Carriage rates and characteristics of Enterobacteriaceae producing extended-spectrum beta-lactamases in healthy individuals: comparison of applicants for long-term care and individuals screened for employment purposes.

AIMS: We compared the prevalence of extended-spectrum beta-lactamase (ESBL) producers in the faecal samples of 1,109 healthy individuals screened for employment purposes and in 531 asymptomatic individuals applying for long-term care (LTC).

METHODS

Eosin-methylene blue agar plates supplemented with 2 mg/l cefotaxime were used to determine which individuals were ESBL producers. ESBL phenotype was confirmed by double-disk synergy test and ESBL genes were identified by sequencing. ESBL producers were characterized by co-resistance and integron carriage.

RESULTS

ESBL producers were more frequent in the LTC applicants than in the employment screening individuals (7.2 vs. 2.0%; p < 0.0001), with 43 Escherichia coli, 18 Klebsiella pneumoniae, 1 Klebsiella oxytoca and 1 Proteus mirabilis being found. In the employment screening individuals, only E. coli was found. Most ESBL genes (79.4%, 50/63) were blaCTX-M type; blaCTX-M-15 was more frequent in the LTC applicants (p < 0.001). Regarding ESBL genes and integron diversity, E. coli isolates from the LTC applicants were more similar to K. pneumoniae than to E. coli from the employment screening individuals.

CONCLUSION

These differences in the characteristics of ESBL producers may represent different sources of colonization. Most LTC applicants harboured K. pneumoniae or E. coli that were probably hospital-acquired whereas the E. coli isolates of many healthy individuals showed similarities to environmental E. coli.