Analysis of incidence and risk factors of the multidrug resistant gastrointestinal tract infection in children and adolescents undergoing allogeneic and autologous hematopoietic cell transplantation: a nationwide study

Hematopoietic stem cell transplant recipients are at very high risk of bacteremia which can occur early after transplantation. There are two major insults to their innate immune system. Firstly, they have prolonged neutropenia and lack of phagocytes. Secondly, conditioning regimen leads to severe gastrointestinal (GI) mucositis, causing damage of their mucosal barrier. These two factors establish a high-risk setting for bacteremia caused by enteric organisms and other severe complications from these infections [1]. Functional and kinetic immune recovery in the allogeneic HCT recipient are influenced by donor’s factor (age, gender, immune function), graft (graft source, HLA matching), treatment (type of conditioning regimen, total body irradiation), recipient’s factor (age, presence of comorbidities, underlying disease previous therapy, organ dysfunction, changes in microbiome), and HCT complications (presence of GVHD, use of supportive care, or other medications). Defects and delays in immune reconstitution strongly associate with decreased overall survival and increased transplant-related morbidity and mortality [2].

One of the major challenges among HCT recipients are multidrug-resistant (MDR) bacterial pathogens: MDR Enterobacteriaceae, including extended-spectrum β-lactamase (ESBL)–producing and carbapenem-resistant Enterobacteriaceae (CRE), Pseudomonas aeruginosa metallo-beta-lactamase producing (MBL), AMPc strains, high-level aminoglycoside-resistant Enterococcus (HLAR), and vancomycin-resistant Enterococcus (VRE). These bacteria are very common causes of infections, associated with the high mortality rates. Carbapenems remain the “gold standard” treatment for serious infections due to ESBL-producing Enterobacteriaceae in HSCT recipients. Administration of β-lactam agents as an extended infusion is associated with better outcomes in patients with severe infections caused by P. aeruginosa. Older medications used for the treatment of CRE and MDR P. aeruginosa infections, such as polymyxins and aminoglycosides, have major limitations. On the other hand, new agents, such as ceftazidime-avibactam and ceftolozane-tazobactam, have a great potential for the treatment of Klebsiella pneumoniae carbapemenase-producing CRE and MDR P. aeruginosa, respectively, but more clinical data are needed to better evaluate their efficacy [1, 3].

The impact of the gut microbiota on anticancer therapy, including allo-HCT, receives increased attention nowadays. Recent studies in mice and humans suggest important relationships between the gut microbiota and outcome of allo-HCT. Currently several clinical trials on the role of microbiota in allo-HCT recipients are ongoing [3]. Associations between certain bacteria and allogeneic transplant outcomes have been found in many studies which have shown that the commensal microorganisms residing in the lumen of the intestines play an important role in the pathophysiology of GVHD [4, 5]. The aim of this multi-center study was to determine the incidence, risk factors, clinical course, and outcome of MDR GTI in pediatric patients after allogeneic and autologous HCT. We hypothesized there are transplant-related risk factors contributing to GI tract infections with MDR bacteria.

We analyzed incidence and the clinical risk factors for MDR GTI after allo-HCT and auto-HCT in pediatric population. Incidence was 44% among enrolled patients. It was lower among autologous recipients (19%) than in allogeneic setting (56%). According to many authors, the risk of infection is higher in patients after allo-HCT than auto-HCT [8‐10].

The most common bacteria species were Clostridium difficile (CDI), found in approximately 18% overall, 22% of allogeneic transplantation and 8.6% of autologous transplant. These results are in line with Boyle et al. who found that 11% of adults and 17% of children developed episode of CDI by day + 100 [11]. The incidence of CDI in HCT pediatric group varies between 2 and 27% according to some authors [12, 13]. When we compare it with our previous study [7], describing patients from years 2012 to 2015, the incidence in allogeneic and autologous setting is much higher nowadays (8.9% vs 22% and 6.7% vs 8.6%, respectively).

