Identification of nine sequence types of the 16S rRNA genes of Campylobacter jejuni subsp. jejuni isolated from broilers.

Ingrid Hansson,Marianne Persson,Linda Svensson,Karl-Erik Johansson,Eva Olsson Engvall

doi:10.1186/1751-0147-50-10

Ingrid Hansson, Marianne Persson + Show 3 more

Open Access

https://doi.org/10.1186/1751-0147-50-10

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Abstract

BackgroundCampylobacter is the most commonly reported bacterial cause of enteritis in humans in the EU Member States and other industrialized countries. One significant source of infection is broilers and consumption of undercooked broiler meat. Campylobacter jejuni is the Campylobacter sp. predominantly found in infected humans and colonized broilers. Sequence analysis of the 16S rRNA gene is very useful for identification of bacteria to genus and species level. The objectives in this study were to determine the degree of intraspecific variation in the 16S rRNA genes of C. jejuni and C. coli and to determine whether the 16S rRNA sequence types correlated with genotypes generated by PFGE analysis of SmaI restricted genomic DNA of the strains.MethodsThe 16S rRNA genes of 45 strains of C. jejuni and two C. coli strains isolated from broilers were sequenced and compared with 16S rRNA sequences retrieved from the Ribosomal Database Project or GenBank. The strains were also genotyped by PFGE after digestion with SmaI.ResultsSequence analyses of the 16S rRNA genes revealed nine sequence types of the Campylobacter strains and the similarities between the different sequence types were in the range 99.6–99.9%. The number of nucleotide substitutions varied between one and six among the nine 16S rRNA sequence types. One of the nine 16S rRNA sequence profiles was common to 12 of the strains from our study and two of these were identified as Campylobacter coli by PCR/REA. The other 10 strains were identified as Campylobacter jejuni. Five of the nine sequence types were also found among the Campylobacter sequences deposited in GenBank. The three 16S rRNA genes in the analysed strains were identical within each individual strain for all 47 strains.ConclusionC. jejuni and C. coli seem to lack polymorphisms in their 16S rRNA gene, but phylogenetic analysis based on 16S rRNA sequences was not always sufficient for differentiation between C. jejuni and C. coli. The strains were grouped in two major clusters according to 16S rRNA, one cluster with only C. jejuni and the other with both C. jejuni and C. coli. Genotyping of the 47 strains by PFGE after digestion with SmaI resulted in 22 subtypes. A potential correlation was found between the SmaI profiles and the 16S rRNA sequences, as a certain SmaI type only appeared in one of the two major phylogenetic groups.

Highlights

Campylobacter is the most commonly reported bacterial cause of enteritis in humans in the EU Member States and other industrialized countries
All isolates were identified as representing either C. jejuni or C. coli by 16S rRNA sequence analysis
The nucleotide sequences of the 16S rRNA genes of the 47 strains were determined and compared with 16S rRNA sequences of 21 strains of C. jejuni, 2 strains of C. doylei, one strain each of C. lari and C. upsaliensis and 16 strains of C. coli retrieved from RDP-II (Table 2)

Summary

Introduction

Campylobacter is the most commonly reported bacterial cause of enteritis in humans in the EU Member States and other industrialized countries. Sequence analysis of the 16S rRNA gene is very useful for identification of bacteria to genus and species level. In the present paper Campylobacter jejuni subsp. Sequence analysis of the 16S rRNA gene has proved extremely useful for evolutionary studies of prokaryotes [10] and constitutes the basis for the revised taxonomy of bacteria [11]. This method has been successfully used for identification of Campylobacter spp. Several PCR assays have successfully been applied for detection of Campylobacter with improved accuracy in identification of Campylobacter spp. from various sources

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