Population structure and resistance genes in antibiotic-resistant bacteria from a remote community with minimal antibiotic exposure

Lucia Pallecchi, Chiara Lucchetti, Alessandro Bartoloni, Filippo Bartalesi, Antonia Mantella, Herlan Gamboa, Alessandra Carattoli, Franco Paradisi, Gian Maria Rossolini

Research output: Contribution to journalArticle

Abstract

In a previous study, we detected unexpectedly high levels of acquired antibiotic resistance in commensal Escherichia coli isolates from a remote Guarani Indian (Bolivia) community with very low levels of antibiotic exposure and limited exchanges with the exterior. Here we analyzed the structure of the resistant E. coli population from that community and the resistance mechanisms. The E. coli population (113 isolates from 72 inhabitants) showed a high degree of genetic heterogeneity, as evidenced by phylogenetic grouping (77% group A, 10% group B1, 8% group D, 5% group B2) and genotyping by randomly amplified polymorphic DNA (RAPD) analysis (44 different RAPD types). The acquired resistance genes were always of the same types as those found in antibiotic-exposed settings [blaTEM, blaPSE-1, cmlA6, cmlA6, tet(A), tet(B), dfrA1, dfrA7, dfrA8, dfrA17, sul1, sul2, aphA1, aadA1, aadA2, aadA5, aadB, and sat-1]. Class 1 and class 2 integrons were found in 12% and 4% of the isolates, respectively, and harbored arrays of gene cassettes similar to those already described. The cotransferability of multiple-resistance traits was observed from selected isolates and was found to be associated with resistance conjugative plasmids of the F, P, and N types. Overall, these data suggest that the resistance observed in this remote community is likely the consequence of the dissemination of resistant bacteria and resistance genes from antibiotic-exposed settings (rather than of an independent in situ selection) which involved both the clonal expansion of resistant strains and the horizontal transfer/recombination of mobile genetic elements harboring resistance genes.

Original languageEnglish
Pages (from-to)1179-1184
Number of pages6
JournalAntimicrobial Agents and Chemotherapy
Volume51
Issue number4
DOIs
Publication statusPublished - Apr 2007

ASJC Scopus subject areas

  • Pharmacology (medical)

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    Pallecchi, L., Lucchetti, C., Bartoloni, A., Bartalesi, F., Mantella, A., Gamboa, H., Carattoli, A., Paradisi, F., & Rossolini, G. M. (2007). Population structure and resistance genes in antibiotic-resistant bacteria from a remote community with minimal antibiotic exposure. Antimicrobial Agents and Chemotherapy, 51(4), 1179-1184. https://doi.org/10.1128/AAC.01101-06