Question 1

Restriction enzymes are?

Accepted Answer

Answer reason: Restriction endonucleases are part of the bacterial restriction–modification defense system that recognizes specific DNA sequences and cleaves foreign DNA. This protects bacteria from bacteriophage infection by cutting invading phage genomes while the host genome is protected via methylation. “Splice” refers to ligation/joining of nucleic acids, which is performed by DNA ligase (and RNA splicing by spliceosomes), not restriction enzymes. Viral destruction of host DNA is not the defining mechanism being tested for restriction enzymes in biotechnology/microbiology.

Question 2

The study of genetic material taken directly from the environment is?

Accepted Answer

Answer reason: Metagenomics is the analysis of DNA/RNA recovered directly from environmental samples (e.g., soil, water, human microbiome) without first isolating and culturing individual organisms. This approach captures genetic material from entire microbial communities, including unculturable species, making it the best match to “taken directly from the environment.” Bioinformatics is a computational toolset used to analyze data rather than the sampling strategy itself, and proteomics focuses on proteins rather than genetic material. The other options describe different specialized approaches not defined by direct environmental nucleic-acid sampling.

Question 3

A clone is?

Accepted Answer

Answer reason: A clone refers to a population of organisms or cells that all originate from one progenitor and therefore share the same genetic makeup (barring new mutations). This definition is commonly applied in microbiology where a single bacterium replicates to form a genetically uniform group. A colony on agar describes the visible growth mass, but it is a culture morphology term and can be mixed unless isolated from one cell, so it is not the defining concept. A taxon composed of species refers to a genus, and genetic engineering is a separate process from cloning.

Question 4

The terms "run" and "tumble" are generally associated with?

Accepted Answer

Answer reason: Bacterial motility uses alternating straight swimming and reorientation to navigate chemical gradients. A “run” is relatively straight movement driven by coordinated flagellar rotation, while a “tumble” is a brief reorientation event that changes direction. By adjusting the frequency of tumbles, bacteria bias their net movement toward attractants and away from repellents (chemotaxis). The other choices describe structural properties or biosynthesis processes rather than directed motility behavior.

Question 5

The DNA found in most bacterial cells?

Accepted Answer

Answer reason: Most bacteria are prokaryotes, so their chromosome is located in a nucleoid region rather than enclosed by a nuclear membrane. The typical bacterial genome consists of a single, double-stranded circular chromosome, which distinguishes it from eukaryotic nuclear DNA that is usually linear. Classical histone-based chromatin packaging is a eukaryotic feature (with limited exceptions in some archaea), making that distractor incorrect for most bacteria. While bacteria can carry extra DNA elements like plasmids, the core chromosomal DNA in most bacterial cells is not defined by being present in multiple copies.

Question 6

Functions of the glycocalyx include all of the following EXCEPT?

Accepted Answer

Answer reason: The glycocalyx (capsule/slime layer) is an external polysaccharide/protein layer that primarily supports adherence and protection rather than cell division. It promotes attachment to surfaces and to other bacteria, enabling biofilm formation and contributing to persistence in hosts and on devices. It can increase virulence by helping organisms evade phagocytosis and resist environmental stresses such as desiccation, reducing dehydration risk. Binary fission is a reproductive process driven by DNA replication and cell wall/membrane division machinery, not a function of the glycocalyx.

Question 7

Which of the following is NOT a functionally analogous pair?

Accepted Answer

Answer reason: Thylakoids are internal membrane stacks within chloroplasts where the light-dependent reactions of photosynthesis occur, so they are a substructure of the chloroplast rather than a distinct counterpart in another organism. In contrast, nucleus vs nucleoid and eukaryotic 9+2 flagella vs bacterial flagella represent different structures serving similar overarching functions (genetic storage/organization and motility, respectively). Therefore this pair is not analogous; it is a whole organelle paired with one of its own components.

Question 8

Where are phospholipids most likely found in a eukaryotic cell?

