Dissemination in Distinct Brazilian Regions of an Epidemic Carbapenem-resistant Pseudomonas Aeruginosa Producing SPM Metallo-beta-lactamase

Background: In Brazil, carbapenem use has been limited by high carbapenem-resistance rates among Pseudomonas aeruginosa isolates.

Objective: The main objective of this study was to evaluate the presence of an epidemic P. aeruginosa strain in unrelated Brazilian hospitals. We also aimed to search for the gene blaSPM, which encodes production of SPM, a novel metallo-beta-lactamase (MBL).

Methods: A reference broth microdilution method was used for antimicrobial susceptibility testing. The isolates were typed by ribotyping and pulsed-field gel electrophoresis (PFGE). A disc-approximation test using MBL inhibitors was employed to screen isolates for MBL production. PCR was used to search for the gene blaSPM.

Results: A total of 43 clinical isolates of carbapenem-resistant P. aeruginosa were collected from 12 hospitals. Colistin retained greatest activity in vitro. A single ribogroup included 17 P. aeruginosa isolates (39.5%) collected from seven unrelated hospitals located in five Brazilian states. Sixteen of these isolates showed an identical PFGE pattern, and 15 produced an SPM-1-like MBL. The remaining 26 isolates were grouped into 25 diverse ribogroups; none were MBL producers.

Conclusions: The emergence and dissemination of an epidemic clone has contributed to the high carbapenem resistance rates among P. aeruginosa isolates in Brazil. In addition, the production of SPM MBL has an important role in carbapenem resistance in this region. This is the first report of dissemination of an SPM-1-like-MBL-producing strain of P. aeruginosa among unrelated Brazilian hospitals.