Strain and host characteristics of Campylobacter jejuni infections in Finland

The relative importance of different risk-factors for Campylobacter infections and the role of bacterial strain and host characteristics are uncertain. Swimming in natural sources of water was recently described as a novel independent risk-factor for domestically-acquired Campylobacter infections. The present study investigated exposure factors and demographical characteristics (collected in a questionnaire), and determined whether Campylobacter jejuni serotypes could be linked to each other or to the severity of the disease in domestically-acquired sporadic C. jejuni infections during a seasonal peak in Finland. Swimming was associated positively with an age of 相似文献   

Descriptive epidemiology of infections due to thermotolerant Campylobacter spp. in Norway, 1979-1988.

This report reviews the first ten years of Campylobacter surveillance in Norway. During 1979-1988, a total of 3,545 isolates of thermotolerant Campylobacter spp. were reported. The isolation rate increased from 1.8 per 100,000 persons per year in 1979 to 13.1 in 1988. The highest isolation rate for both sexes occurred during the first five years of life (31.0 per 100,000). A smaller second peak was detected in the age group 15-24 years (11.1 per 100,000). The male-to-female ratio was 1.52:1 for infants less than five years of age, compared with a ratio of 1.35:1 for all ages combined. Thirty-eight percent of the infections had most probably been acquired abroad. The isolation rate in urban areas (12.4 per 100,000) was over twice that observed in rural agricultural municipalities (5.5 per 100,000). However, this difference was largely due to a higher proportion of imported cases in urban areas, only small variations in isolation rate were observed when imported cases were excluded. The seasonal distribution of Campylobacter isolates showed a peak during the warm months of the year. Travel activity during summer holidays did not account for this trend, since the summer peak became even more pronounced when imported cases were excluded. A north-south gradient in the seasonality was observed; when domestic cases were considered, the summer peak became more accentuated with increasing latitude reaching a maximum in subarctic areas. This might be explained by corresponding variations in occurrence of campylobacters in surface water sources.     

Morphological and morphometric characteristics of the large-intestinal mucosa in Campylobacter infections]

Twenty-two biopsy specimens of colon mucosa were obtained from 16 patients with gastrointestinal campylobacteriosis histologically, histochemically and morphometrically. At the height of the disease colon mucosa of these patients showed a morphological picture of acute hemorrhagic and erosive--hemorrhagic colitis. When compared with such for other intestinal infections (shigellosis, salmonellosis, rotaviral gastroenteritis), the morphological features appeared to vary permitting a differential diagnosis with acute colitis due to above infections, but objective criteria to differentiate campylobacter-induced colitis from colitis in aggravation of nonspecific ulcerative one and Crohn's disease still remains to be found.     

Trends in the epidemiology of invasive fungal infections.

Invasive fungal infections have increased in importance, largely because of the increasing size of the population at risk. Candida species remain the fourth most important cause of hospital-acquired bloodstream infections. Infections with Candida species other than C. albicans appear to have become more common, but significant geographic variation has been reported. Invasive aspergillosis and other mould infections are a leading cause of infection-related death in hematopoietic stem cell transplant recipients. Although Aspergillus fumigatus remains the most frequent cause of infection, A. terreus has emerged as an important pathogen, at least among certain populations. Despite marked reductions in the rates of AIDS-associated fungal infections, such as cryptococcosis, in the United States and other developed countries, the burden of these diseases in developing countries is large and increasing. Enhanced surveillance and reporting will be critical to improve our understanding of the importance of invasive fungal infections, to enable prioritization of research and prevention efforts, and to evaluate prevention strategies.     

Campylobacter infections of the pericardium and myocardium

Members of the genus Campylobacter are notorious for their ability to cause gastroenteritis. However, increasing numbers of case reports now suggest that they may have a wider pathogenic repertoire. Pericarditis and myocarditis are increasingly being recognised as sequelae of Campylobacter infection. Although rare, these presentations are important, as misdiagnosis may result in inappropriate thrombolysis or angioplasty, with potential accompanying complications. Extraintestinal Campylobacter infections, and the resulting pathogenesis, remain an important challenge for the 21st century, particularly as immunocompromised patients are likely to become increasingly common.     

