MicroBiology MCQs with Answer and Explnation | Chapter 51

Answer: Absence of cellwall itself.

Mycoplasmas are unique among bacteria because they lack a cell wall. This rigid structure, typically made of peptidoglycan in other bacteria, provides shape and protection. The absence of a cell wall makes mycoplasmas the smallest and most flexible bacteria known, allowing them to squeeze through tight spaces and evade the immune system.

The other options are incorrect:

• Presence of chitin in cell wall: Chitin is not a common component of bacterial cell walls. It is typically found in the exoskeletons of insects and fungi.
• Presence of teichoic acid in cell wall: While some bacteria have teichoic acid in their cell walls, it is not a defining characteristic and is not exclusive to mycoplasmas.
• Presence of lipoprotein in cell wall: Lipoproteins are found in the outer membrane of some bacteria, which mycoplasmas lack due to the absence of a cell wall.

Answer: Christian Gram.

The Gram stain, a fundamental tool in bacteriology, is named after its inventor, Hans Christian Gram, a Danish scientist. He developed the technique in 1884 while working with Carl Friedländer in Berlin.

The other options are incorrect:

• Alfred Gram: This appears to be a misspelling of the correct answer.
• Robert Cook: There is no significant historical figure named Robert Cook associated with the development of the Gram stain.
• Leuis Pasteur: While Louis Pasteur is a renowned scientist who made significant contributions to microbiology, he did not invent the Gram stain.

Answer: Catalase Test

The catalase test differentiates between Staphylococcus and Streptococcus based on the presence of the enzyme catalase. Staphylococci are catalase-positive, meaning they produce catalase, which breaks down hydrogen peroxide (H₂O₂) into water and oxygen gas. Streptococci, on the other hand, are catalase-negative, lacking this enzyme and not producing visible bubbles when exposed to H₂O₂.

The other options are incorrect:

• Coagulase Test: While the coagulase test helps differentiate between Staphylococcus aureus (coagulase-positive) and other staphylococcal species (coagulase-negative), it is not specific to differentiating between Staphylococcus and Streptococcus in general.
• Urase Test: The urase test differentiates bacteria based on their ability to break down urea. While some Staphylococcus and Streptococcus species might be positive or negative in this test, it is not a reliable differentiating factor for the entire genera.
• Oxidase Test: The oxidase test identifies bacteria based on their ability to utilize oxygen in specific metabolic pathways using the enzyme cytochrome oxidase. This test is not specific to differentiating between Staphylococcus and Streptococcus, as both can be oxidase-negative.

Answer: Coagulase Test

The coagulase test is the primary method used to differentiate Staphylococcus aureus from other Staphylococcus species. This test detects the presence of coagulase, an enzyme produced by S. aureus that can convert fibrinogen in plasma to fibrin, causing clumping (coagulation). Other Staphylococcus species typically lack coagulase and are therefore coagulase-negative.

The other options are incorrect:

• Catalase Test: While both Staphylococcus and Streptococcus are typically catalase-positive, meaning they produce catalase, this test cannot distinguish between S. aureus and other Staphylococcus species.
• Urase Test: The urase test determines an organism’s ability to break down urea. While some Staphylococcus species might be positive or negative in this test, it is not a reliable differentiating factor for S. aureus specifically.
• Oxidase Test: The oxidase test identifies bacteria based on their ability to utilize oxygen in specific metabolic pathways using the enzyme cytochrome oxidase. Most Staphylococcus species, including S. aureus, are oxidase-negative, making this test unsuitable for differentiating S. aureus from other Staphylococci.

Answer: Motility

Salmonella and Shigella can be differentiated based on the motility test. Salmonella species are typically motile, while Shigella species are non-motile. The motility test involves observing the movement of bacterial cells in a semisolid medium, such as a motility agar.

The other options are incorrect:

• Gram Stain: Both Salmonella and Shigella are Gram-negative bacteria, meaning they stain pink under a Gram stain. This test cannot differentiate them.
• Catalase Test: Both Salmonella and Shigella are catalase-positive, meaning they can break down hydrogen peroxide. This shared characteristic is not useful for differentiation.
• Indole Test: While the Indole test can differentiate some bacterial genera, it does not reliably distinguish between Salmonella and Shigella. Both can be either positive or negative in this test.

Answer: Streptococcus Pyogenes

Streptococcus pyogenes, also known as group A Streptococcus, is a major cause of post-streptococcal glomerulonephritis (PSGN), a type of kidney inflammation that can occur after a strep throat or skin infection. The bacteria triggers an immune response that damages the glomeruli, the tiny filtering units in the kidneys.

The other options are incorrect:

• Staphylococcus aureus: While S. aureus can cause various infections, including kidney infections, it is not typically associated with PSGN.
• Staphylococcus epidermidis: This usually harmless skin bacteria rarely causes serious infections, including PSGN.
• Streptococcus pneumoniae: S. pneumoniae is primarily associated with respiratory infections like pneumonia. While it can rarely cause other complications, PSGN is not a common consequence.

