Abstract
Since the first description of a plasmid-mediated colistin resistance gene (mcr-1) in November 2015 multiple reports of mcr-1 positive isolates indicate a worldwide spread of this newly discovered resistance gene in Enterobacteriaceae. Although the occurrence of mcr-1 positive isolates of livestock, food, environment and human origin is well documented only few systematic studies on the prevalence of mcr-1 are available yet. Here, comprehensive data on the prevalence of mcr-1 in German livestock and food isolates are presented. Over 10.600 E. coli isolates from the national monitoring on zoonotic agents from the years 2010–2015 were screened for phenotypic colistin resistance (MIC value >2 mg/l). Of those, 505 resistant isolates were screened with a newly developed TaqMan-based real-time PCR for the presence of the mcr-1 gene. In total 402 isolates (79.8% of colistin resistant isolates) harboured the mcr-1 gene. The prevalence was depending on the food production chain. The highest prevalence was detected in the turkey food chain (10.7%), followed by broilers (5.6%). A low prevalence was determined in pigs, veal calves and laying hens. The mcr-1 was not detected in beef cattle, beef and dairy products in all years investigated. In conclusion, TaqMan based real-time PCR provides a fast and accurate tool for detection of mcr-1 gene. The overall detection rate of 3.8% for mcr-1 among all E. coli isolates tested is due to high prevalence of mcr-1 in poultry production chains. More epidemiological studies of other European countries are urgently needed to assess German prevalence data.
Highlights
Colistin and polymyxin B are polypeptide antibiotics which interact with LPS and phospholipids in the outer cell membrane of gram-negative bacteria
A variety of resistance mechanisms of gram-negative bacteria against colistin and polymyxin B are well-known with a chromosomal localisation [1,2]
To get more detailed information about the spread of mcr-1 in Germany, this study describes the systematic screening of E. coli isolates from German livestock and food samples derived from the German monitoring program on antimicrobial resistance in zoonotic agents during the years 2010– 2015
Summary
Colistin (polymyxin E) and polymyxin B are polypeptide antibiotics which interact with LPS and phospholipids in the outer cell membrane of gram-negative bacteria. Both polymyxins differ by only one aminoacid with almost equal biological activity. Because of their site effects, polymyxins are rarely used in human medicine but widely used in veterinary medicine. A variety of resistance mechanisms of gram-negative bacteria against colistin and polymyxin B are well-known with a chromosomal localisation [1,2]. PLOS ONE | DOI:10.1371/journal.pone.0159863 July 25, 2016
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