Septic keratitis in dogs, cats, and horses in Switzerland: associated bacteria and antibiotic susceptibility

An assessment of bacterial contamination of indirect ophthalmoscopes and condensing lenses used in clinical practice: A multi-center study

PURPOSE

To investigate bacterial contamination of indirect ophthalmoscopes and condensing lenses used in three UK veterinary referral centers, and the impact of an implemented cleaning protocol.

METHODS

Bacteriology samples from 10 indirect ophthalmoscopes and 10 condensing lenses were taken at each center (n = 30 T0), before initiating one of three cleaning frequencies (every 2 weeks/once weekly/daily) for 28 days. The most contaminated indirect ophthalmoscope and condensing lens from each center were re-sampled 30 min prior to (T1; n = 9) and 30 min after (T2; n = 9) the final clean. Sensitivity testing was completed using MIC.

RESULTS

Seventy-three isolates representing 15 different bacterial populations (genus/species) were cultured from 36 of 48 (75%) swabs tested. The most frequently cultured isolates were Staphylococcus spp. 30%, Micrococcus 22%, and Bacillus 14%. Pseudomonas aeruginosa, Pantoea, and Staphylococcus pseudintermedius demonstrated resistance to >50% of antibiotics against which they were tested. Eighty-three percent of T0 samples (54 isolates across 11 species, median 2 isolates/swab), all T1 samples (15 isolates across 8 species, median 2 isolates/swab), and 22% of T2 samples (4 isolates across 4 species, median 0 isolates/swab) were contaminated. Head contact points were most contaminated irrespective of time point. A T1 sample was 57 times more likely (95% CI: 2.4-1376) to have a positive culture than a T2 sample (p = .01).

CONCLUSIONS

Baseline contamination was high, representing a potential source of nosocomial infection in ophthalmic patients and handlers of diagnostic equipment. No center implemented a cleaning protocol prior to this study. Routine cleaning reduces bacterial contamination.

Progressive ulcerative keratitis in dogs in the United Kingdom: Microbial isolates, antimicrobial sensitivity, and resistance patterns

OBJECTIVES

The objective of the study was to identify bacterial pathogens and their antimicrobial sensitivity profile associated with cases of canine progressive ulcerative keratitis.

MATERIALS AND METHODS

Analysis of microbial culture and sensitivity results from dogs with progressive ulcerative keratitis presenting to a UK referral practice between December 2018 and August 2020.

RESULTS

Positive bacterial cultures were obtained from 80/148 (54%) of the canine ulcers sampled with 99 bacterial isolates cultured. Streptococcus canis (n = 29), Pseudomonas aeruginosa (n = 19), and Staphylococcus pseudintermedius (n = 16) were the most common isolates. Pseudomonas aeruginosa was more likely to be isolated whether the ulcer was clinically malacic at the time of sampling (OR = 10.1, p < .001). Ulcers treated prior to culture with fusidic acid were 7.6 times more likely to be positive than those treated with any other antimicrobial(s). Bacterial isolates demonstrated resistance against neomycin (85%), fusidic acid (78%), and tetracycline (68%). Conversely, isolates were most likely to be sensitive to gentamicin (88%), ofloxacin (77%), ciprofloxacin (73%), and chloramphenicol (64%). Antimicrobial combinations of chloramphenicol or gentamicin with a fluoroquinolone (ofloxacin or ciprofloxacin) or chloramphenicol combined with gentamicin were the most effective on in vitro analysis (over 90% susceptibility of all isolates).

CONCLUSION

The most common bacterial species associated with canine progressive ulcerative keratitis in a UK referral population were S. canis, P. aeruginosa, and S. pseudintermedius. Combination antimicrobial therapy is recommended pending culture and sensitivity results given the varied antimicrobial susceptibility profiles and significant bacterial in vitro resistance to antimicrobial monotherapy.

Prevalence and antibiotic resistance in bacterial isolates of dogs with ulcerative keratitis in São Paulo State, Brazil

OBJECTIVE

Identify microorganisms present in canine eyes affected by ulcerative keratitis and assess its resistance profile to available antimicrobial drugs.

METHODS

Samples were collected from 88 canine eyes that exhibited ulcerative keratitis. They were identified using MALDI-TOF and subjected to antimicrobial susceptibility testing by disk diffusion.

RESULTS

Among the assessed subjects, brachycephalic dogs accounted for 74.48% (50/83) of the evaluated canines. Among the 88 evaluated eyes, 90.9% (80/88) showed positive cultures, with 11.33% (10/88) of the samples isolating more than one species of bacteria. Of all bacterial isolates identified (90), Gram-positive bacteria accounted for 63.33% (57/90), while Gram-negative bacteria constituted 36.66% (33/90), with predominance of Staphylococcus spp. at 35.55% (32/90) being, Staphylococcus pseudintermedius at 68.75% (22/32), and Pseudomonas aeruginosa at 15.55% (14/90), respectively. Staphylococcus spp. exhibited resistance to penicillin (89.29%), sulfadiazine and trimethoprim (60.71%), and tetracycline (67.86%), while doxycycline (88.89%), cefotaxime (85.71%), chloramphenicol (82.14%), gentamicin, and moxifloxacin (78.57%) showed the highest sensitivity rates. Pseudomonas aeruginosa displayed sensitivity (100%) to gentamicin and imipenem, and resistance (8.33%) to norfloxacin, ciprofloxacin, and cefepime. Similarly, the Enterobacteriaceae family showed higher sensitivity to amikacin and gentamicin (88.89%), imipenem (88.24%), and levofloxacin (87.5%), with pronounced resistance to amoxicillin-clavulanate (50%) and cefazolin (47.06%). This highlights multiresistance in 23.33% (21/90) of the isolates.

CONCLUSIONS

The most isolated species in canine ulcerative keratitis are S. pseudintermedius and P. aeruginosa. However, other species were also isolated, demonstrating diversity in ocular microbiota infection. There is a high-rate multidrug resistance associated with canine ulcerative keratitis. Nevertheless, these strains exhibited sensitivity to antimicrobials commonly used in veterinary ophthalmology.

Equine ulcerative keratitis in the Netherlands (2012-2021): Bacterial and fungal isolates and antibiotic susceptibility

BACKGROUND

Ulcerative keratitis is a common ophthalmic disease in horses which can be complicated by microbial infection and requires immediate, accurate treatment to prevent loss of visual function or the eye.

OBJECTIVES

To report the results of microbial cultures, antibiotic susceptibility tests and corneal cytology in horses with ulcerative keratitis presented to a referral clinic, to assess agreement between cytology and culture results, to investigate whether previous topical treatment affected microbial culture results and whether the incidence of antimicrobial resistance changed during the study period.

STUDY DESIGN

Retrospective analysis.

METHODS

Case characteristics and results of cytology and microbial cultures were retrieved. Statistical analyses included descriptive statistics, χ2 or Fisher's exact test and McNemar test.

