Biomedical subjects

N van Leeuwen

Publications and source records attributed to N van Leeuwen.

6 recordsLinked to original sources

PubMed2002

Listeria monocytogenes meningitis: serotype distribution and patient characteristics in The Netherlands, 1976-95.

Two hundred and seven cases of listeria meningitis that occurred in The Netherlands over 20 years were reviewed to study associations between Listeria monocytogenes serotype, age, underlying disease, and outcome. The mean annual incidence per 100,000 population was 0.12 in 1981-90, decreasing to 0.07 in 1991-5. Underlying disease was present in 50% of non-neonatal patients, most often haematological malignancy (15%) and the use of immunosuppressive therapy (14%). The meningitis-related case fatality rate was 16%; a significantly higher rate was associated with the presence of underlying disease (30%) or age > or = 70 years (29%). Serotype 4b was most frequent (65%) and L. monocytogenes types 1/2a, 1/2b, or 1/2c (30% of cases) were significantly more often isolated from non-neonatal patients with underlying disease, suggesting a higher virulence of listerial serotype 4b.

Adolescent↗

PubMed1999

Validation of binary typing for Staphylococcus aureus strains.

Most of the DNA-based methods for genetic typing of Staphylococcus aureus strains generate complex banding patterns. Therefore, we have developed a binary typing procedure involving strain-differentiating DNA probes which were generated on the basis of randomly amplified polymorphic DNA (RAPD) analysis. We present and validate the usefulness of 15 DNA probes, according to generally accepted performance criteria for molecular typing systems. RAPD analysis with multiple primers was performed on 376 S. aureus strains of which 97% were methicillin resistant (MRSA). Among the 1,128 RAPD patterns generated, 66 were selected which identified 124 unique DNA fragments. From these amplicons, only 12% turned out to be useful for isolate-specific binary typing. The nature of the RAPD-generated DNA fragments was investigated by partial DNA sequence analysis. Several homologies with known S. aureus sequences and with genes from other species were discovered; however, 87% of the probe sequences are of previously unknown origin. The locations of most of the DNA probes on the chromosome of S. aureus NCTC 8325 were determined by hybridization. Seven fragments were randomly dispersed along the genome, five were clustered within the 2500- to 2600-kb position of the genome, and the remaining four did not recognize complementary sequences in S. aureus NCTC 8325. A total of 103 S. aureus strains (69% MRSA) were used for the validation of the binary typing technique. The 15 DNA probes provided stable epidemiological markers, both in vitro (type consistency after serial passages on culture media) and in vivo (comparison of sequential isolates recovered from cases of persistent colonization). The discriminatory power of binary typing (D = 0.998) exceeded that of pulsed-field gel electrophoresis (D = 0.966) and RAPD analysis (D = 0.949). Reproducibility, measured by analyzing multiple strains belonging to a multitude of different epidemiological clusters, was comparable to that of other genotyping techniques used. Contribution of the DNA probes to the discriminatory power of the system was analyzed by comparison of dendrograms. This study demonstrates that binary typing is a robust tool for the genetic typing of S. aureus isolates.

Base Sequence↗

PubMed1999

Rapid slide latex agglutination test for detection of methicillin resistance in Staphylococcus aureus.

The MRSA screen test (Denka Seiken Co., Ltd.), a commercially available, rapid (20-min) slide latex agglutination test for the determination of methicillin resistance by detection of PBP 2a in Staphylococcus aureus, was compared with the oxacillin agar screen test and PCR detection of the mecA gene. A total of 563 S. aureus isolates were tested. Two hundred ninety-six of the isolates were methicillin-susceptible isolates from cultures of blood from consecutive patients. Also, 267 methicillin-resistant isolates that comprised 248 different phage types were tested. Methicillin resistance was defined as the presence of the mecA gene. Of the 267 mecA gene-positive isolates, 263 were positive by the MRSA screen test (sensitivity, 98.5%), and all the mecA-gene negative strains were negative by the MRSA screen test (specificity, 100%). The oxacillin agar screen test detected methicillin resistance in 250 of the mecA gene-positive isolates (sensitivity, 93.6%). The sensitivity of the MRSA screen test was statistically significantly higher than the sensitivity of the oxacillin agar screen test (P < 0. 05). The MRSA screen test is a highly sensitive and specific test for the detection of methicillin resistance. Also, it offers results within half an hour and is easy to perform, which makes this test a valuable tool in the ongoing battle against methicillin-resistant S. aureus.

