Molecular alterations of VanA element in vancomycin-resistant enterococci isolated during a survey of colonized patients in an Italian intensive care unit.
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.
Campanile
Floriana
F
Department of Microbiological and Gynecological Sciences, University of Catania, 95124 Catania, Italy.
Bartoloni
Alessandro
A
Bartalesi
Filippo
F
Borbone
Sonia
S
Mangani
Valerio
V
Mantella
Antonia
A
Nicoletti
Giuseppe
G
Paradisi
Franco
F
Russo
Giovanni
G
Strohmeyer
Marianne
M
Stefani
Stefania
S
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001426:Bacterial Proteins / Q000235:genetics*; D019729:Carbon-Oxygen Ligases / Q000235:genetics*; D002648:Child; D004269:DNA, Bacterial / Q000235:genetics; D003625:Data Collection; D016521:Electrophoresis, Gel, Pulsed-Field; D016983:Enterococcus / Q000187:drug effects* / Q000235:genetics*; D005243:Feces / Q000382:microbiology; D005260:Female; D016680:Genome, Bacterial; D016908:Gram-Positive Bacterial Infections / Q000453:epidemiology / Q000382:microbiology*; D006801:Humans; D017053:Infection Control; D007362:Intensive Care Units; D007558:Italy / Q000453:epidemiology; D008297:Male; D008826:Microbial Sensitivity Tests; D008875:Middle Aged; D005810:Multigene Family / Q000235:genetics; D011110:Polymorphism, Genetic / Q000235:genetics; D012150:Polymorphism, Restriction Fragment Length; D011446:Prospective Studies; D020133:Reverse Transcriptase Polymerase Chain Reaction; D020713:Vancomycin Resistance / Q000235:genetics*
D001426:Bacterial Proteins; D004269:DNA, Bacterial; C071437:VanA ligase, Bacteria; D019729:Carbon-Oxygen Ligases