Biofilm Formation In Clinical Isolates Research Articles

Olive oil nanoemulsion containing curcumin: antimicrobial agent against multidrug-resistant bacteria.

The present work aimed to develop, characterize, and evaluate the antibacterial and antibiofilm activity of two nanoemulsions (NEs) containing 500µg/mL of curcumin from Curcuma longa (CUR). These NEs, produced with heating, contain olive oil (5%) and the surfactants tween 80 (5%) and span 80 (2.5%), water q.s. 100mL, and were stable for 120days. NE-2-CUR presented Ø of 165.40 ± 2.56nm, PDI of 0.254, ζ of - 33.20 ± 1.35mV, pH of 6.49, and Entrapment Drug Efficiency (EE) of 99%. The NE-4-CUR showed a Ø of 105.70 ± 4.13nm, PDI of 0.459, ζ of - 32.10 ± 1.45mV, pH of 6.40 and EE of 99.29%. Structural characterization was performed using DRX and FTIR, thermal characterization using DSC and TG, and morphological characterization using SEM, suggesting that there is no significant change in the CUR present in the NEs and that they remain stable. The MIC was performed by the broth microdilution method for nine gram-positive and gram-negative bacteria, as well as Klebsiella pneumoniae clinical isolates resistant to antibiotics and biofilm and efflux pump producers. The NEs mostly showed a bacteriostatic profile. The MIC varied between 125 and 250µg/mL. The most sensitive bacteria were Staphylococcus aureus and Enterococcus faecalis, for which NE-2-CUR showed a MIC of 125µg/mL. The NEs and ceftazidime (CAZ) interaction was also evaluated against the K. pneumoniae resistant clinical isolates using the Checkerboard method. NE-2-CUR and NE-4-CUR showed a synergistic or additive profile; there was a reduction in CAZ MICs between 256 times (K26-A2) and 2 times (K29-A2). Furthermore, the NEs inhibited these isolates biofilms formation. The NEs showed a MBIC ranging from 15.625 to 250µg/mL. Thus, the NEs showed physicochemical characteristics suitable for future clinical trials, enhancing the CAZ antibacterial and antibiofilm activity, thus becoming a promising strategy for the treatment of bacterial infections caused by multidrug-resistant K. pneumoniae. KEY POINTS: • The NEs showed physicochemical characteristics suitable for future clinical trials. • The NEs showed a synergistic/additive profile, when associated with ceftazidime. • The NEs inhibited biofilm formation of clinical isolates.

Inhibition of Salmonella Enteritidis adhesion and biofilm formation by β-glucosidase B from Microbacterium sp. BG28

SalmonellaEnteritidis is the most commonly reported pathogen for foodborne illness outbreaks in both underdeveloped and developed regions. S. Enteritidis biofilms, which form on various food contact surfaces, are resistant to conventional physical and chemical cleaning and disinfection procedures routinely used in food processing. The aim of this study was to identify novel, industrially applicable enzymes that are active against S. Enteritidis biofilms. We describe the properties and anti-biofilm activity of heterologously expressed β-glucosidase B derived from the environmental strain Microbacterium sp. BG28 (BglB-BG28) collected from gills of bream fish. The enzyme inhibited adhesion and the early stages of biofilm formation in clinical isolates of S. Enteritidis. At a concentration of 200 μg/mL, BglB-BG28 effectively reduced biofilm formation, by decreasing biofilm biomass by 50% and metabolic activity within biofilms by 80%. The enzyme reduced the formation of air-liquid biofilms on various surfaces, including plastic, glass and metal, as observed by fluorescence microscopy. BglB-BG28 inhibited biofilm formation in Escherichia coli, another important food pathogen that also forms cellulose-rich biofilms. Using o-NPG as substrate, the enzyme showed activity at temperatures up to 50 °C and in a pH range between 4 and 8, high tolerance to sodium chloride and glucose, and compatibility with nonionic detergents. Importantly, no toxicity was observed in the model system Caenorhabditis elegans even at an enzyme concentration of 1 mg/mL. These results suggest that the β-glucosidase BglB-BG28 is a promising candidate for the development of a new enzyme-based disinfection protocol that can be used in food processing facilities.

