FDA Releases 2014 NARMS

The U.S. Food and Drug Administration has released its 2014 National Antimicrobial Resistance Monitoring System (NARMS) Integrated Report, highlighting antimicrobial resistance patterns in bacteria isolated from humans, retail meats, and animals at slaughter. Specifically, the report focuses on major foodborne bacteria that are resistant to antibiotics that are considered important to human medicine, and on multidrug resistant organisms (described as resistant to three or more classes of antibiotics).

NARMS monitors foodborne bacteria to determine whether they are resistant to various antibiotics used in human and veterinary medicine. Specifically NARMS screens:

• non-typhoidal Salmonella
• Campylobacter
• Escherichia coli
• Enterococcus

Salmonella and Campylobacter are the leading bacterial causes of foodborne illness. While E. coli and Enterococcus may cause foodborne illness, they are included in NARMS mainly to help track the occurrence and spread of resistance.

For Salmonella from human infections, all isolates exhibiting resistance to any antimicrobial drug were subject to WGS. For Salmonella-positive retail meat samples and carcass samples (cecal), WGS was performed on every isolate recovered in 2014. In addition, the WGS has been determined for historical Salmonella (over 4,500 isolates) recovered from retail meat sources since testing began in 2002. The genomes have been uploaded to the public database at the National Center for Biotechnology Information (NCBI). As these data accumulate, NARMS reports will evolve to incorporate temporal changes in the resistome along with the susceptibility information.

Findings

The points listed below summarize important observations from the 2014 NARMS Integrated Report. There are few changes from the 2012-2013 NARMS Integrated Report. Overall resistance continues to remain low for most human infections and there have been measurable improvements in resistance levels in some important areas.

Right Direction:

• The prevalence of Salmonella in both retail chicken meat (9.1 percent) and retail ground turkey (5.5 percent) was at its lowest level since retail meat testing began in 2002. The prevalence of Campylobacter in retail chicken meat samples has gradually declined over time to 33 percent, the lowest level since testing began.
• Approximately 80 percent of human Salmonella isolates are not resistant to any of the tested antibiotics. This has remained relatively stable over the past ten years. Resistance for three critically-important drugs (ceftriaxone, azithromycin, and ciprofloxacin) in human non-typhoidal Salmonella isolates remained below 3 percent.
• Overall, ceftriaxone resistance continued to decline in non-typhoidal Salmonella from all NARMS sources with the exception of retail turkey meat isolates, where it rose slightly. This was paralleled by a decline in ceftriaxone-resistant E. coli from retail chicken meat (from 13 percent in 2011 to 6.6 percent in 2014). In cattle, Salmonella isolates from carcasses collected at processing plants as part of Pathogen Reduction/Hazard Analysis Critical Control Point (PR/HACCP) testing, ceftriaxone resistance reached its lowest level (7.6 percent) since 1999. In 2014, ceftriaxone resistance in human Salmonella Heidelberg isolates was 8.5 percent, down from a peak of 24 percent in 2010.
• Among all Salmonella serotypes, the percentage of human isolates resistant to at least ampicillin, chloramphenicol, streptomycin, sulfonamides, and tetracyclines (ACSSuT) continued a steady decline to 3.1 percent, the lowest since testing began in 1996 (8.7 percent). Similarly, ACSSuT resistance in cattle PR/HACCP Salmonella typhimurium isolates declined sharply from 67 percent in 2009 to 7 percent in 2014, the lowest level since this testing began in 1997.
• With the exception of five isolates in the past ten years, no resistance has been detected in Enterococcus bacteria isolates to three important drugs: daptomycin, linezolid, and vancomycin.
• While a majority of the observations in the 2014 NARMS Integrated Report show desirable trends, there are a few findings of potential concern.

Still of Concern:

• Decreased susceptibility to ciprofloxacin has increased in human and cattle (PR/HACCP) Salmonella serotype Dublin isolates since 2003, with slight declines since 2012. While the incidence of human Salmonella Dublin infections is relatively low, it can cause invasive disease with more severe outcomes, and ranks among the top four serotypes isolated from retail ground beef and cattle PR/HACCP samples.
• MDR Salmonella from turkey PR/HACCP samples has increased from approximately 27 percent to 41 percent over the past ten years.
• High and increasing levels of ciprofloxacin resistance were detected in Campylobacter jejuni from human (26.7 percent) and chicken PR/HACCP samples (28 percent) in 2014, and remained above 35 percent in Campylobacter coli from humans.