Question 1

Pertussis is another name for?

Accepted Answer

Answer reason: Pertussis is the clinical name for whooping cough, a contagious respiratory infection caused by Bordetella pertussis. It is characterized by paroxysmal coughing fits that may end with an inspiratory “whoop,” especially in children. The other options are different conditions: diphtheria is caused by Corynebacterium diphtheriae, and scarlet fever is associated with Group A Streptococcus.

Question 2

Gonorrhea is caused by?

Accepted Answer

Answer reason: Gonorrhea is a sexually transmitted infection caused by the bacterium Neisseria gonorrhoeae, a gram-negative diplococcus. Viral, fungal, and protozoal pathogens cause different STIs (e.g., HSV/HPV, Candida, Trichomonas) and do not cause gonorrhea. Therefore, the correct etiology is bacterial.

Question 3

Plasmodium enters the human body as ____?

Accepted Answer

Answer reason: The infective form of Plasmodium transmitted to humans during the bite of an infected female Anopheles mosquito is the sporozoite, which is injected from the mosquito’s salivary glands into the bloodstream. Sporozoites rapidly travel to the liver and invade hepatocytes to begin the exoerythrocytic (hepatic) stage. Trophozoites occur later within human hepatocytes and red blood cells, and haemozoin is a heme polymer pigment produced during hemoglobin digestion, not an entry form. Therefore, the organism enters the human body as a sporozoite.

Question 4

Which organism is most commonly responsible for lactational mastitis?

Accepted Answer

Answer reason: Lactational mastitis is most commonly caused by Staphylococcus aureus, which colonizes the skin and can enter the breast through cracked nipples during breastfeeding. This organism is the typical pathogen in acute infectious mastitis and may lead to abscess formation if untreated. Streptococci can also cause mastitis but are less common than Staphylococcus. Listeria and Neisseria are not typical causes of lactational mastitis.

Question 5

Which of the following is an example of ‘Arthropod’?

Accepted Answer

Answer reason: Arthropods are invertebrates with a chitinous exoskeleton, segmented body, and jointed appendages; arachnids (including scorpions) are a major arthropod class. A blood-sucking leech and an earthworm are annelids (segmented worms), not arthropods. Hookworm is a nematode (roundworm). Therefore, scorpion is the correct example of an arthropod.

Question 6

The classical triad of malaria includes?

Accepted Answer

Answer reason: Malaria classically presents with paroxysms consisting of chills (cold stage) followed by fever (hot stage) and then profuse sweating as the temperature falls. This pattern corresponds to synchronous rupture of infected red blood cells and release of merozoites/pyrogens. The other options include symptoms not considered part of the classic malarial paroxysm triad.

Question 7

Measles is commonly spread during which stage of illness?

Accepted Answer

Answer reason: Measles (rubeola) is most contagious during the prodromal phase, when fever, cough, coryza, and conjunctivitis are present. Viral shedding from the respiratory tract is high before the rash appears and continues into the early rash period. Because transmission commonly occurs before diagnosis based on rash, the prodromal stage is the key period for spread.

Question 8

What type of virus is HIV?

Accepted Answer

Answer reason: HIV is a retrovirus (a lentivirus) that carries single-stranded RNA and uses reverse transcriptase to synthesize DNA from its RNA genome. The newly formed viral DNA integrates into the host cell genome, enabling persistent infection. While HIV contains RNA, the defining classification is “retrovirus” because of this reverse transcription step.

Question 9

Which disease is most commonly known as "breakbone fever"?

Accepted Answer

Answer reason: “Breakbone fever” is a classic name for dengue fever due to its prominent severe myalgias and arthralgias that can feel like bones are breaking. Dengue is caused by a Flavivirus transmitted by Aedes mosquitoes and can progress to severe dengue with plasma leakage and bleeding. Typhoid, malaria, and mumps have different characteristic symptom patterns and are not commonly referred to by this nickname.

Question 10

Which bacteria cause tuberculosis?

