Microbiology MCQs with Answer and Explnation | Chapter 7

Answer: Ring worm of scalp

Tinea capitis is ringworm of the scalp. It is a fungal infection that affects the hair and scalp.

Ringworm can also affect other parts of the body, such as the feet (tinea pedis), the groin (tinea cruris), and the body (tinea corporis).

The symptoms of tinea capitis can include:

Hair loss in patches
Scaly patches on the scalp
Redness and inflammation of the scalp
Itching
Tinea capitis is treated with antifungal medications, which can be taken orally or applied to the scalp.

The other options are not correct:

• Ringworm of the foot is tinea pedis.
• Ringworm of non-hairy skin of body is tinea corporis.

Answer: Fungi imperfecti

Fungi imperfecti, also known as deuteromycetes, are a group of fungi that reproduce only asexually. This means that they do not produce spores through sexual fusion of two nuclei. Instead, they reproduce by producing conidia, which are asexual spores that are produced by mitosis.

Fungi imperfecti are a diverse group of fungi that includes many common species, such as Penicillium, Aspergillus, and Candida. They are found in all environments and play a variety of roles, including decomposing organic matter, causing diseases in plants and animals, and producing antibiotics.

The other options are not correct:

• Phycomycetes are a group of fungi that produce spores in sporangia. They can reproduce both sexually and asexually.
  Ascomycetes are a group of fungi that produce spores in sacs called asci. They can reproduce both sexually and asexually.
• Basidiomycetes are a group of fungi that produce spores on club-shaped structures called basidia. They can reproduce both sexually and asexually.

Answer: All of these

CFT (Complement Fixation Test): This test detects antibodies to Leishmania parasites in the blood. It is a sensitive and specific test, but it can be expensive and time-consuming.
Peripheral smear: This test involves examining a thin layer of blood under a microscope to look for Leishmania parasites. It is a simple and inexpensive test, but it is not as sensitive as the CFT.
Blood culture: This test involves incubating blood in a special culture medium to see if Leishmania parasites grow. It is a sensitive test, but it can be expensive and time-consuming.

Answer: CD4 lymphocytes

CD4 lymphocytes are a type of white blood cell that plays a vital role in the immune system. They help to coordinate the immune response against infection. HIV attacks and destroys CD4 lymphocytes, weakening the immune system and making people more susceptible to opportunistic infections and other health problems.

The other options are not correct:

• CD3 lymphocytes are a type of white blood cell that helps to activate CD4 lymphocytes. They are not infected by HIV.
• CD2 lymphocytes are a type of T lymphocyte that helps to regulate the immune response. They are also not infected by HIV.
• Blymphocytes are a type of white blood cell that produces antibodies. They can be infected by HIV, but this is not as common as infection of CD4 lymphocytes.

Answer: Pnemocystis carnii

The most common infection in AIDS is Pneumocystis carinii pneumonia, now known as Pneumocystis jirovecii pneumonia. It is a lung infection caused by a fungus that takes advantage of a weakened immune system. People with AIDS are at a much higher risk of developing PCP than people with healthy immune systems.

The other options are also common infections in AIDS, but they are not as common as PCP:

• Lymphogranuloma venereum (LGV) is a sexually transmitted infection caused by a type of bacteria called Chlamydia trachomatis.
• Cytomegalovirus (CMV) is a type of herpes virus that can cause a variety of infections, including pneumonia, retinitis, and encephalitis.
• Syphilis is a sexually transmitted infection caused by a type of bacteria called Treponema pallidum.

Answer: Inhaling infected dust

Tick typhus is a bacterial infection that is spread by ticks. The bacteria can be found in the tick’s feces and saliva. When a tick bites a person, the bacteria can enter the person’s bloodstream and cause infection.

Tick typhus can also be spread by inhaling infected dust. This can happen when tick feces and saliva dry and become airborne.

The other options are not the most common ways to get tick typhus:

• Drinking milk of sick animals: Tick typhus is not typically spread through milk.
• Tending cattle: Cattle are not a common source of tick typhus infection.

