Amikacin and bacteriophage treatment modulates outer membrane proteins composition in Proteus mirabilis biofilm

Relationship between Desiccation Tolerance and Biofilm Formation in Shiga Toxin-Producing Escherichia coli

Shiga toxin-producing Escherichia coli (STEC) is a major concern in the food industry and requires effective control measures to prevent foodborne illnesses. Previous studies have demonstrated increased difficulty in the control of biofilm-forming STEC. Desiccation, achieved through osmotic stress and water removal, has emerged as a potential antimicrobial hurdle. This study focused on 254 genetically diverse E. coli strains collected from cattle, carcass hides, hide-off carcasses, and processing equipment. Of these, 141 (55.51%) were STEC and 113 (44.48%) were generic E. coli. The biofilm-forming capabilities of these isolates were assessed, and their desiccation tolerance was investigated to understand the relationships between growth temperature, relative humidity (RH), and bacterial survival. Only 28% of the STEC isolates had the ability to form biofilms, compared to 60% of the generic E. coli. Stainless steel surfaces were exposed to different combinations of temperature (0 °C or 35 °C) and relative humidity (75% or 100%), and the bacterial attachment and survival rates were measured over 72 h and compared to controls. The results revealed that all the strains exposed to 75% relative humidity (RH) at any temperature had reduced growth (p < 0.001). In contrast, 35 °C and 100% RH supported bacterial proliferation, except for isolates forming the strongest biofilms. The ability of E. coli to form a biofilm did not impact growth reduction at 75% RH. Therefore, desiccation treatment at 75% RH at temperatures of 0 °C or 35 °C holds promise as a novel antimicrobial hurdle for the removal of biofilm-forming E. coli from challenging-to-clean surfaces and equipment within food processing facilities.

Virulence-related factors and antimicrobial resistance in Proteus mirabilis isolated from domestic and stray dogs

Introduction

Proteus mirabilis is a multi-host pathogen that causes diseases of varying severity in a wide range of mammals, including humans. Proteus mirabilis is resistant to multiple antibiotics and has acquired the ability to produce expanded spectrum of β-lactamases, leading to serious public health problems. However, the available information on P. mirabilis isolated from feces of dogs, is still poorly understood, as is the correlation between its virulence-associated genes (VAGs) and antibiotic resistance genes (ARGs).

Method

In this study, we isolated 75 strains of P. mirabilis from 241 samples, and investigated the swarming motility, biofilm formation, antimicrobial resistance (AMR), distribution of VAGs and ARGs, as well as the presence of class 1, 2, and 3 integrons in these isolates.

Results

Our findings suggest a high prevalence of intensive swarming motility and strong biofilm formation ability among P. mirabilis isolates. Isolates were primarily resistant to cefazolin (70.67%) and imipenem (70.67%). These isolates were found to carry ureC, FliL, ireA, zapA, ptA, hpmA, hpmB, pmfA, rsbA, mrpA, and ucaA with varying prevalence levels of 100.00, 100.00, 100.00, 98.67, 98.67, 90.67, 90.67, 90.67, 90.67, 89.33, and 70.67%, respectively. Additionally, the isolates were found to carry aac(6')-Ib, qnrD, floR, bla_CTX-M, bla_CTX-M-2, bla_OXA-1, bla_TEM, tetA, tetB and tetM with varying prevalence levels of 38.67, 32.00, 25.33, 17.33, 16.00, 10.67, 5.33, 2.67, 1.33, and 1.33%, respectively. Among 40 MDR strains, 14 (35.00%) were found to carry class 1 integrons, 12 (30.00%) strains carried class 2 integrons, while no class 3 integrons was detected. There was a significant positive correlation between the class 1 integrons and three ARGs: bla_TEM, bla_CTX-M, and bla_CTX-M-2. This study revealed that P. mirabilis strains isolated from domestic dogs exhibited a higher prevalence of MDR, and carried fewer VAGs but more ARGs compared to those isolated from stay dogs. Furthermore, a negative correlation was observed between VAGs and ARGs.

