Role Of E Coli And Salmonella Food Spoilage Biology Essay

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Food is sometimes contaminated with pathogenic microorganisms, there are many sort of Pathogenic bacteria it is very dangers for human, animal, salmonella one of them, it is frequently found in fowl ,eggs ,raw approved by pets similar to turtles and birds, salmonella is bacterium which is one of the commonest causes of food spoilage worldwide , there are more than 2,000 dissimilar sorts of salmonella , but with the omission of the little which typhoid or parity ,fever the sickness they cause is related, also there is a common sort of bacteria call E.coli it is akin to beef and vegetables , E.coli is short for the medical dumpy Escherichia coli is short for thing about these bacteria and lots of other bacteria is that they're not constantly harmful to you. (1,8)

E.coli generally lives indoors your intestines where it helps your body split down and digest the

food you eat , Ecoli be able to get from the insides into the blood , this is a rare sickness but it can

cause a extremely serious infection food is the commonest sources of salmonella for humans . the food may have been contaminated bacteria the source, animal or bird was infected salmonella is common with chickens some studies in 1990 showing that about 50%of of frozen and fresh chicken hold the bacteria .infections in dairy herds may show the way to contamination of milk.( 4,7 )

Outbreaks of gastroenteritis suitable to contaminated food have been reported in extra parts of the world. The probable causes of these outbreaks were suitable to the consumption of food contaminated with pathogens bacteria. Studies from many countries have given away that the microbiological quality of food manufactured for make use of in foods and drinks might be a cause for concern. (1)

Ecoli was discovered by German pediatrician and bacteriologist Theodor Escherichia in 1885, and is now classified as piece of the enterobacteriacea. (5)

Salmonella was discovered by D.E salmon, the American veterinary pathologist who original

described salmonella cholera sues in 1900. (5)

In fact several microorganisms can stay alive in food, even though food is very important to the

maintenance of life, it can also be conscientious for ill health. (1)

Structure and function of E coli Bacteria

The find structure of bacterial cells has been studied in some detail using electron microscopy of

whole cells and cells broken up into separate components.(4)

1.1 - the organism and its characteristics

Escherichia coli is a kind of gram negative bacteria, this is usually found living indoors the lower

intestine of human beings as well as animals , there are quite a few different strains of E coli

bacteria , most of which are practically, harmless.( 10 )

Although they form a very minor component of the intestinal flora, the E coli bacteria aid in the

digestion and break down of the ingested food. (6)

E coli is the type of genus, it is a catalase-positive, oxidase -negative, fermentative,

short, gram-negative, non-sporing rod, although it ferments the sugar lactose. The following

figure illustrates the size of bacteria under the electron microscope. (2)

Figure1.1-electron micrograph of

E coli.

1.1.1-solation and identification of the isolates

Colonies were isolated from the Trypticase Soy Agar plates (TSA) (Oxoid UK) and Triple Sugar

Iron slants (TSI) (Oxoid UK) and incubated at 37oC for 24 hour. The isolated bacterial was

identified by cultural morphology, Gram-stain and biochemically, the colonies that showed

typical reaction in TSI and positive for cytochrom oxidase test and catalase test were confirmed

by using Analytical Profile Index 20E (API 20E). The colonies which are gives Gram positive

cocci identified by used catalase, coagulase and DNase test. (2)

1.1.2 - What these bacteria do is that they produce loads of vitamin

Amino acids and other growth factors which are immediately absorbed and used by the body.

