Abstract
Leptospirosis is a worldwide zoonotic disease determined by pathogenic spirochetes of the genus Leptospira. The control of bovine leptospirosis involves several measures including antibiotic treatment of carriers. Despite its importance, few studies regarding antimicrobial susceptibility of strains from bovine origin have been conducted. The aim of this study was to determine the in vitro susceptibility of Leptospira strains obtained from cattle in Rio de Janeiro, Brazil, against the main antibiotics used in bovine veterinary practice. A total of 23 Leptospira spp. strains were investigated for minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) using broth macrodilution. At the species level, there were not differences in MIC susceptibility except for tetracycline (P < 0.05). Nevertheless, at the serogroup level, differences in MIC were observed among Sejroe strains, mainly for ceftiofur, doxycycline and in MBC for streptomycin (P < 0.05). One strain presented MBC values above maximum plasmatic concentration described for streptomycin and was classified as presenting reduced susceptibility. Efficacy of antimicrobial therapy on bovine leptospirosis could be compromised due to occurrence of infection by Leptospira strains presenting reduced susceptibility.
Highlights
Leptospirosis is a worldwide zoonotic disease determined by pathogenic spirochetes of the genus Leptospira
Strains of leptospires belonging to the same sg (Sejroe) from different species, L. interrogans and L. santarosai showed differences in their antimicrobial susceptibility, being these differences observed in the minimum inhibitory concentrations (MICs) values for ceftiofur (P = 0.025) and doxycycline (P = 0.032) and in minimum bactericidal concentrations (MBCs) values of streptomycin (P = 0.022)
When MIC90 and MBC90 values of antimicrobial agents were compared, penicillin G and streptomycin were the drugs with the lowest values
Summary
Leptospirosis is a worldwide zoonotic disease determined by pathogenic spirochetes of the genus Leptospira. Species are serologically classified into serogroups (sg) and serovars (sv), useful for serodiagnosis and for epidemiological understanding at a regional or population level [3] In cattle, this disease is characterised mainly by reproductive problems such as infertility, prolonged intervals between births, abortion and occurrence of stillbirths, leading to important economic losses [4, 5]. This disease is characterised mainly by reproductive problems such as infertility, prolonged intervals between births, abortion and occurrence of stillbirths, leading to important economic losses [4, 5] This agent has been identified in the uterus of non-pregnant cows, and infection of the reproductive tract may be the most important manifestation in pathogenesis of bovine leptospirosis [6]. Leptospires from sg Sejroe are the major agents of bovine leptospirosis, and members of that sg are distributed among different species and genotypes, such as Leptospira interrogans (strain Hardjoprajitno), L. borgpetersenii (strain Hardjobovis) and L. santarosai (strain Guaricura) [7]
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