Enterococcus hirae implicated as a cause of diarrhea in suckling rats

A Lancefield group D enteric streptococcus was isolated from diarrheic suckling rats that had been inoculated orally with stool from a diarrheic human. After oral administration of the organism to other suckling rats, diarrhea was reproduced, and the enteric streptococcus was reisolated. The brush border of small intestinal villi in affected animals was coated with numerous adherent gram-positive cocci. The organism was identified as Enterococcus hirae by a battery of biochemical tests. These and previous studies indicate that certain enterococci should be considered as etiologic agents of diarrheal disease in neonatal animals.

Duration and pattern of asymptomatic rotavirus shedding by hospitalized children

Fecal shedding of rotaviruses by infants and children without gastrointestinal symptoms has recently been recognized, but little is known about the duration or frequency of virus shedding in such patients. We therefore evaluated rotavirus shedding by 16 infants and children during the course of their prolonged hospitalizations. Repeated fecal specimens were obtained from these patients and examined for the presence of rotavirus by means of immunoassay, electron microscopy and polyacrylamide gel electrophoresis. Asymptomatic rotavirus shedding was observed in each of the 16 patients, and more than 1 episode of virus excretion was detected in 15 of these. Electropherotype analysis indicated that some of these episodes were probably the result of reinfection with different strains of rotavirus. Asymptomatic shedding may be important in transmission of rotaviruses. Its role should be taken into consideration in future investigations of the epidemiology and control of this nosocomial pathogen.

Prevalence of enteric pathogens in homosexual men with and without acquired immunodeficiency syndrome

We studied 388 homosexual or bisexual men from the Baltimore-Washington area to define the spectrum of enteric pathogen carriage in a population at high risk for "gay bowel syndrome" in association with human immunodeficiency virus infection. Seventy-seven patients with acquired immunodeficiency syndrome, 68 gay men with symptoms of acute diarrhea or proctitis, and 243 gay men without gastrointestinal symptoms and participating in a natural history study of human immunodeficiency virus infection were selected for study. Approximately 12% of the asymptomatic men harbored at least one enteric pathogen; the most frequently recovered were Chlamydia trachomatis, herpes simplex virus, and Giardia lamblia. Men carrying a pathogen were more likely to be human immunodeficiency virus seropositive (48%) than men without a pathogen (25%) (p = 0.018), more likely to have fewer T helper cells (p = 0.015), and more likely to have a mucopurulent exudate (p = 0.014). We recovered an agent of enteric disease from 68% of gay men presenting with diarrhea or proctitis. Campylobacter species, herpes simplex virus, Neisseria gonorrhoeae, C. trachomatis, G. lamblia, and Shigella species were identified most frequently. The most common pathogen associated with diarrhea in acquired immunodeficiency syndrome was Cryptosporidium (16% of 49 cases). Other agents identified were Clostridium difficile, Vibrio parahemolyticus, Campylobacter species, G. lamblia, Isospora, and cytomegalovirus. Approximately half of the identifiable etiologic agents of diarrhea in acquired immunodeficiency syndrome patients were treatable with antibiotics, but these agents required special culture procedures for detection.

Antibodies to rotaviruses in chickens' eggs: a potential source of antiviral immunoglobulins suitable for human consumption

The prevalence of antibodies to human rotaviruses in commercially available eggs and egg products that are suitable for human consumption was investigated. The yolks of virtually all of the individual eggs and pasteurized pooled egg preparations contain antirotavirus antibodies detectable by means of enzyme immunoassay systems. Also, the eggs and egg preparations are capable of inhibiting the growth of two strains of rotaviruses in tissue culture. Chromatographic studies indicated that the antigen-binding activity is limited largely to the immunoglobulin fractions of the egg yolks. The antibody levels in eggs can be increased by the immunization of hens with purified rotavirus preparations, and the immunoglobulins isolated from the eggs of immunized hens can prevent the development of rotavirus gastroenteritis in experimentally infected animals. Egg preparations might serve as a practical source of antiviral antibodies suitable for consumption by infants and young children.

Gastrointestinal inflammation after bone marrow transplantation: graft-versus-host disease or opportunistic infection?