Use of auxotyping for epidemiological studies of Campylobacter jejuni and Campylobacter coli infections.

A chemically defined medium developed for Neisseria gonorrhoeae was modified to support the growth of Campylobacter jejuni and Campylobacter coli. A total of 76 isolates of C. jejuni and 14 isolates of C. coli were tested on this medium, which was designated Campylobacter defined medium (CDM), over a 3-month period. Although none of the C. coli isolates appeared to require amino acids, 51% of the C. jejuni tested required one and 7% required multiple amino acids for growth. An analysis of isolates obtained from three household outbreaks of campylobacteriosis demonstrated that auxotyping identified the epidemic strain within each outbreak. Among 70 isolates of C. jejuni examined, no correlation could be drawn between a specific serotype and auxotype or between auxotype and plasmid profile.     

Murine intranasal challenge model for the study of Campylobacter pathogenesis and immunity.

Campylobacter jejuni infection of mice initiated by intranasal administration was investigated as a potential model for studies of pathogenesis and immunity. By using a standard challenge (5 x 10(9) CFU), C. jejuni 81-176 was more virulent for BALB/c (72% mortality) than for C3H/Hej (50%), CBA/CAJ (30%), or C58/J (0%). Intranasal challenge of BALB/c was used to compare the relative virulence of three reference strains; C.jejuni 81-176 was more virulent (killing 83% of challenged mice) than C. jejuni HC (0%) or C. coli VC-167 (0%). The course of intranasally initiated C. jejuni 81-176 infection in BALB/c was determined. C. jejuni was recovered from the lungs, intestinal tract, liver, and spleen at 4 h after challenge, the first interval evaluated. After this initial interval, three distinct patterns of infection were recognized: (i) a progressive decline in number of C. jejuni CFU (stomach, blood, lungs), (ii) decline followed by a second peak in the number of organisms recovered at 2 or 3 days postchallenge (intestine, liver, mesenteric lymph nodes), and (iii) persistence of approximately the same number of C.jejuni CFU during the course of the experiment (spleen). Intranasally induced infection initiated with a sublethal number of bacteria or intranasal immunization with killed Campylobacter preparations resulted in both the generation of Campylobacter antigen-specific immune responses and an acquired resistance to homologous rechallenge. The model was used to evaluate the relative virulence of nine low-in vitro-passage (no more than five passages) isolates of C. jejuni species from patients with diarrhea. The patient isolates were differentially virulent for mice; one killed all exposed mice, three were avirulent (no deaths) and the remainder showed an intermediate virulence, killing 17 to 33%. Mouse virulence of Campylobacter strains showed a trend toward isolates originating from individuals with watery diarrhea; however, no association was found between mouse virulence and other signs or symptoms. There were no observed relationships between mouse virulence and bacterial Lior serotype or Fla polymorphic group. Intranasal challenge of BALB/c with C. jejuni is a useful model for the study of infection and vaccination-acquired immunity to this agent.     

Mixed strain infections and strain-specific protective immunity in the rodent malaria parasite Plasmodium chabaudi chabaudi in mice

Important to malaria vaccine design is the phenomenon of "strain-specific" immunity. Using an accurate and sensitive assay of parasite genotype, real-time quantitative PCR, we have investigated protective immunity against mixed infections of genetically distinct cloned "strains" of the rodent malaria parasite Plasmodium chabaudi chabaudi in mice. Four strains of P. c. chabaudi, AS, AJ, AQ, and CB, were studied. One round of blood infection and drug cure with a single strain resulted in a partial reduction in parasitemia, compared with levels for na?ve mice, in challenge infections with mixed inocula of the immunizing (homologous) strain and a heterologous strain. In all cases, the numbers of blood-stage parasites of each genotype were reduced to similar degrees. After a second, homologous round of infection and drug cure followed by challenge with homologous and heterologous strains, the parasitemias were reduced even further. In these circumstances, moreover, the homologous strain was reduced much faster than the heterologous strain in all of the combinations tested. That the immunity induced by a single infection did not show "strain specificity," while the immunity following a second, homologous infection did, suggests that the "strain-specific" component of protective immunity in malaria may be dependent upon immune memory. The results show that strong, protective immunity induced by and effective against malaria parasites from a single parasite species has a significant "strain-specific" component and that this immunity operates differentially against genetically distinct parasites within the same infection.     

