FIGURE 1.

Fitness cost of pAZJ221 in A. baumannii ATCC 17978 with or without imipenem pressure. The growth curve (a), the area under the curve (b), and the maximum OD₆₀₀ (c) of ATCC 17978 and ATCC 17978/pAZJ221 in MH broth and imipenem (IPM)‐containing MH broth were assessed and compared. ATCC 17978 could not grow in IPM‐containing MH broth, pAZJ221 imposed a fitness cost on ATCC 17978, and ATCC 17978/pAZJ221 exhibited significantly decreased fitness under sub‐MIC imipenem pressure compared with the antibiotic‐free environment. Box plots show median, lower, and upper quartiles, the minimum value, and the maximum value. Data were collected for 20 h at 37°C with shaking. Statistical analyses were performed through unpaired t‐tests with Welch's correction for unequal variances. When the data did not follow normal distribution, Mann–Whitney test was performed. *p < 0.05; ****p < 0.0001