Etiology of diarrhea in patients undergoing allogeneic bone marrow transplantation in South India

Considerations for medical nutrition therapy management of the critically ill patient with hematological malignancies: A narrative review

Patients with hematological malignancies (HMs) are more frequently admitted now than in the past to the intensive care unit (ICU) due to more aggressive approaches in primary therapy of HMs and the need for critical care support. Pathophysiological alterations derived from HMs and the different hematological therapies, such as chemotherapy, negatively affect gastrointestinal (GI) function, metabolism, and nutrition status. Further, malnutrition strongly influences outcomes and tolerance of the different hematological therapies. In consequence, these critically ill patients frequently present with malnutrition and pathophysiological alterations that create challenges for the delivery of medical nutrition therapy (MNT) in the ICU. Frequent screening, gauging tolerance, and monitoring nutrition status are mandatory to provide individualized MNT and achieve nutrition objectives. The present review discusses how HM impact GI function and nutrition status, the importance of MNT in patients with HM, and specific considerations for guidance in providing adequate MNT to these patients when admitted to the ICU.

Parasitic infections in hematopoietic stem cell transplant recipients

INTRODUCTION

Hematopoietic stem cell transplantation (HSCT) is a vital treatment for various hematological disorders. However, HSCT recipients face increased risks of infectious complications due to immunosuppression. Parasitic infections are a significant concern in this vulnerable population and can lead to substantial morbidity and mortality. This review examines parasitic infections in HSCT recipients, focusing on major infections affecting different organ systems, including intestinal parasites (Giardia spp., Entamoeba histolytica, and Cryptosporidium spp.), hematologic parasites (Plasmodium spp. and Babesia spp.), and tissue/visceral parasites (Toxoplasma gondii, Leishmania spp., and Trypanosoma cruzi).

METHODS

A systematic search of relevant literature was conducted and included studies up to August 2023. Databases included PubMed, Google Scholar, were queried using specific keywords related to parasitic infections in HSCT patients. The epidemiology, risk factors, clinical presentation, diagnostic methods, and treatment approaches for each infection were evaluated.

RESULTS AND CONCLUSION

Knowing the epidemiology, risk factors, and clinical presentations are crucial for timely intervention and successful management. By emphasizing early detection, effective therapies, and the unique challenges posed by each of these infections, this review highlights the importance of tailored strategies for HSCT recipients. Future research can further refine management protocols to enhance care and outcomes for these patients.

How I approach diarrhea in hematological transplant patients: A practical tool

Diarrhea in hematopoietic stem-cell transplantation (HSCT) remains a multifactorial challenge that demands a nuanced diagnostic approach. The causes of infectious diarrhea in HSCT recipients are diverse and influenced by patient-specific risk factors, the post-transplant timeline, and local epidemiology. During the past decade, our understanding of diarrhea in HSCT has witnessed a transformative shift through the incorporation of gastrointestinal (GI) multiplex polymerase chain reaction (PCR) panels. However, the judicious application of these panels is imperative to avoid overtesting and prevent adverse outcomes. The challenge lies in distinguishing between the diverse causes of diarrhea, ascertaining the clinical significance of detected pathogens, and navigating the diagnostic uncertainty presented by several non-infectious conditions such as mucositis, intestinal dysbiosis, and acute graft-versus-host disease (aGvHD), all of which mimic infection. This review examines the landscape of infectious diarrhea in the HSCT population, encompassing both established (e.g., Cytomegalovirus, Clostridioides difficile, and norovirus) and emerging pathogens (e.g., sapoviruses, astroviruses). We propose a multifaceted diagnostic algorithm that combines clinical assessment, risk stratification, and tailored utilization of molecular platforms. While multiplex GI panels present invaluable opportunities for rapid and comprehensive pathogen detection, their judicious use is pivotal in preserving diagnostic stewardship. Customization of diagnostic algorithms tailored to local epidemiology ensures optimal patient care and resource utilization.

