Conjunctival sac bacterial flora isolated prior to cataract surgery

Chikako Suto^1,2, Masahiro Morinaga^1,2, Tomoko Yagi^1,2, Chieko Tsuji³, Hiroshi Toshida^4
1Department of Ophthalmology, Saiseikai Kurihashi Hospital, Saitama; ²Department of Ophthalmology, Tokyo Women's Medical University, Tokyo; ³Department of Clinical Laboratory, Saiseikai Kurihashi Hospital, Saitama; ⁴Department of Ophthalmology, Juntendo University Shizuoka Hospital, Izunokuni, Shizuoka, Japan

Objective: To determine the trends of conjunctival sac bacterial flora isolated from patients prior to cataract surgery.
Subjects and methods: The study comprised 579 patients (579 eyes) who underwent cataract surgery. Specimens were collected by lightly rubbing the inferior palpebral conjunctival sac with a sterile cotton swab 2 weeks before surgery, and then cultured for isolation of bacteria and antimicrobial sensitivity testing. The bacterial isolates and percentage of drug-resistant isolates were compared among age groups and according to whether or not patients had diabetes mellitus, hyperlipidemia, dialysis therapy, oral steroid use, dry eye syndrome, or allergic conjunctivitis.
Results: The bacterial isolation rate was 39.2%. There were 191 strains of Gram-positive cocci, accounting for the majority of all isolates (67.0%), among which methicillin-sensitive coagulase-negative staphylococci was the most frequent (127 strains, 44.5%), followed by methicillin-resistant coagulase-negative staphylococci (37 strains, 12.7%). All 76 Gram-positive bacillary isolates (26.7%) were from the genus Corynebacterium. Among the 16 Gram-negative bacillary isolates (5.9%), the most frequent was Escherichia coli (1.0%). The bacterial isolation rate was higher in patients >60 years old, and was lower in patients with dry eye syndrome, patients under topical treatment for other ocular disorders, and patients with hyperlipidemia. There was no significant difference in bacterial isolation rate with respect to the presence/absence of diabetes mellitus, steroid therapy, dialysis, or a history of allergic conjunctivitis. Methicillin-resistant coagulase-negative staphylococci showed a significantly higher detection rate in diabetic patients than nondiabetic patients (20.3% versus 7.0%, P < 0.05). The percentage of all isolates resistant to levofloxacin, cefmenoxime, and tobramycin was 14.0%, 15.2%, and 17.9%, respectively, with no significant differences among these drugs.
Conclusion: The high bacterial isolation rate in patients >60 years old and the high methicillin-resistant coagulase-negative staphylococci isolation rate in patients with diabetes are important to consider for prevention of perioperative infections.

Keywords: endophthalmitis, cataract surgery, conjunctival sac, bacterial flora, diabetes mellitus