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Mucociliary clearance in cystic fibrosis knockout mice infected with Pseudomonas aeruginosa.

In this study, we examined whether mucociliary clearance differed between cystic fibrosis (CF) knockout mice and wildtype controls. Additionally, we investigated whether infection with Pseudomonas aeruginosa, a common pathogen in the CF lung, affected this important host defence mechanism. Ciliary beat frequency (fcb) and particle transport (PT) were recorded using an in vitro lung explant preparation. Measurements were made from uninfected cystic fibrosis transmembrane conductance regulator (CFTR) knockout (-/-) mice and littermate controls (+/+) and compared to measurements from infected animals. While there were no differences detectable in fcb between CFTR -/- mice and their +/+ controls either in the presence or absence of P. aeruginosa, PT rates were different between these groups; interestingly, PT rates appeared dependent on both CFTR and infection status, with uninfected CFTR +/+ animals demonstrating higher rates of PT than their -/- littermates, while CFTR +/+ P. aeruginosa-infected mice demonstrated lower PT than knockout mice. These data demonstrate differences in mucociliary clearance between cystic fibrosis transmembrane conductance regulator knockout mice and controls, and further that Pseudomonas aeruginosa infection affects mucociliary clearance in the peripheral airways of mice. Additionally, the observed differences in particle transport suggest that cystic fibrosis transmembrane conductance regulator knockout mice demonstrate different mucociliary responses to infection.

Analysis of Variance↗

[Nosocomial Pseudomonas pickettii infection. Danger of the use of ion-exchange resins].

In a recent nosocomial outbreak of Pseudomonas pickettii infection at the general hospital of Corbeil-Essonnes, France, two patients were moderately affected, but two others, who were diabetic, died of septicemia. The infection was transmitted by 0.05% aqueous solutions of chlorhexidine, the treatment of water for these solutions being the cause of contamination. The ion-exchange resin in the deionization cartridges allowed the surviving bacteria in the city water supply to grow while the bacteriological filters downstream only lowered the contamination level. The 0.05% chlorhexidine aqueous solutions failed to prevent growth up to 4 X 10(6) bacteria/ml. P. pickettii is resistant to aminoglycosides and colistine.

Adolescent↗

Simple model for the study of Pseudomonas aeruginosa infections in leukopenic mice.

A simple, reproducible model of fatal Pseudomonas aeruginosa sepsis in mice during immunosuppression was developed. Mice were rendered leukopenic (less than or equal to 800 leukocytes per mm3 of blood) for a period of 5 days by multiple injections of cyclophosphamide. Mice were challenged at the onset of leukopenia by instilling the bacteria onto a 0.5-mm incision made into the back. The mean lethal dose (LD50) for P. aeruginosa PA220 and M-2 was less than 20 bacteria. The mean time to death for these strains ranged from 46 to 59 h. Leukopenic mice were comparatively resistant when challenged with Klebsiella pneumoniae (LD50 = 1.5 x 10(6)) or Staphylococcus aureus (LD50 greater than 10(6)). Infection with P. aeruginosa was characterized by rapid bacterial multiplication in the skin at the site of infection, producing ecthyma gangrenosum. Bacteremia and colonization of the liver were pronounced 21 h postinfection. This model should prove to be a useful tool for studying the pathogenesis of P. aeruginosa infections under immunosuppressed conditions.

Animals↗

[Therapy against intractable respiratory infections with Pseudomonas aeruginosa].

Patients with diffuse panbronchiolitis (DPB) are frequently affected by Pseudomonas aeruginosa superinfection. To elucidate the predisposing factors of Pseudomonas aeruginosa superinfection in patients with DPB, we analyzed the age of onset, duration of the disease, chest X-ray findings, blood gas levels, lung function, and bacteriological findings. These data were compared with those of patients who had not developed Pseudomonas aeruginosa superinfection. The administration of antibiotics and corticosteroids did not influence the incidence of Pseudomonas aeruginosa superinfection in DPB patients. The patients with long duration, more severe lung function and more deteriorated roentgenological findings developed Pseudomonas aeruginosa superinfection more easily. These infections in the lower respiratory tract significantly affect the prognosis of DPB patients. Using long-term administrations of a new quinolone antibacterial agent against DPB, acute exacerbations were controlled in some patients and the frequency of their admission to hospital was lessened. A multicomponent vaccine raised antibody titers against OEP, elastase, protease and exotoxin in DPB patients. Further clinical investigations are under way in our hospital to confirm the clinical usefulness of the Pseudomonas aeruginosa multicomponent vaccine in DPB from prophylactic and therapeutic points of view.

