Inhibition of Biofilm Formation in Cutibacterium acnes, Staphylococcus aureus, and Candida albicans by the Phytopigment Shikonin.

Skin microbiota, such as acne-related Cutibacterium acnes, Staphylococcus aureus, and fungal Candida albicans, can form polymicrobial biofilms with greater antimicrobial tolerance to traditional antimicrobial agents and host immune systems. In this study, the phytopigment shikonin was investigated against single-species and multispecies biofilms under aerobic and anaerobic conditions. Minimum inhibitory concentrations of shikonin were 10 µg/mL against C. acnes, S. aureus, and C. albicans, and at 1-5 µg/mL, shikonin efficiently inhibited single biofilm formation and multispecies biofilm development by these three microbes. Shikonin increased porphyrin production in C. acnes, inhibited cell aggregation and hyphal formation by C. albicans, decreased lipase production, and increased hydrophilicity in S. aureus. In addition, shikonin at 5 or 10 µg/mL repressed the transcription of various biofilm-related genes and virulence-related genes in C. acnes and downregulated the gene expression levels of the quorum-sensing agrA and RNAIII, α-hemolysin hla, and nuclease nuc1 in S. aureus, supporting biofilm inhibition. In addition, shikonin prevented multispecies biofilm development on porcine skin, and the antimicrobial efficacy of shikonin was recapitulated in a mouse infection model, in which it promoted skin regeneration. The study shows that shikonin inhibits multispecies biofilm development by acne-related skin microbes and might be useful for controlling bacterial infections.

Hydroquinones Inhibit Biofilm Formation and Virulence Factor Production in Staphylococcus aureus.

Staphylococcus aureus is one of the major pathogens responsible for antimicrobial resistance-associated death. S. aureus can secrete various exotoxins, and staphylococcal biofilms play critical roles in antibiotic tolerance and the persistence of chronic infections. Here, we investigated the inhibitory effects of 18 hydroquinones on biofilm formation and virulence factor production by S. aureus. It was found that 2,5-bis(1,1,3,3-tetramethylbutyl) hydroquinone (TBHQ) at 1 µg/mL efficiently inhibits biofilm formation by two methicillin-sensitive and two methicillin-resistant S. aureus strains with MICs of 5 µg/mL, whereas the backbone compound hydroquinone did not (MIC > 400 µg/mL). In addition, 2,3-dimethylhydroquinone and tert-butylhydroquinone at 50 µg/mL also exhibited antibiofilm activity. TBHQ at 1 µg/mL significantly decreased the hemolytic effect and lipase production by S. aureus, and at 5−50 µg/mL was non-toxic to the nematode Caenorhabditis elegans and did not adversely affect Brassica rapa seed germination or growth. Transcriptional analyses showed that TBHQ suppressed the expression of RNAIII (effector of quorum sensing). These results suggest that hydroquinones, particularly TBHQ, are potentially useful for inhibiting S. aureus biofilm formation and virulence.

Antibiofilm Activity of Phorbaketals from the Marine Sponge Phorbas sp. against Staphylococcus aureus.

Biofilm formation by Staphylococcus aureus plays a critical role in the persistence of chronic infections due to its tolerance against antimicrobial agents. Here, we investigated the antibiofilm efficacy of six phorbaketals: phorbaketal A (1), phorbaketal A acetate (2), phorbaketal B (3), phorbaketal B acetate (4), phorbaketal C (5), and phorbaketal C acetate (6), isolated from the Korean marine sponge Phorbas sp. Of these six compounds, 3 and 5 were found to be effective inhibitors of biofilm formation by two S. aureus strains, which included a methicillin-resistant S. aureus. In addition, 3 also inhibited the production of staphyloxanthin, which protects microbes from reactive oxygen species generated by neutrophils and macrophages. Transcriptional analyses showed that 3 and 5 inhibited the expression of the biofilm-related hemolysin gene hla and the nuclease gene nuc1.

Inhibition of Candida albicans and Staphylococcus aureus biofilms by centipede oil and linoleic acid.

