Long-lasting effect of mercury contamination on the soil microbiota and its co-selection of antibiotic resistance

Antibiotic resistance genes (ARGs) in the environment are an exposure risk to humans and animals and is emerging as a global public health concern. In this study, mercury (Hg) driven co-selection of ARGs was investigated under controlled conditions in two Australian non-agricultural soils with differing pH. Soils were spiked with increasing concentrations of inorganic Hg and left to age for 5 years. Both soils contained ARGs conferring resistance to tetracycline (tetA, tetB), sulphonamides (sul1), trimethoprim (dfrA1) and the ARG indicator class 1 integron-integrase gene, intI1, as measured by qPCR. The last resort antibiotic vancomycin resistance gene, vanB and quinolone resistance gene, qnrS were not detected. Hg driven co-selection of several ARGs namely intI1, tetA and tetB were observed in the alkaline soil within the tested Hg concentrations. No co-selection of the experimental ARGs was observed in the neutral pH soil. 16S rRNA sequencing revealed proliferation of Proteobacteria and Bacteriodetes in Hg contaminated neutral and alkaline soils respectively. Multivariate analyses revealed a strong effect of Hg, soil pH and organic carbon content on the co-selection of ARGs in the experimental soils. Additionally, although aging caused a significant reduction in Hg content, agriculturally important bacterial phyla such as Nitrospirae did not regrow in the contaminated soils. The results suggest that mercury can drive co-selection of ARGs in contaminated non-agricultural soils over five years of aging which is linked to soil microbiota shift and metal chemistry in the soil.

Inadequate adherence to antiretroviral treatment and prevention in hospital and community sites in Burkina Faso and Mali: a study by the ATARAO group

Our objective was to determine the prevalence and identify the factors that influence antiretroviral therapy (ART) adherence among patients in Bamako and Ouagadougou. A cross-sectional study was conducted among 94 men and 176 women receiving ART. Data were collected through questionnaires and chart reviews. Logistic regressions were performed to isolate determinants of adherence.

Overall, 58% of the patients were adherent, but there were differences in the levels of adherence according to country and treatment site. Sociodemographic factors were not associated with adherence. However, social characteristics such as having children, in Ouagadougou, or being a housewife and not planning to have a child in the next year, in Bamako were associated with adherence. Time on ART was negatively associated with adherence in both countries with decline occurring later in Bamako.

Levels of adherence are inadequate particularly among more experienced patients. Further adherence research and monitoring using longitudinal designs are warranted to assess the extent to which adherence is declining with time on treatment.

High level of primary drug resistance in Mali

BACKGROUND

As access to antiretroviral drugs increases in developing countries, it will become increasingly important to monitor the emergence of resistance and to define the molecular pathways involved to identify optimal therapeutic regimens.

METHODS

We performed genotypic resistance testing on plasma obtained from 101 HIV-infected treatment-naïve individuals from Mali. Genotyping was carried out using the Virco protocols and HXB2 was used as the reference strain.

RESULTS

CRF02_AG was the most common subtype, present in 71.3% of our patient population. Other subtypes included B, C, G, CRF06_CPX, CRF09_CPX, CRF01_AE, A2/CRF16_A2D, A1 and CRF13_CPX. A total of 9.9% [95% confidence interval (CI) 6.9-12.9%] of patients had at least one resistance mutation. The prevalences of mutations conferring resistance to nucleoside reverse transcriptase inhibitors (NRTIs), nonnucleoside reverse transcriptase inhibitors (NNRTIs) and protease inhibitors (PIs) were 5% (95% CI 0.7-9.2%), 6% (95% CI 1.3-10.6%) and 0%, respectively. The most frequent mutations were T215A/Y for NRTIs and K103N/T for NNRTIs. One patient harboured three NRTI resistance mutations and one NNRTI mutation. This is the first reported case of multi-drug-resistant viral transmission in Mali. Polymorphisms at protease codons 10I/V and 33F potentially associated with resistance were observed in 18.8% and 1% of patients, respectively. Several polymorphisms in the C-terminal domain of reverse transcriptase were observed: A371V (in 63.4% of patients), G335D (76.2%), E399D (10.9%) and G333E (1%).

