Infections caused by non-tuberculous mycobacteria in recipients of hematopoietic stem cell transplantation.

Non-tuberculous mycobacteria (NTM) are acid-fast bacteria that are ubiquitous in the environment and can colonize soil, dust particles, water sources, and food supplies. They are divided into rapidly growing mycobacteria such as Mycobacterium fortuitum, Mycobacterium chelonae, and Mycobacterium abscessus as well as slowly growing species such as Mycobacterium avium, Mycobacterium kansasii, and Mycobacterium marinum. About 160 different species, which can cause community acquired and health care-associated infections, have been identified. NTM are becoming increasingly recognized in recipients of hematopoietic stem cell transplantation (HSCT) with incidence rates ranging between 0.4 and 10%. These infections are 50-600 times commoner in transplant recipients than in the general population and the time of onset ranges from day 31 to day 1055 post-transplant. They have been reported following various forms of HSCT. Several risk factors predispose to NTM infections in recipients of stem cell transplantation and these are related to the underlying medical condition and its treatment, the pre-transplant conditioning therapies as well as the transplant procedure and its complications. Clinically, NTM may present with: unexplained fever, lymphadenopathy, osteomyelitis, soft tissue and skin infections, central venous catheter infections, bacteremia, lung, and gastrointestinal tract involvement. However, disseminated infections are commonly encountered in severely immunocompromised individuals and bloodstream infections are almost always associated with catheter-related infections. It is usually difficult to differentiate colonization from true infection, thus, the threshold for starting therapy remains undetermined. Respiratory specimens such as sputum, pleural fluid, and bronchoalveolar lavage in addition to cultures of blood, bone, skin, and soft tissues are essential diagnostically. Susceptibility testing of mycobacterial isolates is a basic component of optimal care. Currently, there are no guidelines for the treatment of NTM infections in recipients of stem cell transplantation, but such infections have been successfully treated with surgical debridement, removal of infected or colonized indwelling intravascular devices, and administration of various combinations of antimicrobials. Monotherapy can be associated with development of drug resistance due to new genetic mutation. The accepted duration of treatment is 9 months in allogeneic stem cell transplantation and 6 months in autologous setting. Unfortunately, eradication of NTM infections may be impossible and their treatment is often complicated by adverse effects and interactions with other transplant-related medication.

Infections Caused by Stenotrophomonas maltophilia in Recipients of Hematopoietic Stem Cell Transplantation.

Stenotrophomonas maltophilia (S. maltophilia) is a globally emerging Gram-negative bacillus that is widely spread in environment and hospital equipment. Recently, the incidence of infections caused by this organism has increased, particularly in patients with hematological malignancy and in recipients of hematopoietic stem cell transplantation (HSCT) having neutropenia, mucositis, diarrhea, central venous catheters or graft versus host disease and receiving intensive cytotoxic chemotherapy, immunosuppressive therapy, or broad-spectrum antibiotics. The spectrum of infections in HSCT recipients includes pneumonia, urinary tract and surgical site infection, peritonitis, bacteremia, septic shock, and infection of indwelling medical devices. The organism exhibits intrinsic resistance to many classes of antibiotics including carbapenems, aminoglycosides, most of the third-generation cephalosporins, and other ß-lactams. Despite the increasingly reported drug resistance, trimethoprim-sulfamethoxazole is still the drug of choice. However, the organism is still susceptible to ticarcillin-clavulanic acid, tigecycline, fluoroquinolones, polymyxin-B, and rifampicin. Genetic factors play a significant role not only in evolution of drug resistance but also in virulence of the organism. The outcome of patients having S. maltophilia infections can be improved by: using various combinations of novel therapeutic agents and aerosolized aminoglycosides or colistin, prompt administration of in vitro active antibiotics, removal of possible sources of infection such as infected indwelling intravascular catheters, and application of strict infection control measures.

Infections Caused by Acinetobacter baumannii in Recipients of Hematopoietic Stem Cell Transplantation.

