Introduction to Infection

Question 1

What is an infection

Answer 1

Invasion of a hosts tissue by micro organisms and disease is caused by toxins produced by the microorganisms , microbial multiplication and host response

Question 2

How are infections caused ?

Answer 2

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

Question 3

How do people get infections :commensals

Answer 3

• 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

Question 4

How do people get infections : source and intermediary causes

Answer 4

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

Question 5

How do people get infections : environment

Answer 5

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

Question 6

How is cystitis caused ?

Answer 6

• 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.

Question 7

What are examples of horizontal transmission ?

Answer 7

1) direct , indirect , vector contact
2) inhalation ( aerosols and droplets)
3) ingestion ( faecal-oral transmission)

Question 8

What are examples of vertical transmission ?

Answer 8

• mother to birth ( before or during pregnancy)

Question 9

What is aerosol transmission ?

Answer 9

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

Question 10

What is droplet infection

Answer 10

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

Question 11

What are the two disease determinants ?

Answer 11

1) the pathogen

2) the patient

Question 12

What factors about the pathogen should be considered as a disease determinants ?

Answer 12

1) in inoculum size ( number of actual microorganisms)
2) virulence factors eg exotoxins , endotoxins
3) antimicrobial resistance of the microorganisms

Question 13

What factors do we need to consider about the patient as a disease determinants ?

Answer 13

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)

Question 14

What are the 4 questions we need to consider when assessing a patient for an infection ?

Answer 14

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.

Question 15

What do we need to consider when taking a medical history of a patient?

Answer 15

• 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)

Question 16

What particular organs would be examine when it comes to infections?

Answer 16

Liver and kidneys because we need to see if they are functioning well enough to give a dosage of medicine.

Question 17

What are the two types of investigations doctors would carry out to see if patient has an infection ?

Answer 17

1) specific

2) supportive

Question 18

What is the difference between specific and supportive investigations?

Answer 18

1)Specific investigations are to to try identify the name of bacteria

Question 19

What is a supportive investigation ?

Answer 19

Investigationused to confirm there is an infection

Question 20

Give ways of how supportive investigations are conducted

Answer 20

1) full blood count to identify neutrophil an lymphocyte count
2) C- reactive protein count which is a sign of inflammation
3) kidney function tests and liver function tests