Slit lamps and lenses: a potential source of nosocomial infections?

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.

Efficacy of patient-sided breath shields for slit-lamp examination

OBJECTIVE

To evaluate the efficacy of patient-sided breath shields in preventing oronasal droplet transmission during slit-lamp examination.

DESIGN

Experimental study testing the efficacy of patient-sided breath shields on a slit lamp.

METHODS

Two commercially available patient-sided breath shields and a 3-dimensional (3D)-printed shield designed by the authors were attached to a slit-lamp chin rest for testing. Each shield was exposed to 3 standardized sprays of coloured dye from a spray gun with its nozzle adjusted to simulate the angular dispersion of a human sneeze. Any overspray not blocked by the shields was recorded and compared with spray with no shield (control). Image-processing software was used to ascertain the surface area of overspray not blocked by the tested shield compared with the control of no shield.

RESULTS

With typical use, both commercially available patient-sided shields and the 3D-printed shield blocked 100% of forward-travelling measurable droplets from a simulated sneeze spray. Even when set to the furthest distance setting to simulate the worst-case scenario, shield 1 and the 3D-printed shield blocked 99.96% and 99.65% of overspray, respectively. However, slow-motion footage did reveal that a considerable amount of spray rebounded off the shields and extended peripherally past its borders.

CONCLUSIONS

With typical use, all tested shields prevented 100% of oronasal transmission. To encourage accessibility, the authors offer a free 3D model and instructions for creating the tested patient-sided breath shield. Patient-sided shields should be combined with other infection-control measures to minimize transmission.

Comprehensive Compositional Analysis of the Slit Lamp Bacteriota

Slit lamps are routinely used to examine large numbers of patients every day due to high throughput. Previous, cultivation-based results suggested slit lamps to be contaminated with bacteria, mostly coagulase-negative staphylococci, followed by micrococci, bacilli, but also Staphylococcus aureus. Our study aimed at obtaining a much more comprehensive, cultivation-independent view of the slit lamp bacteriota and its hygienic relevance, as regularly touched surfaces usually represent fomites, particularly if used by different persons. We performed extensive 16S rRNA gene sequencing to analyse the bacteriota, of 46 slit lamps from two tertiary care centers at two sampling sites, respectively. 82 samples yielded enough sequences for downstream analyses and revealed contamination with bacteria of mostly human skin, mucosa and probably eye origin, predominantly cutibacteria, staphylococci and corynebacteria. The taxonomic assignment of 3369 ASVs (amplicon sequence variants) revealed 19 bacterial phyla and 468 genera across all samples. As antibiotic resistances are of major concern, we screened all samples for methicillin-resistant Staphylococcus aureus (MRSA) using qPCR, however, no signals above the detection limit were detected. Our study provides first comprehensive insight into the slit lamp microbiota. It underlines that slit lamps carry a highly diverse, skin-like bacterial microbiota and that thorough cleaning and disinfection after use is highly recommendable to prevent eye and skin infections.

Impurities in Drug Vials Intended for Intravitreal Medication

Sterility is an important prerequisite for minimizing the risk of severe vision loss due to endophthalmitis after intravitreal injections. We describe three cases series of incidents where an unclear contamination of the drug solution or syringe caused the injection process to stop and continue with a new preparation. During a period of 12 months with 30,502 intravitreal injections at a tertiary center, wherein 7,076 were of the drug Aflibercept drawn up from a glass vial, three cases of the critical incident reporting system relating to intravitreal injections were identified: (1) After a typical contact with the filter cannula, the glass of an Aflibercept vial was no longer intact. (2) In the course of another injection, there was a clear deposition of debris on the outer edge of the syringe when removing the attached filter cannula. (3) After inserting the syringe into the rubber top of the vial, a whitish particle of unclear origin was identified within the drug solution. Later, this contamination/particle was identified as part of the greyish rubber that was punched out with the cannula, according to the analyses of the material sent in and the manufacturer's investigations. Thus, even in busy clinics, visual inspection of the injection solution and materials used for impurities, preferably before and after pulling them out of a vial, must be an essential part of the injection process. Even when using ready-to-use prefilled syringes (PFS), vigilance must be kept high, knowing the risk of potential contamination.