Microbial biofilms are associated with persistent infections because of their high tolerance to antimicrobial agents and host defenses. The effects of centipede oil from Scolopendra subspinipes mutilans and its main components were investigated to identify non-toxic biofilm inhibitors. Centipede oil and linoleic acid at 20 µg ml-1 markedly inhibited biofilm formation by two fluconazole-resistant Candida albicans strains and three Staphylococcus aureus strains without affecting their planktonic cell growth. Also, both centipede oil and linoleic acid inhibited hyphal growth and cell aggregation by C. albicans. In addition, centipede oil and linoleic acid showed anti-biofilm activities against mixed C. albicans and S. aureus biofilms. Transcriptomic analysis showed that centipede oil and linoleic acid downregulated the expressions of several hypha/biofilm-related genes in C. albicans and α-hemolysin in S. aureus. Furthermore, both compounds effectively reduced C. albicans virulence in a nematode infection model with minimal toxicity.

The anti-biofilm and anti-virulence activities of trans-resveratrol and oxyresveratrol against uropathogenic Escherichia coli.

Uropathogenic Escherichia coli (UPEC) is the primary causative agent of urinary tract infections, which are one of the most common infectious disease types in humans. UPEC infections involve bacterial cell adhesion to bladder epithelial cells, and UPEC can also form biofilms on indwelling catheters that are often tolerant to common antibiotics. In this study, the anti-biofilm activities of t-stilbene, stilbestrol, t-resveratrol, oxyresveratrol, ε-viniferin, suffruticosol A, and vitisin A were investigated against UPEC. t-Resveratrol, oxyresveratrol, and ε-viniferin, suffruticosol A, and vitisin A significantly inhibited UPEC biofilm formation at subinhibitory concentrations (10-50 µg ml-1). These findings were supported by observations that t-resveratrol and oxyresveratrol reduced fimbriae production and the swarming motility in UPEC. Furthermore, t-resveratrol and oxyresveratrol markedly diminished the hemagglutinating ability of UPEC, and enhanced UPEC killing by human whole blood. The findings show that t-resveratrol, oxyresveratrol, and resveratrol oligomers warrant further attention as antivirulence strategies against persistent UPEC infections.

Thermostable xylanase inhibits and disassembles Pseudomonas aeruginosa biofilms.

Pseudomonas aeruginosa biofilms are problematic and play a critical role in the persistence of chronic infections because of their ability to tolerate antimicrobial agents. In this study, various cell-wall degrading enzymes were investigated for their ability to inhibit biofilm formation of two P. aeruginosa strains, PAO1 and PA14. Xylanase markedly inhibited and detached P. aeruginosa biofilms without affecting planktonic growth. Xylanase treatment broke down extracellular polymeric substances and decreased the viscosity of P. aeruginosa strains. However, xylanase treatment did not change the production of pyochelin, pyocyanin, pyoverdine, the Pseudomonas quinolone signal, or rhamnolipid. In addition, the anti-biofilm activity of xylanase was thermally stable for > 100 days at 45°C. Also, xylanase showed anti-biofilm activity against one methicillin-resistance Staphylococcus aureus and two Escherichia coli strains.

Indole-associated predator-prey interactions between the nematode Caenorhabditis elegans and bacteria.

Indole is an intercellular and interkingdom signalling molecule found in diverse ecological niches. Caenorhabditis elegans is a bacterivorous nematode that lives in soil and compost environments and a useful model host for studies of host-microbe interactions. Although various bacteria and some plants produce large quantities of extracellular indole, little is known about the effects of indole, its derivatives, or of indole-producing bacteria on the behaviours of C. elegans or other animals. Here, they show that C. elegans senses and moves toward indole and several indole-producing bacteria, but avoids non-indole producing pathogenic bacteria. Furthermore, it was found indole-producing and non-indole-producing bacteria exert divergent effects on the egg-laying behaviour of C. elegans, and that various indole derivatives also modulate chemotaxis, egg-laying behaviour and the survival of C. elegans. In contrast, indole at high concentration can kill C. elegans, which in turn, has the ability to detoxify indole by oxidation and glucosylation. Transcriptional analysis showed indole markedly up-regulated the gene expressions of cytochrome P450s, UDP-glucuronosyltransferases and glutathione S-transferase, which well explained the modification of indole by C. elegans while indole down-regulated the expressions of collagen and F-box genes. Their findings suggest that indole and its derivatives are important signalling molecules during bacteria-nematode interactions.

Inhibitory effects of the essential oils α-longipinene and linalool on biofilm formation and hyphal growth of Candida albicans.

