Genetic characteristics of chromosomally integrated carbapenemase gene (blaNDM-1) in isolates of Proteus mirabilis.

OBJECTIVE: This study aims to conduct an in-depth genomic analysis of a carbapenem-resistant Proteus mirabilis strain to uncover the distribution and mechanisms of its resistance genes. METHODS: The research primarily utilized whole-genome sequencing to analyze the genome of the Proteus mirabilis strain. Additionally, antibiotic susceptibility tests were conducted to evaluate the strain's sensitivity to various antibiotics, and related case information was collected to analyze the clinical distribution characteristics of the resistant strain. RESULTS: Study on bacterial strain WF3430 from a tetanus and pneumonia patient reveals resistance to multiple antibiotics due to extensive use. Whole-genome sequencing exposes a 4,045,480 bp chromosome carrying 29 antibiotic resistance genes. Two multidrug-resistant (MDR) gene regions, resembling Tn6577 and Tn6589, were identified (MDR Region 1: 64.83 Kb, MDR Region 2: 85.64 Kbp). These regions, consist of integrative and conjugative elements (ICE) structures, highlight the intricate multidrug resistance in clinical settings. CONCLUSION: This study found that a CR-PMI strain exhibits a unique mechanism for acquiring antimicrobial resistance genes, such as blaNDM-1, located on the chromosome instead of plasmids. According to the results, there is increasing complexity in the mechanisms of horizontal transmission of resistance, necessitating a comprehensive understanding and implementation of targeted control measures in both hospital and community settings.

Emergence and genomic chion of Proteus mirabilis harboring blaNDM-1 in Korean companion dogs.

Proteus mirabilis is a commensal bacterium dwelling in the gastrointestinal (GI) tract of humans and animals. Although New Delhi metallo-ß-lactamase 1 (NDM-1) producing P. mirabilis is emerging as a threat, its epidemiology in our society remains largely unknown. LHPm1, the first P. mirabilis isolate harboring NDM-1, was detected from a companion dog that resides with a human owner. The whole-genome study revealed 20 different antimicrobial resistance (AMR) genes against various classes of antimicrobial agents, which corresponded to the MIC results. Genomic regions, including MDR genes, were identified with multiple variations and visualized in a comparative manner. In the whole-genome epidemiological analysis, multiple phylogroups were identified, revealing the genetic relationship of LHPm1 with other P. mirabilis strains carrying various AMR genes. These genetic findings offer comprehensive insights into NDM-1-producing P. mirabilis, underscoring the need for urgent control measures and surveillance programs using a "one health approach".

Occurrence and characterization of Proteus mirabilis from infected farmed African catfish in Ogun State, Nigeria.

BACKGROUND: Bacterial pathogens are the causative agents of some of the most serious disease problems in cultured fish causing mortalities and severe economic losses. This study was conducted to determine the occurrence and characterization of Proteus mirabilis from infected farmed African catfish in Ogun State, Nigeria. METHODOLOGY: The bacteria were isolated from diseased farmed African catfish (Clarias gariepinus, n=128) with clinical signs of skin haemorrhages, ulceration, and ascites purposively sampled from farms within three senatorial districts namely Ogun East (OE; n=76), Ogun Central (OC; n=30) and Ogun West (OW; n=22) in Ogun State. The isolates were identified based on morphological characteristics, biochemical tests, and 16S rRNA gene characterisation. The 16S rRNA gene sequences were analysed using BLAST, submitted to the NCBI database, and an accession number was generated. RESULTS: The occurrence of Proteus mirabilis in infected Clarias gariepinus was 13.16%, 25%, and 31.25% in OE, OC, and OW, respectively. A significantly higher incidence was recorded in OW compared to other areas. All the Proteus mirabilis isolates were motile, gram-negative, short rod, non-lactose fermenter bacteria that showed positive catalase reactions, negative oxidase, and positive for methyl-red. The Proteus mirabilis isolates (OP 594726.1) were closely related to isolates from Pakistan, Italy, and India CONCLUSIONS: We conclude that Proteus mirabilis colonises farmed Clarias gariepinus in Ogun State, Nigeria and the identified strain showed an evolutionary relationship with known pathogenic NCBI reference strains from other countries.