Evolving Patterns of Cryptosporidiosis: Issues and Implications in the Context of Public Health in India

Cryptosporidiosis is one of the major causes of diarrhea in immune-compromised individuals and children besides causing sporadic water-borne, food-borne, and zoonotic outbreaks. In 2016, Cryptosporidium species infection was the fifth leading cause of diarrhea and acute infection causing more than 4.2 million disability-adjusted life years lost besides a decrease in childhood growth. Human cryptosporidiosis is primarily caused by two species/genotype: Cryptosporidium hominis (anthroponotic) and Cryptosporidium parvum (zoonotic) besides other six rare species/genotypes. Transmission intensity, genetic diversity, and occurrence of genetic recombination have shaped the genus Cryptosporidium population structures into palmitic, clonal, and epidemic. Genetic recombination is more in C. parvum compared with C. hominis. Furthermore, parasite–host co-evolution, host adaptation, and geographic segregation have led to the formation of “subtype- families.” Host-adapted subtype-families have distinct geographical distribution and host preferences. Genetic exchanges between subtypes played an important role throughout the evolution of the genus leading to “adaptation introgression” that led to emergence of virulent and hyper-transmissible subtypes. The population structure of C. hominis in India appears to be more complex where both transmission intensity and genetic diversity are much higher. Further, study based on “molecular strain surveillance” has resulted newer insights into the epidemiology and transmission of cryptosporidiosis in India. The identification at the species and genotype levels is essential for the assessment of infection sources in humans and the public health potential of the parasite at large. The results of the study over three decades on cryptosporidiosis in India, in the absence of a national surveillance data, were analyzed highlighting current situation on epidemiology, genetic diversity, and distribution particularly among vulnerable population. Despite creditable efforts, there are still many areas need to be explored; therefore, the intent of this article is to facilitate future research approaches for mitigating the burden associated with this disease.

Predictors of a short hospitalization in bone marrow transplantation patients presenting to the emergency department

BACKGROUND

Despite the advantages of bone marrow transplantation (BMT), patients receiving this intervention visit the emergency department (ED) frequently and for various reasons. Many of those ED visits result in hospitalization, and the length of stay varies.

OBJECTIVES

The objective of our study was to identify the patients who were only briefly hospitalized and were thus eligible for safe discharge from the ED.

METHODS

This was a retrospective cohort study conducted on all adult patients who have completed a successful BMT and had an ED visit that resulted in hospitalization.

RESULTS

Our study included 115 unique BMT with a total number of 357 ED visits. Around half of those visits resulted in a short hospitalization. We found higher odds of a short hospitalization among those who have undergone autologous BMT (95%CI [1.14-2.65]). Analysis of the discharge diagnoses showed that patients with gastroenteritis were more likely to have a shorter hospitalization in comparison to those diagnosed with others (95%CI [1.10-3.81]). Furthermore, we showed that patients who presented after a month from their procedure were more likely to have a short hospitalization (95%CI [1.04-4.87]). Another significant predictor of a short of hospitalization was the absence of Graft versus Host Disease (GvHD) (95%CI [2.53-12.28]). Additionally, patients with normal and high systolic blood pressure (95%CI [2.22-6.73] and 95%CI [2.81-13.05]; respectively), normal respiratory rate (95%CI [2.79-10.17]) and temperature (95%CI [2.91-7.44]) were more likely to have a shorter hospitalization, compared to those presenting with abnormal vitals. Likewise, we proved higher odds of a short hospitalization in patients with a quick Sepsis Related Organ Failure Assessment score of 1-2 (95%CI [1.29-5.20]). Moreover, we demonstrated higher odds of a short hospitalization in patients with a normal platelet count (95%CI [1.39-3.36]) and creatinine level (95%CI [1.30-6.18]).

CONCLUSION

In our study, we have shown that BMT patients visit the ED frequently and many of those visits result in a short hospitalization. Our study showed that patients presenting with fever/chills are less likely to have a short hospitalization. We also showed a significant association between a short hospitalization and BMT patients without GvHD, with normal RR, normal T °C and a normal platelet count.