Answer: Pseudomonas

Pseudomonas is a Gram-negative bacterium that is aerobic, oxidase-positive, and motile. It is characterized by its rod-shaped morphology and is known for its diverse metabolic capabilities and widespread distribution in various environments.

The other options are incorrect:

• E. coli: While E. coli is Gram-negative and motile, it is oxidase-negative.
• Proteus: Proteus is also Gram-negative and motile, but it is oxidase-negative.
• Salmonella: Salmonella shares the Gram-negative and motile characteristics, but it is oxidase-negative.

Answer: Mycobacterium

Ziehl-Neelsen stain is used for the identification of acid-fast bacteria, particularly Mycobacterium species. This staining technique helps in visualizing the characteristic acid-fast bacilli, which include Mycobacterium tuberculosis, the causative agent of tuberculosis.

The other options are incorrect:

• Streptococcus: Streptococcus is a Gram-positive bacterial genus and does not require the ZN stain for identification. They are typically stained with routine methods like Gram stain.
• H. influenzae: Haemophilus influenzae is also a Gram-negative bacterium and does not require the ZN stain. It can be identified using other staining techniques.
• Bacillus sp.: Bacillus species are diverse, but none are typically identified using the ZN stain. They can be Gram-positive or -negative and require different staining methods depending on the specific species.

Answer: Vibrio Cholera

A “rice water stool” is characteristic of a patient infected with Vibrio cholerae. Cholera is an acute diarrheal disease caused by the ingestion of contaminated water or food with the bacterium Vibrio cholerae. The term “rice water stool” refers to the watery and pale appearance of the diarrhea, which resembles water used to wash rice.

The other options are incorrect:

• Clostridium botulinum: This bacterium produces neurotoxins that cause botulism, a paralytic illness affecting the nervous system. It does not cause “rice water stool” as a primary symptom.
• Salmonella Typhi: While Salmonella Typhi causes typhoid fever, characterized by fever, headache, and gastrointestinal distress, “rice water stool” is not a typical symptom. The diarrhea associated with typhoid fever is usually loose and may contain blood or mucus.
• Shigella dysenteriae: Shigella infection, also known as shigellosis, primarily causes dysentery, characterized by frequent, bloody stools with abdominal cramps. “Rice water stool” is not a common feature of shigellosis.

Answer: Corynebacterium diphtheriae

Leoffler’s medium is used as a primary isolation medium for Corynebacterium diphtheriae, the bacterium that causes diphtheria. This medium provides a suitable environment for the growth of C. diphtheriae and aids in the identification of the pathogen.

The other options are incorrect:

• Bordetella pertussis: While Bordetella pertussis, the causative agent of whooping cough, also requires enriched media, it is typically isolated on Bordet-Gengou agar, specifically designed for this bacterium.
• Clostridium tetani: Clostridium tetani, responsible for tetanus, is an anaerobic bacterium and requires specialized media that create anaerobic conditions, unlike the aerobic Loeffler’s medium.
• Streptococcus pyogenes: Streptococcus pyogenes, the bacterium causing strep throat and other infections, grows well on various routine media like blood agar and does not require the specific features of Loeffler’s medium.

Answer: Optimal Growth at 42°C

The characteristic feature of Campylobacter jejuni is its optimal growth temperature, which is around 42°C. This bacterium is thermophilic and thrives at higher temperatures, making it distinct from many other bacteria.

The other options are incorrect:

• Catalase Negative: While C. jejuni can be catalase-negative or -positive depending on the strain, this is not a universally defining feature.
• Non-motile: Some C. jejuni strains are motile, possessing a single polar flagellum. Motility testing can be variable depending on the specific strain and growth conditions.
• Oxidase Negative: Similar to catalase, C. jejuni can be oxidase-positive or -negative depending on the strain. It is not a reliable sole identifier.

Answer: Lysine decarboxylase

Citrobacter typically produces hydrogen sulfide (H2S), while Salmonella does not. This difference in H2S production is a reliable and commonly used tool for distinguishing between these two bacterial genera in clinical settings.

The other options are incorrect:

• H₂S production: While both Citrobacter and Salmonella can produce hydrogen sulfide (H₂S) under certain conditions, this is not a consistent or reliable differentiating factor. Some strains of each genus may be positive or negative for H₂S production, making it unreliable for definitive identification.
• Indole production: Similar to H₂S production, the ability to produce indole from tryptophan can vary within both Citrobacter and Salmonella species. This inconsistency makes it unsuitable as the primary differentiating characteristic.
• Urase production: Both Citrobacter and Salmonella species can possess the enzyme urease, which breaks down urea. Since they can be either positive or negative for this test, it cannot definitively differentiate these bacteria.

Answer: Hemophilus

The X-factor (hemin) and V-factor (NAD) are essential growth factors required by Haemophilus bacteria. They lack the enzymes to synthesize these molecules themselves and need them from the environment. This unique requirement differentiates Haemophilus from other listed bacteria.

