Lecture 11 - Infections On Surfaces Flashcards
What is a surface?
Interface between a solid and either a liquid or gas
What virus can cause warts?
Papilloma
What virus causes cold sores?
Herpes simplex
What are some very Gram positive bacteria on the skin?
Staphylococcus aureus
Coagulase negative staphylococci (Staphylococcus which are not S.aureus)
What are some gram negative bacteria present on the skin?
Enterobacteriaceae
Where are gram negative bacteria like Enterobacteriaceae more commonly found on the skin?
Below the waist
Due to exiting the large bowel
What are Dermatophytes?
Skin fungi which are moulds (NOT yeasts)
What diseases do dermatophytes cause?
Athletes foot
Ring worm
What can happen if normal flora is displaced from its normal location?
Can cause disease
What are Coagulase negative staphylococci?
Staphylococcus species that are not staphylococcus aureus
They do not produce the enzyme Coagulase
What is the importance of Lactobacilli in the vagina?
Produce lactic acid maintaining low pH
Low pH prevents opportunistic infections like Candida Albicans
What are Coliforms?
Microorganism found in the digestive tract
What can happen if you get an infection from Helicobacter pylori in the stomach? (It is normal flora there)
Can lead to inflammation of stomach lining (Gastritis) and can cause stomach ulcers
What are commensals/ our microbiota?
Our normal flora of microorganisms that are found on the skin and mucosal surfaces
What can happen if Microbiota/commensals are transferred to other sites?
Can be harmful an d cause disease/infection
How can people get infections from their own commensals or Microbiota?
Invasion
Migration
Inoculation
Haematogenous
They have been displaced
What is an example of Invasion of commensals causing a disease and what is the causative organism?
Pharyngitis
Streptococcus pyogenes
What is an example of Migration of commensals causing a disease and what is the causative organism?
Urinary Tract Infection (UTIs)
Escherichia coli
What is an example of Innoculation of commensals causing a disease and what is the causative organism?
Prosthetic joint infection
Coagulase-negative Staphylococcus
What is an example of Haematogenous infection of commensals causing a disease and what is the causative organism?
Infective endocarditis
Viridans streptococcus
What are some external natural (not prosthetic) surface infections?
Cellulitis
Pharyngitis
Conjunctivitis
Gastroenteritis
UTIs
Pneumonia
What are some internal natural (not prosthetic) surface infections?
Endocarditis
Septic arthritis
Osteomyelitis
Emphysema
What is gastroenteritis?
Inflammation of large bowel mucosa
What is endocarditis?
Infection of heart valve
What is septic arthritis?
Infection in joint that then spreads through the blood stream
What is Osteomyelitis?
Surface infection in cancellous spongy bone
What is Empyema?
Infection of plural space around the lungs
What is the danger with inserting objects into the body?
Anything inserted can act as a source of infection
What are some example so prosthetic surface infections?
IV Lines
Prosthetic joints
Peritoneal dialysis catheters
Cardiac valves
Pacing wires
Endovascular grafts
Ventricular-peritoneal shunts
What is a ventriculo-peritoneal shunt?
Shunt / tubing that allows the build up of CSF in the brain to drain into the peritoneal cavity where it can then be reabsorbed, helps treat the hydrocephalus
What is a Bicuspid aortic valve?
Congenital cardiac defect where 2 of the 3 cusps of the aortic valve fuse
This produces a smaller fused cusp and a normal single cusp
Why are people with a Bicuspid aortic valve at an increased risk of Endocarditis?
Blood flows abnormally over the abnormal valve, the microbes can then stick to the valves as a result and produce a biofilm
What helps determine the route of infection for Prosthetic valve endocarditis?
The time that somebody develops Prosthetic Valve endocarditis POST OPERATION helps determine the route of infection
What is the normal causative organism for Prosthetic valves endocarditis if they had their surgery less than a year ago?
Coagulase negative staphylococci
Like Staphylococcus epidermidis
What is the mechanism of infection if someone develops Prosthetic Valve Endocarditis within less than a year of the operation?
Coagulase negative staphylococci during the surgery invade from the skin or are already on the prosthetic heart valve
What are the normal causative organisms for Prosthetic valve endocarditis if they had their surgery more than a year ago?
