Endemicity of Pseudomonas aeruginosa producing IMP-18 and/or VIM-2 MBLs from the high-risk clone ST111 in Central America

Abstract

Background: Pseudomonas aeruginosa is an important cause of serious nosocomial infections. Despite the overall genetic diversity of this species, highly conserved clonal complexes (CCs) have been observed among MDR isolates. Many of these CCs are associated with MBL-producing isolates.

Objectives: To evaluate five P. aeruginosa isolates from Central America that carried IMP-18- and/or VIM-2-encoding genes from the SENTRY Antimicrobial Surveillance Program (2017-2018).

Methods: Susceptibility testing was performed by broth microdilution (CLSI). WGS was performed using MiSeq (Illumina) and MinION (Oxford Nanopore). Assembled contigs from short and long reads were combined for in silico screening of resistance genes, MLST, core genome (cg)MLST and SNP analysis.

Results: The P. aeruginosa isolates were collected in Panama and Mexico from patients with urinary tract infections or pneumonia. Isolates were categorized as XDR (CLSI/EUCAST). All isolates belonged to ST111 but carried different combinations of resistance-encoding genes. Transposon-associated MBL genes, bla_IMP-18 and/or bla_VIM-2, were chromosomally located. bla_IMP-18 was detected in an In1666 integron whereas bla_VIM-2 was embedded in an In59-like integron. Isolates were closely related based on cgMLST (average allele distance 2-34) and SNP analysis (5-423 different SNPs).

Conclusions: MBL-producing ST111 P. aeruginosa have become endemic in Panama and may have spread to Mexico via clonal dissemination. Recombination events are apparent in the evolution of this CC. Surveillance is warranted to track the expansion and movement of this clone.

Figure 1.

Summary of cgMLST and SNP analysis performed on the 1928 Diagnostics platform. (a) cgMLST—Unweighted Pair Group Method with Arithmetic Mean (UPGMA) clustering output for P. aeruginosa isolates in this study. The x-axis denotes the number of alleles. Core is the percentage of core genome included in the analysis. (b) Distance matrices using exclusion parameter 0 or 10 compared with P. aeruginosa AG1 from Costa Rica. MiSeq data were used for this analysis. Exclusion parameter 0 considered all possible SNPs between the samples and the reference. Exclusion parameter 10 used less stringent criteria to account for possible recombination events or other factors that might cause SNPs to accumulate in certain areas.