Proteus mirabilis: taxonomic position, peculiarities of growth, components of the cell envelope

Proteus mirabilis and Klebsiella pneumoniae as pathogens capable of causing co-infections and exhibiting similarities in their virulence factors

The genera Klebsiella and Proteus were independently described in 1885. These Gram-negative rods colonize the human intestinal tract regarded as the main reservoir of these opportunistic pathogens. In favorable conditions they cause infections, often hospital-acquired ones. The activity of K. pneumoniae and P. mirabilis, the leading pathogens within each genus, results in infections of the urinary (UTIs) and respiratory tracts, wounds, bacteremia, affecting mainly immunocompromised patients. P. mirabilis and K. pneumoniae cause polymicrobial UTIs, which are often persistent due to the catheter biofilm formation or increasing resistance of the bacteria to antibiotics. In this situation a need arises to find the antigens with features common to both species. Among many virulence factors produced by both pathogens urease shows some structural similarities but the biggest similarities have been observed in lipids A and the core regions of lipopolysaccharides (LPSs). Both species produce capsular polysaccharides (CPSs) but only in K. pneumoniae these antigens play a crucial role in the serological classification scheme, which in Proteus spp. is based on the structural and serological diversity of LPS O-polysaccharides (OPSs). Structural and serological similarities observed for Klebsiella spp. and Proteus spp. polysaccharides are important in the search for the cross-reacting vaccine antigens.

Complicated catheter-associated urinary tract infections due to Escherichia coli and Proteus mirabilis

Catheter-associated urinary tract infections (CAUTIs) represent the most common type of nosocomial infection and are a major health concern due to the complications and frequent recurrence. These infections are often caused by Escherichia coli and Proteus mirabilis. Gram-negative bacterial species that cause CAUTIs express a number of virulence factors associated with adhesion, motility, biofilm formation, immunoavoidance, and nutrient acquisition as well as factors that cause damage to the host. These infections can be reduced by limiting catheter usage and ensuring that health care professionals correctly use closed-system Foley catheters. A number of novel approaches such as condom and suprapubic catheters, intermittent catheterization, new surfaces, catheters with antimicrobial agents, and probiotics have thus far met with limited success. While the diagnosis of symptomatic versus asymptomatic CAUTIs may be a contentious issue, it is generally agreed that once a catheterized patient is believed to have a symptomatic urinary tract infection, the catheter is removed if possible due to the high rate of relapse. Research focusing on the pathogenesis of CAUTIs will lead to a better understanding of the disease process and will subsequently lead to the development of new diagnosis, prevention, and treatment options.

Structural analysis of the core region of lipopolysaccharides from Proteus mirabilis serotypes O6, O48 and O57

The structure of lipid A core region of the lipopolysaccharides (LPS) from Proteus mirabilis serotypes O6, O57 and O48 was determined using NMR, MS and chemical analysis of the oligosaccharides, obtained by mild acid hydrolysis, alkaline deacylation, and deamination of LPS: [see text for structure]. Incomplete substitutions are indicated by bold italic type. All sugars are present in pyranose form, alpha-Hep is the residue of L-glycero-alpha-D-manno-Hep, alpha-DD-Hep is the residue of D-glycero-alpha-D-manno-Hep, L-Ara4N is 4-amino-4-deoxy-L-arabinose, Qui4NAlaAla is the residue of 4-N-(L-alanyl-L-alanyl)-4-amino-4,6-dideoxyglucose. All sugars except L-Ara4N have D-configuration. beta-GalA* is partially present in the form of amide with 1,4-diaminobutane (putrescine)-HN(CH2)4NH2 or spermidine-HN(CH2)3NH(CH2)4NH2.

The structure of the carbohydrate backbone of core-lipid A region ofthe lipopolysaccharides from Proteus mirabilis wild-type strain S1959 (serotype O3) and its Ra mutant R110/1959

The following structure of core-lipid A region of the lipopolysaccharide (LPS) from Proteus mirabilis strain 1959 (serotype O3) and its rough mutant R110/1959 (Proteus type II core) was determined using NMR and chemical analysis of the core oligosaccharide, obtained by mild acid hydrolysis of LPS, and of the products of alkaline deacylation of the LPS: Incomplete substitutions are indicated by italics. All sugars are in pyranose form, alpha-Hep is the residue Lglycero-alpha-Dmanno-Hep, alpha-DD-Hep is the residue Dglycero-alpha-Dmanno-Hep. The differences with the previously reported structures are discussed.

