Hazards Found in Seafood

Part I-Bacteria.

PATHOGENIC BACTERIA

• Pathogenic bacteria are defined as those bacteria that that may cause illness in humans.

• Food-borne pathogenic bacteria are few among the different types of seafood bacteria.

• Mode of transmission . - food intoxication. - food-borne bacterial infection.

Microorganisms

others are able to spoil food. “Some

pathogenic bacteria are transmitted to humans via food”.

Bacterial food poisoning or intoxication.

- causative organism multiplies in the food where it produces its toxins.

- characterized by rapid onset of the illness (typically symptoms are nausea, vomiting).

-intoxications require that the toxin producing bacteria have grown to high numbers (105– 108 cfu/g). Food-borne infections.

- the infectious agent may or may not have multiplied in the food.

- ingested viable bacteria continue to grow within the host’s body.

Minimum Infective Dose, MID - MID, varies considerably between bacterial species.

- the MID - high (>105-106 cells) for pathogenic Vibrio species.

- low for Salmonella typhi and Shigella species.

• Seafood-borne pathogenic bacteria - divided into 3 groups according to their ecology and origin, 1. the aquatic environment

-the general environment.

- the animal/human reservoir.

Level of human pathogenic bacteria

- quite low in fish.

- highest concentrations are found in molluscs.

Ambient temperature, other factors facilitate the growth in raw seafoods.

human pathogenic bacteria can be detected in the fish that have not undergone any bactericidal treatment.

Safety concerns The safety concerns related to pathogenic bacteria in seafood is

demonstrated in table below,

no safety concern

• Presence (in low numbers) of pathogens in aquatic and general

environment.

safety concern

• Presence of pathogens from the

animal/human reservoir is a serious

Heat resistance Control measures can be carried out by preventing its growth in food or destroying it

completely.

The D-value used to determine heat-resistance indicates the length of time (seconds, minutes) which is required at a given temperature to reduce the population to 10% of its initial count (decimal reduction).

Clostridium botulinum

Classification

toxin types from A to G.

types A, B, E and F – toxic to human pathogens.Divided into two groups

proteolytic types A,B & Fheat resistant,

mesophilic, NaCl tolerant

non-proteolytic B,E & Fheat sensitive

psychrotolerant, NaCl sensitive

Epidemiological aspects

•toxins produced by types A, B, E and F - causes of human botulism - symptoms develop within 12 to 36 hours.

•generally nausea and vomiting neurological symptoms such as visual impairment loss of normal mouth and throat function lack of muscle coordination and respiratory impairment,

•type E botulism - most rapid onset of symptoms, •type A botulism - tend to be the most severe.

Toxin production in smoked fish

Botulinum toxin - most potent of all poisons,

- min. conc. for causing death as low as 30-100 ng (Lund and Peck, 2000), - sensitive to heat and pH above 7.

For safe inactivation-time/temperature combinations of 20 min. at 79°C or 5 min. at 85°C.

Prevalence in fish and fishery products

Non-proteolytic C. botulinum types - type E - widely distributed in the aquatic (marine and fresh water) environment in the temperate and arctic zones.

-present in sediment samples from sample areas – closed, shallow fjords and aquaculture.

-absent in fish caught from high seas.

- other types than type E are frequently found in fish from warm tropical waters.

Prevention and controlControl of C. botulinum in fishery products can be achieved by,

•a salt-on-water concentration ≥ 3.5% or aw ≤ 0.97 throughout the food

combined with chill storage (<10°C).

•storage at all times at <3.3°C

•storage at 5-10°C and a shelf life of <5 days

•a heat treatment of 90°C for 10 min combined with chill storage (<10°C)

Vibrio species

It belong to the Vibrionaceae family.

13 species can cause - wound infections, septicaemia & gastroenteritis.

- marine and / or estuarine environments.

- require NaCl (2-3%) to grow.

- isolated from fish and crustaceans.

- mesophilic .

- the genus comprises of 34 species.

Seafood-borne diseases are primarily caused by

•Vibrio parahaemolyticus,•Vibrio vulnificus,•Vibrio cholerae,•V. harveyi

Vibrio parahaemolyticusEpidemiological aspects-gastroenteritis in humans,

- raw or inadequately cooked seafoods.

- incubation period ranges from 8 to 72 hours.

- the onset of disease is very sudden with explosive diarrhoea.

- symptoms typically subside within 48 to 72 hours.

- ingestion of 2 x 105 to 3 x 107 cells is required to cause disease.

Prevalence in fish and fishery products

-especially in bivalve molluscs.

-levels fluctuate with temperature.

-isolated in the warmer months.