RESULTS

Samples for bacterial culturing (n = 187), fungal culturing (n = 153) and cytology (n = 153) were collected from 178 horses. Bacterial and fungal cultures were positive in 36% (n = 67) and 20% (n = 30), respectively. Staphylococcus (n = 35/67; 48%), Streptococcus (n = 12/67; 16%) and Aspergillus species (n = 22/30; 81%) were most frequently found. Microorganisms were observed in 14% of cytology samples (n = 22/153). Acquired antibiotic resistance was commonly observed amongst Streptococcus and Staphylococcus species. Acquired antibiotic resistance to gentamicin was more common in cases previously treated with gentamicin (p < 0.001). The incidence of acquired antibiotic resistance did not increase significantly between Cohort 2012-2017 and Cohort 2018-2021. Neither bacterial nor fungal culturing results were in agreement with cytology findings (p < 0.001 and p = 0.02, respectively). In 6 of 104 samples that were negative on fungal culturing, cytology revealed fungal elements.

MAIN LIMITATIONS

Due to the retrospective nature of this study, some case characteristics and test results were unavailable.

CONCLUSIONS

Acquired resistance was commonly observed amongst Streptococcus and Staphylococcus species, and in bacteria previously exposed to topical gentamicin. The incidence of acquired antibiotic resistance did not increase over time. When fungal cultures prove negative, cytology may have some added benefit in identifying keratomycosis.

Argon cold atmospheric plasma eradicates pathogens in vitro that are commonly associated with canine bacterial keratitis

Purpose

To investigate the antimicrobial effect of cold atmospheric plasma (CAP) on pathogens associated with canine bacterial keratitis.

Materials and methods

Pseudomonas aeruginosa, Staphylococcus pseudintermedius, and Streptococcus canis strains, which were obtained from dogs with infectious keratitis, were subjected to testing. For each species, four isolates and a reference strain were cultivated on Columbia sheep blood agar and treated with the kiNPen Vet® plasma pen from Neoplas GmbH, Greifswald, Germany. Various continuous treatment durations (0.5, 2, and 5 min) were applied, along with a 0.5-min treatment repeated four times at short intervals. These treatments were conducted at distances of 3 and 18 mm between the agar surface and the pen.

Results

CAP treatment reduced bacterial growth in all three species. The most effective treatment duration was 5 min at 3 mm distance, resulting in inhibition zones ranging from 19 to 22 mm for P. aeruginosa, 26-45 mm for S. pseudintermedius and an overall reduction of bacterial growth for Str. canis. Inhibition zones were smaller with decreasing treatment duration and larger distance. Treatment times of 30 s repeated four times and 2 min showed comparable results. Treatment with argon alone did not lead to visible reduction of bacterial growth.

Conclusion

Argon cold atmospheric plasma demonstrated a potent in vitro antimicrobial effect on P. aeruginosa, S. pseudintermedius and Str. canis strains with the latter showing the highest sensitivity.

Corneal stromal ulcerations in a referral population of dogs and cats in the Netherlands (2012-2019): Bacterial isolates and antibiotic resistance

OBJECTIVE

To evaluate bacterial isolates from corneal stromal ulcerations in dogs and cats in the Netherlands, review their antibiotic susceptibility, determine whether recent topical treatment affected bacterial culture results, and investigate whether (multi-drug) resistance patterns changed over time.

ANIMALS STUDIED

Client-owned dogs and cats were diagnosed with corneal stromal ulceration at the Utrecht University Clinic for Companion Animals between 2012 and 2019.

PROCEDURES

Retrospective analysis.

RESULTS

In total, 163 samples were collected from 122 dogs (130 samples) and 33 cats. Positive cultures were obtained from 76 canine and 13 feline samples (59% and 39%, respectively) and included Staphylococcus (42 in dogs, 8 in cats), Streptococcus (22 in dogs, 2 in cats), and Pseudomonas (9 in dogs, 1 in cats) species. Significantly fewer positive cultures were found in dogs and cats previously treated with topical antibiotics (χ2  = 6.52, p = .011 and χ2  = 4.27, p = .039, respectively). Bacterial resistance to chloramphenicol was more common in dogs previously treated with chloramphenicol (χ2  = 5.24, p = .022). The incidence of acquired antibiotic resistance did not increase significantly over time. In dogs, the incidence of multi-drug-resistant isolates increased significantly between 2012-2015 and 2016-2019 (9.4% vs. 38.6%, p = .0032).

CONCLUSIONS

Staphylococcus, Streptococcus, and Pseudomonas species were the most common bacteria associated with canine and feline corneal stromal ulcerations. Previous treatment with antibiotics affected bacterial culture results and antibiotic sensitivity. Although the overall incidence of acquired antibiotic resistance did not change over time, the incidence of multi-drug-resistant isolates in dogs increased over an 8-year period.

Evaluation of risk factors for treatment failure in canine patients undergoing photoactivated chromophore for keratitis - corneal cross-linking (PACK-CXL): a retrospective study using additive bayesian network analysis

BACKGROUND

Infectious keratitis is a common ophthalmic condition in canine patients. Sequelae can include keratomalacia and corneal perforation, a vision threatening outcome. Photoactivated chromophore for keratitis - corneal cross-linking (PACK-CXL) is a non-surgical, adjunctive treatment method for infectious keratitis. The goal of this retrospective, multicenter study was to determine risk factors for treatment failure following PACK-CXL in canine patients suffering from suspected infectious keratitis. Medical records from four veterinary ophthalmology services were reviewed, and information related to patient demographics, ophthalmic findings, the PACK-CXL protocol used, and epithelialization time was collected and analyzed. Due to the potential for intervariable relationships, an additive Bayesian network (ABN) analysis was performed to evaluate these complex relationships.

RESULTS

Records for 671 eyes (668 dogs) were included in the analysis. Based on the ABN, in the population included here, patients who underwent an accelerated PACK-CXL protocol were less likely to experience treatment failure versus patients treated with a slow protocol. Mutual dependencies between exposure variables were identified by ABN, which would have been overlooked using classical regression. Corneal re-epithelialization time was shortened following PACK-CXL combined with topical medical therapy compared to PACK-CXL alone.

CONCLUSIONS

No risk factors associated with treatment failure were identified in the population included in the present study. Canine patients may benefit from the use of accelerated PACK-CXL protocols, especially when combined with topical antibiotics and anti-collagenolytic therapy. The reasons for this apparent positive impact on treatment outcome remain unclear.

In Vitro Antimicrobial Activity of N-Acetylcysteine against Pathogens Most Commonly Associated with Infectious Keratitis in Dogs and Cats

To determine the in vitro antimicrobial activity of N-acetylcysteine (NAC) against common pathogens associated with infectious keratitis in dogs and cats, clinical isolates of Staphylococcus (S.) pseudintermedius (n = 20), Streptococcus (St.) canis (n = 10) and Pseudomonas (P.) aeruginosa (n = 7) of canine and feline infectious ulcerative keratitis and a quality control strain (P. aeruginosa DSM 19880) were tested. The minimal inhibitory concentration (MIC) of NAC concentrations was determined using microdilution methodology. For S. pseudintermedius and P. aeruginosa, NAC concentrations in the range of 1.56 mg/mL (0.156%) to 100 mg/mL (10%), and for St. canis, concentrations ranging from 0.195 mg/mL (0.0195%) to 6.25 mg/mL (0.625%) were tested. For S. pseudintermedius, the MIC was 3.12 mg/mL (0.312%) for all tested isolates. For P. aeruginosa isolates and the quality control strain, the MIC ranged from 3.12 mg/mL (0.312%) to 6.25 mg/mL (0.625%). For St. canis, the MIC ranged from 1.56 mg/mL (0.156%) to 3.12 mg/mL (0.312%). NAC has an in vitro antimicrobial activity against three bacterial species commonly found in infectious keratitis in dogs and cats and therefore may be a promising alternative or adjuvant to topical antibiotics. The results warrant a clinical pilot study to assess the potential of NAC to reduce or replace the use of topical antibiotics in line with the One Health approach.