Accepted Answer

Answer reason: In eukaryotic cells, this bilayer composition applies to the plasma membrane and to the membranes that enclose many organelles (e.g., nucleus, mitochondria, ER). Eukaryotic flagella are membrane-bound extensions of the cell surface, so their outer covering is continuous with the cell membrane and contains phospholipids. Ribosomes are ribonucleoprotein particles without a lipid bilayer, making them an incorrect location for phospholipids.

Question 9

Epstein-Barr virus has been implicated in all of the following EXCEPT?

Accepted Answer

Answer reason: EBV primarily infects B lymphocytes and is classically associated with infectious mononucleosis and several malignancies through latent infection and oncogenic effects. It has strong epidemiologic and mechanistic links to Burkitt's lymphoma (especially endemic forms), nasopharyngeal carcinoma, and a subset of Hodgkin lymphoma. In contrast, infective endocarditis is most commonly due to bacteria (e.g., Staphylococcus aureus, viridans streptococci, enterococci) and is not a typical EBV-associated disease. Therefore, this is the best exception among the listed conditions.

Question 10

The symptoms of gas gangrene are due to all of the following EXCEPT?

Accepted Answer

Answer reason: Exotoxins (e.g., lecithinase/alpha toxin) drive hemolysis and necrosis, while proteolytic enzymes and hyaluronidase facilitate invasion through tissue planes. Microbial fermentation in devitalized, anaerobic tissue produces gas, leading to crepitus and tissue distention. Endocarditis is an infection of the heart valves and is not a pathogenic mechanism producing the local tissue findings of gas gangrene, making it the exception.

Question 11

Which of the following is NOT typically treated with penicillin?

Accepted Answer

Answer reason: g., streptomycin or gentamicin) rather than penicillin because this pathogen is not reliably susceptible to penicillin-class antibiotics. Penicillin is commonly used for prophylaxis/treatment of susceptible streptococcal infections, which underlies prevention of rheumatic fever. Penicillin also has established roles against several penicillin-susceptible organisms involved in soft-tissue/wound infections, and it is a standard option for rat-bite fever (Streptobacillus moniliformis). Therefore, among the options listed, tularemia is the one not typically treated with penicillin.

Question 12

Which of the following is NOT a recognized form of anthrax?

Accepted Answer

Answer reason: Recognized clinical syndromes of Bacillus anthracis infection are classically categorized by route of entry: cutaneous, inhalational, and gastrointestinal. Systemic spread with bacteremia and severe toxemia can present as septicemia/septic shock and is a recognized manifestation/complication of anthrax rather than a separate, incorrect entity. Because each listed term corresponds to a known presentation (or systemic form) of anthrax, no single option A–D is “not recognized.” Therefore the best answer is that none of A–D is incorrect.

Question 13

Which of the following is the same for both relapsing fever and undulant fever?

Accepted Answer

Answer reason: Relapsing fever (typically Borrelia) shows recurrent febrile episodes separated by afebrile intervals, while undulant fever (brucellosis) classically produces an “undulating” rise and fall in temperature over time. In contrast, their transmission routes and reservoirs differ (arthropod-borne Borrelia vs zoonotic Brucella from animals/unpasteurized dairy), and rash is not a shared defining feature. Therefore, the common feature tested is the fluctuating fever pattern.

Question 14

Which of the following pairs is mismatched?

Accepted Answer

Answer reason: Pasteurella multocida is instead most associated with cellulitis and soft-tissue infection after animal bites or scratches (especially cats and dogs), not the typical lymphadenitis syndrome of cat-scratch disease. The other pairings are standard: Borrelia with relapsing fever, Yersinia pestis with plague, and both Streptobacillus moniliformis and Spirillum minus as causes of rat-bite fever. Therefore, the Pasteurella pairing is the mismatch.

Question 15

You advise your pregnant friend to not adopt a new kitten from her neighbor because she could contract?

