Campylobacter jejuni Colonization in the Crow Gut Involves Many Deletions within the Cytolethal Distending Toxin Gene Cluster

Abstract

spp. are major causes of gastroenteritis worldwide. The virulence potential of shed in crow feces obtained from a roost area in Bothell, Washington, was studied and compared with that from isolates from other parts of Washington and from a different crow species 7,000 miles away in Kolkata, India. organisms were isolated from 61% and 69% of the fecal samples obtained from Washington and Kolkata, respectively, and were confirmed to be The cytolethal distending toxin (CDT) gene cluster from these isolates revealed a truncated sequence of approximately 1,350 bp. Sequencing of the gene cluster revealed two types of mutations: a 668-bp deletion across and and a 51-bp deletion within Some strains had additional 20-bp deletions in In either case, a functional toxin is not expected; a functional toxin is produced by the expression of three tandem genes,, , and Reverse transcriptase PCR with total RNA extracted from the isolates showed no expression of A toxin assay performed with these isolates on HeLa cells failed to show cytotoxic effects on the cells. However, the isolates were able to colonize the chicken ceca for a period of at least 4 weeks, similar to that of a clinical isolate. Other virulence gene markers, flagellin A and CadF, were present in 100% of the isolates. Our study suggests that crows carry the bacterium but with a dysfunctional toxin protein that is expected to drastically reduce its potential to cause diarrhea. Campylobacters are a major cause of gastroenteritis in humans. Since outbreaks have most often been correlated with poultry or unpasteurized dairy products, contact with farm animals, or contaminated water, historically, the majority of the studies have been with campylobacter isolates from poultry, domestic animals, and human patients. However, the bacterium has a broad host range that includes birds. These reservoirs need to be investigated, because the identification of the source and a determination of the transmission routes for a pathogen are important for the development of evidence-based disease control programs. In this study, two species of the human-commensal crow, from two different geographical regions separated by 7,000 miles of land and water, have been examined for their ability to cause disease by shedding campylobacters. Our results show that the crow may not play a significant role in campylobacteriosis, because the campylobacter organisms they shed produce a nonfunctional toxin.

Emergence of Genetic Diversity and Multi-Drug Resistant Campylobacter jejuni From Wild Birds in Beijing, China

“…All wild birds isolates had flaA genes, cadF genes, and cdt gene clusters, which in agreement with the previous study (Sen et al, 2018). The results suggest that these three genes are conserved amongst different sources.…”

“…The results suggest that these three genes are conserved amongst different sources. As before, C. jejuni isolates from crows had a truncated gene cluster of about 1400 bp (Sen et al, 2018), C. jejuni isolates from daurian jackdaw also had a truncated gene cluster (Kovanen et al, 2019). However, the most unexpected results were isolates from silver pheasant which also have a truncated gene cluster of about 1400 bp.…”

“…Five hundred and twenty fecal samples were collected from 33 species in 12 sites, Beijing, China, between January 2018 and April 2018 (Figure 1 and Table 1). Samples were collected in sterile tubes and stored at 4 to 7°C for 2 to 6 h before culturing in Lab (Sen et al, 2018). Fecal samples were inoculated onto Modified Charcoal Cefoperazone Deoxycholate Agar (mCCDA) containing Cefoperazone, Rifampicin, and Amphotericin B (Qingdao Hope Bio-Technology, Co., Ltd.), with incubation at 37°C under microaerophilic conditions (CampyGen; Oxoid Limited, Hampshire, United Kingdom) for 48 to 168 h. Then picked white to translucent colonies subculture onto mCCDA for further characterization.…”

“…All positive samples were used to extract DNA by adding 100 μl 0.25% SDS and boiling in a heater block at 95°C for 10 min, followed by centrifugation at 12,000 g for 5 min. Template DNA was stored at −20°C until used for PCR and at least 1 year without any degradation (Sen et al, 2018). Then Campylobacter spp.…”

Antibiotic Resistance of E. coli Isolated From a Constructed Wetland Dominated by a Crow Roost, With Emphasis on ESBL and AmpC Containing E. coli

“…Samples were collected by spreading plastic sheets on the ground underneath the trees where the crows roosted in the evening. Fresh fecal samples from free flying crows were collected the following morning with sterile swabs and placed in sterile vials kept on ice as described previously (Sen et al, 2018). Sixty one samples were collected in five rounds of sampling.…”