1 www.eurosurveillance.org Letter Letter to the editor: Escherichia coli harbouring mcr-1 gene isolated from poultry not exposed to polymyxins in Brazil SA Lentz 1 2 , D de Lima-Morales 2 3 , VM Cuppertino ¹ , LdS Nunes ³ , AS da Motta ¹ , AP Zavascki ⁴ , AL Barth ³ , AF Martins 1 3 1. 1. ICBS – Instituto de Ciências Básicas da Saúde, UFRGS - Univ. Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil 2. These authors contributed equally to this work. 3. LABRESIS – Lab. de Pesquisa em Resistência Bacteriana, HCPA - Hosp. de Clínicas de Porto Alegre, Porto Alegre, RS, Brazil 4. Infectious Diseases Service, Hospital de Clínicas de Porto Alegre, Porto Alegre, RS, Brazil Correspondence: Afonso Luis Barth (albarth@hcpa.edu.br) Citation style for this article: Lentz SA, de Lima-Morales D, Cuppertino VM, Nunes LdS, da Motta AS, Zavascki AP, Barth AL, Martins AF. Letter to the editor: Escherichia coli harbouring mcr-1 gene isolated from poultry not exposed to polymyxins in Brazil. Euro Surveill. 2016;21(26):pii=30267. DOI: http://dx.doi.org/10.2807/1560-7917. ES.2016.21.26.30267 Article submitted on 21 June 2016 / accepted on 30 June 2016 / published on 30 June 2016 To the editor: The recent paper by Fernandes et al. [1] described the presence of the mcr-1 gene in Escherichia coli from pigs and poultry in Brazil. The authors stated that microbiology laboratories worldwide should be aware of mcr-1 isolates resistant to polymyxins in patients living in or returning from Latin American countries and highlighted that the mcr-1 gene dissemi- nation results from polymyxins’ misuse as growth pro- moter in food animals. In view of the concerning spread of antibiotic resistance, we screened E. coli isolates obtained from a poultry slaughterhouse in southern Brazil with official reports on antibiotic use. Poultry rectal swabs were collected between August and October 2015. A total of 340 chickens farmed in Brazil and belonging to 17 batches were included in the study. All poultry had received bacitracin, narasin and nicarbazin during a first period of life (between the 2nd and the 18th day) and avilamycin and salinomycin dur- ing a second period (between the 20th and 35th day); the chickens of batches 10 and 11 had also received doxycycline during at total of 3 days, in the second period of life. Poultry included in this study were not exposed to polymyxin during their entire life (around 40 days). A total of 343 isolates were evaluated by polymer- ase chain reaction (PCR) for the mcr-1 gene [2] and 10 (3%) were positive. The mcr-1 gene was confirmed by sequencing the PCR amplicon. The mcr-1 positive iso- lates were obtained from 10 different chickens belong- ing to three batches from three different breeders. The polymyxin B minimum inhibitory concentrations (MIC) of the 10 mcr-1 positive isolates were 2 mg/L (8 iso- lates), 1 mg/L and 0.25 mg/L and they could be clas- sified as susceptible to polymyxin B, according to the European Committee on Antimicrobial Susceptibility Testing (EUCAST) (resistance > 2 mg/L). In contrast, most reports indicate that the mcr-1 gene is usually found in isolates presenting resistance to polymyxins [2-6]. The mcr-1 positive isolates were submitted to DNA mac- rorestriction typing by pulsed-field gel electrophoresis (PFGE) and five isolates, from the same batch, proved to be clonally related while the other five isolates were unrelated. Conjugation experiments with the E. coli J53 were successful for two mcr-1 positive isolates which confirmed that the mcr-1 gene was located in a plas- mid. The transconjugants presented positive results by PCR for the mcr-1 gene and had a polymyxin B MIC of 2 mg/L. According to Brazilian law, all slaughterhouses must submit in advance to the Federal Inspection Service of the Ministry of Agriculture, the bulletin of health of each batch of animals to be slaughtered. It is of note that the chickens evaluated in this study have received antibiotics as growth promoters, but polymyxins were not included among these compounds. This goes against the hypothesis that the emergence of the mcr-1 gene is linked to the use of polymyxins in animal feed in Brazilian livestock [1] and suggests that others com- pounds or factors may also be involved in the selection of this gene. Finally, the fact that the mcr-1 was originally described in China and thereafter in several other countries including Europe indicates that this gene is already widespread in the world. Therefore, isolates with mcr-1 should be considered in any patient, regardless of whether they were living in or returning from Latin America or not.