Molecular interactions in biofilms

An integrated quorum quenching biocatalytic nanoplatform for synergistic chemo-photothermal eradication of P. aeruginosa biofilm infections

Decontamination of biofilm-associated infections presents a significant challenge due to the physical and chemical barrier created by the formation of extracellular matrices. This barrier restricts the access of antibiotics to the bacterial communities within the biofilm and provides protection to the persister cells, potentially leading to antibiotic resistance. In this study, we have developed an integrated quorum quenching biocatalytic nanoplatform for the synergistic chemo-photothermal eradication of P. aeruginosa biofilm infections. Ciprofloxacin (Cip), a model antibiotic, was absorbed onto PDA NPs through π-π stacking. Additionally, acylase (AC) was immobilized on PDA NPs through Schiff base reaction and Michael addition, resulting in the formation of the biocatalytic nanoplatform (PDA-Cip-AC NPs). This biocatalytic nanoplatform was able to enzymatically degrade AHL signaling molecules, thus achieving efficient quorum quenching activity to prevent biofilm formation. Furthermore, the NIR light-triggered on-demand Ciprofloxacin release further enhanced the eradication of P. aeruginosa biofilm infections with a synergy of local hyperthermia. We envision that this integrated quorum quenching nanoplatform provides a reliable tool for combating P. aeruginosa biofilm infections. STATEMENT OF SIGNIFICANCE: An integrated quorum quenching biocatalytic nanoplatform has been developed for the eradication of P. aeruginosa biofilm infections. Quorum-sensing signals play a crucial role in modulating bacterial cell-to-cell communication, biofilm formation, and secretion of virulence factors. This biocatalytic nanoplatform efficiently degrades AHL signaling molecules, thereby blocking cell-to-cell communication and preventing biofilm formation. Additionally, local hyperthermia and on-demand Ciprofloxacin release were achieved through NIR irradiation, working synergistically to eradicate P. aeruginosa biofilm infections.

Volatile anesthetic isoflurane exposure facilitates Enterococcus biofilm infection

Enterococcus faecalis (E. faecalis) is one of the major pathogenic bacteria responsible for surgical site infections. Biofilm infections are major hospital-acquired infections. Previous studies suggested that ions could regulate biofilm formation in microbes. Volatile anesthetics, frequently administered in surgical setting, target ion channels. Here, we investigated the role of ion channels/transporters and volatile anesthetics in the biofilm formation by E. faecalis MMH594 strain and its ion transporter mutants. We found that a chloride transporter mutant significantly reduced biofilm formation compared to the parental strain. Downregulation of teichoic acid biosynthesis in the chloride transporter mutant impaired biofilm matrix formation and cellular adhesion, leading to mitigated biofilm formation. Among anesthetics, isoflurane exposure enhanced biofilm formation in vitro and in vivo. The upregulation of de novo purine biosynthesis pathway by isoflurane exposure potentially enhanced biofilm formation, an essential process for DNA, RNA, and ATP synthesis. We also demonstrated that isoflurane exposure to E. faecalis increased cyclic-di-AMP and extracellular DNA production, consistent with the increased purine biosynthesis. We further showed that isoflurane enhanced the enzymatic activity of phosphoribosyl pyrophosphate synthetase (PRPP-S). With the hypothesis that isoflurane directly bound to PRPP-S, we predicted isoflurane binding site on it using rigid docking. Our study provides a better understanding of the underlying mechanisms of E. faecalis biofilm formation and highlights the potential impact of an ion transporter and volatile anesthetic on this process. These findings may lead to the development of novel strategies for preventing E. faecalis biofilm formation and improving patient outcomes in clinical settings.

Comparative analysis of outer membrane vesicles from uropathogenic Escherichia coli reveal the role of aromatic amino acids synthesis proteins in motility

Uropathogenic Escherichia coli (UPEC) are causative agent that causes urinary tract infections (UTIs) and the recent emergence of multidrug resistance (MDR) of UPEC increases the burden on the community. Recent studies of bacterial outer membrane vesicles (OMV) identified various factors including proteins, nucleic acids, and small molecules which provided inter-cellular communication within the bacterial population. However, the components of UPEC-specific OMVs and their functional role remain unclear. Here, we systematically determined the proteomes of UPEC-OMVs and identified the specific components that provide functions to the recipient bacteria. Based on the functional network of OMVs' proteomes, a group of signaling peptides was found in all OMVs which provide communication among bacteria. Moreover, we demonstrated that treatment with UPEC-OMVs affected the motility and biofilm formation of the recipient bacteria, and further identified aromatic amino acid (AAA) biosynthesis proteins as the key factors to provide their movement.

Immunometabolism in biofilm infection: lessons from cancer

BACKGROUND

Biofilm is a community of bacteria embedded in an extracellular matrix, which can colonize different human cells and tissues and subvert the host immune reactions by preventing immune detection and polarizing the immune reactions towards an anti-inflammatory state, promoting the persistence of biofilm-embedded bacteria in the host.

MAIN BODY OF THE MANUSCRIPT

It is now well established that the function of immune cells is ultimately mediated by cellular metabolism. The immune cells are stimulated to regulate their immune functions upon sensing danger signals. Recent studies have determined that immune cells often display distinct metabolic alterations that impair their immune responses when triggered. Such metabolic reprogramming and its physiological implications are well established in cancer situations. In bacterial infections, immuno-metabolic evaluations have primarily focused on macrophages and neutrophils in the planktonic growth mode.

CONCLUSION

Based on differences in inflammatory reactions of macrophages and neutrophils in planktonic- versus biofilm-associated bacterial infections, studies must also consider the metabolic functions of immune cells against biofilm infections. The profound characterization of the metabolic and immune cell reactions could offer exciting novel targets for antibiofilm therapy.

Legionella pneumophila-Virulence Factors and the Possibility of Infection in Dental Practice

Legionella pneumophila is defined as a bacterium that can cause severe pneumonia. It is found in the natural environment and in water, and is often found in water tanks. It can be an integral part of biofilms in nature, and the protozoa in which it can live provide it with food and protect it from harmful influences; therefore, it has the ability to move into a sustainable but uncultured state (VBNC). L. pneumophila has been shown to cause infections in dental practices. The most common transmission route is aerosol generated in dental office water systems, which can negatively affect patients and healthcare professionals. The most common way of becoming infected with L. pneumophila in a dental office is through water from dental instruments, and the dental unit. In addition to these bacteria, patients and the dental team may be exposed to other harmful bacteria and viruses. Therefore, it is vital that the dental team regularly maintains and decontaminates the dental unit, and sterilizes all accessories that come with it. In addition, regular water control in dental offices is necessary.