CONCLUSION

Primary resistance was seen in 9.9% of subjects, which is higher than previously reported in Mali. Taking into consideration other polymorphisms in protease such as L10I/V and 33F, primary resistance could reach 28.7% (95% CI 19.9-37.5%). Our study reflects the need to monitor the evolution of resistance on a regular basis and trends of transmitted resistance.

MHC haplotype and susceptibility to experimental infections (Salmonella Enteritidis, Pasteurella multocida or Ascaridia galli) in a commercial and an indigenous chicken breed

In three independent experimental infection studies, the susceptibility and course of infection of three pathogens considered of importance in most poultry production systems, Ascaridia galli, Salmonella Enteritidis and Pasteurella multocida were compared in two chicken breeds, the indigenous Vietnamese Ri and the commercial Luong Phuong. Furthermore, the association of the Major Histocompatibility Complex (MHC) with disease-related parameters was evaluated, using alleles of the LEI0258 microsatellite as markers for MHC haplotypes. The Ri chickens were found to be more resistant to A. galli and S. Enteritidis than commercial Luong Phuong chickens. In contrast, the Ri chickens were more susceptible to P. multocida, although production parameters were more affected in the Luong Phuong chickens. Furthermore, it was shown that the individual variations observed in response to the infections were influenced by the MHC. Using marker alleles of the microsatellite LEI0258, which is located within the MHC region, several MHC haplotypes were identified as being associated with infection intensity of A. galli. An association of the MHC with the specific antibody response to S. Enteritidis was also found where four MHC haplotypes were shown to be associated with high specific antibody response. Finally, one MHC haplotype was identified as being associated with pathological lesions and mortality in the P. multocida experiment. Although not statistically significant, our analysis suggested that this haplotype might be associated with resistance. These results demonstrate the presence of local genetic resources in Vietnamese chickens, which could be utilized in breeding programmes aiming at improving disease resistance.

Fishborne zoonotic trematodes in raw fish dishes served in restaurants in Nam Dinh Province and Hanoi, Vietnam

Fishborne zoonotic trematode (FZT) parasites are a serious food safety problem in Asian countries because of their tradition of eating raw fish. In northern Vietnam, the prevalence of FZT metacercariae (MC) in wild-caught and cultured fish is quite high. The objective of this study was to assess the risk for acquiring these parasites from raw fish dishes prepared in restaurants. Samples of fish meat (body muscle) and remainder parts (head, gills, fins, skin, and muscle tissue from the tail) were obtained from 39 restaurants located in Nam Dinh province, an area endemic for FZTs, and from 74 restaurants in the capital city of Hanoi. Six species of zoonotic intestinal trematodes were recovered from a total of nine freshwater and brackish water fish species. Overall, the prevalence of MC in meat samples was 6.1% and in remainder samples, 34.9%; freshwater fish were more often infected (39.4%) than brackish water species (16.0%). Dishes from Nam Dinh restaurants were more often infected (11.8%) than those from Hanoi (3.1%). The dominant trematode species, Haplorchis pumilio, exhibited a strong predilection for encystment in remainder fish parts (36.5%) compared with meat (3.9%). The mean density of MC in meat samples overall was low (1.0 to 1.5 MC per 50 g); however, the potential for parasites to accumulate over years of eating raw fish could result in significant clinical disease, as occurs with liver flukes. Also, the high densities of MC in the remainder parts (2.3 to 72.9 MC per 50 g) pose a threat for cross-contamination during dish preparation.