Viridans streptococci
Enterococcus faecalis
Staphylococcus aureus
Gram negative bacteria from the HACEK group
Candida albicans
How can viridans streptococci cause prosthetic valves endocarditis?
Viridans streptococci normally found in mouth + around teeth
Haematogenous infection, gums get abrased, dental issues like gum disease, viridans streptococci enter blood and get stuck/adhere to the prosthetic valve
Why are organisms like viridans streptococci able to adhere to the prosthetic heart valve?
Flow over this valve more turbulent than a natural valve
More likely to adhere to the valve and form a biofilm
What gut organism can cause prosthetic valve endocarditis that’s is normally found in the gut?
Enterococcus faecalis
Why do you need to do bowel investigations if a patient has Enterococcus endocarditis?
Likely issues there if a gut organism has ended up in the blood and at the heart
Endocarditis associated with which microorganism is very likely with IV drug use?
Staphylococcus aureus
What are the 2 main causative organisms for Prosthetic joint infections?
Coagulase negative staphylococci
Staphylococcus aureus
What are the risk factors of getting prosthetic joint infections?
Joint replacement surgery:
-Obesity
-Diabetes Mellitus
-Rheumatoid arthritis
How do you treat a prosthetic joint infection?
Remove the prosthetic to sterilise the joint
Why can you not just give antibiotics to target the causative organisms of the prosthetic joint infection?
They produce a biofilm which antibiotics struggle to penetrate due to bacteria reducing and having a low metabolic rate in the biofilm
When inserting a pacing wire (pacemaker) which vein is commonly used?
Subclavian vein
What are the common organisms which cause cardiac pacing wire endocarditis and where do they come from?
Coagulase negative staphylococci
Staphylococcus aureus
Usually picked up by the wire on insertion from the skin
What are the 3 steps in the pathogenesis of infection at surfaces?
1.) Adherence/sticking to host cells or prosthetic surface
2.) Biofilm formation
3.) Invasion and multiplication
What structures allow adherence of microbes to host cells?
Pilli
Fimbriae
What is a Biofilm?
Microbial communities attached to surfaces and encased in an extracellular matrix produced by the microbes
How does a Biofilm form in 3 simple steps?
1.) Surface attachment (forms monolayer along surface)
2.). Start producing ECM so Micro colonies form since the bacteria stick together which starts maturing the biofilm
3.) 3 Dimensional structure forms (Macro-colonies), bacteria can detach or whole colonies can detach to go onto to other sites of infection
What is the host response to infection at surfaces?
Pyogenic (neutrophils, later die and form pus)
Granulomatous (fibroblasts, lymphocytes and macrophages) forms Nodular inflammatory lesions
What is Quorum sensing?
The ability to detect and respond to the cell population density by gene regulation
What substance is produced by bacteria in a biofilm which allows for Quorum sensing?
Autoinducers
What is the advantage of bacteria in a biofilm producing autoinducers allowing for Quorum sensing?
Induce all bacteria in the biofilm to express certain genes which confer some type of advantage (e.g multi drug resistance)
Why are bacteria in biofilms resistant to many antibiotics?
ECM of biofilm restricts penetration of antibiotics
Quorum sensing may stimulate all bacteria do reduce their metabolic rate to avoid being targeted by antibiotics
What are the 3 steps to quorum sensing ?
Autoinducers produced (Signalling molecules)
Bacteria in biofilm detect Autoinducers on receptors
Gene expression changed
What is the general aim in managing infections at surfaces/biofilms?
Identify infecting organism and its anti microbial susceptibilities
Sterilise tissue
Reduce bio burden
Why is a biofilm good for bacteria?
Protects from antibiotics
Protects from phagocytes
Helps preserve nutrients in times of low resources
How can you prevent biofilm formation on natural surfaces?
Maintain surface integrity
Prevent bacterial surface colonisation
Remove colonising bacteria
How can you prevent biofilm formation on prosthetic surfaces?
Prevent contamination
Inhibit surface colonisation
Remove colonising bacteria
How can a biofilm forming on a heart valve lead to problems?
Vegetation formed by the bacterial biofilm
Vegetation can lead to perforation of the walls of the valves
What are some common symptoms of infective Endocarditis?
Splinter haemorrhages
Oslers nodes
Janeway lesions
Petechiae
