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Biomedical subjects

G Middlebrook

Publications and source records attributed to G Middlebrook.

At least 19 recordsLinked to original sources
PubMed1984

Rapid radiometric methods to detect and differentiate Mycobacterium tuberculosis/M. bovis from other mycobacterial species.

Rapid methods for the differentiation of Mycobacterium tuberculosis/M. bovis (TB complex) from other mycobacteria (MOTT bacilli) were developed and evaluated in a three-phase study. In the first phase, techniques for identification of Mycobacterium species were developed by using radiometric technology and BACTEC Middlebrook 7H12 liquid medium. Based on 14CO2 evolution, characteristic growth patterns were established for 13 commonly encountered mycobacterial species. Mycobacteria belonging to the TB complex were differentiated from other mycobacteria by cellular morphology and rate of 14CO2 evolution. For further differentiation, radiometric tests for niacin production and inhibition by Q-nitro-alpha-acetyl amino-beta-hydroxy-propiophenone (NAP) were developed. In the second phase, 100 coded specimens on Lowenstein-Jensen medium were identified as members of the TB complex, MOTT bacilli, bacteria other than mycobacteria, or "no viable organisms" within 3 to 12 (average 6.4) days of receipt from the Centers for Disease Control. Isolation and identification of mycobacteria from 20 simulated sputum specimens were carried out in phase III. Out of 20 sputum specimens, 16 contained culturable mycobacteria, and all of the positives were detected by the BACTEC method in an average of 7.3 days. The positive mycobacterial cultures were isolated and identified as TB complex or MOTT bacilli in an average of 12.8 days. The radiometric NAP test was found to be highly sensitive and specific for a rapid identification of TB complex, whereas the radiometric niacin test was found to have some inherent problems. Radiometric BACTEC and conventional methodologies were in complete agreement in Phase II as well as in Phase III.

Cells, Cultured↗
PubMed1981

Evaluation of rapid radiometric method for drug susceptibility testing of Mycobacterium tuberculosis.

A total of 106 isolates of Mycobacterium tuberculosis were tested for drug susceptibility by the conventional 7H11 plate method and by a new rapid radiometric method using special 7H12 liquid medium with 14C-labeled substrate. Results obtained by the two methods were compared for rapidity, sensitivity, and specificity of the new test method. There was 98% overall agreement between the results obtained by the two methods. Of a total of 424 drug tests, only 8 drug results did not agree, mostly in the case of streptomycin. This new procedure was found to be rapid, with 87% of the tests results reportable within 4 days and 98% reportable within 5 days as compared to the usual 3 weeks required with the conventional indirect susceptibility test method. The results of this preliminary study indicate that the rapid radiometric method seems to have the potential for routine laboratory use and merits further investigations.

Antitubercular Agents↗
PubMed1981

Resistance to rifampicin and isoniazid in strains of Mycobacterium tuberculosis.

Drug susceptibility studies on strains of Mycobacterium tuberculosis isolated from widely different populations of patients and tested by two different techniques indicated that all 55 strains resistant to rifampicin were also resistant to isoniazid, while many strains resistant to isoniazid were found to be susceptible to rifampicin. This observation, which has as yet unknown laboratory and clinical significance, may be particularly useful in management of patients. Further studies are called for to establish this relation.

Drug Resistance, Microbial↗
PubMed1981

Rapid drug-susceptibility testing of Mycobacterium tuberculosis.

