Gram negative infections in cystic fibrosis: a review of preventative and treatment options

Infection of the airways remains the primary cause of morbidity and mortality in persons with cystic fibrosis (CF). This review describes salient features of the epidemiologies of microbial species that are involved in respiratory tract infection in CF. The apparently expanding spectrum of species causing infection in CF and recent changes in the incidences and prevalences of infection due to specific bacterial, fungal, and viral species are described. The challenges inherent in tracking and interpreting rates of infection in this patient population are discussed.

Patients were defined each successive month as either 'chronic' when more than 50% of the preceding 12 months were PA culture positive, 'intermittent' when < or =50% of the preceding 12 months were PA culture positive, 'free of PA', with no growth of PA for the previous 12 months, having previously been PA culture positive, or 'never infected', when PA had never been cultured. Cross-sectional analysis of 146 children attending the Leeds Regional Cystic Fibrosis Centre was performed to assess relationship between the new definition and clinical scores and investigations. The response variable was regressed on age and sex and the residuals analysed using the Kruskal-Wallis test. The 'chronic' group (18% of patients) had significantly worse Shwachman-Kulczycki (SK) and Northern chest X-ray scores, and % predicted FEV(1) values than the 'free' (28%) or 'never' (20%) categories (P<0.004). The 'intermittent' group (34%) had a significantly higher SK score than the 'chronic' group (P<0.0001), and a significantly lower % predicted FEV(1) value than the 'free' or 'never' groups (P<0.0003). 'Chronic' patients were significantly associated with a positive, and 'never' patients with a negative, PA antibody result (P<0.001). The validity and importance of identifying these four subgroups is demonstrated. Previous definitions may over-estimate the prevalence of chronic infection.

Patients with cystic fibrosis periodically experience pulmonary exacerbations. Previous studies have noted that some patients' lung function (FEV(1)) does not improve with treatment. To determine the proportion of patients treated for a pulmonary exacerbation that does not recover to spirometric baseline, and to identify factors associated with the failure to recover to spirometric baseline. Cohort study using the Cystic Fibrosis Foundation Patient Registry from 2003-2006. We randomly selected one pulmonary exacerbation treated with intravenous antibiotics per patient and compared the best FEV(1) in the 3 months after treatment with the best FEV(1) in the 6 months before treatment. Recovery to baseline was defined as any FEV(1) in the 3 months after treatment that was greater than or equal to 90% of the baseline FEV(1). Multivariable logistic regression was used to estimate associations with the failure to recover to baseline FEV(1). Of 8,479 pulmonary exacerbations, 25% failed to recover to baseline FEV(1). A higher risk of failing to recover to baseline was associated with female sex; pancreatic insufficiency; being undernourished; Medicaid insurance; persistent infection with Pseudomonas aeruginosa, Burkholderia cepacia complex, or methicillin-resistant Staphylococcus aureus; allergic bronchopulmonary aspergillosis; a longer time since baseline spirometric assessment; and a larger drop in FEV(1) from baseline to treatment initiation. For a randomly selected pulmonary exacerbation, 25% of patients' pulmonary function did not recover to baseline after treatment with intravenous antibiotics. We identified factors associated with the failure to recover to baseline, allowing clinicians to identify patients who may benefit from closer monitoring and more aggressive treatment.