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Biomedical subjects

B W Allen

Publications and source records attributed to B W Allen.

At least 19 recordsLinked to original sources
PubMed1992

The early bactericidal activity of rifabutin measured by sputum viable counts in Hong Kong patients with pulmonary tuberculosis.

Previously untreated patients with smear-positive pulmonary tuberculosis were randomly allocated to treatment with 600, 300, 150 or 75 mg doses of rifabutin (LM427, ansamycin), 600, 300 or 150 mg of rifampicin, 300 mg isoniazid or to no drug daily for 2 days. The fall in viable counts of Mycobacterium tuberculosis in sputum collections during the 2 days, termed the early bactericidal activity (EBA), was estimated from counts of colony-forming units (cfu) on selective 7H-11 agar medium. The EBA for rifabutin ranged from -0.039 (an increase in counts) to 0.049 log10 cfu/ml/day whereas the EBA increased from 0.071 for 150 mg rifampicin to 0.293 log10 cfu/ml/day for 600 mg rifampicin and was 0.43 log10 cfu/ml/day for 300 mg isoniazid. The difference between the EBAs for rifabutin and rifampicin just attained significance (P = 0.05) suggesting that rifabutin was inactive or less active than rifampicin against the extracellular bacilli in pulmonary cavities. Peak plasma concentrations of rifabutin after the initial doses were found to be proportional to dose size and were approximately 7 times lower than those after the same dose size of rifampicin. The lower EBA of rifabutin as compared to rifampicin is probably due to the low plasma concentrations which are not fully compensated for by slightly greater antituberculosis activity of rifabutin in vitro.

Adolescent↗
PubMed1992

Counts of viable tubercle bacilli in sputum related to smear and culture gradings.

Pairs of sputum specimens obtained pre-treatment from 166 smear-positive patients with pulmonary tuberculosis were examined by direct smear, culture on Löwenstein-Jensen medium after decontamination by the Petroff method, and by quantitative colony counting on selective 7H11 medium after digestion with dithiothreitol. The selective medium counts ranged from no growth to 8.3 log10 cfu/ml with the largest numbers in the range 3.5-7.0 log10 cfu/ml. Although there was overlap in counts between specimens with negative and positive direct smears, a specimen with a count of 4.0 log10 cfu/ml or more was likely to have a positive smear while a negative smear was likely if the count was lower. This demarcation value should be increased to 4.5 log10 cfu/ml to account for under-estimation in the selective medium counts. The corresponding demarcation estimate for LJ cultures was 80 colonies. In distinguishing between patients in the bacterial contents of their sputum, the selective medium counts were better than the gradings of either LJ cultures or direct smears.

Bacteriological Techniques↗
PubMed1991

Comparison of three methods for decontamination of faeces for isolation of Mycobacterium tuberculosis.

Sputum and faeces were obtained from 276 patients on admission to a study of drug resistance in Hong Kong. Acid-fast bacilli were detected microscopically in 103 (37%) sputum specimens and 135 (49%) yielded Mycobacterium tuberculosis on culture. Three methods were used to decontaminate faeces prior to dilution and culture in selective liquid Kirchner medium. A total of 61 faecal specimens were positive for M. tuberculosis on culture and, of these, pretreatment with sodium hydroxide yielded 60 (98%), Portaels modification of Wolinsky and Rynearsons's method 28 (46%) and the combined use of benzalkonium chloride and 1-hexdecylpyridinium chloride yielded 32 (52%). It is recommended that faeces should be treated with sodium hydroxide followed by dilution and culture in selective media, although it may be necessary to formulate new selective media for mycobacterial species other than M. tuberculosis.

Bacteriological Techniques↗
PubMed1989

Slide culture sensitivity tests.

A new method for slide culture sensitivity tests of Mycobacterium tuberculosis is described in which smear-positive sputum spread on slides is incubated without prior decontamination in a selective lysed human blood medium. Results are available 7 days after setting up the tests and are particularly useful for guiding the treatment of smear-positive patients with a long history of unsuccessful chemotherapy. Drug concentrations and definitions of resistance are suggested for tests against isoniazid, streptomycin, PAS, rifampicin ethambutol and ethionamide. A good correlation was seen between the results of these tests and those of standard indirect sensitivity tests.

Antitubercular Agents↗
PubMed1989

Isolation of Mycobacterium tuberculosis from faeces.

