Isolation and characterization of Campylobacter bacteriophages from retail poultry

Abstract

The ability of phages to survive processing is an important aspect of their potential use in the biocontrol of Campylobacter in poultry production. To this end, we have developed a procedure to recover Campylobacter bacteriophages from chilled and frozen retail poultry and have validated the sensitivity of the method by using a characterized Campylobacter phage (i.e., NCTC 12674). By using this method, we have shown that Campylobacter phages can survive on retail chicken under commercial storage conditions. Retail chicken portions purchased in the United Kingdom were screened for the presence of endogenous Campylobacter phages. Thirty-four Campylobacter bacteriophages were isolated from 300 chilled retail chicken portions, but none could be recovered from 150 frozen chicken portions. The phage isolates were characterized according to their lytic profiles, morphology, and genome size. The free-range products were significantly more likely to harbor phages (P < 0.001 by single-factor analysis of variance) than were standard or economy products. This study demonstrates that Campylobacter bacteriophages, along with their hosts, can survive commercial poultry processing procedures and that the phages exhibited a wide range of recovery rates from chicken skin stored at 4 degrees C.

FIG. 1.

(A) Recovery of phage φ2 (NCTC 12674) from chicken skin stored for 10 days under fresh (4°C; ⋄) and frozen (−20°C; ♦) conditions. Triplicate 10-cm² sections of chicken thigh skin were inoculated with 10⁸ PFU of φ2, and then percent recovery of this inoculum (± SD) was recorded at 24-h intervals. (B) Recovery of six Campylobacter bacteriophage chicken skin isolates exhibiting different lytic spectra. 10⁸ PFU of each phage were applied to fresh chicken thigh skin in triplicate and stored for 10 days at 4°C. The percent recovery of the initial inoculum (± SD) was recorded at 24-h intervals. Key: ▴, W2; •, W3; ▵, W4; □, W5; X, W8; and ○, W10. In all cases, the initial samples (day 1) were collected 1 h after inoculation.

FIG. 2.

Gel showing restriction fragments generated from digesting phage genomes with endonuclease HhaI. Lanes are as follows: 1, λ/HindIII marker; 2, undigested W2; 3, digested W2; 4, undigested W3; 5, digested W3; 6, undigested W4; 7, digested W4; 8, undigested W5; 9, digested W5; 10, undigested W8; 11, digested W8; 12, undigested W10; 13, digested W10.

FIG. 3.

Electron photomicrographs of phages isolated from fresh chicken skin representing eight lytic spectra classes. The icosahedral head and rigid contractile tail are typical features of the Myoviridae family. A, W2; B, W3; C, W4; D, W5; E, W8; F, W10; G, W19; H, W20. Bar represents 250 nm. All electron photomicrographs taken at ×100,000 magnification with a JEOL 100CX transmission electron microscope.