Biofilm Eradication Concentration Values Research Articles

Biofilm Formation and Phospholipase and Proteinase Production in Cryptococcus neoformans Clinical Isolates and Susceptibility towards Some Bioactive Natural Products.

Cryptococcosis is one of the most common fungal infections in immunocompromised patients, which is caused by Cryptococcus neoformans. However, relatively little is known about the virulence factors of C. neoformans and the incidence of antifungal drug resistance in C. neoformans is rapidly increasing. This study was undertaken to investigate the virulence factors in C. neoformans, thymol, curcumin, piperine, gallic acid, eugenol, and plumbagin for their potential antimicrobial activity against C. neoformans. The production of phospholipase and proteinase was detected using standard methods. Biofilm formation was determined using the microtiter plate method. The broth microdilution method was used to determine the antifungal activity. The antibiofilm activity was assessed using the safranin staining method. All isolates of C. neoformans produced biofilms with optical density values ranging from 0.16 to 0.89. A majority of C. neoformans isolates that were tested exhibited strong phospholipase (7/8) and proteinase (5/8) production. Plumbagin (with minimum inhibitory concentration values ranging from 4 to 16 μg/mL) showed the highest antifungal activity followed by thymol (with minimum biofilm inhibitory concentration values ranging from 8 to 64 μg/mL). In addition, plumbagin showed the highest antibiofilm activity with minimum biofilm inhibitory concentration and minimum biofilm eradication concentration values ranging from 4 to 16 μg/mL and 32 to 256 μg/mL, respectively. Plumbagin, compared to other natural products studied, was the most efficient in terms of antifungal and antibiofilm activities. Hence, plumbagin could be used in combination with antifungals for the development of new anticryptococcal drugs.

Antimicrobial, Antibiofilm, and Antioxidant Potentials of Four Halophytic Plants, Euphorbia chamaesyce, Bassia arabica, Fagonia mollis, and Haloxylon salicornicum, Growing in Qassim Region of Saudi Arabia: Phytochemical Profile and In Vitro and In Silico Bioactivity Investigations.

The current study aimed to investigate the phytochemical contents and antioxidant, antimicrobial, and antibiofilm activities of four halophytic plants, namely, Euphorbia chamaesyce, Bassia arabica, Fagonia mollis, and Haloxylon salicornicum, native to central Saudi Arabia. The alcoholic extract of E. chamaesyce was found to be the most potent in various bioactivities-based evaluations and rich in polyphenols and flavonoid secondary metabolites, with 68.0 mg/g and 39.23 mg/g gallic acid and quercetin equivalents, respectively. Among all plants' extracts, the alcoholic extract of E. chamaesyce had the highest DPPH scavenging and metal chelating antioxidant activities at 74.15 Trolox equivalents and 16.28 EDTA equivalents, respectively. The highest antimicrobial activity of E. chamaesyce extract was found to be against Shigella flexneri, with a mean zone of inhibition diameter of 18.1 ± 0.2 mm, whereas the minimum inhibitory concentration, minimum biocidal concentration, minimum biofilm inhibitory concentration, and minimum biofilm eradication concentration values were 12.5, 25, 25, and 50 mg/mL, respectively. The LC-ESI-MS/MS analysis of the E. chamaesyce extract showed the presence of six flavonoids and ten phenolic constituents. The in silico binding of the E. chamaesyce extract's constituents to Staphylococcus aureus tyrosyl-tRNA synthetase enzyme displayed -6.2 to -10.1 kcal/mol binding energy values, suggesting that these constituents can contribute to the antimicrobial properties of the plant extract, making it an essential medicinal ingredient. In conclusion, these results warrant further investigation to standardize the antimicrobial profiles of these plant extracts.

Antibiofilm Activity of Essential Fatty Acids Against Candida albicans from Vulvovaginal Candidiasis and Bloodstream Infections.

