Pathogenic Bacteria

The pathogenic bacteria which can cause some diseases in human being after the consumption of sea food are of two types.

1.      Indigenous bacteria

2.      Non- indigenous bacteria

1.       Indigenous bacteria

They are widely distributed in aquatic environment. These pathogens occur in minimum number in non polluted water body and are not a serious problem in fresh fish. However their growth and multiplication in sea food and is serious problem and cause disease in human being, e. g Vibrio spp, C. botulinum, Aeromonas spp.

2.      Non- indigenous bacteria

            They occur in sea food as a result of contamination. The source include polluted aquatic environment, sewage, excreta from animals, birds, human being, & unhygienic condition of works. Handling the material as well as the surface & environment where the seafood is processed e.g. Salmonella, E.coli, S. aureus, and Vibrio cholerae.

                                   

Salmonella

Salmonella among gram negative road shaped bacteria causing food born diseases, the most important are members of the genus salmonella. Salmonella gram negative road shaped bacteria mostly motile and they do not form spore, the primary habitat of salmonella is the gut of infected warm blooded animals and men. From the gut it is excreted out though faces and hence found in sewage, some people are carriers of salmonella. Salmonella food poisoning symptoms are due to the liberation of toxin from the cell by the action of stomach. The usual symptoms are nausea, vomiting, abdominal pain, & headache which last for 2 to 3 days. Fresh fish collected from open sea is free from salmonella. However, fish from polluted coastal water by are usually infected with salmonella. The most important species is S. typhi, the causative agent for typhoid fever. Human infection results from the injection of contaminated food. Limit of these bacteria should be 0.

E-coli

It is gram –ve road shaped Non- spore forming bacteria. Primary habitat of E-coli is the intestinal track of many worm blooded animal. Therefore its presence in fish is indicated that fecal contamination. E-coli is very sensitive to subzero temperature or low temperature about 95% E-coli can be destroyed during freezing at -40⁰C. The maximum acceptable limit for E-coli is 20 colonies cfu 1/ gm.

Staphylococcus aureus

It is gram positive Cocci, non-motile non-spore forming bacteria. The primary habitat S. aureus is man himself. Hand, face, sweat, nosal cavities, throat etc. of man contain this organism is in considerable numbers. Therefore this organism is useful indicators of human hygiene in a process involving human handling. A few staphylococci per gm of food material may be harmless but the organism can multiply rapidly and produce toxin at room temperature. Hence adequate refrigeration of the material during handling and processing is highly essential in preventing further multiplication. The toxin once form will not be affected even at 100⁰c temperature. Limit of these bacteria should be 100 cfu/gm.

Clostridium botulinum

C. botulinum anaerobic gram +ve spore forming road shaped bacteria. When these bacteria grow in food they produce toxin that can cause food poisoning in human. This food poisoning is called botulism, this toxin is neurotoxin. The source of botulism food poisoning is preserved food such as meat and meat products, canned vegetables and fish, salted and smoked fish, surimi and surimi products. The spores of clostridium are resistance to heat & can survive for several hours at 20 min at 120⁰C. The toxin produce from C. botulinum is heat labile (it can be destroying by heat) it can be destroyed at 80⁰C in 30 – 40 min and 100⁰C in 10 min. The fish caught from seas and oceans are relatively free from human pathogenic micro-organism. The major exceptions are c. botulinum and some species of pathogenic Vibrio. Bottom feeding fish usually have highest level of contamination of C. botulinum. Limit of these bacteria should be 0.

Vibrio cholerae

Vibrio cholerae are comma shaped or curved rod, gram –ve non-spore forming and for actively motile by a single polar flagella (for movement). It aerobic and optimum growth temperature is 37⁰C. It is one of the most rapidly multiplying bacteria. It is usually tolerant of alkali growing in media as alkaline as P^H 9.2, the property utilized from primary isolation of this organism. The only known natural habitat of Vibrio cholerae is man or human being and it is transmitted from man to man though the environment usually food, water, flies and contaminated hands of food handlers play a prominent role in the transmission of these organisms. Human being suffers from disease called cholera due to the consumption of fish contaminated with V. cholerae. Mostly shellfishes and crustacean are involved in cholera outbreak. The vibrios can entered the gastrointestinal track of man and can survive for 1 to 2 month at low temperature and 15 to 20 days at high temperature.

Vibrio parahaemolyticus

This is of marine origin can be found in sea water, sediments, plankton, fin fishes and shellfishes of coastal and estuarine environment. It is unable to survive at deep ocean hydrostatic pressure. Morphologically it is gram –ve rod shape bacteria. In India the occurrence of V. parahaemolyticus in fish and aquatic environment has been reported by several works. Incidence in fresh, marine and brackish water fish varied from 35 to 55%. It is facultative anaerobic halophilic bacteria. It can grow in ordinary media containing 1 to 8% sodium chloride. It prefers alkaline pH (optimum range 4 to 5% salt). The recommended pH for culture is 4.7 to 8.5 and the optimum temperature required is 37⁰ C. It is very heat sensitive can be inactivated by mild heat (60 to 80⁰C for 15 min.). It is also very sensitive to drying and smocking. In human being it usually causes either diarrhea or dysentery.

Listiria monocytogen

This pathogen is becoming one of the deadly pathogen only in the last few years following several outbreaks in North America and Europe.

Why Listiria monocytogen is important in sea food.                      

1)      It is pathogen.

2)      It is tough organism. It is survive freezing and thawing. Relatively heat resistance.

3)      It can even grow in refrigerated condition even at 1⁰c.

4)      Relatively resistance to common salt (20% NaCl).

5)      High mortality rate in case of human beings.

6)      The biggest threat is the carriers of this pathogen will shade organism for more than three years.

Habitat   

            This is widely distributed in nature the organism has been isolated from

1.      Sewage

2.       Soil

3.      Mud

4.      Fecal matter

5.      Leaves, grasses

6.      Tomatoes, fruits

7.      Insects

8.      Worm blooded animals.

Infection cause by these organisms is called as listeriosis. Mortalities are as high as 30%. Everybody who gets infected with Listiria monocytogen did not become sick. In some cases the infection produces only flue like symptoms. It can be even a threat to pregnant women, new born babies, old people with low immune system. It is sensitive to penicillin and ampicilline.

            A unique micro-organism: - This organism is called unique because it is capable to growing in refrigerated conditions, it is resistance to pasteurization temperature and it can even survive at 20% salt concentration. It can even survive at -18⁰ C for over 40 months.

Shigella

It is bacteria belong to family Entrobacteriaceae and is often associated with diseases like dysentery. It is a short gram –ve rod, non-motile, non spore former and facultative anaerobes. They can grow best in temperature range of 10 – 40⁰C and optimum temperature at 37⁰C & pH is 7.4. The natural habitat of this pathogen is human being itself. This pathogen is not highly resistance and can kill easily at 60⁰C in 10min.

Control measures for prevention of contamination from pathogenic bacteria

1.       Avoid fishing from polluted water.

2.      Avoid washing with near shore water.

3.      Avoid storing the catch on sea beaches.

4.      Use only chlorinated water for processing and ice manufacture.

5.      Workers may be periodically examined to dialect carriers of pathogen.

6.      Those who are suffering from vomiting and diarrhea should keep away from work.

7.      Before starting work all fish handlers may wash and disinfect the hands.

8.      Entry of rodents to the processing hall may be avoided.

9.      Before starting and after finishing each day’s work all utensils use for the processing may be clean and disinfected.