The other options are incorrect:

• Brucella: Brucella does not require X-factor or V-factor for growth. Brucella is a genus of bacteria known for causing brucellosis in animals and humans.
• Legionella: Legionella species do not have a specific requirement for X-factor or V-factor. Legionella is associated with causing Legionnaires’ disease.
• Salmonella: Salmonella does not have a specific requirement for X-factor or V-factor. Salmonella is a genus of bacteria known for causing foodborne illnesses such as salmonellosis.

Answer: Glucose

Neisseria meningitidis (N. Meningitis) is a bacterium that primarily ferments glucose. It does not ferment maltose, sucrose, or lactose. This characteristic helps in differentiating it from other bacteria, including Neisseria gonorrhoeae.

The other options are incorrect:

• Maltose: Meningitis does not ferment maltose. This differentiates it from certain other bacteria.
• Sucrose: Sucrose fermentation is not a characteristic of N. Meningitis. This can be a distinguishing feature in microbiological identification.
• Lactose: N. Meningitis does not ferment lactose. This is important for differentiation from other bacteria, including some Enterobacteriaceae.

Answer: Corynebacterium diphtheriae

Corynebacterium diphtheriae is characterized by Chinese letter arrangement (pleomorphic club-shaped rods), metachromatic granules (when stained with certain dyes), tellurite hydrolysis (ability to reduce tellurite to metallic tellurium), and the Elek test (used for toxigenicity of diphtheria).

The other options are incorrect:

• Listeria monocytogenes: While a pathogenic bacterium, it lacks the characteristic Chinese letter arrangement, metachromatic granules, and specific reactions in tellurite and Elek tests.
• Bacillus anthracis: This bacterium forms endospores, is non-motile, and has a different cell morphology compared to C. diphtheriae. It also lacks metachromatic granules and reactions specific to the Elek and tellurite tests.
• Moraxella catarrhalis: This bacterium is Gram-negative, non-motile, and coccobacillary in shape. It does not exhibit the characteristics mentioned for C. diphtheriae.

Answer: Proteus

Proteus bacteria are characterized by being urase positive (producing urease enzyme), indole positive (producing indole from tryptophan), and H2S positive (forming hydrogen sulfide). These biochemical characteristics are part of the identification process in microbiology.

The other options are incorrect:

• Escherichia (Escherichia coli): Escherichia coli is urase positive but indole negative and H2S negative. It is a common bacterium found in the intestines.
• Salmonella: Salmonella is urase negative, indole negative, and H2S positive. It differs from Proteus in its indole production.
• Shigella: Shigella is urase negative, indole negative, and H2S negative. It lacks the specified characteristics of Proteus.

Answer: Campylobacter Jejuni

The “Seagull wing” appearance is characteristic of Campylobacter jejuni when observed under a microscope. This visual pattern resembles the wings of a seagull.

The other options are incorrect:

• Vibrio cholerae: Vibrio cholerae does not exhibit the “seagull wing” appearance. It is associated with causing cholera.
• E. coli (Escherichia coli): Escherichia coli does not show the seagull appearance. It is a common bacterium found in the intestines, and different strains may have various characteristics.
• Salmonella: Salmonella does not display the seagull wing appearance. It is known for causing various types of foodborne illnesse

Answer: Treponema pallidum

Treponema pallidum, the bacterium responsible for syphilis, stains with silver impregnation techniques and can be visualized under dark-field microscopy. The silver staining enhances the visibility of the spirochetes, and dark-field microscopy allows for the observation of living and unstained organisms.

The other options are incorrect:

• Homeopathic influenza: “Homeopathic influenza” is not a recognized term in microbiology, and it does not refer to a specific bacterium or microorganism.
• Streptococcus pyogenes: Streptococcus pyogenes does not stain well with silver impregnation, and it is not typically observed under dark-field microscopy. It is a Gram-positive bacterium responsible for various infections, including strep throat.
• Spirillum minus: Spirillum minus is a bacterium that causes rat bite fever, but it is not known for staining with silver impregnation or being visible under dark-field microscopy. It has a spiral shape but does not have the characteristics described for Treponema pallidum.

Answer: Mycobacteria

Lowenstein-Jensen (LJ) medium is a selective and enriched medium specifically designed for the isolation and cultivation of Mycobacteria. It supports the growth of slow-growing mycobacterial species, including the ones responsible for diseases such as tuberculosis and leprosy.

The other options are incorrect:

• Staphylococcus: These are Gram-positive bacteria commonly associated with various skin and soft tissue infections. They can be readily cultivated on standard bacterial growth media like blood agar, which is much simpler and faster than LJ medium.
• Streptococcus: Similar to Staphylococcus, these are Gram-positive bacteria and do not require the specialized conditions provided by LJ medium. They also grow well on standard media like blood agar.
• Neisseria: These are Gram-negative bacteria, including the Neisseria gonorrhoeae and Neisseria meningitidis species responsible for gonorrhea and meningitis respectively. They have different growth requirements compared to Mycobacteria and can be cultured on enriched media like Thayer-Martin agar which caters specifically to their needs.

