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MICROBIOLOGY -HONOURS 2023 Paper: CC-14 (Medical Microbiology) Full Marks : 50 CC-14

Dr. Aamarpali Roy Phd. Chemistry Contact for Tuition All Boards (English Medium) MOBILE Number :9051345485 For Class 8th -10th:- Science (Physics/chemistry/biology/maths) Class 11th and 12th :- Chemistry/Physics/Biology) B.sc. Part-I/II/III: - Chemistry (Organic/inorganic/physical chemistry) M.sc Part-I & II:-Chemistry (Organic/inorganic/physical chemistry/ spectroscopy)) MOBILE Number :9051345485

MICROBIOLOGY -HONOURS

Paper: CC-14 (Medical Microbiology)

Full Marks : 50

CC-14

1 Question

(a) Why are some parts of the respiratory tract difficult to colonize by bacteria?

(a) Some parts of the respiratory tract are challenging for bacteria to colonize due to several reasons. The upper respiratory tract, including the nasal passages and throat, has mechanisms like mucociliary clearance, which helps trap and remove bacteria. Additionally, the respiratory tract has a lining of mucus and antimicrobial substances that can inhibit bacterial growth. Moreover, the presence of immune cells like macrophages and antibodies helps to defend against bacterial invasion, making it difficult for bacteria to establish colonies in these areas.

b) What is the cause of dental caries? Name the causative agent?

(b) Dental caries, commonly known as tooth decay, is primarily caused by the interaction of bacteria with sugars from the diet, leading to the production of acids that demineralize the tooth enamel. The primary causative agent of dental caries is Streptococcus mutans, a bacteria commonly found in the oral cavity. When sugars are consumed, S. mutans metabolizes them, producing acids that erode the tooth enamel, eventually leading to cavities if left untreated.

c) What are anti-microbial peptides?

(c) Antimicrobial peptides are small proteins produced by various cells in the body, including immune cells and epithelial cells. These peptides play a crucial role in the innate immune system's defense against pathogens. Antimicrobial peptides have broad-spectrum antimicrobial activity, meaning they can target a wide range of bacteria, fungi, and viruses. They disrupt microbial cell membranes, leading to cell death and helping to control infections.

(d) Mention how do enveloped and non-enveloped human viruses adhere to the host cell membrane receptors.

(d) When it comes to how enveloped and non-enveloped human viruses adhere to host cell membrane receptors, there are differences in their mechanisms. Enveloped viruses, like the influenza virus, typically use viral envelope proteins to bind to specific receptors on the host cell membrane. These envelope proteins facilitate the fusion of the viral envelope with the host cell membrane, allowing the virus to enter the cell.

On the other hand, non-enveloped viruses, such as the adenovirus, often use specific proteins on their capsid (outer shell) to interact with receptors on the host cell surface. This interaction can trigger processes that lead to the entry of the virus into the host cell, usually through endocytosis.

e) How antibiotic resistance is related to the normal microflora of our body? Differentiate between pathogenicity and virulence.

(e) antibiotic resistance and our body's normal microflora. Antibiotic resistance can develop in normal microflora when antibiotics are used inappropriately or excessively. When antibiotics are taken, they not only target harmful bacteria but can also affect the beneficial bacteria in our normal microflora. This disruption can create an environment where antibiotic-resistant strains of bacteria within the normal microflora can thrive, leading to potential infections that are challenging to treat.

Pathogenicity and virulence are related but have distinct meanings. Pathogenicity refers to the ability of a microorganism to cause disease in a host, while virulence specifically describes the severity or harmfulness of the disease caused by the microorganism. In simpler terms, pathogenicity is the capacity to cause disease, while virulence is the degree of harm caused by the disease.

 

f) Describe Widal test?

(f) The Widal test is a diagnostic test used to detect specific antibodies in the blood of individuals infected with certain types of bacteria that cause typhoid fever or other enteric fevers. It helps in the diagnosis of typhoid and paratyphoid fevers caused by Salmonella typhi and Salmonella paratyphi, respectively.

During the Widal test, the patient's blood serum is mixed with a solution containing antigens derived from the Salmonella bacteria. If the patient has been exposed to these bacteria and has developed specific antibodies against them, a visible reaction will occur, indicating a positive result for the presence of these antibodies.

The test measures the levels of antibodies, including anti-O and anti-H antibodies, which are specific to the Salmonella bacteria. The results are interpreted based on the levels of these antibodies present in the patient's blood serum.  The Widal test is an essential tool in diagnosing and monitoring typhoid and paratyphoid fevers, especially in regions where these diseases are prevalent. It is crucial to interpret the results accurately and in conjunction with other clinical findings to ensure an accurate diagnosis.

h) How docs bacterial LPS contribute to pathogenicity?

