Deoxyribonucleic acid methylation in mycobacteria

Deoxyribonucleic acid modification in six strains of mycobacteria was investigated. The presence of 5-methylcytosine in the virulent strain Mycobacterium tuberculosis H37Rv and its absence in the avirulent strain M. tuberculosis H37Ra and other saprophytic, fast-growing mycobacteria appear to be the salient features. However, deoxyribonucleic acid from M. smegmatis SN2 lysogenized with the temperature phage I3 showed the presence of 5-methylcytosine. All of the strains had N6-methyladenine.

Tubercle bacilli retain pathogenicity after seven weeks chemotherapy

Guinea pig inoculation of sputum from patients on anti-tuberculous therapy shows that, in some cases, the tubercle bacilli retain their pathogenicity for seven weeks or more. It is and has been accepted in general for many years now that patients with active pulmonary tuberculosis receiving anti-tuberculous drugs become noninfectious in a relatively rapid time. Several factors have been said to contribute to this. Among these are: (i) patients on chemotherapy have a reduced cough and consequently expel fewer tubercle bacilli into the atmosphere; (ii) it has been suggested that patients receiving antituberculous drugs excrete these in the sputum droplets along with the tubercle bacilli and evaporation of the droplets causes concentrations of the anti-tuberculous drugs to increase, thereby reducing or destroying the viability of the organism; and (iii) chemotherapy rapidly reduces the number of bacilli excreted in sputum and this in itself may reduce the possibility of infection.

Distribution of ethambutol in primate tissues and cells

Ethambutol (EMB) concentrations that kill Mycobacterium tuberculosis in vitro accumulated in squirrel monkey tissues and cells known to be sites of tubercular infections. After oral administration of a clinically relevant 25 mg/kg dose, the whole-body distribution and intracellular localization of EMB were studied by radioautography. Tissue concentrations of drug were assayed by radiochemical and microbiological methods. The EMB was distributed rapidly and widely to most body tissues including lung and localized within pulmonary alveolar and axillary lymph node macrophages. The EMB in lung at 2 and 5 h after drug administration was markedly higher than the corresponding plasma concentrations and exceeded concentrations that are bactericidal in vitro for tubercle bacilli. These observations may help explain the early bactericidal activity of EMB in humans. Similarities in plasma and tissue concentrations of the drug in both species suggest the usefulness of the squirrel monkey as a model for the use of EMB in humans.

Influence of the virulence of Mycobacterium tuberculosis on protection induced by bacille Calmette-Guérin in guinea pigs

The protective efficacy of two bacille Calmette-Guérin (BCG) vaccines was examined in guinea pigs infected by the respiratory route with strains of Mycobacterium tuberculosis differing in virulence. Virulence was defined as the degree of tissue damage (weight) of primary lesions excised from lungs of unvaccinated guinea pigs killed 28-42 days after infection. Groups of animals vaccinated with BCG-Copenhagen (strain no. 1331), a vaccine of high potency, or those vaccinated with BCG-Prague (strain no. 725), an experimental vaccine of low potency, and groups given placebo were challenged six weeks later with one of three challenge strains differing in virulence. Protection was assessed from the difference in the number of tubercle bacilli recovered from excised primary lung lesions or from primary lesion-free lung lobes of vaccinated vs. unvaccinated animals. The virulence of the challenge strain influenced the efficacy of BCG vaccination; however, the results of other studies with a laboratory strain were in general replicated.

Extrapulmonary tuberculosis: a potential source of laboratory-acquired infection

A three-year retrospective study has demonstrated the effect of extrapulmonary tuberculosis on safety within a routine bacteriology laboratory. The investigation showed that, from 112 patients, 162 specimens considered to present a risk to laboratory staff were processed outside of the B1 protective area. However, it was estimated that only 51 of those specimens were heavily positive. Of these 57% were sputum 30% pus, and 10% urine. Specimens of pus and urine account for 50% of specimens received for non-tuberculosis investigations, and it would be impossible to process all specimens that might present a risk in B1 accommodation and still maintain a high degree of safety. It is recommended that request forms which accompany specimens should clearly indicate potential high-risk specimens.

