Stewardship / Resistance Scan for Feb 24, 2017

New diagnostic tests
Antibiotic prescribing frequency
Possible Candida auris drug
MRSA pattern shifts

FDA clears two diagnostic tests for expanded use, marketing

The US Food and Drug Administration (FDA) yesterday cleared the expanded use of a diagnostic test for lower respiratory tract infections and sepsis and allowed marketing for a test that can identify organisms that cause bloodstream infections, according to two agency news releases.

Expanded use was cleared for the Vidas Brahms PCT Assay, a test that was first approved to help clinicians predict a patient's risk of dying or becoming sicker from sepsis. Under expanded use, healthcare providers will be able to use the test determine if antibiotic treatment should be started or stopped in patients with lower respiratory tract infections, and stopped in patients with sepsis.

The test measures the amount of procalcitonin (PCT), a protein associated with the body's response to bacterial infection, in a patient's blood. High levels of PCT are an indication of a bacterial infection, while low levels suggest a viral infection. The test does not identify the exact cause of symptoms.

The decision was based on data from clinical trials that showed a significant decrease in antibiotic use for patients who received PCT-guided therapy, without affecting safety.

"Unnecessary antibiotic use may contribute to the rise in antibiotic-resistant infections," Alberto Gutierrez, PhD, director of the Office of In Vitro Diagnostics and Radiological Health at the FDA’s Center for Devices and Radiological Health, said in a news release. "This test may help clinicians make antibiotic treatment decisions."

The agency allowed marketing for the PhenoTest BC Kit, the first test to identify organisms that cause bloodstream infections and provide information about antibiotics that could be effective against those organisms.

The test works by comparing the genetic material of the infection-causing organism to DNA of specific bacteria or yeast. It then mixes the organism with an antibiotic and measures its growth. If the organism doesn't grow in the presence of the antibiotic, it means that antibiotic could be used to treat the patient. The test can identify 14 different species of bacteria and two types of yeast, provide antibiotic sensitivity on 18 different antibiotics, and identify the presence of two indicators of antibiotic resistance.

The PhenoTest BC Kit is also much faster than traditional identification and antibiotic susceptibility tests, which can take 1 to 2 days. It can identify bacteria or yeast from a positive blood culture in approximately 1.5 hours.

In a primary clinical study of 1,850 positive blood cultures, the PhenoTest BC Kit correctly identified the infection-causing organism more than 95% of the time, and results for antibiotic sensitivity were also accurate when compared to traditional tests.
Feb 23 FDA news release
Feb 23 FDA news release


UK Study finds subset of sick patients getting majority of antibiotics

More than half of the antibiotics prescribed to adults in primary care settings in the United Kingdom go to less than 10% of patients, according to a new study in the Journal of Antimicrobial Chemotherapy.

Using data from a primary care database that includes records from more than 12 million UK patients registered with general practices, researchers at the University College London set out to measure variation in the rates of antibiotic prescribing between individual patients. They were looking to investigate the relationship between individual-level antibiotic prescribing and age, gender, and comorbidity, in order to determine the extent to which prescribing variation is driven by behavioral, clinical, and demographic characteristics.

Overall, the investigators included data from nearly 2 million patients over a 3-year period (from 2011 through 2013). On average, 30.1% of patients were prescribed at least one antibiotic per year. Of the total antibiotics prescribed over the 3-year period, 53.3% were prescribed to just 9% of registered patients, each of whom was prescribed at least five antibiotics.

Those patients, the investigators found, tended to be the sicker ones. The presence of at least one comorbidity increased the rate of antibiotic prescribing by 44%, while the presence of two comorbidities nearly doubled it. Individuals with heart failure, asthma, or peripheral arterial disease were prescribed 53% - 69% more antibiotics than patients without those conditions, while patients with diabetes and coronary artery disease were prescribed 47% more antibiotics.

"Our results highlight the importance of high-frequency antibiotic use in a subset of patients with high rates of comorbidity," the authors write.

Gender and age were factors as well. Rates of antibiotic prescribing in women exceeded those in men by 62% and were higher in older patients compared to younger patients, though the association was more marked in men.

The authors say assessing the feasibility of reducing antibiotic prescribing in those with the highest frequency of use should be considered in the context of antibiotic stewardship initiatives.
Feb 21 J Antimicrob Chemother study


Scientists say experimental drug may be effective against Candida auris

The hard-to-treat Candida auris may be vulnerable to an investigational drug, scientists reported yesterday in the first systematic study of the yeast species, which can cause deadly infections.

The US Centers for Disease Control and Prevention first warned the public health and medical communities about the disease last June after cases were reported in several countries. The agency then confirmed the first 13 US cases in November. The pathogen was first reported in 2009. Some strains are resistant to all commercially available antifungal drugs.

Investigators at Case Western Reserve University analyzed 16 C auris strains from infected patients in Germany, Japan, India, and South Korea. They tested the isolates against 11 drugs belonging to different classes of antifungals to identify concentrations that could fight infection. While most samples were at least partially resistant to the tested drugs, low concentrations of an investigational drug called SCY-078 "severely distorted" the fungus and impaired its growth and ability to replicate.

Previous studies have shown the drug is effective against other Candida species that cause catheter-associated infections, including C albicans and C tropicalis, according to a Case Western Reserve news release.

The researchers reported that C auris does not germinate and produce spores like other fungi, a surprise given its ability to rapidly spread in hospitals. The researchers also noted that only certain strains produce the destructive enzymes that typically aid fungi in infection.

People with long hospital stays appear to be most at risk of infection.
Feb 21 Antimicrob Agent Chemother study
Feb 22 Case Western Reserve news release
Nov 4, 2016, CIDRAP News Story "CDC reports first US cases of drug-resistant Candida auris"


German study notes MRSA decline but shifts in resistance patterns

An analysis of Staphylococcus aureus samples from a German antimicrobial surveillance system found that methicillin-resistant S aureus (MRSA) infections declined across a range of healthcare settings from 2010 to 2015, but the co-resistance profile changed markedly. A team based at the Robert Koch Institute published its findings yesterday in BMC Infectious Diseases.

The analysis covered 148,561 S aureus isolates collected over the 6-year study period. The proportion of MRSA isolates declining steady from 16% in 2010 to 10% in 2015, with the drop seen across all types of care and for most sample types, including blood culture, urine, swabs, respiratory, and lesions.

Resistance to tobramycin, ciprofloxacin, moxifloxacin, clindamycin, and erythromycin declined markedly, but resistance increased to tetracyclines (6% to 9%) and gentamicin (3% to 6%). The group also found that resistance among MRSA isolates was fortunately rare to last-line antibiotics, including linezolid, teicoplanin, tigecycline, and vancomycin.

The researchers concluded that Germany's decline in MRSA infections is consistent with other reports and that control measures have likely played a role. They noted, however, that normally occurring changes in circulating strains may also be a factor. The increased resistance they saw to tetracycline was associated with factors such as young age and samples from outpatient settings, a finding they said is consistent with livestock-associated MRSA, a finding that warrants more investigation.

They added that the change in co-resistance patterns should be explored further with genotyping studies.
Feb 23 BMC Infect Dis abstract

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