Effect of selected disinfectants on biofilm-forming clinical isolates of Staphylococcus aureus in Lagos State, Nigeria

Background and Aims: Staphylococcus aureus is one of the most important pathogens of public health concern and a leading cause of nosocomial infections. In this study, we evaluated the effect of routinely used disinfectants in hospitals for surface decontamination on biofilm-forming S. aureus. Materials and Methods: forty-eight S. aureus isolates were phenotypically evaluated for biofilm formation using the Tissue Culture Plate (TCP) technique. Effect of disinfectants (Dettol®, Izal®, Jik® and Savlon®) on biofilm was tested and time-kill kinetics evaluated. PCR was used to confirm the identity of S. aureus using species-specific primers. Results: biofilm formation assay revealed that 15 (31.2%) of the isolates formed biofilm with 7 (14.5%) and 8 (16.6%) considered as strong and moderate biofilm formers, respectively. Biofilm formation was time-dependent (p<0.0001). Jik® was significantly effective (p<0.0001) as it disrupted biofilm formed in all 15 (100%) isolates, followed by Izal® 13 (86.6%), Savlon® 11 (73.3%) and Dettol® 9 (60%). Time-kill kinetics of the four disinfectants revealed Dettol®, Jik® and Savlon® achieved total (100%), (7 log10) lethality against isolates within 1 h contact time while Izal® attained complete lethality at 6 h contact time. Conclusions: of the four disinfectants evaluated Jik®, a chlorine- based formulation, was more effective in destroying biofilmforming S. aureus. The need to use effective disinfectants in sanitization is imperative to facilitate the control and prevention of hospital and community-acquired infections.

Extracellular DNA enhances biofilm integrity and mechanical properties of mucoid Pseudomonas aeruginosa.

Pseudomonas aeruginosa is one of the most common biofilm-forming pathogens responsible for lung infections of individuals with cystic fibrosis (CF). P. aeruginosa becomes tolerant to antimicrobials in the biofilm state and is difficult to treat. Production of extracellular polymeric substances (EPS), such as alginate and extracellular DNA (eDNA), can allow adherence to abiotic and biotic surfaces, antimicrobial evasion, and resilience to environmental pressures. Alginate-producing mucoid variants of P. aeruginosa are frequently isolated from CF airway samples and are associated with worsening patient outcomes. While eDNA is a major structural component of nonmucoid P. aeruginosa biofilms, the potential role of eDNA in mucoid biofilms is unclear. Here, we investigate how eDNA contributes to clinical mucoid biofilm physiology and integrity. We predicted that eDNA plays a structural and mechanical role in mucoid biofilms. To test this, we quantified biofilm eDNA in mucoid biofilms and used microscopy and rheology to visualize eDNA and detect changes in biofilm structure and mechanics upon DNaseI treatment. We showed that biofilm eDNA abundance is diverse across clinical mucoid strains and observed a temporal increase in foci of eDNA within intact mucoid biofilms. Increased cell dispersal and reduced biomass were also observed following DNaseI treatment of mucoid biofilms. Degradation of eDNA also impacted the mechanical integrity of mucoid biofilms by increasing the stiffness and decreasing the cohesion of the biofilm. These findings advance our understanding of clinical mucoid P. aeruginosa biofilms and facilitate the development of new approaches to target biofilms by exploiting the functions of EPS components. IMPORTANCE Understanding the role of eDNA in mucoid Pseudomonas aeruginosa biofilms will lead to therapeutic strategies that combat the biophysical and structural function of EPS for the eradication of bacteria in mucoid biofilms during chronic infections. This knowledge can be used to further identify unknown matrix component interactions within pathogenic biofilm-forming clinical isolates.

K-aurein: A notable aurein 1.2-derived peptide that modulates Candida albicans filamentation and reduces biofilm biomass.

