Salmonella contamination in commercial layer feed in Japan

Feed Safety and the Development of Poultry Intestinal Microbiota

Simple Summary

Intensive gut colonisation of animals starts immediately after birth or hatch. Oral route of colonisation, and consequently the first feed, plays a significant role in the continual defining of the intestinal microbial community. The feed can influence colonisation in two ways: providing the microbial inoculum and providing the nutritional requirements that suit a specific type of microbes. In combination with environmental factors, feed shapes animal’s future health and performance from the first day of life. The objective of this review was to investigate feed safety aspects of animal nutrition from the gut colonisation aspect.

Abstract

The first feed offered to young chicks is likely the most important meal in their life. The complex gut colonisation process is determined with early exposure and during the first days of life before the microbial community is formed. Therefore, providing access to high-quality feed and an environment enriched in the beneficial and deprived of pathogenic microorganisms during this period is critical. Feed often carries a complex microbial community that can contain major poultry pathogens and a range of chemical contaminants such as heavy metals, mycotoxins, pesticides and herbicides, which, although present in minute amounts, can have a profound effect on the development of the microbial community and have a permanent effect on bird’s overall health and performance. The magnitude of their interference with gut colonisation in livestock is yet to be determined. Here, we present the animal feed quality issues that can significantly influence the microbial community development, thus severely affecting the bird’s health and performance.

Salmonella detection in commercially prepared livestock feed and the raw ingredients and equipment used to manufacture the feed: A systematic review and meta-analysis

Salmonella contamination of livestock feed is a serious veterinary and public health issue. In this study we used a systematic review to assess the prevalence and characterization of Salmonella isolates detected in raw feed components, feed milling equipment and finished feed from 97 studies published from 1955 to 2020 across seven global regions. Eighty-five studies were included in a meta-analyses to estimate the combined prevalence of Salmonella detection and to compare the risk of contamination associated with different sample types. We found the overall combined prevalence estimate of Salmonella detection was 0.14 with a prevalence of 0.18 in raw feed components, 0.09 in finished feed and 0.08 in feed milling equipment. Animal based raw feed components were 3.9 times more likely to be contaminated with Salmonella than plant based raw feed components. Differences between studies accounted for 99 % of the variance in the prevalence estimate for all sample types and there was no effect of region on the prevalence estimates. The combined prevalence of Salmonella detection in raw feed components decreased from 0.25 in 1955 to 0.11 in 2019. The proportion of Salmonella isolates that were resistant to antimicrobials was largest for amikacin (0.20), tetracycline (0.18) streptomycin (0.17), cefotaxime (0.14) and sulfisoxazole (0.11). The prevalence of Salmonella contamination of animal feed varies widely between individual studies and is an ongoing challenge for the commercial feed industry. Control relies on the vigilant monitoring and control of Salmonella in each individual mill.

A Comparison of Colonizing Ability Between Salmonella Enteritidis and Salmonella Heidelberg in Broiler Chickens Challenged Through Feed Administration

With over 1 million estimated cases per year in the United States, foodborne salmonellosis is an important public health issue. Chicken products are frequent sources of foodborne Salmonella infection. These bacteria readily colonize the gastrointestinal tract of broiler chickens, and feed is a known vector. Past research has demonstrated that the survivability of Salmonella in feed is dependent on the serovar and strain. Therefore, the objective of this research was to compare colonization incidence of these two serovars in broiler chicken tissues by administration of feed contaminated with Salmonella enterica serovar Enteritidis (SE) or Salmonella enterica serovar Heidelberg (SH). A comparison was made with equal conditions so that there was no influence of other factors. Birds were inoculated by addition of Salmonella to the feed (1 × 10⁴ colony-forming unit [CFU]/g of feed) at 14 days of age, and the following tissue samples were collected from each bird after grow-out (days 34-41 depending on the trial): abdominal cavity swab, bone marrow swab, cloaca swab, lung swab, breast, bursa and thymus, ceca, crop, kidney, liver and spleen, skin, spinal cord, thigh, and trachea. A higher percentage of birds inoculated with SE were positive in at least one tissue compared with SH (68% and 9%, respectively), and the SE inoculated birds also showed a higher number of positive tissue samples than SH (13.1% and 0.7%, respectively). Recovery of SH was low for all tissue samples. However, recovery of SE was variable between samples, with ceca showing the highest percentage (50%). These results indicate that challenge at day 14 through feed administration results in greater colonization by SE compared with SH, suggesting that monitoring and control methods for Salmonella in feed should focus on SE to have the greatest positive effect.

