Growth Of Planktonic Bacteria Research Articles

Mechanisms of action of berberine hydrochloride in planktonic cells and biofilms of Pseudomonas aeruginosa

The increasing prevalence of extensively drug- and pan-drug-resistant Pseudomonas aeruginosa is a major concern for global public health. Therefore, it is crucial to develop novel antimicrobials that specifically target P. aeruginosa and its biofilms. In the present study, we determined that berberine hydrochloride inhibited the growth of planktonic bacteria as well as prevented the formation of biofilms. Moreover, we observed downregulation in the expression of pslA and pelA biofilm-related genes. Compared with existing antibiotics, berberine hydrochloride exhibits multiple modes of action against P. aeruginosa. Our findings suggest that berberine hydrochloride exerts its antimicrobial effects by damaging bacterial cell membranes, generating reactive oxygen species (ROS), and reducing intracellular adenosine triphosphate (ATP) levels. Furthermore, berberine hydrochloride showed minimal cytotoxicity and reduced susceptibility to drug resistance. In a mouse model of peritonitis, it significantly inhibited the growth of P. aeruginosa and exhibited a strong bacteriostatic action. In conclusion, berberine hydrochloride is a safe and effective antibacterial agent that inhibits the growth of P. aeruginosa.

Polydopamine Nanocarriers with Cascade-Activated Nitric Oxide Release Combined Photothermal Activity for the Therapy of Drug-Resistant Bacterial Infections.

Antibiotic abuse leads to increased bacterial resistance, and the surviving planktonic bacteria aggregate and secrete extracellular polymers to form biofilms. Conventional antibacterial agents find it difficult to penetrate the biofilm, remove the bacteria wrapped in it, and produce an excellent therapeutic effect. In this study, a dual pH- and NIR-responsive nanocomposite (A-Ca@PDA) was developed to remove drug-resistant bacteria through a cascade of catalytic nitric oxide (NO) release and photothermal clearance. NO can melt in the outer package of the biofilm, facilitating the nanocomposites to have better permeability. Thermal therapy further inhibits the growth of planktonic bacteria. The locally generated high temperature and the burst release of NO together aggravate the biofilm collapse and bacterial death after NIR irradiation. The nanocomposites achieved a remarkable photothermal conversion efficiency of 47.5%, thereby exhibiting significant advancements in energy conversion. The nanocomposites exhibited remarkable efficacy in inhibiting multidrug-resistant (MDR) Escherichia coli and MDR Staphylococcus aureus, thus achieving an inhibition rate of >90%. Moreover, these nanocomposites significantly improved the wound-healing process in the MDR S. aureus-infected mice. Thus, this novel nanocomposite offers a novel strategy to combat drug-resistant bacterial infections.

Comprehensive Study of Components and Antimicrobial Properties of Essential Oil Extracted from Carum carvi L. Seeds.

Carum carvi L. belongs to the Apiaceae family and is widely used as a vegetable, food spice, preservative, and herbal medicine. This study investigated the impact of essential oil extracted from Carum carvi L. seeds (CEO) on methicillin-resistant Staphylococcus aureus (MRSA) and its possible action mechanism. The dominant chemical components of CEO determined by GC-MS were carvone and limonene. It was observed that CEO had a considerable inhibitory effect against the growth of planktonic bacteria and biofilm in MRSA cells. Untargeted metabolomics based on GC-Q-TOF-MS was used to analyze the possible mechanism of the interaction of MRSA with CEO. It was determined that there were 63 different metabolites based on fold change values greater than 1.5 or less than 1.5, p < 0.05, VIP > 1, which demonstrated amino acid metabolism in MRSA was significantly affected by CEO. In conclusion, CEO has a potent antimicrobial property and has promising potential for use in food and drugs.