Candida albicans is considered one of the most important opportunistic fungi due to the large arsenal of virulence factors that help throughout the progress of the infection. In this sense, antimicrobial peptides (AMPs) appear as an alternative, with great antifungal action. Among these, aurein 1.2 has been widely explored, becoming the basis for the discovery of new AMPs, such as K-aurein (K-au). Thus, this study evaluated the anti-C. albicans potential of K-au against virulence factors, planktonic growth, and biofilm formation of clinical isolates. Firstly, K-au antifungal activity was determined by the microdilution method and time-kill curve. The inhibition of hydrolytic enzyme secretion (proteinase, phospholipase, and hemolysin) and germ tube formation was tested. Then, the antibiofilm potential of K-au was verified through biomass quantification and scanning electron microscopy (SEM). All tests were compared with the classical antifungal drug, amphotericin B (AmB). The outcomes showed fungicidal action of K-au at 62.50µgmL-1 for all isolates, with a time of action around 150-180min, determined by the time-kill curve. K-au-treated cells decreased by around 40% of the germinative tube compared to the control. Additionally, K-au inhibited the biofilm formation by more than 90% compared to AmB and the control group. SEM images show apparent cellular disaggregation without the formation of filamentous structures. Therefore, the findings suggest a promising anti-C. albicans effect of K-au due to its fungicidal activity against planktonic cells, or its ability to inhibit important virulence factors like germ tube and biofilm formation. Thus, this peptide could be explored as a useful compound against C. albicans-related infection.

Biologically-Relevant Staphylococcus Aureus Biofilm Phenotype Characterisation And Liability To Novel Antibiofilm Drugs.

To characterise the biofilm matrix composition of a newly described Staphylococcus aureus biofilm phenotype. This experimental study was conducted at the Faculty of Pharmacy, Helwan University, Cairo, Egypt, from January 2021 to March 2022, and comprised methicillin-resistant Staphylococcus aureus and methicillin-susceptible Staphylococcus aureus biofilm-forming clinical isolates which were allowed to construct biofilms under two distinct culture conditions; one a commonly used condition, and the other one a novel, more biologically-relevant condition. The formed biofilms were analysed for matrix composition through treatment with proteinase,sodium meta-periodate, and streptokinase. The efficacy of Cis-2-Decenoic acid and hamamelitannin on the biologically-relevant biofilms was evaluated using biofilm viability assay based on a colorimetric assay for measuring cell metabolic activity and scanning electron microscope imaging. Data was analysed using GraphPad Prism 5.01. Of the 58 isolates, 45(77.6%) were methicillin-resistant Staphylococcus aureus and 13(22.4%) were methicillin susceptible Staphylococcus aureus. There was significant difference in responses to streptokinase, proteinase and sodium meta-periodate (p<0.05) among the differentially-developed biofilms in methicillin-resistant Staphylococcus aureus isolates. Regarding the methicillin-susceptible Staphylococcus aureus isolates, the differentially-developed biofilms showed significantly different liabilities to streptokinase only (p<0.05). Mean biofilm inhibition for Cis-2- Decenoic acid was 54.27±27.93% and mean biofilm dispersion was 71.92±11.59% while the corresponding valuesfor hamamelitannin were 83.03±13.95% and 70.48±7.116% against the newly described methicillin-resistant Staphylococcus aureus biofilm phenotype. Applying biologically-relevant culture conditions on staphylococci biofilms and antibiofilm drugs is recommended.

MICROBIOLOGICAL FEATURES OF STAPHYLOCOCCUS ASSOCIATED WITH COMPLICATIONS OF DENTAL IMPLANTATION.

