Biofilm Formation Characteristics Research Articles

Stutzerimonas frequens strain TF18 with superior heterotrophic nitrification-aerobic denitrification ability for the treatment of aquaculture effluent

Currently, microbial techniques have been comprehensively exploited in aquaculture effluent treatment. However, strains for bioaugmentation face many issues, such as poor adaptability, long colonization time, and unsatisfactory treatment effect. Herein, an efficient heterotrophic nitrifying-aerobic denitrifying bacterium Stutzerimonas frequens strain TF18 was isolated from the Whiteleg shrimp (Penaeus vannamei) mariculture environment. Strain TF18 exhibited strong biofilm formation and auto-aggregation characteristics, which indicated its robust adaptability and short colonization time. Remarkably, the total ammonia nitrogen, NO2--N, and NO3--N removal efficiencies of the strain were 89.21 %, 99.76 %, and 96.16 %, respectively, in the presence of sodium acetate as carbon source and carbon-nitrogen ratio of 10. Most importantly, identification of genes related to nitrogen removal, including nirS, norB, nosZ, nasA, napA, narG, and nirB, and their relative expression further demonstrated the existence of nitrate transformation pathways in strain TF18. These results provided new guidance for practical application of S. frequens strain TF18 in aquaculture effluent treatment.

Synthesis of Bio-Based Polybenzoxazine and Its Antibiofilm and Anticorrosive Activities.

Candida albicans are highly widespread pathogenic fungi in humans. Moreover, its developed biofilm causes serious clinical problems, leading to drug failure caused by its inherent drug tolerance. Hence, the inhibition of biofilm formation and virulence characteristics provide other means of addressing infections. Polymer composites (PCs) derived from natural products have attracted increasing interest in the scientific community, including antimicrobial applications. PCs are a good alternative approach to solving this challenge because of their excellent penetration power inside biofilms. The main objectives of this study were to synthesize a novel curcumin-based polybenzoxazine polymer composite (poly(Cu-A) PC) using Mannich condensation reaction and evaluate their potency as an antibiofilm and anticorrosive candidate against C. albicans. In addition, their anticorrosive efficacy was also explored. PC exhibited significant antibiofilm efficacy versus C. albicans DAY185 by the morphologic changing of yeast to hyphae, and>90% anticorrosive efficacy was observed at a higher dose of PC. These prepared PC were safe in vivo against Caenorhabditis elegans and Raphanus raphanistrum. The study shows that a polybenzoxazine polymer composite has the potential for controlling biofilm-associated fungal infections and virulence by C. albicans, and opens a new avenue for designing PCs as antifungal, anticorrosive agents for biofilm-associated fungal infections and industrial remediation.

Analysis of biofilm formation in nosocomial Stenotrophomonas maltophilia isolates collected in Bulgaria: An 11-year study (2011-2022).

The present study aimed to explore the genotypic and phenotypic characteristics of biofilm formation in Bulgarian nosocomial Stenotrophomonas maltophilia isolates (n = 221) during the period 2011-2022, by screening for the presence of biofilm-associated genes (BAG) (spgM, rmlA and rpfF), their mutational variability, and assessment of the adherent growth on a polystyrene surface. The methodology included: PCR amplification, whole-genome sequencing (WGS) and crystal violet microtiter plate assay for biofilm quantification. The overall incidence of BAG was: spgM 98.6%, rmlA 86%, and rpfF 66.5%. The most prevalent genotype was spgM+/rmlA+/rpfF+ (56.1%), followed by spgM+/rmlA+/rpfF- (28.5%), and spgM+/rmlA-/rpfF+ (9.5%), with their significant predominance in lower respiratory tract isolates compared to those with other origin (P < 0.001). All strains examined were characterized as strong biofilm producers (OD550 from 0.224 ± 0.049 to 2.065 ± 0.023) with a single exception that showed a weak biofilm-forming ability (0.177 ± 0.024). No significant differences were observed in the biofilm formation according to the isolation source, as well as among COVID-19 and non-COVID-19 isolates (1.256 ± 0.028 vs. 1.348 ± 0.128, respectively). Also, no correlation was found between the biofilm amounts and the corresponding genotypes. WGS showed that the rmlA accumulated a larger number of variants (0.0086 per base) compared to the other BAG, suggesting no critical role of its product to the biofilm formation. Additionally, two of the isolates were found to harbour class 1 integrons (7-kb and 2.6-kb sized, respectively) containing sul1 in their 3' conservative ends, which confers sulfonamide resistance. To the best of our knowledge, this is the first study on S. maltophilia biofilm formation in Bulgaria, which also identifies novel sequence types (ST819, ST820 and ST826). It demonstrates the complex nature of this adaptive mechanism in the multifactorial pathogenesis of biofilm-associated infections.

