Good and Bad News in Latest NARMS Report

FSIS collects samples from livestock slaughter plants to help track antimicrobial resistance trends.

The latest report from the National Antimicrobial Resistance Monitoring System (NARMS) shows antibiotic resistance remains low for most human infections, and resistance has declined in some instances. The report also shows increases in the level of antimicrobial resistance in some foodborne pathogens.

Three federal agencies, the FDA, the Centers for Disease Control and Prevention (CDC) and the USDA’s Food Safety and Inspection Service ) FSIS, collaborate in collecting and reporting NARMS data. The integrated report highlights antimicrobial resistance patterns in bacteria isolated from humans (by CDC), raw retail meats (by FDA), and animals at slaughter (by USDA). The report also provides information derived from whole genome sequence data about resistance genes for all Salmonella and some Campylobacter isolates.

Notably, the latest report compiles data from 2015, before implementation of the FDA’s Guidance for Industry 213, which ended the use of medically important antibiotics for growth promotion in livestock, and the current veterinary feed directive (VFD) rules, which place the use of most medicated feeds under the supervision of veterinarians. Future NARMS reports should help measure the effect of those rules on resistance trends in animal agriculture.

Key findings include:

• Most Salmonella isolates from humans (76%) had no resistance to any of the 14 antimicrobial drugs tested.
• Multidrug resistance (MDR) increased from 9% to 12% of human Salmonella, driven largely by an increase in combined resistance to ampicillin, streptomycin, sulfonamides, and tetracycline among Salmonella serotype I.
• Ceftriaxone resistance either continued to decline or remained low in non-typhoidal Salmonella from all NARMS sources except turkey hazard analysis and critical control point (HACCP) samples, where the percent resistance in 2015 (15.7 percent) was the same as 2010 levels.
• While still rare, azithromycin resistance occurred in Salmonella, in some cases in strains with resistance to other antibiotics.
• Erythromycin resistance in Campylobacter coli increased three-to five-fold between 2011 and 2015 in isolates from humans (2.7 percent to 12.7 percent) and from chicken carcasses (3.4 percent to 12.8 percent).
• Transmissible quinolone resistance in Salmonella may be increasing. The underlying resistance traits reside on mobile genetic elements and therefore have the potential to be shared, either alone or together with other resistance genes, with susceptible strains of Salmonella.
• From 2014 to 2015, there was a decline from 73 percent to 57 percent in the proportion of retail ground turkey Salmonella isolates resistant to at least one antimicrobial. Historically, the majority of isolates from turkey sources have been resistant to at least one antimicrobial.
• In addition to resistance trends, the report includes sales data for Antimicrobials Sold or Distributed for Use in Food-Producing Animals. According to the 2015 report, for medically important agents, tetracyclines accounted for 71% of sales, penicillins for 10%, macrolides for 6%, sulfonamides for 4%, aminoglycosides for 4%, lincosamides for 2%, and phenicols, cephalosporins, and fluoroquinolones each for less than 1%. Domestic sales and distribution increased by 26% from 2009 through 2015, while the increase from 2014 to 2015 was 2%. Aminoglycoside posted the highest percentage increase, at 13% from 2014 through 2015.

Read the full 2015 NARMS report.