[Show abstract][Hide abstract] ABSTRACT: Pseudomonas aeruginosa is an opportunistic pathogen that can, like other bacterial species, exist in antimicrobial resistant sessile biofilms and as free-swimming, planktonic cells. Specific virulence factors are typically associated with each lifestyle and several two component response regulators have been shown to reciprocally regulate transition between biofilm-associated chronic, and free-swimming acute infections. Quorum sensing (QS) signal molecules belonging to the las and rhl systems are known to regulate virulence gene expression by P. aeruginosa. However the impact of a recently described family of novel quorum sensing signals produced by the Pseudomonas Quinolone Signal (PQS) biosynthetic pathway, on the transition between these modes of infection is less clear. Using clonal isolates from a patient developing ventilator-associated pneumonia, we demonstrated that clinical observations were mirrored by an in vitro temporal shift in isolate phenotype from a non-secreting, to a Type III cytotoxin secreting (TTSS) phenotype and further, that this phenotypic change was PQS-dependent. While intracellular type III cytotoxin levels were unaffected by PQS concentration, cytotoxin secretion was dependent on this signal molecule. Elevated PQS concentrations were associated with inhibition of cytotoxin secretion coincident with expression of virulence factors such as elastase and pyoverdin. In contrast, low concentrations or the inability to biosynthesize PQS resulted in a reversal of this phenotype. These data suggest that expression of specific P. aeruginosa virulence factors appears to be reciprocally regulated and that an additional level of PQS-dependent post-translational control, specifically governing type III cytotoxin secretion, exists in this species.
[Show abstract][Hide abstract] ABSTRACT: Chronic rhinosinusitis (CRS) is a common disease with a complex pathophysiology involving a microbial component. Culture-independent molecular analysis represents a promising new approach to clarify the microbiology of CRS, but standardized, optimized sampling methods still have not been defined. This study was designed to compare nucleic acid extraction rates and recovery of bacteria for two methods of sampling the maxillary sinus, mucosal biopsy, and brushing.
Samples were obtained from 20 patients undergoing maxillary sinus surgery. Total extracted nucleic acid concentration and bacterial burden were compared between sample types.
Total nucleic acid concentration varied across patients. No statistically significant difference in mean total DNA concentration from mucosal biopsy specimens or brushings was observed. However, compared with biopsy specimens, brush samples possessed a significant (p < 0.035) increase in bacterial copy number.
Endoscopically directed mucosal brushings of the maxillary sinus provide equivalent concentrations of total DNA to mucosal biopsy specimens but possess greater concentrations of bacterial DNA, likely because of the greater surface area sampled by this method. Given the additional advantage of lower risk associated with obtaining brush samples, we suggest they represent the preferred sampling method for future genomic sinus studies.
American Journal of Rhinology and Allergy 07/2010; 24(4):263-5. DOI:10.2500/ajra.2010.24.3472 · 1.81 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The human superorganism is a conglomerate of mammalian and microbial cells, with the latter estimated to outnumber the former by ten to one and the microbial genetic repertoire (microbiome) to be approximately 100-times greater than that of the human host. Given the ability of the immune response to rapidly counter infectious agents, it is striking that such a large density of microbes can exist in a state of synergy within the human host. This is particularly true of the distal gastrointestinal (GI) tract, which houses up to 1000 distinct bacterial species and an estimated excess of 1 x 10(14) microorganisms. An ever-increasing body of evidence implicates the GI microbiota in defining states of health and disease. Here, we review the literature in adult and pediatric GI microbiome studies, the emerging links between microbial community structure, function, infection and disease, and the approaches to manipulate this crucial ecosystem to improve host health.