Elisa Balletto and Małgorzata Mikulska
Division of Infectious Diseases, IRCCS San Martino University Hospital – IST, Genoa, Italy. Department of Health Sciences, University of Genoa, Genoa, Italy
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Bacterial infections are major complications after Hematopoietic Stem Cell Transplant (HSCT). They consist mainly of bloodstream infections (BSI), followed by pneumonia and gastrointestinal infections, including typhlitis and Clostridium difficile infection. Microbiological data come mostly from BSI. Coagulase negative staphylococci and Enterobacteriaceae are the most frequent pathogens causing approximately 25% of BSI each, followed by enterococci, P. aeruginosa and viridans streptococci. Bacterial pneumonia is frequent after HSCT, and Gram-negatives are predominant. Clostridium difficile infection affects approximately 15% of HSCT recipients, being more frequent in case of allogeneic than autologous HSCT.
The epidemiology and the prevalence of resistant strains vary significantly between transplant centres. In some regions, multi-drug resistant (MDR) Gram-negative rods are increasingly frequent. In others, vancomycin-resistant enterococci are predominant. In the era of increasing resistance to antibiotics, the efficacy of fluoroquinolone prophylaxis and standard treatment of febrile neutropenia have been questioned. Therefore, a thorough evaluation of local epidemiology is mandatory to decide the need for prophylaxis and the choice of the best regimen for empirical treatment of febrile neutropenia. For the latter, individualised approach has been proposed, consisting of either escalation or de-escalation strategy. De-escalation strategy is recommended since resistant bacteria should be covered upfront, mainly in patients with severe clinical presentation and previous infection or colonisation with a resistant pathogen.
Non-pharmacological interventions, such as screening for resistant bacteria, applying isolation and contact precautions should be put in place to limit the spread of MDR bacteria. Antimicrobial stewardship program should be implemented in transplant centres.
The most common bacterial infections after HSCT are BSI, pneumonia and gastrointestinal infections. Urinary tract infections are infrequent and usually associated with the presence of the urinary catheter. The reliable data on the aetiology of bacterial infections in the setting of HSCT come mainly from the results of blood cultures. In fact BSI is the most frequent microbiologically documented infection, whereas microbiological documentation is significantly less frequent in case of pneumonia or typhlitis.
|Table 1. The main risk factors associated with BSI due to single bacterial species|
|Figure 1. The aetiology of bloodstream infections according to literature review and questionnaire survey performed for European Conference on Infections in Leukemia (ECIL), reported as median values.|
Clostridium difficile infection
|Table 2. Studies evaluating Clostridium difficile infection in HSCT recipients, 2010 to present.|
|Table 3. Risk factors for developing Clostridium difficile infection in HSCT recipients.|
Recent advances in the management of bacterial infections
Infection control measures
Bacterial infections continue to be one of the most frequent complications after HSCT. The incidence of Gram-negative bacteria and the rate of resistance to antibiotics have been steadily increasing in many centres. However, important differences in the epidemiology of bacterial infections exist among transplant centres worldwide. Therefore, the knowledge of local epidemiology is crucial and should guide the approach to antibiotic prophylaxis, empirical therapy and management of infections. Numerous interesting issues such as the role of surveillance cultures for guiding empirical therapy, the benefits of protocols for screening for resistant bacteria, decolonisation and the current role of antibiotic prophylaxis in HSCT setting await to be addressed in future clinical studies.