Scientific Status Summary Addresses Antimicrobial Resistance

12 Mar 2013 --- A new scientific status summary in Comprehensive Reviews in Food Science and Food Safety outlines the challenges and complexities regarding antimicrobial resistance from the perspectives of four experts in the field.

Authors from University of Georgia, Texas Tech University, Kansas State University and University of Minnesota reviewed the latest research on the public-health impact of antimicrobial use in the food system and the growth and control of antimicrobial resistant pathogens.

According to the authors: “Concerns about the public-health implications of microbial resistance to antibiotics used in both human medicine and food-animal agriculture have led to the publication of the World Health Organization’s (WHO) List of Critically Important Antimicrobials for Human Medicine and the World Organisation for Animal Health’s (OIE) List of Antimicrobials of Veterinary Importance.”

“Although more needs to be done to improve the utility of these designations, such categorization of antimicrobials is helpful in prioritizing and addressing public health concerns and antimicrobial use,” the authors conclude.

The report notes a range of other key findings on antimicrobial resistance, including:

•  Data available thus far fail to implicate methicillin-resistant Staphylococcus aureus (MRSA) as a foodborne pathogen.
•  Various lists of critically important antibiotics, such as those published by WHO and OIE, are a good first step for focusing on what is most important for protecting public health. Subsequent steps will be needed and might include international collaboration to better understand appropriate science-based regulatory oversight and enforcement to meaningfully protect these critically important drugs.
•  Caution should be used in relying on the broad characterization of foodborne pathogens as multi-drug-resistant, as this classification alone may not represent a major threat to public health if the component resistance traits are not considered to be of “critical importance” according to WHO or FDA.
•  The U.S. National Antibiotic Resistance Monitoring System (NARMS) has become a mature and respected system for monitoring changes in antimicrobial resistance in human, animal, and retail meat sources.
•  Several noteworthy findings regarding antimicrobial-resistant microbes have been recorded by NARMS during the past 5 to 12 years, including:
•  Among specific pathogens, resistance to several of the top antibiotic classes on the WHO list of critically important antibiotics has not expanded. For some combinations, resistance increases were noted. For example:
•  Fluoroquinolone and quinolone resistance has remained static among non-Typhi Salmonella serovars. Among exclusively human serovars of Salmonella Typhi and S. Paratyphi that are largely associated with international travel there is a high level of resistance to nalidixic acid, the bellwether of fluoroquinolone resistance.
•  The prevalence of fluoroquinolone resistance of Campylobacter jejuni has remained static at about 22% following bans on its use in poultry. In contrast, other countries in the developing world have seen massive expansion of resistance to this class of antimicrobial.
•  Resistance to third generation cephalosporins has increased for some serovars of Salmonella
•  Emergence of antimicrobial resistance in bacteria associated with co-resident populations of animals and people is a complex issue and does not represent a simple unidirectional pathway from animals to human individuals. While simple interventions have been sufficient to control the prevalence of resistant bacteria in some unique antimicrobial-use and bacteria combinations, many situations call for more complex interventions.
•  The elimination of growth promotion claims from antimicrobial labels in Denmark, often termed the Danish experience, has not resulted in clear improvements in various antimicrobial resistance or health metrics. This may highlight the challenges in detecting and reporting benefits of regional interventions.
•  A national intervention program to reduce antimicrobial resistant bacteria should be based on an understanding of the key factors that can select and co-select for antibiotic resistance.

“It is highly likely that actions will be taken during the next five years to further restrict the availability of critically important antimicrobials and their allowed uses in aquaculture and agriculture, particularly in the developed world. However, such practices may in the near future have trade implications which will apply pressures to those jurisdictions with less control on their antimicrobial practices to develop and implement appropriate risk management policies. To effectively mitigate harmful effects from antimicrobial resistance in the U.S., we must work with global partners to promote prudent use in those countries where regulatory oversight of critically important antimicrobial drugs is underdeveloped,” note the authors.

The authors for this summary include: Michael Doyle, PhD, Regents Professor and Director, Center for Food Safety, University of Georgia; Guy Loneragan, Epidemiologist, International Center for Food Industry Excellence, Texas Tech University; H. Morgan Scott, Professor, Epidemiology, E.J. Frick Professor Veterinary Medicine, Department of Diagnostic Medicine/Pathobiology, Kansas State University; and Randall Singer, Department of Veterinary and Biomedical Sciences, University of Minnesota. This and other scientific status summaries are prepared by IFT as one source of accurate and objective information suitable for many different audiences, including IFT members. Scientific status summaries are rigorously peer-reviewed by individuals with specific expertise in the subject.