• Prevalence, Serotyping, virulence determination, antimicrobial susceptibility pattern, and Molecular Characterization of Antibiotic Resistance Genes in Listeria monocytogenes Isolated from tertiary care hospital in Tehran, Iran
  • Sahar Serajian,1,* Siamak Heidarzadeh,2 Mohammad Mehdi Soltan Dallal,3 Mohammad Reza Pourmand,4
    1. Department of Microbiology and Virology, School of Medicine, Zanjan University of Medical Sciences, Zanjan, Iran
    2. Department of Microbiology and Virology, School of Medicine, Zanjan University of Medical Sciences, Zanjan, Iran
    3. Department of Pathobiology, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran
    4. Department of Pathobiology, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran


  • Introduction: Listeria monocytogenes causes listeriosis which is a highly fatal infection disease that causes miscarriage or stillbirth in pregnant women. The high mortality rate of this disease in pregnant women and newborns is notable. The objective of our study was to detect L. monocytogenes in pregnant women with the history of abortion in the past few years at a tertiary care hospital in Tehran to assess the prevalence, serotypes, antimicrobial susceptibility pattern, resistance genes and virulence factors of L. monocytogenes isolated
  • Methods: A total of 400 clinical samples (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. The isolates were characterized biochemically. Antibiotics susceptibility to a panel of 10 antibiotics was determined using the standard disk diffusion method and the isolates serotyped by the agglutination method. All the positive samples for L. monocytogenes were analyzed for presence of virulence genes (hlyA, actA, inlA, inlC, inlJ and prfA).The antimicrobial-resistant isolates were also screened for the presence of tetM, ermB and dfrD genes by PCR.
  • Results: From 400 samples, a total of 22 L. monocytogenes isolates (5.5%) 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). 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. 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: The resistance to antibiotics most commonly used in human listeriosis treatment is an important public health concern. Therefore, it is necessary to continue monitoring and management antimicrobial resistance and to diminish its further emergence and spread. Furthermore, evaluation of the virulence factors can be utilized to develop effective treatment strategies against L. monocytogenes infections
  • Keywords: Listeria monocytogenes, Serotyping, Antibiotic resistance genes, Antimicrobial susceptibility.