Microbiology

Arthropods and Parasites (1-20)

Q: What organism causes scabies?
A: Sarcoptes scabiei.
Q: What skin finding is characteristic of scabies?
A: Linear burrows or red dots.
Q: What is the primary treatment for scabies?
A: Topical permethrin.
Q: Name a complication that can arise from scabies.
A: Bacterial superinfection with S. aureus.
Q: What is the medical term for head lice?
A: Pediculosis capitis.
Q: What is the causative organism of bed bugs?
A: Cimex lectularius.
Q: What clinical presentation is typical for bed bug bites?
A: Itchy clusters of erythematous lesions.
Q: Which parasite is known to cause river blindness?
A: Onchocerca volvulus.
Q: How is Onchocerca volvulus transmitted?
A: By the bite of the blackfly.
Q: What is the preferred treatment for lice infestations?
A: Topical permethrin.
Q: Name an arthropod that can cause Lyme disease.
A: Ixodes tick.
Q: Which organism causes Lyme disease?
A: Borrelia burgdorferi.
Q: What is the vector for Trypanosoma cruzi (Chagas disease)?
A: Reduviid bug.
Q: Which worm causes elephantiasis?
A: Wuchereria bancrofti.
Q: What is the vector for Wuchereria bancrofti?
A: Mosquito.
Q: What condition does Leishmania donovani cause?
A: Visceral leishmaniasis.
Q: What is the treatment for visceral leishmaniasis?
A: Liposomal amphotericin B.
Q: What is the characteristic presentation of a hookworm infection?
A: Iron-deficiency anemia due to blood loss from the gut.
Q: Which parasite is associated with hydatid cysts?
A: Echinococcus granulosus.
Q: How is Echinococcus granulosus typically contracted?
A: Through contact with dog feces containing eggs.

Viral Infections (21-60)

Q: What virus causes Fifth disease in children?
A: Parvovirus B19.
Q: What is the appearance of Fifth disease?
A: "Slapped cheek" rash.
Q: What strain of HPV is associated with genital warts?
A: HPV 6 and 11.
Q: Which strains of HPV are most commonly associated with cervical cancer?
A: HPV 16 and 18.
Q: What condition is caused by JC virus reactivation in immunocompromised individuals?
A: Progressive multifocal leukoencephalopathy (PML).
Q: Which virus is the most common cause of viral conjunctivitis?
A: Adenovirus.
Q: How is Hepatitis B transmitted?
A: Via blood, sexual contact, and vertical transmission.
Q: What serological marker indicates immunity to Hepatitis B?
A: HBsAb (Hepatitis B surface antibody).
Q: What virus causes roseola in children?
A: Human herpesvirus 6 (HHV-6).
Q: Describe the typical presentation of roseola.
A: High fever followed by a maculopapular rash.
Q: What virus is responsible for causing infectious mononucleosis?
A: Epstein-Barr virus (EBV).
Q: What are atypical lymphocytes in mononucleosis?
A: Reactive CD8+ T cells.
Q: What virus is linked with Kaposi sarcoma in AIDS patients?
A: Human herpesvirus 8 (HHV-8).
Q: What are "owl-eye" inclusions characteristic of?
A: Cytomegalovirus (CMV).
Q: What viral infection presents with vesicular lesions in a dermatomal pattern?
A: Herpes zoster (shingles).
Q: What does the presence of HBeAg indicate in a Hepatitis B infection?
A: Active viral replication and high infectivity.
Q: Which herpesvirus is associated with nasopharyngeal carcinoma?
A: Epstein-Barr virus (EBV).
Q: What is the treatment for severe CMV infections?
A: Ganciclovir.
Q: What is the most common cause of congenital viral infections?
A: Cytomegalovirus (CMV).
Q: What is the treatment for herpes encephalitis?
A: Intravenous acyclovir.
Q: Which virus causes "slapped cheek" disease in children?
A: Parvovirus B19.
Q: What are the long-term complications of untreated Hepatitis B?
A: Cirrhosis and hepatocellular carcinoma.
Q: What are Negri bodies?
A: Eosinophilic cytoplasmic inclusions found in rabies infection.
Q: What is a common complication of mumps virus infection?
A: Orchitis.
Q: What is a severe complication of measles?
A: Subacute sclerosing panencephalitis (SSPE).
Q: What does a positive Monospot test indicate?
A: Epstein-Barr virus infection.
Q: How is Zika virus transmitted?
A: By mosquitoes (Aedes species).
Q: Which RNA virus is known for causing hemorrhagic fever?
A: Ebola virus.
Q: What is the characteristic histopathologic finding in rabies infection?
A: Negri bodies.
Q: Which virus can cause encephalitis in neonates through vertical transmission?
A: Herpes simplex virus (HSV).
Q: What is the treatment for respiratory syncytial virus (RSV) in infants?
A: Ribavirin.
Q: What virus causes erythema infectiosum?
A: Parvovirus B19.
Q: What serological marker indicates a window period in Hepatitis B infection?
A: Positive HBcAb IgM with negative HBsAg and HBsAb.
Q: What is the primary treatment for Kaposi sarcoma?
A: Antiretroviral therapy (for HIV-associated cases).
Q: What virus is associated with Burkitt lymphoma?
A: Epstein-Barr virus (EBV).
Q: What viral infection is characterized by Koplik spots?
A: Measles.
Q: What virus causes chickenpox?
A: Varicella-zoster virus (VZV).
Q: What is the most common cause of viral pneumonia in adults?
A: Influenza virus.
Q: How does rotavirus primarily affect infants?
A: Causes severe diarrhea.
Q: What virus is transmitted via blood transfusion and causes mononucleosis-like symptoms?
A: Cytomegalovirus (CMV).

