1452. Neuroinvasive Bacillus Cereus Infection Amongst Immunocompromised Patients: Epidemiological Investigation of 5 Cases in Patients with Acute Myeloid Leukemia
Authors: Little Jessica S , Coughlin Cassie , Hsieh Candace C R , Lanza Meaghan , Huang Wanyi , Kumar Aishwarya , Dandawate Tanvi , Tucker Robert , Winkler Marisa , Pecora Nicole , Luskin Marlise , Woolley Ann E , Issa Nicolas C , Baden Lindsey R , Brandeburg Christina , Bolstorff Barabara , Fortes Esther D , Doucette Matthew , McHale Eileen , Bunnell Craig , Platt Dana , Desai Sonali , Gross Anne , Fiumara Karen , Rhee Chanu , Klompas Michael , Baker Meghan 
Published: November 2023

Abstract

Background
Bacillus cereus can cause serious nosocomial infections, including neuroinvasive infections in immunocompromised patients. Three patients with AML developed hospital-onset neuroinvasive B. cereus infections in close temporal proximity at our institution in 2022, triggering an extensive epidemiological investigation.

Methods
We identified all patients with AML, positive microbiologic assays for Bacillus species &gt;48 hours after admission, and neurological symptoms with radiologic findings admitted between January 2018 and October 2022 (Figure 1). Infection control practices were observed, environmental samples obtained, and a dietary case-control study was performed. Bacillus isolates were sequenced, including 2 case isolates, 61 environmental specimens, and 19 samples of a protein supplement common to most AML patients.Figure 1.Case Identification and Definitions

Results
Five AML patients with B. cereus neuroinvasive disease were identified. Four were identified via blood culture and one via metagenomic sequencing of plasma cell-free DNA. All patients were hospitalized for induction chemotherapy and were neutropenic (Table 1; Figure 2). Central nervous system findings included intraparenchymal and subarachnoid hemorrhage, and rim-enhancing lesions. All patients were treated with ciprofloxacin and survived without neurologic sequelae. B. cereus was positively identified in 7/61 environmental and 1/19 protein samples. There was no single exposure common to all patients per the dietary case-control study, hospital construction records, or environmental samples. Sequencing confirmed all isolates were unrelated. Ciprofloxacin was added to the empiric antimicrobial regimen for AML patients with neutropenic prolonged or recurrent fevers in September 2022; no new cases have since been identified through April 2023 (Figure 3).Table 1.Clinical Characteristics of Neuroinvasive Bacillus Cereus CasesFigure 2.Timeline of Clinical Presentation of Neuroinvasive Bacillus Cereus InfectionFigure 3.Antimicrobial Protocol for Prevention of Neuroinvasive Bacillus Cereus Infection

Conclusion
B. cereus is ubiquitous in the hospital environment, sometimes leading to pseudoclusters with unrelated isolates. Fastidious infection control practices addressing a broad range of potential exposures are warranted to prevent nosocomial infections. Including B. cereus coverage in empiric regimens for AML patients with prolonged or recurrent neutropenic fever may prevent serious infections from this pathogen.

Disclosures
Nicolas C. Issa, MD, AiCuris: Grant/Research Support|Astellas: Grant/Research Support|Boehringer Ingelheim: Advisor/Consultant|Fujifilm: Grant/Research Support|GSK: Grant/Research Support|Merck: Grant/Research Support|Moderna: Grant/Research Support Chanu Rhee, MD, MPH, Cytovale: Advisor/Consultant|Pfizer: Advisor/Consultant|UpToDate, Inc.: Honoraria Michael Klompas, MD, MPH, UpToDate, Inc.: Royalties for chapters on pneumonia