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J Lassen

Publications and source records attributed to J Lassen.

At least 73 records · Page 4Linked to original sources
PubMed1986

Serotype-related HEp-2 cell interaction of Yersinia enterocolitica.

The ability of human clinical isolates of Yersinia enterocolitica to interact with HEp-2 cells was found to vary considerably between the serotypes O:3, O:8, and O:9. Although all three serotypes adhered initially to the cell surface, regardless of incubation temperature of the bacterial inoculum or presence of the 40- to 48-megadalton virulence plasmid, the ability to localize intracellularly was not uniformly expressed. By using a combined light optical method based on differential interference contrast and UV incident light microscopy, we found that in serotype O:3, resistance to internalization was dependent upon prior growth at 37 degrees C and carriage of the virulence plasmid; in serotype O:9, this property was plasmid dependent but not temperature dependent; in serotype O:8, it was constitutive. The ability of serotype O:3 to resist internalization was correlated with the expression of plasmid-associated fibrillae on the bacterial surface. No relationship between fibrillation and HEp-2 cell interaction was apparent for serotype O:8 or O:9. Serotypes O:8 and O:9, unlike the O:3 strains studied, associated with HEp-2 cells in greater number after cultivation at 22 degrees C than after cultivation at 37 degrees C. We failed to establish a correlation between the expression of surface fibrillae and the ability to evoke guinea pig conjunctivitis.

Animals↗
PubMed1985

Plasmid characterization of Salmonella typhimurium transmitted from animals to humans.

The transmission of pathogenic bacteria from animals to humans is widely studied because of its public health importance. In this study, we show the transmission of Salmonella typhimurium from cattle which had received no growth-promoting antibiotics to humans who had direct contact with the ill animals. On one cattle farm, the veterinarian attending the sick animals became ill, and two other individuals living on the farm later developed salmonellosis. The strains isolated from both humans and animals at one farm were identical as to antibiotic susceptibility and phage type, and they were specifically traced by the presence of a common 24-megadalton plasmid. Restriction enzyme digests of this plasmid from both human and animal strains were identical. At another farm, tetracycline-resistant S. typhimurium strains possessing a different profile (eight plasmids) were isolated from both animals and humans. The tetracycline-resistant clone was also isolated from animals at a third farm, but with animals and humans having no known contact with those of the other two farms.

Animals↗
PubMed1984

Epidemiological aspects of enteritis due to Campylobacter spp. in Norway.

Data pertaining to 249 patients with stool cultures positive for thermophilic campylobacters are presented. Campylobacters were isolated from about 3% of all cases of acute enteritis and occupied second place in the bacterial etiology of this syndrome following Salmonella spp. Concomitant isolation of salmonellae or shigellae or both was achieved in 40 (16.1%) of the patients infected with campylobacters. The results suggest a bimodal age distribution with highest rates in young adults aged 20 to 29 years and children below 10 years of age. A majority of the campylobacters were isolated from travellers returning from abroad, and, to a lesser extent, from immigrants, particularly from Asia. Immigrants accounted for 45.2% of the patients below 10 years of age. The number of cases increased during the warmer months of the year. Travelling habits could, at least in part, explain the observed seasonality, age distribution, and geographical origin of infection. Eight outbreaks of Campylobacter enteritis were detected, five of which were family outbreaks, whereas three involved people from different families.

Adolescent↗
PubMed1984

Serotyping and biotyping of Campylobacter jejuni and Campylobacter coli from sporadic cases and outbreaks in Norway.

Of 172 thermophilic campylobacters isolated from human cases of gastroenteritis in Norway, 149 (86.6%) were classified as Campylobacter jejuni, whereas 23 isolates (13.4%) belonged to Campylobacter coli. C. jejuni biotype 1 comprised 66.3% and C. jejuni biotype 2 comprised 20.3% of the total number. Using 50 unabsorbed antisera, we were able to serotype 109 (80.1%) of 136 campylobacters on the basis of heat-stable antigens identified by means of passive hemagglutination. The typable strains fell into 36 different serotypes. A large proportion of the strains were isolated from travellers returning from abroad, a state of affairs which may have influenced the serotype and biotype distribution. Two family outbreaks were found to be caused by a bio-serotype common to all diseased members of the particular families. A third family outbreak and an outbreak among employees at a poultry processing plant each involved two distinct strains.

Adult↗
PubMed1984

External quality assessment for clinical microbiological laboratories in Norway 1983.

The external quality assessment scheme for clinical microbiology (EQA-M) used in Norway in 1983 is described and the results are evaluated. Altogether three distributions, each consisting of 3--4 simulated clinical specimens, were carried out. All specimens were distributed as "open" tests (identifiable by the participants as EQA-M tests), but two were also simultaneously distributed as "blind" tests (not identifiable by the participants as EQA-M tests). The EQA-M in 1983 has revealed some problem areas concerning the isolation, identification and reporting procedures, the more important being: The clinical information given seems often to be ignored The reported priorities of different microorganisms recovered from one specimen often seem to be accidental rather than the results of thorough considerations The isolation rates of Shigella sp and Yersinia enterocolitica from faecal specimens are too low A great number of laboratories seem to overestimate the quantities of bacteria in dip-slide cultures.

Clinical Laboratory Techniques↗
PubMed1983

Relationship of virulence-associated autoagglutination to hemagglutinin production in Yersinia enterocolitica and Yersinia enterocolitica-like bacteria.

