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Alarming drug resistance | Blog | County Pathology Ltd

Alarming drug resistance

Superbug

Polymyxins remain the last line of defense against antibiotic-resistant Gram-negative bacteria. Now, researchers report that a gene that confers resistance to these drugs is found in a growing number of bacteria from meat samples in China — and from some hospital patients.
Polymyxins remain the last line of defense against antibiotic-resistant Gram-negative bacteria. Now, researchers report that a gene that confers resistance to these drugs is found in a growing number of bacteria from meat samples in China — and from some hospital patients. More worrying is that the gene, mrc-1, is found on small pieces of DNA called plasmids that easily spread between bacteria.

"The implications of this finding are enormous," write David L Paterson, MD, from Royal Brisbane and Women's Hospital Campus in Australia, and Patrick N. A. Harris, MBBS, from Wesley Hospital, also in Brisbane, in an accompanying editorial.

The editorial and research paper, by Yi-Yun Liu, from the College of Veterinary Medicine, National Risk Assessment Laboratory for Antimicrobial Resistance of Microorganisms in Animals, South China Agricultural University, Guangzhou, China, and colleagues, were published online November 18 in the Lancet Infectious Diseases.

The researchers found that in 2011, more than 5% of Escherichia coli isolates from retail chicken and pork meat from China tested positive for the colistin (polymyxin E) resistance gene mrc-1. By November 2014, the last date for which data are available, the percentage of positive isolates had increased to approximately 25%.

Thus, not only have microbes now achieved resistance to polymyxin, but the resistance is spreading quickly. The rapid spread is a result of the fact that mrc-1 is not located on the chromosome, as has been the case for previously identified polymyxin-resistant genes, but is found on plasmids that bacteria exchange regularly.