Prevalence and antimicrobial resistance of Campylobacter isolated from carcasses of chickens slaughtered in Poland – a retrospective study

The aim of the present study was to assess the prevalence of Campylobacter on chicken carcasses tested in Poland during 2014–2018 and to evaluate the antimicrobial susceptibility of the recovered isolates. The results were compared to the previous similar investigations performed in 2009–2013 [Wieczorek K. & Osek J. (2015). A five-year study on prevalence and antimicrobial resistance of Campylobacter from poultry carcasses in Poland. Food Microbiology, 49, 161–165]. A total of 2,367 swab samples from broiler carcasses were collected by official veterinarians in abattoirs where chickens were slaughtered for commercial purposes located in all 16 voivodeships (administrative provinces) of Poland. Susceptibility tests against ciprofloxacin, erythromycin, gentamycin, nalidixic acid, streptomycin, and tetracycline were performed using the minimal inhibitory concentration method. Campylobacter spp. was identified by culture and confirmed by PCR methods in 1,263 (53.4%) chicken carcasses. The prevalence of the bacteria ranged from a minimum of 49.8% in 2014 to a maximum of 58.6% in 2015. The analogous previous study showed that in the period of 2009–2013, 54.4% out of 2,114 chicken carcass samples were positive for Campylobacter. All Campylobacter isolates identified in the present investigation were classified to C. coli (738 out of 2,367 samples; 31.2%) and C. jejuni (525 out of 2,367 samples; 22.2%) and such predominance of C. coli over C. jejuni being found in each year of the study. Variable resistance rates were observed towards the tested antimicrobials, with most of the Campylobacter being resistant to ciprofloxacin (93.1%), nalidixic acid (92.3%), and tetracycline (70.9%). Only a few isolates showed resistance to erythromycin (4.2%); however, there were differences in resistance to this antimicrobial in C. jejuni (1.1% of isolates) and in C. coli (6.4% of isolates). Among a total of 525 C. jejuni tested during 2014–2018, 108 isolates (20.6%) were multiresistant, mainly to ciprofloxacin, nalidixic acid, streptomycin, and tetracycline (94 isolates; 17.9%). In the case of C. coli, 185 out of 738 (25.1%) isolates were multidrug resistant, especially to the same four antimicrobials, as with C. jejuni (139; 18.8% of total isolates). There was a marked increase in the presence of multiresistant Campylobacter compared to the previous study period (1.7% of total isolates tested during 2009–2013), particularly among C. jejuni (only one isolate in the 576 previously investigated). The results of this study provide updates and novel data on the prevalence and antimicrobial resistance of Campylobacter in chicken carcasses in Poland, and indicate the need for implementation of actions to control and reduce the presence of Campylobacter at the broiler slaughter level as well as the necessity to restrict the use of antimicrobials in poultry production.