Multidrug-Resistant Bacterial Pathogens in Allogeneic Hematopoietic Cell Transplantation - a Retrospective Single Center Analysis

Multidrug-resistant bacterial pathogens (MRP) such as extended-spectrum beta-lactamase producing enterobacteriaceae (ESBL), vancomycin-resistant enterococci (VRE) and methicillin-resistant staphylococcus aureus (MRSA) are an emerging challenge in allogeneic hematopoietic cell transplantation (HCT). However, to our knowledge there are no data in the existing literature on the prevalence of MRP and of the impact of these multidrug-resistant pathogens on the outcome after allogeneic HCT. Thus, it was the purpose of this study to systematically analyze the issue of MRP in patients who underwent allogeneic HCT.

PATIENTS AND METHODS: From 06/2010 to 12/2013 a total number of 72 (F: n=23; M: n=49) consecutive patients who received the first allogeneic HCT at our institution were retrospectively analyzed. The underlying diseases were AML (n=44), ALL (n=5), CML (n=4), MPN (n=2), lymphoma (n=5), MDS (n=9), and multiple myeloma (n=3). The conditioning regimen was myeloablative in 23 patients and reduced intensity in 49 patients. Patients were transplanted with peripheral blood stem cells (n=69) or bone marrow (n=3) from matched siblings (n=19), matched unrelated (n=45), mismatched (n=5) or haploidentical donors (n=3). As baseline investigation before commencing with the conditioning all patients underwent a comprehensive screening for MRP, i.e. ESBL, VRE and MRSA. For that reason swabs from nose, throat, axilla, urethra and anus as well as stool and urine were collected. The same screening was performed at discharge from hospital after allogeneic HCT and in case of a new admission into our institution. In addition routine microbiological investigations such as bacterial cultures from blood, urine, swabs, stool or central venous catheters were performed whenever clinically needed. Multidrug-resistant gram negative bacteria were categorized as 4MRGN (resistant to cephalosporins, piperacillin, fluorochinolones and to carbapenems) or as 3MRGN (resistant to 3 of these 4 antimicrobial drug groups). The primary endpoint of this analysis was day 100 non relapse mortality (NRM). Secondary endpoints were NRM and overall survival (OAS) two years post HCT.

RESULTS: 23 out of 72 patients (32%) were colonized by multidrug-resistant bacterial pathogens (MRP+ group) either at baseline (baseline MRP+ group, n=13, 18%) or at any other time point until day 100 post transplantation. Four patients were positive for two MRP either simultaneously at baseline (n=1) or at different time points (n=3). Detected MRP (n=27) were as follows: 3MRGN Escherichia coli or Klebsiella pneumonia (n=11), 4MRGN Pseudomonas aeruginosa (P. aeruginosa, n=4), 3MRGN P. aeruginosa (n=2), 4MRGN Stenotrophomonas maltophilia (n=1), 3MRGN Citrobacter freundii (n=1), VRE (n=7) and MRSA (n=1). Out of these 23 patients 7 patients developed an infection with MRP after HCT: Septicemia with 3MRGN Escherichia coli (n=3), septicemia with 3MRGN Klebsiella pneumonia (n=1), septicemia with P. aeruginosa (4 MRGN n=2, 3MRGN n=1) and one patient with VRE septicemia and 4MRGN P. aeruginosa pneumonia. Out of the 4 patients with multidrug-resistant P. aeruginosa infection three died transplant related (two of these patients had been already colonized with 4MRGN P. aeruginosa at baseline). However, 2-year OAS of MRP colonized versus non-colonized patients was essentially the same (66.6% versus 63.0%, median follow up 23.8 months range 7.0 to 48.0 months). Day 100 NRM was higher in the baseline MRP+ group and in the entire MRP+ group in comparison with non-multidrug-resistant bacterial pathogens colonized patients (23.1% and 17.4% versus 10.2%, not statistically significant [ns]). Data for 2 year NRM were 32.7%, 22.2% and 17.1% (ns), respectively. The increased NRM of MRP+ patients was mainly due to the high NRM of patients infected by multidrug resistant P. aeruginosa.

CONCLUSIONS: Colonization or infection with 3MRGN gram negative non-P. aeruginosa enterobacteriaceae or by VRE has no negative impact on the outcome after allogeneic HCT. Thus allogeneic HCT of patients colonized by MRP is feasible. However, patients colonized by multidrug-resistant P. aeruginosa seem to have a dismal outcome. Allogeneic HCT of these patients should be considered with care. We therefore suggest to include screening for MRP in the pretransplant recipient work up particularly to identify patients colonized by multidrug-resistant P. aeruginosa.