New Antibiotic Resistance Gene That Breaches 'Last Line of Defense' Is Found

저자：   업로드：2015-11-24  조회수：

    A new gene has been discovered that allows bacteria to become resistant to our last line of antibiotic defense. The gene, MCR-1, was found to be widespread in pigs and patients in south China, with some strains having epidemic potential.  MCR-1 was found to enable bacteria to become resistant to polymyxins; the colistin and polymyxin B. These were the last classes of antibiotics in which resistance could not spread from cell to cell.

    "These are extremely worrying results. The polymyxins (colistin and polymyxin B) were the last class of antibiotics in which resistance was incapable of spreading from cell to cell. Until now, colistin resistance resulted from chromosomal mutations, making the resistance mechanism unstable and incapable of spreading to other bacteria," explained co-author Jian-Hua Liu, Ph.D., a professor at the South China Agricultural University in Guangzhou, China. "Our results reveal the emergence of the first polymyxin resistance gene that is readily passed between common bacteria such as Escherichia coli and Klebsiella pneumoniae, suggesting that the progression from extensive drug resistance to pandrug resistance is inevitable."

    The investigators found the mcr-1 gene on plasmids within various bacterial strains, suggesting an alarming potential to spread and differentiate between diverse microbial populations.

    The findings from this study were published recently in The Lancet Infectious Diseases through an article entitled “Emergence of plasmid-mediated colistin resistance mechanism MCR-1 in animals and human beings in China: a microbiological and molecular biological study.”

    The researchers stumbled across the mcr-1 gene while performing routine testing of livestock for antimicrobial resistance on a pig farm in Shanghai. This prompted the researchers to collect bacteria samples from pigs at slaughter across four provinces, and from pork and chicken sold in 30 open markets and 27 supermarkets across Guangzhou between 2011 and 2014. Additionally, the scientists analyzed bacteria samples from patients presenting with infections at two hospitals in Guangdong and Zhejiang provinces.

    What they found was troubling to say the least, as a high prevalence of the mcr-1 gene in E. coli was observed in isolates from animal (166 of 804) and raw meat samples (78 of 523). Moreover, the proportion of positive samples has been observed to be increasing from year to year.

    The scientists also found that the transfer rate of the mcr-1 gene was very high between E. coli strains and that it has a strong potential to spread into other epidemic pathogenic bacterial species such as K. pneumoniae and Pseudomona

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