Risk factors for campylobacteriosis: an epidemiological surveillance study of patients and retail poultry.

Isolates from Campylobacter jejuni-infected patients were collected and fresh poultry meat from retail sources was sampled during the same time period and within the same geographical area. The patients were interviewed about exposure to known risk factors, and a significant correlation between the presence of a poultry subtype in patients and the consumption of fresh poultry meat was observed.

Helicobacter pylori: resurrection of the cancer link.

Helicobacter pylori is one of the most common pathogenic bacterial infections, colonizing an estimated half of all humans. In a subset of individuals, the infection leads to serious gastroduodenal disease such as peptic ulcers and gastric adenocarcinoma. The factors contributing to skewing this, in most cases benign, relationship into disease development are largely unknown. However, factors emanating from the bacterium, host and the environment have been shown to affect the risk for disease, although no factor can be singled out to be most important. The known factors are associated with affecting the risk of disease, and are not absolute. Virulence of H. pylori is affected by the existence and regulation of certain genes present in the bacterial population in a stomach. The effects of H. pylori on gastric cancer development have been challenged and the risk associated with infection with virulent (i.e. Cag PAI positive) H. pylori has likely been underestimated.

Mutation frequency and biological cost of antibiotic resistance in Helicobacter pylori.

Among the several factors that affect the appearance and spread of acquired antibiotic resistance, the mutation frequency and the biological cost of resistance are of special importance. Measurements of the mutation frequency to rifampicin resistance in Helicobacter pylori strains isolated from dyspeptic patients showed that approximately 1/4 of the isolates had higher mutation frequencies than Enterobacteriaceae mismatch-repair defective mutants. This high mutation frequency could explain why resistance is so frequently acquired during antibiotic treatment of H. pylori infections. Inactivation of the mutS gene had no substantial effect on the mutation frequency, suggesting that MutS-dependent mismatch repair is absent in this bacterium. Furthermore, clarithromycin resistance conferred a biological cost, as measured by a decreased competitive ability of the resistant mutants in mice. In clinical isolates this cost could be reduced, indicating that compensation is a clinically relevant phenomenon that could act to stabilize resistant bacteria in a population.

Comparison of genetic divergence and fitness between two subclones of Helicobacter pylori.

Helicobacter pylori has a very plastic genome, reflecting its high rate of recombination and point mutation. This plasticity promotes divergence of the population by the development of subclones and presumably enhances adaptation to host niches. We have investigated the genotypic and phenotypic characteristics of two such subclones isolated from one patient as well as the genetic evolution of these isolates during experimental infection. Whole-genome genotyping of the isolates using DNA microarrays revealed that they were more similar to each other than to a panel of other genotyped strains recovered from different hosts. Nonetheless, they still showed significant differences. For example, one isolate (67:21) contained the entire Cag pathogenicity island (PAI), whereas the other (67:20) had excised the PAI. Phenotypic studies disclosed that both isolates expressed adhesins that recognized human histo-blood group Lewis(b) glycan receptors produced by gastric pit and surface mucus cells. In addition, both isolates were able to colonize, to equivalent density and with similar efficiency, germ-free transgenic mice genetically engineered to synthesize Lewis(b) glycans in their pit cells (12 to 14 mice/isolate). Remarkably, the Cag PAI-negative isolate was unable to colonize conventionally raised Lewis(b) transgenic mice harboring a normal gastric microflora, whereas the Cag PAI-positive isolate colonized 74% of the animals (39 to 40 mice/isolate). The genomic evolution of both isolates during the infection of conventionally raised and germ-free mice was monitored over the course of 3 months. The Cag PAI-positive isolate was also surveyed after a 10 month colonization of conventionally raised transgenic animals (n = 9 mice). Microarray analysis of the Cag PAI and sequence analysis of the cagA, recA, and 16S rRNA genes disclosed no changes in recovered isolates. Together, these results reveal that the H. pylori population infecting one individual can undergo significant divergence, creating stable subclones with substantial genotypic and phenotypic differences.

Genomics and proteomics converge on Helicobacter pylori.

During the past year, a series of studies have provided new perspectives about genetic diversity in Helicobacter pylori. The results illustrate how the current revolution in genomics and proteomics is being used to understand how this organism co-evolves with its host. The approaches should have broad applications to other host-bacterium relationships.

Helicobacter pylori entry into human gastric epithelial cells: A potential determinant of virulence, persistence, and treatment failures.

