Tuberculosis: treatment of latent infection (commonly called ‘prophylaxis’)

Tuberculosis: treatment of latent infection (commonly called ‘prophylaxis’)

Tuberculosis:

Mycobacterium tuberculosis is the cause of most cases of tuberculosis (TB) in Australia. Patients with TB should:

only be managed by specialists with the appropriate training and experience

be notified promptly to the relevant state public health authorities

have contact tracing performed by public health nurses liaising closely with the treating physicians.

Bacterial confirmation of the diagnosis, and drug susceptibility testing, should be strenuously pursued, because of concerns about drug resistance.

Adequate adherence to antituberculous therapy is vital to:

• achieve a satisfactory treatment outcome

• reduce the risk of transmission to contacts

• reduce the risk of relapse

• prevent the emergence of drug resistance.

Measures to improve adherence include comprehensive patient and family education (in the form of verbal and written information), close consistent follow-up, and provision of directly observed therapy (DOT). If problems with supply of antituberculous drugs arise, the state health department should be contacted.

For drug-sensitive infections, the failure rate of modern antituberculous treatment regimens should be less than 1% and the 5-year relapse rate less than 5%.

 treatment of latent infection

Individuals with a positive tuberculin skin test or TB-specific interferon-gamma release assay but no evidence of active TB may have latent tuberculous infection. Seek specialist advice in patients where the size of the tuberculin skin test may be modified by, for example, past BCG (Bacillus Calmette-Guerin) vaccine or immunodeficiency including HIV. Treatment of latent infection can reduce the incidence of progression to active disease, and a single drug can be used because the number of organisms involved is small. After active TB has been excluded, individuals with a positive tuberculin skin test or TB-specific interferon-gamma release assay who should be considered for this treatment are:

patients with HIV infection

close contacts of a patient with smear-positive pulmonary TB

recent tuberculin converters

children and adolescents

patients prior to the commencement of immunosuppressive therapy (including tumour necrosis factor [TNF] inhibitors such as infliximab and etanercept)

patients with underlying medical conditions such as diabetes and chronic renal failure, especially if aged less than 35 years. 

 

The treatment regimen is:

isoniazid 300 mg (child: 10 mg/kg up to 300 mg) orally, daily for 6 to 9 months.[Note 1]

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Monitor liver function as for treatment of active TB , and educate patients about the symptoms of hepatitis. For patients likely to be infected with an isoniazid-resistant organism, or in whom isoniazid cannot be used, seek expert advice.

Note 1: Administer pyridoxine (adult: 25 mg, breastfed baby: 5 mg [see Tuberculosis in pregnancy and breastfeeding) orally, with each dose of isoniazid. (For 5 mg dose, crush a 25 mg tablet, make up to 5 mL with water, give 1 mL.)