Answer: Rotavirus

Rotavirus is a common cause of acute factitious (artificially induced) infantile diarrhea. It is a highly contagious virus that primarily affects infants and young children, leading to gastroenteritis and watery diarrhea. Proper hygiene and vaccination are essential in preventing its spread.

The other options are incorrect:

• Hantavirus: Hantavirus is not a known cause of acute factitious infantile diarrhea. It is primarily associated with rodent-borne infections that can lead to severe respiratory and systemic symptoms in humans.
• HIV (Human Immunodeficiency Virus): HIV does not cause acute factitious infantile diarrhea. HIV is a virus that attacks the immune system, leading to immunodeficiency, but it is not directly associated with infantile diarrhea.
• Rhabdovirus: Rhabdovirus, which includes viruses like the rabies virus, is not a typical cause of acute factitious infantile diarrhea. Rhabdoviruses are more commonly associated with neurological symptoms.

Answer: Nutrient medium with antibiotic

Specimens for viral culture should be transported in a nutrient medium with antibiotics. This medium provides the necessary nutrients to support the growth of viruses while preventing the overgrowth of bacteria that might be present in the specimen. Antibiotics are included to inhibit bacterial contamination.

The other options are incorrect:

Anaerobic Container: An anaerobic container is used to transport specimens for anaerobic bacterial culture, not for viral culture. Viruses require a different set of conditions for growth.
Bovine Albumin: Bovine albumin is not typically used as a transport medium for viral culture. Nutrient media with specific components are preferred for supporting viral growth.
Sheep Blood (5 – 10%): Sheep blood is often used in microbiological media for bacterial culture, but it is not the preferred medium for transporting viral specimens. Viruses have distinct requirements that are better met with specialized nutrient media.

Answer: Incubate yeast subculture at 37°C

The ability of a yeast to grow at a higher temperature (37°C) compared to its typical growth temperature (around 25-30°C) is a key characteristic of dimorphism. Dimorphic fungi can switch between a yeast form (budding unicellular) and a filamentous form (mold) depending on environmental factors like temperature.

The other options are incorrect:

• Carbohydrate Assimilation: While this test can be used to identify the type of yeast based on its ability to utilize different sugars, it doesn’t directly assess dimorphism. Many dimorphic fungi and non-dimorphic yeasts can utilize a variety of carbohydrates.
• Growth on Corn Meal Agar: Cornmeal agar is a general-purpose medium used for growing many fungi, including yeasts. While it can be used to cultivate some dimorphic fungi, it doesn’t specifically identify dimorphism. Many non-dimorphic yeasts can also grow on this medium.
• Urease: This test determines an organism’s ability to produce the enzyme urease, which breaks down urea. While some dimorphic fungi may possess urease, its presence or absence isn’t a defining characteristic of dimorphism. Many non-dimorphic yeasts and fungi can also express urease.

Answer: FTA-Abs

FTA-Abs is a highly specific test for syphilis as it directly detects antibodies against the Treponema pallidum, the bacterium causing the disease. This test is specific because it doesn’t react with antibodies produced against other unrelated organisms.

The other options are incorrect:

• RPR (Rapid Plasma Reagin): RPR is a non-specific screening test that detects antibodies against cardiolipin, a substance present in various tissues. While it’s a common and convenient screening tool for syphilis, a positive RPR can also be caused by other infections like HIV, autoimmune diseases, and even pregnancy.
• TPHA (Treponema Pallidum Hemagglutination Assay): TPHA is another treponemal test, but it’s less specific than FTA-Abs. It can sometimes give false-positive results due to cross-reactions with other treponemes, bacteria similar to T. pallidum.
• VDRL (Venereal Disease Research Laboratory): Similar to RPR, VDRL is a non-specific screening test using cardiolipin as an antigen. It’s less specific than FTA-Abs and can also give false-positive results due to various non-syphilis related factors.

Answer: Peptidoglycan (murein)

Gram-positive bacteria and Gram-negative bacteria differ in the composition and structure of their cell walls. The primary distinction lies in the thickness and complexity of the peptidoglycan layer (murein). Gram-positive bacteria have a thick layer of peptidoglycan, which retains the crystal violet stain during the Gram-staining process, resulting in a purple color under the microscope.

The other options are incorrect:

• Mycolic acid: Mycolic acid is a component found in the cell walls of certain bacteria, such as mycobacteria. However, it is not the defining characteristic that differentiates Gram-positive from Gram-negative bacteria.
• Teichoic acid: Teichoic acid is a component specific to the cell walls of Gram-positive bacteria, but it is not the primary factor used to distinguish between Gram-positive and Gram-negative bacteria.
• All of the above: While Gram-positive bacteria do contain peptidoglycan and teichoic acid, mycolic acid is not a universal component of Gram-positive bacteria. Therefore, “All of the above” is not accurate in the context of distinguishing Gram-positive from Gram-negative bacteria.