Regulatory network controls microbial biofilm development, with Candida albicans as a representative: from adhesion to dispersal

Microorganisms mainly exist in the form of biofilm in nature. Biofilm can contaminate food and drinking water system, as well as cause chronic wound infections, thereby posing a potential threat to public health safety. In the last two decades, researchers have made efforts to investigate the genetic contributors control different stages of biofilm development (adherence, initiation, maturation, and dispersal). As an opportunistic pathogen, C. albicans causes severe superficial or systemic infections with high morbidity and mortality under conditions of immune dysfunction. It has been reported that 80% of C. albicans infections are directly or indirectly associated with biofilm formation on host or abiotic surfaces including indwelling medical devices, resulting in high morbidity and mortality. Significantly, the outcome of C. albicans biofilm development includes enhanced invasion, exacerbated inflammatory responses and intrinsic resistance to antimicrobial chemotherapy. Thus, this review aimed at providing a comprehensive overview of the regulatory network controls microbial biofilm development, with C. albicans as a representative, served as reference for therapeutic targets.

Role of biofilms in the survival of Legionella pneumophila to sodium chloride treatment

Background and Objectives

Legionnaires' disease continues to be a public health concern. Colonized water distribution systems are often implicated in Legionella transmission, despite the use of various disinfection strategies, the bacterium is capable to persist and survive in water systems. The aim of this study was to investigate the persistence of Legionella pneumophila to sodium chloride over time at different temperatures and analysing the role of biofilms in the survival of this bacteria.

Materials and Methods

L. pneumophila serogroup 1 and L. pneumophila serogroup 2-15 were used to study the effect of sodium chloride on planktonic and sessile cells. The tested concentrations were: 0.5%, 1%, 2%, 3%, 4%, 6% and 8% (W/V) NaCl. Biofilms were grown on 24-well microplates.

Results

At 20°C, L. pneumophila planktonic cells were able to survive in sodium chloride concentrations up to 2%. However, at 37°C, a sodium chloride concentration over 1.5%, reduced systematically the numbers of bacterial cells. Biofilms were grown for 20 days in the absence and presence of sodium chloride. The results show that bacterial strains were able to survive and regrow after the sodium chloride shock (2-3%). Moreover, it seems that this effect is less expressed with the age of the biofilm; old biofilms were more persistent than the young ones.

Conclusion

Results from this study demonstrate that the sodium chloride disinfection strategy was effective on Legionella pneumophila planktonic cells but not on biofilms, which demonstrate the role of biofilms in the persistence and recolonization of L. pneumophila in water distribution systems.

Contributions of Escherichia coli and Its Motility to the Formation of Dual-Species Biofilms with Vibrio cholerae

Biofilm formation is important in both the environmental and intestinal phases of the Vibrio cholerae life cycle. Nevertheless, most studies of V. cholerae biofilm formation focus on monospecies cultures, whereas nearly all biofilm communities found in nature consist of a variety of microorganisms. Multispecies biofilms formed between V. cholerae and other bacteria in the environment and the interactions that exist between these species are still poorly understood. In this study, the influence of Escherichia coli on the biofilm formation of V. cholerae was studied in the context of both in vitro coculture and in vivo coinfection. To understand the underlying synergistic mechanisms between these two species and to investigate the role of E. coli in V. cholerae biofilm formation, different pathotypes of E. coli and corresponding deletion mutants lacking genes that influence flagellar motility, curli fibers, or type I pili were cocultured with V. cholerae. Our findings demonstrate that the presence of commensal E. coli increases biofilm formation at the air-liquid interface in vitro and the generation of biofilm-like multicellular clumps in mouse feces. Examination of laboratory E. coli flagellar-motility ΔfliC and ΔmotA mutants in dual-species biofilm formation suggests that flagellar motility plays an important role in the synergistic interaction and coaggregation formation between V. cholerae and E. coli. This study facilitates a better understanding of how V. cholerae resides in harsh environments and colonizes the intestine. IMPORTANCE Biofilms play an important role in the V. cholerae life cycle. Until now, only monospecies biofilm formation of V. cholerae has been well studied. However, in nature, bacteria live in complex microbial communities, where biofilm is mostly composed of multiple microbial species that interact to cooperate with or compete against each other. Uncovering how V. cholerae forms multispecies biofilms is critical for furthering our understanding of how V. cholerae survives in the environment and transitions to infecting the human host. In this work, the dual-species biofilm containing V. cholerae and Escherichia coli was investigated. We demonstrate that the presence of commensal E. coli increased overall biofilm formation. Furthermore, we demonstrate that the motility of E. coli flagella is important for V. cholerae and E. coli to form coaggregation clumps in a dual-species biofilm. These results shed light on a new mechanism for understanding the survival and pathogenesis of V. cholerae.

Photodynamic Inactivation Using Natural Bioactive Compound Prevents and Disrupts the Biofilm Produced by Staphylococcus saprophyticus

Staphylococcus saprophyticus, the food-borne bacteria present in dairy products, ready-to-eat food and environmental sources, has been reported with antibiotic resistance, raising concerns about food microbial safety. The antimicrobial resistance of S. saprophyticus requires the development of new strategies. Light- and photosensitizer-based antimicrobial photodynamic inactivation (PDI) is a promising approach to control microbial contamination, whereas there is limited information regarding the effectiveness of PDI on S. saprophyticus biofilm control. In this study, PDI mediated by natural bioactive compound (curcumin) associated with LED was evaluated for its potential to prevent and disrupt S. saprophyticus biofilms. Biofilms were treated with curcumin (50, 100, 200 µM) and LED fluence (4.32 J/cm², 8.64 J/cm², 17.28 J/cm²). Control groups included samples treated only with curcumin or light, and samples received neither curcumin nor light. The action was examined on biofilm mass, viability, cellular metabolic activity and cytoplasmic membrane integrity. PDI using curcumin associated with LED exhibited significant antibiofilm activities, inducing biofilm prevention and removal, metabolic inactivation, intracellular membrane damage and cell death. Likewise, scanning electronic microscopy observations demonstrated obvious structural injury and morphological alteration of S. saprophyticus biofilm after PDI application. In conclusion, curcumin is an effective photosensitizer for the photodynamic control of S. saprophyticus biofilm.

