Biofilm Formation Capability Research Articles

Multi-drug resistant Staphylococcus epidermidis from chronic wounds impair healing in human wound model.

Venous leg ulcers (VLUs) represent one of the most prevalent types of chronic wounds characterised by perturbed microbiome and biofilm-forming bacteria. As one of the most abundant skin-commensal, Staphylococcus epidermidis is known as beneficial for the host, however, some strains can form biofilms and hinder wound healing. In this study, S. epidermidis distribution in VLUs and associated resistome were analysed in ulcer tissue from patients. Virulence of S. epidermidis isolates from VLUs were evaluated by whole genome sequencing, antimicrobial susceptibility testing, in vitro biofilm and binding assays, and assessment of biofilm-forming capability and pro-inflammatory potential using human ex vivo wound model. We demonstrated that S. epidermidis isolates from VLUs inhibit re-epithelialization through biofilm-dependent induction of IL-1β, IL-8, and IL-6 which was in accordance with impaired healing outcomes observed in patients. High extracellular matrix binding ability of VLU isolates was associated with antimicrobial resistance and expression levels of the embp and sdrG, responsible for bacterial binding to fibrinogen and fibrin, respectively. Finally, we showed that S. epidermidis from VLUs demonstrate pathogenic features with ability to impair healing which underscores the emergence of treatment-resistant virulent lineages in patients with chronic ulcers.

Effect of amikacin-humic acid combination on Acinetobacter baumannii biofilm: an in vitro and in silico study.

Aim: Acinetobacter baumannii (AB) is a clinically important bacterial pathogen responsible for nosocomial infections. The biofilm-forming capability of these pathogens reduces the antibiotic penetration and its efficacy, thereby complicating the treatment. The current work aims to isolate the most potent biofilm-forming Acinetobacter species from clinical isolates of the patient samples and to evaluate the efficacy of the amikacin-humic acid combination against it.Methods: The combination effect of Amikacin-Humic (AMK-HUM) acid against the highest biofilm-producing A. baumannii SLMK001 was studied via in-vitro (microscopic analysis) and in-silico (Network Pharmacology) analysis.Results: The amikacin-humic acid combination significantly inhibited both the biofilm formation and cell viability of A. baumannii SLMK001. The images observed via Scanning Electron Microscope (SEM) showed a significant decrease in the biofilm matrix. Confocal Laser Scanning Microscope (CLSM) confirmed a reduction of the Z value of its three-dimensional structure. Further, the Network Pharmacology approach supported these experimental findings by identifying the key targets of the amikacin-humic acid combination against the biofilm pathways of A. baumannii.Conclusion: The in-vitro results aligned with the in-silico findings, indicating that the AMK-HUM combination is a promising treatment that significantly activates the key proteins against A. baumannii biofilm formation and pathogenesis.

Effects of aminolevulinic acid photodynamic therapy combined with antibiotics on Mycobacterium abscessus skin infections: an in vitro and in vivo study

BackgroundMycobacterium abscessus skin infections have emerged as a major medical issue. Traditional antibiotic treatments are challenging, prolonged, and often lead to recurrence, creating an urgent need for new therapies. This study investigates the effectiveness of aminolevulinic acid photodynamic therapy (ALA-PDT) combined with antibiotics in treatmenting M. abscessus, using both in vitro and in vivo methods. MethodsWe treated eight patients with M. abscessus skin infections following cosmetic surgery, using ALA-PDT (ALA concentration: 20%; red light: 80J/cm2) combined with oral or intravenous antibiotics,including clarithromycin, moxifloxacin and amikacin, to treat 8 patients with M. abscessus skin infection after medical cosmetic surgery, and assessed the treatment outcomes. Additionally, four bacterial strains (MAB-A1, MAB-A2, MAB-B1, and MAB-B2) isolated from patients were tested in vitro for ALA-PDT efficacy to determine the optimal ALA-PDT dosage. Furthermore, the strains’ single colony morphology, biofilm formation, and genome characteristics of were analyzed to explore the factors influencing ALA-PDT's bactericidal effects. Finally, a combined ALA-PDT and antibiotics sterilization experiment was conducted in vitro. ResultsClinically, ALA-PDT combined with antibiotics showed strong efficacy in treating M. abscessus skin infections, with no recurrence observed during follow-up. In vitro, ALA-PDT effectively killed M. abscessus, although MAB-B1 and MAB-B2 required a higher ALA-PDT dose compared with MAB-A1 and MAB-A2. Compared to MAB-A1 and MAB-A2, MAB-B1 and MAB-B2 exhibited stronger biofilm formation capabilities and bacterial virulence as well as genome mutations primarily affecting fatty acid synthesis and metabolism, potentially explaining their increased ALA-PDT dosage requirement. Notably, the combination of ALA-PDT and antibiotics exerted markedly higher bactericidal effects in vitro compared with antibiotics alone. ConclusionsALA-PDT combined with antibiotics emerged as an effective treatment for M. abscessus skin infections. However, optimal dosage and antibiotic combinations should be tailored to the characteristics of specific clinical strains.

