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We analyzed the outer membrane (OM) ultrastructure of four pathogenic members of the family Spirochaetaceae by freeze fracture. The OM of Treponema pallidum subsp. pertenue contained a low intramembranous particle concentration, indicating that it contains few OM transmembrane proteins. The concave OM fracture faces of Treponema hyodysenteriae and Borrelia burgdorferi contained dense populations of particles, typical of gram-negative organisms. A relatively low concentration of particles which were evenly divided between a small and a large species was present in the concave OM fracture face of Borrelia hermsii; the convex OM fracture face contained only small particles. As for gram-negative bacteria, the convex OM fracture face particle concentrations of these pathogens were low. These spirochetes cleaved preferentially within the OM, in contrast to typical gram-negative bacteria, which tend to fracture within the inner membrane. The OM ultrastructure of T. palldum subsp. pertenue provides an explanation for the lack of antigenicity of the treponemal surface and may reflect a mechanism by which this pathogen evades the host immune response.Treponema pallidum subsp. pertenue, Treponema hyodysenteriae, Borrelia burgdorferi, and Borrelia hermsii are the etiologic agents of yaws, swine dysentery, Lyme borreliosis, and relapsing fever, respectively. Although the diseases caused by these spirochetes (family Spirochaetaceae) have been well described, research on the biology of these pathogens has been hampered by several factors. Rich, serum-containing media are required to cultivate the agents of Lyme borreliosis, relapsing fever, and swine dysentery; none of the treponemes responsible for disease in humans can be cultivated continuously in vitro. No systems for introducing DNA into members of the family Spirochaetaceae have been developed. The spirochetal outer membrane (OM) tends to be easily damaged by mild physical and chemical manipulations (3,12,14,15,27,28,32). Work with spirochetes such as Treponema pallidum subsp. pallidum, the etiologic agent of syphilis, has indicated that this fragility has not been adequately addressed by the techniques used to define the OM constituents of gram-negative bacteria (12, 26-28, 30, 38).Freeze-fracture electron microscopy has allowed examination of the ultrastructure of the OM of T. pallidum subsp. pallidum (30,38). The OM of this spirochete was shown to be unusual in that it contains a low intramembranous particle (IMP) concentration in both the concave and convex fracture faces, indicating that the OM of T. pallidum subsp. pallidum contains few transmembrane proteins (30,38). In this study, we used the techniques of freeze-fracture and freeze-etch electron microscopy to examine the OM of T. pallidum subsp. pertenue provided by Paul H. Hardy, Jr., The Johns Hopkins University School of Medicine, Baltimore, Md. The strain was cultivated by passage in New Zealand White male rabbits and harvested as previously described for T. pallidum subsp. pallidum (23). T. hyodysenteriae ...

We conducted a retrospective study to update the bacteriology of 46 cases of anaerobic empyema that were originally studied between 1976 and 1993 at the Wadsworth Anaerobic Bacteriology Clinical Research Laboratory (Los Angeles). Anaerobic bacteriologic studies were completed for all 46 pleural fluid specimens, and aerobic bacteriologic studies were completed for 41 of these specimens. Thirty-seven clinical charts were available for review. A total of 161 anaerobic isolates (3.5 per patient) representing 64 species or groups were recovered. The most common isolates were as follows: Fusobacterium nucleatum (19); Prevotella oris-buccae group (13, 9 of which were P. oris); Bacteroides fragilis group (11, 4 of which were B. fragilis); pigmented Prevotella species (17, 8 of which were in the Prevotella intermedia-nigrescens group); Peptostreptococcus species (17, 9 of which were Peptostreptococcus micros); Eubacterium species (7); Lactobacillus species (8); Actinomyces species (7); and Clostridium species (7). Nineteen if the cases were of purely anaerobic etiology; of these, eight were caused by a single organism: F. nucleatum (five cases); B. fragilis (two cases); and Prevotella mangus (one case). Of the 45 aerobic isolates (1.1 per patient), viridans streptococci were most common (21 isolates), followed by group D nonenterococcal streptococcus (four isolates). Only nine gram-negative rods (six enteric and three nonenteric organisms) and one Staphylococcus aureus isolate were recovered. The susceptibility to penicillin of 64 isolates was examined with the use of the spiral gradient method; 21 (33%) of these isolates were beta-lactamase positive (MICs ranged from 1.1 to > or = 54 micrograms/mL vs < or = 0.27 micrograms/mL for beta-lactamase-negative strains).