Virulence of mucoid Pseudomonas aeruginosa strains in cystic fibrosis: New sequential infection model

Macrolides long-term therapy has demonstrated beneficial effects on pulmonary status in CF patients, but there is a lack of literature on microbiological variations possibly associated with it. We studied lung function (FEV1%), nutritional status (BMI) and sputum culture in 65 CF patients (32 males, mean age 29.11 years), in whom long-term Azithromycin therapy (250–500mg/die, 3/7 days a week, for at least 1 year) was performed. Moreover we compared, for sputum cultures results, 10 patients (Group A: 4 males, mean age 23.5 years, range 12.5−44, Sputum culture: S.a.oxa S in 7/10, S.a. oxa R in 1/10, S.a.+ P.a. in 2/10) out of these series, with 10 CF patients (Group B) matched for age and sputum culture, in whom long-term Azithromycin therapy was never performed. In 44/65 patients (68%) mean BMI improved (T0: 19.64; T12: 19.83); in 41/64 patients (63%) mean FEV1% increased (T0: 56.17%; T12: 60.21%); in 20/65 patients sputum bacteria showed new multiresistance antibiotic pattern and in 14/65 (21.5%) sputum cultures exhibited small colony variant (SCV) as new bacterial phenotypes: S.a. in 9 pts, P.a. in 6 pts and mucoid P.a. in 1 pt. The sputum culture comparison between Group A and Group B showed no difference on new multiresistence antibiotic bacteria developement, but 2 SCV S.a. and 1 SCV P.a. in Group A and no SCV bacteria in Group B were isolated. In conclusion our data, according to international leterature, demonstrate that long-term Macrolides therapy have a positive impact on respiratory function and nutritional status in CF, but we hypothesize that this therapy could be associated with SCV bacteria development in CF sputa.