The opportunistic pathogen Pseudomonas aeruginosa is responsible for systemic infections in immunocompromised individuals and chronic respiratory disease in patients with cystic fibrosis. Cyclic nucleotides are known to play a variety of roles in the regulation of virulence-related factors in pathogenic bacteria. A set of P. aeruginosa genes, encoding proteins that contain putative domains characteristic of diguanylate cyclases (DGCs) and phosphodiesterases (PDEs) that are responsible for the maintenance of cellular levels of the second messenger bis-(3′-5′)-cyclic dimeric GMP (c-di-GMP) was identified in the annotated genomes of P. aeruginosa strains PAO1 and PA14. Although the majority of these genes are components of the P. aeruginosa core genome, several are located on presumptive horizontally acquired genomic islands. A comprehensive analysis of P. aeruginosa genes encoding the enzymes of c-di-GMP metabolism (DGC- and PDE-encoding genes) was carried out to analyze the function of c-di-GMP in two disease-related phenomena, cytotoxicity and biofilm formation. Analysis of the phenotypes of DGC and PDE mutants and overexpressing clones revealed that certain virulence-associated traits are controlled by multiple DGCs and PDEs through alterations in c-di-GMP levels. A set of mutants in selected DGC- and PDE-encoding genes exhibited attenuated virulence in a mouse infection model. Given that insertions in different DGC and PDE genes result in distinct phenotypes, it seems likely that the formation or degradation of c-di-GMP by these enzymes is in highly localized and intimately linked to particular targets of c-di-GMP action.

Because of their extensive wounds, burn patients are chronically exposed to inflammatory mediators. Thus, burn patients, by definition, already have "systemic inflammatory response syndrome." Current definitions for sepsis and infection have many criteria (fever, tachycardia, tachypnea, leukocytosis) that are routinely found in patients with extensive burns, making these current definitions less applicable to the burn population. Experts in burn care and research, all members of the American Burn Association, were asked to review the literature and prepare a potential definition on one topic related to sepsis or infection in burn patients. On January 20, 2007, the participants met in Tucson, Arizona to develop consensus for these definitions. After review of the definitions, a summary of the proceedings was prepared. The goal of the consensus conference was to develop and publish standardized definitions for sepsis and infection-related diagnoses in the burn population. Standardized definitions will improve the capability of performing more meaningful multicenter trials among burn centers.

The transfer of gram-positive bacteria, particularly multiresistantStaphylococcus aureus (MRSA) and vancomycin-resistant enterococci (VRE), among patients is a growing concern. One critical aspect of bacterial transfer is the ability of the microorganism to survive on various common hospital surfaces. The purpose of this study was to determine the survival of 22 gram-positive bacteria (vancomycin-sensitive and -resistant enterococci and methicillin-sensitive and -resistant staphylococci) on five common hospital materials: smooth 100% cotton (clothing), 100% cotton terry (towels), 60% cotton–40% polyester blend (scrub suits and lab coats), 100% polyester (privacy drapes), and 100% polypropylene plastic (splash aprons). Swatches were inoculated with 104to 105 CFU of a microorganism, assayed daily by placing the swatches in nutritive media, and examining for growth after 48 h. All isolates survived for at least 1 day, and some survived for more than 90 days on the various materials. Smaller inocula (102) survived for shorter times but still generally for days. Antibiotic sensitivity had no consistent effect on survival. The long survival of these bacteria, including MRSA and VRE, on commonly used hospital fabrics, such as scrub suits, lab coats, and hospital privacy drapes, underscores the need for meticulous contact control procedures and careful disinfection to limit the spread of these bacteria.

The role of pyoverdin, the main siderophore in iron-gathering capacity produced by Pseudomonas aeruginosa, in bacterial growth in vivo is controversial, although iron is important for virulence. To determine the ability of pyoverdin to compete for iron with the human iron-binding protein transferrin, wild-type P. aeruginosa ATCC 15692 (PAO1 strain) and PAO pyoverdin-deficient mutants were grown at 37؇C in bicarbonate-containing succinate medium to which apotransferrin had been added. Growth of the pyoverdin-deficient mutants was fully inhibited compared with that of the wild type but was restored when pyoverdin was added to the medium. Moreover, when growth took place at a temperature at which no pyoverdin production occurred (43؇C), the wild-type PAO1 strain behaved the same as the pyoverdin-deficient mutants, with growth inhibited by apotransferrin in the presence of bicarbonate and restored by pyoverdin supplementation. Growth inhibition was never observed in bicarbonate-free succinate medium, whatever the strain and the temperature for growth. In vivo, in contrast to results obtained with the wild-type strain, pyoverdin-deficient mutants demonstrated no virulence when injected at 10 2 CFU into burned mice. However, virulence was restored when purified pyoverdin originating from the wild-type strain was supplemented during the infection. These results strongly suggest that pyoverdin competes directly with transferrin for iron and that it is an essential element for in vivo iron gathering and virulence expression in P. aeruginosa. Rapid removal of iron from [ 59 Fe]ferritransferrin by pyoverdin in vitro supports this view.