-
Question 1
Incorrect
-
What characteristic do Entamoeba histolytica and Aspergillus fungi have in common?
Your Answer: Cell wall
Correct Answer: Membrane-bound nucleus
Explanation:Protozoa vs Fungi: the Differences
Protozoa and fungi are two distinct groups of organisms that share some similarities but also have significant differences. Protozoa are unicellular and mostly motile, while fungi are multicellular and mostly immobile. Both groups are eukaryotic, meaning they have a membrane-bound nucleus, but protozoa have an anal pore and pseudopods that are not found in fungi.
The anal pore in protozoa is used for excretion of substances, while pseudopods are projections of membrane used to engulf substances for uptake. These structures are not present in fungi, which have a cell wall instead. Aspergillus, for example, is a multicellular fungus with a cell wall, while most protozoa, including Entamoeba, do not have a cell wall.
the differences between protozoa and fungi is important for various fields, including medicine, agriculture, and ecology. For instance, protozoa can cause diseases such as malaria, while fungi can be used for food production or as biocontrol agents against pests. By studying the unique characteristics of these organisms, we can better appreciate their diversity and complexity in the natural world.
-
This question is part of the following fields:
- Microbiology
-
-
Question 2
Incorrect
-
What is the antibiotic that cannot be absorbed orally, but can be effective in treating antibiotic-induced diarrhea?
Your Answer: Gentamicin
Correct Answer: Vancomycin
Explanation:Antibiotic-Associated Diarrhoea and Clostridium Difficile Infection
The majority of cases of antibiotic-associated diarrhoea are non-infective and are caused by changes in the normal gut flora. However, in certain patients, the use of broad-spectrum antibiotics can lead to the development of Clostridium difficile infection. This Gram-positive bacillus causes a colitis that results in profuse watery diarrhoea. In severe cases, the entire colonic mucosa is affected, leading to the formation of a pseudomembrane and severe dilatation of the colon, which can be life-threatening.
C. difficile is first-line treated with metronidazole, but if this is ineffective, oral vancomycin is used as a second-line treatment. Vancomycin is a glycopeptide antibiotic that has zero oral bioavailability, meaning that if it is given orally, none of it will enter the bloodstream. This makes it an ideal treatment for infections that are limited to the gastrointestinal tract, but it would not be useful for treating a systemic infection.
-
This question is part of the following fields:
- Microbiology
-
-
Question 3
Incorrect
-
What is the obligate intracellular pathogen that can cause respiratory and genital tract infections?
Your Answer:
Correct Answer: Chlamydia species
Explanation:The obligate intracellular pathogen that can cause respiratory and genital tract infections is Chlamydia trachomatis.
Chlamydia trachomatis is a bacterium that can cause a variety of infections in humans, including respiratory infections such as pneumonia and genital tract infections such as urethritis, cervicitis, and pelvic inflammatory disease (PID). It is transmitted through sexual contact and can also be transmitted from mother to newborn during childbirth, leading to neonatal conjunctivitis and pneumonia.
-
This question is part of the following fields:
- Microbiology
-
-
Question 4
Incorrect
-
What is the structure utilized by bacteria to penetrate dense mucus?
Your Answer:
Correct Answer: Flagella
Explanation:Cell Surface Projections
Flagella, fimbriae, and pili are all types of cell surface projections found in bacteria. Flagella are composed of flagellin and have a motor pump at the base that propels the filamentous structure to allow bacteria to move. This movement is important for bacteria such as Helicobacter pylori to penetrate through gastric mucus. Fimbriae and pili are short projections that aid in attachment. They can be used to attach to an epithelial layer, which increases virulence, or to attach to other bacteria, which facilitates the exchange of genetic material.
In contrast, microvilli are cell surface projections found on the apical surfaces of human epithelial cells, such as enterocytes. They increase the surface area for absorption, allowing for more efficient nutrient uptake. Overall, these cell surface projections play important roles in bacterial movement, attachment, and nutrient absorption in human cells.
-
This question is part of the following fields:
- Microbiology
-
-
Question 5
Incorrect
-
A 16-year old girl comes to the clinic with a complaint of fever. Upon examination, Gram negative diplococci are observed in her blood cultures. What is the probable causative agent?
Your Answer:
Correct Answer: Neisseria meningitidis
Explanation:Meningococcus: A Unique Gram Negative Diplococcus
Meningococcus, also known as Neisseria meningitidis, is a rare Gram negative organism that presents itself as diplococci. This means that the bacteria are paired together, forming two spherical shapes that resemble a pair of eyes. While other Neisseria species and Diphtheria are also Gram negative organisms, meningococcus is the only possible organism that presents as diplococci.
Meningococcus is a dangerous pathogen that can cause meningitis, septicaemia, or both. It is important to note that meningococcus is not the only organism that can cause these illnesses, but it is one of the most common culprits.
In contrast, Escherichia coli is a Gram negative rod-shaped bacterium that is not present as diplococci. It is a single organism that does not form pairs. Haemophilus influenzae are Gram negative coccobacilli, but they do not present as paired organisms. Staphylococcus aureus and Streptococcus pyogenes are both Gram positive bacteria and are not related to meningococcus.
-
This question is part of the following fields:
- Microbiology
-
-
Question 6
Incorrect
-
How do trimethoprim, dapsone, and co-trimoxazole share a mechanism of action?
