Svend Stenvang Pedersen

Management of Pseudomonas Aeruginosa Lung Infection in Danish Cystic Fibrosis Patients

ABSTRACT. The annual mortality rate of cystic fibrosis patients with chronic Pseudomonas aeruginosa lung infection at the Danish CF‐centre ranged from 10 to 20% in the years 1970–1975. In this period the patients received antipseudomonal chemotherapy only during acute exacerbations of infection. From 1976 99 patients acquired chronic P. aeruginosa infection and were given regular and intensive antipseudomonal treatment 3–4 times per year. The patients were followed for 612 patient‐years; 7 died and the 10‐year survival rate after onset of P. aeruginosa infection was 90%±4%. The annual mortality rate is now 1–2%. Although precipitating antibodies against P. aeruginosa increased significantly, pulmonary function did not deteriorate with duration of infection. Cross‐infection between patients caused an increased incidence of chronic P. aeruginosa infection which was reduced by hygienic measures.

Induction of experimental chronic Pseudomonas aeruginosa lung infection with P. aeruginosa entrapped in alginate microspheres

Alginate‐producing, mucoid P. aeruginosa is frequently found in the lungs of patients with cystic fibrosis (CF), where it causes a chronic infection. The importance of alginate in the pathogenesis was demonstrated by the ability to establish chronic P. aeruginosa lung infection in rats if P. aeruginosa entrapped in minute alginate‐beads were inoculated transtracheally. Alginate beads containing P. aeruginosa were formed by nebulizing a suspension of seaweed sodium‐alginate and P. aeruginosa into a calcium solution. The alginate bead method of establishing infection was compared to an agar‐bead method and proved to be quantitatively similar after 4 weeks. The ability of the two methods to induce formation of precipitins, IgA and IgG antibodies against P. aeruginosa antigens, including outer membrane proteins, flagella, exoenzymes and alginate, was assessed by crossed immunoelectrophoresis, enzyme‐linked immunosorbent assay and immunoblotting. The two methods of inducing infection were comparable and infected rats had significantly higher antibody response than rats inoculated with sterile beads. We suggest that the alginate bead model closely resembles the later stages of CF‐lung infection and that it offers the theoretical advantage of using a substance which is chemically similar to the alginate produced in vivo by P. aeruginosa.

Development of antibiotic resistance in Pseudomonas aeruginosa during two decades of antipseudomonal treatment at the Danish CF Center.

At the Danish CF Center patients with chronic Pseudomonas aeruginosa lung infection were treated 3–4 times a year (from 1976) with a 2‐week intravenous antipseudomonal course which included preferentially an aminoglycoside and a β‐lactam antibiotic. We investigated the development of antibiotic resistance in P. aeruginosa strains isolated from Danish CF patients over a period of 18 years by testing the in vitro efficacy of carbenicillin, piperacillin, ceftazidime, tobramycin and ciprofloxacin against P. aeruginosa strains collected in 1973 (51 strains), 1980 (80 strains), 1985 (58 strains), and 1991 (100 strains). All the strains were screened and assayed semiquantitively for β‐lactamase activity by use of nitrocefin. We found a significant (p<0.005) increase in the MIC values of the P. aeruginosa strains against piperacillin and ceftazidime. However, no significant correlation was found between the MIC and the number of antipseudomonal courses of antibiotics. The proportion of resistant in vivo selected P. aeruginosa strains, presumed to be stably derepressed producers of chromosomal β lactamase, also increased significantly during the period studied. Our results confirm that the β lactamase production is an important mechanism of antibiotic resistance in P. aeruginosa.

Chronic Pseudomonas aeruginosa lung infection in normal and athymic rats

We have compared a chronic lung infection with Pseudomonas aeruginosa embedded in alginate beads in normal and athymic rats with an acute infection with free live P. aeruginosa bacteria. The following parameters were observed and described: mortality, macroscopic and microscopic pathologic changes, and antibody responses. The rats challenged with P. aeruginosa alginate beads experienced a generally more severe lung pathology and the antibody responses were more homogeneous with less dispersion as compared to the rats having free live P. aeruginosa bacteria. In general, manifestations were more severe in the athymic rats compared to the normal rats. It is, however, notable that the athymic rats developed similar microscopic lung manifestations as the normal rats when given a large number of P. aeruginosa in the beads, with dense accumulation of neutrophil granulocytes and microcolonies comparable to the lesions seen in cystic fibrosis (CF) patients. Early transitory IgM titers were demonstrated in both normal and athymic rats. Whilst athymic rats produced much lower IgG titers than the normal rats, presumably due to the absence of CD4+ cells, higher primary IgA titers were achieved. These two models in normal and athymic rats of the chronic lung infection resembling that seen in CF lungs make it possible to study the influence of the various components of the specific and nonspecific defence systems on the course of the chronic P. aeruginosa lung infection and to evaluate the effect of various immunization schedules and immunomodulatory drugs.

Effect of oral N-acetylcysteine administration on human blood neutrophil and monocyte function

N‐acetylcysteine (NAC) is known to be a scavenger of free oxygen radicals, and recent in vitro studies have demonstrated that it is also able to inhibit leukocyte function. The clinical significance of these effects is, however, not known. In this study we have measured the effect on human blood neutrophil and monocyte function of a single 400 mg dose of NAC administered orally. Administration of NAC to ten healthy volunteers resulted in significant reduction of neutrophil chemiluminescence response following activation by opsonized zymozan as compared to four non‐treated persons acting as controls. No effect was observed on the chemotaxis of either cell type or on monocyte chemiluminescence response. These findings suggest that NAC may be beneficial in clinical conditions like cystic fibrosis, where tissue damage may be a consequence of the effects of increased release of toxic oxygen radicals and proteolytic enzymes.

