Multiple antibiotic resistance gene recruitment onto the enterohemorrhagic Escherichia coli virulence plasmid

Abstract

Enterohemorrhagic Escherichia coli (EHEC) strains are zoonotic pathogens responsible for a range of severe human disease. The repertoire of virulence determinants promoting EHEC disease is encoded on both the main chromosome and virulence plasmid. We examined a multiply antibiotic-resistant O26 EHEC strain for carriage of resistance genes on the virulence plasmid. The EHEC virulence plasmid containing a complex antibiotic-resistance gene locus, designated as pO26-CRL, was purified from EHEC O26:H(-) (patient with hemorrhagic colitis) and subjected to shotgun-sequencing and bioinformatic analysis. Determination of the 111,481-bp sequence of pO26-CRL revealed genes encoding a functional enterohemolysin operon (ehxCABD), STEC-specific extracellular serine protease (espP), putative EHEC adhesin (toxB), catalase/peroxidase (katP), and myristoyl transferase (msbB) involved in lipid A synthesis. A 22,609-bp Tn21 derivative is inserted within the conjugal transfer gene traC and encodes resistance to trimethoprim, streptomycin, sulfathiozole, kanamycin, neomycin, beta-lactams, and mercuric chloride. Plasmid pO26-CRL is nonconjugative but is mobilizable. This is the first report of an EHEC virulence plasmid containing a complex antibiotic resistance locus, and raises the concern that antibiotic use will coselect for virulence determinants, leading to increased disease potential in both commensal and pathogenic E. coli populations.-Venturini, C., Beatson, S. A., Djordjevic, S. P., Walker, M. J. Multiple antibiotic resistance gene recruitment onto the enterohemorrhagic Escherichia coli virulence plasmid.

Virulence Genes and Antimicrobial Susceptibilities of Hemolytic and Nonhemolytic Escherichia coli Isolated from Post-Weaning Piglets in Central Thailand

“…Most of the HEC isolates containing virulence factors seemed to have a greater ability to tolerate this antimicrobial selective pressure than the NHEC isolates. Previously, a weak positive correlation was reported between hemolysin production and resistance to tetracycline and chloramphenicol in chicken strains of E. coli [42]; the genes for these phenotypes were located on the same plasmid, and this was also detected in an isolate from a patient with EHEC [36]. Moreover, the resistance phenotype was associated with biofilm formation, resulting in increased pathogenicity [35].…”

Virulence Gene Profiles and Clonal Relationships of Escherichia coli O26:H11 Isolates from Feedlot Cattle as Determined by Whole-Genome Sequencing

“…Resistance to antibiotics has been described in other O26 strains from cattle (Scotland; 2004), although the percent resistance to one or several antibiotics was below 2% (51). The mechanism for resistance to multiple antibiotics in O26:H11 strains is not new, and antibiotic resistance has been described previously in a stx ϩ O26:H11 strain (O6877) isolated from a clinical case in Australia as part of an integron element (52). The integron was located in the 111-kb virulence plasmid (pO26-CRL) (52).…”

Recent Advances in Understanding Enteric Pathogenic Escherichia coli

“…Furthermore, there is significant resistance to ampicillin, streptomycin, and trimethoprim, which can be more frequent in non-O157 STEC isolates. Plasmids have been found to be a source of antimicrobial resistance genes in STEC isolates (35,394). Recently, an extended-spectrum ␤-lactamase (ESBL) plasmid, rarely found in STEC O157:H7, was isolated from a 2-year-old child in Denmark (395).…”