Microbial keratitis at a single tertiary eye care in Andhra Pradesh: A 12-year analysis of microbiological profile and in vitro susceptibility of bacterial isolates.

Context: Microbial keratitis is a potentially vision-threatening emergency that demands prompt diagnosis and treatment to ensure better vision recovery. Empirical use of broad-spectrum antimicrobial therapies is often the primary treatment modality, which is then tailored according to clinical response, cultured organisms, and their sensitivities. Since the spectrum of microbial agents associated with corneal ulcers is wide and varies from one geographical location to another, it is imperative that local microbial trends and susceptibility patterns are analyzed to enable better care in the management of these patients.

Aims: The aim of the study was to report the microbiological profile and in vitro drug susceptibility patterns of bacterial isolates obtained from patients with microbial keratitis in a single tertiary center in Andhra Pradesh over 12 years.

Methods: Microbiology records of culture-positive microbial keratitis that underwent a diagnostic corneal scraping and cultures from the years 2010 to 2021 were reviewed. Trends in bacterial and fungal etiology along with the antibiotic susceptibility profile of bacteria were analyzed.

Statistical analysis used: Frequency distribution was obtained, and percentages were calculated.

Results: Of the 8529 microbial keratitis samples, 3581 corneal scrapings were culture positive which included Gram-positive bacteria (1054/3581, 29.4%), Gram-negative bacteria (476/3581, 13.2%), fungi (2051/3581, 57.2%), and parasites (369/3581, 10.3%). The most common fungal isolate was Fusarium species (557/1748, 31.8%) followed by Aspergillus flavus (495/1748, 28.3%). Similarly, the most common Gram-positive bacteria included Streptococcus pneumoniae (297/891, 33.3%) and Staphylococcus species (213/891, 23.9%), and the most common Gram-negative bacteria was Pseudomonas aeruginosa (294/403, 72.9%). Overall susceptibility patterns showed that Gram-positive bacteria were susceptible to vancomycin (92%), cefazolin (88%), and chloramphenicol (86%), while Gram-negative bacteria were most susceptible to gentamicin and amikacin (81%). The susceptibility to amikacin and gentamicin increased significantly from 71% in 2010 to 92% in 2021 and 74% in 2010 to 92% in 2021, respectively. In comparison, the susceptibility of fluoroquinolones for both Gram-positive and Gram-negative bacteria did not show any significant change over the study period.

Conclusions: The prevalence of fungal and bacterial keratitis has remained unchanged over the years. This study reinforced that fluoroquinolones and vancomycin continue to be good empiric therapies for treating bacterial keratitis in Andhra Pradesh.