Molecular characterization and genotype of multi-drug resistant Staphylococcus epidermidis in nasal carriage of young population, Mahasarakham, Thailand.

Staphylococcus epidermidis, a coagulase-negative staphylococcus, is a prevalent skin commensal that has increasingly been recognized as a significant pathogen, particularly in hospital environments, where it is associated with device-related infections. The emergence of multi-drug resistance and its ability to form biofilms complicate the clinical management of infections caused by this organism, posing a growing public health concern. This study aimed to investigate the nasal carriage of S. epidermidis among healthy young individuals and to analyze its antibiotic resistance patterns, resistance genes, and biofilm formation capabilities. Nasal swabs were collected from 40 undergraduate students at Mahasarakham University, Thailand, aged between 20 and 22 years. A total of 38 isolates were confirmed as S. epidermidis through both phenotypic and molecular characterization. Antibiotic susceptibility testing demonstrated resistance to various classes of antimicrobials, including beta-lactams, macrolides, and tetracyclines. Notably, five isolates exhibited methicillin resistance S. epidermidis (MRSE). Resistance genes, such as mecA, ermA, tetM, tetL, and tetK, were identified across the isolates, contributing to the observed resistance profiles. Biofilm formation assays revealed that most isolates displayed weak to moderate biofilm formation, with only one isolate demonstrating strong biofilm-forming capacity. Genetic analysis indicated a significant correlation between biofilm formation and the presence of the icaA gene, which is crucial for biofilm production. This study suggests the necessity for ongoing surveillance of nasal carriage of S. epidermidis to enhance understanding of its role in the dissemination of antimicrobial resistance and biofilm-associated infections, particularly within healthcare settings.

Emergence and spread of resistant and biofilm-forming Acinetobacter baumannii in critically ill COVID-19 patients

The COVID-19 pandemic has raised concerns beyond the viral infection itself. Bacterial co-infections, particularly those involving Acinetobacter baumannii, have become a significant worry in critically ill COVID-19 patients. A. baumannii is an opportunistic pathogen that can cause nosocomial infections, especially in patients with compromised immune systems. This study investigated 36 A. baumannii isolates obtained from COVID-19 patients during a concurrent outbreak. The isolates were collected over two years through routine medical requests sent to the Clinical Microbiology laboratory. Identification of the strains was confirmed through biochemical tests, the Phoenix BD® Automated Microbiology System, and MALDI-TOF Mass Spectrometry. The study assessed the antimicrobial sensitivity of the isolates, with a specific focus on resistance to the beta-lactam group as well as aminoglycosides. The presence of specific antibiotic resistance genes (blaOXA-23, -24, -51 and -58, blaKPC, blaSHV, blaIMP, blaVIM, aac(6')-Ib, ant(3'')-Ia, and aph(3')-Ia) was investigated using PCR and Sanger DNA sequencing. Biofilm-forming capabilities of the isolates were also evaluated. The findings revealed diverse resistance profiles, with a high prevalence of resistant strains, including resistance to carbapenems. Genetic analysis suggested potential clonal spread of certain strains within the hospital setting. Moreover, a significant proportion of the isolates demonstrated strong biofilm-forming abilities, which can enhance persistence and antibiotic resistance. In conclusion, this study highlights the need for vigilant monitoring and targeted interventions to address bacterial co-infections in COVID-19 patients. The diversity in resistance patterns, potential clonal spread, and robust biofilm-forming abilities among A. baumannii isolates underscore the importance of addressing this issue to better manage and treat critically ill COVID-19 patients.

