title: Prolonged outbreak of infection due to TEM-21-producing strains of Pseudomonas aeruginosa and enterobacteria in a nursing home.
abstract: Over a 6-year period, 24 extended-spectrum beta-lactamase (ESBL)-producing isolates of Pseudomonas aeruginosa were collected from 18 patients living in a nursing home. These isolates had a delayed development of a red pigment and exhibited a similar antibiotype (resistance to all beta-lactams except for imipenem and to gentamicin, tobramycin, netilmicin, ciprofloxacin, and rifampin) associated with the production of the TEM-21 beta-lactamase and a type II 3'-N-aminoglycoside acetyltransferase [AAC(3)-II] enzyme. Surprisingly, serotyping showed that these isolates belonged to four successive serotypes (P2, P16, P1, and PME), although molecular typing by PCR methods and pulsed-field gel electrophoresis yielded identical or similar profiles. Moreover, in all isolates the bla(TEM-21) gene was part of a chromosomally located Tn801 transposon truncated by an IS6100 element inserted within the resolvase gene, and the aac(3)-II gene was adjacent to this structure. During the same period, 17 ESBL-producing isolates of enterobacteria were also collected from 10 of these patients. These isolates harbored a similar large plasmid that contained the bla(TEM-21) and the aac(3)-II genes and that conferred additional resistance to sulfonamides and chloramphenicol, as well as to kanamycin, tobramycin, netilmicin, and amikacin, conveyed by an AAC(6')-I enzyme. The bla(TEM-21) gene was part of the Tn801 transposon disrupted by IS4321. Thus, a single clone of P. aeruginosa that had undergone a progressive genetic drift associated with a change in serotype appeared to be responsible for an outbreak of nosocomial infections in a nursing home. This strain has probably acquired the bla(TEM-21)-encoding plasmid that was epidemic among the enterobacteria at the institution, followed by chromosomal integration and genomic reorganization.
authors.affiliation: Laboratoire de Microbiologie, Faculté de Pharmacie, Université de Bordeaux 2, 146 rue Léo Saignat, 33076 Bordeaux Cedex, France. veronique.dubois@bacterio.u-bordeaux2.fr
authors.forename: Véronique
authors.initials: V
authors.lastname: Dubois
authors.forename: Corinne
authors.initials: C
authors.lastname: Arpin
authors.forename: Patrick
authors.initials: P
authors.lastname: Noury
authors.forename: Catherine
authors.initials: C
authors.lastname: Andre
authors.forename: Laure
authors.initials: L
authors.lastname: Coulange
authors.forename: Claudine
authors.initials: C
authors.lastname: Quentin
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D015373:Bacterial Typing Techniques; D003428:Cross Infection / Q000453:epidemiology* / Q000382:microbiology; D004196:Disease Outbreaks; D004755:Enterobacteriaceae / Q000187:drug effects / Q000201:enzymology*; D005260:Female; D006801:Humans; D008297:Male; D008826:Microbial Sensitivity Tests; D008875:Middle Aged; D009735:Nursing Homes; D010957:Plasmids; D011550:Pseudomonas aeruginosa / Q000145:classification / Q000187:drug effects / Q000201:enzymology*; D013997:Time Factors; D001618:beta-Lactamases / Q000096:biosynthesis / Q000235:genetics*
chemical_list: D001618:beta-Lactamases; C472386:beta-lactamase TEM-21, Pseudomonas aeruginosa