Fact or fiction: Antibiotics used in animals are the cause of major human drug resistant diseases.
Fact or fiction: 80% of antibiotics in the US are used in healthy animals.
Fact or fiction: Multiple Drug Resistant (MDR) Salmonella in retail meats is a major public health threat
Myth: “Animal antibiotics kill more people than breast and prostate cancer” screamed a blogger in the wake of an AP story on antibiotics used to keep food animals healthy.
Activists who oppose the use of antibiotics to keep food animals healthy have attempted to tie animal use to the estimates from the Centers for Disease Control that show antibiotic resistance kills 65,000 people each year and costs $4 to $5 billion annually.
Fact: The major resistant bacteria/drug combinations that are in the news and are severe problems in human health settings are not related to the use of antibiotics in animals.
Review of one reputable source for categorizing the major resistance problems in humans shows that these resistance problems have little or nothing to do with animal use of antibiotics. Let’s examine.
The Infectious Disease Society in America (IDSA) publishes a website called “Facts about Antibiotic Resistance”. They discuss the specific bacterial infections that present the biggest challenges to doctors and healthcare facilities from resistance to antibiotics:
- Staphylococcus infections (MRSA) – these are mainly hospital nosocomial infections but have been found in communities associated with schools and athletic facilities. These infections are a result of human to human transmission or contact with contaminated materials. IDSA says that 1% of people carry MRSA in their nasal passages. CDC investigates cases of MRSA and has concluded that animal contact is not a risk factor for these infections. Furthermore, they have also concluded that MRSA is not a foodborne infection and cannot be acquired by eating meat.
- Acinetobacter baumanni is an opportunistic pathogen associated with a high rate of infections in soldiers wounded in Iraq. It is most often associated with wound infections in hospitals and other medical facilities. It is inherently resistant to many antibiotics and has no connection to food animals or antibiotic use in food animals.
- Vancomycin Resistant Enterococcus (VRE) is another hospital nosocomial infection that has developed resistance due to extensive use of vancomycin in U.S. hospitals. Vancomycin or drugs in its class have never been approved for or used in food producing animals.
- Pseudomonas aeruginosa is another opportunistic pathogen found in intensive care units that have become resistant to fluoroquinolone antibiotics. It occurs uncommonly in food producing animals where it can cause mastitis in dairy cows. Fluoroquinolones are not approved for use in dairy cows and furthermore Pseudomonas is not a foodborne pathogen.
- Streptococcus pneumoniae resistant to several classes of antibiotics is strictly a human pathogen that causes respiratory infections. This organism has no known connection to food producing or companion animals.
- Neisseria gonorrhea is strictly a human pathogen that causes venereal infections transmitted through human sexual contact. Resistance develops because of poor patient compliance with the prescribed course of antibiotic therapy. There is no connection with animals or antibiotic use in animals.
- Drug resistant tuberculosis, Clostridium difficile, and Klebsiella species are other bacteria that are mentioned in the IDSA fact sheet. There is no known connection between these pathogens and food producing animals.
Notably, the bacteria that are not mentioned in the fact sheet such as Salmonella and Campylobacter are the most likely bacteria that could be transmitted from animals to humans via uncooked meat or poultry. Apparently they do not represent major problems to infectious disease specialists for drug resistance and treatment.
The attempt to link animal use to these cost and death estimates in unfounded. Further, it is preposterous to suggest that reducing or eliminating the use of antibiotics to keep food animals healthy will address either of these issues.
Myth: “Food animals get 80% of the antibiotics used in the U.S. — mostly in ways that can lead to the growth of drug-resistant superbugs,” Reads one WebMD Health News article. Since 2010, bloggers and the media quote 80% as the de facto number for antibiotic usage in animals. 80 percent is a nice big number, but it’s wrong and misleading, for several reasons.
Fact: This statistic has no foundation in fact, according to the Food and Drug Administration.
- The 80 percent figure was deduced from comparing two sets of data that are not comparable. The number for animal use was collectively used a wholly different methodology than the estimate presented for human use. The first rule learned in Statistics 101 is if the data sets measure different universes in different ways, the data cannot be compared. FDA clearly warns against the comparability of the human and animal data in a letter to Congresswoman Louise Slaughter and in a caution on the FDA website.
- In addition, 35 percent of the use attributed to animals are compounds not used in human medicine, thus having no potential for reducing the effectiveness of antibiotics used to treat human disease. The 35 percent is included by others only to inflate the animal use number and mislead readers.
- One more fact: Most antibiotics used in animals are used for therapuetic purposes of treating, controlling and preventing disease. According to AHI data, in 2007 about 87 percent of all antibiotics used in animals were used for these therapeutic purposes.
For more than 40 years, antibiotics approved by the Food and Drug Administration have been used to treat sick animals, prevent and control illness and maintain their overall health. Livestock and poultry producers rely on these products so they can provide U.S. consumers with the safest food possible.
Multiple drug resistant (MDR) Salmonella in retail meats is a major public health threat
Myth: “…when you go to the supermarket to buy one of these brands of pre-ground meat products, there’s a roughly 25 percent chance you’ll consume a potentially fatal bacteria that doesn’t respond to commonly prescribed drugs.” wrote New York Times Columnist Mark Bittmann.
Concerns have been raised that the finding of multi-drug-resistant (MDR) Salmonella in retail meats, particularly in poultry, means that infections that might occur in humans from consuming these products will be resistant to treatment with antibiotics, thus leading to prolonged or more serious medical outcomes.
Fact: It is important to understand just how prevalent salmonella is, what it means when bacteria test as resistant in a lab, and what the typical treatment is for human infection of salmonella, or salmonellosis. Let’s examine the facts and put these concerns in perspective.
The Center for Disease Control and Prevention estimates that about 48 million episodes of foodborne illness occur each year in the U.S. Of these, an estimated 9.4 million are caused by 31 major pathogens of which about 1 million or 11% of are due to non-typhoidal Salmonella, the type most commonly associated with human infections.
- Human MDR Salmonella are a small subset of all Salmonella bacteria isolated from meats. According to the 2009 National Antimicrobial Resistance Monitoring System (NARMS) Executive Report, 83% of Salmonella isolates from humans were susceptible to all antibiotics tested. However, for treatment of salmonella infections, antibiotics are generally not recommended except in severe cases in high risk patients, or in bloodstream infections.
- Data from SENTRY(JMI Laboratories), a human isolate antimicrobial resistance surveillance system indicate that Salmonella are isolated from less than 1% of all reported bacterial bloodstream infections.1 Susceptibility testing of isolates from those infections showed resistance to fluoroquinolones to be less than 1% and resistance to 3rd or 4th generation cephalosporins between 2-3%, the two drug classes of choice for treatment of severe Salmonella infections.2
- All Salmonella bacteria regardless of whether it is resistant or sensitive to antibiotics are virtually 100% destroyed by proper cooking.
- Scallan E, Hoekstra RM, Angulo FJ, Tauxe RV, Widdowson MA, Roy SL, Foodborne illness acquired in the United States—major pathogens. Emerg. Infect Dis. 2011; 17:7–15. PubMed
- Doern, G, Brecher S, The Clinical Predictive Value (or Lack Thereof) of the Results of In Vitro Antimicrobial Susceptibility Tests. 2011. J. Clin. Micro. 49 (9 Suppl.):S11–S14.