APMB: Escherichia coli

What are faecal coliforms?

Faecal coliorms are coliforms which grow at 44.5 degrees C

How does Escherichia coli cause Urirary Tract Infections (UTI)?

Most common in women, because of the short distance between the vagina and the anus

Drinking water and regular irnations can reduce the chance of UTI

What are the Pathogenic strains of E.coli?

Enterotoxigenic (ETEC)

Enteropathogenic (EPEC)

Enterohemorrhagic (EHEC) 

Enteroinvasive (EIEC)

O157H7

Difference between ETEC, EHEC, EPEC and EIEC

ETEC:

• Produces enterotoxin responisblw for diarrhea

EHEC:

• Bleeding caused by damage to the interstinal lining

• These bacteria can invade the body causing organ damage and death

EPEC:

• Bacteria bind to the instestinal mucosa but DONT invade it

• Mucosa cells change in structure → Diarrhea

EIEC:

• Bacteria bind to the intestinal mucosa using their adhesin proteins and INVADE them

Sources of E.coli O157:H7

1) Direct contamination from raw/undercooked meat

2) Cross contamination from raw meat to vege while cooking

3) Contaminated water

4) Unhygienic habits of food handlers 

Signs and smptoms of infection by O157:H7

• Severe abdominal pain

• Bloody diarrhea

• Vommiting may occur

Result of E.coli on MacConkey Agar (MAC)

Red colonies 

• Fermentation of lactose to acid (turn neutral red indicator red)

Result of E.coli on Crystal Violet Neutral Red Bile Agar

Red-pink colonies

Result of E.coli on EMB agar

Black colonies with metallic sheen

• Strong acid production from E.coli causes the Eosin an Methylene blue to react to form the result

• ONLY E.coli produces sufficient strong acid to create this result