Antimicrobial resistance

Abstract

There is an incoming tide of concern about the problems of antimicrobial resistance. For several years alarm has been expressed in the United States,1 and the past 12 months have seen two World Health Organisation meetings prompted by increasing anxieties about the role of antimicrobials in animal husbandry2; a report by Britain’s House of Lords on antimicrobial resistance; and a report from the US Institute of Medicine on emerging infections.3 This week the Danish Chief Medical Officer, Einar Krag, has called together colleagues from the European Union and their advisors for a conference on “the microbial threat” to “assess the strategies to prevent and control the emergence and spread of antimicrobial resistant micro-organisms.” Is all this activity warranted? We believe it is: in the words of the House of Lords’ report, “Resistance to antibiotics ... constitutes a major threat to public health and ought to be recognised as such more widely than it is at present.” This issue of the BMJ is helping to broadcast this message. The causes of these problems and gloomy portents are not difficult to find. In the past 50 years people in both the developed and developing worlds have accepted antibiotics as their right—to obtain a prescription at the first sign of a trivial infection or treat themselves with a handful of cheap antibiotics. We cannot conceive a return to the pre-antibiotic days, yet the unbridled use of these agents in man and animals is inexorably propelling us in that direction. Most antibiotic use is in two areas: in humans in the community, and in animals for growth promotion and prophylaxis (see table). The data in the table suggest that up to 75% of antibiotic use is of questionable therapeutic value.3 What seems less controversial is the long term risk of spraying fruit trees in some parts of the world with antibiotics and adding 50-60 kg of an antimicrobial to each acre of salmon farm.4 Bacteria have evolved very sophisticated means of exchanging DNA, both within their own genus and species and across them. The widespread use of antibiotics will tilt the delicate balance between us and the bacteria. There seems to be an inevitability about this problem. Society demands easy answers to its health problems. The increasing resistance problems of recent years are probably related to the use of increasingly broad spectrum agents (cephalosporins and fluoroquinolones) and crowding of the most vulnerable members of society in day care centres and nursing homes. These problems are compounded by the world wide phenomena of pressure on health care systems for greater efficiency, with higher bed occupancies and stretched nursing and medical care. Added to this are pressures to allow over the counter use of antibiotics in western countries so as to reduce healthcare costs. To effect change much will be required by the medical profession, politicians, the pharmaceutical industry, and not least patients. Without doubt antibiotic prescribing in humans and animals must be prudent, but by how much must antibiotic use be reduced (10-50%?) and to what extent will this affect antibiotic resistance in different bacteria? Will we see a return to more susceptible populations or just keep the current problem in check? Some see the problem as particularly gloomy.3 There are suggestions that as resistant bacteria increase and the available antibiotics decrease transmission from inpatients to the larger population will increase and become a problem to the general public. Certainly, the veterinary profession will be required to change practices, and we commend the House of Lords’ views on the control of valuable agents in animal husbandry. There are some encouraging signs that this may be occurring: at least in developed countries, fish farming is using new techniques such as immunisation instead of antimicrobials. The Swedish experience in reducing the reliance on growth promoters shows that progression can be made without reducing production. Initial problems in the form of increased morbidity and mortality in pig and poultry production were overcome by enhancing the rearing systems.5 There is a need to keep a sharp eye on the development of resistance in animals, but not at the expense of inaction. Secondly, both patients and doctors must reduce their expectations. Antibiotics are commonly prescribed, mainly for the respiratory tract, where the vast majority of infections are caused by viral pathogens. The pressures on both patient and doctor are easily understood: an anxious parent, a sick child, and a doctor faced with diagnostic uncertainty. The solutions are not straightforward. Patients must be educated that most such infections do not require antibiotics—that they may actually be harmful to them and their families (through their effect on beneficial bacteria in the body) and to society at large (through encouraging resistance). All this requires considerable effort and time, not easily ac