Structure of the O-specific polysaccharide of a serologically separate strain Proteus penneri 2 from a new proposed serogroup O66

O-specific polysaccharide chain of Proteus penneri strain 2 lipopolysaccharide was studied by full and partial acid hydrolysis, Smith degradation, methylation analysis, and NMR spectroscopy, including two-dimensional rotating-frame NOE spectroscopy (ROESY) and 1H,13C heteronuclear multiple-quantum coherence (HMQC) experiments. Together with D-glucose and 2-acetamido-2-deoxy-D-glucose, the polysaccharide was found to contain two rarely occurring sugars, 6-deoxy-L-talose (L-6dTal) and 2,3-diacetamido-2,3,6-trideoxy-L-mannose (L-RhaNAc3NAc), and the following structure of a non-stoichiometrically O-acetylated tetrasaccharide repeating unit was established: [equation: see text] The O-specific polysaccharide studied has a unique composition and structure and, accordingly, P. penneri 2 is serologically separate among Proteus strains. Therefore, we propose for P. penneri 2 a new Proteus O-serogroup O66 where this strain is at present the single representative.

Potential virulence factors of Proteus bacilli

The object of this review is the genus Proteus, which contains bacteria considered now to belong to the opportunistic pathogens. Widely distributed in nature (in soil, water, and sewage), Proteus species play a significant ecological role. When present in the niches of higher macroorganisms, these species are able to evoke pathological events in different regions of the human body. The invaders (Proteus mirabilis, P. vulgaris, and P. penneri) have numerous factors including fimbriae, flagella, outer membrane proteins, lipopolysaccharide, capsule antigen, urease, immunoglobulin A proteases, hemolysins, amino acid deaminases, and, finally, the most characteristic attribute of Proteus, swarming growth, enabling them to colonize and survive in higher organisms. All these features and factors are described and commented on in detail. The questions important for future investigation of these facultatively pathogenic microorganisms are also discussed.

The structure and serological specificity of Proteus mirabilis O43 O antigen

On the basis of sugar analysis and NMR spectroscopy, including selective spin-decoupling, one-dimensional NOE, two-dimensional homonuclear and 13C,1H-heteronuclear correlation spectroscopy, the following structure of the acidic O-specific polysaccharide of Proteus mirabilis O43 was established: -->4)-alpha-D-GalpA-(1-->3)-alpha-D-GalpA-(1-->3)-alpha-D-Gl cpNAc-(1-->4)-alpha - D-Glcp-(1-->, where GalA is galacturonic acid and Galp is galactopyranose. No serological cross-reactivity was observed between lipopolysaccharides of P. mirabilis O43 and other studied Proteus strains, except for P. mirabilis O10. The O-specific polysaccharide of P. mirabilis O43 was serologically active in precipitation and inhibition tests but the activity was lost after periodate oxidation. These data suggest that the O43 specificity is determined by a wide epitope with the immunodominant role of 4-substituted D-Glc or/and D-GalA, which are destroyed by periodate oxidation.

Structure and epitope characterisation of the O-specific polysaccharide of Proteus mirabilis O28 containing amides of D-galacturonic acid with L-serine and L-lysine

The O-specific polysaccharide of Proteus mirabilis O28 was found to contain D-galactose, D-galacturonic acid (GalA), 2-acetamido-2-deoxy-D-glucose, L-serine, L-lysine, and O-acetyl groups in molar ratios 1:2:1:1:1:1, the amino acids being linked via their alpha-amino group to the carboxyl group of GalA. The polysaccharide was studied using 1H- and 13C-NMR spectroscopy, including selective spin-decoupling, one-dimensional total correlation spectroscopy, two-dimensional homonuclear correlation spectroscopy (COSY), heteronuclear 13C,1H COSY, one-dimensional NOE, and two-dimensional rotating-frame NOE spectroscopy and partial acid hydrolysis followed by borohydride reduction, methylation, and GLC/MS analysis of the derived glycosyl alditols. The following structure of the repeating unit was established: [formula: see text] Epitope specificity of the P. mirabilis O28 polysaccharide was analysed using a homologous rabbit polyclonal antiserum in quantitative precipitation, passive immunohemolysis, and inhibition of passive immunohemolysis. Study with related synthetic glycopolymers (2-acrylamidoethyl glycosides of amides of alpha-D-GalA with amino acids copolymerised with acrylamide) showed the importance of D-GalA(L-Lys) for manifesting serological specificity of the O-antigen. Serological cross-reactions between P. mirabilis O28, S1959, and R14/S1959 (a transient-like form) are discussed.