Does Centralized Treatment of Cystic Fibrosis Increase the Risk of Pseudomonas aeruginosa Infection

ABSTRACT. Two hundred and forty Danish patients with cystic fibrosis (97% of the total CF population in Denmark) participated in a point‐prevalence study of Pseudomonas aeruginosa infection. One hundred and ninety‐two patients were treated at the Danish CF centre and 48 patients were treated in other places. The age distribution was significantly different as no patients older than 19 years were found in the non‐centre group. Pathogenic bacteria were isolated from the sputum of 96% of the patients. P. aeruginosa was more prevalent in patients from the centre, whereas Staphylococcus aureus was more prevalent in the non‐centre group. No difference in serogroup and phage pattern of P. aeruginosa was found. There was a tendency that non‐centre treated patients acquired chronic broncho‐pulmonary P. aeruginosa infection later, but at the age of 16 years 90% of all patients will be chronically infected. Chronic P. aeruginosa infection was significantly more common in the age group 10‐14 years at the centre than outside the centre. It is not possible to prevent chronic P. aeruginosa infection in CF patients treated in small groups and because of the better prognosis of centralized treatment the latter must be recommended.

Mucosal immunity to Pseudomonas aeruginosa alginate in cystic fibrosis.

Patients with cystic fibrosis commonly acquire chronic pulmonary infection with alginate‐producing Pseudomonas aemginosa. The infection remains localized at the mucosal surfaces of the airways. Using enzyme‐linked immunosorbent assays immunoglobulin concentrations and titers of specific antibodies to purified P. aeruginosa alginate and to P. aemginosa sonicated antigens were measured in tears, saliva, sputum and serum. CF patients had significantly higher concentrations of IgG, IgA and SIgA in serum and saliva than controls. They also had significantly higher levels of specific antibodies to alginate and sonicated antigen in secretions and serum. Local production of IgA, IgG and IgM antibodies to P. aeruginosa was demonstrated. Only a minor proportion of specific IgA antibodies were present as secretory IgA in tears, saliva and sputum. The ratio of alginate‐specific SIgA to specific monomeric IgA in sputum was significantly lower than the similar ratio in saliva, whereas the same ratio for specific P. aeruginosa sonicate antigens was found in saliva and sputum.

Increased IgG2 and IgG3 Concentration Is Associated with Advanced Pseudomonas Aeruginosa Infection and Poor Pulmonary Function in Cystic Fibrosis

ABSTRACT. The concentrations of IgG subclass immunoglobulins were determined by radial immunodiffusion in serum from 126 patients with cystic fibrosis (CF). The results were compared to values from age‐matched healthy children and adults and correlated to patients age, duration of chronic Pseudomonas aeruginosa infection and lung function parameters. Fifty‐two percent of the patients had an elevated concentration of at least one of the IgG subclasses; IgG1 28%, IgG2 16%, IgG3 18% and IgG4 48%. There was significant correlation between elevated serum levels of IgG2, and to a lesser extent IgG3, with decreased lung function (for FEV1; p=0.0001, and p=0.001 respectively) and high levels of antipseudomonas precipitins (p=0.008, and p=0.002). A similar correlation was not found for IgG1 and IgG4. IgG subclasses vary in their ability to promote phagocytosis and to activate complement and it is possible that individual differences in the IgG subclass pattern could explain the variable course of this disease.

Rb/1bSr isochrons for the granitic plutons around Farsund, southern Norway

Abstract The granitic and charnockitic intrusions in the Precambrian migmatites around Farsund in southern Norway have previously been shown to be successively intruded as well as being geochemically different. Rb- and Sr-isotope data support the conclusion that they are intruded with a separate time interval and that the Farsund charnockite is younger (852±41 m.y.) than the Lyngdal hornblende granite (932±38 m.y.). Furthermore, the different initial ratios (0.7128 and 0.7054, respectively) disprove a comagmatic origin unless large-scale contamination has occurred.

Experimental immunization with Pseudomonas aeruginosa alginate induces IgA and IgG antibody responses.

We tried experimentally to induce a specific antibody response against Pseudomonas aeruginosa locally in the airways and systemically in rats by three different routes of immunization; intragastric feeding, intratracheal inoculation or subcutaneous vaccination. Three groups of rats were immunized with live mucoid P. aeruginosa PAO 579 by intragastric feeding or with killed PAO 579 intratracheally or subcutaneously. Three other groups were immunized with purified P. aeruginosa alginate either by intragastric feeding, intratracheally or subcutaneously. At weekly intervals for four weeks animals were sacrificed and serum and bronchial fluid were obtained. The specific IgA and IgG antibody response in lavage fluid and serum was measured. Only traces of antibodies could be detected in the bronchial lavage fluids. Anti‐alginate IgA and IgG antibodies developed in all rats immunized with alginate but no antibodies against other P. aeruginosa antigens were detected. The highest IgA and IgG titer against alginate was induced by the subcutaneous immunization. IgA and IgG antibodies against other P. aeruginosa antigens developed in rats immunized with live and sonicated bacteria. The highest IgA and IgG titers were obtained after intratracheal and subcutaneous immunization with sonicated bacteria. The present work has shown that IgA and IgG antibodies develop with high specificity after immunization. The different titers obtained do not necessarily reflect different degrees of protection.