BMS2052 EXAM COMPREHENSIVE LIST OF
CERTIFICATION QUESTIONS AND VALIDATED
ANSWERS
328 QUESTIONS AND ANSWERS
What is normal microbiota - ANSWER The microbiota existing in the human
body which is either in commensal or mutualistic relationship.
What is pathogenesis - ANSWER The process by which a pathogen causes
disease.
What are the three types of relationships between microbiota and the host -
ANSWER Mutualism = both benefit, Commensalism = one benefit, no harm to
either, Parasitism = one benefits at the expense of the other
What is the microbiome vs microbiota - ANSWER Microbiota is the organisms
existing in the host, whereas the microbiome is the genetic material of these
organisms.
What are Kochs postulates - ANSWER 1. the pathogen must be present in all
cases of disease and absent in healthy individuals 2. the pathogen must be able
to be isolated and cultured 3. when re implanted into a new host, the pathogen
must cause the same disease 4. when reisolated, the pathogen must be identical
to the original isolated pathogen
What are the limitations of Kochs postulates - ANSWER Doesn't consider the
host immune system. Has a strong emphasis on ability to culture organisms.
Some organisms lose virulence in labs. Diseases can replicate without hosts.
Requires animal models
What are opportunistic pathogens - ANSWER An organism which only causes
disease under certain circumstances.
,What are nosocomial infections - ANSWER Infections acquired in hospitals,
through surfaces or health care workers
What are primary pathogens - ANSWER Cause disease in normal, healthy host.
What is Mims Model - ANSWER The body represented as 3D sphere, with a
hollow tube (the GI tract) running through it. The sphere has a few areas which
can be penetrated by pathogens, or through which pathogens can exit.
What are the steps in infection and disease pathogenesis - ANSWER
Exposure/entry, attachment, colonisation, evasion, multiplication, damage to
host.
What are some virulence factors - ANSWER Bacteriophages - viruses which
infect organisms and can cause pathogenicity. pathogenicity islands - stretches
of DNA containing VFs. transposons - stretches of DNA which move around
the genome.
What are some barriers against entry of pathogens - ANSWER Physical
barriers = many layers of skin, reflex reactions. Chemical barriers = secretions,
chemotactic agents, pH
What are some barriers to colonisation of pathogens - ANSWER Normal
microbiota, cilia.
What are some virulence factors involved in colonisation - ANSWER Urease =
releases ammonia, creates a more basic environment allowing for pathogens to
stick. Flagella = creates motility, allows pathogens to travel to niches where
they can exist. Adhesions
What are the three types of adhesion - ANSWER Afimbriael - short,
monomeric structures, strong/close adhesions. Fimbriae - pili and fimbria -
loose adhesions, adhere to capsule. Capsule - thick, sticky, helps pathogens
stick to each other and the host, polymeric
Why do bacteria invade - ANSWER Invading helps evade immune system and
allows dissemination.
,What are invasins - ANSWER Specialised cells, mediate invasion, allow entry
into non-phagocytic cells.
What is the zipper mechanism of invasion - ANSWER Cell surface interacts
with ligand. interactions outside the cell results in binding and activation of
actin. pseudopod formation. normal cell function hijacked
What is the trigger mechanism of invasion - ANSWER T3SS triggers
transduction pathway. delivers injectable proteins into the host cell. interactions
within the cell result in actin rearrangement and pseudopod formation. normal
cell function hijacked
What are the main steps in phagocytosis - ANSWER Phagosome engulfs
bacteria, fuses with lysosome, forms phagolysosome, destroys pathogen and
exocytoses contents.
What does the phagocyte use to recognise the pathogen - ANSWER C3b, PRR,
Fc receptor
What are the functions of the complement pathway - ANSWER Complement is
serum of the innate immune system, activates a cascade, Coats the protein to be
recognised by phagosomes, Creates a pore forming complex, which creates
holes in the MAC complex, resulting in cell lysis, Fragments at the end of the
pathway are chemotactic agents
How does a pathogen avoid detection by the host immune system - ANSWER
Biofilms: don't allow access, inhibits phagocytosis. Capsules: hides PAMPs,
prevents complement binding and antibody recognition. Host mimicry: by
looking like the host, it can avoid phagosomes. Antigenic variation: turns on/off
genes for surface components, can hide from phagocytes. Fc receptor binding:
prevents binding of immune cells. Intracellular growth: by growing within other
cells the pathogen cannot be detected
How can pathogens acquire iron - ANSWER Siderophores: high affinity iron
chelators, collect host iron and steal it. Have iron capture protein receptors.
