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63-448: SaPIs can infect many strains that are resistant to phages and can readily be transferred to Listeria monocytogenes even though staphylococcal phages cannot grow in Listeria cells. SaPIs occur infrequently in other staphylococcal species, but SaPI-like elements are common and widespread in other Gram-positive cocci . SaPI DNA is maintained in a prophage -like state under the control of

126-455: A bacillus, L. monocytogenes septates in the middle of the cell, thus has one new pole and one old pole) are capable of binding the Arp2/3 complex , thereby inducing actin nucleation at a specific area of the bacterial cell surface. Actin polymerization then propels the bacterium unidirectionally into the host cell membrane. The protrusion formed may then be internalized by a neighboring cell, forming

189-485: A bacterial protein internalin (InlA/InlB), which attaches to a protein on the intestinal cell membrane "cadherin" and allows the bacteria to invade the cells through a zipper mechanism. These adhesion molecules are also to be found in two other unusually tough barriers in humans — the blood-brain barrier and the fetal–placental barrier, and this may explain the apparent affinity that L. monocytogenes has for causing meningitis and affecting babies in utero . Once inside

252-411: A beta hemolysin , which causes destruction of red blood cells. This bacterium exhibits characteristic tumbling motility when viewed with light microscopy. Although L. monocytogenes is actively motile by means of peritrichous flagella at room temperature (20−25 °C), the organism does not synthesize flagella at body temperatures (37 °C). The genus Listeria belongs to the class Bacilli and

315-429: A component of dental plaque , metabolizes dietary sugar and produces acid as a waste product. The acid decalcifies the tooth surface to cause dental caries . Endotoxins are the lipid portions of lipopolysaccharides that are part of the outer membrane of the cell wall of gram-negative bacteria . Endotoxins are released when the bacteria lyses , which is why after antibiotic treatment, symptoms can worsen at first as

378-491: A double-membrane vacuole from which the bacterium must escape using LLO and PlcB. This mode of direct cell-to-cell spread involves a cellular mechanism known as paracytophagy . The ability of L. monocytogenes to successfully infect depends on its resistance to the high concentrations of bile encountered throughout the gastrointestinal tract. This resistance is due, in part, to the nucleotide excision repair protein UvrA that

441-494: A glycolipid moiety, such as a galactosyl-glucosyl-diglyceride, is covalently linked to the terminal phosphomonoester of the teichoic acid. This lipid region anchors the polymer chain to the cytoplasmic membrane. These lipoteichoic acids resemble the lipopolysaccharides of Gram-negative bacteria in both structure and function, being the only amphipathic polymers at the cell surface. L. monocytogenes has D-galactose residues on its surface that can attach to D-galactose receptors on

504-400: A hundred. By contrast, several thousand species are part of the gut flora present in the digestive tract . The body is continually exposed to many species of bacteria, including beneficial commensals , which grow on the skin and mucous membranes , and saprophytes , which grow mainly in the soil and in decaying matter. The blood and tissue fluids contain nutrients sufficient to sustain

567-466: A master repressor and is induced to excise and replicate by helper phages encoding proteins that counter the SaPI repressor . One set of SaPIs is induced  by other co-resident SaPIs which must first be induced by helper phages, setting up a 3-way cascade For most SaPIs, following replication, concatemeric SaPI DNA is packaged by the headful mechanism, utilizing a small terminase subunit (TerS) encoded by

630-554: A powerful staphylolytic enzyme. The production of these transformed SaPI2s, known as antibacterial drones (ABDs), is greatly enhanced by deleting the helper prophage’s t erS gene so that only ABD DNA is packaged. The ABDs cure experimental staph infections in mice and are being further developed for clinical use. To preclude the development of resistance, ABDs for potential clinical use will always contain at least two different antibacterial modules that act by different mechanisms. Listeria monocytogenes Listeria monocytogenes

