Micro Lec 7

Question 1

What is pneumonia

Answer 1

the single most common cause of infection-related mortality

Question 2

What can pneumonia be treated with

Answer 2

antibiotics, but less than 29% of children with pneumonia receive the antibiotics they need (WHO, 2012)

Question 3

Who does community acquired pneumonia (CAP) affect

Answer 3

Typically affects age range between mid 50s and beyond

Occurs all year but peaks in mid-winter and early spring

Most patients (up to 90%) have underlying medical conditions
COPD, diabetes, CVD

Question 4

What is pneumonia characterised by

Answer 4

fluid build up in teh lungs (alveoli) , inflamed and swollen bronchioles, inflammation in alveoli

Question 5

What is hospital acquired pneumonia (HAP)

Answer 5

Respiratory infection which develops more than 48 hours after hospital admission

Question 6

What is a major riks factor for HAP

Answer 6

Mechanical ventilation (vap)

Question 7

What increases the risk of infection of HAP

Answer 7

presence of underlying disease and by various interventions and procedures

Question 8

What are some clinical considerations and challenges of pneumonia

Answer 8

Multifactorial nature of causative agents

Both clinical and aetiological diagnosis becomes difficult

No single empiric antimicrobial course can cover all of the potential causes

Challenges are becoming more complicated with the emergence of AMR

Question 9

Outline the features of streptococcus pneumoniae

Answer 9

Gram-positive diplococcus, alpha-haemolysis on blood agar, polysaccharide capsule
Does not have Lancefield antigens
Carriage rate highest in first two years then declines
Infections of the respiratory tract include otitis media, sinusitis, pneumonia
Meningitis and bacteraemia

Question 10

SLIDE

Answer 10

10

Question 11

What are unencapsulated strains of S. pneumoniae

Answer 11

usually avirulent

Question 12

What does S. pneumoniae capsule do

Answer 12

Prevents mechanical removal from phagocytes
Masks PAMP to which complement proteins or antibodies bind
Binds to factor H to degrade complement protein C3b

Question 13

What are the targets of S. pneumoniae

Answer 13

Pneumococcal Conjugate Vaccine: Serotypes 1, 3, 4, 5, 6A, 6B, 7F, 9V, 14, 18C, 19A, 19F, and 23F
More common in young children
Does not provide protection against other serotypes

Pneumococcal Polysaccharide Vaccine: All 23 serotypes
People over 65 years old or long term medical conditions
Not very effective in children younger than 2
Between 50-70% efficacy

Question 14

What does alpha haemolysis suggest

Answer 14

S. pneumoniae (optochonin sensitive)
Viridans (optochonin resistant)

Question 15

What does beta haemolysis suggest

Answer 15

S. pyogenes (bacitracin sensitive)
S. agalactiae (bacitracin resistant)

Question 16

What does gamma haemolysis/no haemolysis suggest

Answer 16

E. faecalis
E. faecium

Question 17

What is COPD (chronic obstructive pulmonary disorder) characterised by

Answer 17

airway inflammation and decrease in lung function

Question 17

What compromised patients may be susceptible to respiratory tract infections

Answer 17

Organ transplantation
Cystic fibrosis
Diabetes
COPD
HIV

Question 18

What does COPD do

Answer 18

significantly increase the rate of lung deterioration

Question 19

Outline the features of haemophillus influenzae

Answer 19

Aerobic, gram-negative coccobacillus

Common commensal of the nasopharynx and throat but common pathogen of the lungs

37°C, CO2 enriched atmosphere – chocolate agar

Question 20

What are haemophillus influenzae specific growth requirements

Answer 20

Cannot grow on unsupplemented blood agar
Requires factor X (haemin)
Requires factor V (NAD)
H. influenzae requires both factors

Question 21

What does haemophillus influenzae do

Answer 21

Colonises the URT Non-encapsulated 25-80% carriage
Capsulated 5-10% carriage

Cause both invasive and non-invasive infections

Some strains have a polysaccharide capsule
Serotypes a-f, B is the most common
Non-encapsulated strains referred to as ‘Nontypeable Haemophillus influenza’

Question 22

What is oneof the 12 WHO priority pathogens

Answer 22

Haemophilus influenza

Question 23

Why is Haemophilus influenzae on teh WHO 12 priority pathogens list

Answer 23

it is linked to resistance to the beta lactam antibiotic ampicillin

Question 24

What is group B haemophillus influenzae commonly associated with

Answer 24

invasive disease such as meningitis

Question 25

What vaccine is available for haemophillus influenzae

Answer 25

Hib vaccine

Question 26

Outline the features of Moraxella catarrhalis

Answer 26

Aerobic, gram-negative diplococcus Common commensal of the upper respiratory tract and causes a variety of infections 37°C, aerobic– blood and chocolate agar Most strains are β-lactamase positive Incidence thought to be underappreciated in COPD

Question 27

What is antimicrobial susceptibility testing (AST)

Answer 27

Microbiological techniques where a pure culture of a single microbe is grown in the presence of an antimicrobial agent

Question 28

What can AST do

Answer 28

AST can provide a direct analysis of the susceptibility of a microbe to an antimicrobial at specific concentrations – in vitro Some methods allow for quantitative analysis which can define the MIC of the antimicrobial MIC – minimum inhibitory concentration Findings can then tailor antimicrobial prescribing to the patient

Question 29

What is one method of AST

Answer 29

Disc diffusion

Question 30

How does Disc diffusion work

Answer 30

Analysis based on the zone of inhibition (ZOI) of growth on solid agar ZOI – the area around where the antimicrobial has been positioned (usually a disc). The radius of the ZOI correlates with the susceptibility of the organism to the antimicrobial Laboratory automation can now dispense disc and measures ZOI automatically

Question 31

Automatic processes allow for more rapid result turnaround, how quickly

Answer 31

4, 6 and 8 hrs directly from positive blood samples

Question 32

What is another method of susceptibilty testing

Answer 32

ETEST

Question 33

How does ETEST work

Answer 33

ETEST strip is a predefined gradient of antimicrobial concentrations and can determine the MIC

Question 34

What does ETEST allow for the testing of

Answer 34

slow growing organisms which automated testing cannot work with

Question 35

SLIDE

Answer 35

23

Question 36

What is another method of susceptibility testing

Answer 36

Vitek 2

Question 37

What is Vitek 2 and how does it work

Answer 37

Automated system which uses growth-based technology and colorimetric cards which can both identify bacteria and perform AST Integrated with LIMS Can detect >100 resistance mechanisms

Question 38

SLIDE

Answer 38

25, 26