Vibrio Cholerae – Cholera

 

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Vibrio Cholerae – Cholera

Introduction

Vibrio cholerae is a type of bacteria that is associated with cholera. It can cause an acute illness which cause severe diarrhea which results to dehydration and can cause death within a very short time. It is a gram negative bacterium (Faruque&Nair, 2008). V. cholerae is comma shaped and it has and it has a flagellum at one end. A flagellum is a protrusion that is usually at one end of a cell body. The main function of the flagellum is to help the cell in locomotion as well as to act as a sensory organ. It is also facultatively anaerobic. V. cholerae can be observed in two categories. These are: Vibrio choleraeSerogroup 01 and Vibrio choleraeserogroup non-01. The former is the most common cause of cholera. There are many species of V. Cholerae that belong to the later. These species do not cause diarrhea apart from Vibrio choleraeSerogroup 0139 (Schoenstadt, 2012).

  1. cholerae is an important organism in human beings. One of the reasons as to why it is important is due to the fact that it causes so many deaths across the world. The bacteria kill so many people especially those who live in poor conditions. People in slums and displaced persons camps are at a high risk of contracting the disease. In addition, poor basic infrastructure also increases the risk of the disease. Across the world, there are an approximated 3 – 5 million people who are infected by V. cholerae. Out of these, about 100 000 – 120 000 people will die out of the illness (WHO 2012).The disease is rare in the industrialized nations. However, the rest of the nations still experience cholera pandemics. Since 1817 only 7 cholera pandemics have occurred.

In America, there are rare cases of cholera if at all they are there. The bacteria are commonly in the Ganges delta in India. It is also common in Bangladesh. Currently, there is an on going pandemic of the bacteria in Africa, Asia as well as in Latin America. These pandemics have been reported within thelast forty years. Of these pandemics, 80 percent was from Africa (Schoenstadt, 2012).

The following is an image of Vibrio cholerae.

 

Mechanisms of Pathogenesis

The Vibrio cholerae pathogen is associated with the disease cholera as it has been mentioned earlier. The disease can be in mild form or it can be asymptomatic. There are also severe forms of cholera which cause serious diarrhea and eventually death which can occur within a very short time.

Cholera is a disease that is very virulent. It can affect people of all ages ranging from children to adults. It is one of the diseases that can cause death within a very short time. It can actually kill within hours.Symptoms are developing depending on the severity of the disease. Severe forms of the disease will hardly show any symptoms. The bacteria might have lasted in the body for up to a week before death occurs but no signs will be seen. In fact, 75 percent of the people who are infected by the disease do not show any signs. In case of any symptoms, 80% of the people will show mild signs or they will show moderate symptoms. The main symptoms of cholera are diarrhea and dehydration. The diarrhea can be watery and profuse. Other symptoms that are specific to cholera include; muscle cramps and vomiting.Stool appearance changes. It appears greyish in color and it has some mucus. In addition, the stool has a characteristic appearance that is “rice- water”. Watery diarrhea appears suddenly. The diarrhea is usually painless. As fluid is lost from the body through vomiting and diarrhea, the person becomes weak and thirsty. Urine production decreases. At the very final stages of the disease, the rate of heartbeat increases then coma and death occur (Schoenstadt, 2012).

The microorganisms affect the intestines. This is where they start to multiply. The organism is said to be an environmental as well as a human intestinal pathogen. The bacteria cause toxins in the intestines.This toxin that is produced by V. cholerae has the ability to stimulate an enzyme referred to as the adenylatecyclase. This is an enzyme that is responsible for the production of cyclic adenosine monophosphate also known as the cyclic AMP. Cyclic AMP is produced from adenosine triphosphate (ATP). The toxin which is a prototypical enterotoxin is the one that causes aprofuse diarrhea.It causes the intestines to produce fluid that contains sodium bicarbonate as well as potassium. This content is too much for the intestines to absorb and hence the occurrence of diarrhea (Sack, Sack, Nair and Siddique,2004).Encodingvirulence factors of the genes are grouped in two regions of the chromosome. One is on the pathogenicity island and the other one is on a filamentous bacteriophage. As a result of these clustering of the genes, it means that a horizontal gene transfer is likely to result to occurrence of new endemic problems. It is important to note that the environmental conditions are the once responsible for regulating and coordinating multiple virulence genes (Butterton 2012).

For the organism to reach the intestine, it has to get through the body defensive mechanisms which are on the gastro intestinal tract. The mechanism contains acids. However, the organisms do not have the ability to resist acids. Therefore, for them to get through the tract they must be in large numbers so as to withstand the acidity (Thaker, 2011). The bacteria are transmitted through consumption of contaminated water. It can also be transmitted through ingestion of contaminated food.

