What is a surface?
• Interface between a solid and either a liquid or a gas
What are the two main surfaces of the body?
- Skin
* Mucosal surface
Give three aspects of skin surfaces
- Epithelim
- Hair
Nails
Give three aspects of muscosal surfaces
- Conjunctival
- Gastrointestinal
- Respiratory
- Genitourinary
What are microbiota also known as?
Commensals
What are microbiota?
• Micro-organisms carried on skin and mucosal surfaces
Harmless, or even beneficial
When can microbiota be harmful?
- When they transfer to a distant site
* Immunodeficiency
Give four methods by which people get infections?
- Invasion - Strep Pyogenes (Pharyngitis)
- Migration - E.coli (UTI)
- Inoculation - Coagulase negative staphylocoocus (prosthetic joint infection)
- Haematogenous - Strep viridians (endocarditis
Give two viruses normally found on the skin
- Papilloma
* Herpes simplex
Give three types of gram positive bacteria carried on the skin
- Staphylococcus aureus
- Coagulase negative staphylococci
- Corynebacterium
Give one gram negative bacteria found on the skin
Enterobacteriase (Faecal bacteria)
Give two types of fungi found on the skin
- Yeasts
* Dermatophytes (cause skin infection)
Give a type of parasite found on the skin
Mites
Give three types of surface which can get infected
- External surface
- Internal surface
- Prosthetic surface infections
Give three types of infection of external surface infection
- UTI
- Gastroenteritis
- Cellulitis
Give three types of internal surface infection
- Endovascular
- Septic arthritis
- Osteomyelitis
Give three areas of vulnerability for prosthetic surface infection
- Intravascular lines
- Prosthetic joints
- Cardiac valves
What is native valve endocarditis?
• Inflammation and infections of valve of the hear
What is the bacteria which causes native valvular endocarditis? Where is it found?
- Viridions Streptoccoci
* Gums and teeth, usually
How can endocarditis be caused?
- Poor dental hygiene
- Bacteria enter circulation from gums
- Bacteria attach to hear valve
Who is particularly susceptible to endocarditis?
- People with abnormal valves
* Blood turbulent and slowed as moves through valve
What is the bacteria which causes prosthetic valve endocarditis?
• Coagulase negative staphylococci (found on skin of surgeons!)
What organism causes prosthetic joint infection?
- Coagulase negative staphylococci
* Staphylococcus aureus
Why are prosthetic joint infections dangerous?
- Poor blood supply
* Hard for antibiotics to treat
What two organisms cause pacing wire endocarditis?
• Coagulase negative staphylococci
Staphylococcus aureus
Outline the four main steps of pathogenesis of infection at surfaces
- Adherence to host cells or prosthetic surface
- Biofilm formation
- Inflammation and multiplication
- Host response
What are two kinds of host response?
• Pyogenic (neutrophils -> Pus)
Granulomatous (fibroblasts, lymphocytes, macrophages -> Nodular infammatory lesions)
How do bacteria adhere to host cell membrane surfaces?
• Pili or fimbriae extend and allow them to connect
What are the four stages of biofilm develpment?
- Initial attachment:
- Irreversible attachment:
- Maturation I:
- Maturation II:
Dispersion:
What occurs in initial attachment?
• Bacteria attach via van der waals forces
What is the primary aim in the diagnosis of infection?
• Identifying infecting organism and its antimicrobial susceptibilities
Give two challenges to treatment which could be discovered upon identification of organisms
- Ädherent organsims
* Low metabolic state/small colony variants
What two ways can bacteria be identified?
- Blood cultures
* Tissue/prosthetic material sonication (supersonic loosening) and culture
How can you tell if a central line is infected?
- Flushing drugs causes pyrexia
* Implies drug has washed part of central lines biofilm into blood stream
What are the two main aims of treatment of a surface infection?
- Sterilise tissue
* Reduce bioburden
Give three methods of sterilising tissue and reducing bioburden
- Antibacterials
- Remove prosthetic material
- Surgery - Resect infected material
Give three challenges of infection management
- Poor antibacterial penetration into biofilm
- Low metabolic activity of biofilm micro-organisms
Dangers/difficulties of surgery
Give three methods of preventing infection of natural surfaces
- Maintain surface integrity
- Prevent bacterial surface colonisation
- Remove colonising bacteria
Give three methods of preventing infection of prosthetic surfaces
- Prevent contamination (incorporate substances such as Ag to prevent infection)
- Inhibit surface colonisation
- Remove colonising bacteria
Describe Cellulitis
Infection of deeper layer of skin and underlying tissue
Usually seen on legs
Skin will be red, painfully swollen and hot
– can causes septicaemia
What causes cellulitis?
Group A streptococcus or staphylococcus aureus
– enters through damaged skin
Who is more vulnerable to cellulitits?
People with athletes foot of eczema
– enters though small breaks or cracks in skin
Describe pharyngitis
Causes a sore throat due to inflammation of the oropharynx.
Leads to sore throut, fever, enlarged lymph nodes, cough, headache, difficulty or pain when swallowing
What causes pharyngitis?
Usually has a viral cause but can be due to group A streptococcus
What are some complications of pharyngitis?
Tonsilitis
Ear infection
Sinus infection
Throat and peritonsilar abscesses
Describe conjunctivitis
Pink eye, with pus or watery discharge and crust on the eyelashes. Inflammation of the conjunctiva.
What causes conjunctivitis?
Usually has a viral cause (adenovirus) but most are treated with antibiotics despite the low incidence of bacterial cause.
What can cause endocarditis of a native cardiac valve?
Viridans streptococci
What can cause endocarditis of a prosthetic valve?
Coagulase negative staphylococci
What causes prosthetic joint infections?
Coagulase negative staphylococci
Staphylococcus aureus