In order to compete effectively with other microorganisms in the anaerobic, nutritionally sparse conditions of the gut, Salmonella needs to be able to take up limited nutrients effectively and to adapt to rapidly changing conditions. Bile sales, fatty acids and glycerides all have detergent-like actions. The intestinal lumen is replete with proteases and lipases, and these must be prevented from gaining access to the vicinity of the cytoplasmic membrane where they will cause damage to the membrane structures. (pg 21)
In 1958 it was discovered that Salmonella’s ability to agglutinate certain species of erythrocytes and its association between fimbriae and erythrocytes included mannose-containing carbohydrates in lectin-based interactions (pg 35)
The major factor for intestinal penetration is encoded by genes that are clustered in a large area (40kb) on the chromosome designated Salmonella pathogenicity island 1 (SPI1) (pg 61) Studies using murine ligated ileal loops revealed that the genes located on SPI1 are necessary for invasion of M cells in the FAE (follicle associated epithelium) of Peyer’s Patches.
Symptoms associated with Salmonella were markedly decreased by treatment with nitrogen mustard, an agent that depletes the polymorphonuclear neutrophil (PMN)… which also inhibits fluid secretion induced by cholera toxin) (pg 62)
As the host mounts an inflammatory response at the site of mucosal invasion, Salmonella genes involved in defence against inflammation have to be expressed subsequently to bacterial entry into the epithelium. Coordinated expression of these virulence genes appears to be mediated by PhoPQ, a two-component regulatiory system that changes gene expression in response to changes in the external Mg2+ and Ca2+ concentrations. Ca2+ and Mg2+ cations stabilize the outer membrane by neutralizing the negative charge of phosphate groups and bridging adjuacent LPS molecules. The intracellular parasitophorous vacuole in which salmonella resides was shown to be low in Mg2+ and Ca2+. In such environments, PhoPQ activates pmrAB, two genes encoding a second two-component regulatory system. Activation of PmrAB increases the substitution of phosphates in both the core oligosaccharide and the lipid A part of the LPS with 4-amino-4-deoxy-L-arabinose, thereby compensating for the lack of Ca2+ and Mg2+ cations. These structural changes in LPS result in increased resistance to bacteriacidal/permeability increasing protein (BPIs), a cationic antibacterial protein that is released by human PMN during inflammation. Furthermore, in response to low Mg2+ and Ca2+ concentrations, PhoPQ activates a second pmrAB-independent pathway, which results in increased resistence to defensins released by recruited PMN and crypdins produced by Paneth cells located in the intestinal crypts. (pg 63)
Only 1% of the inoculum survives the low pH during the passage through the stomach. The surviving bacteria then reach the small intestine, which contains bacteriacidal compounds, such as bile salts. About 80% of the bacteria that survive the passage through the stomach are passed with the faeces within 6-10 hours post-infection, About 15% remain localized in the lumen of the caecum and large intestinge, and only 5% manage to penetrate the intestinal wall of the small intestine and reach the GALT (Gut associated lymphatic tissue).
An important factor that impedes colonization by salmonella serovars is the normal gut flora. Disruption in the indogenous flora by streptomycin treatment results in a 100,000 fold reduction in the 50% implantation dose. The phenomenon of the indogenous flora being able to prevent colonization by exogenous bacteria is known as bacterial interference. Some of these things are production of inhibitory substances, competition for tissue adhesion sites, and limiting resources.
Peyers patches serve as the main port of entry for Salmonella serovars.
Intestinal perforations at areas of Peyer’s patches are the most frequent cause of death during typhoid fever. (Pg 59)
Calves could be protected from lethal salmonella challenge when fed colostrum from salmonella infected cows although this protection could not be coorelated with serum antibodies to flagellar or somatic antigens (pg 76)
The predominant immunoglobin of mucosal immunity is IgA although IgG and/or IgM responses can also be observed. IgA has been shown to mediate protection against infection through anti-body dependent cellular cytotoxicity, potentiate bacteriacidal action by iron-sequestering compounds, serve as a possible opsonin for mucosal phagotyes, inhibit bacterial adherence, and neutralize toxin moieties. Secretory IgA therefore exhibits exceptional diversity in its ability to mediate protection at mucosal surfaces. (pg76)
Cytokines play a critical role in the protection mediated by the immune system. They regulate whether a predominately humoral or cell-mediated response will be mounted . Besides modulating the type and intensity of an immune response, these protein signals can also alter the response, these protein signals can also alter the activity of the effector cells. In mice, IFN-y was shown to activate macrophages resulting in increased killing capacity of the cells for a variety of microbials pathogens. Incubation of the macrophages with recombinant IFN-y enhanced their activity against s. typhimurium and mice administered exogenous IFN-y exhibited reduced disseminated infection by that organism. Similar protection against salmonella infection was observed in mice receiving tumour necrosis factor alpha (TNF-a) an inflammatory cytokine, or IL-12 (pg 77)
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5644655/ “Little evidence also exists on the significance of raw meat feeding on the shedding of Campylobacter, Salmonella, and enteropathogenic Yersinia in the feces of pets.”
Results (3): Enteric pathogens were detected in 28% of the RMBDs, originating from 12 producers… Salmonella was detected in only 2% of the samples…”
Discussion (4): Salmonella was rarely detected in our study and the occurrence (2% by PCR and <1% by culturing) was clearly lower than reported in Canada and USA.
