BIOL243 - L13 Opportunistic Infection

  • Created by: Katherine
  • Created on: 28-04-17 11:15
What is a pathogen?
An organism that can cause infection in individuals with normal host defences.
1 of 51
What is commensal bacteria?
An organism that is found normally on those parts of the body that are exposed to, or communicate with, the external environment - 'the normal flora'
2 of 51
What is an opportunistic pathogen?
An organism that can cause infection in individuals with abnormal host defences. Commensals may be opportunistic pathogens.
3 of 51
How do we know that a given pathogen causes a specific disease?
Koch's postulates
4 of 51
What are Koch's postulates?
the pathogen is present in every case of disease, the pathogen is isolated from the disease and grown in pure culture, the specific disease must be produced when a pure culture of the pathogen is inoculated into host, the pathogen must be recoverabl
5 of 51
What are the limitations to Kock's postulates?
It's difficult to grow viruses in culture, polymicrobil infections (there may be a disease outcome only when more than one bacteria is present), it depends on the infecting doses and host effect (some individuals don't have symptoms ect)
6 of 51
What is virulence?
The likilhood that infection with a pathogen will lead to disease. e.g. 100% for rabies, 50% for rubella and 0.1-1% for poliomyelitis.
7 of 51
Are virlence and infectivity the same?
No
8 of 51
What is pathogenicity?
The disease burden (how ill you get)
9 of 51
What is the pathogenicity, virulence and infectivity of the cold?
P= low, V = low, I = high
10 of 51
What is the pathogenicity, virulence and infectivity of influenza?
P = medium, V = Medium, I = high
11 of 51
What is the pathogenicity, virulence and infectivity of HIV?
P= high, V = high, I = low
12 of 51
What is the pathogenicity, virulence and infectivity of plague
P = high, V = high, I = low
13 of 51
What are virulence factors?
Toxins, capsules and adhesins - the things that cause disease
14 of 51
What type of virulence factor does diptheria, tetanus, cholera, clostridium difficile and toxic shock have?
Toxins
15 of 51
What type of virulence factor does streptococcus pnemoniae and haeophilus influenzae have?
Capsules
16 of 51
What type of virulence factor do E.coli have?
Adhesins
17 of 51
How can virulence factors be treated?
By exploitation
18 of 51
How are toxins exploited?
Antitoxin and toxoid immunisation
19 of 51
How are capsules exploited?
Vaccines
20 of 51
How are adhesins exploited?
They aren't yet.
21 of 51
What is the effect of infecting dose on disease incidence?
A massive effect - it's not a linear releationship though - Generally a larger infecting dose results in more infected, unless the does is huge, which alerts the immune system.
22 of 51
What is the clinical significance of the pathogens?
The presence of a bacteria doesn't mean it's responsible for disease. In bacterial disease, they need to be isolated in abundance, in a pure culture, from deep tissues.
23 of 51
What are the commensal flora?
Bacteria on the body - there are more bacterial cells (10^14) associated with the human body than there are human ones (only 10^13).
24 of 51
What are the commensal flora?
Bacteria, protozoa, fungi, archaea, viruses and possibily metazoa.
25 of 51
Where are commensal flora found?
Skin and mucosa
26 of 51
What is the composition of flora?
Normal flora varies from individal to individual - some bacterial species carried only transiently. most fairly permanent. difficult to alter compoition of the normal flora of the gut in a healthy individual.
27 of 51
WHere is the largest commenal microbial load? And smallest?
In the large intestine (10^14), the smallest is 10^10 found in the throat, nose, mouth and vagina
28 of 51
Where are the most anaerobic flora found?
In the large intestine (1000:1), then the vagina (10:1) and then on the skin (1:1)
29 of 51
What are the body defences?
Intact integument, surface antibody, lysozyme/fatty acids, cilia, normal flora, immune system: B cells, T cells, antibodies, complement ect
30 of 51
What induces changes in normal flora?
Hormonal physiology and development, when antibiotics select for a resistant flora. New organisms may be acquired
31 of 51