An Update on the Ocular Surface Bacterial Microbiota in Small Animals

High-throughput sequencing (HTS) techniques have revolutionized the way we understand microbial communities in both research and clinical settings and are bringing new insights into what constitutes a healthy ocular surface (and a diseased one). As more diagnostic laboratories incorporate HTS into their technique repertoire, practitioners can expect this technology to become increasingly accessible for clinical practice, potentially becoming the new standard. However, particularly regarding ophthalmic microbiota, considerable research remains to render HTS accessible and applicable.

Susceptibility pattern of bacterial isolates in equine ulcerative keratitis: Implications for empirical treatment at a university teaching hospital in Sydney

Corneal ulceration is a common ophthalmic condition in horses. It is frequently caused by trauma to the corneal surface, followed by secondary infection by commensal or pathogenic organisms including Streptococcus equi subspecies zooepidemicus, Pseudomonas aeruginosa and Staphylococcus spp. Emerging antimicrobial resistance amongst these organisms has raised the need for appropriate antimicrobial therapy selection, to optimise treatment efficacy while minimising further antimicrobial resistance. Medical records of 38 horses presented at the University Veterinary Teaching Hospital Camden for ulcerative keratitis between 2010 and 2020 were reviewed to identify those with positive bacterial cultures and antimicrobial susceptibility profiles (13/38). Common susceptibility patterns were identified and used to guide the empirical treatment of equine bacterial corneal ulcers. Pseudomonas spp. (64.3%), Streptococcus equi subspecies zooepidemicus (14.3%) and Actinobacillus spp. (14.3%) were most commonly identified. Susceptibility to amikacin, gentamicin and ciprofloxacin was observed in 100%, 66.7% and 85.7% Pseudomonas spp. isolates respectively. Resistance to polymyxin B and neomycin occurred in 85.7% and 71.4% of Pseudomonas spp., respectively. All Streptococcus equi subspecies zooepidemicus organisms in this study were susceptible to ceftiofur, cephalexin, penicillin and ampicillin, while they were all resistant to gentamicin, neomycin, enrofloxacin and marbofloxacin. Predominating in this study, Pseudomonas spp. maintained overall aminoglycoside susceptibility despite some emerging resistance, and good fluoroquinolone susceptibility. High resistance to Polymyxin B could have arisen from its common use as first-line therapy for bacterial corneal ulcers. Although further research is required, these new findings about predominant bacteria in equine corneal ulceration in the Camden region and their antimicrobial susceptibility patterns can be used to guide the empirical treatment of bacterial corneal ulcers in horses.

Antibiotic Recommendations for Treatment of Canine Stromal Corneal Ulcers

The aim of the study was to identify the aerobic bacterial isolates and determine corresponding antibiotic susceptibility profiles in vitro in canine clinical specimens with stromal corneal ulcers, with the goal of providing recommendations for first-line treatment with antibiotics. A total of 198 canine corneal stromal ulcer samples were studied between 2018 and 2021. A corneal swab was collected and cultured under aerobic conditions. Bacterial organisms were identified at the species level by MALDI-TOF mass spectrometry. Antibiotic susceptibility testing for commonly used topical and systemic antibiotics was performed by disk diffusion. Bacterial growth was obtained from 80% of samples. A variety of bacterial species were identified wherein the most common specimens were represented by Staphylococcus pseudintermedius (22%), Staphylococcus epidermidis (12%), Staphylococcus capitis (11%), and Pseudomonas aeruginosa (10%). Based on the overall antibiotic susceptibility data, neopolybac alone (96%) or a combination of neopolybac with either ofloxacin or amikacin (each 99%) showed the best coverage for commonly isolated bacterial organisms from canine corneal stromal ulcers. Results of this study support the use of the combined antibiotics as the first-line response for the treatment of canine corneal stromal ulcers. A statically significant increase in acquired bacterial resistance was detected during the longitudinal data observation.

Evaluation of conjunctival graft procedures and factors that lead to graft complications in canine cases

PURPOSE

To describe the complications of conjunctival graft surgery occurring in cases at a referral ophthalmic service and evaluate factors that lead to occurrence of complications in canine cases.

METHODS

A retrospective case-control study was completed using data from the Veterinary Medical Center at the Western College of Veterinary Medicine, Saskatoon, Canada, between May 2015 and March 2020. Case records from dogs that underwent conjunctival pedicle graft surgery and subsequently either did or did not develop a conjunctival graft complication were reviewed.

RESULTS

One hundred and six dogs undergoing conjunctival graft surgeries were identified. Sixteen conjunctival graft complications occurred, of which, eight led to negative outcomes. Univariable analysis comparing canine eyes that developed complications to control eyes revealed potential (p ≤ .05) differences between the groups in post-operative fluoroquinolone use, Streptococcus canis isolation, intraoperative intravenous cefazolin use, corneal stromal white cell infiltrate, and mean ulcer diameter. The use of intraoperative cefazolin could not be effectively evaluated with available data; however, no dogs (n = 22) receiving intraoperative cefazolin developed complications. Multivariable analysis revealed that dogs that were treated with a second-generation fluoroquinolone and that had S. canis isolated had higher odds of experiencing complications than dogs that were not treated with a second-generation fluoroquinolone and that were S. canis negative (Odds ratio = 64.7 [95% CI 6.3-669], p < .0001).

CONCLUSIONS

Streptococcus species played a role in conjunctival graft complications in our study. Empiric selection of second-generation fluoroquinolone monotherapy may need reconsideration given the frequent isolation of Streptococcus spp. from canine ulcers. The use of intraoperative cefazolin may be associated with a lower complication rate.

Impact of multi-drug resistance on clinical outcomes of dogs with corneal ulcers infected with Staphylococcus pseudintermedius

Objective

Compare characteristics and clinical outcomes of dogs with infectious keratitis from Staphylococcus pseudintermedius considered to be multidrug-resistant (MDR) or not.

Procedures

Staphylococcus pseudintermedius isolated as the primary pathogen from canine patients with ulcerative keratitis were considered MDR if resistant to at least one agent in three or more classes of antibiotics. Medical records were reviewed for history, patients' characteristics, clinical appearance, therapeutic interventions, and clinical outcomes.