Accepted Answer

Answer reason: Tuberculosis is caused by Mycobacterium tuberculosis, an acid-fast bacillus transmitted primarily via airborne droplet nuclei. Mycobacterium leprae causes leprosy (Hansen disease), not TB. Bacillus anthracis causes anthrax, and Corynebacterium diphtheriae causes diphtheria, making them incorrect for tuberculosis.

Question 11

Vertical transmission of HIV occurs through?

Accepted Answer

Answer reason: Vertical transmission refers specifically to mother-to-child transmission (during pregnancy, labor/delivery, or breastfeeding). Among the listed options, breastfeeding is a true vertical route because HIV can be transmitted via breast milk. Sexual contact and blood transfusion are horizontal transmission routes and do not fit the definition of vertical transmission. Therefore, “All of the above” is incorrect despite those being valid HIV transmission routes in general.

Question 12

Which Hepatitis virus can cause infection only in presence of Hepatitis B virus?

Accepted Answer

Answer reason: Hepatitis D virus (HDV) is a defective RNA virus that requires hepatitis B surface antigen (HBsAg) from HBV to assemble and infect humans. Therefore, HDV infection occurs only as a coinfection with HBV or as a superinfection in a person already chronically infected with HBV. This dependence on HBV is unique to hepatitis D among the listed options.

Question 13

Koch’s postulates are related to?

Accepted Answer

Answer reason: Koch’s postulates are criteria used to establish a causal relationship between a specific microorganism and a specific disease. They focus on proving that an organism is the etiologic agent by demonstrating its presence in diseased hosts, isolating it in pure culture, reproducing disease upon inoculation, and re-isolating it. This framework is foundational for understanding infectious disease causation rather than treatment, routine diagnosis, or immunity.

Question 14

Hepatitis C is commonly spread through?

Accepted Answer

Answer reason: Hepatitis C virus is primarily transmitted through blood-to-blood exposure, most commonly via sharing contaminated needles/syringes and, historically, via blood transfusions before widespread donor screening. It is not spread through food, water, or airborne routes. Thus, the option describing blood transfusion and needle sharing best matches the known epidemiology of HCV transmission.

Question 15

42 years old man comes to ER complaining form Dyspnea, fever, and cough, he did visit China before 10 days ago, and he didn't response to symptomatic treatment, physical examination shows bilateral talkers, x-ray shows diffuse infiltration, which infection organisms is more possible cause of these symptoms?

Accepted Answer

Answer reason: The presentation of fever, cough, dyspnea with bilateral lung findings and diffuse infiltrates on chest X-ray is most consistent with viral pneumonia/ARDS, and a recent travel history to China strongly points to SARS-CoV-2 infection. Rhinovirus typically causes mild upper respiratory infection without diffuse infiltrates, and adenovirus pneumonia is less strongly linked to this travel epidemiology. MERS-CoV is classically associated with the Arabian Peninsula rather than China, making it less likely in this scenario.

Question 16

The most common route of transmission of typhoid is?

Accepted Answer

Answer reason: Typhoid fever (Salmonella enterica serovar Typhi) is transmitted primarily by the fecal–oral route, most commonly through ingestion of food or water contaminated with human feces from infected persons or carriers. This is why outbreaks are strongly associated with poor sanitation and unsafe water supplies. Blood transfusion is not a typical route, insect bites are not involved, and "direct contact" is not the main transmission pathway unless it results in fecal–oral ingestion.

Question 17

Hydrophobia is another name for?

Accepted Answer

Answer reason: Hydrophobia is a classic symptom and historical name for rabies, caused by a Lyssavirus that infects the central nervous system. Patients can develop painful pharyngeal spasms and autonomic instability, making swallowing difficult and triggering fear/avoidance of water. Typhoid, cholera, and malaria do not characteristically cause hydrophobia; they primarily present with systemic febrile illness and/or gastrointestinal symptoms.

Question 18

Which bodily fluids does not transmit the AIDS virus?