Cobalt phosphide nanowires as efficient near-infrared light-driven antibacterial agents with high stability and cytocompatibility

Rapid emergence of antibiotic-resistant bacteria has brought huge threat to global healthcare systems. Alternative strategies are urgently needed to fight against these superbugs. In this study, we synthesized a series of cobalt phosphide nanoarchitectures and characterized their physicochemical properties as well as their antibacterial activities. We found that all nanomaterials showed an impressive photothermal property as indicated by their strong near-infrared (NIR) absorption capacity. In particular, 1D-CoP nanowires exhibited the optimal photothermal efficiency due to their higher aspect ratio. Under NIR light illumination, the temperature of the 1D-CoP nanowires suspension was increased by 45.4 °C within 20 min. In contrast, the temperatures of 2D-CoP nanoplates and 3D-CoP nanocubes were increased by 25.5 °C and 26.9 °C, respectively. The growth of planktonic bacteria can be effectively inhibited by 99% within 30 min under NIR irradiation with the presence of 1D-CoP nanowires in suspension. In comparison, up to 60% of the bacteria could be killed when treated with 2D-CoP nanoplates and 3D-CoP nanocubes. Moreover, all nanomaterials displayed high cytocompatibility. This work emphasizes that the anisotropy plays an important role in governing the photothermal properties of NIR-driven materials. Furthermore, the application of CoP nanowires is a promising strategy to treat antibiotic-resistant bacteria.

Overcoming reduced antibiotic susceptibility in intracellular Salmonella enterica serovar Typhimurium using AR-12.

Host-directed therapies (HDTs) could enhance the activity of traditional antibiotics. AR-12 is a promising HDT against intracellular pathogens including Salmonella enterica serovar Typhimurium, and has been shown to act through modulation of autophagy and the Akt kinase pathway. Since AR-12 does not inhibit the growth of planktonic bacteria but only works in conjunction with the infected host-cell, we hypothesized that AR-12 could enhance the activity of antibiotics in less-susceptible strains in the intracellular host environment. We found that repetitive passaging of S. typhimurium in macrophages in the absence of antibiotics led to a 4-fold reduction in their intracellular susceptibility to streptomycin (STR), but had no effect on the bacteria's sensitivity to AR-12. Moreover, when the host-passaged strains were treated with a combined therapy of AR-12 and STR, there was a significant reduction of intracellular bacterial burden compared to STR monotherapy. Additionally, co-treatment of macrophages infected with multi-drug resistant S. typhimurium with AR-12 and STR or ampicillin showed enhanced clearance of the intracellular bacteria. The drug combination did not elicit this effect on planktonic bacteria. Overall, AR-12 enhanced the clearance of less susceptible S. typhimurium in an intracellular environment.

Effects of Cigarette Smoke Condensate on Growth and Biofilm Formation by Mycobacterium tuberculosis.

Materials and Methods The planktonic and biofilm-forming cultures were prepared in Middlebrook 7H9 and Sauton broth media, respectively, using Mtb strain, H37Rv. The effects of CSC at concentrations of 0.05-3.12 mg/L on growth, biofilm formation and structure were evaluated using microplate Alamar Blue assay, spectrophotometric procedure and scanning electron microscopy (SEM), respectively. Involvement of reactive oxygen species in CSC-mediated biofilm formation was investigated by including catalase in biofilm-forming cultures. Results CSC did not affect the growth of planktonic bacteria, but rather led to a statistically significant increase in biofilm formation at concentrations of 0.4-3.12 mg/L, as well as in the viability of biofilm-forming bacteria at CSC concentrations of 0.2-1.56 mg/L. SEM confirmed an agglomerated biofilm matrix and irregular bacterial morphology in CSC-treated biofilms. Inclusion of catalase caused significant attenuation of CSC-mediated augmentation of biofilm formation by Mtb, implying involvement of oxidative stress. These findings demonstrate that exposure of Mtb to CSC resulted in increased biofilm formation that appeared to be mediated, at least in part, by oxidative stress, while no effect on planktonic cultures was observed. Conclusion Smoking-related augmentation of biofilm formation by Mtb may contribute to persistence of the pathogen, predisposing to disease reactivation and counteracting the efficacy of antimicrobial chemotherapy.

