week 5 Flashcards
what percentage of the cells in our body are off human origion? What makes up the rest of our cells?
10%
Human commensal flora/human microbiota –> mainly bacteria but also some fungi and protista
what factor affects the type of microbial flora in our body?
the anatomical sight
what type of bacteria is in our teeth and what disease can it cause?
Streptococcus mutans which can cause tooth decay
what type of bacteria is found in our tongue and other soft tissue in our mouth?
home to large numbers of Streptococcus salivarius
how can Streptococcus mutans in the teeth cause a disease?
to much sugar will cause Streptococcus mutans to produce acid which will decay the teeth
what do we substance do we depend on microorgansims providing?
Continous supply of vitamin K in our body and also provide most of our fixed supply of nitrogen
who discovered that infection agents can cause disease and what is the name of the criteria?
Robert Koch and the criteria is called Koch’s Postulates
what are Koch’s postulates state?
The causative organism must be isolated from every individual suffering from the disease in question;
The causative organism must be cultivated artificially in pure culture;
When the causative organism is inoculated from pure culture, the typical symptoms of the infection must result;
The causative organism must be recoverable from individuals who are infected experimentally.
what is Koch’s Postulates for genes ?
Genes encode virulence factors:
The gene encoding the trait of interest should be present and transcribed/translated in a virulent strain;
The gene encoding the trait of interest should NOT be present or should be silent in a strain that does not cause disease;
Disruption of the gene in a virulent strain should result in the formation of a strain that is incapable of causing disease;
Introduction of the gene into a strain that previously did not cause disease should transform the strain into one that does cause disease;
The gene must be expressed during infection
Antibodies raised against the gene product or the appropriate cell-mediated immunity should protect experimental subjects against disease.
what are the problems of koch’s postulates?
difficulty of isolation the causative agent;
impossible to grow some pathogens in artificial culture;
ethical objections;
animal models not sufficient.
what does a virus comprimise off?
a nucleic acid core wrapped around in a protein coat made up of capsomeres
what is the envelope of a virus made off and do all virus have one?
Made up of lipids that has been derived from the cell it is infecting. Not all virus’s have envelope
how do retrovirus work?
They have a RNA and upon infecting a cell they integrate there RNA into the cells DNA using reverse transcriptase and then cause production of mRNA. This contains the viral frgaments and more and more virus is produced –> example HIV
What type of virus attacks bacteria?
bacteriophage
What virus infection do plants suffer from?
viroids –> naked infectious RNA that is not associated with any proteins
what causes spongiform encephalopathies and give examples?
Caused by prions. Example of infection are mad cow disease (BSE)/CJD
what is the structure of microfungi?
They are eukaryotic and have a cell wall made of chitin. This is a polymer of N-acetyl glucosamine
how do moulds grow?
moulds are fungi that grow in mats of tiny filaments known as hyphae and form mats called mycelia
what structure subdivides mycelia?
They are subdivided into seperate compartments by by septa which are cross walls. Not all are subdivided
What cellular type is mould and what is it kind of related to?
Moulds are multicellular and to some degree related to muschrooms and toad stoles
What cellular type is yeast?
They are unicellular fungi
what is the most common type of yeast infection and what is it caused by?
Thrush and caused by Candida albicans
Give example of superfecial mould infections
athletes foot and ringworm
what are the classes of protista?
apicomplxa (formerly sporozoa),
flagellate protista,
ciliate Protista –> no causes of infection
amoebae –> cause diarrhoea or meningitis
what type of cells do protista have?
unicelleular eukaryotes which most are free living but some cause serious infections
Give examples of protista infection?
toxoplasmosis, amoebic meningitis, malaria, trypanosomiasis, leishmaniasis (Kala-Azar) amoebic dysentery diarrhoea.
what protista cause vaginal infection?
