Genetic properties of conjugative R plasmids in Escherichia coli and Salmonella isolated from feral and domestic pigeons, crows and kites

Abstract

A total of 62 conjugative R plasmids detected in 48 Escherichia coli and 19 conjugative R plasmids in 16 Salmonella strains from domestic (carrier and emerald) and feral pigeons, crows (Japanese jungle crows and carrion crows) and black kite, were examined for genetic properties. Out of the 62 E. coli R plasmids examined for fertility inhibition (Fi), 29 (46.8%) were Fi+, and the remainder were Fi-. Among the 62 R plasmids, 16 (25.8%) were classified into incompatibility (Inc) group FII, 15 (24.2%) into I alpha, 7 (11.3%) into H1 and 2 (3.2%) into N. The remaining 23 R plasmids could not be classified in this study. Among the 19 Salmonella R plasmids, 4 showed thermosensitive (ts) transfer. Out of the 18 plasmids tested, 13 (72.2%) including 4 ts-R plasmids were Fi-, and the remaining 5 (27.8%) were Fi+. Five R plasmids containing 4 Fi- were IncI alpha, while 4 ts-R plasmids belonged to IncH1 (1 R plasmid) and H2 (3 R plasmids). The remainings were not tested. In E. coli strains, IncFII and I alpha were widely (4 of 6 lots of birds, respectively) distributed, followed by N (2 lots) and H1 (1 lot). IncN R plasmid was detected from domestic pigeons and crows, but not from feral pigeons. In Salmonella strains from 5 lots of birds, IncFII and N plasmids which were detected from E. coli were not found, but IncH2 was detected from domestic pigeons (1 lot) and kite (1 lot). IncI alpha was detected from feral pigeons (1 lot) and kite (1 lot). The potential transfer of R plasmids between Salmonella and E. coli, and of dissemination of the plasmids among the free-flying birds, animals and humans is discussed.