Results

Twenty-eight dogs (28 eyes) were included. Compared to non-MDR cases, MDR diagnosis was significantly more common in dogs with recent (≤30 days) anesthesia (7/15 vs. 1/13, P = 0.038) and more common in non-brachycephalic dogs (8/15 vs. 2/13, P = 0.055). Clinical appearance (ulcer size/depth, anterior chamber reaction, etc.) did not differ significantly between groups (P ≥ 0.055). Median (range) time to re-epithelialization was longer in MDR vs. non-MDR eyes [29 (10-47) vs. 22 (7-42) days] but the difference was not significant (P = 0.301). Follow-up time was significantly longer in dogs with MDR keratitis [47 (29-590) vs. 29 (13-148) days, P = 0.009]. No other significant differences were noted between MDR and non-MDR eyes in regard to time for ulcer stabilization [4 (1-17) days vs. 4 (1-12), P = 0.699], number of eyes requiring surgical stabilization (7/15 vs. 7/13, P = 0.246) or enucleation (1/15 vs. 2/13, P = 1.000), success in maintaining globe (14/15 vs. 11/13, P = 0.583) or success in maintaining vision (12/15 vs. 10/13, P = 1.000).

Conclusions

MDR infections may prolong corneal healing time but did not appear to affect overall clinical outcomes in dogs with bacterial keratitis. Further research is warranted in a larger canine population and other bacterial species.

An eye on the Shih Tzu dog: Ophthalmic examination findings and ocular surface diagnostics

OBJECTIVE

To characterize the ocular surface parameters and determine the prevalence of ocular pathology in Shih Tzu dogs.

ANIMAL STUDIED

Fifty Shih Tzu dogs (28 male, 22 female).

PROCEDURES

Each dog underwent a complete ophthalmic examination (recording any pathology) and a series of diagnostics, allowing for a 10 min-interval between tests: intraocular pressure (IOP), blink rate, palpebral fissure length (PFL), corneal tactile sensation (CTS), Schirmer tear test, and nasolacrimal reflex without (STT-1, NL-STT1) and with topical anesthesia (STT-2, NL-STT2), tear ferning, strip meniscometry test (SMT), tear film breakup time (TFBUT), and punctate fluorescein staining (PFS) of the cornea.

RESULTS

Mean ± SD test values were as follows: IOP (17.9 ± 3.7 mmHg), blink rate (2.4 ± 1.4 blinks/min), PFL (23.8 ± 1.8 mm), CTS (1.8 ± 0.7 cm), STT-1 (22.0 ± 5.5 mm/min), NL-STT1 (24.2 ± 4.7 mm/min), STT-2 (16.9 ± 6.5 mm/min), NL-STT2 (18.5 ± 7.5 mm/min), SMT (7.5 ± 3.5 mm/5 s), TFBUT (5.3 ± 2.4 s), tear ferning (1.3 ± 0.7), and PFS (1.6 ± 0.6). PFL was significantly greater in male vs. female Shih Tzus (p< .001). Age was negatively correlated with TFBUT results (r = -0.31, p = .027). Lagophthalmos was observed in 82% eyes. Ocular surface pathology was common, including adnexal abnormalities (100% eyes with caruncular trichiasis and medial lower lid entropion) and corneal opacification (27% pigmentation, 20% fibrosis, 12% neovascularization).

CONCLUSIONS

Qualitative tear film deficiency (low TFBUT), along with several anatomical abnormalities that promote ocular irritation and reduce globe protection, together help explain the concerningly high prevalence of ocular surface disease in the Shih Tzu breed. Prophylactic measures (e.g., medial canthoplasty, topical lubrication) could be considered to improve ocular health in Shih Tzus.

Bacterial Prevalence in Skin, Urine, Diarrheal Stool, and Respiratory Samples from Dogs

The emergence of bacterial infections in companion animals is a growing concern as humans can also be infected through the transmission of pathogenic bacteria. Because there have been few studies conducted on companion animals, the extent and significance of prevalence in veterinary practices remain unknown. This is the first nationwide surveillance report aimed at elucidating the prevalence pattern and associated infections of isolated bacteria from dogs in Korea. Bacterial isolates were collected from seven different laboratories participating in the Korean Veterinary Antimicrobial Resistance Monitoring System from 2018 to 2019. The samples were obtained from the diarrheal stool, skin/ear, urine, and respiratory samples of veterinary hospital-visited dogs. Isolation and identification of bacterial species was carried out using a bacterial culture approach and then confirmed with matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry (MALDI-TOF) and polymerase chain reaction (PCR). Out of 3135 isolates in dogs, 1085, 1761, 171, and 118 were extracted from diarrheal stool, skin/ear, urine, and respiratory samples, respectively. The overall prevalence of bacteria was higher among two age groups (1-5 and 6-10 years) with a 66.5 percent prevalence. This study showed that Escherichia coli was the most prevalent species among isolated bacterial species of diarrheal and urine origin, whereas Staphylococcus pseudintermedius was the most prevalent among skin and respiratory sample isolates. The data on the prevalence of bacteria for each dog specimen could provide basic information to estimate the extent of bacterial infection and antimicrobial resistance development and to guide veterinarians in therapeutic decisions in clinical practices throughout Korea.

The bactericidal effect of two photoactivated chromophore for keratitis-corneal crosslinking protocols (standard vs. accelerated) on bacterial isolates associated with infectious keratitis in companion animals

Background

Bacterial corneal infections are common and potentially blinding diseases in all species. As antibiotic resistance is a growing concern, alternative treatment methods are an important focus of research. Photoactivated chromophore for keratitis-corneal crosslinking (PACK-CXL) is a promising oxygen radical-mediated alternative to antibiotic treatment. The main goal of this study was to assess the anti-bactericidal efficacy on clinical bacterial isolates of the current standard and an accelerated PACK-CXL treatment protocol delivering the same energy dose (5.4 J/cm²).

Methods

Clinical bacterial isolates from 11 dogs, five horses, one cat and one guinea pig were cultured, brought into suspension with 0.1% riboflavin and subsequently irradiated. Irradiation was performed with a 365 nm UVA light source for 30 min at 3mW/cm² (standard protocol) or for 5 min at 18mW/cm² (accelerated protocol), respectively. After treatment, the samples were cultured and colony forming units (CFU’s) were counted and the weighted average mean of CFU’s per μl was calculated. Results were statistically compared between treated and control samples using a linear mixed effects model.

Results

Both PACK-CXL protocols demonstrated a significant bactericidal effect on all tested isolates when compared to untreated controls. No efficacy difference between the two PACK-CXL protocols was observed.

Conclusion

The accelerated PACK-CXL protocol can be recommended for empirical use in the treatment of bacterial corneal infections in veterinary patients while awaiting culture results. This will facilitate immediate treatment, the delivery of higher fluence PACK-CXL treatment within a reasonable time, and minimize the required anesthetic time or even obviate the need for general anesthesia.

