Serious infections caused by bacteria that have become resistant to commonly used antibiotics have become a major global healthcare problem in the 21st century. They not only are more severe and require longer and more complex
treatments, but they are also significantly more expensive to diagnose and to treat (Alfonso, 2005). In recent years, there has been increasing concern that the use of antibiotics in food-producing animals, particularly their long term use for growth promotion, contributes to the emergence of antibiotic-resistant bacteria in animals. In the recent years, incidence of multidrug resistance in pathogenic and opportunistic bacteria has been increasingly documented (Jones et al., 2004). Great attention has been paid to foodproducing animals as one of several potential sources of antibiotic-resistant bacteria in humans (Janet et al., 2002).