An Outbreak of Foodborne Illness Among Attendees of a Wedding Reception in Wisconsin Likely Caused by Arcobacter butzleri

Background: Arcobacter species, primarily Arcobacter butzleri, are widely distributed among animals, infrequently isolated from humans, and previously not associated with outbreaks of foodborne illness. We report results of an investigation of a foodborne outbreak that occurred among attendees of a wedding reception in Wisconsin, United States, and was likely caused by A. butzleri. Methods: We conducted a case-control study among reception attendees and a laboratory investigation to determine the extent, source, and cause of the outbreak. A clinical case was defined as diarrhea in an attendee with illness onset <= 7 days following the wedding reception. Results: The case-control study included 47 of 51 case patients and 43 non-ill attendees. Results demonstrated that consuming broasted chicken was the only factor significantly associated with illness (odds ratio 10.51; 95% confidence interval 1.28, 476.4). Five patients provided stool specimens. Comprehensive culture and polymerase chain reaction (PCR) testing did not detect common bacterial or viral pathogens. Subsequent testing with PCRs targeting 16S/23S rDNA of the three most clinically relevant Arcobacter spp. and the rpoB/C gene of A. butzleri provided products confirmed as A. butzleri (four patients) and A. cryaerophilus (one patient) by sequence analysis. Conclusions: The results of this investigation suggest that A. butzleri should be considered an agent that can cause outbreaks of foodborne illness. Rigorous investigation of outbreaks of undetermined etiology is valuable for incrementally increasing our understanding of emerging agents causing foodborne illnesses.