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S Lauwers

Publications and source records attributed to S Lauwers.

At least 19 recordsLinked to original sources
PubMed2005

Biologically active bisbenzylisoquinoline alkaloids from the root bark of Epinetrum villosum.

Methanol and water extracts of the root of Epinetrum villosum (Exell) Troupin (Menispermaceae) were found to exhibit antimicrobial and antiplasmodial activities. Investigation of the active methanol fraction led to the isolation of four bisbenzylisoquinoline alkaloids, i.e., cycleanine, cycleanine N-oxide, isochondodendrine and cocsoline. Structures were established by spectroscopic methods. Cocsoline displayed antibacterial and antifungal activities (MIC values of 1000-15.62 and 31.25 microg/ml, respectively). Isochondodendrine was found to have the most potent antiplasmodial activity (IC50 = 0.10 microg/ml), whereas the IC50 on HCT-116 human colon carcinoma cells was 17.5 microg/ml (selectivity index 175). Cycleanine acted against HIV-2 (EC50=1.83 microg/ml) but was at least 10-fold less active against HIV-1. Cycleanine N-oxide showed no activity towards all tested microorganisms.

Alkaloids↗
PubMed2005

External quality assessment for molecular detection of Bordetella pertussis in European laboratories.

Although the PCR for the detection of Bordetella pertussis is routinely performed in diagnostic laboratories, no quality assessment program has so far been described. We report on the results obtained with two external quality assessment proficiency panels sent to European laboratories. The first proficiency panel contained a series of dilutions of three previously characterized B. pertussis clinical isolates and two negative controls. No false-positive results were reported by six laboratories providing seven data sets. The reported limits of detection of the three B. pertussis strains varied between 4 and 4,000, 9 and 9,000, and 3 and 30,000 CFU/ml, respectively. The second proficiency panel, composed of a series of dilutions of reference strains of B. pertussis, B. holmesii, B. hinzii, and B. bronchiseptica, as well as negative controls, was sent to nine laboratories. One laboratory reported a negative result for a sample and reported a B. parapertussis-positive sample to be positive for B. pertussis. By using the B. pertussis-specific target gene pertactin, one laboratory detected B. pertussis with 100% specificity. All other laboratories, which used IS481-based assays, reported positive results for the samples containing B. holmesii and B. bronchiseptica, species that have occasionally been recovered from human respiratory samples. These data show that the choice of the target gene is particularly critical for the species specificity of B. pertussis PCR assays.

Bordetella pertussis↗
PubMed2004

[Screening for Staphylococcus aureus with a reduced susceptibility to vancomycin in: a Belgian hospital].

The aim of the present study was to investigate the prevalence of vancomycin resistance in clinical methicillin resistant Staphylococcus aureus (MRSA) isolates in our hospital by screening on Mueller-Hinton agar with 5 mg/l teicoplanin (MH-Teico), as recommended by the Comite de l'Antibiogramme of the Societe Francaise de Microbiologie (CA-SFM). Seventeen of 1002 clinical MRSA isolated from 404 patients showed in 2003 growth of at least four colonies on this medium, but only one was confirmed as homogeneous vancomycin-resistant S. aureus (VISA) and five as heterogeneous VISA (hVISA) by population analysis. None of the patients presented with severe infection but awareness is needed and screening on MH-Teico as recommended by CA-SFM is a convenient method. Surveillance should be focused on patients with risk factors for selection of such strains: patients with a prolonged course of glycopeptide therapy and persistence of MRSA infection or colonization.

Anti-Bacterial Agents↗
PubMed2003

Quantitative RT-PCR ELISA to determine the amount and ratio of positive- and negative strand viral RNA synthesis and the effect of guanidine in poliovirus infected cells.

