Public Health Risks of Seafood Associated Bacterial Intoxication: An Overview

TABLECREATED

Table 4: Bacterial toxins and their actions causing intoxication.

Bacillus cereus intoxication

Characteristics of etiological agent: Bacillus cereus species are Gram positive, motile, facultative anaerobic, ubiquitous bacteria, characterized by their ability to form resistant spore coats. The sizes vary from 1.0–1.2μm by 3.0–5.0μm. There are about 48 known species in the genus Bacillus but only B. anthracis and B. cereus are associated with food poisoning in human. The food poisoning is a result of ingesting heat-stable enterotoxins. These are mesophilic bacteria that produce heat-resistant endosopores and grow between 10°-50°C and with an optimum temperature of 35°C and 40°C [12,13]. Bacillus cereus is commonly present in food production environments by virtue of its highly adhesive endospores, which spread to all kinds of foods. B. cereus toxicity ranges from the strains used as probiotics for humans [14] to highly toxic strains reported for food-related intoxications [15-17]. The bacteria cause two types of gastrointestinal disease, the diarrheal and the emetic syndromes, which are caused by very different types of toxins.

The emetic syndrome is caused by emetic toxin produced by the bacteria during the growth phase in the food. The diarrheal syndrome is caused by diarrheal toxins produced during growth of the bacteria in the small intestine [18].

Public health effects: Two distinct foodborne disease types, emetic and diarrheal, are associated with B. cereus. Both are generally mild and self-limiting. The symptoms of B. cereus diarrheal type food poisoning are similar to those of Clostridium perfringens food poisoning. The onset of watery diarrhea, abdominal cramps, and pain occurs 6-15 hours after consumption of contaminated food. Nausea may accompany diarrhea, but vomiting rarely occurs. Symptoms persist for 24 hours in most instances. The emetic type of food poisoning is characterized by nausea and vomiting within minutes to 6 hours after consumption of contaminated foods. Occasionally, abdominal cramps and diarrhea may also occur. Duration of symptoms is generally less than 24 hours. The symptoms of this type of food poisoning are similar to those caused by Staphylococcus aureus foodborne intoxication.

Risky seafood: B. cereus is commonly associated in seafoods like squid and prawn. The bacillus spores could sporulate because of the incorrect chilling after finishing the pasteurizing process (unpublished results).

Types of intoxications: B. cereus associated foodborne illness occurs as two distinct intoxication syndromes: emetic and diarrheal.

I. Emetic syndrome: Incubation: 0.5-6 hours [19,20].

Symptoms: Nausea, vomiting, malaise, occasionally followed by diarrhea.

II. Diarrheal syndrome: Incubation: 8-16 hours [21].

Symptoms: Abdominal pain, watery diarrhea, occasional nausea.

Causative toxins: The organism produces the following enterotoxins which are involved in a food borne intoxication: Two diarrheal enterotoxins: - hemolysin BL enterotoxin, non-hemolytic enterotoxin, and Emetic toxin. The emetic toxin causes emesis (vomiting) which is resistant to heat, pH and proteolysis but not antigenic [22]. The emetic toxin has been named cereulide, and consists of a ring structure of three repeats of four amino and/ or Oxy acids: [d-O-Leu-d-Ala-l-O-Val-l-Val]. This ring structure (dodecadepsipeptide) has a molecular mass of 1.2 kDa, and is chemically closely related to the potassium ionophore valinomycin [23].

Three types of enterotoxins associate with the diarrheal form of the disease. These are: the three component Enterotoxin Haemolysin BL (HBL), the three component Non-Haemolytic Enterotoxin (NHE) and the single component enterotoxin cytotoxin K. After consumption of food containing B. cereus, the enterotoxins are released into the small intestine during vegetative growth following spore germination, and by any surviving vegetative cells [24].

Toxicity: The lethal dose for enterotoxin (causing emetic syndrome) produced by B. cereusis 15 mg i.v. in mice [25]. The infective dose of B. cereus ranges from 104 to 1011 cells per gram of food [26].

Incubation period: The diarrheal form of B. cereus has an onset period of 8-16 h while the emetic form has an onset period of 1-6 hours. Recovery is usually complete in 24 hours [27,28].

Signs and symptoms: There are two types of illnesses associated with B. cereus. The most common is a diarrheal illness caused by a heat-labile toxin, accompanied by abdominal pain. An incubation period of 4-16 hours is followed by symptoms lasting 12-24 hours. The second type of disease state is an emetic illness caused by a heatstable toxin, often associated with ingestion of rice that is not properly refrigerated after cooking. This illness is characterized by vomiting and nausea that usually occur within 1-5 hours upon ingestion of the contaminated food. This is sometimes referred as an intoxicant.

Pathogenesis: B.cereus causes self-limiting (24-48 hours) food-poisoning syndromes (a diarrheal type and an emetic type), opportunistic infections and is associated with clinical infections. The diarrheal form of B. cereus food poisoning is characterized by abdominal cramps, watery diarrhea, rectal tenesmus, and, occasionally, fever and vomiting. The emetic form of B. cereus food poisoning is characterized by nausea, vomiting, and malaise, occasionally with diarrhea [28]. B. cereus can cause wound infections, bacteremia, septicemia, meningitis, pneumonia, central nervous system infections, endocarditis, pericarditis, respiratory infections, and peripheral [27,29].

Infection in immunocompromised individuals can be lifethreatening [30]. B. Cereus strains which harbor a plasmid bearing B. anthrax-like virulence factors can cause severe pneumonia in immunocompetent people [31]. Modes of transmission: The primary mode of transmission is via the ingestion of B. cereus contaminated food [32,33].

It forms spores and spreads easily [34]. In hospitals, B. cereus can be transmitted via contaminated linen [35,36].

Morbidity and mortality: Illness caused by B. cereus usually lasts less than 24 h. But in a few patients symptoms may last for a longer period [37,38].