Prevalence, biofilm formation, and mass spectrometric characterization of linezolid-resistant Staphylococcus capitis isolated from a tertiary hospital in China

Linezolid-resistant Staphylococcus capitis (LRSC) has become a new challenge for clinical anti-infective therapy. The present study aimed to investigate the trends of LRSC prevalence in a tertiary hospital of China 2017-2020. The resistance mechanisms, virulence genes, biofilm formation, and mass spectrometric characteristics of LRSC isolates were also analysed. This study retrospectively analysed the antibiotic resistance trends of coagulase negative staphylococci (CoNS) isolated from clinical samples collected between 2017-2020. Antimicrobial resistance profiles were tested by micro-broth dilution and the E-test method. Antimicrobial resistance genes and virulence genes were detected by polymerase chain reaction, and dru-typing sequences were obtained by Sanger sequencing. Crystal violet staining in 96-well plates was used to detect biofilm formation ability. Mass spectrometric characterization of LRSC was analysed by matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) coupled with ClinProTools. The linezolid resistance rate in 3575 CoNS clinical strains was 1.6%, wherein the great majority of was LRSC (91.1%, n=51/56), with a resistant rate of 15.5% (n=51/328) in all S. capitis isolates. In this study, 48 out of the 51 LRSC strains and 54 of 277 linezolid-susceptible S. capitis (LSSC) strains were enrolled. G2576T, C2104T, T2130A, C2163T, and T2319C mutations in the 23S rRNA V region and acquisition of cfr were the main linezolid resistant mechanisms in LRSC. The biofilm-forming ability of LRSC was more potent than LSSC, with a higher detection rate of bap (P < 0.05). Eleven mass spectrometric peaks of interest were identified by using MALDI-TOF MS and ClinProTools, which were differently distributed between LRSC and LSSC strains, with the area under the receiver operating characteristic curve of more than 0.8, especially for 5465.37 m/z. Linezolid resistance was mediated by mutations in the 23S rRNA V region and presence of the cfr gene in LRSC strains. LRSC strains have stronger biofilm-forming ability than LSSC strains, which maybe associated with the adhesion-related gene of bap. Further, linezolid-resistant and linezolid-susceptible S. capitis could be rapidly identified with mass spectrometric characterization. To the best of our knowledge, this study is the first to document the biofilm formation ability of LRSC and the potential usefulness of MALDI-TOF MS for the discrimination of LRSC and LSSC.

Hydroquinones Including Tetrachlorohydroquinone Inhibit Candida albicans Biofilm Formation by Repressing Hyphae-Related Genes.

ABSTRACTCandida albicans is an opportunistic pathogenic fungus responsible for candidiasis. The pathogen readily forms antifungal agent-resistant biofilms on implanted medical devices or human tissue. Morphologic transition from yeast to filamentous cells and subsequent biofilm formation is a key virulence factor and a prerequisite for biofilm development by C. albicans. We investigated the antibiofilm and antifungal activities of 18 hydroquinones against fluconazole-resistant C. albicans. Tetrachlorohydroquinone (TCHQ) at subinhibitory concentrations (2 to 10 μg/mL) significantly inhibited C. albicans biofilm formation with an MIC of 50 μg/mL, whereas the backbone hydroquinone did not (MIC > 400 μg/mL), and it markedly inhibited cell aggregation and hyphal formation. Transcriptomic analyses showed that TCHQ downregulated the expressions of several hyphae-forming and biofilm-related genes (ALS3, ECE1, HWP1, RBT5, and UME6) but upregulated hyphae- and biofilm-inhibitory genes (IFD6 and YWP1). Furthermore, it prevented C. albicans biofilm development on porcine skin and at concentrations of 20 to 50 μg/mL was nontoxic to the nematode Caenorhabditis elegans and did not adversely affect Brassica rapa seed germination and growth. This study indicates that hydroquinones, particularly TCHQ, diminish the virulence, biofilm formation, and animal tissue adhesion of C. albicans, which suggests hydroquinones should be considered potential candidate antifungal agents against drug-resistant C. albicans strains.IMPORTANCE Persistence in chronic infections by Candida albicans is due to its ability of biofilm formation that endures conventional antifungals and host immune systems. Hence, the inhibition of biofilm formation and virulence characteristics is another mean of addressing infections. This study is a distinctive one since 18 hydroquinone analogues were screened and TCHQ efficiently inhibited the biofilm formation by C. albicans with significantly changed expressional profile of hyphae-forming and biofilm-related genes. The antibiofilm efficacy was confirmed using a porcine skin model and chemical toxicity was investigated using plant seed germination and nematode models. Our findings reveal that TCHQ can efficiently control the C. albicans biofilms and virulence characteristics.

