This document discusses different types of chest infections including acute bronchitis, acute exacerbation of chronic bronchitis, and community acquired pneumonia. It outlines the typical bacteria that cause each infection and symptoms. Guidelines are provided on when antibiotics are appropriate and which antibiotics to use for different situations. Amoxicillin is usually recommended initially but alternatives like erythromycin are suggested if no improvement occurs.

1. Chest Infections
Lawrence Pike

2. Chest Infections
• Acute bronchitis
• Acute exacerbation of chronic bronchitis
• Community acquired pneumonia

3. Acute bronchitis
• Acute bronchitis is typically self-limiting lasting 7
to 14 days.
• Usually caused by adenovirus, rhinovirus or
influenza virus.
• Bacteria rarely cause acute bronchitis, however,
they may act as secondary invaders following a
viral infection. Bacteria implicated include
Streptococcus pneumoniae, Haemophilus
influenzae, Moraxella catarrhalis and occasionally
Staphylococcus aureus (especially during
influenza epidemics).

4. Acute exacerbation of chronic
bronchitis
• Increased purulent sputum, worsening
cough, pyrexia and increased
breathlessness.
• Haemophilus influenzae, Streptococcus
pneumoniae and Moraxella catarrhalis are
commonly grown from sputum samples.

5. Community acquired pneumonia
• An acute lower respiratory tract infection with purulent
sputum, cough, fever, breathlessness combined with
signs on examination and changes on chest x-ray.
• Usual bacteria implicated
– include Streptococcus pneumoniae (most common),
Haemophilus influenzae, Moraxella catarrhalis and occasionally
Staphylococcus aureus (especially during influenza epidemics).
• Atypical infections
– include those caused by Mycoplasma pneumoniae, Chlamydia
pneumoniae, Chlamydia psittaci and Legionella pneumoniae.

6. Incidence
• 17% of all 'acute' consultations are for acute
respiratory infections
• In previously healthy subjects acute bronchitis is
usually self-limiting in nature. However, around
5% are pneumonias
• Acute exacerbation of chronic bronchitis is
associated with viral infections in 50% of cases.
• Mycoplasma pneumoniae occurs in epidemics
with a 4-year cycle. It is most common in
children

7. Symptoms and Signs
• Clinical presentations range from cough without sputum
or chest signs, to an illness characterised by
expectoration of mucopurulent sputum, fever, dyspnoea,
pleuritic chest pain and diffuse or focal signs in the
chest.
• Consider pneumonia in any patient, of any age, with
cough and dyspnoea, tachypnoea and pleuritic chest
pain; and/or focal signs in the chest, especially if they
are systemically unwell.
• Legionella pneumonia should be considered if risk
factors such as recent travel or recent repair of plumbing
are present.

8. Differential Diagnosis
• Influenza
• Congestive cardiac failure
• Chronic obstructive airways disease
• Pulmonary embolism
• Acute pulmonary oedema
• Chest infection with underlying malignancy
• Subdiaphragmatic pathology: e.g. cholecystitis,
pancreatitis, perforated duodenal ulcer,
subphrenic/hepatic abscess

9. Should I use an antibiotic ?
• Cough may persist for 2 to 3 weeks after presentation
and is unlikely to resolve or improve more quickly as a
result of antibiotic therapy.
• Unnecessary use of an antibiotic may cause resistance of
organisms to the drug and increased patient
expectations of antibiotics for future minor illness.
Antibiotics may also cause side-effects.
• Resistance of Streptococcus pneumoniae to penicillin V
has increased from 0.3% in 1989 to 7.5% in 1996; and
to erythromycin has increased from 3.3% in 1989 to
11.8% in 1996.

10. Should I use an antibiotic ?
• To minimise resistance, it is important to
prescribe only when appropriate and necessary.
• Antibiotics may be of benefit if two or preferably
three of the following are present:
– increased sputum volume
– purulent sputum
– dyspnoea.
• In children the probability of a viral cause is
higher than in adults.

11. Should I use an antibiotic ?
• Antibiotic therapy should be considered for
the following groups:
1. Reduced resistance to infection.
2. Co-existing illness, diabetes, congestive
cardiac failure, asthma.
3. History of previous persistent
mucopurulent cough.
4. Clinical deterioration.

12. Which Antibiotic?
• Most cases of bacterial chest infection in the
community remain sensitive to amoxycillin
• If treatment with amoxycillin shows no
improvement within 48 hours, erythromycin
should be substituted.
• Erythromycin is first choice if an atypical
organism is suspected. However, azithromycin or
clarithromycin may be more active than
erythromycin against Haemophilus influenzae
and also have less GI upset.

13. Which Antibiotic?
• For exacerbations of chronic bronchitis
• Amoxycillin or a Tetracycline (and
erythromycin in pencillin allergy) are
appropriate first choices if any antibiotic is to
be used.
• 5% of Streptococcus pneumoniae and 5% of
Haemophilus influenza strains are tetracycline-
resistant. 15% H. influenza strains are amoxycillin-
resistant.

14. Which Antibiotic?
• Pneumonia in a previously healthy chest - amoxycillin is still the first
choice antibiotic.
• If Staphylococcus aureus is suspected e.g. after influenza or
measles - add flucloxacillin. Staphylococcal pneumonia requires
treatment for 2 to 3 weeks, then, if symptoms persist, seek advice
from a specialist.
• If Mycoplasma pneumoniae (consider this during an outbreak) or
Legionella infection suspected (e.g. recent travel), use
erythromycin. Legionella pneumonia, will require a prolonged course
of antibiotic until proven resolution, and admission should be
strongly considered or specialist advice sought in all cases.
Erythromycin is the historical drug of choice, although the newer
macrolides may be an alternative.

15. Which Antibiotic?
• Chlamydia infections- use a tetracycline or erythromycin
for 10 to 14 days.
• Quinolones (Ciprofloxacin, Ofloxacin) have poor activity
against Streptococcus pneumoniae and should not be
used as single agents in "blind therapy" of chest
infections.
• First generation cephalosporins, e.g. cephalexin, are not
an appropriate choice for lower respiratory infections.
• Co-amoxiclav should be considered if B-lactamase
resistant strains are locally a problem - consult local
protocols - or for treatment of pneumonia during
influenza epidemics.