Conclusions (5): These pathogens were not found by culturing, indicating a low contamination level in frozen commercial RMBDs produced in Finland. Salmonella and enteropathoenic Yersinia were detected only in dogs fed RMBDs: however, the infection source and transmission routes remained unclear.
https://pdfs.semanticscholar.org/1bd6/123a6ba70af32f68d0f496814d142db1add2.pdf Salmonella is considered to be a ‘universal pathogen’ as it is successfully isolated from all vertebrates and many insects.
Recent studies show that a mechanism making one serovar virulent for one animal species could make the same serovar less or completely avirulent in another animal host . In addition, other factors like the dose of infection, the age during which the host is infected and their immune response contribute equally to a successful infection .
Hence, current research is mainly focused on understanding the acquired ability of Salmonella’s host preference by Salmonella.
Out of these 2,500 serovars nearly 1500 belong to the Salmonella subsp. enterica. Figure represents different Salmonella serovars with core genome and with unique genes marked in black .
The first group includes serovars which have a broad host range also called as unrestricted serovars as these infect nearly all animals. This group includes serovars like Salmonella Typhimurium and Salmonella Enteritidis.
Although the severity of disease increases in young hosts when compared to adults, this is because of their inability to counter the mature immune responses in older hosts .
The second group includes serovars which cause highly severe systemic infection in their preferred host and are usually excreted without any clinical symptoms when they accidentally infect hosts others then their most adapted or preferred. Serovars such as Dublin, Choleraesuis fall into this category, as these prove to only cause systemic infection in cattle and pigs respectively [13, 14]; however these upon infection into other hosts like rodents and humans are usually excreted making these hosts as ‘carriers’. Serovars of this group are referred to as the ‘Host-adapted Serovars’.
The third group comprises of serovars which are restricted very strictly with one very specific host only; these serovars are called ‘host–restricted serovars’. They exclusively cause systemic infection, which often proves to be fatal within their host. Serovars such as Typhi, Gallinarum, Abortusequi etc belong to this group.
Salmonella thrives on the Payer’s patches, which is abundant with specialized epithelial M cells, and are considered as the primary site for infection. Upon breaching the mucosal layer, it then translocate to lymphoidal follicles and mesenteric lymph nodes . Salmonella has developed mechanisms to infect and proliferate both in phagocytic and non-phagocytic cells. These include the epithelial cells, macrophages, dendritic cells, enterocytes and neutrophils . The entry of Salmonella within cells is either by phagocytosis, Salmonella mediated through Type Three Secretion System-1 (T3SS1) or T3SS1 independent . The process involves secretion of virulence factors called effector proteins encoded by SPI-1, which bring about actin re-modulation, leading to ruffling and extension of the plasma membrane of the host and hence resulting in invasion of the bacterium [10, 19, 20]. Once inside the epithelial cells, Salmonella develops around it a niche called the Salmonella Containing Vacuole (SCV). These SCVs interact with the endocytic vesicles within the host, thereby accumulating various factors in the process . These include Rho GTPase such as Rab5 and Rab7 and also lysosomal associated membrane protein LAMP-1 . From the SCV, the bacterium secrets another set of effector proteins encoded by SPI-2 genes that are responsible for intracellular replication and survival [23, 24]. After 4-6hrs of invasion the replicating bacteria within the SCV results in formation of tubular network like filaments called the Salmonella induced filaments (Sifs), which helps in maintain the integrity of the SCV . These Sif ’s tend to grow outwards to the plasma membrane accumulating various host constituents. The formation of these Sif ’s is facilitated by TTSS-2 effector protein called SifA [21, 23, 24]. These Sif ’s are highly enriched in cholesterol and LAMP-1. Internalization of Salmonella, also affects other cellular process such as apoptosis, cell division, cytokine production and antigen presentation .
Although the precise mechanisms leading to host specificity by Salmonella is not very well understood, however the pathogenicity of Salmonella serovars is influenced by selective pressure within a particular host and its surroundings [5, 8].
Serovars such as a Salmonella Typhimurium, Enteritidis, Pullorum, Gallinarium Dublin and Paratyphi C are a classic example which has undergone gene deletions . As a result, these serovars have lost the ability to replicate in the intestinal lumen of their respective host, although these successfully cause systemic infections .
Mannose sensitive pathogenicity determinants like FimH adhesins play an important role in adhesion of Salmonella on its host cell surface .
Apart from genetic factors, other paradigms such as physiological state of host cell, availability of amino acids and the ability of one serovar over other to replicate, has a critical role to play in the virulence pattern of a serovar .
Regardless of various genetic and physiological parameters effecting host specificity, it is also observed that stress has a significant role to play in pathogenicity and virulence of Salmonella in various hosts leading to its consistent presence in the food chain and environment.
http://legacy.iica.int/Esp/regiones/sur/uruguay/Documentos%20de%20la%20Oficina/CursoBPPPA/Literatura/ScientificTechnicalFactorsSalmonellaRawPoultry.pdf A particular concern for the group was the use of criteria implying a zero tolerance for Salmonella and suggesting complete absence of the pathogen. The notion can be interpreted differently by various stakeholders and was considered inappropriate because there is neither an effective means of eliminating Salmonella from raw poultry nor any practical method for verifying its absence.