Answer: Pox Virus

Poxviruses are among the largest known viruses, with a diameter ranging from 170 to 300 nanometers (nm). This size allows them to encode a much larger genome compared to many other viruses.

The other options are incorrect:

• Parvo Virus: Parvoviruses are some of the smallest known viruses, with a diameter of only around 18-22 nm. They have a very simple structure and a small genome.
• Herpes Virus: Herpesviruses are considered medium-sized viruses, with a diameter ranging from 120 to 200 nm. They are larger than parvoviruses but smaller than poxviruses.
• Mycoplasma: Mycoplasmas are not viruses but rather bacteria. They are even smaller than the smallest viruses, with a size range of 0.1-0.8 μm (100-800 nm). They lack a cell wall and have a simpler structure compared to bacteria and viruses.

Answer: Peplomers

Peplomers, also known as spike proteins, are the projecting structures found on the surface of enveloped viruses. These protein structures play a crucial role in viral attachment, entry, and fusion with host cells, facilitating infection.

The other options are incorrect:

Capsid:The capsid is the protein shell that encloses the viral genome inside an enveloped virus. It lies beneath the envelope and peplomers, providing protection for the viral genetic material.
Capsomer: Capsomeres are the individual subunits that assemble to form the viral capsid. They are not the projecting structures on the viral surface.
Cilia: Cilia are hair-like structures found on the surface of some eukaryotic cells, including certain prokaryotic cells like bacteria. They are not related to viral structures and serve different functions, such as movement and sensory perception.

Answer: All of above

All of the provided methods—Incubation in embryonated egg, Animal Inoculation, and Tissue Culture—are used for the cultivation of viruses, depending on the characteristics and requirements of the specific virus. The choice of method depends on factors such as the nature of the virus, the host organism it infects, and the experimental goals.

The other options are incorrect:

Incubation in Embryonated Egg: This method involves injecting the virus into a fertilized bird egg. The virus can replicate and propagate within the egg, and various stages of embryonic development can be used for different types of viruses.
Animal Inoculation: In this method, the virus is inoculated into susceptible animals to observe the effects of infection. Different animals are used depending on the virus and the type of disease it causes.
Tissue Culture: Tissue culture involves growing cells in vitro and exposing them to viruses. This method is particularly useful for studying viruses that infect human or animal cells.

Answer: Liquid Media & Selective Media Both

Enrichment media is designed to increase the number of a specific microorganism present in a sample, often containing rich nutrients and no selective agents to encourage growth of a wide variety of organisms, including those with particular nutritional needs. Liquid media allows for better distribution of nutrients and easier detection of growth, making it ideal for this purpose.

The other options are incorrect:

• Solid Media: While some enrichment media can be solidified (e.g., with agar), the primary form is liquid for better nutrient distribution and growth detection.
• Selective Media: Selective media inhibits the growth of specific microorganisms, whereas enrichment media promotes the growth of all or a broad range of organisms. They serve opposite purposes.
• Liquid Media & Selective Media Both: This option combines two contrasting characteristics. Enrichment media is typically liquid and not selective.

Answer: Aedes

The primary mosquito responsible for transmitting the dengue virus is the Aedes aegypti species. These mosquitoes are found in tropical and subtropical regions and thrive in urban environments, breeding in stagnant water sources near human habitation.

The other options are incorrect:

• Anopheles: Anopheles mosquitoes are the primary vectors for malaria, not dengue fever.
• Culex: Culex mosquitoes can transmit various diseases, including West Nile virus and filariasis, but not dengue fever.
• All the above: While various mosquito species can carry and transmit diseases, only Aedes aegypti plays a significant role in spreading dengue fever.

Answer: All Option

Cloudiness in a urine specimen can result from various factors, and all the options listed—Bacteria, RBC (red blood cells), and Pus cells—are potential contributors to cloudy urine. Each of these elements, when present in elevated levels, can cause turbidity or cloudiness in the urine.

The other options are incorrect:

• Bacteria: Bacteria in the urine, especially in cases of urinary tract infections (UTIs), can lead to cloudiness.
• RBC (Red Blood Cells): High levels of red blood cells in the urine, known as hematuria, can cause the urine to appear cloudy.
• Pus cells: Pus cells, which indicate an inflammatory response often due to infection, can contribute to cloudiness in urine.

Answer: Haematuria

Hemato literally translates to “blood” in Greek, and -uria refers to “urine” in medical terminology. Therefore, hematuria signifies the presence of blood in the urine, which can manifest as reddish or pinkish discoloration or be microscopic, detectable only through analysis.

