E. Coli

E.COLI (Escherichia Coli)

Discovery/History

It was discovered in 1885 by German bacteriologist Theodor Escherich (Dr. Escherich) in human colon hence it called coli. Initially it was called "Bacterium Coli" latter it changed to Escherichia Coli to honor of its discover.

More than 700 serotype of E Coli have been identified. The 'O' and 'H' antigens on the bacteria and their flagella distinguish the different serotype.

The useful or harmless strain are the part of normal microbiota of gut, they produces vitamin K2 and helpful in prevention of colonization of pathogenic strain in intestine.   

The O157:H7 is the pathogenic strain and was first recognize on 1982. This strain relentlessly evolving organism, constantly mutating and aquaring new characteristics.

Biological Classification 

Domain : Bacteria (Domain designed by Carl Woese, three domains Archaea, Bacteria and Eukarya)

Kingdom: Bacteria (Six kingdom -Archaebacteria, Eubacteria, Protista, Fungi, Plantae and Animalia)

Phylum: Proteobacteria 

Class: Gammaproteobacteria

Order: Enterobacteriales

Family: Enterobacteriaceae

Genus: Escherichia

Species: E. Coli

Physiology of E Coli:

• It is rod shaped bacteria
• Length : 2.0 µm
• Diameter: 0.25 to 1.0 µm
• Gram negative
• Facultative anaerobic

GROWTH PARAMETERS:

Nutrient:

Lysogeny, Luria broth most commonly used media for faster growth of E coli.

Temperature:

E Coli can grow on wide range of temperature from 4 to 45  ͦc. The optimum temperature is 37  ͦc. At low temperature it can survive but growth decrease due to protein initiation become rate limiting factor. 

It has been studied that with different growth rate at the same temperature ribosomes are working with same rate but in fast growth rate number of ribosomes per cell is higher compare to slow growth rate. Hence in recombinant protein production technology bacteria cells are grow at exponential growth phase, as higher the ribosomes more protein produce.

It has also studied that cells shape and size are impacted by temperature, cells growing at low temperature are smaller and thicker compare to those growth at 37 ͦc. 

pH:

Most bacteria including E coli grow fastest at neutral pH (6.5 to 7). As at low and high pH catalytic activity of enzyme lost and metabolism halted hence their growth rate decreases. So in routine life we added vinegar or lemon in food as it lower the pH and to prevent bacterial growth in food.

Aeration:

E coli is facultative anaerobe so it can grow with and without oxygen, but it grow faster in presence of oxygen and release more energy from nutrients metabolism. In fermentation technology normally E coli grow at 30% saturation of dissolve oxygen concentration but it was studied that it can grow up to 300% dissolve oxygen concentration. At higher oxygen stress SoxRS regulon activate and it support against high stress of dissolve oxygen.

Source of infection

• Ground meat in food
• Untreated milk
• Vegetables and Fruits
• Yogurt
• Cheese
• Dirty Water 

Symptoms 

It causes diarrhea, food poisoning, Pneumonia and Urinary tract infection (75 to 90%) caused by E Coli, hemolytic uremic syndrome. During urinary tract infection you feel frequent urgency to urinate yet pass little urine when you go. Urine might be cloudy, blood tinged and strong smelling.

If E.coli enter from rectum to vagina it can enter to urethra and infect the bladder.

Some E Coli strains are producing shiga toxin and they are called shiga toxin producing E coli (STEC). 

One bad strains O157:H7 causes sick abdominal cramps, vomiting, bloody diarrhea, acute kidney failure, Fever. constant fatigue, 

For the normal infection concern to doctor and use antibiotic but for shiga toxin antibiotic is not helpful as it support to produce more shiga toxin.

Shiga toxin has multiple variants (Stx1, Stx2 ans Stx2c) and acts like plant toxin ricin by inhibiting protein synthesis in endothelial and other cells. Endothelial cell lines are the interior surface of blood vessel.

Control:

• Proper cooked meat
• Use pasteurized milk or boil before use
• Maintain hygiene during cook
• Refrigerate food at 41 °F or below 
• Use clean or boiled water
• Addition of acid/vinegar in food