Biofilm Formation Plays a Role in the Formation of Multidrug-Resistant Escherichia coli Toward Nutrients in Microcosm Experiments

Type 1 fimbrial phase variation in multidrug-resistant asymptomatic uropathogenic Escherichia coli clinical isolates upon adherence to HTB-4 cells

The adherence of bladder uroepithelial cells, subsequent expression, and regulation of type 1 fimbrial genes (key mediator of attachment) in clinical multidrug-resistant uropathogenic Escherichia coli (MDR-UPECs) isolated from individuals with asymptomatic bacteriuria (ABU) remain unexplored till date. Therefore, this study aimed to investigate the underlying molecular mechanisms associated with the adherence of clinical MDR-ABU-UPECs to human a uroepithelial cell line (HTB-4), both in the absence and presence of D-Mannose. These investigations focused on phase variation, expression, and regulation of type 1 fimbriae and were compared to a prototype ABU-strain (E. coli 83972) and symptomatic MDR-UPECs. Discordant to the ABU prototype strain, MDR-ABU-UPECs exhibited remarkable adhesive capacity that was significantly reduced after D-mannose exposure, fairly like the MDR symptomatic UPECs. The type 1 fimbrial phase variation, determined by the fim switch analysis, asserted the statistically significant incidence of "both OFF and ON" orientation among the adherent MDR-ABU-UPECs with a significant reduction in phase-ON colonies post-D-mannose exposure, akin to the symptomatic ones. This was indicative of an operative and alternating type 1 fimbrial phase switch. The q-PCR assay revealed a coordinated action of the regulatory factors; H-NS, IHF, and Lrp on the expression of FimB and FimE recombinases, which further controlled the function of fimH and fimA genes in ABU-UPECs, similar to symptomatic strains. Therefore, this study is the first of its kind to provide an insight into the regulatory crosstalk of different cellular factors guiding the adhesion of ABU-UPECs to the host. Additionally, it also advocated for the need to accurately characterize ABU-UPECs.

Biofilm Prevention and Removal in Non-Target Pseudomonas Strain by Siphovirus-like Coliphage

Background/Objectives. Bacteriophages have gained significant interest as a potential solution to combat harmful bacteria, especially in the fight against antimicrobial resistance. With the rise in drug-resistant microorganisms, the medical community is increasingly exploring new alternatives to traditional antibiotics, and bacteriophages offer several advantages in this regard. However, phage applications still face some challenges, such as host specificity. Methods. In this study, a somatic Siphovirus-like coliphage (SOM7) was tested for inhibiting the biofilm-forming capacity of the non-target strain Pseudomonas aeruginosa (ATTC 10145). The phage-sensitive strain E. coli WG5 was used as a control. The selected microorganisms were first tested for growth in the presence of SOM7 at three different concentrations (105, 107, and 109 PFU/mL). Results. As expected, the phage-sensitive E. coli WG5 was fully inhibited by the coliphage, and no phage-related affection on the growth rate was observed for the SOM7-resistant P. aeruginosa. More notably, increasing concentrations of SOM7 significantly reduced both the biofilm-forming capacity and the amount of pre-established bacterial biofilm of the phage-insensitive P. aeruginosa (24.9% and 38.8% reduction in the biofilm-forming ability, and 18.8% and 28.0% biofilm degradation for 107 PFU/mL and 109 PFU/mL SOM7, respectively; p < 0.05). These results were supported by transmission electron microscopy (TEM) imaging, providing unprecedent evidence for the interaction of the somatic coliphage with the non-host strain. Conclusions. Although more studies in other biofilm models are necessary, our results show for the very first time that bacteriophages could potentially be used as an alternative to achieve desired anti-biofilm and biofilm-degrading activity in non-host bacterial strains.

Genotypic and phenotypic characterization of determinants that mediate antimicrobial resistance in Escherichia coli strains of clinical origin in South-Western Nigeria

Background

Multidrug resistant bacterial pathogens employ different mechanisms in evading the action of antibiotics. Multidrug resistance is wide spread among strains of Escherichia coli implicated in several infections including urinary tract infections, gastrointestinal infections, meningitis and bacteraemia.

Aim/Objective

This study investigates the antibiotic resistance profile, efflux pump activity and biofilm formation ability of E. coli strains isolated from clinical samples.