When causes changes in hormonal physiology and development
E.g. female genital tract and lactobacilli
32 of 51
What are the harmful effects of gut bacteria?
Escape of normal flora to abnormal sites - e.g. perforated appendix leads to peritonitis with bacteroides (septicaemia), cholecytitis and cholangitis (inflammation of gall bladder usually due to build up (gall stones), UTI and vaginal candidasis
33 of 51
What leads to harmful alterations to gut flora?
Antibiotic use = sensitive gut flora killed = overgrowth with resistance flora (inc c difficile) = c.difficile toxin production = diarrhoea ect.
34 of 51
What is the treatment to harmful alterations to gut flora?
Stop precipitating antibiotic, give oral metronidazole or vancomycin (effective against c.diff), recovery requires re-establishement of normal flora using probiotics or faecal transplant.
35 of 51
What is an opportunistic infection?
Where the occurrence or severity of an infection is determined by patient, not microbial factors
36 of 51
Name the causes of opportunistic infection:
Immunosuppressin (Cancer, transplantation), Breaching defences (IV access, urinary catheter, wound), Foreign body (prosthesis, splinter), debility (malnutrition, ill health, old age).
37 of 51
How does mucormycosis arise?
it is in the sinus region - a woman had leukaemia and died because of it.
38 of 51
What is a disease example that shows that t cell immunity can lead to different immunity levels?
Polar leprosy - good t cell immunity = skin lesion, poor t cell immunity = extreme apperances
39 of 51
What is ventilator aquired pneumonia?
By using a ventilator and breaching the ciliated surfaces of the ungs, its easy for bacteria to be introduced to the lungs.
40 of 51
Immunosuppression is becoming more of an issue, why?
Because more transplants are being carried out, and patients are immunosuppressed after transplants so they don't reject the organ
41 of 51
What are the causes of infection in immunosuppressed patients?
Shift from infections due to gram-positive to gram negative pathogens. Increased importance of fungi, especially Candida sp. Increasing incidence of resistant pathogens (ORSA, VRE, Candida).
42 of 51
Give some exampels of latent pathogens: VIRAL
Cytomegalovirus (CMV), Epstein Barr (EBV), Herpes simplex (HSI & II), Varicella zoster (VZV)
43 of 51
Give some exampels of latent pathogens: BACTERIAL
Syphilis, Tuberculosis
44 of 51
Give some exampels of latent pathogens: FUNGAL
Cryptococcus neoformans, Blastomyces dermatitidis
45 of 51
Give some exampels of latent pathogens: PARASITIC
Pneumocytis carinii, Toxoplasma gondii
46 of 51
What happens to CD4 in an HIV infection?
CD4 count depleats - and opportunistic infections arise
47 of 51
How is infectino prevented?
Immunization, appropriate infection control (washing hands), engineering controls, selected screening for latent infectino with appropriate treatment and/or suppression, prophylaxis
48 of 51
How can antibiotic resistance be resisted?
Proper infection contol and proper antibiotic utilization
49 of 51
What are the engineering contols to prevent antibiotc resistance? Aspergillus prevention
Aspergillus prevention - filtered hospital air, barrier protectino during renovation or construction. Protective isolation for stem cell transplants. Provide respiratory protection when patients leave protected environments.
50 of 51
What are the engineering contols to prevent antibiotc resistance? Legionella prevention
Prohibit showers (use sponge baths), implement surveillance for legionella cases, monitor water supply - if legionella present, initiate decontamination
51 of 51

Other cards in this set

Card 2

Front

What is commensal bacteria?

Back

An organism that is found normally on those parts of the body that are exposed to, or communicate with, the external environment - 'the normal flora'

Card 3

Front

What is an opportunistic pathogen?

Back

Preview of the front of card 3

Card 4

Front

How do we know that a given pathogen causes a specific disease?

Back

Preview of the front of card 4

Card 5

Front

What are Koch's postulates?

Back

Preview of the front of card 5
View more cards

Comments

No comments have yet been made

Similar Biology resources:

See all Biology resources »See all Medical resources »