Future trends the way forward for susceptibility testing

The demonstration by Smith (2008b) that many laboratories are currently failing to correctly identify resistant strains (Table 7.2) underlines the urgent 

As noted above there will be an inevitable loss of precision associated with universal, laboratory-independent interpretive criteria. Ultimately, the decision as to whether the advantages of universality outweigh the disadvantage of this loss of precision will be made by those who use the interpretive criteria. It is probable that, in making that decision, they will be influenced by the frequency with which they encounter strains with low-level but clinically signiflcant resistance. Any imprecision in interpretive criteria renders detection of such strains unreliable. Luckily, the decision as to whether universal or laboratory-specific values are the most appropriate goal can be postponed. Much of the work needed to achieve either is the same, and possession of the data produced by that work will enable making the correct choice much easier. 

The ability of bacteria to become clinically resistant to antibiotics is a major threat to the continued therapeutic use of these agents in aquaculture. As the emergence of resistance is an automatic consequence of antibiotic use, it follows that we will be able to conserve this therapy only if we learn to use antibiotics prudently. The essence of prudent use is that we use them as little and as wisely as possible. In this chapter it has been argued that reductions in antibiotic use could be achieved in a number of ways. Improvements in husbandry and management will reduce both the incidence and severity of infectious diseases that give rise to need for therapy. Development of vaccines, in hosts with competent immune systems, will augment this reduction. Improvements in diagnosis will, if they include a correct evaluation of 

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