(h) Bacterial LPS (lipopolysaccharides) contributes to pathogenicity by acting as an endotoxin. When bacteria containing LPS are destroyed or shed, the LPS can trigger a strong immune response in the host, leading to inflammation and potentially harmful effects. LPS can activate the immune system, causing the release of inflammatory mediators that can lead to symptoms of infection and contribute to the virulence of the bacteria.

i) Distinguish between Sabin and Salk Polio Vaccine.

(i) The Sabin and Salk polio vaccines are both used to prevent polio, but they differ in their composition and administration. The Sabin vaccine is an oral polio vaccine that contains weakened (attenuated) live poliovirus strains and is administered orally. In contrast, the Salk vaccine is an inactivated polio vaccine that contains killed poliovirus strains and is administered via injection.

j) Define an opportunistic pathogen. Give one example.

(j) An opportunistic pathogen is a microorganism that normally does not cause disease in healthy individuals but can become pathogenic under certain conditions, such as a weakened immune system or changes in the host's environment. An example of an opportunistic pathogen is Pneumocystis jirovecii, which can cause pneumonia in individuals with compromised immune systems.

k) Which part of the human body can be affected by Candida infection?

(k) Candida infections can affect various parts of the human body, with the most common being mucous membranes and moist areas such as the mouth (oral thrush), skin, and genital areas (vaginal yeast infections). Candida can also cause systemic infections in immunocompromised individuals.

l) Write down two examples of normal flora found in urogenital tract.

(l) Two examples of normal flora found in the urogenital tract are:

1. Lactobacillus species: These bacteria are commonly found in the vagina and help maintain a healthy acidic environment, preventing the overgrowth of harmful microorganisms.

2. Escherichia coli: While some strains of E. coli can be pathogenic, certain strains are part of the normal flora in the urogenital tract and play a role in maintaining the microbial balance in the gut and urinary tract.

m) Name the pathogen responsible for causing Chikungunia.

m) The pathogen responsible for causing Chikungunya is the Chikungunya virus, which is primarily transmitted to humans through the bite of infected Aedes mosquitoes.

 

n) Why antibiotics have no effect on viruses?

(n) Antibiotics have no effect on viruses because antibiotics specifically target bacterial cells' structures or processes that are different from those of viruses. Viruses are not considered living organisms; they are essentially genetic material (DNA or RNA) surrounded by a protein coat. Since viruses replicate inside host cells using the host's cellular machinery, antibiotics, which target bacterial cell structures like cell walls or protein synthesis, are ineffective against viruses.

o) Why does poliomyelitis virus attack motor neurons but not sensory neurons?

(o) The poliomyelitis virus attacks motor neurons but not sensory neurons because the virus has a preference for certain types of cells. In the case of poliovirus, it has a tropism (affinity) for motor neurons in the spinal cord. When the virus infects motor neurons, it disrupts the signals sent from the brain to the muscles, leading to muscle weakness and paralysis. Sensory neurons, which transmit sensory information like touch and pain, are not the primary target of the poliovirus, explaining why it mainly affects motor function.

 

2. Question

(a) How does the influenza virus cause the symptoms associated with flu?

(a) The influenza virus causes the symptoms associated with flu by infecting the respiratory tract, specifically the nose, throat, and sometimes the lungs. The virus enters the body through the respiratory route, usually via droplets from coughs or sneezes of an infected person. Once inside the body, the virus replicates rapidly, leading to inflammation and damage to the respiratory epithelium. This process triggers the body's immune response, resulting in symptoms such as fever, cough, sore throat, muscle aches, fatigue, and sometimes respiratory issues. (b) What are the main routes of transmission of poliovirus? What are the symptoms?

(b) The main routes of transmission of the poliovirus are through the fecal-oral route and respiratory droplets. The symptoms of poliovirus infection can vary from asymptomatic or mild flu-like symptoms to more severe cases where the virus attacks the nervous system, leading to paralysis, particularly in the legs.

(c) Write down the causative agent, symptoms and treatment  for Japanese Encephalitis

(c) Japanese Encephalitis is caused by the Japanese encephalitis virus (JEV), which is transmitted through mosquito bites, particularly the Culex species. Symptoms of Japanese Encephalitis include fever, headache, neck stiffness, stupor, disorientation, coma, tremors, and paralysis. Treatment for Japanese Encephalitis mainly involves supportive care to manage symptoms. There is also a vaccine available for Japanese Encephalitis, which is recommended for travellers to areas where the disease is endemic.

 

3. Question

(a) Treatment of fungal infections generally has been less successful than the bacteria Why?

(a) Treatment of fungal infections generally has been less successful than bacterial infections because fungi are eukaryotic organisms like humans, making it challenging to find antifungal drugs that target the fungi without harming human cells. This similarity in cellular structure makes it harder to develop medications that specifically target fungal cells without causing significant side effects in the patient.

