Microbiology Exam V - Summer 2011

Helicobacter pylori is a type of bacteria that is commonly found in the stomach. It is known to cause ulcers by damaging the lining of the stomach or small intestine. Additionally, it has been linked to an increased risk of stomach cancer. Therefore, the correct answer is ulcers AND stomach cancer, indicating that Helicobacter pylori is associated with both conditions.

Anopheles is the correct answer because it is the primary carrier of malaria. Malaria is a mosquito-borne infectious disease caused by the Plasmodium parasite, which is transmitted to humans through the bite of infected female Anopheles mosquitoes. These mosquitoes are specifically adapted to transmit the disease and are found in many parts of the world, particularly in tropical and subtropical regions. Therefore, Anopheles is the most relevant option among the given choices as it directly relates to the transmission of malaria.

Infections caused by obligate anaerobes such as Clostridium perfringens are sometimes treated by putting the patients in hyperbaric chambers. Hyperbaric chambers are pressurized chambers that allow patients to breathe in 100% oxygen at higher than normal atmospheric pressure. This high-pressure environment helps to increase the amount of oxygen dissolved in the blood, which can inhibit the growth of anaerobic bacteria like Clostridium perfringens. By exposing the infection to high levels of oxygen, hyperbaric therapy can help to kill the bacteria and promote healing.

Saxitoxin is a neurotoxin produced by dinoflagellates. It is a potent toxin that can cause paralytic shellfish poisoning in humans. It blocks the channels responsible for the movement of sodium ions in nerve cells, leading to muscle paralysis and potentially respiratory failure. This toxin is commonly found in shellfish, such as clams and mussels, that have consumed dinoflagellates. It is important to avoid consuming shellfish from areas where saxitoxin contamination is suspected to prevent poisoning.

Schistosoma spp. refers to a group of parasitic blood flukes that infect humans. These flukes cause a disease called schistosomiasis, which is a major public health problem in many developing countries. The other options listed are not related to schistosoma spp. For example, bordetella pertussis causes whooping cough, ghon complexes are associated with tuberculosis, listeria monocytogenes causes listeriosis, and neuraminidase is an enzyme produced by influenza viruses. Therefore, schistosoma spp. is the correct answer in this context.

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Corynebacterium is the correct answer because it is a genus of bacteria that includes the species Corynebacterium diphtheriae, which causes diphtheria. The other options, malaria, puerperal sepsis, alveolar macrophages, and trichomonas vaginalis, are not related to Corynebacterium or diphtheria.

The correct answer is exfoliative toxin. Exfoliative toxin is produced by certain strains of Staphylococcus aureus and is responsible for causing blisters and desquamation of the skin in scalded skin syndrome. This toxin acts by causing the separation of the epidermis from the underlying dermis, leading to the characteristic symptoms of the disease. Enterotoxin is responsible for causing food poisoning, hemolysin causes destruction of red blood cells, toxic shock syndrome toxin causes toxic shock syndrome, and erythrogenic toxin is responsible for the rash seen in scarlet fever.

Candida albicans is a fungus. Fungi are a group of organisms that include yeasts, molds, and mushrooms. Candida albicans is a type of yeast that is commonly found in the human body, particularly in the mouth, throat, and genital area. It can cause infections, such as oral thrush and vaginal yeast infections, especially in individuals with weakened immune systems. Therefore, the correct answer is fungus.

Ischemia refers to the loss of blood supply to tissue. This can occur due to various reasons such as blockage of blood vessels or reduced blood flow. When tissue is deprived of oxygen and nutrients, it can lead to tissue damage and cell death. Necrosis is the death of cells or tissues, which can occur as a result of ischemia. Gangrene is a type of necrosis that is characterized by tissue death and decay. Inflammation, on the other hand, is the body's response to injury or infection and is not specifically related to the loss of blood supply. Therefore, the correct answer is ischemia.

Streptococcus mutans is a bacterium commonly found in the oral cavity and is a major contributor to the development of dental caries. It produces acids as a byproduct of metabolizing sugars, which leads to the demineralization of tooth enamel and the formation of cavities. This bacterium thrives in an acidic environment and is able to adhere to the tooth surface, forming biofilms known as dental plaque. The presence of Streptococcus mutans in the oral cavity, along with poor oral hygiene and excessive sugar consumption, increases the risk of developing dental caries.