Answer: R.mooseri

Endemic typhus is a form of typhus fever caused by the bacterium Rickettsia mooseri. It is transmitted to humans through the bites of infected fleas, particularly the Oriental rat flea (Xenopsylla cheopis). This type of typhus is typically associated with a milder form of the disease and is often found in specific regions or populations, rather than causing widespread epidemics.

Answer: all

Endemic cholera is cholera that is constantly present in a community or region.
Epidemic cholera is a sudden outbreak of cholera that affects a large number of people in a short period of time.
Sporadic cholera is cholera that occurs occasionally and randomly in a community or region.
Cholera is most common in developing countries with poor sanitation and hygiene. It is spread through contaminated water and food. Cholera can be fatal if it is not treated promptly

Answer: Strains are catalase positive

Staphylococcus aureus is characterized by “Strains are catalase positive.” It is an important diagnostic test to differentiate it from other staphylococci, which are catalase negative. The other characteristics listed are not typically associated with Staphylococcus aureus.

Answer: Both Finding bacteria in pathological fluids and Isolation of bacteria by culture from exudates or blood

Finding bacteria in pathological fluids can be done by microscopy or by using a Gram stain. Microscopy is a simple and quick way to look for bacteria in fluids, but it is not as sensitive as a Gram stain. A Gram stain is a type of staining that allows bacteria to be classified into two groups: Gram-positive and Gram-negative. This information can be helpful in choosing the right antibiotic treatment.

Isolation of bacteria by culture is a more sensitive way to diagnose a bacterial infection. It involves taking a sample of fluid or tissue from the infected area and growing it in a special culture medium. If bacteria are present, they will grow in the culture medium. Once the bacteria have grown, they can be identified and tested for antibiotic sensitivity.

The best method for diagnosing a bacterial infection will depend on the individual patient and the suspected infection. In some cases, both microscopy and culture may be needed to make a diagnosis.

Answer: Cell membrane

Freeze-etching is a technique used to prepare samples for electron microscopy. It involves freezing the sample, fracturing it, and etching the surface to reveal the internal structure of the cell. Freeze-etch particles are structures that are embedded in the cell membrane. They can be proteins, lipids, or carbohydrates.

Freeze-etch particles are often studied to learn more about the structure and function of the cell membrane. They can also be used to identify and diagnose diseases.

The other options are not correct:

• Cytoplasm: The cytoplasm is the fluid inside the cell that contains the organelles. Freeze-etch particles are not found in the cytoplasm.
• Cell wall: The cell wall is a rigid structure that surrounds the cell membrane. It is not found in all cells, and it does not contain freeze-etch particles.
• Nucleus: The nucleus is the control center of the cell. It contains the genetic material of the cell. Freeze-etch particles are not found in the nucleus.

Answer: Both M.tuberculosis and Legionella pneumophila

Lysosomes are organelles that contain enzymes that break down cellular waste and foreign particles. However, some organisms, such as M. tuberculosis and Legionella pneumophila, have developed mechanisms to evade lysosomal digestion.

M. tuberculosis has a waxy coat that protects it from lysosomal enzymes. Legionella pneumophila can multiply inside lysosomes, where it is protected from the enzymes.

This resistance to lysosomal digestion allows M. tuberculosis and Legionella pneumophila to survive inside host cells and cause disease.

• M. leprae is a bacteria that causes leprosy. It is also resistant to lysosomal digestion, but it does this in a different way than M. tuberculosis and Legionella pneumophila. M. leprae can inhibit the fusion of lysosomes with phagosomes, which prevents the lysosomal enzymes from reaching the bacteria.

Answer: All of these

Size and shape of individual organisms
Characteristic arrangement or grouping of cells
Motility of the organism
Wet mount slides are made by placing a drop of specimen fluid on a microscope slide and covering it with a coverslip. This creates a thin layer of fluid that suspends the specimen and makes it easier to view under the microscope.

Wet mount slides are a quick and easy way to prepare specimens for microscopy. They are also useful for viewing living organisms, such as bacteria and protozoa.

Answer: Differential stain

Ziehl-Neelsen stain is a differential stain. It is used to stain acid-fast bacteria, such as Mycobacterium tuberculosis, which causes tuberculosis. Acid-fast bacteria are able to resist decolorization with acids, which allows them to be distinguished from other types of bacteria.

