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PubMed1991

The relationship of microbial pathogens to acute infectious diarrhoea of childhood.

Bacterial, viral and parasitic enteric pathogens were detected in 692 of 916 children below 36 months of age with acute diarrhoea and in 289 of 587 matched controls. The rates of identification of only four groups of pathogens, rotavirus, Shigellae, Salmonella typhimurium and enterotoxigenic E. coli, were significantly higher in the patients. The prevalence of a variety of other enteric pathogens was similar in controls of patients. Shigellosis had a characteristic clinical profile but none of the other agents could be suspected on clinical grounds. The high prevalence of pathogens in controls suggested that the population may be partially protected against a variety of enteric pathogens and that final common pathways leading to diarrhoea may be activated by changes in the microbial ecology of the gut lumen.

Acute Disease↗
PubMed1990

[Epidemiologic study of pathogens causing nosocomial infections].

Nosocomial infection is a global problem. It significantly adds to the expected duration of hospitalization resulting with an increased economic burden and represents a leading cause of death. The characteristics of nosocomial infection vary from country to country and also changes with time. In order to understand the pathogens causing nosocomial infection in the large teaching hospital in Taiwan, we collected and analysed the surveillence data of nosocomial infection at the National Taiwan University Hospital from 1981 to 1989. We found that the nosocomial infection rate had been around 4-5% annually since 1981 till 1989. As ranked according to the site of infection, surgical wound infections were the most common, followed by the urinary tract, respiratory tract, and blood stream infections. However, the incidence of surgical wound infections had decreased gradually. About one third of nosocomial infections were caused by multiple microorganisms. The most frequently isolated pathogen has changed from Escherichia coli in early years to Pseudomonas aeruginosa in the most recent years. Gram-negative aerobic bacteria has been the major pathogens resulting in nosocomial infections for the past 9 years, accounting for 55-66%. In contrast, fungi have increased rapidly from 1.8% of total isolates in 1981 to 7.7% in 1989. Gram-positive cocci have also increased in recent years. The leading pathogen by infection site was P. aeruginosa in surgical wound infections, E. coli in urinary tract infections, and P. aeruginosa in respiratory tract infections. In earlier years E. coli was the major isolate in bacteremic cases, but glucose non-fermenters, including P. aeruginosa, Acinetobacter calcoaceticus and others, plus Enterobacter species-emerged as the major pathogens of recent years.(ABSTRACT TRUNCATED AT 250 WORDS)

Cross Infection↗
PubMed1991

[Pork meat as a source of pathogenic Yersinia enterocolitica].

During a period of eight months, samples of carcasses, tonsils, tongues and rectal swabs were taken in four pig slaughter halls. Porcine head meat was sampled in a meat products factory and samples of minced pork were taken in butcher's shops. Pathogenic strains of Yersinia enterocolitica (serological groups O:3, O:9 and O:5.27) were isolated from 36 (42 per cent) of 86 porcine tonsils, 8 (20 per cent) of 40 tongues, 17 (17 per cent) of 100 rectal swabs and from 4 (1 per cent) of 400 pork samples. Pathogenic strains of Yersinia were not isolated from samples of 210 pig carcasses and from 20 samples of porcine head meat. These results confirm that pigs are an important reservoir of pathogenic Y. enterocolitica. However, contamination of carcasses during the process of slaughter with Yersinia from either faecal material or from the tonsillary region does not seem to occur frequently, which may also explain the low rate of contamination with pathogenic Y. enterocolitica observed in pork. As pork is rarely contaminated with pathogenic Y. enterocolitica, the possibilities for growth of these organisms in raw pork are limited, the minimum infective dose is probably high and pork is usually not eaten raw, it is not likely that pork is an important source of yersiniosis in the Netherlands.

Animals↗
PubMed1990

Comparative pathogenicity of selected bovine viral diarrhea virus isolates in gnotobiotic lambs.

