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J O Kilburn

Publications and source records attributed to J O Kilburn.

At least 37 records · Page 2Linked to original sources
PubMed1990

Modified method for testing the quality of albumin-containing enrichments used in growth media for mycobacteria.

Many commercially available media for cultivation of mycobacteria have failed to support the growth of these organisms. This is especially true of media prepared with albumin-containing enrichments. Earlier, we developed a method for rapid identification of good albumin enrichments for agar-based media used to test the susceptibility of tubercle bacilli to pyrazinamide. The method was modified to make testing of the acceptability of albumin enrichments for primary isolation media for mycobacteria possible. We describe here a simple turbidimetric test using a specific Bacillus subtilis strain to assay quickly (24 h) different lots of albumin-containing enrichments that may be used in the preparation of growth media for mycobacteria.

Albumins↗
PubMed1990

High-performance liquid chromatography patterns of mycolic acids as criteria for identification of Mycobacterium chelonae, Mycobacterium fortuitum, and Mycobacterium smegmatis.

Rapidly growing mycobacteria of clinical significance were identified by mycolic acids detected with high-performance liquid chromatography. Mycolic acids from whole cells were extracted, derivatized, and detected by a modified high-performance liquid chromatography procedure in less than 3 h. Use of an internal standard allowed differentiation of Mycobacterium chelonae and Mycobacterium fortuitum by comparison of relative retention times. Peak height ratios were used for subidentification of M. chelonae strains; however, M. fortuitum and Mycobacterium smegmatis could not be separated by this system.

Chromatography, High Pressure Liquid↗
PubMed1989

Inhibition of synthesis of arabinogalactan by ethambutol in Mycobacterium smegmatis.

Ethambutol at 3.0 micrograms/ml inhibited the transfer of label from D-[14C]glucose into the D-arabinose residue of arabinogalactan in whole cells of a drug-susceptible strain of Mycobacterium smegmatis. This inhibition began almost immediately after exposure of the cells to the drug. When drug-resistant M. smegmatis was used in a similar experiment, no such drug inhibition was detected. A much higher concentration of ethambutol (greater than 50 micrograms/ml) was required to show this inhibition. The drug also inhibited synthesis of arabinose-containing oligosaccharides when a cell-free enzyme system was used. These results suggest that the site of action of ethambutol is somewhere on the pathway between the conversion of D-glucose to D-arabinose and the transfer of arabinose into arabinogalactan. The primary mode of action of ethambutol appears to be inhibition of arabinogalactan synthesis.

Cell Wall↗
PubMed1988

Identification of major slowly growing pathogenic mycobacteria and Mycobacterium gordonae by high-performance liquid chromatography of their mycolic acids.

A rapid, reverse-phase high-performance liquid chromatography method was used to detect rho-bromophenacyl mycolic acid ester patterns for strains of four major pathogenic Mycobacterium species and for the most commonly encountered saprophytic species, Mycobacterium gordonae. Mycobacteria in low numbers (2.5 X 10(6) CFU) were detected and identified to the species level. Standard chromatographic patterns characteristic of each species were established. Simple pattern recognition enabled rapid identification of M. tuberculosis, M. kansasii, M. avium, M. intracellulare, and M. gordonae.

Acetophenones↗
PubMed1987

High-performance liquid chromatography analysis of mycolic acids as an aid in laboratory identification of Rhodococcus and Nocardia species.

High-performance liquid chromatography analysis of the p-bromophenacyl esters of mycolic acids from whole organisms gave chromatographic patterns that were useful in differentiation of Rhodococcus and Nocardia species. Rhodococcus equi, R. erythropolis, and R. rhodochrous contained more-polar mycolic acids and were easily separated from the less-polar mycolic acid-containing species of R. sputi, R. bronchialis, R. corallinus, R. rubropertinctus, and R. terrae. The less-polar mycolic acid-containing Rhodococcus species showed chromatographic patterns that partially overlapped (in elution times) the patterns of Nocardia asteroides, N. otitidiscaviarum, and N. brasiliensis, but the larger number of peaks in the last species made separation between the genera possible. Distinct chromatographic patterns were found for most species, except for R. equi strains that showed two different patterns. Strains of R. rubropertinctus and R. terrae appeared identical. N. asteroides and N. otitidiscaviarum showed similar mycolic acid patterns.

