Bacterial drug resistance in meat animals: a review

Prolonged oral or parenteral administration of antibiotics has led to the development of resistant strains of microorganisms. Bacteria acquire drug resistance by mutation, conjugation and transduction. Oral antibiotics by a process of selection pressure facilitate the proliferation of resistant population of bacteria. Drug resistant bacteria are capable of transferring their resistance to drugs to other bacteria by the process of transferable drug resistance (TDR). This can lead to multiple resistance to a vast number of therapeutically useful antibiotics which will, therefore, become ineffective for treatment. TDR can occur between pathogenic organism, between organism of different species, such as E. coli, Salmonella and Shigella; and also between pathogenic and non-pathogenic organisms. Faecal contamination of meat during slaughter may result in the transfer of antibiotic resistant E. coli to the meat. In the human gut this E. coli could transfer resistance to other gut flora, namely E. coli or Salmonella. Antibiotic-resistant coliforms have been isolated from carcases, fresh and cooked meat, raw meat handlers and livestock handlers. Handling of raw market meat by buyers in Nigeria could also lead to contamination of meat with resistant microorganisms. Veterinary drugs are sold and used without much control in Nigeria. This practice may have created a population of resistant bacteria in the meat animals. The presence of antibiotic residues in meat, milk and their products pose potential health hazards for man. Allergic skin conditions, nausea, vomiting, anaphylactic shock and even death have resulted from the ingestion of residues. Cooking and freezing have minimal effect on residues. Resistance to antibiotics have been detected in food poisoning bacteria, namely Salmonella typhimurium, Staphylococcus aureus and Clostridium perfringens. Some epidemiological link has been established between S. typhimurium of calves and food poisoning in man. Judicious use of antibiotics, public education on the health risks of the promiscuous use of drugs in livestock production; and hygienic slaughter at the slaughter houses, will help to reduce bacterial drug resistance in man and animals.