Characterization of Leptospira interrogans serovar Pomona isolated from swine in Brazil.

INTRODUCTION: Leptospira interrogans swine infection is a cause of serious economic loss and a potential human health hazard. In Brazil, the most common serovars associated with swine infections are Pomona, Icterohaemorrhagie and Tarassovi. Cross-reactions among serovars and the failure of infected animals to seroconvert may complicate the interpretation of serological tests. Molecular methods with better discriminatory powers are useful tools for swine leptospirosis characterization and diagnosis. METHODOLOGY: This study evaluated nine L. interrogans isolates from the States of Sao Paulo and Minas Gerais during different time periods. Isolates from diseased and apparently healthy swine were characterized by microscopic agglutination tests with polyclonal antibodies and were genotyped by VNTR, PFGE and MLST techniques. Broth microdilution was used to determine the minimal inhibitory concentration of the antimicrobials of veterinary interest. RESULTS: The strains were identified as L. interrogans serogroup Pomona serovar Pomona Genotype A, while MLST grouped all of the isolates in sequence type 37. The PFGE analysis resulted in two pulsotypes with more than 70% similarity, distinguishing serovar Pomona isolates from the serovar Kennewicki reference strain. All of the isolates presented low MIC values to penicillin, ampicillin, ceftiofur and tulathromycin. High MIC values for fluoroquinolones, tiamulin, gentamicin, tetracyclines, neomycin, tilmicosin and sulfas were also observed. CONCLUSIONS: All molecular techniques were concordant in L. interrogans serovar Pomona identification. This serovar may have a different antibiotic susceptibility profile than previously reported for Leptospira isolates.

[Development of a method to determine the minimum inhibitory concentration in reference strains from leptospiras]. / Desarrollo de un método para determinar la concentración mínima inhibitoria en cepas de referencias de leptospiras.

A method to determine the minimum inhibitory concentration for leptospiras was developed, since there is not a standard method to measure it at the international level. Reference strains from the pathogenic complex L. interrogans and L. biflexa were used against penicillin, cyprofloxacine, chloramphenicol, rifampicine and tetracycline. The minimum inhibitory concentration was defined as the lowest concentration of antibiotic where it was observed the inhibition of the bacterial mobility by direct examination in dark field. Ranges for penicillin were from 0.095 to 152 microg/mL, for tetracycline from 0.156 to 3.13 microg/mL, for chloramphenicol, from 0.08 to 12.52 microg/mL, for rifampicine from 0.08 to 1.56 microg/mL, and for cyprofloxacine from 0.15 to 2.4 microg/mL. The antibiotics that showed the lowest values were cyprofloxacine, rifampicine and tetracycline, whereas the most elevated value was obtained against chloramphenicol and penicillin. The strains from the serogroups circulating more frequently in Cuba were used in this research. This study will allow in a near future to determine the antimicrobial susceptibility in autochthonous strains isolated from patients with Leptospirosis at the national level.