Sputum induction improves detection of pathogens in children with cystic fibrosis

Abstract

Background Sputum induction is a safe, well tolerated means of obtaining lower airway secretions from children with cystic fibrosis (CF), particularly for assessment of airway inflammation but the clinical value in diagnosing outpatient infections has not been extensively studied. Objectives Investigate the success rate and microbiologic yield of induced sputum (IS) compared to oropharyngeal swabs (OP) and expectorated sputum (ES) samples in children with CF, and determine if IS culture results impact treatment. Methods Two cohorts were included in this prospective, longitudinal comparative study. In one cohort, simultaneously collected OP, ES and IS specimens were obtained from 17 CF children at three visits over one year. In the second group, sputum induction was performed in 35 CF subjects at four annual visits and culture results were compared to their nearest respiratory culture within four months. Antimicrobial treatment regimens were captured retrospectively. Results Sputum induction was successful in 149 of 158 (94%) visit encounters. Polymicrobial infection (combined p=0.005) and gram negative organisms (combined p=0.003) were detected more frequently in IS samples compared to OP, as were the individual pathogens Pseudomonas aeruginosa (combined p=0.04) and Stenotrophomonas maltophilia (combined p= 0.05). The microbiologic yield of serial IS samples collected over one year was stable. IS culture results led to antibiotic changes in 6% of visit encounters. However, based on current practice 13% of visits could have resulted in treatment changes. Conclusions Sputum induction is feasible in the outpatient setting and appears to improve pathogen detection in children with CF.

Pseudomonas aeruginosa identified as a key pathogen in hospitalised children with aspiration pneumonia and a high aspiration risk

“…Second, respiratory cultures were collected by a suction catheter during physiotherapy. This method was chosen because it is noninvasive, feasible for use in nonexpectorating children and has a good microbiologic yield and confirmed validity . Moreover, our respiratory culture results were highly clinically significant, with a 91% rate of correlation between the clinical response to treatment and the susceptibility pattern of the isolated pathogen.…”

Diagnostic accuracy and distress associated with oropharyngeal suction in cystic fibrosis

“…However, these methods have been shown to have variable diagnostic accuracy when compared to BAL [6][7][8] or expectorated sputum [9][10][11]. Furthermore, common CF pathogens are present in the upper airways of healthy children [12,13], further complicating meaningful interpretations of positive upper airway bacterial cultures.…”

Assessment of serology and spirometry and the combination of both to complement microbiological isolation for earlier detection of Pseudomonas aeruginosa infection in children with cystic fibrosis

“…Culture-based detection of P. aeruginosa in respiratory samples is the current gold standard for infection confirmation [27]. In children acquisition of sputum is not always possible and induced sputum, deep throat swabs or aspirates are used as a surrogate [10–12, 14]. Non invasive methods that could complement isolation of P. aeruginosa for earlier detection of infection in children with CF would be beneficial.…”

“…Culture-based methods are currently the gold standard for the detection of P. aeruginosa in respiratory samples of CF patients [14, 27]. They are relatively inexpensive and standardized, and have the ability to identify only viable organisms, which can then be tested for antibiotic susceptibility and stored for further study [12]. On the other hand, culture-independent methods such as quantitative real-time polymerase chain reaction (PCR), 16S rRNA sequencing, and next-generation sequencing allow faster and precise identification of organisms if used with large sequence databases, but it is possible for non-viable organisms to also be detected [14, 33, 34].…”

“…Sputum is usually produced in patients with progressive CF or those that are in exacerbation and acquisition of BAL in children requires bronchoscopy under general anesthesia. In non-sputum-producing CF patients induced sputum has been shown to improve detection of pathogens, including P. aeruginosa [12]. Induced sputum can be difficult to acquire in children under the age of 5 years and in such instance can be replaced by deep throat aspirates or swabs [13].…”