Siamak Heidarzadeh - 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.
Mohammad Mehdi Soltan Dallal - Food Microbiology Research Center, Tehran University of Medical Sciences, Tehran, Iran.
Sahar Serajian - Department of Microbiology and Virology, School of Medicine, Zanjan University of Medical Sciences, Zanjan, Iran
Faezeh Hadidi - Department of Microbiology and Virology, School of Medicine, Zanjan University of Medical Sciences, Zanjan, Iran
Mohhamad Javad Mohammad Rezaie - Department of Microbiology and Virology, School of Medicine, Zanjan University of Medical Sciences, Zanjan, Iran

Introduction and Objectives: Listeria monocytogenes is the etiological agent of listeriosis, a highly fatal infection which causes miscarriage or stillbirth in pregnant women. The objective of this study was to detect the prevalence, serotypes, antimicrobial susceptibility and virulence factors of L. monocytogenes isolated from the pregnant women with vaginitis, at a tertiary care hospital in Tehran, Iran. Materials and Methods: During September 2015 to February 2017, a total of 400 clinical samples (vaginal swabs) were collected from the pregnant women with vaginitis at a tertiary care hospital in Tehran, and tested for the presence of L. monocytogenes. The presumptive isolates were characterized biochemically. All L. monocytogenes isolates were further analyzed by serotyping and antimicrobial susceptibility tests. All the positive samples for L. monocytogenes were analyzed for presence of virulence genes (hlyA, actA, inlA, inlC, inlJ and prfA). Results: Twenty-two (5.5%) of the samples found positive for the presence of L. monocytogenes. Percentage of isolates resistant to antibiotics in this study was as following: penicillin G 45.45%, gentamicin 36.36%, ampicillin 45.45%, trimethoprim 81.82%, tetracycline 45.45%, ciprofloxacin 18.18%, sulfamethoxazole 81.82%, erythromycin 45.45%, streptomycin 45.45%, and chloramphenicol 54.55%. The majority of tested isolates (59.10%) belonged to serotype 4b, followed by 1/2a (22.73%), 1/2b (13.63%), and 3c (4.54%). The hlyA, actA, and inlA were detected in all of the 22 L. monocytogenes isolates but, two, three and five isolates were found to lack inlC, inlJ and prfA, respectively. Only one isolate lacked three inlC, inlJ and prfA genes, also two isolates simultaneously lacked both inlJ and prfA genes. Conclusion: In conclusion, evaluation of the virulence factors and antimicrobial susceptibility can be highly helpful to develop effective treatment strategies against L. monocytogenes infections. This study is noteworthy in that it documents prevalence, virulence characteristics, and antimicrobial resistance of L. monocytogenes.

Listeria monocytogenes, Pregnant women, Antimicrobial susceptibility, Serotyping, Virulence genes, Iran.