Antibiotic Resistance in P. aeruginosa

Vitreous samples from patients were investigated using an institutional protocol as described earlier.¹⁸ (link) Briefly, the sample was inoculated onto an array of bacterial and fungal media, which were incubated at 37°C and 25°C, respectively, for 7 days. Following growth on culture media, P. aeruginosa strains were identified using a VITEK 2 (bioMérieux, Craponne, France) after confirmation by biochemical tests. For antibiotic susceptibility testing, minimum inhibitory concentration was determined using E-test strips (HiMedia, Mumbai, India) or VITEK 2 antibiotic susceptibility testing cards according to the manufacturer's protocol.¹⁹ Antibiotics tested included ciprofloxacin, moxifloxacin, gatifloxacin, ofloaxacin, ceftazidime, gentamicin, tetracycline, amikacin, tobramycin, piperacillin, norfloxacin, colistin, and imipenem. All results were compared to the Clinical and Laboratory Standards Institute interpretative guidelines, and the isolates were classified as susceptible or multidrug-resistant.³⁴ (link) Multiple drug-resistant phenotypes were assigned for strains that were resistant to three or more classes of antibiotics.