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FDA: Antibiotic resistance data require context

FDA: Antibiotic resistance data require context
"Oversimplifying" NARMS data provides "misleading" conclusions, says the Food & Drug Administration as it takes on EWG report.

THE Food & Drug Administration issued a statement of caution April 22 regarding the interpretation of antimicrobial resistance data.

The FDA statement came on the heels of a recent Environmental Working Group (EWG) report of its interpretation of the "2011 Retail Meat Annual Report" of the National Antimicrobial Resistance Monitoring System (NARMS).

While FDA said it is always concerned about antimicrobial resistance, the agency believes the EWG report oversimplifies the NARMS data and provides misleading conclusions. FDA said it does not believe that EWG fully considered important factors that put these results into context, including:

* Whether the bacterium is a foodborne pathogen. The report highlights resistance to enterococcus, but this is not considered a foodborne pathogen. Instead, FDA includes it because its behavior is helpful in understanding how resistance occurs.

* Which drug(s) the bacterium is naturally resistant to. For example, most Enterococcus faecalis is naturally resistant to the antibiotic class of lincosamides. Because this resistance is known and expected, FDA is not as concerned with resistance in this species as it would be with resistance in true pathogens like salmonella and campylobacter.

* Why NARMS includes certain drugs in its testing design. Some antibiotics are included for epidemiology purposes -- to track the spread of certain bacteria or genes -- but resistance to them doesn't reflect a danger to public health.

* Whether the antibiotics commonly used to treat patients are still effective. NARMS data indicate that first-line treatments for all four bacteria that are tracked (salmonella, enterococcus, Escherichia coli and campylobacter) are still effective.

* What the 2011 data indicate relative to similar data reported for prior years.

Additionally, FDA said it believes it is inaccurate and alarmist to define bacteria that are resistant to one or a few antimicrobials as "superbugs" if these same bacteria are still treatable by other commonly used antibiotics. This is especially misleading when speaking of bacteria that do not cause foodborne disease and have natural resistances, such as enterococcus.

When taking such factors into account, FDA said it believes the notable findings in the 2011 NARMS report include:

* In the critically important class of fluoroquinolone antimicrobials, the 2011 data showed no fluoroquinolone resistance in salmonella from any source. This is the drug of choice for treating adults with salmonella.

* Fluoroquinolone resistance in campylobacter has stopped increasing and has remained essentially unchanged since FDA withdrew the use of this drug class in poultry in 2005. Trimethoprim-sulfonamide is another drug used to treat salmonella infections, and resistance remains low (at 0-3.7%).

* Macrolide antibiotic resistance in retail chicken isolates remains low, with 2011 results at 0.5% of Campylobacter jejuni and 4.3% of Campylobacter coli. The macrolide antibiotic erythromycin is the drug of choice for treating campylobacter infections.

* Multi-drug resistance is rare in campylobacter. Only nine out of 634 campylobacter isolates from poultry were resistant to three or more antimicrobial classes in 2011. However, gentamicin resistance in C. coli markedly increased from 0.7% in 2007 (when it first appeared in the NARMS retail meat report) to 18.1% in 2011. Gentamicin has been suggested as a possible second-line therapy for campylobacter infections, although it is not commonly used.

* Between 2002 and 2011, resistance to third-generation cephalosporins, which are used to treat salmonellosis, has increased in salmonella from chicken (from 10.0% to 33.5%) and turkey (from 8.1% to 22.4%) meats. FDA noted this development in previous years and has already taken action by prohibiting certain extra-label uses of cephalosporins in cows, pigs, chickens and turkeys and continues to closely monitor resistance to these drugs.

FDA reiterated that antimicrobial resistance is a serious and challenging issue and noted that it is critically important to continue efforts to minimize antimicrobial resistance, including promoting appropriate and judicious use of antimicrobials in both humans and animals.

More details on FDA's statement can be found online at www.fda.gov/AnimalVeterinary/NewsEvents/CVMUpdates/ucm348794.htm?source=govdelivery.

In response to FDA's statement, the Animal Health Institute said, "The Animal Health Institute applauds FDA for setting the record straight with regard to EWG's report conclusions and further underscoring the importance of providing consumers with factual and accurate information. ... Antimicrobial resistance is a challenging issue and one our industry takes seriously. We work to ensure that veterinarians and farmers use antibiotics responsibly to keep animals healthy while protecting public health."

Volume:85 Issue:17

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