No abstract

Microorganisms develop biofilms on indwelling medical devices and are associated with device-related infections, resulting in substantial morbidity and mortality. This study investigated the effect of pretreating hydrogel-coated catheters with Pseudomonas aeruginosa bacteriophages on biofilm formation by P. aeruginosa in an in vitro model. Hydrogel-coated catheters were exposed to a 10 log 10 PFU ml ؊1 lysate of P. aeruginosa phage M4 for 2 h at 37°C prior to bacterial inoculation. The mean viable biofilm count on untreated catheters was 6.87 log 10 CFU cm ؊2 after 24 h. The pretreatment of catheters with phage reduced this value to 4.03 log 10 CFU cm ؊2 (P < 0.001). Phage treatment immediately following bacterial inoculation also reduced biofilm viable counts (4.37 log 10 CFU cm ؊2 reduction; P < 0.001). The regrowth of biofilms on phage-treated catheters occurred between 24 and 48 h, but supplemental treatment with phage at 24 h significantly reduced biofilm regrowth (P < 0.001). Biofilm isolates resistant to phage M4 were recovered from catheters pretreated with phage. The phage susceptibility profiles of these isolates were used to guide the development of a five-phage cocktail from a larger library of P. aeruginosa phages. The pretreatment of catheters with this cocktail reduced the 48-h mean biofilm cell density by 99.9% (from 7.13 to 4.13 log 10 CFU cm ؊2 ; P < 0.001), but fewer biofilm isolates were resistant to these phages. These results suggest the potential of applying phages, especially phage cocktails, to the surfaces of indwelling medical devices for mitigating biofilm formation by clinically relevant bacteria.Indwelling medical devices of various kinds may become colonized with microorganisms, resulting in the formation of microbial biofilms (16). Biofilm-associated organisms are tolerant to antimicrobial agents, can evade the host immune system, and can act as a nidus for infection (16). As a result, device-related infections, such as catheter-associated bloodstream infections, cause substantial morbidity and mortality among specific patient populations (9). Attributable mortality rates for healthcare-associated bloodstream infections have been estimated to be 25% (44).A number of novel strategies have been proposed to more effectively prevent and control device-associated biofilms, either by minimizing microbial attachment to device surfaces or by targeting the biofilm after it has developed. One such strategy is to use bacteriophages (phages) (17). Phages have been used for the treatment of infectious diseases in plants (26), animals (6), and humans (33,39,43). The use of phages to control biofilms has potential for several reasons. Phages can replicate at the site of an infection, thereby increasing in numbers where they are most required. During the lytic replication cycle, the infection of a bacterial host cell by a single phage virion will result in the production of dozens or hundreds of progeny phage, depending on the particular phage and host strains. Some phages also have been shown to...

Background-Nitric oxide (NO) deficiency contributes to diabetic wound healing impairment. The present study tested the hypothesis that increased cutaneous superoxide (O 2 Ϫ ) levels in type 1 diabetic mice cause NO deficiency and delayed wound healing. Methods and Results-Wound healing was markedly delayed in streptozotocin-induced type 1 diabetic mice compared with the normal controls. There were significantly reduced levels of endothelial NO synthase (eNOS) protein and constitutive NOS activity in diabetic wounds, whereas O 2 Ϫ levels were markedly increased. A single regimen of cutaneous gene therapy of eNOS or manganese superoxide dismutase (MnSOD) restored such healing delay, with a concomitant suppression of wound O 2 Ϫ levels and augmentation of both eNOS protein and constitutive NOS activity. Gene therapy of MnSOD also increased cutaneous MnSOD activity. Cutaneous O 2 Ϫ levels were also increased in Ins2Akita diabetic mice. In vitro glucose treatment of cutaneous tissues from normal mice for 24 hours increased O 2