Have receptors for haemoglobin. Toxins which release host iron from iron
transporting proteins
, What are the two types of toxins and when are they released - ANSWER
Exotoxins are within the cell, are released upon lysis/cell death. Endotoxins are
within the cell wall and are hence released during cell wall degradation.
What are the three types of damage to the host - ANSWER Indirect: damage
via expanded immune response. Direct: in the immediate vicinity of release,
quite quickly after release. Toxigenic: no pathogen in host, instead the toxin has
been ingested causing disease
What are the three types of heat labile toxins - ANSWER Type 1: superantigen
- activate immune response. Type 2: membrane disrupting - disrupts cell wall.
Type 3: A-B toxin - disrupts normal cell function
How do superantigens work - ANSWER Potent toxins, MHCII/superantigen
complex activates CD4+ T cells, this activates an intense immune response,
which leads to a cytokine storm. This is indirect damage. Examples: staph and
strep
How do membrane disrupting toxins work - ANSWER Cause direct effects,
phospholipases cause damage/lysis of cells. Causes pore formation and
therefore loss of nutrients. Examples: S. aureus, clostridium perifinges
How do A-B toxins work - ANSWER A is the catalytic subunit, whereas B
binds to the host. B binds to host, toxin is endocytosed, A/B separate, A is
transported to cytoplasm where it exerts it effect. Examples: diphtheria, cholera
What are the main features of viruses - ANSWER Highly genetically diverse,
unrelated. Hijack host machinery for replication. No growth or division.
Surrounded by capsid
What are the three structural forms of viruses and an example - ANSWER
Spherical, helical and complex
What are the steps of virus life cycle - ANSWER Attachment,
penetration/uncoating, gene expression/replication, assembly of virions, release
of virions
CERTIFICATION QUESTIONS AND VALIDATED
ANSWERS
328 QUESTIONS AND ANSWERS
What is normal microbiota - ANSWER The microbiota existing in the human
body which is either in commensal or mutualistic relationship.
What is pathogenesis - ANSWER The process by which a pathogen causes
disease.
What are the three types of relationships between microbiota and the host -
ANSWER Mutualism = both benefit, Commensalism = one benefit, no harm to
either, Parasitism = one benefits at the expense of the other
What is the microbiome vs microbiota - ANSWER Microbiota is the organisms
existing in the host, whereas the microbiome is the genetic material of these
organisms.
What are Kochs postulates - ANSWER 1. the pathogen must be present in all
cases of disease and absent in healthy individuals 2. the pathogen must be able
to be isolated and cultured 3. when re implanted into a new host, the pathogen
must cause the same disease 4. when reisolated, the pathogen must be identical
to the original isolated pathogen
What are the limitations of Kochs postulates - ANSWER Doesn't consider the
host immune system. Has a strong emphasis on ability to culture organisms.
Some organisms lose virulence in labs. Diseases can replicate without hosts.
Requires animal models
What are opportunistic pathogens - ANSWER An organism which only causes
disease under certain circumstances.
,What are nosocomial infections - ANSWER Infections acquired in hospitals,
through surfaces or health care workers
What are primary pathogens - ANSWER Cause disease in normal, healthy host.
What is Mims Model - ANSWER The body represented as 3D sphere, with a
hollow tube (the GI tract) running through it. The sphere has a few areas which
can be penetrated by pathogens, or through which pathogens can exit.
What are the steps in infection and disease pathogenesis - ANSWER
Exposure/entry, attachment, colonisation, evasion, multiplication, damage to
host.
What are some virulence factors - ANSWER Bacteriophages - viruses which
infect organisms and can cause pathogenicity. pathogenicity islands - stretches
of DNA containing VFs. transposons - stretches of DNA which move around
the genome.
