Extended-spectrum beta-lactamase-mediated resistance among bacterial isolates recovered from ocular infections.

PURPOSE: To evaluate resistances mediated by extended-spectrum ß-lactamases (ESBLs) and AmpC ß-lactamases among Gram-negative bacteria recovered from ocular infections. METHODS: As per the Clinical Laboratory Standards Institute M100-S-16 document, a total of 135 Gram-negative bacilli were recovered from ocular specimens and were subjected to phenotypic confirmation for ESBL production by the double-disc synergy test, cephalosporin and clavulanate combination disc test and E test, and, for AmpC ß-lactamase, the modified double-disc approximation method and AmpC disc test. RESULTS: In the double-disc synergy test, 21 (15.5%) isolates showed positive results against the cefpodoxime disc, 19 (14%) against cefpodoxime and cefotaxime, 15 (11%) against cefpodoxime, cefotaxime and ceftriaxone and 10 (7%) isolates were against cefpodoxime, cefotaxime, ceftriaxone and ceftazidime discs. In the cephalosporin/clavulanate combination disc test, 19 (14%) isolates showed positive results against cefotaxime with clavulanic acid and 10 (7%) isolates against ceftazidime with clavulanic acid. In the E test, 10 (7%) isolates displayed positive results against ceftazidime and 19 (14%) against cefotaxime. In the AmpC disc test for phenotypic confirmation, indentations were observed in 15 (11%) isolates with flattening also occurring in 10 (7%) isolates. CONCLUSION: The incidences of ESBL- and AmpC ß-lactamase-mediated resistances are found to be 7 and 18.5% among ocular isolates, respectively, and are more prevalent among the strains of Escherichia coli and Klebsiella pneumoniae.