693-401: A process that is different in the pathogen from that found in the host. For example, the antibiotics chloramphenicol and tetracyclin inhibit the bacterial ribosome but not the structurally different eukaryotic ribosome, so they exhibit selective toxicity. Antibiotics are used both in treating human disease and in intensive farming to promote animal growth. Both uses may be contributing to

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756-450: A role in determining the animal host specificity of S. aureus . The toxin and other accessory genes are expressed by the integrated and repressed SaPI genomes, as are the toxin genes of converting prophages. One of the original SaPIs, SaPI2, has been converted to a non-antibiotic therapeutic agent for the treatment of staphylococcal and listerial infections. This conversion involved the removal of all toxin and other virulence genes , and of

819-1260: A systemic inflammatory response resulting in massive vasodilation, shock, and death. Other bacteria are opportunistic pathogens and cause disease mainly in people with immunosuppression or cystic fibrosis . Examples of these opportunistic pathogens include Pseudomonas aeruginosa , Burkholderia cenocepacia , and Mycobacterium avium . Obligate intracellular parasites (e.g. Chlamydophila , Ehrlichia , Rickettsia ) are only able to grow and replicate inside other cells. Infections due to obligate intracellular bacteria may be asymptomatic , requiring an incubation period . Examples of obligate intracellular bacteria include Rickettsia prowazekii ( typhus ) and Rickettsia rickettsii , ( Rocky Mountain spotted fever ). Chlamydia are intracellular parasites. These pathogens can cause pneumonia or urinary tract infection and may be involved in coronary heart disease . Other groups of intracellular bacterial pathogens include Salmonella , Neisseria , Brucella , Mycobacterium , Nocardia , Listeria , Francisella , Legionella , and Yersinia pestis . These can exist intracellularly, but can exist outside host cells. Bacterial pathogens often cause infection in specific areas of

882-458: A variety of other tests. Total time to identification takes five to seven days, but the announcement of specific non-radiolabelled DNA probes should soon allow a simpler and faster confirmation of suspect isolates. Recombinant DNA technology may even permit two- to three-day positive analysis in the future. Currently, the FDA is collaborating in adapting its methodology to quantitate very low numbers of

945-430: A vector to deliver genes in vitro . Current transfection efficiency remains poor. One example of the successful use of L. monocytogenes in in vitro transfer technologies is in the delivery of gene therapies for cystic fibrosis cases. Listeria monocytogenes is being investigated as a cancer immunotherapy for several types of cancer. A live attenuated Listeria monocytogenes cancer vaccine , ADXS11-001 ,

1008-520: Is a Gram-positive bacterium , in the phylum Bacillota . Its ability to grow at temperatures as low as 0 °C permits multiplication at typical refrigeration temperatures, greatly increasing its ability to evade control in human foodstuffs. Motile via flagella at 30 °C and below, but usually not at 37 °C, L. monocytogenes can instead move within eukaryotic cells by explosive polymerization of actin filaments (known as comet tails or actin rockets). Once Listeria monocytogenes enters

1071-781: Is important to differentiate infection and colonization , which is when the bacteria are causing little or no harm. Caused by Mycobacterium tuberculosis bacteria, one of the diseases with the highest disease burden is tuberculosis , which killed 1.4 million people in 2019, mostly in sub-Saharan Africa . Pathogenic bacteria contribute to other globally important diseases, such as pneumonia , which can be caused by bacteria such as Staphylococcus , Streptococcus and Pseudomonas , and foodborne illnesses , which can be caused by bacteria such as Shigella , Campylobacter , and Salmonella . Pathogenic bacteria also cause infections such as tetanus , typhoid fever , diphtheria , syphilis , and leprosy . Pathogenic bacteria are also

1134-420: Is necessary for repair of DNA damages caused by bile salts . Pathogenic bacteria Pathogenic bacteria are bacteria that can cause disease . This article focuses on the bacteria that are pathogenic to humans. Most species of bacteria are harmless and are often beneficial but others can cause infectious diseases . The number of these pathogenic species in humans is estimated to be fewer than

