Biomedical subjects
Publications and source records attributed to B Olsen.
A Swedish tourist was admitted to a Cuban hospital due to epileptic seizures caused by brain tumors. Upon return to Sweden and admission to our hospital, methicillin-resistant Staphylococcus aureus (MRSA) was isolated. He was later considered to be free of MRSA but then developed a brain abscess from which MRSA was isolated.
On Bird Island, South Georgia, albatrosses (n = 140), penguins (n = 100), and fur seals (n = 206) were sampled for Campylobacter jejuni. C. jejuni subsp. jejuni was recovered from three macaroni penguins (Eudyptes chrysolophus). These isolates, the first reported for the subantarctic region, showed low genetic diversity and high similarity to Northern Hemisphere C. jejuni isolates, possibly suggesting recent introduction to the area.
On Bird Island, South Georgia, a new strain of Chlamydophila abortus was detected in one Brown skua out of 37 specimens from six different seabird species. Phylogenetic analysis of the rnpB and omp1 genes indicated the strain to be more closely related to C. abortus than to 6BC, the type strain of Chlamydophila psittaci.
Haemophilus ducreyi is resistant to killing by normal serum antibody and complement. We discovered an H. ducreyi outer membrane protein required for expression of serum resistance and termed it DsrA (for "ducreyi serum resistance A"). The dsrA locus was cloned, sequenced, and mutagenized. An isogenic mutant (FX517) of parent strain 35000 was constructed and characterized, and it was found to no longer express dsrA. FX517 was at least 10-fold more serum susceptible than 35000. DsrA was expressed by all strains of H. ducreyi tested, except three naturally occurring, avirulent, serum-sensitive strains. FX517 and the three naturally occurring dsrA-nonexpressing strains were complemented in trans with a plasmid expressing dsrA. All four strains were converted to a serum-resistant phenotype, including two that contained truncated lipooligosaccharide (LOS). Therefore, serum resistance in H. ducreyi does not require expression of full-length LOS but does require expression of dsrA. The dsrA locus from eight additional H. ducreyi strains was sequenced, and the deduced amino acid sequences were more than 85% identical. The major difference between the DsrA proteins was due to the presence of one, two, or three copies of the heptameric amino acid repeat NTHNINK. These repeats account for the variability in apparent molecular mass of the monomeric form of DsrA (28 to 35 kDa) observed in sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Since DsrA is present in virulent strains, is highly conserved, and is required for serum resistance, we speculate that it may be a virulence factor and a potential vaccine candidate.
We developed a new enzyme immunoassay (rpEIA) for use in determining the seroprevalence of chancroid. Three highly conserved outer membrane proteins from Haemophilus ducreyi strain 35000 were cloned, overexpressed, and purified from Escherichia coli for use as antigens in the rpEIA. Serum specimens from patients with and without chancroid were assayed to determine optimum sensitivity and specificity and to establish cutoff values. On the basis of these data, rpEIA was found to be both sensitive and specific when used to test a variety of serum specimens from patients with genital ulcers and urethritis and from healthy blood donors.
Exposure of lung endothelial monolayers to tumor necrosis factor (TNF)-alpha causes a rearrangement of the fibrillar fibronectin (FN) extracellular matrix and an increase in protein permeability. Using calf pulmonary artery endothelial cell layers, we determined whether these changes were mediated by FN multimerization due to enhanced transglutaminase activity after TNF-alpha (200 U/ml) for 18 h. Western blot analysis indicated that TNF-alpha decreased the amount of monomeric FN detected under reducing conditions. Analysis of (125)I-FN incorporation into the extracellular matrix confirmed a twofold increase in high molecular mass (HMW) FN multimers stable under reducing conditions (P < 0.05). Enhanced formation of such HMW FN multimers was associated with increased cell surface transglutaminase activity (P < 0.05). Calf pulmonary artery endothelial cells pretreated with TNF-alpha also formed nonreducible HMW multimers of FN when layered on surfaces precoated with FN. Inhibitors of transglutaminase blocked the TNF-alpha-induced formation of nonreducible HMW multimers of FN but did not prevent either disruption of the FN matrix or the increase in monolayer permeability. Thus increased cell surface transglutaminase after TNF-alpha exposure initiates the enhanced formation of nonreducible HMW FN multimers but did not cause either the disruption of the FN matrix or the increase in endothelial monolayer permeability.
