Table 3.

Appearance of cells with normal morphologies at various times after antibiotic exposure (2 h) and removal

Time (min) after removalb% normal cellsc
NEGCEFPIP
15>95<5<5
30>95<5<5
45>95<5<5
60>95<5<5
75>9512 ± 28 ± 2
90>9538 ± 336 ± 4
105>9553 ± 369 ± 3
120>9564 ± 475 ± 4
135>9578 ± 378 ± 2
150>9586 ± 387 ± 4
  • a Values are means ± standard errors. Data are based on direct counts of five microscope fields for each value determined.

  • b Time after antibiotic is removed and cells are resuspended in antibiotic-free medium.

  • c Percentage of the cells in the total cell population, including filamentous cells of 1.5 to 6 μm in length. Abbreviations: NEG, negative control (no antibiotic in medium); CEF, exposed to 0.5 μg of cefotaxime per ml for 2 h; PIP, exposed to 16 μg of piperacillin per ml for 2 h.