Acinetobacter baumannii (A. baumannii) is a Gram-negative, strictly aerobic, non-fermentative coccobacillus, which is widely distributed in nature. Recently, it has emerged as a major cause of health care-associated infections (HCAIs) in addition to its capacity to cause community-acquired infections. Risk factors for A. baumannii infections and bacteremia in recipients of hematopoietic stem cell transplantation include: severe underlying illness such as hematological malignancy, prolonged use of broad-spectrum antibiotics, invasive instrumentation such as central venous catheters or endotracheal intubation, colonization of respiratory, gastrointestinal, or urinary tracts in addition to severe immunosuppression caused by using corticosteroids for treating graft versus host disease. The organism causes a wide spectrum of clinical manifestations, but serious complications such as bacteremia, septic shock, ventilator-associated pneumonia, extensive soft tissue necrosis, and rapidly progressive systemic infections that ultimately lead to multi-organ failure and death are prone to occur in severely immunocompromised hosts. The organism is usually resistant to many antimicrobials including penicillins, cephalosporins, trimethoprim-sulfamethoxazole, almost all fluoroquinolones, and most of the aminoglycosides. The recently increasing resistance to carbapenems, colistin, and polymyxins is alarming. Additionally, there are geographic variations in the resistance patterns and several globally and regionally resistant strains have already been described. Successful management of A. baumannii infections depends upon appropriate utilization of antibiotics and strict application of preventive and infection control measures. In uncomplicated infections, the use of a single active beta-lactam may be justified, while definitive treatment of complicated infections in critically ill individuals may require drug combinations such as colistin and rifampicin or colistin and carbapenem. Mortality rates in patients having bacteremia or septic shock may reach 70%. Good prognosis is associated with presence of local infection, absence of multidrug resistant strain, and presence of uncomplicated infection while poor outcome is associated with severe underlying medical illness, bacteremia, septic shock, multi-organ failure, HCAIs, admission to intensive care facilities for higher levels of care, and culture of certain aggressive genotypes of A. baumannii.

Brucella bacteremia in a recipient of an allogeneic hematopoietic stem cell transplant: a case report.

BACKGROUND: Brucellosis is an important cause of morbidity and mortality in patients living in areas that are endemic for the infection. CASE PRESENTATION: A 20 years old Saudi male was diagnosed to have severe aplastic anemia at King Faisal Specialist Hospital and Research Centre in Riyadh in April 2006. One hundred and twelve days following his successful allogeneic hematopoietic stem cell transplant, he presented with pyrexia in addition to neutropenia and mild thrombocytopenia. Brucella serology was strongly positive and blood cultures grew Brucella melitensis. The bacteremic episode of brucellosis was successfully treated with streptomycin, doxycyclin and ciprofloxacin at the outpatient clinic. To our knowledge, this is the first case of a naturally occurring Brucella infection complicated by Brucella bacteremia in a recipient of hematopoietic stem cell transplant. CONCLUSION: Brucellosis may cause systemic infections, complicated bacteremias and serious morbidity in immunocompromised patients living in countries that are endemic for the infection. It should be considered as a possible cause of fever and pancytopenia in hematopoietic stem cell transplant recipients living in these geographical locations. Nevertheless, the infection is curable provided the diagnosis is made early and an appropriate antimicrobial therapy is promptly initiated.

Klebsiella oxytoca bacteremia causing septic shock in recipients of hematopoietic stem cell transplant: Two case reports.

BACKGROUND: Klebsiella oxytoca can cause various infectious complications in healthy as well as in immunocompromised individuals. CASE PRESENTATIONS: Case 1: A 49 year old female with multiple myeloma received an autologous hematopoietic stem cell transplant in October 2005. Eight days following her autograft she developed septic shock caused by Klebsiella oxytoca bacteremia which was successfully treated with intravenous meropenem and gentamicin. Case 2: A 29 year old female with sickle cell anemia and severe aplastic anemia underwent an allogeneic hematopoietic stem cell transplant in July 2005. Seven months following her unsuccessful allograft, she developed septic shock due to Klebsiella oxytoca bacteremia caused by a urinary tract infection. The septic episode was successfully managed with intravenous meropenem and gentamicin. Both patients were treated at King Faisal Specialist Hospital and Research Centre in Riyadh, Saudi Arabia. To our knowledge, they are the first reports of Klebsiella oxytoca bacteremias and septic shocks in hematopoietic stem cell transplant recipients. CONCLUSION: Klebsiella oxytoca should be considered as a possible cause of severe infections in recipients of various forms of hematopoietic stem cell transplantation. However, these infections may be complicated by bacteremias, septic shocks, systemic dysfunctions and even deaths if not managed promptly and appropriately.

Successful management of multifactorial colitis in a recipient of hematopoietic stem cell transplant: a case report.

