Nasal boost with adjuvanted heat-killed BCG or arabinomannan-protein conjugate improves primary BCG-induced protection in C57BL/6 mice.

Today it is generally accepted that the Bacillus Calmette-Guerin (BCG) vaccine protects against childhood tuberculosis (TB) but this immunity wanes with age, resulting in insufficient protection against adult pulmonary TB. Hence, one possible strategy to improve the protective efficacy of the BCG vaccine would be to boost in adulthood. In this study, using the mouse model, we evaluated the ability of two new TB vaccine candidates, heat-killed BCG (H-kBCG) and arabinomannan-tetanus toxoid conjugate (AM-TT), given intransally in a novel Eurocine adjuvant, to boost a primary BCG-induced immune response and to improve protection. Young C57BL/6 mice were vaccinated with conventional BCG and, 6 months later, boosted intranasally with adjuvanted H-kBCG or AM-TT, or subcutaneously with BCG. Ten weeks after the booster, mice were challenged intravenously with M. tuberculosis (Mtb) strain H37Rv. In spleens, there was a significant reduction of cfu counts in mice boosted with either H-kBCG or AM-TT vaccines compared to the non-boosted BCG-vaccinated mice. None of the boosting regimens significantly reduced bacterial loads in lungs, compared to non-boosted BCG vaccination. However, the extent of granulomatous inflammation was significantly reduced in the lungs of mice that received two of the booster vaccines (AM-TT and conventional BCG), as compared with sham-vaccinated mice. All boosted groups, except for mice boosted with the AM-TT vaccine, responded with a proliferation of spleen T cells and gamma interferon production comparable to that induced by a single BCG vaccination.

A mycobacterial lipoarabinomannan specific monoclonal antibody and its F(ab') fragment prolong survival of mice infected with Mycobacterium tuberculosis.

Lipoarabinomannan (LAM) is a major structural carbohydrate antigen of the outer surface of Mycobacterium tuberculosis. High antibody titres against LAM are often seen in active tuberculosis (TB). The role of such LAM-specific antibodies in the immune response against TB is unknown. Here we have investigated a monoclonal antibody (MoAb) SMITB14 of IgG1 subclass and its corresponding F(ab')(2) fragment directed against LAM from M. tuberculosis strain H37Rv. MoAb SMITB14 was shown by immunofluorescence to bind to whole cells of the clinical isolate M. tuberculosis strain Harlingen as well as to M. tuberculosis H37Rv. The binding of MoAb SMITB14 to LAM was inhibited by arabinomannan (AM) and oligosaccharides (5.2 kDa) derived from LAM, showing that the MoAb binds specifically to the AM carbohydrate portion of LAM. In passive protection experiments BALB/c mice were infected intravenously with M. tuberculosis Harlingen. MoAb SMITB14 was added intravenously either prior to, or together with, the bacteria. The antibody proved to be protective against the M. tuberculosis infection in terms of a dose-dependent reduction in bacterial load in spleens and lungs, reduced weight loss and, most importantly, increased long-term survival.

Immunization with heat-killed Mycobacterium bovis bacille Calmette-Guerin (BCG) in Eurocine L3 adjuvant protects against tuberculosis.