Accidental contamination of diagnostic cultures of mycobacteria and phage identification of the contaminating strain

Phage typing of mycobacteria is a new technique not yet widely used for classification and intraspecies differentiation. Systematic long-term studies organized by the WHO have succeeded, using a battery of 11 different mycobacterial phages, in dividing M. tuberculosis into 3 different phage sub-groups, preliminarily labelled as A, B and C. A special case of phage-typing is presented which enabled identification of a virulent mycobacterial strain causing accidental contamination of diagnostic mycobacterial cultures. The strain was an old laboratory one, H37Rv, belonging to phage subgroup B.

Three types of mycolic acid from Mycobacterium tuberculosis Brévanne: implications for structure-function relationships in pathogenesis

Saponification of the chloroform-soluble wax from Mycobacterium tuberculosis Brévanne led to the isolation of three classes of mycolic acid containing characteristic functional groups along the methylene backbone: type alpha (two cyclopropane rings); type beta (methoxyl, methyl, and cyclopropane); and type gamma (ketone, methyl, and cyclopropane). The structures of these acids were elucidated principally by mass spectrometry. The high mass region of the keto mycolate is presented showing the meromycolal and molecular ion regions. This is first time a molecular peak for this mycolic acid has been reported. The structure of the keto mycolate was further substantiated by study of the mass spectral fragmentation of its dithioketal derivative. Within each type of acid, a series of homologs was encountered, varying according to the number of methylene units in the backbone chain. Chromatographic and infrared spectrophotometric evidence is presented for the alkali-induced isomerization of the three types of mycolates.

Immunosuppression by mycobacterial arabinomannan

The means by which mycobacteria elude host defence mechanisms to cause human disease is unknown. This report provides the initial demonstration of a soluble product of Mycobacterium tuberculosis with immunosuppressive activity which may contribute to the pathogenicity of this organism.

Mycobacterial D-arabino-D-mannan (AM), purified from culture filtrates of M. tuberculosis by Concanavalin A-Sepharose affinity chromatography did not itself induce ³H-thymidine incorporation or migration inhibitory factor production by peripheral blood mononuclear cells from tuberculin skin-test-positive healthy humans although it produced weak delayed skin-test reactions in these subjects. However, this mycobacterial cell wall polysaccharide suppressed the response of human lymphocytes to mycobacterial and other antigens as assessed with these in vitro correlates of delayed hypersensitivity. Immunosuppression by arabinomannan was not contingent upon prior exposure of the individual to M. tuberculosis, since it occurred with lymphocytes from tuberculin skin-test non-reactive as well as reactive subjects. Nor was it due to cytotoxicity, an antimitotic effect of the polysaccharide preparation or generation of suppressor cells. Rather, AM seemed to suppress macrophage-dependent, antigen-induced activation of human lymphocytes. This immunosuppressive substance elaborated by mycobacteria has potential relevance to the pathogenesis of human tuberculosis and the nature and limitation of the resulting host response.

The correlation of bacteriophage types of Mycobacterium tuberculosis with guinea-pig virulence and in vitro-indicators of virulence

Among 58 isoniazid-sensitive strains of Mycobacterium tuberculosis from India, Burma and East Africa, 23 were of phage type A, 31 of type I (intermediate), 4 of type B and none of type C. Type I strains differed from type A strains in being attenuated in the guinea-pig, susceptible to H2O2, sensitive to thiophen-2-carboxylic acid hydrazide and resistant to thiacetazone and p-aminosalicylic acid; the content of strongly acidic lipids and of sulphatide lipids was low and the attenuation indicator lipid was present. The pattern of results with the type B strains did not correspond to the patterns for types A or I. Strains of type I appear to be a distinct group within the species M. tuberculosis.

Virulence of Mycobacterium tuberculosis and susceptibility to peroxidative killing systems

At sub-bactericidal concentrations of hydrogen peroxide, Mycobacterium tuberculosis was killed by hydrogen peroxide/peroxidase/halide microbicidal systems. The halide cofactor could be either iodide or, with much lower efficiency, chloride. Omission of any one of the reactants eliminated the tuberculocidal effect. Differences in susceptibility between different strains of M. tuberculosis did not correlate with virulence differences. The observations are discussed in the context of host defence mechanisms against tuberculosis.