Acanthamoeba keratitis is a type of eye infection caused by the amoeba Acanthamoeba. It is commonly associated with unsanitary contact lenses, as the amoeba can thrive in the stagnant water that accumulates on the lenses. This infection can cause severe damage to the cornea, leading to vision impairment or even blindness if left untreated. Therefore, the given answer correctly identifies the freshwater amoeba that is associated with unsanitary contact lenses and causes corneal damage.

Rheumatic fever is the correct answer because it is a disease that occurs as a result of an autoimmune complication of repeat Streptococcus pyogenes infections. This means that when a person has multiple infections caused by Streptococcus pyogenes, their immune system mistakenly attacks their own body tissues, leading to the development of rheumatic fever. This condition primarily affects the heart, joints, skin, and brain, causing symptoms such as fever, joint pain, rash, and neurological problems.

Pneumocystis is a protozoan parasite that can be found in healthy human lungs. It remains dormant in the lungs until the host's immune system becomes compromised, providing an opportunity for the parasite to infect the host. This can occur in individuals with weakened immune systems, such as those with HIV/AIDS or undergoing immunosuppressive therapy. Pneumocystis pneumonia is a common opportunistic infection in these individuals.

Bacterial conjunctivitis is characterized by symptoms such as redness, swelling, and discharge from the eyes. The discharge is typically thick and yellow or green in color, not clear. Therefore, the statement "Has a clear discharge" is not true of bacterial conjunctivitis.

Macules are flat, reddened lesions on the skin. They are small, distinct, and do not have any elevation or palpable changes in texture. Macules can be caused by various conditions such as viral infections, allergic reactions, or inflammatory skin diseases. They are different from other skin lesions like papules or plaques, which have different characteristics. In this case, the presence of flat reddened lesions suggests macules as the correct answer.

Bacterial meningitis is an infection of the membranes surrounding the brain and spinal cord. It is commonly caused by bacteria such as Streptococcus pneumoniae, Neisseria meningitidis, and Haemophilus influenzae. However, Naegleria fowleri is not a bacterium but a free-living amoeba found in warm freshwater environments. It can cause a rare and severe form of meningitis called primary amoebic meningoencephalitis (PAM), but it is not classified as bacterial meningitis. Therefore, Naegleria fowleri is the exception among the given options.

Cryptococcus neoformans is a soil fungus commonly found in pigeon and chicken droppings. When inhaled, it can cause a form of meningitis in humans. This infection has a mortality rate of approximately 30%. Therefore, Cryptococcus neoformans is the correct answer as it matches the description provided in the question.

Tinea cruris, also known as ringworm of the groin, is the correct answer. It is a fungal infection that affects the groin area and is commonly referred to as jock itch. This infection is characterized by a red, itchy rash in the groin region, which can spread to the inner thighs and buttocks. Tinea cruris is caused by the same type of fungus that causes athlete's foot, known as dermatophytes. It is often seen in individuals who sweat excessively or wear tight clothing, as these conditions create a warm and moist environment that promotes fungal growth.

Keratin is a protein found in the outermost layer of the skin, known as the epidermis. It forms a tough, waterproof barrier that protects the skin from abrasions, water damage, and the entry of microorganisms. Keratin also helps to maintain the structural integrity of the skin and prevents it from drying out. This makes it an essential component in providing overall protection to the skin.

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Schistosoma is the correct answer because it is a type of blood fluke that causes schistosomiasis, a parasitic disease. Schistosoma parasites infect humans when they come into contact with contaminated freshwater, such as rivers or lakes. The parasites penetrate the skin and migrate to the blood vessels around the intestines or bladder, causing various symptoms including fever, abdominal pain, and blood in urine or stool. Schistosomiasis is a significant public health problem in many tropical and subtropical regions, affecting millions of people worldwide. Therefore, Schistosoma is the most appropriate answer among the given options.

Streptomyces is a valuable source of many commercial antibiotics. Streptomyces is a genus of bacteria that produces a wide range of antibiotics, including streptomycin, tetracycline, and erythromycin. These antibiotics are commonly used to treat various bacterial infections in humans and animals. Streptomyces bacteria are known for their ability to produce secondary metabolites, including antibiotics, which makes them an important resource in the pharmaceutical industry. Therefore, streptomyces is the correct answer as it is a valuable source of many commercial antibiotics.