Looking for MDR Gram-negative bacteria incidence in our study, it was 26% overall. Balletto and Mikulska [14] showed similar incidence, highlighting that Enterobacteriaceae are the most frequent pathogens causing approximately 25% of BSI followed by pneumonia and gastrointestinal infections. In contrast Patriarca et al. presented in their study lower GN incidence at about 10% overall and 18% in allogeneic setting [15]. Incidence of Klebsiella pneumoniae ESBL positive in our study was 7.4%, E. coli ESBL positive was 4% overall, in allogeneic transplantation it was approximately 10% and 5%. In majority of the European countries, over 10% of all invasive infections caused by E. coli in 2012 were due to strains unsusceptible to 3rd-generation cephalosporins and the prevalence of ESBL producing strains in patients with hematological malignancies varies from 13% in Spain to 48% in Japan [16, 17].

Apart from Clostridium difficile and GN multidrug-resistant bacteria, we observed enterococcal infections quite often. Incidence of Enterococcus HLAR was 4% (n = 7/175 cases), and vancomycin-resistant Enterococcus (VRE) was 2% (n = 3/175 cases). According to Shono et al., in patient after allo-HSCT, simultaneous use of prophylactic antibiotics and antibiotic treatment of febrile neutropenia (FUO) leads to microbial diversity, which increases susceptibility to infections [3]. Whereas a healthy individual usually carries on the order of thousand different species, after allo-HCT, near dominance of the intestinal flora, particularly by a single species of Proteobacteria, Enterococcus or Streptococcus, is frequently observed. In particular exposure to the metronidazole and vancomycin is associated with Enterococcus domination. In accordance with the general European data [18, 19], there is a low incidence of VRE in European hematological centers with less than 5% of enterococci, being VRE in 67% according to the ECIL-4 questionnaire. In our study, incidence was much lower—VRE accounted for 20% of all enterococcal infections—but our data concerned only pediatric population.

Donor type seems to be an important risk factor causing infections after HCT including GTI. Styczyński et al. highlighted that the risk of infections after HSCT depends on the type of transplantation. The low-risk group is concerning autologous HSCT; moderate-risk, matched sibling donor HSCT with no GVHD; and high-risk, unrelated, mismatched, haploidentical, cord blood HSCT [8]. Similarly, in our study in multivariate analysis, incidence of GTI was higher in matched unrelated donor transplantation (MUD) than in children transplanted from siblings. Other studies have presented that they did not observe any significant correlation between donor type and occurrence of MDR infections [15].

Full HLA matching was connected with lower incidence of gastrointestinal tract infections in our analysis. Similarly, among children with CDI, significantly lower incidence of Clostridium difficile infection was found in children with full matched donor. It was not in line with other studies, where no significant impact was found for HLA match and infection incidence [20].

The connection between gastrointestinal infections and GVHD has been studied for many years. Majority of authors observed that risk of infections is higher in patients after allogeneic transplantation and in those with GVHD [8‐10, 14].These observation are in line with results of our uni-analysis, where patient with GVHD before infection, had higher incidence of GTI overall. In a CDI group, we did not observe such correlation. Significantly lower incidence of Clostridium difficile infection was found in children with presence of acute GVHD and gut GVHD. More recent retrospective study of 15 pediatric patients presented by Waldrip et al. reported that the use of antibiotics effective against anaerobic bacteria has resulted in a significant increase in GVHD with a reduction of gut anti-inflammatory Clostridia. More over addition of clindamycin to levofloxacin in a mouse model of GVHD reduced Clostridia and exacerbated GVHD [21]. Similarly, other studies showed that Clostridiales may play important anti-inflammatory homeostatic roles, including upregulation of Treg cells through the production of the short-chain fatty acids (SCFA) butyrate, which increased the recovery of intestinal epithelial cells (IEC) damage after allo-HSCT, and the re-introduction of a mixture of 17 strains of human Clostridiales isolates, which produce high levels of butyrate, prolonged the survival of mice with GVHD. Clinical data indicate that increased abundance of the Blautia genus, which belongs to the class Clostridia, is significantly associated with less GVHD-related mortality and improved overall survival [22‐27].

There was no significant impact of neutrophil engraftment on incidence of gastrointestinal infection in our study, although there was a trend towards higher incidence of GTI in patients whose neutrophil recovery was longer than 15 days. It was in line with other studies, where incidence and severity of infections after HCT strongly correlated with time of neutrophil engraftment [9, 10, 15].