Laboratory diagnosis: Confirmation of B. cereus as the etiologic agent in a foodborne outbreak requires either (1) Isolation of strains of the same serotype from the suspected food (≥ 105 B. cereus organisms per gram from food) (CDC, 1994) and feces or vomitus of the patient,

(2) Isolation of large numbers of a B. cereus serotype known to cause foodborne illness from the suspect food or from the feces or vomitus of the patient, or

(3) Isolation of B. cereus from suspect foods and determining their enterotoxigenicity by serological (diarrheal toxin) or biological (diarrheal and emetic) tests. The rapid onset time to symptoms in the emetic form of disease, coupled with some good evidence, is often sufficient to diagnose this type of food poisoning. MALDI-TOF MS has shown to be a competent tool for the rapid and accurate identification of B. cereus with reference to strain id: ATCC 14893 [33].

Treatment: Medication such as antibiotics may be prescribed as these are effective against bacterial infections. However, some strains of bacteria have developed a resistance to them, which cancels out their effectiveness. Vancomycin hydrochloride in combination with an aminoglycoside ensures more consistent antibiotic coverage of Bacillus species ocular infections. Other drugs that are highly active and likely to be bactericidal include imipenem, ciprofloxacin and gentamicin. Tetracycline, chloramphenicol, clindamycin and erythromycin have activity against Bacillus species.

Clostridium botulinum intoxications

Characteristics of etiological agent: Clostridium botulinum is Gram positive (Gram variable) anaerobic heat resistant spore bearing, non-capsulated bacilli that is widely distributed in soil, sediments of lakes, ponds and sea. They are highly pleomorphic and usually 5μM×1μm in size. Seven different strains of the bacteria (A-G) are categorized based on serologic specificity and toxins. Most reported human outbreaks are associated with fish and seafood products. Botulism in animals is caused mainly due to type C and D and rarely type A and B. All toxin-producing strains have placed under one of four groups; I, II, III and IV. The group I contains the proteolytics, group II the non proteolytic and group IV serological type G. Cl. botulinum type E is most common in seafood and its products is of major concern because it grows at very low temperatures 3°–5°C and produces little noticeable evidence of spoilage. Group III consists of type C and D [39].

Publichealth effects: Cl.botulinumproduces one of the most highly toxic substances. Seven toxin types (A, B, C, D, E, F, and G) are responsible for botulism symptoms botulinum toxin type A, a neurotoxin with a high fatality, is about 1,000 times more toxic than tetanus toxin. Types A, B, E, and F are mainly involved in botulism in humans, while types C and D are mainly involved in animals [40].

Clostridium botulinum bacterium forms small spores that are resistant to drought and heat and capable of growing into new organisms. Under conditions with little oxygen (anaerobic), botulinum spores can germinate, resulting in the growth of bacteria and the production of the toxin.

Botulism is not transmitted from person to person. Botulism develops if a person ingests the toxin (or rarely, if the toxin is inhaled or injected) or if the organism grows in the intestines or wounds and toxin is released.

Risky Seafood: Many of the seafood-associated cases are caused by Cl.botulinum toxin type E as a result of eating fermented salmon heads, salmon eggs, and blubber and skin from marine animals (muktuk) [41]. C. botulinum type E spores are commonly found in fish and aquatic animals [38]. They can also be found inshellfish, fish intestines and gills and in mud from the sea. They grow and form toxin at a much lower temperature than the other types; they can grow at 5°C in fish products [42-44].

Types of intoxications:

I. Food-borne botulism is usually spread by consuming food contaminated with the botulism toxin or spores. The genus Clostridium produces more protein toxins than other genera of bacteria [45].

II. Wound botulism occurs when the spores of Clostridum botulinum get into an open wound and are able to reproduce. It is a very rare condition. The toxin is produced at the site of infection and is absorbed later [37].

III. Infant botulism occurs when infants ingest Clostridum botulinum spores.The spores get deposited in the gut and later produce toxin.This is considered as toxicoinfection which usually occur in infants under 6 months. Honey and corn syrup are the food sources of infant botulism. Botulinum toxin can also be produced by Cl. butyricum, Cl. barati, and Cl. argentiniense, causing infant botulism [46].

IV. Adult intestinal colonization botulism is another form of botulism. It is similar to infant botulism, but occurs in older children and adults with bowel abnormalities such as colitis, intestinal bypass procedures.

Causative toxins: Cl.botulinum produces a very powerful endotoxin that is responsible for its pathogenicity.The toxin differs from other endotoxins in that it is not released during the life of the organism.It is produced intracellularly and appears in the medium after death, andanalysis of the cell.

The toxin has been isolated as a pure crystalline protein, which can be considered the most toxic substance known. It is a neurotoxin and acts slowly. It has a molecular weight of MW70, 000 and lethal dose for humans is probably 1-2μg [47]. The lethal dose is far below that is required to induce an antibody response.

Toxicity: The lethal doses (in mice) for Cl.botulinum neurotoxins Type A, B, E and F causing diseases in human are1.2 ng i.p. [48], 0.5 ng [49], 1.1 ng [50] and 2.5 ng i.v. [51], respectively.

Incubation period: For Foodborne botulism, it is typically 12-36 hours after toxin ingestion, but in rare cases as early as 6 hours or as late as 10 days after ingesting toxin.

Signs and symptoms: Botulism is a serious illness that causes paralysis or muscle weakness, including weakness in muscles needed for breathing. Signs and symptoms of foodborne botulism generally begin between 12 and 36 hours after ingestion of food. But, the start of symptoms can range from a few hours to several days, depending on the amount of toxin ingested. The toxin is produced at the site of infection.

