P-2163. Inconsistent identification of Corynebacterium species by MALDI-TOF MS and molecular characteristics of Corynebacterium jeikeium complex isolates causing invasive infections in Japan
Authors: Harada Sohei , Komori Kohji , Yukawa Kenya , Hayama Brian , Yamada Kageto , Doi Asako , Saga Tomoo , Sasaki Masakazu , Hadano Yoshiro , Doi Yohei , Doi Yohei , Yokota Kyoko , Suzuki Jun , Kikuchi Koki , Tateda Kazuhiro 
Published: January 2025

Abstract

Background
Corynebacterium spp. is increasingly identified due to widespread use of MALDI-TOF MS in clinical laboratories. However, accuracy of identification of Corynebacterium spp. and genetic characteristics of clinical isolates are unclear.

Methods
We collected 17 isolates from cases diagnosed as infections caused by Corynebacterium spp. at a single center in Japan. Species identification was performed using MALDI Biotyper with reference library BDAL v11 (Bruker). Whole-genome sequencing (WGS) was also performed using MiSeq (Illumina), and the species were genetically identified using a threshold of ≥ 95% average nucleotide identity (ANI) with type strains. Regarding Corynebacterium jeikeium complex, an additional analysis was performed using 32 isolates detected from multiple sets of blood cultures at eight additional centers in Japan.Figure.Phylogenetic tree of Corynebacterium macclintockiae clinical isolates collected in this study.Pairs of strains detected at the same facility with SNP differences of &lt; 20/genome per year difference in isolation time are marked with red squares.

Results
In the single-center study, eight isolates (2: blood, 5: intraabdominal fluid, 1: urine) and three isolates (3: intraabdominal fluid) were identified as Corynebacterium striatum and Corynebacterium amycolatum, respectively, by MALDI Biotyper, and the identification was confirmed by WGS. However, all six isolates identified as C. jeikeium by MALDI Biotyper (1: blood, 4: intraabdominal fluid, 1 perivertebral abscess) had an ANI of 87-88% with C. jeikeium NCTC 11915T and were genetically identified as Corynebacterium macclintockiae with ANI of 97-98% with C. macclintockiae c9Ua_112T (Table). Of the 32 isolates detected in blood cultures at eight institutions and identified as C. jeikeium by MALDI Biotyper, 31 were identified as C. macclintockiae by WGS (Table). Core-genome phylogenetic analysis of 37 C. macclintockiae isolates identified multiple clades spread in the same center and three pairs of isolates with SNP differences of &lt; 20/genome per year difference in isolation time (Figure).

Conclusion
Identification of C. striatum and C. amycolatum by MALDI Biotyper was consistent with the genetic identification. The vast majority of C. jeikeium complex isolates causing infections in Japan were genetically identified as C. macclintockiae, but MALDI Biotyper identified them as C. jeikeium with high score values. SNP analysis suggested that some C. macclintockiae isolates may spread by nosocomial transmission.

Disclosures
Sohei Harada, MD, PhD, MSD: Honoraria|Shionogi: Honoraria Tomoo Saga, M.D., Ph.D., Asahi Kasei Pharma: Honoraria|Beckman-Coulter: Honoraria|Miyarisan Pharmaceutical: Honoraria|Pfizer: Honoraria|Shionogi: Honoraria|Sumitomo Pharma: Honoraria 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 Kyoko Yokota, M.D, MSc, Chugai pharmaceutical Co.,Ltd: Honoraria|Meiji Seika Pharma Co.,Ltd: Honoraria Jun Suzuki, M.D., Eiken Chemical: Honoraria|Kyorin Pharmaceutical: Honoraria Koki Kikuchi, M.D., bioMérieux: Honoraria|Pfizer: Honoraria Kazuhiro Tateda, PHD, GSK: Honoraria|Moderna: Honoraria|Pfizer: Honoraria|Shionogi: Honoraria