Cerebral prostaglandin synthesis during the dietary and pathological stresses of essential fatty acid deficiency and experimental allergic encephalomyelitis

Rats of the Lewis strain were fed diets adequate or deficient in essential fatty acids (EFA). At 70-80 days of age experimental allergic encephalomyelitis (EAE) was induced using adjuvants containing either Mycobacterium butyricum or Mycobacterium tuberculois H37Ra. When the former Mycobacterium was used, the incidence of EAE was greater in the EFA-deficient than in EFA-adequate controls; but when the rats challenged with M. tuberculosis, the incidence of the disease was the same in both dietary groups. Brain slices from EFA-deficient rats had a marginally depressed synthesis of prostaglandin F (PGF) compared to that of controls. Immunochallenge with adjuvant alone or adjuvant plus antigen tended to depress further PGF synthesis by brain slices from EFA-deficient rats and significantly depressed synthesis by slices from rats receiving adequate EFA. Whether or not rats were paralyzed had no effect on PGF synthesis when the diet was adequate in EFA, but a significant difference was seen in the EFA-deficient group. The results indicate a possible role for PGF synthesis in the degree of susceptibility of the rats to EAE under different dietary regimens.

[Effect of surface-active agents on Mycobacterium tuberculosis and Mycobacterium bovis. Obtaining chromogenic mycobacteria]

In 18 strains of M. tuberculosis and M. bovis it has been possible to demonstrate the existence, in pure cultures, of elements able to grow in vitro in scotochromogenic mycobacteria. The experimental method used includes a dispersion, under shaking, of organisms in different surface-active agents. The chromogenic strains isolated during the experimentation are eugonic, and PAS- and INH-resistant. Their experimental virulence is different from that of tubercle bacillus. We discuss the signification of this dissociation phenomenon inductible by surface-active agents.

Virulence and resistance to superoxide, low pH and hydrogen peroxide among strains of Mycobacterium tuberculosis

Six strains of Mycobacterium tuberculosis of different virulence in guinea-pigs were compared with regard to their resistance to low pH, to hydrogen peroxide (H2O2) at different pH values and to superoxide (O2-). Low virulence was associated with susceptibility to H2O2 in native and isoniazid-resistant strains but not in laboratory-attenuated strain H37Ra. H2O2 resistance was only partly related to catalase content. Low virulence was not associated with susceptibility to an acid environment but the tuberculocidal effect of H2O2 was significantly increased at low pH. The strains were uniformly resistant to O2- and contained similar amounts of superoxide dismutase. The implications of these observations are discussed in the context of mechanisms of host defence in tuberculosis.

[Detection of pathogenic mycobacteria in the environment of the medical units and of the slaughter-house of an African town (author's transl)]

The authors have made investigations about the presence of pathogen mycobacteria in puddles of rain water and in rill waters of sanitary formations and municipal slaughter-house of Yaoundé. 19 strains of pathogen mycobacteria have been isolated from 84 water samples : 15 M. tuberculosis strains, especially present in the environment of sanitary formations, 4 M. bovis strains, especially present in the environment of the slaughterhouse. The third part of isolated M. tuberculosis strains belongs to the africanum variety of this species, although this variety is prevalent in the human pathologic products. 13 from 19 strains are I.N.H. susceptible.

Infection of Clethrionomys G. glareolus Schreb. (red mice) with Mycobacterium tuberculosis and Mycobacterium bovis injected subcutaneously

Groups of red mice were injected with doses from 10 mg to 10(-8) mg semidried culture of a strain of M. tuberculosis and with doses from 10(-1) to 10(-8) mg of a strain of M. bovis. Some animals were killed about 1 1/2 and 3 months after injection and the remainder lived until death occurred spontaneously. The number of tubercle bacilli in the organs was evaluated by microscopy of smears, in some cases by quantitative culture. Among the mice injected with M. tuberculosis in doses of up to about 2 million viable units, not one case of death occurred which could be attributed to tuberculosis. The autopsy findings consisted exclusively of lesions at the site of injection and in the regional lymph glands. Quantitative culture showed growth of a few viable units in the lymph glands, spleen or lungs, but no sign of progressive infection. Out of 10 mice injected with a giant dose of 3 X 10(7) viable units, only two died of tuberculosis. M. bovis provoked fatal tuberculosis in all animals injected with doses from 6.9 million to 7 viable units. Severe caseous lesions developed at the site of injection, in the lymph glands, in the lung, and often also in liver and spleen. The number of bacteria in the organs was enormous, particulary in the spontaneously dead animals. The survival times, which were dependent on dosage, varied from 51 to 159 days.