The current live attenuated vaccine against tuberculosis, BCG, poses a risk of disseminated infections in immunocompromised subjects. Therefore, in this study we compared the protective effect of a heat-killed bacille Calmette-Guerin (H-kBCG) vaccine given in a new adjuvant (Eurocine L3) with the protection provided by the conventional live attenuated BCG vaccine in mice (C57BL/6 and BALB/c) challenged with virulent Mycobacterium tuberculosis (strain Harlingen). The H-kBCG vaccine alone, in accordance with earlier studies, did not give any or only gave slight protection compared to sham-vaccinated controls. However, the same vaccine given with Eurocine L3 adjuvant, either formulated as a suspension or as an emulsion, afforded significant levels of protection. This protection was at least as good as that of the control live attenuated BCG vaccine. The Eurocine L3 adjuvant is approved for human use as a nasal vaccine adjuvant and a successful phase I trial with nasal immunization with diphtheria vaccine has recently been performed in Sweden. Here we show that, in mice, intranasal priming with H-kBCG in Eurocine L3 adjuvant followed by intranasal booster resulted in the same level of protection as subcutaneous priming followed by intranasal booster. All H-kBCG formulations in the Eurocine L3 adjuvant elicited mycobacterial antigen-specific serum IgG and IFN gamma responses. In general, among the different vaccine formulation(s) in the Eurocine L3 adjuvant those that produced a relatively high Th2 response, as measured by IgG1/IgG2a ratio and IFN gamma production in vitro, were the most protective. In conclusion, H-kBCG in Eurocine L3 adjuvant could represent a safe and a more stable alternative to the conventional live BCG vaccine.

RAPD-PCR and PFGE as tools in the investigation of an outbreak of beta-haemolytic Streptococcus group A in a Swedish hospital.

We evaluated the random amplified polymorphic DNA (RAPD) and pulsed-field gel electrophoresis (PFGE) techniques for studying an outbreak of beta-haemolytic streptococci group A (GAS) occurred at two maternity wards at Danderyd hospital, Stockholm, Sweden. All the isolates were of T-type 8,25. The RAPD technique revealed that all RAPD-PCR profiles were identical. PFGE showed that all the patterns but one were identical. These patterns were compared with 10 different T-type GAS from the strain collection of the Swedish Institute for Infectious Disease Control (SMI) and T-type 8,25 from different years and locations. The SMI strains exhibited patterns different from each other and all different from the isolates from Danderyd hospital. Moreover, RAPD could not differentiate among the T-type 8,25 isolates from different years and locations but PFGE showed differences among the amplicons. Our results indicated that the RAPD and PFGE techniques could be efficient tools in epidemiological studies of GAS.

The mtp40 gene is not present in Mycobacterium bovis.

The mtp40 gene was initially reported to be lacking in classical Mycobacterium bovis strains, while being specific to classical M. tuberculosis strains. Later two clinical isolates reported to be M. bovis were shown to possess the mtp40 gene (A. Weil, B.B. Plikaytis, W.R. Butler, C.L. Woodley and T.M. Shinnik, J Clin Microbiol 1996; 34: 2309-2311). The two strains were, however, not fully characterized biochemically or genotypically. By PCR amplification of whole cell lysates and subsequent spoligotyping, which classifies isolates within the M. tuberculosis complex, the two strains were found to possess the spacers 40-43 which typically are lacking in classicalM. bovis, but had a spoligotyping pattern compatible with M. africanum. We conclude that the two strains, previously designated M. bovis, should be designated M. africanum. This reinvestigation has implications for the phylogenetic classification of M. bovis.

Dynamics of penicillin-susceptible clones in invasive pneumococcal disease.

In a 10-year period, 1987-1997, there was a >4-fold increase in the rate of pneumococcal bacteremia in Sweden. Invasive pneumococcal isolates (n=1136), which were obtained from 18 Swedish clinical microbiology laboratories from 1987 through 1997, and other national and international isolates were serotyped, and their clonal relationships were determined by molecular typing. The increase in invasive pneumococcal disease in Sweden during this period was associated particularly with an increase in isolates of serotypes 1 and 14. A 3-fold increase of type 14 was seen from 1987 through 1992, and a 10-fold increase of type 1 occurred from 1992 through 1997. One dominating penicillin-susceptible clone of type 14 was responsible for the increase of type 14 during the first 5 years. This clone also was found in Canada and the United States and was shown by multilocus sequence typing to correspond to a previously identified hyper-virulent clone. A novel penicillin-susceptible clone of type 1, which was not found among invasive isolates from 1987 or 1992, was responsible for the increase of serotype 1 during the last 5 years. These results illustrate the ability of virulent penicillin-susceptible pneumococcal clones to emerge and spread rapidly within a country.