We did not find significant impact of bone marrow source, TBI on incidence of gastrointestinal infection. In contrary to our analysis, Patriarca et al. observed that such factors as conditioning regimen, stem cell sources were significantly associated with development of infections caused by GN MRD bacteria [15]. Conditioning regimen with TBI was an important risk factor for developing CDI too in other studies [13, 28, 29]. Presented authors have analyzed adult or mixed (adult and/or children) population, so it could influence results. In other pediatric analysis concerning CDI in children after HCT, the authors did not find conditioning regiment, and TBI is a significant factor for CDI [7].

The main symptoms of GTI in our study were diarrhea, vomiting, fever, abdominal pains, and syndromes of typhlitis. There were 5 patients who developed symptoms of septic shock and one with megacolon toxicum. According to Tuncer et al., infectious etiologies of diarrhea account for only 10–15% of cases, yet diarrhea at any time after transplant should always prompt obtaining stool studies for CDI as well as bacterial, parasitic, and viral cultures if indicated [30‐32]. Lee et al. presented in their study that the major infectious complication of GI after HCT were typhlitis, and pseudomembranous enterocolitis [33]. The clinical manifestation included abdominal pain or tenderness, fever accompanied by neutropenia. Symptoms occurred mainly during 30 days after HCT. Megacolon toxicum was caused by motility problems related to CDI infection or mega-chemotherapy. It appeared during post-engraftment period (days 31–100 after HCT) [30, 34]. In our study, majority of typhlitis cases appeared between 20 and 60 days after HCT, one case of megacolon was diagnosed 90 days after transplant. The median time to develop all GTI infection in our study was 22 days (range 0–318 days) from the beginning of conditioning regimen.

The influence of gastrointestinal tract infection after HCT on survival is crucial. According to some studies, gastrointestinal system involvement is one of the main complications seen in the recipients of HCT, and it is also a major cause of morbidity and death [15, 34]. Balletto et al. highlighted that bacterial infections consisting from bloodstream infection followed by pneumonia and gastrointestinal infections are the major complications after HCT. Infections caused by Gram-negative rods used to be the main cause of infection-related mortality in patients with neutropenia [35]. In contrast, some authors think that, although MDR GN infections have been recognized as leading cause of mortality after solid organ transplantation, their epidemiology and impact on patients after HCT and with hematologic malignancies have been not enough studied [36‐39]. In that study, the main cause of deaths was not attributed to GTI infection but rather to progression of underlying disease. We observed 16 deaths, including 11, who had experienced GTI; however, no death was attributed to MDR gastrointestinal infection directly. In 6/16 cases, the death was secondary to generalized inflammatory response syndrome and MOF, caused by other infections (bacterial, viral, or fungal). The primary cause of other deaths was progression of underling disease, CNS complications, and road accident.

Our study has several limitations. Firstly, there was no unification in approach to fluoroquinolone prophylaxis in children below 4 years of life which differed between centers and screening for GTI which could influence incidence of bacterial infections/colonization too. Second, we studied both (in one cohort) autologous and allogeneic transplant recipients who had different risk of infections and mortality. Another limitation was lack of appropriate unified measures used to classify patient as “GTI positive.” Inclusion was based on positive stool culture and presence of clinical symptoms, but it was subjective and done in a few centers.

In conclusion, MDR GTI remain frequent and troublesome particularly in clinically severe stage, often causing longer hospitalization but rarely contributed to death among children after HCT. GTI occurred in 44% of enrolled children. We have identified different risk factors in HCT recipients of developing MDR GTI, although there are limitations to this analysis. HLA matching is influencing predisposition to develop MDR GTI. Patients transplanted from full HLA match donor have lower chance to develop GTI. Donor type seems to be an important risk factor causing infections after HCT including MDR GTI. Children transplanted from MUD are more predisposed to develop GTI infection. Acute GVHD has been shown to be an important risk factor for developing GTI, but only among children with GN MDR infections. Children having CDI are at the lowest risk of GVHD, what is connected with beneficial role of Clostridiales and production of SCFA butyrate. MRD GTI rarely cause death, but very often breakthrough strains with non-resistant bacteria can be fatal (and responsible for more than 30% of deaths in these population).