1197-700: Is now widely recognized as an important hazard in the food industry. Invasive infection by L. monocytogenes causes the disease listeriosis. When the infection is not invasive, any illness as a consequence of infection is termed febrile gastroenteritis. The manifestations of listeriosis include sepsis, meningitis (or meningoencephalitis ), encephalitis , corneal ulcer, pneumonia, myocarditis, and intrauterine or cervical infections in pregnant women, which may result in spontaneous abortion (second to third trimester) or stillbirth . Surviving neonates of fetomaternal listeriosis may suffer granulomatosis infantiseptica — pyogenic granulomas distributed over

1260-655: Is quite hardy and resists the deleterious effects of freezing, drying, and heat remarkably well for a bacterium that does not form spores. Most Listeria monocytogenes strains are pathogenic to some degree. Listeria monocytogenes has been associated with such foods as raw milk , pasteurized fluid milk, cheeses (particularly soft-ripened varieties), hard-boiled eggs, ice cream , raw vegetables , fermented raw-meat sausages , raw and cooked poultry , raw meats (of all types), and raw and smoked fish . Most bacteria can survive near freezing temperatures, but cannot absorb nutrients, grow or replicate; however, L. monocytogenes has

1323-618: Is the species of pathogenic bacteria that causes the infection listeriosis . It is a facultative anaerobic bacterium, capable of surviving in the presence or absence of oxygen. It can grow and reproduce inside the host's cells and is one of the most virulent foodborne pathogens. Twenty to thirty percent of foodborne listeriosis infections in high-risk individuals may be fatal. In the European Union , listeriosis continues an upward trend that began in 2008, causing 2,161 confirmed cases and 210 reported deaths in 2014, 16% more than in 2013. In

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1386-424: Is the third most common cause of meningitis in newborns. Listeria monocytogenes can infect the brain, spinal-cord membranes and bloodstream of the host through the ingestion of contaminated food such as unpasteurized dairy or raw foods. L. monocytogenes is a Gram-positive , non- spore-forming , motile, facultatively anaerobic, rod-shaped bacterium. It is catalase -positive and oxidase -negative, and expresses

1449-400: Is to exploit the junction-forming apparatus of the host into internalizing the bacterium. L. monocytogenes can also invade phagocytic cells (e.g., macrophages ), but requires only internalins for invasion of nonphagocytic cells. Following internalization, the bacterium must escape from the vacuole/ phagosome before fusion with a lysosome can occur. Three main virulence factors that allow

1512-417: Is under development as a possible treatment for cervical carcinoma . Researchers have found Listeria monocytogenes in at least 37 mammalian species , both domesticated and feral, as well as in at least 17 species of birds and possibly in some species of fish and shellfish . Laboratories can isolate Listeria monocytogenes from soil , silage , and other environmental sources. Listeria monocytogenes

1575-431: Is unknown, but may range from a few days to 3 weeks. The onset time to gastrointestinal symptoms is unknown, but probably exceeds 12 hours. An early study suggested that L. monocytogenes is unique among Gram-positive bacteria in that it might possess lipopolysaccharide , which serves as an endotoxin . Later, it was found to not be a true endotoxin. Listeria cell walls consistently contain lipoteichoic acids , in which

1638-463: Is used in the identification of L. monocytogenes ; instillation of a culture into the conjunctival sac of a rabbit or guinea pig causes severe keratoconjunctivitis within 24 hours. Listeria species grow on media such as Mueller-Hinton agar. Identification is enhanced if the primary cultures are done on agar containing sheep blood, because the characteristic small zone of hemolysis can be observed around and under colonies. Isolation can be enhanced if

