Week 11 Science and Scholarship: Pathogens Flashcards
identify the different types of microorganisms
eukaryotes, prokaryotes and acellular organisms
examples of eukaryotes
protists and fungi
examples of prokaryotes
bacteria, mycobacteria, and mycoplasma
examples of acellular organisms
bacteriophages (non living and divide with bacteria) ; viruses
name the taxonomic ranks in descending order
domain, kingdom, phylom, class, order, family,genus, species
“Dear King Philip Came Over For Good Soup”
name the functions of bacteria on earth
Global ecosystems, saprophytes , economic biotechnology
nuisance and pathogens
how does bacteria contribute to global ecosystems
carbon, nitrogen, phosphorous and sulphur cycling
how are bacteria saprophytes
turnover over of organic material eg compost, recycling
how do bacteria contribute to economic biotechnology
production of ethanol, amino acids, food supplements and antibiotics
how are bacteria nuisances
spoilage of foods , biofilms
how are bacteria pathogens
contribute to infectious disease of plants and animals; bioterrorism
describe the chromosome in bacteria
single circular chromosomes in the cytoplasm
describe the plasmid in bacteria
circular, double stranded DNA
-range from 2-200kb
-can be 1-30 per cell
bacteria with larger genomes need ____ nutrients from environment
less
list the genetic variation methods in bacteria
point mutation
tranformation
conjugation
transduction
how do point mutations offer genetic variation in bacteria
insertion, deletion or substitution of DNA nucleotide bases offer variation
how does transformation offer genetic variation in bacteria
uptake of ‘free’ DNA, allowing acquisition of new genes and traits
how does conjugation offer genetic variation in bacteria
transfer of DNA by direct cell-cell contact using specialised pills, movement of genes between host and recipient
how does transduction offer genetic variation in bacteria
transfer of DNA by bacteriophage eg bacterial viruses allows for new genes and traits
name the functions of the bacterial plasma cell membrane
maintaining homeostasis
ATP generation
transportation
how does the plasma cell membrane of bacteria allow maintenance of homeostasis
maintains the gradients of NA + and K+
how does plasma cell membrane of bacteria allow for ATP generation
site of electron transport chain (aerobic respiration)
how plasma cell membrane of bacteria allow for transportation
imports nutrients, exports wastes, toxins and antibiotics
describe the structure of endospores
-complex, intracellular structures
-can be terminal, sub terminal or central
-stimulated by desiccation, radiation, chemical agents, enzymes etc
describe formation of endospores
-DNA is replicated
-cellular divison of cytoplasmic membrane
-prespore formation begins
-cortex formation
-spore coat formation begins
-maturation begins exosporium formation
-mother cell releases mature spore
name what bacterial cell walls are made of
peptidoglycan
cell walls can be either ___ or ___
gram positive or gram negative
name the shapes of bacterial cell walls
rods (bacilli) or spirals or spheres
describe rod (bacilli) bacterial cell wall
bacteria with rod like shape eg E.coli
describe spiral bacterial cell wall
bacteria with helical or spiral shape eg T.pallidium
describe sphere bacterial cell wall
bacteria with spherical or round shape eg S.pneumonia
what are gram positive bacterial cell walls
-bacteria that retain the crystal violet stain the gram staining method
-characterised by a thick peptidoglycan layer in cell wall
what are gram negative bacterial cell walls
-bacteria that do not retain the crystal violet stain in gram staining method
-characterised by thinner peptidoglycan layer in cell wall
purpose of gram staining
reveals bacteria shape and arrangement; some antibiotics are more effective against +gram bacteria
describe mycobacterial cell walls
-waxy hydrophobic cell wall: outer lipid layer, mycolic acids, arabinogalactan, peptidoglycan
name the structures external to bacterial cell walls
flagella
pili/fimbriae
capsule
structure of flagella
long whip like appendages on surface of bacteria
function of flagella
enable bacteria to move and navigate their environment
structure of fimbriae/ pili
short, hair like structures on surface of bacteria
function of fimbriae / pili
aid attachment to surface eg to host cells or other bacteria
structure of capsule
