679. Predominance of Acinetobacter baumannii Sequence Type 2 (ST2) among Clinical Isolates from Two Detroit Hospitals using Whole Genome Sequencing
Authors: Chatterjee Piyali , Jinadatha Chetan , Kaye Keith S , Choi Hosoon , Allton Yonhui , Stibich Mark , Kilgore Paul E , Dhar Sorabh 
Published: January 2021

Abstract

Background
Healthcare-associated infections (HAIs) caused by Acinetobacter baumannii, an opportunistic gram-negative pathogen, often contribute to morbidity and mortality among hospitalized patients. To determine molecular epidemiology of circulating hospital Acinetobacter strains in Detroit area in a non-outbreak situation, we performed whole genome sequencing (WGS) and whole genome multilocus sequence typing (wgMLST) analysis to characterize genomic diversity.

Methods
We performed WGS on patient isolates from two disparate, geographically distinct tertiary care Detroit hospitals admitted to 16 intensive care units (ICU) and non-ICU wards between 2017-2019. The samples were obtained 48 hours following admission and WGS was performed using the Illumina NextSeq instrument. The contigs were de novo assembled using SPAdes and WgMLST analysis was performed using BioNumerics software v7.6. Minimum spanning tree (MST) was constructed to demonstrate the clusters in each hospital and their wards.

Results
WgMLST analysis was performed on a total of 62 Acinetobacter baumannii patient isolates, 33 of which were from hospital # 1 (H1) and 29 were from hospital # 2 (H2). ST2 (52%) was the predominant sequence type for both hospitals. In addition to ST2, ST93 (8%) and ST406 (8%) clusters were also found in H1. Most of the isolates were predominantly clustered in the intensive care unit (ICU) setting. Several identical sequence types of ST93 (2 identical in H1), ST36 (2 identical in H1) and ST2 (5 identical for H1 and 2 identical for H2) were also observed from different patients in both hospitals. Unlike H1, H2 only has ST2 as a predominant cluster. Other sporadic sequence types such as ST119, ST36, ST49, ST212, ST667 for H1 and ST395, ST214, ST427 and ST268 for H2 were also observed.
Figure 1. MInimum Spanning Tree of Acinetobacter strains in hospitals (H1 and H2) and different wards (U1-U12). For identical strains circles are marked with dividing lines. Different sequence types (STs) are marked om the side bar.

Conclusion
Our data suggests that ST2 is the predominant sequence type circulating in both the geographically distinct hospitals and is endemic to the ICU. There was in hospital spread of this distinct Acinetobacter sequence type from one patient to the other, raising concerns about infection control practices and the role of environment in the spread of these infections. Early detection of these endemic strains within the hospital may be critical in preventing healthcare-associated infections in the future.

Disclosures
Chetan Jinadatha, MD, MPH, AHRQ (Research Grant or Support)Department of Veterans Affairs (Other Financial or Material Support, Owner: Department of Veterans Affairs. Licensed to: Xenex Disinfection System, San Antonio, TX)Inventor (Other Financial or Material Support, Methods for organizing the disinfection of one or more items contaminated with biological agents)NiH/NINR (Research Grant or Support)NSF (Research Grant or Support)Xenex Healthcare Services (Research Grant or Support) Mark Stibich, PhD MHS, Xenex Disinfection Services, Inc (Board Member, Employee)