Thursday, August 7, 2014

Escherichia Coli

These are Gram negative, rod-shaped organisms 1-3 a X 0.4 to 0.7 p in size, arranged singly or in pairs. The organism is motile though some strains may be nonmotilc. It grows easily in ordinary media. It is usually a harmless inhabitant of the intes-tines of man and animals. Excreted in the faeces, it remains viable for a few days only. Detection of E. coli in drinking water is therefore taken as evidence of recent pollution with human or animal faeces. E. coli is the commonest cause of urinary in-fections, cystitis, pyclitis or pyeloncpbritis. When it gets into the peritoneum it causes peritonitis. It may also cause pneumonia, and, suppuration elsewhere in the body.

 Some varieties or strains of E. coil cause gastroenteritis particularly in hospital nurseries. The specimens to be sent to the laboratory depend on the disease under investigation. They arc midst/ram specimens of urine (catheterisa-tion for collecting a specimen of urine is neither advisable nor necessary) in cases of urinary in-fection, pus in pyogenic infections and faeces in gastroenteritis. In hospitals, cross infection should be avoided. Sterilisation of feeding bottles, teats and strict personal hygiene on the part of the nurse have to be rigorously enforced. Catheterisation should be avoided and when inevitable the utmost pre-caution should be taken.

These are a large group of Gram negative bacilli. They are about 1-3 A X 05-0.8 si in size. They are all motile except for Salmonella pullomm-gallthanon. They grow in ordinary media. They are all pathogenic and cause disease of the small bowel. They can be considered under two broad groups — the enteric fever group and the food.
The enteric fever group: Salmonella typhi, Salmo-nella paratyphi A, Salmonella paratyphi B and Sal-monella paratyphi C belong to this group. S. typhi (Fig 9.5) is the causative organism of typhoid fever. S. paratyphi A and S. paratyphi B cause paratyphoid fever which resembles typhoid fever. S. paratyphi C may also cause paratyphoid fever, but more often leads to septicaemia with suppurative complications. Salmonellae such as S. enteritidis, S. typhimurium and a few others have on occasion caused a typhoid-like fever. These are Gram negative bacilli, 1-3 to 9( 05-0.8 it in size and motile. They grow readily in ordinary media. Salmonellae are strict parasites of -animls or man. the infection is acquired by the ingestion of contaminated food, water or milk. They in-vade the lymphatics in the Peyer's patches of the small intestine. After an incubation period of about two weeks (5-20 days) they reach the bloodstream. The patient becomes very ill with rising fever. Metastatic abscesses may occur in almost any part of the body. The intestinal wall.

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