PurposeThe biofilm formation of Candida albicans is an important virulence factor as it can increase tolerance to conventional antifungal drugs and the host immune system. The study aimed to assess the effect of essential fatty acids (EFAs) against biofilm formation and mature biofilms of C. albicans strains, which were isolated from vulvovaginal candidiasis and candidemia.MethodsThe biofilm formation ability of C. albicans and antifungal activities of fluconazole were determined. Additionally, the effects of six EFAs [α-linolenic acid (ALA), eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), linoleic acid (LOA), γ-linolenic acid (GLA), and arachidonic acid (AA)] against C. albicans under planktonic and biofilm conditions were evaluated.Results94.1% of C. albicans exhibited biofilm formation capacity, and 98.5% of C. albicans were susceptible to fluconazole. The biofilms of C. albicans were highly resistant to fluconazole with minimum biofilm eradication concentration values ≥ 64 µg/mL. The EFAs attenuated biofilm formation in a dose-dependent manner, and GLA displayed a remarkable inhibitory activity against biofilm formation of C. albicans. In addition, EPA, DHA, and GLA at 0.1 mM could inhibit the biofilm formation of C. albicans without affecting the planktonic growth rate. Notably, EPA and AA at 1 mM had both inhibitory and eradication activities on C. albicans biofilms.ConclusionThis is the first study to directly compare different EFAs for their capacity to affect C. albicans biofilm formation as well as biofilm eradication. These results suggest EPA and AA could serve as potential new antifungal agents for the treatment of clinical infections caused by C. albicans biofilms.

The Antibacterial and Anti-biofilm Traits of the Novel BMAP-27-Melittin Conjugated Peptide Nanoparticle Against Streptococcus mutans: Clinical Isolates from Oral Cavity

Background & Objective: The spread and development of drug-resistant bacterial strains has prompted the hunt for novel antibacterial polypeptides undergoing conformational changes to confer rapid bactericidal effects. The aim of this study was to evaluate the effect of novel BMAP27-Melittin conjugated peptide- nanoparticle (NP) against Streptococcus mutans as the primary pathogen from subgingival plaques.Methods: Sixty subgingival plaque samples were collected, and 39 S. mutans isolates were identified. The BMAP27-Melittin conjugated peptide was purchased from GenScript Company, USA. Minimum Inhibitory Concentration (MIC), Minimum Bactericidal Concentration (MBC), Biofilm Inhibitory Concentration (BIC), and Biofilm Eradication Concentration (BEC) of BMAP27-Melittin-NP were calculated using the microtiter method.Results: Thirty-nine infected subjects were reported, including 24 males and 15 females (P=0.299). MIC, MBC, BIC, and BEC of BMAP27-Melittin–NP against S. mutans were 1.8, 2.9, 2.1, and 3.8μg/mL, respectively. The mean MBC, BEC, and BIC values were significantly lower among clinical isolates than S. mutans ATCC 35688 standard strain (P=0.032, 0.001, and 0.001, respectively).Conclusion: BMAP27-Melittin-NP demonstrated significant antibacterial and anti-biofilm effects against clinical isolates of S. mutans which can be considered a promising compound to prevent or treat dental caries and eradicate the oral infections.

The Antibacterial and Anti-biofilm Traits of the Novel BMAP-27-Melittin Conjugated Peptide Nanoparticle Against Streptococcus mutans: Clinical Isolates from Oral Cavity.