Identification of mechanisms modulating chlorhexidine and octenidine susceptibility in Proteus mirabilis.

AIMS: We aimed to identify mechanisms underlying the tolerance of P. mirabilis-a common cause of catheter associated urinary tract infection-to the clinically used biocides chlorhexidine (CHD) and octenidine (OCT). METHODS AND RESULTS: We adapted three clinical isolates to grow at concentrations of 512 µg ml-1 CHD and 128 µg ml-1 OCT. Genetic characterisation and complementation studies revealed mutations inactivating the smvR repressor and increasing smvA efflux expression were associated with adaptation to both biocides. Mutations in mipA (encoding the MltA interacting protein) were less prevalent than smvR mutations and only identified in CHD adapted populations. Mutations in the rppA response regulator were exclusive to one adapted isolate and were linked with reduced polymyxin B susceptibility and a predicted gain of function after biocide adaptation. Biocide adaptation had no impact on crystalline biofilm formation. CONCLUSIONS: SmvR inactivation is a key mechanism in both CHD and OCT tolerance. MipA inactivation alone confers moderate protection against CHD, and rppA showed no direct role in either CHD or OCT susceptibility.

Potential antivirulence activity of sub-inhibitory concentrations of ciprofloxacin against Proteus mirabilis isolates: an in-vitro and in-vivo study.

BACKGROUND: Proteus mirabilis is a significant nosocomial pathogen that is frequently associated with a wide range of infections, necessitating heightened attention to mitigate potential health risks. Hence, this study was performed to investigate the impact of sub-minimum inhibitory concentrations (MICs) of ciprofloxacin (CIP) on Proteus mirabilis clinical isolates. METHODS: The sub-MICs of CIP were selected using the growth curve approach. The untreated and treated isolates with sub-MICs of CIP were assessed for their biofilm development, motilities on agar, and other virulence factors. The cell morphology of untreated and treated isolates with sub-MIC of CIP was explored using electron microscope. Moreover, the expression levels of the virulence genes in isolates were measured using quantitative real-time PCR. RESULTS: Data revealed that sub-MICs of CIP significantly (p < 0.05), in a concentration-dependent manner, inhibited biofilm formation and other virulence factors in the selected isolates. Electron microscope analysis showed cell enlargement and various abnormalities in the cell wall and membrane integrity. CONCLUSION: Sub-MICs of CIP exhibited inhibition of virulence and alterations in morphological integrity against P. mirabilis isolates.

Emergence of extensive drug resistance and high prevalence of multidrug resistance among clinical Proteus mirabilis isolates in Egypt.

BACKGROUND: Proteus mirabilis is an opportunistic pathogen that has been held responsible for numerous nosocomial and community-acquired infections which are difficult to be controlled because of its diverse antimicrobial resistance mechanisms. METHODS: Antimicrobial susceptibility patterns of P. mirabilis isolates collected from different clinical sources in Mansoura University Hospitals, Egypt was determined. Moreover, the underlying resistance mechanisms and genetic relatedness between isolates were investigated. RESULTS: Antimicrobial susceptibility testing indicated elevated levels of resistance to different classes of antimicrobials among the tested P. mirabilis clinical isolates (n = 66). ERIC-PCR showed great diversity among the tested isolates. Six isolates (9.1%) were XDR while all the remaining isolates were MDR. ESBLs and AmpCs were detected in 57.6% and 21.2% of the isolates, respectively, where blaTEM, blaSHV, blaCTX-M, blaCIT-M and blaAmpC were detected. Carbapenemases and MBLs were detected in 10.6 and 9.1% of the isolates, respectively, where blaOXA-48 and blaNDM-1 genes were detected. Quinolone resistant isolates (75.8%) harbored acc(6')-Ib-cr, qnrD, qnrA, and qnrS genes. Resistance to aminoglycosides, trimethoprim-sulfamethoxazole and chloramphenicol exceeded 80%. Fosfomycin was the most active drug against the tested isolates as only 22.7% were resistant. Class I or II integrons were detected in 86.4% of the isolates. Among class I integron positive isolates, four different gene cassette arrays (dfrA17- aadA5, aadB-aadA2, aadA2-lnuF, and dfrA14-arr-3-blaOXA-10-aadA15) and two gene cassettes (dfrA7 and aadA1) were detected. While class II integron positive isolates carried four different gene cassette arrays (dfrA1-sat1-aadA1, estXVr-sat2-aadA1, lnuF- dfrA1-aadA1, and dfrA1-sat2). CONCLUSION: P. Mirabilis ability to acquire resistance determinants via integrons may be held responsible for the elevated rates of antimicrobial resistance and emergence of XDR or even PDR strains limiting the available therapeutic options for management of infections caused by those strains.