1701-688: The respiratory pathogen Haemophilus influenzae specialise in using other carbon sources such as lactate that are abundant in the human body Typically identification is done by growing the organism in a wide range of cultures which can take up to 48 hours. The growth is then visually or genomically identified. The cultured organism is then subjected to various assays to observe reactions to help further identify species and strain. Bacterial infections may be treated with antibiotics , which are classified as bacteriocidal if they kill bacteria or bacteriostatic if they just prevent bacterial growth. There are many types of antibiotics and each class inhibits

1764-459: The 1920s, it was not recognized as a significant cause of neonatal infection , sepsis , and meningitis until 1952 in East Germany . Listeriosis in adults was later associated with patients living with compromised immune systems, such as individuals taking immunosuppressant drugs and corticosteroids for malignancies or organ transplants, and those with HIV infection. L. monocytogenes

1827-457: The 1980s. L. monocytogenes was first described by E.G.D. Murray (Everitt George Dunne Murray) in 1924 based on six cases of sudden death in young rabbits, and published a description with his colleagues in 1926 . Murray referred to the organism as Bacterium monocytogenes before Harvey Pirie changed the genus name to Listeria in 1940. Although clinical descriptions of L. monocytogenes infection in both animals and humans were published in

1890-517: The EU, listeriosis mortality rates also are higher than those of other foodborne pathogens. Responsible for an estimated 1,600 illnesses and 260 deaths in the United States annually, listeriosis ranks third in total number of deaths among foodborne bacterial pathogens, with fatality rates exceeding even Salmonella spp. and Clostridium botulinum . Named for Joseph Lister , Listeria monocytogenes

1953-624: The SaPI in phage-like particles that are released in numbers approaching 10/ml by phage-induced lysis. A subset of SaPIs have acquired a cos site and use the phage’s TerS for packaging by the cos  mechanism.' The released SaPI particles infect other staphylococcal cells, injecting their DNA which integrates into a specific chromosomal attachment site of which there are 5 in S. aureus . SaPIs are ancestrally related to Siphoviridae and possess phage-related genes enabling their integration/excision, replication, and packaging. They lack structural phage proteins and lysis proteins and utilize those of

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2016-400: The ability to grow at temperatures as low as 0 °C which permits exponential multiplication in refrigerated foods. At refrigeration temperature, such as 4 °C, the amount of ferric iron can affect the growth of L. monocytogenes . The primary site of infection is the intestinal epithelium, where the bacteria invade nonphagocytic cells via the "zipper" mechanism. Uptake is stimulated by

2079-434: The bacteria are killed and they release their endotoxins. Exotoxins are secreted into the surrounding medium or released when the bacteria die and the cell wall breaks apart. An excessive or inappropriate immune response triggered by an infection may damage host cells. Iron is required for humans, as well as the growth of most bacteria. To obtain free iron, some pathogens secrete proteins called siderophores , which take

2142-429: The bacteria to use the host cell's actin polymerization machinery to polymerize the cytoskeleton to give a "boost" to the bacterial cell so it can move in the cell. The same mechanism also allows the bacteria to travel from cell to cell. L. monocytogenes can act as a saprophyte or a pathogen , depending on its environment. When this bacterium is present within a host organism, quorum sensing and other signals cause

2205-431: The bacterium to escape are listeriolysin O (LLO encoded by hly ) phospholipase A (encoded by plcA ) and phospholipase B ( plcB ). Secretion of LLO and PlcA disrupts the vacuolar membrane and allows the bacterium to escape into the cytoplasm, where it may proliferate. Once in the cytoplasm, L. monocytogenes exploits host actin for the second time. ActA proteins associated with the old bacterial cell pole (being

2268-416: The bacterium. The U.S. Food and Drug Administration (FDA) approved a cocktail of six bacteriophages from Intralytix, and a one-type phage product from EBI Food Safety designed to kill L. monocytogenes . Uses would potentially include spraying it on fruits and ready-to-eat meat such as sliced ham and turkey. Because L. monocytogenes is an intracellular bacterium, some studies have used this bacterium as

