Microbiology Practice Test 3
Microbiology NCLEX Practice Test
Microbiology is a key topic within the NCLEX test plan, located under Nursing Science → Clinical Foundations → Microbiology. This section explains pathogens, host defenses, and antimicrobial stewardship essential for infection control. Each test contains 50 questions designed to mirror the difficulty and variety of the real exam.
This is the 3rd part of the Microbiology series. To explore all practice tests under this topic, use the “Back to Main Topic” button at the end of the page.
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Microbiology Practice Test 3
Koplik’s spots are the clinical feature of?
- Chickenpox
- Pertussis
- Measles
- Cholera
Explanation: Answer reason: Koplik spots are small bluish-white lesions on the buccal mucosa that are pathognomonic for measles (rubeola).
HIV virus belongs to which of the following groups-?
- Flavivirus
- Hepadnavirus
- Rhabdovirus
- Retrovirus
Explanation: Answer reason: HIV is a member of the Retroviridae family (genus Lentivirus), an enveloped positive-sense ssRNA virus that uses reverse transcriptase.
What does the term 'sporadic' mean in the context of disease occurrence?
- Sudden outbreak of disease in a given area
- Infectious disease that has spread through human populations across a large region, for instance multiple continents or worldwide
- Disease occurs at irregular intervals only in few places in a scattered or isolated manner
- The constant presence of infection in a given geographical area without any external input
Explanation: Answer reason: Sporadic describes diseases that occur irregularly and infrequently in scattered or isolated locations. The other options define epidemic, pandemic, and endemic patterns.
What does sporadic mean in terms of disease occurrence?
- Sudden outbreak of disease in a given area
- Infectious disease that has spread through human populations across a large region or multiple continents
- Disease occurs at irregular intervals only in few places in scattered or isolated manner
- The constant presence of infection in a given geographical area without any external input
Explanation: Answer reason: Sporadic diseases occur infrequently and irregularly with scattered, isolated cases. A describes an outbreak, B a pandemic, and D an endemic state.
A child admitted with fever and respiratory distress with bull neck appearance is suspected of having which throat examination finding?
- Swollen tonsils with white exudate
- Strawberry tongue
- Thick gray membrane covering the throat
- Red inflamed throat without exudate
Explanation: Answer reason: Bull neck with fever and respiratory distress suggests diphtheria, which characteristically presents with a thick gray pseudomembrane in the throat.
Swine flu is caused by?
- Bacteria
- Fungus
- Protozoa
- H1N1 Virus
Explanation: Answer reason: Swine flu is an influenza A infection caused by the H1N1 virus.
What does pleomorphism mean in the characteristic rash of chickenpox?
- The rash advances quickly through the stages of macule, papule, vesicle, and scab
- All the stages of the rash such as macule, papule, vesicle, etc. may be seen simultaneously at one time in the same area
- There is unequal distribution of rash on the body
- There is equal distribution of rash all over the body
Explanation: Answer reason: Pleomorphism in chickenpox describes lesions in multiple stages—macules, papules, vesicles, and crusts—appearing simultaneously in the same area.
Which mosquito specie is primarily responsible for spreading dengue?
- Aedes mosquito
- Culex mosquito
- Anopheles
- Vivax
Explanation: Answer reason: Dengue virus is transmitted primarily by Aedes mosquitoes, especially Aedes aegypti; Culex spreads filariasis, Anopheles spreads malaria, and Vivax is a Plasmodium species, not a mosquito.
Which of the following bacteria is gram positive?
- Stapylococcus aereus
- Pseudomonas aeruginosa
- Salmonella typhi
- Escherichia coli
Explanation: Answer reason: Staphylococcus aureus is a Gram-positive coccus; the others listed are Gram-negative rods.
Dengue fever is caused by bites of which mosquito?
- Aedes aegypti mosquito
- Female anopheles mosquito
- Male anopheles mosquito
- Culex mosquito
Explanation: Answer reason: Dengue virus is transmitted primarily by the bite of the Aedes aegypti mosquito.
Which mosquito lays eggs singly?
- Aedes
- Anopheles
- Culex
- Mansonia
Explanation: Answer reason: Aedes mosquitoes lay eggs singly on damp surfaces; Culex lay eggs in rafts and Mansonia attach eggs in clusters to plants.
What does the acronym DOTS stand for in tuberculosis treatment?
