Tehran University of Medical Sciences Iranian Journal of Public Health 2251-6085 50 1 2020 12 28 170 179 Siamak HEIDARZADEH Department of Pathobiology, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran AND Department of Microbiology and Virology, School of Medicine, Zanjan University of Medical Sciences, Zanjan, Iran Mohammad Reza POURMAND Department of Pathobiology, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran Saeedeh HASANVAND Department of Microbiology, Damghan Branch, Science and Research Islamic Azad University, Damghan, Iran Reyhaneh PIRJANI Department of Obstetrics & Gynecology, Arash Hospital, Tehran University of Medical Sciences, Tehran, Iran Davoud AFSHAR Department of Microbiology and Virology, School of Medicine, Zanjan University of Medical Sciences, Zanjan, Iran Matina NOORI Department of Obstetrics & Gynecology, Arash Hospital, Tehran University of Medical Sciences, Tehran, Iran Mohammad Mehdi SOLTAN DALLAL Department of Pathobiology, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran AND Food Microbiology Research Center, Tehran University of Medical Sciences, Tehran, Iran 2019 02 26 2019 06 19 Background: Listeria monocytogenes show high mortality among pregnant women and newborns. This study aimed to detect L. monocytogenes in pregnant women with a history of abortion and assess the serotypes, antibiotic susceptibility patterns, and its resistance genes. Methods: Overall, 400 vaginal swabs were taken from pregnant women with a history of abortion in the past few years in a tertiary care hospital in Tehran, Iran, during 2015-2018. Antibiotics susceptibility to a panel of 10 antibiotics was determined using the standard disk diffusion method and the isolates serotyped by the agglutination method. The antimicrobial-resistant isolates were also screened for the presence of tetM, ermB and dfrD genes by PCR. Results: Overall, 22 L. monocytogenes isolates were identified. High rates of resistance were observed for trimethoprim (50%; n=11), sulphamethoxazole (50%; n=11), tetracycline (45.45%; n=10) and gentamicin (36.36%; n=8). From 22 L. monocytogenes isolates, 13 (59.10 %), 5 (22.73%), 3 (13.63%) and 1 (4.54%) belonged to serotypes 4b, 1/2a, 1/2b, and 3c, respectively. The genetic determinant tetM was detected in 70% of the tetracycline-resistant isolates. Out of 11 trimethoprim-resistant isolates, 27.27% isolates contained dfrD. Moreover, the ermB gene was found in 83.33% of the erythromycin-resistant isolates. Conclusion: Ampicillin and partly penicillin consider to be suitable antimicrobial agents to treat human listeriosis. Moreover, due to resistance against many antibiotics, it is necessary to continue monitoring and managing antimicrobial resistance. https://ijph.tums.ac.ir/index.php/ijph/article/view/16373 https://ijph.tums.ac.ir/index.php/ijph/article/download/16373/7108