Evaluation of sputum culture and respiratory tract multiplex PCR parameters in patients followed up with cystic fibrosis exacerbation

Introduction and Purpose: Cystic fibrosis (CF) is an autosomal recessive inherited disease that can lead to significant morbidity and mortality in both childhood and adulthood. Patients with CF are prone to acute respiratory exacerbations. Multiplex polymerase chain reaction (PCR), a highly sensitive and specific molecular technique, enables the detection of viral RNA in respiratory samples. This study aimed to retrospectively evaluate the demographic characteristics and microbiological agents responsible for respiratory exacerbations in pediatric patients diagnosed with CF and to provide insights for more effective treatment strategies based on the findings. Materials and Methods: In this study, 120 patients who presented to the Pediatric Pulmonology outpatient clinic of Dicle University Faculty of Medicine between January 1, 2017, and December 31, 2024, and were diagnosed with cystic fibrosis exacerbation were included. Patients in whom a microbiological agent was isolated in at least one of the throat culture, sputum culture, or respiratory multiplex PCR tests were classified as "Group 1," while those without any isolated pathogens were classified as "Group 2." The clinical, sociodemographic characteristics, and laboratory parameters of the cases were compared between the two groups. Results: The mean age at presentation was significantly higher in Group 1 compared with Group 2 (p=0.003). Among clinical symptoms, cough was significantly more common in Group 1 (p<0.001), whereas wheezing (p=0.035) and fatigue (p=0.047) were significantly more frequent in Group 2. The frequency of recurrent hospital visits was markedly higher in Group 1 (p<0.001).Microbiological analysis revealed Rhinovirus as the most frequently detected pathogen (4.2%). In throat cultures, Staphylococcus aureus and Pseudomonas aeruginosa were the most common bacterial isolates, each detected in 6.7% of cases (n=8). In sputum cultures, P. aeruginosa was the predominant pathogen (15.8%). Antibiotic susceptibility testing demonstrated high susceptibility rates of P. aeruginosa isolates to aminoglycosides (73.6%) and carbapenems (68.4%), while susceptibility to fluoroquinolones was moderate. Conclusion: In respiratory tract infections, the presence of specific microbiological agents appears to be associated with certain clinical features, particularly cough and recurrent hospital visits. The higher prevalence of cough may be explained by further impairment of mucociliary clearance and an intensified inflammatory response during infection. Despite the high analytical sensitivity of PCR, a considerable proportion of negative results was observed, likely due to the retrospective nature of the study and non-standardized specimen collection procedures. While throat and sputum cultures have limited yield in pathogen detection, they remain valuable for monitoring antimicrobial resistance patterns. The high susceptibility rates of P. aeruginosa isolates to aminoglycosides and carbapenems align with previously published data, whereas the moderate susceptibility to fluoroquinolones warrants attention. These findings underscore the role of diagnostic methods in respiratory infections and highlight the need for further studies with larger cohorts to validate and expand upon these results. Keywords: Cystic fibrosis, exacerbation, sputum culture, respiratory multiplex PCR