Prevalence, antimicrobial susceptibility, serotyping and virulence genes screening of Listeria monocytogenes strains at a tertiary care hospital in Tehran, Iran

BACKGROUND 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 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 vaginal swabs were collected from pregnant women. The presumptive isolates were characterized biochemically. All L. monocytogenes isolates were further analyzed by serotyping and antimicrobial susceptibility tests. All 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 were found positive for presence of L. monocytogenes. Most isolates are resistant to trimethoprim/sulfamethoxazole (81.82%) 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, and two isolates simultaneously lacked both inlJ and prfA genes. CONCLUSION: Evaluation of 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.