S M Finegold

Many pathogenic microbes can induce a complex series of immunologic, endothelial-cell, and hemorheological activation cascades and dysfunctions and can cause interactions of various components of the vessel wall with formed and noncellular elements of the blood. These interactions can result in manifold vasculitides. This article reviews the pathogenetic, clinicopathologic, and therapeutic aspects of infection-related vasculitides; it includes a brief discussion of parasitic, drug-related, and immunization-associated vasculitides as well as of the infection-related features of vasculitides of the central nervous system, retinal vasculitides, ecthyma gangrenosum, and erythema nodosum. Viruses are mainly associated with small-vessel vasculitides, whereas bacterial infections affect vessels of all sizes, including the aorta. The vasculitides associated with fungal infection usually are characterized by erythema nodosum and involve large vessels. The search for microbes as causes of or contributors to vasculitides should continue. Infectious vasculitides may become increasingly important as the number of immunocompromised patients grows.

Several species of anaerobic bacteria display variable Gram stain reactions which often make identification difficult. A simple, rapid method utilizing a 3% solution of potassium hydroxide to distinguish between gram-positive and gram-negative bacterial was tested on 213 strains of anaerobic bacteria representing 19 genera. The Gram stain reaction and KOH test results were compared with the antibiotic disk susceptibilities (vancomycin and colistin) the preliminary grouping of anaerobic bacteria. All three procedures were in agreement for the majority of strains examined. Some strains of clostridia, eubacteria, and bifidobacteria stained gram negative or gram variable; the KOH and antibiotic disk susceptibility tests correctly classified these strains as gram-positive. The KOH test incorrectly grouped some strains of Bacteroides sp., Fusobacterium sp., Leptotrichia buccalis, and Veillonella parvula, but all Gram stain results for these strains were consistent for gram-negative bacteria. The KOH test is a useful supplement to the Gram stain and antibiotic disk susceptibility testing for the initial classification of anaerobic bacteria.

Legionnaires' disease was diagnosed in 32 patients with nosocomially acquired pneumonia by using direct immunofluorescence examination of respiratory tract secretions, indirect immunofluorescence determinations of antibody titer, and/or culture of Legionella pneumophila from respiratory tract secretions. Cultures of specimens for Legionella pneumophila were positive for 13 of 21 patients for whom appropriate specimens were submitted. Using a positive culture as a definition of Legionnaires' disease, the sensitivity of direct immunofluorescence examination was 62%; that of indirect immunofluorescence serologic studies, 75%. Using any positive test as a definition of Legionnaires' disease, the sensitivity of direct immunofluorescence examination of respiratory tract secretions was 50%, that of indirect immunofluorescence serologic studies (using all 4 serogroups), 80%; that of culture, 65%. A negative control group of 21 patients without Legionnaires' disease was used to estimate the specificity of the tests. The specificity of direct immunofluorescence examination was 94%; that of indirect immunofluorescence serologic studies, 75%. Culture of specimens was necessary to diagnose some cases of Legionnaires' disease because the other 2 tests were negative. All 3 tests should be performed for optimal sensitivity and specificity.

Rifampin, 7-chlorolincomycin, vancomycin, and metronidazole (Flagyl® were evaluated for bactericidal activity against Bacteroides fragilis. Tetracycline, a bacteriostatic agent, was included for comparative purposes. Standard tube-dilution determinations of MICs were done with brucella broth (Pfizer) plus 5% laked blood, followed by subculture onto blood-agar plates for determination of minimal bactericidal concentration (MBC). Metronidazole and 7-chlorolincomycin inhibited all 19 strains tested at concentrations readily achieved in serum; however, only metronidazole was consistently bactericidal (MBC, 0.78–6.25 µg/ml). All strains were resistant to vancomycin and eight were resistant to tetracycline. Rifampin, although generally very active, demonstrated the “skip-tube phenomenon,” suggesting that resistance to this agent may be a problem with anaerobes as with other organisms. In conclusion, metronidazole and 7-hlorolincomycin were effective in vitro against 19 strains of B. fragilis. Only metronidazole was consistently bactericidal. This agent, therefore, might be of benefit in the therapy of infections due to B. fragilis, particularly endocarditis.