Integron, Plasmid and Host Strain Characteristics of Escherichia coli from Humans and Food Included in the Norwegian Antimicrobial Resistance Monitoring Programs

Abstract

Antimicrobial resistant Escherichia coli (n=331) isolates from humans with bloodstream infections were investigated for the presence of class 1 and class 2 integrons. The integron cassettes arrays were characterized and the findings were compared with data from similar investigations on resistant E. coli from meat and meat products (n=241) produced during the same time period. All isolates were obtained from the Norwegian monitoring programs for antimicrobial resistance in human pathogens and in the veterinary sector. Methods used included PCR, sequencing, conjugation experiments, plasmid replicon typing and subtyping, pulsed-field-gel-electrophoresis and serotyping. Integrons of class 1 and 2 occurred significantly more frequently among human isolates; 45.4% (95% CI: 39.9-50.9) than among isolates from meat; 18% (95% CI: 13.2 -23.3), (p<0.01, Chi-square test). Identical cassette arrays including dfrA1-aadA1, aadA1, dfrA12-orfF-aadA2, oxa-30-aadA1 (class 1 integrons) and dfrA1-sat1-aadA1 (class 2 integrons) were detected from both humans and meat. However, the most prevalent cassette array in human isolates, dfrA17-aadA5, did not occur in isolates from meat, suggesting a possible linkage between this class 1 integron and a subpopulation of E. coli adapted to a human host. The drfA1-aadA1 and aadA1 class 1 integrons were found frequently in both human and meat isolates. These isolates were subjected to further studies to investigate similarities with regard to transferability, plasmid and host strain characteristics. We detected incF plasmids with pMLST profile F24:A-:B1 carrying drfA1-aadA1 integrons in isolates from pork and in a more distantly related E. coli strain from a human with septicaemia. Furthermore, we showed that most of the class 1 integrons with aadA1 were located on incF plasmids with pMLST profile F51:A-:B10 in human isolates. The plasmid was present in unrelated as well as closely related host strains, demonstrating that dissemination of this integron also could be attributed to clonal spread. In conclusion, among the systematically collected isolates from two different sources, some significant differences concerning integron prevalence and integron variants were observed. However, closely related plasmids as vehicles for specific class 1 integrons in isolates from meat and from a human with bloodstream infection were found. The occurrence of similar multi-resistance plasmids in bacteria from a food source and from a human clinical sample highlights the possible role of meat as a source of resistance elements for pathogenic bacteria.

Characterization of Integrons and Antimicrobial Resistance in Escherichia coli Sequence Type 131 Isolates

“…Two different gene cassettes were detected (Table 2), which correlated with resistance to a variety of aminoglycosides (aac and aad), chloramphenicol (cmlA), and trimethoprim (dfrA17), and the dfrA17-aadA5 (84.2%) gene cassette dominated in integron-positive isolates in this study, which may contributed to resistance to SXT. e gene cassettes identified were not novel in this study, and it was also the most prevalent gene cassette in E. coli in other previous studies [26,27]. According to the database in GenBank, a novel cassette array, aac(6′)-Ib-cr-cmlA5, was first reported in E. coli, suggesting the ability of integrons to capture and integrate resistance gene and to form novel cassettes that mediate resistance and multidrug resistance of E. coli ST131 clinical isolates.…”

Classes 1 and 2 integrons in faecal Escherichia coli strains isolated from mother-child pairs in Nigeria

“…IncF plasmids represent one of the most prevalent incompatibility types and have been identified worldwide in Enterobacteriaceae from different origins and sources [ 42 , 43 ]. These plasmids appear to significantly contribute to the dissemination of antibiotic resistance in Enterobacteriaceae and some have been associated with specific genes conferring resistance to β-lactams, quinolones, and aminoglycosides [ 42 , 44 , 45 , 46 ]. Therefore the preponderance of IncFIB in integron containing isolates may indicate its contribution to the dissemination of integron-borne cassettes in this environment.…”

Antimicrobial Resistance in Commensal Escherichia coli Isolated from Pigs and Pork Derived from Farms Either Routinely Using or Not Using In-Feed Antimicrobials

“…As with previous cross-sectional surveys, no relationship was found between molecular types that contained genes encoding ESBLP and aminoglycoside resistance on the farm and their presence in the abattoir. 31 …”