scholarly journals Evaluation of Changes Induced in the Probiotic Escherichia coli M17 Following Recurrent Exposure to Antimicrobials

2021 ◽  
pp. 158-167
Author(s):  
M. J. A. Mbarga ◽  
I. V. Podoprigora ◽  
E. G. Volina ◽  
A. V. Ermolaev ◽  
L. A. Smolyakova
Keyword(s):  
Escherichia Coli ◽  
Growth Rate ◽  
Silver Nanoparticles ◽  
Biofilm Formation ◽  
Fold Increase ◽  
Bacterial Attachment ◽  
Diffusion Method ◽  
Cross Resistance ◽  
Microdilution Method ◽  
Similar Work

Introduction: It is already well known that the exposure of certain bacteria, pathogenic or not, to antimicrobials is likely to increase their virulence and induce the development of direct or cross resistance to antimicrobials, but there is almost no information available regarding probiotics. Aim: To assess the changes induced in susceptibility to antibiotics, biofilm formation, growth rate and relative pathogenicity in the probiotic Escherichia coli M17 (EC-M17) after long exposure to antimicrobials namely ampicillin, kanamycin, cefazolin and silver nanoparticles (AgNPs). Methods: After determining the minimum inhibitory concentrations (MIC) and minimum bactericidal concentrations (MBC) of the 4 antimicrobials above-mentioned by the microdilution method, EC-M17 was exposed to increasing subinhibitory doses ranging from MIC/8 to MIC for 8 days. The susceptibility to antibiotics of the mutants obtained was assessed by the Kirby Bauer disc diffusion method, biofilm formation by the Congo red agar method and with crystal violet bacterial attachment assay, and relative pathogenicity was assessed using a Galleria melonella waxworm model. Results: Exposure to antimicrobials induces noticeable changes in EC-M17. The highest adaptation to antimicrobials was observed on AgNPs with 8-fold increase in MIC and 16-fold increase in MBC of AgNPs. EC-M17 exposed to ampicillin, kanamycin and silver nanoparticles became resistant to ampicillin, ceftazidime, ceftazidime/clavulanate and tetracycline while exposure to cefazolin induced a significant decrease in sensitivity to tetracycline and ampicillin and resistance to ceftazidime/clavulanate and ceftazidime. The strain exposed to ampicillin was the only one to produce more biofilm than the control strain and except the EC-M17 exposed to cefazolin, all other EC-M17 strains were more pathogenic on G. melonella model than the control. Conclusion: Data in this investigation suggest that repeated exposure of the probiotic EC-M17 to antimicrobials may induce changes in antimicrobials susceptibility, biofilm formation, growth rate, and relative pathogenicity. Therefore, as far as possible, the probiotic E. coli M17 should not be used in combination with antibiotics and further investigations are required to expand similar work on more probiotics in order to avoid resistance build-up which might be transmitted by horizontal transfer.

scholarly journals Prolonged Exposure to Antimicrobials Induces Changes in Susceptibility to Antibiotics, Biofilm Formation and Pathogenicity in Staphylococcus aureus

2021 ◽  
pp. 140-151
Author(s):  
Mbarga M. J. Arsene ◽  
Podoprigora I. Viktorovna ◽  
Volina E. Grigorievna ◽  
Anyutoulou K. L. Davares ◽  
Das M. Sergeevna ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Growth Rate ◽  
Biofilm Formation ◽  
Hypochlorous Acid ◽  
Prolonged Exposure ◽  
Galleria Mellonella ◽  
Bacterial Attachment ◽  
Diffusion Method ◽  
Frequent Exposure

