infections at a surface

Question 1

what is a surface?

Answer 1

interface between a solid and a liquid/gas
Infections can affect either the external natural body surface (eg skin, GI tract, urinary tract) or an internal natural body surface

Question 2

how do people get infections?

Answer 2

invasion
migration
innoculation
haematogenous

Question 3

what is pathophysiology of infections at surface?

Answer 3

1. Adherence to host cells or prosthetic surface
2. Biofilm formation
3. Invasion and multiplication
4. Host response = inflammation (2 types)
   - Pyogenic (neutrophils ‐> pus)
   - Granulomatous (fibroblasts, lymphocytes, macrophages form nodular inflammatory lesions)

Question 4

what is a biofilm?

Answer 4

microbial communities that are attached to surfaces and encased in an extracellular matrix of microbial origin
* most hospital- acquired infections are due to biofilms because they can be life-threatening colonizers of biomedical devices.
* biofilms protect the bacteria by prevent bacterial phagocytosis, antibodies and complement recognition/binding of receptors

Question 5

which 2 bacteria commonly cause hospital acquired infections?

Answer 5

staphylococci and enterococci

Question 6

how are biofilms formed?

Answer 6

1. surface attachment - reversible or irreversible attachment
2. microcolonies - cell proliferation + coaggregation
3. macrocolonies - mushroom and tower like structures then cell detatchment

Question 7

what is quorum sensing?

Answer 7

• the ability to detect and respond to cell population density by gene regulation
• molecules induce all the bacteria within the biofilm to express certain genes which confer some kind of advantage to the colony such as the production of a multi drug resistant efflux pump or antibiotic production to kill other bacteria in vicinity so less competition

Question 8

what is the biofilm hypothesis?

Answer 8

1. bacterial adherence
2. biofilm growth and maturation
3. recurrent biofilm production causing persistent inflammation, dispersion of biofilm fragments causing septic embolisation and new biofilm formation

Question 9

how do we treat patients who are suffering from infection with biofilms?

Answer 9

sterilise tissue and reduce bioburden on tissue
surgical removal of prosthetics