Assessment of prevalence, antibiotic resistance, and virulence profiles of biofilm-forming Enterococcus faecalis isolated from raw seafood in Bangladesh

Enterococcus faecalis are often resistant to different classes of antibiotics, harbor virulence determinants, and produce biofilm. The presence of E. faecalis in raw seafood exhibits serious public health significance. This study aimed to identify antibiotic resistance patterns and virulence factors in biofilm-forming E. faecalis strains extracted from seafood in Bangladesh. A total of 150 samples of raw seafood, comprising 50 shrimps, 25 crabs, and 75 fish, were collected and subjected to culturing, biochemical, and PCR assays to detect E. faecalis. The biofilm-forming abilities of the isolates were determined by Congo Red agar (CRA) plate and Crystal Violet Micro-titer Plate (CVMP) tests. Antibiotic resistance profiles were evaluated using the disk diffusion method. Virulence genes of the isolates were detected by PCR assay. The occurrence of E. faecalis was 29.3 % (44/150), which was higher in crabs and fish (36 %) than in shrimps (16 %). In CRA and CVMP tests, biofilm-forming abilities were observed in 88.64 % of the isolates, whereas 11 (25 %) and 28 (63.6 %) were strong- and intermediate-biofilm formers, respectively. All the isolates contained at least two virulence genes, including pil and ace (97.7 %), sprE (95.5 %), gelE (90.9 %), fsrB (79.6 %), agg (70.5 %), fsrA (68.2 %), and fsrC (61.4 %). All the isolates were phenotypically resistant to penicillin, followed by ampicillin and rifampicin (86.4 %), erythromycin (13.7 %), and tetracycline, vancomycin, norfloxacin, and linezolid (2.3 %). Resistant gene blaTEM was found in 61.4 % of the isolates. Moreover, the study found that E. faecalis strains with strong biofilm-forming capabilities had significantly higher levels of virulence genes and antibiotic resistance (p < 0.05) compared to those with intermediate and/or no biofilm-forming abilities. To the best of our knowledge, this research represents the first instance in Bangladesh of assessing antibiotic resistance and identifying virulence genes in biofilm-forming E. faecalis strains isolated from seafood samples. Our study revealed that seafood is a carrier of antibiotic-resistant, virulent, and biofilm-forming E. faecalis, demonstrating a potential public health threat.

Variation in heat resistance and biofilm formation of Bacillus cereus spores in various fermented soybean foods

This study investigated the heat resistance of Bacillus cereus spores (as well as spores in intact biofilm) in two types of Korean fermented soybean foods and presumed the potential key parameters (physicochemical and nutritional properties) associated with their heat resistance. For example, the D100°C-values of B. cereus ATCC 10987 and CH3 spores with strong heat resistance and prolific biofilm-forming capability were compared in various Jjigae-type (Cheonggukjang jjigae, Doenjang jjigae, and Gochujang jjigae) and Jang-type (Cheonggukjang, Doenjang, and Gochujang) foods commonly consumed in Korea. The D100°C-values of planktonic spores were significantly different depending on the type of food, that is, Jang and Jjigae. Compared with Jjigae-type foods, a higher heat resistance of B. cereus spores was found in Jang-type foods (particularly Doenjang and Gochujang) with low water activity and high salinity. In Jjigae-type foods, spore heat resistance showed a positive correlation with the pH of Jjigaes, indicating that an acidic environment weakens the spores. A negative correlation between the total fat content and spore heat resistance was found in Jjigae-type foods but not in Jang-type foods. Meanwhile, regarding the heat resistance of B. cereus spores in intact biofilm, the D100°C-values were significantly higher (up to 6.5-fold) than those of planktonic spores in all Jjigae-type foods. The slightly acidic pH and amount of carbohydrates are likely related to the large formation of extracellular polymeric substances and strong heat resistance of B. cereus spores in biofilm. This study may provide a comprehensive understanding of the relationship between the key parameters of foods and heat resistance of B. cereus spores with or without intact biofilm and methods to control their risks in different types of fermented soybean foods.

