Browsing by Autor "Chiara Lucchetti"

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Multidrug-resistant Commensal<i>Escherichia coli</i>in Children, Peru and Bolivia
(Centers for Disease Control and Prevention, 2006) Alessandro Bartoloni; Lucia Pallecchi; Marta Benedetti; Connie Fernandez; Yolanda Vallejos; Elisa Guzmán; Ana Liz Villagrán; Antonia Mantella; Chiara Lucchetti; Filippo Bartalesi
Using a rapid screening method, we investigated the prevalence of fecal carriage of antimicrobial drug-resistant Escherichia coli in 3,174 healthy children from 4 urban settings in Peru and Bolivia. High resistance rates were observed for ampicillin (95%), trimethoprim-sulfamethoxazole (94%), tetracycline (93%), streptomycin (82%), and chloramphenicol (70%). Lower resistance rates were observed for nalidixic acid (35%), kanamycin (28%), gentamicin (21%), and ciprofloxacin (18%); resistance to ceftriaxone and amikacin was uncommon (<0.5%). In a random sample of 1,080 resistant E. coli isolates, 90% exhibited a multidrug-resistance (MDR) phenotype. The 2 most common MDR phenotypes (ampicillin/tetracycline/trimethoprim-sulfamethoxazole and ampicillin/tetracycline/trimethoprim-sulfamethoxazole/chloramphenicol) could be transferred en bloc in conjugation experiments. The most common acquired resistance genes were blaTEM, tet(A), tet(B), drfA8, sul1, sul2, and catI. These findings underscore the magnitude of the problem of antimicrobial drug resistance in low-resource settings and the urgent need for surveillance and control of this phenomenon.
Population Structure and Resistance Genes in Antibiotic-Resistant Bacteria from a Remote Community with Minimal Antibiotic Exposure
(American Society for Microbiology, 2007) Lucia Pallecchi; Chiara Lucchetti; Alessandro Bartoloni; Filippo Bartalesi; Antonia Mantella; Herlan Gamboa; Alessandra Carattoli; Franco Paradisi; Gian María Rossolini
In a previous study, we detected unexpectedly high levels of acquired antibiotic resistance in commensal Escherichia coli isolates from a remote Guaraní 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, catI, 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.