Structural and serological studies of the O-polysaccharide of strains from a newly createdProteusO78 serogroup prevalent in Polish patients

Structural and Serological Characterization of the O Antigen of Proteus mirabilis Clinical Isolates Classified into a New Proteus Serogroup, O84

Two closely related Proteus mirabilis smooth strains, Kr1 and Ks20, were isolated from wound and skin samples, respectively, of two infected patients in central Poland. Serological tests, using the rabbit Kr1-specific antiserum, revealed that both strains presented the same O serotype. Their O antigens are unique among the Proteus O serotypes, which had been described earlier, as they were not recognized in an enzyme-linked immunosorbent assay (ELISA) by a set of Proteus O1-O83 antisera. Additionally, the Kr1 antiserum did not react with O1-O83 lipopolysaccharides (LPSs). The O-specific polysaccharide (OPS, O antigen) of P. mirabilis Kr1 was obtained via the mild acid degradation of the LPSs, and its structure was established via a chemical analysis and one- and two-dimensional ¹H and ¹³C nuclear magnetic resonance (NMR) spectroscopy applied to both initial and O-deacetylated polysaccharides, where most β-2-acetamido-2-deoxyglucose (N-acetylglucosamine) (GlcNAc) residues are non-stoichiometrically O-acetylated at positions 3, 4, and 6 or 3 and 6, and a minority of α-GlcNAc residues are 6-O-acetylated. Based on the serological features and chemical data, P. mirabilis Kr1 and Ks20 were proposed as candidates to a new successive O-serogroup in the genus Proteus, O84, which is another example of new Proteus O serotypes identified lately among serologically differentiated Proteus bacilli infecting patients in central Poland.

The prevailing O serogroups among the serologically differentiated clinical Proteus spp. strains in central Poland

In the years 2006–2011, 617 Proteus spp. strains isolated mostly from urine and wounds or other clinical sources were collected in Łódź, Poland, to determine the offensive O serotypes frequently occurring among patients. P. mirabilis exhibited the most intensive swarming growth and was dominating species (86.9%), followed by P. genomospecies, P. vulgaris, and P. penneri. Ninety four per cent strains were recognized as S (smooth) forms. Serological studies (involving ELISA—enzyme-linked immunosorbent assay and Western blotting using native and adsorbed rabbit antisera) enabled classification of 80% S isolates into respective Proteus O serogroups among the 83 ones, described so far. The remaining strains seemed to be serologically unique. Despite the observed big serological variety of Proteus spp. isolates, we found the O78 serogroup recently described in Poland as dominating and identified other widespread serotypes: O3, O6, O10, O11, O27, O28, and O30 reported earlier as predominating also in other countries; O77 and O79 detected lately in Poland; O16, O18, O20, and O50. No unique structural feature of the prevalent O serotypes has been indicated. However, the prevalence of some O serogroups indicates that particular serotypes may be in some ways beneficial to the strains producing these kinds of O antigen.

Pathogenic Factors Correlate With Antimicrobial Resistance Among Clinical Proteus mirabilis Strains

Proteus mirabilis is the third most common etiological factor of urinary tract infection. It produces urease, which contributes to the formation of a crystalline biofilm, considered to be one of the most important virulence factors of P. mirabilis strains, along with their ability to swarm on a solid surface. The aim of this study was to analyze the pathogenic properties of two selected groups of clinical P. mirabilis isolates, antimicrobial susceptible and multidrug resistant (MDR), collected from hospitals in different regions in Poland. The strains were examined based on virulence gene profiles, urease and hemolysin production, biofilm formation, and swarming properties. Additionally, the strains were characterized based on the Dienes test and antibiotic susceptibility patterns. It turned out that the MDR strains exhibited kinship more often than the susceptible ones. The strains which were able to form a stronger biofilm had broader antimicrobial resistance profiles. It was also found that the strongest swarming motility correlated with susceptibility to most antibiotics. The correlations described in this work encourage further investigation of the mechanisms of pathogenicity of P. mirabilis.

Significance and roles of synonymous codon usage in the evolutionary process of Proteus

