Lecture 1 (justin chu) Flashcards
What is molecular microbiology?
molecular microbiology is the study of micro-organisms (ie: prokaryotes, eukaryotes, virus, bacteria) at a molecular level, this includes the analysis of genetic expression, genetic transfer, synthesis of macromolecules, cell communication and molecular aspects of pathogenicity and virulence.
What is virulence?
virulence measures the amount of damages a pathogen can cause in its host, how likely it is to result in disease in its host
What are the 4 pattern of transition that contributes to rapid spread of emerging and re-emerging diseases?
1) close proximity: when people are in close proximity with each other this encourages the spread
2) civilization: neighboring civilization made contact with each other through trade and war encourages the spread
contact allowed the exchange of pools of infectious organisms and vectors between populations
3) colonization: newly identified populations lacks herd immunity and comes into contact with never seen before pathogens within their population
4) modern world problems: travel, climate change, urbanization, increase population density, poverty, technology, land clearance
examples of molecular microbiology techniques
PCR, ELISA, western blot, gel electrophoresis
describe how PCR is conducted (reverse transcriptase PCR & real time PCR)
in both PCR test, there must be prior knowledge of the gene if interest in order to design a sequence specific primer to initiate PCR.
the purpose of conducting PCR is to amplify the genome and increase the concentration of the pathogens
real time PCR eg: using SYBR green dye or taqman probe
essentially, real time PCR enables real time observation of the amplification process, every time the machine amplifies the gene of interest, the SYBR green dye would bind to it and fluorescence. (amplification curve, melting curve and number of cycle it took)
DNA sequencing
DNA sequencing can be used for microbial identification
the most common sequence used for microbe identification is 16S rRNA gene
PCR is used to amplify the 16s rRNA gene
16s rRNA sequence is unique to certain groups of organisms and useful in their identification
classification of organism
microorganism can be classified based on their genus and species
host-pathogen relationship
for pathogen the interaction depends on
- the pathogen’s ability to evade or overcome the hosts defense
- the pathogen’s ability to increase in numbers
- the pathogen’s ability to identify transmission mechanisms to new host
for host, the interaction depends on
- host having useful functioning defenses
- hose’s susceptibility to infection
- degree of compromise found within the host immune system
Pathogens must be able to accomplish the 5 requirements for infection, what are they?
1) successfully attach and penetrate through host cells
2) replicate and propagate within the host cell
3) defend themselves against host immune system
4) cause apoptosis of the host cells
5) be transmissible
bacteria can carry a cluster of virulence genes known as?
pathogenicity island, these virulence genes are present in their plasmids and plasmids is transferrable between cells via horizontal gene transfer
What are biofilms and where can it develop?
bacteria can grow in aggregated assemblies within their host, these assemblies are called biofilms
biofilms are important because:
- they can retain and capture nutrients for their own growth
- they block antibiotics and disinfectant
- they prevent phagocytosis
they can grow prosthetic equipment, plaque build up on teeth
what is quorum sensing?
is when the bacteria are able to sense their surrounding based off the population density and decide when to turn on and off certain genes, only when there is a large number of them
What are the three methods used for control of bacteria spreading/infection
1) isolation
advantage: isolation is imposed when the individual is confirmed to have been displaying symptoms of an infection (symptomatic and infectious) –> this is to prevent the spread of the virus/pathogens
disadvantage: can be difficult to achieve as it cannot be imposed until firm diagnosis
2) quarantine
- it lasts as long as the incubation period for the disease in question
- if there are no longer any symptoms, the quarantine is lifted
advantage: exposed humans/animals are separated form the general population
disadvantage: rarely used because difficult to enforce
3) vector control
advantage: vector control of mosquito breeding can help to contain and reduce the spread of the virus
disadvantage: population negligence and ignorance
Herd immunity
herd immunity can be acquired through vaccination or being exposed to the pathogen naturally
when a population has herd immunity, it reduces the chances of getting re-infected/infected by the pathogen
3 major methods for controlling microbial growth
1) chemical (chemical agents such as gases and liquid ie: alcohol)
2) physical (heat and radiation)
3) mechanical removal
Chemical control of microbial growth
gases (halogens, oxidizing agents): sterilization and disinfection
liquid (alcohol): sterilization, disinfection and antisepsis
Physical control of microbial growth
Heat
1) dry heat –> incineration and dry oven
2) moist heat
- sterilization
steam + pressure
- disinfection
boiling water, pasteurization
radiation
1) ionizing rays (gamma and X-ray) > causes bond breaking in DNA = sterilization
2) non ionizing rays (UV radiation) > causes formation of abnormal bonds within DNA sequences = disinfection
mechanical removal control of microbial growth
filtration sterilization
Terminologies
disinfection
antisepsis
sterilization
aseptic
pasteurization
sanitization
-static
-cidal
- disinfection: associated with inanimate objects
- antisepsis: associated with human skin and tissue
- sterilization: removal of all microbes including endospores
- aseptic: environment or procedure free from contamination
- pasteurization: steam + pressure to kill pathogens
- sanitization: not sterilization but uses the same technique (steaming, high pressure, high temperature, washing and scrubbing)
-static: agent that inhibits the growth of microbes
-cidal: agent that kills microbes
what affects the rate of microbial death in a clinical setting
numbers
duration of exposure
temperature
environment
endospore formation