Actinomycetales↗
PubMed1986

High-performance liquid chromatography of mycolic acids as a tool in the identification of Corynebacterium, Nocardia, Rhodococcus, and Mycobacterium species.

High-performance liquid chromatography of bromophenacyl esters of mycolic acid was used as an aid to assign a particular organism to one of four mycolic acid-containing genera. A gradient elution system, with methanol and chloroform, was used to distinguish representative mycolic acid patterns for the genera Corynebacterium, Rhodococcus, Nocardia, and Mycobacterium.

Actinomycetales↗
PubMed1985

Infection and disease among contacts of tuberculosis cases with drug-resistant and drug-susceptible bacilli.

Three hundred ninety-eight tuberculosis patients with tubercle bacilli resistant to isoniazid and/or streptomycin were matched by age, race, sex, and geographic area to an equal number of patients with tubercle bacilli susceptible to 9 drugs, including isoniazid and streptomycin, in an effort to determine whether the risk of infection and disease among contacts of patients with resistant bacilli is different from the risk among contacts to patients with susceptible bacilli. The risk of infection among contacts of previously untreated patients was not significantly different, regardless of whether the bacilli were drug-resistant or susceptible. However, the risk of infection increased if the index patient with resistant bacilli had been previously treated. We found no evidence of a lower risk of infection among contacts exposed to bacilli resistant to the highest concentration of isoniazid tested or among contacts exposed to bacilli resistant to both isoniazid and streptomycin. There was a strong association between infection risk among contacts and the age of the index case; younger patients were more infectious. Index cases tended to infect most (or all) or few (or none) of their contacts. The investigation of contacts of patients excreting drug-resistant bacilli should be given high priority.

Adolescent↗
PubMed1983

Susceptibility of Mycobacterium tuberculosis to pyrazinamide and its relationship to pyrazinamidase activity.

Pyrazinamidase activity has been associated with pyrazinamide-susceptible Mycobacterium tuberculosis strains. The detection of pyrazinamidase activity by the Wayne method was found to be of limited value when compared with the results of standard pyrazinamide susceptibility tests, especially when a high level of pyrazinamide resistance was found. When resistance to pyrazinamide reached a level of 150 to 200 micrograms/ml, there was too much variability in Wayne test results to accurately define pyrazinamide susceptibility.

Amidohydrolases↗
PubMed1982

Improved method for testing susceptibility of Mycobacterium tuberculosis to pyrazinamide.

The acid medium required to test susceptibility of Mycobacterium tuberculosis to pyrazinamide (PZA) is a major problem in obtaining reliable test results. Satisfactory growth is usually obtained on Middlebrook and Cohn 7H10 medium at pH 5.5 if albumin-dextrose-catalase (ADC) supplement rather than oleic acid-albumin-dextrose-catalase is used; however, some lots of ADC supplement still fail to support growth at this low pH. A rapid turbidimetric test was developed to determine the growth-supporting potential of ADC enrichment for M. tuberculosis at pH 5.5. An atmosphere supplemented with 5 to 10% carbon dioxide, used to stimulate growth of tubercle bacilli on 7H10 medium, counteracted the growth-inhibiting effects of PZA. By using optimum conditions of medium and pH, the susceptibility of 90% of M. tuberculosis strains to PZA was determined.

Bacillus subtilis↗
PubMed1982

In vitro susceptibility of Mycobacterium avium complex and Mycobacterium tuberculosis strains to a spiro-piperidyl rifamycin.