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.

Differential Distribution of Salmonella Serovars and Campylobacter spp. Isolates in Free-Living Crows and Broiler Chickens in Aomori, Japan

Salmonella and Campylobacter cause foodborne enteritis mainly via the consumption of raw/undercooked contaminated poultry meat and products. Broiler flocks are primarily colonized with these bacteria; however, the underlying etiology remains unclear. The present study was conducted in order to obtain further information on the prevalence and genotypic distribution of Salmonella and Campylobacter in free-living crows and broiler flocks in a region for 2 years, thereby facilitating estimations of the potential risk of transmission of C. jejuni from crows to broiler flocks. Salmonella serovars Bredeney and Derby were isolated from 8 and 3 out of 123 captured crows, respectively, both of which are not common in broiler chickens. Campylobacter were isolated from all 89 crows tested and C. jejuni was prevalent (85 crows). Pulsed field gel electrophoresis showed broad diversity in the crow isolates of C. jejuni. However, 3 crow isolates and 2 broiler isolates showing similar banding patterns were assigned to different sequence types in multi-locus sequence typing. These results indicate that crows do not share Salmonella serovars with broilers, and harbor various genotypes of C. jejuni that differ from those of broiler flocks. Thus, our results indicate that crows are not a potential vector of these bacteria to broiler flocks in this region.

Impact of desiccation and heat exposure stress on Salmonella tolerance to acidic conditions

In a recent study, the pH of commonly used Salmonella pre-enrichment media became acidic (pH 4.0 to 5.0) when feed or feed ingredients were incubated for 24 h. Acidic conditions have been reported to injure or kill Salmonella. In this study, cultures of four known feed isolates (S. montevideo, S. senftenberg, S. tennessee, and S. schwarzengrund) and four important processing plant isolates (S. typhimurium, S. enteritidis, S. infantis, and S. heidelberg) were grown on meat and bone meal and later subjected to desiccation and heat exposure to stress the microorganism. The impact of stress on the isolates ability to survive in acidic conditions ranging from pH 4.0 to 7.0 was compared to the non-stressed isolate. Cell injury was determined on xylose lysine tergitol 4 (XLT4) and cell death determined on nutrient agar (NA). When measured by cell death in non-stressed Salmonella, S. typhimurium was the most acid tolerant and S. heidelberg was the most acid sensitive whereas in stressed Salmonella, S. senftenberg was the most acid tolerant and S. tennessee was the most acid sensitive. The pH required to cause cell injury varied among isolates. With some isolates, the pH required for 50% cell death and 50% cell injury was similar. In other isolates, cell injury occurred at a more neutral pH. These findings suggest that the pH of pre-enrichment media may influence the recovery and bias the serotype of Salmonella recovered from feed during pre-enrichment.

Epizootiologic role of feeds in the epidemiology of Salmonella Senftenberg contamination in commercial layer farms in eastern Japan

In total, 40 commercial layer farms and 32 replacement pullet farms with a combined population of 7.5 million adult layers and 6.6 million replacement pullets from six prefectures in eastern Japan were investigated for Salmonella Senftenberg contamination. We randomly collected 17,956 environmental samples, 5816 feed samples, and 218,470 egg samples from commercial layer farms; and 427 feed samples and 2896 environmental samples from replacement pullet farms. We monitored all samples for Salmonella. Samples were primarily enriched in Hajna tetrathinoate broth for 24 hr at 37 C followed by incubation in desoxycholate hydrogen sulfide lactose agar for 18 hr at 37 C. Salmonella colonies were confirmed and identified by biochemical tests and serotyped using Salmonella O and H antigens. We recorded 171 environmental samples (0.95%) and 10 feed samples (0.17%) that were positive for Salmonella spp. in which 36 environmental samples (0.20%) and six feed samples (0.10%) were identified as Salmonella Senftenberg. All Salmonella Senftenberg strains were isolated from nine replacement pullet farms. No Salmonella Senftenberg strains were isolated from adult layer farms and from eggs. Pulse field gel electrophoresis of BlnI-digested chromosomal DNA of 19 Salmonella Senftenberg isolates from feeds and environmental samples yielded a single identical DNA pattern. Traceback information showed that all positive feed samples were from a single feed source. Timeline studies showed that Salmonella Senftenberg contamination occurred first mostly in the feeds and then spread to the environment and other farms. This study demonstrated that the prevalence of Salmonella Senftenberg contamination in commercial layer facilities in eastern Japan is very low. Moreover, feed contamination played a major role in the epizootiology and spread of this pathogen in commercial poultry flocks. Given the resilient and persistent nature of this particular Salmonella serotype, routine monitoring and strict quality control measures at the feed level are recommended to prevent the colonization of poultry facilities with Salmonella Senftenberg that may lead to future outbreaks.