Introduction: Frequent exposure to certain biocidal agents such as hypochlorous acid (HOCl), triclosan and benzalkonium chloride (BAC) has been reported to induce significant changes in Staphylococcus aureus. However, very few studies of this type have been conducted with conventional antimicrobials. Aim: The current investigation aimed to explore the phenotypic changes (susceptibility to antibiotics, biofilm formation and relative pathogenicity) that occur in S. aureus after recurrent exposure to antimicrobials. Methods: We compared the effects of long-term exposure to ampicillin, cefazoline, kanamycin and silver nanoparticles (AgNPs) on their susceptibility to antibiotics, biofilm formation, growth rate and pathogenicity in Staphylococcus aureus ATCC 6538. The minimum inhibitory concentrations (MIC) were determined using the microplate mircodilution method and the bacteria were exposed to increasing concentrations of each antimicrobial (MIC/2 to MIC) prepared in the BHIB for 8 days. The sensitivity of bacteria to antibiotics was assessed using the Kirby-Bauer disc diffusion method, the biofilm formation with crystal violet bacterial attachment assay and relative pathogenicity was assessed through a Galleria mellonella waxworm model. Results: The data in this investigation indicate that long-term exposure to antimicrobials may induce several changes in S. aureus. The exposure to ampicillin induced resistance to ceftazidime, tetracycline and ceftriaxone while the susceptibility to ceftazidime decreased in bacteria exposed to cefazolin and Kanamycin. Meanwhile, exposure to AgNPs induced some changes in susceptibility to trimethoprim and ceftazidime without causing resistance. Similarly, the strains exposed to ampicillin and kanamycin grew more rapidly and produced more biofilms than the control strains whereas the strains exposed to the AgNPs produced less biofilms. On G. melonella model, cefazolin seems to have attenuated the pathogenicity while the 3 other strains were more pathogenic than the controls. Conclusion: Long term exposure of S. aureus to antibiotics and AgNPs induces several changes in susceptibility to other antibiotics, growth rate, biofilm formation and pathogenicity; and these changes should be taken into account when choosing antibiotics for treatment of diseases caused by S. aureus.

scholarly journals Evaluation of bactericidal and anti-biofilm activities of silver nanoparticles against multidrug-resistant Gram-negative bacilli isolated from burn wound infections

2018 ◽  
Vol 14 (1) ◽  
pp. 72-77
Author(s):  
Issam Jumaa Nasser
Keyword(s):  
Escherichia Coli ◽  
Silver Nanoparticles ◽  
Biofilm Formation ◽  
Multidrug Resistant ◽  
Diffusion Method ◽  
Klebsiella Pneumonia ◽  
Wound Infections ◽  
Burn Wound ◽  
Gram Negative ◽  
Bactericidal Effects

Background: The emergence and spread of multidrug-resistant Gram-negative bacilliin burn wound infections related to biofilm formation, which lend to challenge in treatment with conventional antibiotics andprompting to search for novel antimicrobial agents to control the infections.Silver nanoparticles (AgNPs) have wide spectrum biological properties with different mechanisms of action and less toxicity towards human cells. Objective:The goal of this study was to evaluated the anti-bacterial and anti-biofilm activities of AgNPs alone and in combination with aminoglycoside (Amikacin) and β-lactam (Ampicillin) antibiotics against multidrug resistant Gram-negative bacilli (Pseudomonas aeruginosa, Escherichia coli, klebsiellapneumoniae) isolated from burn wound infections. Type of the study: Cross –sectional study. Methods: 70   clinical isolates of GNBtested for susceptibility tests by disk diffusion method against 10 antibiotics. The minimum inhibitory concentrations (MICs) of AgNPs and antibiotics were carried out according to the standard broth microdilution method, while synergistic interactions were evaluated by time kill-kinetic assays.  Calgary method was applied for anti-biofilm activity. Results:Pseudomonas aeruginosa represented the majority of GNBisolated from burn wound infections 34 (48.5 %)followed by Klebsiella pneumonia 21 (30 %) and Escherichia coli 15 (21.5 %). Silver nanoparticles showed remarkable antibacterial activity against GNB that isolated from burn wound infections with the MICs between 25- 75 µg/ml.  Aztreonam, amikacin and cefepime were the most effective antimicrobial drugagainst GNB isolates.Synergistic bactericidal effects were observed in two-drug combinations of AgNPswith broad-spectrum aminoglycoside (Amikacin) and β-lactam (Ampicillin) antibiotics against multidrug resistant GNB. In addition,AgNPsalone or in combination with ampicillin inhibited biofilm activity about 60 % – 75 % ofGNB,while combination of AgNPs withamikacin exhibited a powerful anti-biofilm activity and inhibition biofilm formation by 75% to 80%. Conclusion: The results confirmed a synergistic bactericidal effects and significant enhancing of anti-biofilm activity of AgNPs in combination with antibiotics (amikacin and ampicillin) against multidrug resistant GNB isolated from burn wound infections. These data suggest that AgNPs could beapplied as nanodrug for treatment of burn wound infections

