Detection of CTX-M-15-Producing Escherichia coli Isolates of Lineages ST131-B2 and ST167-A in Environmental Samples of a Tunisian Hospital

To investigate the possible role of the hospital environment in the dissemination of extended-spectrum-beta-lactamase (ESBL)-producing Escherichia coli isolates, 300 samples were taken during 2013 from abiotic surfaces (n = 250), healthcare worker hands (n = 27), and hands of patients (n = 23) in a Tunisian Hospital. ESBL-producing E. coli isolates were recovered in 3.7% of analyzed samples (4% abiotic surfaces; 4.3% hands of patients; 0% in healthcare worker hands), and one isolate/sample was further studied. The characterization of beta-lactamase genes, as well as the genetic environment of bla(CTX-M) gene, was performed by PCR and sequencing. The ESBL genes found were as follows: bla(CTX-M-15) (eight isolates), bla(CTX-M-15)+bla(SHV-12) (two isolates), and bla(SHV-12) (one isolate). The bla(TEM-1b) gene was detected in seven ESBL-positive isolates. The orf477 was found downstream of bla(CTX-M-15) gene in 10 strains, whereas the ISEcp1 sequence was identified upstream of this gene in two isolates. The analysis of class 1 integrons by PCR and sequencing revealed five positive isolates with the following gene cassette arrangements: dfrA1-aadA1 (two isolates), aadA1 (two isolates), and aadA2 (one isolate). The virulence-encoding genes aer, eae, bfp, and hly were detected by PCR in six, four, four, and three isolates, respectively. The following sequence types and associated phylogroups were detected among ESBL-producing strains: ST167-phylogroup-A (six isolates) and ST131-phylogroup-B2 (two isolates). In conclusion, the hospital environment could be a reservoir of multiresistant bacteria, including ESBL-positive E. coli isolates, which could be acquired by the patient population, and strict control measures should be established to minimize this problem.