Biofilm Production Activity and Antibiotics Susceptibility of Streptococcus mutans Isolates from Patients with Dental Caries

Dental caries, a prevalent chronic infectious ailment, commences with the adherence of cariogenic bacteria to the teeth, particularly Streptococcus mutans. These microorganisms utilize sugars to produce acid, resulting in the gradual demineralization of the dental structure. Streptococcus mutans a gram positive bacterium is found to play the most significant role in the dental caries in terms of being the earliest colonizer in the formation of caries. The current research focuses on the isolation and identification of the Streptococcus mutans pathogen in individuals affected by dental caries. The isolated strains were cultured on specific media, with one hundred samples of dental caries obtained from human teeth. Among these samples, fifty were identified as positive bacterial isolates utilizing MS-agar (Mitist Salivares agar), with ten isolates categorized under the group Streptococci and twenty isolates identified as S. mutans. Identification of bacterial isolates was carried out based on morphological and cultural characteristics, biochemical tests, and VITEK-II. Additionally, an antibiogram assay was conducted to assess the susceptibility and resistance of the pathogen to various drugs. The findings revealed that all locally isolated S. mutans strains displayed 100% resistance to Cefepime, while showing different levels of resistance and susceptibility to other antibiotics such as Doxycycline, Amoxicillin-clavulanic acid, Trimethoprim-sulfamethoxazole, Vancomycin, Tetracycline, Ampicillin, and Meropenem. In this study, ELISA was employed to differentiate between Streptococcus. mutans isolates that produced biofilms and those that did not by utilizing the optical density at 630 nm. Bacterial biofilms contribute to chronic diseases that pose challenges in treatment. Twenty distinct isolates were evaluated for their biofilm-forming capabilities, with 9 (45%) identified as strong biofilm producers, 7 (35%) classified as moderate biofilm producers, and 4 (20%) categorized as weak biofilm producers

Beyond Harmful: Exploring Biofilm Formation by Enterococci Isolated from Portuguese Traditional Cheeses.

This study investigated the biofilm-forming capabilities of Enterococcus isolates from Portuguese traditional cheeses with protected designation of origin (PDO) status, specifically Azeitão and Nisa. Given the absence of added starter cultures in the cheesemaking process, the characteristics of these cheeses are intrinsically linked to the autochthonous microbiota present in the raw materials and the production environment. Our findings demonstrate that all isolates possess biofilm production abilities, which are crucial for their colonization and persistence within cheese factories, thereby maintaining factory-specific microbial heritage. Through an integrated analysis utilizing principal component analysis (PCA), a direct correlation between biofilm formation and cell viability was established. Notably, these results underscore the adaptive capacity of enterococci to survive environmental fluctuations and their role in the unique characteristics of Portuguese traditional cheeses. Overall, this research enhances our understanding of the microbial dynamics in cheese production and highlights the importance of enterococci in preserving cheese quality and heritage.

Surfactins and Iturins Produced by Bacillus velezensis Jt84 Strain Synergistically Contribute to the Biocontrol of Rice False Smut

Rice false smut, caused by the plant pathogenic fungus Ustilaginoidea virens, is widespread in rice-growing regions globally, severely compromising rice quality and production. Employing Bacillus spp. to control rice false smut represents an effective and environmentally sustainable strategy for disease management. The lipopeptides produced by Bacillus velezensis Jt84 demonstrated robust inhibitory effects against U. virens, resulting in abnormal mycelial morphology and spore germination. Iturins were identified as essential for the antifungal activity against U. virens, as confirmed by mutagenesis experiments that suppressed iturin biosynthesis. The surfactin-deficient mutant exhibited inhibitory effects against U. virens comparable to the wild-type, indicating that the absence of surfactins did not diminish its antifungal activity. Both the Jt84∆srf and Jt84∆itu mutants displayed reduced biofilm formation capabilities compared to the wild-type, with the Jt84∆srf mutant being particularly impaired and unable to form a complete biofilm. Regarding swarming motility, the ∆srf mutant exhibited a significant reduction compared to the wild-type, whereas the Jt84∆itu mutant showed a modest increase. Colonization experiments revealed that the Jt84∆srf mutant strain had significantly lower colonization on rice leaf surfaces than the wild-type strain, highlighting the critical role of surfactins in the colonization of B. velezensis Jt84 on rice leaves. In conclusion, our research demonstrated that surfactins and iturins have distinct functionalities and act synergistically to contribute to the biocontrol of rice false smut in B. velezensis Jt84. This synergy is achieved through their potent antifungal effects, biofilm formation, and successful colonization.

