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 Viva Questions and Answers Related to Bacteriology

  1. What is bacteriology?
    • Bacteriology is the branch of microbiology that studies bacteria, their structure, function, classification, and their roles in various processes.
  1. Name the three basic shapes of bacteria.
    • Cocci (spherical), Bacilli (rod-shaped), and Spirilla (spiral).
  1. What is the Gram stain?
    • The Gram stain is a laboratory technique used to differentiate bacteria into two groups based on the characteristics of their cell walls: Gram-positive and Gram-negative.
  1. Explain the difference between Gram-positive and Gram-negative bacteria.
    • Gram-positive bacteria have a thick peptidoglycan layer in their cell walls and retain the crystal violet stain in the Gram stain. Gram-negative bacteria have a thinner peptidoglycan layer and are decolorized during the Gram stain.
  1. What is the significance of endospores in bacteria?
  1. Name a bacterial species that forms endospores.
    • Clostridium and Bacillus species are known for forming endospores.
  1. Define bacterial conjugation.
    • Bacterial conjugation is the transfer of genetic material, usually in the form of plasmids, between bacterial cells through direct cell-to-cell contact.
  1. What are the three types of horizontal gene transfer in bacteria?
    • Transformation, transduction, and conjugation.
  1. Explain antibiotic resistance in bacteria.
    • Antibiotic resistance occurs when bacteria develop mechanisms to withstand the effects of antibiotics, making the drugs ineffective in treating bacterial infections.
  1. Name a common bacterial pathogen causing urinary tract infections.
    • Escherichia coli (E. coli).
  1. What is the causative agent of tuberculosis?
    • Mycobacterium tuberculosis.
  1. Define bacterial growth curve.
    • The bacterial growth curve is a graph depicting the growth of a bacterial population over time, typically divided into four phases: lag phase, log (exponential) phase, stationary phase, and death phase.
  1. What is quorum sensing in bacteria?
    • Quorum sensing is a communication system used by bacteria to coordinate their behavior based on population density.
  1. Name a bacterium known for its role in nitrogen fixation.
  1. Explain the difference between obligate aerobes and obligate anaerobes.
    • Obligate aerobes require oxygen for growth, while obligate anaerobes cannot survive in the presence of oxygen.
  1. What is the function of bacterial capsule?
    • The bacterial capsule protects the bacterium from phagocytosis and helps in adherence to surfaces.
  1. Name the bacteria responsible for dental caries.
    • Streptococcus mutans.
  1. What is the significance of Koch’s postulates in bacteriology?
    • Koch’s postulates are criteria used to establish the causative relationship between a microorganism and a disease.
  1. Define bacteriophage.
    • Bacteriophages are viruses that infect and replicate within bacteria.
  1. Name a gram-negative bacteria causing food poisoning.
    • Salmonella spp.
  1. What is the role of fimbriae in bacteria?
    • Fimbriae are hair-like appendages that help bacteria adhere to surfaces and facilitate the formation of biofilms.
  1. Explain the concept of selective toxicity in antimicrobial therapy.
    • Selective toxicity refers to the ability of an antimicrobial agent to target and inhibit or kill the pathogenic microorganism without harming the host.
  1. Name a sexually transmitted bacterial infection.
    • Neisseria gonorrhoeae (causing gonorrhea).
  1. What is the difference between a plasmid and a chromosome in bacteria?
    • Chromosomes carry essential genetic information, while plasmids are small, extrachromosomal DNA elements that may carry non-essential genes.
  1. Define biofilm.
    • A biofilm is a community of microorganisms embedded in a self-produced extracellular matrix, adhering to each other and often to surfaces.
  1. Name a bacterium causing peptic ulcers.
    • Helicobacter pylori.
  1. Explain the significance of the Kirby-Bauer disk diffusion test.
    • The Kirby-Bauer test is used to determine the susceptibility of bacteria to various antibiotics by measuring the zone of inhibition around antibiotic-impregnated disks.
  1. Name a bacterium responsible for the production of botulinum toxin.
    • Clostridium botulinum.
  1. What is the function of the bacterial cell wall?
    • The bacterial cell wall provides structural support and protection to the cell.
  1. Define bacteremia.
  1. Name a bacterium causing pneumonia.
    • Streptococcus pneumoniae.
  1. Explain the concept of a superbug.
    • A superbug is a bacterium that has developed resistance to multiple antibiotics, making it challenging to treat.
  1. Name a bacterium causing urinary tract infections in catheterized patients.
    • Pseudomonas aeruginosa.
  1. What is the function of bacterial flagella?
    • Bacterial flagella are whip-like appendages that allow bacteria to move in liquid environments.
  1. Define the term “probiotics.”
    • Probiotics are live microorganisms that confer health benefits when consumed in adequate amounts.
  1. Name a bacterium causing sexually transmitted infections and pelvic inflammatory disease.
    • Chlamydia trachomatis.
  1. Explain the principle of the polymerase chain reaction (PCR).
    • PCR is a laboratory technique used to amplify a specific DNA segment through repeated cycles of DNA denaturation, primer annealing, and DNA synthesis.
  1. Name a bacterium causing foodborne illness due to undercooked poultry.
    • Campylobacter jejuni.
  1. What is the role of the bacterial cell membrane?
    • The bacterial cell membrane regulates the passage of substances into and out of the cell and provides a site for various metabolic processes.
  1. Define the term “nosocomial infection.”
    • Nosocomial infections are infections acquired in a hospital or healthcare setting.
  1. Name a bacterium causing Lyme disease.
    • Borrelia burgdorferi.
  1. Explain the difference between coccobacilli and vibrios.
    • Coccobacilli are bacteria with a shape intermediate between cocci and bacilli, while vibrios are curved or comma-shaped bacteria.
  1. What is the role of the bacterial cytoplasm?
    • The bacterial cytoplasm contains the cellular machinery for various metabolic processes and is the site of cellular activities.
  1. Name a bacterium causing dental plaque.
    • Streptococcus mutans.
  1. Explain the concept of bacterial transformation.
    • Bacterial transformation is the process by which bacteria take up foreign DNA from their environment and incorporate it into their own genome.
  1. Name a bacterium causing food poisoning from contaminated dairy products.
    • Listeria monocytogenes.
  1. What is the function of bacterial pili?
    • Bacterial pili are involved in the attachment of bacteria to surfaces and play a role in bacterial conjugation.
  1. Define the term “zoonosis.”
    • Zoonosis refers to diseases that can be transmitted from animals to humans.
  1. Name a bacterium causing syphilis.
    • Treponema pallidum.
  1. Explain the role of bacterial ribosomes.
    • Bacterial ribosomes are the cellular structures responsible for protein synthesis, translating genetic information into functional proteins.