BACKGROUND AND OBJECTIVES: Intracellular location of Helicobacter pylori in human gastric epithelial cells has been observed in biopsies. Whether this reflects an ability to invade host cells and establish an intracellular niche remains to be determined. METHODS: The interactions between a clinical isolate of H. pylori and primary cell cultures from human gastric epithelium or the human epithelial cell line HEp-2 were monitored using time-lapse photography. This technique allows studies of the dynamics of host-microbial interactions. RESULTS: H. pylori cells readily approached and established close contacts with epithelial cells followed by uptake of the bacteria into the cellular cytoplasm. Entry into epithelial cells was achieved through an active process of bacterial motility and penetration of the cell membranes. In conventional invasion assays using HEp-2 cells, an increased internalization in a strain producing the vacuolating cytotoxin was observed, compared to the isogenic VacA knockout mutant. CONCLUSION: Invasion of gastric epithelium represents a hitherto unappreciated trait of H. pylori that could contribute to the bacterium's ability to establish persistent infection that evades the mucosal immune defense and sometimes also antimicrobial therapy. A small number of bacterial cells with a transient intracellular habitat could serve as a seeder population, providing a backup for a constantly challenged and fluctuating luminal population.

Booster effect of low doses of tetanus toxoid in elderly vaccinees.

In order to improve the immunity to diphtheria, the recommended booster dose of diphtheria/tetanus vaccine for adults in Sweden was changed in 1986 from 0.5 ml of tetanus vaccine with a small diphtheria dose to 0.25 ml of a diphtheria/tetanus vaccine containing 7.5 Lf tetanus toxoid and 30 Lf diphtheria toxoid/ml. This change resulted in an increase in the dose of diphtheria toxoid from 0.5 Lf to 7.5 Lf, but a decrease in the recommended booster dose of tetanus toxoid from 3.75 Lf to 1.9 Lf. The aim of the present study was to investigate whether this lower dose of tetanus toxoid was also sufficiently protective for elderly people. Two hundred adults (median age 76 years, range 60-92 years) with no history of tetanus vaccination during the past 10 years volunteered for the study. One hundred two vaccinees were inoculated with 1.9 Lf tetanus toxoid (0.25 ml) and 98 with 3.75 Lf tetanus toxoid (0.5 ml). Paired serum samples were analysed by the toxin-binding inhibition assay. Side effects were few and mild, without significant differences between the groups. Response rates were similar, with the 3.75 Lf dose eliciting a marginally higher antitoxin response. The prevaccination geometric mean titre was the same for both groups: 0.03 IU/ml. Postvaccination geometric mean titres were 1.18 IU/ml for the 3.75 Lf group and 1.93 IU/ml for the 7.5 Lf group, respectively (difference not significant). Forty-seven percent of the vaccinees had a prevaccination titre of < or =0.01 IU/ml. Postvaccination, 85% had a titre >0.01 IU/ml. Booster vaccination with tetanus vaccine containing only 1.9 Lf of tetanus toxoid was thus found to induce an excellent immune response in elderly people, with few side effects resulting.

Occurence of resistance mutation and clonal expansion in Helicobacter pylori multiple-strain infection: a potential risk in clarithromycin-based therapy.

In a previous study, a patient was shown by means of DNA fingerprinting to be infected with different Helicobacter pylori strains before and after clarithromycin treatment. The strain isolated before treatment was susceptible (ClaS), whereas the strain isolated after 3 months of treatment was resistant (ClaR). Eighty H. pylori colonies from primary isolates were analyzed by DNA fingerprinting and restriction enzyme digestion of the 23S rRNA product of polymerase chain reaction in order to distinguish between ClaS and ClaR strains. One of the 40 colonies from isolates recovered before treatment showed a DNA fingerprint similar to that of the 40 from after treatment. However, a notable difference was that this isolate was not ClaR before treatment. Two ClaS H. pylori strains were present in the patient before treatment. The underrepresented strain gained a resistance mutation in the 23S rRNA gene and underwent clonal expansion during treatment. Recrudescence of the H. pylori infection therefore was the result.

Rapid PCR detection of Helicobacter pylori-associated virulence and resistance genes directly from gastric biopsy material.

