Microbiological and antimicrobial resistance trends for keratitis and conjunctivitis in a reference center in Mexico City

Abstract

Purpose : To describe and analyze the frequency and antimicrobial resistance trends of pathogens that cause keratitis and conjunctivitis in a reference center in Mexico City over a period of 8 years.

Methods : A retrospective and observational study was performed with patients diagnosed with infectious keratitis and conjunctivitis through January 2012 - December 2019. The database of the Ocular Microbiology and Proteomics laboratory was analyzed to identify corneal and conjunctival scrapings obtained in this period. Microbiological data, stains and sensitivity/resistance antibiograms of isolated pathogens were analyzed. Mean and deviation were used for continuous variables; percentages for categorical variables. Difference between proportions of pathogens was compared with chi-squared test; resistance patterns were examined with trend analysis.

Results : From 2337 scrapings, a total of 1770 samples were positive cultures (75.7%). 91.5% of positive cultures had bacterial origin. Gram-positive isolates represented 86.4% (n=1399), Staphylococcus epidermidis was the most common pathogen. Gram-negative isolates embodied 13.6% (n=220) with Pseudomonas aeruginosa as the most common species. Fungi represented 7.3% (n=129) of positive isolates, the most frequent was Fusarium sp. Gram-negative bacilli (GNB) and coagulase-negative Staphylococcus (CNS) showed a positive trend throughout the study evaluated by annual percentage change. A significant increase in Kocuria spproportion was evidenced, representing 7.1% of total positive isolates (P=0.01). Resistance to moxifloxacin in S. epidermidis increased significantly (4.1% to 50.6%) along the 8-year study (P=0.02). Pseudomonas sp had an average sensitivity of 97.4% to ceftazidime through the study period.

Conclusions : Most frequently isolated microorganisms were S. epidermidis and P. aeruginosa in the group of gram-positive and gram-negative bacteria, respectively. An increase in the biodiversity of pathogens previously not involved in ocular infections, such as Kocuria sp, was evidenced. A 12-fold increase in resistance to moxifloxacin was noted as previously reported in gram-positive bacteria.

This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.