scholarly journals Antibiofilm and antivirulence potential of silver nanoparticles against multidrug-resistant Acinetobacter baumannii

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Helal F. Hetta ◽  
Israa M. S. Al-Kadmy ◽  
Saba Saadoon Khazaal ◽  
Suhad Abbas ◽  
Ahmed Suhail ◽  
...  
Keyword(s):  
Silver Nanoparticles ◽  
Antibacterial Activity ◽  
Acinetobacter Baumannii ◽  
Biofilm Formation ◽  
Microtiter Plate ◽  
Diffusion Method ◽  
Resistance Pattern ◽  
Infection Model ◽  
The Impact

AbstractWe aimed to isolate Acinetobacter baumannii (A. baumannii) from wound infections, determine their resistance and virulence profile, and assess the impact of Silver nanoparticles (AgNPs) on the bacterial growth, virulence and biofilm-related gene expression. AgNPs were synthesized and characterized using TEM, XRD and FTIR spectroscopy. A. baumannii (n = 200) were isolated and identified. Resistance pattern was determined and virulence genes (afa/draBC, cnf1, cnf2, csgA, cvaC, fimH, fyuA, ibeA, iutA, kpsMT II, PAI, papC, PapG II, III, sfa/focDE and traT) were screened using PCR. Biofilm formation was evaluated using Microtiter plate method. Then, the antimicrobial activity of AgNPs was evaluated by the well-diffusion method, growth kinetics and MIC determination. Inhibition of biofilm formation and the ability to disperse biofilms in exposure to AgNPs were evaluated. The effect of AgNPs on the expression of virulence and biofilm-related genes (bap, OmpA, abaI, csuA/B, A1S_2091, A1S_1510, A1S_0690, A1S_0114) were estimated using QRT-PCR. In vitro infection model for analyzing the antibacterial activity of AgNPs was done using a co-culture infection model of A. baumannii with human fibroblast skin cell line HFF-1 or Vero cell lines. A. baumannii had high level of resistance to antibiotics. Most of the isolates harbored the fimH, afa/draBC, cnf1, csgA and cnf2, and the majority of A. baumannii produced strong biofilms. AgNPs inhibited the growth of A. baumannii efficiently with MIC ranging from 4 to 25 µg/ml. A. baumannii showed a reduced growth rate in the presence of AgNPs. The inhibitory activity and the anti-biofilm activity of AgNPs were more pronounced against the weak biofilm producers. Moreover, AgNPs decreased the expression of kpsMII , afa/draBC,bap, OmpA, and csuA/B genes. The in vitro infection model revealed a significant antibacterial activity of AgNPs against extracellular and intracellular A. baumannii. AgNPs highly interrupted bacterial multiplication and biofilm formation. AgNPs downregulated the transcription level of important virulence and biofilm-related genes. Our findings provide an additional step towards understanding the mechanisms by which sliver nanoparticles interfere with the microbial spread and persistence.

scholarly journals YdgG (TqsA) Controls Biofilm Formation in Escherichia coli K-12 through Autoinducer 2 Transport