Recipients of allogeneic hematopoietic stem cell transplant can develop life-threatening complications at any time following their transplants. These complications require repeated clinical assessment, appropriate and thorough screening as well as a comprehensive management approach. We report a young adult male who received a sibling allograft in the second complete remission of his acute lymphoblastic leukemia at King Faisal Specialist Hospital and Research Centre in Riyadh. The patient developed severe colitis which was caused by: acute exacerbation of chronic graft versus host disease of the lower gastrointestinal tract, cytomegalovirus disease of the colon and a superadded Salmonella infection caused by food poisoning. The multifactorial colitis was properly investigated and successfully managed. To our knowledge, this is the first case of multifactorial colitis in a recipient of hematopoietic stem cell transplant.

Endocarditis caused by Abiotrophia defectiva.

A 35-year-old man with pre-existing rheumatic heart disease and aortic regurgitation (AR) presented with intermittent fever, ankle swelling and clinical evidence of endocarditis. Transoesophageal echocardiogram (TEE) revealed vegetations and destruction of the aortic valve (AV). Blood cultures grew a gram positive coccobacillus which was phenotypically identified as Abiotrophia defectvia (A.defectiva). A diagnosis of infective endocarditis (IE) due to A.defectiva was made. Treatment, with penicillin and gentamicin, was administered for 4 weeks. Mechanical valve replacement was required few days after starting the antibiotic therapy. The patient had a favorable outcome on follow up. Although A.defectiva is an uncommon cause of endocarditis, early and correct identification of this pathogen is important to improve the outcome and the prognosis of patients with IE due to this organism.

Antimicrobial susceptibility pattern of clinical isolates of Pseudomonas aeruginosa.

OBJECTIVE: To determine the level of resistance to the widely used antipseudomonal antibiotics in clinical isolates of Pseudomonas aeruginosa (P. aeruginosa). METHODS: The microbiology database of all clinical isolates of P. aeruginosa at the Armed Forces Hospital, Riyadh, Kingdom of Saudi Arabia, from January 1999 to December 1999 was reviewed. The antimicrobial susceptibilities were determined by a standardized method. RESULTS: Seven hundred and four P. aeruginosa isolates were tested. These strains were commonly isolated from surgical patients followed by intensive care units. Respiratory tract was the most common source of isolation. The antibiotic susceptibility rates were as follows: ciprofloxacin 92.2%, meropenem 91.6%, imipenem 90.2%, amikacin 85.8%, ceftazidime 81.8% piperacillin/tazobactam 81.3% and gentamicin 77.7%. Among 704 strains 6.4% were designated as being multidrug resistant. These were commonly isolated from respiratory tract specimens of patients in intensive care units. CONCLUSION: The clinical significance of these findings is important in the selection of appropriate empiric treatment of serious P. aeruginosa infections. It emphasizes the importance of a conservative approach to antibiotic therapy and continued antimicrobial susceptibility testing surveillance programs to curtail the problem of antibiotic resistance.

Distribution of Candida species among bloodstream isolates.

OBJECTIVE: To identify the distribution of Candida species causing bloodstream infections. METHODS: This study was conducted at the Armed Forces Hospital, Riyadh, Kingdom of Saudi Arabia. All cases of candidemia from the period 1996 through to 2002 were retrospectively identified through the records from the Department of Clinical Microbiology. RESULTS: Two hundred and ninety-four candidemic episodes were identified, 176 (59.9%) occurred in the intensive care units (ICUs), 32 (10.9%) medical, 30 (10.2%) surgical wards, 24 (8%) from patients with hematologic malignancies and 15 (5%) from pediatric wards. Candida albicans (C. albicans) was the most frequently isolated species with 149 (50.7%) cases, followed by Candida tropicalis (C. tropicalis) 61 (20.7%), Candida parapsilosis 32 (10.9%), Candida krusei (C. krusei) 23 (7.8%) and Candida glabrata 21 (7.1%). Other species were not common. There is an increase in the proportion of non C. albicans species as the causative agents of candidemia. In certain clinical settings, non C. albicans species predominate as in the Adult General Intensive Care Unit with C. tropicalis as the most common. While in patients with hematologic malignancies, C. krusei species is the most common. CONCLUSION: These findings reinforce the need for continued and active surveillance programs to address the changes in the species distribution among candidal bloodstream isolates which will help to develop effective, preventive and therapeutic strategies.