Camelid immunoglobulins and nanobody technology

It is well established that all camelids have unique antibodies circulating in their blood. Unlike antibodies from other species, these special antibodies are devoid of light chains and are composed of a heavy-chain homodimer. These so-called heavy-chain antibodies (HCAbs) are expressed after a V-D-J rearrangement and require dedicated constant gamma-genes. An immune response is raised in these so-called heavy-chain antibodies following classical immunization protocols. These HCAbs are easily purified from serum, and the antigen-binding fragment interacts with parts of the target that are less antigenic to conventional antibodies. Since the antigen-binding site of the dromedary HCAb is comprised in one single domain, referred to as variable domain of heavy chain of HCAb (VHH) or nanobody (Nb), we designed a strategy to clone the Nb repertoire of an immunized dromedary and to select the Nbs with specificity for our target antigens. The monoclonal Nbs are well produced in bacteria, are very stable and highly soluble, and bind their cognate antigen with high affinity and specificity. We have successfully developed recombinant Nbs for research purposes, as probe in biosensors, to diagnose infections, and to treat diseases like cancer or trypanosomosis.

Gender-related factors influencing HIV serostatus disclosure in patients receiving HAART in West Africa

Disclosure of HIV serostatus remains an important tool for the prevention of new infections and early initiation of treatment for HIV-positive individuals' regular sexual partners. Our aim is to identify factors associated with disclosure to partner in patients taking antiretroviral treatment, with a gender- and sex-based approach. In this study conducted in Mali and Burkina Faso, men (154) and women (164) who reported being in a marital or cohabitating relationship were included. Sex-specific bivariate analyses and multivariate logistic regression were performed to identify determinants of disclosure. Disclosure to partner was 72.1% in men and 79.9% in women. Results of bivariate and multivariate analyses indicated that cohabiting with partner was strongly associated with disclosure in both men and women. In men only, older age, literacy and having good communication with the treating doctor were significantly associated with disclosure. Among women, disclosure was associated with having children and high self-reported importance of religion. Future research and interventions promoting disclosure should take into account these differences reflecting the social construction of gender roles in these settings.

Prevalence of multiresistant Gram-negative organisms in a surgical hospital in Ho Chi Minh Cit, Vietnam

OBJECTIVE

To determine resistance patterns of multiresistant Gram-negative organisms at a surgical hospital in Ho Chi Minh City, Vietnam, in order to guide appropriate antibiotic prescribing and improve infection control procedures.

METHOD

All samples sent in for microbiological analysis over a 3-month period were included. A resource neutral double disc-diffusion test was introduced to detect the presence of extended-spectrum beta-lactamase (ESBL) production.

RESULTS

We obtained 350 bacterial isolates from clinical specimens; 87.4% were Gram-negative bacteria (GNB). Of these, 88.9% were Enterobacteriaceae, of which 14.7% produced ESBL. Fifteen (37.5%) of these were isolated within 48 h of admission. Resistance to gentamicin and ciprofloxacin occurred in 70.0% and 72.5% of those organisms that produced ESBL and in 39.5% and 38.7% of those that did not. Resistance to third-generation cephalosporins was common: 36.7% of all GNB were resistant to ceftriaxone, 34.0% to cefotaxime, 19.6% to ceftazidime and 36.7% to cefoperazone.

CONCLUSION

Multiresistant Gram-negative organisms are common and pose a challenge to antibiotic therapy. Successful implementation of a simple test to detect ESBL production allowed reporting of these organisms, appropriate antibiotic prescribing and infection control interventions. Development of antibiotic-prescribing guidelines must take into account these resistance patterns.

A longitudinal study to identify constraints to dairy cattle health and production in rural smallholder communities in Northern Vietnam

The objective of the study was to investigate constraints to dairy cattle health and production in rural smallholder communities in northern Vietnam, one of the target areas of the Vietnam government's dairy development programme. A total of 99 dairy farms (11 per commune) were recruited from 9 of 32 communes in Ba Vi District, using random two-stage cluster sampling. After the initial questionnaire interviews were conducted, farms were visited at three monthly intervals over a period of 1 year. Information on several health and production parameters relating to the study cattle was collected. Using multiple indicator modelling, it was found that Fasciola infestation, farmers who had been involved in dairying for longer (not indicative of better management skills), larger herd size, and cattle being kept in a shed were linked to reduced reproductive performances.