Methods

A total of 32 E. coli strains isolated from clinical samples were characterized and subjected to antibiotic susceptibility testing using standard methods. Isolates were screened phenotypically for biofilm formation and efflux pump activity. While molecular detection of genes encoding curli fimbriae and efflux pump activity was done by PCR.

Results

All 32 (100%) E. coli isolates were resistant to ceftazidime, cefuroxime, cefixime, amoxicillin-clavulanate, ofloxacin and ciprofloxacin. While 30 (93.8%) were resistant to gentamicin, 27 (84.4%) were resistant to cefepime and the least resistance of 15.6% was to imipenem. Efflux pump encoding gene tolC was detected in 13(40.6%) of the isolates, while 1(3.1%) harboured acrA gene. acrB gene was not detected in any of the isolates. Seven (21.9%) of the isolates were strong biofilm formers, while 5 (15.6%) and 20 (62.5%) were moderate and weak biofilm formers respectively. csgA gene was detected in all E. coli isolates.

Discussion

High antibiotic resistance of E. coli strains observed in this study is of public health significance. . It is therefore important to scale up efforts in regular monitoring of antibiotic resistance in both community and hospital settings.

Characterisation of sRNAs enriched in outer membrane vesicles of pathogenic Flavobacterium psychrophilum causing Bacterial Cold Water Disease in rainbow trout

Flavobacterium psychrophilum (Fp) causes Bacterial Cold Water Disease in salmonids. During host-pathogen interactions, gram-negative bacteria, such as Fp, release external membrane vesicles (OMVs) harbouring cargos, such as DNA, RNA and virulence factors. This study aimed to characterise the potential role of the OMVs' small RNAs (sRNAs) in the Fp-rainbow trout host-pathogen interactions. sRNAs carried within OMVs were isolated from Fp. RNA-Seq datasets from whole-cell Fp and their isolated OMVs indicated substantial enrichment of specific sRNAs in the OMVs compared to the parent cell. Many of the OMV-packaged sRNAs were located in the pathogenicity islands of Fp. Conservation of sRNAs in 65 strains with variable degrees of virulence was reported. Dual RNA-Seq of host and pathogen transcriptomes on day 5 post-infection of Fp -resistant and -susceptible rainbow trout genetic lines revealed correlated expression of OMV-packaged sRNAs and their predicted host's immune gene targets. In vitro, treatment of the rainbow trout epithelial cell line RTgill-W1 with OMVs showed signs of cytotoxicity accompanied by dynamic changes in the expression of host genes when profiled 24 h following treatment. The OMV-treated cells, similar to the Fp -resistant fish, showed downregulated expression of the suppressor of cytokine signalling 1 (SOCS1) gene, suggesting induction of phagosomal maturation. Other signs of modulating the host gene expression following OMV-treatment include favouring elements from the phagocytic, endocytic and antigen presentation pathways in addition to HSP70, HSP90 and cochaperone proteins, which provide evidence for a potential role of OMVs in boosting the host immune response. In conclusion, the study identified novel microbial targets and inherent characteristics of OMVs that could open up new avenues of treatment and prevention of fish infections.

Modified Zhibai Dihuang pill alleviated urinary tract infection induced by extended-spectrum β-lactamase Escherichia coli in rats by regulating biofilm formation

CONTEXT

Zhibai Dihuang pill (ZD), a traditional Chinese medicine nourishes Yin and reduces internal heat, is believed to have therapeutic effects on urinary tract infections (UTIs).

OBJECTIVE

To explore the effects and mechanism of modified ZD (MZD) on UTI induced by extended-spectrum β-lactamase (ESBLs) Escherichia coli.

MATERIALS AND METHODS

Thirty Sprague-Dawley rats were randomly divided into control, model (0.5 mL 1.5 × 108 CFU/mL ESBLs E. coli), MZD (20 g/kg MZD), LVFX (0.025 g/kg LVFX), and MZD + LVFX groups (20 g/kg MZD + 0.025 g/kg LVFX), n = 6. After 14 days of treatment, serum biochemical indicators, renal function indicators, bladder and renal histopathology, and urine bacterial counts in rats were determined. Additionally, the effects of MZD on ESBLs E. coli biofilm formation and related gene expression were analyzed.