Ziehl-Neelsen stain is a two-step process:

The slide is stained with a basic fuchsin solution, which stains all bacteria pink.
The slide is then decolorized with an acid-alcohol solution. Acid-fast bacteria retain the fuchsin stain, while other bacteria are decolorized.
Finally, the slide is counterstained with methylene blue, which stains all non-acid-fast bacteria blue.

The other options are not correct:

• Simple stain: A simple stain is a stain that uses a single dye to stain all cells.
• Counter stain: A counter stain is a stain that is used after a primary stain to stain cells that were not stained by the primary stain.

Answer: 8 : 1

The ratio of RNA to DNA in Gram-positive bacteria is 8:1.

This means that Gram-positive bacteria have a higher RNA content than DNA content. This is because RNA is involved in many cellular processes, such as protein synthesis and gene regulation. Gram-positive bacteria need more RNA to support these processes.

The other options are not correct:

• 1:2: This is the ratio of RNA to DNA in Gram-negative bacteria.
• Almost equal: This is not the case. Gram-positive bacteria have a significantly higher RNA content than DNA content.

Answer: All of these

Inhalation of conidia: Conidia are fungal spores that can be inhaled and cause infections in the lungs, such as histoplasmosis and coccidioidomycosis.
Invasion of mucous membrane: Fungi can invade the mucous membranes of the mouth, throat, vagina, and other parts of the body, causing infections such as thrush and candidiasis.
Contamination of wounds with conidia or mycelial fragments: Fungi can contaminate wounds and cause infections such as athlete’s foot and ringworm.

Answer: lack of atrue bacterial cell wall

Mycoplasmas and Chlamydiae are both obligate intracellular parasites, but they have different cell structures. Mycoplasmas have a flexible cell membrane, while Chlamydiae have a cell wall made of peptidoglycan.

This difference in cell structure has several implications. For example, mycoplasmas are more resistant to antibiotics that target the cell wall, such as penicillin. They are also more difficult to detect under the microscope.

The other options are not correct:

• Ability to cause urinary tract infection: Both mycoplasmas and Chlamydiae can cause urinary tract infections.
• Susceptibility to penicillin: Mycoplasmas are resistant to penicillin, while Chlamydiae are susceptible.

Answer: Chlamydia trachomatis

Chlamydia trachomatis is a bacteria that causes chlamydia, a sexually transmitted infection. It is an obligate intracellular parasite, which means that it can only survive inside a host cell.

Chlamydia trachomatis infects cells by entering through the cell membrane. Once inside the cell, it forms a vacuole, which is a bubble-like structure that protects the bacteria from the host cell’s immune system.

Chlamydia trachomatis produces an enzyme called ATP synthase, which is essential for ATP production. ATP is the energy currency of the cell. By inhibiting ATP synthesis, it can retard the penetration of the host cell by an inhibitor of ATP synthesis.

The other options are not correct:

• M. pneumoniae is a bacteria that causes Mycoplasma pneumoniae pneumonia. It is an obligate intracellular parasite, but it does not produce ATP synthase.
• Rickettsia rickettsii is a bacteria that causes Rocky Mountain spotted fever. It is an obligate intracellular parasite, but it does not produce ATP synthase.
• Chlamydia psitacci is a bacteria that causes psittacosis, also known as parrot fever. It is an obligate intracellular parasite, but it does not produce ATP synthase.

Answer: Cell wall

True bacteria have a cell wall made of peptidoglycan, which is a complex carbohydrate. The cell wall gives bacteria their shape and protects them from the external environment.

Mycoplasma are the smallest known bacteria, and they are able to survive without a cell wall because they have a flexible cell membrane. This allows them to change shape and squeeze through tight spaces.

The other options are not correct:

• Flagella: Both true bacteria and mycoplasma can have flagella, which are hair-like appendages that allow them to move.
• ATP synthesis: Both true bacteria and mycoplasma can synthesize ATP, which is the energy currency of the cell.
• A capsule: Both true bacteria and mycoplasma can have a capsule, which is a layer of polysaccharide that protects the cell from the external environment.

