Effect Of Biofilm Formation Research Articles

Effect of biofilm formation in a hostile oxidative stress environment on the survival of Campylobacter jejuni recovered from poultry in Iraqi markets.

Campylobacter jejuni is a major contributor to bacterial enteritis, a common health problem. The resistance of this microaerophilic bacterium to oxidative stress allows it to thrive under aerobic conditions. This study aimed to investigate whether the capacity of C. jejuni to form biofilms in the presence of oxidative stress contributes to the pathogen's ability to thrive in agricultural settings as well as in chicken slaughter lines. Twenty identified strains originating from chicken samples (eight from caeca contents and 12 from frozen chicken carcasses) were previously isolated and identified according to standard bacteriological protocols, followed by confirmation at the species level using multiplex polymerase chain reaction assay. Crystal violet staining was used to evaluate biofilm formation by these bacteria. Two exposure periods to gaseous ozone (1 and 2 min) were used to assess resistance to oxidative damage. Most of the strong biofilm-forming Campylobacter strains came from imported frozen chicken meat (25%), whereas only 10% came from caeca content. After exposure to gaseous ozone at 600 mg/h for 2 min, strong biofilm-producing strains exhibited a higher survival rate with a limited reduction of up to 3 logs, whereas negative biofilm-producing strains exhibited a limited survival rate with a reduction of 6 logs. Based on our findings, we hypothesized that the presence of C. jejuni strains capable of forming biofilms in poultry farms and/or chicken production facilities triggers a public health alarm as this bacterium seems to be able to adapt more easily to live and thrive in hostile environmental conditions.

Effect of biofilm formation and cytotoxicity of biogenic silver nanoparticles (AgNPs) synthesized from a medicinal plant Sterculia foetida L.

The biogenic synthesis of silver nanoparticles mediated by medicinal plant Sterculia foetida was the prime experimental analysis of present study. The most important aim and focus of this study was to synthesis the AgNPs via biological method and the same had been evaluated against bio-film formation and dose dependent cyto-toxicity against cancer cells. This in vitro comprehensive analysis show that Ag had more advantage than other metals, the NPs was mediated by plant residue. And the NPs were further characterized by UV showing the sharp absorption peak at 455 nm; the identification of corresponding functional section proved by the parameter like FTIR, where conversion of Ag ions and capping agent is determined, the analysis on X- ray diffraction demonstrate the AgNPs found to be crystalline nature and face-centered like cubic structure. FESEM cum EDAX has showed the surface morphology with 40-50nm. After the physiochemical characterization, the AgNPs were evaluated with biofilm formation and cancer cells. In cyto-toxic study, two cell lines such as MCF 7 lung cancer cell line and A549 Breast cancer cell line were experimented and the values are AgNPs (IC50 =11.50± 0.05 µg and IC50 = 5.5± 0.05 µg/mL); AgNO3- (IC50 = 5.8± 0.05 µg and IC50 = 6.5± 0.05µg/mL) and Sterculia foetida (IC50 > 5000 µg/mL and IC50 < 5000 µg/mL). Another application of this present study is anti-biofilm assay. The selected bacterial strains are methicillinresistant Staphylococcus aureus; PA 14-Pseudomonas aeruginosa and Vibrio cholerae. Hence, the findings recommend that silver nanoparticles from medicinal plant Sterculia foetida is effective and can be used against bacteria and more precisely for cancer cell study.

Photoacoustic based evaluation of viscoelastic properties of Gram-negative and Gram-positive bacterial colonies

Mechanical properties of bacterial colonies are crucial considering both addressing their pathogenic effects and exploring their potential applications. Viscoelasticity is a key mechanical property with major impacts on the cell shapes and functions, which reflects the information about the cell envelope constituents. Hereby, we have proposed the application of photoacoustic viscoelasticity (PAVE) for studying the rheological properties of bacterial colonies. In this regard, we employed an intensity-modulated laser beam as the excitation source followed by the phase delay measurement between the generated PA signal and the reference for the characterization of colonies of two different types of Gram-positive and Gram-negative bacteria. The results of our study show that the colony of Staphylococcus aureus as Gram-positive bacteria has a significantly higher viscoelasticity ratio compared to that value for Acinetobacter baumannii as Gram-negative bacteria (77% difference). This may be due to the differing cell envelope structure between the two species, but we cannot rule out effects of biofilm formation in the colonies. Furthermore, a lumped model has been provided for the mechanical properties of bacterial colonies.

