Antibacterial and antibiofilm effect of zinc oxide nanoparticles on multidrug-resistant serratia marcescens isolated from Iraqi hospitals

Clinical specimens including wound and burn, urine, sputum, and blood from patients attending hospital in Baghdad including Al Karama Teaching Hospital and Alyarmouk Teaching Hospital between april to july 2022. Out of 350 only 65 isolates were identified as Serratia marcescens, by culture, microscope, biochemical tests, and VITEK system. Kirby-Bauer method showed that S. marcescens were resistant %100 to five antibiotics: Cefazolin, Cefoxitin, Azithromycin ,Ertapenem, Nitrofurantoin, while other seven antibiotics showed variable resistance to: Amikacin, Aztreonam, Nalidixic Acid, Levofloxacin, Tobramycin, Tigecycline, Chloramphenicol. Biofilm formation by microtiter plate method revealed that 35 were stronge, 14 were moderate, 5 were weak, and 11 were negative. To determin Sub-MIC, MIC and MBC of ZnO NPs by microdilution method, 35 isolates of multidrug resistance and strong biofilm were chosen ,the results showed that isolates from Wounds and Burns were (100, 150, 250 µg/ml), urine (125, 175, 275 µg/ml), sputum (150, 225, 300 µg /ml), And from blood (175, 250, 300 µg/ml). The effect of Sub-MIC of ZnO NPs on bacterial biofilm formation, showed that 35 strong isolates converted to 30 weak, and 5 moderate.