Trichomonas vaginalis. The protista causes foul smelling vagina discharge. Males are usually asympotomatic but can cause balanitis. Which is inflammation of the forskin and head of the penis
what microbe was originally thought to be a protest but discovered to be a fungus and why?
Pneumocystis carnii–> thought to be a protest because of its microscopic apearance and behaviour
Important for AIDS infection and some pnuemonia infections
what is the structure of bacteria?
(simple)prokaryotes with a lack of membrane bound nucleus
what shape are bacteria usually?
round (cocci) or rod (bacilli) shaped
what is the structure of gram positive bacteria? What colour is the gram staining?
How susceptible is it to antibiotics
Comprimise of 30 to 40 layers of peptidoglycan and therefore retains the crystalviolet iodine stain and is purple/blue in colour
More susceptible to antibiotics as it lacks the outer membrane that gram negative bacteria has
what is the structure of gram negative bacteria?
How susceptible is it to antibiotics? Finally what is its gram staining?
it has very little peptidoglycan but contains a extra layer –> outer membrane that makes it less susceptible to antibiotics than gram positive bacteria.
Gram staining –> pink
What type of bacteria causes a toxic shock and why and what is the outcome?
gram negative bacteria contain lipopolysaccharide called Lipid A that produced endotoxin. Increase in breathing ocurs, hypertension and leaking of the blood vessels
What type of bacteria have fimbrae and pilli and what are there functions?
Gram negative bacteria have hair like structures called fimbriae that adhered to particular surfaces.
Also able to exchange material via sex pili tube once two cells have conjugated
What do bacteria produce to protect themselves from phagocytosis and how is this identified?
They enclose themselves in capsules
By negative staining and the formation of a halo ring around the cells
what does slime do produced by some bacteria and give a example?
It allows it to stick to surfaces. Example is Streptococcus mutans which uses slime to adhere to teeth to be able to form plaque by the metabolism of sugar rich diet.
what bacteria can causes infection associated with implanted plastic medical devices?
‘Coagulase-negative’ staphylococci live on skin and some strains use slime to stick on plastic which can cause infection
what characteristic does some bacteria have that allows it to live in hazerdous enviroment?
Endospores are highly resistant structures that allow bacteria to resist high heat, radation and disiccation
Give example of person to person spread of infection?
airborne infection –> infectious droplets
Faecal oral route
How does faecal oral route work and give examples?
the contamination of drinking water with faeces. Can cause Typhoid, Hep A, Cholera, dysentery, poliomyelitis
why are pathogens of sexually transmitted infection vulnerable?
They are vulnerable because they cannot survive out of the human body so therefore need close contact to be able to move between bodies
what are the two casues of malaria?
Female anopheles mosquito and caused by protists of the genus Plasmodium.
what are the name of infection in which animals are the resevoir?
zoonoses
what are fomites?
When inaminte objects such as paper, pen, surgical instruments are the vector for infection
what factors are needed to control spread of infection?
identifying the mode of spread, interuppting the cycle of infection, spread and replication
what does a cycle of microorganism need to spread?
the cycle of infection required for the infectious pathogen to infect a host, to multiply within the host and spread to other hosts
what are Intoxication illnesses?
The cuase of the disease is not encoutering the microorganism but being exposed to a toxin. For example tetanus.
what type of toxin causes tetanus?
exotoxin
what type of toxin causes gram negative shock?
endotoxin
what sort of enviroment is good to harbour flora microorganism?
wet moist areas not dry areas like teh skin
what is the definition of normal flora?
organism found in a given location in state of health
what is colonisation?
it is the establishment of a sight in the body
what is symbiosis?
it is where two or more organisms living in close physical associated
what is Mutualism variation of symbiosis?
when both organisms benefit in symbiosis
what is neutralism varation of symbiosis?
it is when neither organism benefits from symbiosis
what is Commensalism varation of symbiosis?
it is when one organism benefits but the other does not niether benefit or harm
what is Parasitism varation of symbiosis?
One organism (parasite) benefits at the expense of the other (host)