Candida albicans is one of the most common fungal pathogens, and causes systemic and invasive infections in humans. C. albicans biofilms are composed of yeast and hyphal and pseudohyphal elements, and the transition of yeast to the hyphal stage could be a virulence factor. In this study, diverse essential oils were initially investigated for anti-biofilm activity against C. albicans strains, and cascarilla bark oil and helichrysum oil and their components α-longipinene (a major constituent of both) and linalool were found to markedly inhibit biofilm formation without affecting planktonic cell growth. Moreover, α-longipinene and linalool were found to synergistically reduce biofilm formation. Notably, treatments with cascarilla bark oil, helichrysum oil, α-longipinene, or linalool clearly inhibited hyphal formation, and this appeared to be largely responsible for their anti-biofilm effect. Furthermore, the two essential oils, α-longipinene and linalool, reduced C. albicans virulence in Caenorhabditis elegans.

Streptomyces-derived actinomycin D inhibits biofilm formation by Staphylococcus aureus and its hemolytic activity.

Staphylococcus aureus is a versatile human pathogen that produces diverse virulence factors, and its biofilm cells are difficult to eradicate due to their inherent ability to tolerate antibiotics. The anti-biofilm activities of the spent media of 252 diverse endophytic microorganisms were investigated using three S. aureus strains. An attempt was made to identify anti-biofilm compounds in active spent media and to assess their anti-hemolytic activities and hydrophobicities in order to investigate action mechanisms. Unlike other antibiotics, actinomycin D (0.5 µg ml(-1)) from Streptomyces parvulus significantly inhibited biofilm formation by all three S. aureus strains. Actinomycin D inhibited slime production in S. aureus and it inhibited hemolysis by S. aureus and caused S. aureus cells to become less hydrophobic, thus supporting its anti-biofilm effect. In addition, surface coatings containing actinomycin D prevented S. aureus biofilm formation on glass surfaces. Given these results, FDA-approved actinomycin D warrants further attention as a potential antivirulence agent against S. aureus infections.

The multifaceted roles of the interspecies signalling molecule indole in Agrobacterium tumefaciens.

Bacteria utilize signal molecules to ensure their survival in environmental niches, and indole is an interspecies and interkingdom signalling molecule, which is widespread in the natural environment. In this study, we sought to identify novel roles of indole in soil-borne bacterium Agrobacterium tumefaciens. Agrobacterium tumefaciens was found not to synthesize indole and to degrade it rapidly. The addition of exogenous indole dose-dependently inhibited A. tumefaciens growth and decreased its motility. Surprisingly, indole markedly increased A. tumefaciens biofilm formation on polystyrene, glass and nylon membrane surfaces and enhanced its antibiotic tolerance. Transcriptional analysis showed that indole markedly up-regulated several biofilm-related (celA, cheA, exoR, phoB, flgE, fliR and motA), stress-related genes (clpB, dnaK, gsp, gyrB, marR and soxR) and efflux genes (emrA, norM, and Atu2551) in A. tumefaciens, which partially explained the increased biofilm formation and antibiotic tolerance. In contrast, the plant auxin indole-3-acetic acid did not affect biofilm formation, antibiotic tolerance or gene expression. Interestingly, indole was found to exhibit several similarities with antibiotics, as it inhibited the growth of non-indole-producing bacteria, whereas these bacteria countered its effects by rapidly degrading indole, and by enhancing biofilm formation and antibiotic tolerance.

Temperature-dependent control of Staphylococcus aureus biofilms and virulence by thermoresponsive oligo(N-vinylcaprolactam).

Bacterial biofilms are associated with persistent infections because they are highly tolerant of antimicrobial agents, and in the case of Staphylococcus aureus, which is a leading cause of nosocomial infections because of its resistance to diverse antibiotics, biofilm formation is a known mechanism of drug resistance. In the present study, we investigated the ability of thermoresponsive oligo (N-vinylcaprolactam) (OVCL) to control biofilm formation by and the virulence of S. aureus. One synthetic and four commercial OVCLs (MW ≤ 240,000) at 50 µg/mL were found to increase S. aureus biofilm formation 7-fold at 25 °C, but to markedly inhibit S. aureus biofilm formation at 37 °C. Confocal and scanning electron microscopy confirmed the temperature-dependent effect of OVCL on S. aureus biofilms. It was found that the addition of OVCL to S. aureus culture caused cells to become dramatically more hydrophilic at 37 °C, which partially supports the biofilm reduction. Also, transcriptional analysis showed that OVCL temperature-dependently regulated biofilm-related genes (aur, agrA, and icaA) in S. aureus. In addition, it was found surface coatings containing OVCL effectively controlled S. aureus biofilm formation on solid glass surfaces. Furthermore, OVCL inhibited the hemolysis of human red blood cells by S. aureus at 37 °C and attenuated S. aureus virulence in the nematode Caenorhabditis elegans. These results suggest that OVCL has potential use for controlling bacterial biofilm formation and virulence.