An example is the different criteria (and subsequent actions in the case of noncompliance) addressing the presence of Salmonella on raw chicken, all of which depend on the stage in the food chain, the sensitivity of the sampling plan and method, and the analytical method used.
Increasingly, risk-based concepts are being adopted for both domestic policy and international trade, despite sometimes being poorly understood and not always applied consistently or with transparency.
A recent risk assessment of Salmonella contamination in Belgian chicken meat preparations revealed that levels greater than 1 CFU/g were most likely to be associated with human salmonellosis (185).
Legislation has been introduced that makes testing compulsory and specifies deadlines for establishing the required targets in chicken breeders, layers, and broilers and in turkeys (56, 57)
Serovar-specific control measures. In some parts of the world, strategies have been adopted to target specific Salmonella serovars associated with both poultry and human salmonellosis. Salmonella Enteritidis caused a pandemic of human illness from infected layer and broiler flocks beginning in the 1980s (3). Particular strains of Salmonella TABLE 1. Prevalence of Salmonella-positive broiler flocks in the EU, 2005 and 2006 (61) Member state No. of flocks sampleda % flocks positive for Salmonella Austria 365 7.7 Belgium 373 15.3 Cyprus 248 10.9 Czech Republic 334 22.5 Denmark 295 3.1 Estonia 131 2.2 Finland 360 0.3 France 381 8.9 Germany 377 17.2 Greece 245 27.3 Hungary 359 65.7 Ireland 351 27.9 Italy 313 30.4 Latvia 121 9.1 Lithuania 156 5.1 Poland 357 57.7 Portugal 367 42.8 Slovakia 230 8.3 Slovenia 326 3.1 Spain 388 42.3 Sweden 291 0.0 The Netherlands 362 10.2 United Kingdom 382 10.7 a The number of samples taken was statistically determined. Pooled fecal samples were obtained from boot swabs, and five swabs per flock were tested. J. Food Prot., Vol. 73, No. 8 SALMONELLA ON RAW POULTRY 1569 Enteritidis with an apparent predilection for the reproductive tract of the laying hen were responsible for contamination of egg contents, resulting in vertical transmission
For Salmonella Enteritidis and Salmonella Typhimurium in particular there is a clear linkage between human illness and poultry consumption. Conversely, although all Salmonella serovars are considered to be potentially pathogenic to humans, some of those found in poultry are rarely if ever associated with human illness. A classical example is Salmonella serovar II 1,4,12,:b:[e,n,x], also known as Salmonella Sofia, which is often isolated from chicken in Australia but rarely from human salmonellosis cases there (146).
Predominant poultry serovars differ among countries and can change over time within a single country or region (76), and successful control of one serovar may allow another to predominate. For example, epidemiological evidence suggests that Salmonella Enteritidis may have filled the ecological niche occupied previously by the antigenically related Salmonella Gallinarum, which was eradicated in most of the major poultry producing countries by the 1970s (148).
Feed can be a latent source of Salmonella for food animals because it is made from a wide range of potentially contaminated ingredients (44, 151). When present in dry feed, Salmonella can survive for more than 1 year, and even low numbers may be significant because for some strains ,1 cell per g is sufficient to colonize young chicks (157).
The heat sensitivity of nonsporulating bacteria, including Salmonella, is influenced by the temperature and time and the prevailing water activity of the feed. The heating process aims to eliminate Salmonella during pelleting, expansion, or extrusion and minimize any adverse effect on the nutritional quality of the feed (42, 50, 104, 119, 126). However, there is a significant risk of recontamination during postpelleting stages of the milling operation and during storage and transport of feed. Because of this risk, various chemical treatments have been considered, e.g., addition of certain short-chain fatty acids, such as formic and propionic acids. These acids have many of the attributes that are desirable in a feed treatment (92, 113, 151, 189, 195).
Instead of depending on extensive product testing, a better alternative is to apply good manufacturing practices (GMPs) and hazard analysis critical control point (HACCP) principles to the manufacturing process.
Effective implementation of the HACCP system requires measures to prevent recontamination of the feed after heat treatment. As with raw ingredients, these measures involve adequate storage conditions (including rigorous dust control), appropriate control of transport vehicles, regular cleaning and disinfection of the vehicles, and protection of the load up to and including the point of delivery.
when used with water-immersion chilling systems, reduces the organic load in the chill water (168), making any added chlorine more effective. However, the removal of bacteria from carcasses in the spray washing process is not enhanced by using chlorine and/or hot water (137), probably because organisms that become firmly attached to the tissues are protected from the effects of these agents and are not easily removed (118, 138).
Chilling of poultry carcasses to about 4uC or lower ensures that any Salmonella present will be unable to multiply…or exposure to cold air either by passing carcasses through an air blast system or holding them in a chill room. The continuous immersion system has a washing effect that reduces microbial contamination by up to 1 log unit (131).
The U.S. system (170) also includes a zero-tolerance policy for visible fecal contamination on carcasses entering the chilling process (181) and the need for a HACCP plan to ensure that avoidance of fecal contamination is a critical control point (182). Otherwise, the determination of critical control points is a matter for the individual company, and their number and location are likely to differ among establishments (180).