Giardia lamblia mimicking acute graft versus host disease after allogeneic hematopoietic stem cell transplantation: A case report

RATIONALE

As the major complications post allogeneic hematopoietic stem cell transplantation (allo-HSCT), gastrointestinal disorders were most commonly ascribed to acute graft-versus-host disease (aGVHD) and opportunistic infections. Though Giardia lamblia (G lamblia) is the most common waterborne parasite of intestinal infection worldwide, seldom has it been reported in a patient with acute severe aplastic anemia after allo-HSCT.

PATIENT CONCERNS

A 23-year-old male with severe aplastic anemia developed diarrhea, abdominal cramps, bloating, nausea, vomiting, fever, weight loss, and fatigue after allo-HSCT.

DIAGNOSIS

Stool examinations for ova and parasites showed Giardia trophozoites and cysts.

INTERVENTIONS

Methylprednisolone was stopped and the patient was intravenously treated with a 7-day course of metronidazole (500 mg, tid.). Simultaneously, cyclosporine (5 mg/kg) was continually utilized for suspicious gut GVHD.

OUTCOMES

The Giardia lamblia in stool turned negative and his symptoms were resolved after the 7-day course.

LESSONS

Incorporating non-invasive monitoring of stool examination for ova and parasites in the follow-up algorithm for post-HSCT patients can expedite clinical decision-making in the differential diagnoses for aGVHD even in the non-endemic area. Metronidazole therapy can be well-tolerated in HSCT patients with giardiasis.

Parasitic Infections of the Stem Cell Transplant Recipient and the Hematologic Malignancy Patient, Including Toxoplasmosis and Strongyloidiasis

Hematopoietic stem cell transplantation (HSCT) recipients may infrequently develop parasitic infections at the time of the procedure via contamination from allograft tissue or blood products, and in the post-transplantation period through the traditional route of infection or as a reactivation caused by immunosuppression related to the transplant. To reduce risk, efforts should be directed at performing a comprehensive history, maintaining a high index of suspicion, and adhering to preventive measures. Additional strategies for the prevention, screening and careful follow-up, identification, and pre-emptive treatment of parasitic infections are required to reduce morbidity and mortality in HSCT patients.

Clostridium difficile infection in low- and middle-human development index countries: a systematic review

OBJECTIVE

To describe the impact and epidemiology of Clostridium difficile infection (CDI) in low- and middle-human development index (LMHDI) countries.

METHOD

Prospectively registered, systematic literature review of existing literature in the PubMed, Ovid and Web of Science databases describing the epidemiology and management of C. difficile in LMHDI countries. Risk factors were compared between studies when available.

RESULTS

Of the 218 abstracts identified after applying search criteria, 25 studies were reviewed in detail. The weighted pooled infection rate among symptomatic non-immunosuppressed inpatients was 15.8% (95% CI 12.1-19.5%) and was 10.1% (95% CI 3.0-17.2%) among symptomatic outpatients. Subgroup analysis of immunosuppressed patient populations revealed pooled infection rates similar to non-immunosuppressed patient populations. Risk factor analysis was infrequently performed.

CONCLUSIONS

While the percentages of patients with CDI in LMHDI countries among the reviewed studies are lower than expected, there remains a paucity of epidemiologic data evaluating burden of C. difficile infection in these settings.

Clinical-associated characteristics and microbiological features of bloodstream nontyphoidal salmonella infection in adult patients receiving allogeneic hematopoietic stem cell transplantation