Resveratrol oligomers inhibit biofilm formation of Escherichia coli O157:H7 and Pseudomonas aeruginosa.

Biofilm formation is closely related to bacterial infection and is also a mechanism of antimicrobial resistance. Hence, the antibiofilm approach provides an alternative to an antibiotic strategy. In this study, the antibiofilm activities of resveratrol (1) and five of its oligomers, namely, ε-viniferin (2), suffruticosol A (3), suffruticosol B (4), vitisin A (5), and vitisin B (6), were investigated against enterohemorrhagic Escherichia coli O157:H7 and Pseudomonas aeruginosa PA14. Vitisin B (6), a stilbenoid tetramer, was found to inhibit biofilm formation by the two bacteria the most effectively and at 5 µg/mL inhibited E. coli O157:H7 biofilm formation by more than 90%.

'Should I stay or should I go?' Bacterial attachment vs biofilm formation on surface-modified membranes.

A number of techniques are used for testing the anti-biofouling activity of surfaces, yet the correlation between different results is often questionable. In this report, the correlation between initial bacterial deposition (fast tests, reported previously) and biofilm growth (much slower tests) was analyzed on a pristine and a surface-modified reverse osmosis membrane ESPA-1. The membrane was modified with grafted hydrophilic polymers bearing negatively charged, positively charged and zwitter-ionic moieties. Using three different bacterial strains it was found that there was no general correlation between the initial bacterial deposition rates and biofilm growth on surfaces, the reasons being different for each modified surface. For the negatively charged surface the slowest deposition due to the charge repulsion was eventually succeeded by the largest biofilm growth, probably due to secretion of extracellular polymeric substances (EPS) that mediated a strong attachment. For the positively charged surface, short-term charge attraction by quaternary amine groups led to the fastest deposition, but could be eventually overridden by their antimicrobial activity, resulting in non-consistent results where in some cases a lower biofilm formation rate was observed. The results indicate that initial deposition rates have to be used and interpreted with great care, when used for assessing the anti-biofouling activity of surfaces. However, for a weakly interacting 'low-fouling' zwitter-ionic surface, the positive correlation between initial cell deposition and biofilm growth, especially under flow, suggests that for this type of coating initial deposition tests may be fairly indicative of anti-biofouling potential.

Thermoresponsive oligomers reduce Escherichia coli O157:H7 biofouling and virulence.

Thermoresponsive polymers have potential biomedical applications for drug delivery and tissue engineering. Here, two thermoresponsive oligomers were synthesized, viz. oligo(N-isopropylacrylamide) (ONIPAM) and oligo(N-vinylcaprolactam) (OVCL), and their anti-biofouling abilities investigated against enterohemorrhagic E. coli O157:H7, which produces Shiga-like toxins and forms biofilms. Biofilm formation (biofouling) is closely related to E. coli O157:H7 infection and constitutes a major mechanism of antimicrobial resistance. The synthetic OVCL (MW 679) and three commercial OVCLs (up to MW 54,000) at 30 µg ml(-1) were found to inhibit biofouling by E. coli O157:H7 at 37 °C by more than 80% without adversely affecting bacterial growth. The anti-biofouling activity of ONIPAM was weaker than that of OVCL. However, at 25 °C, ONIPAM and OVCL did not affect E. coli O157:H7 biofouling. Transcriptional analysis showed that OVCL temperature-dependently downregulated curli genes in E. coli O157:H7, and this finding was in line with observed reductions in fimbriae production and biofouling. In addition, OVCL downregulated the Shiga-like toxin genes stx1 and stx2 in E. coli O157:H7 and attenuated its in vivo virulence in the nematode Caenorhabditis elegans. These results suggest that OVCL has potential use in antivirulence strategies against persistent E. coli O157:H7 infection.

Antibiofilm activity of lawsone against polymicrobial enterohemorrhagic Escherichia coli O157:H7 and Candida albicans by suppression of curli production and hyphal growth.