Bacterial Infections (61-100)

Q: What are the three major virulence factors of Streptococcus pneumoniae?
A: Capsule, IgA protease, and pneumolysin.
Q: What bacterial infection presents with a "strawberry tongue"?
A: Scarlet fever (caused by Streptococcus pyogenes).
Q: What is the treatment for Neisseria gonorrhoeae infection?
A: Intramuscular ceftriaxone plus oral azithromycin.
Q: What pathogen is associated with "rice-water stool"?
A: Vibrio cholerae.
Q: Which bacteria cause "wool-sorter's disease"?
A: Bacillus anthracis.
Q: What is the main virulence factor of Staphylococcus aureus?
A: Protein A.
Q: What is the preferred treatment for MRSA?
A: Vancomycin.
Q: How does Clostridium botulinum toxin cause paralysis?
A: Inhibits acetylcholine release at the neuromuscular junction.
Q: What are the classic symptoms of tetanus?
A: Trismus (lockjaw), opisthotonos, and muscle spasms.
Q: What is the treatment for diphtheria?
A: Antitoxin plus antibiotics (penicillin or erythromycin).
Q: What organism is responsible for toxic shock syndrome?
A: Staphylococcus aureus.
Q: What is the characteristic lesion in cutaneous anthrax?
A: Black eschar with surrounding edema.
Q: Which bacteria produce spores?
A: Clostridium and Bacillus species.
Q: What is the first-line treatment for streptococcal pharyngitis?
A: Penicillin.
Q: Which bacteria is associated with gas gangrene?
A: Clostridium perfringens.
Q: What antibiotic is used to treat Clostridium difficile infection?
A: Oral vancomycin.
Q: What causes neonatal meningitis?
A: Group B Streptococcus, Listeria monocytogenes, and E. coli.
Q: What organism is associated with a "school of fish" arrangement on microscopy?
A: Haemophilus ducreyi (chancroid).
Q: How is Helicobacter pylori infection diagnosed?
A: Urea breath test or stool antigen test.
Q: What is the causative agent of syphilis?
A: Treponema pallidum.
Q: What is the hallmark finding in primary syphilis?
A: Painless chancre.
Q: What pathogen is associated with Pontiac fever and Legionnaires' disease?
A: Legionella pneumophila.
Q: What bacteria causes whooping cough?
A: Bordetella pertussis.
Q: What is the treatment for pertussis?
A: Macrolides, such as azithromycin.
Q: What is the first-line treatment for Lyme disease?
A: Doxycycline.
Q: What is the causative agent of Hansen's disease (leprosy)?
A: Mycobacterium leprae.
Q: What condition does Rickettsia rickettsii cause?
A: Rocky Mountain spotted fever.
Q: What is a common presentation of leptospirosis?
A: Fever, jaundice, and conjunctival suffusion.
Q: What organism causes Q fever?
A: Coxiella burnetii.
Q: What is the treatment for Q fever?
A: Doxycycline.
Q: What pathogen causes a "currant jelly" sputum?
A: Klebsiella pneumoniae.
Q: What bacteria cause atypical pneumonia?
A: Mycoplasma pneumoniae, Chlamydia pneumoniae, Legionella pneumophila.
Q: What is the main cause of lobar pneumonia in adults?
A: Streptococcus pneumoniae.
Q: What is the mechanism of action of the diphtheria toxin?
A: Inhibits protein synthesis by ADP-ribosylating elongation factor 2 (EF-2).
Q: What bacteria is associated with Guillain-Barré syndrome?
A: Campylobacter jejuni.
Q: What is the causative agent of chancroid?
A: Haemophilus ducreyi.
Q: What bacteria is commonly associated with cat bites?
A: Pasteurella multocida.
Q: Which bacterial infection is associated with erythema migrans?
A: Lyme disease.
Q: What is the first-line treatment for Haemophilus influenzae meningitis?
A: Ceftriaxone.
Q: What bacteria causes rheumatic fever?
A: Streptococcus pyogenes.