The manifestations are nausea, vomiting and abdominal cramps, blurred or double vision, muscle weakness, drooping eyelids, difficulty swallowing, lethargy, poor feeding, pooled oral secretion and loss of head control. These symptoms appear when the toxin interrupts nerve impulses to the muscles, which paralyzes the muscles. If untreated, paralysis may lead to involve the hands, legs, and muscles of the respiratory tract.Death normally results from respiratory failure.

Pathogenesis: Cl. botulinum secretes one of the most powerful biological toxins. Its pathogenicity is due to the action of the toxin.The spores of Cl.botulinum are heat and acid resistant so they can easily lie dormant in most environments for long periods of time. If the spores are not killed, they will germinate in improperly cooked food and produce toxin.If the toxin is once ingested, it travels to the intestinal tract.It is able to pass through the high acidity of the stomach without any complications. The neurotoxin is not inactivated by gastric acid or proteolytic enzymes. The toxin goes to the peripheral nervous system through the blood and inhibits motor neurons. Once the neuron is compromised by the toxin the cell cannot secrete acetylcholine. As a result, the axon is impaired and the nerve is unable to function.The insertion of the neurotoxin is referred to as “intoxication” rather than an “infection” in the cell. In some cases, the toxin can spread to the central nervous system, but it is very rare.

Among the three types of botulism found (foodborne botulism,wound botulism and infant botulism), foodborne botulism is due to ingestion of pre-formed toxin. Human disease is usually caused by type A,B,E and very rarely F.Type C and D are usually associated with outbreaks in cattle and wild fowl.

Modes of transmission: Ingestion of toxin pre-formed in the food. This may occur when raw or improperly processed foods are stored in low oxygen conditions that allow growth of the organism. Most outbreaks occur due to fault in the preservation process of (e.g. Canning, fermentation, curing, smoking)

Examples of foods involved include vegetables (e.g. Fish and seafood products) (type E). Honey is a common vehicle of transmission of infant botulism.

Morbidity and mortality: Duration of botulism is long term and sometimes it may lead to death also [52].

Laboratory diagnosis: Diagnosis may be confirmed by the identification and isolation of the bacillus or the toxin in the food. Gram positive bacilli may be identified easily by the smear from the food. Typing is done by passive protection with type specific antitoxin. The toxin may sometime demonstrable from the patient’s blood.Serological detection of a specific toxin remains the essential procedure for diagnosis in man and animals [53].

A retrospective diagnosis may be made by detection of antitoxin in patient’s blood serum.

In recent years new techniques like MALDI-TOF MS have been developed for the identification of this species (Clostridium botulinum with reference to strain id: ATCC 19397) from seafood samples [33].

Treatment: Gas gangrene is treated with antibiotics and surgical debridement of gangrenous wounds. Tetanus and botulism require antibiotics, antitoxins and additional life-supporting measures. Antibiotic-associated diarrhea is treated by the withdrawal of antibiotics from patients and the use of metronidazole if necessary. Cl. perfringens food-poisoning is self limiting. Oral rehydration therapy is used in case of acute food poisoning syndromes, and antibiotics are seldom required.

Clostridium perfringens intoxication

Characteristics of etiological agent: Clostridium perfringens is a plump, Gram positive, pleomorphic, capsulated nonmotile bacillus with straight parallel sides and rounded ends and spore forming. It is about 4-6μm×1μm in size usually found singly or in chains. Spores are central or subterminal.

Among all the species of Clostridium, Cl.perfringens (Cp) is the most widely distributed pathogen [54]. This species can produce up to 17 different types of toxins.Four of these, alpha, beta, epsilon, and iota, are responsible for the tissue lesions and the host’s death [55-58] and are considered to be major toxins.

Public health effects: This organism was isolated from 2-3% of the seafood samples from SanFrancisco and Seattle retail markets in USA [59]. The way that Cl. perfringens enters the body determines the possible influence it will have about the person. A person can become infected with Clostridium perfringens from eating contaminated food. Once in the intestines, these bacteria produce toxins. It is the toxins that cause human illness. Epidemiological evidence suggests that Cl.perfringens plays an important role in the pathogenesis of both food-borne and non-food-borne human gastrointestinal (GI) illnesses.

Causative toxins: On the basis of type of toxin produced, Cl.perfringens strains are classified into five types A,B,C,D and E [60].

Cl.perfringens is one of the most prolific of toxin producing bacteria. Among these toxins, four major toxins (alpha, beta, epsilon, iota) are responsible for the pathogenicity.

I. Alpha toxin: The alpha toxin, found in type A strains of Cl. Perfringens causes gas gangrene and also hemolysis in infected species. For the mechanism of the alpha toxin of Cl. perfringens, requires zinc for activation, after which the toxin binds to the surface of the host cell, whereby a series of pathways lead to increased permeability in blood vessels [61].

II. Beta toxin: This lethal toxin is found in Cl. perfringens type B and type C strains. This toxin also results in necrosis by way of increased blood pressure, which is brought on by the presence of catecholiamine. Beta toxin is vulnerable to being degraded by proteolytic enzymes.The mechanism of action is still unknown, but it is clear that endogenous levels of trypsin in the intestinal tract of humans and mammals act as a defense against beta toxin infection [62].

III. Epsilon toxin: This toxin is produced by type B and type D strains of Cl. perfringens. It is isolated from animals, particularly sheep, goats, and cattle, but rarely from humans. Similar to the other toxins, epsilon toxin creates pores in tissues, which can result in leaked potassium ions and fluid leakage, which leads to greater complications, giving way to the symptoms associated with Cl. Perfringens infection [63].

IV. Iota toxin: The iota toxin is produced solely by type E strain of Cl. perfringens and is known as an AB toxin.In these types of toxins, one of the domains, A is usually the active portion, while the other domain, B, is the part of the toxin that binds to a receptorsite on the membrane of the host cell [64]. The iota toxin can cause tissue death in infected individuals.

Toxicity: The lethal doses (in mice) of Perfringens enterotoxin Alpha, Beta and Delta are 3μg i.v. [65]; <400ng [66] and 5μg i.v. [67], respectively.