The infectivity and pathogenicity of selected bovine viral diarrhea virus (BVDV) isolates were determined in gnotobiotic, colostrum-deprived neonatal lambs. Five-day-old cesarean-derived gnotobiotic lambs were exposed to 1 of 10 BVDV isolates via aerosol suspension. These isolates were from tissues or secretions of calves or lambs affected with respiratory tract disease, weak neonatal calves, aborted bovine fetuses, or reference Singer or Draper BVDV. The pathogenicity of each isolate, relative to the others, was evaluated in lambs by measurement of the neutralizing antibody response, virus isolation from nasal secretions or tissues, and postmortem lesions. The BVDV isolates varied in their infectivity and pathogenicity. Singer, the cytopathic reference strain, was the most lymphotrophic isolate and stimulated the greatest neutralizing antibody response. Encephalitis was the most consistent lesion observed and was used as the final determinant of relative pathogenicity of the viruses. The most neuropathogenic isolates were the 2 viruses originating from lambs affected with respiratory tract disease, the 2 weak neonatal calf isolates, and 1 isolate from an aborted bovine fetus. The least pathogenic isolates were the 2 reference isolates, Draper and Singer; the 2 mucosal disease isolates; and 1 isolate originating from an aborted bovine fetus.

Animals↗
PubMed1990

Mutants of rabies viruses in skunks: immune response and pathogenicity.

In studies to develop an oral rabies vaccine for wildlife, the immune response to and pathogenicity of two types of mutants of rabies viruses were examined. Forty-five small plaque mutants were selected from cultures of ERA rabies virus treated with 8-azaguanine or 5-fluorouracil and tested for pathogenicity in mice. Two of these mutants AZA 1 and AZA 2 (low pathogenicity in mice) were given to skunks by oral (bait), intestinal (endoscope) and intramuscular routes. Additionally, challenge virus standard (CVS) rabies virus and mutants of this and ERA rabies virus (CVS 3766 and 3713, and ERA 3629) that were resistant to neutralization by specific antiglycoprotein monoclonal antibodies (and apathogenic in mice) were tested by various routes in skunks. Skunks given AZA 1 and AZA 2 were challenged at three months postinoculation with street rabies virus. After oral administration, there were very low rates of seroconversion with AZA 1 and AZA 2 and on challenge only 2/7 given AZA 1 and 1/8 given AZA 2 survived. None of the skunks given the other mutants orally seroconverted. AZA 2 produced a high rate of seroconversion (8/8) by the intestinal route and all challenged skunks in this group survived (7/7). All skunks vaccinated intramuscularly with AZA 1 (4/4) or AZA 2 (4/4) developed high levels of rabies neutralizing antibodies and survived challenge. The mutant CVS 3766, while apathogenic when given intracerebrally to adult mice, was consistently pathogenic by this route (and intranasally) in skunks. These results demonstrate that skunks are highly resistant to oral immunization by live rabies virus vaccines and that pathogenicity (by intracerebral route) of the mutant CVS 3766 is markedly different in mice and skunks.

Animals↗
PubMedDate not supplied

Studies on interferon induction by infectious bursal disease virus (IBDV). II. Interferon production in White Leghorn chickens infected with an attenuated or pathogenic isolant of IBDV.

Infectious bursal disease virus (IBDV) isolants that differed in virulence for chickens, were compared as to: 1) induction of interferon in serum and tissues; and 2) stimulation of IBDV serum antibody. Specific-pathogen-free chickens were infected at one day and four weeks of age by the subcutaneous and intranasal routes of inoculation. The pathogenic isolant induced a more generalized interferon response than the attenuated isolant, independent of age or route of inoculation. Pathogenic IBDV stimulated interferon in serum, kidney, lung, thymus, spleen, and bursa of Fabricius. The attenuated virus induced interferon only in the bursa. The serum interferon response was greater following inoculation with pathogenic IBDV than with the attenuated virus. Serum interferon titers peaked 2-3 1/2 days after inoculation. The pathogenic and attenuated viruses stimulated similar IBDV-neutralizing antibody responses, which occurred after peak serum interferon activity.

Animals↗
PubMed1989

T cell receptor alpha/beta expressing double-negative (CD4-/CD8-) and CD4+ T helper cells in humans augment the production of pathogenic anti-DNA autoantibodies associated with lupus nephritis.

