Emergence of rmtD1 gene in clinical isolates of Pseudomonas aeruginosa carrying bla and/or bla genes in Brazil.

Objectives: The aim of the present study is to describe clinical aminoglycoside- or carbapenem-resistant Pseudomonas aeruginosa isolates collected between 2018 and 2019 in a hospital in Recife City, Northeastern Brazil. It was done based on phenotypic and molecular markers of antimicrobial resistance, as well as on the clonal diversity of the investigated isolates.

Methods: Thirty-four carbapenem- and/or aminoglycoside-resistant P. aeruginosa isolates were collected in a hospital in Recife City-PE, Brazil. Their antimicrobial susceptibility profile was identified based on the automated BD Phoenix ™ system. In addition, broth microdilution was performed to determine the MICs of tobramycin and polymyxin B. Eventually, isolates were subjected to PCR and sequencing in order to detect the carbapenemase enzyme (bla, bla, bla, bla, and bla) and 16S rRNA methylase (armA, rmtB, rmtD, rmtF, and rmtG) genes; ERIC-PCR was conducted for clonal profile determination purposes.

Results: Thirty-four of the 64 isolates evaluated in the present study were selected for complementary molecular phenotypic tests, based on sample inclusion criteria. The bla and bla genes were identified in 32.4% (11/34) and 38.2% (13/34) of tested isolates, respectively. The rmtD1 gene was detected in 32.4% (11/34) of analyzed isolates. Eight isolates carried both the bla and rmtD1 genes, whereas bla and rmtD1 genes co-occurrence was detected in three strains; one isolate had all bla, bla, and rmtD1 genes. ERIC-PCR molecular typing has evidenced cross-transmission of three pathogenic clones among patients in the hospital.

Conclusions: The present study is a pioneer in describing isolates harboring both bla and rmtD1 genes. Moreover, it emphasizes the need of conducting local molecular epidemiology studies at different time intervals in order to monitor measures adopted to prevent nosocomial infections in different hospital units.