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Biomedical subjects

D C Shanson

Publications and source records attributed to D C Shanson.

At least 37 records · Page 2Linked to original sources
PubMed1992

The in-vitro bactericidal activities of combinations of antimicrobial agents against clinical isolates of Mycobacterium avium-intracellulare.

The in-vitro activities of five antimicrobial agents (rifabutin, clarithromycin, ethambutol, ciprofloxacin and amikacin), alone and in combination, were evaluated against 21 strains of Mycobacterium avium-intracellulare isolated from patients with AIDS. The combined activities of these agents were studied on solid medium by a full chequerboard method. Synergy was demonstrated most frequently (28-71% of isolates) with those combinations that included ethambutol. In killing curve experiments where double and triple combinations of agents were tested against two of the strains, 99% kill was achieved in seven days at concentrations well below those that are attainable in serum. However, an additive rather than a synergic effect was seen in most instances. Although ciprofloxacin alone had the greatest bactericidal activity against these two strains, its activity was antagonized in the presence of rifabutin; this antagonism became inapparent when a third agent was added. Demonstration of bactericidal activity in broth culture may be more relevant than the results of susceptibility testing on solid medium when choosing antimicrobial therapy for patients with this infection.

Anti-Bacterial Agents↗
PubMed1992

Salmonella, Campylobacter and Shigella in HIV-seropositive patients.

OBJECTIVE: To study the incidence, clinical features, treatment and outcome of patients with Salmonella, Shigella or Campylobacter infection. DESIGN: Retrospective analysis. SETTING: Two dedicated HIV units within a London teaching hospital. METHODS: All patients with Salmonella, Shigella or Campylobacter infection were reviewed retrospectively by correlating the records of the gastrointestinal and microbiology departments with the computerized records of all HIV-positive patients attending the two clinics. RESULTS: Between July 1985 and June 1991, 56 episodes of Salmonella, 37 of Campylobacter and eight of Shigella infection were documented in HIV-seropositive patients. Shigella was most likely to occur early in HIV disease, whilst patients with Campylobacter or Salmonella were more likely to have had a previous AIDS diagnosis. Septicaemica was most common in patients with Salmonella and was especially likely to occur in individuals with an AIDS diagnosis. Relapse of infection was common in patients with Salmonella, especially in those with low CD4 lymphocyte counts, those with an initial septicaemic illness and those not treated with ciprofloxacin. CONCLUSIONS: Patients with Salmonella who have low CD4 lymphocytes counts and/or a septicaemic illness should be considered for life-long secondary prophylaxis with ciprofloxacin because of the high rate of relapse observed. Administration of zidovudine or cotrimoxazole as prophylaxis against Pneumocystis carinii pneumonia may prevent the development of salmonellosis: significantly fewer patients with this infection were taking these drugs than patients with Campylobacter.

AIDS-Related Opportunistic Infections↗
PubMed1992

The clinical comparison of Oxoid Signal with Bactec blood culture systems for the detection of streptococcal and anaerobic bacteraemias.

Blood cultures were taken from 47 patients 1-2 min after dental extraction. These samples were tested by the radiometric Bactec 460 and Oxoid Signal systems for the detection of streptococcal and anaerobic bacteraemias. Streptococci were isolated from 19 (40%) patients and anaerobes from 15 (32%). In this study the Oxoid Signal system was significantly better for isolating oral anaerobes than the Bactec system; five isolates were obtained with the Bactec system and 14 with the Signal system. There was no significant difference in the isolation of streptococci between these two systems (Bactec 14, Oxoid Signal 10). The contamination rate was 4.1% for Bactec and 7.5% for the Oxoid Signal system.

Adult↗
PubMed1992

Clinical comparison of Sentinel, a novel blood culture system, with radiometric Bactec 460 and Isolator 10 in the detection of streptococcal and anaerobic bacteraemias.