Proteus spp. bacteria frequently serve as opportunistic pathogens that can infect many animals and show positive survival and existence in various natural environments. The evolutionary pattern of Proteus spp. is an unknown topic, which benefits understanding the different evolutionary dynamics for excellent bacterial adaptation to various environments. Here, the eight whole genomes of different Proteus species were analyzed for the interplay between nucleotide usage and synonymous codon usage. Although the orthologous average nucleotide identity and average nucleotide identity display the genetic diversity of these Proteus species at the genome level, the principal component analysis further shows that these species sustain the specific genetic niche at the aspect of synonymous codon usage patterns. Interestingly, although these Proteus species have A/T rich genes with underrepresented G (guanine) or C (cytosine) at the third codon positions and overrepresented A or T at these positions, some synonymous codons with A or T end are obviously suppressed in usage. The overall codon usage pattern reflected by the effective number of codons (ENC) has a significantly positive correlation with GC3 content (GC content at the third codon position), and ENC has a significantly negative correlation with the adaptation index for these species. These results suggest that the mutation pressure caused by nucleotide composition constraint serves as a dominant evolutionary dynamic driving evolutionary trend of Proteus spp., along with other selections related to natural selection, replication and fine-tune translation, and so on. Taken together, the analyses help to understand the evolutionary interplay between nucleotide and codon usage at the gene level of Proteus.

Structural and serological characterization of the O82 antigen of a Proteus mirabilis strain isolated from a patient in Poland

P. mirabilis strains Kro 45 and Kwy 46 were isolated from the pus and the muscular fluid, respectively, of a hospitalized 61-year-old female in Łódź, Poland. Both strains demonstrated a good swarming ability on a solid medium, and the Dienes test for differentiation of swarming strains indicated their identity. The strains were serologically identical and did not belong to any of the known Proteus O1-O81 serogroups. In this work, we studied the O-specific polysaccharide (O antigen) of P. mirabilis Kwy46, which defines the immunospecificity of the strain. The O-polysaccharide was obtained by mild acid degradation of the lipopolysaccharide, and the following structure of its oligosaccharide repeat (O-unit) was established by sugar analysis along with 1D and 2D ¹H and ¹³C NMR spectroscopy: where (S)-lac indicates an (S)-1-carboxyethyl group [an (S)-lactic acid residue], which forms an ether with a GlcNAc residue (so called glycolactilic acid). This structure is unique among Proteus O-polysaccharides but shares a trisaccharide fragment with that of P. mirabilis O5. Studies of the cross-reactivity between P. mirabilis Kwy 46 O antiserum/lipopolysaccharide and Proteus O1-O81 lipopolysaccharides/O antisera allowed identification of a putative Kwy 46 O-antigen epitope. Based on the data obtained, it is proposed to create a new O82 serogroup within the genus Proteus represented by the studied P. mirabilis isolates.

Chemical characterization and serological properties of a unique O-polysaccharide of the Proteus mirabilis Sm 99 clinical strain - Identification of a new, O81, serotype

The current serological classification scheme of the medically important bacteria from the genus Proteus consists of 80 O serogroups, the last four of which (O77-O80) were created from clinical strains from Łódź, Poland. There are more serologically unique strains isolated from patient that do not fit into the existing scheme, such as Proteus mirabilis strain Sm 99 isolated from urine of a 74-year-old woman in Łódź. Serological investigation involving ELISA and Western blotting failed to classify the Proteus mirabilis strain Sm 99 into any of the 80 Proteus O serogroups. Sugar analysis along with two-dimensional NMR spectroscopy showed that the O-polysaccharide is composed of branched pentasaccharide repeating units containing one residue each of d-Glc, d-GlcNAc, d-GalNAc, d-glucuronic acid, and 4-[(R)-3-hydroxybutanoylamino]-4,6-dideoxy-d-glucose. The chemical and serological data show that the O antigen of P. mirabilis Sm 99 is unique among the known Proteus O antigens. Based on this finding, it is proposed to extend the current serological classification scheme of Proteus by adding a new serogroup, O81, which at present consists of P. mirabilis strain Sm 99 only.

Structures and serospecificity of threonine-containing O polysaccharides of two clinical isolates belonging to the genus Proteus and their classification into O11 subserogroups

Two clinical isolates from Polish patients, Proteus mirabilis 9B-m and Proteus genomospecies 3J-r, were found to be serologically related to P mirabilis O11. However, serological studies involving ELISA and Western blotting methods, using lipopolysaccharides (LPSs) extracted from the strains as antigens and native or adsorbed rabbit polyclonal O antisera, specific to the studied strains, revealed slight differences in the cross-reactivity and specificity of the two studied Proteus isolates, when compared to P. mirabilis O11. Two different O polysaccharides containing N-(d-galacturonoyl)-l-threonine were isolated from the LPSs of the isolates. Their structures were determined by chemical analysis and NMR spectroscopy and found to be related to the P. mirabilis O11 antigen structure established earlier, the 9B-m structure differing in the absence of the lateral glucose residue and the 3J-r structure in non-stoichiometric O-acetylation of the threonine residue only. Thus, the Proteus O11 serogroup should be divided into two subgroups: O11a, represented by the 9B-m isolate and O11a, b possessing the additional b epitope, containing the lateral residue of glucose and formed by the 3J-r isolate as well as P. mirabilis 25/57 belonging to O11 serogroup so far. O11a is the sixth new serotype found in Proteus spp. strains recently isolated from patients in central Poland.