The Ecoli bacteria that colonize in the lower intestine by adhering to intestinal lumen. (9)

However, some strains of E coli are also able of causing deadly health problems such as

severe stomach characterized by cramps and belly pain, vomiting and severe diarrhea.(10)

1.2- Structure and function of salmonella

1.2.1 -the organism and its characteristics

According to the(Adams, M and Moss, M ,1995) salmonella bacteria are the most common

cause of food borne sickness in the united states there are more than 2500 serotypes of

salmonella, only some of which cause illness in humans.(1 )

Salmonellas are members of the enterbacteracese they are gram - negative, non-spore

forming rods (typically o,5 m by 1.3m) which are faculatively anaerobic , catalase -positive,

oxidise-negative. The following figure illustrates the size of bacteria under the electron

microscope (4)

Figure1.2.1 electron micrograph of salmonella


E.coli was discovered by German pediatrician and bacteriologist Theodor Escherichia in 1885,

and is now classified as piece of the Enterobacteriace family.(1)

the largest part E.coli strains are harmless, but some such as serotype 0157:H7, but some such as serotype 0157:H7, can cause serious food poisoning in humans.(2)

Salmonella is closely related the Escherichia genus, and some classified as part of the

enterobacteriace.( 1 )

Many Ecoli and salmonellas are responsible for a number of different clinical syndromes,

grouped here as enteritis and systemic disease.

bad stomach cramps and belly pain, vomiting, diarrhea, sometimes with blood in it two very bad

strain of Ecoli and salmonella were found in fresh spinach in 2006. ( 2 )

on the other hand, some strains of e coli and salmonella are also capable of causing deadly health

problems such as severe stomach upsets characterized by cramps and belly pain, vomiting and

severe diarrhea.( 4 )


-E coli can be differenced from salmonella on the basis of a figure of sugar-fermentation, and

other biochemical tests.(10)

-E. coli is indole positive or methyl red positive, but salmonella was negative.

-E.coli is atypical mesophile growing from 7-10c up to 50c with an optimum around 37c. (3)

-Contamination of eggs especially with salmonellas is a long-recognized problem but in the most

cases this was due to contamination of the eggshell. (4)

-furthermore biochemical tests between E coli and salmonella is difference, so typically significant group of tests used for the ability to produce:

i) Indole from tryptophan.

ii) Sufficient acid to reduce PH. (8)

-Any member of the genus salmonella presents some degree of hazard to human health, such as

S.gallinarum, typhi and pullorum. (3)


In many previous studies on the quality food microbiology criteria for the food and intake

water to these recommended by world health organization. This is because lots of countries do

not have specific notional microbiological for food spoilage.

Although, many good bacteria are needed in your body to assist it work properly, a few of these

bacteria assist you digest food (normal flour), and keep your skin clean.

However, other types of bacteria can make you ill, also convinced bacteria invade your badly and attack, causing infection.

Good hygiene and good handling practices are all prerequisites to the manufacture of good value food.

WHO's microbiological guideline for food and drinking-water quality (6)

Plate count (cfu/100ml)



E. coli





Not specified


1-Adams, M and Moss, M (1995) food microbiology, the royal society of chemistry,Thomas graham house (pp.181-202).

2-Anonymous. 2002. Microbiological quality of ice for cooling drinks.

Food safety authority of Ireland available from:

3-Doyle,M,beuchat,L,Montville,T,Montville,T(2001)Food Microbiology, the united states of american,washingtion(pp141-193)

4-Garbutt,J(1997) Essentials of food microbiology ,Great Britain, London pp(5-137)

5-Icmsf international commission on microbiological specification for foods (1996).

Microorganisms in foods. 5. Microbiological specifications of food pathogens

Characteristics of microbial pathogens. London, UK: blackie academic &

Professional (pp. 45-65).

6-International Commission on Micrological Specifications for foods (icmsf) (1986) microorganisms in foods (2), sampling for microbiological analysis: principles and specific applicationns.2th, university of Toronto, Canada.

7-Montville, T, Matthews, k (2005) Food Microbiology, A American Society for Microbiology, Washington pp (85-111)

8-Ray, B (2004) Fundamental Food Microbiology, Bibekray 3rd Ed, USAPP (257-269)

9- Who guidelines for drinking-water quality, vol. 1. (3rd ed.) 2004

available from:

10-Wilson, I.g., Hogg, G.M. and Barr, j.g. microbiological quality of food in

Hospital and community. j. hospital infect. 1997; 36:171-180.