Multidrug-Resistant Organisms from Ophthalmic Cultures: Antibiotic Resistance and Visual Acuity

Microbial distributions in the conjunctiva and lacrimal sacs of patients with chronic dacryocystitis in a tertiary hospital

BACKGROUND

The aim was to clarify the distributions of bacteria in the conjunctival sac and lacrimal sac in patients with chronic dacryocystitis.

METHODS

In total, 297 (322 eyes) chronic dacryocystitis patients who underwent nasal endoscopic dacryocystorhinostomy (EN-DCR) were included. Conjunctival sac secretions from the affected eye were collected preoperatively, and lacrimal sac retention fluid from the affected side in the same patient was collected intraoperatively. Bacterial culture and drug sensitivity testing were performed to determine bacterial distributions.

RESULTS

In total, 127 bacterial isolates (49 species) were detected in 123 eyes in the conjunctival group, with a positivity rate of 38.2% (123/322); 85 bacterial isolates (30 species) were detected in 85 eyes in the lacrimal sac group, with a positivity rate of 26.4% (85/322). The positivity rates were significantly different (P = 0.001) between two groups. The gram-negative bacilli proportion in the lacrimal sac group (36/85, 42.4%) was significantly higher than that in the conjunctival sac group (37/127, 29.2%) ( P = 0.047). Positive conjunctival sac secretion culture (123/322) was significantly associated with increased ocular secretion (281/322, 87.3%) (P = 0.002). Among the culture-positive bacteria in the conjunctival sac group and the lacrimal sac group, 30/127, 23.6% and 43/127, 26.7% and 21/85, 24.7% and 20/85, 23.5% were resistant to levofloxacin and tobramycin, respectively.

CONCLUSIONS

This study illustrated differences in bacterial distributions between conjunctival sac secretions and retained lacrimal sac fluid in chronic dacryocystitis patients, with a higher proportion of gram-negative bacilli in lacrimal sac secretions. The ocular surface flora in chronic dacryocystitis patients is partially resistant to levofloxacin and tobramycin, which need to be considered by ophthalmologists.

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.