The other options are incorrect:

• Polyuria: Polyuria refers to the excessive production of urine, exceeding 2.5 liters per day. It is not related to the number of RBCs in the urine.
• Oligouria: Oligouria is the opposite of polyuria and indicates an abnormally low urine output, typically less than 500 ml per day. It is also not directly associated with RBC count in the urine.
• Pyuria: Pyuria specifically refers to the presence of white blood cells (WBCs), particularly neutrophils, in the urine, often indicating urinary tract inflammation or infection. While infections can sometimes cause hematuria, pyuria and hematuria are distinct conditions.

Answer: All of above

The slide culture technique is a versatile method used for the identification of various types of fungi, including yeasts, molds, and yeast-like fungi. This technique involves growing fungi on a small, transparent slide with a nutrient medium, allowing for microscopic examination of their morphology and characteristics.

The other options are incorrect:

• Yeast: Unicellular fungi, often readily observed due to their size and morphology.
• Molds: Filamentous fungi with visible hyphae and spores, easily visualized on slides.
• Yeast-like Fungi: Fungi with characteristics resembling both yeasts and molds, making slide culture valuable for distinguishing them from true yeasts.

Answer: 1 % Sulphuric Acid

Mycobacterium tuberculosis is an acid-fast bacillus, meaning it retains a specific stain (carbol fuchsin) even after treatment with a weak acid-alcohol solution. This characteristic is due to the waxy cell wall of these bacteria, which is highly impermeable and resists decolorization with weak acids like 1% sulfuric acid.

The other options are incorrect:

• 20% Sulphuric Acid: Such a high concentration of acid would decolorize both the bacteria and the stain, rendering the test ineffective for identifying M. tuberculosis.
• 5 % Sulphuric Acid: While stronger than 1% acid, 5% sulfuric acid might still be insufficient to decolorize the waxy cell wall of M. tuberculosis entirely, potentially leading to misidentification.
• 10 % Sulphuric Acid: Similar to 5% acid, 10% sulfuric acid is likely too strong and would decolorize both the stain and the bacteria, rendering the test useless for diagnostic purposes.

Answer: Bacteriology

The study of bacteria is called bacteriology. Bacteriology is a branch of microbiology that specifically focuses on the morphology, physiology, genetics, and ecology of bacteria. It involves the identification and classification of bacteria and the study of their roles in various biological processes.

The other options are incorrect:

• Microbiology: Microbiology is the broader scientific discipline that encompasses the study of microorganisms, including bacteria, viruses, fungi, and parasites. Bacteriology is a subset of microbiology.
• Haematology: Haematology is the study of blood and blood-related disorders. It does not specifically focus on bacteria; its primary emphasis is on blood components and related diseases.
• Microscopy: Microscopy is a technique involving the use of microscopes to observe objects that are too small to be seen by the naked eye. While microscopy is a tool used in bacteriology, it is not the study itself.

Answer: Rabies

Negri bodies are specific cytoplasmic inclusions found in the nerve cells of individuals infected with the rabies virus. They consist of aggregates of viral ribonucleoproteins and are considered pathognomonic, meaning their presence is highly indicative of rabies infection.

The other options are incorrect:

• Smallpox: Smallpox is caused by the variola virus and does not involve the formation of Negri bodies. Its diagnosis relies on clinical presentation and specific laboratory tests.
• HIV: HIV is a retrovirus that does not produce Negri bodies. It attacks the immune system and is diagnosed through various tests like antibody and viral load tests.
• Tuberculosis: Tuberculosis is caused by the Mycobacterium tuberculosis bacterium and does not involve the formation of Negri bodies. Diagnosis involves chest X-rays, sputum cultures, and skin tests.

Answer: Bacteriophage

Bacteriophages, also known as phages, are viruses that specifically infect and replicate within bacteria. They are incredibly abundant and diverse, playing a crucial role in regulating bacterial populations in the environment.

The other options are incorrect:

• Mycophage: Mycophages are organisms that decompose or eat fungi, not bacteria. They can be various types of organisms, including bacteria, fungi, and animals.
• Virdois: This term is not commonly used in biology. It is likely a misspelling of viroid, which is a type of infectious agent even smaller than a virus. However, viroids do not infect bacteria, they specifically infect plants.
• Infection:Infection is a broader term referring to the invasion and multiplication of an infectious agent (like bacteria or viruses) in a host organism. It is not specific to a particular type of virus or its host.

Answer: Gram Positive bacteria have thick peptidoglycan then gram negative

The statement that “Gram Positive bacteria have thick peptidoglycan than gram negative” is true. In Gram-positive bacteria, the cell wall has a thick layer of peptidoglycan, which retains the crystal violet stain during the Gram-staining procedure, giving a purple color. In contrast, Gram-negative bacteria have a thinner peptidoglycan layer surrounded by an outer membrane.

The other options are incorrect:

• Viruses have both DNA & RNA: While some viruses can have either DNA or RNA as their genetic material, they do not typically possess both simultaneously.
• Protozoa are prokaryotic: Protozoa are eukaryotic organisms, meaning their cells possess a true nucleus and membrane-bound organelles, unlike prokaryotic bacteria which lack these features.
• Bacteria have either DNA & RNA: All bacteria contain DNA as their genetic material. However, some bacteria might also harbor small, circular plasmids containing additional genetic information, which can be either DNA or RNA.

