Tehran University of Medical Sciences Iranian Journal of Microbiology 2008-3289 16 6 2024 12 08 745 754 Golnar Rahimzadeh Pediatric Infectious Diseases Research Center, Communicable Diseases Institute, Mazandaran University of Medical Sciences, Sari, Iran Shaghayegh Rezai Department of Medical Microbiology and Virology, Faculty of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran Ghazal Abbasi Students Research Committee, Mazandaran University of Medical Sciences, Sari, Iran Saman Soleimanpour Department of Medical Microbiology and Virology, Faculty of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran Reza Valadan Molecular and Cell Biology Research Center, Mazandaran University of Medical Sciences, Sari, Iran Laleh Vahedi Department of Pathology, School of Medicine, Mazandaran University of Medical Sciences, Sari, Iran Somayeh Sheidaei Department of Pathology, School of Medicine, Mazandaran University of Medical Sciences, Sari, Iran Faezeh Sadat Movahedi Pediatric Infectious Diseases Research Center, Communicable Diseases Institute, Mazandaran University of Medical Sciences, Sari, Iran Raha Rezai Pediatric Infectious Diseases Research Center, Communicable Diseases Institute, Mazandaran University of Medical Sciences, Sari, Iran Mohammad Sadegh Rezai Pediatric Infectious Diseases Research Center, Communicable Diseases Institute, Mazandaran University of Medical Sciences, Sari, Iran 2024 07 06 2024 10 31 Background and Objectives: Klebsiella pneumoniae is a common pathogen associated with healthcare-related infections. It is particularly notable for its ability to develop resistance to multiple antibiotics, making treatment challenging. During the COVID-19 pandemic, increased antibiotic use to manage critically ill patients was contributed to the rise of multidrug-resistant Klebsiella pneumoniae. This study evaluated the antibiotic resistance patterns of multidrug-resistant, ESBL-producing Klebsiella pneumoniae in northern Iran after the COVID-19 pandemic. Materials and Methods: This cross-sectional study was conducted between September 2022 and October 2023. Clinical samples were collected from patients with nosocomial infections at hospitals in Sari. This study included 114 multidrug-resistant ESBLs-producing Klebsiella pneumoniae isolates. Antimicrobial susceptibility was assessed using broth macro-dilution, and resistance genes were detected by multiplex PCR. Results: Gentamicin, ampicillin-sulbactam, co-amoxiclav, and ceftazidime displayed the lowest activity against multidrug-resistant Klebsiella pneumoniae. In contrast, piperacillin-tazobactam showed the highest activity. The prevalence of resistance genes was as follows: blaTEM (99.12%), blaSHV (74.56%), blaCTX (88.60%), blaIMP (64.04%), acrA -B (92.98%), and OqXA -B (67.54%). Conclusion: This study identified over 50% of antibiotic-resistance genes. Over half of multidrug-resistant Klebsiella pneumoniae isolates showed resistance to antibiotics except piperacillin-tazobactam, which is recommended for treating multidrug-resistant Klebsiella pneumoniae infections. https://ijm.tums.ac.ir/index.php/ijm/article/view/4892 https://ijm.tums.ac.ir/index.php/ijm/article/download/4892/1725