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Journal of Clinical Microbiology, April 1999, p. 1077-1083, Vol. 37, No. 4
NSW Agriculture,
Received 26 August 1998/Returned for modification 11 December
1998/Accepted 19 January 1999
Definitive diagnosis of Johne's disease in ruminants depends on
confirming the presence of the causative bacterium, Mycobacterium avium subsp. paratuberculosis, in tissues of the
host. This is readily achieved in most ruminant species by culture.
However, culture of clinical specimens from sheep in many countries has been unrewarding. Such a culture from sheep was achieved recently in
Australia by using a radiometric culture medium. The aims of the
present study were to evaluate the culture of M. avium
subsp. paratuberculosis from sheep by using modified BACTEC
12B radiometric medium, to determine the sensitivity of culture in
relation to histopathology, and to evaluate a range of solid media.
Culture of M. avium subsp. paratuberculosis
from sheep with Johne's disease is a sensitive method of diagnosis:
intestinal tissues from all 43 animals with multibacillary disease and
all 22 animals with paucibacillary disease were culture positive, while
98% of feces from 53 animals with multibacillary disease and 48% of
feces from 31 animals with paucibacillary disease were culture
positive. Of sheep without histological evidence of Johne's disease
from infected flocks, intestinal tissue from 32% of 41 were culture positive, while feces from 17% of 41 were culture positive.
Consequently, culture is recommended as the "gold standard" test
for detection of ovine Johne's disease. Of the wide range of solid
media that were evaluated, only modified Middlebrook 7H10 and 7H11
agars, which were very similar in composition to modified BACTEC 12B medium, yielded growth of ovine strains of M. avium subsp.
paratuberculosis. The sensitivity of detection of M. avium subsp. paratuberculosis on solid media was
slightly lower than that in modified BACTEC 12B radiometric medium.
Both egg yolk and mycobactin J were essential additives for growth of
ovine strains of M. avium subsp.
paratuberculosis in both liquid and solid media.
0095-1137/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Evaluation of Modified BACTEC 12B Radiometric
Medium and Solid Media for Culture of Mycobacterium avium
subsp. paratuberculosis from Sheep
*
Corresponding author. Mailing address: NSW Agriculture,
Elizabeth Macarthur Agricultural Institute, PMB 8, Camden NSW 2570, Australia. Phone: 61 46406343. Fax: 61 46406384. E-mail:
Richard.Whittington{at}agric.nsw.gov.au.
Journal of Clinical Microbiology, April 1999, p. 1077-1083, Vol. 37, No. 4
0095-1137/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
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