Prolonged Outbreak of Infection Due to TEM-21-Producing Strains ofPseudomonas aeruginosaand Enterobacteria in a Nursing Home

Abstract

Over a 6-year period, 24 extended-spectrum ␤-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 ␤-lactams except for imipenem and to gentamicin, tobramycin, netilmicin, ciprofloxacin, and rifampin) associated with the production of the TEM-21 ␤-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.Pseudomonas aeruginosa is a saprophytic organism widespread in nature, particularly in moist environments (water, soil, plants, and sewage). This bacterial species is endowed with only a weak pathogenic potential in immunocompetent persons (2, 17, 21, 23) but can cause severe and even fatal infections in patients with impaired specific or nonspecific defense systems (40). Thus, P. aeruginosa is rarely involved in community-acquired infections, while it is responsible for a wide range of hospital-acquired infections, such as pneumonia, urinary tract infections (UTIs), and bacteremia. Moreover, a series of outbreaks due to this important and frequent nosocomial pathogen has been reported in hospital intensive care, burn wound, and cancer units (6, 13, 42). In contrast, little has been reported on P. aeruginosa-induced infections in long-term-care facilities, including nursing homes; and most of the studies that have reported such infections have described sporadic cases rather than outbreaks (16,22,44).Linked to its nosocomial status, P. aeruginosa is intrinsically resistant to most antimicrobials. In addition, resistance to the main active agents, i.e., ␤-lactams and aminoglycosides, by gene acquisition is common. However...

Diversity of β-Lactamases Produced by Ceftazidime-Resistant Pseudomonas aeruginosa Isolates Causing Bloodstream Infections in Brazil

“…Specific primers were used under standard PCR conditions to detect ESBL-and MBL-encoding genes, namely, bla TEM , bla SHV , bla CTX-M , bla GES , bla PER , bla VEB , bla BEL , bla KPC , bla IMP , bla VIM , bla SPM , bla GIM , and bla AIM (7,12,15,16,17,20,23,26,29,30,38,42). The genetic environment of bla IMP was determined by PCR using the previously published specific primers to anneal at the 5Ј and 3Ј conserved sequences (CSs) of class 1 integrons, followed by sequencing (24).…”

“…The ESBLs reported for P. aeruginosa are SHV, TEM, PER, VEB, BEL, GES, and, more recently, CTX-M types (1,7,8,16,20,23,29). The GES-type enzymes are unusual since point amino acid changes in their active sites may extend their hydrolytic activity to carbapenems (31,39,40).…”

Construction and characterization of a highly redundant Pseudomonas aeruginosa genomic library prepared from 12 clinical isolates: Application to studies of gene distribution among populations

“…The differences measured for P. aeruginosa strains equate to a coding capacity for more than 500 proteins with an average size of 50 kilo Daltons (KD). Genomic plasticity via the acquisition of horizontally-transmitted genes has been associated with the evolution of epidemic strains for animals, plants, and humans among the P. aeruginosa [5][6][7]. Lewis et al identified and characterized a transmissible cystic fibrosis strain, designated at MA, which contains a unique pathogenicity island that includes 18 genes from two prophages and a cholera-toxin-like gene [8].…”

Extended-Spectrum-β-Lactamase-Producing Enterobacteriaceae Strains in Various Types of Private Health Care Centers

“…Indeed, most of the 50 strains were resistant to aminoglycosides, including 24 that exhibited a TNt(A) phenotype (tobramycin, netilmicin, and low-level amikacin resistance) associated with an aac(6Ј)-I gene, 1 strain with a GTNt phenotype (gentamicin, tobramycin, and netilmicin resistance) related to an aac(3)-II gene, and 12 strains with the combined GTNtA phenotype and both enzyme-encoding genes, as verified by PCR amplifications (2,3,8,9). The strains also exhibited resistances to sulfonamides (78%), trimethoprim (74%), chloramphenicol (64%), and tetracycline (37%) ( Table 1).…”