Accepted Answer

Answer reason: HIV is transmitted through specific infectious body fluids such as blood, semen, vaginal/rectal secretions, and breast milk, typically via mucous membrane contact, bloodstream exposure, or perinatal routes. Feces are not considered a transmitting fluid for HIV in routine circumstances because HIV is not transmitted by the fecal-oral route and stool does not normally contain infectious levels of virus. While stool may contain blood in some illnesses, the transmission risk would be from the blood, not the feces itself. Therefore, among the options listed, feces is the correct choice.

Question 19

Ringworm is caused by a?

Accepted Answer

Answer reason: Ringworm (tinea) is a superficial dermatophyte infection caused by fungi, most commonly Trichophyton, Microsporum, or Epidermophyton species. Despite the name, it is not caused by a worm, nor is it bacterial, viral, or protozoal. It typically produces an annular, scaly rash with central clearing due to fungal growth in keratinized tissue (skin, hair, nails). Therefore, the correct choice is fungi.

Question 20

What is the incubation period of HIV before symptoms may appear?

Accepted Answer

Answer reason: HIV infection can remain clinically asymptomatic for a prolonged period after initial infection, often for years, before progressing to symptomatic HIV disease or AIDS if untreated. While acute retroviral syndrome may occur within weeks after exposure, the question asks when symptoms may appear overall, which commonly can be several years later. Therefore, “Several years” best matches the typical incubation/latency period referenced in many nursing and microbiology texts.

Question 21

The most common mode of transmission of Hepatitis C is?

Accepted Answer

Answer reason: Hepatitis C is primarily transmitted via blood-to-blood exposure (parenteral transmission). Among the listed options, blood transfusion best represents bloodborne transmission (noting that today transfusion risk is very low due to screening, while injection drug use is now the most common overall route). Feco-oral spread is typical of hepatitis A, and HCV is not spread by airborne droplets or mosquito bites. Therefore, the correct choice from the given options is blood transfusion.

Question 22

HIV can be transmitted through which of the following?

Accepted Answer

Answer reason: HIV is transmitted via exposure to infected blood and certain body fluids, including through percutaneous injury. Sharing needles can introduce contaminated blood directly into the bloodstream, making it a high-risk route of transmission. Casual contact such as hugging or shaking hands does not transmit HIV because intact skin is an effective barrier. Sharing food also does not transmit HIV, as the virus is not spread through saliva or via the gastrointestinal route in typical social settings.

Question 23

ELISA test is used for the diagnosis of?

Accepted Answer

Answer reason: ELISA (enzyme-linked immunosorbent assay) is a common screening immunoassay used to detect antibodies to HIV (and/or HIV antigen in some test formats), making it widely used in the diagnosis/screening process for HIV infection. While ELISA-based assays can also be used for certain hepatitis markers, the classic and most tested association in basic nursing/microbiology MCQs is HIV screening by ELISA. Tuberculosis is typically diagnosed with sputum microscopy/culture or NAAT, and malaria with peripheral blood smear or rapid antigen tests rather than ELISA as the primary diagnostic method.

Question 24

Bacteria reproduces by?

Accepted Answer

Answer reason: Most bacteria reproduce primarily by binary fission, where one parent cell replicates its DNA and divides into two genetically identical daughter cells. This is an asexual method of reproduction and is the standard mechanism for bacterial population growth. "Sexual reproduction" does not occur in bacteria in the true sense; they may exchange genetic material via conjugation/transformation/transduction, but that is gene transfer, not reproduction. Therefore, "All of the above" is incorrect.

Question 25

The incubation period of diphtheria is?

Accepted Answer

Answer reason: Diphtheria (Corynebacterium diphtheriae) typically has an incubation period of about 2–5 days, though it can range roughly from 1 to 10 days. This time frame fits classic teaching for respiratory diphtheria and is used for contact tracing and monitoring exposed individuals. The shorter choices (hours or 1–3 days) are less typical, and 7–10 days is more consistent with the upper tail of the range rather than the most common period.