No feasible sampling plan can guarantee the absence of Salmonella, but sampling on a regular basis will reveal changes in infection or contamination so that corrective action can be taken, as required. The sampling strategy should be defined according to the public health risk involved, the anticipated prevalence of the target organism, the desired level of confidence in the results obtained, and the general principles of statistical control, which will indicate the degree of confidence offered by negative results. Other factors to consider are the stage in the food chain at which samples should be taken, the type of sample in each case, how many samples to take at any one time, how often material is collected, and what quantity of the material to collect. Standardized methods of analysis should always be used; methods advocated for international adoption are provided by organizations such as the International Organization for Standardization (ISO) and the World Organization for Animal Health (OIE). There also is the question of who should carry out the sampling, although regulations may specify that sampling must be done, at least in part, by a competent authority (71). An effective control strategy requires detailed consideration of the nature of the food chain and the points at which sampling will provide the most meaningful information. No single sampling site is ever sufficient. Testing for Salmonella at any stage should always have a clear objective that is related to control of the organism, allowing appropriate action to be taken on the basis of the results obtained. Other factors include the likelihood of infection or contamination at a particular stage and whether there are practices or interventions that might minimize the risk. Resources can then be allocated appropriately and costeffectively in relation to the risk involved. However, feasible levels of sampling are not usually sufficient to determine fully the effectiveness of a specific control measure.
In monitoring the mill environment, Jones and Richardson (104) noted that TABLE 2. Sampling for Salmonella at different stages of the supply chain Stage in supply chain What to sample When to sample Feed manufacture Bulk ingredients Before use Mill environment and equipment Finished feed Grandparent or parent flocks Litter Sampling should be more intensive for grandparent stock; sample before and just after moving to production house Dead birds Dust Feces Surfaces and equipment After cleaning and disinfection Hatchery Internal surface of hatching cabinet After hatching Chick box liners Eggshells Meconium Dead-in-shell chicks Culled chicks Surfaces and equipment After cleaning and disinfection Broiler flocks Litter Before slaughter Dust Feces Surfaces and equipment After cleaning and disinfection Slaughter and processing Neck skin or carcass rinse After carcass chilling Plant environment and equipment After cleaning and disinfection Portioning and deboning Meat surface and skin As required Plant environment and equipment After cleaning and disinfection Wholesale (fresh and frozen) Meat surface and skin As required Retail Meat surface and skin As required J. Food Prot., Vol. 73, No. 8 SALMONELLA ON RAW POULTRY 1575 dust was consistently contaminated with Salmonella throughout the mill and especially near pellet coolers, which draw in large amounts of air. Thus, sampling of dust and the mill environment is much more effective than monitoring the end product, and the sampling should be done as part of a HACCP program (63, 197).
Sampling at retail. Testing products at the retail stage rather than during processing is more relevant to the exposure of consumers to Salmonella via raw poultry meat. The results obtained can be of greater value in assessing the human health risk, which is required in risk assessments, and in verifying the effectiveness of Salmonella control measures for different types of product. This information will provide a scientific basis for any new criteria that are deemed necessary. The sampling strategy should be based on statistical methods and related to the sources of Salmonella exposure for the majority of the population, i.e., it should be largely focused on retail products that are on display in major towns and cities and in the principal retail outlets from which most poultry meat is sold. All the main forms in which poultry products are marketed should be sampled, e.g., whole carcasses, portions, meat preparations, and fresh and frozen products, and it will be important to distinguish between domestic and imported products
The adoption of quantitative risk assessment practices in microbiological food safety underscores the reality that zero risk is unattainable for all raw foods, a reality in everyday events and everyday life. The choice of zero tolerance, implying the complete absence of a hazard, may be regarded as the expression of a regulatory preference for the precautionary principle and has little to do with food safety and human health (80, 176). In the United States, the Committee on the Review of the Use of Scientific Criteria and Performance Standards for Safe Foods formed under the National Research Council (135) noted that the term ‘‘zero tolerance’’ is commonly used but generally poorly defined or understood. Use of this language in expressing objectives is troublesome because the terminology has different meanings for different audiences, as highlighted by the definition the Committee offered for its own purposes: ‘‘lay audience perception of the absence of a hazard that cannot be scientifically assured, but is operationally defined as the absence of a hazard in a specified amount of food as determined by a specific method.’’ To some people, zero tolerance implies a notional concept of zero risk associated with the food or zero prevalence of a pathogen in the food commodity. Such a misunderstanding could easily arise from the pending EU requirement for the absence of Salmonella in 25 g of fresh (raw) poultry meat (56) because no details are given on how this requirement would be interpreted. In the absence of any means of eliminating the pathogen from a raw food product, the ‘‘zero’’ concept is misleading to those consumers who may interpret such regulations as implying no risk; these consumers would have unrealistic expectations of the effectiveness of regulatory action. If a hazard exists, there is some probability it will cause an adverse effect, no matter how small (85). Zero tolerance may also imply that both minor and major deviations from a policy will be treated with the same severity. This is obviously not a sensible approach to identifying and resolving problems. Internationally, there is no consistency in interpreting the concept and what action should result from any deviations. The purpose of a zero tolerance policy should be to provide an alert, leading to a review of control policies and procedures while permitting distribution of the final product to the marketplace in situations where withdrawal would not give a risk reduction proportional to cost and other practical considerations. Little is to be gained when dealing with food safety management practices based on microbiological criteria for end product testing alone (accept or reject) because even when a process is completely under control some, albeit small, probability exists for exceeding the established parameters (191, 203). Without knowledge of the degree of variability in a process or product or of where the uncertainties of a food process lie, the likelihood of exceeding the limits is unknown. Several other challenges exist to applying a zero tolerance policy for Salmonella in poultry meat: defining the accuracy, sampling intensity, sampling material, and method sensitivity. At which point is the assessment to be made, preharvest or postharvest, who bears the repercussions for enforcement, and who has and what is the enforcement capacity? Ultimately, regulatory choices in establishing control policies must be verified through scientific evidence for their effectiveness for reducing risk so that social costs can be made transparent (80).