4-Quinolones↗

[Is the quantitative antibiogram a reliable epidemiological marker for Pseudomonas aeruginosa infections? Comparison with pulsed field electrophoresis].

Epidemiologic supervision of P. aeruginosa infections is a daily care for microbiologists. The aim of this study is to evaluate quantitative antibiogram, which compare strains by calculation of euclidian distances from inhibition zone diameters on agar, compared with pulse field gel electrophoresis (PFGE) results. 53 isolates of P. aeruginosa obtained from bronchial secretions of 26 patients in intensive care unit are typed by conventional disk diffusion test on agar with 11 usual antibiotics. Dendrogram of euclidian distances is performed by Taxotron computer program (P.A.D. Grimont, Institute Pasteur, Paris); results are compared with 53 PFGE patterns after restriction with Spe I (Genepath system, BIO-RAD). Quantitative antibiogram has a high discriminatory power for beta-lactamin resistant strains: 27 isolates from 11 patients clustered in 5 types where PFGE discerned 5 patterns. The discriminatory power is low for beta-lactamin sensible strains: 26 isolates from 15 patients clustered in 8 types where PFGE discerned 19 patterns, but serotyping method combined with quantitative antibiogram restore a high disriminatory power for beta-lactamin sensible strains.

Bronchoalveolar Lavage Fluid↗

Use of pharmacokinetics and pharmacodynamics to optimize antimicrobial treatment of Pseudomonas aeruginosa infections.

The study of pharmacodynamics has greatly enhanced our understanding of antimicrobials and has enabled us to optimize dosing regimens. Applying this knowledge to the clinical setting can be critical for the treatment of Pseudomonas aeruginosa infections. Because of its selectively permeable outer membrane and multiple efflux pump mechanisms, P. aeruginosa has high intrinsic resistance to many available antimicrobials. Numerous studies have established pharmacodynamic values for concentration-dependent agents (maximum serum concentration : minimum inhibitory concentration [MIC] and area under the serum concentration-time curve : MIC) and concentration-independent agents (i.e., percentage of time that the drug concentration remains greater than the MIC) that help predict the probability of a successful outcome. Current therapies attempt to meet these target values. However, to reduce the risk of clinical failures, combination therapy (typically, a beta -lactam with an aminoglycoside or fluoroquinolone) is commonly used to enhance eradication rates and decrease the risk of developing resistance. Although combination therapy ensures a greater chance of selection of appropriate treatment, timely initial administration of antimicrobial therapy remains a key factor for reducing the likelihood of death for these patients.

Anti-Bacterial Agents↗

Urokinase receptor-deficient mice have impaired neutrophil recruitment in response to pulmonary Pseudomonas aeruginosa infection.

Leukocytes express both urokinase-type plasminogen activator (uPA) and the urokinase receptor (uPAR, CD87). Evidence in vitro has implicated uPAR as a modulator of beta2 integrin function, particularly CR3 (CD11b/CD18, Mac-1). Pseudomonas aeruginosa infection has been demonstrated to recruit neutrophils to the pulmonary parenchyma by a beta2 integrin-dependent mechanism. We demonstrate that mice deficient in uPAR (uPAR-/-) have profoundly diminished neutrophil recruitment in response to P. aeruginosa pneumonia compared with wild-type (WT) mice. The requirement for uPAR in neutrophil recruitment is independent of the serine protease uPA, as neutrophil recruitment in uPA-/- mice is indistinguishable from recruitment in WT mice. uPAR-/- mice have impaired clearance of P. aeruginosa compared with WT mice, as demonstrated by CFU and comparative histology. WT mice have diminished neutrophil recruitment to the lung when an anti-CD11b mAb is given before inoculation with the pathogen, while recruitment of uPAR-/- neutrophils is unaffected. We conclude that uPAR is required for the recruitment of neutrophils to the lung in response to P. aeruginosa pneumonia and that this requirement is independent of uPA. Further, we show that uPAR and CR3 act by a common mechanism during neutrophil recruitment to the lung in response to P. aeruginosa. This is the first report of a requirement for uPAR during cellular recruitment in vivo against a clinically relevant pathogen.

Animals↗