[Antibiotic therapy in cystic fibrosis. II Antibiotic strategy]

Antibiotherapy is one of the main treatments of cystic fibrosis, contributing to a better nutritional and respiratory status and a prolonged survival. The choice of antibiotics depends on quantitative and qualitative analysis of sputum, bacteria resistance phenotypes and severity of infection. Haemophilus influenzae infection can be treated orally with the association of amoxicillin-clavulanic acid or a cephalosporin. Staphylococcus aureus generally remains sensitive to usual antibiotics; in case of a methicillin-resistant strain, an oral bitherapy or a parenteral cure can be proposed. Treatment of Pseudomonas aeruginosa is different in case of first colonization or chronic infection: in first colonization, parenteral antibiotherapy (beta-lactams-aminoglycosids) followed by inhaled antibiotherapy may eradicate the bacteria; in chronic infections, exacerbations require parenteral bi-antibiotherapy (beta-lactams or quinolons and aminoglycosids) for 15 to 21 days, inhaled antibiotics between the cures being useful to decrease the number of exacerbation. A careful monitoring of antibiotherapy is necessary because of possible induction of bacterial resistance, nephrotoxicity and ototoxicity of aminosids and allergy to beta-lactams.

[Antibiotic therapy in cystic fibrosis. I. Pharmacologic specifics of antibiotics]

Antibiotherapy is one of the main treatment in cystic fibrosis. Antibiotic administration schedules are different from normal patients because of pharmacokinetic and pharmacodynamic particularities. In moderate disease, the digestive resorption of antibiotics is delayed and their half-life is reduced due to an increase in total clearance. In severe disease, the volume of distribution of antibiotics is increased due to the higher proportion of lean mass in these malnourished patients. Other particularities limit the action of antibiotics such as thick sputum, which limits drug penetration; the property of Pseudomonas aeruginosa to be surrounded by a biofilm; alteration of local antibacterial defense; and inhibition of antibiotics by local factors. Systematic prescription of a biotherapy beta-lactam-aminoglycoside and obtaining high antibiotic concentration in situ might limit this antagonism. In spite of particular therapeutic schedules such as single daily dose for aminoglycoside and continuous infusion for beta-lactams, the intervals between administrations must be narrowed for time-dependent antibiotics, and the total daily dose increased by 20 to 30% for concentration-dependent antibiotics.

Rapid improvement of intracranial tuberculomas after addition of ofloxacin to first-line antituberculosis treatment

Reported here is the case of a 9-year-old girl presenting with disseminated tuberculosis, the manifestations of which included mediastinal adenopathy, an osteolytic parietal lesion with a large associated scalp abscess, cerebral empyema, meningoencephalitis, and tuberculomas. No clear improvement was observed after 4 weeks of first-line antituberculosis treatment (10 mg/kg rifampin, 15 mg/kg isoniazid, 30 mg/kg ethambutol, 30 mg/kg pyrazinamide). The isolation of an isoniazid-resistant organism prompted institution of ofloxacin. Introduction of this drug was associated with dramatic improvement. Its good penetration into the central nervous system and its distribution into macrophages suggest that this drug may be of interest for the treatment of intracranial tuberculomas, particularly those due to isoniazid-resistant strains.

A large subset of neutrophils expressing membrane proteinase 3 is a risk factor for vasculitis and rheumatoid arthritis

