The introduction and assimilation of chemotherapy to treat pulmonary tuberculosis (TB) during the mid-twentieth century appears at first sight to be a success story dominated by the use of streptomycin in a series of randomised clinical trials run under the auspices of the Medical Research Council (MRC). However, what this standard rhetoric overlooks is the complexity of TB chemotherapy, and the relationship between this and two other ways of treating the disease, bed rest and thoracic surgery. During the late 1940s and 1950s, these three treatment strands overlapped one another, and determining best practice from a plethora of prescribing choices was a difficult task. This article focuses on the clinical decision-making underpinning the evolution of successful treatment for TB using drugs alone. Fears over the risk of streptomycin-resistant organisms entering the community meant that, initially, the clinical application of streptomycin was limited. Combining it with other drugs lessened this risk, but even so the potential of chemotherapy as a curative option for TB was not immediately apparent. The MRC ran a series of clinical trials in the post-war period but not all of their recommendations were adopted by clinicians in the field. Rather, a range of different determinants, including the timing of trials, the time taken for results to emerge, and whether these results ‘fitted’ with individual experience all influenced the translation of trial results into clinical practice.

In dry cow therapy (DCT), antibiotics are usually injected direct into the mammary gland after the last milking of the lactation. Most products are designed to eliminate existing intramammary infections (IMI) caused by Staphylococcus aureus and Streptococcus agalactiae and to prevent the establishment of new IMI caused by major pathogens during the early non-lactating period (Nickerson et al. 1999). Systemic therapy has been attempted as a way of improving the cure rates of intramammary treatments of clinical and subclinical mastitis during lactation (Ziv, 1980a; Calvinho et al. 1988; Owens et al. 1988). For systemic therapy to be useful, effective passage of the drug from blood to the foci of infection must be achieved. Maintaining an effective antibacterial concentration in the udder depends on the physicochemical properties of the drug, the dose, the bioavailability of the injected formulation, and the sensitivity of the pathogen (Ziv et al. 1980a, b). The theoretical pharmacokinetic and pharmacodynamic basis for systemic DCT has been reported (Soback, 1988). When used in an attempt to improve cure rates of IMI, subcutaneous injection of tilmicosin at drying-off was ineffective against Staph. aureus IMI (Nickerson et al. 1999) and intramuscular (i.m.) oxytetracycline, in combination with intramammary cephapirin dry-cow treatment did not improve the cure rate for Staph. aureus mastitis (Soback et al. 1990a; Erskine et al. 1994). Nevertheless, i.m. tylosin treatment 2 weeks before the expected day of calving decreased IMI after calving (Zecconi et al. 1999) and subcutaneous norfloxacin nicotinate applied at the cessation of milking proved useful in controlling Staph. aureus infections (Soback et al. 1990a). Moreover, the incidence of this pathogen after systemic DCT may be significantly lower compared with untreated control groups (Soback et al. 1990a, b).