Answer: Enriched media

Enriched media aims to support the growth of fastidious organisms, which are microorganisms with specific nutritional requirements beyond basic nutrients. These special requirements often include growth factors, such as vitamins, amino acids, or specific carbohydrates, that encourage their growth and proliferation.

The other options are incorrect:

• Transport media: Transport media are designed to maintain the viability of microorganisms during transport from the collection site to the laboratory, not necessarily for promoting growth. They typically contain minimal nutrients and no selective agents to prevent overgrowth of any specific organism.
• Differential media: Differential media incorporate specific ingredients that differentiate between different types of microorganisms based on their metabolic activities or physical characteristics. These media typically do not require additional growth factors beyond basic nutrients.
• Simple media: Simple media, also known as basal media, provide the essential nutrients and basic components required for the growth of a wide range of non-fastidious organisms. They do not typically contain additional growth factors, relying on the organism’s ability to synthesize what they need for growth.

Answer: Plasmid

Bacteria primarily store their genetic information in a single, circular chromosome. However, they can also carry extrachromosomal genetic elements, independent of the chromosome, known as plasmids.

The other options are incorrect:

• Chromosome: As mentioned above, the chromosome is the main genetic element within a bacterial cell, not an extra chromosomal element.
• Ribosomes: Ribosomes are cellular organelles responsible for protein synthesis. They are not genetic elements but are essential for utilizing the genetic information encoded in the chromosome.
• Conjugation: Conjugation is a process through which bacteria exchange genetic material, not an extra chromosomal element itself. Plasmids can be transferred between bacteria during conjugation.

Answer: Ivanovosky

Dmitri Ivanovsky is often considered the father of virology. In the late 19th century, he conducted groundbreaking research on the tobacco mosaic disease, which led to the discovery of a novel infectious agent that could pass through a filter designed to trap bacteria. Ivanovsky’s work laid the foundation for the field of virology.

The other options are incorrect:

• Robert Koch: While Robert Koch made significant contributions to microbiology, including the development of Koch’s postulates for identifying infectious agents, he is not specifically associated with the field of virology.
• Louis Pasteur: Similar to Robert Koch, Louis Pasteur, known for his work on vaccines and pasteurization, did not directly contribute to the foundation of virology.
• Antony Van Leevenhoek: Antony van Leeuwenhoek, known as the “father of microbiology”, is credited with pioneering the use of microscopes and observing various microorganisms, but his work predates the discovery of viruses and the establishment of virology.

Answer: Tetrads

Cocci present in a group of four, forming a square arrangement, are called tetrads. Tetrads are a specific bacterial arrangement where the cocci divide in two perpendicular planes, resulting in a group of four cells.

The other options are incorrect:

• Staphylococcus: As mentioned earlier, staphylococci are known for forming grape-like clusters, not pairs of four.
• Streptococcus: Streptococci form chains, not squares of four.
• Sarcina: While sarcina form packets, the number of cells typically exceeds four and arranges differently compared to tetrads.

Answer: Pock formation

Virus culture inside the embryonated egg is often detected by observing pock formation. Pock formation is a characteristic lesion or indentation on the chorioallantoic membrane of the embryonated egg caused by certain viruses. It is a visible sign of viral replication and can aid in the identification of the virus.

The other options are incorrect:

• Cytopathic effect: Cytopathic effects (CPE) are observable changes in host cells due to viral infection in cell culture, not in embryonated eggs.
• Turbidity: Turbidity refers to cloudiness in a liquid, but it is not a specific indicator of virus culture inside embryonated eggs.
• Bubbles formation: Bubbles formation is not a typical sign of virus culture in embryonated eggs. It may occur due to other factors but is not a specific indicator of viral infection.

Answer: Catalase

Staphylococcus produces the enzyme catalase, which breaks down hydrogen peroxide (H₂O₂). This breakdown process produces visible bubbles, indicating a positive test result. Conversely, Streptococcus does not produce catalase, resulting in a negative test.

The other options are incorrect:

• Indole: This test differentiates between members of the Enterobacteriaceae family. Neither Staphylococcus nor Streptococcus typically belong to this family.
• Motility: Both Staphylococcus and Streptococcus are generally non-motile, meaning they cannot move on their own. Therefore, this test cannot effectively differentiate between them.
• Coagulase: While the coagulase test helps identify specific Staphylococcus species, it cannot differentiate between Staphylococcus and Streptococcus in general.

Answer: Proteus

Among the listed options, only Proteus exhibits swarming motility. This specific type of motility involves the coordinated movement of large bacterial populations, resulting in a spreading, film-like pattern.