Molecular characterization of a carbon dioxide-dependent Proteus mirabilis small-colony variant isolated from a clinical specimen.

INTRODUCTION: Carbon dioxide-dependent Proteus mirabilis has been isolated from clinical specimens. It is not clear whether mutations in carbonic anhydrase are responsible for the carbon dioxide dependence of P. mirabilis. The pathogenicity of carbon dioxide-dependent P. mirabilis also remains unclear. The purpose of this study was to determine the cause carbon dioxide dependence of P. mirabilis and its pathogenicity. METHODS: The DNA sequence of can encoding carbonic anhydrase of a carbon dioxide-dependent P. mirabilis small colony variant (SCV) isolate was analyzed. To confirm that impaired carbonic anhydrase activity is responsible for the formation of the carbon dioxide-dependent SCV phenotype of P. mirabilis, we performed complementation experiments using plasmids with intact can. Additionally, mouse infection experiments were performed to confirm the change in virulence due to the mutation of carbonic anhydrase. RESULTS: We found that the can gene of the carbon dioxide-dependent P. mirabilis SCV isolate showed had a frameshift mutation with a deletion of 1 bp (c. 173delC). The can of P. mirabilis encodes carbonic anhydrase was also found to function in Escherichia coli. The cause of the carbon dioxide-dependent SCV phenotype of P. mirabilis was an abnormality in carbonic anhydrase. Nevertheless, no changes were observed in virulence due to the mutation of carbonic anhydrase in mouse infection experiments. CONCLUSIONS: The can gene is essential for the growth of P. mirabilis in ambient air. The mechanisms underlying this fitness advantage in terms of infection warrant further investigation.

The Cd resistant mechanism of Proteus mirabilis Ch8 through immobilizing and detoxifying.

Cadmium (Cd) pollution is a serious global environmental problem, which requires a global concern and practical solutions. Microbial remediation has received widespread attention owing to advantages, such as environmental friendliness and soil amelioration. However, Cd toxicity also severely deteriorates the remediation performance of functional microorganisms. Analyzing the mechanism of bacterial resistance to Cd stress will be beneficial for the application of Cd remediation. In this study, the bacteria strain, up to 1400 mg/L Cd resistance, was employed and identified as Proteus mirabilis Ch8 (Ch8) through whole genome sequence analyses. The results indicated that the multiple pathways of immobilizing and detoxifying Cd maintained the growth of Ch8 under Cd stress, which also possessed high Cd extracellular adsorption. Firstly, the changes in surface morphology and functional groups of Ch8 cells were observed under different Cd conditions through SEM-EDS and FTIR analyses. Under 100 mg/L Cd, Ch8 cells exhibited aggregation and less flagella; the Cd biosorption of Ch8 was predominately by secreting exopolysaccharides (EPS) and no significant change of functional groups. Under 500 mg/L Cd, Ch8 were present irregular polymers on the cell surface, some cells with wrapping around; the Cd biosorption capacity exhibited outstanding effects (38.80 mg/g), which was mainly immobilizing Cd by secreting and interacting with EPS. Then, Ch8 also significantly enhanced the antioxidant enzyme activity and the antioxidant substance content under different Cd conditions. The activities of SOD and CAT, GSH content of Ch8 under 500 mg/L Cd were significantly increased by 245.47%, 179.52%, and 241.81%, compared to normal condition. Additionally, Ch8 significantly induced the expression of Acr A and Tol C (the resistance-nodulation-division (RND) efflux pump), and some antioxidant genes (SodB, SodC, and Tpx) to reduce Cd damage. In particular, the markedly higher expression levels of SodB under Cd stress. The mechanism of Ch8 lays a foundation for its application in solving soil remediation.

Distribution of antimicrobial resistance and virulence markers in chicken originated Proteus mirabilis isolates.

