Block C - Pathogens of the Circulatory System and Skin Flashcards
Staphylococcus species are classified as:
A) Gram-negative cocci
B) Gram-positive cocci
C) Gram-negative rods
D) Gram-positive rods
B) Gram-positive cocci ✅
Which of the following describes the morphology of Staphylococcus spp.?
A) Single rods
B) Diplococci
C) Chains of cocci
D) Clusters of cocci
D) Clusters of cocci ✅
Staphylococcus species are:
A) Obligate aerobes
B) Obligate anaerobes
C) Facultative anaerobes
D) Microaerophiles
C) Facultative anaerobes ✅
Which Staphylococcus species is associated with golden pigmentation?
A) S. epidermidis
B) S. saprophyticus
C) S. aureus
D) S. lugdunensis
C) S. aureus ✅
Staphylococcus species are part of the normal flora primarily found in which areas?
A) Gut and respiratory tract
B) Skin and mucous membranes
C) Liver and kidneys
D) Blood and cerebrospinal fluid
B) Skin and mucous membranes ✅
Which of the following is a major risk factor for S. aureus infection?
A) Vegan diet
B) Colonisation of the nares
C) High iron levels
D) Daily exercise
B) Colonisation of the nares ✅
Which type of infection is commonly caused by S. aureus?
A) Urinary tract infections
B) Pneumonia
C) Skin and soft tissue infections
D) Brain abscess
C) Skin and soft tissue infections ✅
S. aureus can cause which serious systemic condition?
A) Gastroenteritis
B) Sepsis
C) Common cold
D) Dental caries
B) Sepsis ✅
Which Staphylococcus species is a major cause of healthcare-associated infections (HAIs)?
A) S. saprophyticus
B) S. epidermidis
C) S. haemolyticus
D) S. lugdunensis
B) S. epidermidis ✅
What is the role of Protein A (SpA) in S. aureus pathogenesis?
A) It binds the Fc region of IgG to prevent opsonophagocytosis
B) It enhances bacterial motility
C) It destroys neutrophils directly
D) It functions as a bacterial adhesin
A) It binds the Fc region of IgG to prevent opsonophagocytosis ✅
Which of the following is a key feature of the agr operon in S. aureus?
A) It regulates virulence gene expression via quorum sensing
B) It provides resistance to antibiotics
C) It allows for biofilm formation
D) It inhibits toxin production
A) It regulates virulence gene expression via quorum sensing ✅
What is the function of the toxic shock syndrome toxin (TSST-1)?
A) It blocks neutrophil recruitment
B) It acts as a superantigen, leading to excessive immune activation
C) It inhibits cytokine production
D) It degrades host tissues
B) It acts as a superantigen, leading to excessive immune activation ✅
Which enzyme secreted by S. aureus promotes clot formation?
A) Hemolysin
B) Coagulase
C) Catalase
D) Urease
B) Coagulase ✅
Methicillin resistance in S. aureus is mediated by:
A) The mecA gene encoding PBP2a
B) Beta-lactamase production
C) Increased efflux pump expression
D) Mutations in ribosomal RNA
A) The mecA gene encoding PBP2a ✅
What is the mechanism of vancomycin resistance in VRSA (Vancomycin-resistant S. aureus)?
A) Production of beta-lactamase
B) Modification of peptidoglycan precursors from D-Ala-D-Ala to D-Ala-D-Lac
C) Increased efflux of vancomycin
D) Inhibition of quorum sensing
B) Modification of peptidoglycan precursors from D-Ala-D-Ala to D-Ala-D-Lac ✅
Which mobile genetic element is responsible for methicillin resistance in MRSA strains?
A) Staphylococcus aureus pathogenicity islands (SaPIs)
B) Staphylococcal cassette chromosome mec (SCCmec)
C) Conjugative transposons
D) Integrative plasmids
B) Staphylococcal cassette chromosome mec (SCCmec) ✅
Which of the following best describes how MRSA is classified?
A) Healthcare-associated MRSA (HA-MRSA) and community-associated MRSA (CA-MRSA)
B) Gram-positive MRSA and Gram-negative MRSA
C) Environmental MRSA and zoonotic MRSA
D) Toxin-producing MRSA and non-toxin-producing MRSA
A) Healthcare-associated MRSA (HA-MRSA) and community-associated MRSA (CA-MRSA) ✅
Which of the following contributes to S. aureus evasion of the complement system?
