Abstract
The study examines whether crows are carriers of extraintestinal pathogenic E. coli (ExPEC) and avian pathogenic E. coli (APEC)-like strains, and if wetland roost areas contribute to their spread. A total of 10 crow feces (n = 71) and 15 water E. coli isolates (n = 134) from a wetland area could be characterized as potentially ExPEC based on the presence of ≥2 of the five cardinal genes iutA, kpsMT2, papEF, pap A/C, papG, sfa/foc, and afa/dra, while six fecal and 14 water isolates could be characterized as potentially APEC-like based on the presence of plasmid associated genes: iutA, episomal iss, ompT, hlyF and iroN. A total of 32 fecal and 27 water isolates tested carried plasmids based on incompatibility typing. Plasmids from 34 of 38 isolates tested could be transferred to another E. coli strain by conjugation with the antibiotic resistance (AR) profile being transferred, indicating their potential to be transferred to indigenous and non-pathogenic strains in the wetland. APEC-like plasmids could be transferred in six of eight isolates tested. Pathogenic E. coli of importance to the medical community and poultry industry may be detected in high levels in surface water due to corvid activity. Regardless of their role in health or disease, water in wetlands and streams can serve as a media for the dissemination of AR and virulence traits of bacteria, with corvids acting as potential vectors for farther dissemination.
Highlights
Wild birds, including crows, can act as reservoirs and be vectors in the spread of pathogens that are capable of causing diseases in both humans and animals [1,2]
A set of five virulence genes commonly found in extraintestinal pathogenic E. coli (ExPEC) [16] and another set typically found on a colicin encoding plasmid in avian pathogenic E. coli (APEC) strains [17] were examined in 104 crow isolates and 134 wetland water isolates
Strains possessing one of these five genes were rejected as potentially APEC, because a screening of 994 avian isolates had earlier demonstrated that non-pathogenic Avian fecal E. coli or AFEC strains had on the average 1.3 of these virulence genes while APEC strains had three or more [17]
Summary
Wild birds, including crows, can act as reservoirs and be vectors in the spread of pathogens that are capable of causing diseases in both humans and animals [1,2]. A similar analysis of 994 avian isolates, all of which were highly pathogenic strains and previously shown to be capable of causing colisepticemia, was used in identifying five genes that could be used as a predictor of an APEC strain, distinguishing it from an avian fecal commensal non-pathogenic E. coli strain or AFEC strain [17] These VF genes, iutA, iroN (iron metabolism), iss (increased serum survival), hlyF (hemolysis) and ompT (surface exclusion and serum survival) genes were shown to be present on large plasmids, a defining and necessary trait for APEC virulence [10]. The remaining 2 mL of the culture was frozen as stock culture after addition of 600 μL of 50% glycerol
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