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Biomedical subjects

D I Grove

Publications and source records attributed to D I Grove.

At least 19 recordsLinked to original sources

First report of the isolation of an adult worm of the genus Brachylaima (Digenea: Brachylaimidae), from the gastrointestinal tract of a human.

A 78-year-old woman presented with an 18-month history of intermittent diarrhoea. Examination of her stools revealed brachylaimid eggs, which were present in three separate specimens over a week. After treatment with praziquantel a degenerate adult Brachylaima species was recovered from her faeces. She lived in a rural area of South Australia and ate vegetables grown in her own garden which had been infested with helicid snails. In south Australia these introduced European helicid snails are commonly infected with brachylaimid intermediate larval stages and are considered to be the source of the human infection.

Aged

Evaluation of bacteriological transport swabs.

Ten commercial transport swabs were evaluated for their ability to preserve bacteria for 24 and 48 hours. Microorganisms included ATCC strains of Gram-positive and Gram-negative aerobes and anaerobes. There was a wide variation in performance. Swabs using Amies plus charcoal medium or Stuart's medium had better recovery rates than those using Amies medium alone. The nature of the tips of the swabs had little influence. Performance was not correlated with cost of the swabs. These data will assist institutions to make cost-effective decisions when purchasing bacteriological transport systems.

Bacteria

Comparison of culture, histopathology and urease testing for the diagnosis of Helicobacter pylori gastritis and susceptibility to amoxycillin, clarithromycin, metronidazole and tetracycline.

Gastric biopsy specimens were taken from 737 patients undergoing upper gastrointestinal endoscopy and assessed for Helicobacter pylori infection. The diagnostic utilities of H. pylori culture (733 patients), detection of urease production (724 patients) and histopathological examination (469 patients) were compared. Since each of these techniques may fail to diagnose patients infected with H. pylori, an attempt was made to estimate the true rate of infection using a mathematical approach that combined the results of culture, histopathology and urease testing; 34% of the 733 patients were thought to be infected. Using this figure as a benchmark, the sensitivity, specificity, positive predictive value and negative predictive value of H. pylori culture were 73.2%, 100%, 100% and 86.3%, respectively, compared with 58.7%, 100%, 100% and 89.6%, respectively for urease production and 77.0%, 100%, 100% and 82.4%, respectively for histopathology. Thus, histopathological examination was the single most reliable test. A combination of histopathological examination and H. pylori culture diagnosed 99.5% of patients that were estimated to be truly infected. The minimum inhibitory concentrations of a number of antibiotics were measured for 135 isolates of H. pylori. All isolates were susceptible to amoxycillin and tetracycline whereas 5.2% were resistant to clarithromycin and 60% were resistant to metronidazole.

Amoxicillin

Delay in appropriate therapy of Legionella pneumonia associated with increased mortality.

The prognostic significance of delayed therapy in Legionnaires' disease is poorly defined. Thirty-nine consecutive serologically confirmed cases of Legionnaires' disease were reviewed to examine whether an association exists between delayed therapy and prognosis. Clinical and laboratory factors predictive of mortality were also sought. Thirty-one cases (79%) were classified as having severe pneumonia at diagnosis. Thirty-six patients (92%) had community-acquired infection, and three patients (8%) had nosocomial disease. Ten patients died, resulting in a crude mortality rate of 26%. At the first assessment, variables noted for pneumonia associated with death were low diastolic blood pressure (p < 0.02), low serum albumin concentration (p < 0.04), and increased number of days from onset of pneumonia to hospitalisation (prodrome) (p < 0.02). However, multiple logistic regression analysis revealed that the prodrome was the only variable noted at diagnosis that achieved significance (p = 0.024). Mortality also correlated with both delay in the initiation of erythromycin therapy following admission (p < 0.001) and the total delay in starting erythromycin therapy (p < 0.001). It is therefore recommended that erythromycin be included early in the empiric therapy of severe community-acquired pneumonia.

Adult

Comparison of direct and standardized testing of infected urine for antimicrobial susceptibilities by disk diffusion.

A total of 14,272 urine specimens were examined over one year to determine the validity of direct antimicrobial agent susceptibility testing against ampicillin, amoxicillin-clavulanic acid, cephalothin, gentamicin, norfloxacin, and trimethoprim. A comparison between direct and standardized disk diffusion tests was made for a total of 1,106 urine specimens containing > or = 10(5) organisms per ml in pure culture. There were 5,821 individual organism-antimicrobial agent challenges compared for the two testing methods, and there was complete agreement of susceptibility category in 5,492 comparisons (94.3%). Initially, discordant results were reduced from 5.7 to 2.1% when the intermediate category was considered susceptible. Intralaboratory variation was assessed by testing another 453 organisms by the standard National Committee for Clinical Laboratory Standards (NCCLS) method on two consecutive days; there was complete agreement in 96.1% of comparisons. When results of direct and standardized testing were simply classified as susceptible or resistant, there was 1.1% discordance. When simple same-day tests were used together with predictable patterns of susceptibility and resistance, 536 (48.5%) of 1,106 isolates could be identified satisfactorily to the genus or species level. For laboratory reporting purposes, the direct method is equivalent to the standard method when the urine being tested is infected with > or = 10(5) organisms of a single type per ml. The presence or absence of preexisting antimicrobial agents in urine did not appreciably influence the results. This procedure allows the earlier reporting of susceptibility results and facilitates less expensive identification of many organisms. Costs and benefits need to be determined in each institution.

