Comparison of bacterial culture results collected via direct corneal ulcer vs conjunctival fornix sampling in canine eyes with presumed bacterial ulcerative keratitis

Abstract

ObjectiveTo compare aerobic bacterial culture results between samples obtained from the corneal ulcer versus lower conjunctival fornix in eyes with presumed bacterial ulcerative keratitis.Animals studiedFifty five client‐owned dogs diagnosed with ulcerative keratitis.ProceduresOphthalmic examinations were performed on each dog including slit‐lamp biomicroscopy and indirect ophthalmoscopy. Microbial swabs were collected by direct sampling of the infected corneal ulcer as well as the lower conjunctival fornix, of the same eye, using a sterile rayon‐tipped swab. Samples were submitted to an outside reference laboratory for aerobic bacterial culture and sensitivity.ResultsOne hundred twelve samples were obtained from 56 eyes (55 dogs). Sixty‐eight samples yielded bacterial growth. Positive growth from both sites was obtained in 31 eyes (55%). Six eyes yielded bacterial growth from the conjunctival fornix but not from the cornea. No bacterial growth was obtained from either sampling site in 19 eyes. Overall, 31/56 (55%) corneal samples were positive and 37/56 (66%) conjunctival fornix samples were positive. Comparison of organisms isolated from the two collection sites of the same eye revealed an exact correlation in 42/56 (75%) eyes and differed in 14/56 (25%) eyes. Twenty different bacterial isolates were obtained from 68 positive samples. Gram‐positive (71%) organisms were more common than Gram‐negative (29%). The most commonly isolated organisms were Staphylococcus pseudintermedius (25%), beta‐hemolytic Streptococcus spp. (23%), and Pseudomonas aeruginosa (12%). Methicillin‐resistant organisms were isolated in 9% of samples.ConclusionSampling from the conjunctival fornix may be a suitable alternative to direct ulcer sampling in eyes with compromised corneal structural integrity.

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

“…These findings are generally in agreement with other canine studies across the globe ( 2 , 3 , 9 – 11 ), with subtle geographic differences such as a lower prevalence of Staphylococcus species in Australia ( 8 ) or a relatively higher prevalence of Streptococcus species in the Midwestern United States (present study) compared to other locations ( 6 , 7 ). Staphylococcus pseudintermedius was the most common Staphylococcus species (26.7% of all isolates), as recognized in most canine reports ( 2 , 3 , 7 , 10 , 11 ), followed by non-specified Coagulase-negative Staphylococcus species (3%) and Staphylococcus epidermidis (0.6%). Surprisingly, Staphylococcus aureus only accounted for 0.4% of isolates in the present study, while it had previously been reported as more prevalent in canine bacterial keratitis ( 6 , 9 ).…”

“…Surprisingly, Staphylococcus aureus only accounted for 0.4% of isolates in the present study, while it had previously been reported as more prevalent in canine bacterial keratitis ( 6 , 9 ). Streptococcus canis (12%) and Pseudomonas aeruginosa (7.5%) were the most common species cultured for each respective genus, consistent with previous reports ( 3 , 8 , 10 , 11 ).…”

“…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.…”

“…While there are distinct similarities between these regional investigations, there are notable differences in bacterial prevalence and susceptibilities across the world. Further, differences within separate geographic regions of even a single country ( 10 , 11 ) demonstrate that more targeted evaluation of local or regional populations is needed. Most previous reports in veterinary literature are limited to describing the prevalence of bacterial isolates and susceptibility profiles for individual antibiotics ( 6 , 7 , 10 ).…”

Bacterial isolates of indolent ulcers in 43 dogs

“…complex ulcers in dogs indicate Staphylococcus spp., St reptococcus spp., Pasteurella multocida, Pseudomonas aeruginosa, Corynebacterium spp., Neisseria spp., and Escherichia coli. 8 S pseudintermedius, beta-hemolytic Streptococcus spp., P aeruginosa, and methicillin-resistant Staphylococcus organisms were the most common. 8,10 Chronic ofloxacin use over a three-week period following cataract surgery has been described to result in a change in the predominant ocular bacterial population from S pseudintermedius to coagulase-negative Staphylococcus spp., an increase in resistance to ofloxacin, and an overall increase in bacterial load.…”