Experimental and Numerical Analysis of Initial Plasticity in P91 Steel Small Punch Creep Samples.

To date, the complex behaviour of small punch creep test (SPCT) specimens has not been completely understood, making the test hard to numerically model and the data difficult to interpret. This paper presents a novel numerical model able to generate results that match the experimental findings. For the first time, pre-strained uniaxial creep test data of a P91 steel at 600 ∘C have been implemented in a conveniently modified Liu and Murakami creep damage model in order to simulate the effects of the initial localised plasticity on the subsequent creep response of a small punch creep test specimen. Finite element (FE) results, in terms of creep displacement rate and time to failure, obtained by the modified Liu and Murakami model are in good agreement with experimental small punch creep test data. The rupture times obtained by the FE calculations which make use of the non-modified creep damage model are one order of magnitude shorter than those obtained by using the modified constitutive model. Although further investigation is needed, this novel approach has confirmed that the effects of initial localised plasticity, taking place in the early stages of small punch creep test, cannot be neglected. The new results, obtained by using the modified constitutive model, show a significant improvement with respect to those obtained by a 'state of the art' creep damage constitutive model (the Liu and Murakami constitutive model) both in terms of minimum load-line displacement rate and time to rupture. The new modelling method will potentially lead to improved capability for SPCT data interpretation.

The complement-killing of Borrelia burgdorferi. Target antigens and sensitizing antibodies.

It had been previously shown by the Microbial Adherence Immobilization Assay (MAIA) that Borrelia burgdorferi sensu stricto, type strain B31 was clumped, immobilized and killed in vitro by sensitizing antibodies that activated the classical complement pathway and the complement-killing of live borrelia. In the present study, the target antigens and sensitizing antibodies responsible for the complement-killing of borrelia were investigated, using MAIA as a selective identification tool. It was found that the fractions containing the 31 and 34 kDa outer surface proteins from strain B31 were the unique antigens producing sensitizing antibodies in rabbits that activated the complement-killing of B31. An anti-OspB, but not an anti-OspA, monoclonal antibody did activate the B31 complement-killing in MAIA. From these results, constraints on the effectiveness of OspB and OspA as immunogens for the prevention and control of Lyme borreliosis in humans are discussed.

Antibodies to Borrelia burgdorferi in sheep and goats. Alto Adige-South Tyrol, Italy.

A serologic survey for antibodies to Borrelia burgdorferi was conducted on sheep and goat serum samples collected in Alto Adige-South Tyrol, Italy, in 1990. Sera were tested by Indirect Immune Fluorescence Assay (IIFA) and Microbial Adherence Immobilization Assay (MAIA). IIFA and/or MAIA anti-B. burgdorferi antibodies were detected in 14.1% of the 269 sheep and 36.8% of the 133 goats examined. IIFA and MAIA were both positive in 4 out of 38 positive sheep sera (10.5%) and 21 out of 49 positive goat sera (42.8%). These discrepancies suggest that MAIA- and IIFA-detected antibodies do differ from each other. The detection by MAIA of antibodies sensitizing B. burgdorferi to the killing effect of complement seems to be a valid parameter to evaluate the acquired immunity of sheep and goats to B. burgdorferi infections.

Genetic and phenotypic characterization of Borrelia burgdorferi strains isolated from Ixodes ricinus ticks in the Province of Bolzano, Italy.

Lyme disease is caused by three borrelial species, B. burgdorferi sensu stricto, B. garinii and Borrelia group VS461. In a restricted biotope of the Bolzano province, in the Caldaro community, five clones of two borrelial variants were isolated from Ixodes ricinus ticks. A preliminary serological study showed that the two variants cross-reacted with B. burgdorferi B31 and B. garinii N34 strains, respectively. The isolates were genomically related with strains B31 and N34, respectively, sharing a similar plasmid and restriction fragment length polymorphism profile with these strains. The phenotypic pattern of the Caldaro isolates-namely their protein and antigenic profile-showed infra-subspecific variation compared to related strains B31 and N34 respectively. The observed phenotypic variability between strains isolated from the same biotope and in the same tick host strongly indicated the variability of gene-encoded characters is a constant characteristic of borrelial strains, even when from the same ecological niche.

Survey on the prevalence of leptospira infections in the Italian population.