- Directly Observed Tuberculosis Services
- Directly Observed Treatment Short Course
- Directly Observed Therapeutic
- Directly Observed Treatment Scheme
Explanation: Answer reason: DOTS is the WHO-endorsed TB strategy meaning Directly Observed Treatment, Short-course, ensuring adherence to anti-tuberculosis therapy.
Which statement about infections caused by Escherichia coli is NOT true?
- Enteroaggregative E. coli is associated with persistent diarrhea
- Enterohemorrhagic E. coli can cause hemolytic uremic syndrome
- Enteroinvasive E. coli produces disease similar to salmonellosis
- Enterotoxigenic E. coli is a common cause of travelers' diarrhea
Explanation: Answer reason: EIEC causes a dysentery-like illness resembling shigellosis, not salmonellosis. The other statements are correct: EAEC causes persistent diarrhea, EHEC can lead to HUS, and ETEC commonly causes travelers' diarrhea.
What is a transport host in parasitology?
- Parasite passes its sexual stage
- Parasite remains asexual
- Organism remains alive but does not undergo development
- Life cycle is not complete
Explanation: Answer reason: A transport (paratenic) host harbors the parasite without further development, serving only to carry it to another host.
What is an infection called when it is present in an individual but not sufficient to result in disease?
- Latent infection
- Clinical infection
- Subclinical infection
- Secondary infection
Explanation: Answer reason: An infection present without sufficient intensity to cause disease or noticeable symptoms is termed subclinical (inapparent) infection. Clinical infection is symptomatic; latent infection is dormant with potential reactivation; secondary infection follows a primary infection.
Which agent factors are responsible for the occurrence of disease?
- Biological and physical agents
- Mechanical and chemical agents
- Vertical and inoculation agents
- Nutrient and living agents
Explanation: Answer reason: Vertical transmission and inoculation are agent-related transmission mechanisms that contribute to the occurrence of infectious disease.
In which age group does COVID-19 spread and cause illness?
- COVID-19 occurs in all age groups
- Coronavirus infection is mild in children
- Older persons and persons with pre-existing medical conditions are at high risk to develop serious illness
- All the above are correct
Explanation: Answer reason: COVID-19 can affect all ages, tends to be milder in many children, and severe disease risk is higher in older adults and those with comorbidities; therefore all statements are true.
Chorioamnionitis (intra-amniotic infection) is typically caused by which of the following organisms?
- Group B beta-hemolytic streptococcus (GBS)
- Escherichia coli
- Staphylococcus aureus
- Ureaplasma urealyticum
- Multiple pathogens
Explanation: Answer reason: Intra-amniotic infection is usually an ascending, polymicrobial infection involving multiple vaginal and gastrointestinal organisms (e.g., Ureaplasma, Mycoplasma, GBS, E. coli, anaerobes). Therefore the most accurate choice is multiple pathogens.
What is the time period between the entry of a disease agent into the body and the occurrence of clinical signs and symptoms called?
- Incubation period
- Fastigium
- Defervescence
- Defection
Explanation: Answer reason: The interval from pathogen entry to the onset of symptoms is the incubation period. Fastigium is the peak of illness; defervescence is the decline of fever; defection is recovery.
Malaria can be caused by which type of mosquito?
- All anopheles mosquitoes
- All culex mosquitoes
- Only males Culex mosquitoes
- Only female anopheles mosquitoes
Explanation: Answer reason: Malaria is transmitted to humans by the bite of infected female Anopheles mosquitoes; only females blood-feed, and Culex species do not transmit malaria.
Which organism is primarily responsible for oral candidiasis?
- Streptococcus mutans
- Candida albicans
- Lactobacillus acidophilus
- Herpes simplex virus
Explanation: Answer reason: Oral candidiasis (thrush) is caused by the yeast Candida albicans; the other options are linked to dental caries or viral lesions, not candidiasis.
Loeffler Bacillus is the name of which of the following bacteria?
- Clostridium tetani
- Corynebacterium diphtheriae
- Lactobacillus
- Hemophilus influenzae
Explanation: Answer reason: Loeffler’s bacillus is the historical name for Corynebacterium diphtheriae, the causative agent of diphtheria.
What is the full form of MRSA?
- Methicillin resistant streptococcus aureus
- Methicillin resistant staphylococcus aureus
- Methicillin resistant pseudomonas aureus
- None of the above
Explanation: Answer reason: MRSA stands for methicillin-resistant Staphylococcus aureus; the other organisms listed are incorrect.