Accepted Answer

Answer reason: Pregnancy increases the clinical importance of certain zoonotic infections because transplacental transmission can cause severe fetal harm. Cats, especially kittens, can shed Toxoplasma gondii oocysts in feces, and exposure during litter handling is a classic route of maternal infection. Primary infection in pregnancy can lead to congenital toxoplasmosis with complications such as chorioretinitis, hydrocephalus, and intracranial calcifications. Listeriosis is more linked to contaminated foods (e.g., unpasteurized dairy, deli meats) rather than kitten exposure, making it a less fitting choice in this context.

Question 16

Scrapings from a patient's rash reveal cercariae. The disease is most likely?

Accepted Answer

Answer reason: Cercariae are the free-swimming larval form of schistosomes that penetrate human skin after freshwater exposure, causing a pruritic papular dermatitis. Finding cercariae in skin scrapings points to cercarial dermatitis rather than a bacterial or rickettsial rash. Tick-borne illnesses like Lyme disease and Rocky Mountain spotted fever do not involve cercariae and would not show larval parasites on scraping. Chagas disease is due to Trypanosoma cruzi transmitted by triatomine bugs and is not characterized by cercarial skin invasion.

Question 17

All of the following are gram-negative rods that cause gastroenteritis EXCEPT?

Accepted Answer

Answer reason: The key principle is that Enterobacterales and related enteric pathogens (e.g., E. coli, Salmonella, Shigella, Yersinia) are gram-negative rods commonly implicated in infectious gastroenteritis. Clostridium perfringens is instead a gram-positive, spore-forming anaerobic bacillus, so it does not fit the “gram-negative rods” category even though it can cause foodborne diarrhea. The other listed organisms are classic gram-negative bacilli associated with diarrheal illness or enteric infection. Therefore, the exception is the only organism that is not gram-negative.

Question 18

Helicobacter pylori can grow in the stomach because it?

Accepted Answer

Answer reason: H. pylori survives gastric acidity primarily by producing urease, which converts urea into ammonia and carbon dioxide, creating a locally alkaline microenvironment. This buffering effect protects the organism from acid-mediated killing and allows colonization of the gastric mucous layer. A capsule is not the key mechanism for acid survival in this organism, and it does not produce gastric acid. While it can adhere to and damage gastric epithelium, the defining adaptation that permits growth in the stomach is its acid-neutralizing enzymatic activity.

Question 19

Which of the following statements about salmonellosis is FALSE?

Accepted Answer

Answer reason: Salmonellosis is typically a self-limited bacterial gastroenteritis in immunocompetent hosts, with low overall mortality when managed with hydration and supportive care. The inoculum size and host factors (e.g., gastric acidity, immune status) influence symptom severity and likelihood of invasive disease, making the dose–response concept valid. Asymptomatic carriage can occur, and some individuals shed organisms after clinical recovery, supporting the existence of a carrier state. High mortality is not characteristic of routine non-typhoidal salmonellosis; deaths are more associated with severe invasive infection in infants, older adults, or immunocompromised patients, not the usual presentation.

Question 20

The most common mode of HAV transmission is?

Accepted Answer

Answer reason: HAV is transmitted primarily by the fecal–oral route, most often through close person-to-person spread or ingestion of food contaminated by infected handlers. Food can become contaminated when an infected person prepares food without adequate hand hygiene after toileting, making this a classic and common transmission pathway. Parenteral exposures like transfusion or needle contamination are typical concerns for hepatitis B and C rather than hepatitis A. Airborne spread is not a recognized route for HAV.

Question 21

The most common route of central nervous system invasion by pathogens is through?

Accepted Answer

Answer reason: Hematogenous spread is the predominant mechanism by which many pathogens reach the CNS, typically after a primary infection in the respiratory tract or other tissues. Once in the bloodstream, organisms can cross the blood–brain barrier or blood–CSF barriers (e.g., at the choroid plexus) and seed the meninges or brain parenchyma, producing meningitis or encephalitis. This route explains why bacteremia and viremia are major risk factors for CNS infection and why blood cultures can be diagnostic in suspected meningitis. In contrast, direct neural spread is classically associated with a smaller set of pathogens (e.g., rabies, HSV along peripheral nerves) and is not the most common overall route.

