Sensitivity to Drugs of Australian Leptospiral Serotypes

Abstract

The in vitro susceptibilities to antibiotics of stock strains of various Australian leptospiral serotypes were established. Leptospira pomona was highly susceptible to penicillin and erythromycin, susceptible to streptomycin and tetracyclines, but resistant to chloramphenicol and novobiocin. In general, the twelve serotypes tested were susceptible to streptomycin, penicillin and tetracycline, but L. icterohaemorrhagiae, L. canicola and L. zanoni were more resistant than the other serotypes, especially to penicillin. A newly isolated strain of L. zanoni was more sensitive to penicillin, streptomycin, and tetracycline than was the stock strain. Against L. australis high concentrations both of penicillin and of streptomycin-were bactericidal. In lower concentrations penicillin was bacteriostatic. In high concentrations penicillin caused lysis of leptospirae, but streptomycin and the tetracyclines did not. These results do not agree well with those on the chemotherapy of experimental infections.Information is lacking on the susceptibility in vitro to drugs of many of the serotypes of leptospirae occurring in Australia. Previous studies on susceptibility in vitro and on chemotherapy in laboratory animals were concerned mainly with Leptospira icterohaemorrhagiae and L. canicola. These serotypes are important in other countries because of their high incidence and the clinical severity of the disease they cause in man and animals. The relatively high pathogenicity of L. icterohaemorrhagiae for guinea-pigs may also have influenced the choice of this serotype for studies of chemotherapy in vivo.Thirteen leptospiral serotypes are known to cause human infection in Australia. Infections both with L. icterohaemorrhagiae and with L. canicola occur, but numerically they are not important. L. australis (L. australis A) and L. zanoni (L. australis B) are the serotypes responsible for the majority of cases of human infection (Derrick, 1957

Chemotherapy of Experimental Leptospiral Infection in Mice

“…These observations are not entirely in accord with findings on the sensitivity of leptospirae to antibiotics in vitro (Spradbrow, 1963). In general, these organisms were susceptible to very low concentrations of erythromycin and of penicillin, moderate concentrations of the tetracyclines and of streptomycin, but only to high concentrations of novobiocin, and they showed complete resistance to chloramphenicol.…”

Use of Antibiotics in the Preparation of Canine Kidney Tissue Culture Vaccines to Eliminate Leptospiral Infection Hazards1

“…The antileptospiral effects of the penicillin-streptomycin and polymyxin B-dihydrostreptomycin treatments were relatively rapid when compared with those of neomycin and chloramphenicol. The observed inhibitory effect of chloramphenicol on leptospires in tissue cultures was surprising in view of the reported refractiveness of leptospires to the action of this antibiotic at comparable and higher concentrations (Dunn and Thompson, 1953); Spadbrow, 1963).…”

“…With the exception of chloramphenicol, the known growth-inhibitory substances for leptospires in the medium were the tested antibiotics: penicillin-streptomycin, neomycin, and polymyxin B-dihydrostreptomycin. These antibiotics were present in concentrations well above the known in vitro bacteriostatic or bactericidal levels (Felsenfeld et al, 1950;Kolochine and Mailloux, 1962;Spadbrow, 1963;Van Thiel, 1957), and were responsible for the elimination of leptospires from tissue cultures. The antileptospiral effects of the penicillin-streptomycin and polymyxin B-dihydrostreptomycin treatments were relatively rapid when compared with those of neomycin and chloramphenicol.…”