Molecular epidemiological study of Pseudomonas aeruginosa strains isolated from hospitals in Brazil by MLST and CRISPR/Cas system analysis

The CRISPR/Cas system defends bacteria and archaea against invasive pathogens, such as phages, establishing an immunological memory from this interaction. Pseudomonas aeruginosa, an opportunistic pathogen, represents a significant public health concern due to its multidrug resistance. This study conducted a molecular epidemiological analysis of clinical isolates of Pseudomonas aeruginosa in Brazil using multilocus sequence typing (MLST) and characterization of CRISPR/Cas system. Most P. aeruginosa isolates harbored the type I-F CRISPR/Cas system (83%), with a subset also exhibiting the type I-E system. Additionally, some isolates presented incomplete CRISPR/Cas systems in their secondary loci. Notably, the isolate Pae93 exhibited a genetic composition rich in phage-related proteins proximal to the orphan CRISPR locus. The identification and characterization of spacer sequences, including previously undocumented ones, revealed a remarkable diversity of predatory mobile genetic elements (MGEs) among the P. aeruginosa isolates studied. The spacer sequences were incorporated into the MGE library. Additionally, the study identified the existence of prophages and anti-CRISPR genes. Two new sequence types (STs 3383 and 3384) were identified and added to the PubMLST database. No discernible correlation was established between the observed STs and the previously delineated CRISPR genotypes. However, the CRISPR system remains valuable for elucidating specific interactions between microorganisms and MGEs. The Brazilian population of clinical P. aeruginosa isolates was shown to be genetically heterogeneous with a non-clonal distribution, as revealed by MLST analysis. The presence of high-risk clones, such as ST 244 and ST 235, underscores the importance of robust epidemiological surveillance and infection control strategies for P. aeruginosa, especially in healthcare settings. This study significantly contributes to the understanding of the molecular epidemiology of these isolates in Brazil.