Methods of Growth in the Lab

Cultivation

  1. cholerae is can strictly be classified as a water bornepathogen. In addition, the pathogens are facultatively anaerobic. They therefore would require sodium chloride (NaCl) for their growth. It is sodium chloride that usually stimulates their growth. These pathogens are said to reduce nitrates into nitrites. They cannot grow in a broth that does not contain sodium chloride. Sodium chloride has to be added to the broth for the pathogens to grow in it. V. cholerae can be studied in the laboratory. It has the ability to grow in a defined culture medium. One of the cultures that have been identified in which the pathogen can grow in was proposed by Nakashi back in the year 1962. It was later modified by Kobayashi and his colleagues in the year 1963. The culture is referred to as Thiosulfate Citrate Bile Sucrose Agar or simply the TCBS Agar. The culture is the best recommended for distinguished and selective cultivation of the cholera causing pathogen as well us other vibrios which areenteropahtogenic. The culture medium has been recommended by the World Health Organization since it complies with its regulations.It provides conditions for rapid growth of the pathogen and other Vibrio spp. (Merck KGaA 2002). Other cultures such as the heart infusion agar, triple sugar iron agar and Kligler’s iron agar can be used (CDC, n.d.).

Incase of a negative reaction, no color change will be observed on the culture. It is important to note that the incubation period for the pathogen in the culture will be about 48 hours. The specimen will be taken from a stool sample or from a food sample that is contaminated. The culture is very selective to an extent that it has the capability to suppress non vibrios which might be part of the contaminant. In addition, it has all the nutritional requirements that the Vibrio spp requires for its growth. The nutrients that are contained in the culture include; yeast extracts which have nitrogenous compounds, amino acids as well as vitamin B complex all of which are essential for growth of the microorganism. The culture also has oxbile and sodium citrate. These two are important since they help to inhibit the growth of gram positive bacteria which cause contamination such as the enterococci.Sulphur in combination with ferric citrate is able to detect any hydrogen sulfide that might be produced. These two compounds are contained in sodium thiosulfate. Sucrose provides carbohydrates required by Vibrios for growth while NaCl is essential to stimulate growth. The indicators bromothymol blue together with the thymol blue are responsible for color change (Sigma-Aldrich, Inc).

The Vibrio spp. will produce a color change to form a yellow colony.It will appear as below;

(Merck KGaA)

Laboratory Test

Tests can be carried out in the laboratory to detect V.cholerae in a specimen. Lab test are used as a confirmatory diagnosis since there are other diseases which have similar symptoms as those of cholera.V. cholerae can be identified in the laboratory simply by carrying out a serological test on a stool specimen. This just a simple test and it can be confirmed further by carrying out more tests such as the biochemical tests to single out the microorganismscharacteristics from those of others which may have some similar characteristics.Tests such as bio typing, hemolysis antimicrobial sensitivity assays as well as molecular subtyping can be used to confirm the presence of V. cholerae 01. However, the use of antisera is regarded as the most rapid and also the most specific of identifying the presence of V. cholerae. Identification of the enterotoxins produced by the V. cholerae as well as biochemical identification can fully confirm the presence of the bacteria (CDC, n.d).

Disease Treatment and Prevention

Cholera is a disease that can be treated by use of oral rehydration salts. According to WHO (2012), over 80 percent cases of cholera have been treated successfully. Since the disease cause so much loss of body fluids, constant replacement of the fluids is important. In fact, in case of a severe diarrhea which causes severe dehydration, the fluids are replaced intravenously. In order to reduce the duration of diarrhea, administration of antibiotics is important. This will help in reducing the volume of rehydration fluids required. In addition, antibiotics will help to reduce the duration for removing the bacteria V. cholerae from the body. It is important to note that antibiotics should not be administered in large amounts. There are two reasons behind this. The first one is the fact that large amounts of antibiotics do not have any effect on the spread of V. cholerae. The second reason behind restriction of antibiotics is that too much of them will be likely to increase antimicrobial resistance. Timely access to treatment is of utmost importance for effectiveness. With effective treatment, death rate is almost un-significant.

Prevention

Vibrio cholerae pathogen is associated with contaminated water. It can however be found in contaminated food. Therefore, the first step that can be taken to prevent cholera is to ensure that the water available for consumption is clean. Multidisciplinary approach should be used in preventing the occurrence and spread of the disease. In order to prevent the spread of the disease through travel, surveillance systems can be put in place. They should be effective. They will be important in controlling the disease in endemic areas. In addition, they will help to mitigate cholera outbreaks. These measures will reduce the spread of cholera, cholera outbreaks will also be reduced as well as the number of deaths caused by cholera (WHO, 2012).

Conclusion

Cholera is a disease that is very common in crowded places and in slums where the infrastructure is poor.It is rarely found in industrialized countries. It is caused by bacteria Vibrio choleraewhose main habitants in water. The disease is important in human beings in that it causes deaths in so many people. It also has the ability to cause death within a very short time. It can however be treated. The effectiveness of treatment will depend with timely and early access. Its symptoms might not be noted hence increasing its risk. Prevention measures can however be adapted to reduce its incidences.

 

 

 

 

 

 

 

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