To the Editor,
In 2018, our group published a paper reporting on the reduced antimicrobial susceptibility of Leptospira strains of animal origin in this prestigious journal [Reference Correia, Loureiro and Lilenbaum1]. Meanwhile, new strains were characterised, enlarging the epidemiological profile of leptospirosis in our scenario. We followed the same methodology of the previous paper and tested them against streptomycin sulphate. In this context, the goal of this letter is to enlarge and update the knowledge about the susceptibility of leptospiral strains against streptomycin sulphate.
The current study determined the minimum inhibitory and bactericidal concentrations (MIC and MBC) of streptomycin sulphate, in comparison with six local strains of serogroups Sejroe, Icterohaemorrhagiae, Grippotyphosa and Pomona, belonging to species Leptospira interrogans, L. santarosai and L. kirschneri (Table 1). Strains were maintained in liquid nitrogen, belonging to the Bacteria Collection of Veterinary Interest of the Universidade Federal Fluminense, Rio de Janeiro, Brazil (http://labv.uff.br/ccbvet/#).
In this study, MIC values of streptomycin across the different Leptospira strains ranged from 0.39 to 3.13 μg/ml, with MBCs ranging from 1.56 to 25 μg/ml (Table 1). These results showed a wide variation in the susceptibility of the strains against streptomycin, not only regarding MIC, but also MBC. The obtained outcomes are consistent with the values observed in other studies such as Correia et al. [Reference Correia, Loureiro and Lilenbaum1] and Liegeon et al. [Reference Liegeon, Delory and Picardeau2], and could define all studied strains as sensitive to streptomycin. These findings validate the usage of streptomycin in field conditions, a fact that can be considered positive, since this is the most common antibiotic used for the treatment of leptospirosis in livestock, particularly ruminants.
Data availability statement
Data are available on request from the authors.