Effect of biofilm formation by antimicrobial-resistant gram-negative bacteria in cold storage on survival in dairy processing lines

Antimicrobial-resistant gram-negative bacteria in dairy products can transfer antimicrobial resistance to gut microbiota in humans and can adversely impact the product quality. In this study, we aimed to investigate their distribution in dairy processing lines and evaluate biofilm formation and heat tolerance under dairy processing line-like conditions. Additionally, we compared the relative expression of general and heat stress-related genes as well as spoilage-related gene between biofilm and planktonic cells under consecutive stresses, similar to those in dairy processing lines. Most species of gram-negative bacteria isolated from five different dairy processing plants were resistant to one or more antimicrobials. Biofilm formation by the bacteria at 5 °C increased with the increase in exposure time. Moreover, cells in biofilms remained viable under heat treatment, whereas all planktonic cells of the selected strains died. The expression of heat-shock-related genes significantly increased with heat treatment in the biofilms but mostly decreased in the planktonic cells. Thus, biofilm formation under raw milk storage conditions may improve the tolerance of antimicrobial-resistant gram-negative bacteria to pasteurization, thereby increasing their persistence in dairy processing lines and products. Furthermore, the difference in response to heat stress between biofilm and planktonic cells may be attributed to the differential expression of heat stress-related genes. Therefore, this study contributes to the understanding of how gram-negative bacteria persist under consecutive stresses in dairy processing procedures and the potential mechanism underlying heat tolerance in biofilms.

Investigation of Biofilm Formation Efficiency in ESβLs of Pathogenic Escherichia coli Isolates

Up to 70 clinical Escherichia coli samples were examined, with 30 identified as extended-spectrum β-lactamase (ESβL) isolates. These isolates were gathered from inpatients and outpatients at some Baghdad hospitals. Urine, pus, feces, and blood samples were obtained from government hospital patients of both genders and diverse age groups. Production of ESβL and the quick antibacterial diagnosis was checked using the VITEK2 for susceptibility experimentation and identification of the bacterial sample. The results showed that 30 isolates only in the current study were ESβL producers. Furthermore, all showed biofilm formation after 24 hours of incubation some of these isolates were the ability of biofilm formation decreased after 48 hours compared with negative control. The formation of biofilm has founded a vary from strong to weak. The variation in the bacterial study may depend on their antibiotic resistance and the sample’s source. Therefore, this study considers the need to focus in subsequent studies on the effect of biofilm formation and resistance of isolates, which produce beta-lactamase enzymes for many antibiotics, thus avoiding the occurrence of double health crises for infected patients.

Isolation and identification of Biofilm-producing E. coli from drinking water.

Background: The increasing rate of water-borne diseases in Karachi demands the characterization of associated pathogens. Nowadays, water-borne infections become more resistant to treatment due to biofilm formation and excessive use of antibiotics. Biofilm formation in water deteriorates the quality of water. This study identified and characterized biofilm-producing E. coli in drinking water. Methodology: Water samples were analyzed for heterotrophic plate count and total coliforms, fecal coliforms, and E. coli. The Kirby disk bar diffusion method was used to investigate antibiotic susceptibility in biofilm-producing E. coli. The Congo red and tube ring methods were used to identify biofilm producers. The effect of biofilm formation on the hydrophobicity of E. coli was performed by the BATH method. The soft agar method determines the colony spreading ability of biofilm and non-biofilm producers. Molecular characterization of virulence genes of E. coli was performed by a PCR. Scanning electron microscopy for biofilm construction was conducted. Results: The total 120 water samples were tested for heterotrophic plate count and total coliforms, fecal coliforms, and E. coli. 78% were unfit in this study, and 21.66% were fit. 38 E. coli strains were found in water samples. According to findings, the hydrophobicity of biofilm-producing isolates increased with the incubation period. Colony-forming unit drops one logarithm in the biofilm state compared to the planktonic stage. Biofilm producers were more resistant to antibiotics. The virulence genes, pet, lt, and stx2, were used for the molecular characterization. Conclusion: The presence of biofilm-producing E. coli in drinking water is alarming, and it indicates inappropriate treatment of the water supply system. To prevent rapid water-borne diseases, adequate actions are required to control drinking-water biofilm producers.

