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ANTRES Report Summary

Project ID: ICA4-CT-2001-10014
Funded under: FP5-INCO 2
Country: Italy

Analysis of resistance mechanisms and genotypes

Confirmed E. coli isolates were subjected to molecular analysis investigating resistant mechanisms and genotypes with special emphasis on resistance determinants of clinical relevance and useful as markers in molecular epidemiology. Deliverables included data on the distribution of multi-drug resistant phenotypes and relevant resistance genes in the commensal microbiota of 3174 children aged 6-72 months from Bolivia and Peru. A widespread dissemination of MDR isolates and co-transferable resistance determinants could be described. In a random sample of 1.080 resistant E. coli isolates, 90% exhibited a multi-drug-resistance (MDR) phenotype.

The two most common MDR phenotypes (ampicillin/tetracycline/trimethoprim-sulphamethoxazole and ampicillin/tetracycline/trimethoprim-sulphamethoxazole/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. Investigating the acquired resistance to sulphonamides, it was possible to describe for the first time in America the presence of sul3 gene. Moreover, 4 ceftriaxone-resistant E. coli isolates were collected, one from each urban area. These isolates were shown to produce CTX-M-type extended-spectrum-?-lactamases (ESBL): CTX-M-2 (the isolates from Camiri, Villa Montes and Moyobamba) and CTX-M-15 (the isolate from Yurimaguas).

This was the first report of CTX-M-type enzymes in Bolivia and Peru, and also the first detection of CTX-M-15 in Latin America. Mechanisms of resistance spreading were complex and involved both clonal expansion of antimicrobial-resistant strains and horizontal transfer/recombination of mobile genetic elements harbouring resistance genes. Two years later the antimicrobial resistance screening has been repeated in the same study area enrolling 3193 healthy children in the same age cohort.

The results revealed a notable trend toward the dissemination of CTX-M genes in commensal E. coli, which could represent an important reservoir of these emerging resistance determinants in the community. 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.

Related information

Reported by

Dipartimento di Biologia Molecolare - Ospedale le Scotte
Viale Bracci
53100 Siena
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