Abstract
The rapid emergence of multidrug-resistant (MDR) bacteria is a global health problem. Mobile genetic elements like conjugative plasmids, transposons, and integrons are the major players in spreading resistance genes in uropathogenic Escherichia coli (UPEC) pathotype. The E. coli BH100 strain was isolated from the urinary tract of a Brazilian woman in 1974. This strain presents two plasmids carrying MDR cassettes, pBH100, and pAp, with conjugative and mobilization properties, respectively. However, its transposable elements have not been characterized. In this study, we attempted to unravel the factors involved in the mobilization of virulence and drug-resistance genes by assessing genomic rearrangements in four BH100 sub-strains (BH100 MG2014, BH100 MG2017, BH100L MG2017, and BH100N MG2017). Therefore, the complete genomes of the BH100 sub-strains were achieved through Next Generation Sequencing and submitted to comparative genomic analyses. Our data shows recombination events between the two plasmids in the sub-strain BH100 MG2017 and between pBH100 and the chromosome in BH100L MG2017. In both cases, IS3 and IS21 elements were detected upstream of Tn21 family transposons associated with MDR genes at the recombined region. These results integrated with Genomic island analysis suggest pBH100 might be involved in the spreading of drug resistance through the formation of resistance islands. Regarding pathogenicity, our results reveal that BH100 strain is closely related to UPEC strains and contains many IS3 and IS21-transposase-enriched genomic islands associated with virulence. This study concludes that those IS elements are vital for the evolution and adaptation of BH100 strain.
Highlights
Escherichia coli are Gram-negative bacteria naturally found in the intestinal tract of several animal species and humans, where some strains can coexist with the host in a symbiotic relationship while others may cause disease (Moulin-Schouleur et al, 2007; Römer et al, 2012; Poolman and Wacker, 2016; Kittana et al, 2018)
We show that a Tn21 was detected in the recombined region of pApR (NZ_CP025252.1) from BH100 MG2017 (Figure 5 and Supplementary Figure 2)
This study has described E. coli BH100 genetic diversity, especially concerning functional mobile elements associated with MDR and virulence genes potentially related to uropathogenesis
Summary
Escherichia coli are Gram-negative bacteria naturally found in the intestinal tract of several animal species and humans, where some strains can coexist with the host in a symbiotic relationship while others may cause disease (Moulin-Schouleur et al, 2007; Römer et al, 2012; Poolman and Wacker, 2016; Kittana et al, 2018). A subset of E. coli strains is capable of causing extra-intestinal disease, including urinary tract infection (UTI), in which the pathotype uropathogenic E. coli (UPEC) accounts for 90% of global cases (Marrs et al, 2005) In this context, multidrugresistant (MDR) strains have been considered as a major bottleneck limiting the effective control of infections. E. coli BH100 was isolated in the city of Belo Horizonte in 1974 from urine samples from women with UTI (Chartone-Souza, 2017) This bacterium is a non-colicin producer, lactose fermenter (lac +) and harbors two plasmids, pBH100 and pAp, of approximately 60 and 10 MDa respectively. The smaller plasmid, pAp, can be mobilized by pBH100 and seems to provide resistance to β-lactams (Nascimento et al, 1992; Nascimento and Chartone-Souza, 2003) These previous phenotyping and molecular approaches allowed the description of the individual and small clusters of resistance elements. The long-term cultivation of BH100 in artificial conditions has promoted genetic variability, which resulted in the emergence of sub-strains (Chartone-Souza, 2017)
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