Measurement of logarithmic phase and toxicity in Leptospira

• 1、College of Veterinary Medicine, Jilin University, Changchun, Jilin Province 130062

Abstract：【Aim】 To explore the growth characteristics and toxicity of leptospira for the next research . 【Method】 Leptospira was incubated in EMJH medium using a shaker at 28-30 ℃ and used bacteria count plate and dark-field microscope to measure the viable count every 6 hours.Chosed 4 groups 4 to 6-week-old female Golden hamsters,each group having four hamsters.Intraperitoneal challenge of hamster with different concentrations' leptospiroses ,keeping a record of how many days did these hamsters die an half.Besides,chosed 3 groups hamsters , intraperitoneally challenged 1E6 leptospiroses living in logarithmic phase,measuring the lethal dose and geted the infected hamsters'kidneys、livers and lungs to do histopathological examination.【Result】 During 0 to 150 hours,leptospira growth showed S curve.During 0 to 60 hours,it growed slowly,developed rapidly in 80 to 105 hours but in 130 to 150 hours came into stable phase.Intraperitoneally challenging hamsters of 1E2-1E5 leptospira all died an half but 3 groups of hamsters intraperitoneally challenged 1E6 all died in 5 to 7 days. Histopathological examination showed that infected hamsters'lungs bled obviously,livers'cells tight coupling broadened,kidney tubules also bled. 【Conclusion】 The logarithmic phase of leptospira was 80 to 105 hours in EMJH medium at 28 to 30℃ .The medium lethal dose of leptospira in 4 to 6-week-old female Golden hamster was 100,lethal dose was 1E6.Infected hamsters showed obviously pathological damage.

Keywords： leptospira logarithmic LD50；pathology