Conjunctival sac flora and drug susceptibility analysis in normal children in East China

Abstract

Purpose: To study the conjunctival sac flora distribution characteristics and analyze the drug susceptibility of commonly used topical antimicrobial agents in normal children <18 years in East China. Methods: Microorganism cultures of conjunctival sac were analyzed for 1258 children (2516 eyes; average age, 6 years) in Qingdao Eye Hospital of Shandong First Medical University in 2019. Patients with ocular surface diseases and those who used any topical antimicrobial agent recently were excluded. The operation followed the M-38A protocol (microdilution method; investigators read the minimum inhibitory concentration [MIC] values) by the Clinical and Laboratory Standards Institute to analyze the conjunctival sac microorganism species and drug susceptibility. Results:The incidence of conjunctival sac microorganism in children was 32.87% (827/2516), a total of 541 cases (male 293, female 248). Patients with conjunctival sac flora in a single eye were 255 and in both eyes were 286 (no statistical difference, P>0.05). The concordance rate of patients with binocular conjunctival sac flora was 32.16% (174/541; male 84, female 90). A total of 42 species of bacteria were detected; patients with Gram-positive cocci accounted for the highest proportion, 91.54% (757/827). The top three bacteria with the highest detection rates were Staphylococcus epidermidis (S. epidermidis; 52.12%), Streptococcus (12.09%), and Staphylococcus aureus (S. aureus; 10.76%). Streptococcus mitis (5.20%) accounted for the highest proportion of Streptococcus. The drug susceptibility analysis showed that S. epidermidis was most sensitive to gatifloxacin (98.61%), while it had the highest resistance rate to erythrocin (87.94%). S. aureus had the highest susceptibility to moxifloxacin (100%). Streptococcuswas most sensitive to moxifloxacin (96.97%) and had the highest resistance rate to tobramycin (92.93%). Conclusions: Conjunctival sac flora in children was dominated by Gram-positive cocci, mainly S. epidermidis, S. aureus, and Streptococcus. S. epidermidisincreased with age; the proportion of Streptococcus was higher than S. aureus among children aged 0–6 years. The typical conjunctiva sac flora was generally sensitive to quinolones, such as moxifloxacin and gatifloxacin; Streptococcusdisplayed high resistance to tobramycin antibiotics; and the female children had higher resistance to tobramycin than the male children.