| Summary: | <p>Abstract</p> <p>Background</p> <p>The invasion associated marker (<it>iam</it>) has been detected in the majority of invasive <it>Campylobacter jejuni </it>retrieved from humans. Furthermore, the detection of <it>iam </it>in <it>C. jejuni </it>isolated from two important hosts, humans and chickens, suggested a role for this marker in <it>C. jejuni</it>'s colonization of multiple hosts. However, no data exist regarding the occurrence of this marker in <it>C. jejuni </it>isolated from non-poultry food-animals such as cattle, an increasingly important source for human infections. Since little is known about the genetics associated with <it>C. jejuni</it>'s capability for colonizing physiologically disparate hosts, we investigated the occurrence of the <it>iam </it>in <it>C. jejuni </it>isolated from cattle and assessed the potential of <it>iam</it>-containing cattle and human isolates for chicken colonization and human cell invasion.</p> <p>Results</p> <p>Simultaneous RAPD typing and <it>iam</it>-specific PCR analysis of 129 <it>C. jejuni </it>isolated from 1171 cattle fecal samples showed that 8 (6.2%) of the isolates were <it>iam</it>-positive, while 7 (54%) of human-associated isolates were <it>iam</it>-positive. The <it>iam </it>sequences were mostly heterogeneous and occurred in diverse genetic backgrounds. All <it>iam</it>-positive isolates were motile and possessed important genes (<it>cad</it>F, <it>cia</it>B, <it>cdt</it>B) associated with adhesion and virulence. Although certain <it>iam</it>-containing isolates invaded and survived in INT-407 cells in high numbers and successfully colonized live chickens, there was no clear association between the occurrence, allelic sequence, and expression levels of the <it>iam </it>and the aforementioned phenotypes.</p> <p>Conclusions</p> <p>We show that the prevalence of <it>iam </it>in cattle <it>C. jejuni </it>is relatively lower as compared to isolates occurring in humans and chickens. In addition, <it>iam </it>was polymorphic and certain alleles occur in cattle isolates that were capable of colonizing and invading chickens and human intestinal cells, respectively. However, the <it>iam </it>did not appear to contribute to the cattle-associated <it>C. jejuni</it>'s potential for invasion and intracellular survival in human intestinal cells as well as chicken colonization.</p>
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