A regulatory network involving Rpo, Gac and Rsm for nitrogen-fixing biofilm formation by Pseudomonas stutzeri

Biofilm and nitrogen fixation are two competitive strategies used by many plant-associated bacteria; however, the mechanisms underlying the formation of nitrogen-fixing biofilms remain largely unknown. Here, we examined the roles of multiple signalling systems in the regulation of biofilm formation by root-associated diazotrophic P. stutzeri A1501. Physiological analysis, construction of mutant strains and microscale thermophoresis experiments showed that RpoN is a regulatory hub coupling nitrogen fixation and biofilm formation by directly activating the transcription of pslA, a major gene involved in the synthesis of the Psl exopolysaccharide component of the biofilm matrix and nifA, the transcriptional activator of nif gene expression. Genetic complementation studies and determination of the copy number of transcripts by droplet digital PCR confirmed that the regulatory ncRNA RsmZ serves as a signal amplifier to trigger biofilm formation by sequestering the translational repressor protein RsmA away from pslA and sadC mRNAs, the latter of which encodes a diguanylate cyclase that synthesises c-di-GMP. Moreover, RpoS exerts a braking effect on biofilm formation by transcriptionally downregulating RsmZ expression, while RpoS expression is repressed posttranscriptionally by RsmA. These findings provide mechanistic insights into how the Rpo/Gac/Rsm regulatory networks fine-tune nitrogen-fixing biofilm formation in response to the availability of nutrients.

Potential strategies to prevent encrustations on urinary stents and catheters - thinking outside the box: a European network of multidisciplinary research to improve urinary stents (ENIUS) initiative

Introduction: Urinary stents have been around for the last 4 decades, urinary catheters even longer. They are associated with infections, encrustation, migration, and patient discomfort. Research efforts to improve them have shifted onto molecular and cellular levels. ENIUS brought together translational scientists to improve urinary implants and reduce morbidity.Methods & materials: A working group within the ENIUS network was tasked with assessing future research lines for the improvement of urinary implants.Topics were researched systematically using Embase and PubMed databases. Clinicaltrials.gov was consulted for ongoing trials.Areas covered: Relevant topics were coatings with antibodies, enzymes, biomimetics, bioactive nano-coats, antisense molecules, and engineered tissue. Further, pH sensors, biodegradable metals, bactericidal bacteriophages, nonpathogenic uropathogens, enhanced ureteric peristalsis, electrical charges, and ultrasound to prevent stent encrustations were addressed.Expert opinion: All research lines addressed in this paper seem viable and promising. Some of them have been around for decades but are yet to proceed to clinical application (i.e. tissue engineering). Others are very recent and, at least in urology, still only conceptual (i.e. antisense molecules). Perhaps the most important learning point resulting from this pan-European multidisciplinary effort is that collaboration between all stakeholders is not only fruitful but also truly essential.

The establishment of the CBE launched biofilms as a field of specialized research

The Center for Biofilm Engineering was the first center of excellence focused on biofilms and was originally funded through the Engineering Research Center Program from the U.S. National Science Foundation. After almost 30 years, biofilm continues to be a stand-alone scientific topic of inquiry that has broad implications for fundamental and applied science and engineering of bio-systems. However, much remains to be done, not only for research discovery but also education and outreach, to increase and grow the biofilm paradigm as well as our understanding of the microbial world.

Evolution of Antibiotic Resistance in Surrogates of Francisella tularensis (LVS and Francisella novicida): Effects on Biofilm Formation and Fitness

Francisella tularensis, the causative agent of tularemia, is capable of causing disease in a multitude of mammals and remains a formidable human pathogen due to a high morbidity, low infectious dose, lack of a FDA approved vaccine, and ease of aerosolization. For these reasons, there is concern over the use of F. tularensis as a biological weapon, and, therefore, it has been classified as a Tier 1 select agent. Fluoroquinolones and aminoglycosides often serve as the first line of defense for treatment of tularemia. However, high levels of resistance to these antibiotics has been observed in gram-negative bacteria in recent years, and naturally derived resistant Francisella strains have been described in the literature. The acquisition of antibiotic resistance, either natural or engineered, presents a challenge for the development of medical countermeasures. In this study, we generated a surrogate panel of antibiotic resistant F. novicida and Live Vaccine Strain (LVS) by selection in the presence of antibiotics and characterized their growth, biofilm capacity, and fitness. These experiments were carried out in an effort to (1) assess the fitness of resistant strains; and (2) identify new targets to investigate for the development of vaccines or therapeutics. All strains exhibited a high level of resistance to either ciprofloxacin or streptomycin, a fluoroquinolone and aminoglycoside, respectively. Whole genome sequencing of this panel revealed both on-pathway and off-pathway mutations, with more mutations arising in LVS. For F. novicida, we observed decreased biofilm formation for all ciprofloxacin resistant strains compared to wild-type, while streptomycin resistant isolates were unaffected in biofilm capacity. The fitness of representative antibiotic resistant strains was assessed in vitro in murine macrophage-like cell lines, and also in vivo in a murine model of pneumonic infection. These experiments revealed that mutations obtained by these methods led to nearly all ciprofloxacin resistant Francisella strains tested being completely attenuated while mild attenuation was observed in streptomycin resistant strains. This study is one of the few to examine the link between acquired antibiotic resistance and fitness in Francisella spp., as well as enable the discovery of new targets for medical countermeasure development.

Evaluation of Enzymatic Cleaning on Food Processing Installations and Food Products Bacterial Microflora

Biofilms are a permanent source of contamination in food industries and could harbor various types of microorganisms, such as spoiling bacteria. New strategies, such as enzymatic cleaning, have been proposed to eradicate them. The purpose of this study was to evaluate the impact of enzymatic cleaning on the microbial flora of installations in a processing food industry and of the final food product throughout its shelf life. A total of 189 samples were analyzed by classical microbiology and 16S rDNA metagenetics, including surface samples, cleaning-in-place (CIP) systems, and food products (at D₀, D_{end of the shelf life}, and D_{end of the shelf life +7 days}). Some surfaces were highly contaminated with spoiling bacteria during conventional cleaning while the concentration of the total flora decreased during enzymatic cleaning. Although the closed circuits were cleaned with conventional cleaning before enzymatic cleaning, there was a significant release of microorganisms from some parts of the installations during enzymatic treatment. A significant difference in the total flora in the food products at the beginning of the shelf life was observed during enzymatic cleaning compared to the conventional cleaning, with a reduction of up to 2 log CFU/g. Metagenetic analysis of the food samples at the end of their shelf life showed significant differences in bacterial flora between conventional and enzymatic cleaning, with a decrease of spoiling bacteria (Leuconostoc sp.). Enzymatic cleaning has improved the hygiene of the food processing instillations and the microbial quality of the food throughout the shelf life. Although enzymatic cleaning is not yet commonly used in the food industry, it should be considered in combination with conventional sanitizing methods to improve plant hygiene.

