Prevalence and Eradication of Colonizing Staphylococcus Aureus in Patients Undergoing Allogeneic Hematopoietic Cell Transplantation
Authors: Wilk C. Matthias , Weber Isabel , Rachmühl Carole , Seidl Kati , Holzmann Bürgel Anne , Müller Antonia MS , Schanz Urs , Zinkernagel Annelies S. 
Published: October 2019

Abstract
Hematopoietic cell transplant (HCT) recipients are at increased risk for infections. Staphylococcus aureus (SA) colonizes 20-50% of healthy individuals and is a risk factor for subsequent invasive SA infections. Colonization rates in patients undergoing allogeneic HCT and clinical relevance for the time of aplasia and severely reduced immune function following HCT are not known. Only some retrospective data on methicillin-resistant SA infection rates are available. In this study, we prospectively assessed the prevalence of SA colonization in 110 consecutive patients before and during allo-HCT in a single-center observational study from June 2013 to January 2016.
All patients undergoing allo-HCT were screened for nasal, pharyngeal and inguinal SA colonization weekly beginning at the time of admission to the transplant unit until neutrophil recovery. After swabs for the initial SA screening were taken all patients were put on oral gentamicin and vancomycin for gut decontamination until neutrophils had recovered. Quantitative stool analyses were performed weekly. In case of fever or increased of inflammatory laboratory parameters (C-reactive protein) blood cultures were drawn.
In our cohort we found a SA prevalence of 14.5% (16/110 patients) at the time of admission to the transplant unit. All SA strains detected were sensitive to methicillin. Most patients colonized with SA in the nose (13/16), while pharyngeal and inguinal colonization was found less frequently (n=5 and n=6, respectively). Patients aged 60-67 years (n=14) showed the highest SA carrier rate (5/14, 36%, RR=1.36, p=0.02). There was no correlation between SA colonization and sex, underlying disease or chemotherapeutic pretreatment. Prior systemic antibiotic treatments using SA effective drugs within six months before admission to the transplant unit did not have relevant impact on SA prevalence at the time of screening.
Within the group of the 16 SA-positive patients there were 2 patients (12.5%) who had received oral antibiotic gut decontamination (vancomycin and /or gentamicin) within twelve weeks prior to admission (during induction chemotherapy). In the SA negative group a similar proportion of patients had received oral gut decontamination (12/94; 12.8%).
Despite the severe immunosuppression and skin and mucosal lesions incl. indwelling catheters no systemic SA infections (including bacteremia) were found during hospitalization in any of the HCT patients. All SA positive patients became SA negative within three weeks. These observations imply that decolonization is achieved by the consistent oral gut decontamination that all patients received in conjunction with the antibacterial soaps used.
In conclusion, the SA colonization prevalence in our cohort of patients undergoing allogeneic HCT was 14.5% which is lower than described previously in the literature. Of note, our cohort did not comprise patients with MRSA. Here, we demonstrate in a prospective study that oral gut decontamination with vancomycin and gentamicin in addition to strict hygiene measures resulted in eradication of SA colonization in all 16 colonized patients within three weeks.

Disclosures
No relevant conflicts of interest to declare.