RESULTS

MZD significantly decreased the count of white blood cells (from 13.12 to 9.13), the proportion of neutrophils (from 43.53 to 23.18), C-reactive protein (from 13.21 to 9.71), serum creatinine (from 35.78 to 30.15), and urea nitrogen (from 12.56 to 10.15), relieved the inflammation and fibrosis of bladder and kidney tissues, and reduced the number of bacteria in urine (from 2174 to 559). In addition, MZD inhibited the formation of ESBLs E. coli biofilms (2.04-fold) and decreased the gene expressions of luxS, pfS and ompA (1.41-1.62-fold).

DISCUSSION AND CONCLUSION

MZD treated ESBLs E. coli-induced UTI inhibited biofilm formation, providing a theoretical basis for the clinical application of MZD. Further study on the clinical effect of MZD may provide a novel therapy option for UTI.

Regulation of major bacterial survival strategies by transcripts sequestration in a membraneless organelle

TmaR, the only known pole-localizer protein in Escherichia coli, was shown to cluster at the cell poles and control localization and activity of the major sugar regulator in a tyrosine phosphorylation-dependent manner. Here, we show that TmaR assembles by phase separation (PS) via heterotypic interactions with RNA in vivo and in vitro. An unbiased automated mutant screen combined with directed mutagenesis and genetic manipulations uncovered the importance of a predicted nucleic-acid-binding domain, a disordered region, and charged patches, one containing the phosphorylated tyrosine, for TmaR condensation. We demonstrate that, by protecting flagella-related transcripts, TmaR controls flagella production and, thus, cell motility and biofilm formation. These results connect PS in bacteria to survival and provide an explanation for the linkage between metabolism and motility. Intriguingly, a point mutation or increase in its cellular concentration induces irreversible liquid-to-solid transition of TmaR, similar to human disease-causing proteins, which affects cell morphology and division.

Biofilm formation on polyethylene microplastics and their role as transfer vector of emerging organic pollutants

Microplastic (MP)-colonizing microorganisms are important links for the potential impacts on environmental, health, and biochemical circulation in various ecosystems but are not yet well understood. In addition, biofilms serve as bioindicators for the evaluation of pollutant effects on ecosystems. This study describes the ability of three polyethylene-type microplastics, white (W-), blue (B-), and fluorescent blue (FB-) MPs, to support microbial colonization of Pseudomonas aeruginosa, the effect of mixed organic contaminants (OCs: amoxicillin, ibuprofen, sertraline, and simazine) on plastic-associated biofilms, and the role of biofilms as transfer vectors of such emerging pollutants. Our results showed that P. aeruginosa had a strong ability to produce biofilms on MPs, although the protein amount of biomass formed on FB-MP was 1.6- and 2.4-fold higher than that on B- and W-MP, respectively. When OCs were present in the culture medium, a decrease in cell viability was observed in the W-MP biofilm (65.0%), although a general impairing effect of OCs on biofilm formation was ruled out. Microbial colonization influenced the ability of MPs to accumulate OCs, which was higher for FB-MP. In particular, the sorption of amoxicillin was lower for all bacterial-colonized MPs than for the bare MPs. Moreover, we analysed oxidative stress production to assess the impact of MPs or MPs/OCs on biofilm development. The exposure of biofilms to OCs induced an adaptive stress response reflected in the upregulation of the katB gene and ROS production, particularly on B- and FB-MP. This study improves our understanding of MP biofilm formation, which modifies the ability of MPs to interact with some organic pollutants. However, such pollutants could hinder microbial colonization through oxidative stress production, and thus, considering the key role of biofilms in biogeochemical cycles or plastic degradation, the co-occurrence of MPs/OCs should be considered to assess the potential risks of MPs in the environment.

Accessing the In Vivo Efficiency of Clinically Isolated Phages against Uropathogenic and Invasive Biofilm-Forming Escherichia coli Strains for Phage Therapy

Escherichia coli is one of the most common members of the intestinal microbiota. Many of its strains are associated with various inflammatory infections, including urinary or gut infections, especially when displaying antibiotic resistance or in patients with suppressed immune systems. According to recent reports, the biofilm-forming potential of E. coli is a crucial factor for its increased resistance against antibiotics. To overcome the limitations of using antibiotics against resistant E. coli strains, the world is turning once more towards bacteriophage therapy, which is becoming a promising candidate amongst the current personalized approaches to target different bacterial infections. Although matured and persistent biofilms pose a serious challenge to phage therapy, they can still become an effective alternative to antibiotic treatment. Here, we assess the efficiency of clinically isolated phages in phage therapy against representative clinical uropathogenic and invasive biofilm-forming E. coli strains. Our results demonstrate that irrespective of host specificity, bacteriophages producing clear plaques with a high burst size, and exhibiting depolymerizing activity, are good candidates against biofilm-producing E. coli pathogens as verified from our in vitro and in vivo experiments using Galleria mellonella where survival was significantly increased for phage-therapy-treated larvae.