2006 ◽  
Vol 188 (2) ◽  
pp. 587-598 ◽  
Author(s):  
Moshe Herzberg ◽  
Ian K. Kaye ◽  
Wolfgang Peti ◽  
Thomas K. Wood
Keyword(s):  
Escherichia Coli ◽  
Biofilm Formation ◽  
Acid Production ◽  
Polysialic Acid ◽  
Fold Increase ◽  
Uncharacterized Protein ◽  
Biofilm Thickness ◽  
Autoinducer 2 ◽  
Membrane Spanning ◽  
K 12

ABSTRACT YdgG is an uncharacterized protein that is induced in Escherichia coli biofilms. Here it is shown that deletion of ydgG decreased extracellular and increased intracellular concentrations of autoinducer 2 (AI-2); hence, YdgG enhances transport of AI-2. Consistent with this hypothesis, deletion of ydgG resulted in a 7,000-fold increase in biofilm thickness and 574-fold increase in biomass in flow cells. Also consistent with the hypothesis, deletion of ydgG increased cell motility by increasing transcription of flagellar genes (genes induced by AI-2). By expressing ydgG in trans, the wild-type phenotypes for extracellular AI-2 activity, motility, and biofilm formation were restored. YdgG is also predicted to be a membrane-spanning protein that is conserved in many bacteria, and it influences resistance to several antimicrobials, including crystal violet and streptomycin (this phenotype could also be complemented). Deletion of ydgG also caused 31% of the bacterial chromosome to be differentially expressed in biofilms, as expected, since AI-2 controls hundreds of genes. YdgG was found to negatively modulate expression of flagellum- and motility-related genes, as well as other known products essential for biofilm formation, including operons for type 1 fimbriae, autotransporter protein Ag43, curli production, colanic acid production, and production of polysaccharide adhesin. Eighty genes not previously related to biofilm formation were also identified, including those that encode transport proteins (yihN and yihP), polysialic acid production (gutM and gutQ), CP4-57 prophage functions (yfjR and alpA), methionine biosynthesis (metR), biotin and thiamine biosynthesis (bioF and thiDFH), anaerobic metabolism (focB, hyfACDR, ttdA, and fumB), and proteins with unknown function (ybfG, yceO, yjhQ, and yjbE); 10 of these genes were verified through mutation to decrease biofilm formation by 40% or more (yfjR, bioF, yccW, yjbE, yceO, ttdA, fumB, yjiP, gutQ, and yihR). Hence, it appears YdgG controls the transport of the quorum-sensing signal AI-2, and so we suggest the gene name tqsA.

scholarly journals Loss of Function inEscherichia coliExposed to Environmentally Relevant Concentrations of Benzalkonium Chloride

2018 ◽  
Vol 85 (4) ◽  
Author(s):  
Sarah Forbes ◽  
Nicola Morgan ◽  
Gavin J. Humphreys ◽  
Alejandro Amézquita ◽  
Hitesh Mistry ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Growth Rate ◽  
Biofilm Formation ◽  
Benzalkonium Chloride ◽  
Loss Of Function ◽  
Free Medium ◽  
Content Type ◽  
Expression Of Genes ◽  
Repeated Passage

