Biology

I. A missionary couple, living in West Africa brought their 4-year old son to the office of their physician on the second day of a visit home to Minnesota. The boy had severe  continuous diarrhea about seven hours earlier. His mother described his diarrhea as whitish with flakes in. There was blood however when a blood film was made whole blood cell could be identified.
1. This disease is most likely caused by what bacteria and what is the name of the disease
The disease is most likely caused by the bacterium Vibrio cholerae and the disease is Cholera.
What would confirm your choice
To confirm my choice, I would perform a laboratory tests that include the stool gram stain (gram negative rods) culture dark field microscopy or stool Polymerase Chain Reaction (PCR), depending on the testing kit available.
The boy had all of his vaccines so why does he have such an infection
This is because Cholera has no vaccine, thus one is susceptible to it.
What course of treatment would you order
I could order rapid intravenous replacement of the lost fluid and ions. Then followed by administration of isotonic maintenance solution (Oral Rehydration Therapy) continuous until the diarrhea ceases.
What could be the likely source of this infection
Likely source of infection could be through consumption of raw or undercooked shellfish, water or food, contaminated with V. cholerae.
II. A 7 weeks baby girl was brought into the hospital with a rash on hands and feet, fever, cough and high WBC count. The baby was premature 35 weeks at a weight of 2.97kg. She was treated with Penicillin G for 14 days  testing after that showed the treatment was successful. The parents were treated too.
What infection did she have
 
      She had congenital syphilis.


Name the causative agent.

Causative agent is the bacterium Treponema pallidum.


How did she contract this microbe

She contracted it through transmission from the mother during pregnancy as blood containing the bacteria reached the fetus through the placenta, the organ that nourishes the developing baby.

At what stage of the infection was she, and why

She was at the secondary stage of the infection. This is because most infants born with syphilis have no symptoms of the disease. Almost all develop symptoms by three months of age, which according to the symptoms she had it is already in the secondary stage of syphilis. The primary stage symptoms include a chancre where the bacterium entered and enlarged lymph nodes at the groin, indicating that the syphilis is in the secondary stage. 






Why were the parents treated too

The parents were treated because they had contracted the disease that was eventually transmitted to their daughter. Hence, the diagnosis was to prevent further infections in the family.

III. A 24-year old female presents herself at the doctors office. She complains of fever and of pain in her digestive tract. She had diarrhea that was bloody. A blood film was made of her stool and no blood cells were noticed. Physical examination showed the patient had a tender abdomen. She had eaten at a fast food place 4 days ago  she felt ill for the past couple of days, she had vomiting and fever too. Microbial analysis showed gram negative non-spore forming rods. 
What type of food disease do you believe she has
She has Shigellosis a form of food infection that may result when foods containing Shigella bacteria are consumed.
2.  What are the factors that assist you in your identification of the causative agent and why
The factors that assisted me in identification of the causative agent are the physical examination that revealed a tender abdomen bloody diarrhea that had no blood cells analysis that showed gram-negative non-spore forming rods and the incubation days for the symptoms to appear. These were vital in differentiating the causative agent from Vibrio cholerae, E. coli, Salmonella, Yersinia entercolitica and Campylobacter fetus, which are related to Shigella.
3. What agents (at least 3) you would not consider  why
I would not consider Vibrio cholerae, because the microbial analysis did not show diarrhea as whitish with flakes nor blood film showing presence of whole blood cells. I would also rule out Salmonella and E. coli, because their symptoms do not include bloody diarrhea.
4. What treatment will you advise  why
I would advise a bactericidal antibiotic for instance metronidazole Oral Rehydration Therapy (ORT) for treatment of dehydration and antispasmodics if at all the cramps are severe. This is because virulent Shigella strains produce disease after invading the intestinal mucosa the organism only rarely penetrates beyond the mucosa, thus the bactericidal will kill the virulent Shigella strain that produces the disease. The ORT is to restore the lost fluid and antispasmodics are to relieve the pain.
5. What is the virulence factor in such an infection
Shigellae do not produce enterotoxins and they are not haemolytic. As a prerequisite of Shigella virulence, the bacteria have to penetrate into the intestinal epithelial cells and proliferate there. This is penetration is arbitrated by a Shigella-induced phagocytic event. The products of the genes encoded in the large virulence plasmid as well as some chromosomal genes are involved in this step.
IV.   A 27-year old white female presented her self at her local physician on August 15. On physical exam, the patient had a fever of 38.5C. She appeared fatigued, had tender abdomen and complained of headache, stiff neck and backache with diarrhea. The physician noted an irregular heartbeat. The patient complained of lack of ability to concentrate. The patient gave the following history She is a graduate student in the wildlife program at the University in her town. She was in the field for three weeks in Wisconsin during the months of May and June. She tracks small mammals in the field and studies their behavior. It had been a warm, wet spring and she complained of a large number of flies in the area. She felt sick the last day there after eating some canned food, as there was no cooler there. You had no time for culturing, as you need to take action fast.
What is your best diagnosis of this case
My best diagnosis of this case could be treatment with beta-lactam antibiotics such as ampicillin andor the addition of gentamicin frequently for its synergistic effects. Also I could administer intravenous or oral rehydration therapy to control dehydration, and some pain killers to relieve fever and pain.
What features are critical to your diagnosis
The features that are critical to my diagnosis are Headache, stiff neck, diarrhea, fever and irregular heartbeat.
3.   What further steps should be taken to precisely identify the case  why
Further steps to be taken is to culture for pathogens from the blood or Cerebrospinal fluid, this is because of lack of reliable serological or stool tests to test for my assumed pathogen . The whole issue is to establish the causative agent which I suspect to be Listeria monocytogenes, because the central nervous system (CNS) has been affected resulting into a stiff neck and loss of concentration.
4.  What microbes you will not consider and why name 2.
I will not consider Clostridium botulinum and Bacillus cereus. This is because their symptoms dont include a stiff neck which is symptomatic for meningitis, as a result of CNS infection with Listeria monocytogenes.