Here are some viva questions and answers related to Streptococci and Staphylococci:

Streptococci:

  1. Q: What is the distinguishing feature of Streptococci regarding their cellular arrangement?
    • A: Streptococci are characterized by their cellular arrangement in chains.
  1. Q: Differentiate between Group A and Group B Streptococci.
    • A: Group A Streptococci (e.g., Streptococcus pyogenes) cause throat infections, while Group B Streptococci (e.g., Streptococcus agalactiae) are often associated with infections in newborns.
  1. Q: How does Streptococcus pneumoniae evade the immune system?
    • A: Streptococcus pneumoniae can evade the immune system by producing a capsule, which inhibits phagocytosis.
  1. Q: Mention a disease caused by Streptococcus pneumoniae.
  1. Q: What is the significance of the Lancefield classification for Streptococci?
    • A: The Lancefield classification categorizes Streptococci based on the type of antigens present in their cell walls, aiding in their identification.
  1. Q: Explain the role of Streptococcus mutans in oral health.
    • A: Streptococcus mutans is associated with dental caries as it produces acids that contribute to the demineralization of tooth enamel.
  1. Q: How does Streptococcus pyogenes contribute to the pathogenesis of rheumatic fever?
    • A: Streptococcus pyogenes can trigger an autoimmune response leading to rheumatic fever through molecular mimicry.
  1. Q: What is the hemolysis pattern observed in beta-hemolytic Streptococci?
    • A: Beta-hemolytic Streptococci exhibit complete lysis of red blood cells, forming clear zones around the colonies on blood agar.
  1. Q: Name a virulence factor produced by Group B Streptococci.
    • A: Group B Streptococci produce a polysaccharide capsule as a virulence factor.
  1. Q: Describe the significance of the ASO (Anti-Streptolysin O) test.
    • A: The ASO test is used to detect the presence of antibodies against streptolysin O, an enzyme produced by Streptococci. Elevated levels indicate recent streptococcal infection.

