Abstract Rationale Primary Ciliary Dyskinesia (PCD) is a rare autosomal recessive ciliopathy caused by defects in the structure and function of motile cilia. The RSPH4A genetic variant is highly prevalent in Puerto Rican patients and is characterized by recurrent respiratory infections and impaired mucociliary clearance. Chronic bacterial colonization, particularly Pseudomonas aeruginosa, contributes to progressive lung-function decline, and frequent antibiotic exposure predisposes patients to increased antimicrobial resistance. Understanding local resistance trends is essential for guiding empiric therapy and optimizing long-term management in this genetically defined population. This study characterized the microbiological profile, antibiotic resistance patterns, and their relationship with age, sex, and lung function. Methods A retrospective review of 64 sputum cultures collected between 2015 and 2025 from 18 patients with genetically confirmed Primary Ciliary Dyskinesia was performed. Culture results and antimicrobial susceptibility data were gathered from electronic medical records. Multidrug resistance (MDR) was defined as resistance to ≥ 3 antibiotic classes. All available cultures were included, and FEV1 (%predicted) values nearest to the date of sample collection were recorded. Results A total of 64 sputum cultures from 18 PCD-confirmed patients were analyzed. Pseudomonas aeruginosa was the predominant organism, isolated in 55% of cultures, with 41% non-mucoid and 14% mucoid phenotypes. Other organisms included Escherichia coli (8%), Haemophilus parainfluenzae/influenzae (6%), Acinetobacter baumannii complex (4%), and Serratia marcescens (3%). Normal respiratory flora was reported in 22% of cultures. Multidrug resistance (MDR) was present in 26.6% (17/64) of cultures. The highest resistance rates were observed against folate pathway inhibitors (55%), tetracyclines (47%), and glycylcyclines (43%), while no resistance was detected to glycopeptides, oxazolidinones, polymyxins, or rifamycins. MDR infections were significantly more frequent in females compared to males (37%vs 9%,p0.05). Age was also associated with MDR status (p 0.05), with MDR infections being significantly more common in adults aged 18-40 compared to those under 18 or over 40. FEV1 (%predicted) did not differ significantly between MDR and non-MDR groups (p 0.05). Conclusion In this cohort of RSPH4A-associated PCD, Pseudomonas aeruginosa (particularly the non-mucoid phenotype) was the most common pathogen isolated from sputum cultures. A substantial proportion of isolates demonstrated MDR, most frequently to folate pathway inhibitors and tetracyclines. MDR was significantly associated with female sex and with patients aged 18-40 years. These findings highlight the importance of routine microbiologic monitoring and the need for tailored antibiotic stewardship in this population. Continued longitudinal assessment correlating microbiological trends with clinical outcomes may inform future management strategies and resistance-mitigation efforts. This abstract is funded by: None
Rivera et al. (Fri,) studied this question.
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