Antimicrobial Resistance Scan for Sep 15, 2016

NDM-1 in Vibrio isolates
MDR-TB cure rates

NDM-1 detected in 27 Vibrio fluvialis isolates in India

Although MCR-1 has often garnered drug-resistance headlines of late, an earlier gene that also confers antimicrobial resistance, NDM-1 (New Delhi metallo-beta-lactamase) has not gone away, as evidenced by a study yesterday in Emerging Infectious Diseases. Researchers reported the gene in 27 Vibrio fluvialis isolates in Kolkata, India.

NDM-1 was first discovered in 2009, with the first US cases reported in 2010. It has been reported most commonly in India and Pakistan. MCR-1 was first detailed in a report late last year and renders pathogens resistant to the last-line antibiotic colistin. Most NDM-1 strains are susceptible to colistin but resistant to most commonly used antibiotics.

In the new study, Indian researchers were screening samples from hospitalized patients who had diarrhea when they identified the 27 NDM-1 V fluvialis isolates, which were resistant to all antimicrobials tested except doxycyline. The genes flanking the NDM-1 genes were identical to those identified in a comparison NDM-1 Escherichia coli bacterium isolated previously.

The scientists were also able to transfer the NDM-1-containing plasmid to other pathogens such as E coli, but those pathogens exhibited a slightly less extensive antimicrobial resistance profile.

The authors concluded, "The pathogenicity of V. fluvialis to humans and its ubiquitous presence in the environment call for constant monitoring of this species for emerging antimicrobial drug resistance."
Sep 14 Emerg Infect Dis report


Study says WHO guidelines might underestimate cure in MDR-TB patients

A new study suggests that the way the World Health Organization (WHO) defines "cure" for patients with multidrug-resistant tuberculosis (MDR-TB) may underestimate how many people recover from the disease.

The study, published in the New England Journal of Medicine, evaluated treatment outcomes for 380 European MDR-TB patients according to WHO definitions and compared them with simplified definitions of treatment outcomes. Under the WHO guidelines, cure was defined as treatment completion with at least three negative cultures after the intensive phase of therapy in the absence of treatment failure. Under the simplified definition, cure was defined as a negative culture status 6 months after treatment initiation, no positive culture thereafter, and no relapse within 1 year after treatment completion.

The study found that relapse-free cure was achieved in 61% of patient with MDR-TB, 52% of patients with pre-extensively drug-resistant (XDR) TB, and 39% of patients with XDR-TB. Under the WHO definition, 31%, 27%, and 24% of patients, respectively, were considered cured.

"In conclusion, current WHO definitions may underestimate cure in patients with MDR tuberculosis," the study authors wrote. "These definitions could be simplified while incorporating the assessment of post-treatment relapse."
Sep 15 N Engl J Med correspondence

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