P-1353. Molecular Heterogeneity of Stenotrophomonas maltophilia Isolates Associated with Human Infections in the US and Colombia
Authors: Mojica Maria F , van Duin David , Reyes Luis Felipe F , Mendez Lina , Rao Gauri G , Fouts Derrick , Bonomo Robert 
Published: January 2025

Abstract

Background
Stenotrophomonas maltophilia (Sma) is an increasingly important opportunistic bacterial pathogen that commonly causes bloodstream infection (BSI) or pneumonia. Sma is intrinsically resistant to most antibiotics and may acquire additional resistance. Despite its significant clinical impact, Sma is remarkably understudied. Consequently, critical gaps persist in our understanding of Sma’s genomic and microbiological characteristics, which may impact treatment outcomes. Herein, we characterized 121 Sma isolates by whole genome sequencing (WGS).Figure 1.Putative association of specific types of L1 and L2 β-lactamases with genomic groups of Stenotrophomonas spp.A consensus UPGMA tree of core genomes shows the structure of the studied population (n = 121). Branch length represents the genetic distance, with the scale bar indicating the number of substitutions per nucleotide position. The genomic group designation is indicated by the colored internal ring. Presence/absence of L1 and L2 types is indicated by full or empty squares or circles, respectively.

Methods
Sma isolates were subjected to WGS using Illumina technology. Genomes were annotated using Prodigal gene prediction software. Resistome was predicted using RGI, which uses the CARD database.

Results
Phylogenetic analysis revealed that isolates were grouped into 8 genomic groups. Of those, GG6, GG4, GGC and GG1 represented 41%, 22%,18% and 17% isolates, respectively. Notably, we did not notice outstanding differences between isolates collected from different geographical locations or diverse biological sources, including from CF patients. Consistent with our previous report (PMID: 31266860), we observed a perfect correlation between GG6 and L1B-C-like and L2B-like B-lactamases (BLs). Further analysis demonstrated that these BLs display increased catalytic activities towards 3rd gen. cephalosporins and carbapenems. Surprisingly, we also observed that all isolates from the GG1 harbored a specific type of L1 (L1J-like) and L2 (L2E), which are novel types of L1 and L2 BLs (Fig. 1). The most distant genomic group, presumably a new Stenotrophomonas species, clustered isolates which only harbored a new type of L2, L2I. The distribution of qnr and mfpA genes among the genomic groups of Sma does not seem to be segregated by genomic groups. However, an in-depth analysis of 11 selected GG6 (n = 6) and non-GG6 strains (n = 5) strains shows that the SmeS efflux pump and AAC(6')-Iz aminoglycoside modifying enzyme are exclusively associated with GG6.

Conclusion
Sma strains belonging to the GG6, which has been exclusively associated with human infections and accounts for the majority of the isolates in the US, have a distinct resistome. The impact of Sma GGs with different resistomes on treatment outcomes is unknown.

Disclosures
David van Duin, MD, PhD, Merck: Advisor/Consultant|Merck: Grant/Research Support|Pfizer: Advisor/Consultant|Qpex: Advisor/Consultant|Roche: Advisor/Consultant|Shionogi: Advisor/Consultant|Shionogi: Grant/Research Support Gauri G. Rao, PharmD, MS, Merck: Grant/Research Support Robert Bonomo, MD, Merck: Grant/Research Support|Shionogi: Grant/Research Support