Multi-Strain and -Species Investigation of Volatile Metabolites Emitted from Planktonic and Biofilm Candida Cultures.

Candida parapsiliosis is a prevalent neonatal pathogen that attains its virulence through its strain-specific ability to form biofilms. The use of volatilomics, the profiling of volatile metabolites from microbes is a non-invasive, simple way to identify and classify microbes; it has shown great potential for pathogen identification. Although C. parapsiliosis is one of the most common clinical fungal pathogens, its volatilome has never been characterised. In this study, planktonic volatilomes of ten clinical strains of C. parapsilosis were analysed, along with a single strain of Candida albicans. Headspace-solid-phase microextraction coupled with gas chromatography-mass spectrometry were employed to analyse the samples. Species-, strain-, and media- influences on the fungal volatilomes were investigated. Twenty-four unique metabolites from the examined Candida spp. (22 from C. albicans; 18 from C. parapsilosis) were included in this study. Chemical classes detected across the samples included alcohols, fatty acid esters, acetates, thiols, sesquiterpenes, and nitrogen-containing compounds. C. albicans volatilomes were most clearly discriminated from C. parapsilosis based on the detection of unique sesquiterpene compounds. The effect of biofilm formation on the C. parapsilosis volatilomes was investigated for the first time by comparing volatilomes of a biofilm-positive strain and a biofilm-negative strain over time (0–48 h) using a novel sampling approach. Volatilomic shifts in the profiles of alcohols, ketones, acids, and acetates were observed specifically in the biofilm-forming samples and attributed to biofilm maturation. This study highlights species-specificity of Candida volatilomes, and also marks the clinical potential for volatilomics for non-invasively detecting fungal pathogens. Additionally, the range of biofilm-specificity across microbial volatilomes is potentially far-reaching, and therefore characterising these volatilomic changes in pathogenic fungal and bacterial biofilms could lead to novel opportunities for detecting severe infections early.

Effect of biofilm formation on different types of plastic shopping bags: Structural and physicochemical properties

Plastics and biofilms have a complicated relationship that has great interest. Bacterial cell attachment and biofilm formation is considered to cause health and environmental risks from plastic waste accumulation. In water, plastic waste could serve as a new substrate for bacteria. In our study, the attachment of Escherichia coli K12, to four types of plastic shopping bags (biodegradable polylactic acid and the non-biodegradable polypropylene, polyethylene and polyvinyl chloride) was investigated. The change in physicochemical phenomena of each plastic, such as reduced hydrophobicity and higher exopolysaccharide concentrations (total extractable protein and carbohydrate) resulted in increased biofilm content on the plastic surfaces. The bacterial colonization of different plastic surfaces controls the ionic strength of the nutrition sources. The adhesion of Escherichia coli K12 cells on the surfaces were revealed by SEM images. The finding shows that increases surface roughness, besides favor for adhesion of bacterial cells due to hydrophobicity leading to a rapid attachment of Escherichia coli K12 on the surfaces. In addition, we used Derjaguin-Landau-Verwey-Overbeek theory to predict the attachment of Escherichia coli K12, which gave result of adhesion due to the high energy barrier. This present study added to our knowledge of the possible consequences of plastics acting as a new habitat for microbes in different aquatic condition.

Effect of Natural Polysaccharide Matrix-Based Selenium Nanocomposites on Phytophthora cactorum and Rhizospheric Microorganisms.