A tandem GGDEF-EAL domain protein-regulated c-di-GMP signal contributes to spoilage-related activities of Shewanella baltica OS155

Cyclic diguanylate (c-di-GMP) is a second messenger involved in the regulation of various physiological processes in bacteria. However, its function in spoilage bacteria has not yet been addressed. Here, we studied the function of a tandem GGDEF-EAL domain protein, Sbal_3235, in the spoilage bacterium Shewanella baltica OS155. The deletion of sbal_3235 significantly reduced the c-di-GMP level, biofilm formation, and exopolysaccharide, trimethylamine (TMA), and putrescine production; sbal_3235 deletion also downregulated the expression of the torS and speF genes and affected membrane fatty acid composition. Site-directed mutagenesis in conserved GGDEF and EAL motifs abolished diguanylate cyclase (DGC) and phosphodiesterase (PDE) activity, respectively. These data indicate that Sbal_3235 is an essential contributor to the c-di-GMP pool with bifunctional DGC and PDE activity, which is involved in the biofilm formation and spoilage activity of S. baltica OS155. Our findings expand the biochemical role of c-di-GMP and uncover its link to spoilage activities, providing novel targets for food quality and safety controlling.

The Effects of Subcellular Nanograting Geometry on the Formation and Growth of Bacterial Biofilms

Biofilm formation by bacteria protects them against environmental stresses such as desiccation, shear forces and antimicrobial agents, making them much harder to remove and increasing their virulence and persistence in industrial water systems and biomedical equipment. One promising method of disrupting biofilm formation and growth is to employ passive surface structures to inhibit bacterial adhesion and aggregation. However, most studies thus far have mainly focused on the early stages of biofilm formation and it is unclear if the influence of surface topography in the early phase will propagate to later stages. Here, we attempt to address this with an investigation into the biofilm formation of Pseudomonas aeruginosa on 25 different nanograting geometries, with dimensions that were systematically varied from subcellular to cellular sizes. The biofilms were characterized from the exponential growth phase to the decline phase, in intervals of 24 H over 4 days, using confocal scanning laser microscopy. Comparing the maximum volume of biofilm formed on each surface over 96 H, it was found that approximately 1/3 of the nanograting geometries exhibited 72 ± 16 % lower biovolume density than a flat surface. Bacteria on these nanogratings were also observed to form 40 ± 11 % smaller microcolonies that were 17 ± 6 % less compact than that found on the control surface. The majority of these nanogratings had deep trenches (i.e. depth ≥ 70% of the cell diameter). Furthermore, P. aeruginosa cells were observed to multiply at approximately twice the rate on almost all the nanogratings compared to flat surfaces, but these cell populations also began to decline 24 H earlier than those on a flat surface. Using available literature on P. aeruginosa, a qualitative model was put forth, attributing the results to increased cell motility, decreased exopolysaccharide formation and disrupted psl adhesin/signal trails on nanogratings. These factors, together, led to the net effects of reduced attachment, increased scattering of cells and rapid decline of the biofilms on nanogratings. The insights derived from this study suggest that passive surface geometries can be designed and optimized to successfully control/inhibit biofilm formation and growth.

Evaluation of the efficacy of commonly used disinfectants against isolated chlorine-resistant strains from drinking water used in Egyptian cattle farms

BACKGROUND AND AIM

Drinking water of poor microbiological quality contains high percentages of microbes causing outbreaks of mainly coliform-related diseases. These microbes could be controlled by many hygienic standards including disinfection, but disinfectants misuse causes the developing of disinfectant-resistant strains. The present study aimed to investigate drinking water bacterial profile, determine chlorine-resistant strains, and statistically correlate that with the used disinfectant and disinfection process variables. In vitro evaluation of the bactericidal effect of the most commonly used disinfectants in cattle operations against the isolated chlorine-resistant strains and detection of qacE resistance gene in the isolated chlorine-resistant Escherichia coli strains in some cattle farms suffering coliform and non-coliform related disease around Egypt.

MATERIALS AND METHODS

A structured questionnaire is used to survey a convenience sample of 132 Egyptian cattle beef and dairy farms suffering emerged epidemics to identify commonly used disinfection process, disinfectant types, disinfectants frequency, and rate of use. One hundred and thirty-two water samples were collected for microbiological analysis to obtain water bacterial profile and testing resistance to chlorine. Statistical analysis was performed to identify the level of association between microbial profile and presence of chlorine-resistant strains in each farm with used disinfection, disinfectant types, and rate of use in these farms.

RESULTS

A wide range of disinfectant types used for variable purposes inside cattle farms with a different frequency of use and the highest percent of farms 25.8% use 4-5 types of disinfectants, followed by 25% of farms use two types, then 18.9% use three types. Microbial profile of water samples revealed isolation of E. coli, Streptococcus faecalis, Pseudomonas aeruginosa, Klebsiella spp., Proteus spp., Salmonella spp., Enterobacter spp., Citrobacter spp., Shigella flexneri, Serratia marcescens, and Yersinia enterocolitica in percent (98.5, 97.7, 97.7, 76.5, 66.7, 36.4, 78.8, 74.2, 30.3, 29.5, and 14.4% of cattle farms, respectively), from which five E. coli, four Salmonella, four Pseudomonas, two Klebsiella, and four Streptococcus strains expressed chlorine resistance. Statistical analysis showed weak to moderate correlation (rho 0.15-0.46) between bacterial profile strains count and presence of resistant strains with different farm disinfection, disinfectant types, and rate of use. Experimental evaluation of the bactericidal effect of the eight selected disinfectants on the chlorine-resistant isolated strains revealed that peroxymonosulfate killed 19/19 isolated strains/15 min contact time, and quaternary ammonium compounds killed only 3/19 strains/15 min contact time. The qacE resistance gene was detected in 3/4 isolated chlorine-resistant E. coli strains.

CONCLUSION

Drinking water microbial profile strains and resistance to disinfectants are widely varied in cattle farms, and this variance depends on critical factors among which the disinfection process types used disinfectant types and frequency of disinfectants use or change.

