Molecular characterization, genetic diversity and antibacterial susceptibility ofEscherichia coliencoding Shiga toxin 2f in domestic pigeons

Abstract

This study aimed to evaluate prevalence, characteristics, genotypic diversity and antibacterial susceptibility of Escherichia coli encoding Shiga toxin 2f in domestic pigeons in different provinces of Iran. A total of 117 faecal samples were collected from pigeons and were subjected to molecular detection of stx2f. In total, 20, 25·8, 21·4 and 9% of pigeons from Tehran, Ferdows, Garmsar and Babol cities carried stx2f+ isolates, respectively. Of the 460 E. coli isolates examined, 43 were stx2f+ and most also carried eae (95·3%) and astA (97·7%) genes. Some of the stx2f+ isolates harboured cnf (9·3%), but all were negative for stx1, stx2 (other subtypes) and ehly. Most Strains (90%) were assigned to B1 phylogroup and possessed Intimin-β. Fingerprinting of the stx2f+ isolates using either enterobacterial repetitive intergenic consensus sequences (ERIC) or random amplified polymorphic DNA (RAPD)-polymerase chain reaction revealed seven distinct profiles by each method, with one prevailing (65·1 and 46·5%, respectively). By the combination of methods, 10 profiles were recognized. Ten isolates from different profiles were shown to belong to O20, O78 and O115 serogroups, and eight were 100% identical in the stx2f gene sequence. The strains were consistently resistant to amoxicillin and lincospectin and commonly resistant to tetracycline (88·4%) and doxycycline (74·4%). Overall, the results indicate a limited degree of genetic diversity in stx2f-harbouring E. coli from pigeons. Significance and impact of the study: Carriage of stx2f gene tends to be underreported in pigeon Escherichia coli isolates because most routine genetic and phenotypic tests cannot efficiently target this gene or detect the toxin. Nevertheless, pigeons frequently carry E. coli strains that are stx2f-positive, and this situation is not limited to any distinct geographical area. The current results suggest that genetic background of stx2f-encoding E. coli is distinct from most Shiga toxin-producing E. coli strains. However, the factors that contribute to host preferences and pathogenicity remain unclear. These findings have public health significance that should be addressed in future research.

Prevalence of Shiga Toxin-Producing and Enteropathogenic Escherichia coli in Wild and Pet Birds in Iran

“…Additionally, Wen-Jie et al (2008) study showed the presence of stx2f gene in avian pathogenic E. coli (APEC) strains in China. Similar to our observation, previous studies showed that stx2f-harboring strains lack other stx subtypes and mostly possess the eae gene (Askari Badouei et al, 2014;Schmidt et al, 2000;Morabito et al, 2001). The strains possessing the stx2f/eae genes in this study isolated from a duck, two geese and a lesser kestrel.…”

“…In general, pigeons are known as natural reservoirs of stx2f-harboring STEC strains (Kobayashi et al, 2002;Schmidt et al, 2000;Kobayashi et al, 2009; Badouei et al, 2014). The prevalence of stx2f+ strains reported in pigeons ranged from 4% to18.8% in different studies (Askari Badouei et al,2014;Schmidt et al, 2000;Farooq et al,2009).…”

“…Strains harboring the stx2f gene have been considered as emerging pathogens (Prager et al, 2009). Various methods have been applied for identification of STEC strains in birds, but most of them were unable to target the stx2f subtype (Askari Badouei et al, 2014;Ziebell et al, 2002;Feng et al, 2011).…”

Whole-Genome Characterization and Strain Comparison of VT2f-ProducingEscherichiacoliCausing Hemolytic Uremic Syndrome

“…The intimin subtyping has been performed in silico through a BLAST search ( 22 ) of the eae gene sequences from the WGS against the National Center for Biotechnology Information nucleotide repository. The intimin types of the VT2f-producing strains isolated from pigeons have been published ( 6 , 10 ). …”

“…The finding of such a high prevalence of VTEC in pigeons living in Rome led to further research into these bacteria in this and other bird species worldwide. Almost all these studies succeeded in isolating VTEC, with prevalence ranging 3% to >19% in different countries and bird species; most VTEC isolated from pigeon feces and cloacal swab samples harbored the genes encoding the VT2f subtype ( 7 – 10 ). These findings emphasize the existence of a strict association between VTEC carrying the vtx2f genes and pigeons, which represent a reservoir for such strains.…”