Gastrointestinal inflammation after allogeneic bone marrow transplantation may be due to acute graft-versus-host disease (GVHD) and/or superinfection with opportunistic organisms. Twenty-eight patients with barium studies suggesting gastrointestinal inflammation after bone marrow transplantation and either acute GVHD, viral infection, or both were studied to characterize the radiographic appearances of each disease and to determine whether acute GVHD could be distinguished from viral superinfection on the basis of radiographic findings. Thirteen patients had minimal or no acute GVHD, with viral infection proved in eight and strongly suspected in four others; the remaining patient was thought to have nonspecific inflammatory bowel disease. Five patients had pure acute GVHD, and 10 patients had viral enteritis superimposed on acute GVHD. Radiographic abnormalities were found in the gastrointestinal tract in both acute GVHD and viral infection and were more extensive than previously reported. Findings were similar in both entities, although gastric abnormalities were not seen in pure acute GVHD but only in viral infection, either alone or together with acute GVHD. Prolonged small bowel barium coating occurred in both viral infection and acute GVHD. Fold thickening evolved into fold effacement with a shaggy contour in two patients with viral infection. Colonic findings in all groups mimicked ulcerative colitis. Our data indicate that differentiation between acute GVHD and viral enteritis is not possible on the basis of radiographic findings alone. Both entities should be considered when gastrointestinal inflammation occurs after bone marrow transplantation.

Kinetics of intestinal replication of group B rotavirus and relevance to diagnostic methods

Non-group-A rotaviruses have been implicated with increasing frequency as causes of acute gastroenteritis in humans and other animals. However, the incidence and significance of infection with these agents, as well as appropriate diagnostic strategies for making these determinations, are largely unknown. Studies to make these determinations could be more accurately conducted if the relationship between the viral replication kinetics and the particular diagnostic method used is understood. We thus utilized the murine model of group B rotavirus infection to establish the viral replication kinetics by a variety of commonly used diagnostic methods. Enzyme immunoassay, routine negative-stain electron microscopy, solid-phase immunosorbent electron microscopy, polyacrylamide gel electrophoresis, and a dot hybridization assay were used in these studies. By enzyme immunoassay, 100% of experimentally infected suckling rats tested positive for group B rotaviral antigens at 1, 4, and 5 days postinoculation. However, only 70 and 20% of infected animals tested positive at days 2 and 3 postinoculation, respectively. Dot hybridization with a complementary DNA probe also suggested a biphasic pattern of viral antigen excretion. Evidence of the virus causing infectious diarrhea in infant rats was found only on day 1 postinoculation in samples examined by routine negative-stain electron microscopy and by polyacrylamide gel electrophoresis. Rotaviruslike particles were observed by solid-phase immunosorbent electron microscopy on days 1, 2, and 4 after viral inoculation suckling rats but were clearly the most numerous on day 1. Additionally, the enzyme immunoassay was used to quantitate the kinetics of group B rotaviral replication in the intestines of the experimentally infected animals. Levels of murine group B rotaviral antigens in intestinal samples peaked on days 1 and 4 postinoculation; however, only peak 1 represented actual intraepithelial replication of the virus. These studies thus indicate that early sample collection and selection of the appropriate diagnostic method are critical if the incidence and significance of group B and possibly other non-group-A rotaviral infections are to be accurately assessed.

Neonatal rotavirus-associated necrotizing enterocolitis: case control study and prospective surveillance during an outbreak

After the death of a premature infant from rotavirus-associated necrotizing enterocolitis, we instituted prospective surveillance for this disease in our neonatal intensive care unit. During the 4-month study period an additional six cases of necrotizing enterocolitis and eight cases of hemorrhagic gastroenteritis occurred. Rotavirus infection was documented in 11 of these 15 symptomatic infants, in comparison with only eight rotavirus infections in 147 asymptomatic or minimally symptomatic babies (P less than 0.0001). Stools from 110 nursery personnel tested during the outbreak did not contain rotavirus. However, 12 of 59 staff members had serum IgM antibody against rotavirus, suggesting recent infection. In a case-control study we compared babies with severe gastrointestinal illness with a control group randomly selected from asymptomatic babies in the nursery during the time of the outbreak. Univariate analysis found six categorical variables and nine continuous variables that were significantly associated with disease. Multivariate logistic regression analysis, however, found only birth weight (P less than 0.0001), rotavirus infection (P less than 0.0001), and age at time of first nonwater feeding (P less than 0.02) to be associated with gastrointestinal illness. This study provides further evidence for the role of infection in some cases of neonatal necrotizing enterocolitis and hemorrhagic gastroenteritis.

