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close this bookBasic Laboratory Procedures in Clinical Bacteriology (WHO; 1991; 128 pages)
View the documentPreface
View the documentIntroduction
open this folder and view contentsQuality assurance in microbiology
close this folderPart I. Bacteriological investigations
open this folder and view contentsBlood
open this folder and view contentsCerebrospinal fluid
open this folder and view contentsUrine
open this folder and view contentsStool
close this folderLower respiratory tract infections
View the documentIntroduction
View the documentThe most common infections
View the documentCollection of sputum specimens
View the documentProcessing of sputum in the laboratory (for non-tuberculous infections)
View the documentCulture for Mycobacterium tuberculosis
View the documentGeneral note on safety
open this folder and view contentsUpper respiratory tract infections
open this folder and view contentsSexually transmitted diseases
open this folder and view contentsPurulent exudates, wounds, and abscesses
open this folder and view contentsAnaerobic bacteriology
open this folder and view contentsAntimicrobial susceptibility testing
open this folder and view contentsPart II. Essential media and reagents for isolation and identification of clinical pathogens
View the documentSelected further reading
View the documentSelected WHO publications of related interest
View the documentBack Cover


Lower respiratory tract infections (LRTI) are infections occurring below the level of the larynx, i.e., in the trachea, the bronchi, or in the lung tissue (tracheitis, bronchitis, lung abscess, pneumonia). Sometimes, in pneumonia, the adjacent membranous covering of the lung is involved, resulting in roughening (pleurisy) and sometimes production of fluid in the pleural cavity (pleural effusion).

A special form of LRTI is pulmonary tuberculosis, which is common in many countries. The patient may cough up aerosols containing tubercle bacilli (Mycobacterium tuberculosis) which can be inhaled by other people. This form of the disease (“open” tuberculosis) is easily spread from person to person, and is therefore a serious communicable disease.

Many patients with LRTI cough up purulent (pus-containing) sputum that is generally green or yellowish in colour; this sputum may be cultured and examined grossly and microscopically.

There are other infections in which little or no sputum is produced: Legionnaires’ disease (caused by Legionella pneumophila) and pneumonia due to Mycoplasma pneumoniae (“primary atypical pneumonia”). Both these diseases require specialized techniques for their diagnosis and will not be discussed further here. Apart from pulmonary tuberculosis (see below), most requests for sputum microscopy and culture concern patients with respiratory infections associated with purulent sputum.

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