Antibiotic resistance, biofilm formation, and virulence factors of isolates of staphylococcus pseudintermedius from healthy dogs and dogs with keratitis

Canine bacterial keratitis is a common infection that can potentially threaten vision. Staphylococcus pseudintermedius (S. pseudintermedius) is an opportunistic pathogen that has been isolated from the canine conjunctival sac but there are only a few reports on the role of this bacterium in canine keratitis. This study focused on the distribution rate of S. pseudintermedius in the canine conjunctival sac, and the antibiotic resistance, biofilm-producing ability, and dissemination of virulence factors in strains of S. pseudintermedius isolated from healthy dogs and dogs with keratitis. The study included 35 healthy dogs and 40 dogs with keratitis. Bacterial species were confirmed by matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI–TOF MS). Strains of S. pseudintermedius were screened for resistance against nine different antibiotics by the Kirby–Bauer assay. The ability to produce biofilm was investigated by microtiter plate assay (MtP) and amplification of icaA and icaD genes. Virulence factors in the strains were also evaluated. A total of 132 aerobic bacteria were isolated from the 119 samples in the study. Among them, 67 bacterial strains were isolated from 70 eyes of healthy dogs, and 65 bacterial strains were isolated from 49 eyes of dogs with keratitis. The prevalence of S. pseudintermedius, which was the most frequent bacterial isolate in both the groups, was 20.9% in the healthy group and 23.08% in the keratitis group. Most of the isolates of S. pseudintermedius were sensitive to rifampin (96.6%), oxacillin (100%), and neomycin (96.6%), and resistant to tetracycline (96.6%). Virulence factors such as lip (96.6%), hlgB (96.6%), and hlgA (96.6%) were found in most of the isolates, and 89.66% of isolates were classed as biofilm producers. In conclusion, S. pseudintermedius was the common bacterium in the conjunctivital sac of the healthy dogs and dogs with keratitis in Yangzhou, China, and the presence of virulence factors and biofilm-formation ability were high in the strains isolated from the dogs with keratitis.

Case Report: The First Report on Moraxella canis Isolation From Corneal Ulcer in a Bulldog

A 5-year-old castrated male bulldog was diagnosed with a corneal ulcer accompanied by edema and conjunctival hyperemia. Ophthalmic examination and microbiological analysis were performed, and the bacteria were found to be gram-negative and globular. The isolated clone was identified as Moraxella canis (MZ579539) via MALDI-TOF MS and 16S rDNA sequencing. Antimicrobial susceptibility testing showed that the bacteria were sensitive to tetracycline and chloramphenicol, but resistant to levofloxacin and ciprofloxacin. After a conjunctival flap was placed, tobramycin ophthalmic solution and 5% sodium hyaluronate were administered. Following surgery, the ulcer was effectively controlled, and after 3 weeks, the cornea healed. This is the first case report of a canine corneal ulcer associated with M. canis, which should be considered when corneal ulceration or keratitis were suspected.

MCC950 attenuates inflammation-mediated damage in canines with Staphylococcus pseudintermedius keratitis by inhibiting the NLRP3 inflammasome

BACKGROUND

Bacterial keratitis is a common eye disease in dogs and can seriously affect vision. This study investigated the anti-inflammatory effect of MCC950 in the cornea of canines infected with Staphylococcus pseudintermedius (S. pseudintermedius).

METHODS

In vitro, canine cornea epithelial cells were pretreated with MCC950 and PDTC and then infected with S. pseudintermedius. The key proteins of the NF-κB pathway and NLRP3 inflammasome were detected by Western blotting, the levels of inflammatory factors were detected by qPCR, and the levels of MDA and LDH were detected by assay kit. In vivo, the canine keratitis model was established by injecting S. pseudintermedius into the corneal stroma layer. After treatment with MCC950, slit-lamp examinations were performed. Cornea tissue protein and RNA were extracted, and Western blotting was used to detect key proteins of the NF-κB pathway and NLRP3 inflammasome. qPCR was used to detect the inflammatory factors. Paraffin sections of corneal tissue were prepared for HE staining and immunohistochemical staining.

RESULTS

After MCC950 treatment, the expression levels of key proteins in the NF-κB pathway and NLRP3 inflammasome in canine cornea epithelial cells and corneal tissues were decreased, and the expression levels of IL-1β, IL-6, IL-8, IL-18 and TNF-α were reduced. Cellular MDA and LDH levels were decreased. In vivo, the degree of corneal opacity, edema, neovascularization and corneal injury area decreased after MCC950 treatment. Canine corneal sections showed that MCC950 attenuated neutrophil infiltration.

CONCLUSION

MCC950 alleviates the inflammatory response to canine keratitis caused by S. pseudintermedius by inhibiting the activation of the NLRP3 inflammasome.

Equine ulcerative keratitis in Belgium: Associated bacterial isolates and in vitro antimicrobial resistance in 200 eyes

PURPOSE

To describe bacterial isolates and associated antibiotic resistance from horses with ulcerative keratitis in Belgium.

METHODS

Medical records from horses with ulcerative keratitis presented to the ophthalmology service of the Veterinary teaching hospital of Liege, Belgium, between 2014 and 2021 were evaluated. Bacterial isolates were identified and VITEK^® 2 (Biomérieux) provided antimicrobial susceptibility testing and resistance detection.

RESULTS

Two hundred eyes of 196 horses were sampled. Ninety-seven eyes had a positive bacterial culture (48.5%) and 139 bacterial isolates were identified. Staphylococcus (63/139: 45.3%) and Streptococcus (33/139: 23.7%) were the most frequent genus isolated. Staphylococcus aureus (21/139: 15.1%) was the most frequent species isolated of which half were methicillin-resistant (MRS). Streptococcus equi subsp. zooepidemicus (19/139: 13.7%) was the second most identified bacterial isolate. Only two Pseudomonas species were isolated (2/139: 1.4%). The overall resistance of all bacterial isolates against chloramphenicol (12.4%) and fluoroquinolones (14.3%) was low. Resistance against tobramycin, polymyxin B, gentamicin, fusidic acid, tetracycline, and neomycin ranged from 40.8% to 58.6%. When separating the MRS from the other staphylococci, a significant difference was noted in percentage of resistance to gentamicin (p = .00026) and tetracycline (p = .00015). MRS were highly resistant to gentamicin (75%) and tetracycline (100%), whereas the remaining staphylococci were significantly less resistant to gentamicin (17%) and tetracycline (40.4%).

CONCLUSION

Although Pseudomonas species has been rarely cultured, our results are roughly consistent with previous studies. Multiple drug resistance was high and resistance to first-choice antibiotics in ulcerative keratitis was noted. These results warrant continued monitoring of susceptibility profile.

