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BMI2603 – MEDICAL MICROBIOLOGY
PAST EXAM PAPER SOLVED
QUESTION 1 [20]
In your own understanding, briefly discuss the following topics and include appropriate examples.
1.1. Methicillin resistant Staphylococcus aureus (MSRA) (5)
Methicillin-resistant Staphylococcus aureus (MRSA) is a type of bacteria that is resistant to certain antibiotics, including
methicillin, penicillin, and amoxicillin. This means that these antibiotics are not effective in treating infections caused by
MRSA. MRSA is most commonly found in healthcare settings, such as hospitals and nursing homes, but it can also occur
in the community.
Examples of MRSA infections include skin infections (such as boils or abscesses), surgical wound infections, and
pneumonia. MRSA can also cause blood stream infections, which can be life-threatening if not treated promptly.
Preventative measures for MRSA include practicing good hygiene, such as regular hand washing, and keeping cuts and
scrapes clean and covered. MRSA can also be spread through contact with contaminated surfaces or equipment, so it is
important to clean and disinfect frequently-touched surfaces, such as bed linens and medical equipment.
Treatment for MRSA infections typically involves using antibiotics that are effective against MRSA. Vancomycin is often
used as a first-line treatment for severe MRSA infections. Some other antibiotics like daptomycin, tigecycline, and
linezolid can also be effective against MRSA.
1.2. Exudative lesions (5)
Exudative lesions are skin conditions characterized by the presence of fluid or pus in or around the affected area.
Examples of exudative lesions include:
Acne: Acne is a common skin condition characterized by the presence of pimples, blackheads, and whiteheads. These
lesions are caused by a buildup of oil and bacteria in the pores, resulting in inflammation and the formation of pus-filled
pimples.
Impetigo: Impetigo is a contagious skin infection caused by bacteria. It typically appears as red sores that are filled with
pus and are surrounded by a yellowish crust.
Eczema: Eczema is a chronic skin condition characterized by dry, itchy, and inflamed skin. In some cases, eczema can
lead to the formation of small, fluid-filled blisters called vesicles.
Psoriasis: Psoriasis is a chronic skin condition characterized by thick, scaly, and red patches of skin. In some cases,
psoriasis can lead to the formation of small, fluid-filled blisters called pustules.
Cellulitis: Cellulitis is a bacterial skin infection that typically appears as a red, swollen, and painful area of skin. In severe
cases, cellulitis can lead to the formation of abscesses, which are collections of pus that form under the skin.
Overall, exudative lesions are a common symptom of various skin conditions and infections. They are typically
characterized by the presence of fluid or pus in or around the affected area and may be accompanied by redness,
inflammation, and pain. It is important to consult with a healthcare professional for an accurate diagnosis and treatment
plan for these types of skin conditions.
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1.3. Nosocomial infections (5)
Nosocomial infections are infections that occur in a healthcare setting, such as a hospital or nursing home. These
infections can occur in patients, healthcare workers, and visitors. They can be caused by a variety of microorganisms,
including bacteria, viruses, and fungi.
One common example of a nosocomial infection is a urinary tract infection (UTI). UTIs can occur in patients who have
had a catheter placed in their bladder for an extended period of time. These patients are at a higher risk of developing a
UTI because the catheter can provide an entry point for bacteria to enter the urinary tract.
Another example of a nosocomial infection is a surgical site infection (SSI). SSIs can occur after surgery and can be
caused by bacteria entering the surgical wound. They can be prevented by using proper surgical techniques and
sterilization procedures, as well as administering antibiotics to the patient before and after surgery.
Healthcare workers can also be at risk of nosocomial infections. One example is methicillin-resistant Staphylococcus
aureus (MRSA), which is a type of bacteria that is resistant to many antibiotics. This can be spread through contact with
contaminated surfaces or equipment and can cause serious infections in healthcare workers.
Prevention of nosocomial infections is important to protect patients, healthcare workers, and visitors. Measures such as
proper hand hygiene, infection control procedures, and appropriate use of antibiotics can help to reduce the risk of
nosocomial infections.
1.4. Antiphagocytic factors (5)
Antiphagocytic factors are molecules or structures produced by certain microorganisms that help them evade the host
immune system by preventing phagocytosis, the process by which cells of the immune system engulf and destroy
pathogens. These factors can include:
Capsules: Many bacteria produce a thick, protective capsule around their cells that makes them difficult for phagocytes
to adhere to and engulf. For example, Streptococcus pneumoniae, a common cause of pneumonia, has a capsule
composed of a polysaccharide that helps it evade the host immune system.
Surface proteins: Some microorganisms produce surface proteins that interact with host cells in ways that prevent
phagocytosis. For example, the bacteria that cause Lyme disease, Borrelia burgdorferi, produce a surface protein called
OspA that binds to a receptor on host cells and prevents phagocytosis.
Enzymes: Some microorganisms produce enzymes that help them evade phagocytosis. For example, the bacteria that
cause strep throat, Streptococcus pyogenes, produce an enzyme called streptokinase that breaks down the fibrinogen in
blood clots, making it difficult for phagocytes to adhere to the bacteria.
