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Open Access Highly Accessed Research article

A large sustained endemic outbreak of multiresistant Pseudomonas aeruginosa: a new epidemiological scenario for nosocomial acquisition

Cristina Suarez1, Carmen Peña16*, Olga Arch1, M Angeles Dominguez2, Fe Tubau2, Carlos Juan3, Laura Gavaldá4, Mercedes Sora5, Antonio Oliver3, Miquel Pujol1 and Javier Ariza1

Author Affiliations

1 IDIBELL, Infectious Diseases Service, Hospital Universitari de Bellvitge, University of Barcelona, Barcelona, Spain

2 IDIBELL, Microbiology Service, Hospital Universitari de Bellvitge, University of Barcelona, Barcelona, Spain

3 Microbiology Service, Hospital Son Espases, Palma de Mallorca, Spain

4 IDIBELL, Preventive Medicine Service, Hospital Universitari de Bellvitge, University of Barcelona, Barcelona, Spain

5 IDIBELL, Pharmacy Service, Hospital Universitari de Bellvitge, University of Barcelona, Barcelona, Spain

6 Infectious Diseases Service, Hospital Universitari de Bellvitge, L'Hospitalet de Llobregat, Barcelona, Spain

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BMC Infectious Diseases 2011, 11:272  doi:10.1186/1471-2334-11-272

Published: 13 October 2011

Abstract

Background

Studies of recent hospital outbreaks caused by multiresistant P.aeruginosa (MRPA) have often failed to identify a specific environmental reservoir. We describe an outbreak due to a single clone of multiresistant (MR) Pseudomonas aeruginosa (PA) and evaluate the effectiveness of the surveillance procedures and control measures applied.

Methods

Patients with MRPA isolates were prospectively identified (January 2006-May 2008). A combined surveillance procedure (environmental survey, and active surveillance program in intensive care units [ICUs]) and an infection control strategy (closure of ICU and urology wards for decontamination, strict compliance with cross-transmission prevention protocols, and a program restricting the use of carbapenems in the ICUs) was designed and implemented.

Results

Three hundred and ninety patients were identified. ICU patients were the most numerous group (22%) followed by urology patients (18%). Environmental surveillance found that 3/19 (16%) non-ICU environmental samples and 4/63 (6%) ICU samples were positive for the MRPA clonal strain. In addition, active surveillance found that 19% of patients were fecal carriers of MRPA. Significant changes in the trends of incidence rates were noted after intervention 1 (reinforcement of cleaning procedures): -1.16 cases/1,000 patient-days (95%CI -1.86 to -0.46; p = 0.003) and intervention 2 (extensive decontamination): -1.36 cases/1,000 patient-days (95%CI -1.88 to -0.84; p < 0.001) in urology wards. In addition, restricted use of carbapenems was initiated in ICUs (January 2007), and their administration decreased from 190-170 DDD/1,000 patient-days (October-December 2006) to 40-60 DDD/1,000 patient-days (January-April 2007), with a reduction from 3.1 cases/1,000 patient-days in December 2006 to 2.0 cases/1,000 patient-days in May 2007. The level of initial carbapenem use rose again during 2008, and the incidence of MRPA increased progressively once more.

Conclusions

In the setting of sustained MRPA outbreaks, epidemiological findings suggest that patients may be a reservoir for further environmental contamination and cross-transmission. Although our control program was not successful in ending the outbreak, we think that our experience provides useful guidance for future approaches to this problem.