Outbreak of Carbapenem-Resistant Pseudomonas aeruginosa Producing VIM-8, a Novel Metallo-β-Lactamase, in a Tertiary Care Center in Cali, Colombia

Abstract

The prevalence of imipenem resistance among Pseudomonas aeruginosa isolates at a 195-bed tertiary care medical center in Cali, Colombia, rose from 2% in 1996 to 28% in 1997 and to over 40% in 2003. Many isolates showed high-level multiresistance, and phenotypic characterization suggested the spread of a predominant strain with minor variants. Sixty-six resistant isolates collected between February 1999 and July 2003 from hospitalized patients (n ‫؍‬ 54) and environmental samples (n ‫؍‬ 12) were subjected to a fuller analysis. Genetic fingerprints were compared by pulsed-field gel electrophoresis (PFGE) of SpeI-digested genomic DNA, and bla IMP and bla VIM genes were sought by PCR. PFGE and serotyping indicated that 52 of the 66 isolates belonged to a single strain, with 82% similarity; the PFGE pattern for this organism was designated pattern A. Two further pairs of isolates represented single strains; the remaining nine isolates were unique, and in the case of one isolate, no satisfactory PFGE profile could be obtained. The pattern A isolates were mostly of serotype O12 and were highly resistant to imipenem (MICs, 32 to >256 g/ml), with this resistance decreased eightfold or more in the presence of EDTA. They yielded amplicons with bla VIM -specific primers, and sequencing of DNA from a representative isolate revealed bla VIM-8 , a novel allele with three polymorphisms compared with the sequence of bla VIM-2 . Two of these nucleotide changes were silent, but the third determined a Thr139Ala substitution. Only 4 of 13 resistant isolates (2 clinical isolates and 2 environmental isolates) assigned to other PFGE types carried bla VIM alleles, whereas the others were less multiresistant and mostly had lower levels of imipenem resistance (MICs, <32 g/ml) which was not significantly reduced by EDTA. No bla IMP alleles were detected. During 2003, when the environmental study was undertaken, serotype O12 isolates with bla VIM were recovered from sinks and stethoscopes in the most-affected units, although not from the hands of staff; the problem declined once these reservoirs were disinfected and hygienic precautions were reinforced.

Characterization by phenotypic and genotypic methods of metallo-β-lactamase-producing Pseudomonas aeruginosa isolated from patients with cystic fibrosis

“…Knowledge of these enzymes conferring resistance is required to prevent the spread of the infection among clinical samples. Numerous nosocomial outbreaks of P. aeruginosa producing metallo-lactamases have been reported, with an urgent requirement to implement infection control programs (18)(19)(20)(21). Thus, the present study was undertaken to detect the presence of MBL-producing P. aeruginosa isolates from the sputa of CF patients by phenotypic and genotypic methods.…”

Prevalence of Metallo-β-lactamases Encoding Genes Among Pseudomonas aeruginosa Strains Isolated From the Bedridden Patients in the Intensive Care Units

“…The presence of MBL-producing strains makes treatment difficult and sometimes ineffective (5,6). The carbapenems-resistant agents are impor-tant not only in treatment failure, but also in horizontal transmission of resistance genes to the other bacteria (5,7,8). There are evidences showing that MBL producing P. aeruginosa strains casus high mortality (9).…”

Resistencia Antimicrobiana en Unidades de Cuidado Intensivo de Bogotá, Colombia, 2001-2003

“…El estudio MYSTIC mostró que la prevalencia de este tipo de microorganismos varía de forma importante en los países europeos, oscilando entre menos de 3 % y 50 % (30). Estos clones deben ser detectados oportunamente por los laboratorios clínicos y por los comités de infecciones intrahospitalarias de forma que se pueda evitar su diseminación, especialmente cuando estos pacientes tienen alternativas terapéuticas limitadas en nuestro país (31), y más aún cuando recientemente se describe en nuestro país la aparición de carbapenemasas (32). La frecuencia y resistencia de A. baumanni creció durante los años estudiados en todos los hospitales y especialmente se ha incrementado el número de gérmenes multiresistentes (27).…”