Incubation period:Food Poisoning: 8-24 hours,Gas Gangrene: 1-4 days after the injury, but may also start within 10 hours.

Signs and symptoms: Cl. perfringens are found in soil, in the stool, and in the intestines of healthy people and of animals. Packages of uncooked meat or poultry, preserved fish, sea food frequently contains this species. Spores of Clostridium survive cooking. When the temperature drops back to less than about 140 degrees Fahrenheit, the spores germinate and begin to multiply.Symptoms are caused by a toxin produced by the multiplying bacteria.

The onset of Clostridium food poisoning is sudden, watery diarrhea accompanied by abdominal pain that may range from mild to severe. It does not spread directly from person to person, but someone with dirty hands can introduce Clostridium into food, where it will germinate and multiply.

Pathogenesis: Cl.perfringens produces the following human diseases:

I. Food poisoning: Some strains of typeA can produce food poisoning. They are characterized by having heat resistant spores. Stomach pain followed by diarrhea may begin after having contaminated food.

II. Gas gangrene: Cl.perfringens type A is mainly responsible for causing gas gangrene. Gas gangrene is also known as Clostridial myonecrosis. The alpha toxin produced by Cl.perfringens destroys tissue and generates gas. The alpha-toxin enters into the plasma membrane of the cells and produces holes in the plasma membrane which disrupts the normal cell function and the tissue will begin to decompose from the inside out.All clostridial wound infection does not lead to gas gangrene rather to wound infection. But when the muscle tissues are invaded it may lead to producing gas gangrene.

III. Necrotising enteritis: Cl.Perfringens type C are mainly responsible for causing this severe and often fatal necrotizing enteritis.This condition is rare, but sporadic cases have been reported from different countries.This disease is said to be caused by the beta toxin characterized by the sudden onset of acute inflammation and necrosis of intestinal mucosa resulting in bloody diarrhea, abdominal cramps and shock [68].

IV. Billiary tract infection: Cl.perfringens has been reported to produces two very rare infection of the biliary tract-emphysyematous cholecystitis and postcholecystectomy septicaemia [69].

Modes of transmission: There are many direct and indirect methods by means of which Cl.perfringens can cause infection

Food Poisoning: Food-borne illness acquired by ingestion of large number of Cl. perfringens vegetative cells present in the food [70,71]. Food sources are usually cooked meat, vegetables, fish and other seafood which have been stored at ambient temperatures for a long time after cooking.

Gas Gangrene/ Anaerobic Cellulitis: Infection can occur through contamination of wounds (fractures, bullet wounds) with dirt or any foreign material contaminated with Cl. perfringens.

Morbidity and mortality: Most people who suffer from Clostridium perfringens intoxication are uncomfortable, but death is not common. People usually recover in 24 hours or less. It is unknown how deadly a release of purified toxin would be, but any effects will be related to the strain of bacteria used and the amount taken into the body.

Laboratory diagnosis: Cl. perfringens can be diagnosed by Nagler’s reaction in which the suspect organism is cultured on an egg yolk medium plate. One side of the plate contains anti-alphatoxin, while the other side does not. A streak of suspect organism is placed through both sides. An area of turbidity will form around the side that does not have the anti-alpha-toxin, indicating uninhibited lecithinaseactivity [72].

The Cl. perfringens can be identified by MALDI-TOF MS by taking some reference strains of the same species [33].

Treatment: Laboratories diagnose Cl. perfringens food poisoning by detecting a type of bacterial toxin in feces or by tests to determine the number of bacteria in the feces. Oral rehydration or, in severe cases, intravenous fluids and electrolyte replacement can be used to prevent or treat dehydration. Antibiotics are not recommended.

Staphylococcus aureus intoxication

Characteristics of etiological agent: Staphylococcus aureusisGram positive, non-motile, facultative anaerobic, spherical non-sporing cocci, approximately 1μm in diameter, arranged in grape-like clusters. This cluster formation is due to cell division occurring in three plains with daughter cells lying in close proximity. S. aureus is one of the main causes of hospital and communityacquired infections, which can result in serious consequences [73]. Nosocomial S. aureus infections affect the bloodstream, skin, soft tissues and lower respiratory tracts.It can be a cause of central venous catheter-associated bacteremia. S. aureus is often responsible for toxin-mediated diseases, such as Toxic Shock Syndrome (TSS), scalded skin syndrome and Staphylococcal Foodborne Diseases (SFD) like Staphyloenterotoxocosis or Staphyloenterotoxemia caused by enterotoxins.

Public health effects: S. aureus have long been recognized as one of the most important bacteria that cause disease in humans. Staphylococcus aureus is an important pathogen due to a combination of toxin-mediated virulence, invasiveness, and antibiotic resistance. This bacterium is a significant cause of nosocomial infections, as well as community-acquired diseases. The spectrum of staphylococcal infections ranges from pimples and furuncles to toxic shock syndrome and sepsis. On the other hand, some infections, such as staphylococcal food poisoning, rely on one single type of virulence factor: the Staphylococcal enterotoxins. The symptoms of staphylococcal food poisoning are abdominal cramps, nausea, vomiting, sometimes followed by diarrhea (never diarrhea alone). The onset of symptoms is rapid (from 30 min to 8 hours) and usually spontaneous remission is observed after 24 hours.

Risky seafood: Oysters, Frozen marine shrimps are found to begood sources of S. aureus [74].

Causative toxins: Many S. aureus virulence factors can be described as toxins. Toxins are usually defined as poisonous substances. Staphylococcus aureus produces a wide variety of exoproteins that contribute to its ability to colonize and cause disease in mammalian hosts.

