From Pigs to Patients: Transmissible, Single Gene-mediated Resistance to Colistin

Abstract

The last decade has seen a stark increase in the number of multidrug resistant Gram-negative bacterial pathogens. Of particular importance are highly carbapenem resistant Escherichia coli and Klebsiella pneumoniae, as well as fluoroquinolone resistant Pseudomonas aeruginosa and Acinetobacter baumanii [1]. Owing to the lack of new drugs entering the marketplace, physicians are increasingly revisiting older drugs that had fallen out of common use. One such drug is colistin and it has increasingly become the drug of last resort for these infections [2]. Colistin is a polymyxin type of antimicrobial lipopeptide that is produced by Paenobacillus species. The polymxyins were discovered 65 years ago but have limited clinical use due to their neurotoxic and nephrotoxic side effects. Despite this toxicity in humans, colistin is used extensively in agriculture as growth promoters and estimates of global colistin usage in agriculture is >12,000 tonnes per annum. A recent report in the Lancet Infectious Diseases describes the first example of a transmissible plasmid that encodes colistin resistance by the mcr-1 gene. Colistin resistance was first detected in Escherichia coli isolates from pigs, but was ultimately found in meats for sale, and later in Chinese patients [3].