Clinical use
Detection of bacterial and fungal respiratory infection.
All BAL and cystic samples will automatically receive bacterial and fungal investigations.
Sputum samples must be sent with separate bacterial and fungal investigation requests if required.
Background
Respiratory tract infections (RTIs) are any infection of the sinuses, throat, airways or lungs. They are usually caused by viruses but can be caused by bacteria. RTIs are thought to be one of the main reasons why people visit their GP or pharmacist. The common cold is the most widespread RTI. Healthcare professionals generally make a distinction between upper and lower RTIs. The expression lower respiratory tract infection (LRTI) includes pneumonia, where there is inflammation of the lung parenchyma, and infections such as bronchiolitis that affect the small airways. Lung abscess, where the lung parenchyma is replaced by pus filled cavities, and empyema, where pus occupies the pleural space, are less common manifestations of LRTI.
Cystic fibrosis (CF) is caused by a defect in the CF transmembrane conductance regulator gene that affects the transport of ions and water across the epithelium. This leads to progressive pulmonary disease associated with pulmonary infections, which are the major cause of morbidity and mortality in CF patients. The major pathogens are S. aureus, H. influenzae (usually non-encapsulated in CF patients),S. pneumoniae and pseudomonads, particularly mucoid P. aeruginosa strains. Strains of P. aeruginosa with differing antibiotic susceptibilities may be isolated from a single sample.
Patient preparation
Sputum should be expectorated by deep coughing and be the result of a single expectoration. Specimens are best produced early in the morning before the patient eats, drinks or cleans their teeth.
Bronchoalveolar lavage samples (BAL) should be collected in accordance with routine protocol.
Cough swabs should be collected in cystic fibrosis patients ONLY.
Specimen requirements
White top sterile universal should be used for the collection of:
- BAL
- Sputum
- NPA
Cough swabs (pink top) are only accepted from cystic fibrosis patients.
Saliva and pernasal secretions are not suitable.
Minimum volume
- Sputum: 5ml is optimal, with a minimum volume of 1ml.
- BAL: as large a volume as possible is preferred.
Limitations and restrictions
Sputum and BAL should be sent in collection pots that can be adequately sealed. Lids with suction tubes attached should not be used as samples will leak in transit and may be rejected.
Where possible samples should be sent before antimicrobial therapy. If this is not possible this must be stated on the request form.
Turnaround time
- Bacterial Culture: 4 days
- Fungal Culture: up to 10 days
- Cystic investigation: up to 10 days
Analysing laboratory
Microbiology Lab, James Cook University Hospital, Marton Road, TS4 3BW
Additional information
Testing is referred for:
- Mycobacteria investigation
- Pneumocystis jirovecii (PCP)
- Legionella spp.
Please see the appropriate test page for further information. If delays in delivery to the laboratory are expected samples should be refrigerated at 2-8°C.