Answer: All of these

• Equal susceptibility to hydrolysis by lysozyme: Lysozyme is an enzyme that can break down peptidoglycan, the major component of the bacterial cell wall. Both Gram positive and negative bacteria are equally susceptible to hydrolysis by lysozyme.
• Peptide crosslinks between polysaccharides: The peptidoglycan layer in both Gram positive and negative bacteria consists of two polysaccharides, N-acetylglucosamine and N-acetylmuramic acid, that are crosslinked by peptides. This crosslinking gives the cell wall its rigidity and strength.
• Rigid peptoglycon activity: The peptidoglycan layer in both Gram positive and negative bacteria is rigid. This rigidity provides the cell with shape and protection from the external environment.
• Greater resistance to drying than vegetative cell: The peptidoglycan layer in both Gram positive and negative bacteria helps to protect the cell from drying out. This is why spores, which are dormant forms of bacteria with a thick peptidoglycan layer, are so resistant to drying.

Answer: BCG

The BCG vaccine contains an attenuated form of the bacteria Mycobacterium bovis, which is closely related to Mycobacterium tuberculosis, the bacteria that causes tuberculosis. The BCG vaccine is used to protect against tuberculosis.

The other options do not contain attenuated forms of bacteria:

• TAB vaccine: The TAB vaccine contains inactivated forms of the bacteria Salmonella typhi, Salmonella paratyphi A, and Salmonella paratyphi B. It is used to protect against typhoid fever.
• Polio vaccine: The polio vaccine contains inactivated or live attenuated forms of the poliovirus. It is used to protect against polio.
• Cholera vaccine: The cholera vaccine contains inactivated forms of the bacteria Vibrio cholerae. It is used to protect against cholera.

Answer: Plasmodium

Premunition is a state of partial or complete immunity to a disease that is acquired through previous infection with the same disease. It is thought to be caused by the development of long-lasting memory B cells and T cells that are specific to the pathogen.

Premunition has been observed in a number of infectious diseases, including malaria, yellow fever, and dengue fever. In the case of malaria, premunition is thought to be mediated by the development of immunity to specific Plasmodium proteins, such as the circumsporozoite protein (CSP).

People who are premune to malaria may still experience mild symptoms if they are infected with the parasite, but they are less likely to develop severe disease or die.

The other options are not correct:

• Ascaris: Ascaris lumbricoides is a roundworm that causes ascariasis. Premunition has not been observed in ascariasis.
• Giardia: Giardia lamblia is a protozoan that causes giardiasis. Premunition has not been observed in giardiasis.

Answer: Balantidium coli

Balantidium coli can grow to be up to 200 micrometers long, which is significantly larger than other human protozoan parasites, such as Entamoeba histolytica (10-60 micrometers) and Trichomonas vaginalis (15-30 micrometers).

Balantidium coli is transmitted through the fecal-oral route, meaning that infection can occur by ingesting contaminated food or water. Once inside the human body, Balantidium coli can invade the intestinal lining and cause a variety of symptoms, including diarrhea, abdominal pain, and bleeding.

Answer: Inhibits phagocytosis

A polysaccharide capsule present on Cryptococci serves multiple functions, including “Inhibiting phagocytosis,” which helps the fungus evade the host’s immune system. It is also “an aid to diagnose” cryptococcal infections, as detecting the capsule’s presence is a diagnostic marker. However, it does not “cross react with rheumatoid factor

Answer: All of these

Fungi are eukaryotic organisms, whereas bacteria are prokaryotic. Fungi have nuclear membranes, unlike bacteria, and they do not contain peptidoglycan, which is a component of bacterial cell walls. Fungi are susceptible to antifungal drugs like griseofulvin, which do not affect bacteria.

Answer: Found in the walls of Gram positive bacteria

Teichoic acids are found in the walls of Gram-positive bacteria. They are not found in the walls of Gram-negative bacteria. Teichoic acids do not make up the outer wall of Gram-negative bacteria. Teichoic acids do not provide receptors for phages. Teichoic acids may influence the permeability of the membrane.