Question 26

Which microbe causes tetanus?

Accepted Answer

Answer reason: Tetanus is caused by the bacterium Clostridium tetani, an anaerobic, spore-forming gram-positive rod found in soil and animal feces. The disease results from production of the neurotoxin tetanospasmin, which blocks inhibitory neurotransmitter release and leads to muscle rigidity and spasms. Therefore, among the listed microbe types, the correct cause is bacteria.

Question 27

Entry of Salmonella typhi in the body is usually through?

Accepted Answer

Answer reason: Salmonella typhi is transmitted by the fecal–oral route, most commonly through ingestion of contaminated food or water. The organism enters via the gastrointestinal mucosa (notably through intestinal lymphoid tissue such as Peyer patches) and then can disseminate systemically. Skin and respiratory routes are not typical portals of entry for typhoid fever, and blood transfusion is not a usual mode of transmission.

Question 28

The fever pattern in Plasmodium vivax malaria is?

Accepted Answer

Answer reason: Plasmodium vivax has an erythrocytic schizogony cycle of about 48 hours, producing febrile paroxysms every third day by classic naming (tertian malaria). This periodic fever corresponds to synchronized rupture of infected RBCs and release of merozoites and pyrogenic substances. By contrast, quartan fever (72 hours) is classically associated with P. malariae, and daily fever is more typical of P. falciparum or mixed/asynchronous infection.

Question 29

Causative organism of syphilis is —?

Accepted Answer

Answer reason: Syphilis is caused by the spirochete bacterium Treponema pallidum. Neisseria gonorrhoeae causes gonorrhea, Chlamydia trachomatis causes chlamydial infections (e.g., cervicitis/urethritis), and Trichomonas vaginalis is a protozoan that causes trichomoniasis. Therefore the correct causative organism for syphilis is Treponema pallidum.

Question 30

Which of the following is symbiotic nitrogen fixing bacteria?

Accepted Answer

Answer reason: Rhizobium species are classic symbiotic nitrogen-fixing bacteria that live in root nodules of leguminous plants, converting atmospheric nitrogen into ammonia for plant use. Rhizobium trifolii specifically forms symbiosis with clover (Trifolium). In contrast, Azotobacter and Clostridium pasteurianum are free-living nitrogen fixers (not symbiotic), and Escherichia coli does not fix nitrogen.

Question 31

Which one of the following diseases is caused by a protozoan?

Accepted Answer

Answer reason: Malaria is caused by Plasmodium species, which are protozoan parasites transmitted primarily by the bite of an infected female Anopheles mosquito. In contrast, cholera is caused by the bacterium Vibrio cholerae, tuberculosis by Mycobacterium tuberculosis, and typhoid by Salmonella Typhi. Therefore, among the options, malaria is the only protozoan disease.

Question 32

What is the term for a virus that infects and replicates within a bacterial cell?

Accepted Answer

Answer reason: A bacteriophage (phage) is a virus that specifically infects bacteria and uses the bacterial cellular machinery to replicate. "Viroid" and "virusoid" are subviral agents (small circular RNA) that infect plants and depend on host polymerases, not bacterial cells. "Proviron" is not a standard microbiology term for a bacterial virus (it resembles a brand/drug name rather than a virology entity). Therefore, the correct term is bacteriophage.

Question 33

Which type of Hepatitis is associated with high maternal mortality during pregnancy?

Accepted Answer

Answer reason: Hepatitis E infection is classically associated with severe disease in pregnancy, especially in the third trimester, with a higher risk of fulminant hepatic failure and increased maternal mortality. This association is much stronger for HEV than for hepatitis A, B, or C in typical clinical teaching. Therefore, Hepatitis E is the single best answer.

Question 34

HIV infection is detected by?

Accepted Answer

Answer reason: Screening for HIV infection is commonly done using an ELISA (enzyme-linked immunosorbent assay) to detect antibodies to HIV (and/or p24 antigen in 4th-generation assays). ESR is a nonspecific inflammation marker and does not diagnose HIV. VDRL is a screening test for syphilis, and Widal is used for typhoid fever, so neither detects HIV infection.