This organism produces 5 serologically different enterotoxins that are involved in foodborne intoxication. They are:

1. Staphylococcal enterotoxinA(SEA)

2. Staphylococcal enterotoxinB(SEB)

3. Staphylococcal enterotoxinC(SEC)

4. Staphylococcal enterotoxinD(SED)

5. Staphylococcal enterotoxinE(SEE)

Nearly all strains secrete a group of enzymes and cytotoxins which includes four hemolysins (alpha, beta, gamma, and delta), nucleases, proteases, lipases, hyaluronidase and collagenase.

I. Membrane damaging toxins: These toxins cause pore formation in the membrane, leading to the efflux of vital molecules and metabolites, and therefore are cytolytic.

II. Toxins that interfere with the receptor: S. aureus produces a variety of cytolytic toxins. Most are infamous for lysing red and/or white blood cells. Those that lyse red blood cells are called hemolysins. Alpha-toxin is probably the best-known toxin of S. aureus independently, alpha-toxin also causes apoptosis in human monocytes, T and B cells [75].

III. Secreted enzymes: These toxins degrade host molecules or affect important host defense mechanisms.

Enterotoxins are secreted toxins of ~ 20 to 30 kD that interfere with intestinal function and typically cause emesis and diarrhea. The most famous S. aureus superantigen, the 22-kD Toxic Shock Syndrome toxin (TSST), causes toxic shock syndrome (TSS) by stimulating release of IL-1, IL-2, TNF-a, and other cytokines (Todd, 1988).

S. aureus beta-toxin is a sphingomyelinase of type C that degrades the sphingomyelin present on the surface of a variety of host cells, leading to cell lysis.

Toxicity: The lethal doses (in mice) of S. aureusenterotoxin A and Alpha toxin are 40-60 ng i.v. [76,77] and 110 ng i.v. [78], respectively.

Incubation period: Onset of symptoms after consuming contaminated food is usually 30 minutes to 8 hours [79]. Colonies of S. aureus can be carried for an undetermined amount of time; some individuals may carry it chronically, and some may carry it intermittently [80].

Signs and symptoms: S.aureus may cause disease due to the production of toxins. Boils, impetigo, food poisoning, cellulitis, and toxic shock syndrome are all examples of diseases that can be caused by this species.

Symptoms and signs of a localized staph infection include a collection of pus, such as a boil, furuncle, or abscess. The area is typically tender or painful and may be reddened and swollen. Staphylococcal food poisoning is a gastrointestinal illness. It is caused by eating foods contaminated with toxins produced by Staphylococcus aureus. Food workers who carry Staphylococcus and then handle food without washing their hands contaminate foods by direct contact.

Staphylococcal toxins are fast acting, sometimes causing illness in as little as 30 minutes after eating contaminated foods, but symptoms usually develop within three to six hours. Patients typically experience several of the following: nausea, retching, vomiting, stomach cramps, and diarrhea within 24 to 48 hours. The illness cannot be passed to other people and it typically lasts for one day, but sometimes it can last up to three days.

Pathogenesis: S.aureus expresses many cell surface-associated and extracellular proteins that are potential virulence factors. Staphylococcal diseases may be classified as cutaneous and deep infections, acute toxemia including food poisoning, exfoliative diseases and ‘Toxic Shock Syndrome’.

The commonest deep infection is acute osteomyelitis, the majority of which is caused by Staphylococcus spp.Staphylococcal food poisoning results when food contaminated with enterotoxin produced by Staphylococcus aureus. The types of food generally responsible are meat, fish, milk and milk products.After consumption of food, the organisms grow and produce enterotoxin resulting diarrhea and vomiting within 6 hours.

Stripping of the superficial layers of the skin from the underlying tissues by the exfoliative toxin is the cause for exfoliative syndrome.

The Toxic Shock Syndrome is a multisystem dysfunction (Todd, 1988) caused by S.aureus which exhibits symptoms like vomiting, fever, diarrhea, and hypotension.TSST-1 is responsible for most cases of Toxic Shock Syndrome.

Modes of transmission: Staphylococcal food poisoning occurs when food is consumed that contains Staphylococcal enterotoxin produced by S. aureus. Food handlers carrying enterotoxinproducing S. aureus in their noses or on their hands are regarded as the main source of food contamination via direct contact or through respiratory secretions [81].

Morbidity and mortality: Staphylococcal food poisoning is a very common disease whose actual incidence is probably underestimated for many reasons, which includemisdiagnosis, unreported minor outbreaks, improper sample collection and improper laboratory examination [82].

Laboratory diagnosis: Direct microscopy with Gram stained smear is useful in case of pus. The organism is readily cultured from nasopharynx or skin, or by culture of suspicious lesions. Staphylococci has a characteristic glistening, opaque, yellow to white appearance on blood agar. Patterns of a or β hemolysis may also be visible. Further identification of staphylococcal isolates is available using commercial test kits. S. aureus isolates may also be identified by phage typing or by 16S ribosomal DNA typing. Serological tests may sometimes be done in the diagnosis of deep infections.Determination of causative agent if present in food sources is done with relevant epidemiological markers- eg: Biotyping, Serotyping, PCR, Phage typing etc.PCRbased techniques are commonly used for typing, as they are easy, fast, and cost-effective.

MALDI-TOF MS can also be used for the accurate detection of the bacteria present in the seafood by taking some references from the same species [33].

Treatment: As S.aureus is resistant to many of the drugs; appropriate antibiotic should be chosen on the basis of the antibiotic sensitivity tests. Benzyl penicillin is the most effective antibiotic, if the strain is found to be sensitive [83].

Discussion and Conclusion

Bacterial seafood intoxication refers to the ingestion of toxins (poisons) contained within the seafood, including exotoxins produced by bacteria. All are Gram positive, one is aerobic, cocci, cluster shaped non spore-forming (Staphylococcus aureus), the rest three are bacilli but among them one is aerobic and spore-forming (Bacillus cereus) whereas, the other two are anaerobic and spore-forming (Clostridium botulinum and Clostridium perfringens) are predominant seafood intoxicant bacteria.