Question 22

The most effective control of mosquito-borne disease is?

Accepted Answer

Answer reason: Vector-borne transmission is best controlled by interrupting the vector stage of the pathogen’s life cycle. Reducing or eliminating mosquitoes lowers human exposure and breaks ongoing transmission regardless of the reservoir host. Treating infected humans may help some diseases but does not prevent new bites from infected vectors and is often impractical for population-level control. Avoiding endemic areas is an individual preventive strategy, not the most effective public health control measure.

Question 23

Microscopic examination of cerebrospinal fluid reveals gram-positive rods. What is the organism?

Accepted Answer

Answer reason: The other common bacterial meningitis organisms on the list have different Gram stain morphology: Haemophilus and Neisseria are gram-negative, and Streptococcus are gram-positive cocci rather than rods. Naegleria is a free-living amoeba and would not appear as gram-positive rods on a standard Gram stain. Therefore, the described microscopic finding best matches Listeria.

Question 24

Which of the following is/are a free-living amoeba that can cause encephalitis?

Accepted Answer

Answer reason: Naegleria species (classically N. fowleri) cause primary amoebic meningoencephalitis after warm freshwater exposure with nasal inoculation. Acanthamoeba species are also free-living and can cause granulomatous amoebic encephalitis, especially in immunocompromised hosts, and are also associated with keratitis. Entamoeba is primarily an intestinal parasite associated with dysentery and liver abscess rather than being a typical free-living CNS pathogen, making the combined Naegleria-plus-Acanthamoeba option the best answer.

Question 25

The prodromal (i.e. pre-acute disease stage)symptoms of bacterial meningitis is/are?

Accepted Answer

Answer reason: Prodromal manifestations are the early, nonspecific symptoms that occur before classic meningeal irritation is fully established. Early bacterial meningitis commonly begins with systemic inflammatory signs such as fever and a generalized headache. Nuchal rigidity/stiff neck is a hallmark sign that more strongly reflects established meningeal irritation rather than the earliest prodrome. Seizures/convulsions are potential later complications and would not be expected as typical pre-acute symptoms.

Question 26

The patient has a sore throat. What is the etiology of the symptoms?

Accepted Answer

Answer reason: A sore throat (pharyngitis) is a non-specific symptom that can be caused by multiple pathogens, most commonly viruses but also bacteria. The stem provides no distinguishing findings (e.g., fever, cough, rhinorrhea, exudates, tender anterior cervical nodes, pseudomembrane, or characteristic cough pattern) and no testing information (rapid strep, throat culture). Because the listed organisms are associated with different syndromes and sore throat can occur across several of them, selecting any single pathogen would be unsupported. The safest, most evidence-based choice is to recognize the information is insufficient to determine a specific etiology.

Question 27

The patient is suffocating because of an inflamed epiglottis. What is the etiology of the symptoms?

Accepted Answer

Answer reason: This organism is a key respiratory pathogen targeted by the Hib vaccine and is strongly associated with abrupt onset fever, sore throat, drooling, and tripod positioning. Corynebacterium diphtheriae more typically causes a pseudomembranous pharyngitis, not primary epiglottic swelling. Bordetella causes pertussis, Mycobacterium is linked to tuberculosis, and RSV is a common cause of bronchiolitis rather than isolated epiglottitis.

Question 28

Which of the following is mismatched?

Accepted Answer

Answer reason: Classic clinical teaching emphasizes high fever, toxic appearance, drooling, dysphagia, muffled “hot potato” voice, and inspiratory stridor, often with minimal or absent oropharyngeal findings. By contrast, pharyngitis is directly characterized by sore throat, and laryngitis commonly presents with hoarseness or voice loss. Therefore this pairing is the least accurate match compared with the other symptom-disease associations listed.

Question 29

Which of the following is mismatched?