Staphylococci:

  1. Q: What is the characteristic cellular arrangement of Staphylococci?
    • A: Staphylococci are characterized by their cellular arrangement in clusters.
  1. Q: Differentiate between Staphylococcus aureus and Staphylococcus epidermidis.
    • A: Staphylococcus aureus is often pathogenic and produces coagulase, while Staphylococcus epidermidis is part of the normal skin flora and lacks coagulase.
  1. Q: How does Staphylococcus aureus evade the immune system?
  1. Q: Mention a disease caused by Staphylococcus aureus.
    • A: Staphylococcal skin infections, including boils and impetigo.
  1. Q: Explain the significance of coagulase in Staphylococcus aureus.
    • A: Coagulase is an enzyme produced by Staphylococcus aureus that causes plasma to clot, helping the bacterium evade phagocytosis.
  1. Q: What is MRSA, and why is it a concern in healthcare settings?
    • A: MRSA (Methicillin-resistant Staphylococcus aureus) is a strain of Staphylococcus aureus resistant to multiple antibiotics, making it challenging to treat and a concern in healthcare-associated infections.
  1. Q: Name a toxin produced by Staphylococcus aureus that causes food poisoning.
    • A: Staphylococcal enterotoxin.
  1. Q: Describe the role of Staphylococcus epidermidis in medical device-related infections.
    • A: Staphylococcus epidermidis is often associated with biofilm formation on medical devices, leading to infections.
  1. Q: What is the distinguishing feature of alpha-hemolytic Staphylococci on blood agar?
    • A: Alpha-hemolytic Staphylococci exhibit partial lysis of red blood cells, resulting in a greenish discoloration around colonies on blood agar.
  1. Q: Explain the significance of the catalase test in differentiating Staphylococci from Streptococci.
    • A: Staphylococci are catalase-positive, producing bubbles when hydrogen peroxide is added, whereas Streptococci are catalase-negative.

These questions cover a range of topics related to Streptococci and Staphylococci, including their classification, pathogenicity, virulence factors, and diagnostic methods.

Here are some viva questions and answers related to toxins produced by Streptococci:

  1. Q: Name a major virulence factor produced by Streptococci.
  1. Q: Differentiate between streptolysin O and streptolysin S.
    • A: Streptolysin O is oxygen-labile and immunogenic, while streptolysin S is oxygen-stable and less immunogenic.
  1. Q: How does streptolysin O contribute to the pathogenesis of Streptococci?
    • A: Streptolysin O is a hemolysin that lyses red blood cells and allows the bacterium to evade phagocytosis.
  1. Q: Which type of hemolysis is associated with streptolysin O?
    • A: Beta-hemolysis.
  1. Q: Explain the role of streptokinase in Streptococci.
    • A: Streptokinase is an enzyme produced by Streptococci that activates plasmin, promoting fibrinolysis and facilitating the spread of bacteria.
  1. Q: Name a disease associated with streptococcal pyrogenic exotoxins.
    • A: Scarlet fever.
  1. Q: How do streptococcal pyrogenic exotoxins contribute to disease?
    • A: These toxins can cause toxic shock-like syndrome and are implicated in the development of scarlet fever.
  1. Q: What is the mechanism of action of streptococcal superantigens?
    • A: Streptococcal superantigens stimulate an exaggerated immune response by activating a large number of T cells, leading to excessive cytokine production.
  1. Q: Name a toxin associated with Streptococcus pneumoniae.
  1. Q: How does pneumolysin contribute to the pathogenesis of Streptococcus pneumoniae?
    • A: Pneumolysin is a cytotoxin that damages host cells and is involved in the evasion of the host immune response.
  1. Q: Describe the role of streptococcal hyaluronidase.
    • A: Streptococcal hyaluronidase facilitates the spread of bacteria by hydrolyzing hyaluronic acid, a component of connective tissues.
  1. Q: What is erythrogenic toxin, and which Streptococcal species produces it?
    • A: Erythrogenic toxin is produced by Streptococcus pyogenes and is responsible for the characteristic rash in scarlet fever.
  1. Q: How does Streptococcus pyogenes contribute to the development of necrotizing fasciitis?
    • A: Streptococcus pyogenes produces toxins like streptolysins and enzymes like hyaluronidase, contributing to tissue destruction in necrotizing fasciitis.
  1. Q: What is the role of streptococcal C5a peptidase in immune evasion?
    • A: Streptococcal C5a peptidase cleaves and inactivates the complement component C5a, reducing the effectiveness of the host immune response.
  1. Q: Explain the concept of molecular mimicry in the context of streptococcal toxins.
    • A: Molecular mimicry refers to the similarity between bacterial antigens and host tissues, which may lead to autoimmune responses. Streptococcal toxins can trigger autoimmune reactions by mimicking host components.

These questions cover various aspects of toxins produced by Streptococci, including their types, mechanisms of action, and their roles in the pathogenesis of diseases caused by Streptococcal infections.

Here are some viva questions and answers related to Streptococcus pneumoniae (pneumococcus):

  1. Q: What is the common name for Streptococcus pneumoniae?
    • A: Pneumococcus.
  1. Q: Describe the morphological characteristics of Streptococcus pneumoniae.
    • A: Streptococcus pneumoniae is a Gram-positive, lancet-shaped diplococcus.
  1. Q: How is Streptococcus pneumoniae differentiated from other alpha-hemolytic streptococci on blood agar?
    • A: Streptococcus pneumoniae exhibits alpha-hemolysis with a zone of inhibition around colonies called the “greening” effect.
  1. Q: What is the primary reservoir for Streptococcus pneumoniae in humans?
    • A: The human nasopharynx.
  1. Q: Name the virulence factor produced by Streptococcus pneumoniae that contributes to colonization and evasion of host defenses.
  1. Q: How does the pneumococcal capsule contribute to the pathogenesis of pneumonia?
    • A: The capsule prevents phagocytosis by inhibiting recognition and engulfment by host immune cells.
  1. Q: What type of hemolysis is associated with Streptococcus pneumoniae?
    • A: Alpha-hemolysis.
  1. Q: Which diseases are commonly caused by Streptococcus pneumoniae?
    • A: Pneumonia, otitis media, sinusitis, and meningitis.
  1. Q: Explain the role of pneumolysin in pneumococcal pathogenesis.
    • A: Pneumolysin is a cytotoxin that damages host cells and is involved in the evasion of the host immune response.
  1. Q: What is the Quellung reaction, and how is it used in the identification of Streptococcus pneumoniae?
    • A: The Quellung reaction is a method using specific antisera to identify the capsule of Streptococcus pneumoniae under a microscope.
  1. Q: What population is particularly vulnerable to invasive pneumococcal disease?
    • A: Young children, the elderly, and individuals with weakened immune systems.
  1. Q: How is pneumococcal pneumonia different from other types of bacterial pneumonia?
    • A: Pneumococcal pneumonia often presents with a sudden onset of high fever and a productive cough with rusty-colored sputum.
  1. Q: Name a vaccine used for the prevention of pneumococcal infections.
    • A: Pneumococcal conjugate vaccine (PCV) and Pneumococcal polysaccharide vaccine (PPSV).
  1. Q: Explain the concept of serotypes in Streptococcus pneumoniae.
    • A: Serotypes are variants of Streptococcus pneumoniae distinguished by differences in the composition of their capsule polysaccharides.
  1. Q: What is the mechanism of action of the pneumococcal vaccine in preventing infections?
  1. Q: How does Streptococcus pneumoniae contribute to otitis media?
    • A: The bacterium can ascend from the nasopharynx through the Eustachian tube, leading to infection and inflammation in the middle ear.
  1. Q: What is the role of the autolysin in the pathogenesis of Streptococcus pneumoniae?
    • A: Autolysin facilitates the release of pneumococci from the cell wall, promoting the spread of the bacterium.
  1. Q: Describe the symptoms of pneumococcal meningitis.
    • A: Symptoms may include fever, headache, stiff neck, and altered mental status.
  1. Q: How is antibiotic resistance a concern in pneumococcal infections?
    • A: Pneumococcal strains with resistance to antibiotics, particularly penicillin, have emerged, making treatment more challenging.
  1. Q: Name a laboratory test used to confirm the identification of Streptococcus pneumoniae.
    • A: Optochin susceptibility testing.