What are some barriers against entry of pathogens - ANSWER Physical
barriers = many layers of skin, reflex reactions. Chemical barriers = secretions,
chemotactic agents, pH
What are some barriers to colonisation of pathogens - ANSWER Normal
microbiota, cilia.
What are some virulence factors involved in colonisation - ANSWER Urease =
releases ammonia, creates a more basic environment allowing for pathogens to
stick. Flagella = creates motility, allows pathogens to travel to niches where
they can exist. Adhesions
What are the three types of adhesion - ANSWER Afimbriael - short,
monomeric structures, strong/close adhesions. Fimbriae - pili and fimbria -
loose adhesions, adhere to capsule. Capsule - thick, sticky, helps pathogens
stick to each other and the host, polymeric
Why do bacteria invade - ANSWER Invading helps evade immune system and
allows dissemination.
,What are invasins - ANSWER Specialised cells, mediate invasion, allow entry
into non-phagocytic cells.
What is the zipper mechanism of invasion - ANSWER Cell surface interacts
with ligand. interactions outside the cell results in binding and activation of
actin. pseudopod formation. normal cell function hijacked
What is the trigger mechanism of invasion - ANSWER T3SS triggers
transduction pathway. delivers injectable proteins into the host cell. interactions
within the cell result in actin rearrangement and pseudopod formation. normal
cell function hijacked
What are the main steps in phagocytosis - ANSWER Phagosome engulfs
bacteria, fuses with lysosome, forms phagolysosome, destroys pathogen and
exocytoses contents.
What does the phagocyte use to recognise the pathogen - ANSWER C3b, PRR,
Fc receptor
What are the functions of the complement pathway - ANSWER Complement is
serum of the innate immune system, activates a cascade, Coats the protein to be
recognised by phagosomes, Creates a pore forming complex, which creates
holes in the MAC complex, resulting in cell lysis, Fragments at the end of the
pathway are chemotactic agents
How does a pathogen avoid detection by the host immune system - ANSWER
Biofilms: don't allow access, inhibits phagocytosis. Capsules: hides PAMPs,
prevents complement binding and antibody recognition. Host mimicry: by
looking like the host, it can avoid phagosomes. Antigenic variation: turns on/off
genes for surface components, can hide from phagocytes. Fc receptor binding:
prevents binding of immune cells. Intracellular growth: by growing within other
cells the pathogen cannot be detected
How can pathogens acquire iron - ANSWER Siderophores: high affinity iron
chelators, collect host iron and steal it. Have iron capture protein receptors.
Have receptors for haemoglobin. Toxins which release host iron from iron
transporting proteins
, What are the two types of toxins and when are they released - ANSWER
Exotoxins are within the cell, are released upon lysis/cell death. Endotoxins are
within the cell wall and are hence released during cell wall degradation.
What are the three types of damage to the host - ANSWER Indirect: damage
via expanded immune response. Direct: in the immediate vicinity of release,
quite quickly after release. Toxigenic: no pathogen in host, instead the toxin has
been ingested causing disease
What are the three types of heat labile toxins - ANSWER Type 1: superantigen
- activate immune response. Type 2: membrane disrupting - disrupts cell wall.
Type 3: A-B toxin - disrupts normal cell function
How do superantigens work - ANSWER Potent toxins, MHCII/superantigen
complex activates CD4+ T cells, this activates an intense immune response,
which leads to a cytokine storm. This is indirect damage. Examples: staph and
strep
How do membrane disrupting toxins work - ANSWER Cause direct effects,
phospholipases cause damage/lysis of cells. Causes pore formation and
therefore loss of nutrients. Examples: S. aureus, clostridium perifinges
How do A-B toxins work - ANSWER A is the catalytic subunit, whereas B
binds to the host. B binds to host, toxin is endocytosed, A/B separate, A is
transported to cytoplasm where it exerts it effect. Examples: diphtheria, cholera
What are the main features of viruses - ANSWER Highly genetically diverse,
unrelated. Hijack host machinery for replication. No growth or division.
Surrounded by capsid
What are the three structural forms of viruses and an example - ANSWER
Spherical, helical and complex
What are the steps of virus life cycle - ANSWER Attachment,
penetration/uncoating, gene expression/replication, assembly of virions, release
of virions