Spread of drug-resistant pulmonary tuberculosis in Estonia.

Restriction fragment length polymorphism (RFLP) analysis of 209 Mycobacterium tuberculosis clinical isolates obtained from newly detected pulmonary tuberculosis patients (151 male and 58 female; mean age, 41 years) in Estonia during 1994 showed that 61 isolates (29%) belonged to a genetically closely related group of isolates, family A, with a predominant IS6110 banding pattern. These strains shared the majority of their IS6110 DNA-containing restriction fragments, representing a predominant banding pattern (similarity, >65%). This family A comprised 12 clusters of identical isolates, and the largest cluster comprised 10 strains. The majority (87.5%) of all multidrug-resistant (MDR) isolates, 67.2% of all isolates with any drug resistance, but only 12% of the fully susceptible isolates of M. tuberculosis belonged to family A. These strains were confirmed by spoligotyping as members of the Beijing genotype family. The spread of Beijing genotype MDR M. tuberculosis strains was also frequently seen in 1997 to 1999. The members of this homogenous group of drug-resistant M. tuberculosis strains have contributed substantially to the continual emergence of drug-resistant tuberculosis all over Estonia.

Rapid diagnosis of tuberculosis by detection of mycobacterial lipoarabinomannan in urine.

There is an urgent need for improved tools for laboratory diagnosis of active tuberculosis (TB). Here, we describe two methods, a catch-up ELISA and a dipstick test based on the detection in urine of lipoarabinomannan (LAM). LAM is a major and specific glycolipid component of the outer mycobacterial cell wall. Preliminary experiments showed that LAM is excreted in the urine of mice injected intraperitoneally with a crude cell wall preparation of Mycobacterium tuberculosis. Both methods were highly sensitive, detecting LAM at concentrations of 1 ng/ml and 5 pg/ml, respectively. Of 15 patients with active TB, all showed intermediate to high levels of LAM in their urine (absorbance values from 0.3 to 1.2, mean 0.74). Only one sample showed an absorbance value below the chosen cut off value of 0.4. All but one of the urine samples from 26 healthy nursing workers exhibited OD value below 0.4 cut off. These methods may prove valuable for rapid and simple diagnosis of TB in particular in developing countries lacking biosafety level 3 (BSL3) facilities.

Differentiation of avian pathogenic Escherichia coli (APEC) strains by random amplified polymorphic DNA (RAPD) analysis.

Here we describe the application of a random amplified polymorphic DNA (RAPD) analysis for molecular genetic typing avian pathogenic Escherichia coli (APEC) strains. The RAPD technique was shown to be highly reproducible. Stable banding patterns with a high discriminatory capacity were obtained using two different primers. Overall, 55 E. coli strains were analyzed with a RAPD technique. The RAPD analysis showed that the E. coli strains isolated from poultry in Thailand and Sweden could be grouped into 50 of RAPD types by using these two different primer sets. Most of these different E. coli RAPD types were not geographically restricted. There was, as expected, a tendency of higher genetic relationship among E. coli strains isolated from the same farm. It is suggested that the RAPD technique may provide a rapid, low cost, simple and powerful tool to study the clonal epidemiology of avian E. coli infections.

Comparison of Mycobacterium avium complex (MAC) strains from pigs and humans in Sweden by random amplified polymorphic DNA (RAPD) using standardized reagents.

Infections with atypical mycobacteria belonging to the Mycobacterium avium/intracellulare complex (MAC) can cause infection in both animals and humans. Using a standardized reagents commercial kit for random amplified polymorphic DNA (RAPD) analysis, 49 MAC strains isolated from 32 slaughter pigs and 17 humans in Sweden were identified and sorted out, yielding 6 RAPD types. By combining the results of RAPD primers 4 and 5 and the primer IS1245A, we found that pigs and humans may be infected with the same types of MAC strains, since 14 strains from humans and 8 strains from pigs were essentially identical and together, comprised RAPD type 2, the largest group of strains (44.8% of strains). With respect to grouping of strains, serotype and RAPD type were uncorrelated, except for serotype 20 and RAPD type 6. Using standardized beads, RAPD analysis is a reproducible technique for typing MAC strains, as the indistinguishable banding patterns obtained with repeated analyses of two isolates from each strain in this study demonstrate. However, primer selection and DNA purity were crucial for differentiating closely related strains.