Cellular immunity and herpesvirus infections in cardiac-transplant patients.

We observed severe infection with herpes simplex virus in cardiac-transplant patients despite their high serum antibody levels to this virus. Therefore, we sought to correlate clinical susceptibility to two herpesvirus (simplex and zoster) infections with specific cellular immunity, assessed by the transformation and interferon responses of peripheral blood mononuclear cells to heat-inactivated antigens. Transformation and interferon response to herps simplex virus was maximally depressed immediately after transplantation, the time when severe and prolonged infection with herps simplex virus occurred. Six months to six years after transplantation, both clinical susceptibility and cellular immunity to herpes simplex virus were normal. Herpes zoster infections were more frequent than normal at all times after cardiac transplantation; depressed or absent cellular responses to the varicella zoster virus paralleled that susceptibility. In these patients the risk of severe herpesvirus infections correlated with depressed cellular immune responses to the specific viral agent involved.     

Outer membrane characteristics of Campylobacter jejuni.

Outer membranes were isolated from type strains and wild-type isolates of Campylobacter jejuni and Campylobacter coli by sodium lauryl sarcosinate extraction, and the polypeptide complement and lipopolysaccharide (LPS) content were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The protein profiles exhibited by membranes from both species were quite similar, but could be distinguished from the type strain of the genus, C. fetus subsp. fetus CIP5396. The sodium dodecyl sulfate electrophoretograms of C. jejuni and C. coli were dominated by a major polypeptide band. In the reference strain C. jejuni VC74, this polypeptide had an apparent molecular weight of 45,000, was heat modifiable, and was shown to be transmembrane by virtue of its peptidoglycan association and surface exposure. Two other proteins with approximate molecular weights of 37,000 and 73,000 were also surface exposed on C. jejuni VC74 and represented potential surface antigens. The LPS of C. jejuni and C. coli was of low molecular weight, suggesting that serotypic differences due to LPS were based on different carbohydrate compositions of core LPS. In contrast, the LPS of C. fetus CIP5396 exhibited O antigen polysaccharide chains of intermediate chain length. Fragments of outer membranes released during growth of C. jejuni VC74 displayed a polypeptide profile which differed from that of sarcosinate-extracted outer membranes. Radiolabeling demonstrated that the proteins exposed on the surface of this released membrane differed from those exposed on the cell surface and would likely contribute to the antigenic complexity of C. jejuni.     

Innate immunity and its role against infections.

LEARNING OBJECTIVES: This article reviews current concepts of the innate immune system that offers protection against infections. It offers an overview for the readers to understand how innate immunity, consisting of different receptors, cells, and mediators recognizes pathogens and exerts protective function against pathogens. DATA SOURCES AND STUDY SELECTION: MEDLINE-search articles including original research papers, review articles, textbooks, and references identified from bibliographies of relevant articles. RESULTS AND CONCLUSIONS: The innate immune system is nonspecific immunity present since birth not requiring repeated exposure to pathogens. It is capable of differentiation between self and nonself. Because of its nonspecificity, it has a broad spectrum of resistance to infection. Further, it is thought to play an important role in the control of adaptive immunity by regulating co-stimulatory molecules and effector cytokines. Innate immunity includes pattern recognition molecules/receptors, antimicrobial peptides, the complement system, inflammatory mediators, and cytokines produced by immune cells. Pattern recognition molecules/receptors recognize pathogen-associated molecular patterns that are essential for microorganisms' survival and pathogenicity. Although innate immunity has recently gained increasing importance, further studies are necessary for a better understanding of its role.     

Broiler chickens as potential source of Campylobacter infections in humans.

