The annual National Antibiotic Resistance Monitoring System (NARMS) report was just released covering results for the year 2015. Of course, the Veterinary Feed Directive (VFD) and the ban on using antibiotics important to human medicine as growth promoters in animals just went into effect Jan. 1, 2017, so we will have to wait a few years to see if those FDA actions have an impact on antibiotic resistance in food-borne pathogens.
There is not much in the latest report for those groups who want antibiotics banned for control and prevention of disease in our herds and flocks to lament or crow about.
No Chicken Littles here, the sky is not falling; but more on that later.
First, so we are all on the same page, NARMS is celebrating its 20th year with this report. It has morphed over those years, and sometimes comparing one year with another is like comparing buffalo with catfish.
But the essentials remain the same.
Three federal agencies, the Center for Disease Control & Prevention, the Food & Drug Administration and the U.S. Department of Agriculture, collect samples assisted by local and state health departments.
CDC enters data from human stool samples from patients suffering a food-borne illness, FDA or the locals collect retail raw meat and poultry samples, and USDA collects data from both cecal (large intestine) samples at slaughter and HACCP testing.
Human samples come from all 50 states. Retail meats are only sampled in 14 states but that will be expanding to 21 soon.
The meats that are tested are ground beef, ground turkey, chicken and pork chops.
The bacteria that are tested for antibiotic resistance are salmonella, campylobacter, enterococcus and E. coli.
Testing is done for resistance to 14 antibiotics commonly used in human medicine.
FDA uses this data to protect public health by regulating the use of antibiotics in animals raised for food, such as the ban on fluoroquinolones in poultry in 1995 and prohibiting off-label use in other animal species in 1997 as resistance to this new class of drug developed quite rapidly.
So, on to the findings of the 2015 NARMS report:
Seventy-six percent of salmonella isolated from human specimens had no resistance to any of the 14 antibiotics tested.
While multi-drug resistance in salmonella isolated from human specimens did increase slightly to 12%, the resistance most often was to a combination of ampicillin, streptomycin, sulfa and tetracycline. None of these antibiotic classes would be used as a first-line drug of choice for salmonellosis in humans.
One class of antibiotics that would be used to treat salmonellosis, especially in children too young to take the drug of choice for adults from the fluoroquinolone class, is third-generation cephalosporins, of which ceftriaxone is a member.
Cephalosporins were drastically restricted from use in animals raised for food in 2008 by FDA because of climbing resistance rates, so it is comforting to see resistance to ceftriaxone continue to decline in Salmonella since then. Good job FDA.
One worrisome finding is the apparent increasing fluoroquinolone resistance in salmonella that is transmissible from bug to bug. I say apparent because the testing methodology for quinolone resistance has undergone a lot of changes, but NARMS testing showed the resistance gene on plasmids which, while not prevalent, is a scary new finding.
This plasmid-borne gene can even jump from one genus specie to another.
Although the testing methodologies are different for NARMS than for most of the testing USDA does for baseline studies, it was satisfying to see that for retail chicken meat, which, of course, is what we ultimately put in our kitchens and stomachs, the salmonella recovery rate was 6.1%, the lowest in the 14 years NARMS has been testing retail meat.
A similar decline rate was seen in the ground turkey meat.
Surprising to many is the revelation that market swine and sows had the highest prevalence of salmonella.
FDA’s 2015 Summary Report on Antimicrobials Sold or Distributed for Use in Food-Producing Animals showed that of antibiotics used in both animal and human health, fluoroquinolones and cephalosporins each constituted less than 1% of total sales, while tetracyclines, rarely used anymore in human medicine, made up 71% of sales.
Fluoroquinolones and cephalosporins account for 25% of human sales, and tetracyclines less than 3%.
The other top three antibiotic classes used in human medicine (example in parenthesis) and the percent of sales for use in animal medicine are penicillin (Augmentin) at 10%, macrolides (Z-Pak) at 6% and sulfa (Bactrim) at 4%.
In the meantime, we need to realize that all is not perfect in the raw meat and poultry world, and reminded to clean, separate, cook and chill.
That means using a digital thermometer to assure that poultry is cooked to 165 degrees Fahrenheit, ground beef to 160 degrees and pork to 140 degrees.