Wide but variable distribution of a hypervirulent Campylobacter jejuni clone in beef and dairy cattle in the United States

Abstract

<p><em>Campylobacter jejuni</em> clone SA is the major cause of sheep abortion and contributes significantly to foodborne illnesses in the United States. Clone SA is hypervirulent because of its distinct ability to produce systemic infection and its predominant role in clinical sheep abortion. Despite the importance of clone SA, little is known about its distribution and epidemiological features in cattle. Here, we describe a prospective study on <em>C. jejuni</em> clone SA prevalence in 35 feedlots in 5 different states in the U.S. and a retrospective analysis of clone SA in <em>C. jejuni</em> isolates collected by National Animal Health Monitoring System (NAHMS) Dairy Studies 2002, 2007 and 2014. In feedlot cattle feces, the overall prevalence of <em>Campylobacter</em> was 72.2%, 82.1% of which were <em>C. jejuni</em>. Clone SA accounted for 5.8% of the total <em>C. jejuni</em> isolates, but its prevalence varied by feedlot and state. Interestingly, starlings on the feedlots harbored <em>C. jejuni</em> in feces including clone SA, suggesting it may play a role in the transmission of <em>Campylobacter</em>. In dairy cattle, the overall prevalence of clone SA was 7.2%, but a significant decrease in the prevalence was observed from 2002 to 2014. Whole genome sequence analysis of the dairy clone SA isolates revealed that it was genetically stable over the years and most of the isolates carried the tetracycline resistance gene <em>tet(O</em>) in the chromosome. These findings indicate clone SA is widely distributed in both beef and dairy cattle, and provide new insights into the molecular epidemiology of clone SA in ruminants.</p>