José Luis Lezana-Fernández

Pseudomonas aeruginosa is an opportunistic pathogen frequently infecting the lower airways of individuals with cystic fibrosis (iwCF). We investigated colistin (CST) resistance mechanisms in P. aeruginosa ST3351 (Psa-ST3351) and their impact on bacterial virulence. Psa-ST3351, a novel CST-resistant sequence type, was isolated from a child with CF. We demonstrate that CST resistance in Psa-ST3351 depends on the addition of 4-amino-4-deoxy-L-arabinose to lipid A. Moreover, exposure to CST induced a non-mucoid-to-mucoid phenotypic switch characterized by enhanced swarming motility, decreased susceptibility to aminoglycosides, impaired ExoS secretion via the type-III secretion system, and increased bacterial competition, all hallmarks of a chronic infection phenotype. CST-treated Psa-ST3351 also exhibited reduced phagocytosis by macrophages, despite the induction of pro-inflammatory cytokines remaining unaffected, and enhanced the pathogenicity in a mouse pneumonia model. These findings suggest that CST-induced mucoid conversion in CST-resistant Psa-ST3351 May contribute to disease progression in iwCF, particularly when CST resistance and mucoid conversion remain undetected during CST nebulized therapy.

Background/Objectives: Cystic fibrosis (CF) is a multisystem disease caused by CFTR gene variants, with a high prevalence of vitamin D (VitD) deficiency despite the supplementation and schedules specifically developed for this population. Lower VitD levels have been associated with an increased risk of respiratory infections and pulmonary exacerbations in CF, with some pilot studies indicating the potential benefits of supplementation during acute episodes. This study aimed to describe the occurrence of VitD deficiency according to the supplemented dose in pediatric patients with CF. Methods: A cross-sectional analytical study was conducted to assess serum VitD levels in a pediatric population with cystic fibrosis. Clinical and biochemical data were collected, along with information on VitD intake and pancreatic enzyme dosage at the time of evaluation. Results: A total of 48 patients were included in the study. Normal VitD levels were observed in 41.7% of the patients, insufficiency in 31.3%, and deficiency in 27%. The median VitD intake was 2050 IU. A statistically significant difference was observed in patients with a daily intake exceeding 2000 IU. Only 10% of patients achieved levels above 30 ng/mL with a lower dose. No statistically significant association was identified between the pancreatic enzyme dosage and vitamin D levels. Conclusions: Vitamin D deficiency/insufficiency is a persistent problem in the pediatric CF population; the interventions targeting factors associated with this condition are required to refine supplementation schedules. These findings underscore the need for personalized strategies to optimize vitamin D status in PwCF. Ideally, these strategies should consider all associated factors, including genetic variants; however, with limited resources, our results suggest that a daily dose of 2000 IU of vitamin D may represent a reasonable and effective starting point for supplementation.

Cystic fibrosis (CF) is a rare autosomal recessive disease most commonly affecting the Caucasian population. CF diagnosis can be a challenge due to the large spectrum of pathogenic variants in the CFTR gene and the effects of complex alleles. Next-generation sequencing has improved our understanding of the contribution of these complex alleles to the wide spectrum of CF clinical symptoms and to the response to medications. Herein, we studied nine CF patients from six unrelated families carrying the complex allele p.[Ile148Thr;Ile1023_Val1024del] with a frequency of 0.18%. All patients were from Central Mexico. This complex allele was found in trans with Class I and II pathogenic variants such as p.(Phe508del), and p.(Phe1078Profs*77)]. A targeted search of a dataset of 2217 exomes from healthy individuals revealed that eight individuals (0.18%) carried the p.(Ile148Thr) variant, but only one (0.022%), who was also born in Central Mexico, was a carrier of the complex allele. These findings show an enrichment of this p.[Ile148Thr;Ile1023_Val1024del] complex allele in Mexican CF patients in this region of Mexico. Finally, protein modeling revealed that this complex allele disrupts the secondary structure of the CFTR protein and might alter the ion flow.

Cystic fibrosis (CF) diagnosis can be a challenge due to the large spectrum of pathogenic variants in the CFTR gene and the effects of complex alleles. Next-generation sequencing has improved our understanding of the contribution of these complex alleles to the wide spectrum of CF clinical symptoms and to the response to medications. Herein, we studied nine CF patients from six unrelated families carrying the complex allele p.[Ile148Thr;Ile1023_Val1024del] with a frequency of 0.18%. All the patients were from Central Mexico. This complex allele was found in trans with Class I and II pathogenic variants (PVs) such as [c.1521_1523del, p.(Phe508del), and c.3231_3232del, p.(Phe1078Profs*77)]. A targeted search of a dataset of 2,217 exomes from healthy individuals revealed that eight individuals (0.18%) carried the p.(Ile148Thr) variant, but only one (0.022%), who was also born in Central Mexico, was a carrier of the complex allele. These findings led us to hypothesize a founder effect for the p.[Ile148Thr;Ile1023_Val1024del] complex allele in Mexican patients with CF, probably through migration from the French-Canadian population in Mexico. Finally, protein modeling revealed that this complex allele disrupts the secondary structure of the CFTR protein and might alter the ion flow.

Patients with cystic fibrosis (CF) have airway inflammation that contributes to symptoms and to pulmonary function derangement. Current drugs used to diminish airway inflammation improve the clinical and spirometric status of patients with CF, but their use is limited due to their undesired side effects, for example, glucose intolerance, growth retardation, and cataracts with corticosteroids, gastrointestinal toxicity with ibuprofen, and macrolide resistance with azythromycin. Glycine is known to decrease activation of inflammatory cells, including alveolar macrophages and neutrophils, and is relatively inexpensive, palatable, and virtually devoid of untoward effects. These features make glycine a good candidate for antiinflammatory treatment of CF. Thus, we aimed to explore whether glycine can exert a beneficial effect in a population of patients with CF. This was a randomized, double blinded, cross-over pilot clinical trial. Subjects with CF received, in random order, oral glycine (0.5 g/kg/day, dissolved in any liquid) and placebo (glass sugar), each during 8 weeks with an intermediate 2-week wash-out period. Thirteen subjects aged 6–23 years, 8 females, completed the two arms of the study. As compared with placebo, after glycine intake patients had better symptom questionnaire scores (p = 0.02), mainly regarding sputum features and dyspnea. While spirometric variables tended to decline during placebo intake, they remained stable or even increased during glycine treatment (p = 0.04 to p = 0.003). In this context, FEV1 declined 8.6% after placebo and increased 9.7% at the end of the glycine period. Pulse oximetry improved after glycine intake (p = 0.04 vs. placebo). TNF-α in serum and IL-6 and G-CSF in sputum tended to decline at the end of the glycine period (p = 0.061, p = 0.068 and p = 0.04, respectively, vs placebo). Glycine was remarkably well tolerated. The clinical, spirometric and inflammatory status of subjects with CF improved after just 8 weeks of glycine intake, suggesting that this amino acid might constitute a novel therapeutic tool for these patients. Thus, further studies are warranted. www.clinicaltrials.gov, registration number: NCT01417481, date of registration: March 12, 2012.