The aim: To describe microbiological features of the Staphylococcus spp. involved in complications of dental implantation. Materials and methods: The main method was bacteriological. Indentification of the obtained isolates was done using commercially available test kits. Adhesive properties were evaluated using Brillis technique. Biofilm-forming ability was studied according to Christensen et al. Antimicrobial susceptibility testing was done following EUCAST recomendations. Results: There were 26 smears taken from the peri-implant area and gingival pockets of 12 patients. We obtained 38 isolates. Most of the patients were positive for Streptococcus spp. - 94% and Staphylococcus spp. - 90%. Among the representatives of Staphylococcus spp., the initial share of clinical isolates was S. aureus (34.21%) with inherent coagulase-positive properties. Coagulase-negative pathogens accounted for 65.79% of Staphylococcus spp., among them S. epidermidis, S. hominis, S. warneri were the main. All obtained isolates had typical properties, but appearance of small colonial variants of S. aureus was also recorded. Antimicrobial susceptibility testing was performed in 100% of cases. Among 13 isolates of S. aureus there were 2 cultures resistant to cefoxitin, i. e. methicillin-resistant by phenotype. Clinical isolates of S. aureus, colonizing peri-implant tissues in infectious-inflammatory complications of dental implantation, also had high adhesive and biofilm-forming properties. Clinical isolates of S. epidermidis an average ability to form biofilms. Conclusions: There is a prooved direct correlation between biofilm-forming ability and adhesive properties in highly biofilm-forming clinical isolates involved in the occurrence of purulent-inflammatory complications in peri-implant site.

Role of Biofilm Formation in Mediation of Drug Resistance in E. Coli

Aim: Measure biofilm formation in clinical isolates of Escherichia coli and compare the survival of bacteria by treatment of ciprofloxacin, ceftriaxone and amoxicillin/clavulanic acid in the presence and absence of biofilm formation. Methodology: A total of ninety isolates of Escherichia coli were included in the study. All isolates were identified for biofilm production by microtiter assay. Antibiotic susceptibility test for all E. coli strains along with ATCC E. coli 25922 as a control was performed by agar dilution method (CLSI 2016) using three antibiotics e.g. ciprofloxacin, ceftriaxone and amoxicillin/clavulanic acid Result: Out of ninety E. coli isolates, 18(20%) were strong biofilm formers, 54(60%) were moderate and non-biofilm formers were 18(20%). Resistance to ciprofloxacin, ceftriaxone and amoxicillin/clavulanic acid were 75.5%, 63.3% and 22.2% respectively in all tested isolates. The rate of antibiotic resistance of strong biofilm formers, moderate formers and non-biofilm formers were 83.3%, 74% and 77.7% respectively for ciprofloxacin. Similarly, for ceftriaxone resistance pattern of strong, moderate and non-biofilm former were 66.6%, 66.6% and 50% respectively. Strong, moderate and non-biofilm forming E. coli were 11.1%, 27.7% and 22% respectively resistant to amoxicillin/clavulanic acid. Conclusion: Biofilm is not essentially involved in mediating drug resistance in E. coli against tested ciprofloxacin, ceftriaxone and amoxicillin/clavulanic acid. Biofilm formers showed more resistance to antibiotics than non-biofilm formers but statistical analysis of both groups against three antibiotics showed that there was no significant difference of resistance observed among them. There may be another molecular and enzymatic mechanism that allows bacteria to mediate resistance. Keywords: Biofilm formation, antibiotic resistance, minimum inhibitory concentration

Eradication of Klebsiella pneumoniae biofilms and persister cells using silver nitrate

To perceive the relationship between the emergences of antibiotics persistence, biofilm formation, and to study the role of silver nitrate in fighting these microbes, a total 50 clinical Klebsiella pneumonae isolates were collected from clinical sources and identified using genotypic identification by using specific primer (rpoB gene) from housekeeping genes. Detection of their biofilm-forming abilities were carried out. The eradication effect of silver nitrate to control bacterial persistence and reducing the biofilm-forming abilities were studied. We found that 40 isolate (80%) were biofilm-formers. From bacterial persisters, (75%) were biofilm-formers. Silver nitrate showed a great role to eradicate persister cells and inhibition of bacterial biofilm formation of clinical isolates of K. pneumoniae.

