Application of simplified MLST scheme for direct typing of clinical samples from human leptospirosis cases in a tertiary hospital in the Philippines

Abstract

Despite the major threat of leptospirosis to public health in the Philippines, its epidemiologic data remain scarce. Multilocus sequence typing (MLST) is a method often used for identification of circulating Leptospira species and disease surveillance. Unfortunately, molecular typing of Leptospira isolates is not routinely done in most hospital settings. A simplified MLST scheme targeting three loci (adk, lipL41, mreA) was performed for rapid direct typing of Leptospira in clinical specimens. Blood samples from suspected or clinically diagnosed cases (n = 50) were initially screened via polymerase chain reaction (PCR) targeting 23S rRNA, 16S rRNA (rrs2), and lipL32 genes. From the nine positives, seven had interpretable data from MLST. Allelic profiles identified L. interrogans in all positive samples. Six were assigned to ST12 of serovar Manilae (serogroup Pyrogenes) while one sample cannot be clearly differentiated between two serovars/serogroups, Bataviae/Losbanos (serogroup Bataviae) or Australis (serogroup Australis), indicating possibility of a new ST. Phylogenetic analysis confirmed that the application of simplified MLST scheme produces consistent results with the seven-loci genetic profile of published Leptospira MLST schemes. Reduced scheme addressed the challenges often encountered in the amplification of full MLST genetic profile of Leptospira. The approach is a potential alternative to serological tests for rapid typing of clinical specimens and can also aid in investigations on disease epidemiology specifically to monitor occurrence, pathogen transmission, host specificity and susceptibility, and other factors that could lead to potential outbreaks.