High abundance and diversity of antimicrobial resistance determinants among early vancomycin-resistant Enterococcus faecium in Poland

Abstract

The purpose of this study was to investigate the clonal structure, antimicrobial resistance phenotypes and their determinants among early vancomycin-resistant Enterococcus faecium (VREm) isolates in Poland. Two hundred and eighty-one VREm isolates collected between 1997 and 2005 were studied. VREm isolates were characterised by multilocus sequence typing (MLST). The presence of antimicrobial resistance determinants, transposon-specific genes, IS16 and esp Efm was checked by polymerase chain reaction (PCR). Ciprofloxacin and ampicillin resistance determinants were investigated by sequencing. Two hundred and twenty-two (79 %) and 59 (21 %) VREm isolates were vanA- and vanB-positive, respectively. Among 135 representative isolates, MLST yielded 33 different sequence types (STs), of which 29 were characteristic of hospital-associated E. faecium; 128 (94.8 %) and 123 (91.1 %) isolates harboured the IS16 and esp Efm genes, and all 135 isolates were resistant to ciprofloxacin and ampicillin. Resistance to tetracycline (71.1 % isolates) was mostly associated with tetM (75.0 %) and the concomitant presence of the Tn916 integrase gene. High-level resistance to streptomycin (93.3 % of isolates) and high-level resistance to gentamicin (94.1 % of isolates) were due to ant(6')-Ia and aac(6')-Ie-aph(2″) genes, respectively, the latter of which is known to be located on various Tn4001-type transposons. Fifteen combinations of mutations in the quinolone-determining regions of GyrA and ParC were identified, including changes not previously reported, such as S83F and A84P in GyrA. Twenty-three variants of the penicillin-binding protein PBP5 occurred in the studied group, and novel insertions at amino acid positions 433 and 568 were identified. This analysis revealed the predominance of hospital-associated strains of E. faecium, carrying an abundant and divergent range of resistance determinants among early VREm isolates in Poland.

Typing of Enterococcus spp. strains in 4 hospitals in the Małopolska region in Poland

“…2,19,22 However, in our study, E. faecium VanA phenotype strains were in the minority, while VanB phenotype isolates were in the majority. This seems to be the characteristic feature for VREfm from the Małopolska region, because in other provinces VanA phenotype is predominant.…”

“…29 In agreement with other studies from Poland, also ours, the spread of the aac(6')-Ie-aph(2")-Ia gene, which encodes the bifunctional enzyme AAC(6')-APH(2") and eliminates the synergistic effect between β-lactams or glycopeptide antibiotics and aminoglycosides, was responsible for high-level resistance to gentamicin among the majority of enterococci. 22,28 Thus, it precludes its therapeutic application in severe infections caused by enterococci, including bacteremia and endocarditis. 28,29 If the strains are resistant to high concentrations of gentamicin with simultaneous sensitivity to streptomycin (HLGR), streptomycin can be used in combination with β-lactams and glycopeptides.…”

“…30 In our study, all strains belonging to the E. faecium species showed the presence of IS16, which is a similar result to other studies from Poland. 19,22,23,30 …”

Diversity of plasmids and Tn1546-type transposons among VanA Enterococcus faecium in Poland

“…Part of the isolates analyzed in this work correspond to strains partially tested in previous surveillance studies, including: 108 VanA representatives of the VR Efm collection from 1997 to 2005 [17] and 20 representative isolates of a E. faecium VanA outbreak in 2009 [18]. The majority of isolates ( n  = 137) were derived from 11 VanA outbreaks and the remaining 79 isolates were reported as single isolations.…”

Molecular Analysis of VanA Outbreak ofEnterococcus faeciumin Two Warsaw Hospitals: The Importance of Mobile Genetic Elements

“…PCR for the rep pLG1 [9] was performed with primers designed previously [35]. The presence of plasmid addiction systems, relaxase genes, and the intA integrase gene of integrative and conjugative element ICE Efm1 was also verified by PCR [36–38]. …”