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 bla_CTX-M type; bla_CTX-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.

26Background: Faecal carriage of extended-spectrum beta-lactamase (ESBL) producing Enterobacteriaceae 27 in healthy individuals was examined and compared to previous results obtained in such individuals a few 28 years earlier. 29Methods: Faecal samples from 779 individuals screened for employment purposes and from 225 30 applicants to long-term care (LTC) were screened between November 2013 and May 2014. 31Results: The overall rate of fecal carriage was 3.0% (30/1004). The carriage rate was significantly higher 32 in applicants for LTC (5.3% vs. 2.3%; p=0.019). All isolates carried CTX-M ESBLs, with an 33 overwhelming dominance of bla (84.4%) in both groups and in both E. coli and Klebsiella 34 pneumoniae. 35Conclusions: The prevalences were comparable to those in the earlier study, but a marked decrease of the 36 diversity of ESBL genes in E. coli from the employment screening group was found, suggesting that the 37 ESBL-producing isolates originating from diverse sources are being replaced by highly successful bla CTX- 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 To screen for ESBL production, faecal samples were inoculated onto eosin methylene blue agar plates 60 supplemented with 2 mg/l cefotaxime. Confirmation of ESBL phenotype was performed using double 61 disk synergy test (Oxoid, Basingstoke, UK). The isolates were identified by MALDI Biotyper (Bruker, 62Bremen, Germany) and by species-specific PCRs. Susceptibility to ertapenem, meropenem, imipenem, 63 cefotaxime, ceftazidime, cefepime, ciprofloxacin, co-trimoxazole, colistin, amikacin, gentamicin and 64 tobramycin was tested by disk diffusion according to EUCAST recommendations. All isolates were 65 screened for the genes bla TEM , bla SHV , and bla CTX-M , amplified genes were sequenced. Five 66 aminoglycoside resistance genes aac(3')-IIa, aac(6')-Ib, aph(3')-Ia, ant(2")-Ia, ant(3")-Ia, and class 1 67 and 2 integrons were sought for by PCRs. Gene cassette arrays were determined by sequencing. For 68 Escherichia coli phylogenetic group and the clone O25b-ST131 were determined by PCRs. All technical 69 protocols were described in our earlier publication [5] Resistance to other antibiotic classes than beta-lactamases was common. Eleven, twelve, eight and 13 of 84 14 isolates were resistant to ciprofloxacin, co-trimoxazole, gentamicin and amikacin, respectively, in the 85 LTC group, while these numbers were eleven, eleven, six and six of 18 isolates in healthy individuals. 86This difference in susceptibility to amikacin was also evident when comparing only E. coli isolates. 87Integron carriage rates were comparable. In the LTC group class 1 integrons were detected in four K. 0/18, p=0.02, respectively). This applied when comparing only E. coli isolates from the two groups (5/7 96 vs. 2/18, p=0.007 and 3/7 vs. 0/18, p=0.015, respectively). Phylogroup distributions wer...