Answer: Monotrichate

• Monotrichate bacteria have a single flagellum attached at one end of the cell. This flagellum allows them to swim in a straight line.
• Amphitrichate bacteria have multiple flagella attached at both ends of the cell. This allows them to swim in a tumbling motion.
• Iophotrichate bacteria have multiple flagella attached at a tuft at one end of the cell. This allows them to swim in a corkscrew motion.
• Peritrichate bacteria have multiple flagella attached all over the cell. This allows them to swim in any direction.

Answer: Cl. tetani

• Salmonella is a facultative anaerobe, meaning it can grow with or without oxygen.
• Vibrio cholera is a facultative anaerobe as well.
• Clostridium tetani (Cl. tetani) is an obligate anaerobe, meaning it can only grow in the absence of oxygen.
• Sarcinae is a facultative anaerobe.

Answer: Absorption of heat

Bacteria are capable of obtaining energy from a variety of sources, including oxidation of inorganic compounds, oxidation of organic compounds, and utilization of visible light. However, they cannot obtain energy from absorption of heat.

• Oxidation of inorganic compounds is a process called chemosynthesis. This process is carried out by a group of bacteria called chemolithotrophs. Chemolithotrophs use the energy released from the oxidation of inorganic compounds to synthesize ATP, which is the energy currency of cells.
• Oxidation of organic compounds is a process called heterotrophic respiration. This process is carried out by most bacteria. Heterotrophs use the energy released from the oxidation of organic compounds to synthesize ATP.
• Utilization of visible light is a process called photosynthesis. This process is carried out by a group of bacteria called phototrophs. Phototrophs use the energy of visible light to synthesize ATP.

Absorption of heat is not a way for bacteria to obtain energy. This is because heat is not a form of chemical energy that can be used by cells to synthesize ATP.

Answer: Clostridium

Clostridium is not an acid-fast structure. Clostridium is a genus of bacteria, and it does not possess the unique cell wall characteristics that make bacteria like Mycobacteria and Nocardia acid-fast. Bacterial spores, on the other hand, are also not acid-fast. The term “Exoskeleton” is not typically used in the context of acid-fast staining or structures, so it doesn’t apply in this context.

Answer: All of these

Bacterial spores are highly refractile, usually dehydrated, and sensitive to formaldehyde. These characteristics help them to resist harsh environmental conditions, such as heat, desiccation, and radiation.

Highly refractile: Bacterial spores have a thick, multilayered coat that refracts light. This makes them appear bright and shiny under a microscope.
Usually dehydrated: Bacterial spores are typically about 70% water, which is much less than the water content of vegetative cells. This dehydration helps to protect the spore’s DNA and other enzymes from damage.
Sensitive to formaldehyde: Formaldehyde is a disinfectant that can kill vegetative cells. However, bacterial spores are more resistant to formaldehyde than vegetative cells. This is because the spore’s coat protects the DNA from damage.

Answer: Helps in adherence of bacteria to surface in its environment

The bacterial capsule is a sticky layer of polysaccharides or proteins that surrounds the cell wall of some bacteria. It helps to protect the bacteria from desiccation, harmful chemicals, and phagocytosis by immune cells. It also helps the bacteria to adhere to surfaces, such as host cells or tissues, which can be important for infection.

The bacterial capsule is not involved in the production of new organisms from phagocytosis. Phagocytosis is a process by which immune cells engulf and destroy foreign particles, such as bacteria. The bacterial capsule can make it more difficult for immune cells to phagocytose bacteria, but it does not directly produce new organisms.

Answer: C.diphtheriae

Daisy head colony formation is typically associated with “C. diphtheriae.” It is a characteristic appearance of colonies of Corynebacterium diphtheriae when grown on Loeffler’s medium, and it helps in the identification of this bacterium. It is not associated with M. tuberculosis or Cl. tetani.

Answer: All of these

Salmonella Typhi, the causative agent of typhoid fever, can be detected in stool, bile, and urine samples from carriers. Stool culture is the most common method for detecting Salmonella Typhi in carriers, as the bacteria are shed in the feces of infected individuals. Bile culture can also be used to detect Salmonella Typhi in carriers, as the bacteria can also be found in the bile. Urine culture is less commonly used to detect Salmonella Typhi in carriers, as the bacteria are less frequently shed in the urine.

