Stewardship / Resistance Scan for Apr 07, 2017

KFC cuts antibiotics
MRSA incidence in the US
Potential MDR-TB drugs

KFC says its chicken will be free of medically important antibiotics

Kentucky Fried Chicken (KFC) has become the latest fast food chain to announce it will stop selling chicken raised with medically important antibiotics.

KFC, a subsidiary of Yum! Brands, says that by the end of 2018, all chicken bought by its 4,200 restaurants will be free of antibiotics that are also used in human medicine.

"We're constantly working to meet the changing preferences of our customers, while ensuring we deliver on the value they expect from KFC. Offering chicken raised without medically important antibiotics is the next step in that journey," Kevin Hochman, president and chief concept officer for KFC US, said in a company press release.

McDonald's made a similar pledge in 2015, and as of August 2016 said it had completed its commitment to phase out chicken raised with medically important antibiotics from its menu. Wendy's, Chik-fil-A, and Restaurant Brands International (owner of Burger King and Tim Hortons) have also committed to antibiotic-free chicken, with Chik-fil-A pledging that its chicken will be free of all antibiotics.

But Lena Brook, a food policy advocate with the Natural Resources Defense Council (NRDC), says KFC's policy will have an even wider impact on chicken production in the United States, since the company doesn't buy all the chickens in any given flock.

"This commitment from the nation's most iconic fast food chicken chain will have a major impact on the way the birds are raised in the U.S. and in the fight against the growing epidemic of drug-resistant infections," Brook said in an NRDC press release.

According to estimates, about 70% of all medically important antibiotics sold in the United States are used in poultry and livestock production. Public health officials are concerned that the widespread use of medically important antibiotics in food-producing animals is contributing to antibiotic resistance.
Apr 7 KFC press release
Apr 7 NRDC press release


Study finds wide variation in US estimates of MRSA incidence

A review of epidemiologic studies on the incidence of methicillin-resistant Staphylococcus aureus (MRSA) infections in the United States has found a wide variation in estimates and no firm evidence of significant decline, researchers report today in Antimicrobial Resistance and Infection Control.

The researchers reviewed five reports on MRSA incidence with data acquisition periods that ended on or before 2011. The reports—which came from the Emerging Infection Program (EIP), the Surveillance Network (TSN), the University Healthcare Consortium (UHC), the National Healthcare Safety Network (NHSN), and the Veterans Administration (VA) Healthcare Systems—measured different types of MRSA infections, different patient populations (including patients in military facilities, patients in acute care settings, pediatric patients, and patients in the general population), and used different data gathering methodologies. The differences made direct comparisons difficult.

Some of the reports indicated significant declines in MRSA incidence. An EIP study showed a 54.2% decrease in hospital-onset invasive MRSA at hospitals in nine diverse metropolitan areas, while a VA study showed a 43% decrease in hospital-onset MRSA bacteremia at military healthcare facilities. But another EIP study found a decrease in invasive MRSA among pediatric patients of only 2.6%, and a TSN study reported a stable rate of MRSA-related hospitalizations for pneumonia and bloodstream infections. A UHC study, meanwhile, found that MRSA infections doubled at 420 academic medical centers.

The authors say the lack of uniformity of MRSA reporting is hindering the United States' ability to formulate control strategies and shows the need for a comprehensive tracking system for MRSA and other multidrug-resistant organisms. "Without this, the difficulty achieving the 2020 MRSA reduction goal of 50% will be hindered," they write.
Apr 7 Antimicrob Resist Infect Control study


Researchers discover new class of potential drugs against resistant TB

Scientists at Rutgers University have discovered a new class of potential anti-tuberculosis (TB) drugs that kill rifampin-resistant and multidrug-resistant (MDR) Mycobacterium tuberculosis,the bacterium that causes TB, according to a study yesterday in Molecular Cell.

The researchers mapped the three-dimensional (crystal) structure of Mtb RNA polymerase (Mtb RNAP), the M tuberculosis enzyme inhibited by rifampin, a first-line TB drug and a cornerstone of treatment for decades. They also detailed the three-dimensional structure of Mtb RNAP as it binds to rifampin to help uncover what alterations in the binding site produce rifampin resistance.

In the study, the scientists report the discovery and properties of new compounds unrelated to rifampin—Na-aroyl-N-aryl-phenylalaninamides (AAPs) —that potently and selectively inhibit Mtb RNAP and kill TB bacteria. They also detailed the structures of Mtb RNAP bound to an AAP and Mtb RNAP bound to both an AAP and rifampin. These structures show that AAPs inhibit Mtb RNAP through a binding site that does not overlap the rifampin binding site and thus can inhibit rifampin-resistant Mtb RNAP and kill rifampin-resistant TB bacteria.

The results further show that AAPs, when co-administered with rifampin, produce an additive effect and can suppress resistance. Taken together, the results show that AAPs are promising compounds for TB drug development, according to a Rutgers news release.

"The structure of Mtb RNAP has been the 'Holy Grail' for TB drug discovery targeting Mtb RNAP," said lead author Richard Ebright, PhD, in the release.

"AAPs represent an entirely new class of Mtb RNAP inhibitors and are, without question, the most promising Mtb RNAP inhibitors for anti-TB drug development since rifampin," Ebright said. "We are very actively pursuing AAPs. We have synthesized and evaluated more than 600 novel AAPs and have identified AAPs with high potencies and favorable intravenous and oral pharmacokinetics."
Apr 6 Mol Cell study
Apr 6 Rutgers news release

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