Diverse Enterococcus faecalis strains show heterogeneity in biofilm properties

Biofilm formation is important for Enterococcus faecalis to cause healthcare-associated infections. It is unclear how E. faecalis biofilms vary in parameters such as development and composition. To test the hypothesis that differences in biofilms exist among E. faecalis strains, we evaluated in vitro biofilm formation and matrix characteristics of five genetically diverse E. faecalis lab-adapted strains and clinical isolates (OG1RF, V583, DS16, MMH594, and VA1128). Biofilm formation of all strains was repressed in TSB+10% FBS. However, DMEM+10% FBS enhanced biofilm formation of clinical isolate VA1128. Crystal violet staining and fluorescence microscopy of biofilms grown on Aclar membranes demonstrated differences between OG1RF and VA1128 in biofilm development over a 48-h time course. None of the biofilms were dispersed by single treatments of sodium (meta)periodate, DNase, or Proteinase K alone, but the biofilm biomass of both OG1RF and DS16 was partially removed by a sequential treatment of sodium (meta)periodate and DNase. Reversing the treatment order was not effective, suggesting that the extracellular DNA targeted by DNase was obscured by carbohydrates that are susceptible to sodium (meta)periodate degradation. Fluorescent staining of biofilm matrix components further demonstrated that more carbohydrates bound by wheat germ agglutinin comprise OG1RF biofilms compared to VA1128 biofilms. This study highlights the existence of heterogeneity in biofilm properties among diverse E. faecalis strains, which may have implications for the design of novel anti-biofilm treatment strategies.

Clinical and microbiological characteristics of biofilm formation on new and reused dental healing abutments during implantation procedure

Clinical and microbiological characteristics of biofilm formation on new and reused dental healing abutments during implantation procedure

Characteristics of Initial Attachment and Biofilm Formation of Pseudomonas aeruginosa on Microplastic Surfaces

The toxic effect of microplastics on living organisms is emerging as a serious environmental issue nowadays. The biofilm formed on their surface by microorganisms can further increase the toxicity, but the mechanism of biofilm formation on microplastics is not yet fully understood because of the complexities of other factors. This study aimed to identify the factors with an important influence on biofilm formation on microplastic surfaces. The microtiter plate assay was used to evaluate the biofilms formed by Pseudomonas aeruginosa PAO1, a model microorganism, on four types of microplastics, including polyethylene, polystyrene, polypropylene, and polytetrafluoroethylene. The density of microplastics was found to be a key factor in determining the amount of biofilm formation because the density relative to water has a decisive effect on the behavior of microplastics. Biofilm formation on plastics with densities similar to that of water showed remarkable differences based on surface characteristics, whereas biofilm formation on plastics with a higher density was significantly influenced by particle movement in the experimental environment. Furthermore, biofilm formation was inhibited by adding a quorum quenching enzyme, suggesting that QS is critical in biofilm formation on microplastics. This study provides useful information on biofilm formation on microplastic surfaces.

A Literature Review on Biofilm Formation on Silicone and Poymethyl Methacrylate Used for Maxillofacial Prostheses.

