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Published on: June 16, 2017
Targeting biofilm-related genes in a clinical methicillin-resistant Staphylococcus aureus isolate using CRISPR-Cas9
Aysegul Ates1, Sohret Aydemir2, Safak Ermertcan1
1Department of Pharmaceutical Microbiology, Faculty of Pharmacy, University of Ege, Izmir, Türkiye.
Background:
Methicillin-Resistant Staphylococcus aureus (MRSA) is a major clinical challenge due to its biofilm-forming ability. Innovative therapeutic strategies are essential to prevent bacterial attachment and disrupt biofilm structures. This study investigates the potential of CRISPR technology as a tool to combat resistance by targeting the biofilm-associated genes icaA, icaD, and bap in MRSA.
Methods:
Specific guide RNAs were cloned into pCasSA plasmids to target the icaA, icaD, and bap genes. Gene expression changes were quantified using quantitative PCR (qPCR), and mutations were confirmed through Sanger sequencing. Biofilm formation was assessed by crystal violet assay, and antimicrobial susceptibility was evaluated by broth microdilution and disk diffusion methods.
Results:
qPCR analyses confirmed significant reductions in gene expression: 3.3-fold for icaA, 2.3-fold for icaD, and 1.7-fold for bap. Sanger sequencing confirmed point mutations and indels within the target regions of genes. Biofilm formation decreased markedly, with 6-fold in icaA-mutant, 5.6-fold in icaD-mutant, and threefold in bap-mutant strains. MIC values were substantially reduced in all mutant strains: oxacillin MIC decreased 64-fold, 16-fold, and 4-fold in icaA-, icaD-, and bap-mutants, respectively, and ciprofloxacin MIC decreased 64-128-fold. Zone diameters for cefoxitin, norfloxacin, and gentamicin increased up to twofold across all mutant strains. All strains remained resistant according to EUCAST clinical breakpoints.
Conclusion:
This study demonstrates that CRISPR-Cas9-mediated disruption of biofilm-associated genes is an effective strategy for inhibiting biofilm formation in MRSA. Targeted disruption of icaA, icaD, and bap significantly reduced biofilm formation and partially attenuated antimicrobial resistance phenotypes. These findings highlight the potential of pathogen-specific CRISPR-based anti-virulence strategies as complementary approaches for the treatment of biofilm-associated infections.
Insights
CRISPR-Cas9 gene editing effectively reduced biofilm formation in Methicillin-Resistant Staphylococcus aureus (MRSA) by targeting key genes. This approach shows promise for combating MRSA infections and overcoming antimicrobial resistance.
Area of Science:
- Microbiology
- Genetics
- Biotechnology
Background:
- Methicillin-Resistant Staphylococcus aureus (MRSA) poses a significant clinical threat due to its robust biofilm-forming capabilities.
- Developing novel strategies to inhibit bacterial attachment and disrupt existing biofilms is crucial for effective treatment.
- This research explores CRISPR technology as a potential therapeutic tool against MRSA biofilms.
Purpose of the Study:
- To investigate the efficacy of CRISPR-Cas9 technology in targeting and disrupting biofilm-associated genes (icaA, icaD, bap) in MRSA.
- To assess the impact of gene disruption on MRSA biofilm formation and antimicrobial susceptibility.
- To evaluate CRISPR-based anti-virulence strategies as a complementary approach for treating MRSA infections.
Main Methods:
- CRISPR-Cas9 system with specific guide RNAs was employed to target icaA, icaD, and bap genes in MRSA.
- Quantitative PCR (qPCR) and Sanger sequencing were used to confirm gene expression changes and mutations.
- Biofilm formation was quantified using crystal violet assays, and antimicrobial susceptibility was determined via broth microdilution and disk diffusion methods.
Main Results:
- CRISPR-Cas9 targeting led to significant reductions in icaA (3.3-fold), icaD (2.3-fold), and bap (1.7-fold) gene expression.
- Biofilm formation decreased substantially (6-fold for icaA, 5.6-fold for icaD, 3-fold for bap mutants).
- Antimicrobial resistance was partially attenuated, with notable reductions in Minimum Inhibitory Concentrations (MICs) for oxacillin and ciprofloxacin.
Conclusions:
- CRISPR-Cas9-mediated disruption of biofilm-associated genes effectively inhibits MRSA biofilm formation.
- Targeting icaA, icaD, and bap genes partially reverses antimicrobial resistance phenotypes in MRSA.
- CRISPR-based anti-virulence strategies represent a promising complementary therapeutic approach for biofilm-associated MRSA infections.
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