SECTION II SHORT ANSWERS 8X1080PTS
1.  What are parasites and their virulence factors List 4 diseases that are parasitic.
Parasites are organisms that derive all of their nutrients from other organisms called hosts. The parasites can be either ecto-parasite or endo-parasite. The parasites dont contribute anything to the host and thus they harm the host or can even kill it in some cases. Parasites possess surface antigens with amino acid repeats. Making up the interface between host and pathogen such repetitive proteins may be virulence factors involved in immune evasion or cytoadherence. Diseases that are parasitic are Malaria caused by the endoparasite protozoan Plasmodium spp. Trichomoniasis caused by the endoparisite protozoan Trichomonas vaginalis Toxoplasmosis (Parasitic pneumonia) caused by the endoparisite protozoan Toxoplasma gondii and Schistosomiasis (bilharzia) caused by Schistosoma sp.
2.  Do you think that recombinant protein vaccines could work for HIV, why
No Recombinant protein vaccines can not work for HIV. This is because, HIV is highly mutable, this is,  the virus has an ability to swiftly counter to selective pressures imposed by the immune system, the count of virus in an infected individual typically evolves so that it can evade the two major weapons of the adaptive immune system humoral  and cellular immunity. Also, HIV isolates are themselves highly variable, this is, it can be categorized into multiple clades and subtypes with a high degree of genetic divergence. Therefore, the immune responses raised by any vaccine need to be broad enough to account for this variability. Any vaccine that lacks this breadth is unlikely to be effective.


3.  Name 2 bacterial  2 viral STDs and their causative agents. Name 3 possible symptoms that may indicate an STD infection
Two bacterial STDs are Syphilis and Gonorrhea. Two viral STDs are Genital Warts (HPV) and Herpes. Three symptoms that may indicate an STD infection include Burning or pain during urination, unusual vaginal or penile discharge, and blisters or sores on the genitals, anus, or surrounding areas.
4.  Name the most identifying feature for each stage of syphilis. What do you understand by the term Latency period
The primary stage (first stage) is identified by appearance of a chancre. The secondary stage disseminated stage (second stage) is identified by appearance of allergic like hives at the palms of the hands and soles of the feet. The tertiary stage or late stage is identified by infection of any body tissue. The term Latency period is the period between secondary and tertiary stages of syphilis, it can last for many years before the tertiary or late stage evolves.


5. What is diarrhea  why diarrhea is important in identifying food infections  Give 3 examples of food illness that could be identified via their diarrhea

Diarrhea is loose stools that last for several days or even more. Diarrhea is important in identifying food infections, because the characteristic of the stool, for instance color and its contents like mucous and blood depicts a specific type of food infection. Three examples of food illness that could be identified via their diarrhea are Cholera, Shigellosis and Salmonellosis.