Albumin in Tears Modulates Bacterial Susceptibility to Topical Antibiotics in Ophthalmology

Bacterial keratitis is a serious and vision-threatening condition in veterinary and human patients, one that often requires culture and susceptibility testing to adjust therapy and improve clinical outcomes. The present study challenges the antimicrobial susceptibility testing (AST) paradigm in ophthalmology, enabling more accurate in vitro-to-in vivo translation by incorporating factors normally present during host-pathogen interactions in clinical patients. Thirty bacteria (10 Staphylococcus pseudintermedius, 10 Streptococcus canis, 10 Pseudomonas aeruginosa) were isolated from canine patients with infectious keratitis. For each isolate, commercial plates (Sensititre™ JOEYE2) were used to assess the minimal inhibitory concentration (MIC) of 17 different antibiotics in the absence (0% albumin, control) or presence of canine albumin (0.01–2%). For Staphylococcus pseudintermedius, the experiment was repeated with actual tear fluid collected from canine eyes with ocular surface inflammation. Kruskal-Wallis, Wilcoxon signed rank test and Spearman's correlation tests were used for statistical analysis. Clinical outcomes were unfavorable in selected canine patients with bacterial keratitis (e.g., globe perforation, graft dehiscence) despite standard AST (i.e., 0% albumin in test medium) confirming that most corneal infections (93%) were susceptible to ≥1 topical antibiotics used at the initial visit. Albumin levels ≥0.05% increased MICs in a dose-dependent, bacteria-specific, and antibiotic-specific manner. No significant differences (P = 1.000) were noted in MICs of any antibiotic whether albumin or tear fluid was added to the Mueller-Hinton broth. Percent protein binding inherent to each antibiotic was associated with clinical interpretations (Spearman's rho = −0.53, P = 0.034) but not changes in MICs. Albumin in tears impacted the efficacy of selected ophthalmic antibiotics as only the unbound portion of an antibiotic is microbiologically active. The present findings could improve decision making of clinicians managing bacterial keratitis, reduce development of antimicrobial resistance, influence current guidelines set by the Clinical and Laboratory Standards Institute, and serve as a reference for bacteriological evaluations across medical fields and across species.

Comparison of antimicrobial resistance patterns in dogs with bacterial keratitis presented to a veterinary teaching hospital over two multi-year time periods (1993-2003 and 2013-2019) in the Southeastern United States

OBJECTIVE

To report clinical characteristics of dogs with bacterial keratitis, identify the most common bacterial isolates within this population, characterize the bacterial isolates' antimicrobial resistance patterns, and compare those resistance patterns to previously reported resistance patterns.

ANIMAL STUDIED

Dogs diagnosed with bacterial keratitis between 2013 and 2019.

PROCEDURES

Data pertaining to breed; Schirmer tear test I results; use of cyclosporine, tacrolimus, or corticosteroids at time of ulcer diagnosis; bacterial genus or species isolated; and resistance to selected antimicrobials as measured by Kirby-Bauer disk diffusion were collected. Resistance patterns were compared to those reported by Tolar et al. (2006).

RESULTS

One hundred seventy bacterial isolates were cultured from 138 eyes from 130 dogs. Of these dogs, 45% were brachycephalic, 62% had STT <15 mm/min, and 28% were receiving a corticosteroid at the time of examination. The most common isolates were Staphylococcus pseudintermedius (31%), β-hemolytic Streptococcus spp. (28%), and Pseudomonas aeruginosa (18%). Compared to the 1993-2003 study period, there were significant increases in resistance to cephalothin and polymyxin B among S. pseudintermedius isolates. β-hemolytic Streptococcus spp. and P. aeruginosa isolates had no significant changes in resistance to the tested antimicrobials.

CONCLUSION

Isolates of S. pseudintermedius, β-hemolytic Streptococcus spp., and P. aeruginosa had minimal changes in resistance between the two study periods. In this population, monotherapy with ciprofloxacin or combination therapy of tobramycin and a first-generation cephalosporin continue to be appropriate for use in cases of suspected bacterial keratitis while awaiting results of susceptibility testing.

Melting corneal ulcers (keratomalacia) in dogs: A 5-year clinical and microbiological study (2014-2018)

OBJECTIVES

To identify bacterial microorganisms associated with canine keratomalacia, review their antimicrobial sensitivity, and evaluate clinical outcomes compared to results of microbial culture.

METHODS

Retrospective analysis of clinical records of dogs diagnosed with a melting corneal ulcer presented to a referral hospital in Hertfordshire, UK between 2014 and 2018.

RESULTS

One hundred and ten melting corneal ulcers were sampled in 106 dogs. The most common pure bacterial isolate was Pseudomonas aeruginosa (n = 26) followed by β-hemolytic Streptococcus (n = 12). Melting corneal ulcers that cultured coagulase-positive Staphylococcus, coliform bacteria, Pasteurella multocida, Enterococcus, and Streptococcus viridans presented in smaller numbers and were analyzed together (n = 16). Multiple cultures were identified in nine cases (n = 9). Forty-seven cultures yielded no bacterial growth (n = 47). The susceptibility to fluoroquinolones remained high with the exception of β-hemolytic Streptococci. There was no significant difference in the ulcer severity at presentation in regard to the cultured bacteria. Overall, 63 eyes (57%) received surgical grafting in addition to medical treatment. In 14 cases (13%), the progression of corneal melting despite medical ± surgical treatment resulted in enucleation. Fifty-seven percent (8/14) of the enucleated eyes cultured pure Pseudomonas aeruginosa isolates. In contrast, all β-hemolytic Streptococcus-associated ulcers healed.

CONCLUSIONS

The most common bacterial species associated with canine keratomalacia were Pseudomonas aeruginosa and β-hemolytic Streptococcus. Because of the variation in antibacterial sensitivity between these two species, bacterial culture and sensitivity testing should be performed in all dogs presenting with keratomalacia. Melting corneal ulcers associated with pure Pseudomonas infection were significantly more likely to result in globe loss than melting corneal ulcers associated with other cultures.

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

The objective of this study was to describe bacterial culture and antibiotic susceptibility results in 476 dogs presenting with suspected bacterial keratitis in Iowa and surrounding Midwestern states, further detailing trends in patient characteristics, seasonality, and antimicrobial resistance. Corneal swabs yielded 465 bacterial isolates and 220 cultures (46.2%) with no apparent growth (0–5 isolates per culture). The most frequent bacterial genera were Staphylococcus (32.3%), Streptococcus (19.1%), and Pseudomonas (12.5%), while the most common bacterial species were Staphylococcus pseudintermedius (26.7%), Streptococcus canis (12%), and Pseudomonas aeruginosa (7.5%). Compared to mixed-breed dogs, canine breeds most likely to be examined for ulcerative keratitis included Boston terrier, Cavalier King Charles spaniel, miniature pinscher, pug, rat terrier, Saint Bernard, shih tzu, and silky terriers. In summer, the likelihood to yield a negative culture was reduced while the likelihood to culture Pseudomonas species was increased. Bacteria considered multidrug resistant (MDR, resistant to ≥ 3 antibiotic classes) represented 20% of all canine isolates and were most prevalent for Staphylococcus species (33%). An alarming, escalating trend of MDR prevalence was noted between 2016 (5%) and 2020 (34%). Individual ophthalmic preparations (i.e., single antibiotics or commercially available antibiotic combinations) with highest efficacy against all bacterial isolates included chloramphenicol (83%), ceftiofur (79%), amikacin (77%), neomycin-polymyxin B-bacitracin (77%), and gentamicin (74%). Efficacy of systemic antibiotics and combinations of ophthalmic preparations was also evaluated. Based on the present findings, triple antibiotic (Neo-Poly-Bac) is recommended as empirical monotherapy for prophylactic antibiotic therapy in dogs with simple corneal ulcers, while a chloramphenicol-ciprofloxacin combination is empirically recommended for therapeutic management of infected corneal ulcers. Pending culture and susceptibility results, appropriate selection of empiric antibiotic therapy is important to enhance therapeutic outcome and reduce antibacterial resistance in dogs with corneal ulceration.