These questions cover various aspects of Streptococcus pneumoniae, including its morphology, virulence factors, diseases caused, prevention through vaccination, and laboratory identification methods.

Here are some viva questions and answers related to Neisseria:

  1. Q: Name two species of Neisseria that are important human pathogens.
    • A: Neisseria gonorrhoeae and Neisseria meningitidis.
  1. Q: Differentiate between Neisseria gonorrhoeae and Neisseria meningitidis in terms of their clinical manifestations.
  1. Q: Describe the Gram staining characteristics of Neisseria species.
    • A: Neisseria species are Gram-negative diplococci.
  1. Q: What is the primary reservoir for Neisseria gonorrhoeae?
    • A: Humans are the only natural reservoir for Neisseria gonorrhoeae.
  1. Q: Explain the clinical presentation of gonorrhea in males and females.
    • A: In males, gonorrhea may cause urethritis with purulent discharge, while in females, it can lead to cervicitis with vaginal discharge. Both genders can experience asymptomatic infections.
  1. Q: How is Neisseria gonorrhoeae transmitted?
    • A: Neisseria gonorrhoeae is primarily transmitted through sexual contact.
  1. Q: Name a complication associated with untreated gonorrhea in females.
    • A: Pelvic inflammatory disease (PID).
  1. Q: Describe the laboratory method used to identify Neisseria gonorrhoeae.
    • A: Gram staining of urethral or cervical discharge and culture on selective media, such as Thayer-Martin agar.
  1. Q: What is the role of the pilus in Neisseria gonorrhoeae infection?
  1. Q: What is the recommended treatment for gonorrhea?
    • A: Treatment typically involves antibiotics such as ceftriaxone, often in combination with azithromycin.
  1. Q: Name a vaccine-preventable form of meningitis caused by Neisseria meningitidis.
    • A: Meningococcal meningitis.
  1. Q: How is Neisseria meningitidis transmitted?
    • A: Neisseria meningitidis is transmitted through respiratory droplets.
  1. Q: Describe the clinical features of meningococcal meningitis.
    • A: Symptoms include fever, headache, stiff neck, and a characteristic petechial rash. The infection can progress rapidly and lead to septicemia.
  1. Q: What is the significance of the polysaccharide capsule in Neisseria meningitidis?
    • A: The capsule is a major virulence factor that helps the bacterium evade the host immune system.
  1. Q: Name a laboratory test used for the identification of Neisseria meningitidis.
    • A: Gram staining of cerebrospinal fluid (CSF) and culture on selective media.
  1. Q: Explain the concept of herd immunity in the context of meningococcal vaccination.
  1. Q: What is the quadrivalent meningococcal vaccine designed to protect against?
    • A: The quadrivalent meningococcal vaccine protects against serogroups A, C, W, and Y of Neisseria meningitidis.
  1. Q: How does Neisseria meningitidis adhere to mucosal surfaces in the nasopharynx?
    • A: Neisseria meningitidis expresses pili that aid in adherence to mucosal epithelial cells.
  1. Q: Name a complication associated with meningococcal septicemia.
    • A: Disseminated intravascular coagulation (DIC).
  1. Q: Describe the recommended antibiotic prophylaxis for contacts of individuals with meningococcal disease.
    • A: Rifampin, ciprofloxacin, or ceftriaxone may be used as antibiotic prophylaxis for contacts of individuals with meningococcal disease.

