Link to Pubmed [PMID] – 29305960
Int. J. Antimicrob. Agents 2018 Jan;
Leptospirosis is the most common zoonotic disease and is endemic worldwide. The antibiotic susceptibilities of Leptospira isolated from both humans and animals are poorly documented. This issue is particularly important for isolates from food-producing animals which are regularly exposed to antibiotic treatments. In this study, we assess the susceptibility of 35 Leptospira strains isolated from food-producing animals of diverse geographical origins between 1936 and 2016 to the antimicrobial agents most commonly used in animals. We used a broth microdilution method to determine the susceptibilities of Leptospira strains isolated from livestock to 11 antibiotics. All the isolates were susceptible to penicillin, amoxicillin, clavulanate, cephalexin, ceftriaxone, doxycycline, tetracycline, streptomycin, enrofloxacin, and spectinomycin, but not polymyxin (MIC ≥4mg/L). For tetracycline and doxycycline, the MIC was significantly higher for the recent isolates from Sardinia, Italy than for the other isolates. Antimicrobial susceptibilities were also determined with 10- and 100-fold-higher inocula. High inocula significantly diminished the antibacterial effect by at least ten-fold for enrofloxacin (MIC ≥256mg/L), streptomycin (MIC ≥16mg/L), and tetracycline (MIC ≥32mg/L) suggesting selection of resistant strain for high inoculum. Our findings contribute to the assessment of whether certain antibiotics are potentially useful for the treatment of leptospirosis, and point out the risk of failure for some antibiotics during infection with a high inoculum in both animals and humans. This study strengthens the need to detect and prevent the emergence of antimicrobial resistance of this major emerging zoonotic pathogen.