ASP Scan for Jul 08, 2016

Resistance to MDR-TB drugs
Viral vs bacterial infection test
Reduced antibiotics

Five-nation study finds range of resistance to essential MDR-TB drugs

A new study from the World Health Organization (WHO) is shedding some light on the extent of resistance to drugs that are considered essential for the treatment of multidrug-resistant tuberculosis (MDR-TB).

The study, published yesterday in The Lancet Infectious Diseases, used population-based surveys from Azerbaijan, Bangladesh, Belarus, Pakistan, and South Africa to investigate the levels of resistance to pyrazinamide and fluoroquinolones among TB patients.

Pyrazinamide and fluoroquinolones are "second line" drugs used mainly for the treatment of MDR-TB, and they are considered essential for treating TB that is resistant to the "first line" drug rifampicin. They are also an important component of shorter, more easily administered regimens for the treatment of MDR-TB.

In a retrospective analysis of samples from 4,972 TB patients, the researchers found that levels of pyrazinamide resistance varied substantially in the five countries—from 3.0% to 42.1%—but were significantly associated with rifampicin resistance. This is important, the authors said, because it means that treatments that include pyrazinamide may be no more effective than first-line treatments for patients with rifampicin-resistant TB, and therefore should be carefully evaluated.

Among the 5,015 patients tested for susceptibility to fluoroquinolones, the overall prevalence of resistance in the five countries was low, with the exception of Pakistan, where high levels of ofloxacin resistance were detected. The authors said that could be the result of extensive and unregulated use of fluoroquinolones in Asia. But they were encouraged by negligible resistance in all countries to two newer fluoroquinolones—moxifloxacin and gatifloxacin.

The authors said more studies of this nature are needed to avoid the risk of introducing ineffective treatments for MDR-TB that could amplify the development of drug resistance.

The WHO estimates that 480,000 people developed MDR-TB in 2014, and 190,000 people died from it.
Jul 7 Lancet Infect Dis study


Blood test shown to distinguish between viral, bacterial infections

Originally published Jul 7.

A team of researchers from Stanford University School of Medicine and Cincinnati Children's Hospital Medical Center has developed a blood test that could one day enable doctors to quickly determine whether an infection has been caused by a bacterium or a virus. Their research was published yesterday in Science Translational Medicine.

The test, according to a Stanford University news release, is based on a set of seven genes—derived from publicly available patient gene expression data—whose activity changes in response to an infection. When the infection is bacterial, four of the genes become more active; when the infection is viral, three of the genes become more active. For the study, researchers tested the seven-gene test on blood samples from 96 critically ill children and found that the overall sensitivity and specificity for bacterial infection were 94.3% and 52.2%, respectively.

The researchers say the new test is an improvement over previous gene-expression tests because so few genes are involved. Those earlier tests, they write in the study, contain too many genes to translate into a useful clinical tool. But the seven-gene test is still likely years away from clinical use, as it still needs to be tested in clinical settings.

Ultimately, the researchers say, they hope to combine the seven-gene test with an 11-gene test they created last year. That test can determine whether the patient has an infection at all. The hope is that both tests would be run at the same time, and that doctors could have the results back within an hour.

The ability to quickly determine the nature of an infection means doctors could act faster with patients who have potentially deadly conditions like sepsis and need antibiotics. At the same time, it could help antibiotic stewardship efforts by reducing inappropriate use of the drugs.
Jul 6 Sci Transl Med study
Jul 6 Stanford University news release


Reduced antibiotics for RTIs could lead to slight increase in pneumonia

Originally published Jul 5.

A large new study out of the United Kingdom shows that a reduction in antibiotic prescribing for self-limiting respiratory tract infections (RTIs) might lead to a slight increase in some bacterial infections like pneumonia but not in several others.

According to the study, published yesterday in BMJ, about 50% of antibiotics prescribed in UK primary care practices are for RTIs such as common colds, sore throat, acute bronchitis, and sinusitis. This is despite the fact the antibiotics offer little benefit for such ailments, and UK health officials recommend a no-antibiotic-prescribing approach to RTIs as part of a strategy to reduce the inappropriate use of antibiotics and the risks of antibiotic resistance.

Some doctors, however, continue to prescribe antibiotics for RTIs over concerns about potential complications from those infections—including pneumonia, peritonsillar abscess, mastoiditis, empyema, bacterial meningitis, intracranial abscess, and Lemierre's syndrome.

To determine whether reducing unnecessary antibiotic prescribing for RTIs could increase the risk of these complications, researchers looked at electronic health records from more than 600 general practices in the United Kingdom from 2005 to 2014, a period that saw antibiotic prescriptions for RTIs decrease from 53.9% to 50.5% in men and from 54.5% to 51.5% in women. They then extrapolated the findings to determine the expected number of complications that might occur if a general practice with a population of 7,000 patients reduced antibiotic prescriptions for RTIs by 10% over a decade.

The study showed that while no increase is likely for mastoiditis, empyema, bacterial meningitis, intracranial abscess, or Lemierre's syndrome, general practitioners might see a slight increase in treatable cases of pneumonia (about one additional case a year) and peritonsillar abscess (about one additional case a decade). At the same time, the authors note, a 10% reduction in antibiotic prescribing for RTIs would likely reduce the risks of antibiotic resistance and the side effects of antibiotics.
Jul 4 BMJ study

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