Accepted Answer

Answer reason: Therefore pairing Q fever with “Rickettsia” is not the accurate organism match. The other pairs are standard associations: epiglottitis classically with Haemophilus influenzae type b, psittacosis with Chlamydia (C. psittaci), whooping cough with Bordetella (B. pertussis), and melioidosis with Burkholderia (B. pseudomallei). This makes the Q fever pairing the single best mismatch.

Question 30

Which of the following does NOT cause otitis media?

Accepted Answer

Answer reason: Streptococcus pneumoniae, Haemophilus influenzae (nontypeable), and Moraxella catarrhalis are the major typical pathogens, and Streptococcus pyogenes is a recognized (though less common) cause. Coxiella burnetii is an obligate intracellular organism associated with Q fever (often atypical pneumonia, hepatitis, and endocarditis risk), not routine middle-ear infections. Therefore it is the best choice for an organism that does not cause otitis media.

Question 31

Which of the following etiologic agents results in the formation of abscesses?

Accepted Answer

Answer reason: Staphylococci (especially S. aureus) produce enzymes and toxins that promote tissue destruction and walled-off suppurative infection, making them a prototypical cause of abscesses in skin and deep tissues. In contrast, Mycoplasma more often causes atypical pneumonia without purulent abscess formation, and Streptococcus more commonly causes diffuse spreading infections (e.g., cellulitis) rather than well-circumscribed abscesses. The fungal options can cause pulmonary disease and dissemination but are not the classic single best association for abscess formation tested at this level.

Question 32

Infection by which of the following is often confused with viral pneumonia?

Accepted Answer

Answer reason: The organism does not have a cell wall and tends to cause less lobar consolidation than typical bacterial pathogens, contributing to the “viral-like” clinical picture. In contrast, Streptococcus pneumoniae more often produces abrupt high fever and lobar consolidation typical of bacterial pneumonia. Fungal pneumonias (Blastomyces, Coccidioides) and tuberculosis (Mycobacterium) usually have distinct epidemiologic or chronic features that make them less commonly mistaken for routine viral pneumonia.

Question 33

Which of the following diseases has a cutaneous form, especially in individuals over 30 years of age?

Accepted Answer

Answer reason: Coccidioidomycosis (Coccidioides spp.) is a respiratory-acquired dimorphic fungal infection that can disseminate and present with cutaneous lesions, and disseminated disease is reported more commonly in older adults and other higher-risk groups. The other listed respiratory infections are not classically described as having a distinct “cutaneous form” as a typical clinical variant. A common distractor is scarlet fever, which causes a rash from toxin-mediated streptococcal pharyngitis but is not a cutaneous form of a respiratory pathogen in the same sense as disseminated coccidioidomycosis.

Question 34

Microscopic examination of a lung biopsy shows spherules. What is the etiology of the symptoms?

Accepted Answer

Answer reason: This finding distinguishes it from other endemic dimorphic fungi, which are typically described as yeasts (e.g., broad-based budding for Blastomyces, small intracellular yeasts for Histoplasma). Mycobacteria would be suggested by acid-fast bacilli and granulomatous inflammation rather than spherules. Pneumocystis is characterized by cysts on special stains (e.g., silver stain) and foamy alveolar exudates, not tissue spherules.

Question 35

Which of the following is likely to spread MRSA among athletes?

Accepted Answer

Answer reason: MRSA commonly spreads via direct skin-to-skin contact and through contaminated objects (fomites), especially in settings with crowding and frequent minor skin breaks. Athletic environments facilitate transmission through close physical contact during play and through shared equipment that can carry bacteria between users if not properly disinfected. Shared wet environments such as whirlpool baths can increase exposure risk when skin is macerated or has abrasions, allowing easier inoculation. Products applied by multiple people or from contaminated containers (e.g., taping gels) can also serve as a fomite when hygiene and single-use practices are not followed.

Question 36

All of the following are protective factors of the skin and its secretions EXCEPT?