Silicone elastomers are considered the most suitable maxillofacial materials for extraoral prostheses to date due to their superior physicochemical properties. The aim of this review was to describe the characteristics of biofilm formation on silicone and polymethyl methacrylate used for maxillofacial prostheses and review different strategies of biofilm management for silicone maxillofacial prosthesis. A structured literature search was conducted using the following databases - PubMed, Google Scholar, ScienceDirect, LILACS, IndeMED, OVID, EMBASE, NIH Clinical Trials - for reports related to the biofilms. English language articles were only included in the study. Biofilms induced various systemic infections if they are not treated at an early stage. Biofilms are formed due to various reasons like fungal, bacterial and mixed infections of the patient and also due to prosthetic appliances. The manual or mechanical pressure physically removes the biofilm and most biofilm molecules from surfaces. Treatment must be given with utmost caution and concern irrespective of the presence or absence of biofilm. With regards to the materials used for fabricating maxillofacial substitutes, it has been defined that both acrylic resin and silicone may harbour microorganisms, however, the larger porosities in silicone make it vulnerable to microbial adhesion. The major limitations of these materials are that they have numerous porosities on their surface and, along with the modification of the anatomy of the facial tissues as a result of the lesion, may compromise the natural balance of the microbial flora, favouring microbial colonization and formation of biofilms.

Characteristics of Staphylococcus aureus small colony variants isolated from wound specimen of a tertiary care hospital in China.

BackgroundSmall colony variants (SCVs) of Staphylococcus aureus (S. aureus) frequently lead to chronic and recurrent infections, but they are always ignored and there are few researches on their clinical isolates. We intended to investigate the prevalence and characteristics of S. aureus SCVs.MethodsNone‐duplicated S. aureus strains isolated from wound samples were collected from January 2018 to December 2020. The characteristics (i.e. colony morphology, growth rate, coagulase, biofilm formation, and pathogenic characteristics), antimicrobial susceptibilities, and resistance mechanisms of SCVs were also investigated. The genetic background of SCVs was analyzed through staphylococcal protein A (SPA) typing, sequence typing, and pulse field gel electrophoresis (PFGE).ResultsThree SCVs were screened from 278 S. aureus strains (1.1%). They formed pinpoint white colonies on blood agar plates with weak hemolysis. The reproduction speed in liquid medium was very slow for SCVs strains. The coagulase weakened or disappeared, and the ability to form biofilm varied greatly. Only slight inflammation was triggered when wound infected. The SPA typing was t2592, t233, and t023, and the sequence typing was ST88, ST239, and ST965, respectively. The PFGE revealed three SCVs were singletons.ConclusionsThe rate of SCVs in wound sample is low in our hospital, and the formation is associated with the usage of antimicrobial. SCVs grow slowly, and their colony morphology and biochemical characteristics are significantly different from classic S. aureus. SCVs may cause chronic infection and weak inflammation. SCVs form in resistant or susceptible strains, and there is no clonal epidemic in this hospital.

Analysis of Bacterial Diversity and Prediction of Phenotype in Rice Wine Koji from Different Regions

A rice wine koji collected from Nanning of Guangxi province and Xiaogan of Hubei province were used to sequence its 16S rRNA V3~V4 region based on Illumina Miseq high-throughput sequencing technology, combined with bioinformatics and multivariate statistical methods to analysis the bacterial diversity of rice wine koji in the two regions, while the bacterial taxa phenotypes were predicted. Results showed that, the Shannon index of the bacterial taxa in the rice wine koji from Nanning area was significantly lower than that of the Xiaogan area (P<0.05). Principal coordinate analysis based on weighted UniFrac distances showed a clear separation trend between the samples from the 2 regions in spatial arrangement. Multivariate analysis of variance indicated that the bacterial community structures of the rice wine koji in the 2 regions were significantly different (P<0.05). The bacterial taxa of rice wine koji in Nanning area were mainly Lactobacillus with an average relative abundance of 62.03%, while Weissella was predominant in the Xiaogan area with an average relative abundance of 50.14%. Phenotypic prediction showed that rice wine koji from Nanning area exhibited a significantly higher (P<0.01) abundance of gram-positive and aerobic bacteria, while a significantly lower (P<0.01) abundance of oxidative stress tolerance, biofilm formation, gram negative, pathogenic potential and facultative anaerobic characteristics. It could be concluded that there are some differences in the bacterial taxa of rice wine koji from different regions.