Bacterial isolates of indolent ulcers in 43 dogs

PURPOSE

To determine whether bacteria are isolated from canine indolent ulcers and evaluate their influence on clinical outcomes.

METHODS

Swabs for anaerobic and aerobic culture were collected from indolent ulcers of 43 client-owned dogs presenting to the University of Saskatchewan Veterinary Medical Centre. Outcomes were compared between ulcers with bacterial isolates and those without. Medical therapy was reviewed.

RESULTS

Bacteria were isolated in 8/43 ulcers: Three cultured two isolates and five cultured single isolates. Staphylococcus was the most common genus isolated and was present in six ulcers: Species included unspecified [2], pseudintermedius [2], schleiferi [1], and hominis [1]. Streptococcus was the second most common isolate present in two ulcers: Species included canis and agalactiae. Tobramycin was the most common antibiotic used in ulcers with bacterial isolates prior to referral (n = 3). One case did not have conclusive follow-up data from the referring veterinarian and was therefore excluded from further analysis. All seven culture-positive ulcers were recorded as healed without complication: six healing after one procedure and one healing after two procedures. Thirty-five ulcers were culture-negative. There was no difference in outcome between indolent ulcers with bacterial isolates and those with negative cultures (P = .7475).

CONCLUSIONS

Bacteria were isolated from 19% of indolent ulcers, and Staphylococcus was the most common isolate. Bacterial isolation did not influence outcome.

Changes in antimicrobial resistance patterns of ocular surface bacteria isolated from horses in the UK: An eight-year surveillance study (2012-2019)

PURPOSE

To identify temporal changes in antimicrobial resistance of ocular surface bacteria isolated from clinically symptomatic equine eyes in the South West of the UK.

STUDY DESIGN

Retrospective.

METHODS

Clinical and laboratory records of horses treated for suspected bacterial ocular surface disease (ulcerative and non-ulcerative) at a single facility between January 2011 and December 2019 were reviewed. Cases were included if they underwent ocular surface sampling, aerobic bacterial culture, and antimicrobial susceptibility testing. Cases were split into two time periods based on when sampling occurred: "early" (2012-2015) and "late" (2016-2019) to enable identification of temporal trends in resistance to chloramphenicol, gentamicin, fusidic acid, neomycin, cloxacillin, ofloxacin, and polymyxin B.

RESULTS

A total of 125 samples from 110 horses were included in analyses. Culture-positive isolates were identified in 76/110 (60.8%) samples. Principal isolates included Staphylococci spp. (n = 45; 64.3%), Streptococci spp. (n = 14; 20%), and Enterobacter spp. (n = 11; 15.7%). There was a significant increase in resistance to chloramphenicol over time (P = .007) and a decrease in resistance to ofloxacin that approached significance (P = .059). Chloramphenicol (100%) and gentamicin (85.7%) had the highest overall in-vitro efficacy during the early and late periods, respectively. There was no significant difference in the type of bacteria isolated across the two time periods.

CONCLUSIONS

These results suggest a potential increase in resistance to chloramphenicol among bacteria isolated from the ocular surface of horses in the South West UK, reinforcing the value of surveillance to guide the empirical use of antimicrobials.

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

OBJECTIVES

To identify the minimum inhibitory concentration (MIC) distribution for commonly used topical antibiotics from isolates of dogs and horses with ulcerative bacterial keratitis, and to investigate changes in MIC values over time and following treatment with topical fluoroquinolones.

ANIMALS STUDIED

One hundred thirty-four client-owned dogs and 20 client-owned horses with bacterial ulcerative keratitis.

PROCEDURE

Minimum inhibitory concentration values for 14 topical antibiotics were reported for canine and equine cases of bacterial ulcerative keratitis between 2013 and 2018. Changes in MIC values over time and after treatment with topical fluoroquinolones were reported.

RESULTS

The three most common bacterial genera isolated were Staphylococcus, Streptococcus, and Pseudomonas. Together, these represented 79.4% of canine cases and 77.4% of equine cases. Overall, isolates from horses tended to have lower MIC values, as did Pseudomonas isolates from both dogs and horses, compared to other bacterial genera, especially Staphylococcus spp. The MIC values of erythromycin and trimethoprim sulfa for Staphylococcus spp., and the MIC value of moxifloxacin for Pseudomonas significantly increased over time. Previous topical fluoroquinolone use was associated with a significant increase in the MIC value of ofloxacin in canine and equine Staphylococcus isolates and current topical fluoroquinolone use was associated with significant increases in the MIC values of ciprofloxacin, moxifloxacin, and ofloxacin in canine Staphylococcus isolates.

CONCLUSION

Patients previously or currently treated with topical fluoroquinolones, particularly in Staphylococcus infections, may require alternative antibiotics or additional antibiotic classes other than fluoroquinolones. Bacterial culture with MIC susceptibility testing should be highly recommended when a Staphylococcal infection is suspected.

Outcome of medical therapy for keratomalacia in dogs

OBJECTIVES

To evaluate the clinical and visual outcomes following intensive medical therapy for keratomalacia in dogs.

MATERIALS AND METHODS

Medical records were screened to identify dogs with corneal ulcers and keratomalacia. All patients were given the same topical treatment protocol with frequent administrations of tobramycin in combination with equine serum. Surgical treatment during the first 15 days of follow-up was considered as medical treatment failure.

RESULTS

We report on 57 ulcers with keratomalacia from 53 dogs. Medical treatment was successful in 31 of 57 ulcers with a median healing time of 5 days (range 2 to 15 days). At 60 days after epithelialisation, 14/15 medically-treated eyes were visual. In one case, corneal perforation was observed 1 month after healing and required surgical stabilisation.

CLINICAL SIGNIFICANCE

Intensive medical therapy has the potential to achieve healing of some ulcers with keratomalacia. Surgical stabilisation in response to progression of stromal loss was required in less than half of the cases.

Characterization of the normal equine conjunctival bacterial community using culture-independent methods

BACKGROUND

The equine conjunctival microbiota has often been reported to be dominated by Gram-positive species such as Staphylococcus sp., Bacillus sp., and Corynebacterium sp. However, traditional culture-based methods can only recover a fraction of the bacterial species present in the sample.

OBJECTIVES

This pilot study aimed at exploring the diversity of the equine conjunctival microbiota using culture-independent methods.

STUDY DESIGN

Eight horses were included in this study, and only eyes with normal ophthalmic examination (n = 15 eyes) were sampled.

METHODS

Conjunctival biopsies (culture-independent) were collected, and DNA was extracted from the tissues. Bacterial communities in conjunctival biopsies were characterized by next-generation sequencing of the 16S rRNA genes. Individual reads were ascribed to operational taxonomic units (OTUs) using BLASTn and Greengenes databases. Species richness, evenness, and Good's coverage were determined for each conjunctiva-associated microbial community.

