High prevalence and diversity of extended-spectrum b-lactamases in faecal Escherichia coli isolates of healthy humans

Abstract number: P632

Vinué L., Martínez S., del Pozo J.P., Sáenz Y., Torres C., Zarazaga M.

Objectives: To study the prevalence and genetic characterisation of extended-spectrum beta lactamases (ESBLs) in faecal Escherichia coli isolates of healthy humans and to analyse the surrounding regions of ESBL genes and its possible inclusion in integrons.

Methods: 105 faecal samples recovered from healthy humans were seeded on Levine agar plates supplemented with cefotaxime (2 mg/L) and were incubated at 37°C for 24 h. One colony per sample with E. coli morphology were identified and screened for ESBL production by double-disk test. All ESBL-positive E. coli isolates were included in this study. Susceptibility testing to 17 antimicrobials was performed by disk-diffusion test and genes encoding CTX-M, SHV and TEM type b-lactamases were analysed by specific PCRs and sequencing. The genetic environment of blaCTX-M genes as well as the presence of integrons and their gene cassette compositions were characterised by PCR and sequencing. The phylogenetic group of ESBL-positive isolates was determined by PCR.

Results: ESBL-producing E. coli isolates were detected in 7 of 105 analysed samples (6.6%). The ESBL genes found were the following ones (number of isolates): blaCTX-M-14a (1), blaCTX-M-14b (1), blaCTX-M-1 (2), blaCTX-M-32 (1), blaCTX-M-8 (1), and blaTEM-52 (1). The genetic environment of blaCTX-M genes were as follows: i) ISEcp1 and IS903 surrounding blaCTX-M-14a gene; ii) IS26/ISEcp1 and orf477 surrounding blaCTX-M-1 gene; iii) ISEcp1 and orf477 surrounding blaCTX-M-32 gene; iv) blaCTX-M-14b included into the integron In60 with dfrA16 plus aadA2 gene cassette arrangement in their variable region; v) the surrounding region of blaCTX-M-8 gene could not be identified. The blaCTX-M-32-positive isolate harboured a class 1 integron which included a variable region of 2000 bp. The phylogenetic groups A, B1 and B2/D were detected in 2, 1 and 4 of our ESBL-positive isolates, respectively.

Conclusions: A high prevalence and diversity of ESBLs are detected in faecal samples of healthy humans, mainly of the CTX-M class. The gene blaCTX-M-14 has been found in structures related with insertion sequences or integrons.

Session Details

Date: 19/04/2008
Time: 00:00-00:00
Session name: 18th European Congress of Clinical Microbiology and Infectious Diseases
Location: Barcelona, Spain
Presentation type:
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