Introduction to Infection Flashcards
What is an infection
Invasion of a hosts tissue by micro organisms and disease is caused by toxins produced by the microorganisms , microbial multiplication and host response
How are infections caused ?
1) sometimes infections are caused by the patients own bacteria for example urinary tract infections are caused by bacteria within themselves
2) patient can have an infection from an animal
3) environment ( water , food , air , surfaces)
4) intermediary sources ( eg mosquitoes)
5) sources of infections eg other infected patients
How do people get infections :commensals
- also known as ‘microbiota’
- entirety of microorganisms within a particular ecological niche - this being the human body
For example , microorganisms carried on skin and mucosal surfaces
- these microorganisms are normally harmless or even beneficial o us ‘ however this is only true if they stay where they are meant to stay
How do people get infections : source and intermediary causes
1) infections can be caused by direct contact with other people who have infections for example sexually transmitted diseases , TB
2) vectors for example mosquitos for malaria
How do people get infections : environment
1) transmission due to ingestion of contained food or water ( for example , in other countries people don’t have toilets and poo in environment - people then eat these plants)
2) inhalation of air contaminated by environmental organisms
3) contact with contaminated surfaces including medial devices for example robots for surgery and difficult to sterilise and commode
How is cystitis caused ?
- often occurs in young females
- this is when bacteria from faeces somehow makes its way into the vagina.
- this causes irritation in urination
- this is an example of ‘microbiota’ where bacteria that is not harmful in faeces , but once moved elsewhere it becomes harmful.
What are examples of horizontal transmission ?
1) direct , indirect , vector contact
2) inhalation ( aerosols and droplets)
3) ingestion ( faecal-oral transmission)
What are examples of vertical transmission ?
- mother to birth ( before or during pregnancy)
What is aerosol transmission ?
Person to person transmission of pathogens through the air by the inhalation of infectious particles
- these particles remain in the air for longer and need to be carefully monitored
- an example would be chicken pox
What is droplet infection
An infection transmitted from one person to another through droplets of moisture expelled from the upper respiratory tract
- does not remain in the air that long , as long as aeorosal
What are the two disease determinants ?
1) the pathogen
2) the patient
What factors about the pathogen should be considered as a disease determinants ?
1) in inoculum size ( number of actual microorganisms)
2) virulence factors eg exotoxins , endotoxins
3) antimicrobial resistance of the microorganisms
What factors do we need to consider about the patient as a disease determinants ?
1) site of infection is very important - for example whether it is the brain or GI tract
2) co-morbidities ( consider that other diseases may make an infection more likely)
What are the 4 questions we need to consider when assessing a patient for an infection ?
1) is there an infection?
2) where is the infection ?
3) what is the cause of the infection ?
4) what is the best treatment ?
- this needs to be asked in order , unless in emergency situations where treatment needs to be administered quickly.
What do we need to consider when taking a medical history of a patient?
- symptoms such as focal symptoms ( isolated symptoms for example irritation when urinating) or systemic symptoms ( general symptoms eg fever )
- severity of symptoms
- duration of symptoms
- potential exposures ( eg where have you been , what have you been doing , were there any animals involved)
