(P-BT-12) Forensic Sequencing of Salmonella Cultured from HPC(A) Products from Two Asymptomatic Donors

Background/Case Studies: Patient A was a 71-year-old male with primary central nervous system B-cell lymphoma who underwent autologous hematopoietic progenitor cell collection by apheresis [HPC(A)] in December 2022. The patient tolerated collection without adverse events. Vital signs were unremarkable before, during, and after collection. Gastrointestinal (GI) symptoms were denied. A sample from the HPC(A) product was cultured, and based off that result, blood cultures were collected from the donor 1 day after HPC(A) collection.

Patient B was a healthy 39-year-old male with no past medical history who underwent allogeneic HPC(A) donation in February 2023. The patient tolerated collection without adverse events. Vital signs were unremarkable before, during, and after collection. GI symptoms were denied. A sample from the HPC(A) product was cultured, and based off that result, a GI pathogen panel and blood cultures were collected 10 days after HPC(A) donation.

Study

Design/Methods: Donor mobilization was performed using 10 ug/kg filgrastim injections for five days. HPC(A) collections were performed on Terumo Optia using the CMNC program and ACD-A anticoagulation. UTGI Pathogen Panel was performed using the BioFire FilmArray (bioMerieux Inc, Salt Lake City, UT) on stool. Blood and HPC(A) product sterility cultures were performed using BD BACTEC (Becton, Dickinson and Co, Franklin Lakes, NJ) aerobic and anaerobic culture vials. Whole genome sequencing of Salmonella isolates was performed at the state public health laboratory (PHL) using the PulseNet program protocols.

Results/Findings: Sterility testing of both HPC(A) products grew Salmonella (Table 1), and subsequent infectious workup of both donors was negative. An epidemiological case review of Patient A identified that the patient had previously eaten at a restaurant known to be involved in a salmonellosis outbreak related to alfalfa sprouts. Sequence analysis confirmed Salmonella serovar Typhimurium from his HPC(A) product, which was indistinguishable to the serovar causing the local foodborne outbreak. Sequencing of the isolate from Patient B identified Salmonella serovar Enteritidis which did not match any recent Salmonella strains sequenced in the PHL and appeared to be an isolated case. Patient B denied having exposure to chicken (or chicken products such as eggs), reptiles or eating alfalfa sprouts.

Conclusions: Three previous cases of HPC(A) contamination with Salmonella from asymptomatic donors have been reported in the past year, which highlight the importance of HPC(A) product sterility culture. Salmonella has an intracellular lifestyle in white blood cells, and subtle cases of bacteremia may be detected when mononuclear cells are concentrated by the apheresis process. These two cases of Salmonella HPC(A) contamination at a single center combined with the three reported cases in the past year may signal an increase in incidence of Salmonella contamination.

Importance of research: HPC(A) product contamination is a rare event, especially with Gram-negative bacteria. This is the first report of an HPC(A) product contaminant being sequenced and tied to a local outbreak of Salmonella. The finding of two cases of Salmonella within a three month timespan at a single center and the three reported cases in the past year may signal an increased incidence of salmonellosis.