A) Binding to CD4 T cells
B) Secretion of complement inhibitors such as aureolysin
C) Inhibiting host mRNA translation
D) Forming a bacterial capsule
B) Secretion of complement inhibitors such as aureolysin ✅
Which two-component system regulates the production of TSST-1 in S. aureus?
A) AgrBDCA
B) SaeRS
C) PhoPQ
D) CiaRH
B) SaeRS ✅
Which factor enables S. aureus to escape neutrophil extracellular traps (NETs)?
A) Coagulase
B) Nuclease
C) Protein A
D) Enterotoxin
B) Nuclease ✅
Which of the following mobile genetic elements is capable of transferring vancomycin resistance genes?
A) SCCmec
B) Tn1546
C) SaPIs
D) Prophages
B) Tn1546 ✅
What role do bacteriophages play in S. aureus virulence?
A) They integrate virulence genes into the bacterial genome
B) They protect the bacteria from immune attack
C) They assist in biofilm formation
D) They serve as a food source for the bacteria
A) They integrate virulence genes into the bacterial genome ✅
Which of the following is a key challenge in MRSA vaccine development?
A) High genetic variability among MRSA strains
B) Lack of known S. aureus virulence factors
C) Ineffective immune response against surface proteins
D) Antibiotic interference with vaccine efficacy
A) High genetic variability among MRSA strains ✅
Which of the following is a promising target for next-generation MRSA therapies?
A) Quorum sensing inhibitors targeting the agr system
B) Enhanced beta-lactam antibiotics
C) Increased use of broad-spectrum antibiotics
D) Passive immunotherapy with IgE antibodies
A) Quorum sensing inhibitors targeting the agr system ✅
What is the primary function of the agr operon in S. aureus?
A) Regulates biofilm formation
B) Controls virulence factor expression via quorum sensing
C) Encodes antibiotic resistance genes
D) Functions as a structural component of the bacterial cell wall
B) Controls virulence factor expression via quorum sensing ✅
The agr operon is activated by:
A) Autoinducer peptides (AIP) binding to AgrC
B) Low oxygen conditions
C) Host iron levels
D) Direct contact with immune cells
A) Autoinducer peptides (AIP) binding to AgrC ✅
Which small RNA molecule is transcribed as part of agr operon activation and regulates virulence factor expression?
A) RNAI
B) RNAIII
C) rpoS
D) PNPase
B) RNAIII ✅
In which phase of growth does S. aureus upregulate toxin production via agr?
A) Lag phase
B) Early exponential phase
C) Late exponential/stationary phase
D) Death phase
C) Late exponential/stationary phase ✅
Which of the following is a major factor in S. aureus biofilm formation?
A) Protein A
B) Polysaccharide intercellular adhesin (PIA)
C) Alpha-toxin
D) Lipoteichoic acid
B) Polysaccharide intercellular adhesin (PIA) ✅
How do biofilms contribute to antibiotic resistance?
A) They increase the expression of beta-lactamases
B) They physically prevent antibiotics from reaching the bacteria
C) They eliminate the need for bacterial cell division
D) They increase mutation rates
B) They physically prevent antibiotics from reaching the bacteria ✅
Which regulator contributes to the shift between biofilm formation and planktonic growth?
A) agr operon ✅
B) SCCmec
C) mecA
D) spa
A) agr operon ✅
Which of the following tests is used to differentiate S. aureus from coagulase-negative staphylococci (CoNS)?
A) Oxidase test
B) Coagulase test
C) Catalase test
D) Indole test
B) Coagulase test ✅
Which test can differentiate MRSA from methicillin-sensitive S. aureus (MSSA)?
A) Novobiocin sensitivity
B) PCR for mecA gene
C) Coagulase test
D) Gram staining
B) PCR for mecA gene ✅
What is the role of MALDI-TOF MS in S. aureus identification?
A) Detects antibiotic resistance
B) Identifies species by protein mass spectrometry
C) Visualizes biofilm formation
D) Measures toxin production
B) Identifies species by protein mass spectrometry ✅
Which immune evasion mechanism is mediated by Staphylococcal protein A (SpA)?