Background & Objective:The spread and development of drug-resistant bacterial strains has prompted the hunt for novel antibacterial polypeptides undergoing conformational changes to confer rapid bactericidal effects. The aim of this study was to evaluate the effect of novel BMAP27-Melittin conjugated peptide- nanoparticle (NP) against Streptococcus mutans as the primary pathogen from subgingival plaques. Methods:Sixty subgingival plaque samples were collected, and 39 S. mutans isolates were identified. The BMAP27-Melittin conjugated peptide was purchased from GenScript Company, USA. Minimum Inhibitory Concentration (MIC), Minimum Bactericidal Concentration (MBC), Biofilm Inhibitory Concentration (BIC), and Biofilm Eradication Concentration (BEC) of BMAP27-Melittin-NP were calculated using the microtiter method.Results:Thirty-nine infected subjects were reported, including 24 males and 15 females (P=0.299). MIC, MBC, BIC, and BEC of BMAP27-Melittin–NP against S. mutans were 1.8, 2.9, 2.1, and 3.8μg/mL, respectively. The mean MBC, BEC, and BIC values were significantly lower among clinical isolates than S. mutans ATCC 35688 standard strain (P=0.032, 0.001, and 0.001, respectively). Conclusion:BMAP27-Melittin-NP demonstrated significant antibacterial and anti-biofilm effects against clinical isolates of S. mutans which can be considered a promising compound to prevent or treat dental caries and eradicate the oral infections.

Synergistic Antibiofilm Efficacy of Thymol and Piperine in Combination with Three Aminoglycoside Antibiotics against Klebsiella pneumoniae Biofilms.

Background Thymol and piperine are two naturally occurring bioactive compounds with several pharmacological activities. In this study, their antibiofilm potential either alone or in combination with three aminoglycoside antibiotics was evaluated against a biofilm of Klebsiella pneumoniae. Methods Determination of antimicrobial susceptibility was performed using the broth microdilution method. Biofilm formation was evaluated by the microtiter plate method. Antibiofilm activity was determined using 3-(4, 5-dimethyl-2-thiazolyl)-2, 5-diphenyl-2H-tetrazolium-bromide (MTT) assay. The combination studies were performed by the checkerboard microdilution method. Results The minimum biofilm inhibitory concentration (MBIC) of streptomycin was reduced by 16- to 64-fold when used in combination with thymol, while the MBIC of kanamycin was reduced by 4-fold when combined with piperine. The minimum biofilm eradication concentration (MBEC) values of streptomycin, amikacin, and kanamycin were, respectively, 16- to 128-fold, 4- to 128-fold, and 8- to 256-fold higher than the planktonic minimum inhibitory concentration (MIC). Thymol combined with streptomycin or kanamycin showed synergic effects against the preformed biofilm with 16- to 64-fold reduction in the minimum biofilm eradication concentration values of each antibiotic in combination. Piperine acted also synergically with kanamycin with an 8- to 16-fold reduction in the minimum biofilm eradication concentration values of kanamycin in combination. Conclusion The association of thymol with antibiotics showed a strong synergistic effect both in the inhibition of biofilm formation and the destruction of the preformed biofilm of K. pneumoniae. This study suggests that a combination of thymol with streptomycin, amikacin, or kanamycin could be a promising alternative therapy to overcome the problem of K. pneumoniae biofilm-associated infections.

The Remarkable Antibiofilm Activity of the Sweet Tooth Mushroom, Hydnum repandum (Agaricomycetes), Displaying Synergetic Interactions with Antibiotics.

This study examines the antioxidant, anticancer, antimicrobial, and antibiofilm activities of Hydnum repandum, an edible and medicinal mushroom known as sweet tooth or wood hedgehog. H. repandum ethanolic extract had a high amount of myricetin and apigenin and displayed antiproliferative effects against the MCF-7 and HT-29 cell lines. Moreover, the extract displayed antimicrobial and antibiofilm activities against methicillin-resistant Staphylococcus aureus ATCC 43300, S. epidermidis ATCC 35984, Escherichia coli ATCC 25922, and Pseudomonas aeruginosa ATCC 27853. Synergetic interactions have been observed when antibiotics such as kanamycin and ampicillin are used together with mushroom extract. The minimum biofilm eradication concentration values were lower for H. repandum extract than for antibiotics. This study demonstrates that H. repandum has antibiofilm potential against biofilms and confronts antibiotic resistance.