Taenia solium taeniasis and cysticercosis in three communities in north Vietnam

OBJECTIVES

(1) To investigate the response to a serum antigen-detecting ELISA for cysticercosis and a stool coproantigen test for taeniasis in two rural communities (mountainous and coastal areas) and one group of (peri-)urban factory workers; and (2) to examine clinical features of human cysticercosis in northern Vietnam.

METHODS

Villagers and factory workers and their families were informed and invited to participate in the study. Blood and faecal samples were collected from the participants and a simple questionnaire on taeniasis/cysticercosis completed. Serum was examined for the presence of circulating cysticercus antigen by a monoclonal-based sandwich ELISA. Ag-ELISA positive persons underwent a clinical examination and a computed tomography (CT) scan. Stool samples were examined microscopically for the presence of Taenia eggs and for copro-antigens. Tapeworms were identified following therapeutic expulsion using morphology and PCR-RFLP.

RESULTS

Circulating cysticercus antigens, suggesting active infection, were detected in 5.3% (16/303), 0.6% (1/175) and 0.0% (0/229) of the sampled individuals from the mountainous, coastal and urban regions, respectively. Clinical examination and CT scan of the cysticercus antigen positive persons showed that active cysticercosis did not cause severe disease in most cases. Taenia copro-antigens were found in 0.3% (1/297), 1.8% (3/166) and 0.0% (0/228) of the stool samples from the mountainous, coastal and urban communities, respectively. Three tapeworms were expelled after treatment: two Taenia solium and one Taenia saginata.

CONCLUSION

This survey points to a focal distribution of taeniasis/cysticercosis and suggests that human cysticercosis is rather acquired due to close contact with a T. solium carrier and self-infection, than through infection from the environment.

Effects of drug resistance on viral load in patients failing antiretroviral therapy

Previous studies on patients who develop drug resistant HIV-1 variants have shown that continued use of failing regimens might provide clinical benefit. However, the effect of long-term exposure to drug resistant variants may lead to emergence of compensatory mutations that may jeopardize this effect. In this study, we assess associations among type and number of drug resistant mutations, viral load and disease progression in patients with long-term follow up. Patients with genotypic testing performed at the time of treatment failure were enrolled. Comparison of viral load and CD4 cell count between different resistance groups was performed using analysis of variance. Multiple linear regression analysis was performed to assess the simultaneous effects of the presence of particular mutations and their accumulation on viral load. Data from 475 patients who were followed for a median of 43 months from October 1999 to July 2005 were studied. A "V shape" relationship was observed between the number of mutations and viral load. Specifically, in patients harboring up to five mutations, viral load was reduced by 0.8 log/copies when compared to wild-type variants. However, with more than six mutations viral load progressively increased. Certain reverse transcriptase mutations such as M184V/I, K70R, V108I, and protease mutations such as L33FIV, M84V, and M36I were associated with reduced viral load. Together, these findings suggest that long-term maintenance of a sub-optimal antiretroviral regimen may have deleterious consequences for the patient.

Emergence and evolution of functional heavy-chain antibodies in Camelidae

Antibodies of jawed-vertebrates are composed of paired heavy (H) and light (L) polypeptide chains. Surprisingly, the sera of camelids, nurse shark and wobbegong shark, and possibly ratfish contain antibodies that lack L-chains. In camelids, these Heavy-chain antibodies (HCAbs) are gamma-isotypes, and are functional in antigen binding. In this review we focus on the dedicated immunoglobulin (Ig) genes that encode the HCAb in Camelidae (camels, dromedaries and llamas), about their origin, and how these camel immunoglobulins evolved and acquire a large and diverse repertoire of antigen binding sites in absence of the H-L combinatorial diversity.