At Bird Island, South Georgia, we studied the effects of the tick Ixodes uriae on survival of chicks at two colonies of the black-browed albatross Diomedea melanophrys, one where most chicks were infested with ticks, the other where most chicks were tick-free. When the two colonies were compared, it was found that the colony heavily-infested with ticks had significantly greater chick mortality than the colony lightly-infested with ticks. However, within each of the two colonies, there was no significant difference in survival between chicks with ticks and those without ticks.
We collected fresh droppings and cloaca samples from feral pigeons Columba livia in the southern Swedish city of Malmö, and isolated the following fungi: Debaryomyces hansenii var. hansenii, Cryptococcus laurentii and Cryptococcus uniguttulatus. The first two species are known to be pathogenic to humans. No strains of Cryptococcus neoformans var. neoformans were found. Our results indicate that feral pigeons can be carriers of medically significant fungi other than Cryptococcus neoformans var. neoformans.
This is the first report on the isolation of Lyme disease Borrelia from seabirds on the Faeroe Islands and the characteristics of its enzootic cycle. The major components of the Borrelia cycle include the puffin (Fratercula arctica) as the reservoir and Ixodes uriae as the vector. The importance of this cycle and its impact on the spread of human Lyme borreliosis have not yet been established. Borrelia spirochetes isolated from 2 of 102 sampled puffins were compared to the borreliae previously obtained from seabird ticks, I. uriae. The rrf-rrl intergenic spacer and the rrs and the ospC genes were sequenced and a series of phylogenetic trees were constructed. Sequence data and restriction fragment length polymorphism analysis grouped the strains together with Borrelia garinii. In a seroepidemiological survey performed with residents involved in puffin hunting on the Faeroe Islands, 3 of 81 serum samples were found to be positive by two commonly used clinical tests: a flagellin-based enzyme-linked immunosorbent assay (ELISA) and Western blotting. These three positive serum samples also had high optical density values in a whole-cell ELISA. The finding of seropositive Faeroe Islanders who are regularly exposed to I. uriae indicate that there may be a transfer of B. garinii by this tick species to humans.
At Bird Island, South Georgia, we surveyed the distribution and abundance of ticks on the vertebrate fauna and found only 1 species Ixodes uriae. We classified all seabird species into 3 groups: (1) seabirds nesting on the surface of the ground solitarily, in dispersed groups of a few nests, or in colonies with well-spaced nests; (2) seabirds nesting on the surface of the ground in dense colonies; and (3) seabirds nesting in dense colonies in burrows or rock crevices. We detected I. uriae only on 3 species of the second group that nested in large, dense, persistent colonies, i.e., black-browed albatross (Diomedea melanophrys), gray-headed albatross (Diomedea chrysostoma), and macaroni penguin (Eudyptes chrysolophus). Ticks were found on the undersides of the feet on albatrosses but not on the undersides of the feet on penguins. We hypothesize that the coarse pebble nests of penguins, combined with the fact that their young walk around more than albatross young, make the environment on the underside of penguin feet more harsh and hostile for ticks than the underside of albatross feet. Despite the great abundance of Antarctic fur seals (Arctocephalus gazella) on the island, we found no ticks on them.
On 17 July 1998 the remains of Tsar Nicholas II and his family were buried, a historic event extensively covered by the media. The remains of four servants liquidated with the royal family were buried with them. Among the servants was the Tsar's personal physician, Jevgenij Botkin. Not often does a doctor follow his patients not only onto death, but into death--the Hippocratic oath leading to liquidation, so to speak. Who was Dr. Botkin? Did he know what to expect, or was he just a chance victim?