Novel insights into biofilm formation and the key differentially expressed genes in Yersinia enterocolitica from meat: Implications for food safety and disease prevention

Yersinia enterocolitica is an important foodborne pathogen that can cause a zoonotic disease known as yersiniosis, which causes symptoms such as acute diarrhea, mesenteric adenitis, terminal ileum inflammation, pseudo appendicitis, sepsis, and other complications. The mechanism of biofilm formation in Y. enterocolitica remains poorly understood, with limited research available on this topic. This study systematically examined the distribution characteristics and biofilm formation ability of Y. enterocolitica isolated from poultry and livestock related samples. Analysis of food samples collected indicated significant presence of Y. enterocolitica (207/670, 30.9 %), particularly in frozen duck meat (7/11, 63.6 %). Majority of the isolated strains did not demonstrate biofilm-forming ability (52.7 %), while a notable percentage exhibited moderate (6.8 %) to strong (11.6 %) biofilm-forming ability. Additionally, a significant percentage of strains (16/207, 7.7 %) displayed extremely high optical density/cut-off OD (OD/ODC) ratios (the average OD value of each sample divided by the average OD value of the negative controls of each 96-well plate plus 3 standard deviations) (exceeding 10). Time-course analysis of biofilm formation in 10 isolates revealed three distinct patterns: (i) rapid increase from 6 h to 12 h, with gradual peak between 48 and 72 h followed by a slight decline and stabilization; (ii) little biofilm formation at 24 h with a gradual increase up to 96 h, maintaining this level until 120 h; and (iii) complete absence of biofilm formation throughout the experiment. Subsequent examination of differentially expressed genes (DEGs) in planktonic cells and biofilms of two strains with distinct biofilm formation capabilities identified seven metabolic pathways, including ribosome, photosynthesis, fatty acid degradation, valine, leucine, and isoleucine degradation, as well as pinene, camphor, and geraniol degradation. Significantly elevated expression levels of genes associated with flagellar assembly, bacterial chemotaxis, and quorum sensing (partially) were observed exclusively in planktonic cells of the selected strain with stronger biofilm-forming ability, implying that the heightened expression of flagellar assembly and bacterial chemotaxis-related genes is an important but not sole determinant of biofilm formation. The study contributes to the elucidation of the underlying mechanisms governing biofilm formation in Y. enterocolitica and may offer valuable insights for the advancement of novel food safety strategies.

6-Methoxyldihydrochelerythrine Chloride Inhibiting Intra and Extracellular Drug-Resistant Bacteria.

Vancomycin-resistant enterococcus (VRE) is a major nosocomial pathogen that exhibits enhanced infectivity due to its robust virulence and biofilm-forming capabilities. In this study, 6-methoxyldihydrochelerythrine chloride (6-MDC) inhibited the growth of exponential-phase VRE and restored VRE's sensitivity to vancomycin. 6-MDC predominantly suppressed the de novo biosynthetic pathway of pyrimidine and purine in VRE by the RNA-Seq analysis, resulting in obstructed DNA synthesis, which subsequently weakened bacterial virulence and impeded intracellular survival. Furthermore, 6-MDC inhibited biofilm formation, eradicated established biofilms, reduced virulence, and enhanced the host immune response to prevent intracellular survival and replication of VRE. Finally, 6-MDC reduced the VRE load in peritoneal fluid and cells significantly in a murine peritoneal infection model. This paper provides insight into the potential antimicrobial target of benzophenanthridine alkaloids for the first time.

Biofilm formation, antibiotic-resistance and clonal relatedness among clinical isolates of Acinetobacterbaumannii

In this work, the antibiotic resistance, biofilm formation capability, and clonal relatedness of 50 A. baumannii isolates collected from three hospitals in Ardabil city, Iran, were evaluated. Antibiotic sensitivity and biofilm formation of isolates were determined by disk diffusion and microtiter-plate methods, respectively. Molecular typing of isolates was also performed using repetitive sequence-based PCR (REP-PCR). The majority of isolates were resistant to cephems, aminoglycosides, and carbapenems, with 80 % classified as multi-drug resistant (MDR). While, only isolates collected from blood and tracheal were resistant to colistin. Additionally, 42 isolates (84 %) had biofilm formation capability. According to rep-PCR results, 34 isolates showed similar banding patterns, while 16 isolates had unique banding patterns. Finally, based on the molecular analysis, there was a direct relationship between biofilm formation and the antibiotic resistance of isolates. In other words, MDR isolates had a higher ability to form biofilm.

