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)
what is the difference between sterile and non sterile sites in terms of flora population?
in sterile sites there is no flora population while in non sterile sites there is flora population
what is non sterile enviroment and give examples
directly or inderictly exposed to the enivorment. GI tract, naso pharyhnx, vagina, skin, conjuctiva –> all non sterile
when does do you produce flora?
after birth. During birth you are fully sterile –> breast feeding and contact with people –> development of flora
how is sterile sites maintained?
Sterility maintained by surface cleaning
Open to the environment
Sterility maintained by barriers that allow uni-directional flow –> Adjacent to non-sterile sites
Sterility maintained by physical separation from non-sterile sites -> Closed cavities
how is the lower respiratory tract mainted sterile?
By surface cleaning. The cilia epithelium in the upper airway means that microorganisms are moved out. Coupled with the production of mucous, cough and sneezing–> sterile enviroment is produced
give examples of Sterility maintained by physical separation
pleural cavity, spinal cord and meninges and peritoneal cavity
give examples of Sterility maintained by barriers
upper genital tract –> barrier is cervix
urinary tract –> barrier is urethra
middle ear –> barrier is eustachian tube
what is tissue tropism?
is the cells and tissues of a host which support growth of a particular virus or bacteria.
what are the physical variables of a enviroment for microorganism growth?
temperature, humidity, PH. moisture, 02 availability, nature of surface
what is the characterstics of skin?
Variable temperature Dry Subject to abrasion Aerobic environment Nutrient-poor Skin surface components
what is the characterstics of gingival crevice?
Constant temperature Moist Few physical challenges (toothbrush) Anaerobic environment Bathed in nutrients Mucosal surface components
What are the 3 bacterias that make up the skin flora?
Coagulase negative staphylococci ( staphylococcus epidermis) lives in moist skin so therefore underneath the arm pits but can also live on dry skin if there is a wound.
staphylococcus aureus (nasal carrier/nostrils)
Propionbacterium species (priopionbacterium acne)
what pathogens are in the pharynx?
Streptococcus pyogenes (group A) Haemophilus influenzae Streptococcus pneumoniae Neisseria meningitidis 7-34% in UK university students1 S. aureus
what microorganisms are in the pre puberty vagina?
Skin flora
Lower GI flora –>Mainly E. coli
what microorganisms are in post puberty vagina?
glycogen produced due to circulating oestrogens
Lactobacillus spp. Lactobacillus acidophilus –> Ferment glycogen
Maintain pH ≈3, preventing overgrowth of other species
Skin flora
A few C. albicans
what is the enviroment of the GI tract of stomach and small intestine?
Low gastric pH inhibits bacterial growth
Predominantly aerobic bacteria
- acid-tolerant Lactobacilli
- Helicobacter pylori
Few or no anerobics
how can h.Pylori survive?
it can surivive in the low Ph by producing urease which converts the urea in ammonia and carbon dioxide
what is the most common type of bacteria in the large intestine and give examples
95-99% Anaerobes, 400 different types
Bacteroides spp., Clostridium spp. Bifidobacteria spp
what type of aerobic bacteria are in the large inestines?
Enteric Gram-negative bacilli
Escherichia coli, Klebsiella spp., Enterobacter spp., Proteus spp., Citrobacter spp. etc.
how does normal flora synthesis and excrete vitamins?
e.g. vitamins K and B12 secreted by enteric bacteria in ileum small intestines
how do normal flora help with colonise resistance?
Environmental manipulation
e.g. reduction in pH –> low PH is a form of defence –> created by bacteria metabolism
Antibacterial agents such as fatty acids and metabolic waste products
what is Clostridium difficile infection, the cause and the risks?
Hospital acquired infection. Usually >60 years
Main risk factor ANTIBIOTIC TREATMENT –> antibiotics disrupt the microbiome and allows the niche needed for C. difficile overgrowth
Leads to toxin production
Diarrhoea. Pseudomembranous colitis
what is feacal transplant mainly used to treat?
C. Difficile–> works 80% of the time
what other disease is feacal transport sometimes used for?
Multiple sclerosis Chronic fatigue Syndrome (ME) Ideopathic thrombotic purpura Ulcerative colitis Irritable bowel syndrome Diabetes mellitus
Overgrowth of flora caused by broad spectrum antibiotics can cause what
vaginal thrush
what clinical conditions are caused by normal flora?
Gastroenteritis, peritonitis Pneumonia Abscesses Dental caries, peridontal disease, -->pharyngitis Endocarditis Urogenital infections
what is pathogenicity?
capacity of a microorganism to cause a infection
what characteristics are needed for a microorganism to be infectious?
transmitible
establish in or on a host
harmful effects
persistant
what is the steps in the chain of infection?