Influence of Ag, Au and Pd noble metals doping on structural, optical and antimicrobial properties of zinc oxide and titanium dioxide nanomaterials

Oxide materials (ZnO, TiO2) doped with noble metals were synthesized using the combustion technique. The results of the addition of Ag, Au, and Pd up to a concentration of 2 mol% on the structural, optical, morphological and antimicrobial properties was considered. X-ray diffraction experiments revealed that the crystal structure of the host materials remained unaltered despite doping with noble metals. From the scanning electron microscopy results, it was evident that the doped nanoparticles aggregated in clusters of different sizes in the host matrix. The plasmonic effect was also observed in the absorbance spectra of the different doped materials. The obtained materials have shown promising antimicrobial features. All ZnO materials exhibited a high antimicrobial activity, with very low minimum inhibitory concentration values, against the planktonic growth of all tested Gram-positive and Gram-negative bacterial strains. All doped materials exhibited very good anti-biofilm activity, the lowest minimal biofilm eradication concentration values being registered for ZnO doped with Au and Pd toward Escherichia coli and for ZnO doped with Ag against Candida albicans. These results indicate the potential that these materials have for antimicrobial applications in the fields of biomedicine and environmental protection.

Antibacterial and anti-biofilm activities of cinnamaldehyde against S. epidermidis

The search for new antimicrobial drugs has been necessary due to the increased bacterial resistance to antibiotics currently in use, and natural products play an important role in this field. The aim of this study was to evaluate the in vitro effect of cinnamaldehyde on S. epidermidis strains, biofilm set-up prevention, as well as its effect on pre-established biofilms. The minimum inhibitory concentration (MIC) ranged from 300 to 500 μg/mL, and the minimum bactericidal concentration (MBC) from 400 to 600 μg/mL. The biofilm inhibitory concentration and biofilm eradication concentration values were four-fold (clinical isolate) and eight-fold (ATCC strain) greater than the concentration required to inhibit planktonic growth. Sub-inhibitory concentrations of cinnamaldehyde attenuated biofilm formation of S. epidermidis strains on polystyrene microtiter plates. The combination of cinnamaldehyde and linezolid was able to inhibit S. epidermidis with a bactericidal effect. Further investigation of the mechanism of action of cinnamaldehyde revealed its effect on the cell membrane permeability, and confocal laser scanning microscopy (CLSM) images illustrated the impact of cinnamaldehyde in the detachment and killing of existing biofilms. Thereby, our data confirmed the ability of cinnamaldehyde to reduce bacterial planktonic growth of S. epidermidis, inhibiting biofilm formation and eradicating pre-formed biofilm.

Formulation Optimization of Chitosan-Stabilized Silver Nanoparticles Using In Vitro Antimicrobial Assay

Antimicrobial resistance at the infected site is a serious medical issue that increases patient morbidity and mortality. Silver has antibacterial activity associated with some dose-dependent toxicity. Silver nanoparticles, due to larger surface area, have antibacterial properties, which make them useful in the treatment of infections. Chitosan-stabilized silver nanoparticles (CH-AgNP) were formulated and evaluated for minimal inhibitory concentration and minimal bactericidal concentration testing against Staphylococcus aureus ATCC 29213, S aureus ATCC 25923, Pseudomonas aeruginosa ATCC 27853, Escherichia coli ATCC 25922, and 20 methicillin-resistant S aureus isolates. Minimum biofilm eradication concentration study was used to evaluate the biofilm reduction, and in vitro antimicrobial checkerboard assays were performed. The effective optimum ratio of AgNP:chitosan solution was 1:4. Minimal inhibitory concentration and minimal bactericidal concentration ranges of CH-AgNP were 4 to 14 times lower compared to AgNP alone against methicillin-resistant S aureus isolates. Minimum biofilm eradication concentration values of CH-AgNP for ATCC PA-01, P aeruginosa isolate 1, and P aeruginosa isolate 2 were found to be >84.59 μg/mL, 42.29 μg/mL, and 21.15 μg/mL, respectively. Thus, CH-AgNP is a potential formulation for wound treatment and management of infected sites associated with antimicrobial resistance.

