Lecture 1- Introduction To Infection Flashcards
What is an infection?
Invasion of a hosts tissues by microorganisms
What causes infection?
Toxins
Host response
Microbial multiplication
What are microbiota or commensals?
Collections of microorganisms that are harmless, however ones that are usually harmless can still cause harm for example if transferred to another site eg surgical site infection or UTI from anus
How do people get infections?
Starts with a source. Can spread directly to patient or through and intermediary such as a healthcare worker who may not be infected. Also get infections from animals and the environment
How are infections spread?
By horizontal transmission and vertical transmission.
Horizontal includes contact which can be direct, indirect from environment and then onto patient or a vector such as malaria from a mosquito bite.
Inhalation which includes droplets like a cough that only travels a short distance or aerosols which remains air borne for a long time .
Ingestion such as faecal oral transmission eg salmonella or food inconctact with faeces
Other type of transmission is vertical where a mother passes infection child eg bacteria from vaginal tract into amniotic fluid
What is a zoonosis?
Animal infection not normally transferred to humans unless through a bite etc eg rabies
How do microorganisms cause disease?
Exposure leads to adherence- invasion- multiplication- dissemination (spreading)
Virulence factors (help the microorganism survive) are exotoxins which hare released and damage cells and endotoxins which are inside microorganism and released on lysis. Host as learned to initiate an immune response in response to these.
Damage to the host is done directly by microorganisms but also by the processes used to destroy them. Hope that benefit outweighs negatives
What is the problem with fighting infection?
Host often does damage to itself
What determines if a microorganism will cause disease?
Pathogen-
Virulence factors
Inoculum size (amount of microorgansim present)
Antimicrobial resistance
Patient-
Site of infection
Co-morbidities (unwell patient affected more diabetics etc)
What are supportive investigations when it comes to investigating infection?
Investigations which help identify severity and likely cause. Looking at indicative factors like blood count, CRP, imaging and histopathology
What are specific investigations?
Looking for microorganisms or testing the microorganisms themselves.
Eg swabs, microscopy, culture, antigen and nucleic acid detection
What i different about detecting viruses?
Tend not to look at virus themselves but antibodies in response to it from patient or antigen detection of the virus. Also look for viral nucleic acid
