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Biofilm Formation, Virulence-Associated Genes, and Antimicrobial Resistance in Proteus mirabilis Isolates from

Mehdi Choori1, Fateh Rahimi1, Ali Qasemi2

  • 1Department of Cell and Molecular Biology & Microbiology, Faculty of Biological Science and Technology, University of Isfahan, Isfahan 81746-73441, Iran.

Microorganisms
|June 26, 2026
PubMed

Insights

Proteus mirabilis causes complicated urinary tract infections (UTIs). This study found most UTI-causing P. mirabilis isolates form biofilms and carry virulence genes, alongside significant antimicrobial resistance and clonal diversity.

Area of Science:

  • Microbiology
  • Infectious Diseases
  • Genetics

Background:

  • Proteus mirabilis is a significant cause of complicated urinary tract infections (UTIs).
  • Biofilm formation and antimicrobial resistance in P. mirabilis contribute to persistent infections and treatment failures.
  • Understanding the genetic and phenotypic characteristics of P. mirabilis is crucial for managing UTIs.

Purpose of the Study:

  • To investigate the biofilm-forming capacity of P. mirabilis clinical isolates.
  • To determine the antimicrobial resistance profiles and identify virulence-associated genes.
  • To evaluate the genetic diversity and clonal relatedness of P. mirabilis isolates from UTI patients.

Main Methods:

  • Analysis of 104 non-duplicate clinical P. mirabilis isolates from UTI patients.
  • Quantification of biofilm formation using microtiter plate assays.
  • Antimicrobial susceptibility testing, ESBL/ESCR detection, and PCR for virulence genes.
  • Genetic diversity assessed using ERIC-PCR.

Main Results:

  • The majority of P. mirabilis isolates exhibited strong (51%) or moderate (45.2%) biofilm formation.
  • High prevalence of virulence and biofilm-associated genes (e.g., zapA, ureC, luxS) was observed.
  • Significant multidrug resistance (30.4%) and notable rates of ESBL (6.7%) and ESCR (12.5%) were detected.
  • ERIC-PCR revealed predominant clonal clusters, particularly among strong biofilm producers.

Conclusions:

  • Uropathogenic P. mirabilis isolates frequently possess strong biofilm-forming capabilities and virulence factors.
  • Coexistence of biofilm formation, virulence determinants, and antimicrobial resistance is common in P. mirabilis.
  • Genetic diversity and clonal expansion contribute to the persistence of P. mirabilis in UTIs.
Keywords:
ERIC-PCRProteus mirabilisantimicrobial resistancebiofilm formationurinary tract infectionvirulence factors

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