L16 & 17 Infection PART 3

Question 1

what are the 4 major groups of pathogenic organisms?

Answer 1

bacteria
viruses
fungi
parasites

Question 2

what are 4 popular bacterial pathogens?

Answer 2

Staphylococcus aureus
Streptococci
Escherichia coli
Tuberculosis

Question 3

what are 4 popular viruses?

Answer 3

Rhinovirus (common cold)
Influenza
Hepatitis B/C
HIV

Question 4

what are 2 popular fungal pathogens?

Answer 4

candida

tinea

Question 5

what are 2 popular parasites

Answer 5

malaria

hookworm

Question 6

what is the difference between non-specific and specific symptoms?

Answer 6

non-specific: 
Fever
Sweats, chills, shivers
Rigors
Loss of appetite +/- weight
Aching muscles (myalgia) or joints (arthralgia)

specific:
According to source
Pneumonia – cough, breathlessness, sputum
Meningitis – headache, neck stiffness, photophobia

Question 7

what information from a history taking could help you formulate a diagnosis?

Answer 7

Conditions that make people more susceptible to infection
Past medical history: diabetes, immunodeficiency e.g. HIV
Drug history: steroids, chemotherapy

Lifestyle activities that bring people in to contact with infection
Occupation: healthcare worker, vet, farmer, sex worker
Travel: ask where, when and what did they get up to…?
Recreation: hobbies (e.g. watersports), food (e.g. takeaways/BBQ), injecting drugs
Contacts: people (including sexual partners), animals, insects

Question 8

in what infection are neutrophil levels elevated?

Answer 8

bacterial infection - pneumococcal pneumonia

Question 9

in what infection are lymphocyte levels elevated?

Answer 9

viral infections - glandular fever (Epstein Barr virus)

Question 10

in what infections are eosinophil levels elevated?

Answer 10

parasitic infections - schistosomiasis (bilharzia)

Question 11

what does C-reactive protein (CRP) test?

Answer 11

it is a marker of inflammation

Question 12

what does U&E test?

Answer 12

urea and electrolyte levels (kidney function)

Question 13

what is lumbar puncture used to test?

Answer 13

it is used to examine cerebrospinal fluid for signs of meningitis

Question 14

What tests do Microbiologists do with the samples you send?

Answer 14

antibody detection
culture
antibiotic sensitivity testing
PCR
antigen detection
microscopy

Question 15

during microscopy, what can the gram, ziehl-neelson and calcofluor tests be used for?

Answer 15

gram - bacteria
ziehl-neelson - TB
calcufluor - fungi

Question 16

which 3 species can be tested using culture?

Answer 16

beta-haemolytic streptococci
salmonella
aspergillus (a fungus)

Question 17

how can we detect organisms that we cannot grow in the lab?

Answer 17

identify part of the organism through proteins ie antigens or through DNA/RNA PCR

identify the body’s immune response to the infection through antibodies eg IgM or IgG antibodies

Question 18

give examples of conditions that can be found using antigen testing?

Answer 18

legionnaire’s disease (pneumonia) via urine test

rapid hep B via blood test

Question 19

what can DNA/RNA identification be used for and which conditions can be tested?

Answer 19

Method of detecting genetic ‘fingerprints’
Identifies unique genetic code sequence for specific infection

meningitis
HIV
hep B and C
respiratory viruses eg flu

Question 20

what is the difference between IgM and IgG antibody testing?

Answer 20

IgM:
intitial antibody response appears within a week, usually disappears after few months

IgG:
later antibody response appears 10-14 days.
Test for rising level (titre) in consecutive samples
Persists throughout life (part of immunological memory)
Also useful to test whether you are immune to an infection

Question 21

what are the problems with antibody testing?

Answer 21

False positives – cross-reactivity

False negatives – sampled too early/late, immunocompromised patient

Not usually helpful in acute setting

Question 22

what is supportive therapy for treating infections?

Answer 22

symptomatic eg paracetamol for fever/aches

dehydration/low bp ‘shock’ - IV fluids

Question 23

what is specific therapy for treating infections?

Answer 23

Antimicrobials (= all drugs/chemicals that kill microorganisms)
An antibiotic = “a chemical substance derived from a mould or bacterium that can kill microorganisms and cure bacterial infections”

NOTE:
For many viral infections there is no specific treatment
Some infections are self-limiting – no treatment is required
Antibiotics must be started immediately for serious infections, e.g. meningitis

Question 24

where is penicillin from?

Answer 24

derived from mould

Question 25

where is mupirocin from?

Answer 25

produced by Pseudomonas fluorescens (bacterium)

Question 26

what are the characteristics of a good antimicrobial? [6]

Answer 26

Selective toxicity (effective against microbe without harming host) Bacteriocidal (= kills the organism) rather than bacteriostatic (= inhibits its growth) No resistance Good pharmacokinetics (i.e reach high level in body and stay there, allowing fewer doses/day) No side effects Not inactivated by enzymes secreted by microbes, or by the host

Question 27

which areas of the cell do antibacterials target? [7]

Answer 27

cell wall synthesis DNA replication (DNA gyrase) DNA-dependent RNA polymerase Protein synthesis (50S inhibitors) Protein synthesis (30S inhibitors) cell membrane folic acid metabolism

Question 28

what are the problems with antimicrobials?

Answer 28

Variable spectrum of activity - Broad spectrum (kills lots of different organisms) - Narrow spectrum (kills few organisms) Some cannot be given orally Many cause side effects which can be serious, e.g. anaphylaxis (severe allergy) Bacterial resistance - some antibiotics are now effective against very few organisms, e.g. penicillin - some organisms are now resistant to many antibiotics, e.g. MRSA

Question 29

how is a new strain of staph aureus introduced?

Answer 29

everytime a new antibiotic is introduced

Question 30

how do you reduce pathogens in the environment generally and in hospital?

Answer 30

general: - clean drinking water - improving sanitation - hygienic food preparation in hospital: - cleaning wards, rooms and equipment - filtered air in operating theatres - Using sterile instruments when operating, taking blood etc

Question 31

what are the different routes of transmission and what are some examples of prevention measure?

Answer 31

food/water bourne - sanitation, clean water, food prep hygiene contact eg MRSA - handwashing, wearing gloves, gowns, masks airbourne eg TB - isolate infected patient in negative pressure room (that filters out-going air) vector bourne eg malaria - avoid bites, insect repellent, bed nets, long sleeves

Question 32

how would a potential host protect themselves with prophylactic treatments?

Answer 32

antimalarials antibiotics given to very immunosuppressed patients (bone marrow transplant recipients)

Question 33

what is the difference between passive and active immunisation?

Answer 33

Passive (with antibodies) - e.g. chickenpox immunoglobulin Active (by stimulating the immune system with something which mimics the infection) – e.g. hepatitis B virus surface antigen

Question 34

what does the notification of communicable diseases by the Health Protection (Notification) Regulations 2010 do?

Answer 34

From Bacillus anthracis (anthrax) to Yersinia pestis (plague) Information on infection Information on patient with infection or suspected infection Used to identify and prevent outbreaks e.g. food poisoning Coordinated by Public Health England