28 April 2016
The U.S. Food and Drug Administration has released a new interim report that measures antimicrobial resistance in Salmonella isolated from raw retail meat and poultry collected through the National Antimicrobial Resistance Monitoring System (NARMS). The 2014-2015 Retail Meat Interim Report contains data from January 2014 – June 2015. It focuses only on Salmonella, a major pathogen of concern in foodborne disease outbreaks. Information includes serotype distribution, prevalence by food source and state, selected resistance patterns, and a list of all the identified antimicrobial resistance genes. To provide data in a timelier manner, the FDA intends to issue retail meat interim reports twice per year. In this report FDA also includes, for the first time, whole-genome sequencing data for Salmonella.
NARMS was established in 1996 as a partnership between the FDA, the Centers for Disease Control and Prevention, and the U.S. Department of Agriculture to track antibiotic resistance in foodborne bacteria for drugs that are considered important in human medicine, including whether they are multidrug resistant (resistant to three or more classes of antibiotics). NARMS is critically important for monitoring trends in antimicrobial resistance among foodborne bacteria collected from humans, retail meats and food animals. In particular, it assists the FDA in making data-driven decisions on the approval of safe and effective antimicrobial drugs for animals.
The retail meat arm of the NARMS program collects samples of grocery store chicken, ground turkey, ground beef and pork chops, and tests for non-typhoidal Salmonella, Campylobacter, Escherichia coli and Enterococcus, to determine whether such bacteria are resistant to various antibiotics used in human and veterinary medicine. Enterococcus and most E. coli are not considered major foodborne pathogens but are included because they are helpful in understanding how resistance occurs and spreads.
Encouraging Trends
In many important categories, encouraging improvements found in 2011 continued to be evident in the latest data. The prevalence of Salmonella in retail poultry is at its lowest level since testing began in 2002. In ground turkey, the prevalence of Salmonella has declined from a high of 19% in 2008 to 6% in 2014. In retail chicken over the same time period, it has dropped from 15% to 9%. Salmonella resistance to ceftriaxone (an important antibiotic used to treat seriously ill patients) from chicken sources continued to decline steadily from a high of 38% in retail chicken meats in 2009 to 18% in 2014, and 5% during the first half of 2015. In ground turkey isolates, ceftriaxone resistance was detected in 7% of 2014 isolates and 4% of 2015 isolates collected through June, which represents an 80% decline since 2011 when resistance peaked at 22%. Fluoroquinolones like ciprofloxacin are classified as critically important for the treatment of Salmonella infections. Ciprofloxacin resistance was absent in Salmonella from poultry and beef, although a single isolate was found in pork. All Salmonella from retail meats were susceptible to azithromycin, another important antibiotic recommended for the treatment of Salmonella and other intestinal pathogens. Multidrug resistance in Salmonella continued to show a downward drift in chicken and turkey from 2011 levels of 45% and 50%, respectively, to 20% and 36% in June 2015.
Findings of Concern
FDA identified the first instance of ciprofloxacin resistance in an isolate from retail pork, and identified the genes associated with this resistance for future tracking. One ceftriaxone-resistant retail chicken isolate from 2014 had the extended-spectrum β-lactamase (ESBL) gene blaCTX-M-65. This is the first time this important class of resistance gene was detected in the U.S. This ESBL gene causes resistance to β-lactam antibiotics, includi