Bloodstream nontyphoidal salmonella (NTS) infection is rare, but its associated characteristics and microbiological features in immunocompromised patients are worth paying attention to, particularly for those receiving allogeneic hematopoietic stem cell transplantation (SCT). No studies so far have analyzed post-transplant bloodstream NTS infection. Therefore, we reviewed 423 adult patients undergoing allogeneic hematopoietic SCT from 2003 to 2014. Nine out of four hundred twenty-three patients (2.13%) developed post-transplant bloodstream NTS infection, including two patients who had subsequent or combined metastatic infections. The median age at SCT was 35 years (interquartile range, 29-46) among the nine patients with bloodstream NTS infection. Male patients were predominant (78%). The median onset of bloodstream NTS infection was at 315 days after SCT (range, 207-629). Multivariate analysis revealed that extensive chronic graft-versus-host disease (GVHD) (OR 8.054, p = 0.003) and nonmyeloablative transplant conditioning (OR 4.604, p = 0.037) were significant associated characteristics for NTS infection. Currently, there are no published data analyzing and exploring post-transplant bloodstream NTS infections in adult allogeneic hematopoietic SCT. Our study determined the associated characteristics and microbiological features for this infection.

Molecular appraisal of intestinal parasitic infection in transplant recipients

BACKGROUND & OBJECTIVES

Diarrhoea is the main clinical manifestation caused by intestinal parasitic infections in patients, with special reference to transplant recipients who require careful consideration to reduce morbidity and mortality. Further, molecular characterization of some important parasites is necessary to delineate the different modes of transmission to consider appropriate management strategies. We undertook this study to investigate the intestinal parasitic infections in transplant recipients with or without diarrhoea, and the genotypes of the isolated parasites were also determined.

METHODS

Stool samples from 38 transplant recipients comprising 29 post-renal, two liver and seven bone marrow transplant (BMT) recipients presenting with diarrhoea and 50 transplant recipients (42 post-renal transplant, eight BMT) without diarrhoea were examined for the presence of intestinal parasites by light microscopy using wet mount, modified Ziehl-Neelsen staining for intestinal coccidia and modified trichrome staining for microsporidia. Genotypes of Cryptosporidium species were determined by multilocus genotyping using small subunit ribosomal (SSUrRNA), Cryptosporidium oocyst wall protein (COWP) and dihydrofolate reductase (DHFR) as the target genes. Assemblage study for Giardia lamblia was performed using triose phosphate isomerase (TPI) as the target gene. Samples were also screened for bacterial, fungal and viral pathogens.

RESULTS

The parasites that were detected included Cryptosporidium species (21%, 8/38), Cystoisospora (Isospora) belli (8%, 3), Cyclospora cayetanensis (5%, 2), G. lamblia (11%, 4), Hymenolepis nana (11%, 4), Strongyloides stercoralis (3%, 1) and Blastocystis hominis (3%, 1). Multilocus genotyping of Cryptosporidium species at SSUrRNA, COWP and DHFR loci could detect four isolates of C. hominis; two of C. parvum, one of mixed genotype and one could not be genotyped. All the C. hominis isolates were detected in adult post-renal transplant (PRT) recipients, whereas the C. parvum isolates included a child with BMT and an adult with PRT. Clostridium difficle, cytomegalovirus and Candida albicans were found in 2, 3 and 2 patients, respectively.

INTERPRETATION & CONCLUSIONS

In the present study, C. hominis was observed as an important parasite causing intestinal infections in transplant recipients. Multilocus genotyping of Cryptosporidium species could detect four isolates of C. hominis; two of C. parvum, one of mixed genotype and one could not be genotyped. Genotyping of G. lamblia revealed that assemblage B was most common.

Fidaxomicin--the new drug for Clostridium difficile infection

Clostridium difficile is one of the many aetiological agents of antibiotic associated diarrhoea and is implicated in 15-25 per cent of the cases. The organism is also involved in the exacearbation of inflammatory bowel disease and extracolonic manifestations. Due to increase in the incidence of C. difficile infection (CDI), emergence of hypervirulent strains, and increased frequency of recurrence, the clinical management of the disease has become important. The management of CDI is based on disease severity, and current antibiotic treatment options are limited to vancomycin or metronidazole in the developing countries. this review article briefly describes important aspects of CDI, and the new drug, fidaxomicin, for its treatment. Fidaxomicin is particularly active against C. difficile and acts by inhibition of RNA synthesis. Clinical trials done to compare the efficacy and safety of fidaxomicin with that of vancomycin in treating CDI concluded that fidaxomicin was non-inferior to vancomycin for treatment of CDI and that there was a significant reduction in recurrences. The bactericidal properties of fidaxomicin make it an ideal alternative for CDI treatment. However, fidaxomicin use should be considered taking into account the potential benefits of the drug, along with the medical requirements of the patient, the risks of treatment and the high cost of fidaxomicin compared to other treatment regimens.