Camel heavy-chain antibodies: diverse germline V(H)H and specific mechanisms enlarge the antigen-binding repertoire

The antigen-binding site of the camel heavy-chain antibodies devoid of light chain consists of a single variable domain (V(H)H) that obviously lacks the V(H)-V(L) combinatorial diversity. To evaluate the extent of the V(H)H antigen-binding repertoire, a germline database was constructed from PCR-amplified V(H)H/V(H) segments of a single specimen of Camelus dromedarius. A total of 33 V(H)H and 39 V()H unique sequences were identified, encoded by 42 and 50 different genes, respectively. Sequence comparison indicates that the V(H)Hs evolved within the V(H) subgroup III. Nevertheless, the V(H)H germline segments are highly diverse, leading to a broad structural repertoire of the antigen-binding loops. Seven V(H)H subfamilies were recognized, of which five were confirmed to be expressed in vivo. Comparison of germline and cDNA sequences demonstrates that the rearranged V(H)Hs are extensively diversified by somatic mutation processes, leading to an additional hypervariable region and a high incidence of nucleotide insertions or deletions. These diversification processes are driven by hypermutation and recombination hotspots embedded in the V(H)H germline genes at the regions affecting the structure of the antigen-binding loops.

Protection of immunoreactivity of dry immobilized proteins on microtitration plates in ELISA: application for detection of autoantibodies in myasthenia gravis

We show the ability of the BSA-trehalose film to convert normally fragile proteins such as mouse monoclonal antibody to the Alzheimer precursor protein A4 (APP695) and cell line TE671 acetylcholine receptor (AChRTE671) into a stable reagent, after its immobilization on microtitration plates. The remarkable property of the dry immobilized proteins are their stability under prolonged exposure to temperatures as high as 50 degrees C. Using the AChRTE671, the proposed method was applied for the measurement of anti-AChR autoantibodies in Myasthenia gravis by means of an enzyme-linked immunosorbent assay (ELISA). The test was shown to be specific and able to detect anti-AChR autoantibodies at concentrations as low as 3 nM. Using the same AchRTE671 as antigen, the results of examination of 34 serum samples for detection of anti-AChR autoantibodies by ELISA were compared with those of the conventional radioimmunoprecipitation assay (RIA). It was concluded that ELISA is another useful method for the diagnosis of M. gravis. The ELISA method offers a rapid, simple, safe and inexpensive means for mass screening of M. gravis.

[Reactions of cells of nasal and sinusoidal mucosa of goats and sheep naturally infected by Oestrus ovis Linné 1758 (Diptera: Oestridae)]

OEstrosis is a very common myiasis of sheep and goats in mediterranean and tropical countries. Goats are suitable hosts for OEstrus ovis but the parasitic burden remain lower than in sheep. Cellular responses (mucous and serous mast cells, eosinophis and globules leucocytes) were measured in 30 infected and 30 non infected sheep and in 23 infected and 24 non infected goats. The presence of OEstrus ovis larvae led to an important inflammatory response in sheep and in goats as well. Furthermore, the intensity of the cellular response correlated with the larva burden, specially with globules leucocytes and eosinophils. Nevertheless, huge differences occurred between sheep and goats responses even in similar larval burden range. Infected sheep showed larger counts of mucous mast cells than goats, the differences were smaller in serous mast cells and eosinophils and no difference was detected in globules leucocytes (intraepithelial mast cells) counts between the two hosts species. These results were compared with those obtained in gastro-intestinal strongyles infections.

Loss of splice consensus signal is responsible for the removal of the entire C(H)1 domain of the functional camel IGG2A heavy-chain antibodies

The molecular basis for the absence of the C(H)1 domain in naturally occurring heavy-chain antibodies of the camelids was assessed by determining the entire Camelus dromedarius gamma2a heavy-chain constant gene. The organization of the camel gamma2a constant heavy-chain gene obtained from a liver genomic library appears to be typical of all other mammalian gamma genes sequenced to date. It contains the switch, CH1, hinge, CH2, CH3, M1 and M2 exons. In contrast to the case in mouse and human heavy chain diseases, the camel gamma2a gene shows no major structural defect, and its equivalent CHI exon is intact. However, sequence analysis has revealed that the splicing site, immediately after the CH1 exon, is defective due to point mutations, especially the G(+1) to A(+1) transversion seems to be detrimental. It is concluded that the loss of the splice consensus signal is responsible for the removal of the entire CH1 domain in camel gamma2a heavy-chain immunoglobulins. Additionally, a closer analysis of the hinge exon suggests the possible involvement of transposons in the genetic variation of mammalian Cgamma hinges.

