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Microbiology 12 |
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Microbiology 12 |
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NOTE: INFORMATION ON THIS PAGE IS INTENDED FOR EDUCATIONAL USE ONLY. FOR MEDICAL ADVICE YOU SHOULD CONSULT WITH A PHYSICIAN
Helical or comma shaped cells, motile by flagella. These organisms thrive in conditions of low free oxygen concentration and enriched CO2.
Representatives:
Campylobacter jejuni
Campylo (curved) bakter (rod) , jejuni (of the intestine)
The organism has emerged to a become a leading cause of foodborne gastroenteritis in the U.S. with over 2 million estimated cases a year. In some regions it has surpassed Salmonella. Campylobacter is widespread in the GI tracts of animals ; almost all retail chicken is contaminated & close to 60% of cattle shed the bacateria in their feces and milk. Bacteria are often spread in the slaughtering process. Undercooked poultry and unpasteurized dairy are most often implicated as a source of C. jejuni. Fever and headache, fatigue appear 3-5 days after injestion of these organisms. GI symptoms sometimes follow lasting 1-4 days and may include severe diarrhea, abdominal pain and cramping. In about 20% of cases symptoms will reoccur for several weeks. Arthritis can occur in children. About 1 in 1000 cases will suffer from a temporary paralysis called Guillan Barre syndrome ( an acute, rapidly ascending paralysis following some respiratory or enteric infections). A surface molecule of the bacterium may mimic lipids in nervous tissue and trigger the production of autoantibodies.
In 1999, C. jejuni became the first food-borne pathogen to have its genome sequenced. The organism may undergo regular mutation in the genes that code for surface lipopolysaccharide and may change the way its surface looks to the immune system. In this way the bacteria may escape antibodies that were made in previous infections.
Treatment and prevention
Fluid and electrolyte replacement is the favored treatment. Sometimes tetracycline is administered. The illness can be prevented by proper cooking of foods, avoiding cross-contamination of foods and unpasteurized milk.
Helicobacter pylori
H. pylori was identified in 1983 by Australian researchers. Strains of this organism are now confirmed to be the cause of the vast majority of cases of chronic gastritis, gastric and duodenal ulcers. Approximately 10 % of the US population will suffer from an ulcer at some point in their lives. In developed nations like the U.S. young children are not commonly infected but after age 20 about 20-30% of the population is infected. In developing countries many more people are infected in childhood probably as a result of lack of sanitation and drinkable water. As a consequence, people in such countries ar infected longer and may suffer more severe effects.
The organism survives the acidity of the stomach by producing the enzyme urease. Urease cleaves urea into carbon dioxide and ammonia which raises the pH of the gut in the area of infection. The organism also causes a decrease in mucus production and tissue becomes eroded by stomach acid. The International Agency for Research on Cancer has grouped the organism as a group 1 carcinogen. A strong association exists between infection with H. pylori and the development of gastric cancer, particularly in people that are infected at a young age. An ulcer can be identified by endoscopy and infection confirmed by culture and microscopy.
Treatment and prevention
The exact means of infection and portal(s) of exit are uncertain for H. pylori which makes avoidance of the organism difficult.
Many people still believe that peptic ulcers are "caused" by the following factors, when in fact they are not:
Such beliefs can be harmful as ignorance of the underlying infection will lead the patient away from a necessary treatment regime.
The FDA has approved at least 5 different treatment regimens. Antibiotic therapy usually lasts between 7-14 days and has cure rates between 70-90% depending on the regimen.
One regimen includes the antibiotic clarithomycin with metronidazole and a suspension of bismuth. Different treatment courses may be necessary to completely eliminate the organisms.