We have developed a PCR-based method to detect macrolide resistance and the virulence gene cagA in Helicobacter pylori within 24 h, thereby improving the lengthy process of culture-based approaches. Total DNA was prepared directly from stomach biopsy specimens. The procedure proved to be rapid and reliable and could be utilized for diagnostic purposes.

Diphtheria antitoxin titres six years after basic immunization of adults.

Diphtheria antitoxin titres were analysed in 160 adults (median age 59 years, range 34-70), who completed basic vaccination with three doses of 7.5 Lf or 15 Lf of diphtheria toxoid (D) in a previous vaccination trial in 1987, in serum samples drawn 6 years later. The median titre had decreased from 3.2 IU ml-1 in the post vaccination samples to 0.2 IU ml-1 after 6 years in the 15 Lf group and 0.1 IU ml-1 in the 7.5 Lf group. An antitoxin titre of < 0.01 IU ml-1, a level usually considered to give no safe protection, was found in 21/73 (29%) individuals, who had received 7.5 Lf and in 12 of 87 (14%), who received 15 Lf diphtheria toxoid (P < 0.05). In the original study, the vaccinees were enrolled as unimmunized based on their own vaccination histories, but many participants had serological evidence of previous immunization. In the subgroup of 48 truly non-immune participants, i.e. without prevaccination titres and without booster response after the first injection, 46% (32% in the 15 Lf group and 58% in the 7.5 Lf group) had antitoxin levels of < 0.01 IU ml-1 6 years after basic vaccination. Therefore, individuals who have received basic vaccination with three doses of diphtheria toxoid need at least one booster injection 5-10 years later.

Influence of high titers of maternal antibody on the serologic response of infants to diphtheria vaccination at three, five and twelve months of age.

Diphtheria antitoxin was determined in serum from 44 pregnant women, of whom 26 had received one injection of diphtheria toxoid during pregnancy. Their infants were vaccinated with a combined diphtheria-tetanus vaccine at 3, 5 and 12 months of age. This vaccination schedule has been used in Sweden since 1986, replacing the old schedule of vaccination at 3, 4.5 and 6 months of age originally designed for diphtheria-tetanus-pertussis vaccine, which had not been used after cessation of general vaccination against pertussis in 1979. Serum samples from the infants were obtained at 3, 7 and 18 months of age. After 2 injections infants of mothers with high antitoxin titers, > or = 0.1 IU/ml, tended to have lower antitoxin titers than infants of mothers with low antitoxin concentrations (P = 0.067). All children had, however, antitoxin above the minimum protective level of 0.01 IU/ml. Median antitoxin titers were 1.6 IU/ml in both groups after the third booster injection. Four infants of mothers who had been vaccinated during pregnancy and who had titers of > or = 0.4 IU/ml did not reach the 0.1 IU/ml level after 2 injections: all 4 responded with high antitoxin titers after the third dose. Thus all infants were primed by 2 doses of vaccine, irrespective of maternal antibody concentration. The repressive effect of maternal antibody on titers noted after 2 doses was no longer observed after the third, booster dose.

Immune status and booster effects of low doses of tetanus toxoid in Swedish medical personnel.

Of 102 medical staff at a Swedish hospital, 81% had tetanus antitoxin titres > or = 0.01 IU/ml in 1984-85. The unprotected individuals (antitoxin titre < 0.01 IU/ml) were all > 30 years of age. Of this group, one-third lacked a protective antibody level against tetanus toxin. Low booster doses of tetanus toxoid (0.75 or 1.9 Lf) were given to 66 vaccinees with a history of previous basic vaccination and no history of booster vaccination within the previous 5 years. The median titre increased from 0.26 IU/ml before to 3.3 IU/ml after vaccination. Low doses of tetanus toxoid may thus still provide an adequate immune response when given as a booster vaccination to individuals with a reliable history of basic immunization.

Increased dosage of diphtheria toxoid for basic immunization of adults.

Basic immunization of adults with increased dosages of a diphtheria toxoid vaccine (2100 flocculation units (Lf)/mg) was evaluated. Three injections of 7.5 Lf or 15 Lf diphtheria toxoid were given to 243 adults who had a history of no more than one previous vaccine injection. Systemic reactions were rare in both groups. Following the first two injections, local reactions (greater than 5 cm) were observed in 6-14% of the adults. After the third injection, 35% of adults in the 15 Lf group reported a local reaction (greater than 5 cm) compared to 11% in the 7.5 Lf group (p less than 0.001). The 15 Lf dose elicited a better antitoxin response than the 7.5 Lf dose. In a seronegative subgroup including 65 vaccinees who showed no booster response to the first vaccination, 79% had a postvaccination titer of greater than or equal to 0.1 IU/ml and 28% a titer of greater than or equal to IU/ml after the third injection of 7.5 Lf. The corresponding numbers in the 15 Lf group were 94% and 44%, respectively. The study demonstrates that 7.5 Lf and 15 Lf diphtheria toxoid of high purity can safely be given to adults for basic immunization. The higher dose is more immunogenic but local reactions increase after the third injection.