(b) Name two antifungal drugs.

(b) Two antifungal drugs are Fluconazole and Amphotericin B.

(c) Write the mechanism of action of Amantadine.

(c) The mechanism of action of Amantadine involves blocking the action of the M2 protein of the influenza A virus. By inhibiting this protein, Amantadine prevents the virus from uncoating and releasing its genetic material into the host cell, thereby stopping viral replication.

 

(d) What is meant by oral thrush infection?

(d) Oral thrush infection, also known as oral candidiasis, is a fungal infection caused by the overgrowth of Candida yeast in the mouth and throat. It appears as white patches on the tongue, inner cheeks, roof of the mouth, and sometimes the throat. Oral thrush is common in infants, older adults, and individuals with weakened immune systems. Treatment usually involves antifungal medications in the form of oral rinses or lozenges to eliminate the fungal infection.

 

4. Question

(a) Compare and contrast between amoebic dysentery and giardiasis.

(a) Amoebic dysentery and giardiasis are both gastrointestinal infections caused by different organisms and exhibit some differences:

- Amoebic dysentery is caused by the parasite Entamoeba histolytica, while giardiasis is caused by the parasite Giardia lamblia.

- Symptoms of amoebic dysentery include bloody diarrhea, abdominal pain, and fever, whereas giardiasis typically presents with diarrhea, gas, greasy stools, and abdominal cramps.

- Both infections are transmitted through contaminated food or water, but amoebic dysentery can also be transmitted through direct contact with feces.

- Treatment for amoebic dysentery usually involves medications like metronidazole, while giardiasis can be treated with drugs like metronidazole or tinidazole.

(b) Discuss the mechanism of resistance for the following antibiotics :

(i) Penicillin

(ii) Streptomycin.

(b) The mechanisms of resistance for Penicillin and Streptomycin are as follows:

(i) Penicillin: Bacteria can develop resistance to penicillin through several mechanisms, with the most common being the production of beta-lactamase enzymes. These enzymes inactivate penicillin by breaking down its beta-lactam ring structure, rendering the antibiotic ineffective. Bacteria can also develop resistance by modifying the target site of penicillin, such as penicillin-binding proteins, making it harder for the antibiotic to bind and inhibit bacterial cell wall synthesis.

(ii) Streptomycin: Resistance to streptomycin can occur through different mechanisms, including the modification of the bacterial ribosomal target site. Bacteria can alter the ribosomal binding site for streptomycin, reducing the antibiotic's ability to bind and inhibit protein synthesis. Additionally, some bacteria can produce enzymes that modify streptomycin, rendering it inactive. Resistance can also develop through decreased uptake of the antibiotic into the bacterial cell or increased efflux of the drug out of the cell, reducing its concentration and effectiveness.

 

5. Question 5

(a) Name two antibacterial drugs of each of the following :

(i) Cell wall synthesis inhibition.

(ii) Protein synthesis inhibition.

(iii) Nucleic acid synthesis inhibition.

(iv) Inhibitor of Metabolism.

a) Here are two antibacterial drugs for each of the following mechanisms of action:

(i) Cell wall synthesis inhibition:

1. Penicillin

2. Vancomycin

(ii) Protein synthesis inhibition:

1. Erythromycin

2. Tetracycline

(iii) Nucleic acid synthesis inhibition:

1. Ciprofloxacin

2. Rifampin

(iv) Inhibitor of Metabolism:

1. Trimethoprim

2. Sulfamethoxazole

(b)          Write down the symptoms and prophylaxis of Kala-azar.

(b.) Kala-azar, also known as visceral leishmaniasis, is a serious parasitic disease caused by the protozoan parasite Leishmania donovani. The symptoms of Kala-azar include prolonged fever, weight loss, fatigue, anemia, and enlargement of the spleen and liver, which can lead to a potbelly appearance.

Prophylaxis for Kala-azar involves preventive measures to reduce the risk of infection, such as:

1. Avoiding travel to areas where Kala-azar is endemic.

2. Using insect repellents and wearing protective clothing to prevent sandfly bites.

3. Sleeping under insecticide-treated bed nets.

4. Early diagnosis and treatment of cases to prevent the spread of the disease within communities.

 

6. Question

 (a) State the mode of action of:

(i) Quinolone

(ii) Streptomycin.

(b) How docs Hepatitis A and 8 virus differ from each other?

(c) Describe schematically PCR-technique for the detection of any pathogen of your interest.

(a) Here are the modes of action of the antibiotics you mentioned:

(i) Quinolone: Quinolones act by inhibiting the enzymes DNA gyrase and topoisomerase IV, which are essential for bacterial DNA replication and repair. By interfering with these enzymes, quinolones prevent DNA synthesis and ultimately lead to bacterial cell death.