Proteus mirabilis is a common enteric bacterium in livestock and humans. The increase and spread of the antimicrobial resistant P. mirabilis is considered alarming worldwide. Transmission mainly occurs through consumption of contaminated poultry products. We investigated antimicrobial resistance (AMR) and virulence markers in broiler chicken-originated P. mirabilis isolates from 380 fecal samples. Phenotypic AMR test was performed against seventeen different antimicrobials. Genotypic AMR test was performed to detect sixteen different AMR genes. The samples were also tested for the presence of eight different virulence genes and biofilm formation. P. mirabilis was isolated in 11% of the samples, with significantly high multidrug-resistant (MDR) prevalence (63%). All isolates were resistant to tetracycline (100%). The combined disc method indicated that all isolates were of extended-spectrum beta-lactamase (ESBL) producers, which was compatible with the high blaTEM prevalence (95%). This was associated with blaTEM being responsible for more than 80% of ampicillin resistance in enteric pathogens. The absence of phenotypically carbapenem-resistant isolates was compatible with the very low prevalences of blaOXA (2%) and blaNDM (0%). All isolates were positive for pmfA, atfA, hpmA, and zapA (100%) virulence genes, while biofilm formation rate (85%) indicated high adherence abilities of the isolates.

Organ agar serves as physiologically relevant alternative for in vivo bacterial colonization.

Animal models for host-microbial interactions have proven valuable, yielding physiologically relevant data that may be otherwise difficult to obtain. Unfortunately, such models are lacking or nonexistent for many microbes. Here, we introduce organ agar, a straightforward method to enable the screening of large mutant libraries while avoiding physiological bottlenecks. We demonstrate that growth defects on organ agar were translatable to bacterial colonization deficiencies in a murine model. Specifically, we present a urinary tract infection agar model to interrogate an ordered library of Proteus mirabilis transposon mutants, with accurate prediction of bacterial genes critical for host colonization. Thus, we demonstrate the ability of ex vivo organ agar to reproduce in vivo deficiencies. Organ agar was also useful for identifying previously unknown links between biosynthetic genes and swarming motility. This work provides a readily adoptable technique that is economical and uses substantially fewer animals. We anticipate this method will be useful for a wide variety of microorganisms, both pathogenic and commensal, in a diverse range of model host species.

Preferential catabolism of l- vs d-serine by Proteus mirabilis contributes to pathogenesis and catheter-associated urinary tract infection.

Proteus mirabilis is a common cause of urinary tract infection, especially in catheterized individuals. Amino acids are the predominant nutrient for bacteria during growth in urine, and our prior studies identified several amino acid import and catabolism genes as fitness factors for P. mirabilis catheter-associated urinary tract infection (CAUTI), particularly those for d- and l-serine. In this study, we sought to determine the hierarchy of amino acid utilization by P. mirabilis and to examine the relative importance of d- vs l-serine catabolism for critical steps in CAUTI development and progression. Herein, we show that P. mirabilis preferentially catabolizes l-serine during growth in human urine, followed by d-serine, threonine, tyrosine, glutamine, tryptophan, and phenylalanine. Independently disrupting catabolism of either d- or l-serine has minimal impact on in vitro phenotypes while completely disrupting both pathways decreases motility, biofilm formation, and fitness due to perturbation of membrane potential and cell wall biosynthesis. In a mouse model of CAUTI, loss of either serine catabolism system decreased fitness, but disrupting l-serine catabolism caused a greater fitness defect than disrupting d-serine catabolism. We, therefore, conclude that the hierarchical utilization of amino acids may be a critical component of P. mirabilis colonization and pathogenesis within the urinary tract.

Isolation, biological and whole genome characteristics of a Proteus mirabilis bacteriophage strain.