AIMS: To compare the performance of the Sentinel blood culture system with two other systems for the recovery of streptococci and anaerobes. METHODS: Blood cultures were taken from 55 patients one to two minutes after dental extraction. The samples were tested by the radiometric Bactec 460; the Isolator 10, which works by lysis centrifugation; and Sentinel, a fully automated system, which detects bacterial growth by changes in the voltage between two electrodes in the media. Positive samples were subcultured and streptococci and anaerobes were further identified. Terminal subcultures were performed on all negative samples. RESULTS: Sentinel was comparable with Bactec, with Sentinel recovering 20 streptococci and 14 anaerobes; Bactec isolated 26 streptococci and 15 anaerobes. The recovery of Streptococcus sanguis was significantly better from Bactec than Sentinel. The Isolator 10 recovered significantly fewer streptococci and anaerobes than either Bactec or Sentinel. Sentinel was noticeably quicker in detecting anaerobes than Bactec 460. However, there was no comparable difference with streptococci. Contaminants were recovered from 10% of Isolator 10, 2.7% of Bactec, and 7.2% of Sentinel bottles. CONCLUSIONS: Sentinel and Bactec 460 were broadly comparable in the detection of viridans streptococci and oral anaerobes, and both systems were significantly better than the Isolator 10. However, the prototype Sentinel, was significantly poorer than Bactec for the recovery of S sanguis.

Adult↗
PubMed1992

Comparison of Sentinel and Bactec blood culture systems.

AIMS: To evaluate the Sentinel automated blood culture system and to compare its performance with that of Bactec. METHODS: The Sentinel blood culture system was evaluated in three centres. The performance of the system was assessed in comparison with the routine blood culture method used in these centres, the Bactec system. RESULTS: Blood culture sets (n = 2180) consisting of Sentinel aerobic and anaerobic, and Bactec aerobic and anaerobic bottles yielded 218 (10%) clinically important isolates. One hundred and fifty five (71%) of the isolates were detected by both systems; 35 (16%) were detected by Sentinel only; and 28 (13%) by Bactec only. For the duration of the evaluation, the Sentinel system was deliberately configured so that it was impossible to detect positive results during the first 12 hours. The times to positivity after the first 12 hours were similar. Data gathered during and subsequent to the evaluation have been used by the manufacturer to refine the algorithm so that positive results can be detected at a minimum of 2.25 hours. CONCLUSIONS: After a period of familiarization the Sentinel system was considered easy to use. Sentinel is a useful addition to the methods available for the detection of bacteria in blood cultures.

Bacteriological Techniques↗
PubMed1991

Should surgical patients be screened for human immunodeficiency virus infection?

There are increasingly strong arguments for the introduction of wider screening of all kinds of patients, including surgical patients, to diagnose otherwise undetected human immunodeficiency virus (HIV) infection in order to facilitate earlier treatment of HIV infection with zidovudine. Wider screening may also help to limit the spread of HIV in the community as infected patients may be counselled and more effective public health measures planned. In areas of high prevalence voluntary universal screening test programmes should be encouraged whereas in areas of low to medium prevalence more selective screening tests would be appropriate on people belonging to risk groups. Screening of patients undergoing elective surgery for infection control purposes is most appropriate in areas of low to medium prevalence so that extra precautions in the operating theatre can be selected for those patients who are screened and deemed to be at high risk. Screening methods include taking a comprehensive clinical history to include specific questions about risk group behaviour, questionnaire methods, serological screening tests and a combination of these three types of approach. Screening HIV antibody tests are recommended, with informed consent, of those patients who belong to risk groups. A further benefit of screening for infection control purposes occurs in the event of a sharps injury when prior testing of the source patient helps to facilitate decision making about the giving of immediate zidovudine prophylaxis.

AIDS Serodiagnosis↗
PubMed1991

Wound healing and infection in pretibial lacerations.

Eighty-eight patients with pretibial lacerations were entered into a study to analyze bacteriological and wound-healing profiles. Fifty-four patients were followed to complete wound healing. A complete photographic record of wounds from time of presentation to healing was available for analysis in 49 of these patients. Staphylococcus aureus was the most common pathogen, but the correlation between clinical wound infection and growth of pathogenic bacteria was poor. Flucloxacillin alone was found to be significantly more effective in controlling wound infection than in combination with metronidazole. Computerized image analysis of the photographic records was performed. There was no significant difference in the healing times of the various classic surgical wound types, and image analysis confirmed that the rates of wound healing were generally similar in all the types of pretibial wounds.

Adolescent↗
PubMed1991

Pseudomonas septicaemia associated with HIV.

