Incidence of Post-Transplant Bacterial Foodborne Pathogens in Hematopoietic Stem Cell Transplant Patients

Background: Diarrhea, abdominal pain and fever are common among patients undergoing hematopoietic stem cell transplant (HCT), but such symptoms are also typical with foodborne infections. The burden of disease caused by foodborne infections in patients undergoing HCT is unknown. We sought to describe the incidence of post-transplant bacterial foodborne infections in a single-center population of HCT recipients.  Methods: We reviewed all patients who received a HCT at the Fred Hutchinson Cancer Research Center in Seattle, WA from 2001 to 2011. Data were collected retrospectively using center databases, which include information from transplant, on-site examinations, outside records, and collected laboratory data. Patients were considered to have a bacterial foodborne illness if Campylobacter jejuni/coli, Salmonella, Shigella, Yersinia or Listeria species were isolated in culture; patients with evidence of non-foodborne origin for infection were excluded. All post-transplant events were classified as early (≤ 100 days post-transplant) or late (>100 days).  Results: A total of 18/4404 (0.4%) patients developed a post-transplant bacterial foodborne illness (Figure 1). Patients had a mean age at infection of 45.8 years (range 1 – 68), and the majority were adults ≥18 years of age (n=14 [78%]) and male gender (n=13, [72%]).  Most cases occurred in patients who had undergone an allogeneic transplant (n=12 [67%]). These infectious episodes occurred at a median of 87.5 days after transplant (IQR 19, 367). The overall incidence rate post-transplant was 0.34 per 100,000 patient days, and 1.9 per 100,000 in the early post-transplant period.  Bacterial foodborne infections occurred evenly between the early and late periods (n=9 early, n=9 late). The most frequent pathogen detected was Campylobacter (n=9 [50 %]) followed by Salmonella (n=5 [28%]), Yersinia (n=2 [11%]) and Listeria (n=2 [11%]); no cases of Shigella were detected.  Diagnoses were made in most patients through positive stool cultures (n=13 [72%]), while a smaller proportion were first positive through blood cultures (n=4 [22%]); one patient was positive simultaneously at both sites.  Mortality due to bacterial foodborne illness was not observed during follow-up.  Conclusions: Our large single-center study indicates that bacterial foodborne infections were a rare complication following HCT. These data provide important baseline incidence for future studies evaluating dietary interventions in HCT patients.