Three methods for rapidly determining the susceptibility of Mycobacterium Tuberculosis isolates to isoniazid, rifampin, ethambutol, streptomycin, and para-aminosalicylic acid were evaluated in a large-scale, blind study. Two of the methods measured evolution of CO2 from radio-labeled substrate (14CO2), and one method measured incorporation of 3H-uracil into ribonucleic acid. Rapid indirect drug-susceptibility test results for nearly 300 isolates were compared with those obtained using a standard modified proportion technique. The 3H-uracil uptake method proved to be unacceptable. Over-all, the results obtained using the 14CO2 methods and the standard method were similar. In general, there was greater agreement between the 14CO2 and proportion techniques with drug-susceptible strains than with drug-resistant strains. Among drug-resistant strains, both 14CO2 methods were more reliable for determining resistance to rifampin than to other drugs. This study demonstrates that large-scale, blind evaluations of new laboratory procedures are valuable. Our results indicate that methods relying o the enzymatic release of 14CO2 should be further refined and evaluated.

Aminosalicylic Acid↗
PubMed1977

Partial purification and properties of an antibacterial product of peritoneal exudate cell cultures from BCG-infected guinea pigs.

Peritoneal exudates elicited in BCG-infected guinea pigs with caseinate yield cell cultures that have been shown to produce soluble material capable of sterilizing certain bacteria if the cultures are incubated with the specific antigen purified protein derivative or the lectin phytohemagglutinin. This material is now shown to have the following properties: (i) strongly adsorbable to glass; (ii) strongly adsorbable to cation- and not to anion-exchange resins but not elutable with mineral acid or solutions of high ionic strength; (iii) strongly adsorbable to cellulose nitrate membrane filter materials and quantitatively elutable with dilute HCl, providing a convenient method for partial purification; (iv) relatively stable over a wide range of pH and temperature; (v) antagonized by polyanions and by iron ions; (vi) active against the three gram-positive bacilli tested and not against the other organisms tested: (vii) more active in alkaline than in acidic media; and (viii) inactivated by proteolytic enzymes.

Animals↗
PubMed1977

Antibacterial product of peritoneal exudate cell cultures from guinea pigs infected with mycobacteria, listeriae, and rickettsiae.

In an in vitro model of cellular immunity, the antibacterial product of immunologically mediated mononuclear cell activation was studied from guinea pigs infected with listeriae and rickettsiae and compared with the product previously described from animals infected with mycobacteria. We found that this product, active against gram-positive bacilli, appeared to be identical in the three different infections with regard to its heat stability, its chromatographic adsorption and elution pattern, its susceptibility to inactivation by proteolytic enzymes, and its antibacterial spectrum

Animals↗
PubMed1977

Automatable radiometric detection of growth of Mycobacterium tuberculosis in selective media.

The formulation of media for selective, automatable, radiometric detection of growth of Mycobacterium tuberculosis in vitro is described. Palmitic-1 acid labeled with carbon-14 and formic-14C acid were compared as substrate sources of [14C]O2 in media deficient in carbohydrate and containing appropriate antimicrobial agents that are not active against tubercle bacilli. A preliminary clinical laboratory study of a medium containing 4 microCi palmitic-1-14C acid per ml showed that this method might provide the basis for practical laboratory use.

Bacteriological Techniques↗
PubMed1976

Some bacteriologic aspects of the epidemiology of pulmonary and extrapulmonary tuberculosis.

A study was carried out to investigate the drug resistance patterns of the prevalent tubercle bacilli in pulmonary and extrapulmonary tuberculosis in and about the city of Lahore, Pakistan. This report includes 168 strains of Mycobacterium tuberculosis isolated from the same number of pulmonary tuberculosis cases (100 untreated cases, defined as patients either having no history of anti-tuberculous therapy or having had chemotherapy for not more than 10 days; 68 treated, defined as having had chemotherapy for more than 10 days), and 162 strains from the same number of extrapulmonary tuberculosis cases (77 untreated, 38 treated and 47 doubtful). The proportion method of drug susceptibility assay was employed. According to the procedures used in this study and with 1% as the critical proportion for resistance, bacterial resistance was found to be very prevalent in pulmonary tuberculosis. Even among those cases in which no history of previous treatment was elicited, 46% were found to be excreting populations of tubercle bacilli having some degree of resistance to one or more of the primary drugs--isoniazid, streptomycin and para-aminosalicylic acid. In treated cases, 86.8% were found to have some resistance to one or more drugs. Overall, resistance to streptomycin was found to be commonest. Drug resistance was observed to be somewhat less common in extrapulmonary than in pulmonary tuberculosis, with streptomycin resistance predominating. Although both catalase-positive and catalase-negative isoniazid-resistant strains of M. tuberculosis were isolated from patients with pulmonary disease, no catalase-negative strains were isolated from patients with extrapulmonary disease, suggesting limited pathogenic potentialities of catalase-negative strains for man. Epidemiologic aspects of these observations are discussed.