Between July 1985 and January 1990, pseudomonas scepticaemia occurred in 19 out of 584 patients with AIDS attending the Westminster and St Stephen's AIDS Unit, London, UK. Ten of these 19 were being treated for active cytomegalovirus infection. Fourteen of the 19 patients had a central venous catheter in situ, which was the source of infection in 11. Seven patients died. Mortality was significantly greater in those patients infected with Pseudomonas aeruginosa, in those patients whose source of infection was not the central venous line, and in those patients whose central line was not removed.

Acquired Immunodeficiency Syndrome↗
PubMed1991

Monoclonal immunofluorescence compared with silver stain for investigating Pneumocystis carinii pneumonia.

Two hundred and eighty two specimens from 220 patients positive for HIV with respiratory tract symptoms, or febrile illness, or both, were examined for the presence of Pneumocystis carinii. Specimens were either induced sputum samples or bronchoalveolar lavage fluids. To establish the optimal method for laboratory diagnosis a comparison was made of detection of the organism by use of monoclonal antibody and immunofluorescence with conventional silver staining methods. Three commercially available reagents for immunofluorescence were also compared. Immunofluorescence was significantly more sensitive than the silver stain and the best results for immunofluorescence were obtained using. Northumbria Biologicals Ltd reagents.

Bronchoalveolar Lavage Fluid↗
PubMed1991

Molecular specificity of two commercial enzyme linked immunosorbent assays for human immunodeficiency virus antigens.

Only "fair" agreement has been shown between the Abbott and DuPont enzyme linked immunosorbent assays when used for the detection of human immunodeficiency virus (HIV) antigen in serum samples from asymptomatic HIV antibody positive homosexual men. To investigate the discrepancies between the two ELISA results, further experiments were performed. The rabbit detector antibody solutions of both tests were western blotted and showed that the DuPont test was specific for p24; the Abbott detector antibody had bands for p18, p41-43, gp120 as well as p24. By using dilutions of a known amount of HIV antigen, the Abbott test could detect 20 pg/ml p24; the DuPont test could detect 30 pg/ml p24. The DuPont test was also more sensitive than the Abbott test at detecting a synthetic 104mer peptide of p24. Within the 104mer sequence two regions (294-318, 334-348 amino acids) inhibited the binding of the DuPont detector antibody, but no blocking was observed with the Abbott antibody. Although the Abbott test was slightly more sensitive at detecting HIV protein than the DuPont test, the major difference between the tests was in the molecular specificity, in that the Abbott test detected proteins other than p24. This may not be important for detecting antigen in cell culture, but it may affect the detection of antigenaemia in patients' sera.

Blotting, Western↗
PubMed1990

Septicaemia in patients with AIDS.

During a 5 year period at St Stephen's hospital, London, septicaemia was detected in 66 patients with the acquired immune deficiency syndrome (AIDS) and in 13 other patients with non-AIDS-associated HIV infections. The most frequent pathogens in patients with AIDS were Mycobacterium avium-intracellulare, Streptococcus pneumoniae, Pseudomonas aeruginosa, Cryptococcus neoformans and staphylococci. A series of HIV-associated septicaemias reported from other centres in different countries has shown great variation in the pattern of aetiological agents observed, which may partly reflect differences in the local socio-economic condition, ethnic backgrounds, other predisposing factors, and blood culture techniques. Salmonella species were a prominent cause of septicaemia in several reports. Most centres have also reported an increasing problem with septicaemias associated with intravenous lines in patients receiving antiviral or other parenteral drug therapy.

Acquired Immunodeficiency Syndrome↗
PubMed1990

Acquired immune deficiency syndrome: recommendations of a Working Party of the Hospital Infection Society.

Unified procedures to control those infections that are transmitted by inoculation of blood are recommended. These should be applied to patients with acquired immune-deficiency syndrome (AIDS), AIDS-related complex, persistent generalized lymphadenopathy or hepatitis B, those with serological evidence of infection by human immunodeficiency virus or hepatitis B virus, and those in medical and social categories with a higher than average prevalence of such infections. When the identification of these categories of patient would be particularly difficult, the precautions should be applied to all patients, in situations of high risk for inoculation incidents. Rational infection-control measures, based on the known mode of spread, permit efficient management of infected patients, with satisfactory protection of staff and other patients.