The aim of the study was to gain knowledge of the diagnosis, length of hospital stay, and ethnic background of refugee and immigrant children admitted to the Paediatric Ward at Aker University Hospital in Oslo, and to find out how well the staff and families of the children communicated. 347 children, admitted from ten districts in the immediate vicinity of the hospital, were included in the study. 133 (38%) children had parents who were both born in a non-western country. 44 of the children came from a refugee background and 89 from an immigrant background. The median stay on the Paediatric Ward was three days for the immigrant children and two days for the refugee children and children from Western countries. None of the groups was admitted more frequently than the others. Refugee and immigrant children were most often admitted because of respiratory diseases or obscure symptoms. Communication between the staff and more than 40% of the families with refugee or immigrant backgrounds was not satisfactory. Three out of four mothers and one out of two fathers were unable to communicate well in Norwegian. One third of the mothers had less than six years of school education and one quarter of the immigrant mothers had never attended school.
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To investigate to what extent wild passerine birds are carriers of Chlamydia psittaci, 312 faecal samples from 18 bird species were collected. Using the PCR technique and subsequent DNA sequencing, C. psittaci DNA was demonstrated in faecal samples from 9 (2.9%) birds of 6 different species. Sera from 65 bird-ringers, highly exposed to wild birds, were tested by microimmunofluorescence assay for the occurrence of IgG and IgM antibodies to C. psittaci. No such antibodies were found. This results indicate that a significant proportion of wild passerine birds are carriers of C. psittaci, but rarely infectious to humans.
By cloning into Escherichia coli and construction of isogenic mutants of Haemophilus ducreyi, we showed that the hemoglobin receptor (HgbA) is TonB dependent. An E. coli hemA tonB mutant expressing H. ducreyi hgbA grew on low levels of hemoglobin as a source of heme only when an intact H. ducreyi Ton system plasmid was present. In contrast, growth on heme by the E. coli hemA tonB mutant expressing hgbA was observed only at high concentrations of heme, was TonB independent, and demonstrated that H. ducreyi HgbA was not sufficient to function as a typical TonB-dependent heme receptor in E. coli. Allelic replacement of the wild-type H. ducreyi exbB, exbD, and tonB loci with the exbB, exbD, and tonB deletion resulted in an H. ducreyi isogenic mutant unable to utilize hemoglobin but able to utilize hemin at the same levels as the parent strain to fulfill its heme requirement. This finding confirms the TonB dependence of HgbA-mediated hemoglobin utilization and suggests that uptake of hemin in H. ducreyi is TonB independent. Additionally, the H. ducreyi Ton system mutant synthesized increased amounts of HgbA and other heme-regulated outer membrane proteins, consistent with derepression of these proteins due to lower intracellular heme and/or iron concentrations in the mutant. Sequencing of the Ton system genes revealed that the arrangement of the genes was exbB exbD tonB. The proximity and structure of these genes suggested that they are transcribed as an operon. This arrangement, as well as the DNA and deduced amino acid sequences of these H. ducreyi genes, was most similar to those from other pasteurellae.
Haemophilus ducreyi is unable to synthesize heme and must acquire it from its only known host, humans. We cloned and sequenced a gene encoding an outer membrane receptor for heme. It was designated tdhA (for TonB-dependent heme receptor A) since it was related by sequence homology to the family of TonB-dependent receptors. TdhA was strikingly similar to open reading frame HI0113 from the genome of Haemophilus influenzae Rd and also shared homology with five other heme receptors, including HxuC, HemR, HmuR, ChuA, and ShuA, from gram-negative bacteria. An Escherichia coli hemA tonB mutant strongly expressing H. ducreyi tdhA grew on low levels of heme as a source of heme only when an intact H. ducreyi Ton system plasmid was present, formally demonstrating functional TonB dependence. tdhA was expressed poorly in vitro by H. ducreyi and only under conditions of heme limitation. A survey of H. ducreyi revealed that all tested strains but one synthesized small amounts of TdhA in vitro under heme-limiting conditions. Surprisingly, an isogenic mutant of tdhA as well as its parent, 35000, both required the same high levels of heme for growth (50 microgram/ml [77 microM] on agar medium). This result, together with previous findings, suggests that in vitro, the uptake of heme by H. ducreyi is mediated by a TonB- and TdhA-independent mechanism, possibly diffusion.
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