Susceptibility of Leptospira serotypes against various antimicrobials by broth microdilution method

Abstract

In developing countries like India, 90% of patients with leptospirosis have mild flu like symptoms and these patients are treated empirically for fever. Broth microdilution method using resazurin dye reduction assay was followed to test the susceptibility of 30 serovars of Leptospira to various antimicrobial drugs that are generally prescribed for fever in India in vitro. Among 19 antimicrobial drugs tested against Leptospira sp., erythromycin, azithromycin, cefatoxime, penicillin G, ampicillin, amoxycillin and levofloxacin produced MIC₉₀ of below the limit of testing i.e.<0.02 μg/ml. Ceftriaxone, ciprofloxacin and gatifloxacin produced MIC₉₀ of 0.05 μg/ml. Cefixime and ofloxacin produced higher₉₀ than the other antimicrobial agents tested in cephalosporins and fluoroquinolones group respectively. All tested aminoglycosides, chloramphenicol and tetracycline group of antimicrobials produced higher MIC₉₀. Erythromycin, azithromycin, cefatoxime, penicillin G, ampicillin, amoxicillin and levofloxacin were active against several leptospiral serovars and can be used for treatment of leptospirosis. Broth microdilution method using resazurin dye is simple, convenient and cost effective testing system to assess the susceptibility of leptospiral isolates against a wide variety of antimicrobial drugs in a short duration.