Genetic diversity of LEE genes of enteropathogenic

Abstract

The aim of this study was to determine the frequency and allele-associations of LEE encoded esp and tir genes among 181 EPEC strains (90 diarrhea-associated and 91 controls) isolated from Peruvian children less than 18 months of age. We have analyzed espA, espB, espD and tir alleles by PCRRFLP. EPEC strains were isolated with higher frequency from healthy controls (92/424, 21.7%) than from diarrheal samples (90/936, 9.6%) (p< 0.001); 28.9% of diarrheal and 17.6% of control samples were typical EPEC (tEPEC). The distribution of espA-alleles (alpha, beta, beta2 and gamma) and espD-alleles (alpha, beta, gamma and a new variant,espD-N1) between tEPEC and atypical EPEC (aEPEC) was significantly different (p< 0.05). espD-alpha was more common among acute episodes (p<0.05). espBtyping resulted in five alleles (alpha, beta, gamma and two new sub-alleles espB-alpha2 and espB-alpha3 ), while tir-beta and tir-gamma2 were the most common intimin receptor subtypes. Seventy two combinations of espA, espB, espD and tiralleles were found; the most prevalent combination was espA-beta, espBbeta, espD-beta, tir-beta (34/181 strains), which was more frequent among tEPEC strains (p<0.05). Our findings indicate that there is high degree of heterogeneity among EPEC strains isolated from Peruvian children and that aEPEC and tEPEC variants cluster.