Chemical composition and biological evaluation of essential oils from some Moroccan plants

&lt;p class="Mabstract"&gt;This study describes the chemical composition and biological activities of essential oils of the Moroccan plants &lt;em&gt;Thymbra capitata&lt;/em&gt; (L.) Cav. and &lt;em&gt;Origanum elongatum&lt;/em&gt; (Bonnet) Emb. &amp;amp; Maire on biofilms of &lt;em&gt;Staphylococcus aureus&lt;/em&gt; strains. The qualitative and quantitative composition of the two essential oils was analyzed by gas chromatography and gas chromatography-mass spectrometry. The Minimum Inhibitory Concentration was determined by the broth microdilution method. The results showed that essential oils of &lt;em&gt;Thymbra capitata&lt;/em&gt; and &lt;em&gt;Origanum elongatum&lt;/em&gt; inhibit biofilm formation in biofilm inhibitory concentrations (0.5 and 2% v/v) and eradicate biofilm at biofilm eradication concentrations (1 and&amp;gt; 4% v/v), specific to each essential oil. Values were twofold or fourfold higher than the concentration required to inhibit or eradicate planktonic bacteria growth. The use of essential oils of &lt;em&gt;Thymbra capitata&lt;/em&gt; and &lt;em&gt;Origanum elongatum&lt;/em&gt; as natural antimicrobial agents may effectively inhibit the growth of biofilms of medical relevance. Results indicated that essential oils of &lt;em&gt;Thymbra capitata&lt;/em&gt; and &lt;em&gt;Origanum elongatum&lt;/em&gt; might be a potential alternative against Staphylococcus resistant strains.&lt;/p&gt;

Potential Application of Protamine for Antimicrobial Biomaterials in Bone Tissue Engineering.

Bacterial infection of biomaterials is a serious problem in the field of medical devices. It is urgently necessary to develop new biomaterials with bactericidal activity. Antimicrobial peptides and proteins (AMPs), alternative antibacterial agents, are expected to overcome the bacterial resistance. The aim of this study was to develop a new intelligent material in bone tissue engineering based on protamine-loaded hydroxyapatite (protamine/HAp) that uses AMPs rather than antibiotics. It was found that the adsorption of protamine to HAp followed the Langmuir adsorption model and was due to electrostatic and/or hydrophobic interactions. In vitro bacterial adhesion and growth on protamine/HAp was inhibited in a protamine dose-dependent manner. Adherent bacteria exhibited an aberrant morphology for high dosages of protamine/HAp, resulting in the formation of large aggregates and disintegration of the membrane. The released protamine from protamine/HAp also prevented the growth of planktonic bacteria in vitro. However, a high dosage of protamine from powders at loading concentrations over 1000 μg·mL−1 induced a cytotoxic effect in vitro, although those exhibited no apparent cytotoxicity in vivo. These data revealed that protamine/HAp (less than 1000 μg·mL−1) had both antimicrobial activity and biocompatibility and can be applied for bone substitutes in orthopedic fields.

Synthetic anti-endotoxin peptides interfere with Gram-positive and Gram-negative bacteria, their adhesion and biofilm formation on titanium.

Implant-associated infections arise from the formation of bacterial biofilms, which are difficult to be treated with conventional antibiotics. Therefore, there is a need for new implant functionalizations, which inhibit biofilm formation. The aim of the present study was to characterize the effect of synthetic peptides to assess their applicability for this purpose. Two synthetic anti-endotoxin peptides, Pep19-2.5 and Pep19-4LF (Aspidasept I and II) were tested against both Gram-positive (Staphylococcus aureus and Streptococcus oralis) and Gram-negative (Pseudomonas aeruginosa and Aggregatibacter actinomycetemcomitans) bacteria associated with implant infections. Their activity was evaluated against different states of biofilm formation on the implant material titanium using CFU, live/dead fluorescence staining and confocal microscopy. Both peptides inhibited planktonic bacteria growth, impacted initial bacterial adhesion, reduced biofilm volume and increased the proportion of dead cells. Additionally, cytotoxicity analyses showed that neither peptide harmed human gingival fibroblasts nor osteoblasts at lower concentrations. A concentration-dependent antibacterial activity of both peptides against biofilms of four clinically relevant bacteria could be demonstrated. The results of this study serve as a promising basis for the improvement of these peptides in order to finally achieve a peptide-equipped antibacterial implant surface.