Acquired Immunodeficiency Syndrome↗
PubMed1990

Clinical relevance of resistance to fusidic acid in Staphylococcus aureus.

The clinical relevance of resistance to fusidic acid in Staphylococcus aureus is reviewed. Resistance due to a one-step chromosomal mutation emerges readily in vitro. These variants appear defective and are not encountered clinically as frequently as would be expected. The majority of strains isolated from patients probably have plasmid-mediated resistance. The plasmid may be unstable both in vitro and in vivo. There appears to be a low incidence of resistance emerging when fusidic acid is used alone to treat acute infections; however, there is a higher incidence in chronic infections. When fusidic acid is given concurrently with another antibacterial agent to treat severe infection, resistance may be acquired in up to 1% of cases. The use of fusidic acid topically to treat acute skin infection in domiciliary practice does not appear to be epidemiologically hazardous. Over the last 20 years, during which fusidic acid has been used widely in the management of staphylococcal infection, the general level of resistance has remained low at 1-2%.

Drug Resistance, Microbial↗
PubMed1990

Blood culture technique: current controversies.

Currently controversial questions include: what is the optimal volume of blood for culture and which blood culture system is most suitable for the rapid and reliable detection of important pathogens? The author has discussed these topics and recommends the following: (1) At least 10 ml blood should be cultured for each set from an adult but the maximum possible volume, up to 30 ml, should be cultured. This is especially advisable when febrile immunocompromised patients and patients with infective endocarditis are investigated. (2) The best routine system for obtaining rapid and reliable blood culture results involves the use of two aerobic diphasic media and one anaerobic broth for the culture of 20 ml blood per set. Two blind subcultures are recommended during the first 24 h incubation. This conventional system is impracticable for some laboratories that process enormous numbers of blood cultures and for these laboratories the infrared Bactec system is recommended. (3) An additional blood culture method, such as the lysis-centrifugation system, should be used together with the routine system when clinical circumstances suggest the need to isolate particular 'difficult organisms' and to facilitate the culture of the maximum volume of blood. (4) It is preferable that the routine system includes one bottle without Liquoid as Liquoid-sensitive organisms may otherwise be inhibited even when gelatin is included in the medium.

Bacteriological Techniques↗
PubMed1990

Blind comparison of Abbott and Dupont HIV antigen ELISA tests for detecting antigenaemia in asymptomatic human immunodeficiency virus antibody positive homosexual men.

Three hundred and ninety eight serum samples from 270 human immunodeficiency virus (HIV) antibody positive asymptomatic homosexual men were tested in the Abbott and Dupont HIV antigen ELISA tests. In the Abbott test 62 (16%) of the sera were positive, according to the manufacturer's instructions, compared with 55 (14%) in the Dupont test. Twenty six sera were positive with the Abbott test but negative with the Dupont test and 19 sera were positive only by the Dupont test. Only 36 (9%) of the sera were positive in both tests. The Abbott confirmatory neutralisation test gave excellent agreement with the initial Abbott HIV antigen ELISA test; the Dupont confirmatory test was only in agreement with the initial positive Dupont antigen ELISA test in one third of the sera tested. Although the overall sensitivity of each of the two commercial assays tested was similar, the Abbott method may be preferable for clinical purposes if confirmation of an initial ELISA positive test result by neutralisation assay is required.

Enzyme-Linked Immunosorbent Assay↗
PubMed1989

Attitudes of operating theatre staff to inoculation-risk cases.

In a 12-month period, 177 patients at risk of infection with human immunodeficiency virus (HIV) or hepatitis B were operated on. Sixty-nine had HIV antibodies. The procedures used to identify these patients and minimize the risk of infection of hospital staff in the operating department are described. All staff working in the operating department were surveyed to determine their caseload, feelings of anxiety, and the incidence of high-risk exposure to infection. Anxiety was not related to workload, but was more common in those who had high-risk exposure. All members of staff who sustained a needlestick injury were tested for HIV antibodies at intervals after injury; 33 also volunteered to be tested in a screening session 3 months after the study period. None had HIV antibodies, suggesting that the risk of acquiring HIV infection in the operating department is low.

Acquired Immunodeficiency Syndrome↗