Evaluation of virulence determinants and cell surface properties associated with biofilm formation in methicillin-resistant Staphylococcus aureus (MRSA) and extended spectrum beta-lactamase (ESBL) Escherichia coli from livestock and poultry origin

Antibiotic resistance poses a persistent threat to modern medicine due to the emergence of novel antibiotic-resistant strains. Therefore, a timely understanding of antibiotic resistance and the virulence biology of pathogenic bacteria, particularly those of public health significance, is crucial for implementing effective mitigation strategies. This study aimed to investigate the virulence profiles of ten S. aureus isolates (NDa to NDj) and ten E. coli isolates (ND1 to ND10) originating from livestock and poultry, and to assess how various cell surface properties and biofilm formation abilities influence antibiotic resistance phenotypes. Antibiotic resistance profiling through phenotypic (AST) and genotypic methods (PCR) confirmed that NDa to NDe were methicillin-resistant S. aureus (MRSA) and ND1 to ND5 were extended-spectrum β-lactamase (ESBL) producing E. coli isolates. Virulence properties such as hemolytic activity, coagulase activity, and nuclease activity were found to be independent of the antibiotic resistance phenotype in S. aureus. In contrast, biofilm formation phenotype was observed to influence antibiotic resistance phenotypes, with MRSA and ESBL E. coli isolates demonstrating higher biofilm formation potency. Chemical and enzymatic analysis of S. aureus and E. coli biofilms revealed proteins and polysaccharides as major components, followed by nucleic acids. Furthermore, cell surface properties such as auto-aggregation and hydrophobicity were notably higher in isolates with strong to medium biofilm-forming capabilities (ESBL and MRSA isolates), corroborated by genomic confirmation of various genes associated with biofilm, adhesion, and colonization. In conclusion, this study highlights that surface hydrophobicity and biofilm formation ability of MRSA (NDa to NDe) and ESBL E. coli (ND1 to ND5) isolates may influence antibiotic resistance phenotypes.

Prevalence and Characteristics of Salmonella from Tibetan Pigs in Tibet, China.

This study aimed to understand the epidemiological characteristics of Salmonella in Tibetan pigs. We isolated, identified, and examined via antimicrobial susceptibility testing on Salmonella from Tibetan pigs breeder farms and slaughterhouses in Tibet, China. A genetic evolutionary tree was constructed on the basis of whole genome sequencing (WGS). A total of 81 Salmonella isolates were isolated from 987 samples. The main serovars were Salmonella Typhimurium and Salmonella London in Tibetan pigs. The isolated Salmonella Typhimurium isolates subjected to antimicrobial susceptibility testing showed varying degrees of resistance to β-lactams, aminoglycosides, fluoroquinolones, sulfonamides, tetracyclines, and amphenicols. WGS analysis was performed on 20 Salmonella Typhimurium isolates in Tibet (n = 10), Jiangsu (n = 10), and 205 genome sequences downloaded from the Enterobase database to reveal their epidemiological and genetic characteristics. They were divided into two clusters based on core genome single-nucleotide polymorphisms: Cluster A with 112 isolates from Tibet and other regions in China and Cluster B with 113 isolates from Jiangsu and other regions. The isolates in Cluster A were further divided into two subclusters: A-1 with 40 isolates including Tibet and A-2 with 72 isolates from other regions. Virulence factors analysis revealed that all isolates from Tibet carried adeG, but this observation was not as common in Salmonella isolates from Jiangsu and other regions of China. Antibiotic resistance genes (ARGs) analysis showed that all isolates from Tibet carried blaTEM-55 and rmtB, which were absent in Salmonella isolates from Jiangsu and other regions of China. Genetic characteristic analysis and biofilm determination indicated that the biofilm formation capabilities of the isolates from Tibet were stronger than those of the isolates from Jiangsu and other regions of China. Our research revealed the epidemic patterns and genomic characteristics of Salmonella in Tibetan pigs and provided theoretical guidance for the prevention and control of local salmonellosis.