BACKGROUND: Most bacteria and fungi form biofilms that attach to living or abiotic surfaces. These biofilms diminish the efficacy of antimicrobial agents and contribute to chronic infections. Furthermore, multispecies biofilms composed of bacteria and fungi are often found at chronic infection sites. PURPOSE: In this study, lawsone (2­hydroxy-1,4-naphthoquinone) and its parent 1,4-naphthoquinone were studied for antimicrobial and antibiofilm activities against single-species and multispecies biofilms of enterohemorrhagic Escherichia coli O157:H7 (EHEC) and Candida albicans. METHODS: Biofilm formation assays, biofilm eradication assays, antimicrobial assays, live cell imaging microscopy, confocal laser scanning microscopy (CLSM), scanning electron microscopy (SEM), extracellular polymeric substances and indole production, cell surface hydrophilicity assay, cell motility, cell aggregation, hyphal growth, dual species biofilm formation, quantitative real-time reverse transcription polymerase chain reaction (qRT-PCR), and toxicity assays on plant seed germination and nematode model were utilized to investigate how lawsone affect biofilm development. RESULTS: Sub-inhibitory concentrations of lawsone (35 µg/ml) significantly inhibited single-and multispecies biofilm development. Lawsone reduced the production of curli and indole, and the swarming motility of EHEC, efficiently inhibited C. albicans cell aggregation and hyphal formation, and increased the cell surface hydrophilicity of C. albicans. Transcriptomic analysis showed that lawsone suppressed the expression of the curli-related genes csgA and csgB in EHEC, and the expression of several hypha- and biofilm-related genes (ALS3, ECE1, HWP1, and UME6) in C. albicans. In addition, lawsone up to 100 µg/ml was nontoxic to the nematode Caenorhabditis elegans and to the seed growth of Brassica rapa and Triticum aestivum. CONCLUSION: These results show that lawsone inhibits dual biofilm development and suggest that it might be useful for controlling bacterial or fungal infections and multispecies biofilms.

Antifungal, anti-biofilm, and anti-hyphal properties of N-substituted phthalimide derivatives against Candida species.

Candida species comprise a ubiquitous pathogenic fungal genus responsible for causing candidiasis. They are one of the primary causatives of several mucosal and systemic infections in humans and can survive in various environments. In this study, we investigated the antifungal, anti-biofilm, and anti-hyphal effects of six N-substituted phthalimides against three Candida species. Of the derivatives, N-butylphthalimide (NBP) was the most potent, with a minimum inhibitory concentration (MIC) of 100 µg/ml and which dose-dependently inhibited biofilm at sub-inhibitory concentrations (10-50 µg/ml) in both the fluconazole-resistant and fluconazole-sensitive Candida albicans and Candida parapsilosis. NBP also effectively inhibited biofilm formation in other pathogens including uropathogenic Escherichia coli, Staphylococcus epidermidis, Staphylococcus aureus, and Vibrio parahaemolyticus, along with the polymicrobial biofilms of S. epidermidis and C. albicans. NBP markedly inhibited the hyphal formation and cell aggregation of C. albicans and altered its colony morphology in a dose-dependent manner. Gene expression analysis showed that NBP significantly downregulated the expression of important hyphal- and biofilm-associated genes, i.e., ECE1, HWP1, and UME6, upon treatment. NBP also exhibited mild toxicity at concentrations ranging from 2 to 20 µg/ml in a nematode model. Therefore, this study suggests that NBP has anti-biofilm and antifungal potential against various Candida strains.

Antifungal and antibiofilm activities of chromones against nine Candida species.

IMPORTANCE: The persistence of Candida infections is due to its ability to form biofilms that enable it to resist antifungals and host immune systems. Hence, inhibitions of the biofilm formation and virulence characteristics of Candida sp. provide potential means of addressing these infections. Among various chromone derivatives tested, four chromone-3-carbonitriles showed antifungal, antibiofilm, and antivirulence activities against several Candida species. Their mode of action has been partially revealed, and their toxicity is reported here using nematode and plant models.

Indole-3-acetaldehyde from Rhodococcus sp. BFI 332 inhibits Escherichia coli O157:H7 biofilm formation.

Pathogenic biofilms have been associated with persistent infections due to their high resistance to antimicrobial agents. To identify nontoxic biofilm inhibitors for enterohemorrhagic Escherichia coli O157:H7, the spent media of a 4,104 Actinomycetes library was screened. The culture spent medium (1%, v/v) of plant pathogen Rhodococcus sp. BFI 332 markedly inhibited E. coli O157:H7 biofilm formation without affecting the growth of planktonic E. coli O157:H7 cells. Rhodococcus sp. BFI 332 produced significant amounts of indole-3-acetaldehyde and indole-3-acetic acid, and the former of which reduced E. coli O157:H7 biofilm formation. Global transcriptome analyses showed that indole-3-acetaldehyde most repressed two curli operons, csgBAC and csgDEFG, and induced tryptophanase (tnaAB) in E. coli O157:H7 biofilm cells. Electron microscopy showed that spent medium of Rhodococcus sp. BFI 332 and indole-3-acetaldehyde reduced curli production in E. coli O157:H7. The spent medium of Rhodococcus sp. BFI 332 also significantly reduced the biofilm formation of Staphylococcus aureus and Staphylococcus epidermidis. Overall, this study suggests that indole derivatives are present in the Actinomycetes strains and they can be used as biofilm inhibitors against pathogenic bacteria.

