Lecture 2: Host-Parasite Relationship Flashcards
Define Symbiosis?
Organise that need each other to survive
Close association of two dissimilar organisms
Mutualism?
All participants benefit
Commensalism?
One benefits and the other is not harmed
Parasitism?
Parasite benefits and other is harmed
Predation?
Parasite actively hunts host
Competition?
Organisms fight against each other
What type of environment is human body for microbes?
Is a diverse environment in which specific niches are present and dynamic relationships exist.
What organisms make up the normal microbiota of human body?
Mainly bacteria (+1000 species). Few eukaryotic fungi (algae) and protists (protozoa). Some ArchaeBacteria at lower G.I tract.
Micro-biome?
All genes of host & microbiota
Total Microbial load of human body?
Greater than 100 trillion microbial cells
Reasons to study human microbiota?
Gain insight into possible infection resulting from injury.
Understand consequences of overgrowth of microbes usually absent.
Increase awareness of role-played by indigenous microbes in stimulating immune responses.
Factors influencing the composition of normal flora?
Anatomical site. Age. Sex. Diet & Nutrition. Environmental. Developmental changes.
What is Nosocomial?
Something picked up from hospital or health facility.
What is a opportunistic pathogen?
normal microbiota that produce disease under certain conditions
What does normal flora have to gain from host?
- Supply of Nutrients
- Stable environment
- Constant Temperature
- Protection
- Transport
What does the host obtain from normal flora in mutualism?
- Nutritional benefits
- Stimulation of the immune system
- Exclusion of potential pathogens
- Antagonism of pathogens
Benefits of having normal flora in human body?
- Provide essential nutrients
- Prevent colonisation by pathogens
- Antagonise other bacteria
- Stimulate development of immune system
What is tissue tropism?
This is specific organisms at specific sites.
Describe the environment of skin?
It is generally considered to be an inhospitable environment with slight acidic pH. It has high concentration of NaCl and is generally low moisture environment. Bacteria numbers are usually low.
What areas of skin will have the highest number of microbes?
Areas high in moisture most protected from the outside environment.
What is a microbiota called that is not usual found at the site of interest?
Transient Microbes.
Microbiota that are usually found at site of interest?
Residential Microbes.
What types of microflora are found at entrance of orifice?
Mixed flora
What is the main type of microbiota found on the skin?
Consists largely of Micrococci and corynebacteria.
- Staphylococcus Epidermis (90%)
- Micrococcus luteus
What type of microflora live below skin follicles, sweat and sebaceous glands?
Anaerobes (eg. Propionibacterium acnes)
What microflora are usually found at the face, hands and nasal cavities? What percentage of people usually have them?
Staphylococcus aureus which is an opportunistic bacteria. Found in 20-40% of population
Define Conjunctiva? Is there many organisms usually present?
Thin membrane covering eyes and inside of eyelids. Low number of organisms present.
What are the main microbiota found at the conjunctiva?
Staphylococcus epidermis, S. aureus.
How is the microbiota kept with in healthy levels in the Conjunctiva?
- Blinking (mechanical cleaning)
- Lachrymal secretions containing lysozyme.
Define the term ‘commensalism’.
This is a form of symbiosis by which one organism benefits where the other is harmed.
List a member of the normal human microbial flora (full genus and species) that is a major cause of human infection and list where it is normally found?
Streptococcus pneumonia is a pathogen found in the upper respiratory tract and can cause infection if population are too high
A patient with a suspected urinary tract infection is asked to provide a mid- stream urine specimen. Why?
This is because mid stream part of urine is most likely to reflect the microbiome that the patient has as it is the microbes that are residential in the urine tract as the temporary one will be flushed out in first part of urine.
What is a nosocomial infection?
A nosocomial infection is something picked up from a hospital or health facility. These are usually dangerous
The lower respiratory tract is normally sterile. Why?
This is because the lower respiratory tract has mechanism in place to prevent microbiome from living growing there. These include cleansing action of ciliated epithelium & mucocilliary blanket. Sneezing, coughing and swallowing. Phagocytic actions of alveolar macrophages and lysosome in mucus.
