Current problems in microbial disease control

Generally resistance arises from both natural and spontaneous mutations, followed by multiplication of the resistant strains. Although some might argue that all resistance is acquired at some level, the acquisition of resistance genes requires that insertion occur either in the chromosome or plasmid, and a logical conclusion is that these insertion sites have been programmed, or have evolved, over time to accommodate molecular 

Improper management such as false diagnosis, incorporation of high concentration of antimicrobials into the feeds, poor methods of administration, prolonged immersion therapy and improper discharge of effluent can also cause resistance to develop. 

Generally, resistance can be transmitted from one bacterium to another that has never been exposed to the antibiotic this phenomenon is known as horizontal gene transfer (Serrano, 2005). Plasmids carry the resistant genes from one bacterium to another thus, while an antimicrobial kills the sensitive bacteria, any resistant bacteria can survive and multiply. The more antimicrobials are used the greater will be the selective pressure favouring resistant strains. This is an example of Darwin s theory of evolution, the survival of the fittest . Antimicrobials create an environment 

3 Public health and ethical issues relating to the use of antibiotics for disease control in aqnacnitnre 

Antimicrobial residues can cause serious illness, and therefore present a hazard to public health. Drug allergies are mediated by a number of different immunological mechanisms, including type 1 immediate immune response mediated through Immunoglobulin E (IgE). Symptoms include anaphylaxis, skin-rashes, urticaria and angioedema (FAO/OIEAVHO, 2006). The antibiotics used in aquaculture, either for prophylactic or therapeutic purposes, often accumulate in the tissue of aquatic animals. 

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