Biofilm Formation and Its Association with Antimicrobial Resistance among Clinical Isolates of Acinetobacter baumanii at a Tertiary Care Hospital in Dhaka City of Bangladesh

Background: Acinetobacter baumanii is responsible for nosocomial infections which are related to the biofilm forming capacity of this pathogen.&#x0D; Objective: The purpose of the present study was to detect biofilm formation in clinical isolates of Acinetobacter baumannii and to observe relationship between biofilm formations with its antimicrobial resistance.&#x0D; Methodology: This cross-sectional study was conducted in the Department of Microbiology of Dhaka Medical College and Hospital, Dhaka, Bangladesh from July 2015 to June 2016. Acinetobacter baumannii was isolated from different specimens and was identified and were screened for biofilm production by tissue culture plate method. Antimicrobial susceptibility test was done by disc diffusion method.&#x0D; Results: A total 300 samples were studied of which 26(8.7%) were Acinetobacter baumannii. From 26 isolated Acinetobacter baumannii, 16(61.5%) were biofilm producers. Biofilm producing Acinetobacter baumannii were 100% resistant to ceftriaxone, ceftazidime, amoxiclav, amikacin and ciprofloxacin. Resistance to imipenem, meropenem, cephotaxime, cefepime and gentamicin were also higher among biofilm producing Acinetobacter baumannii isolates than non-biofilm producers.&#x0D; Conclusions: In conclusion the ability of Acinetobacter baumannii forms biofilm and biofilm production has strong association with antimicrobial resistance.&#x0D; Bangladesh Journal of Infectious Diseases December 2021;8(2):82-86

The Association between icaA and icaB Genes, Antibiotic Resistance and Biofilm Formation in Clinical Isolates of Staphylococci spp.

Sixty-six (66) Staphylococcus bacterial isolates were withdrawn from separate clinical samples of hospitalized patients with various clinical infections. Conventional bacteriological tests identified the species of all isolates, and standard microbiological techniques differentiated them into CoPS or CoNS. Their biofilm development was followed by an analysis via the MTP (microtiter tissue culture plates) technique, and we then investigated the presence/absence of icaA and icaB, which were qualified in the top-30 potent biofilm-forming isolates. Thirteen isolates (46.7%) showed the presence of one gene, six (20%) isolates exhibited the two genes, while ten (33.3%) had neither of them. The formation of staphylococci biofilms in the absence of ica genes may be related to the presence of other biofilm formation ica-independent mechanisms. CoPS was the most abundant species among the total population. S. aureus was the sole representative of CoPS, while S. epidermidis was the most abundant form of CoNS. Antibiotic resistance was developing against the most frequently used antimicrobial drugs, while vancomycin was the least-resisted drug. The totality of the strong and medium-strength film-forming isolates represented the majority proportion (80%) of the total investigated clinical samples. The biochemical pattern CoPS is associated with antibiotic resistance and biofilm formation and can be an alarming indicator of potential antibiotic resistance.

Validated In Silico Model for Biofilm Formation in Escherichia coli.

Using Escherichia coli as the representative biofilm former, we report here the development of an in silico model built by simulating events that transform a free-living bacterial entity into self-encased multicellular biofilms. Published literature on ∼300 genes associated with pathways involved in biofilm formation was curated, static maps were created, and suitably interconnected with their respective metabolites using ordinary differential equations. Precise interplay of genetic networks that regulate the transitory switching of bacterial growth pattern in response to environmental changes and the resultant multicomponent synthesis of the extracellular matrix were appropriately represented. Subsequently, the in silico model was analyzed by simulating time-dependent changes in the concentration of components by using the R and python environment. The model was validated by simulating and verifying the impact of key gene knockouts (KOs) and systematic knockdowns on biofilm formation, thus ensuring the outcomes were comparable with the reported literature. Similarly, specific gene KOs in laboratory and pathogenic E. coli were constructed and assessed. MiaA, YdeO, and YgiV were found to be crucial in biofilm development. Furthermore, qRT-PCR confirmed the elevation of expression in biofilm-forming clinical isolates. Findings reported in this study offer opportunities for identifying biofilm inhibitors with applications in multiple industries. The application of this model can be extended to the health care sector specifically to develop novel adjunct therapies that prevent biofilms in medical implants and reduce emergence of biofilm-associated resistant polymicrobial-chronic infections. The in silico framework reported here is open source and accessible for further enhancements.