Proteus mirabilis, a naturally resistant zoonotic bacterium belonging to the Enterobacteriaceae family, has exhibited an alarming increase in drug resistance. Consequently, there is an urgent need to explore alternative antimicrobial agents. Bacteriophages, viruses that selectively target bacteria, are abundant in the natural environment and have demonstrated potential as a promising alternative to antibiotics. In this study, we successfully isolated four strains of Proteus mirabilis phages from sewage obtained from a chicken farm in Sichuan, China. Subsequently, we characterized one of the most potent lytic phages, Q29, by examining its biological and genomic features. Comparative genomic analysis revealed the functional genes and phylogenetic evolution of Q29 phages. Our findings revealed that Proteus mirabilis bacteriophage Q29 possesses an icosahedral symmetrical head with a diameter of 95 nm and a tail length of 240 nm. Moreover, phage Q29 exhibited stability within a temperature range of 37 ℃ to 55 ℃ and under pH conditions ranging from 4 to 9. The optimal multiplicity of infection (MOI) for this phage was determined to be 0.001. Furthermore, the one-step growth curve results indicated an incubation period of approximately 15 min, an outbreak period of approximately 35 min, and an average cleavage quantity of approximately 60 plaque-forming units (PFU) per cell. The genome of phage Q29 was found to have a total length of 58,664 base pairs and encoded 335 open reading frames (ORFs) without carrying any antibiotic resistance genes. Additionally, genetic evolutionary analysis classified phage Q29 within the family Caudalidae and the genus Myotail. This study provides valuable research material for further development of Proteus mirabilis bacteriophage biologics as promising alternatives to antibiotics, particularly in light of the growing challenge of antibiotic resistance posed by this bacterium.

The first evidence of antibiofilm action of Proteus mirabilis with tetra-cationic porphyrins containing cisplatin by antimicrobial photodynamic therapy.

Biofilms are responsible for up to 80% of antimicrobial-resistant nosocomial infections. Most of these infections are associated with medical devices such as urinary catheters, and in this context, it is estimated that 90-100% of patients who undergo long-term catheterization develop infections. Proteus mirabilis, the most prevalent microorganism, is responsible for 20-45% of these infections. Thus, this study aimed to evaluate, for the first time, the antimicrobial and antibiofilm effects of cationic porphyrins on P. mirabilis. Neutral porphyrins 3-H2TPyP and 4-H2TpyP and tetra-cationic derivatives 3-cis-PtTPyP and 4-cis-PtTPyP were evaluated in broth microdilution tests to determine the minimum inhibitory and bactericidal concentrations. Time-kill curves, checkerboard test, reactive oxygen species (ROS) scavenger assays, conventional biofilm formation, and biofilm assay with catheters were also performed. The microdilution tests showed greater efficacy against P. mirabilis when 3-cis-PtTPyP was exposed to white-light conditions; this also occurred when the microbial time-kill curve was performed at 0, 2, 6, and 12 h. The radical superoxide species was possibly responsible for photoinactivation in the ROS scavenger assays. In biofilm assays (conventional and catheter), 3-cis-PtTPyP obtained better results when irradiated with a white-light source. In the checkerboard assay, the same compound showed no differences when tested in association with ciprofloxacin hydrochloride. Our findings lead us to conclude that antimicrobial photodynamic therapy and cationic porphyrins obtained positive results and are promising alternatives to treat P. mirabilis biofilms.

Characterization of phenyl propiolic acid from Proteus mirabilis DMTMMR-11 and Evaluation of its mode of action against Yersinia enterocolitica (MTCC-840) an in-Vitro and in-Vivo based approach.

Foodborne illnesses are pervasive in raising public health concerns in both developed and developing nations. Yersinia enterocolitica a zoonotic bacterial species that causes food-transmitted infections, and gastroenteritis, is its most prevalent clinical manifestation. This study aims to investigate the differences, dependencies, and inhibitory mechanisms between the host and the microbiome. Proteus mirabilis DMTMMR-11, the bacterium found in the human gastrointestinal tract was used for the extraction of intracellular metabolite, because of its beneficial effects on the normal flora of the human gut. Phenyl propiolic acid was identified as the dominant compound in the metabolite after characterization using FT-IR, NMR, and LC-MS-MS. To assess its inhibitory mechanism against Yersinia enterocolitica, the pathogen was subjected to biological characterization by MBC and MIC, resulting in the rate of inhibition at 50 µg/ml. Anti-bacterial curve supports the inhibited growth of Y. enterocolitica. Mechanism of inhibition at its cellular level was indicated by the increase in alkaline phosphate content, which drastically reduced the cell membrane and cell wall potential expanding its permeability by intruding the membrane proteins, which was observed in SEM Imaging. Phenyl propiolic acid efficiently disrupts the biofilm formation by reducing the adherence and increasing the eradication property of the pathogen by exhibiting 65% of inhibition at the minimal duration of 12h. In-vivo study was carried out through host-pathogen interaction in C. elegans, an efficient model organism assessed for its life-span, physiological, and behavioral assays.

