Bacterial Cross-Contamination in a Veterinary Ophthalmology Setting

Topical blood products modulate the effects of ophthalmic antibiotics against common bacterial pathogens in dogs with infectious keratitis

Bacterial keratitis is a common and serious condition that often leads to vision impairment and potential loss of the eye if not treated promptly and adequately. Topical blood products are often used concurrently with topical antibiotics, helping to mitigate corneal 'melt' from proteases released on the ocular surface. However, blood products are rich in albumin and could affect the efficacy of antibiotics due to drug-protein binding. In this study, serum and plasma samples were harvested from 10 healthy dogs and 10 healthy horses, obtaining fresh and frozen (1 month at -20°C) aliquots for in vitro experiments. Albumin levels were quantified using species-specific ELISA kits. Thirty bacteria (10 Staphylococcus pseudintermedius, 10 Streptococcus canis, 10 Pseudomonas aeruginosa), isolated from canine patients with infectious keratitis, were each tested with blank plates as well as commercial susceptibility plates (Sensititre™ JOEYE2) to assess the minimal inhibitory concentration (MIC) of 17 different antibiotics in the absence (control) or presence of eight test groups: serum or plasma (fresh or frozen) from canines or equines. Albumin concentrations ranged from 13.8-14.6 mg/mL and 25.9-26.5 mg/mL in canine and equine blood products, respectively. A direct antimicrobial effect was observed mostly with equine vs. canine blood products (specifically serum and to a lesser degree plasma), and mostly for Staphylococcus pseudintermedius isolates. MICs generally increased in the presence of blood products (up to 10.8-fold), although MICs also decreased (down to 0.25-fold) for selected antibiotics and ocular pathogens. Median (range) fold changes in MICs were significantly greater (p = 0.004) with the canine blood products [2 (0.67-8.1)] than the equine blood products [2 (0.5-5)]. In practice, clinicians should consider equine over canine blood products (lesser impact on antimicrobial susceptibility), serum over plasma (greater antimicrobial effects), and administering the blood product ≥15 min following the last antibiotic eyedrop to minimize the amount of albumin-antibiotic binding in tear film.

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.

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.

Longitudinal environmental Staphylococcus contamination in a new small animal veterinary hospital and utility of cleaning checklists

Staphylococci are inhabitants of skin and mucous membranes with Staphylococcus pseudintermedius (SP) and Staphylococcus aureus (SA) serving as important pathogens for animals and people, respectively. Previous research has identified the environment as potentially important in hospital-associated infections and zoonotic transmission in veterinary settings. The objective of this pilot study was to determine the longitudinal prevalence over repeated samplings of environmental coagulase-positive Staphylococcus (CPS) in a new veterinary hospital and evaluate associations between contamination and environmental and clinical (caseload, cleaning checklists and staff numbers) factors. Cleaning and disinfection compliance, based on staff-completed checklists, were reviewed for the three shifts immediately prior to sampling. We hypothesized that over time, environmental contamination would increase as the clinic developed and caseload increased and compliance to cleaning checklists would decrease with increasing caseload. Over 18 months, 351 environmental samples were collected at five sampling times (sampling occurred before opening the hospital and every 3 to 6 months thereafter). Overall contamination with CPS was 30.8% (108/351), with SA (16.8%) and SP (13.1%) identified from the contaminated surfaces. Overall, methicillin-resistant strains (MRSA and MRSP) were infrequently recovered (combined n = 3; <1%). Point prevalence of CPS contamination was relatively stable over the study period (22.5%-28.4%), with the exception of an increase at the fourth sampling (52.9%). Cleaning compliance varied over the study period (57.9%-100%); the lowest reported cleaning coincided with the highest proportion of CPS contamination. The most commonly contaminated surfaces were chairs (7/15; 46.7%), examination tables (19/47; 40.4%) and computers (12/35; 34.3%); these items were infrequently included on cleaning lists. Surfaces not included in the checklist were 2.3 times more likely to be contaminated by CPS than those that were included (OR: 2.3, CI 95%: 1.02 -5.35, p-value=.04). MRSA and MRSP were rarely isolated from the environment in the newly opened hospital, indicating it may take time for resistant strains to enter the environment and persist on surfaces. This study identified the possible utility of cleaning checklists for directing cleaning practices and reducing the environmental contamination.