'LABNOTE', a laboratory notebook system designed for academic genomics groups

We have developed a relational laboratory database system, adapted to the daily book-keeping needs of laboratories that must keep track of information acquired on hundreds or thousands of clones in an effective and user-friendly fashion. Data, whether final or related to experiments in progress, can be accessed in many different ways, e.g. by clone name, by gene, by experiment or through DNA sequence. Updating, import and export of results is made easier by specially developed tools. This system, in network version, serves several groups in our Institute and (over the Internet) elsewhere, and is instrumental in collaborative studies based on expression profiling. It can be used in many similar situations involving progressiveaccumulation of information on sets of clones or related objects.

The specific variable domain of camel heavy-chain antibodies is encoded in the germline

The variable domains of the functional heavy-chain antibodies (VHHs) discovered in camels are related to the human VH subgroup III. They are nevertheless clearly distinguishable from the VHs of conventional four-chain immunoglobulins by the presence of important amino acid substitutions, located in the solvent-exposed surface normally covered by the variable domain of the light chain. The analysis of an unrearranged dromedary DNA library revealed that the specific VHH gene with its characteristic amino acid substitutions is encoded in the germline. Therefore, it is concluded that the VHHs do not arise through an ontogenic process of somatic hypermutation. The presence of putative DNA recombination signals that are more prevalent in the camel VHH, compared to the VH germline gene, might play a role in the formation and efficient expansion of the VHH repertoire.

[Mast cells and eosinophils of the respiratory mucosa of sheep with Oestrus ovis (Linné, 1761) infection]

Mast cells and eosinophils have been identified by differential stainings and counted in mucous membrane of nasal septum, turbinates and sinus of 77 ewes naturally infected with Oestrus ovis. Results have been compared with those of nine parasite free lambs. Anova tests indicate significant differences between infected and parasite-free sheep for the cell numbers and their distribution among the septum, the turbinates and the sinus and according to their position in mucous membrane, interglandular chorion of sub-mucosa. In infected sheep, the mean number of mast cells is twice the number present in parasite free animals. The burdens of eosinophils are multiplied by 17 for the septum, 29 for the turbinates and 58 for the sinus. The hypothesis of the development of an hypersensitivity phenomenon in ovine oestrosis is sustained by these results.

[Ca++ ion transport blockers as reversants of the drug resistance of malarial parasites. 1. The effect of verapamil on the resistance to chloroquine in vivo of Plasmodium berghei and in vitro of Plasmodium falciparum]

The reversing action of verapamil on the effect of chloroquine was found in in vivo experiments by using a model P. berghei resistant to chloroquine, an LNK65 isolate having a naturally lower resistance to the agent, and its polyresistant strain with the acquired resistance to chloroquine and fansidar, as well as by employing the chlorine-resistant P. falciparum isolates from the south of the Socialist Republic of Vietnam. The magnitude of this effect was related to the dose of verapamil, the frequency of administration of a combination of the agents in vivo, while that was associated to the concentration of verapamil and the level of isolate resistance to chloroquine in vitro which was the most pronounced. Taking into account the dose-dependent effect of verapamil, it can be suggested that increasing its concentration in combination with chloroquine can provide a more marked reversing action with lower chloroquine concentrations. The parameters accepted by the authors in evaluating the combined effect enable the effect of the verapamil/chloroquine concentration to be regarded as potentiation.

Evaluation of an enzyme-linked immunosorbent assay for detection of antibodies to bovine leukemia virus in serum and milk

The results of examination of 375 bovine serum and 150 bovine milk samples for detection of bovine leukemia virus infection by the immunodiffusion technique were compared with those of an enzyme-linked immunosorbent assay (ELISA). It was concluded that the ELISA is another useful method for the detection of antibodies to bovine leukemia virus in serum and milk. The ELISA provides a quantitative result and has the advantage of being more sensitive and less time-consuming than the conventional immunodiffusion technique.

