• Long delay due to challenges with sample analysis at local labs; • Low recruitment of case and control subjects; • Constant staff turn-over in the sites.

The purpose of this study is to investigate the role of Haemophilus influenzae and other bacteria in causing chronic cough, through a direct comparison of chronic cough cases and healthy controls recruited from paediatric respiratory clinics in the United Kingdom.

Inclusion Criteria:

• Subjects who the investigator believes that parent(s)/ legally acceptable representative can and will comply with the requirements of the protocol.
• A male or female child between, and including, six to 72 months of age at the time of enrolment.
• Written informed consent obtained from the parent(s)/ legally acceptable representative of the subject.
• No antibiotic therapy within four weeks prior to the visit.
• No cystic fibrosis or known major immunodeficiency such as agammaglobulinaemia, T cell deficiency or Human Immunodeficiency Virus / Acquired Immune Deficiency Syndrome.
• No documented evidence or suspicion of gastroesophageal reflux disease.
• No evidence of an upper viral respiratory infection four weeks prior to the visit.

In addition, all subjects regarded as 'cases' must satisfy all the following criteria at study entry:

• Persistent cough greater than eight weeks.
• No response to five-day prednisolone treatment.
• Chest X-ray showing no evidence of a lobar pneumonia or gross structural abnormality.

In addition, all subjects regarded as 'controls' must satisfy the following criteria at study entry:

• No respiratory symptoms four weeks prior to the visit.
• No documented evidence or suspicion of lung disease upon physical examination.

Exclusion Criteria:

• Concurrently participating in another study, at any time during the study period, in which the subject has been or will be exposed to an investigational or a non-investigational product.
• Use of any investigational or non-registered product within 30 days prior to study procedures, or planned use during the study period.
• Any confirmed or suspected immunosuppressive or immunodeficient condition, based on medical history and physical examination.
• Child in care.

Children aged six to 72 months, residing in the United Kingdom. These children will be classified as cases and controls.

Cases will be children who have had persistent cough for greater than eight weeks and are undergoing general anaesthesia for clinically indicated bronchoscopy/ bronchoalveolar lavage as part of the diagnostic process for chronic cough.

Controls will be children who are undergoing general anaesthesia with endotracheal intubation for elective surgery or endoscopy for non-respiratory-related conditions and had no acute or chronic respiratory symptoms during the four weeks prior to the visit.