Source: http://www.asmscience.org/content/book/10.1128/9781555815639.ch26
Timestamp: 2019-04-22 22:09:27+00:00

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This chapter deals with study of antibiotic resistance and its fitness costs has had several interesting evolutionary implications. The effect of antibiotic resistance on the virulence and disease pathology of pathogenic bacteria can be assessed by measuring 50% lethal dose LD50 values in experimental animals or by examining the specific pathology of the disease. An interesting question is whether antibiotic resistance is associated with an altered rate of bacterial transmission between hosts. The most commonly occurring katG mutation in Mycobacterium tuberculosis, Ser315Thr, is both highly resistant to isoniazid and virulent in the mouse model of the disease. A meta-analysis of the literature on isoniazid resistance resulting from the S315T mutation in clinical isolates in relation to ecological factors supports this, suggesting that this mutation provides high-level resistance without diminishing virulence or transmissibility. For the models to be most useful in the context of antibiotic resistance, one needs to know if the transmission rates for susceptible and resistant bacteria differ significantly. The limited amount of data currently available on the biological costs suggests that antibiotic resistance might be less easily reversed than previously anticipated, and the expected rate and extent of reduction are predicted to be at best moderate in community settings. In particular, one needs measurements under conditions that are as similar to the clinical situation as possible. Thus, competition, colonization, and transmission studies in human volunteers are needed, as they are likely to give us the most relevant parameter values.
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