The issue of antimicrobial resistance in pathogenic bacteria is at last being taken seriously at a high level, with calls for more funding for the development of new drugs and action to prevent the overuse of clinically important antibiotics. This is very much a case of ‘better late than never’ – it’s about 45 years since the alarm was first raised – but then human beings always seem content to ignore a developing crisis until it becomes really serious. Whether all the current attention will translate into the money needed to pay for real progress is open to question, but at least science is beginning to answer some of the questions about how resistance spreads and why it is so difficult to tackle.
An important example of this better understanding is a newly published study by Austrian researchers, which reveals that phages present in poultry meat are capable of transferring resistance genes between bacteria. Phages are viruses that infect bacterial cells and can transfer genetic material by a process called transduction. The Austrian research team found that phages able to do that could be found in nearly half of the chicken meat samples they tested. Other recent findings suggest that transduction is a much more frequent mechanism for spreading antimicrobial resistance than was once thought and it is now considered to be an important driver in bacterial evolution. The fact that phages able to transfer resistance, not just between cells of the same species, but between different species, are common in chicken on retail sale suggests that they could be an important factor in the spread of antibiotic resistance in the food chain. Furthermore, phages are relatively resistant to sanitising chemicals and so could be quite persistent in food processing environments. The Austrian authors of the new study suggest that transfer by phages could be one of the main reasons why initiatives designed to tackle antibiotic resistance have so far achieved little success.
This illustrates very clearly the value of scientific investigation into the mechanisms of antimicrobial resistance and its spread. It’s a case of ‘know your enemy’, because it is very hard to devise effective strategies against something that is not properly understood. Interventions that appear sound based on existing knowledge may turn out to be of little value, or may even make things worse. It is becoming clear that the food supply chain plays a part in the development of resistance to clinically important antibiotics. Now that we are beginning to learn more about how resistance can spread between bacterial species in food, historical overuse of antibiotics in meat production is looking like a potentially catastrophic mistake. It needs to be addressed on at least two fronts. Firstly, quite draconian measures are needed to override the vested interests involved and cut antibiotic use in agriculture drastically. Secondly, we need to understand the spread of resistance thoroughly so that we can devise methods of halting that spread and start ridding the food supply of drug-resistant pathogens – if it’s not already too late.