Exoelectrogenic behaviors of Shewanella oneidensis MR-1 and cytochrome knock-out mutants on smooth electrodes of different materials

The development of anodes supporting a high rate of current generation stands as a crucial and challenging aspect in microbial electrochemical systems. A well-defined electrode surface morphology is essential for comprehending the impact of material intrinsic properties on microbial current generation, offering molecular insights into the respiration of exoelectrogens with electrodes made of diverse materials. We fabricated smooth electrodes (root mean square roughness below 10 nm) using four materials, each representing a distinct class of materials commonly utilized to construct bioanodes. These electrodes were employed to investigate current generation, electrochemical characteristics, and biofilm formation by Shewanella oneidensis MR-1 and mutants lacking cytochromes MtrC (ΔmtrC), MtrA (ΔmtrA), or CymA (ΔcymA). In reactors inoculated with MR-1, the poly(3,4-ethylenedioxythiophene) polystyrene sulfonate electrodes demonstrated a current density of 12.5 ± 1.1 μA cm-2, surpassing the 3.57 ± 0.50 μA cm-2 observed with indium tin oxide electrodes, while current generation levels by gold and glassy carbon electrodes fell in between. This disparity was not attributed to distinct biofilm formations by MR-1, as it formed stable monolayer biofilms on all types of working electrodes. At least five electron transfer pathways were identified in the MR-1 Vammograms, with the activities of these pathways depending on the electrode materials. The effectiveness of both endogenous and exogenous electron mediators varied with the electrode materials involved. Additionally, a phenazine compound exhibited diverse formal potentials when interacting with the biofilm and different types of electrodes. The mutants displayed varying degrees of impaired current generation and biofilm formation capabilities, with ΔmtrA and ΔcymA being the most affected regardless of the electrode used. However, for a specific mutant, the overall current generation, relative contribution by individual pathways, and biofilm formations underwent significant changes based on the electrode materials employed.

Biofilm Formation and Antibiotic Resistance Profiles in Carbapenemase-Producing Gram-Negative Rods-A Comparative Analysis between Screening and Pathological Isolates.

(1) Background: Carbapenem-resistant (CR) bacteria pose a significant global public health challenge due to their ability to evade treatment with beta-lactam antibiotics, including carbapenems. This study investigates the biofilm-forming capabilities of CR clinical bacterial isolates and examines the impact of serum on biofilm formation. Additionally, the study evaluates the resistance profiles and genetic markers for carbapenemase production. (2) Methods: Bacterial isolates were collected from the microbiology laboratory of Mures County Clinical Hospital between October 2022 and September 2023. Pharyngeal and rectal swabs were screened for carbapenem-resistant bacteria using selective media. Lower respiratory tract samples were also analyzed for CR Gram-negative bacteria. The isolates were tested for their ability to form biofilms in the presence and absence of fetal bovine serum at 24 and 48 h. Carbapenemase production was detected phenotypically and confirmed via PCR for relevant genes. (3) Results: Out of 846 screened samples, 4.25% from pharyngeal swabs and 6.38% from rectal swabs tested positive for CR bacteria. Acinetobacter baumannii and Klebsiella pneumoniae were the most common species isolated. Biofilm formation varied significantly between clinical isolates and standard strains, with clinical isolates generally showing higher biofilm production. The presence of serum had no significant effect on biofilm formation in Klebsiella spp., but stimulated biofilm formation for Acinetobacter spp. Carbapenemase genes blaKPC, blaOXA-48-like, and blaNDM were detected in various isolates, predominantly in Klebsiella spp., but were not the main determinants of carbapenem resistance, at least in screening isolates. (4) Conclusions: This study highlights the variability in biofilm formation among CR clinical isolates and underscores the differences between the bacteria found as carriage versus infection. Both bacterial species and environmental factors variably influence biofilm formation. These insights are crucial for the development of effective treatment and infection control strategies in clinical settings.

Molecular characterization, antibiotic resistant pattern and biofilm forming potentiality of bacterial community associated with Ompok pabda fish farming in southwestern Bangladesh

Ompok pabda is gaining popularity in the aquaculture industry due to its increasing demand; however research on microbial diversity and antibiotic susceptibility remains limited. The present study was designed to identify the bacterial pathogens commonly found in the pabda farming system with their biofilm forming potential and antibiotic susceptibility. Different bacterial strains were isolated from water, sediments and gut, gill of pabda fish and the isolates were identified based on their morphological traits, biochemical and molecular analysis. Antibiotic susceptibilities, antibiotic resistance gene determination and biofilm formation capabilities were evaluated by disc diffusion method, PCR amplification and Microtiter plate (MTP) assay, respectively. The respective isolates of gill and gut of pabda aquaculture and their environments were: Exiguobacterium spp. (25 %), Enterococcus spp. (20 %), Bacillus spp. (10 %), Acinetobacter spp. (10 %), Enterobacter spp. (10 %), Aeromonas spp. (10 %), Lactococcus spp. (5 %), Klebsiella spp. (5 %) and Kurthia spp. (5 %). Antibiotic resistance frequencies were found to be relatively high, especially for trimethoprim (95 %), sulfafurazole (75 %), ampicillin (60 %), amoxicillin-clavulanic acid (55 %), and cephradine (50 %). 30 % isolates were categorized as DR bacteria followed by 30 % isolates were MDR bacteria and 40 % were classified as XDR bacteria. Moreover, 4 antibiotic resistant genes were detected with sul1 (30 %), dfrA1 (10 %), tetC (40 %), and qnrA (5 %) of isolates. Based on the microtiter plate method, 20 %, 25 %, and 30 % of isolates were found to produce strong, moderate, and weak biofilms, respectively. The findings suggest that biofilm forming bacterial strains found in O. pabda fish farm may be a potential source of numerous antibiotic-resistant bacteria. The study sheds new light on antibiotic resistance genes, which are typically inherited by bacteria and play an important role in developing effective treatments or control strategies.