The role of quorum sensing in granular sludge: Impact and future application: A review

Quorum sensing (QS) is a process widely exist in bacteria, which refers to the cell-cell communication through secretion and sensing the specific chemical signal molecules named autoinducers. This review demonstrated recent research progresses on the specific impacts of signal molecules in the granular sludge reactors, such corresponding exogenous strategies contained the addition of QS signal molecules, QS-related enzymes and bacteria associated with QS process. Accordingly, the correlation between QS signaling molecule content and sludge granulation (including the formation and stability) was assumed, the comprehensive conclusion elucidated that some QS signals (acyl-homoserine lactone and Autoinducer 2) can accelerate the growth of particle diameter, the production of extracellular polymeric substance (EPS), microbial adhesion and change the microbiome structure. But diffusable signal factor (DSF) acted as a significant disincentive to the formation and stability of GS. As a result, it deserved serious attention on the value and role of QS signals in the GS. This review attempts to illuminate the potential method for addressing the main bottleneck: to accelerate the formation of granules and keep the high stability of GS for a long-term reactor. Therefore, review discussed the possible trends of GS: QS and intercellular/intracellular signaling which can lay a theoretical foundation for mechanism of GS formation and stability, would be of practical significance for further application in the future.

Bacterial Film Disintegration with Electrochemically Reduced Water

The aim of this work was to study the fine structure of bacterial films grown on the inner tube surface of a flow reactor. Using the scanning electron microscopy (SEM) approaches, the detailed biofilm relief was visualized. The action of electrochemically reduced water (ERW) on the biofilm ultrastructure generated by the plankton form of E. coli and/or lacto bacteria was investigated. The treatment with an ERW solution destroyed the biofilm organic polymer matrix and bacterial cells embedded in the matrix.

Sulfur-Functionalized Fullerene Nanoparticle as an Inhibitor and Eliminator Agent on Pseudomonas aeruginosa Biofilm and Expression of toxA Gene

Over the last decade, nanotechnology-based therapeutic platforms have been directed toward developing nanoparticles with unique properties to combat biofilms. In this study, we evaluated the antibiofilm activity of the sulfur-functionalized fullerene nanoparticles (SFF Nps) against Pseudomonas aeruginosa and also analyzed the effect of this nanoparticle on the expression of exotoxin A (toxA) gene. The functionalized fullerenes were prepared by chemical vapor deposition method. We assessed the potential of SFF Nps to inhibit biofilm formation and eradicate preformed biofilms. Also, the effect of this nanoparticle on the expression of toxA gene was investigated by real-time PCR. The minimum biofilm inhibitory concentration of SFF Nps was 1 mg/mL. The minimum biofilm-eradication concentration of SFF Nps on the young (24- and 48-hr old) and older (72- and 96-hr old) biofilms was 2 and 4 mg/mL, respectively. Field emission electron scanning microscopy images confirmed the potent ability of SFF Nps to eradicate biofilm of P. aeruginosa. The expression of toxA was downregulated in the presence of SFF Nps. In conclusion, considering the ability of SFF Nps to kill P. aeruginosa biofilm and downregulate the expression of exotoxin A, this nanoparticle can be used for treatment of both chronic and acute P. aeruginosa infections.

Calcium-Binding Polymer-Coated Poly(lactide- co-glycolide) Microparticles for Sustained Release of Quorum Sensing Inhibitors to Prevent Biofilm Formation on Hydroxyapatite Surfaces

Quorum sensing (QS) inhibitor-based therapy is an attractive strategy to inhibit bacterial biofilm formation without excessive induction of antibiotic resistance. Thus, we designed Ca²⁺-binding poly(lactide- co-glycolide) (PLGA) microparticles that can maintain a sufficient concentration of QS inhibitors around hydroxyapatite (HA) surfaces in order to prevent biofilm formation on HA-based dental or bone tissues or implants and, therefore, subsequent pathogenesis. Poly(butyl methacrylate- co-methacryloyloxyethyl phosphate) (PBMP) contains both Ca²⁺-binding phosphomonoester groups and PLGA-interacting butyl groups. The PBMP-coated PLGA (PLGA/PBMP) microparticles exhibited superior adhesion to HA surfaces without altering the sustained release properties of uncoated PLGA microparticles. PLGA/PBMP microparticle-encapsulating furanone C-30, a representative QS inhibitor, effectively inhibited the growth of Streptococcus mutans and its ability to form biofilms on HA surface for prolonged periods of up to 100 h, which was much longer than either furanone C-30 in its free form or when encapsulated in noncoated PLGA microparticles.

Effect of microbial sanitizers for reducing biofilm formation of Staphylococcus aureus and Pseudomonas aeruginosa on stainless steel by cultivation with UHT milk

Biofilm is a serious issue in the dairy factory due to it increases the opportunity for microbial contamination. Staphylococcus aureus and Pseudomonas aeruginosa are the bacteria capable to construct the biofilm on materials and equipments. Therefore, the bacterial growth and efficiency of sanitizing agents to solve the problems were evaluated. These bacteria grew well in UHT milk when they were cultivated at 37 °C, especially S. aureus. The exponential growth phase and biofilm on stainless steel were discovered by short contact time at 2 h. The mature stage of biofilm cycle was found at 4 h during bacteria growth and it was continuously constructed until 48 h. The 10, 24, and 48 h-old biofilm adhering on stainless steel were established with oxisan and chlorine used as microbial sanitizers. The 4% of sanitizing agents was the efficiency concentration to reduce biofilm on stainless steel up to 82% when these bacteria grew in UHT milk.

Antimicrobial blue light photoinactivation of Pseudomonas aeruginosa: Quorum sensing signaling molecules, biofilm formation and pathogenicity

Pseudomonas aeruginosa is a common causative bacterium of acute and chronic infections that have been responsible for high mortality over the past decade. P. aeruginosa produces many virulence factors such as toxins, enzymes and dyes that are strongly dependent on quorum sensing (QS) signaling systems. P. aeruginosa has three major QS systems (las, rhl and Pseudomonas quinolone signal) that regulate the expression of genes encoding virulence factors as well as biofilm production and maturation. Antimicrobial blue light (aBL) is considered a therapeutic option for bacterial infections and has other benefits, such as reducing bacterial virulence. Therefore, this study investigated the efficacy of aBL to reduce P. aeruginosa pathogenicity. aBL treatment resulted in the reduced activity of certain QS signaling molecules in P. aeruginosa and inhibited biofilm formation. in vivo tests using a Caenorhabditis elegans infection model indicated that sublethal aBL decreased the pathogenicity of P. aeruginosa. aBL may be a new virulence-targeting therapeutic approach.