Fungal Infections (101-140)

Q: What fungus causes tinea versicolor?
A: Malassezia furfur.
Q: Which antifungal is used for tinea versicolor?
A: Topical selenium sulfide.
Q: What is the characteristic appearance of Cryptococcus neoformans on India ink?
A: Encapsulated yeast with a halo.
Q: Which fungus is known for causing "fungus balls" in the lungs?
A: Aspergillus species.
Q: What type of fungal hyphae does Mucorales produce?
A: Non-septate hyphae branching at 90-degree angles.
Q: What is the first-line treatment for invasive candidiasis?
A: Echinocandins (e.g., caspofungin).
Q: Which fungus causes pneumonia in immunocompromised patients and is described as having "silver-stained" cysts?
A: Pneumocystis jirovecii.
Q: What is the primary prophylactic treatment for Pneumocystis jirovecii pneumonia?
A: Trimethoprim-sulfamethoxazole (TMP-SMX).
Q: What condition is caused by Histoplasma capsulatum?
A: Histoplasmosis.
Q: What fungal infection is common in spelunkers?
A: Histoplasmosis.
Q: What is the characteristic budding pattern of Blastomyces dermatitidis?
A: Broad-based budding.
Q: Which fungus is associated with the Ohio-Mississippi river valley?
A: Histoplasma capsulatum.
Q: What is the appearance of Coccidioides immitis on histology?
A: Spherules filled with endospores.
Q: Which fungus presents with "captain's wheel" appearance on microscopy?
A: Paracoccidioides brasiliensis.
Q: What is the treatment for Paracoccidioides brasiliensis infection?
A: Itraconazole or amphotericin B for severe cases.
Q: What fungus is responsible for causing rose gardener's disease?
A: Sporothrix schenckii.
Q: What is the appearance of Sporothrix schenckii in culture?
A: Rosette-like clusters of conidiophores.
Q: What are the clinical features of cryptococcal meningitis?
A: Fever, headache, neck stiffness, and photophobia.
Q: How is cryptococcal meningitis diagnosed?
A: CSF analysis with India ink stain or cryptococcal antigen test.
Q: What is the treatment for invasive aspergillosis?
A: Voriconazole.
Q: What is the preferred treatment for oropharyngeal candidiasis?
A: Nystatin mouthwash.
Q: Which fungal infection is characterized by hypopigmented patches on the skin?
A: Tinea versicolor.
Q: What fungus is associated with bat and bird droppings?
A: Histoplasma capsulatum.
Q: What fungal species causes diaper rash?
A: Candida albicans.
Q: What is the first-line treatment for vaginal candidiasis?
A: Fluconazole.
Q: What type of hyphae does Aspergillus form?
A: Septate hyphae with acute-angle branching (45 degrees).
Q: What is the treatment for cutaneous Sporothrix schenckii infection?
A: Itraconazole.
Q: Which fungus causes seborrheic dermatitis?
A: Malassezia furfur.
Q: What is the hallmark sign of Aspergillus otitis externa?
A: Black necrotic tissue in the ear canal.
Q: What fungal infection is most commonly associated with AIDS patients and CD4 counts below 200?
A: Pneumocystis jirovecii pneumonia (PJP).
Q: How is invasive fungal sinusitis commonly acquired?
A: Inhalation of spores by immunocompromised individuals.
Q: What is the main virulence factor of Cryptococcus neoformans?
A: Polysaccharide capsule.
Q: What fungus is commonly found in decaying wood?
A: Blastomyces dermatitidis.
Q: What fungus is associated with valley fever in the Southwestern United States?
A: Coccidioides immitis.
Q: Which fungal pathogen causes pulmonary symptoms similar to tuberculosis?
A: Histoplasma capsulatum.
Q: What condition does Mucorales cause in diabetic patients?
A: Rhinocerebral mucormycosis.
Q: What is the preferred diagnostic test for Pneumocystis jirovecii pneumonia?
A: Bronchoalveolar lavage with silver stain.
Q: Which fungus has narrow-based budding yeast forms?
A: Cryptococcus neoformans.
Q: What is the first-line treatment for fungal meningitis caused by Cryptococcus neoformans?
A: Amphotericin B and flucytosine.
Q: Which fungi are commonly grown on Sabouraud agar?
A: Dermatophytes, Candida, and Cryptococcus.

