Abstract
BackgroundExtensively 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.MethodsOutbreak investigation included ascertainment of cases, tracing of intestinal carriers and environmental surveillance. Contact precautions were adopted for patients with infection or colonization. Isolates were tested for antimicrobial susceptibility; phenotypic confirmation of carbapenemase production was performed, and carbapenemase genes were tested by multiplex polymerase-chain-reaction (PCR). Genotypes were determined by pulsed-field gel electrophoresis (PFGE).ResultsXDR-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.ConclusionsControl measures targeting intestinal carriers are crucial in limiting in-hospital transmission of XDR-PA polyclonal strains, protecting more vulnerable patients, such as severely neutropenic children, from developing clinical infections.Electronic supplementary materialThe online version of this article (doi:10.1186/1471-2334-14-494) contains supplementary material, which is available to authorized users.
Highlights
Drug-resistant Pseudomonas aeruginosa (XDR-PA) isolates are susceptible to only one or two classes of antibiotics
No deaths related to Extensively drug-resistant (XDR) P. aeruginosa (XDR-PA) or within 30 days from laboratory confirmation occurred in patients with other sites of infection or colonization
The observed mortality rate was higher than that reported for multi-drug-resistant P. aeruginosa (MDR-PA) bacteremia cases in children [1], but lower than that described in a nosocomial outbreak of pan-antibiotic-resistant P. aeruginosa [14]
Summary
Drug-resistant Pseudomonas aeruginosa (XDR-PA) isolates are susceptible to only one or two classes of antibiotics. Pseudomonas aeruginosa is one of the leading causes of nosocomial bloodstream infections and pneumonia [1,2]. Nosocomial infections caused by multi-drug-resistant P. aeruginosa (MDR-PA) have been reported in adults and children [7,8,9,10,11]. Multi-drug resistance is defined as non-susceptibility to at least one agent in three or more antimicrobial categories. Drug-resistant (XDR) bacterial isolates remain susceptible to only one or two classes of antimicrobials [12]. We report and characterize an XDR-PA outbreak in a tertiary-care pediatric hospital in Italy
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