Factors Mediating Environmental Biofilm Formation by Legionella pneumophila

Legionella pneumophila (L. pneumophila) is an opportunistic waterborne pathogen and the causative agent for Legionnaires' disease, which is transmitted to humans via inhalation of contaminated water droplets. The bacterium is able to colonize a variety of man-made water systems such as cooling towers, spas, and dental lines and is widely distributed in multiple niches, including several species of protozoa In addition to survival in planktonic phase, L. pneumophila is able to survive and persist within multi-species biofilms that cover surfaces within water systems. Biofilm formation by L. pneumophila is advantageous for the pathogen as it leads to persistence, spread, resistance to treatments and an increase in virulence of this bacterium. Furthermore, Legionellosis outbreaks have been associated with the presence of L. pneumophila in biofilms, even after the extensive chemical and physical treatments. In the microbial consortium-containing L. pneumophila among other organisms, several factors either positively or negatively regulate the presence and persistence of L. pneumophila in this bacterial community. Biofilm-forming L. pneumophila is of a major importance to public health and have impact on the medical and industrial sectors. Indeed, prevention and removal protocols of L. pneumophila as well as diagnosis and hospitalization of patients infected with this bacteria cost governments billions of dollars. Therefore, understanding the biological and environmental factors that contribute to persistence and physiological adaptation in biofilms can be detrimental to eradicate and prevent the transmission of L. pneumophila. In this review, we focus on various factors that contribute to persistence of L. pneumophila within the biofilm consortium, the advantages that the bacteria gain from surviving in biofilms, genes and gene regulation during biofilm formation and finally challenges related to biofilm resistance to biocides and anti-Legionella treatments.

Antimicrobial and antibiofilm efficacy of self-cleaning surfaces functionalized by TiO2 photocatalytic nanoparticles against Staphylococcus aureus and Pseudomonas putida

A photocatalytic sol of TiO₂ nanoparticles has been used for creating self-cleaning antimicrobial flat and porous glass surfaces. The substrates were irradiated to study their photocatalytic properties and behavior in the presence of biofilm-forming bacteria. Smooth glass surfaces and glass microfiber filters were covered with 1.98×10^-3±1.5×10^-4gcm^-2 and 8.55×10^-3±3.0×10^-4gcm^-2 densities, respectively. Self-cleaning properties were analyzed using the methylene blue 365nm UV-A photodegradation test. TiO₂-coated filters achieved rapid and complete photodegradation of methylene blue because of the better TiO₂ dispersion with respect to the glass slides. The effect of functionalized surfaces on the growth and viability of bacteria was studied using the strains Staphylococcus aureus and Pseudomonas putida. After irradiation (2h, 11.2Wm^-2, 290-400nm), the initially hydrophobic surface turned hydrophilic. The antibacterial effect led to extensive membrane damage and significant production of intracellular reactive oxygen species in all TiO₂-loaded irradiated specimens. The reduction of cell viability was over 99.9% (>3-log) for TiO₂ on glass surfaces. However, the polymeric extracellular matrix formed before the irradiation treatment was not removed. This study highlights the importance of bacterial colonization during dark periods and the difficulty of removing the structure of biofilms.

A new model for biofilm formation and inflammatory tissue reaction: intraoperative infection of a cranial implant with Staphylococcus aureus in rats

BACKGROUND

Implant failure is a severe and frequent adverse event in all areas of neurosurgery. It often involves infection with biofilm formation, accompanied by inflammation of surrounding tissue, including the brain, and bone loss. The most common bacteria involved are Staphylococcus aureus. We here test whether intraoperative infection of intracranial screws with Staphylococcus aureus would lead to biofilm formation and inflammatory tissue reaction in rats.

METHODS

Two titanium screws were implanted in the cranium of Sprague-Dawley rats, anesthetized with xylazine (4 mg/kg) and ketamine (75 mg/kg). Prior to the implantation of the screws, Staphylococcus aureus was given in the drill holes; controls received phosphate-buffered saline (PBS). Rats were euthanized 2, 10 and 21 days after surgery to remove the screws for analysis of biofilm formation with a confocal laser scanning microscope. The surrounding tissue composed of soft tissue and bone, as well as the underlying brain tissue, was evaluated for inflammation, bone remodeling, foreign body reaction and fibrosis after H&E staining.

RESULTS

Intraoperative application of Staphylococcus aureus leads to robust and stable biofilm formation on the titanium implants on days 10 and 21 after surgery, while no bacteria were found in controls. This was accompanied by a substantial inflammatory response of peri-implant tissue after infection, also affecting the underlying brain tissue.

CONCLUSIONS

Intraoperative infection of implants with Staphylococcus aureus in rats may be useful as a tool to model new implant materials and surfaces on biofilm formation and inflammatory tissue reaction in vivo.

Curcumin Quantum Dots Mediated Degradation of Bacterial Biofilms

Bacterial biofilm has been reported to be associated with more than 80% of bacterial infections. Curcumin, a hydrophobic polyphenol compound, has anti-quorum sensing activity apart from having antimicrobial action. However, its use is limited by its poor aqueous solubility and rapid degradation. In this study, we attempted to prepare quantum dots of the drug curcumin in order to achieve enhanced solubility and stability and investigated for its antimicrobial and antibiofilm activity. We utilized a newer two-step bottom up wet milling approach to prepare Curcumin Quantum Dots (CurQDs) using acetone as a primary solvent. Minimum inhibitory concentration against select Gram-positive and Gram-negative bacteria was performed. The antibiofilm assay was performed at first using 96-well tissue culture plate and subsequently validated by Confocal Laser Scanning Microscopy. Further, biofilm matrix protein was isolated using formaldehyde sludge and TCA/Acetone precipitation method. Protein extracted was incubated with varying concentration of CurQDs for 4 h and was subjected to SDS–PAGE. Molecular docking study was performed to observe interaction between curcumin and phenol soluble modulins as well as curli proteins. The biophysical evidences obtained from TEM, SEM, UV-VIS, fluorescence, Raman spectroscopy, and zeta potential analysis confirmed the formation of curcumin quantum dots with increased stability and solubility. The MICs of curcumin quantum dots, as observed against both select gram positive and negative bacterial isolates, was observed to be significantly lower than native curcumin particles. On TCP assay, Curcumin observed to be having antibiofilm as well as biofilm degrading activity. Results of SDS–PAGE and molecular docking have shown interaction between biofilm matrix proteins and curcumin. The results indicate that aqueous solubility and stability of Curcumin can be achieved by preparing its quantum dots. The study also demonstrates that by sizing down the particle size has not only enhanced its antimicrobial properties but it has also shown its antibiofilm activities. Further, study is needed to elucidate the exact nature of interaction between curcumin and biofilm matrix proteins.