-during colder months, the organism probably survives in sediments. -highest numbers are seen at 20-25 ppt salinity (FAO/WHO, 2001).

-the incidence seems to be highest in,- molluscan shellfish, - crustaceans

-lowest in finfish (Sumner et al., 2001).

Prevention and control

•Rapid and efficient cooling (time x temperature control) is one of the most important control parameters in prevention of V. parahaemolyticus gastroenteritis.

•Cooling to 5°C will prevent growth.

•High NaCl-concentrations (>10% NaCl in water phase) or acidification as used in severalsemi-preserved products can prevent growth.

Vibrio vulnificusEpidemiological aspects

- cause wound infections in humans,

- a range of fish disease,

- cause a very serious infection transmitted by seafood,

- causes bacteraemia and septicaemia not a gastrointestinal disease.

Source - raw bivalve molluscs such as oysters,

- approximately 85% of strains isolated from human clinical cases are biotype 1 whereas biotype 2 mainly causes infections in eels,

- Biotype 3 was identified recently (Bisharat et al., 1999) and was associated with seafood mediated bacteraemia.

Symptoms- Common symptoms - fever, chills, and nausea.

- Symptoms occur approximately 38 hours after consumption.

- affects people in specific risk groups - underlying medical conditions such as chronic cirrhosis, hepatitis or a history of alcohol abuse (EC, 2001).

- Liver dysfunction and iron overload appears to facilitate infection.

Prevalence in fish and fishery products

- accumulates in oysters up to 104 cfu/g.

- found in levels of up to 106 cfu/g in intestines of fish feeding on oysters.

- Salinity affects its occurrence with optimal salinity at 17 ppt.

- may multiply within the live animal and each oyster may shed up to 106 bacteria per day (Tamplin and Capers, 1992).

Prevention and control

-dies rapidly during heating with D-values of approximately 78 sec at 47°C.

-it is more sensitive to cold storage and

-declines with approximately 0.04 log units per day under “normal” cold storage (FAO/WHO, 2001).

- sensitive to low pH and does not grow below.

- pickled fish do not constitute a risk.

- below 0°C results in reduction of counts of V. vulnificus.

Vibrio choleraeEpidemiological aspects

-may be sub-typed into more than 130 serotypes.

-serotype O1 and O139 are associated with epidemic and pandemic cholera. - both produce the cholera toxin. - the O1 may be further subdivided into the serogroups. - Ogawa or Inaba or Hikojima.

- O1 types may also be subdivided into two biotypes. - classical and - El Tor (haemolytic).

-the main source, - the faeces of acutely infected people.

-the infective dose - 106 cells (Kaysner, 2000), although some suggest it to be 1011 cells.

Prevalence in fish and fishery products

- observed in estuaries, bays and brackish water.

- water temperature and salinity - highest numbers at lower salinities of 2-5 ppt.

- survives for long periods of time in river waters (FAO/WHO, 2001)

- toxigenic forms are isolated from the hindgut of crab (Huq et al. 1996).

- not common on fresh fish, however. -V. cholerae O1 has been isolated from 3.5-18.3% of fresh fish in Mexico

- linked to seafoods - often molluscs.

Prevention and control

• Inadequate sanitation and lack of safe water are the major causes of cholera epidemics. • It can be reliably prevented by ensuring that,

- adequate excreta disposal systems and

- safe drinking water.

Listeria monocytogenes Listeria monocytogenes is a,

•Gram-positive, motile bacteria grows well at 37°C at human body temperature.

•psychrotolerant and halo tolerant.

•Seven species are pathogenic to humans.

•divided into 13 serovars on the basis of somatic (O) and flagellar (H) antigens.

Epidemiological aspectsListeriosis is in its most known form,

•an invasive disease transmitted by food products.

•mostly affects people in particular risk groups (elderly people, HIV infection, transplant patients, pregnant women)

•the disease infects the central nervous system.

•the incubation period is very variable ranging from 1 to 91 days.

•the incidence is approximately 0.5 cases per 100 000 inhabitants.

•caused by processed, industrialized foods that have extended shelf lives atchill temperatures and that are ready-to-eat (RTE).

Prevention and control

Control of listeriosis can be achieved

•using HACCP and GHP.

•packages are subjected to a listericidal process, typically a heat treatment.

•freezing of products will eliminate growth,

•sufficient levels of acid and NaCl will also prevent growth.

•sorbate (0.05-0.1%), combination of lactate (2%) and di-acetate (0.1%) has been shown to eliminate growth in frankfurters (Tompkin, 2001). •chlorine, iodine, acid, anionic and quaternary ammonium-type sanitizers are effective at concentrations of 100 ppm, 25-45 ppm, 200 ppm and 100-200 ppm, respectively.

