Experimental Infection with Mycobacterium Avium, Serotype 2, in Pigs

Abstract

Twelve pigs were inoculated orally with Mycobacterium avium. The doses used were 0.5, 2 or 10 mg daily for 5 days, or 10, 50 or 180 mg once (1 mg = 37 × 10⁶ viable units). Two pigs were used per dose, 1 of which was sacrificed 3 days, the other 28/31 days after the last inoculation (Table 1).

Three days after inoculation, M. avium was found in the tonsils and in the intestinal mucosa of all 6 pigs, and in the mesenteric lymph nodes of 4. Viable unit counts for tonsils and intestinal mucosa were highest in pigs inoculated with 180 mg×1 and 10 mg×5. Histopathologically these pigs showed activation of the lymphoid tissue in the tonsils, Peyer patches and mesenteric lymph nodes. Twenty-eight/31 days after inoculation a spreading of the infection had taken place in all pigs, most often to the liver, less frequently to the spleen and the lungs. The kidneys and the musculature were not infected (Table 4). A correlation was apparent between the size of dose and the number of viable organisms in the tissues. Divided doses gave about 10 times higher viable counts than a single dose with the same total number of organisms (Table 5).

No gross lesions were found 28/31 days after inoculation. Microscopic granulomatous lesions were found in the tonsils of 6 pigs, in the intestinal mucosa of 4 pigs, in the mandibular and mesenteric lymph nodes of 6 pigs, in the retropharyngeal lymph nodes of 3 pigs, and less frequently in the parotid and hepatic lymph nodes (Table 3).

Five of 6 pigs were weakly sensitive to avian tuberculin PPD, 1000 t.u. per dose, when tested 22/25 days after inoculation; 1 of these pigs cross-reacted to human tuberculin (Table 2).

Sammendrag

Tolv grise blev podet peroralt med M. avium i doserne 0,5, 2 og 10 mg daglig i 5 dage eller 10, 50 og 180 mg givet een gang (1 mg= 37×10⁶ viable units). Der blev podet 2 grise pr. dosis, hvoraf den ene blev slagtet 3 dage og den anden 28/31 dage efter sidste podning (Tabel 1).

Ved undersøgelse 3 dage efter podning kunne M. avium dyrkes fra tonsiller og tarmslimhinde fra alle 6 grise og fra lnn. mesenterici fra 4 grise. I tonsiller og tarmslimhinde fandtes de højeste kimtal hos grise podet med 180 mg×1 og 10 mg×5. Ved histologisk undersøgelse af Peyerpletter, tonsiller og Inn. mesenterici fandtes en aktivering af det lymfoide væv, og hos 2 grise podet 5 × kunne påvises makrofagansamlinger. Ved undersøgelse 28/31 dage efter podning fandtes hos alle grisene en spredning af infektionen, oftest til lever og mindre hyppigt til milt og lunge, medens nyre og muskulatur ikke var inficerede (Tabel 4).

Der fandtes korrelation mellem dosisstørrelse og antal bakterier i vævene. Fraktioneret dosering gav ca. 10 gange større kimtal end den samme totaldosis indgivet på een gang (Tabel 5).

Der fandtes ikke makroskopiske forandringer 28/31 dage efter podning, men mikroskopiske processer kunne påvises i tonsiller og lnn. mandibulares og mesenterici hos 6 grise, tarmslimhinde hos 4 grise, lnn. retropharyngei med. hos 3 grise og mindre hyppigt i ln. parotidei og hepatici (Tabel 3).

Fem af 6 grise var svagt positive for aviært PPD tuberkulin, 1000 enh. pr. dosis, 22/25 dage efter podning. Hos een gris fandtes krydsreaktion med humant tuberkulin (Tabel 2).