The clinical manifestations of Lyme disease, caused by vary considerably in different patients, possibly due to infection by strains with varying pathogenicity. Interestingly, the data also indicate that MLST is better able to predict the outcome of localized or disseminated infection than is typing. Introduction Lyme disease is MK0524 a multisystem illness that, in North America, is caused by the spirochete sensu stricto (hereafter referred to as spp. ticks . In the United States, Lyme disease remains the leading cause of all vector-borne human infections with more than 20,000 annually reported cases . The risk of infection is highly localized within 12 states in the northeastern and upper Midwestern regions accounting for 94% of all reported cases . Clinical features of human infection can include a wide variety of symptoms ranging from a characteristic skin lesion known as erythema migrans often seen during the early stages of disease to more severe musculoskeletal, neurologic or cardiovascular manifestations of disseminated infection that arise from hematogenous MK0524 dissemination from the initial site of inoculation in the skin , . Substantial genetic diversity exists within strain identification in the US , , MK0524 C. It has been observed that strains exhibiting restriction fragment length polymorphism in the 16 SC23 S rRNA intergenic spacer designated as RST1 or possessing major groups A, B, H, I and K have a stronger tendency for hematogenous dissemination early in the course of disease , , C. This observation gave rise to the concept that a distinct subset of genotypes is responsible for early disseminated infection in humans, suggesting that some degree of differential pathogenicity exists among strains. Both RST and typing methods provide a useful tool for categorizing strains that vary in their tendency to disseminate in humans. Neither method, however, is suitable for inferring intraspecific relationships among strains that are important IL1R2 antibody for understanding the evolution of pathogenicity and the geographical spread of disease. While RST typing has limited discriminatory power for this purpose ,  the suitability of typing may also MK0524 be restricted since the highly variable gene is subject to recombination and horizontal gene transfer, as well as strong selection by the host immune system , , C. Moreover, phylogenetic analysis of a single locus can often result in erroneous inference of evolutionary relationships , . The most appropriate of the current techniques for large-scale epidemiology, strain identification and understanding of the population structure of bacterial species is multilocus sequence typing (MLST). This method is based on nucleotide sequences of multiple housekeeping genes that are evolving nearly neutrally. MLST analysis has been used successfully to study a number of bacteria (http://www.mlst.net and http://www.pubmlst.org) and has been employed to identify lineages of particular clinical relevance in bacterial pathogens such as in and isolated from Lyme disease patients. MK0524 The genetic diversity of clinical isolates was assessed, and the genetic and evolutionary relationships between strains found in patients with localized versus disseminated infection, and in patients from two different geographical locations in the US, New York and Wisconsin, were evaluated. The data suggest the existence of lineages with differential pathogenic properties in humans. Results MLST and Identification of Clonal Complexes MLST analysis of 146 isolates recovered from Lyme disease patients in New York and Wisconsin revealed 53 sequence types (STs) (Table S1); 23 have been previously identified and reported , C. Twenty-two of the 53 STs were represented by.