Salmonellas in Poultry Feeds—A Worldwide Review

Formic Acid as an Antimicrobial for Poultry Production: A Review

Organic acids continue to receive considerable attention as feed additives for animal production. Most of the emphasis to date has focused on food safety aspects, particularly on lowering the incidence of foodborne pathogens in poultry and other livestock. Several organic acids are currently either being examined or are already being implemented in commercial settings. Among the several organic acids that have been studied extensively, is formic acid. Formic acid has been added to poultry diets as a means to limit Salmonella spp. and other foodborne pathogens both in the feed and potentially in the gastrointestinal tract once consumed. As more becomes known about the efficacy and impact formic acid has on both the host and foodborne pathogens, it is clear that the presence of formic acid can trigger certain pathways in Salmonella spp. This response may become more complex when formic acid enters the gastrointestinal tract and interacts not only with Salmonella spp. that has colonized the gastrointestinal tract but the indigenous microbial community as well. This review will cover current findings and prospects for further research on the poultry microbiome and feeds treated with formic acid.

Formaldehydes in Feed and Their Potential Interaction With the Poultry Gastrointestinal Tract Microbial Community-A Review

As antibiotics continue to be phased out of livestock production, alternative feed amendments have received increased interest not only from a research standpoint but for commercial application. Most of the emphasis to date has focused on food safety aspects, particularly on lowering the incidence of foodborne pathogens in livestock. Several candidates are currently either being examined or are already being implemented in commercial settings. Among these candidates are chemical compounds such as formaldehyde. Formaldehyde has historically been used to inhibit Salmonella in feeds during feed processing. Currently, there are several commercial products available for this purpose. This review will cover both the historical background, current research, and prospects for further research on the poultry gastrointestinal tract and feeds treated with formaldehyde.

Development of rapid detection and genetic characterization of salmonella in poultry breeder feeds

Salmonella is a leading cause of foodborne illness in the United States, with poultry and poultry products being a primary source of infection to humans. Poultry may carry some Salmonella serovars without any signs or symptoms of disease and without causing any adverse effects to the health of the bird. Salmonella may be introduced to a flock by multiple environmental sources, but poultry feed is suspected to be a leading source. Detecting Salmonella in feed can be challenging because low levels of the bacteria may not be recovered using traditional culturing techniques. Numerous detection methodologies have been examined over the years for quantifying Salmonella in feeds and many have proven to be effective for Salmonella isolation and detection in a variety of feeds. However, given the potential need for increased detection sensitivity, molecular detection technologies may the best candidate for developing rapid sensitive methods for identifying small numbers of Salmonella in the background of large volumes of feed. Several studies have been done using polymerase chain reaction (PCR) assays and commercial kits to detect Salmonella spp. in a wide variety of feed sources. In addition, DNA array technology has recently been utilized to track the dissemination of a specific Salmonella serotype in feed mills. This review will discuss the processing of feeds and potential points in the process that may introduce Salmonella contamination to the feed. Detection methods currently used and the need for advances in these methods also will be discussed. Finally, implementation of rapid detection for optimizing control methods to prevent and remove any Salmonella contamination of feeds will be considered.

Cultural and Immunological Detection Methods for Salmonella spp. in Animal Feeds - A Review

Food-borne salmonellosis continues to be a major public health concern, and contamination with Salmonella spp. in pre-harvest animal production is considered a primary contributor to this problem. Animal feeds can easily become contaminated during primary production, feed mixing and processing as well as during feeding. Consequently, monitoring and surveillance of feeds and feed ingredients for Salmonella spp. contamination may be useful or necessary in the prevention and control of this organism. Cultural and immunological detection methods for salmonellae have been used or suggested as possible approaches for use in animal feeds. Cultural methods remain advantageous owing to their ability to detect viable bacterial cells, while immunological methods have the capability of detecting nonculturable bacterial cells. Advancements and improvements in both methodologies offer opportunities for eventual routine use of these detection technologies in animal feed assays.