What is lysozyme and its role in tears?
This is enzyme that act as a chemical barrier released in lachrymal that prevents against pathogens and microbes by breaking down bacterial cell walls.
Which bacteria (full genus and species) is the most common cause of urinary tract infections?
Candida Albicans
List one pathogen (full genus & species) that may be found as a member of the normal flora of the upper respiratory tract?
Neisseria meningitidis
Main microbiota found in Nasal cavity and Nasopharynx?
Staphylococcus epidermis & corynebacteria. (Staphylococcus aureus)
Bacteria in sinus?
Healthy sinus are sterile.
Is there a large number of bacteria species in the upper respiratory tract?
Yes a large number :)(:
What is an example of microbiota found in respiratory tract?
- Alpha heamolytic streptococci
- Neissera meningitidis
Pathogens found in the upper respiratory tract?
- Streptococcus pneumonia
- Streptococcus pyagenes
- Haemophilus influenza
What type of enviroment is expected to be found in the lower respiratory tract?
The lower respiratory tract is virtually pathogen free with a low number of microbiota.
How is the lower respiratory tract kept virtually pathogen free?
These include
- cleansing action of ciliated epithelium & mucocilliary blanket.
- Sneezing, coughing and swallowing.
- Phagocytic actions of alveolar macrophages
- lysosome in mucus.
What type of pathogens could the lower respiratory tract be susceptible?
These can be susceptible to pathogens of upper respiratory tract.
What variety of bacteria occupy the oral cavity?
A large number of bacteria occupy the oral cavity. streptococci, lactobacilli and a great number of anaerobes(candida)
What colonises the oral cavity at birth?
Streptococcus salivarius
What bacteria is responsible for initiating dental decay?
S. mutans
Explain the activities leading to dental decay?
- Produces hydrolytic enzymes that breakdown sucrose → lactic acid (↓pH). More acidic enviroment renders teeth more vunerable to decay
- Organism secretes insoluble glucans/polysaccharides = biofilm of glycoprotein and bacteria – in the oral cavity → plaque build up
What type of environment is the urogenital tract?
Urogenital tract is usually sterile.
Normal flora occupy that anterior (distal) urethra?
- Staphylococcus epidermidis
* Enterococcus faecalis
What microbiota colonise female genital tract soon after birth?
- staphylococci
- streptococci
- E. coli
In the Female genital tract what microbiota dominate between Puberty to menopause?
Lactobacillus acidophilus
Candida albicans are normally present in low numbers in the Female genital tract and responed to changes in?
- pH changes
- hormonal changes
- normal flora changes
What bacteria are present in the Gastrointestinal Tract in breast fed infants?
bifidobacteria (90%)
What other factors does human milk contain?
Human milk contains a growth factor that enriches for growth of bifidobacteria and
prevents colonisation of intestinal tract by non-indigenous or pathogenic species
When breast fed infants are swapped to solids or cows milk what microbiota join the bifidobacteria?
bifidobacteria are progressively joined by:
- enterics
- Bacteroides
- enterococci
- lactobacilli
- clostridia
What kind of bacteria is found in the Oesophagus?
only the bacteria swallowed with saliva and food
Name bacteria found in stomach and what it can lead to?
Helicobacter pylori, causes gastric ulcers, gastric and duodenal cancers
Flora in the proximal small intestine?
relatively sparse Gram-positive flora
lactobacilli
enterococci
Flora of the distal small intestine?
Distal small intestine contains greater variety and numbers of bacteria compared to proximal. lactobacilli, enterococci, Coliforms -Protozoa
Amount of large intestine flora?
10^12/g faeces wet weight
Prodominate organisms in the large intestine?
Predominant organisms are:
Bacteroides
anaerobic lactic acid bacteria
Bifidobacterium
Infection by Normal Flora is facilitated by?
- Damage to the epithelium and mucosal surfaces
- Presence of a foreign body
- Transfer of normal flora to another anatomical site
- Suppression/impaired immune system
- Secondary bacterial infections
- Use of antimicrobial chemotherapy
- Nosocomial infections
