Abstract
BackgroundCampylobacter jejuni, a gram-negative bacterium, is a frequent cause of gastrointestinal food-borne illness in humans throughout the world. There are several reports that the virulence of C. jejuni might be modulated by non-flagellar proteins that are secreted through the filament. Recently, FspA (Flagella secreted proteins) have been described. Two alleles of fspA (fspA1 and fspA2) based on sequence analysis were previously reported and only the fspA2 allele was found in Thai isolates. The aim of this study is to analyze the deduced amino acid sequences fspA and the adjacent putative integral membrane protein from 103 Thai C. jejuni isolates.ResultsA total of 103 representative C. jejuni isolates were amplified by PCR for the fspA gene and the adjacent integral membrane protein gene. Two PCR product sizes were amplified using the same primers, an approximately 1600-bp PCR product from 19 strains that contained fspA and integral membrane protein genes and an approximately 800-bp PCR product from 84 strains that contained only the fspA gene. DNA sequencing was performed on the amplified products. The deduced amino acid sequences of both genes were analyzed separately using CLC Free Workbench 4 software. The analysis revealed three groups of FspA. Only FspA group 1 sequences (19/103) (corresponding to fspA1) consisting of 5 subgroups were associated with the adjacent gene encoding the integral membrane protein. FspA group 2 was the largest group (67/103) consisting of 9 subgroups. FspA group 2p (17/103) consisting of 7 subgroups was found to contain stop codons at a position before the terminal 142 position.ConclusionsThis study reveals greater heterogeneity of FspA (group 1, 2 and 2p) among Thai C. jejuni isolates than previously reported. Furthermore, the subgroups of FspA groups 1 were associated with groups of integral membrane protein. The significance of these different FspA variants to virulence requires further study.
Highlights
Campylobacter jejuni, a gram-negative bacterium, is a frequent cause of gastrointestinal food-borne illness in humans throughout the world
The 103 C. jejuni isolates representing clusters from a previous PFGE (Pulsed Field Gel Electrophoresis) cluster analysis of C. jejuni isolates from the diarrhea studies on adults in Thailand were selected for this study [16]
We investigated the variation of FspA and integral membrane protein by DNA sequencing of PCR products and analyzed their deduced amino acid sequences
Summary
Campylobacter jejuni, a gram-negative bacterium, is a frequent cause of gastrointestinal food-borne illness in humans throughout the world. Two alleles of fspA (fspA1 and fspA2) based on sequence analysis were previously reported and only the fspA2 allele was found in Thai isolates. The aim of this study is to analyze the deduced amino acid sequences fspA and the adjacent putative integral membrane protein from 103 Thai C. jejuni isolates. Campylobacter jejuni is a major cause of gastroenteritis worldwide especially in children, travelers, military personnel deployed to developing countries These pathogens are generally considered invasive, the level of invasion of intestinal epithelial cells in vitro varies among strains [1]. Genomes presenting fspA2 allele (encoded from Cj0859c gene in reference strain NCTC11168) have been reported to systematically lack the adjacent gene Cj0860, a putative integral membrane protein. Another report [15] showed FspA variants and MLST associations among human, poultry and bovine Campylobacter jejuni strains
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