Quantitative reverse transcription-polymerase chain reaction enzyme linked immunosorbent assay (RT-PCR ELISA) is the method of choice to study positive- and negative strand viral RNA synthesis during poliovirus replication. In comparison with other methods used for this purpose, it fulfils all necessary requirements to accurately determine RNA of different polarity. It combines high specificity, high sensitivity, safety, speed, and the ability to perform quantitative analysis. The enterovirus specific RT-PCR ELISA method described in this work, was used to determine quantitatively the amount of de novo poliovirus positive- and negative strand RNA synthesis at different time-points in the viral replication cycle, both in presence and absence of the viral RNA synthesis inhibitor guanidine hydrochloride.

Biotin↗
PubMed2002

Pan-European study on culture-proven Legionnaires' disease: distribution of Legionella pneumophila serogroups and monoclonal subgroups.

This pan-European study included unrelated strains of Legionella pneumophila obtained from 1335 cases of Legionnaires' disease. The isolates were serotyped into the serogroups 1 to 15 by monoclonal antibodies (MAb) and/or rabbit antisera. Additionally, MAb subgrouping was undertaken for isolates belonging to serogroups 1, 4, and 5. Monoclonal types of serogroup 1 were subdivided as having, or not having, the virulence-associated epitope recognized by the MAb 3/1 (Dresden Panel). This epitope is not present on strains belonging to any other serogroups. Taking all Legionella incidents together, MAb 3/1-positive cases were most frequent (66.8%); 11.7% of the isolates belonged to MAb 3/1-negative serogroup 1 subgroups and 21.5% to other serogroups, with serogroups 3 and 6 predominating. Among all serotypes discriminated in this study, monoclonal subtype Philadelphia was the most frequent. If categories of infection were considered, the proportion of MAb 3/1-negative strains differed significantly ( P<0.0005) between community-acquired cases (139/510; 27.3%) and travel-associated (42/295; 14.2%) or hospital-acquired infections (176/329; 53.5%). Moreover, taking distribution in different European areas into account, the proportion of MAb 3/1-negative strains was significantly higher in the Scandinavian region than in the Mediterranean countries or the UK for both community-acquired (48.7% vs. 18.6% or 12.0%; P<0.0005) and nosocomial cases (87.7% vs. 32.6% or 52.6%; P</=0.0007).

Animals↗
PubMed2002

Screening and optimisation of an ELISA method for the quantitative detection of enterovirus specific RT-PCR products by means of a two-level experimental design.

In a previous paper, optimal reaction conditions were determined for the RT-PCR part of a quantitative enterovirus specific RT-PCR ELISA method (J. Pharm. Biomed. Anal., 25 (2001) 131-142). In order to obtain a detection limit as low as possible, the ELISA part of the procedure was optimised as well. This was done by investigating the influence of seven factors at three levels in a multivariate approach. A reflected two-level screening design, derived from a Plackett-Burman design, was used. Optimal reaction conditions were established by calculation and by evaluation of the effects of the factors on the measured absorbance of the ELISA detection. Under these conditions, the linear range and detection limit of the test were determined and compared with the ELISA conditions before optimisation. The optimised RT-PCR ELISA will be used to study a possible longitudinal relationship between enteroviruses and the development of multiple sclerosis and juvenile diabetes.

Enterovirus↗
PubMed2001

Screening of an enterovirus specific RT-PCR ELISA method for the quantification of enterovirus genomes in human body fluids by means of a three-level experimental design.

In order to obtain a detection limit as low as possible for a quantitative enterovirus specific RT-PCR ELISA assay, optimal reaction conditions, which give rise to the highest response, need to be determined. This was done by investigating the influence of 13 factors, selected from RT and PCR, in a multivariate approach by means of a well-balanced three-level screening design, derived from a three-level Plackett--Burman design. Optimal reaction conditions could be determined by calculation and evaluation of the effects of the different factors on the response, i.e. the measured absorbance of the ELISA detection. The method will be used to study a possible longitudinal relationship between enteroviruses and the development of multiple sclerosis and juvenile diabetes.

Body Fluids↗
PubMed2001

Development of an enzyme-linked immunosorbent assay for serotyping ureaplasma urealyticum strains using monoclonal antibodies.

