Experimental indication of a naphthalene-base molecular aggregate for the carrier of the 2175 angstroms interstellar extinction feature.

Experiments where the simple polycyclic aromatic hydrocarbon (PAH) naphthalene (C10H8) is subjected to the energetic environment of a plasma have resulted in the synthesis of a molecular aggregate that has ultraviolet spectral characteristics that suggest it provides insight into the nature of the carrier of the 2175 angstroms interstellar extinction feature and may be a laboratory analog. Ultraviolet, visible, infrared, and mass spectroscopy, along with gas chromatography, indicate that it is a molecular aggregate in which an aromatic double ring ("naphthalene") structural base serves as the electron "box" chromophore that gives rise to the envelope of the 2175 angstroms feature. This chromophore can also provide the peak of the feature or function as a mantle in concert with another peak provider such as graphite. The molecular base/chromophore manifests itself both as a structural component of an alkyl-aromatic polymer and as a substructure of hydrogenated PAH species. Its spectral and molecular characteristics are consistent with what is generally expected for a complex molecular aggregate that has a role as an interstellar constituent.

Management and microbiology of cutaneous abscesses.

Cutaneous abscesses in the perineal region contain primarily anaerobes commonly found in stool. Non-perineal abscesses contain mixed microflora indigenous to the skin. Bacteroides fragilis, the only anaerobe resistant to penicillin, is found predominantly in the perineal area. Staphylococcus aureus, although the most common aerobe found, is seen less frequently than expected and is almost always resistant to penicillin. Escherichia coli and Neisseria gonorrhoeae are rarely found. Incision and drainage is the primary mode of treatment. Fever is rare, though tachycardia is common in patients with normal host defenses. Patients with altered host defenses may require initial culture and Gram-stained smear to determine appropriate antibiotic therapy. The Gram-stained smear reliably indicates sterile and mixed abscesses, as well as those containing pure S aureus. Incision and drainage alone is the only therapy required in the usual patient. Since in these patients antibiotics are not required, initial culture and Gram-stained smear are unnecessary.

Cutaneous abscesses. Anaerobic and aerobic bacteriology and outpatient management.

Specimens from 135 cutaneous abscesses in outpatients were cultured anaerobically and aerobically. Of these, 4% were sterile and 29% yielded pure cultures, predominantly of Staphylococcus aureus. Aerobic species were isolated from all anatomic areas. Anaerobes were found with a frequency comparable to aerobes in all nonperineal areas except the hand. In contrast, abscesses in the perineal region contained a greater variety and frequency of anaerobes. Only two patients were febrile. All abscesses were treated with incision and drainage, and all healed without complication, including those 74% that were treated without adjunctive antibiotics. Primary management of cutaneous abscesses should be incision and drainage. In general, routine culture and antibiotic therapy are not indicated for localized abscesses in patients with presumably normal host defenses.