The correct answer is rabies virus because it is a virus that is transmitted through animal bites, particularly from infected dogs, bats, and other mammals. Once it enters the body, the virus multiplies in the skeletal muscles before spreading to the brain cells. This leads to inflammation of the brain, known as encephalitis, which is a characteristic symptom of rabies infection.

Ixodes is the correct answer because it is a genus of arthropod vectors that are known to carry the causative agent of Lyme disease. Lyme disease is caused by the bacterium Borrelia burgdorferi, which is transmitted to humans through the bite of infected ticks. Ixodes ticks are commonly found in wooded and grassy areas, and they are known to transmit the bacteria to humans during feeding. Therefore, Ixodes is responsible for carrying the causative agent of Lyme disease.

Shingles is the correct answer because it refers to the reactivation of the chickenpox virus, also known as herpes zoster. Shingles is characterized by a painful rash that typically appears in a band or strip on one side of the body. While pneumonia is a respiratory infection and exanthems are a general term for rash or skin eruptions, they are not specific to the reactivation of chickenpox. Therefore, shingles is the most accurate term for the reactivation of chickenpox.

The correct answer is "Symptoms of cryptosporidiosis include headache, sweats, vomiting, severe abdominal cramps, and diarrhea." This answer accurately describes the symptoms commonly associated with cryptosporidiosis, which is an infection caused by the parasite Cryptosporidium. These symptoms are consistent with the gastrointestinal symptoms typically experienced by individuals with this infection.

Dermacentor is the correct answer because it is the only option that is a type of tick. The other options, Rickettsia, Schistosoma, and Anapheles, are not ticks but rather refer to different organisms or diseases. Therefore, Dermacentor is the most appropriate choice in this context.

The serotype of influenza that causes most epidemics is serotype A. Influenza A viruses are known to infect humans, birds, and other animals, and they have the ability to undergo genetic changes through a process called antigenic shift. This allows them to easily adapt and spread among different populations, leading to widespread epidemics. In contrast, serotype B and serotype C influenza viruses generally cause milder illness and do not undergo antigenic shift as frequently as serotype A viruses. Serotype A influenza viruses are therefore considered the most significant in terms of causing epidemics.

Neisseria is the correct answer because it is the genus responsible for causing gonorrhea. Gonorrhea is a sexually transmitted infection caused by the bacterium Neisseria gonorrhoeae. This bacterium is transmitted through sexual contact and can affect both men and women. It primarily infects the genital tract, but can also infect the rectum, throat, and eyes. Neisseria gonorrhoeae can cause symptoms such as pain during urination, discharge from the genitals, and in women, pelvic pain and abnormal vaginal bleeding. If left untreated, gonorrhea can lead to serious complications such as infertility and increased risk of HIV infection.

The given correct answer is "all of the following are pre-disposing factors." This means that none of the options listed (alcoholism, poor nutrition, cancer, diabetes) contribute to haemophilus influenzae pneumonia as pre-disposing factors. In other words, none of these conditions increase the likelihood of developing this type of pneumonia.

Necator and Ancylostoma are both types of hookworms. Hookworms are parasitic worms that infect the intestines of humans. They attach themselves to the intestinal wall and feed on blood, causing anemia and other symptoms. These worms are commonly found in areas with poor sanitation and can be acquired by walking barefoot on contaminated soil. Therefore, the correct answer is hookworms.

MRSAs, or Methicillin-resistant Staphylococcus aureus, are strains of S. aureus bacteria that have developed resistance to penicillin derivatives. This means that they are not affected by the antibiotics that are commonly used to treat infections caused by S. aureus, such as methicillin and other penicillin-based drugs. This resistance is a result of genetic changes in the bacteria that allow them to produce enzymes called beta-lactamases, which break down the antibiotics and render them ineffective. As a result, MRSAs are difficult to treat and can cause severe infections that are resistant to many commonly used antibiotics.