-protective layer of polysaccharides or proteins that surrounds cell wall of some bacteria
function of capsule
provides protection against the host’s immune system, enhancing ability to cause infection
Explain the differences between ‘commensals’ and ‘pathogens’
-commensals colonise all surfaces of host (mucosa of gut and lungs, skin) and provide metabolic benefits / protection eg folate production
-pathogens do not provide any advantage to the host, not part of normal microbiome, damages the host (direct or indirect) if evade immune repose
how can bacteria directly and indirectly damage host
indirect=bacteria could disturb metabolic balance, nutrient acquisition
direct=could secrete harmful toxins
Outline why commensal organisms are important
-help establish mutually beneficial relationships with their hosts
-help aid establishment of diverse ecosystems to provide essential services
-help maintain host health by preventing colonisation of harmful pathogens
-help provide evolutionary benefit to host, aiding adaption
Name the steps in pathogenic cycle
transmission
colonisation
proliferation
evasion
Describe transmission phase in pathogenic cycle
transmission from host or reservoir
describe colonisation phase in pathogenic cycle
colonisation motility, adhérence and invasion
describe proliferation phase in pathogenic cycle
proliferation within host, host provides nutrients for growth, may lead to host damage
describe evasion phase in pathogenic cycle
evasion of host immune response, circumvent hosts defence mechanisms
briefly what is meant by pathogenic cycle
action of pathogen once it enters body
name the routes of transmission
direct contact
indirect contact
aerosol
faecal-oral
self-inoculation
zoonotic
examples direct contact transmission
bites, open wounds, sexual contact
examples indirect contact transmission
via fomites; contact with contaminated objects
examples of aerosol transmission
respiratory aerosol transmission eg influenza
examples of faecal-oral transmission
faecal transmission eg E.coli,Hep A
examples of self-inoculation transmission
food poisoning
examples of zoonotic transmission
spread between animals and people eg bubonic plague
Describe the mechanism of virulence
the degree or intensity of pathogenicity, referring to the ability of a microorganism eg virus, bacterium or parasite to cause disease and the severity of the resulting illness
Describe the mechanism of pathogenesis
the process by which a disease develops and processes within a host organism, the interaction between the pathogen and the host’s immune response and physiological mechanisms
whats ID50
-infectious dose 50
-number of bacteria needed to infect 50% of individuals
-high ID50 indicates harmful impact at lower doses
what are the two categories of bacterial toxins
exotoxins and endotoxins
what are exotoxins
-proteins made and secreted during bacterial growth
-toxic at lower doses
-often categorised by site of activity
what are endotoxins
-are bacterial structural components that have toxic activity
-can cause endotoxic shock
-released on death of bacteria
outline two categories of exotoxins
cytolysins= disrupt membrane homeostasis and cause lysis leading to cell death
two-component=disrupt cellular processes only (A subunit =enzymatic and B subunit=bind to host cell)
name the outcomes of infection
clearance
asymptomatic carriage
symptomatic carriage
describe ‘clearance’ outcome of infection
no apparent disease, often no knowledge that exposure even occurred
describe ‘asymptomatic carriage’ outcome of infection
host may become a reservoir or ‘super spreader’
describe ‘symptomatic carriage’ outcome of infection
symptoms of highly variably severity, followed by clearance, carriage or death,
-may or may not have long term impacts
name disease patterns in terms of timing
acute, chronic and latent
whats acute disease pattern
develops and resolves rapidly eg GI infection
whats chronic disease pattern
develops slowly, persists for days/months/years eg TB
whats latent disease pattern
infection is initially asymptomatic, becoming symptomatic upon activation
name the disease patterns in terms of location
local or systemic
whats local disease pattern
confined to specific area (location and/or organ)
whats systemic disease pattern
affects most/all of body
contrast Acute vs chronic disease
A=sudden vs C=gradual
A=has cure usually vs C= no cure usually