Faeces from patients with Myco, tuberculosis in their sputum was decontaminated using NaOH, acid and an alkaline precipitation method. Treated specimens were diluted, to reduce the number of surviving normal flora, and cultured in liquid selective media. Sub-cultures were made on selective agar and Lowenstein-Jensen medium. Both alkaline methods were superior to acid treatment. Use of all three methods, dilution and culture, yielded growth of Myco, tuberculosis from 90% of patients' faeces, although previous reports have cited only 25-30% of patients excreting bacilli in their faeces.

Bacteriological Techniques↗
PubMed1988

Controlled clinical trial of complete open surgical drainage and of prednisolone in treatment of tuberculous pericardial effusion in Transkei.

240 patients with active tuberculous pericardial effusion received a 4-drug daily antituberculosis regimen for 6 months and have been studied for 24 months or longer. Those willing were randomly allocated to open pericardial biopsy and complete drainage of pericardial fluid on admission or percutaneous pericardiocentesis as required. All patients were randomly allocated to prednisolone or matching placebo for the first 11 weeks, on a double-blind basis. Complete open drainage on admission abolished the need for pericardiocentesis (p less than 0.01) but did not influence the need for pericardiectomy for subsequent constriction or the risk of death. Among patients who did not have open drainage on admission, 2 (3%) of 76 given prednisolone compared with 10 (14%) of 74 given placebo died of pericarditis (p less than 0.05), 6 (8%) and 9 (12%) respectively required pericardiectomy, 7 (9%) and 17 (23%) repeat pericardiocentesis (p less than 0.05), and 3 (4%) and 7 (9%) open surgical drainage. By 24 months, apart from the 16 who died from pericarditis, all but 3 patients (2%) had a favourable status.

Adolescent↗
PubMed1987

Excretion of viable tubercle bacilli by Blatta orientalis (the oriental cockroach) following ingestion of heat-fixed sputum smears: a laboratory investigation.

Adult Blatta orientalis were allowed to feed on heat-fixed tuberculous sputum smears and the faeces collected for examination by microscopy and culture. Mycobacterium tuberculosis was repeatedly isolated from homogenized faecal pellets using liquid and solid selective culture media. Faeces remained positive both microscopically and on culture even after storing for 8 weeks at room temperature. It is recommended that smears, prepared from clinical material which may contain M. tuberculosis or M. leprae, are stored in a closed container and not left exposed to nocturnal omnivorous insects which frequently infest hospitals and laboratories.

Animals↗
PubMed1987

Pathophysiology of pH and Ca2+ in bloodstream and brain.

The highlights of the literature and our work on tetany and hyperventilation are reviewed. Our studies concern the following: (1) the changes of [Ca2+] in circulating plasma caused by respiratory and "metabolic" acidosis and alkalosis; (2) critical plasma [Ca2+] levels associated with signs of tetany and neuromuscular blockade; (3) changes in cerebral [Ca2+]o caused by hypo- and hyper-calcaemia, and the changes in cerebral [Ca2+]o and pHo caused by acute systemic acidosis and alkalosis; and (4) effects of changing [Ca2+]o and pHo levels on synaptic transmission in hippocampal formation. Our main conclusions are (1) changes of plasma [Ca2+] caused by "metabolic" pH changes are greater than those associated with varying CO2 concentration; (2) acute systemic [Ca2+] changes are associated with small cerebral [Ca2+]o changes; (3) the decreases in systemic and cerebral [Ca2+]o caused by hyperventilation are too small to account for the signs and symptoms of hypocapnic tetany; (4) moderate decrease of [Ca2+]o depresses and its increase enhances synaptic transmission in hippocampal formation; and (5) H+ ions in extracellular fluid have a weak depressant effect on neuronal excitability. CO2 is a strong depressant, which is only partly explained by the acidity of its solution. CO2 concentration is a significant factor in controlling cerebral function.

Animals↗
PubMed1986

The bioavailability of isoniazid, rifampin, and pyrazinamide in two commercially available combined formulations designed for use in the short-course treatment of tuberculosis.

The bioavailability of isoniazid, rifampin, and pyrazinamide in 2 combined formulations of the 3 drugs (Rifater) for use primarily in the short-course chemotherapy of tuberculosis has been studied in Chinese patients in Singapore and Hong Kong. One formulation, containing 50 mg isoniazid, 120 mg rifampin, and 300 mg pyrazinamide per tablet is suitable for daily use, whereas the other, containing higher proportions of isoniazid and pyrazinamide, is designed for intermittent treatment, each tablet containing 125 mg isoniazid, 100 mg rifampin, and 375 mg pyrazinamide. Appropriate dosages for the Chinese patients, whose average weight was approximately 50 kg, were 5 and 6 tablets, respectively. Plasma concentrations of the 3 drugs after giving such dosages of the 2 combined formulations were compared in 16 patients, 8 in Singapore and 8 in Hong Kong, by means of a crossover study, with the concentrations obtained when identical doses of the 3 drugs were given using standard separate drug formulations. The concomitant urinary excretions of the drugs and their major metabolites were also estimated. Very similar results were obtained whether the drugs were given as the combined preparations or in their standard separate formulations, demonstrating the excellent bioavailability of all 3 drugs in each of the 2 combined formulations.

