<abstract xmlns="http://www.w3.org/1999/xhtml">

<sec id="j_jvetres-2020-0060_s_005">
<h3>Introduction</h3>
<p>A 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 <italic>mcr-1</italic> gene encoding colistin resistance in <italic>Enterobacteriaceae</italic>, other countries have noted its presence. This study was to find the <italic>mcr-1</italic> gene prevalence in <italic>E. coli</italic> isolated from poultry slaughtered in Poland.</p></sec>
<sec id="j_jvetres-2020-0060_s_006">
<h3>Material and Methods</h3>
<p>Cloacal 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 <italic>mcr-1</italic> gene was confirmed by PCR.</p></sec>
<sec id="j_jvetres-2020-0060_s_007">
<h3>Results</h3>
<p>Isolates containing the <italic>mcr-1</italic> 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.</p></sec>
<sec id="j_jvetres-2020-0060_s_008">
<h3>Conclusion</h3>
<p>The 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 <italic>E. coli</italic> by the time the chickens came to the poultry house.</p></sec></abstract>

Introduction
A 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 Methods
Cloacal 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.

Results
Isolates 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.

Conclusion
The 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.

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

Journal of Veterinary Research

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

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

Introduction
A significant threat to public health is presented by antibiotic-resistant strains of bacteria, selective pressure on which results from...

Number of antibiotics:	Percentage of resistant bacteria (number of strains out of the total 25):
3	12% (3)

4	16% (4)

5	20% (5)

6	28% (7)

7	8% (2)

8	12% (3)

9	4% (1)

	Number of flocks (n)	Percentage of flocks	Number of flocks carryingmcr-1 gene (n)	Percentage of flocks carrying mcr-1 gene
Not treated ( flocks not treated with colistin sulphate )	71	44.94%	8	11.27%

Treated ( flocks treated with colistin sulphate )	87	55.06%	17	19.54%

Total	158	100.00%	25	15.82%

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

Publié en ligne: 16 sept. 2020

Pages: 399 - 405

Reçu: 23 févr. 2020

Accepté: 27 août 2020

DOI: https://doi.org/10.2478/jvetres-2020-0060

Mots clés
poultry, antibiotic resistance, colistin

© 2020 M. Majewski et al. published by Sciendo

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

Fig. 1

Number of E. coli strains resistant to more than two antibiotics

Number of isolated colistin-resistant E. coli in the flocks treated with colistin sulphate and those not treated

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

Publié en ligne: 16 sept. 2020

Pages: 399 - 405

Reçu: 23 févr. 2020

Accepté: 27 août 2020

DOI: https://doi.org/10.2478/jvetres-2020-0060

Mots cléspoultry, antibiotic resistance, colistin

© 2020 M. Majewski et al. published by Sciendo

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

Fig. 1

Number of E. coli strains resistant to more than two antibiotics

Number of isolated colistin-resistant E. coli in the flocks treated with colistin sulphate and those not treated

Mots clés
poultry, antibiotic resistance, colistin