What are the non-motile small appendages on the surface of bacteria that help in the transfer of DNA from one cell to another during conjugation called?
- Fimbriae
- Pili
- Flagella
- None of these
Explanation: Answer reason: Bacterial conjugation uses a sex pilus to transfer DNA. Fimbriae are mainly for adhesion and flagella are motile; therefore the correct term is pili.
Which test is used to measure the incidence of tuberculosis (TB) in a community?
- Sputum smear positive
- Tuberculin test positive
- Sputum culture
- Mantoux test positive
Explanation: Answer reason: Incidence of TB infection in a community is estimated using tuberculin (Mantoux) skin test surveys; smear or culture identify active disease in individuals and do not measure community incidence.
Which of the following must be present for cervical cancer to occur?
- Epstein Barr virus
- Herpes simplex virus
- Human papillomavirus
- Herpes zoster virus
Explanation: Answer reason: High-risk HPV infection (e.g., types 16/18) is a necessary cause of cervical cancer; EBV, HSV, and VZV are not etiologic for cervical cancer.
Which of the following was not discovered by Louis Pasteur?
- Techniques of pasteurisation
- Process of fermentation
- Suppuration of staphylococcus
- Rabies vaccine
Explanation: Answer reason: Pasteur pioneered pasteurization, fermentation studies, and developed the rabies vaccine. The identification of staphylococcus as a cause of suppuration was by Alexander Ogston, not Pasteur.
Who was the first person to view microorganisms such as bacteria and protozoa?
- Robert Brown
- Alexander Flaming
- Edward Janer
- Antony Van Leeuwenhoek
Explanation: Answer reason: Antony van Leeuwenhoek was the first to observe and describe bacteria and protozoa using microscopes he developed; the other figures are known for different discoveries.
In the large intestine, vitamin K is formed by the activity of which type of bacteria?
- Facultative bacteria
- Obligate bacteria
- Parasitic bacteria
- Symbiotic bacteria
Explanation: Answer reason: Gut flora in the colon synthesize vitamin K as part of a mutualistic (symbiotic) relationship with the host.
Smallpox is caused by which of the following?
- Virus
- Bacteria
- Mosquitos
- None of them
Explanation: Answer reason: Smallpox is caused by the variola virus (a poxvirus), so the etiology is viral.
Which substance destroys harmful microbes?
- Bacteriostatic
- Disinfectant
- Detergent
Explanation: Answer reason: Disinfectants kill or destroy microorganisms on inanimate objects. Bacteriostatic agents only inhibit growth, and detergents primarily clean without necessarily killing microbes.
Which hepatitis virus is a DNA virus?
- Hepatitis A
- Hepatitis B
- Hepatitis C
- Hepatitis D
Explanation: Answer reason: Hepatitis B virus (HBV) is a partially double-stranded DNA virus; hepatitis A, C, and D are RNA viruses.
Common cold is caused by which of the following?
- Bacteria
- Rhinovirus
- Fungus
- Protozoa
Explanation: Answer reason: The primary cause of the common cold is rhinoviruses; bacteria, fungi, and protozoa are not typical etiologies.
What organism causes dysentery?
- Amoeba
- Shigella
- Staphylococcus
- Streptococcus
Explanation: Answer reason: Shigella species invade the colonic mucosa causing inflammatory diarrhea with blood and mucus, the classic bacillary dysentery. Staphylococcus and Streptococcus are not causes, and amoebic dysentery is specifically due to Entamoeba histolytica, not generically 'Amoeba.
Which term correctly describes the comma-shaped bacteria?
- Cocci
- Vibrio
- Spiral
Explanation: Answer reason: Comma-shaped bacteria are called Vibrio; cocci are spherical and spirals are helical.
What is the incubation period of Pertussis?
- 2-5 days
- 7-14 days
- 7-21 days
- 5-28 days
Explanation: Answer reason: Pertussis (Bordetella pertussis) has an incubation period typically about 7–10 days with a range up to 21 days; thus 7–21 days is correct.
Typhoid fever is caused by which type of organism?
- Protozoa
- Fungi
- Bacteria
- Virus
Explanation: Answer reason: Typhoid fever is caused by Salmonella Typhi, a gram-negative bacterium.
