Leptospirosis: Time to move to molecular epidemiology Comments on `` Reassessment of MLST schemes for Leptospira spp. typing worldwide'' by Varni and colleagues

摘要

For decades, our knowledge of leptospirosis epidemiology was built from serological studies. Isolates were typed using the reference cross-agglutinin absorption technique into more than 250 serovars, grouped into more than 20 serogroups. Human and animal cases diagnosis as well as animal reservoir studies most frequently identified the putative infecting strain using the reference Microscopic agglutination test, a technique shown to have a low individual predictive value but still useful at a population level (Levett, 2001 and Levett, 2003). More recently, Leptospira typing has moved to the study of DNA sequence polymorphisms using the molecular tools developed and used widely in most bacterial genera, notably Multi Locus Sequence Typing. In parallel, the advent of highly sensitive and highly specific real time PCR techniques has revolutionized the field of human leptospirosis diagnosis. When positive, they allow a confirmatory diagnosis of acute leptospirosis in a couple of hours using a single blood specimen (cerebrospinal or urine are also usable later in the course of the disease). This change was particularly notable in our laboratory in New Caledonia, where the contribution of PCR to the diagnosis of human leptospirosis has increased from 20-30% to more than 90% in less than 10 years. Despite our recommendation of presumptive antibiotic treatment, this rapid turnaround time is probably beneficial for the patients; at very least it allows minimizing medical uncertainty and useless medical explorations before seroconversion. On another hand, this shift in diagnosis techniques is also prone to restrict our knowledge on the contribution of the various Leptospira strains to human cases (and therefore the importance of the various animal reservoirs) both by abandoning the time-consuming and fastidious culture and strain isolation and by depriving reference laboratories of convalescent sera, because they become useless for diagnosis or medical purpose. Molecular techniques were also used for characterizing uncultured Leptospira from clinical ( Agampodi et al., 2013) or animal ( Perez et al., 2011) specimens or even from the environment ( Ganoza et al., 2006 and Viau and Boehm, 2011). However, reconciling the historical serological knowledge with this modern molecular epidemiology data is a real need until animal reservoir studies also move to molecular approaches, but remains very challenging.