The specific effect of gallic acid on Escherichia coli biofilm formation by regulating pgaABCD genes expression.

Escherichia coli (E. coli) is associated with an array of health-threatening contaminations, some of which are related to biofilm states. The pgaABCD-encoded poly-beta-1,6-N-acetyl-D-glucosamine (PGA) polymer plays an important role in biofilm formation. This study was conducted to determine the inhibitory effect of gallic acid (GA) against E. coli biofilm formation. Minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) values of GA against planktonic E. coli were 0.5 and 4mg/mL, and minimal biofilm inhibitory concentration and minimal biofilm eradication concentration values of GA against E. coli in biofilms were 2 and 8mg/mL, respectively. Quantitative crystal violet staining of biofilms and ESEM images clearly indicate that GA effectively, dose-dependently inhibited biofilm formation. CFU counting and confocal laser scanning microscopy measurements showed that GA significantly reduced viable bacteria in the biofilm. The contents of polysaccharide slime, protein, and DNA in the E. coli biofilm also decreased. qRT-PCR data showed that at the sub-MIC level of GA (0.25mg/mL) and expression of pgaABC genes was downregulated, while pgaD gene expression was upregulated. The sub-MBC level of GA (2mg/mL) significantly suppressed the pgaABCD genes. Our results altogether demonstrate that GA inhibited viable bacteria and E. coli biofilm formation, marking a novel approach to the prevention and treatment of biofilm-related infections in the food industry.

In Vitro and In Vivo Efficacy of an LpxC Inhibitor, CHIR-090, Alone or Combined with Colistin against Pseudomonas aeruginosa Biofilm.

With the rapid spread of antimicrobial resistance in Gram-negative pathogens, biofilm-associated infections are increasingly harder to treat and combination therapy with colistin has become one of the most efficient therapeutic strategies. Our study aimed to evaluate the potential for the synergy of colistin combined with CHIR-090, a potent LpxC inhibitor, against in vitro and in vivoPseudomonas aeruginosa biofilms. Four P. aeruginosa isolates with various colistin susceptibilities were chosen for evaluation. The tested isolates of P. aeruginosa exhibited MIC values ranging from 1 to 64 and 0.0625 to 0.5 μg/ml for colistin and CHIR-090, respectively. Against 24-h static biofilms, minimum biofilm eradication concentration values ranged from 256 to 512 and 8 to >128 μg/ml for colistin and CHIR-090, respectively. Interestingly, subinhibitory concentrations of CHIR-090 contributed to the eradication of subpopulations of P. aeruginosa with the highest colistin MIC values. The combination of colistin and CHIR-090 at subinhibitory concentrations demonstrated synergistic activity both in vivo and in vitro and prevented the formation of colistin-tolerant subpopulations in in vitro biofilms. In summary, our study highlights the in vivo and in vitro synergistic activity of the colistin and CHIR-090 combination against both colistin-susceptible and -nonsusceptible P. aeruginosa biofilms. Further studies are warranted to investigate the clinical relevance of the combination of these two antimicrobials and outline the underlying mechanism for their synergistic action.

Coagulase-negative staphylococci: pathogenesis, occurrence of antibiotic resistance genes and in vitro effects of antimicrobial agents on biofilm-growing bacteria.