2331-426: The basis of their carriage of the gene for toxic shock syndrome toxin-1 and they are uniquely responsible for staphylococcal toxic shock. They also carry other superantigen toxins as well as other virulence factors among which is a set of genes enabling their host strains to coagulate farm animal blood plasma . These genes encode different alleles of a coagulase, the von Willebrand factor -binding protein, which has

2394-592: The binding of listerial internalins (Inl) to E-cadherin , a host cell adhesion factor, or Met ( c-Met ), hepatocyte growth factor. This binding activates certain Rho-GTPases, which subsequently bind and stabilize Wiskott–Aldrich syndrome protein (WASp). WASp can then bind the Arp2/3 complex and serve as an actin nucleation point. Subsequent actin polymerization creates a "phagocytic cup", an actin-based structure normally formed around foreign materials by phagocytes prior to endocytosis. The net effect of internalin binding

2457-578: The bloodstream. The infectious dose of L. monocytogenes varies with the strain and with the susceptibility of the victim. From cases contracted through raw or supposedly pasteurized milk, one may safely assume that, in susceptible persons, fewer than 1,000 total organisms may cause disease. L. monocytogenes may invade the gastrointestinal epithelium. Once the bacterium enters the host's monocytes , macrophages , or polymorphonuclear leukocytes , it becomes bloodborne (sepsis) and can grow. Its presence intracellularly in phagocytic cells also permits access to

2520-487: The body. Others are generalists. The symptoms of disease appear as pathogenic bacteria damage host tissues or interfere with their function. The bacteria can damage host cells directly or indirectly by provoking an immune response that inadvertently damages host cells, or by releasing toxins . Once pathogens attach to host cells, they can cause direct damage as the pathogens use the host cell for nutrients and produce waste products. For example, Streptococcus mutans ,

2583-419: The brain and probably transplacental migration to the fetus in pregnant women. This process is known as the "Trojan Horse mechanism". The pathogenesis of L. monocytogenes centers on its ability to survive and multiply in phagocytic host cells. It seems that Listeria originally evolved to invade membranes of the intestines, as an intracellular infection, and developed a chemical mechanism to do so. This involves

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2646-404: The capsid morphogenesis genes, and the addition, by cloning, of antibacterial genes including those encoding CRISPR/cas9 with spacers targeting conserved chromosomal genes. These cause a lethal double-stranded DNA cleavage in the target protospacer . Alternative cargos include CRISPR/dcas9 with spacers targeting and inhibiting genes that regulate bacterial virulence, or the gene for lysostaphin ,

2709-523: The cause of high infant mortality rates in developing countries . A GBD study estimated the global death rates from (33) bacterial pathogens, finding such infections contributed to one in 8 deaths (or ~7.7 million deaths), which could make it the second largest cause of death globally in 2019. Most pathogenic bacteria can be grown in cultures and identified by Gram stain and other methods. Bacteria grown in this way are often tested to find which antibiotics will be an effective treatment for

2772-424: The cell, L. monocytogenes rapidly acidifies the lumen of the vacuole formed around it during cell entry to activate listeriolysin O, a cholesterol-dependent cytolysin capable of disrupting the vacuolar membrane. This frees the pathogen and gives it access to the cytosol of the cell, where it continues its pathogenesis. Motility in the intracellular space is provided by actin assembly-inducing protein, which allows

2835-586: The genus Listeria , was reclassified into the new genus Jonesia . Both L. ivanovii and L. monocytogenes are pathogenic in mice, but only L. monocytogenes is consistently associated with human illness. The 13 serotypes of L. monocytogenes can cause disease, but more than 90% of human isolates belong to only three serotypes: 1/2a, 1/2b, and 4b. L. monocytogenes serotype 4b strains are responsible for 33 to 35% of sporadic human cases worldwide and for all major foodborne outbreaks in Europe and North America since