Clostridium perfringens is an •anaerobic, gram-positive mesophilic spore-former widely distributed in the environment.

•may be found at levels of 103-104 per gram soil. •isolated from water, sediments and from faeces of healthy individuals.

•the sporulating cells produce an enterotoxin of approximately 35 kilo Dalton (kDa).

Clostridium perfringens

Epidemiological aspects

•This results in nausea, abdominal pain, diarrhoea, vomiting 8-24 hours after ingestion.

•typically associated with heated meat products or dishes which are temperature abused or heated slowly for long time.

•Due to its anaerobic nature, it prefers food with low redox potential.

Prevention and control

• does not grow at chill temperatures and grows only slowly below 20°C.

• the vegetative cells are sensitive to acid (minimum pH of 5), salt (maximum 6%).

• do not grow at water activities below 0.95.

• therefore controlling proliferation in seafoods is not complicate

Bacillus cereus

Bacillus cereus ,

•strains are aerobic, gram -positive spore-forming bacteria.

•are widely distributed in the environment.

•the spores are resistant to drying and are easily spread with dust. •occurs only in low numbers especially in raw foods.

EpidemiologyB. cereus causes, •two types of disease - by toxin formation.

•one is characterized by abdominal pain and profuse watery diarrhoea and - symptoms occur 8-16 hours after ingestion.

•the other, the so-called emetic type, - has a shorter incubation period (½ to 5 hours) and - nausea and vomiting are typical effects.

•the diarrhoeal type - toxin formation in the gut •the emetic type is caused by a toxin preformed in the food.

Prevention and ControlMost strains,

mesophilic and do not grow below 10-15°C.

psychrotrophic, toxin-producing strains have been isolated from foods stored at 4-6°C.

mild heat treatment is combined with subsequent cold-temperature storage.

control of B. cereus is efficiently obtained by chilling.

Salmonella species

•The genus Salmonella is a member of the Enterobacteriaceae family.

•Salmonellosis is a leading cause of bacterial enteric disease in both humans and animals.

•only two species of Salmonella are recognised; the S. enterica and the S. bongori.

•S. enterica consists of 6 sub-species. Within each of these, several serotypes exists.

•S. enterica subsp. enterica as the largest group covers approximately 1500 serotypes.

• Examples of such serotypes are Enteritidis, Typhimurium or Typhii.

Epidemiological aspects

•enteric fever - typhoid or paratyphoid strains or as the nontyphoid dependent gastroenteritis.

•non-typhoid salmonellosis - nausea, abdominal cramps, diarrhoea with watery and possibly mucoid stools, fever and vomiting appearing 8-72 hours after exposure to the pathogen.

•Poultry, pork and beef products are important sources of salmonellosis.

•Seafoods are relatively uncommon as causes of salmonellosis.

•The infectious dose of salmonellae is, in general, high – typically around 106 cells.

Control

• Proper cooking,

• holding chilled foods <40oF,

• preventing cross-contamination,

• preventing ill people or carriers from working with food

Shigella spp. Source:

Intestine of humans

Symptoms: Mild diarrhea, fever, abdominal cramps, severs fluid loss

Transmission: Sewage pollution of coastal waters, contamination after harvest

Control: Preventing human waste contamination of water supplies, preventing ill people or carriers from working with food

Campylobacter jejuni

Intestines of poultry, livestock, domestic animals

Diarrhea, abdominal pain, headache, weakness, fever

Contaminated foods & water, person to person

Control: Proper cooking, proper hand and equipment washing, sanitary food handling practices

Escherichia coli

Intestines of animals and humans

Abdominal cramping, water or bloody diarrhea, fever, nausea, vomiting

Sewage pollution of coastal waters, contamination after harvest

Control: Proper cooking, holding chilled foods <40oF, preventing cross-

contamination, preventing ill people from working with food

Staphylococcus aureus Humans and animals, air, dust, sewage.

Nausea, vomiting, abdominal cramps, watery or bloody diarrhea, fever.

Contamination of food by workers or equipment, growth and toxin production in the food.

Control: Minimizing time/temperature abuse of food, especially after

cooking, requiring that food handlers engage in proper hygiene.

Yersinia enterocolitica Soil, water, domesticated and wild animals

Diarrhea, vomiting, abdominal pain, fever

Cross-contamination from raw to cooked seafood, consumption of raw seafood, temperature abuse

Control: Proper cooking of seafood, preventing cross-contamination of cooked seafood, holding seafood <40oF