Coagulase-negative staphylococci (CoNS) are opportunistic pathogens that particularly cause infections in patients with implanted medical devices. The present research was performed to study the virulence potential of 53 clinical isolates of Staphylococcus capitis, Staphylococcus auricularis, Staphylococcus lugdunensis, Staphylococcus simulans, Staphylococcus cohnii and Staphylococcus caprae. All clinical strains were clonally unrelated. Isolates carried genes encoding resistance to β-lactam (mecA) (15 %), aminoglycoside [aac(6')/aph(2″)(11 %), aph (3')-IIIa (15 %), ant(4')-Ia (19 %)] and macrolide, lincosamide and streptogramin B (MLSB) [erm(A) (4 %), erm(B) (13 %), erm(C) (41 %), msr(A) (11 %)] antibiotics. CoNS isolates (64 %) were able to form biofilms. Confocal laser scanning microscopy revealed that these biofilms formed a three-dimensional structure composed mainly of living cells. All biofilm-positive strains carried the ica operon. In vitro studies demonstrated that a combination treatment with tigecycline and rifampicin was more effective against biofilms than one with ciprofloxacin and rifampicin. The minimum biofilm eradication concentration values were 0.062-0.5 µg ml-1 for tigecycline/rifampicin and 0.250-2 µg ml-1 for ciprofloxacin/rifampicin. All CoNS strains adhered to the human epithelial cell line HeLa, and more than half of the isolates were able to invade the HeLa cells, although most invaded relatively poorly. The virulence of CoNS is also attributed to their cytotoxic effects on HeLa cells. Incubation of HeLa cells with culture supernatant of the CoNS isolates resulted in cell death. The results indicate that the pathogenicity of S. capitis, S. auricularis, S. lugdunensis, S. cohnii and S. caprae is multi-factorial, involving the ability of these bacteria to adhere to human epithelial cells, form biofilms and invade and destroy human cells.

Biofilm formation of Francisella noatunensis subsp. orientalis

Francisella noatunensis subsp. orientalis (Fno) is an emergent fish pathogen in both marine and fresh water environments. The bacterium is suspected to persist in the environment even without the presence of a suitable fish host. In the present study, the influence of different abiotic factors such as salinity and temperature were used to study the biofilm formation of different isolates of Fno including intracellular growth loci C (iglC) and pathogenicity determinant protein A (pdpA) knockout strains. Finally, we compared the susceptibility of planktonic and biofilm to three disinfectants used in the aquaculture and ornamental fish industry, namely Virkon®, bleach and hydrogen peroxide. The data indicates that Fno is capable of producing biofilms within 24h where both salinity as well as temperature plays a role in the growth and biofilm formation of Fno. Mutations in the iglC or pdpA, both known virulence factors, do not appear to affect the capacity of Fno to produce biofilms, and the minimum inhibitory concentration, and minimum biocidal concentration for the three disinfectants were lower than the minimum biofilm eradication concentration values. This information needs to be taken into account if trying to eradicate the pathogen from aquaculture facilities or aquariums.

Antimicrobial activity of some essential oils against oral multidrug–resistant Enterococcus faecalis in both planktonic and biofilm state

To evaluate some essential oils in treatment of intractable oral infections, principally caused by biofilm of multidrug-resistant Enterococcus faecalis (E. faecalis), such as persistent endodontic infections in which their treatment exhibits a real challenge for dentists. Ten chemically analyzed essential oils by gas chromatography-mass spectrometry were evaluated for antimicrobial activity against sensitive and resistant clinical strains of E. faecalis in both planktonic and biofilm state using two methods, disk diffusion and broth micro-dilution. Studied essential oils showed a good antimicrobial activity and high ability in E. faecalis biofilm eradication, whether for sensitive or multidrug-resistant strains, especially those of Origanum glandulosum and Thymbra capitata with interesting minimum inhibitory concentration, biofilm inhibitory concentration, and biofilm eradication concentration values which doesn't exceed 0.063%, 0.75%, and 1.5%, respectively. Findings of this study indicate that essential oils extracted from aromatic plants can be used in treatment of intractable oral infections, especially caused by biofilm of multidrug-resistant E. faecalis.