Pathogenic organism–> Of suffecient virulence to cause a disease
Resevoir–> to survive and multiple
Mode of exit out of the source
Transmission from the source to the host
Most of entry into the host
Susceptible host
what does virulence refer too?
the extent in which a microorganism causes a disease
what is Streptococcus mutans?
Type of oral flora
What are spores?
part of a organism that resist damage when it is exposed to the enviorment
what is lethal/infectious doses?
it is the dose at which 50% of animals infected by the infection die
what is infectivity?
The ability of a micro-organism to become established on/in a host
Microbial ligand and Host cell surface receptor
what ligand receptor does E. coli use?
P fimbriae a glycoprotein on human uroepithelial cells that allows the attachement to the urinary tract and cause unirary tract infection
what lingand receptor does S. pyogenes express
protein-F: fibronecti found on connective tissue, cell surface and various body fluids
what is virulence factors and give me some examples?
Components of micro-organisms that result in harmful effects:
Facilitation of adhesion
Toxic effect(s)
Tissue-damage
Interference with host defence mechanisms
Facilitation of invasion
Modulation of the host cytokine responses
Virulence factor coded by virulence genes
what type of bacteria is endotoxin associated with?
Gram negative bacterial cell wall such as e.coli
But also see it in Neisseria Meningitides, where the production of endotoxin causes meningeal cocci septicemia
When is endotoxin released, the active componenet and what is the outcome?
released from damage or dead cell
active component is lipopolysaccharide – LPS
Binds to a number of host cell receptors
Induces a range of uncontrolled host responses
what is lipopolsaccharide made off?
What is the 0 for ecoli?
ligand A –> dissacharide faty acid complex (mixture of polysacharide and fatty acid)
oligosaccharide core
polysaccharide O antigen
E.coli O157
what is the response of the host to endotoxin?
Systemic inflammatory response syndrome (SIRS)
what are the symptoms of Systemic inflammatory response syndrome (SIRS)?
Uncontrolled T-lymphocyte response
……Cytokine release: TNF-α, γ-interferon, interleukin-1
……Fever, rigors, hypotension, tachycardia, collapse
……..Cardiac and/or renal failure
Uncontrolled activation of the clotting cascade
……..Disseminated intravascular coagulation (DIC)
………Depletion of clotting factors
………Bleeding tendency
Unctontrolled activation of the complement
Give examples of systemic inflammatory response syndrome?
septc shock and endotoxic shock
What type of toxin is produced by Neisseria meningitidis? What is the outcome?
Endotoxin and increase in vascular permeability causes loss of protein, fluid and plasma into the tissues, with pathological compensatory vasoconstriction.
Give the characterstic of exotoxins?
What is used to treat exotoxins?
usually proteins produced by the bacteria and have a specific effect on the on the host
Specific antitoxin
What bacteria caues botulism
Clostridium botulinum bacteria
how is botulism caused?
Ingestion of pre-formed toxin –> Contaminated food
Infection of dirty wound–> May be trivial wound
Gastrointestinal colonisation in infants
It is a very strong toxin do not need a lot to cause disease
what is the symptoms of botulism? 5D’s
Diplopia --> double vision. Dysphagia --> difficulty swallowing Dysarthria --> difficult or unclear articulation of speech Dry mouth Death Respiratory failure Respiratory muscle not working anymore
what organism causes tetanus and the mode of infection?
Clostridium tetani
Infection of a dirty wound can be trivial wounds
How does clostridum tatani cause tatanus?
Toxin production Tetanospasmin Produced on germination of spores Binds to nerve synapses Inhibits release of inhibitory neurotransmitters (e.g. gamma-amino butyric acid) in the central nervous system
what is the symptoms of tetanus and how does it cause death?
Opisthotonos –> spasm of the muscles causing backward arching of the head, neck, and spine
the way the body froms the shape depends on the muscles and their relative strenght.
Locked jaw
Also death by respiratory paralysis
what caues Scalded-skin syndrome?
Staph. aureus epidermolysin
what causes chloera?
vibrio cholera
what causes diphtehria?
corynebacterium diphtheria
what caues staphylococcal scalded skin syndrome?
staph. aureus–> can producean exfoliative toxin r
what caues whooping cough
bordetella pertussis
what causes scarlet fever?
Streptococcus pyogenes
What causes C.diff?
Diarrohea and collitis
what type of bacteria is Strep. pyogenes and what is its virulence factor?