Rotavirus in organ transplantation: drug-virus-host interactions

Although rotavirus is usually recognized as the most common etiology of diarrhea in young children, it can in fact cause severe diseases in organ transplantation recipients irrespective of pediatric or adult patients. This comprehensive literature analysis revealed 200 cases of rotavirus infection with 8 related deaths in the setting of organ transplantation been recorded. Based on published cohort studies, an average incidence of 3% (187 infections out of 6176 organ recipients) was estimated. Rotavirus infection often causes severe gastroenteritis complications and occasionally contributes to acute cellular rejection in these patients. Immunosuppressive agents, universally used after organ transplantation to prevent organ rejection, conceivably play an important role in such a severe pathogenesis. Interestingly, rotavirus can in turn affect the absorption and metabolism of particular immunosuppressive medications via several distinct mechanisms. Even though rotaviral enteritis is self-limiting in general, infected transplantation patients are usually treated with intensive care, rehydration and replacement of nutrition, as well as applying preventive strategies. This article aims to properly assess the clinical impact of rotavirus infection in the setting of organ transplantation and to disseminate the interactions among the virus, host and immunosuppressive medications.

Infectious complications of stem cell transplantation

Hematopoietic stem cell transplantation (HSCT) is an accepted treatment for a variety of hematologic malignancies. The profound immunosuppression these patients experience adversely affects their risk of infection. This risk is much higher than in the general population and requires aggressive diagnostic and therapeutic interventions. The chapter will outline the major infections after HSCT.

Clostridium difficile infection among hematopoietic stem cell transplant recipients: beyond colitis

PURPOSE OF REVIEW

To review the most recent data regarding the epidemiology, risks factors, and outcomes among hematopoietic stem cell transplant recipients with Clostridium difficile infection (CDI).

RECENT FINDINGS

With the emergence of an epidemic strain of C. difficile known as NAP1 in the early 2000s, rates of this infection have escalated globally. Hematopoietic stem cell transplant recipients appear to be one of the most vulnerable populations for the development of CDI. Traditional risk factors for CDI including antimicrobial exposure and older age are likely only a piece of the overall risk profile, with recent study results also emphasizing other factors such as transplant type, conditioning regimen, and graft-versus-host disease (GVHD). The relationship between CDI and subsequent development of GVHD, particularly of the gastrointestinal tract, is of specific interest. A bidirectional relationship of association has been highlighted in a number of recent studies and underscores the need for further prospective studies to address the potential indirect effects of alloreactivity induced by CDI.

SUMMARY

CDI has emerged as one of the most common infections in the early transplant period. Recent studies have begun to address the epidemiology of disease, risk factors for, and outcomes after infection in the stem cell transplant. However, more research is needed to unravel the observed relationship between CDI and GVHD.

Cryptosporidiosis: An under-recognized public health problem

Cryptosporidium spp. is under recognized as an important pathogen causing diarrhea in children and HIV-infected individuals with associated high morbidity and mortality. In endemic areas, most symptomatic infections are in childhood and in immunocompromised adults. The immune status of the host plays a critical role in determining the severity of cryptosporidiosis. Infection is self-limited in immunocompetent hosts, but can be severe and persistent in the immunocompromised such as AIDS patients or malnourished children. Cryptosporidiosis in developing countries is a major cause of acute and persistent diarrhea in children and is associated with subsequent impairment in growth, physical fitness, and cognitive function. Despite recognition of the importance of immune status, the correlates of protective immunity in cryptosporidiosis in humans are poorly understood, and treatment modalities are limited.

