Abstract
A porcine strain of Mycobacterium avium, Serotype 2, was used for intravenous inoculation of pigs in doses 5, 1, 10−1, 10−2 and 10−3 mg (1 mg = 78 × 106 viable units), 2 pigs per dose.
Dose 5 mg proved fatal for both of the inoculated pigs, which were killed in extremis 64 and 69 days, respectively, after inoculation. Dose 1 mg caused clinical disease in 1 of 2 pigs, but was not lethal. Post mortem, the clinically affected pigs showed a generalized granulomatous tuberculosis. The other pig given 1 mg and the pigs given smaller doses, showed no clinical signs, and lesions and presence of acid-fasts were mostly limited to the lymph nodes of the lung, liver and digestive tract.
All the pigs showed delayed hypersensitivity to avian PPD tuberculin (1000 t.u.) and some of them cross-reacted with human PPD tuberculin (1000 t.u.). The clinically affected pigs gave a very weak response to tuberculin, the others a strong response.
The smallest dose capable of establishing an infection and producing tuberculous lesions was not determined, but seems to be less than 10−3 mg (78000 viable organisms).
Keywords: Mycobacterium avium, Serotype 2; pathogenicity; intravenous inoculation; pigs.
Sammendrag
En M. avium stamme, Serotype 2, isoleret fra en gris, blev anvendt til intravenøs podning på grise i doserne 5, 1, 10−1, 10−2 og 10−3 mg, 2 grise pr. dosis.
Dosis 5 mg havde letal effekt på begge grise, som blev aflivet i stærkt afmagret tilstand henholdsvis 64 og 69 dage efter podning.
Dosis 1 mg var ikke letal, men forårsagede klinisk påviselig sygdom hos een af 2 podede grise. Post mortem undersøgelse af disse grise viste udbredt granulomatøs tuberkulose med mange bakterier i de undersøgte vævsprøver, mest udtalt for grise podet med 5 mg. De øvrige grise, inklusive den anden gris podet med 1 mg, viste ingen kliniske symptomer, og post mortem undersøgelser viste en tendens til, at tuberkuløse processer og bakterier koncentreredes til leverens, lungens og fordøjelseskanalens lymfekirtler.
Alle grisene reagerede ved tuberkulinprøver med aviært PPD tuberkulin, 1000 enh. pr. dosis og eventuelt med humant PPD tuberkulin, 1000 enh.. De klinisk syge dyr havde svage reaktioner, medens de øvrige dyr havde kraftige reaktioner.
Det lykkedes ikke at påvise den mindste dosis, der var i stand til at etablere en tuberkuløs infektion og forårsage tuberkuløse processer. Denne dosis er sandsynligvis mindre end den mindste dosis (10−3 mg = 78000 bakterier) anvendt i dette forsøg.
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