Anti-Bacterial Agents

Worms in Australia.

Fortunately, Australia does not have many of the parasitic worm infections, such as filariasis, onchocerciasis and dracunculiasis, that are important on a global scale. Nevertheless, several medically important parasitic worms are endemic in Australia. Intestinal nematodes occur mostly in the tropical north although threadworm is ubiquitous. Hydatid disease and tapeworm infections occur especially in sheep and cattle farming regions.

Animals

Analysis of the 18S ribosomal RNA gene of Strongyloides stercoralis.

The entire 1766 bases of the 18S rRNA gene of Strongyloides stercoralis have been sequenced. The gene has a 38% G+C content. Although it is similar in length to the 18S rRNA gene of Caenorhabditis elegans, the only other completely sequenced nematode 18S rRNA gene, it is only 69% identical. Closely related helminths will need to be sequenced in order to delineate sequences specific for the diagnosis of strongyloidiasis.

Animals

Corneal ulceration due to Nocardia asteroides.

A case of corneal ulceration due to infection with Nocardia asteroides is described. Microbiological examination of corneal scrapings permitted accurate diagnosis and suggested appropriate therapy. Nineteen other cases that have been described in the world literature are reviewed.

Adult

Consent, compulsion and confidentiality in relation to testing for HIV infection: the views of WA doctors.

A survey was undertaken of all of the consultant staff members of Perth's major teaching hospitals together with all the fellows of The Royal Australian College of General Practitioners in Western Australia in order to define their views on the issues of informed consent, compulsion in relation to surgery, and confidentiality in a particular circumstance, when testing for infection with the human immunodeficiency virus (HIV). Of the 701 individuals surveyed, 548 (78.2%) responded. Of these, 74.3% considered that it was not always necessary to gain informed consent, 22.0% believed that it was always necessary to do so, while 2.3% were undecided. General practitioners (38.4%) were more likely to think it necessary to obtain consent than were hospital consultants (19.0%), but otherwise the field of specialty had little effect on opinion. Of the respondents, 39.0% believed that testing before elective surgery is mandatory for all patients, while 53.0% considered that it should be compulsory in high-risk groups. Similar views were held about compulsory HIV antibody testing after emergency surgery. Similar responses were obtained from all specialty groups. When asked about whether they would tell a sexual partner of a patient's HIV status when the patient refused, 10.5% of doctors stated they would never advise the partner, 24.7% of doctors would on some occasions, 41.0% of doctors would tell a partner, and 23.8% always were undecided. Many individuals commented that they failed to see why HIV infection was being treated differently from other serious diseases. We have found that the majority opinion of the most senior members of the medical profession is that specific, informed consent should not always be required, that there is great support for compulsory testing, and that confidentiality may be broken under certain circumstances. These views must be recognized by administrators and legislators when framing measures to control this infection.

Acquired Immunodeficiency Syndrome

Strongyloides stercoralis: antigenic analysis of infective larvae and adult worms.

The protein composition of Strongyloides stercoralis infective larvae and adult worms solubilized sequentially in water, sodium deoxycholate and sodium dodecyl sulphate (SDS) and their excretory/secretory products were analysed by one- and two-dimensional SDS-polyacrylamide electrophoresis. These extracts were demonstrated to be complex mixtures containing many proteins, some of which were common and others which were stage-specific. Western blot analysis of these antigens with infected human sera showed most sero-reactivity against larval antigens, whilst normal human sera were unreactive. These data identify immunogenic antigens which may be available for detection in an antigen assay.

Animals

Dissociation of the protective immune response in the mouse to Strongyloides ratti.

The generation of protective immunity by various stages in the life-cycle of Strongyloides ratti and the phases against which resistance is directed has been examined in murine strongyloidiasis. Mice were exposed to natural, complete infections, were treated with thiabendazole (which largely resembles the natural infection), were treated with cambendazole (which restricts infection to the larval stage), or infected directly by oral transfer of adult worms. Mice that were infected with infective larvae alone did not become resistant to infective larvae or the complete infection but were resistant to adult worms implanted directly into the gut. Mice exposed to adult worms alone were resistant to natural infections and adults worms implanted directly but were not resistant to infective larvae. On the other hand, mice that had received prior natural infections showed evidence of resistance to infective larvae, adult worms, and natural, complete infections. It is concluded that there is immunological cross-reactivity between infective larvae and adult worms but that under certain circumstances the infective larvae are able to evade the host's protective immune response.

