What is an infection?
An invasion of a host's tissue by micro-organisms
What is disease caused by?
- Microbial multiplication
- Host response
What is the importance of the host response causing a lot of damage?
When looking at managing patients, need to take into account what the host is doing
How can people get infections?
- Directly from source
- Through an intermediary
- From the environment
- From animals
Give an example of an intermediary that can cause disease
What environmental sources are there of disease?
What is the importance of disease transmitted through water?
Many young children killed by diarrhoea every year, mostly as a result of ingesting contaminated water
What diseases are particularly caused by ingested of contaminated food?
How can air transmit disease?
If it is contaminated by environmental organisms
Give an example of a surface that can become contaminated by pathogens
What is the importance of the contamination of medical devices?
Potentially very important/dangerous infections, e.g. viral hepatitis, HIV
What is it called when a disease is transmitted by an animal?
How can animals get infections?
From the environment, or infect the environment which then infects the patient
How can a person get an infection from themselves?
Organisms that the patient has in one place can spread to another place
What is meant by microbiota?
An ecological collection of microorganisms that are carried on the skin and mucosal surfaces
Are microbiota harmful?
They are normally harmless, or even beneficial, but can be harmful if they transfer to other sites
Give an example of where transfer of the microbiota can cause disease?
E. Coli from the large bowel getting into the urinary tract can use a UTI
What is true of many organisms considered to be pathogenic?
Many organisms considered to be pathogenic are only so when they're in the wrong place
What is meant by microbiome?
It is a description of the entire ecosystem, including the host
Give an example of a group of infections that require physical contact for transmission
Sexually transmitted infections
Give an example of an infection where airborne spread is sufficient for transmission
What are aerosols?
Small particles that can suspend in air
What do aerosols allow?
Air can remain infectious from some hours after someone infected has been in a room
Give an example of an infection where a vector is required for spread
What are the modes of horizontal transport?
What kinds of contact can transmit infection?
What can be inhaled to spread infection?
What kind of transmission is common through ingestion?
What are the modes of vertical transmission?
Mother to child
When can infection be spread from mother to child?
Before or after birth
Give an example of an infection that be transmitted mother to child?
By what process do microorganisms cause disease?
What types of pathogens invade?
All viruses, some bacteria
How are pathogens disseminated?
Either by continous spread, or other ways, such as the haemotaginous route
What is meant by continous spread?
What is meant by haemotaginous spread?
Spread in the blood
What does the mechanism of dissemination determine?
Other aspects of the disease
What are the determinants of disease?
What pathogen factors determine disease?
- Virulence factors
- Inoculum size
- Antimicrobial resistance
What does virulence factors vary between?
- Different organisms
- Individual organisms of the same species
What is the effect of inoculum size on disease?
More likely to get infection if infectious load is large
What patient factors determine disease?
- Site of infection
What co-morbidities affect disease outcomes?
- Recent surgery
What questions must be answered when a patient presents with an infection?
- Is there an infection?
- Where is the infection?
- What is the cause of the infection?
- What is the best treatment?
Why may no treatment be given for an infection?
- There may be no treatment available
- The infection might be self limiting
What must be done to determine what infection a patient has?
What should be determined in the history of a patient with an infection?
- Potential exposures
What information should be gathered about the symptoms of an infection?
- What is the patient complaning of?
- Are they focal or systemic?
- Can be both
- Can be both
Give 3 examples of systemic symptoms of infection
- Weight loss
- General malaise
What questions must be asked to determine potential exposures to an infection?
- Where have they been?
- What have they been doing?
- Who have they been doing it with?
- Were there any animals involved?
What should be looked for on examination of someone with an infection?
What are the categories of investigations in a patient with an infection?
What are the specific investigations into someone with a infection?
What is meant by supportive investigations into infection?
Investigations which help indicate the possibility of infection, severity, and prognosis, and how the patient is responding to treatment
What are the supportive investigations into infection?
- Full blood count
- C-reactive protein (CRP)
- Blood chemistry
What is being looked for in a FBC when investigating infection?
What is CRP indicative of?
What is done when conducting a blood chemistry investigation in infection?
Liver and kidney function
Give an example of where a liver function test can help determine the cause of infection?
In viral hepatitis, transaminases normally go up
What can kidney function tests give in infection?
Dose suggestions for some drugs
What imaging is done when investigating infections?
How is the precise cause of infection determined?
Bacteriology or virology
What specimen types are used in bacteriology?
What can be swabbed to obtain a specimen in bacteriology?
What fluids can be used as the specimen in bacteriology?
What techniques of bacteriology are used?
- M, C, & S
- Antigen detection
- Nucleic acid detection
What is M, C, & S?
- Antibiotic susceptibility
What is looked at in the microscopy phase of M, C, & S?
- Bacterial cells
- Patient cells
What can be used to look at bacterial cells?
What patient cells are looked at in M, C, & S?
How is nucleic acid detected in bacteriology?
Does the bacteria have to be alive to conduct PCR?
What techiques of virology are used?
- Antigen detection
- Antibody detection
- Detecting viral nucleic acid
What happens in antigen detection in virology?
Use antibody to capture antigen, and then demonstrate presence using flourescent marker
What does antigen detection in virology determine?
The presence of a virus
What happens in antibody detection in virology?
Use antigen as capture mechanism
What does antibody detection in virology determine?
The patient's response
What does the detection of viral nucleic acid determine?
DNA or RNA
Who is involved in managing infections?
All clinicians encounter patients with infections, but specialities whos primary interest in infection are;
- Infectious diseases
- Medical microbiology and virology
- Genitourinary medicine
- Health protection