Microbial diseases and prevention Flashcards
Agents of Infectious
Disease include:
- Viruses
- Bacteria
- Protozoa (protists)
- Fungi
- Helminths (worms)
Stages of disease progression:
1. ??? period: time between entry of the microbe and onset of
symptoms.
Incubation
stages of disease progression:
2. ???: mild signs or symptoms.
Prodromal
stages of disease progression:
3. ???: symptoms are most intense and disease-specific. Also called
the climax.
Acute
stages of disease progression:
4. Decline: ???
A period of decline occurs as signs and symptoms subside.
stages of disease progression:
5. Convalescence: ???
Return to normal health
Portal of Exit:
Many portal of exit are DIFFERENt or THE SAME (?) sites as portal of entry. Pathogens often leave the body via bodily secretions and excretions produced at those sites.
the same
The sequence of events leading to disease:
1. pathogen enters the sterile environment of host tissue
2. infectious dose penetrates hosts barriers
3. pathogens move into specific target tissue/organ
4. pathogens cause ???
5. pathogens ???
- tissue damage which leads to disease progression
- leave host to infect another host
Are the following modes of infectious disease transmission DIRECT or INDIRECT?
o Person-person contact
o Exchange of bodily fluids
o Droplet/aerosols
o Animal contact
o During labour or delivery
DIRECT
Are the following modes of infectious disease transmission DIRECT or INDIRECT?
o Inanimate objects
o Vector transmission (arthropods)
(Biological or Mechanical Vector)
o Vehicle Transmission (Water or Food)
Indirect
SARS is an EMERGING or RE-EMERGING (?) infectious
disease caused by the coronavirus
SARS CoV that spreads through close person-to-person contact. Symptoms can be asymptomatic or delayed 2-7 days
emerging
what is similar but more dangerous than SARS?
MERS
SARS – pathogenesis:
Enters the body through respiratory tract. Infects the epithelial cells of the respiratory tract then infects
??? which carry the virus to other organs (spleen, lymphoid tissue etc)
infiltrating and circulating immune cells
SARS - phylogeny: Molecular phylogeny based on the gene sequence of the ??? gene suggests SARS virus is not closely related to other coronaviruses.
Replicase 1A
gene
what is the natural origin/reservoir of SARS?
bats according to Epidemiological (PCR and sequence analysis) studies
Helicobacter pylori - the causative agent of ??? and stomach ulcers
gastritis
TRUE or FALSE: Stomach and duodenal ulcers originally thought to be caused by stress and diet. Treatment by antacids originally but now antibiotics. Approximately 2/3 of the human population is infected with H. pylori, yet the majority do not develop disease
TRUE
TRUE or FALSE: The transmission method of H. pylori is not completely understood, and it is less common with increased age and in less developed countries.
FALSE, it is NOT well understood and is LESS common with increased age
H. pylori resides in the ???. Their helical shape = movement through this layer.
mucosal layers of the stomach
H. pylori urease breaks down ??? in the stomach into ???. The production of an “??? cloud” around the bacterium protects it from the low pH of the stomach, where few other organisms are able to survive.
urea into ammonia
ammonia cloud
TRUE or FALSE: there is no association between stomach cancer and helicobacter pylori
FALSE: There is and association between H. pylori and the development of stomach cancer. H. pylori infection is considered a major
risk factor
Infectious disease severity is governed by;
1. Virulence determinants of pathogens
and
2. ???
Host factors that include
o Human susceptibility
o Resistance genes
virulence determinants of pathogens include:
o ??? systems
o ???
o Self-destruction
o Changing antigens
o Camouflage
Attachment systems
Toxins/enzymes
CCR5 polymorphism is an example of host resistance genes or human susceptibility?
host resistant genes
CD4+ T cells (Th cells) are the primary target of HIV infection. CCR5 and CXCR4 are chemokine receptors present on immune cells. HIV uses CCR5 as a secondary receptor to gain entry into macrophages. Hence when there are mutations in CCR5 progression of disease is FASTER or SLOWER?
SLOWER:
mutations have been associated with a slower progression towards AIDS
What overcomes host resistance conferred by CCR5 mutation?
HIV strains display tropism for
the different chemokine
receptors. Some strains, known as X4-tropic or dual-tropic strains,
can engage CXCR4. This strain can emerge as a result of mutation within the individual which can overcome host resistance conferred by CCR5 mutation
Group A streptococcal invasive diseases include necrotising fasciitis
and toxic shock syndrome. Severity is associated with ??? class II
polymorphism
human leukocyte antigen (HLA)
HLA is the name given to the human form of the expressed ???, a large locus in all vertebrates that encodes for surface proteins essential in immune function. There are two classes
Major Histocompatibility Complex (MHC)
HLA class II (also called MHC class II) are expressed primarily on ??? cells of the immune system, such as macrophages
antigen-presenting cells
Group A streptococci produce superantigens that non-specifically crosslink HLA class II proteins and TCR => massive T cell over-proliferation and ??? which can lead to organ damage and death
inflammatory cytokine production
Class II HLA (MHC II) binds to T cell
receptor ??? and ??? This is a crucial process of the adaptive immune response
specifically and reversibly
what are some examples of public health measures?
