Whole-Genome Sequencing to Detect Numerous Campylobacter jejuni Outbreaks and Match Patient Isolates to Sources, Denmark, 2015-2017.

In industrialized countries, the leading cause of bacterial gastroenteritis is Campylobacter jejuni. However, outbreaks are rarely reported, which may reflect limitations of surveillance, for which molecular typing is not routinely performed. To determine the frequency of genetic clusters among patients and to find links to concurrent isolates from poultry meat, broiler chickens, cattle, pigs, and dogs, we performed whole-genome sequencing on 1,509 C. jejuni isolates from 774 patients and 735 food or animal sources in Denmark during 2015-2017. We found numerous clusters; 366/774 (47.3%) clinical isolates formed 104 clusters of >2 isolates. A total of 41 patient clusters representing 199/366 (54%) patients matched a potential source, primarily domestic chickens/broilers. This study revealed serial outbreaks and numerous matches to concurrent food and animal isolates and highlighted the potential of whole-genome sequencing for improving routine surveillance of C. jejuni by enhancing outbreak detection, source tracing, and potentially prevention of human infections.

Reproducible infection model for Clostridium perfringens in broiler chickens.

Experiments were carried out to establish an infection and disease model for Clostridium perfringens in broiler chickens. Previous experiments had failed to induce disease and only a transient colonization with challenge strains had been obtained. In the present study, two series of experiments were conducted, each involving four groups of chickens with each group kept in separate isolators. A coccidial vaccine given at 10 times the prescribed dosage was used to promote the development of necrotic enteritis. In the first experiment, cultures of C. perfringens were mixed with the feed at day 9, 10, 11, and 12, and the coccidial vaccine was given at day 10, whereas in the second experiment, C. perfringens cultures were mixed with the feed at day 17, 18, 19, and 20, and the coccidial vaccine was given at day 18. Chickens were examined at day 9, 11, 12, and 15 (Experiment 1), and at day 17, 18, 20, and 24 (Experiment 2). There was no mortality in any of the groups; however, chickens in the groups receiving both coccidial vaccine and C. peifringens developed the subclinical form of necrotic enteritis, demonstrated by focal necroses in the small intestine, whereas chickens in control groups or groups receiving only coccidial vaccine or only C. perfringens cultures developed no necroses. The results underline the importance of predisposing factors in the development of necrotic enteritis.

Experimental infections with rifampicin-resistant Clostridium perfringens strains in broiler chickens using isolator facilities.

Experimental infection studies were carried out on the ability of three Clostridium perfringens type A rifampicin-resistant strains to colonize the intestinal tract of broiler chickens kept in isolators from 1-day-old. Various doses of C. perfringens were given orally at 22 days, 9 days or at 1 day old. At 22 days none of the strains, given in doses of approximately 10(10) colony-forming units, caused mortality or clinical necrotic enteritis. None was able to colonize the intestine permanently and all were eliminated within 9 days. One strain given to groups of 9-day-old birds was recovered only from those receiving high doses, but for no longer than 13 days. In chicks infected at 1-day-old there was transient colonization up to 15 days, and the most persistent colonization was in a group given a fresh broth culture of unwashed cells, including extracellular products. Test strains were rapidly replaced by naturally occurring strains of C. perfringens in all groups but they persisted for considerably longer in chickens inoculated at 1-day-old or at 9 days than those at 22 days, indicating a possible resistance to colonization with increasing age. The findings emphasize the difficulties of establishing a reproducible model for infection with C. perfringens in broiler chickens.