Because sublethal concentrations of antibodies can have important effects on bacteria and may aid host defenses, even in the absence of direct microbial killing, the effect of brief sublethal exposures to amphotericin B on Candida albicans blastoconidia was evaluated. Amphotericin B (0.01-1.0 micrograms/ml for 60 min) inhibited germ tube formation and yeast adherence to both serum-coated plastic surfaces and fibrin matrices. These effects were not reversed by cation (K+ or Mg++) supplementation. Amphotericin B pretreatment accelerated clearance of C. albicans from the peritoneal surfaces of mice and reduced the inflammatory stimulus associated with this clearance, at least as measured by neutrophil influx. However, pretreatment did not facilitate killing of C. albicans by either neutrophils or monocytes in vitro. Thus sublethal concentrations of amphotericin B inhibit two activities of C. albicans that probably contribute to surface colonization and tissue invasion. These results provide one explanation for the clinical benefits observed with short courses of amphotericin B therapy for surface-limited candidal infections (e.g., esophagitis).

We showed that brief exposures to amphotericin B (AmB) inhibited the induction of new Candida germ tubes and the lengthening of partially induced germ tubes. Blastoconidia with germ tpbes were more susceptible to AmB killing, and this varied directly with the induction period and the AmB exposure period. AmB did not preferentially affect germ tube adherence to fibrin matrices.We recently showed that sublethal concentrations of amphotericin B (AmB) inhibited germ tube formation in Candida albicans cultures (7). Niimi et al. reported that germ tube-forming cells of C. albicans are more susceptible to clotrimazole-induced killing than are yeast cells (6), and Borgers and co-workers found that pseudomycelium formation was very sensitive to dilute concentrations of imidazoles (1). These studies suggest that the biochemical and morphological changes associated with germ tube formation produce increased susceptibility to antifungal agents.Germ tube formation. In earlier studies with a clinical isolate of C. albicans (11), we observed that AmB inhibited the induction of germ tubes in serum (7). In the experiments described here, we measured the effects of brief exposure to low concentrations of AmB (0.1 ,ug/ml) on germ tube development and lengthening in partially induced cultures. This subsequently increased to 95.5 + 1.1% in control suspensions and to 56.8 + 8.6% in AmB-treated suspensions (P < 0.05 by analysis of variance; n = 6 experiments). We measured the length of germ tubes with scanning electron microscopy after Candida blastoconidia had completed the incubations described above. The primary germ tubes and all germ tubes were significantly longer in control cultures than in AmB-treated cultures

Sixteen strains of 11 facultatively anaerobic species of the genus Bacillus were tested for their ability to sporulate anaerobically on common laboratory media. Reliable data depended on a method providing anaerobic conditions quickly. Bacillus macerans (one strain tested) and B. polymyxa (two out of two strains tested) sporulated anaerobically without added nitrate. But B. licheniformis (one out of two strains tested) required nitrate for "anaerobic" sporulation. Anaerobic sporulation of B. macerans and B. polymyxa on potato extract agar was inhibited by nitrate.