ABSTRACTAssessing the risk of resistance associated with biocide exposure commonly involves exposing microorganisms to biocides at concentrations close to the MIC. With the aim of representing exposure to environmental biocide residues,Escherichia coliMG1655 was grown for 20 passages in the presence or absence of benzalkonium chloride (BAC) at 100 ng/liter and 1,000 ng/liter (0.0002% and 0.002% of the MIC, respectively). BAC susceptibility, planktonic growth rates, motility, and biofilm formation were assessed, and differentially expressed genes were determined via transcriptome sequencing. Planktonic growth rate and biofilm formation were significantly reduced (P< 0.001) following BAC adaptation, while BAC minimum bactericidal concentration increased 2-fold. Transcriptomic analysis identified 289 upregulated and 391 downregulated genes after long-term BAC adaptation compared with the respective control organism passaged in BAC-free medium. When the BAC-adapted bacterium was grown in BAC-free medium, 1,052 genes were upregulated and 753 were downregulated. Repeated passage solely in biocide-free medium resulted in 460 upregulated and 476 downregulated genes compared with unexposed bacteria. Long-term exposure to environmentally relevant BAC concentrations increased the expression of genes associated with efflux and reduced the expression of genes associated with outer-membrane porins, motility, and chemotaxis. This was manifested phenotypically through the loss of function (motility). Repeated passage in a BAC-free environment resulted in the upregulation of multiple respiration-associated genes, which was reflected by increased growth rate. In summary, repeated exposure ofE. colito BAC residues resulted in significant alterations in global gene expression that were associated with minor decreases in biocide susceptibility, reductions in growth rate and biofilm formation, and loss of motility.IMPORTANCEExposure to very low concentrations of biocides in the environment is a poorly understood risk factor for antimicrobial resistance. Repeated exposure to trace levels of the biocide benzalkonium chloride (BAC) resulted in loss of function (motility) and a general reduction in bacterial fitness but relatively minor decreases in susceptibility. These changes were accompanied by widespread changes in theEscherichia colitranscriptome. These results demonstrate the importance of including phenotypic characterization in studies designed to assess the risks of biocide exposure.

scholarly journals Association between Biofilm-Production and Antibiotic Resistance in Uropathogenic Escherichia coli (UPEC): An In Vitro Study

Diseases ◽  
2020 ◽  
Vol 8 (2) ◽  
pp. 17 ◽  
Author(s):  
Payam Behzadi ◽  
Edit Urbán ◽  
Márió Gajdács
Keyword(s):  
Escherichia Coli ◽  
Biofilm Formation ◽  
In Vitro Study ◽  
Point Of View ◽  
Diffusion Method ◽  
Medical Attention ◽  
Disk Diffusion Method ◽  
Biofilm Production ◽  
Tract Infections

Urinary tract infections (UTIs) are among the most common infections requiring medical attention worldwide. The production of biofilms is an important step in UTIs, not only from a mechanistic point of view, but this may also confer additional resistance, distinct from other aspects of multidrug resistance (MDR). A total of two hundred and fifty (n = 250) Escherichia coli isolates, originating from clean-catch urine samples, were included in this study. The isolates were classified into five groups: wild-type, ciprofloxacin-resistant, fosfomycin-resistant, trimethoprim-sulfamethoxazole-resistant and extended spectrum β-lactamase (ESBL)-producing strains. The bacterial specimens were cultured using eosine methylene blue agar and the colony morphology of isolates were recorded. Antimicrobial susceptibility testing was performed using the Kirby–Bauer disk diffusion method and E-tests. Biofilm-formation of the isolates was carried out with the crystal violet tube-adherence method. n = 76 isolates (30.4%) produced large colonies (>3 mm), mucoid variant colonies were produced in n = 135 cases (54.0%), and n = 119 (47.6%) were positive for biofilm formation. The agreement (i.e., predictive value) of mucoid variant colonies in regard to biofilm production in the tube-adherence assay was 0.881 overall. Significant variation was seen in the case of the group of ESBL-producers in the ratio of biofilm-producing isolates. The relationship between biofilm-production and other resistance determinants has been extensively studied. However, no definite conclusion can be reached from the currently available data.

scholarly journals Detection of biofilm among uropathogenic Escherichia coli and its correlation with antibiotic resistance pattern

2019 ◽  
Vol 11 (01) ◽  
pp. 017-022 ◽  
Author(s):  
Rashmi M. Karigoudar ◽  
Mahesh H. Karigoudar ◽  
Sanjay M. Wavare ◽  
Smita S. Mangalgi
Keyword(s):  
Escherichia Coli ◽  
Antibiotic Resistance ◽  
Biofilm Formation ◽  
Agar Plate ◽  
Diffusion Method ◽  
Resistance Pattern ◽  
Susceptibility Pattern ◽  
Sensitivity Testing ◽  
E Coli ◽  
Tract Infections