(ii) Streptomycin: Streptomycin works by binding to the bacterial ribosome and inhibiting protein synthesis. It specifically targets the 30S subunit of the bacterial ribosome, disrupting the translation process and causing the production of faulty proteins, which leads to bacterial cell death.

(b) Hepatitis A virus (HAV) and Hepatitis B virus (HBV) differ in several ways:

- Transmission: HAV is primarily transmitted through the fecal-oral route, often due to contaminated food or water, while HBV is transmitted through exposure to infected blood or body fluids.

- Chronicity: HAV infection is typically acute and does not lead to chronic infection, whereas HBV can result in chronic hepatitis, which may lead to long-term liver complications.

- Vaccine Availability: There is a vaccine available for HAV, providing immunity against the virus, while there is also a vaccine for HBV.

- Treatment: The treatment approaches for HAV and HBV differ, with HBV having specific antiviral medications available for management.

(c) PCR (Polymerase Chain Reaction) is a molecular biology technique used to amplify a specific segment of DNA. Here is a schematic representation of the PCR technique for the detection of a pathogen:

1. Denaturation: The DNA sample containing the pathogen's DNA is heated to separate the double-stranded DNA into single strands.

2. Annealing: Primers (short DNA sequences that are complementary to the target pathogen DNA) are added. These primers bind to the specific sequences flanking the target DNA region.

3. Extension: DNA polymerase extends the primers by adding nucleotides to create a new DNA strand complementary to the target pathogen DNA.

4. Amplification: The process is repeated through multiple cycles (usually around 30 cycles), resulting in exponential amplification of the target DNA region.

5. Detection: The amplified DNA can be visualized using gel electrophoresis or other detection methods to confirm the presence of the pathogen's DNA.

 

7. Write short notes on following  :

(a) Erythrocytic cycle of Plasmodi11m

(b) Polymyxin antibiotics

(c) 'Viremia' in the context of paralytic polio

(d) Cholera toxin

(e) Nosocomial infection

(f). Sandwich ELISA.

(a) Erythrocytic cycle of Plasmodium:

- The erythrocytic cycle of Plasmodium refers to the stage of the malaria parasite's life cycle where it infects and replicates within red blood cells.

- During this cycle, the parasite undergoes several stages, including invasion of red blood cells, replication, and eventual bursting of the infected cells, releasing more parasites into the bloodstream.

- The cycle is responsible for the recurring fevers and symptoms associated with malaria and plays a crucial role in the spread of the disease.

(b) Polymyxin antibiotics:

- Polymyxin antibiotics are a group of antibiotics that are effective against certain Gram-negative bacteria.

- They work by disrupting the bacterial cell membrane, leading to leakage of cellular contents and ultimately bacterial cell death.

- Polymyxins are often used as a last resort for treating multidrug-resistant infections but can have significant side effects, especially on the kidneys and nervous system.

(c) 'Viremia' in the context of paralytic polio:

- Viremia refers to the presence of a virus in the bloodstream. In the context of paralytic polio, viremia indicates the spread of the poliovirus through the blood, allowing it to reach and infect the central nervous system.

- The presence of the virus in the blood during viremia can lead to the development of paralytic polio, where the virus affects the motor neurons in the spinal cord, causing paralysis.

(d) Cholera toxin:

- Cholera toxin is a protein complex produced by the bacterium Vibrio cholerae, responsible for the severe watery diarrhea characteristic of cholera infections.

- The toxin binds to cells in the intestines, leading to the activation of adenylate cyclase and subsequent increase in cyclic AMP levels within the cells.

- This elevation of cyclic AMP disrupts ion transport in the intestines, causing the secretion of large amounts of fluid into the gut, resulting in the profuse watery diarrhea seen in cholera.

(e) Nosocomial infection:

- Nosocomial infections are infections acquired in a healthcare setting, such as hospitals or clinics, by patients receiving medical treatment.

- These infections can be caused by a variety of pathogens, including bacteria, viruses, and fungi, and are often associated with invasive procedures, contaminated medical equipment, or poor infection control practices.

- Preventing nosocomial infections requires strict adherence to infection control protocols, proper hygiene practices, and surveillance to identify and manage outbreaks.

(f) Sandwich ELISA:

- Sandwich ELISA (Enzyme-Linked Immunosorbent Assay) is a type of ELISA used to detect and quantify the presence of an antigen in a sample.

- In this assay, the antigen is sandwiched between two antibodies: a capture antibody immobilized on the surface and a detection antibody linked to an enzyme.

- The enzyme-linked antibody produces a signal when it binds to the antigen, allowing for the detection and quantification of the antigen in the sample.