Respiratory Infection Summary

Respiratory Infection Summary
Local antibiotic treatment guidelines should be consulted when prescribing, however, some general guidance is given here for the following situations:
Upper Respiratory Tract Infection
Sore Throat

Pharyngitis / tonsillitis is most often viral and self limiting, so antibiotics should not be routinely prescribed and symptomatic treatment (paracetamol) is the first line response. Throat swabs for culture are not indicated in routine management of sore throat and should be considered only in recurrent infection or in cases severe enough to be admitted to hospital. See SIGN Guideline 117.

If a bacterial cause of sore throat is identified, it is usually Streptococcus pyogenes (Group A strep) and if this confirmed by culture it should be treated with benzylpenicillin (this is the intravenous form - also called penicillin G) or phenoxymethyl penicillin (the oral form - also called pen V). Amoxicillin should not be used for sore throats as there is a high incidence of rash in patients with EBV infection (Glandular Fever, which may be mistaken for a bacterial sore throat) who are given amoxicillin. Clarithromycin can be used in patients who are allergic to penicillin.

Otitis Media

The evidence for benefit in antibiotic treatment of otitis media is slightly stronger than that for sore throat, but even so, most cases are viral in origin. However, otitis media can be complicated by secondary bacterial infection with respiratory pathogens such as Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis. The SIGN guidelines recommend that antibiotics should not be routinely prescribed as many cases will be self limiting, but that it should be an option after 72 hours if there is no improvement. This may be done by issuing a delayed prescription.

See SIGN guideline 66.

Unlike a sore throat, it is not practicable in otitis media to take a swab and identify the infecting organism, so treatment is empiric. Amoxicillin gives good pneumococcal cover, but since Haemophilus influenzae and Moraxella catarrhalis are often β-lactamase positive, co-amoxiclav is probably the best choice. A five day course is sufficient.
Cystic Fibrosis
The treatment of chest infection in patients with cystic fibrosis (CF) is complex and often requires expert advice or management. The organisms involved are different from those that cause respiratory infection in non CF patients. A typical CF pattern would be to see Staph aureus infections in childhood with a transition to gram negatives in teenage and adult years. Pseudomonas aeruginosa is a common pathogen and the related organism Stenotrophomonas maltophilia can follow this infection. These are very resistant gram negative organisms and often require treatment with a combination of two antibiotics intravenously. The standard anti-pseudomonal antibiotics are piperacilin / tazobactam, ceftazidime, meropenem (but Stenotrophomonas is intrinsically resistant) and ciprofloxacin, all often used in combination with an aminoglycoside such as gentamicin. Burkholderia cepacia is another gram negative organism which is associated with a poor prognosis and is often very difficult to treat.
Exacerbation of COPD Acute Bronchitis
The majority of episodes are viral in origin and should not routinely be treated with antibiotic unless the sputum is purulent or there is an increased white cell count / CRP. There is often debate about the value of sputum culture, since the results often reflect oro-pharyngeal flora and this can give misleading results, especially if the patient has already been on antibiotic for some time.

The main bacterial pathogens are Streptoccocus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis. Prescribing practice has changed considerably in recent years as part of the drive to reduce broad spectrum antibiotic use and as a consequence, the incidence of Clostridium difficile infection. Local guidelines will vary, but oral antibiotics commonly used for chest infections include:
Pneumonia
Pneumonia is most commonly caused by Streptococcus pneumoniae, but there are other possible bacterial causes, including those organisms sometimes referred to as "atypical" because they are difficult to culture by conventional methods e.g. Mycoplasma pneumoniae, Chlamydia pneumoniae, Chlamydia psittaci, Coxiella burnetii, Legionella pneumophila. There are treatment guidelines produced by the British Thoracic Society which differ depending on severity of disease (CURB-65 score) and whether the patient is treated in hospital or at home. British Thoracic Society Pneumonia Guidelines In severe infection the basic approach is to use a penicillin to cover Strep pneumoniae (usually amoxicillin or co-amoxiclav) and a macrolide (usually clarithromycin) to cover atypical causes such as Mycoplasma pneumoniae, both delivered intravenously. In milder cases treated at home, oral amoxicillin is recommended, with clarithromycin as an alternative in penicillin allergic patients. As always, treatment should be in line with local guidelines and should be reviewed in the light of culture and sensitivity results.
TB
TB treatment is a specialist area, but the basic principles are that multiple drug therapy is required to avoid the development of resistance and that therapy must continue for at least 6 months. The standard regimen recommended by NICE involves a combination of 4 drugs for 2 months - rifampicin, isoniazid, ethambutol and pyrazinamide - followed by rifampicin and izoniazid for a further 4 months.

Multi-drug resistant (MDR) tuberculosis is a major problem in some parts of the world and requires expert management as well as patient isolation.
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