We studied the effects of new chemically synthesized selenium (Se) nanocomposites (NCs) based on natural polysaccharide matrices arabinogalactan (AG), starch (ST), and kappa-carrageenan (CAR) on the viability of phytopathogen Phytophthora cactorum, rhizospheric bacteria, and potato productivity in the field experiment. Using transmission electron microscopy (TEM), it was shown that the nanocomposites contained nanoparticles varying from 20 to 180 nm in size depending on the type of NC. All three investigated NCs had a fungicidal effect even at the lowest tested concentrations of 50 µg/mL for Se/AG NC (3 µg/mL Se), 35 µg/mL for Se/ST NC (0.5 µg/mL Se), and 39 µg/mL for Se/CAR NC (1.4 µg/mL Se), including concentration of 0.000625% Se (6.25 µg/mL) in the final suspension, which was used to study Se NC effects on bacterial growth of the three common rhizospheric bacteria Acinetobacter guillouiae, Rhodococcus erythropolis and Pseudomonas oryzihabitans isolated from the rhizosphere of plants growing in the Irkutsk Region, Russia. The AG-based Se NC (Se/AG NC) and CAR-based Se NC (Se/CAR NC) exhibited the greatest inhibition of fungal growth up to 60% (at 300 µg/mL) and 49% (at 234 µg/mL), respectively. The safe use of Se NCs against phytopathogens requires them to be environmentally friendly without negative effects on rhizospheric microorganisms. The same concentration of 0.000625% Se (6.25 µg/mL) in the final suspension of all three Se NCs (which corresponds to 105.57 µg/mL for Se/AG NC, 428.08 µg/mL for Se/ST NC and 170.30 µg/mL for Se/CAR NC) was used to study their effect on bacterial growth (bactericidal, bacteriostatic, and biofilm formation effects) of the three rhizospheric bacteria. Based on our earlier studies this concentration had an antibacterial effect against the phytopathogenic bacterium Clavibacter sepedonicus that causes diseases of potato ring rot, but did not negatively affect the viability of potato plants at this concentration. In this study, using this concentration no bacteriostatic and bactericidal activity of all three Se NCs were found against Rhodococcus erythropolis based on the optical density of a bacterial suspension, agar diffusion, and intensity of biofilm formation, but Se/CAR and Se/AG NCs inhibited the growth of Pseudomonas oryzihabitans. The cell growth was decrease by 15–30% during the entire observation period, but the stimulation of biofilm formation by this bacterium was observed for Se/CAR NC. Se/AG NC also had bacteriostatic and antibiofilm effects on the rhizospheric bacterium Acinetobacter guillouiae. There was a 2.5-fold decrease in bacterial growth and a 30% decrease in biofilm formation, but Se/CAR NC stimulated the growth of A. guillouiae. According to the results of the preliminary field test, an increase in potato productivity by an average of 30% was revealed after the pre-planting treatment of tubers by spraying them with Se/AG and Se/CAR NCs with the same concentration of Se of 0.000625% (6.25 µg/mL) in a final suspension. The obtained and previously published results on the positive effect of natural matrix-based Se NCs on plants open up prospects for further investigation of their effects on rhizosphere bacteria and resistance of cultivated plants to stress factors.

The effect of biofilm formation on the outcome therapy of diabetic foot infections (DFIs) patients in the outpatient clinic and inpatient ward of Dr Sardjito General Hospital Yogyakarta

Introduction: Diabetes is a non-communicable disease with incidence rate of about 1.5 – 2.3% per annum with the most complication is Diabetic Foot Infections (DFIs). Aim: This research was conducted to describe the bacteria responsible for biofilm formation and its ability to cause DFIs in biofilm formation at Dr. Sardjito General Hospital as well as the therapy outcome. Methods: This research was conducted from September to November 2017. Specimens of samples were obtained from wound swabs of DFIs patients who met the inclusion and exclusion criteria (31 outpatients and 15 inpatients), and were then tested for culture and sensitivity and their ability to form biofilms. Results: The DFIs with the biofilm-producing bacteria (weak to moderate) have a different outcome compared to DFIs patients without biofilms.

Effect of biofilm formation on implant abutments with an anti-bacterial coating: A pre-clinical in vivo study.

To analyse the long-term effect of plaque formation on implant abutments with an antibacterial coating and the ensuing host response in peri-implant tissues. Four implants were installed in each mandibular premolar region following tooth extraction in six dogs. Three months later, two test abutments with a titanium-bismuth-gallium (Ti-Bi-Ga) coating and two control titanium abutments were connected to the implants on each side of the mandible. After 2months, ligatures were placed around the implants in one side of the mandible and plaque formation was allowed until the end of the experiment. The ligatures were removed after 4weeks. Radiographs and microbiological samples were obtained from each implant site during the plaque formation period. Biopsies were obtained 8months after abutment connection and prepared for histological analysis. The analysis did not reveal any statistically significant differences in bone loss, bacterial growth and size of inflammatory lesions between implant units with and without the Ti-Bi-Ga coating. Implant sites exposed to the short period of ligature-induced breakdown demonstrated more pronounced bone loss and bacterial growth than non-ligature sites. It is suggested that a Ti-Bi-Ga coating does not prevent biofilm formation on the implant device and does not influence the ensuing host response in the adjacent peri-implant mucosa.

