Enterococci with glycopeptide resistance in turkeys, turkey farmers, turkey slaughterers, and (sub)urban residents in the south of The Netherlands: evidence for transmission of vancomycin resistance from animals to humans?

Abstract

The number of vancomycin-resistant enterococci (VRE) relative to the total number of enterococci was determined in fecal samples from turkeys and three human populations in 1996, each with a different level of contact with turkeys, i.e., turkey farmers, turkey slaughterers, and (sub)urban residents. The percentage of VRE relative to the total enterococcal population (i.e., the degree of resistance) was low (2 to 4%) in all groups (except in six samples). No difference was observed between farmers who used avoparcin and those who did not. The pulsed-field gel electrophoresis (PFGE) patterns of the VRE isolates from the different populations were quite heterogeneous, but isolates with the same PFGE pattern were found among animal and human isolates, in addition to the isolates which were described previously (A. E. van den Bogaard, L. B. Jensen, and E. E. Stobberingh, N. Engl. J. Med. 337:1558-1559, 1997). Detailed molecular characterization of vanA-containing transposons from different isolates showed, that in addition to a previously reported strain, similar transposons were present in VRE isolates from turkeys and turkey farmers. Moreover, similar VanA elements were found not only in isolates with the same PFGE pattern but also in other strains from both humans and animals.

FIG. 1

PFGE patterns of E. faecium strains isolated from turkeys (T), turkey farmers (TF), and turkey slaughterers (TS) after digestion of total DNA with SmaI. Lane 1, molecular weight marker; lane 2, TF6, pattern N7; lane 3, TF16, pattern N; lane 4, TF17, pattern N1; lane 5, TF46, pattern N1; lane 6, TS19, pattern N2; lane 7, TS31, pattern N3; lane 8, TF20, pattern D; lane 9, TF26, pattern D; lane 10, T10, pattern D; lane 11, T44, pattern W; lane 12, TF8, pattern W; lane 13, T5, pattern B; lane 14, TF5, pattern B.

FIG. 2

Genetic maps of Tn1546 and six Tn1546 derivatives. The thick horizontal lines represent Tn1546 (type A1) (3) and Tn1546 types A2 (36), E4 (36), and E8 to E12. The positions of genes and open reading frames (orf’s) and the directions of transcription are depicted by open arrows. Dotted boxes represent insertion sequence (IS) elements. The positions of the first nucleotide upstream and downstream from the insertion sequence insertion sites are depicted. Filled arrows indicate the transcriptional orientation of inserted insertion sequence elements. Deletions have been indicated by dotted lines. The position of the base pair mutation in type A2 is indicated above the transposon type: position 8234, G → T (K → N).