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Biofilm formation ability and swarming motility are associated with some virulence genes in Proteus mirabilis

Mahin Veisi1, Hossein Hosseini-Nave1, Omid Tadjrobehkar2

  • 1Department of Medical Bacteriology & Virology, Afzalipour School of Medicine, Kerman University of Medical Sciences, 22 Bahman Blvd, Pajoohesh Sq, Kerman, Iran.

BMC Microbiology
|July 3, 2025
PubMed

Insights

Proteus mirabilis uses adhesins for biofilm formation and swarming motility to cause urinary tract infections. Virulence genes like zapA and hlyA are linked to these behaviors, suggesting a strategy for colonization and immune evasion.

Area of Science:

  • Microbiology
  • Infectious Diseases
  • Bacterial Pathogenesis

Background:

  • Proteus mirabilis is a common cause of urinary tract infections (UTIs).
  • This pathogen possesses various virulence factors, including biofilm formation and swarming motility.
  • Understanding the genetic basis of these surface behaviors is crucial for combating UTIs.

Purpose of the Study:

  • To investigate the association between virulence-associated genes and the surface behaviors of biofilm formation and swarming motility in Proteus mirabilis.
  • To analyze the prevalence of 10 specific virulence genes in P. mirabilis isolates.
  • To determine the statistical relationship between gene frequencies and observed bacterial behaviors.

Main Methods:

  • 91 P. mirabilis isolates were analyzed for biofilm production using the microtiter plate assay.
  • Swarming motility was evaluated using top-agar travel tracking.
  • Polymerase chain reaction (PCR) was employed to screen for 10 virulence-associated genes.

Main Results:

  • The zapA gene showed 100% frequency, while hlyA was found in 41.8% of isolates.
  • Isolates were categorized as weak, intermediate, or strong biofilm producers (41, 35, and 15 isolates, respectively).
  • Strong biofilm producers showed higher prevalence of adhesin genes (e.g., mrpA).
  • The hlyA gene frequency correlated positively with swarming motility and negatively with biofilm formation.
  • A reverse correlation was observed between biofilm formation ability and swarming motility.

Conclusions:

  • Proteus mirabilis likely utilizes adhesins for biofilm production and colonization, then transitions to strong swarming to invade deeper urinary tract tissues.
  • The HlyA toxin may play a role in evading host immune responses.
  • Virulence gene expression, particularly hlyA, is linked to distinct surface behaviors, offering potential therapeutic targets.
Keywords:
HlyA geneMrpA geneProteus mirabilisBiofilm formationSwarming motilityVirulence associated genes

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