Discussion

Given the increasing antimicrobial resistance of P. mirabilis, veterinarians should adopt a prudent approach towards antibiotics administration in dogs to mitigate the emergence and dissemination of MDR strains that pose a potential threat to public health.

BON domain-containing protein-mediated co-selection of antibiotic and heavy metal resistance in bacteria

The widespread antibiotic resistance of bacteria has become one of the most severe threats to public health. However, the mechanisms that allow microbial acquisition of resistance are still poorly understood. In the present study, a novel BON domain-containing protein was heterologously expressed in Escherichia coli. It functions as an efflux pump-like to confer resistance to various antibiotics, especially for ceftazidime, with a >32-fold increase in minimum inhibitory concentration (MIC). The fluorescence spectroscopy experiment indicated that BON protein could interact with several metal ions, such as copper and silver, which has been associated with the induced co-regulation of antibiotic and heavy metal resistance in bacteria. Furthermore, the BON protein was demonstrated to spontaneously self-assemble into a trimer and generate a central pore-like architecture for antibiotic transporting. A WXG motif as a molecular switch is essential for forming the transmembrane oligomeric pores and controls the interaction between BON protein and cell membrane. Based on these findings, a mechanism termed "one-in, one-out", was proposed for the first time. The present study provides new insights into the structure and function of BON protein and a previously unidentified antibiotic resistance mechanism, filling the knowledge gap in understanding BON protein-mediated intrinsic antibiotic resistance.

Combined Application of Aminoglycosides and Ascorbic Acid in the Elimination of Proteus mirabilis Rods Responsible for Causing Catheter-Associated Urinary Tract Infections (CAUTIs)-A Molecular Approach

Proteus mirabilis is a common cause of catheter-associated urinary tract infections (CAUTIs). In this study, we verified the effectiveness of amikacin or gentamicin and ascorbic acid (AA) co-therapy in eliminating uropathogenic cells, as well as searched for the molecular basis of AA activity by applying chromatographic and fluorescent techniques. Under simulated physiological conditions, a combined activity of the antibiotic and AA supported the growth (threefold) of the P. mirabilis C12 strain, but reduced catheter colonization (≤30%) in comparison to the drug monotherapy. Slight modifications in the phospholipid and fatty acid profiles, as well as limited (≤62%) 2',7'-dichlorofluorescein fluorescence, corresponding to the hydroxyl radical level, allowed for the exclusion of the hypothesis that the anti-biofilm effect of AA was related to membrane perturbations of the C12 strain. However, the reduced (≤20%) fluorescence intensity of propidium iodide, as a result of a decrease in membrane permeability, may be evidence of P. mirabilis cell defense against AA activity. Quantitative analyses of ascorbic acid over time with a simultaneous measurement of the pH values proved that AA can be an effective urine acidifier, provided that it is devoid of the presence of urease-positive cells. Therefore, it could be useful in a prevention of recurrent CAUTIs, rather than in their treatment.

Into the understanding the multicellular lifestyle of Proteus mirabilis on solid surfaces

Indwelling urinary catheterization can lead to the development of catheter-associated urinary tract infections (CAUTIs), an important type of nosocomial infection, as well as other medical issues among institutionalized adults. Recently, Proteus mirabilis was highlighted as the important cause of CAUTIs. The pathogenicity of P. mirabilis is dependent on two multicellular types of surface colonization: the adherence and swarming motility. Adhesion, mostly mediated by fimbrial and nonfimbrial adhesins, is important for the initiation of biofilm formation. Moreover, the production of urease frequently results in biofilm crystallization, which leads to the blockage of catheters. The heterologous polymeric matrix of the biofilm offers protection against antibiotics and the host immune system. P. mirabilis displays remarkable motility abilities. After contact with solid surfaces, hyper-flagellated cells are able to rapidly migrate. The importance of swarming motility in CAUTIs development remains controversial; however, it was indicated that swarming cells were able to co-express other virulence factors. Furthermore, flagella are strong immunomodulating proteins. On the other hand, both biofilm formation and swarming motility implicates multiple inter- and intraspecies interactions, which might contribute to the pathogenicity.