In the tertiary stage of syphilis, permanent cardiovascular and neurological damage is seen. This stage occurs when the infection is left untreated for a long time, usually several years after the initial infection. The bacteria have spread throughout the body, causing damage to various organs, including the heart and the nervous system. This can lead to serious complications such as heart disease, stroke, and neurosyphilis, which can result in paralysis, blindness, and dementia. Treatment at this stage can help manage the symptoms but may not reverse the permanent damage already done.

S. pneumoniae is the correct answer because it is known to be a common cause of bacterial pneumonia in adults requiring hospitalization. It is a pathogenic bacterium that can infect the lungs and lead to pneumonia. The other options, S. pyogenes, S. aureus, and K. pneumonia, are also potential causes of pneumonia, but they are not as commonly associated with hospitalization in adults as S. pneumoniae.

The blood-brain barrier is a protective mechanism in the brain that restricts the entry of substances from the vascular system. It is composed of specialized cells that line the blood vessels in the brain, forming a barrier that prevents the passage of harmful substances, toxins, and large molecules into the brain tissue. This barrier plays a crucial role in maintaining the delicate balance of the brain's internal environment and protecting it from potential damage.

Rhinoviruses are the major agents responsible for the common cold. They are a type of virus that infects the upper respiratory tract, causing symptoms such as a runny or stuffy nose, sore throat, cough, and sneezing. Rhinoviruses are highly contagious and can spread easily from person to person through respiratory droplets. They are most active during the colder months, which is why the common cold is more prevalent during winter. While other viruses like Coxsackie, Influenza, Caliciviruses, and Rotavirus can also cause respiratory illnesses, Rhinoviruses are the most common culprits for the common cold.

Koplick's spots are small red spots with blue-white centers that appear on the oral mucosa. They are a characteristic symptom of measles, which is caused by the Rubeola virus. This virus primarily affects the respiratory system and is highly contagious. The presence of Koplick's spots can help in the diagnosis of measles and differentiate it from other viral infections.

The correct answer is schistoma spp. Schistosoma spp. are a type of blood fluke that infect humans and other mammals. They are responsible for causing the disease schistosomiasis, which is a major public health concern in many parts of the world. Clonorchis sinensis and Fasciola hepatica are also blood flukes, but they are not classified as Schistosoma spp. Therefore, the correct answer is schistoma spp.

Ebola and Marburg are both caused by filoviruses and can disrupt clotting factors in the body. They are transmitted through direct contact with body fluids, such as blood, saliva, and vomit. However, they are not transmitted by mosquitoes. Mosquitoes are not known to be vectors for the transmission of these viruses. Therefore, the statement that they are transmitted by mosquitoes is not true. It is important to note that there is currently no specific treatment for Ebola and Marburg, only supportive care to manage symptoms and prevent complications.

Primary atypical walking pneumonia is caused by Mycoplasma pneumoniae. Mycoplasma pneumoniae is a type of bacteria that commonly causes respiratory infections, particularly in young adults. It is referred to as "atypical" because the symptoms and presentation of the infection are different from those caused by typical bacteria like Streptococcus pneumoniae or Haemophilus influenzae. Mycoplasma pneumoniae infections often present with a gradual onset of symptoms, such as a persistent cough, sore throat, and fatigue. Treatment usually involves antibiotics that target Mycoplasma pneumoniae specifically.

Gram-positive sepsis is caused by various bacteria, including Staphylococci, Streptococci, and Enterococci. However, Micrococci are not typically associated with causing sepsis. Therefore, the correct answer is Micrococci.

Proper antibiotic use cannot break the fecal-oral cycle. Antibiotics are used to treat bacterial infections, but they do not prevent the spread of fecal-oral diseases. The other methods mentioned, such as proper food preparation and storage, proper sewage disposal, and disinfection of drinking water, can help break the fecal-oral cycle by preventing the transmission of pathogens from feces to the mouth.

Clostridium difficile is a bacterium that is known to produce enterotoxin. Enterotoxins are toxins that affect the intestines and cause symptoms such as diarrhea and abdominal pain. Clostridium difficile is a common cause of healthcare-associated infections, particularly in individuals who have been treated with antibiotics. It is responsible for a condition called Clostridium difficile infection (CDI), which can range from mild diarrhea to severe inflammation of the colon. Therefore, the production of enterotoxin is a characteristic of Clostridium difficile.