RESULTS

Culture-independent samples produced a total of 329 bacterial OTUs. The main OTUs identified in the study belonged to the Gram-negative species Ralstonia mannitolilytica (88.0%), Nicoletella semolina (3.3%), and Pseudomonas tolaasii (1.5%).

CONCLUSIONS

Contrary to previously published data based on culture-dependent methods, the horse eye microbial community was dominated by Gram-negative bacteria of the phylum Proteobacteria.

Streptococcus canis multilocus sequence typing in a case series of dogs with ulcerative keratitis

OBJECTIVE

To determine whether four isolates of Streptococcus canis (S canis) recovered from dogs diagnosed with ulcerative keratitis at the Animal Health Trust (AHT) were genetically related to other ocular isolates that are registered in the online database.

ANIMAL STUDIED

Four S canis corneal isolates.

PROCEDURES

Clinical and laboratory records between 2016 and 2017 were searched for dogs with ulcerative keratitis for which microbiology analysis was consistent with the growth of S canis. Genomic DNA was extracted for sequencing (Illumina MiSeq), and multilocus sequence types (STs) were determined using MLST 1.8 relative to the 44 sequence types of S canis available. A neighbor-joining tree was constructed in MEGA v4.0. A two-sided Fisher's exact test was used to determine any associations between the isolated strains and ocular infections of dogs.

RESULTS

Four strains were isolated from pugs (cases 1-4) with ulcerative keratitis. Genome sequencing identified ST-27 (case 1), ST-9 (case 3), and ST-13 (cases 2 and 4). STs 13 and 27 are members of Clonal Complex (CC)-13. Analysis of the multilocus sequence typing database revealed that CC-13 strains accounted for six of the twelve isolates recovered from the eye exudates of dogs (P = .0078).

CONCLUSIONS

There is early evidence that the CC-13 group of S canis is associated with ocular infections in dogs. We provide draft genome sequences toward the future identification of virulence mechanisms associated with streptococcal keratitis in dogs.

Equine infectious keratitis in Finland: Associated microbial isolates and susceptibility profiles

OBJECTIVE

To retrospectively describe laboratory findings, treatment, and outcome associated with equine infectious keratitis in Finland.

ANIMALS AND PROCEDURES

Medical records of horses diagnosed with infectious keratitis in University of Helsinki Equine Hospital from January 2007 to June 2018 were reviewed.

RESULTS

Forty-seven cases were included. Keratomycosis was diagnosed in 27 eyes and bacterial keratitis in 20 eyes. Aspergillus flavus was the most frequent fungal isolate (9/17, 53%), followed by Cylindrocarpon sp. (3/17, 18%) and Aspergillus fumigatus (2/17, 12%). Susceptibility was tested for 10/11 Aspergillus sp. isolates; all were susceptible to voriconazole while only two were susceptible to amphotericin B. Cylindrocarpon sp. isolates were resistant to both agents. Streptococcus equi subsp. zooepidemicus was the most frequent bacterial isolate (9/19, 47%), followed by other streptococci (4/19, 21%). All 13 Streptococcus sp. isolates were susceptible to penicillin, and all tested isolates (n = 11) were also susceptible to chloramphenicol. Mean duration of medical treatment was longer in fungal keratitis (38 days) than in bacterial keratitis (25 days) (P < .001). Twenty-six of the eyes underwent globe-sparing surgery in addition to medical therapy. Recovery was achieved in 66% (31/47) of all cases and in 59% (16/27) and 75% (15/20) (P = .264) of cases with keratomycosis and bacterial keratitis, respectively.

CONCLUSIONS

Although Aspergillus sp. and S zooepidemicus were the most frequently encountered isolates, cytology, culture, and susceptibility testing are essential to differentiate bacterial and fungal keratitis and guide the clinician to choose the most efficient treatment.

Feline bacterial keratitis: Clinical features, bacterial isolates, and in vitro antimicrobial susceptibility patterns

OBJECTIVE

To describe clinical characteristics, bacterial isolates, and in vitro antimicrobial susceptibility patterns for cats with bacterial keratitis.

ANIMALS STUDIED

Eighty one cats with bacterial keratitis.

PROCEDURES

Medical records of cats with a clinical diagnosis of bacterial keratitis, confirmed by corneal culture, were reviewed from June 2004 to July 2017. Animal signalment, bacterial isolates, aerobic bacteria in vitro antimicrobial susceptibility test results, and pertinent clinical features were recorded. Percentages of susceptible aerobic bacterial isolates were statistically compared among selected antimicrobials.

RESULTS

There were 102 aerobic bacterial isolates recovered from corneal samples of the 81 cats presented with bacterial keratitis. The most frequent bacteria isolated were Staphylococcus species, which constituted 55% (56/102) of total isolates. All aerobic bacterial isolates grouped together had the highest percentage of susceptibility to ofloxacin (100%), ciprofloxacin (94%), chloramphenicol (93%), doxycycline (92%), ticarcillin (90%), gentamicin (89%), moxifloxacin (89%), tobramycin (86%), neomycin (85%), amikacin (84%), and cefazolin (84%). The same isolates had the lowest percentage of susceptibility to polymyxin B (2%), bacitracin (15%), and clindamycin (31%). When analyzed separately, the isolated Staphylococcus species had the highest percentage of susceptibility to ofloxacin (100%), tobramycin (93%), and neomycin (85%) and the lowest percentage of susceptibility to polymyxin B (3%) and bacitracin (13%).

CONCLUSIONS

Members of the Staphylococcus genus were the most frequent bacteria isolated from cases of feline bacterial keratitis. On the basis of in vitro susceptibility testing and mechanism of action, ofloxacin, ciprofloxacin, ticarcillin, gentamicin, or moxifloxacin are recommended for initial antimicrobial therapy of suspected bacterial keratitis in cats.

Bacterial contamination of slit lamps in veterinary ophthalmology

PURPOSE

Healthcare-associated infection (HAI) is a well-known problem in human medicine. The contamination of medical devices with pathogenic organisms is less studied in veterinary medicine. The purpose of this multicenter study was to evaluate the bacterial contamination of slit lamps throughout Europe and part of the United States. The efficacy of standard cleaning was additionally investigated.

METHODS

Samples from adjustment wheels of slit lamps were taken by different veterinary ophthalmologists and submitted for culture (n = 29). The efficacy of cleaning protocols was evaluated by taking a second sample after routine cleaning (n = 29). Sensitivity testing was performed for pathogenic bacteria using the minimum inhibitory concentration (MIC) or disc diffusion (Kirby-Bauer) method. Statistical analysis was performed using Fisher's exact test.

RESULTS

Seventeen of 29 slit lamps were contaminated before cleaning. The most frequently cultured bacteria were Staphylococcus spp. and coliform bacteria. Twelve of 29 slit lamps showed no bacterial growth before and after cleaning. There was a significant difference before and after cleaning (P = 0.0008), with only 4/29 contaminated samples after cleaning.

CONCLUSION

Contamination with pathogenic bacterial species is frequent in slit lamps used by veterinary ophthalmologists. A risk of cross-contamination in clinical patients has to be considered. Routine cleaning reduces bacterial contamination significantly.