Organic Acids Secreted by Lactobacillus spp. Isolated from Urine and Their Antimicrobial Activity against Uropathogenic Proteus mirabilis

The natural microbiota of the urinary tract includes Lactobacillus spp., which secrete molecules with antimicrobial properties and have antagonistic activity against many pathogens. This paper focuses on the antibacterial effect of Lactobacillus strains isolated from urine against clinical strains of Proteus mirabilis isolated from kidney stones and from urine with coexisting urolithiasis. The study involved analyzing the main antimicrobial molecules secreted by Lactobacillus. In order to indicate which agent had the strongest antimicrobial effect, the supernatants were made alkaline and treated with catalase and high temperature. Both treated and untreated supernatants were analyzed for their activity. Exposing uropathogens to all untreated cell-free supernatants of Lactobacillus significantly reduced their growth, and it was established that these properties were related to organic acid secretion by these strains. Using LC–MS/MS and spectrophotometric techniques, lactic, citric, and succinic acids were determined qualitatively and quantitatively. The influence of these acids on the P. mirabilis growth and biofilm formation and their influence on membrane permeability were also investigated. The results indicate that organic acids secreted by Lactobacillus strains have a high antibacterial potential and could be used as novel agents in the treatment of urinary tract infections caused by P. mirabilis.

Efficacy of three lytic bacteriophages for eradicating biofilms of multidrug-resistant Proteus mirabilis

Proteus mirabilis is one of the most frequent causes of catheter-associated urinary tract infections (CAUTIs) owing to its capability to colonize and develop crystalline multidrug-resistant (MDR) biofilms. Here, we report the isolation and partial characterization of three novel bacteriophages, vB_PmiM-ES1a, vB_PmiM-ES1b, and vB_PmiM-ES1c, which were active against the planktonic form and biofilms of the MDR P. mirabilis strain ES01, isolated from CAUTIs in Egypt. The antibiotic susceptibility profile of the P. mirabilis isolates showed resistance to most of the antibiotics tested. The isolated phages were identified morphologically using TEM, and each appeared to have myovirus-like morphology. The three phages displayed strong lytic activity and a narrow host range, and they were stable at different ranges of temperatures and pH values. One-step growth kinetics showed a lysis time of 180 min with a burst size of 99.6, 95, and 86 PFU/cell for phage vB_PmiM-ES1a, vB_PmiM-ES1b, and vB_PmiM-ES1c, respectively. The three phages exhibited different digestion patterns using different restriction enzymes. The genome size was estimated to be 59.39 kb, 62.19 kb, and 52.07 kb for phage vB_PmiM-ES1a, vB_PmiM-ES1b, and vB_PmiM-ES1c, respectively. A phage cocktail including the three phages showed a potential ability to reduce and eradicate a biofilm formed by the MDR Proteus mirabilis EG-ES1. Accordingly, a phage cocktail of vB_PmiM-ES1a, vB_PmiM-ES1b, and vB_PmiM-ES1c is considered a promising candidate for use as a biocontrol agent against MDR Proteus mirabilis bacteria.

Bacterial Biofilm Destruction: A Focused Review On The Recent Use of Phage-Based Strategies With Other Antibiofilm Agents

Biofilms are bacterial communities that live in association with biotic or abiotic surfaces and enclosed in an extracellular polymeric substance. Their formation on both biotic and abiotic surfaces, including human tissue and medical device surfaces, pose a major threat causing chronic infections. In addition, current antibiotics and antiseptic agents have shown limited ability to completely remove biofilms. In this review, the authors provide an overview on the formation of bacterial biofilms and its characteristics, burden and evolution with phages. Moreover, the most recent possible use of phages and phage-derived enzymes to combat bacteria in biofilm structures is elucidated. From the emerging results, it can be concluded that despite successful use of phages and phage-derived products in destroying biofilms, they are mostly not adequate to eradicate all bacterial cells. Nevertheless, a combined therapy with the use of phages and/or phage-derived products with other antimicrobial agents including antibiotics, nanoparticles, and antimicrobial peptides may be effective approaches to remove biofilms from medical device surfaces and to treat their associated infections in humans.