6.  What is Epidemiology and how could it be used to prevent the spread of disease

Epidemiology is the study of the distribution and determinants of health-related states or events in specified populations, and the application of this study to the control of health problems. Epidemiology could be used to prevent spread of disease through searching for causes and other factors that influence the occurrence of health-related events such as diseases, syndromes, and injuries. This can then be used in comparing groups with different rates of disease occurrence and with differences in demographic characteristics, genetic or immunologic make-up, behaviors, environmental exposures, and other potential risk factors. Under ultimate circumstances, epidemiologic results provide sufficient proof to direct swift and effective public health control and prevention measures.

7.  How does the toxin action of Clostridium botulinum differ from that of Clostridium tetani

The toxin of Clostridium botulinum is absorbed by the upper part of the gastro-intestinal tract in the duodenum and jejunum, and passes into the blood stream by which it reaches the peripheral neuromuscular synapses. The toxin binds to the presynaptic stimulatory terminals and blocks the release of the neurotransmitter acetylcholine, which is required for a nerve to simulate the muscle. Active Clostridium tetani cells at the tissue level releases an exotoxin called tetanospasmin that causes certain nervous system irregularities by means of retrograde transmission through neurons to the brain. One of the toxins effects includes constant skeletal muscle contraction due to a blockage of inhibitory interneurons that regulate muscle contraction. Tetanospasmin initially binds to peripheral nerve terminals, then are transported within the axon and across synaptic junctions until it reaches the central nervous system. There its rapidly fixed to ganglion sides at the presynaptic inhibitory motor nerve endings, and is taken up into the axon by endocytosis. The toxin blocks the release of inhibitory neurotransmitters across the synaptic cleft these are required to check the nervous impulse. If nervous impulses cannot be checked by normal inhibitory mechanisms, it produces the generalized muscular spasms characteristic of tetanus. Tetanospasmin appears to act by selective cleavage of a protein component of synaptic vesicles this prevents the release of neurotransmitters by the cells. Binding appears to be an irreversible event.


8. What are the main microbial difference between Listeria monocytogenes  Brucella melitensis  their infections

Listeria monocytogenes is non-spore gram-positive rod-shaped bacterium. It is ingested with raw, contaminated food. An invasion toxin secreted by the pathogenic bacteria enables the pathogen to penetrate host cells of the epithelial lining, the infected person experiences vomiting, nausea and diarrhea. It causes Septicemia and meningitis in patients with suppressed immune infection. It also causes listeriosis, which is an inflammation of the brain. While Brucella melitensis is an aerobic coccobacillus gram-negative, non-motile, and non-spore forming bacterium, which enters the body via the skin, respiratory tract, or digestive tract. Once there, this intracellular organism can enter the blood and the lymphatic where it multiplies inside phagocytes and eventually cause bacteremia. Symptoms include fever, headaches, chills, depression, profound weakness, arthralgia, and weight loss.

Brucella melitensis is odd in numerous ways. First, the bacterium does not bear classic virulence factors, such as capsules, secreted proteases, exotoxins, endotoxins, pili andor fimbriae or virulence plasmids, and its lipopolysaccharide pathogenicity is not typical. Second, it exhibits a tendency to invade and persist in the human host through inhibition of involuntary cell death. Its virulence depends on survival and replication properties in different cell types in which Brucella melitensis controls the maturation of its vacuole to avoid innate immune responses and to reach its replicative niche related with the endoplasmic reticulum. While for Listeria monocytogenes, the invasion toxin secreted by the pathogenic bacteria enables the pathogen to penetrate host cells of the epithelial lining. It multiplies not only extra-cellular but also intracellular, within macrophages after phagocytosis, or within parenchyma cells which are entered by induced phagocytosis. After engulfment, the bacterium may escape from the phagosome before phagolysosome fusion occurs mediated by a toxin, which also acts as a hemolysin, listeriolysin O (LLO). The bacterium stimulates a CMI response that includes the production of TNF, gamma interferon, macrophage activating factors anda cytotoxic T cell response. Possibly, in humans, a failure to control L. monocytogenes by means of CMI allows the bacteria to spread systemically. Additionally, unlike other bacterial pathogens, Listeria is able to penetrate the endothelial layer of the placenta and thereby infect the fetus.