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.

No abstract

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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Prior work has indicated that the polycistronic lacZYA mRNA of Escherichia coli is cleaved during decay at approximately intergenic sites (L. W. Lim and D. Kennell, J. Mol. Biol. 135: 369-390, 1979). In this work, we characterized the products by using probes specific for the different cistrons. This analysis indicated that six lac mRNA species are present in the following order of decreasing abundance: lacZ, -A, -ZYA, -ZY, -YA, and -Y. Very little lacYA and lacY mRNAs were present, whereas in cells induced to steady state, there was 10 times more lacZ than lacZYA mRNA. The lacZ mRNA appeared as a discrete species extending to a site in the lacZ-Y intergenic space (ca. residue 3150). This site is just distal to a potential rho-independent termination sequence. We examined the function of this sequence to determine whether it contributes to the distribution of the mRNAs. Although the termination sequence was shown to function in vitro, when it was recloned into an expression vector, no termination was seen in vivo. Moreover, direct examination of the kinetics of lac messenger synthesis revealed that after initiation, most transcription continued to the end of the operon. We conclude that during normal growth, the operon is transcribed in its entirety and that the individual lac mRNAs are formed by cleavage. These results confirm earlier work implying that the lac operon is transcribed in its entirety but are in conflict with several recent reports suggesting that internal termination occurs. Our findings indicate that the natural polarity of the operon (lacZ is expressed sixfold more strongly than lacA) is based on posttranslational effects and not on polarity of transcription.There have been extensive studies of the transcription and decay of the lac operon mRNA (reviewed in reference 18). According to current understanding, the lacZYA mRNA is transcribed polycistronically and then is cleaved at approximately intergenic sites. These cleavages, near the 5' ends of the lacY and lacA transcripts and at an additional site near the 5' end of the lacZ transcript, inactivate the distal mRNAs. The further chemical decay of these mRNAs then occurs as a net 5'-to-3' process. In this process, endonucleolytic cleavages occur on the mRNA that is exposed as ribosomes run off inactivated messages. The resulting fragments are then removed by the 3'-to-5' exonucleases, RNase II, polynucleotide phosphorylase and possibly other enzymes (1,14,18). The endonucleolytic cleavage sites on the lacZ and lacY species have been characterized but the enzyme(s) responsible for the endonucleolytic cleavages has not been identified (7,34). It appears, however, that RNase III is not involved in lac mRNA decay, although it does inactivate a few other mRNA species (2, 18, 27a). A newly described endonuclease has some properties inferred for the enzyme that cleaves the lac transcripts (6).The cleavage of the lacZYA mRNA was first deduced from the observation that the lacA mRNA decays about twice as fast as lacZ mRNA (19). Subsequently, the cleavag...

Human immunodeficiency virus (HIV), formerly termed human T-lymphotropic virus (HTLVIII/LAV), is the etiological agent of acquired immune deficiency syndrome (AIDS). Direct detection of HIV-1 nucleic acid sequences in patient tissue or blood samples is possible in only a minor fraction of cases due to the low percentage of infected cells (Shaw et al., 1984). We report a modification of the polymerase chain reaction method (PCR) (Saiki et al., 1985), in which we amplify sequences from HIV-1 RNA templates, for the identification of HIV-1 in peripheral blood and tissue samples obtained from AIDS and AIDS-related complex (ARC) patients. This method of HIV-1 detection is at least six orders of magnitude more sensitive than standard nucleic acid detection methods and has direct clinical applications. In vitro tissue culturing of the virus is not required for HIV-1 detection. Using this technique, the sequence in the orfB region of HIV-1 has been amplified and detected from less than 1 microgram of total RNA prepared from a few milliliters of peripheral blood samples. This technique enables the rapid and unambiguous clinical detection of potential HIV-infected individuals and can be used to assay the efficacy of anti-HIV-1 drugs. To enhance the efficiency of this technique, we have appended the prokaryotic T7 RNA polymerase promoter sequence to one of the priming oligonucleotides. After several cycles of PCR with the promoter-containing oligo, a small aliquot of the reaction can be utilized to direct specific and efficient T7 RNA polymerase-mediated transcription of the amplified sequences, thus enhancing the sensitivity and simplifying the labor of the experiment.

Background: Primary cutaneous aspergillosis is an uncommon finding in patients with acquired immunodeficiency syndrome (AIDS); only 13 cases have been reported in the literature. Observations: We describe 11 patients with primary cutaneous aspergillosis and AIDS. There does not seem to be an age, sex, race, or human immunodeficiency virus risk factor predisposition. This is a late manifestation of AIDS; patients typically have low CD4 counts (Ͻ0.050 ϫ 10 9 /L [Ͻ50/µL]) and other AIDS-defining illnesses. The most frequent presentation is in patients with cytomegalovirus disease and neutropenia caused by ganciclovir therapy. Lesions developed at the site of occlusive dressings for an indwelling intravenous catheter site

The long-pulsed Nd:YAG laser is effective in attenuating the progression of dissecting cellulitis without appreciable adverse cutaneous side effects. This is a pilot study, and more patients must be treated in other trials to verify these findings.