An outbreak of extremely drug-resistant Pseudomonas aeruginosain a tertiary care pediatric hospital in Italy

Extensively drug-resistant Pseudomonas aeruginosa (XDR-PA) isolates are susceptible to only one or two classes of antibiotics. In 2011–2012, we investigated an outbreak of XDR-PA affecting children with onco-hematological diseases.

XDR-PA was isolated from 27 patients; 12 had bacteremia, 6 other infections and 9 were colonized. Severe neutropenia was significantly associated with bacteremia. Bloodstream-infection mortality rate was 67%. All isolates were resistant to carbapenems, cephalosporins and penicillins + β-lactamase inhibitors. Isolates were susceptible only to colistin in 22 patients, to colistin and amikacin in 4, and to ciprofloxacin and colistin in 1. PFGE results identified 6 subtypes of a single genotype, associated with clusters of cases, and 4 sporadic genotypes. Two sporadic isolates were metallo-β-lactamase producers, negative to PCR. All other isolates were metallo-β-lactamase producers due to the presence of a VIM carbapenemase. Incidence of XDR-PA infections decreased from 0.72 cases/1,000 inpatient-days in March 2011-March 2012, to 0.34/1,000 in April-December 2012, after implementation of active finding of intestinal carriers on all onco-hematological inpatients.