The term ‘‘zero tolerance’’ for specific pathogens such as Salmonella in food products is interpreted differently by scientists and other stakeholders in different countries and therefore has been confusing, misleading, and misapplied. All countries signing the international WTO agreements are entitled to establish sovereign levels of protection. However, with regard to sanitary measures that include MCs, the most appropriate and legally defensible approach is to define such criteria by limits of detection according to the analytical method imposed and confidence limits of sampling and testing. Using terms such as ‘‘zero tolerance’’ or ‘‘absence of a microbe’’ in relation to raw poultry should be avoided unless these terms are defined and explained by international agreement. New metrics, such as POs that are linked to human health outcomes based on risk assessment, should be used throughout the food chain and will define the resultant public health risk.
In addition to principal authors listed above, members of the Salmonella on Raw Poultry Writing Committee include Raphael Andreatti Filho, Sao Paulo State University, Sao Paulo, Brazil; Roy Biggs, Tegel Foods Ltd., Auckland, New Zealand; Jeff Buhr, U.S. Department of Agriculture, Agricultural Research Service, Athens, GA, USA; Sarah Cahill, Food and Agriculture Organization of the United Nations, Rome, Italy; John Cason, U.S. Department of Agriculture, Agricultural Research Service, Athens, GA, USA; Thongchai Chalermchaikit, Chulalongkorn Univeristy, Bangkok, Thailand; Hector Hidalgo, University of Chile, Santiago, Chile; Charles Hofacre, University of Georgia, Athens, GA, USA; Henk Hupkes, Meyn Food Processing Technology, B.V., Oostzaan, The Netherlands; Mogens Madsen, Dianova, Aarhus, Denmark; Roel Mulder, Spelderholt Poultry Consulting and Research, Burg, The Netherlands; Lars Plym Forshell, National Food Administration, Uppsala, Sweden; Martha Pulido Landinez, Universidad National de Colombia, Bogota´, Colombia; Jason Richardson, The Coca-Cola Co., Atlanta, GA, USA; Douglas Smith, North Carolina State University, Raleigh, NC, USA; Yvonne Vizzier Thaxton, Mississippi State University, Mississippi State, MS, USA; Hajime Toyofuku, National Institute of Public Health, Japan; Pirkko Tuominen, Finnish Food Safety Authority, Helsinki, Finland; Mieke Uyttendaele, Ghent University, Ghent, Belgium; Sian Ming Shi, Shanghai Jiaotong University, Shanghai, China; and Marcel Zwietering, Wageningen University, Wageningen, The Netherlands.
Infective Dose of Foodborne Pathogens in Volunteers: A Review (Mahendra Kothary) email@example.com – Division of Virulence Assessment (HFS327) Center for Food Safety and Applied Nutrition, US FDA
“The human infective dose varies depending on the serovar of the organism. Results from the volunteer studies indicated that the infective dose for various serovars was 105 – 1010 organisms. The attack rate depended on the serovar of the organism and ranged from about 16-50%. However, data from outbreaks suggest that infection dose may be as high as 107 – 109 organisms. Various authors of these studies suggested that the high fat and protein content of the food vehicle involved in the outbreaks may have played an important role in protecting the organism from gastric acidity.
http://www.veterinaryworld.org/Vol.6/Oct-2013/1.pdf Salmonella enterica, the most pathogenic species of the genus Salmonella
The differences observed between serovars in their host preference and clinical manifestations are referred to as “serovar-host specificity” or “serovar-host adaptation”. The genus Salmonella, highly adaptive to vertebrate hosts, has many pathogenic serovars showing host specificity
WAITING ON NATE TO HELP ME MAKE THIS SO I CAN COPY AND PASTE IT… MEANWHILE I BROUGHT IT
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2869595/pdf/11117946.pdf The current view of salmonella taxonomy assigns the members of this genus to two species: S. enterica and S. bongori. S. enterica itself is divided into six subspecies, enterica, salamae, arizonae, diarizonae, indica, and houtenae, also known as subspecies I, II, IIIa, IIIb, IV, and VI, respectively  .
The pathogenicity of most of the distinct serotypes remains undefined, and even within the most common serotypes, many questions remain to be answered regarding the interactions between the organism and the infected host.
