Melting corneal ulcers (keratomalacia) in dogs: A 5-year clinical and microbiological study (2014–2018)
Tsvetanova, A. et al (2021), Melting corneal ulcers (keratomalacia) in dogs: A 5‐year clinical and microbiological study (2014–2018). Veterinary Ophthalmology, 24 (3), pp. 265-278
The aim of this retrospective study was to identify bacterial microorganisms associated with melting corneal ulcers (keratomalacia) in dogs and to investigate their prevalence, antimicrobial sensitivity, and clinical outcomes.
Medical records from a single UK referral hospital were reviewed for canine cases of stromal corneal ulcer associated with keratomalacia. Cases that had undergone bacterial culture and sensitivity testing were included in the study.
The study population included 110 melting corneal ulcers from 106 dogs. The study population included 27 breeds, and brachycephalic breeds were overrepresented (63/106, 59%). There were 63 positive bacterial cultures but no positive cultures for fungal infections. Twenty-six melting corneal ulcers cultured pure Pseudomonas aeruginosa and 12 cultured pure β-haemolytic Streptococcus. Multiple cultures were identified in nine cases and 47 cultures yielded no bacterial growth.
Pseudomonas aeruginosa showed the highest sensitivity to gentamycin (100%), orofloxacin (96.5%), ciprofloxacin (96.5%), marbofloxacin (96.5%), polymyxin B (96.5%), enrofloxacin (86%) and neomycin (65.5%). Pseudomonas aeruginosa showed the greatest resistance to doxycycline, fusidic acid, amoxicillin-clavulanate and cephalexin (all at 100%), and chloramphenicol and clindamycin (at 96.5%).
β-haemolytic Streptococcus showed the highest sensitivities to amoxicillin-clavulanate, cephalexin and clindamycin (100%), doxycycline (89.5%) and chloramphenicol (88%). β-haemolytic Streptococcus showed the greatest resistance to polymyxin B, neomycin and fusidic acid (100%), gentamicin (95%), and most were resistant to fluoroquinolones (enrofloxacin and marbofloxacin, at 63% and ciprofloxacin and ofloxacin, at 67%).
There was no significant difference in terms of ulcer severity at presentation regarding the cultured bacteria. Overall, 47 of the ulcers received only medical treatment and surgical grafting was performed on 63 eyes. The ulcers healed in 96 cases, and in 14 cases, progression of corneal melting resulted in enucleation. 57% (8/14) of the enucleated eyes cultured pure Pseudomonas aeruginosa isolates. In contrast, all β-haemolytic Streptococcus-associated ulcers healed.
Limitations of the study include the retrospective nature, clinical details were not fully documented in every case, and the duration of melting keratitis prior to presentation was unknown. As the study used records from a referral practice, the findings may not be generalisable to primary-care practices.
This retrospective study provides some evidence of the importance of bacterial culture and sensitivity testing for all dogs presenting with melting corneal ulcers, to assist clinicians in their treatment choices.
Although the study uses data from a single referral practice, the information it provides is useful and could be used in a first opinion practice where referral is not an option.
Image copyright attribute: Jozef Polc