title: Molecular structure and transferability of Tn1546-like elements in Enterococcus faecium isolates from clinical, sewage, and surface water samples in Iran.
abstract: The molecular structure and transferability of Tn1546 in 143 vancomycin-resistant Enterococcus faecium (VREF) isolates obtained from patients (n = 49), surface water (n = 28), and urban and hospital sewage (n = 66) in Tehran, Iran, were investigated. Molecular characterization of Tn1546 elements in vanA VREF was performed using a combination of restriction fragment length polymorphism analysis and DNA sequencing of the internal PCR fragments of vanA transposons. Long-PCR amplification showed that the molecular size of Tn1546 elements varied from 10.8 to 12.8 kb. The molecular analysis of Tn1546 showed that 45 isolates (31.5%) harbored a deletion/mutation upstream from nucleotide 170. No horizontal transfer of Tn1546 was observed following filter-mating conjugation with these isolates. Nevertheless, the rates of transferability for other isolates were 10(-5) to 10(-6) per donor. Insertion sequences IS1216V and IS1542 were present in 103 (72%) and 138 (96.5%) of the isolates, respectively. The molecular analysis of Tn1546 elements resulted in three genomic organizations. The genomic organization lineage 1 was dominated by the isolates from clinical samples (3.4%), lineage 2 was dominated mostly by sewage isolates (24.5%), and lineage 3 contained isolates obtained from all sources (72.1%). The genetic diversity determined using pulsed-field gel electrophoresis (PFGE) revealed a single E. faecium clone, designated 44, which was common to the samples obtained from clinical specimens and hospital and municipal sewage. Furthermore, the results suggest that lineage 3 Tn1546 was highly disseminated among our enterococcal isolates in different PFGE patterns.
authors.affiliation: Department of Microbiology, Pasteur Institute of Iran, Tehran, Iran.
authors.forename: M
authors.initials: M
authors.lastname: Talebi
authors.forename: M R
authors.initials: MR
authors.lastname: Pourshafie
authors.forename: M
authors.initials: M
authors.lastname: Katouli
authors.forename: R
authors.initials: R
authors.lastname: Möllby
mesh_terms: D001483:Base Sequence; D016000:Cluster Analysis; D004251:DNA Transposable Elements / Q000235:genetics*; D016521:Electrophoresis, Gel, Pulsed-Field; D016984:Enterococcus faecium / Q000235:genetics*; D040481:Genome Components; D006801:Humans; D007297:Inpatients; D007492:Iran; D008969:Molecular Sequence Data; D012150:Polymorphism, Restriction Fragment Length; D017422:Sequence Analysis, DNA; D012722:Sewage / Q000382:microbiology*; D020713:Vancomycin Resistance / Q000235:genetics*; D014871:Water Microbiology
chemical_list: D004251:DNA Transposable Elements; D012722:Sewage