This investigation is the first nationwide survey on the circulation of leptospira infections in human beings in Italy. In nine out of twenty Italian regions, representative samples of the population were investigated for the presence of leptospira infections. Unexpectedly, leptospira infections were found to be widespread, the number of cases being much higher than the diagnosed clinical cases. There were found to be high, medium, and low risk areas. On the whole, the risk for the rural population was no higher than the risk for urban dwellers; leisure activities, contact with animals and residence on the plain versus residence in the hills were important risk factors. There was an unidentified risk factor in urbanites which was absent in the rural population. A changing pattern in infecting serovars was observed, with infections from serogroups Sejroe, Javanica and Australis prevailing over infections from the Icterohaemorrhagiae and Bataviae serogroups, which were the main agents of human leptospirosis during the 1950s. The mechanisms of these changes, the need for epidemiological surveys and improved diagnostic methods of screening are discussed.

Prevalence of antibodies to Borrelia burgdorferi, Borrelia parkeri and Borrelia turicatae in human settlements of the Cordillera Province, Bolivia.

A seroepidemiological study to determine the prevalence of human Lyme borreliosis and tick-borne relapsing fever was carried out in three communities (Camiri, Boyuibe and Gutierrez) of the Cordillera Province, Santa Cruz Department, south-eastern Bolivia. Anti-B. burgdorferi, anti-B. turicatae and anti-B. parkeri antibodies, tested by the indirect immunofluorescent assay (IFA), were detected in 10.8, 16.1 and 8.2% of the serum samples tested, and confirmed by IFA-ABS in 1.3, 1.3 and 1.0%, respectively. This is the first report of the presence of Lyme borreliosis and tick-borne relapsing fever in Bolivia. For Lyme borreliosis these findings represent a further datum to support its existence in South America.

Chromosomal rearrangement and serovar conversion in Leptospira biflexa strains.

A bacterial population change involving chromosomal rearrangement and phenotypic changes in antigens, proteins and lipopolysaccharides is described for strains of Leptospira biflexa that were previously grown in media containing homologous oligoclonal antibodies. The chromosomal rearrangement phenomenon showed that the variants differed from the parent strains, yet they were similar to phenotypically related serovars already occurring in nature. Accordingly, in vitro serovar conversion mediated by chromosomal rearrangement, due to as yet unknown genetic mechanisms, had occurred.

Complement activation and sensitizing antibodies in Lyme borreliosis. A microbial adherence immobilization assay for Borrelia burgdorferi (MAIA-BB).

A report is presented about the capability of complement to directly clump Borrelia burgdorferi. The new phenomenon which has been termed "microbial adherence", is either antibody-independent or requires the presence of "sensitizing" antibodies depending the strains tested. Microbial adherence is associated with immobilization and killing of borrelias. A microbial adherence immobilization assay for B. burgdorferi (MAIA-BB) was developed to detect sensitizing antibodies in patients with Lyme borreliosis and in B. burgdorferi-infected animals.

Evaluation of a passive microcapsule agglutination test for the screening of human leptospirosis.

Microcapsules, absorbed with two mixed antigens--each composed of 3 sonicated leptospira serovars--were developed in the past as a microcapsule agglutination test (MCA-LS) for the screening of clinical leptospirosis. For this study, fifty serum samples, taken at an earlier and at a later stage of illness from 25 Italian in-patients with clinical symptoms of leptospirosis, were tested with both the MCA-LS one-dilution test and the microscopic agglutination (MA) test, the confirmatory test for leptospirosis, with 18 leptospira strains circulating in Italy. Compared with MA, MCA-LS showed a sensitivity of 91.7%, and a specificity of 92.3%, including leptospirosis not sustained by the diagnostic strains used in the MCA-LS kit.

Fatty acid profiles in the family Leptospiraceae.

Fatty acid profiles of six leptospira strains representative of genera, species, and serogroups within the family Leptospiraceae were determined by gas liquid chromatography (GLC) of fatty acid methyl ester (FAME) derivatives. The influence of methodological and biological variables on FAME profiles of the same strain was tested. FAME profiles were sharply affected by the fatty acid composition of the culture medium but not by the growth phase. Twenty-four FAME peaks were selected on the basis of their presence in repeated gas chromatographic runs of single strains. Inter-strain divergences of FAME profiles were quantified by linear regression analysis (LR). Step-wise divergences in FAME profiles were observed between strains at serogroup, species, and genus levels.

Rickettsiae of the spotted fever group associated with the host-parasite system Oryctolagus cuniculi/Rhipicephalus pusillus.