A=short course vs C=long course
A=patient passive vs C=patient active
A=physician dominant vs C=team care w pt
A=likely to return to normal vs C=unlikely to return to normal
A=future uncertainty rare vs C=future uncertainty common
how do bacteria grow
via binary fission
what are the phases of bacteria growth
lag phase, exponential phase, stationary phase, death phase
Outline phases of bacterial growth
*lag=cells adapt to new conditions, enzymes and new metabolites accumulate
*exponential=maximum contact growth
*stationary=oxygen/nutrient demand can’t be met t/f plateau
*death=number of viable cells drop, death>growth
name the environmental factors affecting microbial growth
nutrient concentration
pH
osmolarity
temperature
(light, CO2, mechanical and sonic stress, moisture)
how does nutrient concentration effect microbial growth
bacterial colonisations require nutrients and oxygen to grow
how does pH effect microbial growth
optimal pH ranges depend across species of different bacteria
how does osmolarity effect microbial growth
some bacterial populations can proliferate in high/low salt concentration
how does temperature effect microbial growth
optimal temperature ranges depend across different species of bacteria
name the classes of bacteria
-obligate aerobe
-strict anaerobe
-facultative anaerobe
-aerotolerant anaerobe
-microaerophile
whats an obligate aerobe
-require oxygen as a terminal electron acceptor
-undergo oxidative phosphorylation to meet energy demands
whats a strict anaerobe
can’t survive in oxygen, converted to H2O2 and superoxide O2- which damages DNA and proteins (kills bacteria)
what is a facultative anaerobe
metabolise more efficiently with oxygen but can metabolise via fermentation when its absent
whats an aerotolerant anaerobe
do not use oxygen;however, are not harmed by its presence (indifferent to oxygen)
what are microaerophile
require specific oxygen concentration, less than atmospheric oxygen levels
name the 4 mechanisms by which antibiotics work
-inhibit cell wall synthesis
-inhibit protein synthesis
-inhibit nucleic acid synthesis
-metabolic antagonism
define bacteriostatic
antimicrobial substance that INHIBITS bacteria growth
define bactericidal
antimicrobial substance that KILLS bacteria
define chemotherapeutic agent
substance used to treat diseases, particularly cancer, by inhibiting or killing rapidly dividing cells
define antibiotic
type of chemotherapeutic agent that specifically targets and kills bacterial growth (traits bacterial infection)
briefly how does penicillin work
-binds to proteins involved in peptidoglycan assembly
-inhibits last step, prevents cross linkage of peptidoglycan strands
-lysis occurs (only works on growing bacteria)
briefly how do bacetrial protein synthesis inhibitors work
-bind and inhibit to prokaryotic ribosome or inhibit a stage of protein synthesis
briefly how do metabolic antagonists worm
-interfere with enzymes in folic acid synthesis
-pathogen dies b/c folic acid is a precursor to nucleic acid building blocks (purines and pyrimidines)
briefly how do nucleic acid synthesis inhibitors work
-inhibit DNA replication, transcription or relevant enzymes)
Define the mechanism of antibiotic resistance
-lots of germs and a few are drug resistant
-antibiotics kill illness causing bacteria as well as ‘good’ bacteria that protects body from infection
-the drug resistant bacteria can now grow and take over (b/c no good bacteria left)
-some bacteria give their drug resistant bacteria to others (via transduction, transformation and conjugation)
what are gene cassettes
sets of resistance genes
how can we prevent antibiotic resistance
-prescribe/ take antibiotics in higher concentrations (overpower resistance)
-prescribe/take antibiotics only when necessary
-consider alternative treatments such as bacteriophages to treat diseases
-prescribe/ take more antibiotics at same time (overpower resistance)
what are the ‘processes’ for diagnostic schema
-design and bioinformatics
-experimental verification
-risk evaluation
what are the ‘elements’ and ‘products’ for diagnostic schema
A=target organisms, genomic sequences, alignments primer selection and assay definition –> database of organism signatures
B=specimen types, specimen matrices, specimen preparation, PCR –>nucleic acid analysis (MS), experimental signature generation
C=nucleic acid analysis (MS), experimental signature generation–> reporting filters