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.

Biased samples to study reservoir souring processes: A numerical analysis

Production water samples are commonly used to study reservoir souring process. The aim of this study is to examine the reliability of these samples by using a state of the art coupled Thermo-Hydro-bioChemical numerical model. The transport and growth of five different representative sulfate-reducing strains (SRSs) in a model subsurface environment are simulated numerically by considering various biofilm formation characteristics and injection flow rates. After one pore volume (PV) injection, and assuming no biofilm formation, for three injection flow rates corresponding to pore velocities of 5.58 × 10−8, 83.7 × 10−8 and 167.4 × 10−8 m/s, souring within the reservoir is partially or completely derived by two SRSs that have an optimal growth temperature of 28 and 39 °C. However, the produced water taken after one PV is dominated by a SRS that has an optimal temperature of 82 °C. For a higher pore velocity of 558 × 10−8 m/s, without considering any biofilm formation, produced water sample contains the same SRSs as the reservoir. However, if half of the produced biomass by various SRSs participates in biofilm formation, even for the high pore velocity of 558 × 10−8 m/s, the produced water sample cannot reveal the SRSs that derive souring in the reservoir. Therefore, utilizing produced water samples may be misleading in reservoir souring studies. The results presented in this work suggest that more accurate prediction of reservoir souring requires characterization of the major groups of sulfate reducing bacteria in the injection water and undisturbed formation brine, and understanding their biofilm formation behavior.

Two Lysine Sites That Can Be Malonylated Are Important for LuxS Regulatory Roles in Bacillus velezensis.

S-ribosylhomocysteine lyase (LuxS) has been shown to regulate bacterial multicellular behaviors, typically biofilm formation. However, the mechanisms for the regulation are still mysterious. We previously identified a malonylation modification on K124 and K130 of the LuxS in the plant growth-promoting rhizobacterium B. velezensis (FZB42). In this work, we investigated the effects of the two malonylation sites on biofilm formation and other biological characteristics of FZB42. The results showed that the K124R mutation could severely impair biofilm formation, swarming, and sporulation but promote AI-2 production, suggesting inhibitory effects of high-level AI-2 on the features. All mutations (K124R, K124E, K130R, and K130E) suppressed FZB42 sporulation but increased its antibiotic production. The double mutations generally had a synergistic effect or at least equal to the effects of the single mutations. The mutation of K130 but not of K124 decreased the in vitro enzymatic activity of LuxS, corresponding to the conservation of K130 among various Bacillus LuxS proteins. From the results, we deduce that an alternative regulatory circuit may exist to compensate for the roles of LuxS upon its disruption. This study broadens the understanding of the biological function of LuxS in bacilli and underlines the importance of the two post-translational modification sites.

The Vaginal Microbiota, Bacterial Biofilms and Polymeric Drug-Releasing Vaginal Rings.

The diversity and dynamics of the microbial species populating the human vagina are increasingly understood to play a pivotal role in vaginal health. However, our knowledge about the potential interactions between the vaginal microbiota and vaginally administered drug delivery systems is still rather limited. Several drug-releasing vaginal ring products are currently marketed for hormonal contraception and estrogen replacement therapy, and many others are in preclinical and clinical development for these and other clinical indications. As with all implantable polymeric devices, drug-releasing vaginal rings are subject to surface bacterial adherence and biofilm formation, mostly associated with endogenous microorganisms present in the vagina. Despite more than 50 years since the vaginal ring concept was first described, there has been only limited study and reporting around bacterial adherence and biofilm formation on rings. With increasing interest in the vaginal microbiome and vaginal ring technology, this timely review article provides an overview of: (i) the vaginal microbiota, (ii) biofilm formation in the human vagina and its potential role in vaginal dysbiosis, (iii) mechanistic aspects of biofilm formation on polymeric surfaces, (iv) polymeric materials used in the manufacture of vaginal rings, (v) surface morphology characteristics of rings, (vi) biomass accumulation and biofilm formation on vaginal rings, and (vii) regulatory considerations.