Changes in serotype distribution may hamper efficacy of pneumococcal conjugate vaccines in children.

During the last 10 y we have observed an increased incidence of pneumococcal bacteremia in Sweden. In order to study the serotype distribution over time we collected 1136 invasive pneumococcal isolates from 1987, 1992 and 1997 from Swedish microbiological laboratories. Currently, new pneumococcal conjugate vaccines are being considered for introduction in the general childhood vaccination program in several countries, including Sweden. We studied the potential vaccine coverage rate for the new conjugate vaccines among our Swedish invasive isolates. We found that the serotype distribution fluctuated with time and observed a surprisingly low potential coverage rate for the 7-valent vaccine in Sweden, in contrast to other countries. Therefore we argue that pneumococcal conjugate vaccines have to be tailored to suit current, local serotype patterns and most likely will need to be changed over time.

Application of randomly amplified polymorphic DNA (RAPD) analysis for typing avian Salmonella enterica subsp. enterica.

Randomly amplified polymorphic DNA (RAPD) analysis was performed for the molecular genetic typing of 30 Salmonella enterica subsp. enterica strains isolated from chickens and ducks in Thailand. Six different primers were tested for their discriminatory ability. While some of the primers could only differentiate between the different serovars, the use of multiple primers showed that the RAPD method could also subdivide within a given serovar. The Ready-To-Go RAPD analysis beads used, resulted in reproducible and stable banding patterns. As the RAPD technique is simple, rapid and rather cheap, we suggest that it may be a valuable new tool for studying the molecular genetic epidemiology of S. enterica ssp. enterica, both inter- and intra-serovars.

Specific detection of Plesiomonas shigelloides isolated from aquatic environments, animals and human diarrhoeal cases by PCR based on 23S rRNA gene.

Twenty-five strains of Plesiomonas shigelloides isolated from aquatic environment, 10 strains from human cases of diarrhoea and five strains from animals were identified by the polymerase chain reaction technique based on 23S rRNA gene. For this purpose, two primers targeted against part of the 5' half of the 23S rRNA gene of P. shigelloides (Escherichia coli number C-912, G-1195; Plesiomonas number C-906, G-1189) were designed. Results from our study indicated that this method might serve as a tool for a rapid and sensitive identification of P. shigelloides from different environmental and clinical sources.

Molecular epidemiology of Streptococcus pneumoniae causing invasive disease in 5 countries.

A multicenter study was done during 1993-1995 to investigate prospectively the influence of several prognostic factors for predicting the risk of death among patients with pneumococcal bacteremia. Five centers located in Canada, the United Kingdom, Spain, Sweden, and the United States participated. Clinical parameters were correlated to antibiotic susceptibility and serotyping of the 354 invasive pneumococcal isolates collected and to molecular typing of 173 isolates belonging to the 5 most common serotypes (14, 9V, 23F, 3, and 7F). Serotype 14 was the most common among all isolates, but serotype 3 dominated in fatal cases and in isolates from Spain and the United States, the countries with the highest case-fatality rates. Fewer different patterns were found among the type 3 isolates, which suggests a closer clonal relationship than that among isolates belonging to other serotypes. Of type 3 isolates from fatal cases, 1 clone predominated. Other penicillin-susceptible invasive clones were also shown to spread in and between countries.

Preparation of pneumococcal capsular polysaccharide-protein conjugate vaccines utilizing new fragmentation and conjugation technologies.