Effect of Biofilm Formation on the Escherichia coli Drug Resistance of Isolates from Pigs in Central China

Background: Multi-drug resistant Escherichia coli (E. coli) can cause a variety of diseases that lead to considerable economic losses in the swine industry. In the past, the mainstream view believed that most bacterial resistance was caused by planktonic bacteria, but the ability of bacteria to form biofilms was ignored. Here, we isolated and identified 185 strains of E. coli from pigs in central China and analyzed the relationship between their genetics, antibiotic sensitivity and biofilm formation ability.Methods: First, the isolates were classified according to biofilm formation ability by semi-quantitative staining of crystal violet. Then, Phylogenetic group analysis of isolates by polymerase chain reaction. In addition, E. coli with different biofilm-forming abilities were evaluated for antimicrobial susceptibility in its planktonic and biofilm state. Finally, the drug resistance pattern of the isolates with different biofilm formation capabilities were compared.Result: most of the collected strains showed biofilm formation ability (87.57%, 162/185). The isolated E. coli with biofilm formation ability were classified into the following groups: A (16.05%, 26/162), B1 (10.49%, 17/162), B2 (33.33%, 54/162) and D (40.12%, 65/162). Simultaneously, the isolated E. coli were classified into the following groups according to the biofilm formation ability: Strong (34.57%, 56/162), Moderate (33.33%, 54/162), Weak (32.10%, 52/162) and Absent (12.43%, 23/162). Compared with the planktonic cells, the isolates showed a significant increase in the resistance rate in the biofilm form. And the isolates of the strong biofilm-forming ability group had a high drug resistance pattern. This study provides data of the drug resistance of pig-derived E. coli with different biofilm-forming abilities and provides a scientific basis for guiding veterinary clinical treatment and disease prevention.

Effect of Biofilm Formation by Lactobacillus plantarum on the Malolactic Fermentation in Model Wine.

Biofilm life-style of Lactobacillus plantarum (L. plantarum) strains was evaluated in vitro as a new and suitable biotechnological strategy to assure L-malic acid conversion in wine stress conditions. Sixty-eight L. plantarum strains isolated from diverse sources were assessed for their ability to form biofilm in acid (pH 3.5 or 3.2) or in ethanol (12% or 14%) stress conditions. The effect of incubation times (24 and 72 h) on the biofilm formation was evaluated. The study highlighted that, regardless of isolation source and stress conditions, the ability to form biofilm was strain-dependent. Specifically, two clusters, formed by high and low biofilm producer strains, were identified. Among high producer strains, L. plantarum Lpls22 was chosen as the highest producer strain and cultivated in planktonic form or in biofilm using oak supports. Model wines at 12% of ethanol and pH 3.5 or 3.2 were used to assess planktonic and biofilm cells survival and to evaluate the effect of biofilm on L-malic acid conversion. For cells in planktonic form, a strong survival decay was detected. In contrast, cells in biofilm life-style showed high resistance, assuring a prompt and complete L-malic acid conversion.

Reduction of potential ennoblement of stainless steel in natural seawater by an ecofriendly biopolymer

The effect of biofilm formation on passive stainless steel in seawater environments is of primary importance since it leads to potential ennoblement of surfaces and subsequently to localized corrosion such as pitting and crevice corrosion. This study aims at developing an ecofriendly alginate biopolymer containing both non-toxic calcium and a limited amount of biocidal zinc ions which inhibits this effect. For this purpose, calcium alginate containing less than 1 % of zinc ions localized in the vicinity of the steel surface in natural and renewed seawater is demonstrated to reduce significantly the ennoblement process of steel. After 1 month of immersion, a mass loss of only 4 % of the active material is observed authorizing thereby long-term protection of steel in real environment.