Anti-Biofilm Effect of Bacteriophages and Antibiotics against Uropathogenic Escherichia coli

Escherichia coli is a common cause of biofilm-associated urinary tract infections. Bacteria inside the biofilm are more resistant to antibiotics. Six E. coli strains isolated from patients with urinary tract infections were screened for biofilm-forming capability and antimicrobial susceptibility. Two of the most significant biofilm-producing strains were selected for minimal inhibitory concentration and minimal biofilm eradication concentration in vitro testing using amoxicillin-clavulanic acid, ciprofloxacin, and three commercial bacteriophage cocktails (Pyobacteriophag, Ses, and Intesti). In case of a low phage effect, an adaptation procedure was performed. Although the biofilms formed by strain 021UR were resistant to amoxicillin-clavulanic acid and ciprofloxacin, the three phage cocktails were able to reduce biofilm formation. In contrast, phages did not affect the 01206UR strain against planktonic and biofilm-forming cells. After Pyobacteriophag adaptation, the effect improved, and, regardless of the concentration, the adapted phage cocktail could destroy both planktonic cells and the biofilm of strain 01206UR. Bacteriophages capable of killing bacteria in biofilms can be used as an alternative to antibiotics. However, each case should be considered individually due to the lack of clinical trials for phage therapy. Antimicrobial and phage susceptibility should be determined in biofilm models before treatment to achieve the desired anti-biofilm effect.

A fatal outbreak of neonatal sepsis caused by mcr-10 carrying Enterobacter kobei in a tertiary care hospital in Nepal

BACKGROUND

Enterobacter kobei is an emerging cause of outbreak of nosocomial infections in neonatal intensive care units (NICUs). Between July and September of 2016, an NICU in a tertiary care hospital of Nepal observed an abrupt increase in the number of neonatal sepsis cases caused by Enterobacter spp. infecting 11 of 23 admitted neonates, 5 of whom died of an exacerbated sepsis.

AIM

Main aims of this study were to confirm the suspected outbreak, identify environmental source of infection, and characterize genetic determinants of antimicrobial resistance (AMR) and virulence of the pathogen.

METHODS

We performed whole genome sequencing of all Enterobacter spp. isolated from blood cultures of septic neonates admitted to NICU between May 2016 and December 2017. Also, an environmental sampling was intensified from fortnightly to weekly during the outbreak.

FINDINGS

The genomic analysis revealed that 10 of 11 non-duplicated E. kobei isolated from neonatal blood cultures between July and September 2016 were clonal, confirming the outbreak. The isolates carried AMR genes including bla_AmpC and mcr-10 conferring reduced susceptibility to carbapenem and colistin respectively. The environmental sampling however failed to isolate any Enterobacter spp. Reinforcement of aseptic protocols in invasive procedures, hand hygiene, environmental decontamination, fumigation, and secluded care of culture positive cases successfully terminated the outbreak.

CONCLUSION

Our study underscored the need to implement stringent infection control measures to prevent infection outbreaks. Further, for the first time, we report the emergence of carbapenem and colistin non-susceptible E. kobei carrying mcr-10 gene as an important cause of nosocomial neonatal sepsis in an NICU.

Escherichia coli Strains Isolated from Retail Meat Products: Evaluation of Biofilm Formation Ability, Antibiotic Resistance, and Phylogenetic Group Analysis