Genomes comparison of two Proteus mirabilis clones showing varied swarming ability.

BACKGROUND: Proteus mirabilis is a Gram-negative bacteria most noted for its involvement with catheter-associated urinary tract infections. It is also known for its multicellular migration over solid surfaces, referred to as 'swarming motility'. Here we analyzed the genomic sequences of two P. mirabilis isolates, designated K38 and K39, which exhibit varied swarming ability. METHODS AND RESULTS: The isolates genomes were sequenced using Illumina NextSeq sequencer, resulting in about 3.94 Mbp, with a GC content of 38.6%, genomes. Genomes were subjected for in silico comparative investigation. We revealed that, despite a difference in swarming motility, the isolates showed high genomic relatedness (up to 100% ANI similarity), suggesting that one of the isolates probably originated from the other. CONCLUSIONS: The genomic sequences will allow us to investigate the mechanism driving this intriguing phenotypic heterogeneity between closely related P. mirabilis isolates. Phenotypic heterogeneity is an adaptive strategy of bacterial cells to several environmental pressures. It is also an important factor related to their pathogenesis. Therefore, the availability of these genomic sequences will facilitate studies that focus on the host-pathogen interactions during catheter-associated urinary tract infections.

Infection responsive coatings to reduce biofilm formation and encrustation of urinary catheters.

AIMS: The care of patients undergoing long-term urethral catheterization is frequently complicated by Proteus mirabilis infection. This organism forms dense, crystalline biofilms, which block catheters leading to serious clinical conditions. However, there are currently no truly effective approaches to control this problem. Here, we describe the development of a novel theranostic catheter coating, to simultaneously provide early warning of blockage, and actively delay crystalline biofilm formation. METHODS AND RESULTS: The coating comprises of a pH sensitive upper polymer layer (poly(methyl methacrylate-co-methacrylic acid); Eudragit S 100®) and a hydrogel base layer of poly(vinyl alcohol), which is loaded with therapeutic agents (acetohydroxamic acid or ciprofloxacin hydrochloride) and a fluorescent dye, 5(6)-carboxyfluorescein (CF). The elevation of urinary pH due to P. mirabilis urease activity results in the dissolution of the upper layer and release of cargo agents contained in the base layer. Experiments using in vitro models, which were representative of P. mirabilis catheter-associated urinary tract infections, demonstrated that these coatings significantly delay time taken for catheters to block. Coatings containing both CF dye and ciprofloxacin HCl were able to provide an average of ca. 79 h advanced warning of blockage and extend catheter lifespan ca. 3.40-fold. CONCLUSIONS: This study has demonstrated the potential for theranostic, infection-responsive coatings to form a promising approach to combat catheter encrustation and actively delay blockage.

Quick Detection of Proteus and Pseudomonas in Patients' Urine and Assessing Their Antibiotic Susceptibility Using Infrared Spectroscopy and Machine Learning.

Bacterial resistance to antibiotics is a primary global healthcare concern as it hampers the effectiveness of commonly used antibiotics used to treat infectious diseases. The development of bacterial resistance continues to escalate over time. Rapid identification of the infecting bacterium and determination of its antibiotic susceptibility are crucial for optimal treatment and can save lives in many cases. Classical methods for determining bacterial susceptibility take at least 48 h, leading physicians to resort to empirical antibiotic treatment based on their experience. This random and excessive use of antibiotics is one of the most significant drivers of the development of multidrug-resistant (MDR) bacteria, posing a severe threat to global healthcare. To address these challenges, considerable efforts are underway to reduce the testing time of taxonomic classification of the infecting bacterium at the species level and its antibiotic susceptibility determination. Infrared spectroscopy is considered a rapid and reliable method for detecting minor molecular changes in cells. Thus, the main goal of this study was the use of infrared spectroscopy to shorten the identification and the susceptibility testing time of Proteus mirabilis and Pseudomonas aeruginosa from 48 h to approximately 40 min, directly from patients' urine samples. It was possible to identify the Proteus mirabilis and Pseudomonas aeruginosa species with 99% accuracy and, simultaneously, to determine their susceptibility to different antibiotics with an accuracy exceeding 80%.