It is generally accepted that human Th cells express the surface glycoproteins CD4 and alpha/beta-chain heterodimer of the TCR whereas cytotoxic/suppressor cells are usually CD8+ and alpha/beta TCR+. Another minor set of T cells found in the periphery are CD4-/CD8- (double negative) and express the gamma/delta TCR; these cells can manifest MHC-restricted or nonrestricted cytotoxicity but no helper function. Herein we describe the existence of an unusual Th population in the peripheral blood of humans that are CD4-/CD8- and alpha/beta TCR+. These double-negative Th were markedly expanded in patients with the autoimmune disease SLE and along with CD4+ Th, they induced production of the pathogenic variety of anti-DNA autoantibodies that are IgG in class and cationic in charge. The cationic anti-DNA antibodies induced by the Th were markedly restricted in spectrotype indicating that an oligoclonal population of B cells were committed to produce the pathogenic autoantibodies in active lupus. IL-2-dependent T cell lines were also derived from the patients with active lupus nephritis but the majority of those T cell lines lacked pathogenic autoantibody-inducing capability. Only 4 out of 42 T cell lines from a lupus patient could induce the production of cationic IgG class anti-DNA autoantibodies. The phenotypes of the pathogenic autoantibody-inducing Th lines were similar to the Th subsets: CD4+, alpha/beta TCR+ or CD4-/CD8-, alpha/beta TCR+. These studies suggest that production of pathogenic autoantibodies in human lupus is mediated by mechanisms that are distinct from the generalized, nonspecific polyclonal B cell hyperactivity that leads to excessive production of natural autoantibodies.

Adult↗
PubMed1989

Mouse hepatitis virus 3 replication in T and B lymphocytes correlate with viral pathogenicity.

Viral pathogenicity may be regulated by host defense mechanisms at the virus-immune cell interaction level. The immune system plays an important role in the outcome of acute disease induced by the mouse hepatitis virus type 3 (MHV3) virus. The lymphoid cells act as effectors in the virus elimination as well as targets for viral replication. In order to demonstrate a correlation between MHV3 pathogenicity and viral replication in lymphocytes, genetically-determined resistant A/J and susceptible C57BL/6 mice were infected with pathogenic (L2-MHV3) or nonpathogenic (YAC-MHV3) viral strains. Pathogenicity and histopathologic studies have revealed that lymphoid organs such as thymus and spleen, showed injuries or atrophy in susceptible mice infected with L2-MHV3. No histopathologic lesions in the lymphoid organs occurred in C57BL/6 mice infected with YAC-MHV3 or A/J mice infected with both viruses. The mechanisms involved in the lymphoid injuries were studied regarding viral replication in the lymphoid organs and cells in infected mice. Results indicate that cell depletion in lymphoid organs is caused by a complete viral replication in lymphoid cells. Thy1.2+ and surface IgM+ lymphoid cells from susceptible C57BL/6 mice infected with L2-MHV3 were permissive to viral replication and to subsequent cell lysis. No cell lysis, however, occurred in lymphoid cells from C57BL/6 mice infected with YAC-MHV3 and A/J mice infected with both virus strains. In vitro studies, with purified T and B cell populations were performed to determine the mechanism effecting susceptibility or resistance to viral-induced cell lysis occurring in such cells. A blockade, probably occurring at the viral RNA polymerase activity level, prevents viral replication in resistant cells between the stages of fixation of the virus at the cell-surface receptor and the viral protein translation. These experiments indicate that an intrinsic virus-specific resistant mechanism occurs in lymphoid cells that plays a major role in the viral pathogenicity.

Animals↗
PubMed1989

Effect of exogenous 5-hydroxytryptamine on pathogenicity of Entamoeba histolytica in experimental animals.

In an effort to find out the mechanism(s) operative in enhancing the pathogenicity of E. histolytica in hosts under heat stress reported earlier, effect of 5-hydroxytryptamine (5-HT) on the virulence of the parasite was examined in just weaned Charles Foster strain of albino rats. Pathogenicity of 10 strains of E. histolytica, from various forms of intestinal amoebiasis, grown in modified Boeck and Drbohlav's medium was assessed by caecal scoring. Administration of 5-HT in infected animals significantly enhanced the pathogenicity of all the seven strains tested. Treatment of the host with the 5-HT precursor L-tryptophan also increased the caecal scores examined with three strains of E. histolytica. Prior blocking of tissue 5-HT receptors by administration of methysergide almost completely abolished the pathogenicity enhancing effect of 5-HT treatment. This suggested that 5-HT itself and not any of its metabolites was responsible for the observed increase in pathogenicity of E. histolytica on 5-HT treatment of the host.

Animals↗
PubMed1989

Pathogens associated with mammalian embryo (a review).

The advantages of transporting mammalian preimplantation embryos rather than postnatal living animals include reduced costs of transportation and rapid dissemination of genetic material between countries. However, the risk of transmission of diseases through the embryos must be considered. The disease control potential of embryos will depend on proper handling and washing, and the integrity of zona pellucida. Researches on embryo-pathogen interactions have shown that some pathogens are carried through the gametes and others could not infect the gametes. Some pathogens were found to adhere to the zona pellucida and others could penetrate the zona pellucida. To date, data presented appear to suggest no concrete model guidelines for embryo-pathogen interaction. The interaction seems to depend on the species and the pathogen involved.