Of 46 broiler chickens from a live poultry market in New York City, 38 (83%) harbored Campylobacter fetus subsp. jejuni in their rectal flora. The observed mean number of C. fetus per g of feces was 4.4 x 10(6). The organisms survived in the feces for at least 96 h at 4 degrees C whether stored in the gut or transferred to a vial. The best survival medium for pure cultures of C. fetus subsp.jejuni was heart infusion broth supplemented with sterile blood and kept in a microaerophilic atmosphere.     

Mucosal and systemic immunity to Campylobacter jejuni in rabbits after gastric inoculation.

The mucosal and systemic immune responses to Campylobacter jejuni were studied in rabbits receiving gastric inoculation with live organisms. A lavage procedure was used to facilitate repeated monitoring of the intestinal immune response to C. jejuni. Immunity to C. jejuni was determined by secondary challenge by using the removable intestinal tie adult rabbit diarrhea (RITARD) model and monitoring for resistance to colonization and bacteremia. Oral-gastric inoculation of normal rabbits produced a transient intestinal colonization without diarrhea. C. jejuni serotypes differed in their ability to colonize the intestines of rabbits and to stimulate primary intestinal and serum antibody responses. Animals previously colonized were resistant to recolonization and the development of bacteremia after homologous challenge by the RITARD procedure but were not resistant to heterologous challenges. Anticampylobacter intestinal and serum IgA titers before this secondary infection were the most reliable predictors of resistance to colonization and bacteremia.     

Molecular epidemiology of hepatitis B virus infections in Denmark.

BACKGROUND: Denmark has a low incidence of acute hepatitis B (HBV) infections but the impact of an increasing number of immigrants with chronic HBV infection on HBV transmission is unknown. OBJECTIVES: To characterise individuals with chronic and acute HBV infection in a defined region and to examine the importance of different risk groups for the current HBV transmission. METHODS: During 2000-2001 all consecutive HBV infected individuals routinely diagnosed through the regional HBV serology laboratory in the County of Funen were classified according to ethnicity, presumed route of transmission and stage of infection based on clinical data mainly supplied by the requesting physician. HBV DNA was sequenced and subjected to phylogenetic analysis. RESULTS: Of 309 identified cases, 91 (29%) were classified as acute infection. HBV DNA sequencing was possible in 54 (59%) of these cases. Phylogenetic analysis showed that HBV isolated from injecting drug users (IDUs) was identical or closely related. Among acute cases acquired in Denmark 89% (74/83) were seen in IDUs (65) or in individuals presumably exposed to IDUs (nine) and phylogenetic analysis corroborated the assumption of IDU related transmission in every case with available sequence data. Among 83 ethnic Danes who acquired their HBV infection in Denmark, no new cases of transmission from immigrants were detected. CONCLUSION: Injecting drug use was the single most important factor for hepatitis B transmission in Denmark. The current Danish vaccination strategy is unable to protect IDUs from HBV infection and IDUs pose a greater risk of HBV transmission to the general population than immigrants.     

Local and systemic immunity to influenza infections in ferrets.

To establish whether immunity to influenza infection in the ferret is local or systemic, two sites of challenge were utilized: the nose and the anatomically isolated tracheal pouch. Infection of either site did not spread to the other site, and challenge of either site resulted in seroconversion by 13 days. Simultaneous challenge of both sites 21 days after the primary infection revealed that prior infection of the pouch prevented subsequent reinfection of the pouch, but not infection of the nose. Thus, systemic immunity did not prevent the initiation of nasal influenza infection in the ferret. However, the duration of virus shedding from the nose was reduced to half of that seen when ferrets were infected for the first time, showing that the prior pouch infection did lead to a more rapid recovery from the subsequent nasal infection. Passively administered anti-influenza antibody did not prevent or modify the nasal infection, but it did prevent the pouch infection. This is consistent with the observation that an initial infection of the nose prevented pouch infection upon challenge 21 days later. The prior nasal infection also prevented the subsequent nasal infection. These data suggest that immunity to acquisition of influenza infection in the ferret is a local phenomenon, whereas recovery from active infection is influenced by systemic immune mechanisms.