Erysipelas is a bacterial skin infection caused by Streptococcus bacteria, not Staphylococcus. The other options listed are all staphylococcal skin infections caused by different strains of Staphylococcus bacteria. Erysipelas typically presents as a red, swollen, and painful rash on the skin, often accompanied by fever and chills.

Yersinia is the correct answer because it is not typically found in large numbers in the large intestine. Bacteriodes, Klebsiella, and Lactobacillus are all commonly present in the large intestine, but Yersinia is not a normal resident of this area.

Anthrax is a zoonosis, meaning it can be transmitted from animals to humans. It can be transmitted through contact, inhalation, and ingestion, making it a highly contagious disease. In humans, anthrax can cause a rapidly fatal toxemia and septicemia, leading to severe illness and potentially death. Although anthrax is not commonly seen in the United States, sporadic cases can still occur. Therefore, all of the choices provided are correct explanations of anthrax.

Taena solium, also known as the pork tapeworm, is a parasitic worm that infects humans through the consumption of undercooked pork. It is a common cause of tapeworm infections in humans and can lead to symptoms such as abdominal pain, nausea, and weight loss. The other options listed are different types of parasites but are not specifically associated with pork tapeworm infections.

Clostridium tetani produces a neurotoxin that binds to target sites on spinal cord neurons responsible for inhibiting skeletal muscle contraction. This neurotoxin, called tetanospasmin, blocks the release of inhibitory neurotransmitters, leading to uncontrolled muscle contractions and the development of tetanus. The other options, Clostridium botulinum, Clostridium perfringens, and Clostridium difficile, do not produce this specific neurotoxin and are associated with different diseases or conditions. Therefore, the correct answer is Clostridium tetani.

Retroviruses have RNA as their genetic material, not DNA. They use an enzyme called reverse transcriptase to convert their RNA into DNA, which is then integrated into the host genome. Therefore, the statement "DNA protein" is incorrect as it does not accurately describe the characteristics of retroviruses.

Kaposi's sarcoma is a frequent cancer observed in AIDS patients. It is caused by a virus called human herpesvirus 8 (HHV-8), which is more prevalent in individuals with weakened immune systems, such as those with AIDS. Kaposi's sarcoma usually manifests as purple or red lesions on the skin, but it can also affect other organs like the lungs, liver, and gastrointestinal tract. The virus is transmitted through saliva, sexual contact, and blood transfusions. Treatment options include antiretroviral therapy to boost the immune system, chemotherapy, and radiation therapy.

Neuraminidase is the correct answer because it is an enzyme found on the surface of the influenza virus. It plays a crucial role in the release of newly formed virus particles from infected cells. Neuraminidase cleaves the sialic acid receptors on the surface of host cells, allowing the virus to detach and spread to other cells. This process is essential for the influenza virus to efficiently infect and replicate within the host.

Ascaris is the correct answer because it is a type of human roundworm. It is a common intestinal parasite that infects humans through contaminated food or water. Ascaris infections can cause a range of symptoms including abdominal pain, diarrhea, and malnutrition. It is important to treat and prevent Ascaris infections to avoid complications and improve overall health.

Sarcoptes scabiei is a parasitic mite that burrows into the skin to lay eggs. This action sets up an intense and itchy inflammation in the skin. This condition is commonly known as scabies. Scabies is highly contagious and can spread through close physical contact with an infected person. The intense itching and inflammation are caused by the body's immune response to the mites and their eggs.

The correct answer is "sarcoptes scabiei". Sarcoptes scabiei refers to the mite that causes scabies, a contagious skin condition characterized by intense itching and a rash. The other terms mentioned in the question, such as body louse, mycosis, herpes viruses, and pediculus, are not directly related to sarcoptes scabiei or scabies. Hyperbaric, on the other hand, refers to a type of medical treatment involving increased atmospheric pressure, which is also unrelated to sarcoptes scabiei.

Mycobacterium avium is a species of mycobacterium that commonly infects people with late-stage HIV infections. This bacterium is known to cause a type of infection called Mycobacterium avium complex (MAC), which primarily affects individuals with compromised immune systems, such as those with advanced HIV/AIDS. MAC infections can manifest as disseminated infections, affecting multiple organs in the body, including the lungs, lymph nodes, and intestines. Therefore, mycobacterium avium is the correct answer for this question.