Here is a table summarizing the different culture methods and their effectiveness in detecting Salmonella Typhi in carriers:

Answer: Sulphuric acid

The cholera red reaction is a biochemical test used to identify the presence of the bacterium Vibrio cholerae, the causative agent of cholera. The test is based on the production of a red color when a few drops of concentrated sulfuric acid are added to a 24-hour peptone water culture of Vibrio cholerae. The red color is due to the reaction of the sulfuric acid with indole and nitrites, which are produced by Vibrio cholerae.

The other options are incorrect because:

• Nitric acid does not produce a red color when reacted with indole and nitrites.
• Hydrochloric acid does not produce a red color when reacted with indole and nitrites.
• Carbolic acid does not produce a red color when reacted with indole and nitrites.

Here is a table summarizing the different acids and their ability to produce a red color when reacted with indole and nitrites:

Answer: Phosphate

Phosphate: Streptococcus pyogenes, also known as Group A Streptococcus (GAS), produces various virulence factors such as hyaluronidase (for tissue spread), streptokinase (for fibrinolysis), and hemolysins (for red blood cell lysis). However, it does not secrete phosphate as a specific virulence factor.

Other incorrect options:

1. Hyaluronidase: Streptococcus pyogenes does produce hyaluronidase, an enzyme that breaks down hyaluronic acid, aiding in tissue spread.
2. Hemolysin: Streptococcus pyogenes produces hemolysins that cause the lysis of red blood cells, contributing to its pathogenicity.
3. Streptokinase: This enzyme is produced by Streptococcus pyogenes and functions in fibrinolysis, breaking down blood clots and aiding bacterial spread.

Answer: All of these

Preptostreptococci, strepto viridans, and strepto hemolyticus are all types of streptococci that are destroyed by heating to 60°C for 30 minutes. This is a common method of pasteurizing milk and other foods to kill harmful bacteria.

Here is a table summarizing the different types of streptococci and their sensitivity to heat:

Answer: Both Giesna and Castaneda stains and Macchiavello and Gimnezstains

Rickettsiae are obligate intracellular bacteria that are typically stained using Romanowsky stains like Giemsa or Gimenez. These stains specifically bind to the bacterial DNA, allowing for visualization of the rickettsiae within the host cells.

Malachite green, on the other hand, is a non-specific stain that can stain a variety of microorganisms, including bacteria, fungi, and protozoa. It is not commonly used to stain rickettsiae.

Here is a table summarizing the different stains and their effectiveness in staining rickettsiae:

Answer: Varicella-zoster virus

Varicella-zoster virus (VZV): It’s a member of the herpesvirus family and is responsible for causing chickenpox (varicella) in primary infection. After the initial infection, the virus remains dormant in nerve cells and can reactivate later in life, causing herpes zoster (shingles).

List of incorrect options:

1. Fox virus: There isn’t a virus specifically known as the “Fox virus” responsible for chickenpox. VZV is the primary causative agent.
2. Mumps virus: The mumps virus causes the disease known as mumps, not chickenpox.
3. Measles virus: Measles virus causes measles, a different viral illness characterized by fever, rash, and respiratory symptoms, distinct from chickenpox.

Answer: Arbo virus

Arbovirus: This term stands for arthropod-borne viruses, which are transmitted to humans through the bite of infected arthropods like mosquitoes. The dengue virus, transmitted primarily by Aedes mosquitoes, falls into this category.

List of incorrect options:

1. Echo virus: Echo viruses belong to the Picornaviridae family and are not associated with the dengue fever virus. They are a group of enteroviruses known to cause various infections in humans.
2. Entero virus: Entero viruses, also a type of Picornaviridae, primarily infect the gastrointestinal tract and are not linked to dengue fever.
3. Orthomyxo virus: Orthomyxoviruses, like influenza viruses, are different from the dengue fever virus. They cause respiratory infections and are not classified as arboviruses.

