Use of bacteriophage for biological control of Salmonella Enteritidis infection in chicken

Abstract

Bacteriophage ΦCJ07 with broad host ranges for Salmonella strains isolated from sewage effluent were used to reduce Salmonella Enteritidis (SE) infection in chickens. One-day-old chicks challenged with 5 × 10⁷ colony-forming units/bird of SE were cohabitated with contact chicks and treated with three concentrations (10⁵, 10⁷ and 10⁹ plaque forming units (PFU)/g) of bacteriophage prepared as a feed additive for 21 days after challenge. Salmonella in the intestine was quantified and environmental contamination level was examined at 1, 2 and 3 weeks after challenge. All treatments reduced intestinal SE colonization in challenged and contact chickens and reduced the environmental contamination level, but the reductions produced by 10⁷ and 10⁹ PFU/g of bacteriophage were significant (P < 0.05) as compared with untreated controls. In addition, seven out of 10 (70%) contact chickens treated with 10⁹ PFU/g of bacteriophage had no detectable intestinal Salmonella at 3 weeks after treatment, suggesting that bacteriophage therapy significantly prevented the horizontal transmission of SE. These results provide important insights into preventive and control strategies against SE infection in poultry and indicate that the use of bacteriophage could reduce the incidence of Salmonella food poisoning.

Introduction

Bacterial food poisoning is a major worldwide health problem (Mead et al., 1999, Stark, 2009). Although many food-borne pathogens have recently received considerable attention, salmonellae remain among the leading sources of food-borne illness throughout much of the world (Gast, 1997). Especially, Salmonella enterica serovar Enteritidis (SE) is one of the most frequently identified bacteria in human outbreaks of disease. SE has been epidemiologically associated with the contamination of poultry products with food-borne pathogens, usually resulting from the feces of an infected animal (Borie et al., 2008). Despite preventive and control strategies in chicken commercial flocks, which include increased biosecurity, vaccination, competitive exclusion, and antimicrobials, SE infection has posed a constant problem in the poultry industry (Kim et al., 2007). Moreover, the emergence of SE strains that are resistant to most currently available antimicrobials and the restricted use of antibiotics have increased the need for novel and effective SE control strategies (Dias de Oliveira et al., 2005).

Bacteriophage has the advantage of being natural, nontoxic to natural human or animal microflora populations, and relatively inexpensive, unlike many antibiotics (Sulakvelidze et al., 2001). Although early experiences with bacteriophage therapy showed limited success and the rapid development of chemotherapy led to the discontinuation of research on phage therapy, recent interest in the therapeutic use of bacteriophage cocktails has been spurred by successes relating to their use in controlling infectious pathogens such as Salmonella (Andreatti Filho et al., 2007), Escherichia coli (Huff et al., 2002), and Campylobacter (Goode et al., 2003). Furthermore, the prophylactic and therapeutic effects of bacteriophages, although assumed in many instances, have also not been adequately evaluated in terms of clinical and practical significance to prevent the transmission of SE infection.

The present study evaluated the efficacy of a single bacteriophage (ΦCJ07) against Salmonella in vitro and whether treatment with ΦCJ07 delivered in feed additives could prevent reduce SE colonization and horizontal transmission in commercial layer chickens and release to the environment.