Effects of biofilm formation in bacteria from different perspectives

Effects of biofilm formation in bacteria from different perspectives

Biofilm Formation by Coagulase-Positive Staphylococcus aureus Isolated from Mozzarella Cheese Elaborated with Buffalo Milk and its Effect on Sensitivity to Sanitizers

Background: The buffalo milk mozzarella cheese is a new product in the market, with high consumer acceptance and excellent prospects for trade. The cheese is rich in nutrients, which favors the proliferation of microorganisms that can cause food-borne diseases in the consumer. Staphylococcus aureus can cause gastro-enteritis in humans by the production of enterotoxins in food. One problem that may hinder the elimination of undesirable microorganisms in the food industry is the formation of biofilms. The objective of this study was to determine the effect of biofilm formation by Staphylococcus aureus isolated from buffalo mozzarella cheese on sensitivity to sanitizers.Materials, Methods & Results: Fifty samples of buffalo mozzarella cheese were analyzed to investigate the presence of S. aureus. The isolates were obtained through microbiological analysis and identified by PCR. The similarity of the strains was compared through rep-PCR. The distinct strains were tested for biofilm formation in microtiter plates. Soy Tripticase Broth (TSB) was placed in each well of the microtiter plate and overnight cultures of each strain was added. Wells without bacterial culture were used as controls. A villous cap was then placed on the plate and incubated for 48 h at 37°C. During incubation, the biofilms formed on the surface of the villi of the caps. For quantification of biofilm formation, material that remained attached to the cap was stained with crystal violet, the stained biofilm was extracted and the OD570 of each well was measured. Each strain was classified as non-biofilm forming, weak forming, moderately formed or formative strong. Strong forming and non-biofilm forming strains were tested on high density polyethylene, stainless steel and glass surfaces. Plates of 4 cm² of the different materials were placed in TSB where the culture of each isolate was inoculated separately. At each 48 h incubation the plates were washed to remove unbound cells and re-inserted into TSB without the inoculum. After five replicates of the procedure, sterile swabs were passed over the entire surface of each plate for counting in Baird-Parker agar. They were also tested for sensitivity to sodium hypochlorite and iodine after biofilm formation. The biofilm plates were immersed in flasks containing sanitizers, where they remained for 10 min. At the established contact time, the plates were immersed in neutralizing solution for 30 s. After washing with PBS, a sterile swab was passed on the surface of each plate and counts on Baird-Parker agar were performed. The bands profiles obtained on rep-PCR were identical when compared to isolates from the same sample, indicating that each sample was contaminated with only one S. aureus strain. From the twenty S. aureus strain identified, two isolates were classified as strong biofilm formers, seven as moderate formers, ten weak formers and one as non-biofilm builder. The two strong forming strains produced biofilm on the three surfaces tested. The application of sodium hypochlorite and iodine sanitizers promoted a reduction of approximately 2 log bacterial populations on all surfaces of both the biofilm and non-forming strains.Discussion: Most strains of S. aureus isolated from buffalo milk mozzarella cheese have the ability to form biofilm on the surfaces of equipment and utensils that have stainless steel, glass or high density polyethylene components. Although biofilm forming strains are no longer resistant to sanitizers sodium hypochlorite and iodine than non-forming sanitizers, they reach higher concentrations in the biofilm, resulting in larger bacterial populations remaining after application of the sanitizers. These results support the recommendation that the good hygienic practices adopted by industries processing buffalo milk mozzarella cheese should include specific measures to control the Staphylococcus aureus contamination.

Biofilm formation is not associated with worse outcome in Acinetobacter baumannii bacteraemic pneumonia

The effect of biofilm formation on bacteraemic pneumonia caused by A. baumannii is unknown. We conducted a 4-year multi-center retrospective study to analyze 71 and 202 patients with A. baumannii bacteraemic pneumonia caused by biofilm-forming and non-biofilm-forming isolates, respectively. The clinical features and outcomes of patients were investigated. Biofilm formation was determined by a microtitre plate assay. The antimicrobial susceptibilities of biofilm-associated cells were assessed using the minimum biofilm eradication concentration (MBEC) assay. Whole-genome sequencing was conducted to identify biofilm-associated genes and their promoters. Quantitative reverse transcription polymerase chain reaction was performed to confirm the expression difference of biofilm-associated genes. There was no significant difference in the clinical characteristics or the outcomes between patients infected with biofilm-forming and non-biofilm-forming strains. Compared with non-biofilm-forming isolates, biofilm-forming isolates exhibited lower resistance to most antimicrobials tested, including imipenem, meropenem, ceftazidime, ciprofloxacin and gentamicin; however, the MBEC assay confirmed the increased antibiotic resistance of the biofilm-embedded bacteria. Biofilm-associated genes and their promoters were detected in most isolates, including the non-biofilm-forming strains. Biofilm-forming isolates showed higher levels of expression of the biofilm-associated genes than non-biofilm-forming isolates. The biofilm-forming ability of A. baumannii isolates might not be associated with worse outcomes in patients with bacteraemic pneumonia.