Answer: Paramyxo virus

Paramyxovirus: Paramyxoviruses are RNA viruses, specifically single-stranded RNA viruses, belonging to the Paramyxoviridae family. They include viruses causing diseases like measles and mumps.

List of incorrect options:

1. Parvovirus: Parvoviruses are small, single-stranded DNA viruses, not RNA viruses like paramyxoviruses. They include the parvovirus B19 responsible for various infections, including fifth disease in humans.
2. Herpesvirus: Herpesviruses are a family of large, double-stranded DNA viruses that include the herpes simplex viruses (HSV-1 and HSV-2), varicella-zoster virus (VZV), and others. They are DNA viruses, unlike paramyxoviruses.
3. Pix virus: There isn’t a known virus referred to as the “Pix virus.” This might be a hypothetical term or an error in virus nomenclature. It’s not an established virus type like paramyxoviruses, parvoviruses, or herpesviruses.

Answer: Rickettsiae

Rickettsiae: Neil Mooseri reaction, also known as the Weil-Felix reaction, is a serological test used for the diagnosis of rickettsial infections. This test involves agglutination of Proteus vulgaris antigens by patient serum. The presence of antibodies against Proteus vulgaris antigens in the patient’s serum indicates a possible rickettsial infection.

List of incorrect options:

1. Chlamydiae: Chlamydiae are intracellular bacteria but are not associated with the Neil Mooseri reaction. They have different diagnostic methods for identification.
2. Spirochaetes: Spirochaetes include bacteria like Treponema and Borrelia, but they are not directly related to the Neil Mooseri reaction, which is specific to rickettsial infections.
3. Clostridium perfringens: Clostridium perfringens is a bacterium known for causing gas gangrene but is not linked to the Neil Mooseri reaction, which is a test used for diagnosing rickettsial infections.

Answer: Disinfectant

Disinfectant: Lysol is a commonly used household disinfectant. It contains various compounds such as alkyl dimethyl benzyl ammonium saccharinate and ethanol that help in killing or inactivating microorganisms on surfaces.

List of incorrect options:

1. Sterilent: There isn’t a widely recognized product or substance known as “Sterilent.” It might be a term used for products ensuring sterility, but it’s not commonly used or associated with Lysol.
2. Antiseptic: While Lysol does kill bacteria and viruses on surfaces, it is not intended for use on living tissues or skin. Antiseptics are used on living tissues to prevent infection, unlike Lysol, which is primarily a surface disinfectant.
3. Antifungal agent: Lysol primarily targets bacteria and viruses but is not specifically labeled or designed as an antifungal agent for fungal infections.

Answer: Neutral red

Neutral red: Neutral red is a dye used as a neutral stain in microbiology and histology. It’s called a neutral stain because it carries a balanced charge and is commonly used to stain living cells for microscopic examination without imparting a specific color to the cells.

List of incorrect options:

1. Picric acid: Picric acid is a strong acid and is not a neutral stain. It’s used in stains like Picrosirius red, which is not a neutral stain but a method for staining connective tissues.
2. Giemsa: Giemsa stain is a Romanowsky-type stain and is not a neutral stain. It’s used in the staining of blood films and in the diagnosis of malaria and other blood-borne parasites.
3. Malachite green: Malachite green is a basic dye and not a neutral stain. It’s often used in microbiology for staining specific structures, such as endospores in bacterial cells, due to its affinity for those structures.

Answer: Semisynthetic medium

Semisynthetic medium: This type of medium is prepared by adding specific synthetic ingredients to a base medium derived from natural sources. Peptone water, made by adding peptone (partially digested protein) to water, is an example of a semisynthetic medium.

List of incorrect options:

1. Synthetic medium: Synthetic mediums contain only chemically defined substances and lack any natural components. Peptone water contains peptone, a naturally derived product, making it a semisynthetic medium rather than a purely synthetic one.
2. Differential medium: Peptone water medium is not a differential medium, which typically contains ingredients allowing for the differentiation of organisms based on specific biochemical reactions.
3. None of these: Peptone water is a known type of medium, categorized specifically as a semisynthetic medium due to the combination of natural and synthetic ingredients.