2898-440: The growth of many bacteria. The body has defence mechanisms that enable it to resist microbial invasion of its tissues and give it a natural immunity or innate resistance against many microorganisms . Pathogenic bacteria are specially adapted and endowed with mechanisms for overcoming the normal body defences, and can invade parts of the body, such as the blood, where bacteria are not normally found. Some pathogens invade only

2961-405: The helper phage , which they modify to form small capsids commensurate with their genomes. Their evolutionary divergence from an ancestral prophage has involved not only the loss of structural and lytic proteins, but also the development (or acquisition) of several different means of partially blocking reproduction of their helper phages. These phage interference functions are advantageous both to

3024-760: The host cytoplasm , multiple changes in bacterial metabolism and gene expression help to complete its metamorphosis from soil dweller to intracellular pathogen. Studies suggest that up to 10% of human gastrointestinal tracts may be colonized by L. monocytogenes . Nevertheless, clinical diseases due to L. monocytogenes are more frequently recognized by veterinarians , especially as meningoencephalitis in ruminants . See: listeriosis in animals . Due to its frequent pathogenicity , causing meningitis in newborns (acquired transvaginally), pregnant women are often advised not to eat soft cheeses such as Brie , Camembert , feta , and queso blanco fresco , which may be contaminated with and permit growth of L. monocytogenes . It

3087-411: The host cell walls. These host cells are generally M cells and Peyer's patches of the intestinal mucosa. Once attached to these cells, L. monocytogenes can translocate past the intestinal membrane and into the body. . Alternatively, losses of structural integrity (such as small lacerations) in the gastrointestinal epithelium could allow the microorganism to penetrate from the gastrointestinal tract to

3150-581: The host cell, as they (partially) block predation by exogenous phages, and to the SaPI, as they enable it to keep pace with helper phage reproduction. Unlike the CRISPRs , which simply destroy infecting phages and thus totally block phage-mediated horizontal gene transfer (HGT), the SaPIs  are major agents of phage–dependent HGT, as they only partially block phage reproduction and also package chromosomal fragments as well as their own genomes. SaPIs were discovered on

3213-399: The host, induces the expression of virulence genes in L. monocytogenes . Little is known about how this bacterium switches between acting as a saprophyte and a pathogen; however, several noncoding RNAs are thought to be required to induce this change. L. monocytogenes has three distinct lineages, with differing evolutionary histories and pathogenic potentials. Lineage I strains contain

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3276-482: The infection. For hitherto unknown pathogens, Koch's postulates are the standard to establish a causative relationship between a microbe and a disease. Each species has specific effect and causes symptoms in people who are infected. Some people who are infected with a pathogenic bacteria do not have symptoms. Immunocompromised individuals are more susceptible to pathogenic bacteria. Some pathogenic bacteria cause disease under certain conditions, such as entry through

3339-455: The iron away from iron-transport proteins by binding to the iron even more tightly. Once the iron-siderophore complex is formed, it is taken up by siderophore receptors on the bacterial surface and then that iron is brought into the bacterium. Bacterial pathogens also require access to carbon and energy sources for growth. To avoid competition with host cells for glucose which is the main energy source used by human cells, many pathogens including

3402-402: The majority of human clinical isolates and all human epidemic clones, but are underrepresented in animal clinical isolates. Lineage II strains are overrepresented in animal cases and underrepresented in human clinical cases, and are more prevalent in environmental and food samples . Lineage III isolates are very rare, but significantly more common in animal than human isolates. The Anton test

3465-726: The order Bacillales, which also includes Bacillus and Staphylococcus . Listeria currently contains 27 species: Listeria aquatica, Listeria booriae, Listeria cornellensis, Listeria cossartiae, Listeria costaricensis, Listeria farberi, Listeria fleischmannii, Listeria floridensis, Listeria goaensis, Listeria grandensis, Listeria grayi, Listeria immobilis, Listeria innocua, Listeria ivanovii, Listeria marthii, Listeria monocytogenes, Listeria murrayi, Listeria newyorkensis, Listeria portnoyi, Listeria riparia, Listeria rocourtiae, Listeria rustica, Listeria seeligeri, Listeria thailandensis, Listeria valentina, Listeria weihenstephanensis, Listeria welshimeri . L. denitrificans , previously thought to be part of

