Although pneumonias in early childh...

Although pneumonias in early childhood may be caused by the agency of Staphylococcus aureus, Streptococcus pneumoniae, or Hemophilus influenzae, it is the mucoid colonial form of Pseudomonas aeruginosa which is originate in the sputum of up to 90 percent of all older CF patients. For comparison, the mucoid colonial variant of P aeruginosa (pseudomonas) is erect with a 2 percent prevalence among other chronically ill obstructive airways disease patients who do not have CF The appearance of mucoid pseudomonas in the sputum refinement obtained from a relatively young patient suffering with chronic obstructive airways disease should vehemently suggest the diagnosis of CF Curiously, CF patients are not more susceptible to infections outside of the respiratory tract and bacteremia virtually not at all occurs. The defect permitting pseudomonas to persist is limited to the airways. Colonization in the respiratory tracts of CF patients by means of this unusual gelatinous-coated organism correlates with the progression of bronchial airway pathology, patient age, clinical score, compass of pulmonary disease, severity of roentgenographic changes and flushs of serum immunoglobulins.[1] Clinicians recognize that the appearance of pseudomonas prefigures a poor prognosis, for despite the use of able pseudomonicidal antibiotics, this pathogen is rarely eradicated from the respiratory tract. Pseudomonas aeruginosa is ofttimes the only pathogen recovered from the sputum or lung tissue obtained at thoracotomy or autopsy, and clearly, is the dominant organism to be casted with in this disease.

The aim of this, necessarily circumscribed, review is to relate latter developments of basic mechanisms to clinical airway disease in CF We will focus forward clinical investigations dealing with bacterial adherence, expression and activity of bacterial proteases, and pseudomonas avoidance of the host's immune answer There are recent reviews which more completely review the interaction between the nutritional immune regularity and the growth of pseudomonas[2,3] and more thoroughly discuss the expression of other toxic exoproducts[24]

Mucociliary Clearance and Adherence to the CF Upper Airways

Patients with CF instant an abnormal apical membrane to potential bacterial pathogens. The accrues of in vivo Cl- substitution studies and work with excised CF nasal polyp indicate that the CF airway epithelia are relatively impermeable to Cl- Studies with tracheal lonely dwellings maintained in primary culture forward permeable supports indicate that Cl- impermeability is an intrinsic characteristic of CF epithelial cells and the same studies bring to an end that a circulating factor is not the cause of the ion transport defect[5] In healthy normal individuals, the epithelium actively transports Cl- from the submucosal to the mucosal surface, thereby driving fluid secretions. by the agency of this means, transepithelial electrolyte transport hinders the quantity and composition of the respiratory tract fluid, and thereby, is important in effecting normal mucociliary clearance. It appears likely that CF epithelia provide insufficient water to surface liquids to avoid inspissation of periciliary fluids and airway mucus.

Indeed, a number of alterations in the mucociliary apparatus of CF patients has been described (Table 1) It appear to bes clear that many of the flaws which have been reported to date are secondarily acquired, and of these, many are caused at exoproducts of pseudomonas. The precise details of pseudomonas affinity for CF respiratory epithelial small rooms have not yet been described, moreover it is known that potential receptors include amino sugars in the mucus layer[6] and plasma membrane constituents expos when airway proteases abate surface fibronectin.[7] Studies complet in the last decade are convincing that lectin-like receptors in succession human and murine phagocytes recognized various Gram-positive and Gram-negative bacterial species. These receptors generally exhibit a greatest affinity for D-galactose moieties. [TABULAR DATA OMITTED]

Pili, flexible filaments extending from the polar portion of the pseudomonas exterior membrane, are known to aid as bacterial adhesins mediating epithelial enclosed space adherence for nonmucoid pseudomonas (Fig 1) nevertheless more relevant to CF patients are the studies demonstrating that the gelatinous exopolysaccharide produc by means of CF mucoid variants of pseudomonas appear to be the adhesin to tracheal solitary abode; squalids Although it appears that all P aeruginosa strains contain the gene for alginic acid synthesis, the phenotype is unstable and rapidly dissipated in culture. A number of experimental conditions have been shown to favor the mucoid phenotype seen in CF airways through the nonmucoid strains. Media containing skim milk or carbenicillin have been used to lengthen the mucoid state in vitro and others have insinuateed that the particular [Fe.sup.2+]/[Fe.sup.3+] ratio speculation to be present in the CF airway rears the expression of the mucoid phenotype. novel studies by Kreig et al[8] indicated that refinement conditions felt to represent the CF physiologic state (aeration, nitrogen, and phosphate limited) favored the shooting of mucoid strains; nonmucoid revertants showed an excessive decrease in viability when air was added to cultivation broth at a rate of 05 L/minute.