Accepted Answer

Answer reason: Innate skin defenses include physical barriers and antimicrobial components in secretions that reduce microbial survival on the surface. Keratin and tightly packed epithelial cells provide a tough, intact barrier to entry, while salt in sweat creates an unfavorable (hypertonic) environment for many microbes. Lysozyme is a host enzyme found in some body secretions that can damage bacterial cell walls. Pyocyanin, in contrast, is a pigment/virulence-associated product of Pseudomonas aeruginosa rather than a normal protective factor produced by human skin.

Question 37

All of the following are causative agents of conjunctivitis EXCEPT?

Accepted Answer

Answer reason: Conjunctivitis is most commonly caused by adenovirus (viral) and several bacteria, and classic exam etiologies include Chlamydia trachomatis, Neisseria gonorrhoeae, and Haemophilus influenzae. These organisms are well-established causes of acute, hyperacute, or chronic conjunctival infection in different age groups and clinical contexts (e.g., neonatal, sexually transmitted, community-acquired). Herpes simplex more characteristically causes keratitis (corneal involvement) and blepharoconjunctivitis, with clinical concern for dendritic corneal lesions rather than being a typical primary conjunctivitis pathogen in standard lists. Thus, among the options, it is the best “EXCEPT” choice compared with the classic conjunctivitis agents.

Question 38

Which of the following are incorrectly matched?

Accepted Answer

Answer reason: Fever blisters (herpes labialis) are caused by herpes simplex virus, most commonly HSV-1, not by poxviruses. Poxviruses are more associated with diseases like molluscum contagiosum or (historically) smallpox, which present differently from recurrent labial vesicles. The other pairings are standard: varicella-zoster virus causes chickenpox, parvovirus B19 causes fifth disease, and HHV-6 causes roseola.

Question 39

One form of NGU is lymphogranuloma venereum caused by?

Accepted Answer

Answer reason: Lymphogranuloma venereum is a sexually transmitted infection caused by Chlamydia trachomatis (typically serovars L1–L3) and can present with transient genital lesions followed by painful inguinal lymphadenopathy. NGU refers to urethritis not caused by gonorrhea, and chlamydia is the classic bacterial cause of NGU. Neisseria gonorrhoeae instead causes gonococcal urethritis (GU), not NGU. The other organisms listed are associated with different diseases (leptospirosis, syphilis, and candidiasis) and do not cause LGV.

Question 40

All of the following can cause congenital infection or infections of the newborn EXCEPT?

Accepted Answer

Answer reason: Congenital and neonatal infections classically result from pathogens that can cross the placenta (e.g., Treponema pallidum) or infect the infant during delivery (e.g., Neisseria gonorrhoeae and HSV). These organisms have well-established vertical transmission pathways and recognized neonatal disease syndromes (e.g., congenital syphilis, ophthalmia neonatorum, neonatal herpes). “Nongonococcal urethritis” is a clinical syndrome rather than a single vertically transmitted pathogen diagnosis, and it is not classically listed as a specific cause of congenital infection/newborn infection in the way the other named STIs are. By contrast, the other options denote specific infections with clear neonatal implications and screening/prophylaxis relevance.

Question 41

Which of the following is diagnosed by detection of antibodies against the causative agent?

Accepted Answer

Answer reason: Screening is typically done with nontreponemal antibody tests (e.g., RPR/VDRL) followed by confirmatory treponemal antibody assays, making antibody detection central to diagnosis. In contrast, gonorrhea and many causes of nongonococcal urethritis are usually diagnosed by direct detection (NAAT) rather than serology. Candidiasis is generally diagnosed by microscopy/culture or clinical findings rather than antibody testing.

Question 42

Nongonococcal urethritis can be caused by all of the following EXCEPT?

Accepted Answer

Answer reason: Nongonococcal urethritis (NGU) is defined as urethral inflammation not caused by gonorrhea, so the organism responsible for gonorrhea is excluded by definition. Neisseria gonorrhoeae is the classic cause of gonococcal urethritis and therefore cannot be a cause of NGU. In contrast, a range of other pathogens can produce urethritis presentations that are clinically similar but not due to gonorrhea (including atypical bacteria and certain protozoa/fungi). The key test-taking move is to recognize the term “nongonococcal” as an etiologic exclusion rather than a symptom description.