Tinea manuum refers to a fungal infection that affects the hands. It is commonly known as ringworm of the hand. This infection is caused by dermatophytes, which are a type of fungus. Tinea manuum typically presents with red, scaly patches on the palms, fingers, and between the fingers. It can cause itching, burning, and discomfort. Treatment usually involves antifungal creams or oral medications.

Diphyllobothrium latum is a type of fish tapeworm that infects humans. It is the largest tapeworm that can infect humans and is commonly found in freshwater fish. The infection occurs when humans consume raw or undercooked fish containing the larvae of the tapeworm. Once ingested, the larvae develop into adult worms in the intestines and can cause symptoms such as abdominal pain, diarrhea, and vitamin B12 deficiency. Treatment typically involves medication to kill the tapeworm and its larvae.

Neonatal meningitis is most commonly transmitted through exposure in the birth canal. During childbirth, the baby can come into contact with bacteria or viruses present in the mother's birth canal, leading to an infection in the baby's central nervous system. This mode of transmission is one of the primary ways in which neonatal meningitis occurs.

The statement "All species are human pathogens" is not correct about Mycobacterium species. While some species of Mycobacterium can cause diseases in humans, not all species are human pathogens. Some species are harmless and can be found in the environment. Therefore, it is incorrect to say that all species of Mycobacterium are human pathogens.

Borrelia burgdorferi is the correct answer because it is the bacteria that causes Lyme disease. Lyme disease is a tick-borne illness that can cause a variety of symptoms, including skin manifestations such as macules. Tinea refers to a fungal infection, Rickettsia rickettsii is the bacteria that causes Rocky Mountain spotted fever, and pericarditis is inflammation of the lining around the heart.

Inhalational anthrax is the correct answer because it is known to have a nearly 100% mortality rate. Inhalational anthrax occurs when spores of the bacterium Bacillus anthracis are inhaled into the lungs. These spores can cause severe respiratory distress and can be fatal if not treated promptly. Cutaneous anthrax, subcutaneous anthrax, and gastrointestinal anthrax can also be serious, but they do not have the same high mortality rate as inhalational anthrax. Therefore, none of the other options are correct.

Clonorchis sinensis is the correct answer because it is a type of liver fluke that infects humans. It is commonly found in East Asia, particularly in China, Korea, and Vietnam. This parasite is acquired by consuming raw or undercooked freshwater fish that contain the infective larvae. Clonorchis sinensis can cause a condition called clonorchiasis, which can lead to liver damage, bile duct obstruction, and even liver cancer if left untreated. The other options listed are also types of liver flukes, but they do not specifically refer to Clonorchis sinensis.

Hyaluronidase is a chemical produced by S. aureus that is also known as the "spreading factor". This enzyme helps the bacteria to spread and invade tissues by breaking down hyaluronic acid, a component of connective tissue. This allows the bacteria to move through the tissues and cause infection.

Meningoencephalitis is an infection that affects both the brain and the meninges. The causative organisms for meningoencephalitis are typically Naegleria fowleri and Acanthamoeba, which are amoebas, rather than viruses. Therefore, the statement that causative organisms are viruses is not true for meningoencephalitis.

Taenia solium is a type of tapeworm that infects humans through the consumption of undercooked pork. It is commonly known as the pork tapeworm. Once ingested, the tapeworm can attach itself to the intestinal wall and grow, causing symptoms such as abdominal pain, nausea, and weight loss. In severe cases, the larvae of T. solium can migrate to other parts of the body and cause serious health complications. Proper cooking of pork and good hygiene practices can help prevent the transmission of T. solium.

Tinea unguium is the correct answer because it refers to a fungal infection of the nails, commonly known as ringworm of the nail. This condition can cause the nails to become discolored, thickened, and brittle. It is usually caused by dermatophyte fungi and can be difficult to treat. Tinea cruris refers to a fungal infection of the groin area, tinea pedis is a fungal infection of the feet, tinea barbae is a fungal infection of the beard area, and tinea manuum refers to a fungal infection of the hands.

