Molecular Epidemiology of a Multiresistant Pseudomonas aeruginosa Outbreak in a Paediatric Intensive Care Unit

Abstract

After isolation of multiresistant (MR) Pseudomonas aeruginosa from 3 hospitalized patients in a paediatric intensive care unit (PICU), a prospective surveillance programme was established to detect infected and/or colonized patients in the hospital. Isolates were examined by means of outer membrane protein (OMP) profiles, serotyping and DNA genomic analysis using pulsed-field gel electrophoresis (PFGE). Fifty-five P. aeruginosa strains were isolated from 23 hospitalized patients during September and October 1997. The median hospital stay before isolation of P. aeruginosa was 8 d. PFGE demonstrated that the same clone infected 14 patients, 4 of whom were not hospitalized in the PICU. Susceptibility patterns and OMP profiles correlated with PFGE results in 37.8% and 36.4% of cases, respectively. Serotype O11 correlated with pattern A in 77% of cases and serotype O4 correlated with unrelated strains in 75% of cases but did not discriminate between outbreak and unrelated isolates. Extensive investigation of cultures failed to identify a reservoir of P. aeruginosa. PFGE was superior to OMP analysis and serotyping for discriminating between strains. The possible mode of acquisition for most of the patients infected with the same clone was cross-contamination.

Identification of an imipenem-resistant Pseudomonas aeruginosa clone among patients in a hospital in Rio de Janeiro

“…1,2 Infections by this organism are often difficult to treat because of their intrinsic resistance to various antimicrobial agents and the development of resistance to other drugs during chemotherapy. 3,4 Carbapenems, such as imipenem and meropenem, are effective for treating P. aeruginosa infections due to their high stability to Ambler classes A, C and D b-lactamases compared with other b-lactams.…”

Application of Molecular Techniques to the Study of Hospital Infection

“…Major antimicrobial resistance problems are typically associated with gram-positive nosocomial pathogens, which include glycopeptide (vancomycin)-resistant enterococci (125,172,173,187,280,304), methicillin-resistant Staphylococcus aureus (MRSA) (15,229,253), and, more recently, glycopeptide-intermediate and -resistant S. aureus (255). Among the gram-negative bacilli, extended-spectrum-beta-lactamase-producing strains of Escherichia coli and Klebsiella pneumoniae and fluoroquinolone-resistant strains of Pseudomonas aeruginosa and E. coli have been the primary concerns (180,182,183,231,242,258,278,279,286).…”

Outbreaks of Pseudomonas aeruginosa in pediatric patients – Clinical aspects, risk factors and management

“…Only six studies performed a systematic analysis of risk factors [5,16,[29][30][31][32][33] using different methods and control groups (Table 2). Taking the variable clinical context of the investigation into consideration, the confirmed risk factors were as follows:…”

“…In highrisk units, it is of utmost importance to recognize the temporally related appearance of nosocomial P. aeruginosa infections in more than one patient as a potential onset of an outbreak. Education of healthcare personnel (nurses and physicians) by showing them the results of epidemiological studies will help foster awareness of these problems and their dismal consequences [33].…”

“…Pulsfield gel electrophoresis (PFGE) has consistently been described as the most feasible and discriminatory method in the outbreaks included in this review (Table 3). In those studies that compared serotyping or outer membrane protein analysis with PFGE, the former methods displayed a much lower potential for discrimination [8,33]. It is not recommended to rely on in vitro susceptibility testing alone; clonally related isolates may display different results in antimicrobial testing.…”