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SUMMARYThirty-two different types of anaerobic bacteria isolated from chickens have been tested for anti-salmonella activity in vitro. Under the conditions of the test only Bacteroides hypermegas and a Bifidobacterium sp. were shown to inhibit the salmonellas and this was attributed to the production of volatile fatty acids (VFA's) coupled with a low pH. When these organisms were tested in newly hatched chicks no irnhibition of S. typhimurium occurred. Possible explanations for this observation are considered.The pH value and concentration of VFA's in the caecal material were determined in chicks from 0-84 days. In vitro tests with S. typhimurium indicated that, whilst the organism would be able to multiply at the pH and concentration of VFA's found during the first few days after hatching, the rapid increase inVFA concentration during the first 21 days would make this increasingly difficult. The significance of the developing caecal flora in relation to VFA production and pH is discussed.Because certain feed additives are known to influence the carriage of salmonellas, the sensitivity of various caecal anaerobes to these compounds was determined in vitro, generally at 1, 10 and 100 ltg/ml. The additives tested included flavomycin, furazolidone, nitrovin, tetracycline, tylosin, sulphaquinoxaline, virginiamycin and zinc bacitracin. All the organisms tested were inhibited by 100 ,ugfml furazolidone; none were inhibited by 500 ,tg/ml sulphaquinoxaline.Changes occurring in the VFA concentration, pH value and microflora of the caeca of chicks fed for 49 days or longer on a normal starter diet or the same diet containing 10 or 100 mg/kg nitrovin have been compared. When the chicks were fed on the diet containing 100 mg/kg nitrovin, the Gram-negative non-sporing anaerobes were eliminated as a significant part of the caecal flora. However, the VFA concentration combined with a low pH in chicks from 2 weeks onwards was still sufficient to inhibit salmonella multiplication. Other possibly interrelated factors which might lead to an increased salmonella carrier rate in the nitrovintreated chickens are discussed.

The microbiological condition and changes which may occur during the storage of uneviscerated (New York dressed) and eviscerated chicken and turkey carcasses are described. Whilst a number of different types of organisms which can grow at low temperatures are generally found on an eviscerated carcass, it is the pseudomonads which are the most important in spoilage. The effect of temperature, gaseous environment, pH and type of muscle on the growth of the spoilage organisms and hence the shelf-life of the carcass is discussed.Although many bacteria may be found on a processed poultry carcass only a few (if any) are potentially harmful to man and generally less than 1 in 100 of all the organisms present are involved in spoilage.The food poisoning bacteria which have been mainly implicated in outbreaks attributed to poultry meat are the salmonellae and Clostridium perfringens (welchii) whilst staphylococci are much less frequently involved.lp2 If these organisms are present on the carcass after processing then under faulty and poor hygienic conditions in the kitchen or catering establishment they may survive or reinfect the cooked food and under warm conditions multiply and cause food poisoning when the food is eaten. These bacteria are mesophiles and tend not to grow much below 10°C, their growth Table 1. The effect of temperature on the growth rate of a typical mesophile (E. coli) compared with that of a typical spoilage organism (Pseudomonas sp.) and consequent shelf-life of the carcass Doubling time Shelf-life of Temp. E. c o P

The ceca of newly hatched chicks obtained either from commercial hatcheries or from a carefully controlled experimental hatchery have been shown to contain high numbers of a variety of microorganisms. Fecal streptococci, clostridia, enterobacteria, pediococci, and occasionally Pseudomonas aeruginosa have all been isolated, but never lactobacilli. After the chick has been on feed for 1 day, the numbers of lactobacilli in the crops and ceca are quite variable; by the 3rd day, however, large numbers are present throughout the alimentary tract. Lactobacilli could be established after 1 day by incorporating them in the feed or by treating the chicks with 0.5 ml of a broth culture. Spraying the eggs before hatching did not lead to their early establishment. Lactobacilli given alone to the newly hatched chick failed to prevent the establishment of Salmonella. However, when the chicks were given a complex mixture of facultative anaerobes and anaerobes which had been isolated from an adult bird, cecal colonization with Salmonella was prevented. The possible importance of the facultative anaerobes, particularly Streptococcus faecalis, in lowering the redox potential to encourage the growth of the anaerobes is discussed.