New Delhi metallo-β-lactamase (NDM)-producing bacteria have been identified at a worrying rate in Brazil since 2013. Owing to the need to understand the extent of their spread, this study reports the dissemination of bla _NDM in different species of Gram-negative bacilli in different regions and states of Brazil. A total of 81 isolates from nine states were studied, including 11 species. All isolates carried bla _NDM-1 variant and were considered multidrug resistant. Colistin and amikacin were the agents with higher activity compared with the other drugs tested. The findings indicate that the NDM-1 enzyme is already widespread in the country.

Background: The Brazilian endemic clone Pseudomonas aeruginosa ST277 carries important antibiotic resistance determinants, highlighting the gene coding for SPM-1 carbapenemase. However, the resistance and persistence of this clone is apparently restricted to the Brazilian territory. To understand the differences between Brazilian strains from those isolated in other countries, we performed a phylogenetic analysis of 47 P. aeruginosa ST277 genomes as well as analyzed the virulence and resistance gene profiles. Furthermore, we evaluated the distribution of genomic islands and assessed in detail the characteristics of the CRISPR-Cas immunity system in these isolates. Results: The Brazilian genomes presented a typical set of resistance and virulence determinants, genomic islands and a high frequency of the CRISPR-Cas system type I-C. Even though the ST277 genomes are closely related, the phylogenetic analysis showed that the Brazilian strains share a great number of exclusively SNPs when compared to other ST277 genomes. We also observed a standard CRISPR spacers content for P. aeruginosa ST277, confirming a strong link between sequence type and spacer acquisition. Most CRISPR spacer targets were phage sequences. Conclusions: Based on our findings, P. aeruginosa ST277 strains circulating in Brazil characteristically acquired In163 and PAGI-25, which can distinguish them from strains that do not accumulate resistance mechanisms and can be found on the Asian, European and North American continents. The distinctive genetic elements accumulated in Brazilian samples can contribute to the resistance, pathogenicity and transmission success that characterize the ST277 in this country.

Key words: colistin; polymyxins; multidrug resistance