Socioeconomic factors and antibiotic use in relation to antimicrobial resistance in the Amazonian area of Peru.

Our objective was to correlate antibiotic resistance in gut E. coli flora of children, aged 6-72 months, with use of antibiotics, socioeconomic status (SES) and household characteristics in the urban communities of Yurimaguas and Moyobamba in the Amazonian area of Peru. Caregivers of 1598 children were interviewed using a structured questionnaire in a cross-sectional survey. Faecal samples were collected from the children and the antimicrobial susceptibility of E. coli was analysed by a rapid resistance screening method. Significantly higher odds for resistance were seen for children who had used antibiotics, both during the last 2 weeks and the last 6 months. Children from wealthier families had significantly higher odds for resistance to a number of antibiotics than children from the least wealthy families (Yurimaguas: nalidixic acid, OR = 2.13; ciprofloxacin, OR = 2.09; chloramphenicol, OR = 1.98. Moyobamba: nalidixic acid, OR = 1.59; ciprofloxacin, OR = 1.69). Thus, the children of wealthier families had a significantly increased odds ratio for resistance, also when controlling for the family's antibiotic use. Unknown factors related to socioeconomic status seem to contribute to the results seen in the study area.

Standard and real-time multiplex PCR methods for detection of trimethoprim resistance dfr genes in large collections of bacteria.

Two multiplex PCR (mPCR) methods were developed to screen large collections of trimethoprim-resistant Escherichia coli isolates for the most prevalent resistance determinants. Five common integron-carried genes (dfrA1, dfrA5, dfrA7, dfrA12 and dfrA17) were selected as PCR targets. Primers and conditions for standard mPCRs and real-time mPCRs were selected and tested. Two protocols using essentially the same primer pairs were established. The standard mPCR protocol also included an internal control targeting the E. coli 16S rRNA gene. Both protocols proved to be sensitive and specific for detection of the five selected genes. Screening of three different collections of clinical urinary and blood isolates (n = 368) with the two multiplex methods revealed that the five dfr genes accounted for 75-86% of trimethoprim resistance. The standard mPCR is useful and accessible for most laboratories, while the real-time mPCR requires additional equipment and expensive reagents, but is very convenient for high-throughput screening of large collections of bacterial isolates.

Two new dfr genes in trimethoprim-resistant integron-negative Escherichia coli isolates.

Two Escherichia coli isolates resistant to trimethoprim but negative for integrons carried two new resistance genes, dfrA24 and dfrA26, remotely similar to one another and to the cassette-independent genes dfrA8 and dfrA9. The dfrA24 gene was not associated with known mobile elements, while dfrA26 was associated with the CR1 common region.

Integrons and gene cassettes in clinical isolates of co-trimoxazole-resistant Gram-negative bacteria.

Despite a trend of declining consumption, resistance to co-trimoxazole has increased during a 12-year period in Stockholm. The molecular background to this surprising development was investigated by using PCR to screen for integrons and specific resistance genes, followed by sequence analysis of selected integrons, in 105 clinical urinary isolates of Gram-negative bacteria selected partly for trimethoprim resistance. Sixty-five integrons of class 1 or 2 were detected in a subset of 59 isolates, and of these positive isolates, all but one were resistant to trimethoprim. However, 11 isolates were resistant to trimethoprim, but negative for integrons. Isolates positive for integrons were resistant to an average of 4.2 antibiotics, compared with 1.9 antibiotics for integron-negative isolates. Despite this, the only gene cassettes identified in 19 class 1 integrons analysed were dfr and aadA cassettes. Thus, only resistance to trimethoprim, streptomycin, spectinomycin and sulphonamides could be explained by the presence of integrons in these isolates. A new dfr gene, named dfrA22, was discovered as a single gene cassette in a class 1 integron. In addition, sulphonamide resistance in many isolates was caused by carriage of sul2, which has no known association with integrons. Resistance to co-trimoxazole and many other antibiotics was thus not accounted for fully by the presence of integrons in these isolates.