Out of these, Cl.botulinum is indigenous to the aquatic environment. Cl.perfringens and Bacillus cereus are indigenous to the general environment, whereas, S. aureus are from the animal/human reservoir.But all have been associated with seafood safety risks, through actual intoxication. The intoxication dose often varies from species to species as well as considerably for a number of pathogens based on the health of the consumers.

All these bacteria of particular strains produce enterotoxins which cause seafood intoxications.B.cereus produces two types of toxins: diarrheal (hemolysin BL enterotoxin,non-hemolytic enterotoxin) and emetic toxin. S.aureus producesfive toxins (SEA, SEB, SEC, SED and SEE). Cl.perfringes Produces Enterotoxin (CPE) in the gastrointestinal tract by enterotoxigenic strains of Cl.perfringens. Cl.botulinum produces potent botulinum toxins (A, B, E, F and G which causes human botulism but toxin C and D cause disease in animals).

Seafood intoxications caused by non-invasive bacteria that secrete toxins while adhering to the intestinal wall are enterotoxigenic E.coli, Vibrio cholera and Camphylobacter jejuni.The other seafood intoxications that follow an intracellular invasion of the intestinal epithelial cells, caused by Shigella and Salmonella spp.

Except S. aureus, the rest is heat-resistant. Spore forming bacteria may remain long duration in seafood. Botulinumtoxin is neurotoxic and are of the most lethal poisons. Mortality is high up to 60-100% of the affected persons, hence used as Bioweapon. Botulinum toxin type A, B and E are most commonly associated with human intoxications. There are no Botulism outbreaks associated with Shellfish (Mollusks and Crustaceans). There are some resembles of illness caused by Cl. perfringens and B. cereus. Further, symptomatic similarities to S. aureus intoxication (B. cereus emetic type) or Cl.perfringens food poisoning (B. cereus diarrheal type). Toxin-mediated gastroenteritis is generally self-limited, but cause acute illness.

To prevent outbreaks of intoxicated illnesses, it is imperative to keep seafood refrigerated and to ensure proper cooling of hot seafood to refrigerator temperature. Control strategies include monitoring harvest waters, identification and implementation of process controls as well as consumer education.

Acknowledgement

The authors are grateful to the authorities of VIT University, Vellore-632014, Tamil Nadu, India for the support and facilities.

