Tehran University of Medical Sciences Iranian Journal of Microbiology 2008-3289 17 5 2025 10 14 702 707 Lida Lotfollahi Department of Microbiology and Virology, School of Medicine, Urmia University of Medical Sciences, Urmia, Iran Zahra Shahabi Department of Microbiology and Virology, School of Medicine, Urmia University of Medical Sciences, Urmia, Iran Zahra Mousarezai Department of Microbiology and Virology, School of Medicine, Urmia University of Medical Sciences, Urmia, Iran Shabnam Kimyai Department of Microbiology and Virology, School of Medicine, Urmia University of Medical Sciences, Urmia, Iran Azar Hemmati Department of Microbiology and Virology, School of Medicine, Urmia University of Medical Sciences, Urmia, Iran Ehsan Shojadel Department of Microbiology and Virology, School of Medicine, Urmia University of Medical Sciences, Urmia, Iran 2025 01 15 2025 08 07 Background and Objectives: Group B Streptococcus (GBS) is a common bacterium found in the gastrointestinal tract and genitalia of both humans and animals. GBS infections can lead to a range of conditions, including meningitis, pneumonia, and sepsis. The present study aimed to analyze the colonization rate, antibiotic susceptibility, and serotypes of GBS in pregnant women in Urmia, Iran. Materials and Methods: Following GBS isolation from pregnant women and confirming its presence through PCR, antibiotic susceptibility testing was conducted to assess resistance patterns, followed by amplification of resistance genes (mefA, ermB, ermTR, linB) and molecular serotyping to determine the genetic characteristics of the strains. Results: Out of 400 samples, 31 (7.75%) were positive for GBS, with 22 (70.97%) showing multidrug resistance. Clindamycin had the highest resistance rate (80.65%), while penicillin showed the lowest (3.23%). Serotypes II and V were the most common (38.71% each), followed by Ia (19.35%) and III (3.23%). The ermB gene was detected in 4 strains, while mefA, ermTR, and linB were not found. Conclusion: Optimal management of GBS infections in pregnant women necessitates ongoing surveillance and antibiotic stewardship, considering penicillin resistance and observed resistance patterns. https://ijm.tums.ac.ir/index.php/ijm/article/view/5252 https://ijm.tums.ac.ir/index.php/ijm/article/download/5252/1815