Animals↗
PubMed1987

[Plasmids and mobile genetic elements of pathogenic Yersinia bacteria].

The review of literature is devoted to molecular and genetic organization of movable genetic elements responsible for synthesis of pathogenicity factors of Yersinia bacteria. General characterization of Yersinia pathogenicity factors is given. We analysed the role of plasmids in expression of the pathogenic properties of these bacteria and the role of IS elements of Yersinia in expression of genes encoding synthesis of the pathogenicity factors. Replicative properties of Yersinia plasmids are described. The role of chromosomal genes in regulation of synthesis of the plasmid-specific pathogenicity factors is discussed.

DNA Transposable Elements↗
PubMed1987

Direct and indirect pathogenicity of anaerobic bacteria in respiratory tract infections in children.

Bacteroides sp (Bacteroides melaninogenicus, Bacteroides oralis, and Bacteroides fragilis), peptostreptococci, and fusobacteria are important pathogens in respiratory tract infections (RTI). These organisms are often recovered mixed with other aerobic, facultative, and anaerobic bacteria. Evidence supporting their virulence is provided by studies showing their synergistic potentials in mixed infections and their increased virulence when encapsulated. A recent increase in numbers of beta-lactamase producing strains of anaerobic gram-negative bacteria in RTI has been associated with increased failure rates of penicillins in eradication of these infections. These infections include chronic otitis media, chronic sinusitis and mastoiditis, chronic recurrent tonsillitis, and lung abscesses. The pathogenicity of these organisms is apparent through their ability not only to survive penicillin therapy but also to protect penicillin susceptible pathogens from that drug. These direct and indirect virulence characteristics of anaerobic bacteria require the administration of appropriate antimicrobial therapy directed against all pathogens in mixed infections. The synergy that exists between different aerobic and anaerobic organisms in the respiratory tract is due to several pathogenic mechanisms. These mechanisms include the production of a capsule, which protects organisms from phagocytosis, and the production of beta-lactamase, which inactivates penicillins and first-generation cephalosporins. Both of these mechanisms enhance infection and induce complications. However, more work is necessary to prevent encapsulation and the production of enzymes. Data, thus far, indicate that there are therapeutic modalities that can be used to prevent these occurrences and eliminate many mixed RTI.

Animals↗
PubMed1987

In vitro growth inhibition of mastitis pathogens by bovine teat skin normal flora.

One factor contributing to differences in the susceptibility of cows to mastitis may be differences in the teat skin normal flora, which could inhibit or enhance the growth of pathogenic bacteria. Using in vitro cross-streaking methods, we found that 25% of the isolates of teat normal flora of non-lactating heifers inhibited the growth of selected mastitis pathogens, but enhancers were not detected. Gram-positive pathogens were inhibited to a greater extent than Gram-negative pathogens. Inhibition was not a characteristic of specific genera or species of normal flora, but rather a property of certain variants within a species. This phenomenon of inhibition of mastitis pathogens in vitro by normal flora may be useful as an in vivo biological control method to reduce the incidence of mastitis.

Acinetobacter↗
PubMed1986

[Activity of virion RNA-polymerase in influenza A and B virus variants with different pathogenicities for mice].

RNA polymerase activities in parental strains of influenza A and B viruses nonpathogenic for mice and their pathogenic variants have been studied. The parental strains are A/seal/Massachusetts 1/80, A/USSR 05/81, A/Philippines 2/82, B/Singapore 222/79. The RNA polymerase activity has been also studied in recombinant strains obtained by crossing various parental strains, one of which is pathogenic for mice (AR/PR 8/34), and having different degrees of pathogenicity. The nonpathogenic viruses had low transcriptase activity. RNA polymerase activity in pathogenic variants is shown to be 1.5-3 times higher than that in the parental strains. All the recombinants, whatever their pathogenicity, had approximately the same transcriptase activities which were 1.5-2 times higher than those registered in parental nonpathogenic strains.

Animals↗
PubMedDate not supplied

In ovo pathogenicity of Mycoplasma gallisepticum strains in the presence and absence of maternal antibody.