Ureaplasma urealyticum comprises 14 serotypes. The existing serotyping methods all use polyclonal antibodies. These methods are time-consuming and labor-intensive, and they cannot always be performed on primary isolates; in addition, the results are difficult to interpret. We developed a new enzyme-linked immunosorbent assay (ELISA) method using serotype-specific monoclonal antibodies (MAbs) to enable the serotyping of U. urealyticum isolates from primary broth cultures. Each of the 14 serotype reference strains was tested against 14 selected MAbs. Homologous reactions were very strong, while heterologous reactions were negligible. Three cross-reactions were observed: MAb 5 cross-reacted with serotype 2, MAb 14 cross-reacted with serotype 3, and MAb 8 cross-reacted with serotype 13. Despite the cross-reactions observed, all the serotype reference strains of U. urealyticum could be identified and differentiated using a combination of MAbs. Reproducibility was analyzed with a fractionated antigenic preparation and with several freshly prepared antigens of the same strain. No significant interrun variation was found with the fractionated antigen, but significant variations in optical density (OD) values were found when freshly prepared antigens were tested. However, the variation in OD values did not influence the overall interpretation of the ELISA: reactions with homologous MAbs were always prominent compared to those of the negative controls. This newly developed ELISA using MAbs seems promising for serotyping of U. urealyticum clinical isolates.

Antibodies, Bacterial↗
PubMed2001

Outbreak of necrotizing enterocolitis associated with Enterobacter sakazakii in powdered milk formula.

We describe an outbreak of necrotizing enterocolitis (NEC) that occurred in the neonatal intensive care unit of our hospital. A total of 12 neonates developed NEC in June-July 1998. For two of them, twin brothers, the NEC turned out to be fatal. Enterobacter sakazakii, a known contaminant of powdered milk formula, was isolated from a stomach aspirate, anal swab, and/or blood sample for 6 of the 12 neonates. A review of feeding procedures revealed that 10 of the 12 patients were fed orally with the same brand of powdered milk formula. E. sakazakii was isolated from the implicated prepared formula milk as well as from several unopened cans of a single batch. Molecular typing by arbitrarily primed PCR (AP-PCR) confirmed, although partially, strain similarity between milk and patient isolates. No further cases of NEC were observed after the use of the contaminated milk formula was stopped. With this outbreak we show that intrinsic microbiological contamination of powdered milk formula can be a possible contributive factor in the development of NEC, a condition encountered almost exclusively in formula-fed premature infants. The use of sterilized liquid milk formula in neonatal care could prevent problems with intrinsic and extrinsic contamination of powdered milk formula.

Bacterial Typing Techniques↗
PubMed2000

The clinical impact of early gram-positive bacteremia and the use of vancomycin after allogeneic bone marrow transplantation.

BACKGROUND: Gram-positive bacteremia (GPB) is an increasing infection after allogeneic bone marrow transplantation (BMT). Our purpose was to identify risk factors for GPB, to evaluate its impact on early mortality and morbidity, and to compare prophylactic with empirical intravenous vancomycin. METHODS AND RESULTS: We studied 89 consecutive BMTs in adult patients. Early GPB occurred in 29% of posttransplantation episodes. T-cell depletion (odds ratio [OR]: 0.18) and vancomycin-prophylaxis (OR: 0.28) reduced the risk of GPB. Mortality at 6 weeks was not significantly different in patients with GPB (15% vs. 9.5%, P = 0.669). GPB was associated with the development of major complications, the use of amphotericin B, and prolonged neutropenia. Vancomycin prophylaxis led to an increased risk of early renal dysfunction (OR: 18.7). CONCLUSION: GPB contributes to overall morbidity during the early post-BMT episode but has no impact on mortality. Vancomycin prophylaxis is effective to reduce GPB but has a negative effect on renal function.

Adolescent↗
PubMed2000

In vitro susceptibility of Enterococcus faecium isolated from food to growth-promoting and therapeutic antibiotics.