A total of 339 Yersinia strains were tested for virulence-associated autoagglutination and hemagglutinin (HA) production. Autoagglutination was frequent among human clinical isolates belonging to Y. enterocolitica serogroups O:3, O:8, and O:9 and among porcine isolates of serogroups O:3 and O:9. Positive autoagglutination results were also observed in serogroups O:1 and O:2, associated with outbreaks among chinchillas, hares, and goats. All of 164 environmental isolates were negative in the autoagglutination assay. When subcultured serially in nutrient broth, none of the clinical isolates produced HA at either 22 or 37 degrees C, whereas 22.6% of the environmental yersiniae yielded mannose-resistant HA (MRHA). Six different MRHA patterns were recorded. Eighteen strains, all of which produced MRHA in nutrient broth, yielded similar MRHA patterns after cultivation on colonization factor agar. None of the autoagglutination-positive-(AA+) strains produced MRHA in either nutrient broth or on colonization factor agar. In contrast, a distinct autoagglutination-associated MRHA was detected after growth in Eagle minimal essential medium. Comparison of AA+ and autoagglutination-negative (AA-) derivatives of serogroups O:2, O:3, O:5, O:8, and O:9 showed that all AA+ cultures produced MRHA when grown in minimal essential medium at 37 degrees C overnight, whereas no MRHA was observed with any of the AA- derivatives of the same serogroups. This autoagglutination associated MRHA reacted with guinea pig erythrocytes, but not with erythrocytes from seven other species.

Agglutination↗
PubMed1983

External quality assessment for clinical microbiological laboratories in Norway 1982. 1. Evaluation of the identifications of 24 bacterial strains.

The first general external quality assessment (EQA) for clinical microbiological laboratories in Norway was carried out in 1982. Fifteen of 16 county and regional laboratories participated. Twenty-four pure cultures of different bacterial species were distributed by post. The distribution was "open" in the sense that the participants were aware of the cultures being part of the assessment. The strains had to be treated as routine clinical specimens. The bacterial identifications, the identification methods and the antibiotic sensitivity pattern had to be reported. The mean number of erroneous identifications was 2.7 (11.3%). Eleven strains were correctly identified by all laboratories, whereas four strains were misidentified by four to seven laboratories, accounting for approximately 50% of all misidentifications. All laboratories used "rapid" biochemical methods when identifying Gram-negative rods, mainly the "Three-tube method" and API 20E. Five laboratories used only one method, 10 used a combination of two or three methods. The use of more than one method did not give any substantial advantage. The accuracy of the "rapid" biochemical methods was approximately 88%, contrasting to approximately 96-98% when scientifically evaluated. The necessity of developing a permanent EQA scheme for microbiological laboratories is emphasized and a possible design for this is discussed.

Bacteria↗
PubMed1983

External quality assessment for clinical microbiological laboratories in Norway 1982. 2. Evaluation of the antibiotic sensitivity test results.

An external quality assessment for microbiology included antibiotic sensitivity testing of the 24 bacterial strains submitted. The number of antibiotics selected when sensitivity testing bacteria from different sources varied considerably between the laboratories. The discrepancy between actually reported sensitivity groups and the sensitivity groups calculated on the basis of the reported inhibition zones using the recommended regression lines was as great as 7% of a total of 1922 tests. This was mainly due to the use of outdated zone size break-points, indicating that information concerning changing recommendations may be inadequate. Discrepancies between the results reported by the laboratories and the results of a microdilution method giving the minimal inhibitory concentration for six antibiotics were recorded in 18.6% of the tests. Approximately one third of these discrepancies were characterized as "major" or "very major".

Clinical Laboratory Techniques↗
PubMed1982

Bacterial adhesiveness and invasiveness in cell culture monolayer. 2. In vitro invasiveness of 45 strains belonging to the family Enterobacteriaceae.

The invasive potential of 45 presumptive enteropathogenic and non-enteropathogenic bacterial strains belonging to the family Enterobacteriaceae have been tested using the Serény test and HEp-2 cell monolayers examined by a combined light optical method. All the presumptive enteropathogenic strains of Shigella dysenteriae, S. boydii, S. flexneri, S. sonnei and Salmonella typhimurium showed in vitro invasiveness in the HEp-2 cell culture test. Fourteen presumptive non-enteropathogenic strains of Escherichia coli showed no invasiveness in either of the two test systems. Two strains of S. flexneri and all the 6 strains of S. typhimurium gave a negative result in the Serény test although they were invasive in HEp-2 cell cultures. Otherwise there were correlative results between the cell monolayer test and the Serény test. In the cell monolayer test the different species of enteropathogenic bacteria showed considerable variation in invasive potential.

Adhesiveness↗
PubMed1980

[Brucellosis].

Explore the source record for details and available documents.

Adult↗
PubMed1980

Comparative in vitro activity of tobramycin and gentamicin on three different media.

The minimal inhibitory concentration for tobramycin and gentamicin against 488 clinical isolates of Enterobacteriaceae, Staphylococcus aureus and Pseudomonas spp. were obtained on three different solid media. The results obtained on Antibiotic Sensitivity Medium AB Biodisk (PDM) were markedly different from the results obtained on Mueller-Hinton (MH) and Diagnostic Sensitivity Test Agar Oxoid (DST). It was shown that tobramycin was significantly disfavored relative to gentamicin by PDM agar compared to MH and DST agar.

Anti-Bacterial Agents↗