Significance and Roles of Proteus spp. Bacteria in Natural Environments

Proteus spp. bacteria were first described in 1885 by Gustav Hauser, who had revealed their feature of intensive swarming growth. Currently, the genus is divided into Proteus mirabilis, Proteus vulgaris, Proteus penneri, Proteus hauseri, and three unnamed genomospecies 4, 5, and 6 and consists of 80 O-antigenic serogroups. The bacteria are known to be human opportunistic pathogens, isolated from urine, wounds, and other clinical sources. It is postulated that intestines are a reservoir of these proteolytic organisms. Many wild and domestic animals may be hosts of Proteus spp. bacteria, which are commonly known to play a role of parasites or commensals. However, interesting examples of their symbiotic relationships with higher organisms have also been described. Proteus spp. bacteria present in soil or water habitats are often regarded as indicators of fecal pollution, posing a threat of poisoning when the contaminated water or seafood is consumed. The health risk may also be connected with drug-resistant strains sourcing from intestines. Positive aspects of the bacteria presence in water and soil are connected with exceptional features displayed by autochthonic Proteus spp. strains detected in these environments. These rods acquire various metabolic abilities allowing their adaptation to different environmental conditions, such as high concentrations of heavy metals or toxic substances, which may be exploited as sources of energy and nutrition by the bacteria. The Proteus spp. abilities to tolerate or utilize polluting compounds as well as promote plant growth provide a possibility of employing these microorganisms in bioremediation and environmental protection.

Classification of a Proteus penneri clinical isolate with a unique O-antigen structure to a new Proteus serogroup, O80

Proteus penneri is an opportunistic pathogen, which may cause severe diseases, most frequently urinary tract infections in immunocompromised patients. P. penneri Br 114 exhibiting a good swarming growth ability as an S-form strain was isolated from a wound of a patient in Łódź, Poland. Serological studies using ELISA and Western blotting and chemical analyses along with (1)H and (13)C NMR spectroscopy showed that the O-antigen (O-polysaccharide) of this strain is unique among the known Proteus serotypes O1-O79. It possesses a linear pentasaccharide repeating unit containing a partially O-acetylated amide of D-glucuronic acid (GlcA) with L-serine having the following structure: [structure: see text]. These data are a basis for creating a new Proteus serogroup, O80, so far represented by the single Br 114 isolate. The O80 is the 21st O-serogroup containing P. penneri strains and the fourth serogroup based on Proteus spp. clinical isolates from Łódź, Poland.

Proteus sp. – an opportunistic bacterial pathogen – classification, swarming growth, clinical significance and virulence factors

The genus Proteus belongs to the Enterobacteriaceae family, where it is placed in the tribe Proteeae, together with the genera Morganella and Providencia. Currently, the genus Proteus consists of five species: P. mirabilis, P. vulgaris, P. penneri, P. hauseri and P. myxofaciens, as well as three unnamed Proteus genomospecies. The most defining characteristic of Proteus bacteria is a swarming phenomenon, a multicellular differentiation process of short rods to elongated swarmer cells. It allows population of bacteria to migrate on solid surface. Proteus bacteria inhabit the environment and are also present in the intestines of humans and animals. These microorganisms under favorable conditions cause a number of infections including urinary tract infections (UTIs), wound infections, meningitis in neonates or infants and rheumatoid arthritis. Therefore, Proteus is known as a bacterial opportunistic pathogen. It causes complicated UTIs with a higher frequency, compared to other uropathogens. Proteus infections are accompanied by a formation of urinary stones, containing struvite and carbonate apatite. The virulence of Proteus rods has been related to several factors including fimbriae, flagella, enzymes (urease - hydrolyzing urea to CO2 and NH3, proteases degrading antibodies, tissue matrix proteins and proteins of the complement system), iron acqusition systems and toxins: hemolysins, Proteus toxin agglutinin (Pta), as well as an endotoxin - lipopolysaccharide (LPS). Proteus rods form biofilm, particularly on the surface of urinary catheters, which can lead to serious consequences for patients. In this review we present factors involved in the regulation of swarming phenomenon, discuss the role of particular pathogenic features of Proteus spp., and characterize biofilm formation by these bacteria.

Structure and serology of O-antigens as the basis for classification of Proteus strains

This review is devoted to structural and serological characteristics of the O-antigens (O-polysaccharides) of the lipopolysaccharides of various Proteus species, which provide the basis for classifying Proteus strains to Oserogroups. The antigenic relationships of Proteus strains within and beyond the genus as well as their O-antigenrelated bioactivities are also discussed.