Immune status and booster effects of low doses of diphtheria toxoid in Swedish medical personnel.

During a diphtheria outbreak among Swedish alcoholics in 1984-1985, only 60% of 328 medical staff at risk for exposure had diphtheria antitoxin titers greater than or equal to 0.01 IU/ml, which is usually considered to give relative protection. 21% had levels between 0.01-0.09 IU/ml and the remaining 39% had titers greater than or equal to 0.1 IU/ml. Booster doses of 0.5 Lf-12.5 Lf of diphtheria toxoid were given to 450 vaccinees. Of 72 individuals with low pre-immunization titers, who were immunized with less than or equal to 2.5 Lf diphtheria toxoid, 40% failed to reach greater than or equal to 0.1 IU/ml when analyzed 4 weeks after vaccination. Local tenderness and swelling greater than 5 cm at the site of injection or general discomfort was found in 11% of those immunized with low dose diphtheria toxoid (less than or equal to 2.5 Lf). When the dose 0.5 Lf of diphtheria toxoid was combined with tetanus toxoid (3.75 Lf) the frequency of adverse reactions increased to 34% (p less than 0.001). The study shows that vaccination status in medical personnel must also be continuously examined in countries where diphtheria is rare and that low booster doses of diphtheria toxoid may not achieve an adequate immune response.

Adverse reactions and immunogenicity in adults to regular and increased dosage of diphtheria vaccine.

Booster doses of 3 Lf or 7.5 Lf of a regular diphtheria vaccine were given to 200 previously immunized adult volunteers. The toxoid was prepared from toxin with a purity of 2100 Lf/mg protein nitrogen and adsorbed to aluminium phosphate. Systemic reactions were rare and no severe symptoms were observed. Local reactions occurred in 40-50% of the vaccinees, but in only 7.5% were they of clinical significance, i.e. an area of redness/swelling greater than 5 cm. The two doses did not cause significant differences in reaction rates, and the 7.5 Lf dose elicited a better antitoxin response. Thus, a dose of 7.5 Lf diphtheria toxoid of similar purity can safely be given to adults in vaccines.

An outbreak of diphtheria among Swedish alcoholics.

After 25 years without any indigenous cases of diphtheria in Sweden, an outbreak occurred in the city of Göteborg, during 1984 to 1986. A group of alcoholics constituted the reservoir of Corynebacterium diphtheriae. The outbreak included 13 clinical cases and 65 carriers. The death-to-case ratio and the complication rate among the clinical cases was high, with three fatal cases and six patients developing reversible paralyses. The fatal cases had no history of previous immunization. The outbreak demonstrates the necessity of a good vaccination status to diphtheria, also in countries where the disease was thought to have been eradicated.

Antitoxin antibody levels and the outcome of illness during an outbreak of diphtheria among alcoholics.

During an outbreak of diphtheria among alcoholics in Göteborg, Sweden, a study was made of the diphtheria-antitoxin antibodies in serum samples from 8 clinical cases and 36 carriers of toxin-producing Corynebacterium diphtheriae. 33/36 carriers were antibody-positive and had antitoxin titres greater than 0.01 IU/ml, a level which is regarded as relative protective, while only 1/8 clinical cases had such a titre. This patient presented a mild illness with no complications. The results of the study of this outbreak stress the importance of maintaining adequate antibody levels against diphtheria in highly developed societies.

Cerebellar aspergilloma.

A cerebellar aspergilloma simulating brain tumour in a 48-year-old woman with alveolar proteinosis is described. The course of the disease was recurrent. Despite neurosurgery, ventricular drainage, amphotericin B, flucytosine and other antifungal agents, the disease was ultimately fatal. The diagnostic and therapeutic problems of aspergillosis in the central nervous system are discussed. Suspicion and serology might lead to early diagnosis and a better prognosis.