Abstract BACKGROUND: Escherichia coli accounts for 70%–95% of urinary tract infections (UTIs). UTI is a serious health problem with respect to antibiotic resistance and biofilms formation being the prime cause for the antibiotic resistance. Biofilm can restrict the diffusion of substances and binding of antimicrobials. In this context, the present study is aimed to perform in vitro detection of biofilm formation among E. coli strains isolated from urine and to correlate their susceptibility pattern with biofilm formation. MATERIALS AND METHODS: A total of 100 E. coli strains isolated from patients suffering from UTI were included in the study. The identification of E. coli was performed by colony morphology, Gram staining, and standard biochemical tests. The detection of biofilm was carried out by Congo Red Agar (CRA) method, tube method (TM), and tissue culture plate (TCP) method. Antimicrobial sensitivity testing was performed by Kirby–Bauer disc diffusion method on Muller–Hinton agar plate. RESULTS: Of the 100 E. coli strains, 49 (49%) and 51 (51%) were from catheterized and noncatheterized patients, respectively. Biofilm production was positive by CRA, TM, and TCP method were 49 (49%), 55 (55%), and 69 (69%), respectively. Biofilm producers showed maximum resistance to co-trimoxazole (73.9%), gentamicin (94.2%), and imipenem (11.6%) when compared to nonbiofilm producers. Significant association was seen between resistance to antibiotic and biofilm formation with a P = 0.01 (<0.05). CONCLUSION: A greater understanding of biofilm detection in E. coli will help in the development of newer and more effective treatment. The detection of biofilm formation and antibiotic susceptibility pattern helps in choosing the correct antibiotic therapy.

scholarly journals Distribution of genes encoding adhesins and biofilm formation capacity among Uropathogenic Escherichia coli isolates in relation to the antimicrobial resistance

2020 ◽  
Vol 20 (1) ◽  
pp. 238-247
Author(s):  
Ashraf A Kadry ◽  
Nour M Al-Kashef ◽  
Amira M El-Ganiny
Keyword(s):  
Escherichia Coli ◽  
Urinary Tract ◽  
Antimicrobial Resistance ◽  
Biofilm Formation ◽  
Critical Role ◽  
Uropathogenic Escherichia Coli ◽  
Diffusion Method ◽  
Esbl Production ◽  
Microtitre Plate Assay ◽  
Genes Encoding

Background: Escherichia coli is the most predominant pathogen involved in UTIs. Mainly, fimbrial surface appendages are impli- cated in adherence to urothelium besides non-fimbrial proteins. Objectives: To determine prevalence of genes encoding fimbrial and non-fimbrial proteins among Uropathogenic Escherichia coli (UPEC). Furthermore, distribution of these genes and biofilm formation capacity were investigated in relation to antimicrobial resistance. Methods: Antimicrobial susceptibility of 112 UPEC isolates was performed using disc diffusion method. ESBL production was confirmed by double disc synergy test. Genes encoding fimbrial and non-fimbrial proteins were detected using PCR and biofilm formation was investigated using microtitre plate assay. Results: UPEC isolates exhibited high resistance against doxycyclines (88.39 %), β-lactams (7.14-86.6%), sulphamethoxaz- ole–trimethoprim (53.75%) and fluoro-quinolones (50%). Fifty percent of tested isolates were ESBL producers. PapGII gene was statistically more prevalent among pyelonephritis isolates. SfaS, focG and picU genes were statistically associated with flu- oro-quinolone (FQs) sensitive isolates and Dr/afaBC gene was statistically associated with ESBL production. Moreover, non- MDR isolates produced sturdier biofilm. Conclusion: PapGII adhesin variant seems to have a critical role in colonization of upper urinary tract. There is a possible link between antimicrobial resistance and virulence being capable of affecting the distribution of some genes besides its negative impact on biofilm formation. Keywords: Urinary tract infection; Escherichia coli; UPEC; adhesin genes; ESBL; biofilm.  

