Infection On Surfaces Flashcards
What is a surface?
An interface between a solid and either a liquid or gas
What kind of surfaces are there?
Skin - epithelium, hair, nails.
Mucosal surfaces - Conjunctival, Gastrointestinal, Respiratory, Genitourinary.
Microbial organisms have adapted to live on particular surfaces.
What miscoorganisms can live on skin?
Viruses
Papilloma - causes warts but also cervical cancer
Herpes simplex - cold sores and genital herpes
Bacteria
Gram positive
Staph aureus
Coagulate negative staphylococci - all except staph aureus - only cause disease as a consequence of invasive instruments and procedures
Corynebacterium - disease as a consequence of healthcare
Gram negative
Enterobacteriacae (coliforms) e.g. E. Coli. Mostly in colon but it present on legs ect..
Fungi
Yeasts More after antibiotics e.g. Thrush. Candida
Dermatophytes - Mould fungi - Multicellular. Live on skin. Some specialist for hair / nails. Cause athletes foot and ringworm.
Parasites
Mites - small Arthropods that live on skin and eyelashes ect.. Inflammatory reaction e.g. Rosacea
What is the flora in the eye?
Coagulate negative staphylococci, Diptheroids, saprophytic Neisseria species, viridans group streptococci as partial haemolysis (This is a complex group of organisms.)
What is the flora in nares (nostrils)?
Staph aureus
What is the flora in the Nasopharynx?
Neisseria Meningitids - mostly not cause disease 1 in 10 carry it but no harm.
Streptococci pneumoniae, Haemophilus influenzae
What is the flora in the mouth?
Viridans Streptococci - cause endocarditis, Neisseria, many unnamed anaerobic bacteria such as Lactobacillus, Candida and Geotrichum species.
What is the flora in the stomach?
Helicobacter - cause peptic ulcers. Precursor for gastric cancer and lymphoma.
Streptococci, Staphylococci, Lactobacilli
What is the flora in the Intestine?
Bacteroides, Anaerobic bacteria - usually not named specifically.
What is the flora in the urethra?
Enterobacteriacaea (Causes of UTI), lactobacilli, diptheroids, altha and non-haemolylic streptococci, enterococci
What is the flora in the vagina?
Mostly Lactobacilli which prevents overgrowth of candida.
Others: dipheroids, micrococci, coagulase-negative staphylococci, enterococcus faecalis, microaerophilic and anaerobic streptococci, mycoplasmas, ureaeplasmas, yeasts.
How do people get infections?
Own flora
From source either directly or intermediary
Animals
Environment
How do people get infections from themselves?
Microbiota = “commensals”
- If get new stain of bacteria, it can invade host before they have time to develop resistance. This happens a lot when many people are living in a small space e.g. Army Baracs. -
- Micro-organisms carried on skin and mucosal surfaces
- Normally harmful or even beneficial
- Transfer to other sites can be harmful.
In what ways can people get infections?
Invasion e.g. Strep pyogenes pharyngitis
Migration e.g. Escherichia coli urinary tract infection
Inoculation e.g. Coagulase negative staphylococcus prosthetic joint infection.
Haematogenous - Viridans Strep endocarditis - particularly when they have bicuspid an aortic valve (instead of tricuspid) valves as causes turbulent flow around the valve. Also if poor oral hygiene - Eat lots of sugar.
What are some examples of external surface infections?
- Cellulitis
- Pharyngitis
- Conjuctivitis
- Gastroenteritis
- Urinary tract infection
- Pneumonia
What are some examples of internal surface infections?
- Endovascular - endocarditis and vasculits
- Septic arthrits
- Osteomyelitis
- Empyemia
What are some examples of prosthetic surface that can get infections?
- Intravascular lines
- Peritoneal dialysis catheters
- Prosthetic joints
- Cardiac valves
- Pacing wires
- Endovascular grafts
- Ventriculo-peritoneal shunts.
What are the causes of prosthetic valve endocarditis?
Over a year post op - caused by Viridans Streptococci, Enterococcus faecalis, Staph aureus (IV drug users as inject bacteria along with drugs), HACEK group, Candida
Under a year post up - coagulase negative staphylococci. More prone to infection if you have a prosthetic valve.
What are the causes of prosthetic joint infections or cardiac pacing wire endocarditis?
- Coagulase negative staphylococci
- Staphylococcus aureus
What is the process in the pathogenesis of infection at surfaces?
Adherence to host cells or prosthetic surface
Biofilm formation
Invasion and multiplication
Host response
- Pyogenic (Neutrophils, pus)
- Granulomatous (Fibroblasts, lymphocytes, macrophages - modular inflammatory lesions)
How does adherence occur?
Via pili or fimbriae
What are biofilms?
Biofilms are microbial communities attached to surfaces and encased in an extracellular matrix of microbial origin.
Made of large polysaccharides, proteins and nuclei acid. It is a complex structure. It is the product of many cells together.
It is one of the main strategies for bacterial survival in a variety of sites within the human body
How are biofims formed?
- Surface attachment - Can be reversable or irreversable.
- Microcolonies - cell proliferation, coaggregation
- Macrocolonies - Mushroom and tower like structures, cell detatchment.
What is Quorum sensing?
Little signals that are passed from bacteria to bacteria.
It controls: Sporulation, Biofilm formation, Virulence factor secretion..
Three principles:
Signalling molecules - autoinducers (AI)
Cell surface or cytoplasmic receptors
Gene expression - co-operative behaviours and more AI production.
Recognise how many bacteria are around by this quorum process.