Salmonellosis manifests itself in three major forms: enteritis, septicaemia, and abortion, each of which may be present singly or in combination, depending on both the serotype and the host involved. Although currently over 2300 serovars of Salmonella are recognized, only about 50 serotypes are isolated in any significant numbers as human or animal pathogens [2, 3] and they all belong to subspecies enterica
Only a small number of serotypes typically cause severe systemic disease in man or animals, characterized by septicaemia, fever and}or abortion, and such serotypes are often associated with one or few host species [4–6].
Host-adapted serotypes (Table 1) typically cause systemic disease in a limited number of related species. For example, Typhi, Gallinarum and Abortusovis are almost exclusively associated with systemic disease in humans , fowl  and ovines  respectively
In the past, special attention has been dedicated to nutritional requirements and distinct biochemical characters of Salmonella serotypes. In particular, Salmonella strains had been divided in ‘ ammonium weak’ and ‘ ammonium strong’ strains on the basis of their ability to assimilate nitrogen from ammonia in a defined media that contained simple carbon compounds such as citrate (Simmons citrate agar) or other sugars as sole source of carbon and energy 
Serotypes noted as ‘ ammonium weak’ were all host-adapted (Dublin, Rostock, and Choleraesuis) or host-restricted (Paratyphi A, Abortusovis, Typhisuis, Typhi, and Sendai) . . It is important to note that a negative result of this test might be due also to the failure of the organism to grow in absence of other substances that were not provided with such minimal media.
Fierer and colleagues have examined the biochemical features of several Dublin strains and found them all unable to grow in Simmons citrate agar . In the presence of supplemental nicotinic acid, however, all strains were able to utilize citrate. Similarly, we found Abortusovis strains able to utilize citrate in a minimal defined medium only when cystine and nicotinic acid were supplemented (Uzzau and colleagues, unpublished results). Detailed analysis of the nutritional requirement of Salmonella spp. has led to the observation that whereas ubiquitous Typhimurium and Enteritidis were able to grow in relatively simple defined media, certain amino acids and vitamins must be supplied for most strains of Typhi, Typhisuis, Abortusovis, Gallinarum, Paratyphi A, and Dublin [18, 19]. Auxotrophy therefore, seems to be a characteristic of HR and HA serotypes (Table 2).
The taxonomic classification of salmonella has been continually revised over the years. Beyond the level of subspecies, serotyping is used for differentiation, and serotypes have been described within S. enterica subspecies enterica on the basis of somatic (O), flagellar (H), and capsular (Vi) antigens . Within subspecies enterica, some serotypes are polyphyletic; identical serotypes occur among isolates of distantly related clones that also differ in pathogenic potential and host range. This can be attributed to horizontal genetic transfer and recombination of antigen genes between lineages, an event that has been proposed to happen with relatively high frequency . However, overall the subspecies remain clonal .
Epithelial cell adhesion and invasion may not be uncoupled in Typhi, since all Typhi invasion mutants isolated in recent studies [47, 52] were also adhesion-defective, whereas mutants obtained from UR serotypes like Typhimurium and Enteritidis were found to adhere to cell monolayers but invaded significantly less [53–55].
Other salmonellae which are primarily or exclusively restricted in host range to humans are Paratyphi A and C and Sendai, all of which cause enteric fever. Some strains of Paratyphi B cause human enteric fever, whereas others, designated as Java, produce gastroenteritis in both humans and animals. Miami, which is serologically related to Sendai, is largely limited to humans but causes gastroenteritis rather than enteric fever in animals .
Gallinarum as host-restricted since all reported cases of systemic disease are from avian hosts .
Typhisuis This serotype does not naturally infect animals other than the pig and, for this reason, is considered host restricted to swine
Choleraesuis This serotype is defined as host-adapted on the basis that 99% of incidents are associated with pigs. However, it does naturally infect other host species, including man, in which the disease can be severe. Human infections were well known for severity with 10–40% case mortality and the majority of isolates were from non-intestinal sites (i.e. blood-stream, bones, joints)
Dublin is host-adapted to bovine and affects both young and adult cattle causing enteritis and}or systemic disease. In humans Dublin infection generally occurs in patients with underlying chronic diseases, and arises from contact with animals or via the food chain.
Immediately following the invasion of the organisms beyond the intestinal mucosa, more than 90% of the organisms are destroyed at, or close to, the site of inoculation, primarily by resident phagocytic cells. Surviving organisms disseminate, and bacterial growth occurs in the cells of the reticuloendothelial system. The crucial phase occurs when bacterial multiplication is either controlled or continues in an uncontrolled fashion. Polymorphonuclear leukocytes (PMN) are the first phagocytic cells to be attracted towards infected tissues by means of salmonella-induced cytokines secretion [147, 148]. PMNs have been recognized for many years as having a function in the inflammatory response, and recently PMNs have also been implicated in the modulation of the other immune cells . Salmonella has adapted to grow inside macrophages where it is relatively sheltered from PMN . Macrophages play a dual role in the salmonella infection process. Once activated, they can kill salmonella, but macrophages are also the site of bacterial multiplication. Infected macrophages are therefore responsible for the dissemination of the Serotypes of S. enterica 239 infection via the lymphatic ducts to other organs 
When Salmonella serotypes colonize in the intestinal mucosa of mammals, before progression to a systemic infection in the body, they face to an effective barrier of macrophages that line the lymphatic sinuses of lymph nodes. The granuloma formations caused by the accumulation in inflamed tissue of polynuclear granulocytes in mammals, also exist in avian hosts where it is the heterophiles that are involved, and are morphologically similar to inflammatory lesions in reptiles . Therefore, one of the first steps in the salmonella development towards being a systemic, facultative intracellular pathogen may have been to enter the macrophage in order to escape from the aggressive environment. It is tempting to speculate that it is the ability of HA and HR serotypes to escape cellular defences that has led to the development of host specificity. That pathogens have adopted different tactics to escape immune systems is well known. Immune evasion of virus and helminth parasites related to cytokine activities is beginning to be explored , and also bacteria can be supposed to contain and produce a large number of diverse molecules, which can selectively induce the synthesis of cytokines, as LPS does . Unfortunately, little evidence has been accumulated to date with respect to salmonella.
