Clonal Relationships among Shigella Serotypes Suggested by Cryptic Flagellin Gene Polymorphism

Abstract

The presence of cryptic fliC alleles in the genomes of 120 strains representative of the four Shigella species was investigated. One fragment was obtained by PCR amplification of fliC, with a size varying from 1.2 to 3.2 kbp, depending on the species or serotype. After digestion with endonuclease HhaI, the number of fragments in patterns varied from three to nine, with sizes of between 115 and 1,020 bp. Patterns sharing most of their bands were grouped to constitute an F type. A total of 17 different F types were obtained from all strains included in this study. A unique pattern was observed for each the following serotypes: Shigella dysenteriae 1, 2, 8, and 10 and S. boydii 7, 13, 15, 16, and 17. On the contrary, S. dysenteriae serotype 13 and S. sonnei biotype e were each subdivided into two different F types. S. flexneri serotypes 3a and X could be distinguished from the cluster containing S. flexneri serotypes 1 to 5 and Y. S. flexneri serotype 6 clustered with S. boydii serotypes 1, 2, 3, 4, 6, 8, 10, 11, 14, and 18 and S. dysenteriae serotypes 4, 5, 6, 7, 9, 11, and 12. Two other clusters were outlined: one comprising S. dysenteriae serotypes 3, 12, 13 (strain CDC598-77), 14, and 15 and the other one joining S. boydii serotypes 5 and 9. None of the 17 fliC patterns was found in the fliC HhaI pattern database previously described for Escherichia coli. Overall, this work supports the hypothesis that Shigella evolved from different ancestral strains of E. coli. Moreover, the method outlined here is a promising tool for the identification of some clinically important Shigella strains as well as for confirmation of atypical isolates as Shigella spp.Shigella species and serotypes, except for Shigella boydii serotype 13, show more than 73% DNA relatedness to Escherichia coli K-12 (4

Identification of a group of shigella-like isolates as Shigella boydii 20

“…Analysis of the cryptic flagellin gene (fliC) by amplification and restriction of the amplified product with endonuclease HhaI was done following the method of Machado et al (1998). Patterns were analysed and compared against the established Shigella and E. coli database (Machado et al, 2000;Coimbra et al, 2001a) using the Taxotron package. Molecular masses of the fragments were estimated by the Schaffer and Sederoff algorithm .…”

“…In the work presented here, we have studied the 180 nontypable Shigella isolates above. We describe their characteristics with respect to biochemical test results, presence of pathogenicity genes, ribotype pattern (Grimont & Grimont, 1986;Coimbra et al, 2001c;Machado et al, 1998), molecular serotyping with RFLP of the amplified O-antigen gene cluster (rfb genes) (Coimbra et al, 1999(Coimbra et al, , 2000 and RFLP of the amplified cryptic flagellin gene (fliC) (Coimbra et al, 2001a;Machado et al, 2000), and agglutination by a serum raised against representative strain 00-977. The reference strain of S. boydii 20 (CDC 99-4528), received recently, was agglutinated by anti-00-977 serum, and was studied using the same methods, and compared with the other strains.…”

Molecular typing and phylogenetic analysis of enteroinvasive Escherichia coli using the fliC gene sequence

“…A PCR-RFLP technique was developed to identify and characterise the fliC gene in pathogenic E. coli [9,10]. This method has been shown to be an important tool for the detection bacteria, determining genetic relationship and epidemiological studies [9][10][11][12][13][14][15].…”

Can the fliC PCR-Restriction Fragment Length Polymorphism Technique Replace Classic Serotyping Methods for Characterizing the H Antigen of Enterotoxigenic Escherichia coli Strains?

“…Such distinct patterns could therefore be used to identify the respective H antigens. This method has been shown to be an important tool for the detection of bacteria, for the determination of genetic relationships, and for epidemiological studies (1,2,3,5,9,11,13,18).…”