Correlation of power generation with time-course biofilm architecture using Klebsiella variicola in dual chamber microbial fuel cell

In the present work, the wild type Klebsiella variicola was investigated in double chamber microbial fuel cell (MFC) using palm oil mill effluent as substrate which achieved high power density (4.5 W/m3) and coulombic efficiency (63%) while maintaining the moderate chemical oxygen demand (COD) removal efficiency (58%). The effect of biofilm formation on power generation over time was also evaluated and found that an effective biofilm with the discrete distribution of single layer microorganisms can produce high power corresponding to low charge transfer resistance. The growth of biofilm in multilayers consisting of outnumbered dead cells in the vicinity of the electrode surface caused the polarization resistance and diffusion resistance resulting in a sharp drop in the current generation. The removal of multilayer biofilm from the anode surface positively influenced the cell performance which led to a rapid increase in current generation and thus revealed that effective biofilm predominated by live cells can be an emergent factor for achieving maximum performance in MFC.

Comment on “Effect of biofilm formation by clinical isolates of Helicobacter pylori on the efflux-mediated resistance to commonly used antibiotics”

Attaran et al[1] have recently shown that decreased susceptibility of established Helicobacter pylori (H. pylori) biofilms to specific antibiotics, was associated with the overtly enhanced transcription of two efflux pump genes, hp1165 and hefA, involved in specific resistance to tetracycline and multiple antibiotics, respectively. Apart from antibiotic exposure, secretion of multiple antimicrobial peptides, such as human β-defensins (hβDs), by the gastric epithelium upon Hp challenge, may act as early triggering events that positively impact biofilm formation and thus, antibiotic resistance. In this regard, we undertook genomic transcriptional studies using Hp 26695 strain following exposure to sublethal, similar to those present in the gastric niche, concentrations of hβDs in an attempt to provide preliminary data regarding possible mechanisms of immune evasion and selective sensitivity of Hp. Our preliminary results indicate that hβD exposure ignites a rapid response that is largely due to the activation of several, possibly interconnected transcriptional regulatory networks – origons - that ultimately coordinate cellular processes needed to maintain homeostasis and successful adaptation of the bacterium in the gastric environment. In addition, we have shown that both antibiotic and hβD resistance are mediated by dedicated periplasmic transporters, including the aforementioned efflux pump genes hp1165 and hefA, involved in active export of antibiotics from the cell membrane and/or, as recently suggested, substrate sensing and signalling. Furthermore, it appears that sublethal doses of hβDs may enhance biofilm formation by the sustained expression of, mainly, quorum sensing-related genes. In conclusion, we provide additional data regarding the role of specific innate immune molecules in antibiotic cross-resistance mechanisms that may deepen our understanding in the context of the development of novel eradication regimens.

Effect of biofilm formation by clinical isolates of Helicobacter pylori on the efflux-mediated resistance to commonly used antibiotics.

AIMTo evaluate the role of biofilm formation on the resistance of Helicobacter pylori (H. pylori) to commonly prescribed antibiotics, the expression rates of resistance genes in biofilm-forming and planktonic cells were compared.METHODSA collection of 33 H. pylori isolates from children and adult patients with chronic infection were taken for the present study. The isolates were screened for biofilm formation ability, as well as for polymerase chain reaction (PCR) reaction with HP1165 and hp1165 efflux pump genes. Susceptibilities of the selected strains to antibiotic and differences between susceptibilities of planktonic and biofilm-forming cell populations were determined. Quantitative real-time PCR (qPCR) analysis was performed using 16S rRNA gene as a H. pylori-specific primer, and two efflux pumps-specific primers, hp1165 and hefA.RESULTSThe strains were resistant to amoxicillin, metronidazole, and erythromycin, except for one strain, but they were all susceptible to tetracycline. Minimum bactericidal concentrations of antibiotics in the biofilm-forming cells were significantly higher than those of planktonic cells. qPCR demonstrated that the expression of efflux pump genes was significantly higher in the biofilm-forming cells as compared to the planktonic ones.CONCLUSIONThe present work demonstrated an association between H. pylori biofilm formation and decreased susceptibility to all the antibiotics tested. This decreased susceptibility to antibiotics was associated with enhanced functional activity of two efflux pumps: hp1165 and hefA.