Listeria monocytogenesandSalmonella entericaEnteritidis Biofilms Susceptibility to Different Disinfectants and Stress-Response and Virulence Gene Expression of Surviving Cells

Disinfection of food contact surfaces is a challenging task, aggravated by bacteria's capacity to survive and/or resist antimicrobials by means of mechanisms not yet completely understood. This work evaluated the susceptibility of Listeria monocytogenes and Salmonella enterica biofilms to four disinfectants, and analyzed how those chemical agents influenced stress-response and virulence genes expression by surviving cells. Three strains of each bacterial species mentioned were used, and their biofilms were treated with sodium hypochlorite, benzalkonium chloride, hydrogen peroxide, and triclosan using the Calgary Biofilm Device. Expression of L. monocytogenes and S. enterica stress-response genes cplC and ropS, and virulence genes prfA and avrA, respectively, was analyzed through quantitative real-time polymerase chain reaction. Results showed sodium hypochlorite to have the lowest minimum biofilm eradication concentration values (3.125 μg/ml), whereas triclosan had the worst performance since no S. enterica biofilm eradication was achieved even at the maximum concentration used (4,000 μg/ml). L. monocytogenes stress-response gene and S. enterica virulence gene were significantly upregulated in surviving cells compared with controls. In general, this work points out sodium hypochlorite as the most effective disinfectant against biofilms of both species used, and L. monocytogenes biofilms to be more susceptible to disinfection than S. enterica biofilms. Moreover, it was found that disinfection surviving biofilm cells seem to develop a stress response and/or become more virulent, which may compromise food safety and potentiate public health risk.

The assessment of the antibacterial and antifungal activities of aspirin, EDTA and aspirin-EDTA combination and their effectiveness as antibiofilm agents

To evaluate the antimicrobial activities of aspirin, EDTA and an aspirin-EDTA (A-EDTA) combination against Pseudomonas aeruginosa, Escherichia coli and Candida albicans in planktonic and biofilm cultures. Minimal inhibitory concentrations (MIC) and minimal biocidal concentrations (MBC) were determined using twofold broth microdilution and viable counting methods, respectively. Aspirin's recorded MIC values ranged from 1.2 to 2.7 mg ml(-1). Checkerboard assay demonstrated a synergism in antimicrobial activity upon combination. Aspirin's minimal biofilm eradication concentration values (MBEC) against the established biofilms ranged between 1.35 and 3.83 mg ml(-1). A complete eradication of bacterial biofilms was achieved after a 4-h treatment with the A-EDTA combination. Both aspirin and EDTA possess broad-spectrum antimicrobial activity for both planktonic and biofilm cultures. Aspirin used at the MBEC for 24 h was successful in eradicating P. aeruginosa, E. coli and C. albicans biofilms established on abiotic surfaces. Moreover, the exposure to the A-EDTA combination (4 h) effected complete bacterial biofilm eradication. There is a continuous need for the discovery of new antimicrobial agents. Aspirin and EDTA are 'nonantibiotic drugs', the combination of which can be used successfully to treat and eradicate biofilms established on abiotic surfaces.

Biofilm Formation and Biocides Sensitivity of Pseudomonas marginalis Isolated from a Maple Sap Collection System

The susceptibility of planktonic and biofilm cells of Pseudomonas marginalis toward four commonly used biocides at different temperatures (15 and 30°C) and biofilm growth times (24 and 48 h) was assessed. Using the MBEC biofilm device, biofilm production in maple sap was shown to be highly reproducible for each set of conditions tested. Biofilm formation was influenced by growth temperature and time. A temperature of 15°C and incubation time of 24 h yielded fewer CFU per peg and showed fewer adhered cells and typical biofilm structures, based on scanning electron microscopy observations as compared with other conditions. Minimal biofilm eradication concentration values for P. marginalis were significantly greater (P < 0.001) than were MBCs for planktonic cells and for every biocide tested, with the exception of minimal biofilm eradication concentration values for peracetic acid at 15°C and 24 h. Sodium hypochlorite and peracetic acid sanitizers were able to eliminate P. marginalis biofilms at lower concentrations as compared with hydrogen peroxide– and quaternary ammonium– based sanitizers (P < 0.001). According to the results obtained, sodium hypochlorite and peracetic acid sanitizers would be more appropriate for maple sap collection system sanitation.