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Studies of microbial dispersion; dispersion of labelled B. C. G. in guinea pig

Sternberg, Joseph et Frappier, Armand (1955). Studies of microbial dispersion; dispersion of labelled B. C. G. in guinea pig Revue Canadienne de Biologie , vol. 14 , nº 1. pp. 14-35.

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A study of microbial dispersion may benefit from the use of labelled microbes, providing that following rules are being observed:

- the physical characteristics of the isotope must be adapted to the biological characteristics of the microbe ;

- only a biological control superimpozed upon the radioactivity assay is capable to give the certainty that the detected radiation pertains to a living microbe; therefore, each tissue assayed for labelled microbes must be simultaneously assayed by subcultures and counts of resulting microbial units.

The ratio between the living microbial units and the amount of radioactive isotope found in the same tissue is better interpreted by the notion of "microbial specifie activity", expressed in counts per living microbial unit.

In guinea pig injected with B.C.G. labelled with P32, the microbial specifie activity has been found to be significantly larger in Iiver than in spleen, lungs and inoculation site. This fact could be explained by various mechanisms, the most acceptable to date being the following :

- the labelled microbes are killed or only dephosphorylated at the inoculation site and the labelled phosphorus is released as mineral phosphate into the general circulation. The released P320 4 starts its own metabolic cycle and is concentrated as such in liver among other tissues. The excess of isotope is superimpozed upon the living labelled microbes, bence the increased micrcbial specifie activity.

Several experimental findings are in favour of this hypothesis; significant is the concentration of radiophosphorus in bone, a tissue with a selective affinity for mineral phosphate. The urinary excretion of radiophosphate in vaccinated animais is much slower in the group injected with living microbes than in those injected with killed microbes. This fact suggests that the release of mineral phosphate is a continuous process, possibly a part of the tissular defence reactions at the inoculation site. Indirect proofs for this hypothesis have been brought by the histochemical demonstration of an increase in acid phosphatase in the peripheral cells of the inoculation abscess; this increase bas been related to the intensity of resistance in vaccinated animais. Another indirect proof has been brought by the indication that infected animais have an accelerated turnover of radiophosphorus, especially its mineral fraction. (4)

Our experimental data as weil as the two above quoted findings can be tentatively integrated into a working hypothesis on the mechanism of dispersion of labelled B.C.G. in guinea pig, as follows:

- the labelled microbes arrested at the inoculation site release their labile phosphorus, mainly as mineral phosphate. This metabolite restarts its metabolic cycle as such and is concentrated into the tissues in its metabolic pathway (liver, bone). Simultaneously, the vaccination of animais provokes an acceleration of phosphate turnover, a fact which in its turn increases the accumulation of radiophosphate into liver and bone.

It can be assumed that the release of mineral phosphate from the microbial body is closely related to the mechanism of defence of the infected tissue; the dephosphorylation is a graduai process, occurring during the first three or four days after inoculation. The urinary excretion of the released label is considerably slower in vaccinated animais injected with living B.C.G. than in those injected with beat killed microbes; this fact implies that the annihilation of microbes and the dephosphorylation are sequent, but to date the order of sequence is unknown.

This combination of physiological methods and microbiological procedures can easily be adapted to the study of in vivo behaviour of microbes; a study destined to follow the fa te of microbial bodies will use non metabolites for tagging (Cr51, Po210, etc.) or even the method of double labelling, while a study destined to follow the metabolic deviations provoked by infection, will use an easily diffusible metabolite (P32, 835 or CH) of either organisms or only a metabolite of the infected host (1131).

Type de document: Article
Informations complémentaires: Recueil de tiré-à-part de la bibliothèque: A0100
Mots-clés libres: BCG VACCINATION/experimental; PHOSPHORUS/radioactive; BCG vaccine; phosphate intake; phosphorus; guinea pig; Mycobacterium bovis; radioactivity; vaccination; Guinea Pigs; Phosphorus Radioisotopes; Phosphorus, Dietary
Centre: Centre INRS-Institut Armand Frappier
Date de dépôt: 10 févr. 2020 16:05
Dernière modification: 10 févr. 2020 16:05
URI: https://espace.inrs.ca/id/eprint/8395

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