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. 2021 Jun 10;11(1):85.
doi: 10.1186/s13568-021-01247-z.

Down-regulation of biofilm-associated genes in mecA-positive methicillin-resistant S. aureus treated with M. communis extract and its antibacterial activity

Moj Khaleghi  1   2 , Sadegh Khorrami  3
Affiliations

Down-regulation of biofilm-associated genes in mecA-positive methicillin-resistant S. aureus treated with M. communis extract and its antibacterial activity

Moj Khaleghi et al. AMB Express. .

Abstract

Considering the prevalence of resistance to antibiotics, the discovery of effective agents against resistant pathogens is of extreme urgency. Herein, 26 mecA-positive methicillin-resistant S. aureus (MRSA) isolated from clinical samples were identified, and their resistance to 11 antibiotics was investigated. Next, the antibacterial and anti-biofilm activity of the ethanolic extract of M. communis on these strains was evaluated. Furthermore, the effect of this extract on the expression of biofilm-associated genes, icaA, icaD, bap, sarA, and agr, was studied. According to the results, all isolated strains were multidrug-resistant and showed resistance to oxacillin and tetracycline. Also, 96.15 and 88.46 % of them were resistant to gentamicin and erythromycin. However, the extract could effectively combat the strains. The minimum inhibitory concentration (MIC) against different strains ranged from 1.56 to 25 mg/ml and the minimum bactericidal concentration (MBC) was between 3.125 and 50 mg/ml. Even though most MRSA (67 %) strongly produced biofilm, the sub-MIC concentration of the extract destroyed the pre-formed biofilm and affected the bacterial cells inside the biofilm. It could also inhibit biofilm development by significantly decreasing the expression of icaA, icaD, sarA and bap genes involved in biofilm formation and development. In conclusion, the extract inhibits biofilm formation, ruins pre-formed biofilm, and kills cells living inside the biofilm. Furthermore, it down-regulates the expression of necessary genes and nips the biofilm formation in the bud.

Keywords: M. communis; antibacterial agent; antibiofilm agent, biofilm-associated genes; methicillin-resistant S. aureus.

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Conflict of interest statement

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Figures

Fig. 1
Fig. 1
The presence of the biofilm formation inhibition regard to strains Sa5, Sa8, Sa12, Sa14, Sa19, Sa21 and S. aureus ATCC 33591. Error bars represent standard deviations (SD). *P < 0.05
Fig. 2
Fig. 2
The percentage of reduction of viable bacterial cells (log10 CFU/mL) after exposure to sub-MIC concentration (0.098 mg/ml) of the M. communis extract
Fig. 3
Fig. 3
Effect of sub-MBIC concentration of the extract of M. communis on the expression of icaA, icaD, bap, sar, and agr genes in Sa12 strain. Gene expression data were normalized to the 16 S reference
Fig. 4
Fig. 4
Illustrates the biofilm formation and development process, and the ways through which the extract can combat MRSA. M. communis extract directly inhibits cells proliferation and prevents biofilm formation through down-regulation of genes encoding adhesion factors and biofilm substances. It also ruins the established biofilm and kills the cells living inside the biofilm
See this image and copyright information in PMC

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