It has been shown previously that proteinase 3 (PR3), a neutrophil intracellular protease that is the main antigen of antineutrophil cytoplasm (ANCA) autoantibodies, is present on the plasma membrane of a subset of freshly isolated neutrophils. This study shows that the size of this subset of membrane PR3-positive (mPR3+) neutrophils is a stable feature of a given individual, most likely genetically controlled. It ranges from 0 to 100% of neutrophils and allows us to define a new polymorphism in the healthy population, with three discrete phenotypes corresponding respectively to less than 20% mPR3 + neutrophils (mPR3low) or to a mean percentage of 47% (mPR3intermediate) and 71.5% (mPR3high) mPR3+ neutrophils. The frequency of the mPR3high phenotype was significantly increased in patients with ANCA-associated vasculitis (85% versus 55% in healthy subjects). The percentage of mPR3+ neutrophils was not affected by disease activity, relapses, or therapy, and did not reflect in vivo cell activation. In addition, mPR3+ phenotypes were normally distributed in cystic fibrosis patients, indicating that infection and/or inflammation per se do not lead to a high percentage of mPR3+ neutrophils. The frequency of the mPR3high phenotype was not related to anti-PR3 autoimmunization, since it was increased in vasculitic patients regardless of the ANCA specificity (anti-PR3, anti-myeloperoxidase, or unknown). Interestingly, the frequency of the mPR3high phenotype was also increased in patients with rheumatoid arthritis. It was normal in type I-diabetes, a T cell-dependent autoimmune disease. It is proposed here that a high proportion of membrane PR3-positive neutrophils could favor the occurrence or the progression of chronic inflammatory diseases.

Inflammation and CFTR: might neutrophils be the key in cystic fibrosis?

The aim of this hypothesis is to provide new insights into the still unclear mechanisms governing airway inflammation in cystic fibrosis. Although the genetic basis of cystic fibrosis as well as the molecular structure of cystic fibrosis transmembrane regulator (CFTR), the mutated protein which causes the disease, have been well defined, a clear relationship between the genetic defect and the pulmonary pathophysiology, especially chronic infections and neutrophil-dominated airway inflammation has not been established. Cystic fibrosis is thus a unique pathological situation in that neutrophils can be depicted as both an antiinfectious and a proinflammatory cell. In cystic fibrosis there is an emerging picture of an imbalance between these two roles with both a reduction in the antiinfectious efficacy and an augmentation of the proinflammatory functions. Better knowledge of fundamental defects in neutrophil function in cystic fibrosis as well as a novel cellular function of CFTR, which will be reviewed, will allow identification of potentially new clinical targets and aid selective therapeutic action aimed at counteracting the lethal neutrophil-induced airway inflammation. The rationale for colchicine therapy is a significant example of a drug which might act both at the molecular levels on CFTR expression in epithelial cells and on neutrophils to mediate antiinflammatory effects. Preliminary results are presented in this issue (Med Inflamm 1999; 8: 13-15).

Interest of colchicine for the treatment of cystic fibrosis patients. Preliminary report

Cystic fibrosis (CF) lung disease is characterized by persistent inflammation. Antiinflammatory drugs, such as corticosteroids and ibuprofen, have proved to slow the decline of pulmonary function although their use is limited because of frequent adverse events. We hypothesized that colchicine could be an alternative treatment because of its antiinflammatory properties and upregulatory effect on cystic fibrosis transmembrane regulator (CFTR) closely related proteins. We herein present results obtained in an open study of eight CF children treated with colchicine for at least 6 months. Clinical status was better in all patients and respiratory function tests significantly improved in five. Median duration of antibiotherapy decreased significantly. These preliminary results support our hypothesis of a beneficial effect of colchicine in CF patients and stress the need for a controlled therapeutic trial.

Priming of blood neutrophils in children with cystic fibrosis: correlation between functional and phenotypic expression of opsonin receptors before and after platelet-activating factor priming

Blood phagocyte opsonin receptor CR1 (CD35) and CR3 (CD11b) functions were examined in cystic fibrosis (CF) patients with endobronchial Staphylococcus aureus or Pseudomonas aeruginosa chronic infection, CF patients without infection, heterozygous, non-CF patients with chronic pulmonary infection, and healthy controls. Circulating and platelet-activating factor (PAF)-primed phagocyte luminol luminescence responses to complement-opsonized zymosan were increased in both groups of infected CF and non-CF children relative to uninfected CF children and healthy control children and adults. The ratio between circulating and PAF-primed phagocyte responses was significantly elevated in all children with CF, and in these, the ratio could serve as an indicator of response to antibiotic treatment. The ratios of circulating and PAF-primed phenotypic expression for CR1, CR3, and FcgammaRIII (CD16), but not FcgammaRII (CD32), correlated with the functional ratios. Phagocyte opsonin receptor response capacity might be used for evaluation of inflammation and infection in CF patients.