Toxins: Some microorganisms produce toxins that can damage host cells and make them less effective at phagocytosis.
For example, the bacteria that cause diphtheria, Corynebacterium diphtheriae, produce a toxin that can damage the cilia
in the respiratory tract, making it difficult for phagocytes to clear the bacteria.
Overall, antiphagocytic factors are important mechanisms by which microorganisms evade the host immune system and
persist within the host. Understanding these factors can help us develop better strategies for preventing and treating
infections.
QUESTION 2 [20]
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2.1. With the aid of a hand drawn diagram, describe the life cycle of Rotavirus, including the disease symptoms
observed in humans (10)
The life cycle of Rotavirus begins when the virus is ingested by a human host. The virus binds to the cells lining the small
intestine, where it enters the cells and replicates. The viral particles then travel to the surface of the gut, where they are
released in large numbers in the stool. The virus can remain infectious in the environment for several days, and can be
spread to other individuals through the fecal-oral route, either through contaminated food or water, or by direct contact
with infected individuals.
Symptoms of Rotavirus infection typically appear within 1-3 days of infection and include:
• Diarrhea: The most common symptom of rotavirus infection is watery diarrhea, which can be severe and lead to
dehydration.
• Vomiting: Many individuals with rotavirus infection experience nausea and vomiting, which can make it difficult
to keep fluids down.
• Abdominal cramps: Rotavirus infection can cause abdominal cramps and pain.
• Fever: Some individuals with rotavirus infection may develop a fever.
• Loss of appetite: Rotavirus infection can cause a loss of appetite, which can make it difficult for individuals to get
the nutrients they need.
• Fatigue: Rotavirus infection can cause fatigue, making individuals feel weak and tired.
• Dehydration: The most severe symptoms of rotavirus infection can be caused by dehydration, which can be life-
threatening if not treated promptly.
The symptoms of rotavirus infection typically last for 3-8 days, and most individuals recover fully without any long-term
complications. However, in some cases, rotavirus infection can lead to severe dehydration and require hospitalization.
It is important to note that Rotavirus Vaccines is available and can prevent the severe symptoms of the disease and
death.
2.2. Describe the laboratory techniques used to diagnose Rotavirus (6)
There are several laboratory techniques that can be used to diagnose rotavirus infection, including:
Enzyme-linked immunosorbent assay (ELISA): This test uses antibodies to detect rotavirus antigens in a sample of stool.
ELISA is highly sensitive and specific, making it a reliable method for diagnosing rotavirus infection.
Polymerase chain reaction (PCR): This test amplifies and detects specific genetic sequences in rotavirus, allowing for the
identification of the virus in a sample of stool. PCR is more sensitive than ELISA and can detect the virus even in small
amounts.
Electron microscopy: This test uses an electron microscope to visualize rotavirus particles in a sample of stool. Electron
microscopy is less commonly used for diagnosing rotavirus infection due to the need for specialized equipment and
expertise.
Immunochromatography: This test is a rapid diagnostic test that uses antibodies to detect rotavirus antigens in a sample
of stool. It is a quick and easy method for diagnosis but is less specific than other techniques.
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Immunofluorescence: This test uses fluorescent-labeled antibodies to detect rotavirus antigens in a sample of stool. It is
a highly sensitive and specific method, but it is also less commonly used due to the need for specialized equipment and
expertise.
In most cases, the laboratory technician will use more than one method to diagnose the rotavirus infection, in order to
confirm the results and to get a better understanding of the disease. It is important to note that stool samples should be
collected within the first three days of the onset of symptoms to increase the chance of detecting the virus.
2.3. What measures would you suggest to prevent infection with Rotavirus? (4)
• Wash hands frequently with soap and water
• Practice good hygiene, especially after using the toilet or changing diapers
• Avoid close contact with infected individuals
• Clean and disinfect contaminated surfaces regularly
• Vaccination is the most effective way to prevent rotavirus infection
• Avoid consuming contaminated food and water.
Note: These measures can help prevent the spread of rotavirus, but it is always important to consult with a healthcare
professional for individualized advice and treatment.
QUESTION 3 [15]
In tabular form, compare the similarities and differences between Mycobacterium tuberculosis and Mycobacterium
leprae in relation to pathogenesis, diagnosis and treatment.
Similarities:
1. Both Mycobacterium tuberculosis and Mycobacterium leprae are mycobacteria that belong to the same family.
2. Both can cause chronic infections in humans and are slow-growing bacteria.
3. Both are spread through the air, usually through coughing or sneezing by an infected individual.
4. Both can infect various tissues in the body, including the lungs, skin, and peripheral nerves.
5. Both can have a similar clinical presentation, including a prolonged course of illness and the presence of
granulomas.
Differences:
1. Pathogenesis: M. tuberculosis primarily affects the lungs and is the causative agent of tuberculosis. M. leprae
primarily affects the skin and peripheral nerves and causes leprosy.
2. Diagnosis: M. tuberculosis is diagnosed through a combination of chest X-rays, sputum cultures, and a tuberculin
skin test. M. leprae is diagnosed through skin biopsy and detection of the bacteria through laboratory tests.
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