Multiple viral infections after haploidentical hematopoietic stem cell transplantation in a child with acute lymphoblastic leukemia

After allogeneic hematopoietic stem cell transplantation (HSCT), viral infections/reactivations are a frequent complication, sometimes with fatal outcome. Thus, early diagnosis is recommended by screening of whole blood or plasma preparations using highly sensitive molecular techniques that test for the most common viral pathogens, such as Epstein-Barr virus, cytomegalovirus, and adenoviruses (ADVs). Despite this approach, not every reactivation/infection can be adequately detected or excluded, even with highly sensitive polymerase chain reaction. Particularly after toxic treatment, uncommon infections or infections resistant to first-line treatment can occur, even in unusual locations. Herein, we present the case of a child with Philadelphia chromosome-positive acute lymphoblastic leukemia after allogeneic HSCT who suffered from 5 different viral reactivations/infections, including acyclovir-resistant herpes simplex virus type 1 esophagitis, human herpesvirus 6 encephalitis, rotavirus gastroenteritis, respiratory syncytial virus pneumonia, and ADV esophagitis, despite routinely performed blood examinations for viral pathogens remaining unrevealing at all times.

Clostridium difficile infection in HIV-seropositive individuals and transplant recipients

Immunocompromise is a commonly cited risk factor for Clostridium difficile infection (CDI). We reviewed the experimental and epidemiological literature on CDI in three immunocompromised groups, HIV-seropositive individuals, haematopoietic stem cell or bone marrow transplant recipients and solid organ transplant recipients. All three groups have varying degrees of impairment of humoral immunity, a major factor influencing the outcome of CDI. Soluble HIV proteins such as nef and immunosuppressive agents such as cyclosporin, azathioprine and mycophenalate mofetil modify signalling from the key cellular pathways triggered by C. difficile toxin A, although there is a paucity of data on how these factors may interact with pathways activated by toxin B. Despite this, there has been little direct investigation into the effect of immunosuppression on the pathogenesis of CDI. Epidemiological studies consistently show increased rates of CDI in these populations, which are higher in those with greater degrees of immunocompromise such as individuals with advanced AIDS not receiving combination antiretroviral therapy or allogeneic haematopoietic stem cell transplant recipients. Less consistently data suggests immunocompromise in each group also impacts rates of severe, recurrent or complicated CDI. However all these conditions are characterised by high levels of antibiotic use and prolonged hospital stay, both powerful drivers of CDI risk.

Clostridium difficile infection: clinical spectrum and approach to management

Clostridium difficile is recognized globally as an important enteric pathogen associated with considerable morbidity and mortality due to the widespread use of antibiotics. The overall incidence of C. difficile-associated diarrhea (CDAD) is increasing due to the emergence of a hypervirulent strain known as NAP1/BI/027. C. difficile acquisition by a host can result in a varied spectrum of clinical conditions inclusive of both colonic and extracolonic manifestations. Repeated occurrence of CDAD, manifested by the sudden re-appearance of diarrhea and other symptoms usually within a week of stopping treatment, makes it a difficult clinical problem. C. difficile infection has also been reported to be involved in exacerbation of inflammatory bowel diseases. The first step in the management of a suspected CDAD case is the withdrawal of the offending agent and changing the antibiotic regimens. Antimicrobial therapy directed against C. difficile viz. metronidazole for mild cases and vancomycin for severe cases is needed. For patients with ileus, oral vancomycin with simultaneous intravenous (IV) metronidazole and intracolonic vancomycin may be given. Depending on the severity of disease, the further line of management may include surgery, IV immunoglobulin treatment or high dose of vancomycin. Adjunctive measures used for CDAD are probiotics and prebiotics, fecotherapy, adsorbents and immunoglobulin therapy. Among the new therapies fidaxomicin has recently been approved by the American Food and Drugs Administration for treatment of CDAD.

