Difficult-to-detect carbapenem-resistant IMP13-producing P. aeruginosa: experience feedback concerning a cluster of urinary tract infections at a surgical clinic in France

Abstract

Background: We report a carbapenem-resistant P. aeruginosa clone responsible for a cluster of urinary tract infections in elderly surgery patients, diagnosed during a three-month period in a 59-bed surgical clinic.

Findings: The clonal nature of the cluster was established by molecular study of the P. aeruginosa isolates (PFGE and MLST). Despite an MIC of imipenem in the susceptibility range for two isolates, all were metallo-β-lactamase-producers (IMP13-type, clone ST621). We conducted a review of the medical and surgical procedures. We tested water delivered into the clinic and urological devices for the presence of the epidemic strain. The hygiene nurse observed hygiene practices. A week after the implementation of barrier precautions around the fourth infected patient, we studied the extent to which the patients hospitalised were colonised to assess whether the spread of the epidemic strain had been controlled.

Conclusions: 1/ Our findings indicate the difficulties in the detection of the metallo-β-lactamase in this clone, that resulted in the alert being delayed. 2/ Unlike most investigations of UTI outbreaks described in urology wards, we did not detect any contaminated urological devices or water colonisation. 3/ Consistent with outbreaks involving the IMP-13 clone in critical care units, the observation of inadequate application of standard precautions argued for patient-to-patient transmission during urinary management of the urology patients. 4/ The implementation of barrier precautions around infected patients resulted in control of the spread of the epidemic clone. This report serves as an alert concerning a difficult-to-detect multidrug-resistant P. aeruginosa clone in elderly urology patients.

Figure 1

Pulsed-field gel electrophoresis patterns of the four UTI-associated IMP-13 P. aeruginosa isolates (C1-C4), the ten colonising isolates recovered from carriers (R1-R10), the four environmental isolates recovered from water samples (W1-W4), and three epidemiologically unrelated IMP-13 P. aeruginosa reference isolates (ref. 1–3). ¹PFGE pattern recovered in the course of colonisation study for the previously infected patient C4.