There is a global urgent need for a new efficient and inexpensive vaccine to combat pneumococcal disease, which should also be affordable in developing countries. In view of this need a simple low-cost technique to prepare such a vaccine was developed. The preparation of serotype 14 and 23F pneumococcal capsular polysaccharide (PnPS)-protein conjugates to be included in a forthcoming multivalent PnPS conjugate vaccine is described. Commercial lots of PnPSs produced according to Good Manufacturing Practice from Streptococcus pneumoniae serotype 14 (PS14) and 23F (PS23F) were partially depolymerized by sonication or irradiation in an electron beam accelerator. The PnPS fragments were conjugated to tetanus toxoid (TT) using a recently developed conjugation chemistry. The application of these new simple, efficient and inexpensive fragmentation and conjugation technologies allowed the synthesis of several PnPS-protein conjugates containing PnPS fragments of preselected sizes and differing in the degree of substitution. The PS14TT and PS23FTT conjugate vaccine candidates were characterized chemically and their immunogenicity was evaluated in rabbits and mice. All PnPS conjugate vaccines, unlike the corresponding plain polysaccharides, produced high IgG titres in both animal species. The PS14TT conjugates tended to be more immunogenic than the PS23FTT conjugates. The immune response to the PS14TT conjugates, but not to the PS23FTT conjugates, was related to the size of the conjugated polysaccharide hapten. Both types of conjugates elicited strong booster effects upon secondary immunizations, resulting in high IgG1, IgG2a and IgG2b titres.

Prevalence and diversity of Aeromonas and Vibrio spp. in coastal waters of Southern Italy.

A survey was undertaken to examine sea water and sediment for the presence of Vibrio and Aeromonas spp. along approximately 900 km of coast in Southern Italy during early and late summer. A quantitative analysis was also done to evaluate the water fecal contamination at the stations examined. The results indicate that all the investigated areas were submitted to a wide spatial fluctuation of fecal contamination and that Vibrio and Aeromonas spp. were present in both high and low fecal-contaminated stations. Sixty two percent of the investigated samples were positive for Aeromonas spp., while 42% of samples were positive for Vibrio spp. It was interesting to note that 38% of the positive stations for both Aeromonas and Vibrio spp. showed a fecal coliform contamination of water at < 10(2) cells 100 ml(-1). Thus, these findings support the hypothesis that the bacterial indicators (such as fecal coliforms) do not always satisfactorily reflect the hygienic quality of water. The presence of Vibrionaceae on copepods was also investigated. Copepods were sampled at a station located inside the harbour of the city of Naples and were found contaminated by V. cholerae non-O1, V. alginolyticus, V. fluvialis and A. caviae. Furthermore, the antibiotic resistance patterns of isolated bacteria showed the presence of a number of resistant strains among the isolates. In order to discriminate the isolates on the basis of their biochemical profiles and/or antibiotic resistance patterns, cluster analysis was carried out which showed that no unique assay could fully discern these isolates. However, the best discrimination resulted from complete pattern profile based on both biochemical profiles and antibiotic resistance patterns.

Identification of Escherichia coli recovered from milk of sows with coliform mastitis by random amplified polymorphic DNA (RAPD) using standardized reagents.

A standardized-reagents commercial kit for random amplified polymorphic DNA (RAPD) analysis was used for typing 58 Escherichia coli strains that were recovered from the milk of sows, having coliform mastitis, within a single swineherd in Sweden. Previously, the 58 E. coli strains were characterized serologically and profiled biochemically. They were also evaluated for their serum resistance and their ability to adhere to fibronectin and bovine fetal fibroblasts. The RAPD analysis was fast, easily performed, and required only a nanogram of DNA. The indistinguishable banding patterns obtained with repeated analyses of 2 isolates from each strain demonstrated that RAPD analysis using standardized beads is a technique that provides reproducible results for typing E. coli strains that cause mastitis in sows. The results of the RAPD analyses demonstrated that E. coli sow mastitis strains are highly variable in serotype, biochemical profiles, virulence factors, and RAPD type, and that all 58 strains can be differentiated by means of the RAPD technique. The strains grouped into 24 RAPD types by combining the results of 2 primers, and into 38 groups by combining the results of serotype and RAPD type. No relationship between serotypes, virulence factors and RAPD types was found.