Question 43

The pH of the adult vagina is acidic due to the conversion of _____ to _____ by bacteria?

Accepted Answer

Answer reason: Estrogen increases glycogen deposition in vaginal epithelial cells, and this glycogen becomes substrate for bacterial metabolism. Conversion of glycogen-derived sugars into lactic acid acidifies the vaginal environment, inhibiting overgrowth of many pathogens. Options involving ethanol, acetic acid from protein, or lactic acid derived from urine/mucosal cells do not reflect the primary physiologic mechanism of vaginal acidity.

Question 44

Which of the following is NOT primarily a sexually transmitted infection (STI)?

Accepted Answer

Answer reason: Genital herpes (HSV-2/HSV-1), gonorrhea (Neisseria gonorrhoeae), chancroid (Haemophilus ducreyi), and trichomoniasis (Trichomonas vaginalis) are classically taught as common STIs with sexual transmission as the dominant mode. Lymphogranuloma venereum is caused by Chlamydia trachomatis (L1–L3) and is often categorized as an STI as well, but it is less commonly emphasized as a primary STI in basic STI lists compared with the other options and may be presented as a distinct invasive chlamydial syndrome. On many exam frameworks, the remaining four are the prototypical “primary STI” pathogens, making this option the best fit for the exception prompt. If forced to choose, the others are more straightforwardly and commonly recognized as primarily sexually transmitted.

Question 45

Which one of the following does NOT cause nongonococcal urethritis?

Accepted Answer

Answer reason: Common causes of NGU include Chlamydia trachomatis, Mycoplasma genitalium, and Ureaplasma urealyticum. Therefore, the organism genus most directly associated with gonococcal urethritis is the one that does not fit NGU. A frequent distractor is assuming any STI can cause NGU, but the “non-gonococcal” label specifically rules out gonococci.

Question 46

Recurring vesicles on the surface of human skin are symptoms of?

Accepted Answer

Answer reason: Recurrent clusters of painful vesicles are a classic manifestation of herpes simplex virus infection due to lifelong latency in sensory ganglia with periodic reactivation. This produces episodic, grouped vesicular lesions on skin or mucosa that can ulcerate and recur. In contrast, Gardnerella vaginosis, candidiasis, and trichomoniasis primarily cause vaginitis with discharge/itching rather than vesicular skin lesions. Lymphogranuloma venereum typically presents with transient painless ulcers and then tender inguinal lymphadenopathy, not recurring vesicles.

Question 47

Pyelonephritis usually is caused by?

Accepted Answer

Answer reason: Ascending infection from the lower urinary tract is the most common pathogenesis of acute pyelonephritis, and the dominant uropathogen in community-acquired disease is enteric gram-negative flora. This organism adheres well to uroepithelium via fimbriae, facilitating ascent to the renal pelvis and parenchyma. Other listed gram-negative organisms (e.g., Proteus, Pseudomonas, Enterobacter) can cause pyelonephritis but are comparatively more associated with complicated or healthcare-associated UTIs and are less common overall. Group A streptococcus is not a typical uropathogen for pyelonephritis, making it a poor fit compared with the leading cause.

Question 48

A 25-year-old man presented with fever, malaise, and a rash on his chest, arms, and feet. Which of the following causative agents is most likely to cause these symptoms?

Accepted Answer

Answer reason: This constellation strongly points to Treponema pallidum as the etiologic agent. HPV typically causes genital warts without an acute febrile prodrome or widespread rash, and Candida causes localized mucocutaneous infection rather than a generalized rash with constitutional symptoms. A rash on the extremities including the feet is a high-yield clue for secondary syphilis in STI differentials.

Question 49

The damage caused by ultraviolet radiation is?

