Clinical relevance of virulence genes in Campylobacter jejuni isolates in Bahrain

Abstract

There are no data describing the genetic make-up of Campylobacter strains (an important aetiological agent of diarrhoea) circulating in the Arabian Gulf region. Here, the molecular characterization of two virulence genes in Campylobacter jejuni from Bahrain and the relationship with clinical infection are reported. Molecular screening for cytolethal distending toxin (cdtB) and invasion-associated marker (iam) genes was carried out on C. jejuni stool isolates collected from January 2002 to January 2004 in Bahrain. The molecular characterization was correlated with the patients' socio-demographic and clinical parameters. Of the 96 C. jejuni strains tested, 50 (52 %) were cdtB+/iam+, 30 (31 %) were cdtB+/iam- and 16 (17 %) were cdtB-/iam-. Sixty-nine per cent (66/96) of patients were less than 3 years old, with significantly higher detection of cdtB+/iam+ and cdtB+/iam- strains (P < 0.001 and P < 0.01, respectively) in this age group. Seventy patients (73 %) were symptomatic. In the group that were less than 3 years old, 62 and 85 % of those with cdtB+/iam+ and cdtB+/iam- strains, respectively, were symptomatic compared with 100 % for those over 3 years of age. However, the presence of cdtB-/iam- strains still resulted in clinical infection in the children under 3 years but not in the older patients. This is the first report describing the molecular characterization of virulence genes in Campylobacter isolates from this region. The findings indicate that strains of different virulence genetic make-up are circulating in the population, with children under the age of 3 years being most vulnerable. Further work on the molecular characterization, gene expression and determination of the invasive phenotypes of C. jejuni strains circulating in different regions is needed.