Bacterioplankton reveal years-long retention of Atlantic deep-ocean water by the Tropic Seamount

Seamounts, often rising hundreds of metres above surrounding seafloor, obstruct the flow of deep-ocean water. While the retention of deep-water by seamounts is predicted from ocean circulation models, its empirical validation has been hampered by large scale and slow rate of the interaction. To overcome these limitations we use the growth of planktonic bacteria to assess the retention time of deep-ocean water by a seamount. The selected Tropic Seamount in the North-Eastern Atlantic is representative for the majority of isolated seamounts, which do not affect the surface ocean waters. We prove deep-water is retained by the seamount by measuring 2.4× higher bacterial concentrations in the seamount-associated or ‘sheath’-water than in deep-ocean water unaffected by seamounts. Genomic analyses of flow-sorted, dominant sheath-water bacteria confirm their planktonic origin, whilst proteomic analyses of the sheath-water bacteria, isotopically labelled in situ, indicate their slow growth. According to our radiotracer experiments, it takes the sheath-water bacterioplankton 1.5 years to double their concentration. Therefore, the seamount should retain the deep-ocean water for 1.8 years for the deep-ocean bacterioplankton to grow to the 2.4× higher concentration in the sheath-water. We propose that turbulent mixing of the seamount sheath-water stimulates bacterioplankton growth by increasing cell encounter rate with ambient dissolved organic molecules.

Exploring the antibacterial potential and unraveling the mechanism of action of non-doped and heteroatom-doped carbon nanodots

A comprehensive study of the antibacterial (bacteriostatic and bactericidal) properties of non-doped carbon nanodots (CNDs), nitrogen-doped (N-doped), and nitrogen/sulfur co-doped (N,S-doped) CNDs against Escherichia coli (a model organism) is discussed herein. The CNDs, with a size of ca. 5 nm, were found to be capable of inhibiting the growth of the bacterial biofilm but not significantly the growth of planktonic bacteria. Heteroatom doping was found to considerably improve the potential of CNDs as bactericidal agents. Further experiments were conducted to shed light on the potential mechanism of the antibacterial activity of the CNDs. The results showed that the CNDs do not interact with the cellular membrane via electrostatic forces. Following a simple metabolomic workflow, no alterations of the bacterial metabolome were observed except for the activation of the metabolism of α-linolenic acid. The CNDs neither oxidize cell membrane lipids and intracellular proteins nor elevate the concentration of reactive oxygen species in cells. Finally, the interactions of CNDs with genomic DNA and RNA revealed that CNDs are able to intercalate into their structure. The different affinities of the three kinds of CNDs for DNA/RNA account for the differences in their antibacterial activity and constitute the main mechanism via which CND activity is achieved.

Anti-Biofilm Effects of Synthetic Antimicrobial Peptides Against Drug-Resistant Pseudomonas aeruginosa and Staphylococcus aureus Planktonic Cells and Biofilm.

Biofilm-associated infections are difficult to manage or treat as biofilms or biofilm-embedded bacteria are difficult to eradicate. Antimicrobial peptides have gained increasing attention as a possible alternative to conventional drugs to combat drug-resistant microorganisms because they inhibit the growth of planktonic bacteria by disrupting the cytoplasmic membrane. The current study investigated the effects of synthetic peptides (PS1-2, PS1-5, and PS1-6) and conventional antibiotics on the growth, biofilm formation, and biofilm reduction of drug-resistant Pseudomonas aeruginosa and Staphylococcus aureus. The effects of PS1-2, PS1-5, and PS1-6 were also tested in vivo using a mouse model. All peptides inhibited planktonic cell growth and biofilm formation in a dose-dependent manner. They also reduced preformed biofilm masses by removing the carbohydrates, extracellular DNA, and lipids that comprised extracellular polymeric substances (EPSs) but did not affect proteins. In vivo, PS1-2 showed the greatest efficacy against preformed biofilms with no cytotoxicity. Our findings indicate that the PS1-2 peptide has potential as a next-generation therapeutic drug to overcome multidrug resistance and to regulate inflammatory response in biofilm-associated infections.

