Chromosomal DNA from Streptococcus mutans strain UAB90 (serotype c) was cloned into Escherichia coli K-12. The clone bank was screened for any sucrosehydrolyzing activity by selection for growth on raffinose in the presence of isopropyl-p-D-thiogalactoside. A clone expressing an S. mutans glucosyltransferase was identified. The S. mutans DNA encoding this enzyme is a 1.73-kilobase fragment cloned into the HindIII site of plasmid pBR322. We designated the gene gtfA. The plasmid-encoded gtfA enzyme, a 55,000-molecular-weight protein, is synthesized at 40% the level of pBR322-encoded ,-lactamase in E. coli minicells. Using sucrose as substrate, the gtfA enzyme catalyzes the formation of fructose and a glucan with an apparent molecular weight of 1,500. We detected the gtfA protein in S. mutans cells with antibody raised against the cloned gtfA enzyme. Immunologically identical gtfA protein appears to be present in S. mutans cells of serotypes c, e, and f, and a cross-reacting protein was made by serotype b cells. Proteins from serotype a, g, and d S. mutans cells did not react with antibody to gtfA enzyme. The gtfA activity was present in the periplasmic space of E. coli clones, since 15% of the total gtfA activity was released by cold osmotic shock and the clones were able to grow on sucrose as sole carbon source.

Three different lyric bacteriophages (BPs) were isolated from the sewage system of commercial chicken flocks and used to reduce Salmonella Enteritidis (SE) colonization from experimental chickens. Ten-day-old chickens were challenged with 9.6 x 10(5) colony-forming units (CFU)/ml of a SE strain and treated by coarse spray or drinking water with a cocktail of the three phages at a multiplicity of infection (MO1) of 10(3) plaque-forming units (PFU) 24 hr prior to SE challenge. Chickens were euthanatized at day 20 of age for individual SE detection, quantitative bacteriology, and phage isolation from the intestine and from a pool of organs. SE detection was performed by both bacteriologic culture and genome detection by polymerase chain reaction (PCR). Qualitative bacteriology showed that aerosol-spray delivery of BPs significantly reduced the incidence of SE infection in the chicken group (P = 0.0084) to 72.7% as compared with the control group (100%). In addition, SE counts showed that phage delivery both by coarse spray and drinking water reduced the intestinal SE colonization (P < 0.01; P < 0.05, respectively). BPs were isolated at 10 days postinfection from the intestine and from pools of organs from BP-treated chickens. We conclude that the phage treatment, either by aerosol spray or drinking water, may be a plausible alternative to antibiotics for the reduction of Salmonella infection in poultry.

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A combination of three different Salmonella-specific bacteriophages (BPs) and one competitive exclusion (CE) product were used to reduce Salmonella Enteritidis (SE) colonization in experimentally infected chickens. Equal numbers of 7-day-old chickens were used in each of three groups: a CE group (treated with CE), a BP group (treated with BP), and a CE-plus-BP group (treated with both products). The CE product was administered via coarse spray at 1 day of age and the cocktail of three BPs was given via spray at 6 days of age using a multiplicity of infection of 10(3) plaque-forming units. All the experimental groups, except a healthy control group, were challenged orally with 2.95 x 10(5) colony-forming units (CFU)/ml of an SE strain at 7 days of age. Seven days postchallenge, the chickens were euthanatized for individual SE detection, quantitative bacteriology, and phage isolation from ceca and an internal organ pool. The qualitative bacteriology demonstrated that the use of the CE product diminished the incidence of SE to 75.7% and the mixture of BPs reduced it to 80%; when CE plus BP were used, the incidence dropped significantly to 38.7% (P < 0.0001), as compared with the infection control group (100%). A significant difference in the incidence was observed between the CE and the CE-plus-BP groups, and the BP and the CE-plus-BP groups (P = 0.0027 and P = 0.0010, respectively). The mean SE cecal count diminished with the use of CE plus BP (1.6 x 10(2) CFU/g, P = 0.0003) compared with the control group (1.56 x 10(5) CFU/g), the CE group (4.23 x 10(3) CFU/g), and the BP group (9.48 x 10(3) CFU/g). On the basis of the present study, it may be concluded that the use of both types of biocontrollers can be an effective method for reducing SE colonization in commercial chickens, but further basic and applied research is needed.