Mycoplasma gallisepticum (MG) strains showing marked variation in pathogenicity were examined for virulence in ovo. No correlation was found between in ovo pathogenicity and other in vivo or in vitro methods for pathogenicity evaluation. For certain highly pathogenic strains, there was a clear relationship between the titer of MG inoculated and the embryo mortality and time of death; an LD50 for these strains could be calculated by yolk-sac inoculation. However, not every strain that caused lesions in the respiratory tract in vivo caused embryo mortality. Less pathogenic strains that grow well and colonize the respiratory tract usually caused embryo mortality during the later stages of incubation, and there was no strict correlation between titer of inoculum and embryo mortality. It appeared that embryo death in these cases may have resulted from generalized stress due to mass multiplication of the MG. Embryo mortality due to virulent MG was completely blocked in eggs containing maternal antibody to MG, although the mycoplasma could be reisolated from the yolk-sac membrane of the live embryonated egg after 17 days of incubation. Attempts to mimic the effect of maternal antibody by injecting exogenous MG antiserum were not successful.

Animals↗
PubMed1979

Pathogenicity of the subspecies mycoides of Mycoplasma mycoides for cattle, sheep and goats.

Recent work has shown that strains classified as M. mycoides subsp. mycoides may be separated into 2 types according to their growth rate and their behaviour in certain biochemical tests. The large colony (LC) types, most of which are from goats, are pathogenic for sheep and goats but apparently not for cattle. The small colony (SC) types include the classical contagious bovine pleuropneumonia (CBPP) strains from cattle and four strains from goats. These SC types are potentially pathogenic for cattle, sheep and goats. Strains of M. mycoides subsp. mycoides from CBPP differ in their virulence in cattle. The degree of virulence is correlated with the quantity of galactan produced in cultures of the organism, suggesting an important role for galactan in pathogenicity. This is consistent with the production by galactan of physiological effects in calves and in the enhancement of infection in cattle given galactan at the same time as cultures of the organism. Contagious caprine pleuropneumonia (CCPP) can be produced experimentally in goats using cultures of M. mycoides subsp. capri. Whether the glucan produced in such cultures is a factor in pathogenicity of this organism has not been determined. Hydrogen peroxide demonstrated in tracheal organ cultures of M. mycoides subsp. capri may contribute to its pathogenicity.

Animals↗
PubMedDate not supplied

Pathogenicity of infectious laryngotracheitis virus as measured by chicken embryo inoculation.

A comparison was made between pathogenicities for chicken embryos of unattenuated and attenuated strains or isolates of infectious laryngotracheitis (ILT) virus. All 11-day-old chicken embryos inoculated with 10(3.0) or 10(4.0) TCID50 of unattenuated strain NS175 via allantoic cavity died within 6 days. On the contrary, no chicken embryos of the same age died when inoculated with the same amount of cell-culture-attenuated isolate C7 in a like manner. The mortality index for chicken embryos (MICE) was obtained by dividing the cumulative number of embryos dying within 7 days by the cumulative number of embryos surviving 7 days. The reliability of the MICE test was confirmed by duplicate and triplicate experiments with strain NS175 and isolate C7. MICE obtained in the experiments with 9 different strains or isolates of ILT virus ranged from 0 to 1, and the values were well correlated with the pathogenicities for chickens. The results from the present work suggest that strains or isolates with MICE less than 0.16 would have low or no pathogenicity for chickens, and those with MICE more than 0.27 would be highly pathogenic. Further studies are needed using additional isolates of ILT virus with varied pathogenicities.

Age Factors↗
PubMed1981

Detection of lysozyme production using modified technique as an aid for the identification of pathogenic staphylococci causing some animal and human diseases.

Lysozyme production is an essential character of the potentially pathogenic staphylococci. In the present work 88 strains of animal origin and 40 strains of human origin were tested. Of 103 strains isolated from pathogenic cases of human and animal origin 89 (86.4%) were lysozyme producers and 86 (83.5%) were coagulase positive. Out of 75 strains isolated from pathogenic cases of animal origin 75 (100%) were lysozyme producers and 71 (94.6%) were coagulase positive. On the other hand out of 28 strains isolated from pathogenic human cases 14 (50%) were lysozyme producers and 15 (53.6%) were coagulase positive. This indicates that lysozyme production could be a better index of pathogenic staphylococci than the coagulase measurement specially in cases of animal origin strains. The method used in this work for the determination of the lysozyme production seems to be a simple one if compared with other used methods.

Animals↗