Peptides DLL37-1 and LL37-1, an alternative to inhibit biofilm formation in clinical isolates of Staphylococcus aureus and Staphylococcus epidermidis.

Staphylococcus aureus and Staphylococcus epidermidis have microbial surface components recognizing adhesive matrix molecules (MSCRAMM) adhesion proteins that enhance their biofilm formation ability, as well as virulence factors that influence morbidity and mortality in hospital settings. In this work, four peptides analogous of the peptide LL-37 that were evaluated to inhibit biofilm formation and its action potential on the expression of MSCRAMM proteins in clinical isolates through different tests, such as crystal violet, PCR and qPCR. In total, 96.8% of S. aureus were strong in biofilm formation in contrast to 48.4% of S. epidermidis. sdrG and sdrF genes were present in 100% of S. epidermidis strains and in all isolates. In S. aureus, specific genes that code for MSCRAMM proteins were detected: clfA (89%), clFB, sdrC and fnBA (94%). The peptides did not show hemolytic or cytotoxic activity. In this study, it was evidenced that of the peptides DLL37-1 at a 5 µM concentration was an efficacious antimicrobial agent and depicted greater biofilm inhibition in both bacterial species. Exhibiting a significant inhibition rate in S. aureus, this peptide caused a negative regulation in the expression of the genes clfA and sdrC, showed greater biological activity.

In vitro and in vivo efficacy of natural plant extracts against biofilm-forming clinical isolates of Pseudomonas aeruginosa

In vitro and in vivo efficacy of natural plant extracts against biofilm-forming clinical isolates of Pseudomonas aeruginosa

Antibiotic Susceptibility and Biofilm Formation of Clinical Isolates of Pseudomonas Species From Wounds Specimens

A hallmark of Pseudomonas aeruginosa is its ability to establish biofilm based infections that are difficult to eradicate. Biofilms are less susceptible to host inflammatory and immune response and have higher antibiotic tolerance that frees living planktonic cells. The aim of the study is to investigate biofilm forming capacity and the antibiotic susceptibility profile of Pseudomonas aeruginosa strains isolated from clinical wound specimen. A total number of60 wound specimens will be submitted to the bacteriology laboratory of Abubakar Tafawa Balewa University Teaching Hospital for investigation, and will be screened for Pseudomonas aeruginosa and strains will be identified on the basis of cultural characteristics, Gram staining, biochemical tests such as citrate, urease, indole, fermentation of sugar using triple sugar agar. The biofilm forming capacity of the strains will be tested using the test tube method after the strains are standardized to approximately standard inoculated into a cooked meat broth. The growth rate of Pseudomonas aeruginosa clinical strains after 48 hours incubation will be measured by taking the absorbance using Densi-Check. The strain growth rate will be checked. Biofilm formation at the liquid interface (pllicle) will be observed as a ring and this will be qualitatively scored from the first to the last strain. The cultures will be decanted gently and rinsed twice with sterile distilled water and steained with 0.1% w/v safranin, the stain will be decolorized using 100% alcohol, and the absorbance for strains will be measured at 590nm. The strain with the most and least biofilm formation will be recorded with the absorbance rates. The clinical significance of the Pseudomonas aeruginosa biofilm forming capacity and resistance to antibiotics which could result to none healing, delayed healing, foul smell of wound infection will be checked for the experiment.