D=medically actionable information (clinical) –> reporting filters
*database of organism signatures–> reporting filters–> organism identification
list common procedures for detection and identification of bacteria
genetic tests
serologic tests
culturing
biochemical tests
microscopy
analytical test
Outline how genetic tests are used for detection and identification of bacteria
analysing DNA or RNA to detect specific genetic markers of disease
Outline how serological tests are used for detection and identification of bacteria
testing for antibodies in blood or body fluids
Outline how biochemical tests are used for detection and identification of bacteria
performing tests to determine bacterial metabolic and enzymatic character
Outline how culturing is used for detection and identification of bacteria
growing bacteria to identify growth hallmarks of certain bacteria
Outline how microscopy is used for detection and identification of bacteria
using microscope to visualise bacteria directly, through staining or size analysis
Outline how analysis is used for detection and identification of bacteria
characterising bacteria based on their unique chemical or molecular profiles
what are the two ways culturing can be used
use selective agar plates (inhibit some bacteria) or differential agar plates (contain indicators to observe certain bacteria)
Describe the importance of sensitivity and specificity for interpreting test results
-both are measures of accuracy of clinical diagnosis tests
-low sensitivity produces false negatives, can lead to misidentification of patients with a disease (some will continue to live with their condition, undiagnosed)
-low specificity produces false positives, can lead to unnecessary further testing, wasting various facets of individual and health care system
name the key areas for appropriate lab stewardship
-appropriate test selection
-secure, yet accessible data management
-correct interpretation of results
-sustainable financial resourcing of labs
appreciate the role of virus in ecosystem
-we are surrounded by viruses, regularly inhale them
-viral genomes in our genetic material (1.5%)
-can have positive impacts also
-we have a active virome (bacteriophages)
-viruses can have global impacts and can cause disease
define term ‘virus’
infectious, obligate, intracellular parasites, comprising of genetic material (DNA or RNA), often surrounded by a protein coat and sometimes a membrane
Describe structure of virus
-small (yet vary in size)
-can be enveloped or non enveloped
-do not grow or divide, instead replicate
distinguish between enveloped and non enveloped virus
-enveloped virus possesses a lipid membrane derived from the host cell
-non enveloped virus lacks a lipid membrane, consists solely of a protein coat (capsid)
name some common techniques used to study viral infections
cell culture
cytopathic effect
coral detection assay
describe cell culture to study virus infections
the technique of growing and maintaining cells in a controlled environment to study viral replications and interactions with host
describe cytopathic effect to study virus infections
observable changes in infected cells that results from viral replication, often leading to cell damage, death or morphological alterations
describe visual detection assay to study virus infections
lab techniques used to identify and detect the presence of viral particles or components in samples, enabling diagnosis, monitoring and research on viral infections
name the stages of viral lifecycle
1.viral entry
2.translation and genome replication
3.assembly
describe viral entry stage of viral lifecycle
viruses encounter cells in a random manner, attach to specific cell surface receptor molecules, enters cell passively (with assistance eg passive endocytosis, un-coating etc) and transfers own genome into host
describe translation and genome replication stage of viral lifecycle
viral mRNA is produced, viral genes are expressed, viral proteins are produced
-happens in nucleus or cytoplasm
describe assembly stage of viral lifecycle
formation of enveloped or non enveloped viruses
what specific viruses replicate in nucleus
most DNA viruses and influenza (RNA)
what specific viruses replicate in the cytoplasm
most RNA viruses
what specific viruses replicate in nucleus and cytoplasm
HIV, HBV (bi-phasic)
what are the two types of RNA viruses