Antibiofilm activity of Streptomyces sp. BFI 230 and Kribbella sp. BFI 1562 against Pseudomonas aeruginosa.

Members of the actinomycetes family are a rich source of bioactive compounds including diverse antibiotics. This study sought to identify novel and non-toxic biofilm inhibitors from the actinomycetes library for reducing the biofilm formation of Pseudomonas aeruginosa PAO1. After the screening of 4104 actinomycetes strains, we found that the culture spent medium (1 %, v/v) of Streptomyces sp. BFI 230 and Kribbella sp. BFI 1562 inhibited P. aeruginosa biofilm formation by 90 % without affecting the growth of planktonic P. aeruginosa cells, while the spent media enhanced the swarming motility of P. aeruginosa. Global transcriptome analyses revealed that the spent medium of Streptomyces sp. BFI 230 induced expression of phenazine, pyoverdine, pyochelin synthesis genes, and iron uptake genes in P. aeruginosa. The addition of exogenous iron restored the biofilm formation and swarming motility of P. aeruginosa in the presence of the spent medium of Streptomyces sp. BFI 230, which suggests that the Streptomyces sp. BFI 230 strain interfered iron acquisition in P. aeruginosa. Experiments on solvent extraction, heat treatment, and proteinase K treatment suggested that hydrophilic compound(s), possibly extracellular peptides or proteins from Streptomyces sp. BFI 230 cause the biofilm reduction of P. aeruginosa. Together, this study indicates that actinomycetes strains have an ability to control the biofilm of P. aeruginosa.

Inhibition of Staphylococcus aureus Biofilm Formation and Virulence Factor Production by Petroselinic Acid and Other Unsaturated C18 Fatty Acids.

Staphylococcus aureus is a major human pathogen that secretes several toxins associated with the pathogenesis of sepsis and pneumonia. Its antibiotic resistance is notorious, and its biofilms play a critical role in antibiotic tolerance. We hypothesized fatty acids might inhibit S. aureus biofilm formation and the expressions of its virulence factors. Initially, the antibiofilm activities of 27 fatty acids against a methicillin-sensitive S. aureus strain were investigated. Of the fatty acids tested, three C18 unsaturated fatty acids, that is, petroselinic, vaccenic, and oleic acids at 100 µg/mL, inhibited S. aureus biofilm formation by more than 65% without affecting its planktonic cell growth (MICs were all > 400 µg/mL). Notably, petroselinic acid significantly inhibited biofilm formation of two methicillin-resistant S. aureus strains and two methicillin-sensitive S. aureus strains. In addition, petroselinic acid significantly suppressed the production of three virulence factors, namely, staphyloxanthin, lipase, and α-hemolysin. Transcriptional analysis showed that petroselinic acid repressed the gene expressions of quorum sensing regulator agrA, effector of quorum sensing RNAIII, α-hemolysin hla, nucleases nuc1 and nuc2, and the virulence regulator saeR. Furthermore, petroselinic acid dose-dependently inhibited S. aureus biofilm formation on abiotic surfaces and porcine skin. These findings suggest that fatty acids, particularly petroselinic acid, are potentially useful for controlling biofilm formation by S. aureus. IMPORTANCE Fatty acids with a long carbon chain have recently attracted attention because of their antibiofilm activities against microbes. Here, we report the antibiofilm activities of 27 fatty acids against S. aureus. Of the fatty acids tested, three C18 unsaturated fatty acids (petroselinic, vaccenic, and oleic acids) significantly inhibited biofilm formation by S. aureus. Furthermore, petroselinic acid inhibited the production of several virulence factors in S. aureus. The study also reveals that the action mechanism of petroselinic acid involves repression of quorum-sensing-related and virulence regulator genes. These findings show that natural and nontoxic petroselinic acid has potential use as a treatment for S. aureus infections, including infections by methicillin-resistant S. aureus strains, and in food processing facilities.