Esherichia coli

Presented by : Khairina Atikah Aina

NajahNabil

General E. coli was discovered by Dr. Theodor

Escherich1885 It belongs to the Family

Enterobacteriaceae. From Greek word enterikos (intestines) These organisms inhabit the intestinal

tract of most warm blooded animals

Gram-negative rod Facultative anaerobe Normal flora of the mouth and intestine Protects the intestinal tract from bacterial infection Assists in digestion Produces small amounts of vitamins B12 and K Colonizes newborns GI tract within hours after birth There are more than 700 different serotypes of E. coli

E. coli bacteria normally live in the intestines of people and animals.

Most E. coli are harmless and actually are an important part of a healthy human intestinal tract.

However, some E. coli are pathogenic, meaning they can cause illness, either diarrhea or illness outside of the intestinal tract.

Can cause diarrhea which transmitted through contaminated water or food, or through contact with animals or persons.

Morphology

usually motile, produce peritrichous flagella some produce polysaccharide capsules grow well on non-selective media, forming

smooth, colorless colonies 2-3 mm in diameter in 18h on nutrient agar

temperature (15-45 ) ℃

Some of these strains are friends of humans. In fact, within hours of a human birth, E. coli will colonize the gastrointestinal tract.

Highly successful in this environment, cozying up in the mucus that lines the intestinal walls.

It can live for decades with mutual benefit, a symbiosis between itself and the human host.

The only time these friendly E. coli cause a problem is when the host becomes immunocompromised or the intestines are damaged in some way.

There are also strains of E. coli that are definitely not friends of humans.

These strains carry genes that give them the ability to not only colonize the human intestines like the friendlier strains but also to cause disease in the host.

These strains are defined by different virulence genes they carry and are referred to as pathotypes.

A pathotype is a group of strains that cause the same disease because they share a set of virulence genes. 

Culture They can grow in even simple nutrient media

containing only salts, a source of nitrogen and source of carbon and energy. Division time (40 minutes) normal 20 minutes.

From the bacterial colony the mutants can be selected and analyzed easily.

E.coli in McConkey media gives pink color since it digests lactose.

Identification MacConkey agar (SMAC)

Does not ferment sorbitol rapidly Forms colorless colonies on sorbitol

containing MacConkey agar Serology

Colorless colonies on SMAC are screened for the 0157 antigen

Disease caused by E.coli E. coli is responsible for three types of infections in humans: urinary tract infections (UTI) neonatal meningitis intestinal diseases (gastroenteritis).

Transmitted via food

Ground beef Raw milk Lamb meat Venison jerky Salami and other fermented dried meat products Lettuce, spinach, alfalfa sprouts Unpasteurized apple cider

Transmitted via water Drinking and swimming in unchlorinated water

Direct person to person contact Diaper changing Improper sanitation Day care & chronic adult care facilities

How long does it take to get sick from E.coli

Signs and symptoms of E. coli infections typically begin three or four days after exposure to the bacteria, though you may become ill as soon as one day afterward to more than a week later. Signs and symptoms include: Diarrhea, which may range from mild and watery to severe and bloody.

Prevention in Humans Good hygiene

Hand washingAfter livestock contactBefore eating and drinkingAfter changing diapers

Separate contaminated clothing Isolate infected children?

Don’t cross-contaminate Wash hands, counters, cutting boards, utensils after contact

with raw meat Thoroughly cook meats Avoid unpasteurized products Wash fruits/vegetables before eating Keep livestock away from private water supplies

Treatment

treatment is based on symptomatology. fluid replacement is the primary treatment Antibiotics are generally not used except in severe

disease or disease that has progressed to a systemic stage (e.g. hemolytic-uremia syndrome).

Patients, especially healthy adults need no treatment for E. coli infection because it is self-limited.

This effect occurs because antibiotics destroys the bacterial cell wall, causing them to release even more toxin.

When necessary, treatment includes the replacement of fluids and electrolytes to treat or prevent dehydration.

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