Dual role of iodine, silver, chlorhexidine and octenidine as antimicrobial and antiprotease agents.

OBJECTIVES: The majority of human chronic wounds contain bacterial biofilms, which produce proteases and retard the resolution of inflammation. This in turn leads to elevated patient protease activity. Chronic wounds progressing towards closure show a reduction in proteolytic degradation. Therefore, the modulation of protease activity may lead to the faster healing of chronic wounds. Antimicrobials are used to control biofilm-based infection; however, some of them also exhibit the inhibition of matrix metalloproteinases and bacterial proteases. We investigated the antimicrobial agents used in wound healing for their potential to inhibit bacterial and host proteases relevant to chronic wounds. METHODS: Using in vitro zymography, we tested the ability of povidone-iodine, silver lactate, chlorhexidine digluconate, and octenidine hydrochloride to inhibit selected human proteases and proteases from Pseudomonas aeruginosa, Staphylococcus aureus, Serratia marcescens, and Serratia liquefaciens. We investigated penetration and skin protease inhibition by means of in situ zymography. RESULTS: All the tested antimicrobials inhibited both eukaryotic and prokaryotic proteases in a dose-dependent manner in vitro. The tested compounds were also able to penetrate into skin ex vivo and inhibit the resident proteases. Silver lactate and chlorhexidine digluconate showed an inhibitory effect ex vivo even in partial contact with skin in Franz diffusion cells. CONCLUSIONS: Our in vitro and ex vivo results suggest that wound healing devices which contain iodine, silver, chlorhexidine, and octenidine may add value to the antibacterial effect and also aid in chronic wound healing. Antiprotease effects should be considered in the design of future antimicrobial wound healing devices.

Pyrimidine synthesis inhibition enhances cutaneous defenses against antibiotic resistant bacteria through activation of NOD2 signaling.

Multidrug-resistant bacterial strains are a rapidly emerging healthcare threat; therefore it is critical to develop new therapies to combat these organisms. Prior antibacterial strategies directly target pathogen growth or viability. Host-directed strategies to increase antimicrobial defenses may be an effective alternative to antibiotics and reduce development of resistant strains. In this study, we demonstrated the efficacy of a pyrimidine synthesis inhibitor, N-phosphonacetyl-L-aspartate (PALA), to enhance clearance of methicillin-resistant Staphylococcus aureus (MRSA), Pseudomonas aeruginosa, and Acinetobacter baumannii strains by primary human dermal fibroblasts in vitro. PALA did not have a direct bactericidal effect, but enhanced cellular secretion of the antimicrobial peptides human ß-defensin 2 (HBD2) and HBD3 from fibroblasts. When tested in porcine and human skin explant models, a topical PALA formulation was efficacious to enhance MRSA, P. aeruginosa, and A. baumannii clearance. Topical PALA treatment of human skin explants also resulted in increased HBD2 and cathelicidin (LL-37) production. The antimicrobial actions of PALA required expression of nucleotide-binding, oligomerization domain 2 (NOD2), receptor-interacting serine/threonine-protein kinase 2 (RIP2), and carbamoyl phosphatase synthase II/aspartate transcarbamylase/dihydroorotase (CAD). Our results indicate that PALA may be a new option to combat multidrug-resistant bacterial infections of the skin through enhancement of an integral pathway of the cutaneous innate immune defense system.

Serum adenosine deaminase activity in cutaneous anthrax.

BACKGROUND: Adenosine deaminase (ADA) activity has been discovered in several inflammatory conditions; however, there are no data associated with cutaneous anthrax. The aim of this study was to investigate serum ADA activity in patients with cutaneous anthrax. MATERIAL AND METHODS: Sixteen patients with cutaneous anthrax and 17 healthy controls were enrolled. We measured ADA activity; peripheral blood leukocyte, lymphocyte, neutrophil, and monocyte counts; erythrocyte sedimentation rate; and C reactive protein levels. RESULTS: Serum ADA activity was significantly higher in patients with cutaneous anthrax than in the controls (p<0.001). A positive correlation was observed between ADA activity and lymphocyte counts (r=0.589, p=0.021) in the patient group. CONCLUSIONS: This study suggests that serum ADA could be used as a biochemical marker in cutaneous anthrax.

Erysipelothrix rhusiopathiae neuraminidase and its role in pathogenicity.

The role of the enzyme neuraminidase in pathogenicity of the bacillus Erysipelothrix rhusiopathiae was studied. Different substances with low and high molecular weight were tested as inducers of E. rhusiopathiae neuraminidase biosynthesis. It was found that macromolecular complexes induce the secretion of the enzyme. K(M) values for different substrates showed that the affinity of the E. rhusiopathiae neuraminidase increases in parallel with the enlargement of the molecular weight of glycoproteins. Results from the rabbits skin test confirmed the role of E. rhusiopathiae neuraminidase as a factor of pathogenicity with spreading functions.

Role of hyaluronidase in subcutaneous spread and growth of group A streptococcus.

Group A streptococcus (GAS) depends on a hyaluronic acid (HA) capsule to evade phagocytosis and to interact with epithelial cells. Paradoxically, GAS also produces hyaluronidase (Hyl), an enzyme that cleaves HA. A common assumption is that Hyl digests structurally identical HA in human tissue to promote bacterial spread. We inactivated the gene encoding extracellular hyaluronidase, hylA, in a clinical Hyl(+) isolate. Hyl(+) and an isogenic Hyl(-) mutant were injected subcutaneously into mice with or without high-molecular-weight dextran blue. The Hyl(-) strain produced small lesions with dye concentrated in close proximity. The Hyl(+) strain produced identical lesions, but the dye diffused subcutaneously. However, Hyl(+) bacteria were not isolated from unaffected skin stained by dye diffusion. Thus, Hyl digests tissue HA and facilitates spread of large molecules but is not sufficient to cause subcutaneous diffusion of bacteria or to affect lesion size. GAS capsule expression was assayed periodically during broth culture and was reduced in Hyl(+) strains relative to Hyl(-) strains at the onset and the end of active capsule synthesis but not during peak synthesis in mid-exponential phase. Thus, Hyl is not sufficiently active to remove capsule during peak synthesis. To demonstrate a possible nutritional role for Hyl, GAS was shown to grow with N-acetylglucosamine but not d-glucuronic acid (both components of HA) as a sole carbon source. However, only Hyl(+) strains could grow utilizing HA as a sole carbon source, suggesting that Hyl may permit the organism to utilize host HA or its own capsule as an energy source.

Nitrotyrosine localization to dermal nerves in borderline leprosy.

BACKGROUND: Nerve damage is a common and disabling feature of leprosy, with unclear aetiology. It has been reported that the peroxidizing agents of myelin lipids-nitric oxide (NO) and peroxynitrite-are produced in leprosy skin lesions. OBJECTIVES: To investigate the localization of nitrotyrosine (NT)-a local end-product of peroxynitrite-in leprosy lesions where dermal nerves are affected by a granulomatous reaction. METHODS: We investigated by immunohistochemistry and immunoelectron microscopy the localization of the inducible NO synthase (iNOS) and NT in biopsies exhibiting dermal nerves from patients with untreated leprosy. RESULTS: There were abundant NT-positive and iNOS-positive macrophages in the borderline leprosy granulomas infiltrating peripheral nerves identified by light microscopy, S-100 and neurofilament immunostaining. Immunoelectron microscopy showed NT reactivity in neurofilament aggregates and in the cell wall of Mycobacterium leprae. CONCLUSIONS: Our results suggest that NO and peroxynitrite could be involved in the nerve damage following borderline leprosy.