We found that the in vitro HOCl-resistance profile (PsA > SA > BC > EC > KP) best fits the infection profile observed clinically in CF lungs; that is, the most HOCl-resistant bacteria such as PsA and SA are the most frequent pathogens in CF patients. This finding implies that differential HOCl resistance across microbial species may allow for persistence of some infections over others by subversion of the host innate immunity and supports our previous finding that CF neutrophils with a compromised HOCl production may not be able to clear the most

resistant organisms effectively [12, 13]. From a microbiological point of view, PsA and SA, the relatively more resistant strains to HOCl, would be more likely to survive and be selected for, if the host neutrophils were deficient in their ability to make HOCl. Burns and coworkers did a longitudinal #Selleck Copanlisib randurls[1|1|,|CHEM1|]# study on young children with CF and found that 97% of the children are colonized with PsA [18]. The early isolates tend to be nonmucoid and antibiotic-sensitive. However,

if the initial infection is not effectively eradicated by the host defense, which could happen, for example, if HOCl or other oxidant production was suboptimal, then the bacteria which escape the initial host defenses will grow and spread within the lung, establishing a long-term chronic colonization. Subsequently, environmental pressure in the lung such as antibiotic EPZ5676 clinical trial application selects for the mucoid PsA phenotype. Increased PsA density in the lower respiratory

tract and development of antibiotic-resistant mucoid biofilms causes chronic airway inflammation and deteriorating lung function [19–22]. SA has long been recognized to be among the first organisms to colonize the airways of CF patients [23]. Colonization with SA occurs within the first few months of life, and persistent variants of this organism may arise due to a selective pressure from long-term antibiotic treatment in CF patients [24]. However, SA infection does not usually persist or progress to chronic disease. We would like Autophagy activator to point out that our current study only tested bacteria in log-phase growth. Such an experimental design was intended to study the nonmucoid form which is assumed by the bacteria during the early CF infections. It is important to recognize that only after initial bacterial colonization is established, can chronic persistent infections ensue in CF lungs. Neutrophils are highly specialized for bacterial killing especially in the case of extracellular infections. The cells employ at least two microbicidal mechanisms to execute this function: one is oxidant-mediated and another is non-oxidant-mediated. Pseudomonas bacteria possess tough polysaccharide capsules, which are resistant to nonoxidant killing mechanisms, such as protease and hydrolase digestion [25].