Animals

Surface labelling of Strongyloides ratti: stage-specificity and cross-reactivity with S. stercoralis.

Various methods of radioiodination were compared for their efficacy in labelling the surface of Strongyloides ratti infective larvae and adult worms. The Iodogen method was chosen as the optimal technique for this parasite. The surface location of 125-iodine was confirmed with light microscope autoradiography of transverse sections of labelled worms. Stage-specific surface components were identified when the sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) profiles of infective larvae and adult worms were compared. Labelled surface molecules were solubilized with either the non-ionic detergent Triton-X-100, the anionic detergents sodium deoxycholate (DOC) or sodium dodecyl sulphate (SDS), or the cationic detergent cetyl trimethyl-ammonium bromide (CTAB). The CTAB extract yielded most labelled proteins that retained their antigenicity in an immunoprecipitation assay with hyperimmune mouse sera. Immunoprecipitation analysis with stage-specific mouse sera revealed that the surface of infective larvae is immunogenic and that there are no cross-reactions with adult worms. Adult worms resident in the intestine were not found to be immunogenic and showed a complete absence of reactivity. Antigenic determinants shared between S. ratti and S. stercoralis were identified. Patients infected with S. stercoralis precipitated bands with molecular weights 32 and 34 kD which were not reactive with normal sera. These reactions suggest the potential usefulness of the surface of S. ratti as a source of diagnostic antigens.

Animals

The effects of thiabendazole, mebendazole and cambendazole in normal and immunosuppressed dogs infected with a human strain of Strongyloides stercoralis.

The effects of three benzimidazole anthelmintics in dogs infected with a human strain of Strongyloides stercoralis were investigated. Cambendazole, but not thiabendazole or mebendazole, abrogated the subsequent development of a patent infection when administered at the same time as infection to immunocompetent dogs. None of the drugs eradicated infection when given after the onset of patency in immunosuppressed animals, although worm burdens were greatly reduced in dogs treated with cambendazole. The implications of these findings for the treatment of patients with strongyloidiasis, particularly those with disseminated infections, are discussed.

Animals

Efficacy of albendazole against Strongyloides ratti and S. stercoralis in vitro, in mice, and in normal and immunosuppressed dogs.

In view of conflicting clinical reports, the effects of albendazole on Strongyloides were examined in vitro and in experimentally-infected animals. Albendazole inhibited the hatching and moulting of S. ratti eggs and larvae and prevented the development in vitro of S. stercoralis first-stage larvae. Pre-exposure to the drug did not impair the infectivity of either S. ratti or S. stercoralis third-stage larvae. Albendazole had a dose-dependent inhibitory effect on S. ratti migrating larvae in mice when measured in terms of the numbers of larvae recovered from the skin or lungs or the subsequent development of a patent infection. Likewise, killing of adult S. ratti in the gut and eradication of S. stercoralis third-stage larvae from the muscles of mice were dose-dependent. Albendazole in a dose of 100 mg twice daily for three days given at the time of infection with S. stercoralis of immunocompetent dogs prevented completely the subsequent development of patent infection. When the drug was given in the same dosage to immunosuppressed dogs with patent infections, the larvae disappeared from the stools transiently; when the animals were killed seven weeks after treatment, small numbers of adult worms and rhabditiform larvae were found in the gut. It is concluded that albendazole may be effective treatment for strongyloidiasis if it is given in sufficiently large doses.

Albendazole

Western blot analysis of reactivity to larval and adult Strongyloides ratti antigens in mice.

Mice were infected once, twice or many times with Strongyloides ratti infective larvae, and the parasite was allowed to complete its development. Other mice were infected many times with either infective larvae only, by aborting the infection with cambendazole, or with adult worms transferred by intra-oesophageal intubation. Sera from these animals were analysed by immunoblotting against SDS-PAGE separations of larval and adult worm water-soluble, deoxycholate-soluble, sodium dodecyl sulphate-soluble and excretory/secretory antigens. Minimal antibody responses were observed after primary and secondary infections. Mice exposed to multiple complete infections reacted strongly to both larval and adult antigens but greater responses were observed against the larval preparations. Stage-specific effects were noted in mice infected with larvae only or adult worms only. Mice exposed only to larvae reacted with larval antigens and to a minor degree to somatic adult worm antigens while those mice which were exposed only to adult worms failed to react with any of the antigen preparations. Some cross-reactions were found, however, as mice infected only with larvae displayed strong reactions against both larval and adult excretory/secretory products. These data demonstrate differences in sero-reactivity to infective larvae and adult worms and suggest that humoral immunity is induced by larvae migrating through the tissues and not by adult worms in the gut.

Animals