*positive sense (+) RNA
*negative sense (-) RNA
whats positive sense (+) RNA
RNA is the same polarity as its mRNA
whats negative sense (-) RNA
RNA is an opposing polarity to its mRNA
What are the general rules for RNA virus replication
1.RNA-dependent RNA polymerase (RdRp) is the key entity that replicates viral RNA
2.RNA genome must be copied from end-end with no loss of sequence (5’ to 3’)
Describe the replication of (+) strand RNA viruses
1.+RNA infects host cell, expresses viral genome; proteins including RdRp are produced and accumulate in cell
2.Once RdRp levels are sufficient, the replication complex is created, RdRp creates -RNA
3.-RNA acts as a template for synthesis of +RNA, this mRNA is utilised by hosts translational machinery
Describe the replication of (-) Strand RNA viruses
1.-RNA infects host cell, it caries its own RNA Polymerase enzyme
2.RNA polymerase produces mRNA that codes for viral proteins
3.-RNA is transcribed into +RNA, which is transcribed back into -RNA, this process is viral replication
Describe DNA virus replication
1.attachment and entry (via mediated endocytosis)
2.Host RNA polymerase transcribes immediate, early and late mRNA
-specific translated proteins replicated viral DNA genome
-capsids are assembled in nucleus and release virions
define protein capsid
protective shell that enclosed DNA genome of virus
define virion
complete infectious viral particle (DNA or RNA) enclosed in protein capsid
name the types of viral transmission
direct
indirect
zoonotic
fomite
vector
what is direct viral transmission
transmission between two hosts via physical contact
whats indirect viral transmission
transmission between two hosts via indirect contact
whats fomite viral transmission
transmission through contaminated inanimate objects
what vector viral transmission
transmission between two hosts via a live vector eg mosquito
whats zoonotic viral transmission
tranmission from a animal to a human eg zikavirus
how can viruses enter the body
-mucosal surfaces eg airborne, oral or sexual
-penetration of skin eg blood borne, vector borne, cuts etc
-vertical transmission eg across placenta
how do aerosol transmission of viruses occur
-via very small particles/droplets
-aerosol particles can be inhaled or deposited onto mucous membrane or environmental surfaces
-these viruses are usually enveloped
-eg influenza A and COVID 19
how does faecal/oral tranmsiison of viruses occur
-enteric viruses often arise through ingestion of contaminated water or food
-replicate in intestinal tract, virus binds to cell receptor on GI tract
-eg Poliovirus, Hepatitis A
how does sexual transmission of viruses occur
-virus is present in blood and body section
-occurs in unprotected sex
-virus infects cell at mucosal surfaces and spreads or stays local
-eg HIV or Hepatitis B
how does blood-borne transmission of viruses occur
-‘viraemia’, virus circulation in blood
-can arise from virus replicating in target cells and being released into blood
-transmitted via exposure of infected blood
-eg Hepatitis B,C and HIV
how does vector bone transmission of viruses occur
-viruses can infect and replicated inside a vector, t/f vector becomes infectious
-vector can transmit virus to host
-eg Dengue virus and zhikavirus
name steps in viral pathogenesis
-tranmission
-viral replication
-proliferation
-host defence system
what is meant by transmission
-movement from one host to another; virus enters host cell
-indirect (fomite,vector,aerosol) or direct (blood-borne, mucosal)
what is viral proliferation
virus must proliferate and spread throughout the body, to affect multiple cells
how does the host defence system effect viruses
the host defence system will kick in; this will either limit or prove ineffective against the virus
what is a successful clearance of a viral infection called
transient infection
whats an inability to clear infection called
persistent infection
name the effect of viral infection on a cellular level
cytopathic effect
multinucleated giant cell
malignant transformation
inclusion bodies
no change
whats a cytopathic effect (viral)
cell death; vital functions are taken over, cell bursts upon virus release
whats a mutlinucleated giant cell (viral)
fusion of plasma membrane of adjacent cells
whats a malignant transformation (viral)
unrestricted growth and division; cancerous character
whats inclusion bodies (viral)