References

1. Adam MR, Moss MO. Significance of food borne diseases. Food Microbiology 2. 2013; 163: 160-164.
2. Addis M, Sisay D. A Review on Major Food Borne Bacterial Illnesses. J Trop Dis. 2015; 3: 176.
3. Johnson EA, Schantz EJ. Seafood Toxins. In Foodborne Diseases. 2002; 2: 211-230.
4. Tidwell, James H, Allan Geoff L. Fish as food aquaculture’s contribution. EMBO reports. 2001; 2: 958-963.
5. Eyles MJ. Microbiological hazards associated with fishery products. CSIRO Food Res Q. 1986; 46: 8-16.
6. Khora SS. Health risks associated with seafood. 2015.
7. Mead PS, Slutsker L, DietzV, McCaig LF, Bresee JS, Shapiro C. Food related illness and death. Emerg infect Dis. 1999; 5: 607-625.
8. Meyer KF, Sommer H, SchoenholzN P. Mussel poisoning. J.Prevent.Med. 1982; 2: 195-216.
9. Fleming LE, Katz DJA, Bean R, Hammond. Epidemiology of seafood poisoning. In Seafood and Environmental Toxins. Foodborne disease Handbook. 2001; 2: 287-310.
10. Jensen G, Greenless KJ. Public health issues in aquaculture Revscitech.off. intEpiz. 1997; 16: 641-651.
11. Rippey SR. Infectious diseases associated with molluscan shellfish consumption. Clin. Microbiol Rev. 1994; 7: 419-425.
12. Johnson KM. Bacillus cereus foodborne illness- An update, Journal of Food protection. 1984; 47: 145-53.
13. Claus D, Berkeley RCW. Genus Bacillus Cohn 1872. in Bergey’s Manual of Systematic Bacteriology. Williams and Wilkins Baltimore. 1986; 2: 1105- 1141.
14. Hong HA, Duc LeH, Cutting SM. The use of bacterial spore formers as probiotics. FEMS Microbiol Rev. 1989; 29: 813-835.
15. Mahler H, Pasi A, Kramer JM, Schulte P, Scoging AC, Bar W. et al. Fulminant liver failure in association with the emetic toxin of Bacillus cereus. N Engl J Med. 1997; 336: 1142-1148.
16. Lund T, De Buyser ML, Granum PE. A new cytotoxin from Bacillus cereus that may cause necrotic enteritis. Mol Microbiol. 2000; 38: 254-261.
17. Dierick K, Van Coillie E, Swiecicka I, Meyfroidt G, Devlieger H, Meulemans A, et al. Fatal family outbreak of Bacillus cereus-associated food poisoning. J Clin Microbiol. 2005; 43: 4277-4279.
18. Ehling SM, Fricker M, Grallert H, Rieck MP. Wagner S, Scherer. Cereulide synthetase gene cluster from emetic Bacillus cereus. Structure and location on a mega virulence plasmid related to Bacillus anthracis toxin plasmid pXO1. BMC Microbiol. 2006; 6: 20.
19. Schoeni JL, Wong ACL. Bacillus cereus food poisoning and its toxins. Journal of Food Protection. 2005; 68: 636-648.
20. Senesi S, Ghelardi E. Production, Secretion and Biological Activity of Bacillus cereus Enterotoxins. 2010; 2: 1690-1703.
21. Granum PE, In Doyle MP, Beuchat LR. Food microbiology. Fundamentals and frontiers. 2001; 445-455.
22. Kramer JM, Gilbert RJ. Bacillus cereus and other Bacillus species. In Foodborne Bacterial Pathogens. 1989; 21-70.
23. Agata N, Mori M, Ohta M, Suwan S, Ohtani I, Isobe M. A novel dodecadepsipeptide cereulide, isolated from Bacillus cereus causes vacuole formation in HEp-2 cells. FEMS Microbiology Letters. 1994; 121: 31-34.
24. Wijnands LM, Pielaat A, Dufrenne JB, Zwietering MH, van Leusden FM. Modelling the number of viable vegetative cells of Bacillus cereus passing through the stomach. Journal of Applied Microbiology. 2009; 106: 258-267
25. Michael GD. Bacterial Toxins. A Table of Lethal Amounts. Microbiological Reviews. 1982; 46: 86-94.
26. Mehrdad Tajkarimi. Bacillus cereus. 2007; 250: 1-6.
27. Rosovitz MJ, Voskuil MI, Chambliss GH, Bacillus InL, Collier A, Balows M. et al. Wilson’s Microbiology and Microbial Infection. Systematic Bacteriology. 1998: 9: 709-729.
28. Logan NA, Rodrigez-Diaz M, Bacillus S, Related G, Gillespie SH, Hawkey PM. Principles and Practice of Clinical Bacteriology. 2006; 2: 139-158.
29. Drobniewski FA. Bacillus cereus and related species. Clinical Microbiology Reviews. 1993; 6: 324-338.
30. Le Scanff J, Mohammedi I, Thiebaut A, Martin O, Argaud L, Robert D. Necrotizing gastritis due to Bacillus cereus in an immunocompromised patient. Infection. 2006; 34: 98-99.
31. Avashia SB, Riggins WS, Lindley C, Hoffmaster A, Drumgoole R, et al. Fatal pneumonia among metalworkers due to inhalation exposure to Bacillus cereus Containing Bacillus anthracis toxin genes. Clinical Infectious Diseases. 2007; 44: 414-416.
32. Murray PR, Baron EJ, Jorgensen JH, Landry ML, Pfaller MA. Manual of Clinical Microbiology. American Society of Microbiology Press. 2007; 20: 1-2.
33. Karola BC, Fernández-No JM, Gallardo BC, Pilar Calo-Mat. Safety Assessment of Fresh and Processed Seafood Products by MALDI-TOF Mass Fingerprinting. Food Bioprocess Technol. 2010; 4: 907-918.
34. Kotiranta A, Lounatmaa K, Haapasalo M. Epidemiology and pathogenesis of Bacillus cereus infections. Microbes and Infection. 2000; 2: 189-198.
35. Eric A. Johnson Edward J. Schantz1.Miscellaneous natural intoxicants. Foodborne infections and intoxications. 2013; 19: 663-701.
36. Barrie D, Wilson JA, Hoffman PN, Kramer JM. Bacillus cereus meningitis in two neurosurgical patients: an investigation into the source of the organism. J Infect. 1985; 25 : 291-297.
37. Centers for Disease Control and Preventation. Bacillus cereus Food Poisoning Associated with Fried Rice at Two Child Day Care Centers -Virginia. 1994; 43: 177-196.
38. McLaughlin JB, Sobel JT, Lynn E, Funk, Middaugh JP. Botulism type E outbreak associated with eating a beached whale, Alaska. EmergInfectDis. 2004; 10: 1685-1687.
39. Hall JD, McCroskey LM, Pincomb BJ, Hatheway CL. Isolation of an organism resembling Clostridium barati which produces type F botulinal toxin from an infant with botulism. J Clin Microbiol. 1989; 21: 654-655.
40. Smith GR, Turner A, Till D. Factors affecting the toxicity of rotting carcasses containing C.botulinum type E. Epidem. Inf. 1988; 100: 99-405.
41. Centers for Disease Control and Preventation. Summary of botulism cases. 2010.
42. Houghtby GA, Kaysner CA. Incidence of Cl. Botulinum type E in Alaskan salmon. Appl.Microbiol. 1969; 18: 950-951.
43. Hobbs G. Botulinum and its importance in fishery products. advfood res. 1976; 22: 135-185.