Polymerase chain reaction detection of foodborne Salmonella spp. in animal feeds

Foodborne salmonellosis continues to be a public health issue of considerable concern. Animal feed has been a major link in pre-harvest food animal production. Although monitoring systems and control measures are available to limit Salmonella spp. contamination on animal feeds detection methodology is relatively time consuming in the context of time inputs for feed processing and mixing. Current cultural methods of Salmonella spp. detection in feeds require several days for confirmation. This amount of time represents significant problems if control measures are to be effectively implemented in a fashion that keeps feed processing costs low. Molecular methods offer improved sensitivity and potential reduction in assay time. In particular, several commercial polymerase chain reaction (PCR) assays, and combined PCR-hybridization assays have been suggested as possible means to implement more rapid detection of Salmonella spp. extracted from animal feeds. It has now become possible to rapidly detect and confirm the presence of foodborne Salmonella spp. in feed matrices by commercial amplification detection systems. The primary challenges remaining are to develop more reliable recovery and extraction procedures for routine processing of samples from a wide variety of feed matrices and apply molecular techniques for assessing physiological status of Salmonella spp. contaminants in animal feeds.

Perspectives on the use of organic acids and short chain fatty acids as antimicrobials

Organic acids have a long history of being utilized as food additives and preservatives for preventing food deterioration and extending the shelf life of perishable food ingredients. Specific organic acids have also been used to control microbial contamination and dissemination of foodborne pathogens in preharvest and postharvest food production and processing. The antibacterial mechanism(s) for organic acids are not fully understood, and activity may vary depending on physiological status of the organism and the physicochemical characteristics of the external environment. An emerging potential problem is that organic acids have been observed to enhance survivability of acid sensitive pathogens exposed to low pH by induction of an acid tolerance response and that acid tolerance may be linked to increased virulence. Although this situation has implications regarding the use of organic acids, it may only apply to circumstances in which reduced acid levels have induced resistance and virulence mechanisms in exposed organisms. Evaluating effectiveness of organic acids for specific applications requires more understanding general and specific stress response capabilities of foodborne pathogens. Development and application of molecular tools to study pathogen behavior in preharvest and postharvest food production environments will enable dissection of specific bacterial genetic regulation involved in response to organic acids. This could lead to the development of more targeted strategies to control foodborne pathogens with organic acids.

Bioaerosols from municipal and animal wastes: background and contemporary issues

Global population increases, coupled with intensive animal and livestock production practices, have resulted in the generation, accumulation, and disposal of large amounts of wastes around the world. Aerosolization of microbial pathogens, endotoxins, odors, and dust particles is an inevitable consequence of the generation and handling of waste material. Bioaerosols can be a source of microbial pathogens, endotoxins, and other allergens. Given the close proximity of population centers to concentrated animal-rearing operations and municipal treatment facilities in many parts of the world, there is concern regarding the occupational and public health impacts associated with the exposure to bioaerosols from municipal and animal wastes. Major advances have been made in our understanding of bioaerosol characteristics, identifying the hazards, and identifying possible human and animal health links with aerosolized pathogens and allergens. However, significant knowledge and technology gaps still exist. These include a lack of clear understanding of the fate and transport of bioaerosols, especially within the open environment, an inability to accurately predict the health risks associated with bioaerosolized pathogens, and a lack of standardized bioaerosol sampling protocols, and efficient samplers. This review synthesizes the information related to bioaerosols and addresses the contemporary issues associated with bioaerosols from municipal and animal wastes, with a focus on pathogens.

Reduction in incidence of experimental fowl typhoid by incorporation of a commercial formic acid preparation (Bio-Add) into poultry feed

The experiment described evaluated the effect of a commercial in-feed preparation (Bio-Add) involving a mixture of formic acid and propionic acid on the incidence of experimental fowl typhoid in groups of 41 and 42 1-wk-old Rhode Island Red chickens. The chickens were infected through contact with 12 identical chickens that had been inoculated orally with 10(8) cfu of Salmonella gallinarum strain 9. The incidence of mortality and morbidity due to fowl typhoid was 31/41 (76%) in birds given untreated feed and 14/42 (33%) in birds given feed treated with Bio-Add.

