First Detection of the mcr-1 Colistin Resistance Gene in Escherichia coli in Italy Antonio Cannatelli, a Tommaso Giani, a Alberto Antonelli, a,b Luigi Principe, c Francesco Luzzaro, c Gian Maria Rossolini a,b,d,e * Department of Medical Biotechnologies, University of Siena, Siena, Italy a ; Department of Experimental and Clinical Medicine, University of Florence, Florence, Italy b ; Clinical Microbiology and Virology Unit, Lecco A. Manzoni Hospital, Lecco, Italy c ; Clinical Microbiology and Virology Unit, Florence Careggi University Hospital, Florence, Italy d ; Don Carlo Gnocchi Foundation, Florence, Italy e P olymyxins are old antibiotics that have recently regained pop- ularity for treatment of severe infections caused by extensively drug-resistant (XDR) Gram-negative bacterial strains (1). As a likely consequence, emergence of polymyxin resistance is being increasingly reported in the clinical setting, especially among car- bapenem-resistant Klebsiella pneumoniae isolates (2, 3). Acquired resistance to polymyxins is generally associated with chromo- somal mutations (4, 5), but a new plasmid-mediated transferable resistance determinant, the mcr-1 gene, encoding a phosphoetha- nolamine transferase, has been described recently (6). The mcr-1 gene was originally detected in Enterobacteriaceae (mostly Esche- richia coli) of animal and human origin in China (6) and subse- quently also elsewhere (7–15), suggesting a broader distribution. In this communication, we report on the first detection of mcr-1 in colistin-resistant (COL-R) E. coli isolates from Italy. A retrospective analysis of the laboratory databases from the clinical microbiology laboratories of two Italian hospitals (Flor- ence, central Italy; Lecco, northern Italy) revealed overall stable and low rates of colistin resistance among E. coli clinical isolates in the period 2012 to 2015 (Table 1). In both laboratories, routine susceptibility testing had been performed with the Vitek 2 system (bioMérieux, Marcy l’Etoile, France), and interpretation had been performed according to the EUCAST breakpoints (www.eucast .org). Eleven isolates that had been reported as colistin resistant (COL-R) were available for investigation, and nine of them were confirmed to be COL-R by reference broth microdilution (16). The COL MIC was 8 g/ml in all cases. The presence of mcr-1 was screened for by PCR and sequencing as previously described (6), using also an additional pair of prim- ers (CLR5-F1, 5=-ATGATGCAGCATACTTCTGTGTGG; CLR5- R1, 5=-TCAGCGGATGAATGCGGTGC) targeting the extremi- ties of the mcr-1 gene. Multilocus sequence typing (MLST) was carried out as described previously (17). Eight of the nine COL-R E. coli isolates were positive for the mcr-1 gene. In the sequenced region (positions 25 to 1576), with reference to the mcr-1 coding sequence (accession no. KP347127), the nucleotide sequences from all isolates were identical to that previously reported (6). Isolates positive for mcr-1 were detected from both centers, from inpatients in different wards, and also from two outpatients. Two mcr-1-positive isolates (LC-902/14 and LC-279/13) exhibited a multidrug-resistant phenotype, in- cluding expanded-spectrum cephalosporins, fluoroquinolones, and trimethoprim-sulfamethoxazole, and produced extended- spectrum--lactamase activity (Table 2). The mcr-1-positive isolates belonged to several different se- quence types (STs) (Table 2), some of which have not been previ- ously associated with mcr-1. No clear epidemiological relation- ships could be traced among the mcr-1-positive isolates detected in each setting. Taken together, the present findings revealed that E. coli strains carrying the mcr-1 gene are circulating in Italy, in the clinical set- ting, with a multifocal distribution and have done so at least since 2013. The fact that mcr-1 was detected in the majority of the COL-R E. coli isolates available for investigation suggests that it plays an important role as a polymyxin resistance determinant in this species. Emergence of mcr-1 in clinical isolates of E. coli is alarming, and a broader surveillance of this resistance determi- nant would be advisable, although colistin resistance in E. coli from clinical specimens remains very uncommon and no increas- ing trends were recently observed in our settings. Accepted manuscript posted online 14 March 2016 Citation Cannatelli A, Giani T, Antonelli A, Principe L, Luzzaro F, Rossolini GM. 2016. First detection of the mcr-1 colistin resistance gene in Escherichia coli in Italy. Antimicrob Agents Chemother 60:3257–3258. doi:10.1128/AAC.00246-16. Address correspondence to Gian Maria Rossolini, gianmaria.rossolini@unifi.it. * Present address: Gian Maria Rossolini, SOD Microbiologia, Virologia e Sierologia, Dipartimento dei Servizi, Azienda Ospedaliera Universitaria Careggi, Florence, Italy. Copyright © 2016, American Society for Microbiology. All Rights Reserved. TABLE 1 Rates of colistin resistance among E. coli clinical isolates from two different Italian settings Year Florence Lecco Total no. of tested isolates No. (%) of COL-R isolates Total no. of tested isolates No. (%) of COL-R isolates 2012 6,241 50 (0.8) 1,995 17 (0.9) 2013 8,927 62 (0.7) 2,456 19 (0.8) 2014 10,636 64 (0.6) 2,534 9 (0.4) 2015 9,373 66 (0.7) 2,368 24 (1) LETTER TO THE EDITOR crossmark May 2016 Volume 60 Number 5 aac.asm.org 3257 Antimicrobial Agents and Chemotherapy on June 3, 2020 by guest http://aac.asm.org/ Downloaded from