Exopolysaccharide Carbohydrate Structure and Biofilm Formation by Rhizobium leguminosarum bv. trifolii Strains Inhabiting Nodules of Trifoliumrepens Growing on an Old Zn-Pb-Cd-Polluted Waste Heap Area.

Heavy metals polluting the 100-year-old waste heap in Bolesław (Poland) are acting as a natural selection factor and may contribute to adaptations of organisms living in this area, including Trifolium repens and its root nodule microsymbionts—rhizobia. Exopolysaccharides (EPS), exuded extracellularly and associated with bacterial cell walls, possess variable structures depending on environmental conditions; they can bind metals and are involved in biofilm formation. In order to examine the effects of long-term exposure to metal pollution on EPS structure and biofilm formation of rhizobia, Rhizobium leguminosarum bv. trifolii strains originating from the waste heap area and a non-polluted reference site were investigated for the characteristics of the sugar fraction of their EPS using gas chromatography mass-spectrometry and also for biofilm formation and structural characteristics using confocal laser scanning microscopy under control conditions as well as when exposed to toxic concentrations of zinc, lead, and cadmium. Significant differences in EPS structure, biofilm thickness, and ratio of living/dead bacteria in the biofilm were found between strains originating from the waste heap and from the reference site, both without exposure to metals and under metal exposure. Received results indicate that studied rhizobia can be assumed as potentially useful in remediation processes.

Biofilm Formation Ability and Presence of Adhesion Genes among Coagulase-Negative and Coagulase-Positive Staphylococci Isolates from Raw Cow's Milk.

The capacity for biofilm formation is one of the crucial factors of staphylococcal virulence. The occurrence of biofilm-forming staphylococci in raw milk may result in disturbances in technological processes in dairy factories as well as the contamination of finished food products. Therefore, this study aimed to determine the prevalence and characteristics of staphylococcal biofilm formation in raw milk samples and to explore the genetic background associated with biofilm formation in those isolates. The material subjected to testing included 30 cow’s milk samples acquired from farms in the central part of Poland. A total of 54 staphylococcal strains were isolated from the samples, of which 42 were classified as coagulase-negative (CoNS) staphylococci belonging to the following species: S. haemolyticus, S. simulans, S. warneri, S. chromogenes, S. hominis, S. sciuri, S. capitis, S. xylosus and S. saprophyticus, while 12 were classified as S. aureus. The study examined the isolates’ capacity for biofilm formation and the staphylococcal capacity for slime production and determined the presence of genetic determinants responsible for biofilm formation, i.e., the icaA, icaD, bap and eno and, additionally, among coagulase-negative staphylococci, i.e., the aap, bhp, fbe, embP and atlE. Each tested isolate exhibited the capacity for biofilm formation, of which most of them (79.6%) were capable of forming a strong biofilm, while 5.6% formed a moderate biofilm, and 14.8% a weak biofilm. A capacity for slime production was demonstrated in 51.9% isolates. Most of the tested staphylococcal strains (90.7%) had at least one of the tested genes. Nearly half (47.6%) of the CoNS had the eno gene, while for S. aureus, the eno gene was demonstrated in 58.3% isolates. The frequency of the bap gene occurrence was 23.8% and 25% in CoNS strains and S. aureus, respectively. The fbe gene was demonstrated in only three CoNS isolates. The presence of the icaA was only demonstrated in CoNS strains (24.1%), while the icaD was found in both CoNS strains (21.4%) and S. aureus (100%). Among the CoNS, the presence of the embP (16.7%), aap (28.6%) and atlE (23.8%) was demonstrated as well. The obtained study results indicate that bacteria of the Staphylococcus spp. genus have a strong potential to form a biofilm, which may pose a hazard to consumer health.

Small noncoding RNA sRNA0426 is involved in regulating biofilm formation in Streptococcus mutans.

