Microbiological spectrum and antibiotic sensitivity in endophthalmitis: a 25-year review.

PURPOSE: To identify the spectrum and susceptibility pattern of pathogens responsible for culture-positive endophthalmitis referred to a single institution and investigate possible trends in both pathogens and antibiotic sensitivities over the past 25 years.

DESIGN: A retrospective, laboratory-based study of consecutive microbiological isolates.

PARTICIPANTS: A total of 988 consecutive culture-positive endophthalmitis isolates from 911 eyes.

METHODS: All culture-positive endophthalmitis isolates collected from 1987 to 2011 were identified. Susceptibility rates to a variety of antibiotics were calculated. Chi-square test for trend was used to detect changes in spectrum or susceptibility over time.

MAIN OUTCOME MEASURES: Microbial spectrum and susceptibility pattern over time.

RESULTS: A total of 988 isolates were identified from 911 eyes. The average patient age was 67 ± 18 years, and 55% of the patients were female. The most prevalent pathogens were coagulase-negative staphylococcus (39.4%), followed by Streptococcus viridans species (12.1%) and Staphylococcus aureus (11.1%). Gram-negative organisms and fungi accounted for 10.3% and 4.6% of all isolates, respectively. With the exception of 2 isolates, Enterococcus faecium and Nocardia exalbida, all the other 725 (99.7%) gram-positive bacteria tested were susceptible to vancomycin. Of the 94 gram-negative organisms tested against ceftazidime, 2 were of intermediate sensitivity and 6 were resistant. For 8 antibiotics, increasing microbial resistance over time was observed: cefazolin (P = 0.02), cefotetan (P = 0.006), cephalothin (P<0.0001), clindamycin (P = 0.04), erythromycin (P<0.0001), methicillin/oxacillin (P<0.0001), ampicillin (P = 0.01), and ceftriaxone (P = 0.006). For 3 antibiotics, increasing microbial susceptibility was observed: gentamicin (P<0.0001), tobramycin (P = 0.005), and imipenem (P<0.0001).

CONCLUSIONS: Coagulase-negative staphylococcus remains the most frequently identified cause of endophthalmitis. Vancomycin and ceftazidime seem to be excellent empiric antibiotics for treating endophthalmitis. Although a statistically significant trend toward increasing microbial resistance against a variety of antibiotics, including cephalosporins and methicillin, was observed, a significant trend toward decreasing microbial resistance against aminoglycosides and imipenem also was detected.