Salmonella serotypes capable of disseminate in a particular host may utilize alveolar macrophages and pulmonary intravascular macrophages (PIM) for translocation . Calves, sheep, goats, and pigs, but not man or small rodents, possess PIM densities and clearance capacity in the lung parenchyma similar to that of human and murine Kupffer cells in the liver . Pigs rooting behaviour and the ovine and bovine grazing allow salmonella in the environment an easy access to the nasal cavity and thus to the lungs. Salmonella serotypes (i.e. Dublin, Abortusovis, Choleraesuis, and Typhimurium) able to produce systemic infection in these animals might have developed specific mechanisms to take advantage of both the intestinal and the pulmonary route of entry and dissemination. It is worth noting that salmonella infection of these hosts is often characterized by pneumonia and that bovine-adapted Dublin may cause pneumonia as a major sign of infection in sheep
In vitro studies have demonstrated that host-specific pathogenesis of Salmonella serotypes may depend on the selective recognition of complement receptor (CR) types on the macrophages membrane . Typhi and Typhimurium induced their own uptake by micropinocytosis in both human and murine macrophages, but only Typhi was capable of growth in human macrophages. Conversely, Typhimurium survived in murine macrophages whereas Typhi did not. The molecular basis of such restriction has been hypothesized based on the fact that intracellular survival and replication is only made possible by recognition, in the presence of serum opsonin, of the CR type 1 (CR1) but not of CR type 3 (CR3). Strikingly, Typhi and Typhimurium recognized, respectively, CR1 and CR3 on human macrophages, whereas they recognized, respectively, CR3 and CR1 on murine macrophages. Baker and Morona have recently observed that phorbol myristate acetate (PMA) differentiated U937 (PMA-U937, human) cells restricted the net growth of Typhi but not Typhimurium phoP mutants, suggesting that the phoP}Q locus may control expression of genes involved in host specificity, particularly affecting differential effects on Typhi and Typhimurium LPS .
At least 11 serotypes are known to carry virulence plasmids, which share common and unique sequences . Typhi does not carry virulence plasmids and not all isolates of those serotypes associated with the plasmids do. The role of the virulence plasmid in pathogenesis has been mainly studied using the mouse model of salmonellosis
https://www.fda.gov/food/guidanceregulation/guidancedocumentsregulatoryinformation/salmonella/ucm295271.htm In this document, we use the phrase “adequately reduce” to mean reducing the presence of Salmonella spp. to an extent sufficient to prevent illness. The extent of reduction sufficient to prevent illness is usually determined by the estimated extent to which Salmonella spp. may be present in the food combined with a safety factor to account for uncertainty in that estimate. For example, if it is estimated that there would be no more than 1000 (i.e., 3 logs) Salmonella organisms per gram of food, and a safety factor of 100 (i.e., 2 logs) is employed, a process adequate to reduce Salmonella spp. would be a process capable of reducing Salmonella spp. by 5 logs per gram of food.
https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0145416 Serotype Typhi, for example, is known to exist only in humans, serotype Choleraesuis has a primary reservoir in pigs, and serotype Dublin in cattle
Serotype IV 48:g,z51:− causes sporadic illness from contact with the environment of a marine iguana, the serotype’s only known host
Counts for serotypes I,4,,12:i:− and Typhimurium (including Typhimurium var. 5-) were combined (and labeled Typhimurium+) because not all state laboratories could make the distinction.
CVs for 37 serotypes examined by state, month, age group, and sex are shown in S1 Table. The serotypes with the most evenly distributed rates across all states and regions were Typhimurium+ (CV 30%), Infantis (CV 40%), and Heidelberg (CV 33%). At the other end of the spectrum, serotypes Mississippi (CV 256%), Rubislaw (CV 197%), and Give (CV 195%) were heavily concentrated in the Gulf Coast states. Other serotypes that showed geographic concentration included Norwich (CV 161%), being reported mostly from the lower Midwest into the South, and Javiana (CV 135%), also most frequently reported from the South.
Serotypes with the largest CVs by month were Norwich (CV 87%), Javiana (CV 83%), Mississippi (CV 69%), and Newport (CV 68%). All were highly concentrated in months that are generally warmer in the US, averaging 45% of reported isolates of these four serotypes (range, 41% to 47%) in summer (June-Aug) and 8% (range, 7% to 11%) in winter (Dec-Feb). Conversely, serotypes Senftenberg, Mbandaka, Anatum, and Derby had low CVs by month (18%, 21%, 24%, and 24% respectively), indicating that isolations occurred fairly evenly throughout the year, with an average of 30% (range, 28% to 31%) of isolates reported in summer and 22% (range, 20% to 26%) in winter.