The anti-biofilm potential of triterpenoids isolated from Sarcochlamys pulcherrima (Roxb.) Gaud

Formation of biofilm is the major cause of Pseudomonas aeruginosa associated pathological manifestations in the urinary tract, respiratory system, gastrointestinal tract, skin, soft tissues etc. Triterpenoid group of compounds have shown their potential in reducing planktonic and biofilm form of bacteria. Sarcochlamys pulcherrima (Roxb.) Gaud. is an ethnomedicinal plant traditionally used for its anti-microbial and anti-inflammatory property. In the present study two triterpenoids, have been isolated from this plant, characterised and evaluated for their antibacterial and antibiofilm potential against P. aeruginosa. Compounds were characterised as 2α, 3β, 19α-trihydroxy-urs-12-ene-28-oic acid (Tormentic acid) and 2α, 3β, 23-trihydroxyurs-12-ene-28-oic acid (23-hydroxycorosolic acid) through spectroscopic studies viz. infrared (IR), nuclear magnetic resonance (NMR) and mass spectroscopy (MS). Depolarization of bacterial membrane and zone of inhibition studies revealed that both the compounds inhibited the growth of planktonic bacteria. Compounds were also found to inhibit the formation of P. aeruginosa biofilm. Inhibition of biofilm found to be mediated through suppressed secretion of pyoverdin, protease and swarming motility of P. aeruginosa. Gene expression study, in silico binding analysis, in vivo bacterial load and tissue histology observations also supported the antibiofilm activity of both the compounds. In vitro and in vivo study showed that both compounds were non-toxic. The study has explored the antibacterial and antibiofilm effect of two triterpenes isolated for the first time from S. pulcherrima.

Hypericin inclusion complexes encapsulated in liposomes for antimicrobial photodynamic therapy.

The naturally occurring anthraquinone derivative hypericin is a highly potent photosensitiser. Several in vitro studies show high phototoxicity of the pigment towards gram-positive bacteria. Nevertheless, the highly lipophilic nature and poor bioavailability prevent its application in daily clinical practice thus leading to a limited therapeutic value of hypericin. Liposomal encapsulation could help overcome these limitations and would make hypericin available for daily clinical practice. The use of liposomes as carriers for hypericin in antimicrobial photodynamic therapy (aPDT) is quite new. The aim of this work was to improve the photodynamic efficiency of the previously mentioned carriers by entrapping hypericin in the aqueous compartment of the liposomes. Therefore, a water-soluble inclusion complex of hypericin and (2-hydroxypropyl)-beta-cyclodextrin (Hyp-HPβCD) was prepared. After encapsulation of the inclusion complex into DSPC and DSPC/DPPC/DSPE-PEG liposomes with the dehydration-rehydration vesicle (DRV) method, the formulations were physicochemical characterised. The photodynamic efficiency towards the gram-positive model strain Staphylococcus saprophyticus subsp. bovis. was tested on planktonic cells as well as on biofilms. DSPC liposomes achieved a 4.1log reduction and the DSPC/DPPC/DSPE-PEG liposomes a 2.6log reduction in growth of planktonic bacteria, while Hyp-HPβCD showed total eradication. Even bacterial cells growing in a biofilm could be treated effectively in vitro.

In Vitro Performance of Bioinspired Phenolic Nanocoatings for Endosseous Implant Applications.