Wild rabbits--Oryctolagus cuniculi--living in large numbers in a protected zone of Tuscany, the park of Migliarino--San Rossore--Massaciuccoli, showed to be carriers of the hard tick Rhipicephalus pusillus, previously observed in North Africa and Sicily. Antibodies to Rickettsia conorii and R. slovaca were detected in 78.9 per cent of the wild rabbits captured in that area. Seroconversion towards R. conorii was also observed in guinea pigs inoculated with homogenates of R. pusillus parasitizing the wild rabbits. These results identify an ecological niche of rickettsiae of the Spotted fever group in the host-parasite system O. cuniculi/R. pusillus. Attempts to isolate rickettsiae from the ticks and the wild rabbits were unsuccessful both in the egg yolk sac and in the guinea pig. This failure probably shows the low pathogenicity of the rickettsiae parasitizing the biosystem O. cuniculi/R. pusillus.

Broad reacting surface antigens in Leptospira biflexa serovar andamana.

Previous investigations had demonstrated that genus-specific and species-specific antigens of leptospires are deep-seated within the leptospiral cell. Conversely, the present study has shown that strain CH11, serovar andamana of the non-pathogenic species of Leptospira biflexa is endowed on its surface with two cross-reacting antigens; a newly recognized antigen common to L. interrogans and L. biflexa spp. and an antigenic determinant common to a previously described genus-specific protein antigen (GP-Ag). The serovar andamana, when thimerosal-treated, behaved like an interspecies-specific antigen, cross-reacting in the complement fixation test with sera from rabbits immunized with L. interrogans and L. biflexa spp. and with sera from subjects with leptospirosis from various serovars. In the immuno electron microscopic test, human leptospirotic sera bound to the surface of thimerosal-treated andamana and not to the surface of untreated andamana showing that an interspecies-specific antigen was located underneath the outermost layer of this serovar. In the same test, the monoclonal antibody GP-7 against the GP-Ag bound to the surface of untreated andamana and not to the surface of thimerosal-treated andamana, showing that an antigenic determinant, common to GP-Ag and different from the first one, was located on the outer membrane of andamana. In human leptospirotic sera, antibodies against the cross-reacting antigen of thimerosal-treated andamana demonstrated by the complement fixation test were formed earlier and in a higher percentage of sera than the serovar-specific antibodies against 16 L. interrogans serovars demonstrated by the microagglutination test.

Recent trends in human leptospirosis in Italy.

The recent epidemiological trends of human leptospirosis in Italy were investigated using data collected for the years 1981-1985. A total of 626 hospitalized patients with clinical diagnoses of suspected leptospirosis were reported by hospital centers from several Italian regions. Epidemiological, clinical and seroimmunological data were collected in 517 of these cases and examined by the National Center for Leptospirosis. Serological findings in 33.5% of these subjects met the criteria for confirmation of the disease. In 21.8% of the subjects, low titer antibodies were detected, which possibly reflected previous leptospiral infections. An early antibiotic treatment of the current infection may also have lowered the seroimmunological response in some of these patients. In 59.3% of the confirmed cases, modes of transmission were allotted equally between accidental events and recreational or occupational activities. Drinking water from an open air fountain emerged as an uncommon mode of transmission; it was responsible for an outbreak of 33 cases of leptospirosis. In another 37.07% of the subjects, it was impossible to establish the mode of transmission. Respiratory or influenza-like symptoms were the only clinical signs of illness in 21.2% of the patients with confirmed leptospirosis. In comparison to the sixties and seventies, the prevalence of infecting serovars showed increasing incidence of infections due to serovars of the Javanica (11.0%) and Australis (11.0%) serogroups and an important decrease in the Bataviae serogroup infections (from 58.8% in rice-field workers in the forties to 0.6% in the years 1981-1985). Sejroe serogroup infections accounted for 4.5 per cent of confirmed cases of leptospirosis.(ABSTRACT TRUNCATED AT 250 WORDS)

A waterborne outbreak of leptospirosis.

During the period from July 10-26, 1984, 33 cases of serologically confirmed leptospirosis occurred in a small town in central Italy. The fatality rate, including the deaths of two unconfirmed cases, was 8.6% (3 of 35). Based on serologic evidence, the infection was caused by leptospires of the serogroup Australis. Epidemiologic study showed that the patients contracted the infection by drinking water from a fountain. The source of leptospiral contamination was probably a hedgehog trapped in a reservoir of water not in use but still connected to the water system of the fountain.