The variation in incidence rate by age was highest in serotypes Rubislaw (CV 265%), Mississippi (CV 160%), Poona (CV 151%), and Schwarzengrund (CV 150%)—all found mostly in young children. Enteritidis (CV 24%), Berta (CV 40%), and Braenderup (CV 41%) were the serotypes most equally distributed by age. The rate was highest among young children for 34 of the 37 common serotypes; the exceptions were Senftenberg (highest rates among adults aged 70 years and older), Paratyphi A (highest rates among 20- to 34-year-olds), and Tennessee (highest rate among adults aged ≥74 years).
Serotypes with higher variation in incidence by age group (ie, skewed toward particular ages) were more common among males (Spearman’s correlation p <0.01) and had higher incidence variation by state (p <0.01). There was no correlation between variation by age and season (p = 0.13), sex and season (p = 0.74), or sex and region (p = 0.36). Serotypes whose incidence increased the most in the second half of the 16-year study period had higher incidence variation by season (Spearman’s correlation p <0.01) and by state (p = .02). Changes in incidence did not correlate with variation by age or sex.
http://jfoodprotection.org/doi/pdf/10.4315/0362-028X-40.5.317?code=FOPR-site (this document lists a couple of serovars and their direct affiliations with dogs, but they are interspersed and not, therefore, copied here). The magnitude of this reservoir may be considerable; a survey conducted by Galton et at. (4) revealed 27.6% of 8,157 rectal swabs, collected from dogs, were positive for Salmonella. Dogs, on occasion, have been observed to eat carrion and garbage and to practice coprophagy. Therefore, the mechanism for transmission of Salmonella to dogs, and re-infection among dogs, may be present continually.
Dried dog foods were incriminated as the source of Salmonella infections among colonies of laboratory animals as early as 1952. (5)
Bacteriological examination of a portion, approximately 44 g, of commercial dried dog food, obtained January 24, 1976, from a supply at the home of the index case, yielded isolates of S. enteriditis serotypes lnfantis and Minnesota.
Sampling and testing plans for Salmonella, as employed by the Food and Drug Administration (FDA), have been described (9). It would be prudent for the dried dog food industry to consider adopting the FDA sampling recommendation for foods in Category I.
It is abundantly clear that dogs, infected with Salmonella, can provide a link in disease transmission to humans (7). Therefore, manufacturers of dried dog food should be interested in adopting more stringent laboratory testing to provide evidence that their products present a low consumer risk.
As many as nine serotypes were detected in a single sample. These products were allegedly produced by an expansion extrusion process. It is reasonable to SALMONELLAE IN DOG FOOD 321 consider this a critical control point in production of dried dog food; time, temperature, and moisture parameters lend themselves to continual monitoring for quality control. Methods to eliminate the hazard of post-processing contamination, if it exists, might well be investigated. The possibility that dried dog foods may provide a vehicle to introduce Salmonella into the home is not sufficiently recognized by consumers. This investigation has brought forth the following questions: (a) Is it realistic to expect manufacturers to produce Salmonella-free dried dog food? (b) Should the answer to the first question be negative, what degree of hazard does dried dog food present to pets and to their owners? (c) Should pet owners be cautioned about the handling, storage, and potential for abuse of dried dog foods?
The Hardt Lab – Salmonella Pathogenesis, Institute of Microbiology, ETH Zurich – http://www.micro.biol.ethz.ch/research/hardt.html (research Salmonella shedding from humans)
Salmonella Typhimurium diarrhea reveals basic principles of Enteropathogen Infection and disease-promoted DNA exchange: cell host & microbe – https://www.cell.com/cell-host-microbe/fulltext/S1931-3128(17)30119-1?_returnURL=https%3A%2F%2Flinkinghub.elsevier.com%2Fretrieve%2Fpii%2Fs1931312817301191%3Fshowall%2Dtrue
Precursors like acetyl acid for liver metabolism evidence that creatures have needed fermentation as part of their diet for long enough to have evolved dependencies on it. Natural sources of fermentation: ruminant gut contents and rotten fruits, etc. Adding certain bacteria can result in sterilization of products under conditions of poor storage. Most grain products come with mycotoxins and mildews and pathogens in them, ready to feed on the sugars and starches the moment they are exposed to enough moisture or warmth. The only cost effective way to add a real safety measure is to either eliminate the starches/sugars, or to add these special bacteria.
L. monocytes is submissive to other bacteria. Hpp does not kill it but the presence of other bacteria prevent its proliferation
Karen’s interests for sharing: FDA referenced documents that state the relationship of dry kibble and pathogen risk but urge consumers not to use raw, elaboration on studies referenced in first mercola article, no dogs got sick when fed raw meat that was intentionally contaminated with salmonella strains,
FDA commits to disclose retailer information for some food recalls: Petfoodindustry.com https://www.petfoodindustry.com/articles/7516-fda-commits-to-disclose-retailer-info-for-some-food-recalls?utm_source=KnowledgeMarketing&utm_medium=email&utm_content=Pet%20eNews&utm_campaign=18_10_02_PetENews&eid=223857144&bid=2257026
Raw food trials with pets: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3003575/#!po=0.431034
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