Nontyphoidal Salmonella infection among recipients of hematopoietic SCT

The incidence of nontyphoidal Salmonella (NTS) infections is rising worldwide and several outbreaks have been reported recently. Immunosuppressed patients are particularly vulnerable to NTS infections. We retrospectively examined the clinical features and outcomes of 18 recipients of hematopoietic SCT (HSCT) who were diagnosed with NTS infection at our institution during a 15-year period. Bacteremia was the most common presenting feature and occurred in 67% of cases. Diarrhea was absent in one-third of cases. Among 12 recipients of allogeneic HSCT, 8 presented with bacteremia and only 6 had diarrhea. A total of 9 of these 12 patients had chronic GVHD. Metastatic disease was distinctly rare and occurred in only two patients, whereas one patient died of NTS sepsis. Food safety practices to prevent NTS infection are important in HSCT recipients, particularly for those who have chronic GVHD after allogeneic HSCT.

Waterborne adenovirus

Adenoviruses are associated with numerous disease outbreaks, particularly those involving d-cares, schools, children's camps, hospitals and other health care centers, and military settings. In addition, adenoviruses have been responsible for many recreational water outbreaks, including a great number of swimming pool outbreaks than any other waterborne virus (Gerba and Enriquez 1997). Two drinking water outbreaks have been documented for adenovirus (Divizia et al. 2004; Kukkula et al. 1997) but none for food. Of the 51 known adenovirus serotypes, one third are associated with human disease, while other infections are asymptomatic. Human disease associated with adenovirus infections include gastroenteritis, respiratory infections, eye infections, acute hemorrhagic cystitis, and meningoencephalitis (Table 2). Children and the immunocompromised are more severely impacted by adenovirus infections. Subsequently, adenovirus is included in the EPA's Drinking Water Contaminant Candidate List (CCL), which is a list of unregulated contaminants found in public water systems that may pose a risk to public health (National Research Council 1999). Adenoviruses have been detected in various waters worldwide including wastewater, river water, oceans, and swimming pools (Hurst et al. 1988; Irving and Smith 1981; Pina et al. 1998). Adenoviruses typically outnumber the enteroviruses, when both are detected in surface waters. Chapron et al. (2000) found that 38% of 29 surface water samples were positive for infectious Ad40 and Ad41. Data are lacking regarding the occurrence of adenovirus in water in the US, particularly for groundwater and drinking water. Studies have shown, however, that adenoviruses survive longer in water than enteroviruses and hepatitis A virus (Enriquez et al. 1995), which may be due to their double-stranded DNA. Risk assessments have been conducted on waterborne adenovirus (Crabtree et al. 1997; van Heerden et al. 2005c). Using dose-response data for inhalation from Couch et al. (1966), human health risks of infection, illness and death have been determined for various adenovirus exposures. Crabtree et al. (1997) conclude that, even at an adenovirus concentration of 1 per 1,000 L of drinking water, annual risks of infection exceed the suggested risk recommendation of 1 x 10(-4) per yr (Regli et al. 1991) (Table 8). Using the same exposure and dose-response assumptions, van Heerden et al. (2005c) determined annual risks of infection to be 1-1.7 x 10(-1) for two drinking water samples from South Africa containing 1.40 and 2.45 adenoviruses per 10,000 L, respectively. This present study estimated annual risks of infection associated with varying levels of adenoviruses per 100 L (Table 9). By assuming a 2 L/d exposure and utilizing the exponential model at r = 0.4172 (Haas et al. 1993), yearly risks exceed the risk recommendation of 1 x 10(-4) at every exposure level. There are limited data regarding the removal of adenoviruses by conventional water treatment or other physical-chemical treatment processes, but studies do suggest that adenoviruses are of equal or greater sensitivity to oxidizing disinfectants, when compared to waterborne viruses (the most resistant to ultraviolet light). Data suggest that the chlorine doses applied to control other waterborne viruses are more effective against adenovirus, resulting in a greater than 4-log10 removal of adenoviruses by conventional treatment and chlorination. If treatment can achieve a 4-log10 removal of adenoviruses, then, based on the risk levels presented in Table 9, surface water concentrations should not exceed 0.5 adenoviruses per 100 L (Fig. 2). More data are needed regarding effectiveness of water treatment against adenovirus and the human-virus dose-response relationship to fully understand the role of adenovirus as a waterborne public health threat.

