Emergence and Spread of A Plasmid-Mediated Polymyxin Resistance Mechanism, MCR-1: Are Bacteria Winning?

• Main Author: Chao Yang
• Format: Article
• Language: English
• Published: International Biological and Medical Journals Publishing House Co., Limited 2015-12-01
• Series: Infectious Diseases and Translational Medicine
• Subjects: polymyxin resistance mechanism
• Online Access: http://www.tran-med.com/article/2015/2411-2917-1-2-56.html

The report of the emergence of mcr-1, the first plasmid-mediated polymyxin resistance mechanism, in Enterobacteriaceae in November 2015 challenged our last psychological line of defense. However, we still trusted that this resistance factor had not spread globally. One month later, in December 2015, the detection of mcr-1 in an Escherichia coliisolate from a septicemic patient in Denmark and in five E. coli isolates from imported chicken meat really defeated us. The worst news was that one of the chicken meat isolates belonged to ST131, a spreading epidemic sequence type. In China, 15%-21% of E. coli strains isolated from raw meat and animals carried mcr-1, and about 1% of patient isolates carried this gene, indicating that E. coli carrying this plasmid is not a rare phenomenon. This gene is transferable by conjugation and can be maintained in Klebsiella pneumonia and Pseudomonas aeruginosa, suggesting the risk of transfer between different bacterial genera. The good news is that the strains carrying mcr-1 do not contain genes for pan-resistance profiles, although some Danish strains contain 15 different resistance genes, including genes for extended-spectrum beta-lactam antibiotics, and gene mutations leading to high-level fluoroquinolone resistance. If the mcr-1-bearing strains acquire multidrug resistance, extensive drug resistance, or pandrug resistance, no antibiotic drugs will be available with which clinicians can treat infected patients. Therefore, the use of antibiotics in both hospitals and the animal breeding industry must be strictly regulated. The origin of mcr-1 may be associated with the wide use of colistin in agriculture. There is no evidence that the Danish mcr-1 gene spread from China. Therefore, it is likely that mcr-1 genes originated in multiple sites simultaneously under the pressure of colistin use, because India and Denmark are the world’ s greatest users of this antibiotic. More surveys must be conducted in different regions of the world, especially in those where the use of colistin is extensive. Understanding the distribution of mcr-1 throughout the world will help us formulate good practice in the application of antibiotics. We must also closely monitor the multidrug-resistant, extensively-drug-resistant, and pandrug-resistant bacteria that acquire mcr-1. In the battle against pathogenic bacteria, antibiotics have played an essential role in saving lives. However, bacteria are sufficiently smart to develop a variety of antibiotic resistance mechanisms to protect themselves. Humans and bacteria are both severely challenged in this life-and-death struggle. The development of new strategies with which to combat pathogenic bacteria is a long-term and difficult task.