Structure and Assembly of the Proteus mirabilis Flagellar Motor by Cryo-Electron Tomography.

Proteus mirabilis is a Gram-negative Gammaproteobacterium and a major causative agent of urinary tract infections in humans. It is characterized by its ability to switch between swimming motility in liquid media and swarming on solid surfaces. Here, we used cryo-electron tomography and subtomogram averaging to reveal the structure of the flagellar motor of P. mirabilis at nanometer resolution in intact cells. We found that P. mirabilis has a motor that is structurally similar to those of Escherichia coli and Salmonella enterica, lacking the periplasmic elaborations that characterize other more specialized gammaproteobacterial motors. In addition, no density corresponding to stators was present in the subtomogram average suggesting that the stators are dynamic. Finally, several assembly intermediates of the motor were seen that support the inside-out assembly pathway.

Antigenic and Structural Properties of the Lipopolysaccharide of the Uropathogenic Proteus mirabilis Dm55 Strain Classified to a New O85 Proteus Serogroup.

The aim of the study was the serological and structural characterization of the lipopolysaccharide (LPS) O antigen from P. mirabilis Dm55 coming from the urine of a patient from Lodz. The Dm55 LPS was recognized in ELISA only by the O54 antiserum, suggesting a serological distinction of the Dm55 O antigen from all the 84 Proteus LPS serotypes described. The obtained polyclonal rabbit serum against P. mirabilis Dm55 reacted in ELISA and Western blotting with a few LPSs (including O54), but the reactions were weaker than those observed in the homologous system. The LPS of P. mirabilis Dm55 was subjected to mild acid hydrolysis, and the obtained high-molecular-mass O polysaccharide was chemically studied using sugar and methylation analyses, mass spectrometry, and 1H and 13C NMR spectroscopy, including 1H,1H NOESY, and 1H,13C HMBC experiments. The Dm55 O unit is a branched three-saccharide, and its linear fragment contains α-GalpNAc and ß-Galp, whereas α-GlcpNAc occupies a terminal position. The Dm55 OPS shares a disaccharide epitope with the Proteus O54 antigen. Due to the structural differences of the studied O antigen from the other described Proteus O polysaccharides, we propose to classify the P. mirabilis Dm55 strain to a new Proteus O85 serogroup.

Adjustment in the Composition and Organization of Proteus mirabilis Lipids during the Swarming Process.

Proteus mirabilis, an opportunistic pathogen of the urinary tract, is known for its dimorphism and mobility. A connection of lipid alterations, induced by the rods elongation process, with enhanced pathogenicity of long-form morphotype for the development of urinary tract infections, seems highly probable. Therefore, research on the adjustment in the composition and organization of P. mirabilis lipids forming elongated rods was undertaken. The analyses performed using the ultra-high performance liquid chromatography with tandem mass spectrometry showed that drastic modifications in the morphology of P. mirabilis rods that occur during the swarming process are directly related to deprivation of the long-form cells of PE 33:1 and PG 31:2 and their enrichment with PE 32:1, PE 34:1, PE 34:2, PG 30:2, PG 32:1, and PG 34:1. The analyses conducted by the gas chromatography-mass spectrometry showed negligible effects of the swarming process on fatty acids synthesis. However, the constant proportions between unsaturated and saturated fatty acids confirmed that phenotypic modifications in the P. mirabilis rods induced by motility were independent of the saturation of the phospholipid tails. The method of the Förster resonance energy transfer revealed the influence of the swarming process on the melting of ordered lipid rafts present in the short-form rods, corresponding to the homogeneity of lipid bilayers in the long-form rods of P. mirabilis. Confocal microscope photographs visualized strong Rhod-PE fluorescence of the whole area of swarmer cells, in contrast to weak membrane fluorescence of non-swarmer cells. It suggested an increased permeability of the P. mirabilis bilayers in long-form rods morphologically adapted to the swarming process. These studies clearly demonstrate that swarming motility regulates the lipid composition and organization in P. mirabilis rods.