Comparison of methods for detection of serum antibody to murine rotavirus

Mice are frequently used as animal models for the study of rotaviral infections. Since natural infection is common in laboratory mice, it is important that rotaviral studies, as well as other studies utilizing suckling mice, employ animals of known immune status to murine rotavirus. A variety of homologous and heterologous enzyme immunoassay systems and an immunofluorescence technique were thus compared to determine the immunoassay that is most effective at detecting adult mice seropositive for rotaviral antibody. It was determined that a homologous enzyme immunoassay inhibition technique utilizing murine rotavirus-derived reagents was the most efficient serologic assay evaluated. A serologic response was consistently detected by this assay by 5 days after experimental rotaviral inoculation of adult mice. A homologous antibody-binding enzyme immunoassay, a heterologous inhibition enzyme immunoassay utilizing antigenically related simian rotavirus (SA-11) reagents, and an immunofluorescence technique utilizing Nebraska calf diarrhea virus antigens were found to be less sensitive for detecting serum antibody to murine rotavirus.

Sialic acid glycoproteins inhibit in vitro and in vivo replication of rotaviruses

We investigated the interactions of rotaviruses with glycoproteins and cells that support rotaviral replication. We found that a wide range of naturally occurring glycoproteins, including ovalbumins and ovomucoids from chicken and turkey eggs, and mucin derived from bovine submaxillary glands, inhibit the replication of rotaviruses in MA-104 cells. Our studies further indicated that the glycoproteins bind directly to rotaviruses and that virus-glycoprotein binding is dependent largely upon interactions with sialic acid oligosaccharides. We found that accessible sialic acid oligosaccharides are required for efficient rotavirus infection of MA-104 cells, thus demonstrating that sialic acid oligosaccharides play an important role in the interactions of rotaviruses with both glycoproteins and cells that support rotaviral replication. Bovine submaxillary mucin and chicken ovoinhibitor can also prevent the shedding of rotavirus antigen and the development of rotavirus gastroenteritis in a mouse model of rotavirus infection. Our findings document that a range of glycoproteins inhibit the in vivo and in vitro replication of rotaviruses and suggest that the alteration in the quantity or chemical composition of intestinal glycoproteins is a potential means for the modulation of enteric infections.

Self-contained enzymic membrane immunoassay for detection of rotavirus antigen in clinical samples

A self-contained enzymic membrane immunoassay (SCEMIA) system has been developed for the detection of viral antigens in clinical samples. The assay system makes use of antiviral antibodies bound to a nylon membrane, a flow-through washing procedure, and a clearly visible endpoint of the enzymic reaction. A SCEMIA system with antibodies against rotavirus detected rotavirus antigen, within 15 min, in all faecal samples from children with gastroenteritis that were positive for antigen in a standard microplate enzyme immunoassay, which took 4 h to complete. In addition, the SCEMIA could detect rotavirus in faecal samples collected from infected individuals both before and after antigen could be detected by a standard immunoassay system. Rotavirus antigen was not detectable in control children who did not have evidence of rotavirus infection. SCEMIA systems are an accurate, rapid, and inexpensive means for the practical diagnosis of viral infections in human beings.

Homotypic and heterotypic antibodies for prevention of experimental rotavirus gastroenteritis

We investigated the abilities of homologous and heterologous antibody preparations to neutralize murine rotavirus in a mouse model of rotavirus infection. We found that incubation of virus with murine sera obtained from animals experimentally infected with the homologous epizootic diarrhea of infant mice strain of rotavirus resulted in inability of the virus to cause symptomatic disease in infant mice. Sera from nonimmune mice and mice infected or immunized with a heterotypic strain of rotavirus did not effectively neutralize virus in this system. On the other hand, neutralization was noted after incubation of virus with a number of immunoglobulins from other animal and human sources. The neutralizing activity of the preparations in the murine model correlated partially, but not completely, with the level of in vitro neutralizing antibody to the murine strain of rotavirus measured in a tissue culture system. In most cases, asymptomatic infection after feeding of the virus and the antibody preparation resulted in subsequent generation of an active immune response in infected animals.

Genetic and antigenic relatedness of human and animal strains of antigenically distinct rotaviruses

We used nucleic-acid hybridization and enzymatic and immunofluorescence assay to examine the relatedness of human and animal strains of antigenically distinct rotaviruses (ADRVs). ADRVs isolated from rats and humans in Baltimore, Maryland, were shown to be closely related to bovine and porcine strains of group B rotavirus. A human group B rotavirus associated with epidemics of gastroenteritis in China was also found to share antigenic determinants and genome sequence homology with ADRVs passaged in rats in the United States. Closely related strains of group B rotavirus thus appear to infect human and animal populations in widely separated geographic areas.