Antibiotic Susceptibility and Biofilm Formation of Clinical Isolates of Pseudomonas Species from Wounds Specimens

Purpose: The aim of the study is to investigate biofilm forming capacity and the antibiotic susceptibility profile of Pseudomonas aeruginosa strains isolated from clinical wound specimen. Method: A total number of 60 wound specimens were submitted to the bacteriology laboratory of Abubakar Tafawa Balewa University Teaching Hospital for investigation, and screened for Pseudomonas aeruginosa. The strains were identified on the basis of cultural characteristics, Gram staining, biochemical tests such as citrate, urease, indole, fermentation of sugar using triple sugar agar. The biofilm forming capacity of the strains are tested using the test tube method after standardizing the strains to approximately standard inoculated into a cooked meat broth. The growth rate of Pseudomonas aeruginosa clinical strains after 48 hours incubation are measured by taking the absorbance using Densi-Check. The strain growth rate is also checked. Biofilm formation at the liquid interface (pellicle) is qualitatively scored from the first to the last strain. The clinical significance of the Pseudomonas aeruginosa biofilm forming capacity and resistance to antibiotics which could result to none healing, delayed healing, foul smell of wound infection are checked for the experiment. Results: The analysis of the study shows that the strains are more susceptible to Ciprofloxacin and Streptomycin while the strains are less susceptible to Orfloxacin and Gentamycin. Conclusion: the data derived from human clinical studies make clear that biofilm have an important adverse effect on wound healing. Despite this, more fundamental scientific studies are required to understand what biofilm do to normal wound healing processes from cellular and immunological perspective.

Increased biofilm formation by Staphylococcus aureus clinical isolates on surfaces covered with plasma proteins.

Introduction. Biofilm formation is a major virulence factor associated with Staphylococcus aureus infections. However, the influence of plasma proteins on biofilm formation of clinical isolates in vitro remains unclear.Hypotheses. We hypothesized that coating surfaces with plasma proteins might induce biofilm formation by S. aureus of different clonal lineages.Aim. To evaluate biofilm production by clinical S. aureus isolates of different clonal lineages isolated in Rio de Janeiro hospitals and investigated the presence of biofilm-associated genes.Methodology. This study assessed biofilm production of 60 S. aureus isolates in polystyrene microtitre plates with and without fibrinogen or fibronectin. The biochemical composition of the biofilm matrices was determined and the biofilm formation on fibrinogen-coated surfaces was also evaluated by confocal laser scanning microscopy. The presence of biofilm-related genes was detected by PCR, and the typing and functionality of agr operon was also evaluated.Results. Most of the isolates (45 %) were weak biofilm producers or non-producers. However, most of them presented a significant increase in biofilm production on plates covered with plasma proteins. There was no significant difference in biofilm formation between methicillin-resistant and -susceptible S. aureus isolates, or between different clonal lineages, except for ST30-IV (weak producers) and ST239-III (strong producers). The fnbB gene was associated with higher biofilm production.Conclusion. An increase in biofilm production in the presence of plasma proteins highlights the importance of investigating biofilm formation by S. aureus clinical isolates under different conditions since this virulence factor contributes to persistent infections and increased resistance to antimicrobials.

Evaluating of the Effects of Sub-MIC Concentrations of Gentamicin on Biofilm Formation in Clinical Isolates of Pseudomonas aeruginosa

Background & Objective: The ability of Pseudomonas aeruginosa to form biofilm has an important role in establishment of chronic phase of infections. Biofilm formation can be affected by antibiotics sub-MIC concentrations. The principal aim of the present study was to evaluate the effect of gentamicin at sub-MIC concentrations on biofilm formation in 100 Pseudomonas aeruginosa clinical isolates.Methods: Determination of minimal inhibitory concentration of gentamicin for clinical isolates was done using micro broth dilution method. The amount of biofilm formation in the treated and untreated isolates with gentamicin sub-MIC (1/2&1/4MIC) concentrations was evaluated using microtitre plate assay. pelA and pslA genes were detected in clinical isolates by PCR method.Results: 99% of clinical isolates were biofilm producer. Different changes in amountof biofilm formation were observed in the treated clinical isolates with sub-MIC concentrations of gentamicin. Two dominant changes were observed in 80% of clinical isolates. These concentrations had inhibitory effect on biofilm formation in 46.4% of isolates and caused a significant decrease in its amount. While in 31.3% of the isolates, the biofilm formation was significantly increased. The frequency of pelA and pslA genes among clinical isolates was 100%. Conclusion: gentamicin sub-MIC concentrations cause different changes on biofilm formation of Pseudomonas aeruginosa clinical isolates. Therefore, further studies are needed for discovering new treatment strategies and using sub-MIC concentrations of the antibiotic in prevention and treatment of Pseudomonas aeruginosa infections.