The spiro-piperidyl rifamycins are newly synthesized rifamycin S compounds. One of these compounds, LM 427, was tested in vitro against strains of the Mycobacterium avium complex and strains of M. tuberculosis; LM 427 inhibited 81.3% of 155 strains of the M. avium complex tested at a concentration of 1.0 microgram/ml compared with 5.8% inhibited by the same concentration of rifampin. Twenty-nine strains were resistant to both LM 427 and rifampin at 1.0 microgram/ml. Further testing of these 29 strains showed LM 427 inhibitory for all but 5 strains at 2.0 micrograms/ml and inhibitory for all but 1 at 5.0 micrograms/ml. Rifampin, on the other hand, inhibited none at 2.0 micrograms/ml and 11 strains at 5.0 micrograms/ml. The in vitro activity of LM 427 was also compared with rifampin by testing both compounds against M. tuberculosis at 1.0 microgram/ml. This comparison showed that all strains susceptible to rifampin were also susceptible to LM 427. However, 16 strains were susceptible to LM 427 and resistant to rifampin. The inhibition of drug-resistant mycobacterial species that cause pulmonary disease makes this compound an important consideration for future clinical studies.

Drug Resistance, Microbial↗
PubMed1981

Effects of ethambutol on accumulation and secretion of trehalose mycolates and free mycolic acid in Mycobacterium smegmatis.

We examined the early effects of ethambutol on the synthesis of trehalose monomycolate, trehalose dimycolate, and free mycolic acid in actively growing cells of Mycobacterium smegmatis. At about 1 min after the addition of 3.0 micrograms of ethambutol per ml, the cellular level of trehalose monomycolate began to increase over the control culture. This was followed 8 to 12 min later by the cellular increases in free mycolic acid and trehalose dimycolate over the control culture and the inhibition of incorporation of mycolic acid into the cell wall. Exposure of M. smegmatis to ethambutol for more than 30 min caused all of these lipids to leak out of the cells more rapidly than in the control cells. The mechanism by which ethambutol initiates these events is unknown, but these early imbalances in lipid synthesis may be responsible for the lethal action of this drug.

Cord Factors↗
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↗
PubMed1978

Effect of low temperature on growth, viability, and synthesis of mycolic acids of Mycobacterium tuberculosis strain H37Ra.

Cultures of Mycobacterium tuberculosis strain H37Ra were grownto early logarithmic phase at 37 degrees C and were incubated at 16 degrees, 20 degrees, and 25 degrees C. The decrease in this ability was more rapid at 20 degrees C than at 16 degrees C. Low-temperature incubation caused decreases in the ratios of mycolic acids and monounsaturated C16-19 fatty acids relative to the total of fatty acids synthesized. It also caused an increase in the ratio of saturated C24-26 fatty acids relative to the total of fatty acids synthesized. These ratios were based on the incorporation of radiolabel from 14C-acetate into fatty acids. These results showed that when M. tuberculosis H37Ra was incubated at low temperatures, it did not adapt by increasing the ratio of unsaturated to saturated fatty acids synthesized. The ability of the cells to synthesize mycolic acids was sharply decreased. These changes may lead to the loss of viability of M. tuberculosos H37Ra. Mycolic acid synthesis is similarly affected by exposure of cells to isoniazid, an antimycobacterial drug.

Chromatography, Thin Layer↗
PubMed1977

Effect of ethambutol on the viable cell count in Mycobacterium smegmatis.

Soon after a strain of Mycobacterium smegmatis was exposed to ethambutol (EMB), the number of viable cells increased dramatically above the number in a drug-free control. This rapid rise did not occur when the culture was maintained at 4 degrees C instead of 37 degrees C, when an EMB-resistant mutant was used, when auxotrophs were exposed in medium lacking nutrients essential for growth, nor when the levo form of EMB was used. EMB caused no increase in deoxyribonucleic acid synthesis, nor in septum formation of dividing cells. Treated cells changed morphologically, resulting in a lower surface area-to-volume ratio. Whereas EMB did not eliminate cell clusters, the cluster size decreased markedly as detected by filtration and Coulter counter measurements. We concluded that EMB causes a reduced surface-to-volume ratio, leading to reduced cell cohesion and a consequent reduction in cluster size, reflected in an increase in colony-forming units.

Cell Count↗