Antibacterial Activity, Biofilm Inhibition, and Modulation of Virulence-Associated Gene Expression by Probiotic-Derived Cell-Free Supernatants Against Multidrug-Resistant Serratia marcescens.
- 1Cellular and Molecular Research Center, Qom University of Medical Sciences, Qom, Iran.
- 2Drug Applied Research Center, Tabriz University of Medical Sciences, Tabriz, Iran.
- 3Department of Laboratory Sciences, Faculty of Paramedicine, Tabriz University of Medical Sciences, Tabriz, Iran.
Abstract
Background
Multidrug-resistant (MDR) Serratia marcescens is an important opportunistic pathogen associated with persistent healthcare-associated infections, partly because of its capacity to form biofilms and express virulence-associated factors. Probiotic-derived cell-free supernatants (CFSs) contain secreted metabolites that may provide non-antibiotic approaches for controlling resistant bacteria. However, comparative data on bacterial- and yeast-derived CFSs against S. marcescens remain limited.Methods
CFSs were prepared from Lacticaseibacillus rhamnosus GG, Bacillus coagulans, Bifidobacterium longum, and Saccharomyces boulardii. Metabolite profiles were examined by GC-MS. Antibacterial activity was assessed by disk diffusion and broth microdilution. Biofilm-formation inhibition was evaluated by crystal violet staining at 1/2 and 1/4 MIC. Expression of fimA, bsmA, and shlA was examined by qRT-PCR, and HEK293 cell viability was assessed by MTT.Results
All four CFSs inhibited S. marcescens growth in a concentration-dependent manner. L. rhamnosus GG showed the greatest activity, with a MIC/MBC of 0.375/0.75 mg/mL and a 26-mm inhibition zone at 12 mg/mL. At 1/2 MIC, biofilm-formation inhibition was 71%, 57%, 47%, and 32%, respectively. All four CFSs significantly reduced fimA and bsmA expression, whereas shlA expression was significantly reduced by L. rhamnosus GG, B. coagulans, and B. longum, but not by S. boulardii. HEK293 cell viability remained above 80% under the tested conditions.Conclusion
Probiotic-derived CFSs demonstrated antibacterial and biofilm-formation inhibitory activities and were associated with reduced expression of selected virulence-associated genes in S. marcescens. L. rhamnosus GG-derived CFSs showed the strongest overall activity, supporting further mechanistic and in vivo studies.
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BibTeX
@article{ozma2026antibacterial,
title = {{Antibacterial Activity, Biofilm Inhibition, and Modulation of Virulence-Associated Gene Expression by Probiotic-Derived Cell-Free Supernatants Against Multidrug-Resistant Serratia marcescens.}},
author = {Mahdi Asghari Ozma and Niloofar Fallahi Alileh and Seyyed Reza Moaddab},
journal = {Infection and drug resistance},
year = {2026},
month = oct,
doi = {10.2147/idr.s647738},
url = {https://europepmc.org/article/MED/42948688},
note = {CC BY-NC},
}
RIS
TY - JOUR
TI - Antibacterial Activity, Biofilm Inhibition, and Modulation of Virulence-Associated Gene Expression by Probiotic-Derived Cell-Free Supernatants Against Multidrug-Resistant Serratia marcescens.
AU - Mahdi Asghari Ozma
AU - Niloofar Fallahi Alileh
AU - Seyyed Reza Moaddab
PY - 2026
DA - 2026/10/23
JO - Infection and drug resistance
DO - 10.2147/idr.s647738
UR - https://europepmc.org/article/MED/42948688
AB - Background Multidrug-resistant (MDR) Serratia marcescens is an important opportunistic pathogen associated with persistent healthcare-associated infections, partly because of its capacity to form biofilms and express virulence-associated factors. Probiotic-derived cell-free supernatants (CFSs) contain secreted metabolites that may provide non-antibiotic approaches for controlling resistant bacteria. However, comparative data on bacterial- and yeast-derived CFSs against S. marcescens remain limited.Methods CFSs were prepared from Lacticaseibacillus rhamnosus GG, Bacillus coagulans, Bifidobacterium longum, and Saccharomyces boulardii. Metabolite profiles were examined by GC-MS. Antibacterial activity was assessed by disk diffusion and broth microdilution. Biofilm-formation inhibition was evaluated by crystal violet staining at 1/2 and 1/4 MIC. Expression of fimA, bsmA, and shlA was examined by qRT-PCR, and HEK293 cell viability was assessed by MTT.Results All four CFSs inhibited S. marcescens growth in a concentration-dependent manner. L. rhamnosus GG showed the greatest activity, with a MIC/MBC of 0.375/0.75 mg/mL and a 26-mm inhibition zone at 12 mg/mL. At 1/2 MIC, biofilm-formation inhibition was 71%, 57%, 47%, and 32%, respectively. All four CFSs significantly reduced fimA and bsmA expression, whereas shlA expression was significantly reduced by L. rhamnosus GG, B. coagulans, and B. longum, but not by S. boulardii. HEK293 cell viability remained above 80% under the tested conditions.Conclusion Probiotic-derived CFSs demonstrated antibacterial and biofilm-formation inhibitory activities and were associated with reduced expression of selected virulence-associated genes in S. marcescens. L. rhamnosus GG-derived CFSs showed the strongest overall activity, supporting further mechanistic and in vivo studies.
SN - 1178-6973
ER -