Host-parasite relationships in experimental airborne tuberculosis. VI. Influence of vaccination with Bacille Calmette-Guérin on the onset and/or extent of hematogenous dissemination of virulent Mycobacterium tuberculosis to the lungs

Guinea pigs vaccinated with bacille Calmette-Guérin (BCG) and unvaccinated guinea pigs were challenged by the respiratory route six weeks or six months after vaccination and sacrificed at various intervals after challenge. The six lobes of the lung were cultured separately, and the percentage of culture-positive lobes was calculated, as well as the log10 number of virulent bacilli recovered. The latter was subjected to an analysis of variance, which compared the fate of bacilli in the four largest lobes with the fate of those in the two smallest lobes. The results indicated no difference between the six-week and six-month intervals between vaccination and challenge. In the longer intervals between challenge and sacrifice, small numbers of secondary lesions could be seen on the lobes of the BCG-vaccinated animals. It was concluded that vaccination with BCG retarded the onset and/or reduced the extent of hematogenous dissemination of virulent mycobacteria to the lungs.

[Intracellular activity and phagocytability of freshly-isolated strains as parameters of the pathogenicity of tuberculosis mycobacteria]

Phagocytability and the capacity of intracellular multiplication of Mycobacteria tuberculosis isolated from the patients before the treatment and during it (in 1-5 months and later) were studied in the culture of normal peritoneal guinea pig macrophages. A method of quantitative assessment of the capacity to intracellular reproduction of Mycobacteria tuberculosis by determination of the relative activity index in comparison with the standard strain was elaborated. All the cultures of mycobacteria isolated possessed a different extent of intracellular activity and phagocytability. There proved to be no relationship between the intracellular activity indices and the phagocytability of the strains under study. Mycobacteria tuberculosis cultures isolated from the patients during the treatment possessed higher indices of intracellular activity than the initial cultures isolated before the treatment.

Transmissible agents from human sarcoid and Crohn's disease tissues

Mice were inoculated with human sarcoid tissue homogenates or with a first or a second passage homogenate of mouse tissue (including 0.2 mum membrane filtrates) originating from the inoculation of human sarcoid, Crohn's disease, or control tissue homogenates. Epithelioid and giant cell granulomas were present in the footpads and/or viscera of some of the mice given homogenates originating from each sarcoid or Crohn's disease tissue 15 months after inoculation but were not present in mice given control homogenates. Among mice given homogenates originating from human sarcoidosis, granulomas were present in many organs and tissues; in contrast, a pattern of selective dissemination of visceral granulomas was found among mice given homogenates originating from Crohn's disease. This differential distribution of visceral granulomas also followed the inoculation of 0.2 mum membrane filtrates. Granulomatous responses at Kveim test sites in the ear 9-17 months after inoculation of homogenatesoriginating from human sarcoidosis or Crohn's disease were confined to mice showing granulomas in footpads of viscera. The ability of the transmissible agents to induce granulomas in mice was destroyed when sarcoid or Crohn's tissues were autoclaved or when sarcoid homogenates were stored at -20degreesC for 1 week or exposed to 60Co irradiation (2.5 MR).

The pathogenicity of spheroplasts of Mycobacterium tuberculosis

Guinea pigs were injected with spheroplasts of Mycobacterium tuberculosis and were sacrificed after various intervals to study the state of the organisms and to evaluate the extent of disease. The spheroplasts persisted in the body of the animals for a considerable length of time. Their presence, however, was not associated with either the development of tuberculin hypersensitivity or pathologic changes. It was found that the spheroplasts were pathogenic only when reverted in the animals to bacterial forms. The reversion of the spheroplasts to bacillary state and the subsequent initiation of infection were dependent on the duration of their stay within the host.