Candida-Bacteria Interactions: Their Impact on Human Disease

Candida species are the most common infectious fungal species in humans; out of the approximately 150 known species, Candida albicans is the leading pathogenic species, largely affecting immunocompromised individuals. Apart from its role as the primary etiology for various types of candidiasis, C. albicans is known to contribute to polymicrobial infections. Polymicrobial interactions, particularly between C. albicans and bacterial species, have gained recent interest in which polymicrobial biofilm virulence mechanisms have been studied including adhesion, invasion, quorum sensing, and development of antimicrobial resistance. These trans-kingdom interactions, either synergistic or antagonistic, may help modulate the virulence and pathogenicity of both Candida and bacteria while uniquely impacting the pathogen-host immune response. As antibiotic and antifungal resistance increases, there is a great need to explore the intermicrobial cross-talk with a focus on the treatment of Candida-associated polymicrobial infections. This article explores the current literature on the interactions between Candida and clinically important bacteria and evaluates these interactions in the context of pathogenesis, diagnosis, and disease management.

Scaffold of Selenium Nanovectors and Honey Phytochemicals for Inhibition of Pseudomonas aeruginosa Quorum Sensing and Biofilm Formation

Honey is an excellent source of polyphenolic compounds that are effective in attenuating quorum sensing (QS), a chemical process of cell-to-cell communication system used by the opportunistic pathogen Pseudomonas aeruginosa to regulate virulence and biofilm formation. However, lower water solubility and inadequate bioavailability remains major concerns of these therapeutic polyphenols. Its therapeutic index can be improved by using nano-carrier systems to target QS signaling potently. In the present study, we fabricated a unique drug delivery system comprising selenium nanoparticles (SeNPs; non-viral vectors) and polyphenols of honey (HP) for enhancement of anti-QS activity of HP against P. aeruginosa PAO1. The developed selenium nano-scaffold showed superior anti-QS activity, anti-biofilm efficacy, and anti-virulence potential in both in-vitro and in-vivo over its individual components, SeNPs and HP. LasR is inhibited by selenium nano-scaffold in-vitro. Using computational molecular docking studies, we have also demonstrated that the anti-virulence activity of selenium nano-scaffold is reliant on molecular binding that occurs between HP and the QS receptor LasR through hydrogen bonding and hydrophobic interactions. Our preliminary investigations with selenium-based nano-carriers hold significant promise to improve anti-virulence effectiveness of phytochemicals by enhancing effective intracellular delivery.

Activity of novel inhibitors of Staphylococcus aureus biofilms

Staphylococcus aureus is one of the most important pathogens causing chronic biofilm infections. These are becoming more difficult to treat owing to drug resistance, particularly because S. aureus biofilms limit the efficacy of antimicrobial agents, leading to high morbidity and mortality. In the present study, we screened for inhibitors of S. aureus biofilm formation using a natural product library from the Korea Chemical Bank (KCB). Screening by crystal violet-based biomass staining assay identified hit compounds. Further examination of antibiofilm properties of these compounds was conducted and led to the identification of celastrol and telithromycin. In vitro, both celastrol and telithromycin were toxic to planktonic S. aureus and also active against a clinical methicillin-resistant S. aureus (MRSA) isolate. The effect of the compounds on preformed biofilms of clinical MRSA isolates was evaluated by confocal laser scanning microscopy (CLSM), which revealed the absence of typical biofilm architecture. In addition, celastrol and telithromycin inhibited the production of extracellular protein at selected sub-MIC concentrations, which revealed the reduced extracellular polymeric substance (EPS) secretion. Celastrol exhibited greater cytotoxicity than telithromycin. These data suggest that the hit compounds, especially telithromycin, could be considered novel inhibitors of S. aureus biofilm. Although the mechanisms of the effects on S. aureus biofilms are not fully understood, our data suggest that telithromycin could be a useful adjuvant therapeutic agent for S. aureus biofilm-related infections.

The effects of different seeding ratios on nitrification performance and biofilm formation in marine recirculating aquaculture system biofilter

Rapid start-up of biofilter is essential for intensive marine recirculating aquaculture system (RAS) production. This study evaluated the nitrifying biofilm formation using mature biofilm as an inoculum to accelerate the process in RAS practice. The effects of inoculation ratios (0-15 %) on the reactor performance and biofilm structure were investigated. Complete nitrification was achieved rapidly in reactors with inoculated mature biofilm (even in 32 days when 15 % seeding ratio was applied). However, the growth of target biofilm on blank carrier was affected by the mature biofilm inoculated through substrate competition. The analysis of extracellular polymeric substance (EPS) and nitrification rates confirmed the divergence of biofilm cultivation among reactors. Besides, three N-acyl-homoserine lactones (AHLs) were found in the process, which might regulate the activities of biofilm. Multivariate analysis based on non-metric multidimensional scaling (nMDS) also indicated the great roles of AHLs and substrate supply which might fundamentally determine varied cultivation performance on target biofilm.

Microbial colonisation of transparent glass-like carbon films triggered by a reversible radiation-induced hydrophobic to hydrophilic transition

Vacuum ultraviolet irradiation induces a wettability transition in glass-like carbon films, which renders their surface highly prone to microbial colonisation.

A novel microwave recipe for an antibiofilm titanium surface

A microwave based method for the surface modification of titanium was demonstrated for biomedical applications. The surfaces were characterized using XRD, HR-SEM and Goniometer. The absence of rutile, anatase and brookite phases and the presence of an amorphous near-native oxide film were confirmed. The microwave oxidized (MWO) surfaces exhibited a significant antibiofilm activity against Escherichia coli and Staphylococcus aureus. In the presence and absence of the water pot, the oxidation times of 60 and 20min demonstrated a high antibiofilm property respectively. The surfaces turned more hydrophobic with increasing oxidation time. The viability of L6 cells remained unaffected on the MWO oxidized surfaces, signifying no loss in biocompatibility. This systematic study presents MWO as a promising technique for solving the biofilm problem faced by the otherwise robust titanium.

Intra- and inter-species interactions within biofilms of important foodborne bacterial pathogens

A community-based sessile life style is the normal mode of growth and survival for many bacterial species. Under such conditions, cell-to-cell interactions are inevitable and ultimately lead to the establishment of dense, complex and highly structured biofilm populations encapsulated in a self-produced extracellular matrix and capable of coordinated and collective behavior. Remarkably, in food processing environments, a variety of different bacteria may attach to surfaces, survive, grow, and form biofilms. Salmonella enterica, Listeria monocytogenes, Escherichia coli, and Staphylococcus aureus are important bacterial pathogens commonly implicated in outbreaks of foodborne diseases, while all are known to be able to create biofilms on both abiotic and biotic surfaces. Particularly challenging is the attempt to understand the complexity of inter-bacterial interactions that can be encountered in such unwanted consortia, such as competitive and cooperative ones, together with their impact on the final outcome of these communities (e.g., maturation, physiology, antimicrobial resistance, virulence, dispersal). In this review, up-to-date data on both the intra- and inter-species interactions encountered in biofilms of these pathogens are presented. A better understanding of these interactions, both at molecular and biophysical levels, could lead to novel intervention strategies for controlling pathogenic biofilm formation in food processing environments and thus improve food safety.