Answer: Lypophilization

Lyophilization: It’s a process commonly known as freeze-drying, involving freezing the material and then subjecting it to a vacuum to remove the ice (dehydration) without going through the liquid phase. This method preserves the cells or substances for an extended period without the need for refrigeration.

List of incorrect options:

1. Pasteurization: Pasteurization is a heat treatment process primarily used to eliminate harmful microorganisms from liquids such as milk or juices. It involves heating the substance to a specific temperature to kill pathogens while preserving its quality.
2. Desiccation: Desiccation refers to the removal of moisture from a substance, but it does not involve freezing. It’s a general term for drying that doesn’t specifically involve freezing followed by dehydration in a vacuum.
3. Disinfection: Disinfection is the process of reducing or eliminating microorganisms on surfaces or inanimate objects to a level considered safe for public health, typically through the use of chemicals or heat. It doesn’t involve freezing or dehydration of cells like lyophilization does.

Answer: Sterlization

Sterilization: This process aims to completely eradicate or kill all forms of microorganisms, including bacteria, viruses, fungi, and spores, from an object or surface. It’s commonly achieved through various methods like heat (autoclaving), chemicals, radiation, or filtration.

List of incorrect options:

1. Disinfection: Disinfection reduces the number of viable microorganisms but doesn’t always eliminate all of them. It aims to reduce the microbial load to a safe level for public health but may not eradicate all forms of microorganisms.
2. Surgical sterilization: This term typically refers to sterilizing surgical equipment or instruments, but it doesn’t encompass the complete elimination of all microorganisms from an environment or surface.
3. Disinfection Sterilization: This seems to combine both disinfection and sterilization, but the term is not a recognized technique. Disinfection and sterilization are separate processes with different objectives; disinfection aims to reduce microbial load, while sterilization aims to eliminate all microorganisms.

Answer: Complex

Complex medium: It’s a culture medium containing nutrients derived from natural products like extracts from animal tissues, plants, or yeast. The exact composition and quantities of the components are not precisely defined, making it complex due to its varied and undefined nature.

List of incorrect options:

1. Simple: Simple medium usually contains a known and defined set of nutrients in precise concentrations, unlike a complex medium, which has an undefined composition.
2. Defined: Defined medium is the opposite of a complex medium. It consists of precisely known and defined components in specific concentrations, making it distinct from a complex medium where the components are not precisely known.
3. Natural: While a complex medium does contain components derived from natural sources, the term “natural” doesn’t specifically refer to the lack of knowledge about the medium’s exact composition. It’s more about the varied and undefined nature of the constituents in a complex medium.

Answer: Diphtheria toxin

Diphtheria toxin: Elek’s Gel Diffusion test is a diagnostic method to detect and quantify the presence of diphtheria toxin produced by Corynebacterium diphtheriae, the bacterium causing diphtheria. It involves placing an antitoxin-containing gel near the test organism on a culture plate. If the bacteria produce the toxin, it diffuses into the gel, forming a precipitin line.

List of incorrect options:

1. Tetanus toxin: Elek’s Gel Diffusion test is not used for detecting tetanus toxin. The test is specific to diphtheria toxin and is not applicable for tetanus toxin produced by Clostridium tetani.
2. Cholera toxin: The Elek’s Gel Diffusion test is not designed for the detection of cholera toxin, which causes cholera. Different tests, such as immunological assays, are used to detect cholera toxin.
3. Toxoid: Toxoids are inactivated forms of toxins used in vaccines and are not detected through Elek’s Gel Diffusion test. This test specifically identifies active toxins produced by bacteria.

Answer: Below 100oC

Below 100°C: Pasteurization involves heating a liquid or food product to a specific temperature below the boiling point, typically around 60°C to 85°C, for a specific time to reduce the number of viable pathogens while retaining the product’s taste and nutritional value.

List of incorrect options:

1. Above 150°C: This temperature range is significantly higher than the temperature used in pasteurization. Such high temperatures are more associated with sterilization methods, not pasteurization, as they eliminate all microorganisms, including spores.
2. 110°C: While 110°C is higher than the typical pasteurization temperature, it’s still within the range of sterilization rather than pasteurization.