Some virulence genes and biofilm formation capabilities of Listeria monocytogenes isolates from different sources

In this study, it was aimed to determine the biofilm-forming abilities of both clinical and food-borne isolates of Listeria monocytogenes, to investigate the presence of nine different virulence genes, and to consider the current threat status of this agent. A total of 28 isolates, 21 from food and seven from clinical origin, were used in the study. To determine the biofilm formation abilities of isolates, two different methods namely “tube adherence” and “microplate” were used respectively. For the determination of nine different virulence genes of Listeria monocytogenes (inlA, inlC, inlJ, hylA, luxS, flaA, prfA, inlB, actA), the method of polymerase chain reaction (PCR) was used. As a result, all isolates were found to be able to form a biofilm to varying degrees by both tube and microplate methods. These two methods were similar in terms of their results. All nine different virulence gene regions were detected at various rates in the isolates. Whereas the genes directly related to biofilm formation for the isolates weren't detected, to form biofilm was observed. The virulence genes detected in clinical origin isolates were proportionally higher than in food-borne isolates (except for flaA and prfA gene regions). It was concluded that bacteria of Listeria monocytogenes continue to form biofilm and carry virulence genes regardless they are from food or clinical origin. Also, food-borne contaminations continue to be a severe threat to human health. So, to prevent listeriosis cases of both humans and animals should be taken required precautions and all cases should be considered carefully.

Assessment of biofilm-forming capacity and multidrug resistance in Staphylococcus aureus isolates from animal-source foods: implications for lactic acid bacteria intervention

BackgroundStaphylococcus aureus, a Gram-positive bacterium, poses a significant threat to public health and food safety due to its virulence and its ability to develop antimicrobial resistance (AMR). Moreover, S. aureus can form biofilms in food environments, making it difficult to eradicate and pose a major challenge in foodborne illness prevention.MethodsThe study aimed to investigate the biofilm-forming capabilities and AMR profiles of 107 S. aureus isolates derived from milk, chicken meat, and chicken eggs. Further, the study compared the biofilm formation tendencies between multi-drug resistant (MDR) and non-MDR S. aureus isolates. Additionally, the research explored the antibacterial and anti-biofilm properties of Lactobacillus rhamnosus and Lactobacillus casei, focusing on their aggregation and co-aggregation effects with S. aureus.ResultsAround 70.10% of S. aureus isolates were found to be resistant to at least three antibiotic classes. The biofilm assay revealed that 16.82% isolates were strong biofilm formers. The MDR isolates displayed a strong biofilm-forming ability (i.e., 18.67%) and a higher prevalence of biofilm-associated genes [i.e., icaA (53.33%) and icaD (44.0%)] compared to non-MDR isolates. The LAB strain, L. rhamnosus exhibited a 29.06 mm mean antibacterial inhibition zone, an average reduction of 48.19% in biofilm growth, 55.46% auto-aggregation, and 40.61% co-aggregation with S. aureus. Similarly, L. casei demonstrated a 21.80 mm mean antibacterial inhibition zone, an average reduction of 31.56% in biofilm growth, 45.23% auto-aggregation, and 36.81% co-aggregation with S. aureus isolates.ConclusionThis study provides valuable insights into the biofilm formation of MDR S. aureus and underscores the potential of L. rhamnosus and L. casei as bio-control agents. These findings highlight the necessity for additional research into the mechanisms through which LAB strains inhibit pathogenic biofilms and their potential applications in enhancing food safety.