Selection of antigenic variants from Leptospira interrogans serovar canicola by means of anti-canicola monoclonal antibody.

Antigenic variants were isolated from canicola by a single selection with anti-canicola monoclonal antibody CT-3. The variants were not identical to any serovars of serogroup Canicola and thought to be a new serovar. Variation frequency was calculated at 5.9 X 10(-4). The usefulness of monoclonal antibodies for selection of antigenic variants of leptospiras is discussed.

Prevalence of leptospirosis in man. Pilot survey.

A survey on the prevalence of leptospirosis was performed on the population living in an area of central Italy. The size of the sample was calculated in order to provide significant results in the case of a prevalence of infection in not less than 1% of the population. Results demonstrated an unexpectedly wide circulation of leptospirosis in the surveyed area, showing a prevalence rate of infection of 11.34% for people living in rural areas and 3.08% for people living in the main town. The highest prevalence of infection (17.44%) was found in people between 30 and 44 years of age, living in rural areas. Such a wide circulation of undiagnosed past leptospiral infections was attributed both to the prevalence of mild clinical cases of leptospirosis in humans and the lack of microbiological tests performed to differentiate current leptospirosis from other infectious illnesses. An unexpected persistence in sera of co-agglutinins towards non-pathogenic serovars of L. biflexa was also noticed in healthy people. Criteria were established for the extension of the survey on the prevalence of leptospirosis to cover larger areas by limiting sampling to the more exposed age groups and to areas representative of a larger land belt.

Antigenic population changes of Leptospira biflexa strains grown under the selective pressure of factorial antibodies.

Serovars jequitaia and tororò of Leptospira biflexa were cultured in the presence of homologous factor serum containing factorial antibodies (FcAbs) to their major antigens. After 39 serial passages they were then re-tested to determine whether their major antigens had remained unchanged. It was found that each parent strain had been replaced by an antigenic variant. The disappearance of each parent strain and its replacement by an antigenic variant was attributed to the selective conditions imposed by FcAbs. The antigenic variants behaved like true mutants. They lacked the major serovar antigens of the parent strains and had acquired some major antigens similar to those of two different serovars, one of which belonged to the same serogroup as the parent strain and the other to a different serogroup. A comparison of the major antigens of the parent strains with those of their antigenic variants indicated that factorial antibodies may be used selectively to obtain antigenic variants with a predefined pattern of major antigens.

[Preliminary studies on the occurrence of Rickettsiae of the spotted fever group in Rhipicephalus sanguineus captured in suburban areas]. / Osservazioni preliminari sulla prevalenza di Rickettsie del gruppo delle spotted fevers in Rhipicephalus sanguineus catturati in aree sub-urbane.

In the urban periphery of Rome, two sub-zones could be distinguished, characterized by uncultivated steppeland and by small shacks with large quantities of domestic refuse, respectively. Rhipicephalus sanguineus appeared to be typical of this second sub-zone. R. sanguineus adults and nymphae were captured in different seasonal periods and were checked for the prevalence of rickettsiae of the Spotted Fever (SF) group. Moreover, larvae from hatched eggs, laid by captured R. sanguineus females, were checked for the transovarial transmission of rickettsiae. Ten lots each of three guinea-pigs, seronegative to rickettsiae of the SF group, were inoculated with R. sanguineus extracts, prepared from adults or larvae. Clinical signs of infection, fever and scrotal reaction, could be observed only in one lot of guinea-pigs inoculated with adult parasites. On the other hand, in 8 out of 10 guinea pig lots, antibodies to the soluble antigens of R. conori and R. slovaca were observed by the complement fixation (CF) test. In the remaining two lots only antibodies to R. slovaca were detected. No antibodies to Coxiella burneti could be demonstrated in the same sera.

[The diagnosis of leptospirosis in the hospital microbiology laboratory]. / La diagnosi di leptospirosi nel laboratorio microbiologico ospedaliero.

Confirmatory diagnosis of clinical leptospirosis may be achieved by each hospital laboratory performing all-purpose bacteriological methods. Direct microscopic examination of blood may frequently demonstrate circulating leptospiras in the first few days of pyrexia. Leptospiras may be tentatively cultured from blood in the same initial period of illness, in fluid semisynthetic commercial media according to the original Ellinghausen medium. Sero-conversion for leptospira antibodies is constantly observed on two serum samples taken in the first few days of illness and ten days thereafter respectively, in each case of current leptospirosis.