All three serological assays were equally informative. The very high sensitivity of the assays made it possible to characterize patients with different infection status. Elevated levels of specific anti-Pseudomonas antibodies showed to be the risk factor for developing chronic Pa infection. Due to the specificity of the tests, antibiotic treatment based on serology might be considered in selected cases. There is a window of opportunity for suppression and eradication of initial P. aeruginosa infection making measurement of specific anti-Pseudomonas antibodies helpful.

Background/Objectives: The hallmark of cystic fibrosis (CF) is chronic lung inflammation. The severity of lung disease is closely correlated with immunoglobulin G (IgG) levels. Beyond its contribution to the bone health, the importance of vitamin D has not been fully recognized owing to the lack of human studies providing evidence of its benefit. In the context of the recently described immunomodulatory functions of vitamin D, we aimed to assess the relationship between vitamin D and IgG levels. Subjects/Methods: Eight hundred and ninety-six CF patients were included (0.53-65.9 years) from seven centers in Denmark, Norway and Sweden. Serum 25-hydroxyvitamin D (25OHD) and total IgG were measured, spirometry was carried out and vitamin D intake data were gathered using a 7-day dietary food record. Multiple linear regression analyses were performed for IgG and forced expiratory volume in 1ls (FEV1) as dependent variables, and serum 25OHD, daily food and supplemented vitamin D sources of intake as independent variables. The model was controlled for age, gender, genotype, CF-related diabetes, season, infection/colonization status, long-term oral corticosteroid treatment, long-term treatment with macrolide antibiotics, pancreatic insufficient phenotype and body mass index z-score. Results: Serum total IgG levels were negatively associated with serum 25OHD (adjusted R 2 ¼ 0.376; beta ¼ À0.02; Po0.001), supplemented vitamin D intake per kg bodyweight (adjusted R 2 ¼ 0.375; beta ¼ À0.82; Po0.001) and total vitamin D intake per kg bodyweight (adjusted R 2 ¼ 0.398; beta ¼ À0.60; P ¼ 0.002). Serum 25OHD was positively associated with FEV1 (adjusted R 2 ¼ 0.308; beta ¼ 0.0007; P ¼ 0.025). Conclusions: Increasing vitamin D intake may positively modulate inflammation in CF. This study supports the proposed role of vitamin D in the immune system during infection and substantiates prospective studies.

In total, 40 Pseudomonas aeruginosa isolates from cystic fibrosis (CF) patients were included in this study. Twenty of these were collected in 1994 and 1997, from six CF patients, and the rest were collected from different CF patients in 2000 and 2001. The relative expression of mRNA for the efflux pump protein MexY was determined by real-time PCR and correlated with susceptibilities to amikacin and tobramycin. The chromosomal genes mexZ, rplY, galU, PA5471 and nuoG, which were found to have a role in the gradual increase in MICs of aminoglycoside antibiotics in laboratory mutants of P. aeruginosa, were analysed. MexY mRNA overproduction was found in 17/20 isolates collected in 1994 and 1997, and was correlated with decreased susceptibility to aminoglycosides. Alteration of the MexXY-OprM efflux system has been the main mechanism of resistance to aminoglycoside antibiotics in CF P. aeruginosa isolates over the 3-year period. In several isolates, expression of the PA5471 gene product might have some effect on elevated MICs of aminoglycosides. Inactivation of rplY, galU and/or nuoG may explain the gradual increase in MICs of aminoglycosides in laboratory mutants but probably not in the CF environment, as rplY and galU were unaltered in all isolates, and nuoG was not expressed in only one isolate. No 16S rRNA A-site mutations were found in any of the four copies of the gene in 13 investigated isolates.

Xanthomonas maltophilia was isolated from 25 of 150 patients with cystic fibrosis during a period of 10 years (1983-1992). Twelve patients harboured X. maltophilia chronically, i.e. repeatedly for more than 6 months. No predisposing factors for the colonisation could be identified by studying the clinical and laboratory data of the patients, including preceding and concurrent bacterial colonisation with other bacteria, antibacterial treatments, pulmonary function and biochemical markers. Up to 2 years after the chronic colonisation was established no clinical deterioration could be verified, but the patients with X. maltophilia generally had a worse lung function at the latest follow-up (2-7 years after colonisation) than controls colonised with Pseudomonas aeruginosa (p < 0.05). Our data imply that X. maltophilia is a pathogen and the colonisation appears to follow the same pattern as the colonisation by P. aeruginosa. The development of resistance to different antibiotics, as revealed by analysis of the inhibition zones, was related to antibacterial treatment courses. X. maltophilia showed reduced sensitivity to the most commonly used antibiotics, ceftazidime and tobramycin.