Interventions for Tuberculosis Control and Elimination 2002

ment, mice were assigned to five groups: 1) no treatment, 2) isoniazid for
six months, 3) rifampicin for two months, 4) rifampicin plus isoniazid for
two months, and 5) rifampicin plus isoniazid plus pyrazinamide for two
months (figure 85). From this experiment, it was shown that two months
of rifampicin-containing preventive chemotherapy was as effective as six
months of isoniazid. 900
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Figure 85. Mouse model of latent tuberculous infection and efficacy of various
durations and combinations of preventive therapy on spleen bacillary count.
Reproduced from 900 by the permission of the publisher American Thoracic Society
at the American Lung Association.
In a second experiment, in comparison to isoniazid the relative efficacy
of various combinations with rifampicin of different durations was
evaluated. Mice received 1) six months of isoniazid, 2) three months of
rifampicin plus isoniazid plus pyrazinamide, 3) three months of rifampicin,
or 4) two months of rifampicin plus pyrazinamide. The experiment was
calibrated in such a way as to ensure that viable bacilli remained at cessation
of therapy to allow their culture from spleen at cessation and after
a follow-up of a six-month period without treatment. All rifampicin
combinations proved superior to isoniazid treatment for six months
(figure 86). 900 The best combination was rifampicin plus pyrazinamide
(without isoniazid). Rifampicin alone for three months was also very
effective.