Non-antibiotic quorum sensing inhibitors acting against N-acyl homoserine lactone synthase as druggable target

N-acylhomoserine lactone (AHL)-based quorum sensing (QS) is important for the regulation of proteobacterial virulence determinants. Thus, the inhibition of AHL synthases offers non-antibiotics-based therapeutic potentials against QS-mediated bacterial infections. In this work, functional AHL synthases of Pseudomonas aeruginosa LasI and RhlI were heterologously expressed in an AHL-negative Escherichia coli followed by assessments on their AHLs production using AHL biosensors and high resolution liquid chromatography–mass spectrometry (LCMS). These AHL-producing E. coli served as tools for screening AHL synthase inhibitors. Based on a campaign of screening synthetic molecules and natural products using our approach, three strongest inhibitors namely are salicylic acid, tannic acid and trans-cinnamaldehyde have been identified. LCMS analysis further confirmed tannic acid and trans-cinnemaldehyde efficiently inhibited AHL production by RhlI. We further demonstrated the application of trans-cinnemaldehyde inhibiting Rhl QS system regulated pyocyanin production in P. aeruginosa up to 42.06%. Molecular docking analysis suggested that trans-cinnemaldehyde binds to the LasI and EsaI with known structures mainly interacting with their substrate binding sites. Our data suggested a new class of QS-inhibiting agents from natural products targeting AHL synthase and provided a potential approach for facilitating the discovery of anti-QS signal synthesis as basis of novel anti-infective approach.

Global sensitivity analysis used to interpret biological experimental results

Modeling host/pathogen interactions provides insight into immune defects that allow bacteria to overwhelm the host, mechanisms that allow vaccine strategies to be successful, and illusive interactions between immune components that govern the immune response to a challenge. However, even simplified models require a fairly high dimensional parameter space to be explored. Here we use global sensitivity analysis for parameters in a simple model for biofilm infections in mice. The results indicate which parameters are insignificant and are 'frozen' to yield a reduced model. The reduced model replicates the full model with high accuracy, using approximately half of the parameter space. We used the sensitivity to investigate the results of the combined biological and mathematical experiments for osteomyelitis. We are able to identify parts of the compartmentalized immune system that were responsible for each of the experimental outcomes. This model is one example for a technique that can be used generally.

Biological noise abatement: coordinating the responses of autonomous bacteria in a synthetic biofilm to a fluctuating environment using a stochastic bistable switch

Noise is inherent to single cell behavior. Its origins can be traced to the stochasticity associated with a few copies of genes and low concentrations of protein and ligands. We have studied the mechanisms by which the response of noisy elements can be entrained for biological signal processing. To elicit predictable biological function, we have engineered a gene environment that incorporates a gene regulatory network with the stringently controlled microenvironment found in a synthetic biofilm. The regulatory network leverages the positive feedback found in quorum-sensing regulatory components of the lux operon, which is used to coordinate cellular responses to environmental fluctuations. Accumulation of the Lux receptor in cells, resulting from autoregulation, confers a rapid response and enhanced sensitivity to the quorum-sensing molecule that is retained after cell division as epigenetic memory. The memory of the system channels stochastic noise into a coordinated response among quorum-sensing signal receivers in a synthetic biofilm in which the noise diminishes with repeated exposure to noisy transmitters on the input of a signaling cascade integrated into the same biofilm. Thus, gene expression in the receivers, which are autonomous and do not communicate with each other, is synchronized to fluctuations in the environment.

Modelling the interaction between the host immune response, bacterial dynamics and inflammatory damage in comparison with immunomodulation and vaccination experiments

The immune system is a complex system of chemical and cellular interactions that responds quickly to queues that signal infection and then reverts to a basal level once the challenge is eliminated. Here, we present a general, four-component model of the immune system's response to a Staphylococcal aureus (S. aureus) infection, using ordinary differential equations. To incorporate both the infection and the immune system, we adopt the style of compartmenting the system to include bacterial dynamics, damage and inflammation to the host, and the host response. We incorporate interactions not previously represented including cross-talk between inflammation/damage and the infection and the suppression of the anti-inflammatory pathway in response to inflammation/damage. As a result, the most relevant equilibrium of the system, representing the health state, is an all-positive basal level. The model is able to capture eight different experimental outcomes for mice challenged with intratibial osteomyelitis due to S. aureus, primarily involving immunomodulation and vaccine therapies. For further validation and parameter exploration, we perform a parameter sensitivity analysis which suggests that the model is very stable with respect to variations in parameters, indicates potential immunomodulation strategies and provides a possible explanation for the difference in immune potential for different mouse strains.

Variations in motility and biofilm formation of Salmonella enterica serovar Typhi

Background

Salmonella enterica serovar Typhi (S. Typhi) exhibits unique characteristics as an intracellular human pathogen. It causes both acute and chronic infection with various disease manifestations in the human host only. The principal factors underlying the unique lifestyle of motility and biofilm forming ability of S. Typhi remain largely unknown. The main objective of this study was to explore and investigate the motility and biofilm forming behaviour among S. Typhi strains of diverse background.

Results

Swim and swarm motility tests were performed with 0.25% and 0.5% agar concentration, respectively; while biofilm formation was determined by growing the bacterial cultures for 48 hrs in 96-well microtitre plate. While all S. Typhi strains demonstrated swarming motility with smooth featureless morphology, 58 out of 60 strains demonstrated swimming motility with featureless or bull’s eye morphology. Interestingly, S. Typhi strains of blood-borne origin exhibited significantly higher swimming motility (P < 0.05) than stool-borne strains suggesting that swimming motility may play a role in the systemic invasion of S. Typhi in the human host. Also, stool-borne S. Typhi displayed a negative relationship between motility and biofilm forming behaviour, which was not observed in the blood-borne strains.

Conclusion

In summary, both swimming and swarming motility are conserved among S. Typhi strains but there was variation for biofilm forming ability. There was no difference observed in this phenotype for S. Typhi strains from diverse background. These findings serve as caveats for future studies to understand the lifestyle and transmission of this pathogen.