Acute diarrheal disease in children: epidemiology, prevention, and treatment

Diarrhea is one of the most common causes of morbidity and mortality in children worldwide. The causes of acute diarrhea in children vary with the location, time of year, and population studied. There is increasing recognition of a widening array of enteric pathogens associated with diarrheal diseases. Adequate fluid and electrolyte replacement and maintenance are key to managing diarrheal illnesses. Thorough clinical and epidemiologic evaluation is needed to define the severity and type of illness, exposures, and whether the patient in is immunocompromised to direct the performance of selective diagnosis cultures, toxin testing, parasite studies, and the administration of antimicrobial therapy.

Nosocomial nontyphoidal salmonellosis after antineoplastic chemotherapy: reactivation of asymptomatic colonization?

An increased frequency of nontyphoidal salmonellosis is well established in cancer patients, but it is unclear whether this represents increased susceptibility to exogenous infection or opportunistic, endogenous reactivation of asymptomatic carriage. In a retrospective study, a simple case definition was used to identify the probable presence of reactivation salmonellosis in five cancer patients between 1996 and 2002. Reactivation salmonellosis was defined as the development of nosocomial diarrhea >72 h after admission and following the administration of antineoplastic chemotherapy in an HIV-seronegative cancer patient who was asymptomatic on admission, in the absence of epidemiological evidence of a nosocomial outbreak. Primary salmonellosis associated with unrecognized nosocomial transmission or community acquisition and an unusually prolonged incubation period could not entirely be ruled out. During the same time period, another opportunistic infection, Pneumocystis pneumonia, was diagnosed in six cancer patients. Presumably, asymptomatic intestinal Salmonella colonization was converted to invasive infection by chemotherapy-associated intestinal mucosal damage and altered innate immune mechanisms. According to published guidelines, stool specimens from patients hospitalized for longer than 72 h should be rejected unless the patient is neutropenic or >or=65 years old with significant comorbidity. However, in this study neutropenia was present in only one patient, and four patients were <65 years old. Guidelines should thus be revised in order not to reject stool culture specimens from such patients. In cancer patients, nosocomial salmonellosis can occur as a chemotherapy-triggered opportunistic reactivation infection that may be similar in frequency to Pneumocystis pneumonia.

A review of viral gastroenteritis

PURPOSE OF REVIEW

Since Kapakian first identified a virus in the stool of a patient with diarrhoea in 1972, many viruses have been described that cause diarrhoea directly or indirectly. It is now appreciated that viruses are the most common cause of diarrhoeal illness worldwide. Although bacteria and other pathogens cause significant numbers of gastroenteritis, it is the viruses that are dealt with in this review. The viruses responsible will be discussed individually.

RECENT FINDINGS

Rotavirus remains the leading cause of diarrhoeal disease overall, with the newly designated calicivirus family causing the most outbreaks in the industrialized nations. As diagnostic techniques improve, however, the importance of astrovirus and other previously under-reported pathogens is becoming more apparent and the number of viruses associated with gastroenteritis continues to increase. The emergence of severe acute respiratory syndrome coronavirus, arguably the most important emerging infection of recent years and a cause of significant gastrointestinal disease, is also discussed.

SUMMARY

No effective treatments have been developed for viral gastroenteritis. Current efforts are targeted at the development of suitable vaccines and the implementation of infection control measures.

Gastrointestinal infections in the immunocompromised host

Persons with HIV infection, leukemia, lymphoma, solid organ and bone marrow transplants, and inherited immune deficiencies as well as those on immunosuppressive drugs are at high risk for infections of the gastrointestinal tract. Pathogenic as well as opportunistic viruses, bacteria, fungi, and protozoa cause infections in the esophagus, stomach, small intestine, and large intestine. Symptoms may be mild but more often are severe and even life threatening. This article reviews what is new in the field of gastrointestinal infections in the immunocompromised host during the past year. I will place specific emphasis on articles that are most pertinent to clinical care.