Latex Fixation Tests↗

PubMed1995

Food-initiated outbreak of methicillin-resistant Staphylococcus aureus analyzed by pheno- and genotyping.

An outbreak of methicillin-resistant Staphylococcus aureus (MRSA) involving 27 patients and 14 health-care workers (HCW) was studied. The outbreak started in the hematology unit of the University Hospital Rotterdam, Dijkzigt, The Netherlands, and spread to the surgical unit. Twenty-one patients (77.8%) developed clinical disease, and five died. Subsequently, MRSA was detected in food and in the throat of one of the HCW who prepared food for hematology patients. Food contaminated by an HCW most likely caused the first case of MRSA septicemia. This route of transmission has not been described before. The outbreak strain was probably transmitted to the surgical unit by a colonized nurse, where it caused an explosive outbreak. Airborne probably transmitted to the surgical unit by a colonized nurse, where it caused an explosive outbreak. Airborne MRSA transmission played an important role in disseminating the organism. The outbreak was controlled within 6 months by intensifying surveillance, temporarily closing the affected wards, treating carriers, and instituting an MRSA ward outside the hospital. Phage typing, insertion sequence probing, protein A gene typing, and DNA fingerprinting by PCR revealed that all outbreak-related isolates were identical. By pulsed-field gel electrophoresis, all but one of the outbreak-related isolates were determined to be identical. Protein A gene typing identified numerous (11) repeat units in all outbreak-related isolates, which supports the suggestion that the outbreak strain may have been more virulent and more transmissible than other MRSA strains. Pheno- and genotyping studies underlined the value of DNA fingerprinting methods for investigation of MRSA epidemiology. Optimal discriminatory power was achieved by combining the results of four genotyping methods.

Base Sequence↗

PubMed1993

Comparison of phage typing and DNA fingerprinting by polymerase chain reaction for discrimination of methicillin-resistant Staphylococcus aureus strains.

A typing procedure for methicillin-resistant Staphylococcus aureus (MRSA) based on the polymerase chain reaction (PCR) amplification of both mecA sequences and variable DNA sequences as present in the prokaryotic genome has been developed. Two primers based on the sequences of DNA repeats as discovered in gram-negative members of the family Enterobacteriaceae allow detection of variable regions in the genome of a gram-positive bacterium such as S. aureus, as does a newly described arbitrary primer. This procedure, enabling the detection of 23 different genotypes in a collection of 48 MRSA isolates, was validated by comparisons with phage typing studies. It appeared that within the same group of isolates only 13 different phagovars could be identified. Combination of the results from both phage typing and genotyping allowed the discrimination of 34 of 48 isolates. However, depending on the primer-variable complexity of the PCR fingerprints, which could also be modulated by combination of PCR primers, clear homologies between the groups defined by either phage typing or fingerprinting were observed. An analysis of an MRSA outbreak in a geriatric institution showed a collection of genetically homogeneous isolates. In agreement with phage typing, PCR fingerprinting revealed the identical natures of the MRSA strains isolated from all patients.

Aged↗

PubMed1970

Escherichia coli with resistance factors in vegetarians, babies, and nonvegetarians.

The prevalence of Escherichia coli carrying resistance factors (R factors) was examined in meat-consuming individuals and in those not consuming meat (vegetarians and babies below the age of 6 months). Assuming that the transport of resistant E. coli from animals through meat and meat products to the human consumer is most important, with regard to the incidence of resistant E. coli in man, we expected a significant difference in the proportions of people with resistant E. coli between the two groups. However, the percentage with resistant E. coli was larger in the group of vegetarians and babies than in the group of meat-eating individuals.

Adult↗