Outer membrane permeability barrier to azithromycin, clarithromycin, and roxithromycin in gram-negative enteric bacteria

Mutations which severely affect the function of the outer membrane of Escherichia coli and Salmonella typhimurium (lpxA and firA mutations of lipid A synthesis and rfaE mutation of the lipopolysaccharide inner-core synthesis) were found to decrease the MICs of erythromycin, roxithromycin, clarithromycin, and azithromycin by factors of 32 to 512, 32 to 1,024, 64 to 512, and 16 to 64, respectively. The sensitization factors for three other hydrophobic antibiotics (rifampin, fusidic acid, and mupirocin) ranged from 16 to 300. The outer membrane permeability-increasing agents polymyxin B nonapeptide (3 micrograms/ml) and deacylpolymyxin B (1 microgram/ml) sensitized wild-type E. coli to azithromycin by factors of 10 and 30, respectively. Quantitatively very similar sensitization to the other macrolides took place. Polymyxin-resistant pmrA mutants of S. typhimurium displayed no cross-resistance to azithromycin. Proteus mirabilis mutants which were sensitized to polymyxin by a factor of > or = 300 to > or = 1,000 had a maximal two- to fourfold increase in sensitivity to azithromycin. These results indicate that azithromycin and the other new macrolides use the hydrophobic pathway across the outer membrane and that the intact outer membrane is an effective barrier against them. Furthermore, the results indicate that azithromycin, in contrast to polymyxin, does not effectively diffuse through the outer membrane by interacting electrostatically with the lipopolysaccharide.

The structure of Proteus mirabilis O3 O-specific polysaccharide containing N-(2-hydroxyethyl)-D-alanine

O-Specific polysaccharide was obtained by mild acid degradation of Proteus mirabilis O3 lipopolysaccharide. The polysaccharide was dephosphorylated with 48% HF to give a linear polysaccharide and an amino acid, N-(2-hydroxyethyl)-D-alanine. The structure of the polysaccharide was determined by methylation, Smith degradation and computer-assisted analysis of the 13C-NMR spectra of original and dephosphorylated polymers and oligomers. The structure of the amino acid was investigated by using 1H and 13C-NMR spectroscopy and mass spectrometry (applied to the acetylated methyl ester derivative). Its absolute configuration was established by comparison of the optical rotation value and CD spectrum of the natural and synthetic product. On the basis of the data obtained, it was concluded that the repeating unit of P. mirabilis O3 O-specific polysaccharide has the following structure: (formula; see text) Removal of the amino acid phosphate substituent significantly decreased serological activity of the O-specific polysaccharide, thus showing the immunodominant role of this group. Serological cross-reactions between P. mirabilis O3 and O27 were demonstrated and tentatively substantiated.

The cell-surface antigens of Bacteroides thetaiotaomicron

Three strains of B. thetaiotaomicron of different origin were investigated. Lipopolysaccharides were extracted from the studied strains using a phenol-water method. The best purification of LPS was achieved by digestion with nuclease and subsequent ultracentrifugation. Capsular material (CPS) was obtained from the most heavily encapsulated strain. The preparation were analyzed chemically, and their serological activity was determined. All antigens were active with homologous antibacterial sera in immunodiffusion, crossed immunoelectrophoresis, and passive hemagglutination tests. In the CPS equal amounts of saccharides and proteins were detected. All antigens were analyzed by polyacrylamide gel electrophoresis with SDS. Capsular antigen slowly migrated in the gel in the form of a single band. Migration pattern of lipopolysaccharides of the studied B. thetaiotaomicron strain was characteristic for S-type LPS.

Structure of Proteus mirabilis O27 O-specific polysaccharide containing amino acids and phosphoethanolamine

The following structure of the repeating unit of the O-specific polysaccharide of Proteus mirabilis O27, containing amides of D-glucuronic and D-galacturonic acids with L-lysine and L-alanine, respectively, N-acetyl-D-glucosamine and phosphoethanolamine, has been determined: (sequence; see text) The main methods used for structural analysis of the polysaccharide were selective solvolysis with anhydrous hydrogen fluoride and Smith degradation, as well as NMR spectroscopy and mass spectrometry. The immunodominant role of the lateral N-acetyl-D-glucosamine and phosphoethanolamine in manifesting the serological specificity of P. mirabilis O27 has been established.

The core region of Proteus mirabilis R110/1959 lipopolysaccharide

The complete core structure present in the lipopolysaccharide of the R mutant R110/1959 from Proteus mirabilis (Proteus type II core) was investigated using methylation analysis and a number of degradation methods such as Smith degradation and beta-elimination. These studies combined with earlier work on a Rc-type mutant of P. mirabilis O28 (R4/O28) which shares the same inner core region, allowed formulation of the complete core structure of the Proteus type II core as shown in Scheme 1. (formula; see text) A characteristic feature of the Proteus core of type II is the presence of two units of D-galacturonic acid (DGalA); one in terminal, the other one in a chain-linked position. In addition, the presence of the two isomers of glycero-D-manno-heptose (LDHep and DDHep) and the lack of galactose are conspicuous. DDHep occupies a terminal position in the external core region, whereas the three units of LDHep in addition to dOclA form, as in other enterobacterial core types, the internal core region. The taxonomic significance of the presence of DGalA in the Proteus type II core, but also in all R cores of other Proteeae investigated so far, will be discussed.