ABSTRACT

Escherichia coli is a ubiquitous organism capable of forming a biofilm. This is an important virulence factor and is critical in certain diseases and in the development of antibiotic resistance, which is increased by biofilm synthesis. In the present study, the potential health risk associated with handling and consumption of foods of animal origin contaminated with E. coli-producing biofilm was evaluated. We analyzed the ability of 182 E. coli strains isolated from pork, poultry, and beef, purchased in three different supermarkets in the area of the "Italian Food Valley" (Parma, northern Italy), to form biofilms. Positive strains were also tested for the presence of 12 biofilm-associated genes. Moreover, the 182 E. coli were characterized for antibiotic resistance, presence of multidrug resistance, extended-spectrum β-lactamase strains, and phylogenetic diversity through PCR. Twenty-five percent of the isolates produced biofilm. The majority showed weak adherence, five were moderate, and three were strong producers. E. coli with a strong adherence capability (three of three) harbored eight biofilm-associated genes, while weak and moderate producers harbored only five (frequencies ranging from 80 to 100%). Multidrug resistance was observed in 20 biofilm-producing E. coli, and 15 of these belonged to phylogenetic group D. Among nonbiofilm producers, the percentage of strains belonging to phylogenetic groups B2 and D was approximately 40%, highlighting a potential health risk for consumers and people handling contaminated products. The present study underlines the importance of monitoring the prevalence and characteristics of E. coli contaminating retail meat in relation to the potential virulence highlighted here.

HIGHLIGHTS

Inhibitory Effect of Two Traditional Chinese Medicine Monomers, Berberine and Matrine, on the Quorum Sensing System of Antimicrobial-Resistant Escherichia coli

The quorum sensing (QS) system controls bacterial biofilm formation, which is highly related to the virulence and resistance of pathogens. In the present study, the effect of two traditional Chinese medicine (TCM) monomers, berberine and matrine, on biofilm formation and QS-related gene expression of antimicrobial-resistant (AMR) Escherichia coli strains was investigated by laser scanning confocal microscopy (LSCM) observation and real-time PCR. The results indicated a roughly positive relationship between biofilm formation ability and antimicrobial resistance. LSCM observation showed that berberine and matrine inhibited biofilm formation of AMR E. coli strains at 1/2 minimal inhibitory concentration (MIC) (1/2 MIC berberine at OD₆₃₀: 0.1020; 1/2 MIC matrine: OD₆₃₀: 0.1045); furthermore, abnormal cell morphology such as rounded and elongated cells was also observed. This finding was consistent with the downregulation of QS-related genes: luxS, pfS, sdiA, hflX, motA, and fliA. At 1/2 MIC and 1/4 MIC concentrations of berberine, a significant downregulation of luxS, pfS, hflX, ftsQ, and ftsE was observed. The results indicate that berberine and matrine can inhibit biofilm formation by inhibiting the QS system and that berberine is more effective than matrine.

The role of the phoP transcriptional regulator on biofilm formation of avian pathogenic Escherichia coli

PhoP plays an important role as a transcriptional regulator in the two-component phoP/phoQ regulatory system, which is widely present in Gram-negative bacteria. In this study, we used DNA microarray-based technology to evaluate the role of phoP in biofilm formation in avian pathogenic Escherichia coli (APEC). Differences in gene transcription between APEC wild-type and phoP mutant strains were determined. Mutation of the phoP transcriptional regulator affects the expression profile of genes involved in processes such as flagellar assembly, ABC transporters, quorum sensing, and bacterial chemotaxis. Deletion of phoP in APEC reduced biofilm formation, as indicated by crystal violet staining and scanning electron microscopy (SEM). In addition, the phoP gene was found to be associated with changes in bacterial drug resistance and cell-membrane-related properties. This study shows that phoP plays an important regulatory role in APEC biofilm formation, and provides new insights into strategies for preventing and controlling APEC infection.

Biofilms: Architecture, Resistance, Quorum Sensing and Control Mechanisms

Biofilm is a mode of living employed by many pathogenic and environmental microbes to proliferate as multicellular aggregates on inert inanimate or biological substrates. Several microbial diseases are associated with biofilms that pose challenges in treatment with antibiotics targeting individual cells. Bacteria in biofilms secrete exopolymeric substances that contribute to architectural stability and provide a secure niche to inhabiting cells. Quorum sensing (QS) plays essential roles in biofilm development. Pathogenic bacteria in biofilms utilize QS mechanisms to activate virulence and develop antibiotic resistance. This review is a brief overview of biofilm research and provides updates on recent understandings on biofilm development, antibiotic resistance and transmission, and importance of QS mechanisms. Strategies to combat biofilm associated diseases including anti-biofilm substances, quorum quenching molecules, bio-surfactants and competitive inhibitors are briefly discussed. The review concludes with updates on recent approaches utilized for biofilm inhibition and provides perspectives for further research in the field.