Changing trend in the seroprevalence and risk factors of human leptospirosis in the South Andaman Island, India.

Seroprevalence of leptospirosis among a healthy population of the South Andaman Island was assessed through random sampling. Previous studies have high seroprevalences of up to 55% in general population and 65% in agricultural labourers. The study subjects (1,181 in total, 781 rural and 400 urban) were interviewed and tested for antibodies against Leptospira. Multivariate models were developed to determine the risk factors in the rural and the urban population. The overall seroprevalence was 10.9%, with rural (12.9%) being higher than the urban subjects (7.0%). The commonest infecting serogroup was Icterohaemorrhagiae (53.5%), followed by Grippotyphosa (13.2%). Compared to the earlier observation, seroprevalence was lower and an apparent shift in the infecting serogroup was found. This shift was in concordance with the changing trend in animal population. Significant difference in risk factors, both in rural and urban areas, was also observed. Similar trends in seroprevalence are being observed around the world. Therefore, time to time prevalence studies are needed for the development of effective control measure.

Can Subminimal Inhibitory Concentrations of Antibiotics Induce the Formation of Biofilm in Leptospira?

Antibiotics at subminimal inhibitory concentrations (sub-MICs) are known to induce biofilm formation in numerous bacteria in vitro. In this report, the effect of sub-MIC levels of antibiotics (doxycycline and tetracycline) on biofilm formation by leptospiral reference strains and isolates was investigated. The sub-MIC levels of both tetracycline and doxycycline were able to induce biofilm in some of the leptospiral strains. This is the first report demonstrating the effect of sub-MIC level of antibiotics in inducing biofilm formation in Leptospira. The induction of biofilm may solely be a response to the amount of threshold stress enforced by low levels of antibiotics. The mechanism of biofilm induction by subinhibitory antibiotic concentrations needs to be explored further. Studies are required to understand the clinical relevance of the phenomenon and its contribution to biofilm formation in the host, resulting in the failure of antimicrobial therapy during the treatment of chronic leptospirosis.