In the quest for finding new strategies to enhance tissue integration and to reduce the risk of bacterial colonization around endosseous implants, we report the application of auto-oxidative phenolic coatings made of tannic acid and pyrogallol to titanium surfaces. The functionalized surfaces were screened for their biological performance using cultures of primary human osteoblasts and biofilm-forming bioluminescent staphylococci S. epidermidis Xen43 and S. aureus Xen29. No toxic effect of the coatings on osteoblasts was detected. While tannic acid coatings seemed to induce a delay in osteoblast maturation, they revealed anti-inflammatory potential. Similar effects were observed for pyrogallol coatings deposited for 24 h. Thin pyrogallol coatings deposited for 2 h seemed to promote osteoblast maturation and revealed increased calcium deposition. The effects on osteoblast were found to be related to the release of phenolic compounds from the surfaces. While the phenolic coatings could not inhibit staphylococcal biofilm formation on the titanium surfaces, released phenolic compounds had an inhibitory effect the growth of planktonic bacteria. In conclusion, the assessed coating systems represent a versatile functionalization method which exhibit promising effects for endosseous implant applications.

Comparison of Single and Combined Use of Catechin, Protocatechuic, and Vanillic Acids as Antioxidant and Antibacterial Agents against Uropathogenic Escherichia Coli at Planktonic and Biofilm Levels.

The objective of this study was to evaluate the effect of combining catechin, protocatechuic, and vanillic acids against planktonic growing, adhesion, and biofilm eradication of uropathogenic Escherichia coli (UPEC), as well as antioxidant agents. The minimum inhibitory concentrations (MIC) of protocatechuic, vanillic acids and catechin against the growth of planktonic bacteria were 12.98, 11.80, and 13.78 mM, respectively. Mixing 1.62 mM protocatechuic acid + 0.74 mM vanillic acid + 0.05 mM catechin resulted in a synergistic effect acting as an MIC. Similarly, the minimum concentrations of phenolic compounds to prevent UPEC adhesion and biofilm formation (MBIC) were 11.03 and 7.13 mM of protocatechuic and vanillic acids, respectively, whereas no MBIC of catechin was found. However, combinations of 1.62 mM protocatechuic acid + 0.74 mM vanillic acid + 0.05 mM catechin showed a synergistic effect acting as MBIC. On the other hand, the minimum concentrations to eradicate biofilms (MBEC) were 25.95 and 23.78 mM, respectively. The combination of 3.20 mM protocatechuic acid, 2.97 mM vanillic acid, and 1.72 mM catechin eradicated pre-formed biofilms. The antioxidant capacity of the combination of phenolics was higher than the expected theoretical values, indicating synergism by the DPPH•, ABTS, and FRAP assays. Effective concentrations of catechin, protocatechuic, and vanillic acids were reduced from 8 to 1378 times when combined. In contrast, the antibiotic nitrofurantoin was not effective in eradicating biofilms from silicone surfaces. In conclusion, the mixture of phenolic compounds was more effective in preventing cell adhesion and eradicating pre-formed biofilms of uropathogenic E. coli than single compounds and nitrofurantoin, and showed antioxidant synergy.

Reduced Graphene-Oxide-Embedded Polymeric Nanofiber Mats: An "On-Demand" Photothermally Triggered Antibiotic Release Platform.

The steady increase of antimicrobial resistance of different pathogens requires the development of alternative treatment strategies next to the oral delivery of antibiotics. A photothermally activated platform based on reduced graphene oxide (rGO)-embedded polymeric nanofiber mats for on-demand release of antibiotics upon irradiation in the near-infrared is fabricated. Cross-linked hydrophilic nanofibers, obtained by electrospinning a mixture of poly(acrylic acid) (PAA) and rGO, show excellent stability in aqueous media. Importantly, these PAA@ rGO nanofiber mats exhibit controlled photothermal heating upon irradiation at 980 nm. Nanofiber mats are efficiently loaded with antibiotics through simple immersion into corresponding antibiotics solutions. Whereas passive diffusion based release at room temperature is extremely low, photothermal activation results in increased release within few minutes, with release rates tunable through power density of the applied irradiation. The large difference over passive and active release, as well as the controlled turn-on of release allow regulation of the dosage of the antibiotics, as evidenced by the inhibition of planktonic bacteria growth. Treatment of superficial skin infections with the antibiotic-loaded nanofiber mats shows efficient wound healing of the infected site. Facile fabrication and implementation of these photothermally active nanofiber mats makes this novel platform adaptable for on-demand delivery of various therapeutic agents.