Adult↗
PubMed1976

Ultraviolet susceptibility of BCG and virulent tubercle bacilli.

To test the effectiveness of irradiating the upper air of a room with ultraviolet light at reducing the concentration of airborne tubercle bacilli, the susceptibility to the germicidal effects of ultraviolet light, Z, was determined for various mycobacteria. Virulent tubercle bacilli and bacille Calmette-Guérin (BCG) were equally susceptible to ultraviolet radiation, whereas Mycobacterium phlei had 10 times their resistance (Z, approximately one-tenth that for M. tuberculosis). The effectiveness against BCG of upper air ultraviolet irradiation in a room was tested directly by nebulizing BCG into the air of the room and monitoring its rate of disappearance. With one 17-watt fixture operating, the rate of disappearance increased 6-fold; with 2 fixtures operating (46 watts total), the rate of disappearance increased 9-fold. This implies that under steady-state conditions, the concentrations of airborne organisms with ultraviolet light(s) on would have been one-sixth and one-ninth, respectively. The increase in rate of decay of the airborne organisms using 1 fixture was equivalent to 10 air changes per hour, whereas that using 2 fixtures was approximately 25 air changes per hour (range: 18 to 33 air changes per hour). These increments are less than those reported previously for Serratia marcescens, because the Z value for BCG is approximately one-seventh that for serratia. These findings with BCG are believed to be directly applicable to virulent tubercle bacilli.

Air Microbiology↗
PubMed1974

Serologically active glycolipid families from Mycobacterium bovis BCG. I. Extraction, purification and immunologic studies.

Glycolipids were extracted from mycobacteria with methanol and chloroform and purified by silicic acid chromatography. These glycolipids were studied for their serologic activity by direct and indirect (Coomb's) passive hemagglutination, and by inhibition methods. Three families of serologically active glycolipids called A, B and C, plus cardiolipin, were isolated. The B and C families of glycolipids were reactive with sera from BCG immunized rabbits and also with sera from patients with tuberculosis and leprosy; the A family was reactive only with the human sera. None of the serologically active glycolipids was able to protect rabbits against tuberculosis.

Animals↗
PubMed1974

Serologically active glycolipid families from Mycobacterium bovis BCG. II. Serologic studies on human sera.

Serological tests with serologically active glycolipids from Mycobacterium bovis BCG were investigated for their possible use in the diagonis of mycobacterioses. The results were positive with 95 percent of sera from patients with far advanced and moderately advanced tuberculosis, 80 percent of sera from patients with newly diagnosed tuberculosis and 75 percent of patients with atypical mycobacterial diseases. "False" positive serologic reactions were obtained from 4 percent or less. Furthermore, 39 percent of sera from recent tuberculin converters were positive compared with only 9 percent of sera from unselected PPD positive individuals.

Antibodies, Bacterial↗
PubMed1974

Delayed-type hypersensitivity and immunity against aerogenic tuberculosis in guinea pigs.

In experiments described herein, it was observed that guinea pigs with delayed-type hypersensitivity to tuberculoproteins under various experimental conditions, with or without passive transfer of serum from immune donors, manifested no acquired immunity against aerogenically induced tuberculosis. These results are discussed in relation to the previous observations of other investigators and to the general problem of cellular hypersensitivity and immunity against facultative intracellular bacteria.

Aerosols↗