An attempt to cultivate mycobacteria in simple synthetic liquid medium containing lecithin-cholesterol liposomes

An attempt was made to cultivate mycobacteria in a simple synthetic liquid medium containing lecithin-cholesterol liposomes. This lipid complex showed a marked growth-promoting effect on the submerged growth of M. tuberculosis and M. bovis. The role of lecithin as nutrient was suggested. The bacillary growth in such environment retained good viability, strong acid-fastness, and high virulence in mice. An avirulent strain of tubercle bacilli, H37Ra, did not respond to lecithin-cholesterol liposomes unlike the parent virulent strain, H37Rv. However, this was not a general rule for virulence, as a highly virulent strain of M. bovis (Ravenel) and an attenuated strain (BCG) both grew well in the presence of lipsomes. Lipid analysis showed that cholesterol in the liposome medium was esterified to some extent during the bacterial growth. It was discussed that the culture in the liposome-containing medium may present an experimental model for the study of interaction between mycobacteria and the macrophage membrane.

Susceptibility of newborn and adult guinea pigs to Mycobacterium intracellulare and M. kansasii

Six groups of guinea pigs, each consisting of 30 3-month-old and 20 7-day-old animals, received intraperitoneal inoculations with one of four strains of Mycobacterium intracellulare or one of two strains of M. kansasii. Three similar control groups received either an intraperitoneal injection of M. tuberculosis, no injection, or a sterile injection. Guinea pigs were sacrificed at 3, 5, 10, 20, 30, and 90 days. Lungs, spleen, liver and peritoneal fluid were cultured. Lungs were also examined histologically for inflammatory response. All the guinea pigs sacrificed within 20 days after inoculation showed positive cultures at nearly all sites. Thirty days after inoculation significantly more of the young guinea pigs had positive cultures, and the distribution of mycobacteria in their tissues was wider than was observed with the adult animals. At 90 days, the bacteriological results were similar for both groups. This histological findings were generally similar for both age groups, although acute reactions persisted longer in the young animals. All guinea pigs injected with M. tuberculosis died spontaneously within 90 days after inoculation and showed positive cultures at all sites. The results of the present study indicate that young guinea pigs are more susceptible to M. intracellulare and M. kansasii than are adult animals and should be preferred to old animals for diagnostic inoculations.

The structure of mononuclear phagocytes differentiating in vivo. II. The effect of Mycobacterium tuberculosis

The development and resolution of granulomas induced by Mycobacterium tuberculosis were sequentially traced by correlated light and electron microscopy. The scattered, immature monocytes initially composing the lesions evolved by orderly steps into coalescent, well developed macrophages and ultimately into swirling nests of highly complex epithelioid cells. These ultrastructural changes represent differentiation in vivo of the mononuclear phagocytes. The number of mycobacteria present than waned markedly, and the epithelioid granulomas developed into foreign body granulomas and finally into simple chronic inflammation. Concmonitantly, the epithelioid cells evolved into macrophages and ultimately into immature, monocyte-like forms. These observations suggest that the development of a granuloma represents differntiation in vivo of the constituent mononuclear phagocytes in response to an evoking stimulus. From comparisons with previous studies, mononuclear differentiation in vivo appears to have a fixed pattern and a markedly alterable pace. The observations also suggest a previously undescribed fate for mononuclear phagocytes in developing granulomas. As the granuloma-evoking agent is destroyed, the highly differentiated mononuclear phagocytes change into less mature forms.

A historical basis for modern concepts of the pathogenesis of tuberculosis

Theories of the pathogenesis of tuberculosis accepted by clinicians in this field, receive no mention or little emphasis in textbooks of pathology. These are: the systemic character of the disease from the initial infection; the role of tissue allergy; the subclinical, benign and lifelong character of most tuberculosis infections, yet liable to an endogenous activation by the influence of stress. These concepts go far back in history, and reference is made to Bayle (1816), Koch (1891), Calmette and Guérin (1906), Von Pirquet (1907) and Ghon (1912). The origin of the pulmonary apical lesion was controversial in the 1920s. Assmann formulated a theory of reinfection, which is opposed to Simon's theory of primary origin, which is gaining acceptance today. Histological studies of early lesions by Vorwald show their haematogenous origin and Sweany's work on late lesions emphasises the instability of tubercle at any age of the lesion. Krauses's survey of the pathogenesis anticipates the modern concept of tuberculosis as being mainly a condition of stress.