Evidence suggests that small noncoding RNAs (sRNAs) are involved in the complex regulatory networks governing biofilm formation. Few studies have investigated the role of sRNAs in Streptococcus mutans (S. mutans). In the present study, the association between sRNA and biofilm formation in S. mutans was explored. sRNAs that are differentially expressed in the biofilm and planktonic states of this bacterium were identified by quantitative real‐time PCR (qRT‐PCR). Confocal laser scanning microscopy was used to investigate the characteristics of biofilm formation in a standard strain of S. mutans (UA159, ATCC 700610) and ten clinical strains. Bioinformatics analyses were employed to predict and examine potential sRNA regulatory pathways. The results showed that sRNA0426 has a strong positive relationship with dynamic biofilm formation. Moreover, sRNA0426 expression was positively correlated with exopolysaccharide (EPS) production. Bioinformatics analyses showed that sRNA0426 is involved in biofilm formation such as metabolic pathways, especially carbon metabolism. Five target mRNAs (GtfB, GtfC, GtfD, ComE, and CcpA) involved in the synthesis of EPS were selected for further evaluation; the expression levels of three of these mRNAs (GtfB, GtfC, and CcpA) were positively correlated with sRNA0426 expression levels, and the expression level of one (ComE) was negatively correlated. In conclusion, the results suggested that sRNA0426 may play an important and positive role in the biofilm formation of S. mutans and provide novel insight into the S. mutans biofilm regulatory network.

Biofilm Formation Characteristics of Major Foodborne Pathogens on Polyethylene and Stainless Steel Surfaces

This research was investigated the effects of temperature and time against the formation of biofilms by foodborne pathogens on surfaces of polyethylene and stainless steel. After preliminary experiments with 32 strains from 6 species of foodborne pathogens (Bacillus cereus, Listeria monocytogenes, Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, and Salmonella Typhimurium), one strain from each species with the highest biofilm formation efficiency was selected. All foodborne pathogens showed a tendency toward an increased ability for biofilm formation with increasing temperature, but there was no consistency between the two materials and between foodborne pathogens. At all tested temperatures, the biofilm formation ability of E. coli and P. aeruginosa on the polyethylene surface was higher than that on the stainless steel surface with significant differences. The foodborne pathogens all formed biofilms immediately upon inoculation, and biofilm formation by E. coli, P. aeruginosa, and S. Typhimurium increased on both the polyethylene and stainless steel surfaces at 1 h after inoculation compared to at 0 h. At 7 days after biofilm formation, the other strains except S. aureus showed no difference in survival rates on polyethylene and stainless steel. The ability of these 6 foodborne pathogens to form biofilms showed different trends depending on the type of bacteria and the instrument material, i.e., polyethylene and stainless steel.

The use of multifunctional yeast-lactobacilli starter cultures improves fermentation performance of Spanish-style green table olives

In this work, Lactobacillus pentosus LPG1, Lactobacillus pentosus Lp13, Lactobacillus plantarum Lpl15, and Wickerhanomyces anomalous Y12, all of them previously isolated from fermented table olive biofilms, were used (alone or in combination) as multifunctional starters for Manzanilla Spanish-style green table olive fermentations. Their performances were evaluated through the changes in the key physico-chemical and microbiological parameters, correlation between AI-2 production and biofilm formation, inoculum imposition, metataxonomic analysis and sensory characteristics of the finished products. Inoculation only with lactic acid bacteria (LAB) strains led to higher titratable acidities and lower pH values than the spontaneous fermentation (non-inoculated control), mainly during the first steps of processing. However, the sequential inoculation of the yeast and then the combination of the 3 LAB strains showed the most favourable evolution. LPG1 strain and, particularly Lp13, were excellent biofilms former and showed the major imposition on the fruit epidermis, as corroborated by rep-PCR analysis. Production of AI-2 was lower in the treatment inoculated exclusively with yeast Y12 but had the highest presence in the sequential yeast-LAB inoculum, with its maximum concentration and maximum LAB population on fruits (19th days) strongly related. Metataxonomic analysis of the biofilms at the end of the fermentation revealed, in addition to Lactobacillus, high proportions of sequences from genera Marinilactobacillus, Alkalibacterium, Halolactobacillus, and low levels of Halomonas and Aerococcus. Compositional data analysis of the omics data revealed that Lpl15 was scarcely efficient for controlling the spontaneous microbiota since its treatment presented the highest proportions of Aerococcus genus. Finally, the sensory analysis showed similar characteristics for the treatment inoculated with LPG1 and the spontaneous process, with olives inoculated with the yeast (alone or in combination with Lactobacillus strains) showing attractive scores. Then, inoculation of Spanish-style table olive fermentations with a sequential yeast and LAB combination could be an advisable practice.