en Anti-microbial agents, resistance and treatment protocols Anti-microbial agents, resistance and treatment protocols Original article Original article <span style="font-size:12pt"><span style="line-height:normal"><span new="" roman="" style="font-family:" times=""><span style="color:black"><span style="letter-spacing:0.75pt"><span style="font-weight:bold"><span style="font-size:10.0pt">Introduction:</span> <a name="_Hlk139270934"><i><span style="font-size:10.0pt"><span style="font-weight:normal">Acinetobacter</span></span></i></a><i><span style="font-size:10.0pt"><span style="font-weight:normal"> baumannii</span></span></i><span style="font-size:10.0pt"><span style="font-weight:normal"> is </span></span><span style="font-size:10.0pt"><span style="font-weight:normal">the cause of</span></span><span style="font-size:10.0pt"><span style="font-weight:normal"> nosocomial infections, primarily in intensive care units. The <i>pgaA</i> gene plays an essential role in biofilm formation, making it a promising target for developing new strategies to tackle <i>A. baumannii</i> infections.</span></span><span style="font-size:10.0pt"><span style="font-weight:normal"> This study investigated the meropenem effect on <i>pgaA</i> gene expression and biofilm formation in A.</span></span><i><span style="font-size:10.0pt"><span style="font-weight:normal"> baumannii</span></span></i><span style="font-size:10.0pt"><span style="font-weight:normal">. </span></span><span style="font-size:10.0pt">Methods:</span><span style="font-size:10.0pt"><span style="font-weight:normal"> Over five months, 50 urine samples were taken from patients receiving medical care in the intensive care unit, of which 20 </span></span><i><span style="font-size:10.0pt"><span style="font-weight:normal">A. baumannii</span></span></i><span style="font-size:10.0pt"><span style="font-weight:normal"> isolates were detected. Antibiotic susceptibility was determined with meropenem, imipenem, trimethoprim/sulfamethoxazole, ceftazidime, ciprofloxacin, tetracycline, amikacin, as well as gentamicin disks by the Kirby-Bauer method. The minimum inhibitory concentration (MIC) of meropenem was determined using the microdilution method. Biofilm formation was investigated through the tissue culture plate (TCP) technique and imaged using an atomic force microscope (AFM). Reverse Transcriptase Polymerase Chain Reaction (RT-PCR) determined the expression level of the </span></span><i><span style="font-size:10.0pt"><span style="font-weight:normal">pgaA</span></span></i><span style="font-size:10.0pt"><span style="font-weight:normal"> gene. </span></span><span style="font-size:10.0pt">R</span><span style="font-size:10.0pt">esults: </span><span style="font-size:10.0pt"><span style="font-weight:normal">Antibiotic susceptibility testing revealed that all </span></span><i><span style="font-size:10.0pt"><span style="font-weight:normal">A. baumannii</span></span></i><span style="font-size:10.0pt"><span style="font-weight:normal"> isolates were resistant to meropenem, imipenem, ciprofloxacin, and amikacin, and 71.42% were resistant to tetracycline. The MIC for meropenem could not be determined for isolates. Meropenem prevented biofilm formation in more than 70% of the isolates, and AFM imaging revealed thin biofilms. The RT-PCR showed that exposure to meropenem significantly decreased the </span></span><i><span style="font-size:10.0pt"><span style="font-weight:normal">pgaA</span></span></i><span style="font-size:10.0pt"><span style="font-weight:normal"> expression gene in over 95% of the isolates (</span></span><i><span style="font-size:10.0pt"><span style="font-weight:normal">P</span></span></i><span style="font-size:10.0pt"><span style="font-weight:normal"> < 0.0001).</span></span><span style="font-size:10.0pt"> Conclusion:</span><span style="font-size:10.0pt"><span style="font-weight:normal"> Meropenem inhibited biofilm formation in most </span></span><i><span style="font-size:10.0pt"><span style="font-weight:normal">A. baumannii</span></span></i><span style="font-size:10.0pt"><span style="font-weight:normal"> isolates by downregulating the </span></span><i><span style="font-size:10.0pt"><span style="font-weight:normal">pgaA</span></span></i><span style="font-size:10.0pt"><span style="font-weight:normal"> expression, suggesting a potential role in preventing </span></span><i><span style="font-size:10.0pt"><span style="font-weight:normal">A. baumannii</span></span></i><span style="font-size:10.0pt"><span style="font-weight:normal"> infections by reducing biofilm formation</span></span></span></span></span></span></span></span> Acinetobacter baumannii, atomic force microscope, Biofilm, PgaA, RT-PCR, Antibiotic resistance 86 95 http://jommid.pasteur.ac.ir/browse.php?a_code=A-10-369-1&slc_lang=en&sid=1 Mir Mahdi Najafi mirmahdinajafi@gmail.com 0000-0003-1778-6313 Yes Chemical Injuries Research Center, Systems Biology and Poisonings Institute, Baqiyatallah University of Medical Sciences, Tehran, Iran