Gram-Positive and Gram-Negative Bacteria (141-180)

Q: What is the major distinguishing factor between Staphylococcus and Streptococcus species?
A: Catalase production; Staphylococcus is catalase-positive, and Streptococcus is catalase-negative.
Q: Which bacteria are coagulase-positive?
A: Staphylococcus aureus.
Q: What causes bullous impetigo?
A: Staphylococcus aureus.
Q: What is the mechanism of MRSA resistance to methicillin?
A: Altered penicillin-binding protein (PBP2a).
Q: Which bacteria are considered alpha-hemolytic?
A: Streptococcus pneumoniae and Streptococcus viridans.
Q: What bacteria is the most common cause of endocarditis in IV drug users?
A: Staphylococcus aureus.
Q: What bacteria is associated with cat scratch disease?
A: Bartonella henselae.
Q: What are the common causes of neonatal sepsis?
A: Group B Streptococcus, Listeria monocytogenes, E. coli.
Q: What is the appearance of Listeria monocytogenes on microscopy?
A: Gram-positive rod with tumbling motility.
Q: What organism causes diphtheria?
A: Corynebacterium diphtheriae.
Q: What is the treatment for Bacillus anthracis?
A: Ciprofloxacin or doxycycline.
Q: What bacteria cause Lemierre's syndrome?
A: Fusobacterium necrophorum.
Q: Which bacteria are associated with toxic shock-like syndrome?
A: Streptococcus pyogenes.
Q: What infection does Actinomyces israelii cause?
A: Cervicofacial actinomycosis.
Q: What gram-negative rod is associated with burns and hot tubs?
A: Pseudomonas aeruginosa.
Q: What organism causes typhoid fever?
A: Salmonella typhi.
Q: What is the appearance of Shigella on microscopy?
A: Gram-negative rod.
Q: What bacteria is known for causing "rice-water stools"?
A: Vibrio cholerae.
Q: What is the most common cause of otitis media?
A: Streptococcus pneumoniae.
Q: What is the hallmark feature of botulism?
A: Flaccid paralysis.
Q: What is a common cause of food poisoning from reheated rice?
A: Bacillus cereus.
Q: What is the causative agent of pseudomembranous colitis?
A: Clostridium difficile.
Q: What organism causes Q fever?
A: Coxiella burnetii.
Q: What is the first-line treatment for Neisseria meningitidis meningitis?
A: Ceftriaxone.
Q: What bacteria is associated with fish tank granuloma?
A: Mycobacterium marinum.
Q: What is the cause of atypical pneumonia known as "walking pneumonia"?
A: Mycoplasma pneumoniae.
Q: Which bacteria are lactose fermenters on MacConkey agar?
A: Escherichia coli, Klebsiella, Enterobacter.
Q: What is the treatment for H. pylori infection?
A: Triple therapy with a proton pump inhibitor, clarithromycin, and amoxicillin or metronidazole.
Q: What pathogen is known for causing bloody diarrhea and HUS in children?
A: Enterohemorrhagic E. coli (EHEC).
Q: What infection does Brucella cause?
A: Brucellosis.
Q: What bacteria causes Pontiac fever?
A: Legionella pneumophila.
Q: What is the common presentation of Weil's disease?
A: Jaundice, renal failure, and hemorrhage.
Q: What pathogen is associated with necrotizing fasciitis?
A: Streptococcus pyogenes.
Q: Which bacterium causes tularemia?
A: Francisella tularensis.
Q: What bacteria is typically found in the oropharynx and can cause endocarditis?
A: Viridans streptococci.
Q: What is the characteristic lesion in Yersinia pestis infection?
A: Buboes (swollen lymph nodes).
Q: Which bacteria produce blue-green pigment and a fruity odor?
A: Pseudomonas aeruginosa.
Q: What pathogen causes a painful genital ulcer known as chancroid?
A: Haemophilus ducreyi.
Q: What is the characteristic feature of Borrelia burgdorferi?
A: Spirochete morphology.
Q: What infection does Chlamydia trachomatis commonly cause in neonates?
A: Conjunctivitis and pneumonia.