Chickenpox is caused by which type of organism?
- Bacteria
- Fungus
- Virus
- Parasite
Explanation: Answer reason: Chickenpox is caused by the varicella-zoster virus, making the correct organism type a virus.
AIDS is caused by which type of organism?
- Bacteria
- Fungi
- Viruses (HIV)
- Protozoa
Explanation: Answer reason: AIDS is caused by the Human Immunodeficiency Virus (HIV), a retrovirus, not by bacteria, fungi, or protozoa.
What are the natural reservoirs of plague?
- Field mice
- Gerbils
- Shunks
- All of above
Explanation: Answer reason: Yersinia pestis is maintained in wild small mammals—especially rodents such as field mice and gerbils—and other small mammals can also serve as reservoirs; therefore all listed are reservoirs.
What is the best method of sterilization?
- ETO
- Hypochlorite
- Hot Air Oven
- Autoclave
Explanation: Answer reason: Autoclaving (moist heat under pressure) is the most effective and reliable general method for sterilization, rapidly killing all microorganisms and spores. ETO is for heat-sensitive items, hypochlorite is a disinfectant, and hot air oven is less efficient.
The mechanism of high level INH resistance of M tuberculosis is?
- Reduced expression of the kat G gene
- Decreased intra cellular accumulation of INH
- Both A and B
- None
Explanation: Answer reason: High-level isoniazid resistance in M. tuberculosis is primarily due to mutations/reduced activity in katG (catalase–peroxidase), preventing activation of INH. Decreased intracellular accumulation is not the main mechanism for high-level resistance.
What do prokaryotic cells lack?
- Membrane bounded organells
- Cell membrane
- Cytoplasm
- Cell wall
Explanation: Answer reason: Prokaryotes lack membrane-bound organelles (and a true nucleus) but do have a cell membrane, cytoplasm, and usually a cell wall.
Which of the following precursor is added in the medium to get penicillin G?
- Phenyl carbamic acid
- Phenyl acetic acid
- Ammonium sulphate
- Ammonium chloride
Explanation: Answer reason: Penicillin G (benzylpenicillin) is produced when phenylacetic acid is supplied as the side-chain precursor during fermentation; the ammonium salts are nitrogen sources, not specific precursors.
Vegetable oil, (corn oil or soybean oil) added in the fermentation medium for penicillin, act as?
- Source of nutrients
- Carbon source
- Antifoam agent
- Both (a) and (c)
Explanation: Answer reason: In penicillin fermentation, vegetable oils like corn or soybean oil are added primarily to act as antifoam agents and also provide supplemental nutrients/energy for the organism. Hence both (a) and (c).
Penicillin is produced by?
- Aerobic fermentation
- Anaerobic fermentation
- Aerobic fermentation followed by anaerobic fermentation
- Anaerobic fermentation followed by aerobic fermentation
Explanation: Answer reason: Penicillium chrysogenum produces penicillin under aerobic submerged fermentation; high dissolved oxygen is required for biosynthesis.
Which of the following organism(s) produce(s) tetracycline?
- Steptomyces aureofaciens
- Steptomyces ramosus
- Nocardia sulphurea
- All of these
Explanation: Answer reason: Tetracyclines are naturally produced by actinomycetes, notably Streptomyces aureofaciens, Streptomyces rimosus (listed as ramosus), and some Nocardia species; therefore all listed organisms are producers.
In men, specimens for gonococcal cultures are most commonly obtained from which of the following structures?
- Anus
- Bladder
- Skin
- Testicle
- Urethra
Explanation: Answer reason: Gonorrhea in men typically presents as urethritis; culture or NAAT samples are collected from the urethra via swab.
Which of the following event occurs during second phase of growth of P. chrysogenum?
- Synthesis of penicillin is high
- Mycelial mass increases
- PH increase
- Both (a) and (b)
Explanation: Answer reason: The second phase (idiophase) in P. chrysogenum is the production phase when secondary metabolite synthesis—penicillin—is high; mycelial mass no longer increases, so A is the best choice.
What is the causative agent of tuberculosis?
- Mycobacterium tuberculosis
- Mycobacterium leprae
- Variola virus
- Virus
- None
Explanation: Answer reason: Tuberculosis is caused by Mycobacterium tuberculosis; M. leprae causes leprosy, variola virus causes smallpox, and the other choices are incorrect.
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