Bacterial Respiratory Tract Infections

Question 1

What is the epidemiology of community acquired pneumonia?

Answer 1

5-11 per 1000 population 
Highest is the very young and elderly 
22-42% of patients with community acquired pneumonia get admitted to hospital 
- 30% of them end up in ITU
- 8-14% mortality rate

Question 2

What are the most common typical bacterial causes of community acquired pneumonia?

Answer 2

Streptococcus Pneumoniae
Haemophilus influenzae
Moraxella catharralis -COPD or emphysema

Question 3

What are the most common atypical bacterial causes of community acquired pneumonia?

Answer 3

Mycoplasma pneumoniae
Legionella pneumoniae
Chlamydophilia pneumoniae
Chlamydophilia psittaci

Question 4

What is the number one cause of community acquired pneumoniae?

Answer 4

Streptococcus pneumoniae - gram positive diplococci

Question 5

What are the risk factors for acquiring S.pneumoniae?

Answer 5

Alcohol
Smoking - destroys the innate defences
Immunosuppression - HIV, asplenia, drugs
Airway disease - COPD, asthma
Influenza - relationship between S.Pneumoniae and influenza

Question 6

What is a typical pneumonia presentation? (I.e. If the causative organism if S.Pneumoniae or Haemophilus Influenzae)

Answer 6

Abrupt onset
Cough
Fever
Pleuritic chest pain
Dull percussion - due to increased density of tissue
Coarse crepitus
Increased vocal resonance - this increases when there is increased density tissue mass

Question 7

What is the clinical definition of pneumonia?

Answer 7

Consolidation seen on X-Ray

Question 8

How is pneumonia caused by streptococcus pneumoniae treated?

Answer 8

Penicillin - resistance is rare in UK, but more common in south Europe, Asia and north America.
- amoxicillin
If they have a penicillin allergy or resistance
- macrolides (Clarithromycin)
- tetracyclines (doxycicline)

Question 9

What is the microbiology of Haemophilus influenzae, and who does it normally effect?

Answer 9

Gram negative

Most common in older people and/or those with an underlying lung disease

Question 10

Describe the symptoms of pneumonia caused by a non-typeable Haemophilus influenzae infection?

Answer 10

Red eyes, conjunctivitis, meningitis, headache, otitis media and pneumonia
- good at colonising the upper respiratory tract, eyes and nose

Question 11

How is a Haemophilus influenzae infection treated?

Answer 11

Amoxicillin is the first choice even though 30% of Haemophilus types are resistant (beta-lactamase)
If this doesn't work 
- co-amoxiclav 
- macrolides (Clarithromycin)
- tetracyclines (doxycicline)

Question 12

What is the most common atypical bacteria that causes community acquired pneumonia?

Answer 12

Mycoplasma pneumonia

• smallest free living bacterium
• very difficult to grow

Question 13

Which population of people are most likely to catch mycoplasma pneumoniae?

Answer 13

Young adults (person-to-person spread) in the autumn and winter months

Question 14

What is an atypical pneumonia presentation? (I.e. If the causative organism is an atypical one)

Answer 14

Headache 
Malaise 
Fever
Consolidation on X-Ray
Systemic effects
- Guillain Barre
- Heamolysis - cold type 
- erythema multiforme
- cardiac conduction issues
- arthritis

Question 15

How is mycoplasma pneumoniae diagnosed?

Answer 15

Serology - rise in antibodies (if they have had the infection more long term)
PCR (sputum/throat swab) - identifies the nucleic acid of the organism

Question 16

How is Mycoplasma pneumoniae treated?

Answer 16

Can’t use beta-lactams because the organisms has no cell wall for them to destroy
Macrolides (Clarithromycin) and tetracyclines (doxycicline) can be used as they bind to ribosomes and prevent protein production
Quinolones (ciprofloxacin) can be used as they bind to DNA and prevent nucleic acid replication

Question 17

How is Legionella pneumophila spread?

Answer 17

Ubiquitous in the environment (soil and water)
- immunocompromised patients can catch this from compost
Aerosolisation of the organism - gets into air supply in buildings that use AC

Question 18

How is Legionella diagnosed?

Answer 18

Sputum/throat swab culture
Serology
Urinary antigen test

Question 19

How is Legionella pneumophila treated?

Answer 19

Can’t use beta-lactams because the organisms has no cell wall for them to destroy
Macrolides (Clarithromycin) and tetracyclines (doxycicline) can be used as they bind to ribosomes and prevent protein production
Quinolones (ciprofloxacin) can be used as they bind to DNA and prevent nucleic acid replication

Question 20

What are the components of the CURB65 score (estimates the mortality of community acquired pneumonia)?

Answer 20

Confusion 
Urea >7
Respiratory rate >30
Blood pressure (<60 diastolic or <90 systolic)
65 - being either 65 or over

Question 21

What are the SIRS (systemic inflammatory response syndrome) criteria?

Answer 21

Temperature of over 38C or less than 36C
Heart rate over 90bpm
Respiratory rate over 20/min
White blood cells >12 or <4

Question 22

If a patient comes in with pneumonia, what tests should be run on them?

Answer 22

Blood tests - U&Es, FBC and ABGs
Chest X-Ray
ECG - possibility of endocarditis 
Blood cultures - cant put someone on antibiotics without taking blood cultures from them
Sputum culture
Throat swab
Legionella urine antigen test

Question 23

How is a patient with pneumonia managed?

Answer 23

Dr ABC
Antibiotics are given for the appropriate bacteria once the blood cultures come back. They are IV if;
- CURB65 score is 2 or more and/OR
- SIRS core is 2 or more
- they are hypoxic
When patients are discharged they must be give oral antibiotics and oxygen