A) Inhibiting complement activation
B) Binding to the Fc region of IgG to prevent opsonization
C) Degrading host cytokines
D) Forming biofilms
B) Binding to the Fc region of IgG to prevent opsonization ✅
Which enzyme secreted by S. aureus degrades complement proteins and inhibits neutrophil recruitment?
A) Catalase
B) Aureolysin
C) Nuclease
D) Hyaluronidase
B) Aureolysin ✅
Which virulence factor allows S. aureus to escape neutrophil extracellular traps (NETs)?
A) Panton-Valentine Leukocidin (PVL)
B) Staphylococcal nuclease (Nuc)
C) Coagulase
D) Protein A
B) Staphylococcal nuclease (Nuc) ✅
Which alternative mechanism contributes to beta-lactam resistance beyond mecA in MRSA?
A) Alterations in ribosomal binding sites
B) Overexpression of efflux pumps
C) Increased expression of PBP1a
D) Decreased production of peptidoglycan
B) Overexpression of efflux pumps ✅
What is the primary reason vancomycin-intermediate S. aureus (VISA) strains exhibit reduced susceptibility?
A) Overexpression of mecA
B) Increased production of peptidoglycan
C) Horizontal gene transfer of vanA
D) Loss of teichoic acid synthesis
B) Increased production of peptidoglycan ✅
Which of the following is a novel approach being explored for MRSA treatment?
A) Increasing vancomycin dosage
B) Inhibiting quorum sensing via agr operon-targeting compounds
C) Using tetracycline antibiotics
D) Blocking bacterial biofilm formation with penicillin
B) Inhibiting quorum sensing via agr operon-targeting compounds ✅
Why are monoclonal antibodies being considered as an alternative MRSA treatment?
A) They target host immune cells rather than bacteria
B) They neutralize bacterial toxins and enhance immune clearance
C) They replace antibiotics entirely
D) They disrupt bacterial ribosomes
B) They neutralize bacterial toxins and enhance immune clearance ✅
Which therapy is being explored as a potential alternative to antibiotics for MRSA infections?
A) Bacteriophage therapy
B) RNA-based vaccines
C) Increasing beta-lactam antibiotic concentrations
D) Iron supplementation to starve bacteria
A) Bacteriophage therapy ✅
Which Baltimore classification group do flaviviruses belong to?
A) Group III
B) Group IV
C) Group V
D) Group VI
B) Group IV ✅
What type of genome do flaviviruses have?
A) Double-stranded RNA
B) Single-stranded negative-sense RNA
C) Single-stranded positive-sense RNA
D) Single-stranded DNA
C) Single-stranded positive-sense RNA ✅
Which of the following is a flavivirus?
A) Ebola virus
B) Hepatitis C virus (HCV)
C) Marburg virus
D) Lassa virus
B) Hepatitis C virus (HCV) ✅
How are flaviviruses transmitted?
A) Fecal-oral route
B) Airborne droplets
C) Bloodborne and arthropod vectors
D) Direct contact with respiratory secretions
C) Bloodborne and arthropod vectors ✅
Which of the following is NOT a filovirus?
A) Ebola virus
B) Marburg virus
C) Dengue virus
D) Sudan virus
C) Dengue virus ✅
Which Baltimore classification group do filoviruses belong to?
A) Group IV
B) Group V
C) Group VI
D) Group III
B) Group V ✅
Filoviruses have which type of genome?
A) (+) ssRNA
B) (-) ssRNA
C) dsRNA
D) Circular DNA
B) (-) ssRNA ✅
Which of the following is a primary mode of transmission for Ebola virus?
A) Inhalation of respiratory droplets
B) Direct contact with infected bodily fluids
C) Mosquito bites
D) Contaminated food
B) Direct contact with infected bodily fluids ✅
Which cell type is the primary target for HCV infection?
A) Macrophages
B) Hepatocytes
C) Neurons
D) T cells
B) Hepatocytes ✅
Which receptor is crucial for HCV entry into host cells?
A) CD155
B) Tetraspanin CD81
C) ACE2
D) ICAM-1
B) Tetraspanin CD81 ✅
Which enzyme is responsible for HCV genome replication?
