PRESENTED BY:NOMAN HAFEEZ KHOSA

ABDUL SAMI FARHANMISBAH SADIQANUM AJMAL

Escherichia coli

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Esherichia coli Gram-negative rod Facultative anaerobe

Named for Theodor Escherich German physician (ca. 1885) Demonstrated that particular strains were

responsible for infant diarrhea and gastroenteritis

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

Morphology

• usually motile, produce peritrichous flagella

• some produce polysaccharide capsules

• grow well on non-selective media, forming smooth, colourless colonies 2-3 mm in diameter in 18h on nutrient agar

• temperature (15-45℃)

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Many strains

• O antigen– Somatic – 171 antigens

• H antigen– Flagella– 56 antigens

• K antigen– Capsule and or

fimbrial antigen– 80 antigens

O18ac:H7:K1

18th O antigen 1st K antigen

7th H antigen

Diseases caused by E. coli

• E. coli is responsible for three types of infections in humans:

urinary tract infections (UTI), neonatal meningitis, intestinal diseases (gastroenteritis).

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Neonatal Meningitis E. coli NMEC• Meningitis in an infection of the fluid and membranes that cover the brain and spinal cord

– Bacteria – Viruses – Fungi

• E. coli incites between 1/4 and 1/3 of meningitis cases in newborns– Less than 2% of cases of meningitis at all other ages

• Approximately 1 out of 5 newborns with E. coli meningitis dies – Survivors frequently sustain permanent brain damage

• The majority of cases occur in premature babies• K-1

– 80% of NMEC E. coli strains produce K-1 capsular antigens – K1 capsular polysaccharide – O18ac:H7:K1 – Inhibits phagocytosis

• Siderophore production – Sequesters Fe

• Endotoxin

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Enteric / diarrheal diseases

E. coli can adhere to the mucosa of the large intestine

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• 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

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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

Prevention in Humans

• Good hygiene– Hand washing

• After livestock contact• Before eating and

drinking• After changing diapers

• Separate contaminated clothing

• Isolate infected children?

Prevention in Humans

• 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

Center for Food Security and Public Health, Iowa State University, 2012

Treatment

• treatment is based on symptomatology.

• fluid replacement is the primary treatmen

• Antibiotics are generally not used except in severe disease or disease that has progressed to a systemic stage (e.g.hemolytic-uremia syndrome).