healthy equids. A significant association was found between the frequency of S. aureus isolation from clinically affected equine eyes and risk factors including age and season but not with sex or breed factors. Antimicrobial resistance to common antibiotics used to treat equine eyes was also tested. Overall, the isolates showed the highest sensitivity to sulfamethoxazole (100%) and the highest resistance to cephalosporin (90.67%) and oxacillin (90.48%). PCR was used to demonstrate that mecA was present in 100% of oxacillin- and β-lactam-resistant S. aureus strains. The virulence factor genes Spa (x region), nuc, and hlg were identified in 62.5%, 100%, and 56%, of isolates, respectively, from clinically affected equines eyes. The severity of the eye lesions increased in the presence of γ-toxin-positive S. aureus. The phylogenetic tree of the Spa (x region) gene indicated a relationship with human reference strains isolated from Egypt as well as isolates from equines in Iran and Japan. This study provides insight into the prevalence, potential risk factors, clinical pictures, zoonotic potential, antimicrobial resistance, and β-lactam resistance mechanism of S. aureus strains that cause eye infection in equines from Egypt.

Highlights

Bacterial infection of the eye causes diseases, including conjunctivitis, keratitis, endophthalmitis, and corneal ulcers, of which the bacteria Staphylococcus aureus is considered a major causative agent [1]
24 isolates were from 19 diseased animals and 23 isolates were from 23 healthy equines
The results of this study demonstrated that most S. aureus isolates from clinically affected equine eyes are methicillin-resistant S. aureus (MRSA), as indicated by antibiograms and the detection of relevant genes

Summary

Introduction

Bacterial infection of the eye causes diseases, including conjunctivitis, keratitis, endophthalmitis, and corneal ulcers, of which the bacteria Staphylococcus aureus is considered a major causative agent [1]. The bacterial community that inhabits the corneal and conjunctival spaces of healthy horses includes non-pathogenic and opportunistic Gram-positive (G +ve) bacteria [2]. Threatening eye infections that may disrupt horse training and potentially disqualify the animal from competition may necessitate long and expensive treatment courses [6]. Such infections result in a huge economic loss to the horse sports and trading industry, which is estimated at a million dollars a year in the USA [7]. The bacterial community that inhabits the cornea and conjunctiva of healthy horses includes nonpathogenic and opportunistic Gram-positive (G +ve) bacteria [2]. Another study identified methicillin-resistant S. aureus (MRSA) from a donkey conjunctival swab [9]

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