Accepted Answer

Answer reason: UV light commonly causes pyrimidine (thymine) dimers in DNA, which distort the helix and block normal replication and transcription. The primary high-fidelity correction is nucleotide excision repair, in which the damaged segment is removed and the gap is filled in using the intact strand as a template, then sealed by ligase. This matches the concept of excising the lesion and replacing the nucleotides. Options describing repair during transcription/translation are incorrect because translation does not repair DNA and transcription-coupled repair is a specialized subset but still relies on excision and resynthesis rather than being “during” transcription as the core mechanism.

Question 50

The initial effect of ionizing radiation on a cell is that it causes?

Accepted Answer

Answer reason: Ionizing radiation primarily acts by ejecting electrons from atoms and molecules, producing ions and free radicals (especially via radiolysis of water). These highly reactive species then attack cellular macromolecules, leading secondarily to DNA strand breaks and other lesions. Thymine dimers are classically a direct effect of nonionizing UV radiation rather than ionizing radiation. Heat production is not the relevant biologic mechanism of ionizing radiation injury in cells.

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Restriction enzymes are?

The study of genetic material taken directly from the environment is?

A clone is?

The terms "run" and "tumble" are generally associated with?

The DNA found in most bacterial cells?

Functions of the glycocalyx include all of the following EXCEPT?

Which of the following is NOT a functionally analogous pair?

Where are phospholipids most likely found in a eukaryotic cell?

Epstein-Barr virus has been implicated in all of the following EXCEPT?

The symptoms of gas gangrene are due to all of the following EXCEPT?

Which of the following is NOT typically treated with penicillin?

Which of the following is NOT a recognized form of anthrax?

Which of the following is the same for both relapsing fever and undulant fever?

Which of the following pairs is mismatched?

You advise your pregnant friend to not adopt a new kitten from her neighbor because she could contract?

Scrapings from a patient's rash reveal cercariae. The disease is most likely?

All of the following are gram-negative rods that cause gastroenteritis EXCEPT?

Helicobacter pylori can grow in the stomach because it?

Which of the following statements about salmonellosis is FALSE?

The most common mode of HAV transmission is?

The most common route of central nervous system invasion by pathogens is through?

The most effective control of mosquito-borne disease is?

Microscopic examination of cerebrospinal fluid reveals gram-positive rods. What is the organism?

Which of the following is/are a free-living amoeba that can cause encephalitis?

The prodromal (i.e. pre-acute disease stage)symptoms of bacterial meningitis is/are?

The patient has a sore throat. What is the etiology of the symptoms?

The patient is suffocating because of an inflamed epiglottis. What is the etiology of the symptoms?

Which of the following is mismatched?

Which of the following is mismatched?

Which of the following does NOT cause otitis media?

Which of the following etiologic agents results in the formation of abscesses?

Infection by which of the following is often confused with viral pneumonia?

Which of the following diseases has a cutaneous form, especially in individuals over 30 years of age?

Microscopic examination of a lung biopsy shows spherules. What is the etiology of the symptoms?

Which of the following is likely to spread MRSA among athletes?

All of the following are protective factors of the skin and its secretions EXCEPT?

All of the following are causative agents of conjunctivitis EXCEPT?

Which of the following are incorrectly matched?

One form of NGU is lymphogranuloma venereum caused by?

All of the following can cause congenital infection or infections of the newborn EXCEPT?

Which of the following is diagnosed by detection of antibodies against the causative agent?

Nongonococcal urethritis can be caused by all of the following EXCEPT?

The pH of the adult vagina is acidic due to the conversion of _____ to _____ by bacteria?

Which of the following is NOT primarily a sexually transmitted infection (STI)?

Which one of the following does NOT cause nongonococcal urethritis?

Recurring vesicles on the surface of human skin are symptoms of?

Pyelonephritis usually is caused by?

A 25-year-old man presented with fever, malaise, and a rash on his chest, arms, and feet. Which of the following causative agents is most likely to cause these symptoms?

The damage caused by ultraviolet radiation is?

The initial effect of ionizing radiation on a cell is that it causes?

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The pH of the adult vagina is acidic due to the conversion of _ to _ by bacteria?