3528-671: The organisms in foods. When listeric meningitis occurs, the overall mortality may reach 70%, from sepsis 50%, and from perinatal/neonatal infections greater than 80%. In infections during pregnancy, the mother usually survives. Reports of successful treatment with parenteral penicillin or ampicillin exist. Trimethoprim-sulfamethoxazole has been shown effective in patients allergic to penicillin. A bacteriophage, Listeria phage P100 , has been proposed as food additive to control L. monocytogenes . Bacteriophage treatments have been developed by several companies. EBI Food Safety and Intralytix both have products suitable for treatment of

3591-572: The rapid development of antibiotic resistance in bacterial populations. Phage therapy , using bacteriophages can also be used to treat certain bacterial infections. Infections can be prevented by antiseptic measures such as sterilizing the skin prior to piercing it with the needle of a syringe and by proper care of indwelling catheters. Surgical and dental instruments are also sterilized to prevent infection by bacteria. Disinfectants such as bleach are used to kill bacteria or other pathogens on surfaces to prevent contamination and further reduce

3654-436: The skin via a cut, through sexual activity or through compromised immune function. Some species of Streptococcus and Staphylococcus are part of the normal skin microbiota and typically reside on healthy skin or in the nasopharyngeal region. Yet these species can potentially initiate skin infections. Streptococcal infections include sepsis , pneumonia , and meningitis . These infections can become serious creating

3717-478: The surface epithelium , skin or mucous membrane, but many travel more deeply, spreading through the tissues and disseminating by the lymphatic and blood streams . In some rare cases a pathogenic microbe can infect an entirely healthy person, but infection usually occurs only if the body's defence mechanisms are damaged by some local trauma or an underlying debilitating disease, such as wounding, intoxication , chilling , fatigue, and malnutrition . In many cases, it

3780-614: The tissue is kept at 4 °C for some days before inoculation into bacteriologic media. The organism is a facultative anaerobe and is catalase-positive and motile. Listeria produces acid, but not gas, when fermenting a variety of carbohydrates. The motility at room temperature and hemolysin production are primary findings that help differentiate Listeria from Corynebacterium . The methods for analysis of food are complex and time-consuming. The present U.S. FDA method, revised in September 1990, requires 24 and 48 hours of enrichment, followed by

3843-487: The up-regulation of several virulence genes. Depending on the location of the bacterium within the host organism, different activators up-regulate the virulence genes. SigB, an alternative sigma factor , up-regulates Vir genes in the intestines, whereas PrfA up-regulates gene expression when the bacterium is present in blood. L. monocytogenes also senses the entry to host by examining available nutrient sources. For example L-glutamine , an abundant nitrogen source in

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3906-478: The whole body — and may suffer from physical retardation. Influenza -like symptoms, including persistent fever, usually precede the onset of the aforementioned disorders. Gastrointestinal symptoms, such as nausea, vomiting, and diarrhea , may precede more serious forms of listeriosis or may be the only symptoms expressed. Gastrointestinal symptoms were epidemiologically associated with use of antacids or cimetidine . The onset time to serious forms of listeriosis

3969-505: Was not identified as a cause of foodborne illness until 1981, however. An outbreak of listeriosis in Halifax , Nova Scotia , involving 41 cases and 18 deaths, mostly in pregnant women and neonates, was epidemiologically linked to the consumption of coleslaw containing cabbage that had been contaminated with L. monocytogenes -contaminated sheep manure. Since then, a number of cases of foodborne listeriosis have been reported, and L. monocytogenes

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