scholarly journals Novel Roles for the AIDA Adhesin from Diarrheagenic Escherichia coli: Cell Aggregation and Biofilm Formation

2004 ◽  
Vol 186 (23) ◽  
pp. 8058-8065 ◽  
Author(s):  
Orla Sherlock ◽  
Mark A. Schembri ◽  
Andreas Reisner ◽  
Per Klemm
Keyword(s):  
Escherichia Coli ◽  
Biofilm Formation ◽  
Mammalian Cells ◽  
Gastrointestinal Disease ◽  
Cell Aggregation ◽  
Bacterial Attachment ◽  
E Coli ◽  
Abiotic Surfaces ◽  
Broad Variety ◽  
Self Association

ABSTRACT Diarrhea-causing Escherichia coli strains are responsible for numerous cases of gastrointestinal disease and constitute a serious health problem throughout the world. The ability to recognize and attach to host intestinal surfaces is an essential step in the pathogenesis of such strains. AIDA is a potent bacterial adhesin associated with some diarrheagenic E. coli strains. AIDA mediates bacterial attachment to a broad variety of human and other mammalian cells. It is a surface-displayed autotransporter protein and belongs to the selected group of bacterial glycoproteins; only the glycosylated form binds to mammalian cells. Here, we show that AIDA possesses self-association characteristics and can mediate autoaggregation of E. coli cells. We demonstrate that intercellular AIDA-AIDA interaction is responsible for bacterial autoaggregation. Interestingly, AIDA-expressing cells can interact with antigen 43 (Ag43)-expressing cells, which is indicative of an intercellular AIDA-Ag43 interaction. Additionally, AIDA expression dramatically enhances biofilm formation by E. coli on abiotic surfaces in flow chambers.

Rosemary and Tea Tree Essential Oils Exert Antibiofilm Activities In Vitro against Staphylococcus aureus and Escherichia coli

2020 ◽  
Vol 83 (7) ◽  
pp. 1261-1267
Author(s):  
TING LIU ◽  
JINGFAN WANG ◽  
XIAOMAN GONG ◽  
XIAOXIA WU ◽  
LIU LIU ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Staphylococcus Aureus ◽  
Essential Oil ◽  
Biofilm Formation ◽  
Gas Chromatography Mass Spectrometry ◽  
Tea Tree ◽  
E Coli ◽  
Microdilution Method ◽  
Broth Microdilution Method

ABSTRACT The purpose of the present study was to determine the bioactive compounds in rosemary essential oil (REO) and tea tree essential oil (TEO) and to investigate their antibacterial and antibiofilm activities against Staphylococcus aureus and Escherichia coli in vitro. The MIC and MBC assays were performed to assess the antibacterial activity of these two EOs against S. aureus and E. coli with the broth microdilution method. A crystal violet assay was used to ascertain the effects of EOs on the biofilm formation of the test strains, and a tetrazolium bromide (MTT) assay was used to measure the level of inactivation of mature biofilms by EOs. Gas chromatography–mass spectrometry revealed 15 compounds in REO and 27 compounds in TEO, representing 97.78 and 98.13% of the total EO, respectively. Eucalyptol and α-pinene were found in high concentrations in REO, and the two major compounds in TEO were 4-terpineol and terpinolene. The MICs of REO for the two S. aureus and E. coli test strains were both 0.5 mg/mL, and the MICs of TEO for the two strains were both 0.25 mg/mL. Therefore, these EOs can significantly inhibit the formation of biofilms and induced morphological biofilm changes, as verified by scanning electron microscopy. Both EOs had destructive effects on the mature biofilm of the two test strains. TEO was more inhibitory than REO for biofilm formation by the two test strains. HIGHLIGHTS

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