Identification and antimicrobial susceptibility of microorganisms isolated from severe corneal ulcers of dogs in Thailand

Abstract

This study aims to determine the microbiological profile and risk factors associated with antimicrobial-resistant bacteria in canine severe corneal ulcers. Thirty-two corneal and conjunctival swabs were collected from dogs with diagnosed severe corneal ulcers that presented to Prasu-Arthorn veterinary teaching hospital in Nakhon Pathom, Thailand from June 2015 to June 2016. Microorganisms were identified by means of genotypic and phenotypic approaches. Of 32 ulcers sampled, 26 (81.3%) yielded culturable microorganisms with 24 bacterial isolates and 7 fungal isolates. The most commonly isolated bacteria were Staphylococcus spp. (45.8%, 11/24) and Pseudomonas aeruginosa (20.8%, 5/24). Out of 11 staphylococcal isolates identified, 10 carried the mecA gene providing methicillin resistance. The extended-spectrum β-lactamase (ESBL) encoding genes blaCTX-M and blaVEB-1 were found in an Acinetobacter lwoffii isolate, and blaSHV was found in a P. aeruginosa isolate. Based on the Clinical Laboratory Standards Institute (CLSI) and European Committee on Antimicrobial Susceptibility Testing (EUCAST) breakpoint criteria, minimum inhibitory concentrations values showed that all bacteria, except for staphylococci, were susceptible to current ophthalmic antibiotics. More than 50% of staphylococci were resistant to all generations of fluoroquinolones and fusidic acid. Chloramphenicol was highly active against staphylococci (81.3% susceptible). The width (P=0.02) and the depth (P=0.04) of ulcers predicted greater risk of yielding resistant bacteria. The identification of antimicrobial-resistant bacteria prompts practitioners to be prudent when choosing ophthalmic antibiotics for severe corneal ulcers.

Prevalence and Antibiotic Susceptibility of Bacterial Isolates From Dogs With Ulcerative Keratitis in Midwestern United States

“…The distribution of bacterial populations has been described previously for several geographic regions of the world including Asia ( 3 , 6 , 7 ), Australia ( 1 , 8 ), Europe ( 9 ), North America ( 10 , 11 ), and South America ( 2 ). While there are distinct similarities between these regional investigations, there are notable differences in bacterial prevalence and susceptibilities across the world.…”

Using minimum inhibitory concentration values of common topical antibiotics to investigate emerging antibiotic resistance: A retrospective study of 134 dogs and 20 horses with ulcerative keratitis

“…One recent retrospective study investigating 32 bacterial ulcers in dogs reported the range of MIC values, but not the median or MIC 50 and MIC 90 values, making direct comparisons difficult. 11 However, there are recent publications investigating MIC values of common antibiotics used in humans with bacterial keratitis. 13,14,19 When comparing the results of the present study to the human-based literature, the Streptococcus category had similar MIC 50 and MIC 90 values for all antibiotics tested (chloramphenicol, ciprofloxacin, ofloxacin, and moxifloxacin), as did the Pseudomonas spp.…”

“…For example, although not a primary objective of this study, our findings support previous reports of resistance of Staphylococcus to fluoroquinolones based off of systemic breakpoints alone. 2,11,28 In future studies, investigating clinical outcomes and correlating such data with MIC values of the antibiotics used will add valuable information to the field. A second limitation of this study was that the potential presence of concomitant fungal infections was not recorded in equine cases.…”

“…1,2,5,8 By using disc diffusion and systemic breakpoints, studies have documented increasing resistance among common empirically chosen antibiotics, including aminoglycosides 4 and second-generation fluoroquinolones. 2,8,9,11,12 Unfortunately, studies using MIC in cases of septic keratitis in veterinary medicine are rare. 11,12 However, in human ophthalmology, recent investigations have determined MIC values for common topical antibiotics and correlated these values with clinical outcomes.…”

“…2,8,9,11,12 Unfortunately, studies using MIC in cases of septic keratitis in veterinary medicine are rare. 11,12 However, in human ophthalmology, recent investigations have determined MIC values for common topical antibiotics and correlated these values with clinical outcomes. [13][14][15][16][17][18] These studies not only found that MIC values of fluoroquinolones correlate with clinical outcome, 14,[16][17][18] but that humans previously treated with a topical fluoroquinolone had increased MIC values for all tested fluoroquinolones, indicating that previous fluoroquinolone use was associated with bacterial resistance to antibiotics in this class.…”