Question 35

Organism most likely to be found in extreme environment is ...?

Accepted Answer

Answer reason: Archaea are classically associated with extreme environments (extremophiles), such as high temperature (thermophiles), high salt (halophiles), and extreme acidity or alkalinity. Their unique cell membrane lipids (ether linkages) and distinct cell wall features help them tolerate harsh conditions. While some bacteria can also be extremophiles, the group most commonly and characteristically linked to extreme habitats is archaea. Viruses require host cells to replicate and are not typically described as independent extremophile organisms, and fungi are generally less tolerant of the most extreme conditions.

Question 36

The vector responsible for transmission of malaria is?

Accepted Answer

Answer reason: Malaria is transmitted to humans by the bite of the female Anopheles mosquito, which requires a blood meal for egg development and can inoculate Plasmodium sporozoites during feeding. Male Anopheles mosquitoes do not bite humans for blood and therefore do not transmit malaria. Aedes mosquitoes are classically associated with dengue, Zika, and yellow fever, and Culex with West Nile and filariasis, making them incorrect here.

Question 37

Typhoid is tested by ...?

Accepted Answer

Answer reason: In standard exam contexts, the classic screening serologic test for typhoid fever is the Widal test, which detects agglutinating antibodies (O and H) against Salmonella Typhi antigens. Although PCR and ELISA-based assays can be used in some settings, they are not the traditionally referenced named test for typhoid in many nursing/medical MCQs. Therefore, among the options given, Widal is the best single answer.

Question 38

The most dangerous species of Plasmodium is?

Accepted Answer

Answer reason: Plasmodium falciparum causes the most severe and life-threatening form of malaria. It can infect red blood cells of all ages, leading to high parasitemia and complications such as cerebral malaria, severe anemia, and multi-organ failure. Its propensity for cytoadherence and microvascular sequestration drives much of the severe disease and higher mortality compared with other Plasmodium species.

Question 39

Candidiasis is Caused by?

Accepted Answer

Answer reason: Candidiasis is caused by Candida species, most commonly Candida albicans, which are fungi (yeasts). These organisms are normal flora on skin and mucous membranes but can overgrow when host defenses are altered (e.g., antibiotics, diabetes, immunosuppression). Therefore, the etiologic agent class is fungal, not bacterial, viral, or protozoal.

Question 40

Which of the following is an exception to cell theory?

Accepted Answer

Answer reason: Viruses are acellular and lack the cellular structures required by cell theory (e.g., cytoplasm, organelles, independent metabolism). They cannot reproduce on their own and must use a host cell’s machinery for replication. In contrast, bacteria, protists, and protozoans are true cellular organisms (prokaryotic or eukaryotic) and therefore conform to cell theory.

Question 41

The widespread problem of drug resistance in microorganisms results in ?

Accepted Answer

Answer reason: Drug resistance means microorganisms develop mechanisms (e.g., enzymatic drug inactivation, altered targets, efflux pumps, biofilm formation) that allow them to survive antimicrobial exposure. The clinical result is reduced effectiveness of standard therapies, leading to treatment failure, prolonged illness, and need for broader-spectrum or more toxic/expensive drugs. It does not increase patient immunity, decrease mutation rates, or enhance vaccine effectiveness.

Question 42

What is the primary mode of HIV transmission?

Accepted Answer

Answer reason: HIV is transmitted through exposure to infected blood and certain body fluids (e.g., semen, vaginal/rectal fluids, and breast milk) that contact mucous membranes or the bloodstream, including via sexual contact, needle sharing, or perinatal exposure. It is not spread by airborne droplets or contaminated water because the virus does not survive/transmit efficiently through those routes. Casual skin-to-skin contact does not transmit HIV unless there is direct blood/body fluid exchange through non-intact skin or mucosa. Therefore, the best answer is blood and body fluids.

