P-291. Whole genome sequencing (WGS) demonstrates high relatedness between carbapenemase-producing Klebsiella pneumoniae isolates cultured from paired rectal swab and blood specimens among hospitalized patients in Greece
Authors: Banerjee Ritu , Greenwood-Quaintance Kerryl , Koscianski Christina , Starkey Jordan , Rodning Amanda , Patel Robin , Mantzana Paraskevi , Tychala Areti , Meletis Georgios , Sereni Zoe , Trikoupis Petros , Oikonomou Margarita , Kousouli Elisavet , Roussou Anna , Charami Smaragdi , Rovatsou Alexandra , Louka Christina , Mamali Vasiliki , Chrysos Georgios , Alexandros Baziotis Georgios , Vourli Sophia , Christina Georgiou Panagiota , Louka Styliani , Poulianou Eleni , Karakosta Polyxeni , Protonotariou Efthymia , Pournaras Spyros , Zarkotou Olympia , Skoura Lemonia 
Published: January 2025

Abstract

Background
Intestinal colonization with carbapenem-resistant organisms (CRO) may be considered to inform empiric antibiotic selection for symptomatic infection. However, it is unclear how often gut colonizing CRE isolates are related to bloodstream isolates in hospitalized patients with bacteremia, especially in areas with high CRO prevalence.
Minimum spanning tree of isolate relatedness
Isolates and corresponding patient number (P1-P6) and rectal (R) or blood (B) specimen are noted within circles and allelic differences are numerated on linking lines between the circles. Group 1 and 3 isolates are possibly related to each other. Created with BioRender.com.

Methods
Patients with paired K. pneumoniae carbapenemase (KPC)-producing K. pneumoniae isolates cultured from surveillance rectal specimens and clinically collected blood specimens collected within 1-8 days of each other between 2019-2023 were identified at 3 Greek hospitals. Isolates were frozen and shipped to a reference laboratory in the U.S for whole genome sequencing (WGS) using Illumina MiSeq. Assembly and core genome multilocus sequence typing (cgMLST) analysis were performed with Ridom SeqSphere+ software. Isolate relatedness was based on the total number of allelic differences between each isolate: &lt; 15, related; 16-50, possibly related; ≥ 51, unrelated.

Results
One hundred eight paired isolates were identified from 54 unique patients; 6 pairs and 12 total isolates underwent cgMLST. In 5 of 6 pairs (83%), the rectal isolate was collected prior to the bloodstream isolate. Rectal and bloodstream isolates were related to one another in 5 of 6 (83%) pairs and were unrelated in 1 pair. Two pairs collected from 2 distinct patients admitted to the same intensive care unit (patients 2 and 3, Figure) were possibly related (16-50 allelic differences) to each other.

Conclusion
In this pilot evaluation conducted in a setting of high CRO prevalence, KPC-producing K. pneumoniae isolated from paired rectal and blood specimens from individual patients were often related to each other, suggesting that intestinal colonization by this organism could inform empiric antibiotic treatment for bacteremia. Two patients from the same hospital unit had isolates that were possibly related, suggesting within hospital transmission. WGS is a powerful tool that can inform clinical and infection control practices. WGS of the remaining K. pneumoniae pairs and additional Acinetobacter baumannii pairs is ongoing.

Disclosures
Robin Patel, MD, I already disclosed so please pull from disclosure for other abstracts: Advisor/Consultant|I already disclosed so please pull from disclosure for other abstracts: Grant/Research Support|I already disclosed so please pull from disclosure for other abstracts: Honoraria