Age-related rate of seropositivity of antibody to Giardia lamblia in four diverse populations

We used a solid-phase enzyme immunoassay to determine the age-specific rates of acquisition of antibody to Giardia lamblia in populations living in an inner city area of Baltimore, Md., on an Apache Indian reservation in Arizona, in a rural area of Panama, and in an urban area of Peru (Lima). Antibody to G. lamblia was found in a portion of the adults living in all of the study areas. Similar prevalence rates and quantitative levels of antibody were found in the adults living in Arizona (44%), Panama (48%), and Peru (46%). However, a significantly lower (P less than 0.05) percentage of the adults living in Baltimore (18%) displayed serological evidence of infection. Different patterns of age-associated acquisition of antibody were noted in the study populations. In the United States, children living in Baltimore had low levels of seropositivity throughout childhood, whereas children living on the Arizona Indian reservation showed a progressive acquisition of antibody early in childhood, with adult levels achieved by 8 years of age. In Latin America, children living in Panama attained adult levels of seropositivity between 9 and 20 years of age, whereas children in Peru displayed adult levels of seropositivity in the first 6 months of life. Our findings documented the widespread occurrence of G. lamblia infections in diverse populations. Children living in different areas and under different environmental conditions displayed widely differing rates of acquisition of antibody to G. lamblia, possibly resulting from different levels of sanitation, water contamination, and person-to-person contact. Our studies indicate that quantitative solid-phase immunoassays can be used to study the epidemiology of parasitic infections such as those caused by G. lamblia.

Identification of a bovine enteric syncytial virus as a nongroup A rotavirus

An atypical or nongroup A rotavirus was identified in feces obtained from gnotobiotic calves in which fecal preparations originally derived during an epizootic of neonatal calf diarrhea had been serially passaged. The epizootic was previously reported to be caused by a noncharacterized viral agent that induced the formation of epithelial syncytia on small intestinal villi of experimentally infected calves. This bovine, nongroup A rotavirus was found to be antigenically related to a described atypical rotavirus of rats by immunofluorescence and by enzyme immunoassay. Complementary DNA derived from the atypical rat rotavirus cross hybridized with RNA obtained from the bovine virus, but not with RNA extracted from group A rotaviruses. Complementary DNA derived from SA-11 group A rotavirus cross hybridized with other group A rotavirus RNA, but not with RNA obtained from either the rat or bovine nongroup A isolates. Additionally, another similar, if not identical, bovine atypical rotavirus was identified in a second epizootic of neonatal calf diarrhea that occurred several hundred kilometers and 8 months apart from the original epizootic.

Centrifugation-augmented solid-phase immunoassay (CASPIA) for the rapid diagnosis of infectious diseases

We have devised centrifugation-augmented solid-phase immunoassays (CASPIAs) for the detection of microbial pathogens in human body fluids. The CASPIA format combines several features of latex agglutination and solid-phase immunoassay systems to produce an assay system that is inexpensive and simple to perform. We found that CASPIA systems for the detection of rotaviral, group A streptococcal, and Haemophilus influenzae type b antigens were significantly more sensitive than latex agglutination assays and at least as sensitive as enzyme immunoassay systems using analogous reagents. Because CASPIA reactions could either be read macroscopically, recorded with a standard office photocopying device, or quantitated by means of a microplate colorimeter, the assays were applicable under a wide range of clinical and laboratory conditions.

Enzootic bovine rotavirus is not a source of infection in Panamanian cattle ranchers and their families

Vaccination of humans against rotavirus (RV) diarrhea may be accomplished by oral immunization with attenuated animal strains known to be antigenically very similar to human strains. To define better the degree of infectivity in nature of these animal strains for humans, we conducted surveillance for RV infection/diarrhea in 180 farm workers, their 161 family contacts, and the 566 animals (512 cattle, 35 pigs, and 19 sheep) on 14 farms in rural Panama. No correlation between the high infection rates in farm workers (72%) and their family contacts (78%) and in cattle (56%) could be demonstrated. Heads of families with four or more children with RV infection experienced a twofold greater rate of RV infection compared with heads of families of similar size without RV infection. Despite the close similarity between human and bovine RV, in Panama intrafamilial (particularly child-to-child or child-to-parent) rather than interspecies transmission appeared to be the most important route for the spread of this highly infectious virus.