A total of 76 E. faecium strains, isolated at retail level from raw poultry meat, cheese, raw pork, and preparations of cheese and raw pork, were tested for their susceptibility and resistance to growth-promoting antibacterials used in animals and antibiotics used therapeutically in humans. All strains were uniformly susceptible to the growth promoters bambermycin and avilamycin. Resistance against bacitracin, virginiamycin and narasin was high among strains from poultry meat. With tylosin, a macrolide antibiotic used therapeutically and for growth promotion, resistance was mainly detected in strains originating from poultry meat, though also in some strains from pork and from pork and cheese preparations. The therapeutic antibiotic dalfopristin/quinupristin did not show full cross-resistance with the growth-promoting antibiotic virginiamycin. With dalfopristin/quinupristin two different levels of resistance were found. Only one E. faecium strain isolated from poultry was resistant to the glycopeptides avoparcin and vancomycin. Only one poultry meat strain was highly resistant to ampicillin. However, nearly all poultry meat strains showed decreased sensitivity. Only 3 out of 24 poultry strains were susceptible to minocycline, while all strains from other origins were susceptible to this tetracycline antibiotic. High-level streptomycin resistance was seen in strains of all origins, though infrequently. High-level gentamicin resistance was not found.

Animal Husbandry↗
PubMed2000

In vitro antimicrobial activity of six medicinal plants traditionally used for the treatment of dysentery and diarrhoea in Democratic Republic of Congo (DRC).

Twenty-four crude extracts derived from six medicinal plants highly valued as antidiarrhoeal agents in Congolese folk medicine were screened for antimicrobial activity against several enteric pathogens. The results of this study indicated that the methanolic and aqueous extracts derived from three of them (Roureopsis obliquifoliolata, Epinetrum villosum and Cissus rubiginosa) possessed prominent antibacterial activity, therefore supporting the ethnomedical uses of these species. In addition, phytochemical analysis of these medicinal plants showed that 1/6 plant sample contained alkaloids, 6/6 triterpenes and/or sterols, 4/6 flavonoids, 3/6 tannins and 5/6 saponins. Anthraquinones were not detected in any of these plants.

Alkaloids↗
PubMed2000

Blinded, multicenter quality control study for the quantification of human immunodeficiency virus type 1 RNA in plasma by the Belgian AIDS reference laboratories.

OBJECTIVE: In order to evaluate the interlaboratory variation of HIV-1 RNA measurements in plasma, the Belgian AIDS reference laboratories organized a blinded multicenter quality control study. METHODS: Atest panel of coded spiked HIV-1 plasma samples reflecting the dynamic range of the assay was composed and distributed. The HIV-1 RNA concentration of these samples was determined by the eight Belgian AIDS reference laboratories by means of the Amplicor HIV-1 Monitor version 1.5 assay. RESULTS: Analysis of the results demonstrated that there was little interlaboratory variation for the high concentration range (4.0-5.7 log10 copies/mL), never exceeding 0.2 log10 copies/mL. However the standard deviation for the low concentration range (2.6-3.9 log10 copies/mL) reached up to 0.22 log10 copies/mL. CONCLUSIONS: Since interlaboratory variability never reached 0.5 log10 copies/mL and each of the laboratories was able to detect four-fold differences in plasma HIV-1 RNA levels, the Amplicor assay can be used in multicenter studies without a centralized analysis of samples. Furthermore, this well-characterized proficiency panel of spiked plasma samples could be used as a standard in the study of interassay comparisons.

Belgium↗
PubMed2000

Development of monoclonal antibodies against Ureaplasma urealyticum serotypes and their use for serotyping clinical isolates.