protein aggregates; localised areas in the cell where virus takes place
what is no change outcome (viral infection)
viral genome incorporates into host genome and remains dormant
whats a localised infection
localised to mucous membranes (eg cold) or areas of the skin (warts)
whats systemic infection
infection of a specific area, followed by entry into circulatory system (lymphatic and/or blood) or NS (neurons)
what can impact the effectiveness of the immune response against viruses
rate of viral replication, size of virus dose, route of infection, age of host, ability of virus to evade host immune response
whats epidemiology
the scientific study of distribution, patterns and determinants of disease in a population
what are epidemiologists
track outbreaks, understand dynamics of viral spread and develop strategies for prevention and control
in the context of viruses what three key epidemiological factors must be considered
-viral factors; structure of virus
-transmission factors:route and type of transmission
-host factors: ecological changes, anthropogenic and environmental factors
how has climate change impacted epidemiology of viruses
-water temperatures: can expand the habitats for vectors like mosquitoes
-extreme weather events and shifting ecosystems: disrupt human and animal interactions, facilitating zoonotic viruses
what impact do emerging diseases have
-introduce viral threats into population, often with unpredictable spread
-overwhelm health care systems
-highlight importance of global surveillance and collaboration
define epidemic
sudden increase in case spreading through large population
define endemic
constantly present in a population; relatively low/no spread
define pandemic
sudden increase in cases across several countries, continents or globally
name the factors considered to control viral infections
interfere with transmission
establish protective immunity
establish effective treatment protocol
what is meant by interfering with transmission to control viral infections
develop programs for public education/prevention, barriers, isolation, clean water/needle access
what is meant by establishing protective immunity to control viral infections
develop vaccination programs for consenting, at risk individuals
what is meant by establishing effective treatment protocol to control viral infections
using antiviral drugs to inhibit viral replication, use antibodies for passive immunisation
name the principles for preventing disease outbreak
-hand hygiene; disinfection; sterilisation
-disposal of waste
-surveillance; contact tracing
-public health messaging
what is involved in hand hygiene; disinfection and sterilisation
promoting a clean environment non conductive to viral transmission
what is involved in disposal of waste
promoting a clean environment non conductive to viral transmission
what is involved in surveillance; contact tracing
monitor individuals and viruses so that their spread can be limited
what is involved in public health messaging
keep the public informed on current ‘best’ protocols/measures
what cell type are fungi
eukaryotic
when do we use ‘diagnostic test’ for diagnostic virology
depends on whether we are testing for current (virus particles and/or viral genome and proteins) or previous (serology/and or antibody response) infections
what is the method of collection and test for GI tract infections
-faeces;vomit : test for viral particles, genomes,proteins
-blood: test for serum antibodies
what is the method of collection and test for respiratory infections
nasal swab: test for viral particles, genomes,proteins
blood:serum antibodies
what is the method of collection and test for blood-borne infections
blood:viral particles, genomes,proteins and serum antibodies
liver biopsy sample: viral particles, genomes,proteins and serum antibodies
heparinised: levels of CD4+ T cells (eg HIV)
what is the method of collection and test for STD infections
vesicle fluid: viral paerticles genomes, proteins
blood: serum antibodies
what are the key features transportation of specimens
viable virus is needed
-genome must be indicated
-appropriate temperature (either -80 or 4)
-viral collection kits = gold standard
How do RAT tests work
-look for the presence of COVID 19 antigens
-samples taken via nasopharyngeal swab or saliva
-antigens bind to strips and gives a visual readout, indicated by ‘two lines’
