Pathogens areorganisms that cause diseases in the human beings and animals. Humanpathogens are classified into parasites, such as helminths, bacteriasuch as Clostridium botulinum, Vibrio cholerae, andStreptococcus pneumoniae among others. Another group ofpathogens is fungi such as Aspergillus flavus that causesaflatoxin. The pathogens also include viruses such as the Humanimmunodeficiency virus (HIV), Ebola virus, and swine flu amongothers. The majority of the bacteria produce a poison called toxin.The toxins cause changes in the host body leading to disease. Forexample, Vibrio cholerae produces cholera toxin that causessevere diarrhea in the host. Excess water loss due to diarrhea causessevere dehydration that leads to death the host. Other pathogensattack and kill cells, for example, HIV, target immune cells toweaken the body immunity. Reduced resistance allows foropportunistic pathogens to attack and cause opportunistic diseases(Pommerville, 2014). The essay will discuss the role of Vibriocholerae in human and public health, virulence factors,prevention and treatment strategies. In addition, the article willdiscuss the role of plasmids in genetic engineering.

Roleof Vibrio cholera in Human and Public Health

Vibriocholerae is a pathogen of public health importance. The pathogenis waterborne and poses a great challenge in developing countries dueto lack of clean water and proper sewerage systems. The bacteria isspread through poor sanitary practice. For example, defecating inwater source or failing to wash hands. People drinking thecontaminated water will get the disease. In many cases, choleraoutbreak occurs when there is flooding in an area. Flooding causescontamination of clean water. Cholera has high fatality rates withdeath occurring within 24 hours after symptoms of diarrhea areobserved. Notably, the diarrhea is bloody and watery (Pommerville,2014).

The diagnosis ofVibrio cholerae uses both culture and microscopic examination.In the microscopic examination of Vibrio cholerae, the patientstool sample is prepared in a Petri dish and examined under phasecontrast microscope. The bacteria are motile and appear like shootingstars. For a definitive diagnosis, stool samples are added to asucrose broth. The bacteria are then isolated. The isolated Vibriocholerae is then plated in sucrose plates. If Vibrio choleraeare present, yellow colonies are observed. Apart from microscopy andculture, other techniques include PCR and monoclonal antibody. PCRuses templates to detect and amplify Vibrio cholerae gene. PCR is a more reliable definitive diagnosis for the bacteria due toits specificity and accuracy. ELISA, on the other hand, uses Vibriocholerae antigens to detect antibodies in the host blood.Usually, the body immune cells such as B-cells react to Vibriocholerae by producing antibodies. If the individual has Vibriocholerae, their blood must contain antibodies (Pommerville,2014).

Importanceof Plasmids in Bacteria Genetics and Genetic Engineering

Plasmids areextra-chromosomal genetic material found in bacteria. Thechromosomal genetic material in the nucleus of the bacteria playsimportant roles such as controlling cell division and apoptosis(controlled cell death). Plasmids are round. They are evolutionaryfeatures of the bacteria that help cope with changes in theenvironment. Therefore, plasmids confer bacteria advantages such asantibiotic resistance. One bacterium that has high resistance isMycobacterium tuberculosis. Therefore, genes carried in thebacteria plasmids allow it to survive adverse conditions. Notably,the replication of the plasmids occurs during the cell division. Dueto their ability to replicate, bacteria plasmids have become usefulin genetic engineering (Pommerville, 2014).

Geneticengineering is the application of molecular techniques to manipulatethe genetic make-up of an individual. Genetic engineering can beintended to correct a genetic anomaly in a person, for example,replace defective gene. Genetic engineering may also enhancebeneficial genes of an individual. Genetic engineering is widely usedin the agricultural sector for instance to increase the resistance ofthe plant to pests and yields. Plasmids are used in geneticengineering in the following ways. First, the plasmids are isolatedfrom the target bacteria using bacteriophages, which are viruses thatinfect bacteria. Enzymes known as restriction endonucleases are usedto cut plasmid and the target genes. The plasmid is cut between thepromoter and terminator region. The promoter is the region of thegene that initiates gene transcription. The terminator is the regionthat stops the transcription of the gene (Pommerville, 2014).

The openplasmid, target gene, and enzymes called ligase are incubatedtogether at 370 C overnight. Ligase allows the joining ofthe two free ends of the genes. Another enzyme called integrasepromotes the integration of the target gene into the plasmid. Theplasmids are then tested for integration using methods such aspolyacrylamide gel electrophoresis. In plants, Ti plasmid found inAgrobacterium tumefaciens is used to transfer the target geneto the plant cell and promote its integration (Pommerville, 2014). Once the target gene is integrated into the plant gene, it istranscribed conferring the plant the desired qualities.

HumanMicrobe Relationship &amp Virulence Factors

Useful microbes are called probiotics. For example, in the humangut, bacteria in the large intestines digest roughages producingvitamin K. Such a symbiotic ecosystem benefits both the human and thebacteria. Importantly, normal flora benefits human by preventing theovergrowth of pathogenic microbes. However, normal flora suchEscherichia coli can cause disease in the followingways. First, if the host immune response is reduced, healthy bacteriamay become virulent. Virulence is the extent to which a bacterium cancause disease in the host. Another factor that influences thevirulence of the bacterium is colonization. In colonization, microbesinvade a new area of the body usually a sterile part and causedisease (Pommerville, 2014).

Preventionand Treatment Strategies of Cholera

The firstapproach to preventing the disease is surveillance. Clinicians aremandated to detect and report any suspicion of cholera case to forimmediate interventions. Therefore, monitoring the occurrence of thedisease is vital in preventing the disease (Pommerville, 2014).Thesecond preventive measure is to provide proper water and sanitation.


If the patientis taken to a health facility, cholera can be treated successfully.The first step is to administer oral rehydration solution (ORS) inmild cases. In severe infections, intravenous administration offluids is crucial in stabilizing the patients (Pommerville, 2014). .Antibiotics is used to kill or suppress the multiplication of thebacteria.

In conclusion,microbes are both beneficial and undesirable to humans. For example,Vibrio cholerae is undesirable because it causes disease inhumans. On the other hand, bacteria such as Escherichia coliare probiotics that help in digestion. In addition, bacteria such asAgrobacterium tumafaciens are used in genetic engineering,which is beneficial to humans. Preventive measures should be adoptedto mitigate the undesirable effects of the microbes. In the case ofcholera, the preventive measures include disease surveillance andproviding proper sanitations.


Pommerville, J.C. (2014). Fundamentals of . Burlington: Jones andBartlett Learning