Week 4 Hospital Acquired Infections/ adaptive immunity

Question 1

Name some common viral HCAI?

Answer 1

Blood borne viruses- hep B, C, HIV
Norovirus- winter D&V
Influenza
Chicken pox

Question 2

Name some examples of bacterial HCAI?

Answer 2

Staphylococcus aureus - MRSA_ resistant to wide range of ABs
Clostridium difficile 
Escherichia coli
Klebsiella pneumoniae 
Pseudomonas aeruginosa
TB

Question 3

What are healthcare infection and what characteristics define one

Answer 3

Infections that arise as a consequence of providing healthcare
- can be bacteria, virus, fungi, parasites
In hospital onset at least 48hrs after admission- less that this will have been incubating when admitted.
Eg. C diff takes 72hrs

Question 4

What pt factors predispose people to HCAI?

Answer 4

Extremes of age
- premature babies- receive essential antibodies from mother in last 4 weeks of development, poor skin quality, incubation- invasive instruments

Obesity, diabetes, cancer, immunosuppresed, smokers, surgical patient, emergency admission as no prepared.

Question 5

Describe some pt interventions to prevent HCAI for themselves and spreading to others?

Answer 5

Optimise pt condition- stop smoking, treat diabetes well,
Antimicrobial prophylaxis
Hand hygiene

Isolate infected individuals, protect susceptible pts

Question 6

Describe some healthcare worker interventions to prevent HCAI?

Answer 6

Healthy themselves- disease free, vaccinated

Good practice- sterile non touch,Chandigarh hygiene, PPE, Antimicrobial prescribing

Question 7

In relation to the infection model where can infection prevention intervention occur?

Answer 7

Preventing pathogen
Preventing interaction with pt
Preventing spread to others by recognising infection

Question 8

What are the 4 P’s of infection prevention and how do they apply to hospital acquired infections?

Answer 8

1. Patient- risk factors, interaction with other pts, hc workers and visitors
2. pathogen- virulence factors- toxins, ecological interactions- other bacteria, ABs
3. practice- general and specific activities of HC workers, policies, structure,
4. place- fixed features- where deliver healthcare- no of individual rooms, toilets per pt, variable features- bedding, curtain types

Question 9

Describe some environmental interventions to prevent HCAI?

Answer 9

Space, layout

Question 10

Describe the use of PPE?

Answer 10

Personal protective equipment- gloves, apron, full suit- tailor to suspected infection

Question 11

What are the characteristics of Clostridium difficile, it’s pathogenesis and management?

Answer 11

Gram +ve bacilli,
Opportunistic pathogen- if antibiotic therapy disrupt normal balance of gut flora c.diff dominate causing infection.
Diarrhoea- transported fecal oral route
Possess AB resistance and because of spore forming AB treatment is difficult

Question 12

What are the characteristics of Staphylococcus aureus with regards to hospital acquired infections and drug resistance?

Answer 12

Gram positive cocci
Frequently found in resp tract and skin infections
Methicillin resistant staph aureus is a strain that developed resistance to beta lactam ABs including penicillins and cephalosporins

Question 13

What are the characteristics of Norovirus?

Answer 13

Commonly known as winter vomiting bug - D&V
Most common cause of gastroenteritis
Transmitted by fecally contaminated food or water, by person to person contact or aerosols
Usually self limiting within a few days and not severe

Question 14

Describe the need for APC’s?

Answer 14

T cells cannot recognise pathogens and therefore needs APCs to capture, modify and present pathogens to them in order for T cells to become active - do this by recognising PAMPs

Question 15

What are some common types of health care associated infections (HCAI)?

Answer 15

Gastro intestinal 21%
UTI 20%
Pneumonia 14%
Surgical wound infections 14%
Other 14%
Skin and soft tissue 10%
Primary bloodstream 7%

Question 18

Describe MHC molecules in relation to microbe presentation?

Answer 18

Major histocompatibility complex on APC or HLA in humans

• this is what the T cell sees, have 6- 3 from each parent
• present microbe peptides to T cells
• type 1 found on all nucleated cells
• type 2 found on dendritic cells, macrophage and B cells and also express type 1

Question 20

Decrease T cells and their role in infection?

Answer 20

Produced in bone marrow, mature in thymus 
-CD4+ MHC class 2 activate T helper cell 1 resulting in B cell activation and antibody production alongside macrophage activation leading to phagocytic activity 

-CD8+ MHC class 1 active Cytotoxic T lymphocytes which targets and destroys microbe

Question 21

Describe some features of APCs?

Answer 21

Strategic location- for B and T cell interactions
- skin, mucous membranes, lymphoid organs, blood circulation

Pathogen capture- sense and detect what is harmful and not- phagocytosis

Diversity in pathogen sensors - PRR
- intracellular and extracellular pathogens

Question 22

What is the difference between intracellular and extracellular microbes and what response to each generate?

Answer 22

Intracellular- viruses = cell pendant immunity- cytotoxic T cells, macrophage and antibodies
Extracellular- bacteria= humoral immunity- antibodies and complement

Question 22

Name some types of antigen presenting cells?

Answer 22

• Dendritic cells- in lymph nodes, mucous membranes, blood- present to T and B cells
• langerhans cells- on skin, present to T cells
• macrophages- various locations- present to T cells
• B cells- in lymphoid tissue- present to T cells
  
  • to produce different antibodies, without T cells only have IgM, with have IgG

Question 22

Which MHC class is involved with intracellular and extracellular microbes?

Answer 22

Intracellular- viruses- class 1 MHC
Extracellular- bacteria- class 2

Question 22

Which T cells response to MHC class 1 and 2?l

Answer 22

Class 1 - CD8+ T cells

Class 2- CD4+ T cells

Question 22

Name some clinical problems associated with MHC molecules?

Answer 22

Major cause of organ transplant rejection- HLA molecules mismatch, graft vs host reaction

HLA associated and autoimmune disease
- diabetes

Cross reactivity between microbial and host antigens
- rheumatic heart disease, type 1 DM

Question 23

What are the immune functions of the following antibodies-

IgG, IgM, IgA, IgE?

Answer 23

IgG- phagocytosis, complement activation, neonatal immunity
IgM- complement activation
IgA- mucosal immunity- prevent attachment
IgE- immunity agains helminth, mast cell degranulation- allergies