A) DNA polymerase
B) Reverse transcriptase
C) RNA-dependent RNA polymerase (NS5B)
D) DNA helicase
C) RNA-dependent RNA polymerase (NS5B) ✅
HCV replicates in specialized membrane structures called:
A) Peroxisomes
B) Viral factories
C) Membranous webs
D) Lysosomes
C) Membranous webs ✅
Which host cell process does Ebola virus use for entry?
A) Endocytosis
B) Phagocytosis
C) Macropinocytosis
D) Clathrin-mediated uptake
C) Macropinocytosis ✅
What is the function of Ebola virus RNA-dependent RNA polymerase (RdRp)?
A) Synthesizes viral proteins
B) Transcribes negative-sense RNA into positive-sense mRNA
C) Degrades host mRNA
D) Cleaves glycoproteins
B) Transcribes negative-sense RNA into positive-sense mRNA ✅
Which Ebola virus protein mediates immune evasion by blocking antigen presentation?
A) VP40
B) GP
C) VP35
D) NP
C) VP35 ✅
Which of the following contributes to Ebola virus pathogenesis?
A) Liver necrosis leading to decreased clotting factors
B) Suppression of cytokine production
C) Induction of apoptosis in T cells
D) Direct destruction of neurons
A) Liver necrosis leading to decreased clotting factors ✅
Which host factor is required for HCV genome translation?
A) Ribosomal RNA
B) miRNA-122 ✅
C) TLR4
D) NF-κB
B) miRNA-122 ✅
What is the primary cause of liver fibrosis in chronic HCV infection?
A) Viral replication
B) Activation of hepatic stellate cells
C) Neutrophil recruitment
D) Overproduction of interferon
B) Activation of hepatic stellate cells ✅
Which of the following is a key feature of HCV immune evasion?
A) Rapid mutation of envelope glycoproteins
B) Induction of a strong T cell response
C) Downregulation of interferon-gamma
D) Activation of host immune checkpoints
A) Rapid mutation of envelope glycoproteins ✅
Which of the following immune cells are first targeted by Ebola virus?
A) B cells
B) Dendritic cells and macrophages
C) CD4+ T cells
D) Neutrophils
B) Dendritic cells and macrophages ✅
What is the primary cause of hemorrhagic symptoms in Ebola virus infection?
A) Direct viral destruction of platelets
B) Endothelial cell disruption and cytokine-induced vascular leakage
C) Antibody-mediated immune response
D) Inhibition of clotting factor synthesis
B) Endothelial cell disruption and cytokine-induced vascular leakage ✅
Which test is used to confirm active HCV infection?
A) ELISA antibody test
B) Quantitative RT-PCR
C) Western blot
D) Hemagglutination assay
B) Quantitative RT-PCR ✅
Which antiviral drug class is most effective in treating chronic HCV infection?
A) Reverse transcriptase inhibitors
B) Direct-acting antivirals (DAAs)
C) Protease inhibitors alone
D) Interferon-alpha monotherapy
B) Direct-acting antivirals (DAAs) ✅
What is the primary treatment for Ebola virus infection?
A) Broad-spectrum antivirals
B) Supportive therapy and monoclonal antibodies
C) High-dose interferon therapy
D) Blood transfusions
B) Supportive therapy and monoclonal antibodies ✅
Trypanosomatids are classified as:
A) Fungi
B) Bacteria
C) Single-celled eukaryotic parasites
D) Helminths
C) Single-celled eukaryotic parasites ✅
Which of the following is NOT a trypanosomatid parasite?
A) Trypanosoma brucei
B) Trypanosoma cruzi
C) Leishmania spp.
D) Plasmodium falciparum
D) Plasmodium falciparum ✅
What is the function of the kinetoplast in trypanosomatids?
A) It stores nutrients
B) It contains mitochondrial DNA
C) It is involved in immune evasion
D) It aids in movement
B) It contains mitochondrial DNA ✅
Which of the following best describes the morphology of trypanosomatids?
A) They all have two flagella
B) They contain a single flagellum and a kinetoplast
C) They have segmented bodies
D) They lack mitochondria
B) They contain a single flagellum and a kinetoplast ✅
What disease is caused by Trypanosoma brucei?
A) Chagas disease
B) Malaria
C) Human African trypanosomiasis (sleeping sickness)
D) Leishmaniasis
C) Human African trypanosomiasis (sleeping sickness) ✅
What is the primary vector for Trypanosoma brucei?
