The skin is a milieu for controlled bacterial growth. Skin supports the growth of commensal bacteria, which protect the host from pathogenic bacteria. Environmental and local factors, host immunity, and organism adherence and virulence are intricately related to cutaneous infection. Resident gram-positive bacteria include Staphylococcus, Micrococcus, and Corynebacterium sp. Staphylococcus aureus and Streptococcus pyogenes are notoriously pathogenic in the skin. In order for bacteria to be pathogenic, they must be able to adhere to, grow on, and invade the host. Bacteria possess numerous virulence genes that allow for growth in these privileged niches. Epidermal infections caused by S. aureus and S. pyogenes include impetigo and ecthyma. Dermal infections consist of erysipelas, cellulitis, and necrotizing fasciitis. The pilosebaceous unit is involved in folliculitis, furunculosis, and carbunculosis. Moreover, S. aureus and S. pyogenes produce toxins that may elicit a superantigen response, causing massive release of cytokines. Staphylococcal scalded skin syndrome, toxic shock syndrome, and scarlet fever are all superantigen-mediated. Gram-negative organisms such as Pseudomonas aeruginosa, Pasteurella multocida, Capnocytophaga canimorsus, Bartonella sp., Klebsiella rhinoscleromatis, and Vibrio vulnificus are not typical resident skin microflora but may cause cutaneous infection.
The scission of RNA by the chemical nuclease activity of 1,10phenanthroline-copper (OP-Cu) has been studied using a lac mRNA fragment and tRNAphe as substrates. Since the chemical mechanism of scission involves oxidative attack on the ribose, scission is observed at all nucleotides including dihydrouridine and Y-bases. Specificity for single-stranded loop regions is apparent from the similarity of the reactivity of OP-Cu to the single-strand specific reagents dimethyl sulfate and diethyl pyrocarbonate using the fragment of lac mRNA as a substrate. Similar preference is observed in the reaction with tRNA although scission in the helical acceptor stem is also observed.
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