Persistence of orally administered Salmonella enterica serovars Agona and Montevideo in Atlantic salmon (Salmo salar L.)

The objective of our experiments was to study the persistence and dissemination of orally administered Salmonella in smoltified Atlantic salmon. In experiment 1, salmon kept at 15 degrees C were fed for 1 week with feed contaminated with 96 most-probable-number units of Salmonella Agona per 100 g of feed and then starved for 2 weeks. Samples were taken from the gastrointestinal tract and examined for Salmonella 1, 2, 8, 9, 15, and 16 days after the feeding ended. In experiment 2, Salmonella Agona and Montevideo were separately mixed with feed and administered by gastric intubation. Each fish received 1.0 x 10(8), 1.0 x 10(6), or 1.0 x 10(4) CFU. The different groups were kept in parallel at 5 and 15 degrees C and observed for 4 weeks. Every week, three fish in each group were sacrificed, and samples were taken from the skin, the pooled internal organs, the muscle, and the gastrointestinal tract and examined for the presence of Salmonella. The results from the two experiments showed that the persistence of Salmonella in the fish was highly dependent on the dose administered. Salmonella was not recovered from any of the fish that were fed for 1 week with the lowest concentration of Salmonella. In the fish given the highest dose of Salmonella, bacteria persisted for at least 4 weeks in the gastrointestinal tract as well as, to some extent, the internal organs. The present study shows that under practical conditions in Norway, the risk of Salmonella in fish feed being passed on to the consumer of the fish is negligible.

Salmonella in Commercially Manufactured Feeds

We collected 886 samples (68 feed ingredient samples, 189 dust samples, and 629 feed samples) from 3 feed mills each of which produced between 100,000 and 400,000 tons of feed a year. Samples were collected on 3 d (Monday, Wednesday, and Friday), during 2 seasons (early spring and summer), and between 0700 and 1700 h approximately once per hour. Samples were collected from 5 locations within each mill: ingredient receiving, at the mixer, at the pellet mill, from pellet coolers, and at load-out. Temperatures were taken of the samples obtained at the pellet mill immediately following collection. All samples were analyzed for Enterobacteriaceae counts (EC) and Salmonella. The data confirm that feed ingredients and dust can be a major source of Salmonella contamination in feed mills. There were no differences (P < 0.05) in the Salmonella contamination rates of samples collected in spring as compared with samples collected in summer. Salmonella contamination rates were observed to be higher in samples collected on Friday compared with samples collected on Monday or Wednesday, an effect that may be management related. Data collected at the pellet mill clearly illustrate the uneven distribution of Salmonella contamination in feed as well as the need for control of dust around the pellet mill. Feed samples (both mash and pellets) contaminated with Salmonella contained significantly higher EC than samples not contaminated with Salmonella. Thus, EC may provide some indication of the likelihood of Salmonella contamination in feed samples.

Molecular analyses of Salmonella enterica isolates from fish feed factories and fish feed ingredients

Isolates of the most commonly observed salmonella serovars in Norwegian fish feed factories from 1998 to 2000 (Salmonella enterica serovar Agona, S. enterica serovar Montevideo, S. enterica serovar Senftenberg, and S. enterica serovar Kentucky) were studied by pulsed-field gel electrophoresis (PFGE) and plasmid profile analysis and compared to isolates of the same serovars from fish feed ingredients, humans, and other sources (a total of 112 isolates). Within each serovar, a variety of distinct PFGE types (with similarity levels less than 90%) were observed in the feed ingredients and other sources, while only two distinct types of each serovar were identified in the factories. The combined results of PFGE and plasmid analyses showed that each factory harbored only a few S. enterica clones. Some of these clones persisted for at least 3 years in the factories, indicating that there was long-lasting contamination probably due to inadequate decontamination procedures.