Molecular characterization of invasive and noninvasive Campylobacter jejuni and Campylobacter coli isolates

Campylobacter jejuni is one of the most common causes of bacterial diarrhea worldwide and is the primary bacterial cause of food-borne illness. Adhere nce to and invasion of epithelial cells are the most important pathogenic m echanisms of Campylobacter diarrhea, Molecular characterization of invasive and noninvasive Campylobacter isolates from children with diarrhea and sym ptom-free children was performed by random amplified polymorphic DNA techni ques (RAPD). A distinct RAPD profile with a DNA band of 1.6 lib was observe d significantly more frequently among invasive (63%) than among noninvasive (16%) Campylobacter isolates (P = 0.000005). The 1.6-kb band was named the invasion-associated marker (IAM). Using specifically designed primers, a f ragment of 518 bp of the iam locus was amplified in 85% of invasive and 20% of noninvasive strains (P = 0.0000000). Molecular typing with a PCR-restri ction fragment length polymorphism assay which amplified the entire iam loc us showed a HindIII restriction fragment polymorphism pattern associated ma inly with invasive strains. Although cluster analysis of the RAPD fingerpri nting showed genetic diversity among strains, two main clusters were identi fied. Cluster I comprised significantly more pathogenic and invasive isolat es, while cluster II grouped the majority of nonpathogenic, noninvasive iso lates. These data indicate that most of the invasive Campylobacter strains could be differentiated from noninvasive isolates by RAPD analysis and FCR using specific primers that amplify a fragment of the iam locus.