44. Ali Aberoumand. Occurance of Cl. Boltulinum in fish and fishery products in retail trade, world journal of fish and marine sciences. 2015; 2: 246-250.
45. Eric A, Johnson. Clostridial Toxin as Therapeutic Agents. Benefits of Nature’s most Toxic proteins. Annual Review of Microbiology. 1999; 53: 551-575.
46. Hateway CL. Bacterial sources of clostridial neurotoxins. In Botulinum neurotoxin and tetanus toxin. San Diego. Academic Press inc. 1989; 3-24.
47. Robert L, Findling , Sanjeev Pathak , Willie R, Earley Sherry Liul, J MGIMS. 2000; 3: 153-164.
48. Lamanna C, McElroy E, Eklund HW. The purification and crystallization of Clostridium botulinum Type A toxin. Science. 1946; 103: 613-614.
49. Kozaki S, Sac GS. Purification and some properties of progenitor toxins of Clostridium botulinum type B. Infect. Immun. 1974; 10: 750-756.
50. Gerwing JC, Donma E. Mechanisms of tryptic activation of Clostridium botulinum type E toxin. J. Bacteriol. 1965; 89: 1176-1179.
51. Ohishi I, Sakaguchi G. Purification of Clostridium botulinum type F progenitor toxin. Appl. Microbiol. 1974; 28: 923-928.
52. Michael L, John P, Rachel W, Christopher B. Surveillance for Foodborne- Disease Outbreaks. 2006; 55: 1-42.
53. Smith GR. Individual variation in botulism. Br J Exp Path. 1986; 67: 617-621.
54. Rood JL. Virulence genes of Clostridium perfringens. Annu. Rev. Microbiol. 1998; 52: 333-360.
55. Rood JL, Cole ST. Molecular genetics and pathogenesis of Clostridium perfringens. Microbiol. Rev. 1991; 55: 621-48.
56. Baldassi L, Hipolito M, Calil EMB, Chiba S, Moulin AAP. Observações sobre a incidência da Gangrena Gasosa e do Carbúnculo Sintomático durante 10 anos. no estado de SãoPaulo. O Biológico. 1985; 51: 161-165.
57. Songer JG. Clostridial diseases of domestic animals. Clin.Microbiol. Rev. 1996; 9: 216-234.
58. GorinI LG, Flues FS, Olovnikov AM, Ezepcuk YV. Use of aggregatehemagglutination technique for determining exoenterotoxin of Bacillus cereus. Appl Microbiol. 1975; 29: 201-204.
59. Carlos Abeyta JR. Bacteriological Quality of Fresh Seafood Products from Seattle Retail Markets. Journal of Food Protection. 1983; 46: 901-909.
60. McDonel JL. Clostridium perfringens toxins. PharmacTher. 1980; 10: 617- 655.
61. Morris WE1, Dunleavy Mariana V1, Diodati J, Berra, Guillermo 1, Fernandez- Miyakawa. Effects of Clostridium perfringens alpha and epsilon toxins in the bovine gut. Anaerobe. 2012; 18: 143-147.
62. Gilbert M, Renaud CJ, Popoff MR. Beta-2 toxin, a novel toxin produced by C. Perfringens Gene. 1997; 203: 65-73.
63. Petit L, Gilbert M, Popoff MR. Clostridium perfringens toxin type and genotype. Trends Microbiol. 1999; 7: 104-110.
64. Marvaud, Jean-Christophe, Stiles, Bradley G, Alexandre C, Daniel G, et al. Clostridium perfringens Iota Toxin. Mapping of the Ia domain involved in docking withIb and cellular internalization. The Journal of Biological Chemistry. 2002; 277: 43659-43666.
65. Sato H, Kameyama S, Murata R. Immunogenicity of highly purified a toxoid of Clostridium perfringens. Jpn. J. Med. Sci. Biol. 1972; 25: 53-56.
66. Worthngton RW, Malders MSG. The partial purification of Clostridium perfiringens beta toxin. J. Vet. Res. 1975; 42: 91-98.
67. Alouf JE, Jolivet-Reynaud C. Purification and characterization of Clostridium perfringens deltatoxin. Infect Immun. 1981; 31: 536-546.
68. Wpjseverin AA, Fuente DE, MF Stringer. J Clin Pathol. 1984; 37: 942-944.
69. Antwan A, Tejas R, Pranav P, Robert Patton, Mark Y. Clostridium perfringens bacteremia caused by choledocholithiasis in the absence of gallbladder stones. World J Gastroenterol. 2012; 18: 5632-5634.
70. Johnson EA, Summanen P, Finegold SM. In Manual of Clinical Microbiology. 1987; 9: 889-910.
71. Juneja VK, Novak JS, Huang L, Eblen BS. Increased thermotolerance of Clostridium perfringens spores following sublethal heat shock. Food Control. 2003; 14: 163-168.
72. Van Heyningen WE. The biochemistry of the gas gangrene toxins: Estimation of the alpha toxin of Cl. welchii, type A. Biochem J. 1941; 35: 1246- 1256.
73. Diekema DJ, Pfaller MA, Schmitz FJ, Smayevsky J, Bell J, Jones RN, et al. Survey of infections due to Staphylococcus species frequency of occurrence and antimicrobial susceptibility of isolates. Clin Infect Dis. 2010; 32 : S114-S132.
74. Gilbert RJ. Postgraduate Medical Journal. Staphylococcal food poisoning and botulism. 1974; 50: 603-611.
75. Nygaard TK, Pallister KB, DuMont AL, DeWald M, Watkins RL, Pallister EQ, et al. Alpha-toxin induces programmed cell death of human T cells, B cells, and monocytes during USA300 infection. PLoS one. 2012; 7: e36532.
76. Bernheimer AW, Schwartz LL. Isolation and composition of staphylococcal alpha toxin. J. Gen. Microbiol. 1995; 30: 455-459.
77. Lominskd I, Arbuthnott JP, Spence JB. Purification of staphylococcus alphatoxin. J. Pathol. Bacteriol. 1963; 86: 258-261.
78. Kreger AS, Kim KS, Zaboretzky F, Bahelmer AW. Purification and properties of staphycoccal delta hemolysin. Infect. Immun. 1971; 3: 444-465.
79. Loir Y, Baron F, Gautier M. Staphylococcus aureus and food poisoning. Genetics and Molecular Research. 2003; 2: 63-76.
80. Kluytmans J, Belkum VA, Verbrugh H. Nasal carriage of Staphylococcus aureus. epidemiology, underlying mechanisms, and associated risks. Clinical Microbiology Reviews. 1997; 10: 505-520.
81. María ÁA, María Carmen M, María R, Rodicio. Food Poisoning and Staphylococcus aureus Enterotoxins. Toxins. 2010; 2: 1751-1773.
82. Argudín MÁ, Mendoza MC, Rodicio MR. Food Poisoning and Staphylococcus aureus Enterotoxins. Toxins. 2010; 2: 1751-1773.
83. Hennekinne JA, de Buyser ML , Dragacci. Staphylococcus aureus and its food poisoning toxins. Characterization and outbreak investigation. FEMS Microbiology Review. 2012; 36: 815-836.
84. Granum PE, Lund T. Bacillus cereus and its food poisoning toxins. FEMS Microbiology Letters. 1997; 157: 222-228.
85. Gizachew H. Review on Clostridium Perfringens Food Poisoning. Global Research Journal of Public Health and Epidemiology. 2007; 4: 104-109.
86. Keith R, Schneider R, Goodrich S, Rachael S. Preventing Foodborne Illness. Bacillus cereus. 2015; 43: 84-87.