Question 43

In animals, trypanosoma brucei causes a disease called?

Accepted Answer

Answer reason: Trypanosoma brucei infections in animals (especially livestock) classically cause nagana, also called animal African trypanosomiasis. In contrast, human African trypanosomiasis ("sleeping sickness") is associated with T. brucei gambiense and T. brucei rhodesiense in humans. Cholera is caused by Vibrio cholerae, and malaria is caused by Plasmodium species, so those options are incorrect.

Question 44

Global goal for neonatal tetanus elimination is?

Accepted Answer

Answer reason: The WHO definition of elimination of maternal and neonatal tetanus is achieving an incidence of fewer than 1 case of neonatal tetanus per 1,000 live births per year in every district. This reflects that elimination is a public-health threshold (very low incidence), not necessarily absolute eradication. Therefore, “zero cases” is not the stated elimination goal, and the higher incidence options are incorrect.

Question 45

Which of the following is a common opportunistic infection in AIDS patients?

Accepted Answer

Answer reason: In AIDS, impaired cell-mediated immunity (low CD4+ T cells) predisposes patients to opportunistic infections, including reactivation or new infection with Mycobacterium tuberculosis. Tuberculosis is a well-recognized and common opportunistic infection in HIV/AIDS and may present with pulmonary or disseminated disease. Influenza, chickenpox (varicella), and malaria can occur in immunocompromised people but are not classically emphasized as common AIDS-defining opportunistic infections compared with TB.

Question 46

A 4 year old client was brought to the health center with a chief complaint of severe diarrhea and the passage of "rice water". The client is most probably suffering from which condition?

Accepted Answer

Answer reason: “Rice-water” stools (profuse watery diarrhea with flecks of mucus) are classic for Vibrio cholerae infection due to cholera toxin–mediated secretory diarrhea. This presentation is typically severe and can rapidly cause dehydration and shock, especially in children. Giardiasis more often causes greasy, foul-smelling stools and bloating; amebiasis and dysentery are associated with blood and mucus and tenesmus rather than rice-water stools.

Question 47

Dengue is caused by?

Accepted Answer

Answer reason: Dengue fever is caused by dengue virus (DENV), an enveloped, positive-sense single-stranded RNA virus in the genus Flavivirus (family Flaviviridae). Therefore, the best choice is “Flavi Virus.” Adenovirus causes primarily respiratory and conjunctival infections, not dengue, and “Riyo Virus” is not a standard viral classification for dengue.

Question 48

Causative organism of Gonorrhea is?

Accepted Answer

Answer reason: Gonorrhea is caused by Neisseria gonorrhoeae, a gram-negative intracellular diplococcus that commonly infects mucous membranes of the urogenital tract, rectum, and pharynx. Treponema pallidum causes syphilis, Chlamydia trachomatis causes chlamydial infections (and can co-infect but is not the cause of gonorrhea), and Trichomonas vaginalis is a protozoan causing trichomoniasis. Therefore, Neisseria gonorrhoeae is the correct causative organism.

Question 49

When an anopheles Mosquito " Bites a healthy person it injects?

Accepted Answer

Answer reason: In malaria transmission, the female Anopheles mosquito injects Plasmodium sporozoites in its saliva during a bite. Sporozoites then travel to the liver to initiate the exoerythrocytic (hepatic) stage. Merozoites are released later from the liver to infect red blood cells, while gametocytes are taken up by a mosquito from an infected human. Oocysts form in the mosquito midgut, not injected into humans.

Question 50

Tapeworm lives in the?

Accepted Answer

Answer reason: Adult tapeworms (Taenia spp., Diphyllobothrium latum) typically inhabit the human small intestine, where they attach to the mucosa with a scolex and absorb nutrients across their tegument. Eggs or proglottids are then passed in stool, supporting the intestine as the primary adult habitat. Lungs, kidney, and pancreas are not the usual sites for adult tapeworm residence in humans, though some larval stages can migrate to other tissues in certain species.

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