Prevalence and Antimicrobial Resistance of Campylobacter jejuni and Campylobacter coli from Laying Hens Housed in Different Rearing Systems

SIMPLE SUMMARY: This survey investigated the incidence of Campylobacter (C) jejuni and C. coli infection in laying hens housed in farms which use different rearing systems: cages (A), barns (B) and aviaries (C). Two flocks (1 and 2) for each farm were evaluated. The hen plasma levels of corticosterone and interleukin 6 (IL-6), which are considered welfare indicators, and the sensitivity of detected Campylobacter strains to the antibiotics were investigated. The highest (p < 0.05) levels of IL-6 and corticosterone were found in laying hens housed in aviaries. C. jejuni and C. coli were identified in 77/177 (43.5%) and 69/177 (38.9%) laying hens, respectively. C. jejuni and C. coli were simultaneously detected in 14 laying hens (7.9%). C. jejuni was prevalently found in laying hens housed in barns (B1: 53.3%; B2: 46.7%) and aviaries (C1: 34.6%; C2: 86.7%). C. coli was prevalently identified in laying hens housed in cages (A1: 41.9%; p < 0.001; OR: 10.11, CI(95%): 2.04–50.19; A2: 80%; p < 0.001; OR: 56.00, CI(95%): 10.33–303.68) and, depending on the flock, in barns (B2: 40%) and aviaries (C1 54.8%). In particular, antibiotic resistance to fluoroquinolones and tetracycline was found, and it was mainly detected among C. coli strains. Multidrug resistance was found in 19.7% of C. coli and 17.5% C. jejuni strains, respectively. The incidence of Campylobacter infection found in the farms highlights the opportunity to increase the biosecurity measures to be adopted in the management of laying hen flocks. ABSTRACT: Campylobacter (C.) jejuni and C. coli are responsible for food poisoning in humans. Laying hens may host the bacteria usually without developing symptoms. The aims of this paper were to evaluate the incidence of C. jejuni and C. coli infection in laying hen flocks housed in different rearing systems, the plasma levels of two welfare indicators (corticosterone and interleukin 6, IL-6) and the antimicrobial resistance of the detected Campylobacter strains. Two different flocks (1 and 2) from cage (A), barn (B) and aviary (C) farms were investigated. The highest (p < 0.05) levels of IL-6 were detected in laying hens housed in aviaries. A similar trend emerged in corticosterone level, although differences were found between C1 and C2. C. jejuni and C. coli were identified in 43.5% and 38.9% of birds, respectively. In total, 14 out of 177 (7.9%) hens simultaneously hosted C. jejuni and C. coli. C. jejuni was prevalently detected in hens housed in barns (B1: 53.3%; B2: 46.7%) and aviaries (C1: 34.6%; C2: 86.7%). Conversely, laying hens housed in cages were significantly exposed to infection of C. coli (A1: 41.9%; A2: 80%) while, regarding barns and aviaries, a significant prevalence emerged only in flocks B2 (40%) and C1 (54.8%). Simultaneous infection was statistically significant in barn B1 (36.7%). Antibiotic resistance was mainly detected among C. coli strains, and it was most frequent for fluoroquinolones and tetracycline. Multidrug resistance was also found in C. jejuni (19.7%) and C. coli (17.5%) strains. Based on the results of this study, we recommend increasing biosecurity and hygienic measures to manage hen flocks.