Molecular Structure and Transferability of Tn1546-Like Elements in Enterococcus faecium Isolates from Clinical, Sewage, and Surface Water Samples in Iran

• Published in: Applied and Environmental Microbiology 2008-03, Vol.74 (5), p.1350-1356
• Main Authors: Talebi, M, Pourshafie, M.R, Katouli, M, Möllby, R
• Format: Article
• Language: English
• Subjects: Base Sequence; Biological and medical sciences; Cluster Analysis; DNA Transposable Elements - genetics; Electrophoresis, Gel, Pulsed-Field; Enterococcus faecium; Enterococcus faecium - genetics; Fundamental and applied biological sciences. Psychology; Gene amplification; Genetic diversity; Genome Components; Humans; Inpatients; Iran; Medicin och hälsovetenskap; Microbiology; Molecular biology; Molecular Sequence Data; Molecular structure; Molecules; Polymorphism; Polymorphism, Restriction Fragment Length; Public Health Microbiology; Sequence Analysis, DNA; Sewage - microbiology; Vancomycin Resistance - genetics; Water Microbiology
• ISSN: 0099-2240; 1098-5336; 1098-5336
• DOI: 10.1128/AEM.02254-07

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.