Rotavirus is the correct answer because it is a primary viral cause of chronic diarrhea worldwide. Rotavirus is highly contagious and commonly affects infants and young children. It is transmitted through the fecal-oral route and can cause severe diarrhea, vomiting, and dehydration. Rotavirus infections are responsible for a significant number of hospitalizations and deaths in children under the age of five, particularly in developing countries with limited access to clean water and sanitation facilities. Vaccination against rotavirus has been successful in reducing the burden of rotavirus-related diarrhea globally.

HCV, or Hepatitis C virus, is the most common cause of liver cancer in the US. Hepatitis C is a viral infection that primarily affects the liver and can lead to chronic liver disease, cirrhosis, and eventually liver cancer. It is transmitted through contact with infected blood, such as through sharing needles or unsafe medical procedures. HCV infection often goes undiagnosed for many years, leading to the development of liver cancer in some cases. Effective treatments for Hepatitis C are available, but early detection and prevention are crucial in reducing the risk of liver cancer.

Metronidazole is the correct answer because it is a widely used antiprotozoal drug that is effective against a variety of protozoan diseases. It works by disrupting the DNA of the protozoa, leading to their death. Praziquantel is mainly used to treat parasitic worm infections, not protozoan diseases. Ketoconazole and Imidazole are antifungal drugs, not antiprotozoal drugs. Amphotericin B is an antifungal drug that can also be used to treat some protozoan infections, but it is not the main drug of choice.

Tetanus is a bacterial infection caused by the bacterium Clostridium tetani. It is characterized by muscle stiffness and spasms, including a condition known as opisthotonos, where the back muscles contract causing the body to arch backwards. This condition is commonly associated with tetanus and is one of the key symptoms used to diagnose the disease. The other options listed, Trypanosoma brucei gambiense, Naegleria fowleri, Candidiasis, and Meningococcal, do not typically cause opisthotonos and are not directly related to this symptom.

Ghon complexes are a characteristic pathological feature of tuberculosis infection. They are formed when the immune response to Mycobacterium tuberculosis leads to the formation of granulomas in the lung tissue. These granulomas consist of a central area of infected macrophages surrounded by lymphocytes and fibrous tissue. Ghon complexes are a sign of active tuberculosis infection and can be seen on chest X-rays. They are named after Anton Ghon, an Austrian pathologist who first described them in 1912.

Entamoeba histolytica is a protozoan that feeds on red blood cells (RBCs) and gastrointestinal (GI) tract tissues. It is known for causing amoebic dysentery, an infection that leads to severe diarrhea and abdominal pain. This parasite invades the intestinal lining, causing inflammation and destruction of tissues. It can also spread to other organs, such as the liver, causing abscesses. The feeding behavior of Entamoeba histolytica on RBCs and GI tract tissues is what distinguishes it from the other options listed, making it the correct answer.

Trichenella spiralis is a parasitic worm that infects humans and mammals. After ingestion, the larvae of Trichenella spiralis migrate to the muscles, where they encyst. This can lead to a condition called trichinellosis, which is characterized by muscle pain, fever, and gastrointestinal symptoms. Therefore, the given statement "larvae encyst in muscles of humans and mammals" accurately describes the life cycle of Trichenella spiralis.

The influenza vaccine is a subunit vaccine. This type of vaccine contains only specific parts or components of the influenza virus, such as proteins or antigens, rather than the whole virus. By focusing on these specific components, the subunit vaccine can stimulate an immune response without causing the actual illness. This makes it a safe and effective option for preventing influenza infections.

Invasive Group A streptococcus utilize streptokinases and hyaluronidases to further spread their infection. Streptokinases are enzymes that dissolve blood clots, allowing the bacteria to move more easily through the bloodstream and invade different tissues. Hyaluronidases, on the other hand, break down the connective tissue in the body, facilitating the bacteria's spread and invasion into surrounding tissues. By utilizing both streptokinases and hyaluronidases, the bacteria are able to effectively spread their infection and cause damage to various parts of the body.

Pyocyanin is a blue-green pigment produced by the bacteria Pseudomonas aeruginosa, which is known to cause pseudomonas infections. This pigment contributes to the characteristic blue-green color of the pus in these infections. Therefore, pyocyanin is the correct answer as it directly relates to the blue-green pus seen in pseudomonas infections.