It is a gram positive bacteria that has virulence factors that promotes connective tissue break down and invasion
what syndromes are produced by strep.pyogens?
Streptococcal sore throat difficult condition to diagnose
Erysipelas –> skin infection
Necrotizing fasciitis–> soft tissue infection and rapidly life threating
Scarlet fever -> Streptococcal sore throat produced by erythrogenic toxin
Can cause renal complication
What are the 5 virulent factors for strep.pyogens?
Hyaluronidase and streptokinase–> Break down connective tissue components – facilitate tissue invasion
C5a peptidase–> inactivates complement component C5a
Streptolysins -O and –H –> Lyse red and white blood cells and platelets
Erythrogenic toxin (phage-encoded) –> Causes the rash of scarlet fever
Toxic shock syndrome toxin –> Streptococcal toxic shock syndrome is superficially similar to a syndrome of endotoxin release –> uncontrolled septic cascade
what are the symptoms of Necrotizing fasciitis
and how is it controlled?
Get black area of necrosis with inflammation around it. It cannot be stopped by antibiotics –> does not stop spread of infecton unless the tissue is removed
how does strep.pyogens evade the immune system and prevent being phagocytosed?
M-protein binds fibrinogen and masks bacterial surface, blocking complement binding and opsonisation
how does s.pneumonia (gram positive bacteria) evade the immune system and phagocytosis?
Polysaccharide capsule inhibits opsonisation and therefore phagocytosis1
how to intracellular pathogens evade the immune system and give examples?
evade the immune system –> by invading the cells of the host –> to get to the pathogens the host has to kill its on cells
Mycobacterium tuberculosis
Salmonella typhi
Listeria monocytogenes
what are the three particles which make up the virus?
Genome - RNA or DNA
Capsid – protein
Envelope – lipid bilayer)
where is S.aprophyticus normally found and what can it cause?
is part of the normal vaginal flora, but which can be a frequent cause of cystitis.
what microorganism can cause infection of implants of catheters and heart valves?
S. epidermidis
What other specie as well as fungi use chitin?
Anthropods such as insects use chitin for there cytoskeletin
What two type of toxins can bacteria cause? Give example of disease caused by these toxins
Exotoxins –> produce tetanus
Endotoxins–> produce gram negative shock
What 4 ways can bacteria cause infection?
Production of structures that allow them to adhere to surface to cause disase via pilli and fimbrae
Production of exotoxins and endotoxins
Production of aggresins
Initiating undesirable consequences of the host defences.
What is the consequence of bacteria producing soluble antigens?
They can combine with antibodies and cause circulating immune complex
Under certain circumstances that can become trapped in blood vessels and cause compromise there function
Glomerulonephritis can result from circulating immune complexes after infection by what microorganism?
Streptococcus pyogenes
Give example of direct inoculation?
Sharing of needles
How many microbes do the human habour?
10 to the 14
What does it mean by microenviroments?
Different sites within a site
What type of flora is there on the skin near a body orrifice?
The flora will be similar to the body oriffice regardless of being on the skin
What type of flora is there in the mouth and why is it important?
Oral streptoccoci, anaerobes
Colonisation of normal flora will prevent the colonisation of pathogenic flora
Where is the main carrier site for S.aureus?
Nostrils
what interaction is there in normal flora that can have a protective effect?
Induction of cross reactive antibodies
What diseases are microbiome of the body involved in?
Inflammatory bowel disease Metabolic disorder, Diabetes Cancer Infection Hypertension Obesity
Give example of a disease caused by translocation - from one site to another?
Conjuctivitis caused from a URTI such a runny nose and cough–> get the transfer of heamophilis influenza
Get red eye and conjuctival disarch
What type of flora is involved in a diseases caused by transolcation into a normal sterile site during surgery?
coagulase-negative staphylococci
What infection can cause cross infection?
MRSA
What are the types of transmission of a pathogen?
Feacal oral
Blood borne
Respiratory
Direct contact –> hand to hand or mucous barrier
What is the effect of botulism?
Botulism - flaccid paralysis and respiratory failure (muscles are unable to contract) Botulinum binds pre-synaptically and inhibits release of ACh at neuromuscular junction
What is the generic virus life cycle?
1) Adsorption - receptor ligand interaction
2) Penetration - receptor mediated endocytosis
3) Uncoating - nucleic acid liberated from phagosome and replicated
4) Synthesis - nucleic acid and protein synthesis mediated by host cell enzymes
5) Assembly - Assembly of virus components is mediated by host and/or viral enzymes
6) Release - complete virus particles are released by budding of host cell membrane or disintegration of host cel