The other options are incorrect:

• Vibrio Cholera: While Vibrio cholerae demonstrates swimming motility, this involves individual bacterial movement rather than coordinated swarming.
• Clostridium: Clostridium species are typically non-motile or exhibit minimal motility at best.
• Treponema Palladum: Treponema pallidum displays a unique rotational and flexing movement known as “rotary motility,” but not true swarming.

Answer: Microscopic Examination

The presence of red blood cells (RBC) in urine is typically detected through microscopic examination. This involves examining a urine sample under a microscope to identify and count the number of red blood cells present. Microscopic examination is a crucial step in urinalysis for assessing the cellular components of urine.

The other options are incorrect:

• Physical Examination: Physical examination of urine involves assessing its color, odor, and turbidity. While gross hematuria (visible blood in urine) can be detected through physical examination, it does not provide detailed information about the number of RBC or other cellular elements.
• Chemical Examination: Chemical examination involves testing for the presence of certain substances in urine, such as proteins, glucose, or blood. While it may indicate the presence of blood, it does not distinguish between different blood components like RBC.

Answer: Alberts Stain

Albert’s stain is a specific differential stain used to visualize the metachromatic granules (also called volutin granules or Babes-Ernst granules) present in Corynebacterium diphtheriae. These granules appear bluish-black against a light green background of the bacterial cell.

The other options are incorrect:

• Z.N Stain: This stain, also known as the Ziehl-Neelsen stain, is used to identify acid-fast bacteria, such as Mycobacterium tuberculosis, which Corynebacterium diphtheriae is not.
• Auramine Stain: This stain is used to detect mycobacteria under fluorescent microscopy. While it can stain Corynebacterium diphtheriae, it does not specifically target the metachromatic granules.
• Gram Stain: This stain categorizes bacteria as Gram-positive or Gram-negative based on their cell wall structure. While Corynebacterium diphtheriae is Gram-positive, the Gram stain does not highlight the specific metachromatic granules.

Answer: X and V

Haemophilus influenzae requires both factor X (hemin) and factor V (NAD, nicotinamide adenine dinucleotide) for its growth. These growth factors are essential for the metabolism and survival of Haemophilus influenzae, and their presence in the culture medium is necessary for successful cultivation.

The other options are incorrect:

• X: Factor X alone is not sufficient for the growth of Haemophilus influenzae. Both factors X and V are required.
• V: Similarly, factor V alone is not enough. Haemophilus influenzae requires both factor X and factor V for optimal growth.
• Egg: Egg is not a growth factor but rather a medium. While certain bacteria may be cultured using egg-based media, it does not specifically provide factors X and V required by Haemophilus influenzae.

Answer: M. TB

N-95 masks are effective in filtering airborne particles, including bacteria like Mycobacterium tuberculosis (M. TB), the causative agent of tuberculosis. When worn properly, N-95 masks can block at least 95% of airborne particles, offering protection to healthcare workers and others at risk of inhaling M. TB during procedures or close contact with infected individuals.

The other options are incorrect:

• Ebola Virus: While some healthcare settings might utilize specific respirators for Ebola virus, N-95 masks are not the recommended personal protective equipment (PPE) for this highly contagious virus. Standard precautions, including full-body suits, are typically used for Ebola virus.
• Malaria: Malaria is transmitted by female Anopheles mosquitoes, not airborne particles. Therefore, N-95 masks are not relevant in preventing malaria.
• HIV: The human immunodeficiency virus (HIV) is primarily transmitted through bodily fluids like blood, semen, and vaginal fluids, not airborne particles. N-95 masks offer no significant protection against HIV transmission.

Answer: graduated cylinder

The glassware used to measure 24-hour urine volumes is a graduated cylinder. Graduated cylinders are cylindrical containers with volume graduations along the sides, allowing for precise measurements of liquid volumes. They are suitable for accurately measuring larger volumes of liquids like urine.

The other options are incorrect:

• Volumetric flask: These flasks are specifically designed for preparing precise volumes of solutions and are not ideal for measuring large, variable volumes like 24-hour urine output.
• Beaker: While beakers can hold large volumes, they lack the graduated markings necessary for accurate volume measurement.
• Erlenmeyer flask: Similar to beakers, Erlenmeyer flasks are not graduated and are primarily used for mixing solutions, not precise volume measurement.

Answer: sterilization

Sterilization is the process that completely eliminates or destroys all forms of microbial life, including vegetative bacteria, bacterial spores, fungi, viruses, and prions. This process aims to render an object or substance completely free from any living microorganisms to prevent the spread of infection or contamination.

The other options are incorrect:

• Sanitation: Sanitation involves reducing the microbial population to safe levels but does not necessarily eliminate all microorganisms, especially spores.
• Antisepsis: Antisepsis involves applying antimicrobial substances to living tissues (e.g., skin) to prevent or inhibit the growth of microorganisms. It does not necessarily achieve the complete destruction of all microorganisms.
• Disinfection: Disinfection aims to reduce the number of viable microorganisms on surfaces or objects, but it may not achieve complete sterilization. It typically involves the use of chemicals or physical agents to kill or inhibit microorganisms.