title: Molecular evolution of metallo-beta-lactamase-producing Pseudomonas aeruginosa in a nosocomial setting of high-level endemicity.
abstract: An outbreak of multidrug-resistant Pseudomonas aeruginosa strains producing VIM-type metallo-beta-lactamases (MBLs) has occurred in an Italian hospital since 2000 (C. Lagatolla, E. A. Tonin, C. Monti-Bragadin, L. Dolzani, F. Gombac, C. Bearzi, E. Edalucci, F. Gionechetti, and G. M. Rossolini, Emerg. Infect. Dis. 10:535-538, 2004). In this work, using molecular methods, we characterized 128 carbapenem-resistant isolates (including 98 VIM-positive isolates) collected from that hospital from 2000 to 2002 to investigate the dynamics of the dissemination of MBL producers in the clinical setting. Genotyping by random amplification of polymorphic DNA and pulsed-field gel electrophoresis showed that most VIM-positive isolates belonged to two different clonal lineages, producing either a VIM-1- or a VIM-2-like MBL, whose ancestors were detected for the first time in the hospital in 1999, suggesting that clonal expansion played a predominant role in the dissemination of these isolates. The 86 clonally related isolates carrying a blaVIM-1-like gene on an In70-like integron were clearly related to a VIM-1-positive P. aeruginosa clone circulating in various Italian hospitals since the late 1990s. VIM-negative P. aeruginosa strains related to the VIM-1-positive clone were detected during the same period, suggesting that the latter strain was derived from a clonal lineage already circulating in the hospital. In the VIM-2-like positive clone, the MBL gene was carried by an unusual class 1 integron, named In71, lacking the 3' conserved sequence region typical of sul1-associated integrons. A different class 1 integron with an original structure carrying a blaVIM-2 determinant, named In74, was detected in a sporadic isolate. A retrospective investigation did not reveal the presence of strains related to any of the VIM-producing isolates earlier than 1997.
authors.affiliation: Dipartimento Scienze Biomediche, Università di Trieste, Via Fleming 22, 34127 Trieste, Italy. lagatolla@dsb.units.it
authors.forename: Cristina
authors.initials: C
authors.lastname: Lagatolla
authors.forename: Elisabetta
authors.initials: E
authors.lastname: Edalucci
authors.forename: Lucilla
authors.initials: L
authors.lastname: Dolzani
authors.forename: Maria Letizia
authors.initials: ML
authors.lastname: Riccio
authors.forename: Filomena
authors.initials: F
authors.lastname: De Luca
authors.forename: Erica
authors.initials: E
authors.lastname: Medessi
authors.forename: Gian Maria
authors.initials: GM
authors.lastname: Rossolini
authors.forename: Enrico Angelo
authors.initials: EA
authors.lastname: Tonin
mesh_terms: D015139:Blotting, Southern; D016000:Cluster Analysis; D003428:Cross Infection / Q000453:epidemiology / Q000382:microbiology*; D016172:DNA Fingerprinting; D004269:DNA, Bacterial / Q000032:analysis / Q000737:chemistry / Q000235:genetics*; D004196:Disease Outbreaks; D019143:Evolution, Molecular; D005838:Genotype; D006761:Hospitals; D006801:Humans; D007297:Inpatients; D032023:Integrons / Q000235:genetics; D007558:Italy; D017720:Molecular Epidemiology; D008969:Molecular Sequence Data; D012150:Polymorphism, Restriction Fragment Length; D011552:Pseudomonas Infections / Q000453:epidemiology / Q000382:microbiology*; D011550:Pseudomonas aeruginosa / Q000145:classification / Q000201:enzymology / Q000235:genetics* / Q000302:isolation & purification; D019105:Random Amplified Polymorphic DNA Technique; D017422:Sequence Analysis, DNA; D001618:beta-Lactamases / Q000096:biosynthesis
chemical_list: D004269:DNA, Bacterial; D001618:beta-Lactamases