Immobilized enzyme electrode for creatinine determination in serum

An immobilized enzyme electrode for continuous creatinine determination in blood serum is described. The enzymes creatinine amidohydrolase, creatine amidinohydrolase, and sarcosine oxidase are coimmobilized to the surface of the polypropylene membrane of a Clark-type electrode responsive to oxygen. The immobilized enzymes catalyze the decomposition of creatinine with the consumption of oxygen and thus permit the creatinine measurement. The whole assay takes less than 1 min. Effects of pH and temperature on electrode response are also described. The proposed technique offers a rapid, simple, and inexpensive means to determine creatinine in blood serum within the normal and abnormal ranges. The repeatability of the creatine determination in serum is 2.5% (relative standard deviation), and the detection limit is 3 x 10(-6) mol L-1. The results obtained by this method were compared to those obtained with the Technicon AutoAnalyzer SMAC system based on the Jaffé reaction; the correlation factor between the two methods was found to be r = 0.9997.

[The efficacy of and tolerance for fansimef in the treatment of tropical malaria in the south of the Socialist Republic of Vietnam]

The efficacy of and tolerance to fancimef in 49 patients was compared to the efficacy of and tolerance to quinine in combination with fansidar in 33 patients with moderate P. falciparum malaria. A good tolerance to and a high efficacy of fancimef have been shown, which was manifested in rapid fever arrest, disappearance of parasitemia, absence of the disease relapses, which were observed in 2 patients on quinine combined with fansidar. The advantage of fansimef is one-time administration of the total course dose.

Enzyme immunoassay (ELISA) for detection of Clostridium difficile toxin B in specimens of faeces

Antisera against Clostridium difficile toxin B were prepared in sheep and rabbit and were used in indirect and sandwich enzyme-linked immunosorbent assays (ELISA) for the detection of toxin B. Polyvinyl chloride and polystyrene microtitration plates were tested as solid phases for the assay. Both assays had a lower limit of detection for toxin B of 1 ng/ml. They were used to detect the presence of toxin B in 210 human faecal specimens and also in the culture supernatant fluids of C. difficile strains isolated from the faecal samples. There was a close correlation between the results of sandwich ELISA and those of cytotoxicity tests and isolation of C. difficile. Our sandwich ELISA method seems to be useful as a presumptive test for detection of C. difficile toxin B.

Double-blind studies with mefloquine alone and in combination with sulfadoxine-pyrimethamine in 120 adults and 120 children with falciparum malaria in Vietnam

In 120 adult Vietnamese patients with uncomplicated falciparum malaria the efficacy of, and tolerance to, mefloquine (M) vs the combination of mefloquine + sulfadoxine + pyrimethamine (MSP) was studied in a double-blind, randomized comparative trial with chloroquine. Also, a double-blind dose finding study of MSP was performed in 120 Vietnamese children with uncomplicated falciparum malaria. In the adults the mean parasite clearance time with M was 3.8 d and with MSP 3.6 d. Defervescence occurred in 2.9 and 3.0 d respectively for M and MSP. There was a 36.8% resistance rate in 38 patients treated with chloroquine. 96% of the children were sensitive or showed a delayed RI response. The lowest dose of MSP (10 mg/kg M + 20 mg/kg S + 1.0 mg/kg P, 1 tablet Fansimef) was as effective as 1.5-2x this dose in children weighing 23-30 kg. Side effects were mild, except for vomiting which required alternative therapy in 4 patients.

Clostridium difficile toxin B: characterization and sequence of three peptides

The cytotoxin, also named toxin B, was isolated from a toxigenic strain of Clostridium difficile, purified to homogeneity and partially characterized. The purification procedure included ultrafiltration followed by anion-exchange chromatography. We noticed that a non-specific nucleic material eluted with the protein during the purification. The presence of these nucleic acids appeared to be important for the toxic activity of the protein. Some characteristics of the cytotoxin were examined, especially the amino acid composition and the sequence of three tryptic fragments.