Your Answer:
Correct Answer: Inhibition of folate production
Explanation:The Role of Folate and Anti-Folate Antibiotics in DNA, RNA, and Protein Production
Folate, specifically in the form of tetrahydrofolate (THF), plays a crucial role as a co-factor in the production of DNA (thymine), RNA (purines), and proteins (methionine and glycine). However, certain antibiotics, such as sulphonamides like sulfamethoxazole, inhibit an early stage in the production of dihydrofolate. On the other hand, trimethoprim and pyrimethamine inhibit the conversion of dihydrofolate into tetrahydrofolate. When these two types of antibiotics are given together, as in the case of co-trimoxazole, they have a synergistic effect.
Another anti-folate antibiotic is dapsone, which is also used in the treatment of dermatitis herpetiformis. Overall, the balance between folate and anti-folate antibiotics is crucial for proper DNA, RNA, and protein production in the body.
-
This question is part of the following fields:
- Microbiology
-
-
Question 7
Incorrect
-
What is the enzyme that enables aerobic bacteria to survive in the presence of oxygen without succumbing to 'oxygen toxicity'?
Your Answer:
Correct Answer: Superoxide dismutase
Explanation:Bacterial Survival in the Presence of Oxygen
Bacteria can be categorized into two types: aerobic and anaerobic. Anaerobic bacteria cannot survive in the presence of oxygen due to the formation of oxygen radicals that damage intracellular structures. On the other hand, aerobic bacteria have high levels of the enzyme superoxide dismutase, which breaks down the superoxide anion and prevents oxidative damage. Additionally, aerobic bacteria have several other similar enzymes that protect against oxygen radical-induced injury.
Anaerobic bacteria generate ATP in an oxygen-independent process, such as fermentation of long-chain fatty acids. Facultative anaerobic bacteria prefer an anaerobic environment but have sufficiently high levels of anti-oxidant enzymes that they can survive in an aerobic environment.
Carbonic anhydrase is an enzyme that converts water and carbon dioxide into H+ and HCO3−. Coenzyme Q is part of the electron transport chain, while lactate dehydrogenase converts pyruvate into lactate. NADPH oxidase is used in the ‘respiratory burst’ to generate toxic oxygen radicals.
In summary, the survival of bacteria in the presence of oxygen depends on their ability to protect against oxygen radicals. Aerobic bacteria have high levels of protective enzymes, while anaerobic bacteria generate ATP in an oxygen-independent process. Facultative anaerobic bacteria can survive in both environments due to their high levels of anti-oxidant enzymes.
-
This question is part of the following fields:
- Microbiology
-
-
Question 8
Incorrect
-
What role does clavulanic acid play in co-amoxiclav?
Your Answer:
Correct Answer: Inhibits beta-lactamase enzymes
Explanation:Antibiotics and their Mechanisms of Action
Amoxicillin is an antibiotic that belongs to the penicillin family. It has some resistance against penicillinase enzymes, but it is susceptible to beta-lactamase enzymes, which is a common bacterial resistance mechanism. To increase its resistance to breakdown and broaden its spectrum of activity, clavulanic acid is given in combination with amoxicillin, particularly against Gram-negative organisms. Compared to penicillin V, amoxicillin has better oral bioavailability. However, it has relatively poor bone penetration, which requires long courses of IV antibiotics for bone infections. Some oral antibiotics, such as linezolid and clindamycin, have slightly better bone penetration.
DNA gyrase, also known as topoisomerase II, is an enzyme that helps to hold DNA in place during replication. Fluoroquinolones, such as ciprofloxacin, target DNA gyrase as their mechanism of action. There are several antibiotics that target cell wall synthesis, including penicillins, cephalosporins, and carbapenems.
-
This question is part of the following fields:
- Microbiology
-
-
Question 9
Incorrect
-
What is the definition of a pathogenic microbe?
Your Answer:
Correct Answer: Has the ability to cause disease
Explanation:Pathogenic Organisms
A pathogenic organism has the potential to cause disease, but it does not necessarily mean that it will cause harm. The ability to cause illness depends on the environment in which the organism is present. For instance, Staphylococcus epidermidis is a harmless organism that lives on the skin without causing any harm. However, if it enters a sterile site, it can cause infections such as bone prosthesis infection.
The environment plays a crucial role in determining whether an organism is pathogenic or not. Modifying the environment can cause a previously harmless organism to become pathogenic. For example, Cryptococcus is not a pathogenic organism in a patient with a healthy immune system. However, in an immunocompromised patient, it can cause meningitis.
In conclusion, describing an organism as pathogenic refers to its potential to cause illness. The environment plays a significant role in determining whether an organism is pathogenic or not. Therefore, it is essential to understand the environment in which an organism is present to determine its pathogenicity.
-
This question is part of the following fields:
- Microbiology
-
-
Question 10
Incorrect
-
What causes the 'eclipse phase' during the life-cycle of a virus?
Your Answer:
Correct Answer: Initial viral entry into cells
Explanation:The Eclipse Phase of Viral Life-Cycle
The initial entry of viruses into cells is known as the eclipse phase of the viral life-cycle. When a person is infected with a virus, they receive an inoculating dose, some of which enters the bloodstream, causing viraemia. The inoculating viruses then enter cells to undergo replication, causing the viral load in venous blood to fall. This is because the virions are now intracellular.
After replication, the virions bud-off cells or cause host cell lysis, spilling into the blood and causing the viral count to rise again. In some viral infections, such as hepatitis B, there may be a phase of immune tolerance where the immune system does not respond to the virus. This allows for very high levels of viraemia without almost any host cell damage. However, the immune system will eventually recognize the presence of the virus and enter an immune responsive phase, leading to viral clearance and a decrease in viraemia.
-
This question is part of the following fields:
- Microbiology
-
00
Correct
00
Incorrect
00
:
00
:
00
Session Time
00
:
00
Average Question Time (
Secs)