P-1826. Genomic Epidemiology and Clinical Characteristics of Stenotrophomonas maltophilia at an academic medical center
Authors: Angelo Sahil , Clarke Lloyd , Shields Ryan K , Doi Yohei , Doi Yohei 
Published: January 2025

Abstract

Background
S. maltophilia is an opportunistic pathogen in critically-ill and immunocompromised patients. Distinguishing between colonization and infection is challenging and genomic surveillance data are scarce. This study seeks to define the genomic epidemiology of S. maltophilia and associations between genomic groups (Gg) and clinical outcomes.

Methods
Consecutive patients with S. maltophilia positive cultures were included from 10/21 – 12/23. Whole genome sequencing (WGS) was performed on the Illumina NextSeq 550 platform. Gg were identified by sequence type (ST). Cases were classified as proven infection, possible infection, or colonized (Table 1).

Results
Across 204 patients, 21.1%, 57.3%, and 21.6% were classified as proven infection, possible infection, or colonized, respectively (Table 2). The median (IQR) age was 60 (47-68) years, 38% were women, and 18% were solid-organ transplant recipients. The overall 30- and 90-day mortality rates were 19.6% and 28.9%, respectively; 30-day mortality was higher for patients with proven or possible infection (24%) versus colonization (2%; P=0.004).
Significant diversity was identified across 470 S. maltophilia isolates sequenced (Figure 1). Using the first isolate from the 204 patients included in the study, 31 known STs were identified. ST5 and ST133 were most common (n=8 each). Isolates were classified into 9 different Cg (Figure 2); an additional 22% were unclassified. Gg6 (S. maltophilia) and GgC (S. muris) accounted for 38% and 10% of all isolates, respectively. Across syndromes, Gg6 was most common, accounting for 34% of proven/possible infections compared to 52% of colonization cases (P=0.03). GgC was more often associated with proven infection than colonization (P=0.05). Mortality rates were highest for Cg4 (43%) and lowest for Cg geniculate (5%).Figure 1.Phylogenetic tree of 470 S. maltophilia isolates collected at the study site

Conclusion
S. maltophilia genomic groups are highly diverse and associated with varying clinical syndromes. Specific groups like GgC (S. muris) appear to be associated with high infection rates. Across Cg, mortality rates ranged from 5% to 43%, suggesting that differences may exist. These data support further molecular investigations into S. maltophilia Gg to help distinguish colonizing versus infecting isolates.

Disclosures
Ryan K. Shields, PharmD, MS, Allergan: Advisor/Consultant|Cidara: Advisor/Consultant|Entasis: Advisor/Consultant|GSK: Advisor/Consultant|Melinta: Advisor/Consultant|Melinta: Grant/Research Support|Menarini: Advisor/Consultant|Merck: Advisor/Consultant|Merck: Grant/Research Support|Pfizer: Advisor/Consultant|Roche: Grant/Research Support|Shionogi: Advisor/Consultant|Shionogi: Grant/Research Support|Utility: Advisor/Consultant|Venatorx: Advisor/Consultant|Venatorx: Grant/Research Support Yohei Doi, MD, PhD, bioMerieux: Lecture fees|Entasis: Grant/Research Support|Fujifilm: Advisor/Consultant|Gilead Sciences: Advisor/Consultant|GSK: Advisor/Consultant|KANTO CHEMICAL CO.,INC.: Grant/Research Support|KANTO CHEMICAL CO.,INC.: Patent for genotyping kit|MeijiSeika Pharma: Advisor/Consultant|Moderna: Advisor/Consultant|MSD: Lecture fees|Pfizer: Advisor/Consultant|Shionogi & Co., Ltd.: Grant/Research Support|Shionogi & Co., Ltd.: Lecture fees