Molecular Alterations of VanA Element in Vancomycin-Resistant Enterococci Isolated During a Survey of Colonized Patients in an Italian Intensive Care Unit

Abstract

To screen for vancomycin-resistant enterococci (VRE) colonization in hospitalized patients and to study molecular evolution and alterations of Tn1546-like elements in VRE among potentially at-risk patients, a 3-year surveillance protocol in an Intensive Care Unit was performed. A total of 397 patients were screened in the period June, 1997-June, 2000, and VRE were isolated from rectal swabs taken at admission, weekly, and when clinically indicated. The susceptibility of the enterococci was determined by the disk diffusion and broth dilution methods. The presence of vancomycin-resistance genes (vanA, vanB, and vanC) was assessed by polymerase chain reaction (PCR); genetic clonality of isolates was assessed by pulsed-field gel electrophoresis (PFGE); Tn1546 types were obtained by restriction fragment length polymorphism (RFLP) analysis of Tn1546 PCR fragments. Thirty-four strains, 31 identified as Enterococcus faecium and 3 strains as E. faecalis, were isolated from 12 of the 397 patients (3.0%); all strains were VanA as assessed by PCR and were resistant to the other antibiotics tested and showed high-level resistance to aminoglycosides. Enterococci isolated during the study period showed that different genetic backgrounds of strains, determined by PFGE combined with RFLP of Tn1546, are present in all the strains isolated in the study. PFGE type B was predominant in 1998 and 1999, and insertion sequence movements were found to have a role in the evolution of VanA resistance elements found in all strains. This study demonstrates that single patients may be colonized by closely related VRE with several PFGE types containing a wide variety of VanA elements. Moreover, isolates with identical PFGE types may contain different VanA elements reflecting rearrangements mediated by insertion sequences in VRE strains during their stay in the gastrointestinal tract.

Identification and molecular characterization of Van A-type vancomycin-resistant Enterococcus faecalis in Northeast of Brazil

“…PFGE analyses of SmaI-digested bacterial DNA was performed in Gene Navigator apparatus (Amersham, Upsalla, Sweden) at 180V for 25 h, at 7ºC, as described previously by Campanile et al (2003). The equipment was adjusted for pulses of 20 s for 10 h, 8 s for 10 h, and 3 s for 5 h. DNA banding patterns were visualized at UV light after staining with ethidium bromide.…”

Epidemiology and control of antibiotic resistance in the intensive care unit

“…Epidemic outbreaks can happen [2,18]. Resistance is high in several countries for Gram-positive cocci such as methicillin-resistant Staphylococcus aureus (MRSA) [19-24,25 . ], glycopeptides-intermediate S. aureus (GISA) [26], vancomycinresistant enterococci [27][28][29][30][31][32][33][34] and Gram-negative bacteria [35][36][37], such as Klebsiella spp., other enterobacteriaceae harboring extended-spectrum b-lactamases [38 . , 39,40] and Acinetobacter or Pseudomonas spp., which are sometimes resistant to almost every antibiotic except colimycin [41][42][43][44][45]. Resistance to antibiotics is also increasing in paediatric [46][47][48] and neonatal units [49][50][51][52][53][54][55][56][57][58][59][60], which were relatively protected units until recently.…”

Emergence of Multi-Drug Resistance Gram-Positive Bacteria and New Active Antibiotics

“…Although vancomycin-resistant enterococci have been reported in many European countries and are circulating in restricted nosocomial areas, their overall prevalence is still low, ranging from 0.6% to 4.0% in the community as well as in hospitalized patients [23]. In the European SENTRY project, during 1997-1999, the prevalence of VRE was only 1-3% [201]: the great majority of strains in this study were E.faecalis.…”

“…Enterococcal antimicrobial resistance, especially vancomycin resistance, is of particular concern: multiple resistance phenotypes have been identified, including VanA, B, C, D, E and G. These strains, varying geographically from below 5% to > 30% [23], are often ampicillin-resistant owing to PBPs changes in 80% of E.faecium clinical isolates and 5% of E.faecalis. The rate of high-level resistance to aminoglycoside varies markedly among institutions, some enterococcal species are also highly resistant to macrolides, fluorquinolones, tetracyclines and carbapenems [24,25,26].…”