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Lectures of Dr. oruba.khalid

Lectures of Dr. oruba.khalid. Campylobacter. Family : Campylobacter In this family there are two genera: 1. Genus: Campylobacter; with 18 species. 2. Genus: Acrobacter; with 4 species. Genus: Campylobacter

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Lectures of Dr. oruba.khalid

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  1. Lectures of Dr. oruba.khalid

  2. Campylobacter

  3. Family : Campylobacter In this family there are two genera: 1. Genus: Campylobacter; with 18 species. 2. Genus: Acrobacter; with 4 species. Genus: Campylobacter These microorganisms have long been known as animal pathogens including poultry, dogs, cats, sheep and cattle. There are two important species that can cause human infection: 1. C. jejuni. 2. C. coli. Transmission of these m.o. is usually via contaminated food (as chicken) , milk or water, while person to person transmission plays a minor role .

  4. GENERAL CHARACTERISTICS OF CAMPYLOBACTER • Small, delicate, spirally or curved. • Gram-negative bacteria • Oxidase positive • Fastidious • Microaerophilic • Motile by polar flagella

  5. Morphology: Small gram negative rods comma-shaped or S-shaped. Motility is of darting type with cork screw-like movement. These m.o. have a single polar flagellum. Cultural characteristics: These microorganisms are microaerophilic (requires 5% O2, 10% CO2, and 85% N2) which is provided by Gas-Generating Kit. Also these m.o. are thermophilic (tolerate temperature up to 42-43 C which is useful characteristic in their isolation and differentiation. The important media used for cultivation is: 1. Skirrow’s medium: Contains blood agar and anti-microbials including vancomycin, polymyxin B, and trimethoprim to make it selective for the m.o. 2. Campy-BAP: Similar to (1) but with cephalothin.

  6. Colonies of Campylobacter: The colonies are colourless, rounded and convex. For culturing plates are put at 37 C and others at 42 C. Also, other media containing charcoal, or using filtration can be used. Biochemical Characteristics: Campylobacter are oxidase positive, catalase positive, H2S producers, and can reduce nitrate to nitrite.Also, these m.o. are urease negative (versus Helicobacter).

  7. Pathogenesis and Clinical Picture: The m.o. are acquired by oral route by food and water contaminated with animal faecesor after direct contact with animals (as puppies with diarrhoea). The m.o. are quite sensitive to gastric juice and at least 10000 m.o. are required to breach this barrier. The I.P. is 1-6 days. In the intestine, they multiply and invade the intestinal wall (similar to- but less than Shigella). The m.o. liberate exotoxin and enterotoxin (V. cholerae- ike) causing damage to the intestinal tissue. This results in an acute onset of grossly bloody diarrhoea which is associated with cramps of abdominal pain. The stool contains R.B.C. and leucocytes (pus cells). Occasionally, the m.o. invade to the blood stream and giving picture of enteric fevers.

  8. Treatment of Campylobacter: Replacement of fluid and electrolytes is an essential step in the management. The m.o. are sensitive to erythromycin and nalidixic acid. Recovery occurs usually in one week. Complications: Gullian –barre syndrome ( acute demyelinating peripheral neuropathy with ascending flaccid paralysis) is an important complication. The pathogenesis involves gangliosides like –epitopes in the Campylobacter LPS that cross react with reactive targets in peripheral nerve tissue as well as host susceptibility factors.

  9. Helicobacter

  10. Genus: Helicobacter There are many species of this new genus (proposed in 1989), and only a single species is important to humans which is H. pylori. The latter m.o.is now a well-known cause of gastritis, duodenal and gastric ulcer and is linked to gastric carcinoma and MALT (Mucosal Associated Lymphoid Tumours). Helicobacters are very similar to Campylobacters (even previously they were in the same genus), but are different in being urease positive, while Campylobacter are urease negative. Campylobacters are motile with one polar flagellum, while H. pylori have multiple polar flagella.

  11. Morphology, Culture and Biochemical Tests: H. pyloriare gram negative m.o., spiral in shape, actively motile by multiple flagellae. H. pylori can grow on the same media mentioned for Campylobacter. It is better to supplement the media with horse serum. They best grow at 37 C, and require 3-6 days of incubation. The m.o. are catalase positive, oxidase positive and urease positive. The latter character can be used for: 1. Rapid urease test: In which gastric biopsy material is placed onto a medium containing urea with a colour indicator. If H. pylori is present, the urease splits the urea and results in shift of pH leading to colour change (from yellow to red). 2. Urease Breath Test: In which 14 C –labelled urea is ingested by the patient. If the m.o. is present, the urease activity generates radiolabelled CO2 that can be detected in patient’s breach (by detector).

  12. Pathogenesis of H. pylori: These m.o. attaches to the mucous- secreting cells deep in the gastric mucosa away from the acidity of the stomach. The production of ammonia from urea by the organism’s urease, coupled with an inflammatory response leads to damage of the mucosa. Loss of the protective mucous coating, predisposes to gastritis and peptic ulcer. The ammonia also neutralizes gastric acidity, allowing the organism to survive. It is worth to mention that the m.o. prefer pH of 6-7, but sensitive to gastric juice. H. pylori is responsible for 85% of peptic ulcers. However, 80- 90 % of people in developing counties carry this m.o., while in developed counties the rate is 20- 40%. The main factors of pathogenicity are the active motility, proteases (damage mucosa) & urease.

  13. Diagnosis of H. pylori Infection: 1. Gastric Biopsy specimens: Minced in saline and examined: A. Smears stained with Gram’s or special stains which show the curved or spiral organism. B. Culture (see above). 2. Detection of H. pylori Antibodies in patient’s serum: These antibodies are of 3 classes (IgM, IgG, and IgA). IgM is the first one to appear followed by IgG and IgA. ELISA can detect such antibodies. The detection of these antibodies does not differentiate between current/active and old/inactivate infections. However, these antibodies can be used for follow up of treatment of patients. 3. Detection of H. pylori Antigens in the stool (ELISA). 4. Rapid UreaseTest (see above). 5. Urease Breath Test (see above).

  14. Treatment of H. pylori infection: Peptic ulcers and gastritis could be treated by combination of the following drugs: Triple Therapy: Metronidazole + clarithromycin or amoxicillin or tetracycline + bismuth subcitrate (pepto-bismol). This treatment results in eradication of H. pylori in 70 – 95 % of patients and decreases recurrence rate of peptic ulcers. Immunity: The antibodies could stay for a long time after recovery. These antibodies have no active role in bactericidal effect against H. pylori.

  15. END OF LECTURE

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