FIG. 4.

(A) Culture medium only; (B) electron-dense coccobacillary control NB; (C) etidronate-treated NB with a loss of electron density; (D and E) NB treated with EDTA revealing membrane (arrow labeled m) and septumlike structures (arrows labeled s); possible budding is noted (arrow labeled b); (F) S. aureus ATCC 25923 compared with treated and untreated NB; division planes are evident (arrows); (G and H) NB treated with tetracycline HCl at 0.5 and 4 μg/ml, respectively, illustrating the concentration-dependent loss of electron density; an increasing irregularity of NB borders was observed (arrows); (I and J) NB treated with nitrofurantoin (0.5 and 2.0 μg/ml, respectively) on day 1 demonstrating changes similar to those observed with tetracycline; the cells also enlarged as the concentration increased (J); (K and L) NB treated with ampicillin (15.6 μg/ml) on day 1 showing changes in morphology similar to those observed with the other drugs on day 7; (L) predominance of amorphous debris, as was also observed with tetracycline (data not shown). Bars, 200 nm.