Acetylation↗
PubMed1985

In-vitro inhibition of mycobacteria by viridans streptococci.

Eleven strains of Mycobacterium tuberculosis and 13 other species of mycobacteria were examined for susceptibility to 26 strains of viridans streptococci. Susceptibility was detected by the simultaneous antagonism technique, but not by tests of deferred antagonism. It is concluded that in-vitro inhibition of mycobacterial growth by actively growing streptococci is due to a peroxide-mediated antagonism which is too variable to be of value for identification. However, a standard bactericidal test with hydrogen peroxide is worth investigation because this might provide a simple inexpensive aid for the identification of M. avium-intracellulare serotypes.

Antibiosis↗
PubMed1983

Amikacin in the treatment of pulmonary tuberculosis.

Sensitivity tests on strains from 11 patients with pulmonary tuberculosis, previously treated with kanamycin and/or capreomycin, showed incomplete cross-resistance between amikacin and capreomycin but complete cross-resistance between amikacin and kanamycin. Treatment with amikacin of 4 patients with multiply resistant strains resulted in no response as assessed by sputum smears and cultures, but resistance emerged to amikacin, kanamycin and capreomycin. Amikacin has no role in the treatment of tuberculosis as it cannot be given as an alternative to kanamycin, has no advantages over it and is more expensive.

Adult↗
PubMed1983

Selective Kirchner medium in the culture of specimens other than sputum for mycobacteria.

Over a two-year period, 2949 non-sputum specimens were cultured on two slopes of Löwenstein-Jensen (LJ) medium, two bottles of Kirchner liquid medium, made selective by adding polymyxin B, carbenicillin, trimethoprim and amphotericin B, and a selective 7H11 agar slope. Pus and CSF were inoculated into this set without prior treatment, but other specimens were decontaminated with sulphuric acid. Tissues and fluids were also inoculated without decontamination into additional selective media. The use of the selective media as well as the LJ slopes increased the yield of specimens with cultures of tubercle bacilli from 34 to 53 and decreased specimens with all media contaminated from 34 to 2. Results almost as good, 52 positive specimens and five totally contaminated, would have been obtained by the addition of a single selective Kirchner bottle to the two LJ slopes, and this is recommended for routine use.

Bacteriological Techniques↗
PubMed1983

Contamination of specimen container surfaces during sputum collection.

Sputum specimens from culture-positive tuberculosis patients were examined for the presence of Myobacterium tuberculosis on container surfaces. Although specimens were in transit for several days, M tuberculosis was isolated from 18 (6.5%) of 279 containers examined. Sputum specimens from local patients were examined for evidence of upper respiratory bacterial flora on the outside of containers as an indicator of contamination with sputum. Of 300 containers examined, 41 (14%) were contaminated. A technique for disinfecting specimen containers from tuberculosis patients has been evaluated and recommendations are made for handling sputum containers.

Decontamination↗
PubMed1983

Examination of operation specimens from patients with spinal tuberculosis for tubercle bacilli.

Operation specimens from 52 Hong Kong patients considered to have tuberculosis of the spine were sent at -78 degrees C to London where they were cultured on two Löwenstein-Jensen medium slopes, a slope of 7H11 medium made selective with antibiotics and in two bottles of selective liquid Kirchner medium. Cultures of M tuberculosis, usually with only scanty colonies, were obtained from 37 of the patients. Pus and caseous matter yielded more positive cultures and more numerous colonies than other specimens, but eight of the 37 patients yielded positive cultures only from tissues lining abscess walls or from bone or intervertebral disc specimens. Cultures in Kirchner medium were never contaminated and twice as many were positive as cultures on the slopes; nine patients had cultures positive only on Kirchner medium. It is recommended that (i) a variety of operation specimens, always including pus or caseous material in volumes of at least 1 ml, should be sent for bacteriology; (ii) specimens should be cultured in selective Kirchner medium, with or without Löwenstein-Jensen slopes; (iii) cultures should be incubated for a minimum of 8-9 wk.

Culture Media↗