A longitudinal study on thermophilic campylobacters in turkey flocks: preliminary results

Thermophilic Campylobacter spp. represent the most common zoonotic microorganisms implicated in human food-borne gastroenteritis worldwide. Campylobacter species are widespread in nature and the digestive systems of wild and domestic birds and mammals are the principal reservoirs of these microorganisms. Poultry and poultry products represent the main source of infection for human beings. Notwithstanding the epidemiology of Campylobacter spp. infections in chickens is well known and investigated, few data are still available on the infection in commercial meat turkeys. The aim of this study was to determine the occurrence of thermophilic Campylobacter spp. in commercial meat turkeys and to analyze the trend of infection during the entire production cycle. Furthermore, the antimicrobial susceptibility profiles and the strain diversity of isolates were investigated. Between September 2009 and May 2010, a monitoring was performed in 3 commercial meat turkey flocks belonging to 3 different farms located in Northern Italy (Veneto region). Two flocks of females and one flock of males were monitored (investigation in two flocks is still ongoing). First sampling was carried out at the hatchery, where 60 samples of meconium were collected from day-old birds. Thereafter, 60 cloacal swabs were taken at farm at weekly intervals up to the Campylobacter colonization of the flock, then twice every month up to the transport to the slaughterhouse. Samples were immediately transported to the laboratory and examined within 2-3 hrs to detect the presence of thermophilic Campylobacter spp. following the procedure suggested by OIE (2008). Genus and species identification was carried out by end-point multiplex PCR method as indicated by Yamazaki-Matsune et al. (2007). Out of three flocks, thermophilic Campylobacter spp. were detected only in one female flock. Birds became positive for Campylobacter spp. by day 14 and the infection persisted in the flock up to the transport to the slaughterhouse. Both Campylobacter jejuni and Campylobacter coli were isolated. C. coli was the predominant species at the beginning (sampling at day 14) and at the end of the production cycle (sampling at days 56, 70 and 82), whereas C. jejuni was predominant in the remainder of the cycle. To date (77 days of age), no Campylobacter spp. have been detected in the other two turkey flocks. Among isolates from each sampling, 15 Campylobacter jejuni and 15 Campylobacter coli isolates were selected and tested by the agar disc diffusion method (Kirby-Bauer, 1966) for antimicrobial susceptibility to 20 drugs belonging to the following classes: aminoglycosides, cephalosporins, penicillines, quinolones, lincosamides, macrolides, sulfonamides + diaminopyrimidines, tetracyclines, and phenicols. All C. jejuni and C. coli isolates showed similar antimicrobial-resistance profiles and both were cross-resistant to 3 to 15 antimicrobials. Most of isolates were resistant to cephalosporins (73% to 100%), trimethoprim + sulphamethoxazole (97%), oxytetracycline (93%), ampicillin (93%), and quinolones (83% to 90%). All C. jejuni and C. coli isolates were susceptible to chloramphenicol and most of them to aminoglycosides (97% to 100%), amoxicillin + clavulanic acid (87%), macrolides (83%), and clindamycin (80%). Further, among isolates from each sampling 14 Campylobacter jejuni and 18 Campylobacter coli isolates were selected and analyzed by Random Amplified Polymorphic DNA (RAPD) - PCR with M13 and AP4 primers (Andrighetto et al., 2001) and by flaA short variable region (SVR) DNA sequencing (Levesque et al., 2008). Campylobacter isolates were typed into 7 different profiles by RAPD-PCR with a Simpson’s diversity index (D) equal to 0.22. Among 7 RAPD profiles, only one was conserved throughout the entire production cycle. Genetic diversity was confirmed by SVR-flaA sequencing revealing 8 different alleles among isolates (D index equal to 0.14). As a result, RAPD-PCR typing combined with flaA sequencing showed a high genetic diversity among Campylobacter isolates from the same turkey flock. Although further studies are necessary to better assess the trend of thermophilic Campylobacter spp. infection in turkey flocks, these preliminary results showed that, once the infection enters into a flock, Campylobacter colonization of birds seems to persist throughout the entire production cycle. Furthermore, antimicrobial-resistance and strain variability appear to be widely spread among turkey campylobacters.