A) Triatomine bug
B) Anopheles mosquito
C) Sand fly
D) Tsetse fly
D) Tsetse fly ✅
Which Trypanosoma brucei subspecies causes the chronic form of sleeping sickness?
A) T. brucei rhodesiense
B) T. brucei gambiense
C) T. brucei cruzi
D) T. brucei donovani
B) T. brucei gambiense ✅
What is a major symptom of the late stage of sleeping sickness?
A) Severe diarrhea
B) Jaundice
C) Meningoencephalitic symptoms with sleep cycle disturbances
D) Enlarged spleen
C) Meningoencephalitic symptoms with sleep cycle disturbances ✅
Which disease is caused by Trypanosoma cruzi?
A) Leishmaniasis
B) Sleeping sickness
C) Chagas disease
D) Schistosomiasis
C) Chagas disease ✅
What is the primary vector of Trypanosoma cruzi?
A) Sand fly
B) Tsetse fly
C) Triatomine bug
D) Anopheles mosquito
C) Triatomine bug ✅
Which of the following is a major symptom of chronic Chagas disease?
A) Skin ulcers
B) Cardiomyopathy and megacolon
C) Paralysis
D) Neurological seizures
B) Cardiomyopathy and megacolon ✅
Which life stage of Trypanosoma cruzi is found inside host cells?
A) Trypomastigote
B) Epimastigote
C) Amastigote
D) Promastigote
C) Amastigote ✅
What is the primary vector for Leishmania spp.?
A) Tsetse fly
B) Sand fly
C) Triatomine bug
D) Black fly
B) Sand fly ✅
Which Leishmania species causes visceral leishmaniasis (Kala-Azar)?
A) L. mexicana
B) L. donovani
C) L. major
D) L. braziliensis
B) L. donovani ✅
Which immune cells are primarily infected by Leishmania?
A) Neurons
B) Macrophages
C) Hepatocytes
D) B cells
B) Macrophages ✅
Which organelle in trypanosomatids is involved in compartmentalized glycolysis?
A) Glycosome
B) Lysosome
C) Peroxisome
D) Golgi apparatus
A) Glycosome ✅
Why is the mitochondrion only partially developed in bloodstream forms of T. brucei?
A) They rely solely on glycolysis for ATP production
B) They do not require ATP
C) Their host provides all necessary energy
D) They lack electron transport chains
A) They rely solely on glycolysis for ATP production ✅
Which pathway is a target for the drug miltefosine in Leishmania?
A) Glycolysis
B) Squalene biosynthesis
C) Protein synthesis
D) Electron transport chain
B) Squalene biosynthesis ✅
What is the primary immune evasion strategy used by Trypanosoma brucei?
A) Inhibiting cytokine release
B) Changing its surface glycoproteins (VSG switching)
C) Producing biofilms
D) Inhibiting complement activation
B) Changing its surface glycoproteins (VSG switching) ✅
What is the function of VSG (variant surface glycoproteins) in Trypanosoma brucei?
A) They allow the parasite to adhere to host cells
B) They prevent the host immune system from recognizing the parasite
C) They help the parasite invade macrophages
D) They aid in mitochondrial ATP production
B) They prevent the host immune system from recognizing the parasite ✅
What is unique about gene expression in trypanosomatids?
A) They use RNA polymerase III for mRNA synthesis
B) They lack conventional RNA polymerase II promoters
C) They transcribe genes one at a time
D) They use riboswitches for transcription regulation
B) They lack conventional RNA polymerase II promoters ✅
How do trypanosomatids process their mRNA?
A) Alternative splicing
B) Trans-splicing
C) Ribosomal skipping
D) Reverse transcription
B) Trans-splicing ✅
Which RNA processing feature is unique to trypanosomatids?
A) All mRNAs receive a trans-spliced leader sequence
B) They have polycistronic mRNA similar to bacteria
C) They lack introns
D) They use operon-like transcription
A) All mRNAs receive a trans-spliced leader sequence ✅
What is the function of RNA editing in the kinetoplast?
A) Removal of introns
B) Addition or deletion of uridines in mRNA
C) DNA methylation
D) MicroRNA processing
B) Addition or deletion of uridines in mRNA ✅
