Respiratory tract infections are the most frequent presenting complaint in primary care. Although it is usually an unimportant manifestation in the paediatric population, cough, when persistent, generates anxiety in patients and their families, leading to a significant consumption of health care resources.1,2

Some case series in the literature that include hospitalised patients had led to the hypothesis that protracted bacterial bronchitis (PBB) could be the leading cause of chronic cough in preschool-aged children (up to 40% of cases).1,2,4–6 Although PBB has been established as a clinical entity only recently (2006), similar presentations have been described for decades under the label of “chronic bronchitis of childhood”.3 There is a low awareness of this disease in our country, and it used to not be included in the differential diagnosis of chronic cough, either due to underdiagnosis, inadequate treatment or a lower actual incidence than described in the primary care setting.1–6

We conducted a retrospective review of the cases of 3 patients with suspected PBB managed in a paediatric primary care clinic in Zaragoza (serving 1415 children aged 0–14 years) between September 2018 and September 2019. Our main objective was to increase awareness in clinicians of a disease defined only recently and for which there is a low level of suspicion in everyday clinical practice.

Case 1. Girl aged 5 years with a history of bronchial hyperresponsiveness undergoing treatment with montelukast, that developed a persistent wet cough in the context of cold symptoms. The salient findings of the physical examination were diffuse expiratory wheezing in absence of breathing difficulty or hypoxaemia, leading to initiation of treatment with inhaled salbutamol and oral steroids, which did not improve symptoms. Poorly controlled asthma was suspected, so inhaled budesonide was added for maintenance therapy. The chest radiograph was normal. Given the persistence of the cough at 40 days from onset, a course of oral treatment with amoxicillin-clavulanic acid was prescribed, which achieved resolution of symptoms within 48h.

Case 2. Boy aged 4 years with a history of bronchial hyperresponsiveness currently treated with inhaled budesonide that had onset with persistent wet cough in the context of a febrile cold-like illness. The main findings of the examination were diffuse wheezing and rhonchi in the absence of alarming signs. The initial treatment was inhaled salbutamol combined with an oral corticosteroid, with addition of azithromycin at a later time due to the lack of improvement. The chest radiograph was normal. On account of the persistence of the wet cough for 4 weeks, amoxicillin-clavulanic acid was added, which achieved an improvement in symptoms in the first 24h.

Case 3. Girl aged 2 years with a history of bronchial hyperresponsiveness that developed a persistent wet cough in the context of a respiratory tract infection treated with inhaled salbutamol, an oral antihistamine (springtime) and an oral corticosteroid, without a favourable response. Maintenance therapy with inhaled budesonide was initiated due to the persistence of the cough. Since the patient did not improve in the 5 weeks that followed, amoxicillin-clavulanic acid was added, with evidence of clinical improvement within a few days (Table 1).

Protracted bacterial pneumonia refers to a chronic infection of the lower respiratory tract manifesting as wet or productive cough lasting more than 4 weeks that resolves with antibiotic treatment in the absence of another diagnosis. Although it may appear at any age, its incidence is highest in children aged less than 6 years.1–6

The aetiology of PBB is unknown, but it is associated with abnormalities of mucociliary clearance, immune defects, structural anomalies and the formation of bacterial biofilms. The main causative agents are nontypeable Haemophilus influenzae, Streptococcus pneumoniae and, less frequently, Moraxella catarrhalis.1–6

Its natural history consists of onset with cold-like symptoms and a lower respiratory tract infection that resolve spontaneously with the exception of an isolated persistent wet cough. The findings of the physical examination, imaging tests and pulmonary function tests are normal or nonspecific. Its manifestations may be confused with asthma, and up to 30% of cases occur in asthmatic patients who will not improve until the infection is treated appropriately.4 The differential diagnosis should include rhinosinusitis, although the persistence of abnormal breath sounds on auscultation supports the diagnosis of PBB.

The criteria applied for diagnosis were presence of wet cough of more than 4 weeks’ duration with isolation of a bacterial pathogen from bronchoalveolar lavage with more than 104 colony-forming units, absence of evidence of concomitant infection by Bordetella pertussis or Mycoplasma pneumoniae, and resolution of symptoms within 2 weeks with oral antibiotherapy. Since a flexible bronchoscopy examination is not indicated routinely in children presenting with wet cough, we substituted this test by noting the absence of other signs and symptoms associated with chronic cough, such as dyspnoea, haemoptysis and chest pain.1–6

The recommended antibiotic treatment is amoxicillin-clavulanic acid for a minimum of 2 weeks, which may be prolonged to up to 4–6 weeks in some children. Some of the proposed alternative treatments include cephalosporins, trimethoprim, sulfamethoxazole or macrolides.1–6

The response to treatment is very good and should be considered confirmation of the diagnosis. However, recurrences are frequent (in up to 25% of cases) and may require several courses of antibiotherapy. A poor response or recurrent episodes require ruling out other diseases. There are similarities between PBB, suppurative lung disease and bronchiectasis, which could be conceived of as different stages in a spectrum of airway disease.1–6

In conclusion, PBB should be considered in children presenting with chronic wet cough in absence of clinical or radiological signs suggestive of a different diagnosis. However, the clinical criteria must be applied very strictly and accurately, given their nonspecificity, to prevent unnecessary use of antibiotics and the associated emergence of drug resistance (in our clinic, the criteria were only met by 3 patients out of a caseload of 1415 children in the course of 1year).