# DKsA Modulates Antimicrobial Susceptibility of _Acinetobacter baumanii_
## 2 Results  
### The Effect of dksA on the Antimicrobial Susceptibility of A. baumannii ATCC 17978  
To examine the role of DksA in antimicrobial susceptibility of _A. baumannii_ ATCC 17978, the minimum inhibitory concentrations (MICs) of antimicrobial agents for WT, \(\Delta\)_dksA_ mutant (KM0248D), and _dksA_-complemented (KM0248C) strains were determined. Of the 15 antimicrobial agents tested, MICs of five agents, including quinolones (nalidisic acid, ciprofloxacin, and levofloxacin) and tetracyclines (tetracycline and tigecycline) increased more than two-fold in the \(\Delta\)_dksA_ mutant strain compared with the WT strain (Table 1). However, the MICs of aminoglycos (amikacin, gentamicin, and tobramycin) decreased more than two-fold in the \(\Delta\)_dksA_ mutant strain compared with the WT strain. Quantitative real-time PCR (qPCR) was conducted to determine whether efflux pump genes were responsible for the changes in the MICs of antimicrobial agents against the \(\Delta\)_dksA_ mutant strain. The expression of efflux pump genes, including _adeB_, _adel_, and _adel_ for resistance nodulation cell division (RND)-type multidrug efflux pumps, _tetA_ for a major facilitator superfamily (MFS)-type drug efflux transporter, and _abeM_ for a multidrug and toxic compound extrusion (MATE)-type multidrug efflux transporter, was significantly increased in the \(\Delta\)_dksA_ mutant strain compared with the WT _A. baumannii_ ATCC 17978 strain (Figure 1A). However, the expression of the _adel_ and _adel_ in the _dksA_-complemented strain was not restored compared to the WT strain. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Antibacterial** & \multicolumn{2}{c}{**MIC (\(\mu\)g/mL)**} & \multicolumn{2}{c}{**Fold Change**} & \multicolumn{2}{c}{**MIC (\(\mu\)g/mL)**} & \multicolumn{1}{c}{**Fold Change**} \\ \cline{2-7}
**Agents** & **ATCC 17978** & **KM0248D** & **KM0248C** & **(KM0248D/WT)** & **1656-2** & **NY0298D** & **(NY0298D/WT)** \\ \hline Nalidivic acid & 4 & 16 & 8 & 4 & \textgreater{}256 & \textgreater{}256 & 1 \\ Ciprofloxacinoxacin & 0.125 & 0.5 & 0.125 & 4 & 64 & 64 & 1 \\ Levofloxacin & 0.063 & 0.125 & 0.063 & 2 & 16 & 16 & 1 \\ Cefoxitn & 128 & 128 & 128 & 1 & \textgreater{}256 & \textgreater{}256 & 1 \\ Cefotaxime & 16 & 16 & 16 & 1 & \textgreater{}256 & \textgreater{}256 & 1 \\ Cefetzidine & 4 & 4 & 4 & 1 & \textgreater{}256 & \textgreater{}256 & 1 \\ Imipenem & 0.125 & 0.125 & 0.125 & 1 & 16 & 16 & 1 \\ Meropenem & 0.25 & 0.25 & 0.25 & 1 & 32 & 32 & 1 \\ Amikacin & 1.0 & 0.25 & 0.5 & 0. The Effect of dksA on the Antimicrobial Susceptibility and Cellular Morphology of a Clinical A. baumannii Strain  
To examine the role of DksA in the antimicrobial susceptibility and cellular morphology of a clinical _A. baumannii_ strain, \(\Delta\)_dksA_ mutant (NY0298D) of the clinical 1656-2 strain was constructed (Supplementary Figure S1A). Deletion of _dksA_ in _A. baumannii_ 1656-2 was confirmed by PCR analysis (Supplementary Figure S1B). The expression of _dksA_ was not observed in the \(\Delta\)_dksA_ mutant strain (Supplementary Figure S1C). Additionally, we determined whether _dksA_ deletion changed the antimicrobial susceptibility of the clinical _A. baumannii_ 1656-2 strain. No difference was observed in the MICs of quinolones and tetracyclines between WT and NY0298D strains. However, the NY0298D strain exhibited increased susceptibility to aminoglycosoides (amikacin, gentamicin, and tobramycin) like the \(\Delta\)_dksA_ mutant strain of _A. baumannii_ ATCC 17978 (Table 1). The expression of efflux pump genes, including _adeB_, _adel_, _adel_, and _abeM_, significantly increased in the \(\Delta\)_dksA_ mutant strain, compared with that in the WT strain (Figure 1B). The \(\Delta\)_dksA_ mutant NY0298D strain displayed more morphological heterogeneity than the WT strain at an optical density of \(\Delta\)_dksA_ mutant (Figure 1C). The \(\Delta\)_dksA_ mutant NY0298D strain displayed more morphological heterogeneity than  
of 600 nm (OD\({}_{600}\)) of 0.95-1.05 to 1.75-1.85 (Figure 2).