o clean water
o sewerage systems
o reduction in overcrowding
o better food handling and nutrition
o sterilisation methods
o use of disinfectants and antiseptics
o education on microbial transmission
Chemotherapeutic agents are natural or synthetic substances which are either toxic or ??? and are used internally in humans.
growth inhibitory to microorganisms/cancer
TRUE or FALSE: antibiotics, quinine & artemisinin (for malaria), metronidazole (systemic amoebiasis) are all chemotherapeutics
TRUE: also included in the list are:
Relenza (flu - influenza virus type A, B and C)
Antibiotics (antibacterials - eg. penicillin, streptomycin, vancomycin)
What are natural antibiotics?
secondary metabolites/chemical compounds produced by microbes that are not directly used by the producing organism for growth/reproduction
When are natural antibiotics most likely to be produced during growth of microbe?
during stationary phase to help compete for limited resources
Why are natural antibiotics produced by microbes useful for them?
might help the producer kill competitors that are sensitive to the secondary metabolites/chemicals produced, giving selective advantage for nutrients and space
list the 5 major targets for antibacterial agents:
- cell wall
- cell membrane
- ribosomes (due to protein synthesis)
- Nucleic acid synthesis (RNA and DNA)
- Metabolic reactions
Beta-Lactam Antibiotics, such as ??? target bacterial ??? by interfering with cross-linking of peptidoglycan layers
penicillin, target bacterial cell wall synthesis
beta-lactam antibiotics are active against ???
gram +ve and some gram-ve. More effective against rapidly growing populations rather than more dormant communities
glycopeptide antibiotics inhibit ??? e.g. vancomycin
cell wall synthesis
glycopeptide antibiotics are effective against gram POSITIVE or NEGATIVE? side effects include damage to ?? and ears
positive, damage kidneys and ears
what type of antibiotic is used as a drug of last resort, especially to treat MRSA?
Vancomycin, a glycopeptide antibiotic
Vancomycin is produced by the soil bacterium Amycolatopis orientalis and is used to kill ???
multiple resistant bacteria such as MRSA
Vancomycin interferes with cell wall synthesis by binding to ??? which interferes with transpeptidase activity = no cross-linking of peptidoglycan layers = weakness
D-ala terminus
How did bacteria evolve resistance against vancomycin?
due to overuse of Avoparcin, a drug with a similar chemical structure which was used as a growth promoter in intensive agriculture such as chickens/pigs since the 1960s
What genes encode resistance of bacteria against vancomycin?
Van genes
van genes work by encoding proteins that modify ??? structure = vancomycin loses capacity to bind to these structures
peptidoglycan structure
polypeptide antibiotics target the ??? and are used only as a topical treatment due to ebing able to cause renal failure and respiratory paralysis if internal exposure
cell membrane
Bacitracin is a type of ??? antibiotic that interferes with transport of ??? through the membrane
polypeptide antibiotic
cell wall precursors
Bacitracin is used to treat skin infections caused by gram NEGATIVE or POSITIVE?
both
Polymyxins are a type of polypeptide antibiotics that increase ??? of gram-negative rods = cell death
membrane permeability
aminoglycoside antibiotics affect ??? by attaching to bacterial ribosomes = no transcription
translation
Immunotherapeutics are molecules of the HUMAN or BACTERIAL immune system?
human
interferon alpha is an immunotherapeutic agent produced by B cells, T cells, and ???
macrophages
recombinant interferon alpha is used in the treatment of ??? virus
Hep C
interferon alpha is a part of INNATE or ADAPTIVE immune response to viruses?
innate
IFN alpha induces the expression of other host antiviral proteins such as ??? which block viral production
protein kinase, 2’-5’ oligoadenylate synthetase
broad spectrum antimicrobials affect ???
a broad range of taxonomic groups
antibiotic susceptibility assays: tube dilution method is able to determine the ???
lowest concentration of the antibiotic that is effective
TRUE or FALSE: the minimum bactericidal concentration (MBC) test determines the lowest concentration/amount of drug required to inhibit the microbe
FALSE it determines amount of drug required to KILL bacteria
aquired resistance to antibiotics can be due to either new mutations of chromosomal genes OR aquisition of ??? via transformation, transduction and conjugation
R-plasmids
how have humans contributed to antibiotic resistance in bacteria?
prescription abuse
prescription misuse by individuals or healthcare organisations
methods of limiting antibiotic resistance include:
- maintaining high concentration of drug for sufficient time (no longer, no less)
- use in synergy
- use specific antimicrobials and ONLY when necassary
- ???
- ???
- develop new variations of existing drugs
- search for new ones
bacteriophages cannot ??? on their own, hence take over a host cell
reproduce and survive
lytic (T4) baceriophage life cycle:
1. adsorption to host cell and penetration by injecting DNA into the cell
2. ???
3. release of phage particles
- synthesis of phage nucleic acids and proteins and then assembly of these particles
step 3 of lyic life cycle of bacteriophage can damage host cell membrane by:
- ???
- Lysin - enzyme that breaks host cell wall (lyses them)
Holin- enzyme that destabilises host cell membrane
Which part and what life cycle types of bacteriophage could be used for therapy in bacterial and viral infections?
either complete phage, or holin or lysin proteins
