Challenges in determining the pathogenicity status of Leptospira isolates with phenotypic methods: The need for a polyvalent approach

Abstract

Understanding the pathogenic status of leptospires, the causative agents of leptospirosis, is important for successful laboratory diagnosis and control programmes of this zoonosis. Leptospires are difficult to differentiate morphologically; therefore, their pathogenic, intermediate or saprophytic status is currently determined based on both phenotypic tests like growth response in medium containing 8-azaguanine and growth at low temperature (13°C), and genotypic methods. The present study reports on the pathogenic versus saprophytic characterization of nine Leptospira isolates from animal hosts (rodents and dogs) and humans, with specific interest on a canine isolate coded “Dog109”, which showed an ambiguous or intermediate status according to conventional (phenotypic) and molecular (genotypic) tests. The results strongly indicate the need of a polyvalent analytical approach for improving the differentiation of the pathogenic status of circulating serovars, particularly of fresh Leptospira isolates with an intermediate or controversial taxonomic position. Key words: Characterization, isolates, Leptospira, leptospirosis, pathogenic, saprophytic.