The Susceptibility of Bacterial Endophthalmitis Isolates to Vancomycin, Ceftazidime, and Amikacin: a 23 Year-Review.

PURPOSE

To investigate the susceptibility of Gram-positive and Gram-negative endophthalmitis bacterial isolates to vancomycin, amikacin, and ceftazidime over a 23-year period.

DESIGN

Retrospective non-comparative laboratory case series.

SUBJECTS

Endophthalmitis patients that were culture positive for bacteria.

METHODS

Laboratory records of bacteria isolated from endophthalmitis specimens collected from January 1 1993 to December 31 2015 were reviewed for incidence and standard susceptibility testing.

MAIN OUTCOME MEASURES

The susceptibilities of bacteria cultured from endophthalmitis to vancomycin (VAN), amikacin (AMK), and ceftazidime (CEF).

RESULTS

Patients with endophthalmitis were culture positive for bacteria in 665 cases.. Coagulase negative (CoNS) were the most common bacteria (54.6%), followed by (Strep) species (20.8%), (SA) (10.2%), other Gram-positive (other-GP) bacteria (7.4%) and Gram-negative (GN) bacteria (7.1%). All Gram-positive organisms were susceptible to VAN, with the exception of 2 isolates. The susceptibilities of bacteria to AMK were: CoNS (95.3%), SA (75.0%), Strep (8.0%), GN (95.7%), and other-GP (81.1%). The susceptibilities of bacteria to CEF were: CoNS (58.5%), SA (54.4%), Strep (84.1%), GN (93.6.%), and other-GP (52.8%). There was no difference between AMK (95.7%) and CEF (93.6%) for GN coverage. AMK provided better coverage than CEF for CoNS, SA, and other-GP bacteria respectively (p<0.05, Fisher's exact), however, CEF appeared to provide better coverage (p<0.001, Fisher's exact) for Strep than AMK.

CONCLUSIONS

Based on standard susceptibility testing, vancomycin remains an optimal antibiotic choice for the treatment of Gram-positive endophthalmitis. AMK and CEF appear to provide equal GN coverage, but AMK appears to provide better coverage for CoNS, SA, and other-GP, but not Strep.