Bicarbonate Inhibits Bacterial Growth and Biofilm Formation of Prevalent Cystic Fibrosis Pathogens.

We investigated the effects of bicarbonate on the growth of several different bacteria as well as its effects on biofilm formation and intracellular cAMP concentration in Pseudomonas aeruginosa. Biofilm formation was examined in 96-well plates, with or without bicarbonate. The cAMP production of bacteria was measured by a commercial assay kit. We found that NaHCO3 (100 mmol l-1) significantly inhibited, whereas NaCl (100 mmol l-1) did not influence the growth of planktonic bacteria. MIC and MBC measurements indicated that the effect of is bacteriostatic rather than bactericidal. Moreover, NaHCO3 prevented biofilm formation as a function of concentration. Bicarbonate and alkalinization of external pH induced a significant increase in intracellular cAMP levels. In conclusion, impedes the planktonic growth of different bacteria and impedes biofilm formation by P. aeruginosa that is associated with increased intracellular cAMP production. These findings suggest that aerosol inhalation therapy with solutions may help improve respiratory hygiene in patients with cystic fibrosis and possibly other chronically infected lung diseases.

The effects of environmental factors on planktonic growth and biofilm formation of Serratia odorifera and Serratia marcescens isolated from traditionally made cheese

In this study, the effects of different temperature, pH, salt and glucose concentrations on the planktonic growth, biofilm formation, and formed biofilm of Serratia odorifera and Serratia marcescens, isolated from traditionally made cheese, were investigated using spectrophotometric method. The investigated strains demonstrated best planktonic growth and biofilm formation in Tryptic soy broth. The limiting factors for the planktonic growth and biofilm formation were temperature below 4 °C and salt concentration above 4%. Temperature of 37 °C and 44 °C, as well as various concentrations of glucose, stimulated the planktonic growth of bacteria. Moderate influence on biofilm formation was demonstrated at 37 °C as well as at various concentrations of glucose. These results were in accordance with the origin of bacteria, since the isolates were obtained from cheese.

Antimicrobial Effect of Titanium Hydroxyapatite in Denture Base Resin

In the current study, we investigated the antimicrobial effect of titanium hydroxyapatite (TiHA), a photo-oxidizing organic material, in denture base resin on single-species biofilms formed by laboratory bacteria and on multispecies biofilms formed by bacteria from the human saliva. Although TiHA reportedly restricts the growth of planktonic bacteria upon ultraviolet A (UVA) irradiation, the antimicrobial effect of TiHA on bacterial biofilms remains to be elucidated. Resin specimens were prepared by adding TiHA to polymethyl methacrylate-based, denture base resin. The specimens were incubated with biofilm-forming Streptococcus sanguinis, Actinomyces naeslundii, Staphylococcus aureus, Escherichia coli, or bacteria from the human saliva obtained from volunteers. After UVA irradiation, the colony-forming units (CFUs) from the biofilms formed on the specimens were determined. CFU numbers for S. sanguinis, A. naeslundii, and S. aureus that formed biofilms on TiHA-containing specimens were significantly lower than those formed on specimens without TiHA. TiHA did not reduce the CFUs of biofilm-forming E. coli. In all cases, CFU numbers in the biofilms formed on TiHA-containing specimens by the salivary bacteria were significantly reduced. In addition, neither a 56 h UVA irradiation nor a 28 d soaking in water diminished the antibacterial effect of TiHA. TiHA in denture base resin exerts an antimicrobial effect on single-species bacterial biofilms and biofilms formed by a wide variety of bacteria from human saliva.