Trends in pathogens and antibiotic resistance of corneal culture isolates in infectious keratitis in Sao Paulo, Brazil, over a 5-year period

Abstract

Purpose : Infectious keratitis remains a sight-threatening disease and its prompt diagnosis, detection of the agent and early treatment are imperative. The aim of this study was to investigate the etiology and microbial profile of isolates in scrapes of corneal ulcers in patients referred to the Hospital das Clinicas, School of Medicine, University of Sao Paulo, in a 5-year period.

Methods : A retrospective analysis of corneal scrapes of patients diagnosed with microbial keratitis was performed from January 2013 to December 2017. All microbiological examinations were conducted at the Department of Microbiology of Hospital das Clinicas, University of Sao Paulo. Demographics and microbiological data were collected.

Results : A total of 318 corneal scrapes were performed on eyes of 307 patients, 109 female (35.5%) and 198 male (64.5%), mean age 50.7 years (range:1 to 90). A total of 201 organisms were isolated from 168 (52.8%) positive samples (Table 1). Infections due to a single organism occurred in 140 (83.3%) of positive cultures and in 28 samples (16.7%) more than one agent were found. Bacterial isolates represented 86.1% of positive cultures; 51.2% were gram-positive and 34.8% gram-negative bacteria. Cutibacterium acnes (10.9%), Pseudomonas aeruginosa (10.4%), Serratia marcescens (8.0%), Staphylococcus epidermidis (6.5%) and Streptococcus pneumoniae (5.5%) were the most common bacteria detected. Fungal keratitis represented 13.9% of the positive cultures; Fusarium sp (7.0%) and Candida spp (3.0%) were the main fungi isolated. Eighty-four antibiograms were analyzed (Table 2). Gentamicin-resistance was higher in gram-positive (20%) than in gram-negative isolates (8.5%). All gram-positive tested were sensitive to vancomycin and 98% of the gram-negative were sensitive to ceftazidime. All Pseudomonas aeruginosa isolates were sensitive to gentamicin and ciprofloxacin. Ciprofloxacin-resistance was higher in gram-positive (30%) than in gram-negative (9.9%).

Conclusions : Our study revealed a predominance of gram-positive bacteria in keratitis isolates. Our results suggest that in case of severe bacterial keratitis in our area, vancomycin should be considered as empirical treatment. In case of Pseudomonas keratitis, gentamicin is still a good option.

This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.

 

Table 1: Agents isolated

 

Table 2: Antibiotic susceptibilities of the isolates