Structural studies on the fucosamine-containing O-specific polysaccharide of Proteus vulgaris O19

The polysaccharide chain of Proteus vulgaris O19 lipopolysaccharide contains D-galactose, N-acetyl-D-glucosamine N-acetyl-D-galactosamine and N-acetyl-L-fucosamine in the ratio 1:1:1:1. The structure of the polysaccharide was established by full acid hydrolysis and methylation analysis, as well as by non-destructive methods, i.e. the computer-assisted evaluation of the 13C-NMR spectrum and computer-assisted evaluation of the specific optical rotation by Klyne's rule. The polysaccharide is regular and built up of tetrasaccharide repeating units of the following structure: ----3)-alpha-L-FucNAcp-(1----3)-beta-D-GlcNAcp-(1----3)-alph a-D-Galp- (1----4)-alpha-D-GalNAcp-(1---- The O19-antiserum cross-reacts with lipopolysaccharide from P. vulgaris O42, the structure of which is still unknown. No cross-reactions were observed with O-polysaccharides Pseudomonas aeruginosa O7 and Salmonella arizonae O59 in spite of some structural similarities.

Structural studies on the core and lipid A region of a 4-amino-L-arabinose-lacking Rc-type mutant of Proteus mirabilis

The structure of the 4-amino-L-arabinose-lacking lipopolysaccharide of the Proteus mirabilis Rc-type mutant R4, derived from wild-type O28, was elucidated. The lipopolysaccharide core structure has previously been partially characterized. The linkage between heptose and deoxyoctulosonic acid(dOclA) is now reported, as well as the structure of the lipid A moiety of this mutant strain. Besides the tentative identification of an alpha-linked glucosamine disaccharide in the lipid A backbone accompanying the usual beta 1----6-linked glucosamine-disaccharide, the only significant structural variation to previous studies was the lack of substitution of the C-4' phosphate by 4-amino-L-arabinose. In addition, the substitution at C-8 of one dOclA unit by 4-amino-L-arabinose, previously reported for the R45 mutant of P. mirabilis 1959, is lacking in this R mutant. Also in addition to previous findings, the terminal unit of heptose was found to be substituted at C-7 with phosphorylethanolamine (PEtN) and not only with phosphate, although this substitution is not complete as demonstrated by the relevant signals in 31P-NMR. Additional studies with the wild-type strain P. mirabilis O28 revealed the presence of 4-amino-L-arabinose in both the core and the lipid A regions suggesting that the R4 mutant is defective in the biosynthesis of this amino sugar rather than in its transfer. Otherwise the lipid A regions of the mutant and the wild-type strain show no structural differences. The following formula is proposed for the lipopolysaccharide of 4-amino-L-arabinose-lacking mutant R4/O28 P. mirabilis: (Formula; see text)

Lipopolysaccharide of Providencia rettgeri. Chemical studies and taxonomical implications

The chemical constitutional analysis of the lipopolysaccharide (LPS) isolated from Providencia rettgeri was carried out. Polyacrylamide gel electrophoresis using sodium dodecylsulfate or sodium deoxycholate showed that the lipopolysaccharide mostly consisted of short sugar chains. The lipid A was precipitated out after mild acid hydrolysis of LPS. From the supernatant degraded polysaccharide and unsubstituted core fractions were isolated. Compositional analysis of the core material revealed the presence of galacturonic acid, galactose, glucose, glucosamine, L-glycero-D-manno-heptose, 3-deoxy-D-manno-octulosonic acid, alanine and phosphorus. Methylation analysis of the core material indicated the presence of terminal units of glucose, galacturonic acid and glucosamine. The chemical structure of the lipid A was elucidated. It constitutes a beta-1,6-glucosamine disaccharide substituted on either side by ester and glycosidically-bond phosphate residues. The ester-bound phosphate was found to be substituted by a 4-amino-4-deoxy-L-arabinosyl residue. The amino groups of the backbone disaccharide are N-acylated by 3-O-(14:0)14:0 and 3-O-14:0. Two hydroxyl groups of the disaccharide are esterified by 3-O-(14:0)14:0 and 3-O-14:0. The taxonomical importance of these structural details will be discussed.