Colistin resistance of non-pathogenic strains of Escherichia coli occurring as natural intestinal flora in broiler chickens treated and not treated with colistin sulphate

Abstract

IntroductionA significant threat to public health is presented by antibiotic-resistant strains of bacteria, selective pressure on which results from antibiotic use. Colistin is an antibiotic commonly used in veterinary medicine, but also one of last resort in human medicine. Since the 2015 discovery in China of the mcr-1 gene encoding colistin resistance in Enterobacteriaceae, other countries have noted its presence. This study was to find the mcr-1 gene prevalence in E. coli isolated from poultry slaughtered in Poland.Material and MethodsCloacal swabs were taken from December 2017 to October 2018 from broiler chickens in three regions. The samples (n = 158) were grouped as flocks treated with colistin sulphate (n = 87) and those not treated (n = 71). Resistance to antimicrobials commonly used in poultry was evaluated by minimum inhibitory concentration. The presence of the mcr-1 gene was confirmed by PCR.ResultsIsolates containing the mcr-1 gene were yielded by 11.27% of the samples from not treated flocks and 19.54% of those from treated flocks, but no statistically significant difference in the prevalence of the gene was seen between the groups.ConclusionThe results clearly preclude intensification of selective pressure for colistin resistance due to colistin sulphate treatment because they show that the avian gastrointestinal tract was already inhabited by colistin-resistant E. coli by the time the chickens came to the poultry house.

Susceptibility of Commensal E. coli Isolated from Conventional, Antibiotic-Free, and Organic Meat Chickens on Farms and at Slaughter toward Antimicrobials with Public Health Relevance

“…Recently, Sun et al [ 34 ] demonstrated a significant presence of tigecycline-resistant E. coli strains from raw meat bearing the tet (X) gene. It should also be highlighted that in our investigation, all E. coli strains were susceptible to colistin differently than what was observed in other studies [ 35 , 36 , 37 ]. However, it should be specified that colistin, after being administrated for a long time as a prophylactic and therapeutic agent, is currently in off-label use in Italy and it was banned as a growth promoter [ 35 ].…”

Phenotypic and genotypic characterization of mcr-1-positive multidrug-resistant Escherichia coli ST93, ST117, ST156, ST10, and ST744 isolated from poultry in Poland

“…In our present study, regarding the obtained MIC values for the selected antimicrobial agents, all the investigated mcr-1- positive E. coli strains showed MDR profile (resistance to at least three antimicrobial classes). Similar results were obtained by other authors from Brazil, China, Argentina, and Poland [ 29 – 31 , 35 , 60 ]. Monte et al [ 29 ] showed that most of the mcr-1- positive E. coli isolates exhibited an MDR phenotype and carried genes conferring resistance to aminoglycosides, quinolones, sulfonamides, and tetracyclines.…”

“…A significantly higher percentage of colistin-resistant E. coli strains in Poland was confirmed by studies conducted in 2017–2018, where the presence of the mcr-1 gene occurring in the normal microbiota of chicken broilers, both treated and untreated with colistin sulfate, was tested. Isolates containing the mcr-1 gene were obtained in 11.27% of strains from untreated flocks and in 19.54% of isolates obtained from flocks treated with colistin [ 35 ]. In Europe, the prevalence of E. coli strains isolated from poultry and carrying the mcr-1 gene ranged from 1.5% in the Netherlands [ 28 ] to 13.95% in Portugal [ 54 ].…”

“…Studies on colistin resistance and the prevalence of resistance-associated genes among bacterial strains from various sources have been conducted worldwide. In Poland, studies on colistin-resistant E. coli strains isolated from slaughter and wild animals were conducted by Wasyl et al [ 32 , 33 ], Zając et al [ 34 ], and Majewski et al [ 35 ]. Those studies were mainly focused on the antimicrobial resistance of E. coli strains, the presence of mcr genes, and molecular identification and characterization of resistance mechanisms.…”

From farm to fork: Colistin voluntary withdrawal in Portuguese farms reflected in decreasing occurrence of mcr‐1‐carrying Enterobacteriaceae from chicken meat

“…An association between animal polymyxin consumption and colistin resistance in E. coli from poultry and swine has been suggested in an EU report (ECDC et al ., 2017), but the long‐term impact of ongoing colistin reduction measures on food‐producing farms and, consequently, on food safety (e.g., poultry meat) is still poorly defined. On the other hand, the persistence of colistin resistance and mcr genes, including in non‐treated poultry flocks (Poland) (Majewski et al ., 2020) or pigs (Great Britain) (Duggett et al ., 2018), suggests that other factors beyond colistin consumption might contribute to their selection, but this needs to be further explored and understood.…”