Multiple mutations in the rpoB gene of Mycobacterium leprae strains from leprosy patients in Thailand.

A new finding is reported of multiple mutations in the rpoB gene of 9 Mycobacterium leprae strains from leprosy patients in Thailand, who did not respond to therapy even when rifampicin, the main drug in multi-drug therapy was used. By means of sequence analysis of 9 Thai M. leprae strains, various mutations in 289 bps of the rpoB gene revealed forms of mutation never before described, such as multiple mutations (ie, mutation at two, three, six, seven, eight and nine positions in the rpoB gene), most of which were point-mutation substitutions (a few of which were silent), and some insertions. This investigation demonstrates that mutation in the rpoB gene of M. leprae strains from Thailand involves more variety than previously reported for rpoB mutation patterns in rifampicin resistance M. leprae strains.

Evolution and clonal traits of Mycobacterium tuberculosis complex in Guinea-Bissau.

Two hundred twenty-nine consecutive isolates of Mycobacterium tuberculosis complex from patients with pulmonary tuberculosis in Guinea-Bissau, which is located in West Africa, were analyzed for clonal origin by biochemical typing and DNA fingerprinting. By using four biochemical tests (resistance to thiophene-2-carboxylic acid hydrazide, niacin production, nitrate reductase test, and pyrazinamidase test), the isolates could be assigned to five different biovars. The characteristics of four strains conformed fully with the biochemical criteria for M. bovis, while those of 85 isolates agreed with the biochemical criteria for M. tuberculosis. The remaining 140 isolates could be allocated into one of three biovars (biovars 2 to 4) representing a spectrum between the classical bovine (biovar 1) and human (biovar 5) tubercle bacilli. By using two genotyping methods, restriction fragment length polymorphism analysis with IS6110 (IS6110 RFLP analysis) and spoligotyping, the isolates could be separated into three groups (groups A to C) of the M. tuberculosis complex. Group A (n = 95), which contained the majority of classical human M. tuberculosis isolates, had large numbers of copies of IS6110 elements (mean number of copies, 9) and a distinctive spoligotyping pattern that lacked spacers 33 to 36. Isolates of the major group, group B (n = 119), had fewer IS6110 copies (mean copy number, 5) and a spoligotyping pattern that lacked spacers 7 to 9 and 39 and mainly comprised isolates of biovars 1 to 4. Group C isolates (n = 15) had one to three IS6110 copies, had a spoligotyping pattern that lacked spacers 29 to 34, and represented biovar 3 to 5 isolates. Four isolates whose biochemical characteristics conformed with those of M. bovis clustered with the group B isolates and had spoligotype patterns that differed from those previously reported for M. bovis, in that they possessed spacers 40 to 43. Interestingly, isolates of group B and, to a certain extent, also isolates of group C showed a high degree of variability in biochemical traits, despite genotypic identity in terms of IS6110 RFLP and spoligotype patterns. We hypothesize that isolates of groups B and C have their evolutionary origin in West Africa, while group A isolates are of European descent.

Synthesis and immunologic characterisation of Mycobacterium tuberculosis lipoarabinomannan specific oligosaccharide-protein conjugates.

Lipoarabinomannan (LAM) is a major structural surface component of all mycobacteria, and has been reported to have a wide range of biological effects. Immunogenic LAM specific oligosaccharide protein conjugates were synthesized and immunologically characterized. Oligosaccharides were derived from LAM purified from Mycobacterium tuberculosis H37 Rv and covalently conjugated to tetanus toxoid and cross reactive mutant (CRM197) diphtheria toxoid. Both types of LAM oligosaccharide protein conjugates proved to be highly immunogenic, inducing a boosterable T helper cell dependent IgG response. These conjugates are currently evaluated as components in a subcellular experimental TB vaccine.