-fast process, no experience needed (78% accuracy)
Outline the diagnosis method for virus infection
1.grown virus in vitro in cell lines and identify, observe cells for cytopathic effects
2.look directly for virus using electron microscopy
3.detect virus proteins (antigens), detection relies upon availability of antigen specific ABS
4.detect genome (RNA or DNA) by RT-PCR or PCR
5.detect antibodies in serum or infected patients
term used to describe nutrition of fungi
heterotrophic (rely on external sources. to obtain their nutrition)
fungi cell wall is made of
chitin
name the motility of fungi
non motile
how do fungi reproduce
mainly asexually, sometimes sexually
whats medical mycology
branch of medical science that studies fungi capable of causing disease in humans and animals
what do medical mycologists do
investigate the pathogenic mechanisms of fungi, their ecological niches and modes of transmission and develop antifungal medicines
whats hyphae
branching, thread like filaments that make up the body of the fungus
what are heptae
hyphae that contains cross walls or septa
what are aseptae
hyphae that lack cross walls or septa
what is mycelium
vegetative component of fungus, consist of an aggregated mass of hyphae
whats a spore
reproductive structures produced by fungi, plants and other organisms
what are yeast
fungi that are unicellular throughout their entire life cycle
whats pseudomycelium
yeast cells clinging together
name the types of fungal infections
superficial mycosis , cutaneous mycosis , subcutaneous mycosis , systemic mycosis
whats superficial mycosis
localised to superficial skin layers, hair shafts and nails
whats cutaneous mycosis
localised to dermis
whats subcutaneous mycosis
localised to subcutaneous tissues
whats systemic mycosis
affects multiple organs, including lungs, CNS and bones
symptoms and treatment for superficial mycosis
symptoms=rash, itching and discolouration
treatment=topical or oral anitfungal meds
symptoms and treatment of cutaneous mycosis
symptoms=lesions, inflammation and redness
treatment=topical or oral anitfungal meds
symptoms and treatment of subcutaneous mycosis
symptoms=nodules and ulcers
treatment=antifungal medications, surgery
symptoms and treatment of systemic mycosis
symptoms=respiratory symptoms and weight loss
treatment=antifungal meds
what are the advantages for a parasite living in host
-host supplied food
-constant environment
-free from predation
-free transport
what are the disadvantages for a parasite living in host
-may require remodelling of the environment
-needs to evade host immune response
-escape plan to find new hosts
-infection can kill host
name two categories of intercellular parasites
facultative parasite and obligate parasite
whats a facultative parasite
can reproduce outside of host cell eg salmonella
whats an obligate parasite
cannot reproduce outside host cell eg viruses
List the reasons underlying the rise of emerging viral infectious diseases in Australia
-increasing human population size
-aging global population
-high risk behaviours (drug use, unprotected sex)
-urbanisation
-fast-paced lifestyles
-more children in day care
is there such thing as a ‘new’ virus
generally not, viruses have co-evolved with us for millennia, and simply become detected and/or transmitted to human population (from animals usually)
why doesn’t hay fever cause feverish symptoms
there is no release of endogenous pyrogens
Outline mechanism of fever/pyrexia
-infection/pathogen enters
-macrophages and neutrophils release endogenous pyrogens (IL-1,IL-6,TNF-alpha)
-these messengers travel to the hypothalamus (respiratory centre) via the bloodstream
-hypothalamus releases prostaglandins
-increases temperature set point in body
-this is achieved by vasoconstriction ,piloerection, shivering
-this provides a more hostile environment for the pathogen and increase metabolic rate (more WBC activity)
Outline mechanism of a cough
-stimulation of mechanoreceptors in throat, upper respiratory tract or lungs)
-afferent impulses sent to medulla and pons via vagus nerve
-medulla and pons integrate the sensory input and generate a coordinated response, initiating the cough reflex
- Motor signals are sent from the medulla and pons to the muscles involved in coughing via efferent pathway
-effector:Deep inhalation is followed by compression and rapid expulsion of air, clearing irritants from the respiratory tract