Bacteraemia in red mice (Clethrionomys g. glareolus Schreb.) after intraperitoneal injection of large doses of tubercle bacilli

Römer (1903) has demonstrated that white mice injected intraperitoneally with large doses of tubercle bacilli isolated from man survived longer than mice injected with tubercle bacilli isolated from cattle. The blood of the spontaneously dead animals contained large numbers of tubercle bacilli. In the present study, red mice are injected intraperitoneally with 10 mg doses of different species of mycobacteria, and the number of bacilli in the blood is estimated at various intervals within the first 24 hours after the inoculation. The number of bacteria is considerably higher in the blood of mice injected with M. bovis, but, in contrast to M. bovis, M. avium disappears rapidly from the blood stream. Supplementary experiments show that red mice injected with M. bovis have a shorter survival time than mice injected with M. tuberculosis, and that the bacteraemia induced by M. bovis into white mice is clearly less pronounced than in red mice.

Infection of Microtus arvalis (common vole) with Mycobacterium tuberculosis and Mycobacterium bovis

The aim of the study has been to ascertain whether Microtus arvalis (common vole) is strongly susceptible to M. bovis but resistant to M. tuberculosis, as is the case with other members of the vole family, or whether it is susceptible to both species as demonstrated by Robert Koch. Groups of common voles have been injected subcutaneously or intraperitoneally with varying doses of finely dispersed suspensions of a virulent strain of M. bovis or M. tuberculosis. M. bovis multiplies strongly in the vole organism and a dose as small as 8 viable units provokes a progressive infection with rapid fatal outcome. Autopsy shows considerable processes at the site of injection and in the lymph glands. Tubercles are observed quite frequently in the lungs, bur seldom in the liver, spleen and kidneys. The organs contain a large number of tubercle bacilli, the caseous lymph glands enormous numbers. In contrast, the virulence of M. tuberculosis is low. None of the doses used, the highest being 6 x 10(6) viable units, provokes progressive infection in the animals injected subcutaneously and only in a few of those injected intraperitoneally. The macroscopical findings are inconsiderable, and it is characteristic of the M. tuberculosis infection that the lymph glands are seldom enlarged and have become caseous in exceptional cases only. The number of bacteria in the organs is small, except in the few animals in which the infection becomes progressive. The conclusion drawn from the experiment is that Microtus arvalis is susceptible to M. bovis but strongly resistant to M. tuberculosis, and in this respect resembles other members of the vole family examined hitherto.

Preservation of mycobacterial suspensions at -55 degrees C

Suspensions in dilute Sauton's medium of 14 mycobacterial strains grown under identical conditions were prepared with bacilli harvested at their midlog phase of growth,and were frozen and stored at -55 degrees C. Survivals, estimated by CFU determinations after periodic intervals of storage, showed no adverse effect of freezing and thawing on any of the strains. Effectiveness of preservation, however, varied from strain to strain and no correlation existed between effectiveness and species of mycobacteria. No noticeable changes in the virulence of the H37Rv strain and in the immunizing activity of BCG were detected after prolonged storeage. Results of experimentsperformed with two strains suspended in seven diluents suggest that some are more suitable for long-term preservation, particularly so for the more sensitive one.

[Pathogenesis of certain mycobacterioses in a chemically damaged liver of the rabbit (author's transl)]

Cirrhosis of the liver was provoked in adult rabbits by the administration of CCl4/0,3 ml subcutaneously two times a week during a period of six weeks. It was found that the infection by M. tuberculosis, M. avium and M. kansasii causes a considerably greater dissemination than in the case with the livers of rabbits unaffected by cirrhosis, and that even a non-pathogenic strain (M. intracellulare) is pathogenic, if the liver is affected. Our findings confirm the lowered resistance of a chemically damaged liver to the development of mycobacterial infection.