Phenotypic and Genotypic Characteristics of Biofilm Formation in Clinical Isolates of Acinetobacter baumannii.

BackgroundAcinetobacter baumannii is an important pathogen in clinical infections, and biofilm formation is an effective way for A. baumannii to survive under external pressures. In this study, the aims were to examine the antimicrobial resistance, biofilm formation, and biofilm-specific resistance in clinical isolates of A. baumannii.Materials and MethodsA total of 104 clinical A. baumannii isolates were collected from a large teaching hospital in Southwest China. The antibiotics susceptibilities were tested, and biofilm-forming ability was evaluated by crystal violet staining by confocal laser scanning microscopy (CLSM). Minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), minimum biofilm inhibitory concentration (MBIC), and minimum biofilm eradication concentration (MBEC) of ciprofloxacin, meropenem, and ceftazidime were tested on selected strains by broth microdilution method. Biofilm-associated genes were detected by polymerase chain reaction (PCR), and expression of genes at planktonic stage and biofilm stage were analyzed by real-time reverse transcription PCR (RT-PCR).ResultsMultidrug-resistant (MDR) isolates accounted for 65.4%, but no strain was resistant to tigecycline and polymyxin B. Moreover, non-MDR strains tended to form stronger biofilms than MDR strains, and a negative correlation between biofilm-forming ability and resistance profiles to each of tested antimicrobials were observed. The MBECs and MBICs of ciprofloxacin, ceftazidime, and meropenem were evidently increased compared with MICs and MBCs among all tested strains. Additionally, the biofilm formation ability of the csuD-positive strains was stronger than that of the csuD-negative strains. The strains in MDR group had higher carrying rate of csuA and csuD genes than non-MDR group, while non-MDR strains possessed more ompA gene than MDR group. Finally, abaI gene was significantly up-regulated after biofilm formation.ConclusionThese results revealed valuable data for the negative correlation between antimicrobial resistance and biofilm formation, as well as phenotypic and genotypic characteristics of biofilm formation in A. baumannii.

Investigation of Antibiotic Resistance and Biofilm Formation in Clinical Isolates of Klebsiella pneumoniae.

Aim Klebsiella pneumoniae (K. pneumoniae) is an encapsulated Gram-negative bacterium that can lead to 14–20% of nosocomial infections. The ability of biofilm formation in this bacterium decreases the host immune response and antibiotic efficacy. This may impose a huge impact on patients and healthcare settings. This study aimed to evaluate the antibiotic resistance pattern and biofilm formation in K. pneumoniae strains isolated from two major Hamadan hospitals, west of Iran. Methods A total of 83 K. pneumoniae strains were isolated from clinical samples of patients in different wards of Hamadan hospitals from September 2018 to March 2019. Determination of antimicrobial susceptibility was performed using the disk diffusion method. Biofilm formation was evaluated by the crystal violet method. Data were analyzed by the SPSS software and chi-square test. Results The results showed that clinical samples included 18 urinary tract samples (22%), 6 wound samples (7%), 6 blood samples (7%), 17 tracheal tube aspiration samples (20%), 32 throat cultures (38%), 2 sputum samples (2.5%), and 2 abscess drain cultures (2.5%). High-level resistance to cefotaxime was detected in 92%, and all of isolates were susceptible to colistin. Biofilm formation was seen in 62 (75%) isolates. Strong biofilm formation was observed in 17 (20%) strains. A significant correlation was seen between biofilm formation and antibiotic resistance (P value <0.05). Conclusion Our findings emphasize the need for proper diagnosis, control, and treatment of infections caused by K. pneumoniae especially in respiratory tract infections due to the strong biofilm formation and high antibiotic resistance in these strains.