The eye as the discrete but defensible portal of coronavirus infection

Oculo-centric factors may provide a key to understanding invasion success by SARS-CoV-2, a highly contagious, potentially lethal, virus with ocular tropism. Respiratory infection transmission via the eye and lacrimal-nasal pathway elucidated during the 1918 influenza pandemic, remains to be explored in this crisis. The eye and its adnexae represent a large surface area directly exposed to airborne viral particles and hand contact. The virus may bind to corneal and conjunctival angiotensin converting enzyme 2 (ACE2) receptors and potentially to the lipophilic periocular skin and superficial tear film with downstream carriage into the nasopharynx and subsequent access to the lungs and gut. Adenoviruses and influenza viruses share this ocular tropism and despite differing ocular and systemic manifestations and disease patterns, common lessons, particularly in management, emerge. Slit lamp usage places ophthalmologists at particular risk of exposure to high viral loads (and poor prognosis) and as for adenoviral epidemics, this may be a setting for disease transmission. Local, rather than systemic treatments blocking virus binding in this pathway (advocated for adenovirus) are worth considering. This pathway is accessible with eye drops or aerosols containing drugs which appear efficacious via systemic administration. A combination such as hydroxychloroquine, azithromycin and zinc, all of which have previously been used topically in the eye and which work at least in part by blocking ACE2 receptors, may offer a safe, cost-effective and resource-sparing intervention.

Bacterial Cross-Contamination in a Veterinary Ophthalmology Setting

The present study describes the prevalence of bacterial cross-contamination in a veterinary ophthalmology setting, a serious issue that can result in healthcare-associated (or nosocomial) infections among patients and staff. Retrospective (n = 5 patients) and prospective (n = 23 patients) studies evaluated bacterial isolates in companion animals presenting with ulcerative keratitis, sampling the patients' cornea and surrounding examination room, including the environment (exam table, countertop, floor) and ophthalmic equipment (slit lamp, transilluminator, direct ophthalmoscope, indirect headset, tonometer). Results of bacterial culture and antibiotic susceptibility testing were recorded, and degree of genetic relatedness was evaluated in six pairs of isolates (cornea + environment or equipment) using pulse-field gel electrophoresis (PFGE). Overall contamination rate of ophthalmic equipment, environment, and examination rooms (equipment + environment) was 42.9% (15/35 samples), 23.7% (9/38 samples) and 32.9% (24/73 samples), respectively. Methicillin-resistant Staphylococcus pseudintermedius (MRSP), a multi-drug resistant (MDR) pathogen with zoonotic potential, was isolated in 8.2% (6/73) of samples. The patient's cornea was likely the source of cross-contamination in 50% (3/6) of MRSP pairs as evaluated by PFGE; notably, two of the three similar bacterial strains did not have an exact match of their antibiotic susceptibility profiles, highlighting the importance of advanced diagnostics such as PFGE to assess cross-contamination in healthcare facilities. Future work could examine the contamination prevalence of specific equipment or the efficacy of cleaning protocols to mitigate cross-contamination in veterinary practice.

Review of Hygiene and Disinfection Recommendations for Outpatient Glaucoma Care: A COVID Era Update

This review focuses on best practices and recommendations for hygiene and disinfection to limit exposure and transmission of infection in outpatient glaucoma clinics during the current COVID-19 pandemic.

Hand hygiene and instrument sanitization in ophthalmology clinics

PURPOSE OF REVIEW

This article reviews the various challenges in infection control in eye clinics and successful measures taken to prevent nosocomial infections.

RECENT FINDINGS

The Center for Disease Control recommends hand-washing when hands are visibly soiled, and after direct contact with patients, and inanimate objects such as medical equipment. Published studies have identified poor hygiene in clinical settings as a major cause of nosocomial outbreaks, particularly in cases of epidemic keratoconjunctivitis (EKC). Some studies of EKC outbreaks are able to support direct observation of hygiene lapses with molecular analysis that can match viral strains on particular instruments to those found in infected patients. Although most studies are about adenoviral infection and tonometer use, researchers have found viral and bacterial loads on other common surfaces, indicating a need for further research.

SUMMARY

Proper hygiene in eye clinics requires special attention because of the potential to examine many patients at a time and because multiple instruments are often used during a single exam. Studies reinforce the link between hygiene and outbreak prevention, and more research can be done to determine the specific links between certain instruments and nosocomial infections.