Antibiotics and Resistance Mechanisms (181-200)

Q: What is the mechanism of action of beta-lactam antibiotics?
A: Inhibit cell wall synthesis by binding to penicillin-binding proteins (PBPs).
Q: How do bacteria develop resistance to penicillin?
A: Production of beta-lactamase enzymes.
Q: What is the mechanism of action of vancomycin?
A: Inhibits cell wall synthesis by binding to D-Ala-D-Ala terminus of peptidoglycan precursors.
Q: What antibiotic class targets bacterial DNA gyrase?
A: Fluoroquinolones.
Q: How does Staphylococcus aureus become resistant to methicillin?
A: By acquiring the mecA gene, which alters PBP.
Q: What is the main side effect of aminoglycosides?
A: Ototoxicity and nephrotoxicity.
Q: Which antibiotic class is known to cause tendonitis and tendon rupture?
A: Fluoroquinolones.
Q: What is the mechanism of action of clindamycin?
A: Inhibits protein synthesis by binding to the 50S ribosomal subunit.
Q: Which antibiotic is used for treating vancomycin-resistant Enterococcus (VRE)?
A: Linezolid or daptomycin.
Q: What is the treatment of choice for a MRSA skin infection?
A: Clindamycin, doxycycline, or TMP-SMX.
Q: What is the main adverse effect of metronidazole?
A: Disulfiram-like reaction with alcohol.
Q: What is the first-line treatment for uncomplicated cystitis?
A: Nitrofurantoin or TMP-SMX.
Q: How do macrolides inhibit bacterial growth?
A: By binding to the 50S ribosomal subunit, inhibiting protein synthesis.
Q: What is the mechanism of resistance in carbapenem-resistant Enterobacteriaceae (CRE)?
A: Production of carbapenemase enzymes.
Q: What is the mechanism of action of tetracyclines?
A: Inhibit protein synthesis by binding to the 30S ribosomal subunit.
Q: Which antibiotic is contraindicated in children due to the risk of teeth discoloration?
A: Tetracycline.
Q: What is the treatment for pseudomembranous colitis?
A: Oral vancomycin or fidaxomicin.
Q: What is the major adverse effect of chloramphenicol?
A: Aplastic anemia.
Q: How do sulfonamides work?
A: Inhibit folate synthesis by competing with para-aminobenzoic acid (PABA).
Q: What is the preferred antibiotic for bacterial endocarditis prophylaxis in penicillin-allergic patients?
A: Clindamycin.