## 3 Results
### Prevalence of Efflux Pump and Regulatory Genes  
_MexAB-OprM_ is the most common efflux pump system in this study with the following rates: _MexA_ (96.5%), _MexB_ (100%), and _OprM_ (96.5%). Furthermore, _MexCD-OprJ_ was the second most prevalent, with the following prevalence rates: _MexC_ (100%), _MexD_ (74.1%), and _OprJ_ (63.7%). _MexX and OprN_ had the lowest occurrence, with 89.6% and 51.7% rates, respectively. _MexY_ was not harboured in all _P. aeruginosa_ isolates, as shown in Figure 3. All RND efflux pump genes investigated in this study were detected in 40% of MDR _P. aeruginosa_ isolates. NfxB, a repressor encoded upstream of the MexCD-OprJ operon, was harboured in 31.6% MDR _P. aeruginosa_ isolates. Meanwhile, NaL, NaLD, MexZ and MexR were expressed in 15.8%, 12.2%, 3.5% and 3.5% of _P. aeruginosa_ isolates, respectively, as shown in Figure 4.  
The distribution of efflux pump genes across the antibiotic classes (beta-lactams, fluoroquinolones, carbapenem, and aminoglycosides) shows a similar prevalence rate, with all MDR isolates harbouring MexB and MexC. Meanwhile, other efflux pump genes were found to have the following ranges across the four antibiotics classes: MexA (96-98%), OprM (95-96.5%), MexD (74-76%), OprJ (62-65%), MexX (86-89.6%), and OprN (51-52%). All MDR _P. aeruginosa_ isolates showed unique resistance patterns alongside the efflux pump genes and regulatory proteins. The distribution of efflux pump genes, regulatory proteins and resistance patterns of all MDR _P. aeruginosa_ isolates are represented in Table 3. At the same time, the occurrence of antibiotic resistance to all tested antibiotics and efflux pump genes is shown in Table 4. The arrangement of the efflux pump systems as operons is shown in Table 5. A typical gel picture of all efflux pump genes and regulatory proteins is shown in Supplementary Figures S1-S3. Figure 3: The overall distribution of efflux pump genes and outer membrane proteins in MDR _Pseudomonas aeruginosa_. Figure 4: Distribution of regulatory proteins in MDR _P. aeruginosa_. \begin{table}
\begin{tabular}{l c c c c c c c c c c} \hline
**Isolates** & **MexA** & **MexB** & **OprM** & **MexC** & **MexD** & **OprJ** & **MexX** & **MexY** & **OprN** & **Resistance Pattern** \\ \hline J01 & + & + & + & + & \(-\) & \(-\) & \(-\) & \(-\) & \(-\) & AK-LEV-AT \\ J02 & + & + & + & + & + & + & \(+\) & \(-\) & \(-\) & GM-AK-LEV-CAZ-MEM \\ J03 & + & + & + & + & + & + & + & \(-\) & \(+\) & GM-AK-LEV-CAZ-MEM \\ J04 & + & + & + & + & + & + & \(+\) & \(-\) & \(-\) & AK-CAZ-MEM \\ J05 & + & + & + & + & \(-\) & \(-\) & \(-\) & \(-\) & \(-\) & GM-CIP-AK-CAZ-MEM \\ J06 & + & + & + & + & + & + & \(-\) & \(+\) & GM-AK-LEV-MEM \\ J07 & + & + & + & + & + & + & \(-\) & \(+\) & GM-AK-LEV-MEM \\ J08 & + & + & + & + & + & + & \(-\) & \(+\) & GM-CIP-AK-LEV-NOR-CAZ-MEM \\ J09 & + & + & + & + & + & + & \(+\) & \(-\) & \(-\) & GM-CIP-AK-LEV-CAZ-MEM \\ J10 & + & + & + & + & + & + & \(+\) & \(-\) & \(+\) & GM-CIP-AK-LEV-NOR-CAZ-ATM \\ J11 & + & + & + & + & + & + & \(+\) & \(-\) & \(+\) & GM-CIP-AK-LEV-NOR-CAZ-ATM \\ J12 & + & + & + & + & + & + & \(+\) & \(-\) & \(+\) & GM-CIP-AK-LEV-CAZ-MEM-ATM \\ J13 & + & + & + & + & + & + & \(+\) & \(-\) & \(+\) & GM-CIP-AK-LEV-MEM-ATM \\ J14 & + & + & + & + & + & + & \(+\) & \(-\) & \(+\) & GM-CIP-AK-CAZ \\ J15 & + & + & + & + & + & + & \(-\) & \(+\) & GM-AK-CAZ-MEM \\ J16 & + & + & + & + & + & + & \(-\) & \(+\) & GM-CIP-AK-IM-LEV-NOR-CAZ-MEM-TOB \\ J17 & + & + & + & + & + & + & \(+\) & \(-\) & \(+\) & GM-AK-MEM-ATM \\ J18 & + & + & + & + & + & + & \(+\) & \(-\) & \(-\) & GM-CIP-AK-LEV-ATM \\ J19 & + & + & + & + & + & + & \(+\) & \(-\) & \(+\) & GM-CIP-AK-LEV-MEM \\ J20 & + & + & + & + & + & + & \(+\) & \(-\) & \(+\) & CIP-AK-LEV-NOR-CAZ-ATM \\ J21 & + & + & + & + & + & + & \(+\) & \(-\) & \(-\) & GM-AK-MEM-ATM \\ J22 & + & + & + & + & + & + & \(-\) & \(-\) & GM-CIP-AK-CAZ-MEM \\ J23 & + & + & \(-\) & + & \(-\) & \(-\) & \(-\) & \(-\) & \(-\) & GM-CIP-AK-LEV-NOR-CAZ-MEM-ATM \\ \hline \end{tabular}
\end{table}