Lecture 3 - An Infection Model Flashcards
What is the difference between gram positive and gram negative bacteria?
Gram + have thicker peptidoglycan wall
Gram + bacteria have no outer lipid membrane whereas gram - bacteria do
What is meant by normal flora or the micro biome?
The microorganisms that are normally present in/on the body
What are some gram positive cocci bacteria which are part of the normal flora of the skin?
Staphylococcus aureus
Staphylococcus epidermidis
Streptococcus species
What are some Gram positive bacilli bacteria part of the normal flora of the skin?
Corynebacterium species
Propioibacterium acne’s
What colour do gram positive bacteria stain?
Purple/violet
Why do gram positive bacteria stain purple?
Their thick peptidoglycan wall retains the crystal violet stain
What colour do gram negative bacteria stain?
Red
Why do gram negative bacteria stain red?
Their thin peptidoglycan walls cannot retain the stain
What causes cellulitis?
Infection caused by bacteria that are part of the normal skins micro biome
What microorganism commonly causes Thrush?
Candida albicans
Which bacterial microbe is important in controlling the levels of Candida albicans?
Lactobacillus bacteria
How do Lactobacilli keep number of Candida albicans under control preventing thrush from developing?
Maintain the acidic pH around the genitals in women preventing the overgrowth of Candida albicans
What type of microbe is Streptococcus mutans?
Gram + cocci
Where are Streptococcus mutans normally found?
Oral cavity
High in saliva
Surface of enamel
How do Streptococcus mutans cause infection?
Use glucose and sucros (fermentable carbs) to build their capsule.
They attach to the enamel and digest the enamel
What type of microbe is Streptococcus pneumonia?
Gram positive cocci
Where are Streptococcus normally found?
Mucus layer overlying epithelial surface of the upper respiratory tract
How does Streptococcus pneumonia cause infection?
Directly invades endothelial cells of the upper/middle respiratory tract
What type of microbe is Escherichia coli (E.coli)?
Gram negative bacillus
Where is Escherichia coli normally found?
Lower intestine
How does Escherichia coli cause infection?
What is the method of infection?
How does the infection produce symptoms?
When orally ingested travels down digestive tract releasing the Shiga toxin with damages lining of small intestine
What type of microbe is Candida albicans?
Gram + fungi/yeast
Where is Candida albicans normally found?
Skin
Mouth
Gut
Vagina
How does Candida albicans cause infection?
Infection is when it overgrows Orr enters deep into the body
Hyphae breach mucosal surface and damage underlying tissues
What may lead to the overgrowth of Candida albicans and why?
Antibiotics (amoxicillin)
Destroy Lactobacillus bacteria which maintain the acidic pH at preventing overgrowth
What 2 things are needed for infection to happen?
Pathogen + Host/patient
What factors influence a patients vulnerability to infection?
Age
Gender
Physiological state
Pathological state (underlying conditions)
Social factors
Time of year (winter)
Relative time
Places been
What is relative time?
Time relative to exposure which can lead to disease
When considering place a patient has been, what should you ask?
Where have you been?
What have you been doing?
Who have you been doing it with?
We’re there any animals involved?
What are the different mechanisms of infection?
Contiguous (direct) spread
Inoculation
Haematogenous
Ingestion
Inhalation
Vector
Vertical transmission
What type of mechanism of infection is cellulitis and why?
Contiguous direct spread
Bacteria on skin enter through breaks in the skin entering into the subcutaneous tissue
What is inoculation?
When something like a needle or thorn breaches skin into the subcutaneous tissue
What is the haematogenous mechanism of infection?
Blood borne spread
What mechanism of infection causes all gastroenteritis conditions?
Ingestion
What is vertical transmission?
When mother transmits disease to child during pregnancy or during delivery
What is the process of infection?
Attachment of microorganism (extra or intracellularly)
Toxin production
Interaction of foreign material with host defences causes immune response
Can lead to inflammation and host damage
As well as pathogens producing toxins how else do they cause disease?
Bodies immune responses to the foreign matter can cause disease
What occurs in sepsis?
What are key signs of septic shock?
Bodies immune response is out of control
Tachycardia and hypotension indicative of septic shock
What occurs during management of an infection?
Diagnosis made (history, examinations and investigations)
Then Treatment
Infection prevention measures put in place
What is specific treatment?
Treatment which is aimed at the underlying disease
What is supportive treatment?
Help relieve discomfort or symptoms caused by the underlying disease
What is debridement?
Removal of infected tissue
E.g done in treating endocarditis (infected heart valve)
Why is the point of infection prevention procedures in the hospital and community?
Prevent infection transmission to patients, staff and other contacts
What are the outcomes to infection?
Cured
Death
Chronic infection
Disability
