Vibrio cholerae morphology and culture
Vibrio cholerae belonging to the family Vibrionaceae. The genus Vibrio comprises Gram-negative, mostly curved rods with a length of 1.5-2 m m and a width of approximately 0.5 m m, which have a single polar flagellum. The name Vibrio goes back to the Danish physician and naturalist Otto Friedrich Müller, who observed vigorous movements of the vibrios in a water drop during microscopy. The vibrios can be divided into serotypes based on O-antigens (lipopolysaccharides), like other gram-negative bacteria. The causative agent of cholera are almost exclusively strains of Serovarietät 0:1 with the subgroups Ogawa and Inaba. Due to the physiological characteristics, they are divided into the cholerae and El Tor biotypes. Another cholera pathogen that is particularly widespread in the Indian subcontinent, the serotype 0:139.
Vibrio cholerae can well be cultured on simple culture media at 37 ° C. Because of the strong alkali tolerance they may be selectively cultured at a pH of Figure 9.
The cholera, which only infects humans, is one of the notifiable diseases. In 2006, the Robert Koch Institute, a disease of cholera (biotype Vibrio cholerae 0:1, cholerae serotype Ogawa) has been submitted. In 2005, was unknown and in 2004, three cases of the disease have been reported. WHO in 2005 reported more than 130,000 cholera cases. Of these, by far the largest number of cases was observed in African countries (mainly Senegal, Congo and Gunea Bissau). The disease occurs as a poverty phenomenon in people with very low hygiene standards. The main source of infection is contaminated with faecal water represents the classical cholera vibrios (biotype cholerae) seem to be able to survive a few days without a man. In contrast, the true El Tor biotype as environmentally resistant. In cholera epidemics by the El Tor biotype, the number of subclinically infected is greater than that of the patients. Thus they also provide an important source of infection dar.
Pathogenesis and clinical pictures
The bacteria must first survive the passage through the stomach, because the stomach acid is an effective defensive measure dar. in the upper small intestine they are then due to the prevailing alkaline pH good propagation conditions. The adhesion to the receptor of the epithelial cells takes place by means of the fimbriae. Only the toxin produced by the pathogen responsible for the disease, which causes the increased secretion of chloride, bicarbonate, and potassium in the enterocytes. This explains the main symptom of cholera, the excessive water and electrolyte loss through vomiting and diarrhea very strong. An invasion of the mucosa by the pathogen does not occur.
The incubation period is two to five days. The disease starts with mushy fecal chairs, which are increasingly aqueous and finally Flakes contain mucus ("rice water stool"). Shortly after the first cases occurs even vomiting. The body can lose up to a day as 25 liters of fluid. The result is dehydration with dehydration. The patient first complains about hoarseness and thirst. Later, leg cramps and threatening cardiovascular symptoms such as hypotension, tachycardia, and oliguria follow. In untreated cases, the mortality rate is up to 60% with the classical cholera and 15-30% in cholera by the El Tor biotype.
The diagnosis is based on microscopic and cultural detection of the pathogen. Are suitable samples stool, rectal swabs, vomit and duodenal juice. The test material must as soon as possible or be transported to the laboratory by using a suitable transport medium, as the vibrios may die rapidly by dehydration or shift in pH. For selective enrichment itself is alkaline peptone water. As solid culture media culture media such as thiosulfate-citrate-bile salt-sucrose (TCGS) agar, taurocholate tellurite gelatin (TTG) agar-agar or cholera are used by Felsenfeld and Watanabe. Suspicious colonies were identified biochemically and by detection of the antigen in an agglutination reaction.
The focus of the therapy is fluid and electrolyte replacement and the administration of glucose. In severe cases, 10-30 liters of fluid a day to be fed parenterally. In mild to moderate gradients oral therapy is sufficient. The WHO has for this purpose a saline and glucose solution developed (20 g glucose, 3.5 g NaCl, 2.5 g NaHCO 3, 1.5 g of KCl in 1 liter of water), acquired as "Oral Rehydration Formula" for sale in pharmacies of southern countries can be.
Antibiotic therapy is only secondarily considered. It serves the faster elimination of vibrios in the intestine. When is the suitable dose of 960mg twice daily trimethoprim-sulfamethoxazole (Cotrim, and others), 100 mg of doxycycline (number of preparations) or 250 mg ciprofloxacin (Cipro, etc.) over three days. The once-daily administration of doxycycline 300mg or 1g ciprofloxacin is also possible. Resistance to all three antibiotics have been described.
|Tetracycline||250 - 500 mgs||4 times a day for 5-7 days|
|Pefloxacin||400 mgs|| twice a day for 7 - 14 days|
|Norfloxacin||400 mgs||twice a day for 7-14 days|
|Sulfathiazole||at an initial dose 3-4 g, then 1 g||4 times a day for 3-6 days|
|Polymyxin B||0,5-0,7 mgs/kg (200 mgs - Max in a day)||3-4 times a day for 5 - 7 days|
|Sulfadimidine||1 g||4-6 times a day|
|Ciprofloxacin||500 mgs||twice a day for 7 - 14 days|
|Nifuroxazide||200 mg||4 times a day for 7 days|
|Roxithromycin||300 mgs||once or twice a day|
General preventive measures are adequate food and drinking water hygiene and proper waste disposal. In the individual case must be prevented vibrionenhaltige excreta of patients reach drinking water. Diseased and subclinically infected must therefore isolated and their excreta disinfected. Cholera is a disease of quarantine WHO represents the quarantine period is five days.
Vaccination with killed cholera vibrios is not sufficiently reliable and holds a maximum of six months. An anti-toxin-inducing vaccine does not exist.
According to § 7 IfSG, a reporting requirement for all direct and indirect evidence of Vibrio cholerae 0:1 and 0:139. According to § 6 IfSG suspicion of disease, illness and death from cholera are reported.