Computed tomography of gastrointestinal inflammation after bone marrow transplantation

Overwhelming secretory diarrhea can be a major complication after bone marrow transplantation, associated usually with acute graft-versus-host disease (AGVHD). Radiographic evaluation may be hampered by nausea, vomiting, or debilitation. Computed tomography (CT) in seven such patients demonstrated diffuse wall thickening in the small intestine, colon, and/or mesentery. In two cases, prolonged adherence of oral contrast material to the luminal surface resulted in bizarre patterns of coating. In two others, a layer of low attenuation within the thickened wall produced a target appearance consistent with submucosal edema or hemorrhage. Small bowel dilatation and fold enlargement was the only finding in one patient. The role that superinfection of the gastrointestinal tract with opportunistic organisms can play in this immunocompromised group of patients is less well established. In this group of patients, the findings were due to AGVHD in two, AGVHD and viral enteritis in two, and viral enteritis alone in three. CT may be an alternative to routine contrast studies in assessing the extent of gastrointestinal tract involvement after bone marrow transplantation. Neither contrast studies nor CT were able to differentiate between AGVHD and viral enteritis.

Immunoassays for the diagnosis of viral enteric pathogens

The accurate diagnosis of infectious diseases is important for the optimal management of infected patients as well as for the prevention of disease transmission to susceptible individuals. Because viral gastroenteritis constitutes an important cause of morbidity in children living in developed countries and of mortality in children living in developing countries, there has been a great deal of interest in the development of effective methods for the diagnosis and study of this disease. While there are a number of assay systems that are capable of accurate detection of the agents of viral gastroenteritis in the intestinal contents of infected individuals, solid phase enzyme immunoassays have been used widely for this purpose. The widespread utilization of enzyme immunoassays is based on the advantages inherent in the use of enzymatic markers. These advantages include the stability of enzyme-immunoglobulin conjugates, the high degree of sensitivity inherent in the magnifying nature of enzyme-substrate interactions, and the low cost of assays performed in simple reaction formats. Enzyme immunoassays have thus been developed and widely used for the detection and epidemiologic study of rotaviruses, adenoviruses, coxsackie viruses, hepatitis A virus, and other agents that replicate in the human gastrointestinal tract. In addition, latex agglutination assays and nucleic acid hybridization techniques have been applied to the rapid detection of enteric viruses. It is likely that the application of a number of assay systems will promote accurate identification of a wide range of viral pathogens under different clinical, epidemiologic, and laboratory situations.

Aerosol transmission of experimental rotavirus infection

Several aspects of the epidemiology of rotavirus suggest the possibility that transmission may occur by nonenteral routes. We utilized the mouse model of rotavirus infection to investigate the experimental transmission of rotavirus infection by respiratory droplets. Following exposure to a defined dose of aerosolized rotavirus, the kinetics of viral replication within the lung and gastrointestinal tract was studied using a double antibody enzyme immunoassay and indirect immunofluorescence. These studies documented the efficient transmission of rotavirus infection by means of aerosol in all exposed animals. Rotavirus antigen was detected as early as 12 hours after infection in the pulmonary and gastrointestinal tracts of the infected animals and antigen remained detectable in both sites for at least 8 days following infection. Gastrointestinal illness was clearly demonstrable in the animals while pulmonary pathology was not evident. These studies document that rotavirus infection can be transmitted by aerosol droplets under experimental conditions.

Studies on fastidious adenoviruses in Ontario: a distinct strain associated with gastroenteritis

From 100 cases of gastroenteritis among children caused by adenovirus infection in Ontario, 33 virus isolates were divided into three categories according to their biological behavior in tissue cultures. So far, the results of neutralization tests, structural protein analysis, and DNA restriction patterns showed that the virus of category 1 was similar to adenovirus type 40. However, the adenovirus of category 2 was a distinct adenovirus which shared some similarities with adenovirus type 5. Viruses of category 3 are still under investigation.

Novel chemical method for the preparation of nucleic acids for nonisotopic hybridization

A novel chemical method was used to prepare biotin-labeled nucleic acids for nonisotopic hybridization. The method involves the transamination of unpaired cytosine residues in polynucleotides with sodium bisulfite and ethylenediamine. Primary amino groups on the cytosine derivatives are then reacted with biotinyl-e-aminocaproic acid N-hydroxysuccinimide ester. Biotinylated probes hybridized with 1 to 2 pg of nitrocellulose filter-bound DNA and were visualized with a colorimetric detection technique. This method is simpler and less expensive than other methods for the preparation of nonisotopic probes. In addition, it is more versatile since the chemically modified bases can potentially react with other "indicator" molecules or proteins such as an enzyme. The specificity for unpaired cytosine residues is another advantage which could allow for the selective labeling of a specific region of a double-stranded nucleic acid. This improved labeling method should lead to the wider application of hybridization techniques in diagnostic microbiology and basic research in infectious diseases.