Sequential genotyping of Pseudomonas aeruginosa from upper and lower airways of cystic fibrosis patients

A controversy exists concerning the adequate specimen to characterise colonisation of cystic fibrosis (CF) airways by Pseudomonas aeruginosa. Oropharyngeal, sputum and bronchoalveolar lavage samples were evaluated from 38 stable CF patients for the detection of P. aeruginosa, genetically different isolates within the same host and longitudinal variations in the genotype during repeated examinations. Bacterial isolates were typed by pulsed-field gel electrophoresis of deoxyribonucleic acid macrorestriction fragments. Sensitivity, negative and positive predictive values and specificity to detect P. aeruginosa were 35.7, 73.5, 83.3 and 96.2% for oropharyngeal cultures in nonexpectorating patients and 91.7, 94.1, 100 and 100% for sputum cultures from expectorating patients, respectively. Genotypes of Pseudomonas isolates recovered from oropharyngeal swabs and sputum differed to the strains recovered by bronchoscopy in 55% and 40%, respectively. In 62% longitudinal variations in the genotype occurred. One-half of these alterations were detectable by bronchoscopy only. In conclusion, sputum samples were of equal value as specimens from bronchoalveolar lavage to detect Pseudomonas aeruginosa colonisation. Cultures from the oropharynx are not suitable for characterising bacterial conditions in the cystic fibrosis lung. Different genotypes within the same host and longitudinal genetic alterations are common and may be detectable in the bronchoalveolar lavage fluid exclusively.