Fifty percent colonization dose for Salmonella typhimurium administered orally and intracloacally to young broiler chicks

One and 3-day-old chicks were challenged with varying levels of Salmonella typhimurium by gavage or intracloacal administration. Chicks were killed 5 days postchallenge, and ceca were analyzed for the presence of S. typhimurium. About 100-fold fewer S. typhimurium cells were required to colonize young chicks by the intracloacal route than by gavage. It was hypothesized that the low pH of the upper gastrointestinal tract contributes to the higher levels of Salmonella required to colonize young chicks via the oral route. The pH measurements in the gizzard of freshly killed chicks were variable, but most were low enough to be bactericidal. Presence of salmonellae in the hatchery environment and the low level of cells (2 cfu) required to colonize young chicks via cloacal challenge suggest that day-of-hatch chicks may be at a high colonization risk from salmonellae in the hatchery.

Fate of salmonellas in the alimentary tract of chicks pre-treated with a mature caecal microflora to increase colonization resistance

Oral challenge with a strain of Salmonella kedougou, resistant to nalidixic acid, gave a time-course for salmonella survival in the alimentary tract of chicks pre-treated with a caecal culture from an eight-week-old bird to increase colonization resistance. In untreated, control chicks, salmonella colonization of the caeca resulted in counts of greater than 10(6)/g within 48 h and a mean generation time of 1.6 h. With treated birds, however, the salmonellas failed to multiply in the caeca and decreased to a low level over a 48-h period, thus suggesting a mainly bacteriostatic effect. Pre-treatment of chicks with the caecal culture also reduced the proportion of salmonella-positive crop samples. Growth of the salmonella in a feed-slurry system resembling moistened crop contents occurred rapidly at 37 degrees C but was prevented by addition of the treatment culture, a decline in numbers coinciding with Lactobacillus populations of ca 10(9)/g and a pH value of 5.5. Incorporation of a feed decontaminant, 1% formic acid (pH 4.0), rapidly eliminated both salmonellas and organisms added from the treatment culture.

Poultry meat as a source of human salmonellosis in England and Wales. Epidemiological overview

In England and Wales human salmonellosis is a major public health problem and, although mortality is low, the disease has important social and economic consequences. All surveillance indicators suggest that an epidemic of unprecedented proportions is occurring. Between 1081 and 1980 the number of strains received for serotyping by the Public Health Laboratory Service (PHLS) Division of Enteric Pathogens has increased by 60% (Table 1). This is predominantly due to strains ofSalmonella typhimuriumandS. enteritidis. Smaller but significant increases have occurred in the numbers ofS. virchowandS. Stanley. With the exception of the latter serotype, which seems to come from a bovine reservoir, the indications aro that poultry is the main source of the increase in infections.

Influence of continuous challenge via the feed on competitive exclusion of salmonellas from broiler chicks

In three replicate trials, chicks were treated orally with a culture of caecal contents from an adult hen and then exposed to continuous challenge from a strain of Salmonella kedougou incorporated in feed at a level of ca 10(2)/g. The contaminated feed was introduced at intervals from 0 to 48 h after treatment. Under these conditions, only one of 119 chicks in 12 separate groups was salmonella-positive at 7 d, compared with 36 of 119 controls, but thereafter protection was less consistent and in some cases the subsequent incidence of infected birds increased during the 3-week rearing period. At 21 d, 14 of 60 treated chicks were positive and 32 of 59 controls. Protection was more evident in chicks challenged 24 or 48 h after treatment than in those groups which received the salmonella-contaminated feed at 0 or 5 h and even untreated, control chicks showed greater resistance to salmonella infection from 24 h onwards. In some control and treated groups containing salmonella-positive birds, contamination of the litter reached ca 10(6) salmonellas/g, thus providing a considerable secondary challenge. Introduction of salmonellas via contaminated feed probably reduces the efficacy of protective treatment under field conditions and helps to explain the more limited success in commercial use.