These questions cover various aspects of Neisseria, including its pathogenic species, clinical manifestations, laboratory identification, and preventive measures.

Here are some viva questions and answers related to Corynebacterium diphtheriae:

  1. Q: What disease is caused by Corynebacterium diphtheriae?
    • A: Diphtheria.
  1. Q: Describe the morphology of Corynebacterium diphtheriae.
    • A: Corynebacterium diphtheriae is a Gram-positive, rod-shaped bacterium with characteristic club-shaped swellings at one end.
  1. Q: How is Corynebacterium diphtheriae transmitted?
    • A: Diphtheria is primarily transmitted through respiratory droplets from an infected person.
  1. Q: Name the main virulence factor produced by Corynebacterium diphtheriae.
  1. Q: What is the mechanism of action of the diphtheria toxin?
    • A: The diphtheria toxin inhibits protein synthesis by ADP-ribosylation of elongation factor-2 (EF-2), leading to cell death.
  1. Q: Describe the clinical manifestations of respiratory diphtheria.
    • A: Respiratory diphtheria presents with a sore throat, fever, and the formation of a grayish pseudomembrane in the pharynx.
  1. Q: What are the complications of diphtheria?
    • A: Complications may include airway obstruction, myocarditis, and peripheral neuropathy.
  1. Q: How is the diagnosis of diphtheria confirmed in the laboratory?
  1. Q: Name the types of diphtheria based on the site of infection.
    • A: Respiratory diphtheria and cutaneous diphtheria.
  1. Q: What is the primary treatment for diphtheria?
    • A: Administration of diphtheria antitoxin along with appropriate antibiotics like penicillin or erythromycin.
  1. Q: How is diphtheria prevented through vaccination?
    • A: Diphtheria is prevented by the administration of the diphtheria toxoid as part of the DTP/DTaP vaccine.
  1. Q: Explain the concept of toxoid in diphtheria vaccination.
    • A: Toxoid is an inactivated form of the diphtheria toxin used in vaccines to induce an immune response without causing the disease.
  1. Q: What is the role of the Elek test in the laboratory diagnosis of diphtheria?
    • A: The Elek test is used to detect the production of diphtheria toxin by Corynebacterium diphtheriae.
  1. Q: How does the diphtheria toxin spread throughout the body?
    • A: The diphtheria toxin is disseminated through the bloodstream, affecting distant organs and tissues.
  1. Q: Describe the pathogenesis of cutaneous diphtheria.
    • A: Cutaneous diphtheria occurs when C. diphtheriae infects skin wounds, leading to the formation of an ulcer with a grayish membrane.
  1. Q: Name a reservoir for Corynebacterium diphtheriae in nature.
    • A: Humans are the primary reservoir for Corynebacterium diphtheriae.
  1. Q: Explain the concept of pseudomembrane formation in respiratory diphtheria.
    • A: Pseudomembranes are composed of dead tissue, bacteria, and inflammatory cells that form on the mucous membranes, particularly in the throat, as a result of diphtheria infection.
  1. Q: What is the recommended vaccination schedule for diphtheria in children?
    • A: DTP/DTaP vaccination is typically given in a series of five doses at 2, 4, 6, 15-18 months, and 4-6 years of age.
  1. Q: Name a condition caused by the neurotoxin produced by certain strains of Corynebacterium diphtheriae.
    • A: Diphtheritic polyneuropathy.
  1. Q: What public health measures are taken to control the spread of diphtheria during an outbreak?
    • A: Isolation of cases, treatment of contacts with antibiotics, and vaccination campaigns are key public health measures during a diphtheria outbreak.

These questions cover various aspects of Corynebacterium diphtheriae, including its morphology, virulence factors, clinical manifestations, laboratory diagnosis, treatment, and prevention through vaccination.

 

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