Monoclonal antibodies (MAbs) against Ureaplasma urealyticum serotype 2, 5, 7, 8, 10, 11, 12, and 13 reference strains were developed. The reactivities of these MAbs with the 14 serotype reference strains was verified by colony immunofluorescence assay and Western blot assay. MAbs against serotypes 2, 7, 10, 11, and 12 were serotype specific, whereas MAbs against serotypes 5, 8, and 13 showed cross-reactivity. All MAbs against serotype 5 were cross-reactive with serotype 2, and one showed, in addition, cross-reactivity to serotypes 9 and 10. Mutual cross-reactivities were observed between MAbs against serotypes 8 and 13. The usefulness of the MAbs for the serotyping of U. urealyticum strains was evaluated by serotyping 21 selected clinical isolates. A complete set of MAbs (the newly developed MAbs and the previously described MAbs against serotypes 1, 3, 4, 6, 9, and 14) as well as a complete set of polyclonal antibodies (PAbs), PAbs 1 to 14, were used. MAbs were able to identify 18 of 21 isolates including 2 isolates with mixed serotypes. Polyreactivity, which occurred with 19 of the 21 isolates with PAbs, was not observed by the use of MAbs. MAbs seem to be a more valuable tool than PAbs for serotyping and could help in investigating a possible link between the expression or variability of the serotype-specific antigens and pathogenicity.

Antibodies, Bacterial↗
PubMed1999

A case-control study of sporadic infection with O157 and non-O157 verocytotoxin-producing Escherichia coli.

Potential risk factors for sporadic verocytotoxin-producing Escherichia coli (VTEC) infection in Belgium were investigated in a matched case-control study. Thirty-seven cases, 8 infected with O157 VTEC strains (all eaeA-positive), 29 with non-O157 VTEC strains (13 eaeA-positive and 16 eaeA-negative) and 69 matched controls were interviewed. In a conditional logistic regression analysis, consumption of fish appeared to be a risk factor for infection (adjusted odds ratio (OR) 3.25, P = 0.04). Contact with dogs (OR 0.27, P = 0.04) and consumption of shellfish (OR 0.19, P = 0.05) showed a negative association, corresponding to a decrease in risk. These findings might be explained if low level environmental exposure to VTEC induces protective immunity. Eating raw meat, a frequent habit in Belgium, or hamburgers, or eating in a fast-food restaurant was not more frequently reported by cases than controls. The exposures causing sporadic infections with VTEC, in particular non-O157 strains, may be very different from those which led to outbreaks, and may account for more cases overall.

Adolescent↗
PubMed1999

The influence of alcohol disinfection of nail samples in the laboratory.

Samples of two hundred finger- and toenails cultured after a 70% alcohol disinfection for 2 min were compared with non-disinfected samples cultured on a classical way. Alcohol treatment caused a significant decrease in isolation of yeast and moulds. Both organisms were cultivated at 25.5 and 31%, respectively, when not treated with alcohol, whereas the isolation rate dropped to 10 and 17.5%, respectively, after alcohol treatment. Isolation of dermatophytes decreased from 27.5 to 23.5% when alcohol disinfection was used. In conclusion, although alcohol disinfection of nail samples in the laboratory effectively decreases the isolation rate of unwanted contaminants on Sabouraud glucose agar without cycloheximide, it hampers the isolation of dermatophytes and pathogenic yeasts on cycloheximide-containing media.

Disinfection↗
PubMed1998

Neonatal infections with Pseudomonas aeruginosa associated with a water-bath used to thaw fresh frozen plasma.

In our 15-bed neonatal intensive care unit (NICU), four new-borns were found to be colonized or infected with Pseudomonas aeruginosa within a period of one week. To identify the outbreak source, three independent studies were performed: epidemiological investigation, environmental surveillance and genotypic typing of isolates. Although epidemiological investigation by a case-control study revealed no conclusive results, the transfusion of fresh frozen plasma (FFP) and human albumin (HA) appeared to be the factor with highest risk. Environmental surveillance and random amplification of polymorphic DNA (RAPD) of isolates identified a water-bath used to warm FFP and HA as the likely reservoir for the outbreak. Further spread of the organism did not occur after elimination of this water-bath from the NICU. RAPD identified in addition an isolate from an infant hospitalized in the NICU five months before the outbreak with a pattern matching the one of the outbreak cluster.

Belgium↗