Proteus cibarius sp. nov., a swarming bacterium from Jeotgal, a traditional Korean fermented seafood, and emended description of the genus Proteus

An Update on Novel Taxa and Revised Taxonomic Status of Bacteria Isolated from Domestic Animals Described in 2018 to 2021

Novel bacterial taxonomy and nomenclature revisions can have significant impacts on clinical practice, disease epidemiology, and veterinary microbiology laboratory operations. Expansion of research on the microbiota of humans, animals, and insects has significant potential impacts on the taxonomy of organisms of clinical interest. Implications of taxonomic changes may be especially important when considering zoonotic diseases. Here, we address novel taxonomy and nomenclature revisions of veterinary significance. Noteworthy discussion centers around descriptions of novel mastitis pathogens in Streptococcaceae, Staphylococcaceae, and Actinomycetaceae; bovine reproductive tract pathogens in Corynebacteriaceae; novel members of Mannheimia spp., Leptospira spp., and Mycobacterium spp.; the transfer of Ochrobactrum spp. to Brucella spp.; and revisions to the genus Mycoplasma.

Detection of tet(X6) variant-producing Proteus terrae subsp. cibarius from animal cecum in Zhejiang, China

OBJECTIVES

The prevalence of tet(X) genes threatens the clinical use of last-line tigecycline. tet(X6) gene has been reported in Proteus strains, but its genetic context is rarely reported. This study aimed to investigate the prevalence and genetic contexts of tet(X6) gene in Proteus spp.

METHODS

A tet(X6) variant-bearing P. terrae subsp. cibarius strain was subjected to susceptibility testing, determination of growth curves, scanning electron microscopy, transmission electron microscopy and whole-genome sequencing (WGS). The genomic contexts of the tet(X6)-positive strain were analyzed by sequence comparison and annotation.

RESULTS

ZJ19PC, a P. terrae subsp. cibarius strain harboring the tet(X6) variant, was isolated from 20 cecum samples collected in Zhejiang, China. The chromosome size of ZJ19PC was 3,952,084 bp and that the GC content was 38.2%, and hugA, sul2, tet(H), floR, dfra1, aadA1, aac(3)-IV, and aph(4)-la were found in addition to the tet(X6) variant. Proteus spp. could be classified into three groups based on the tet(X6) gene contexts. Strain ZJ19PC belongs to Group 1 (sra-sul2-ISCR2-floR-ISCR2-floR-ISCR2- tet(X6)_variant-tnpA-ISEc59-aph(4)-la-aac(3)-Iva-IS26), and this region of Group 1 was inserted between modA and guaA. The common antimicrobial resistance (AMR) genes of the three types of AMR gene islands were sul2, floR, tet(X6) and aac(3). The tet(X6) gene contexts and SNP tree showed that ZJ19PC was homologous to HNCF44W and HNCF43W, which indicated that these strains may be clonally transmitted.

CONCLUSION

This study analyzed the genetic contexts of the tet(X6) gene in Proteus spp., and highlighted the significance of monitoring tigecycline-resistant P. terrae subsp. cibarius.

Genomic and biological characterization of vB_PvuS_Pm34, a novel lytic bacteriophage that infects Proteus vulgaris

Proteus phage vB_PvuS_Pm34 (Pm34) isolated from the sewage, is a novel virus specific to Proteus vulgaris. Pm34 belonged to the family Siphovirodae with an icosahedron capsid head and a non-contractile tail. Its genome was 39,558 bp in length with a G + C content of 41.4%. Similarity analysis showed that Pm34 shared low identities of 27.6%-38.4% with any other Proteus phages, but had the 96% high identity with Proteus mirabilis AOUC-001. In the genome of Pm34, 70 open reading frames was deduced and 32 had putative functions including integrase and host lysis proteins. No tRNAs, antibiotic resistance and virulence genes were detected. Pm 34 presented a broad pH (4-8) and good temperature tolerance (<40 °C). This is the first report of the bacteriophage specific to P. vulgaris, which can enrich the knowledge of bacteriophages of Prouteus bacteria and provide the possibility for the alternative treatment of P. vulgaris infection.

Genome-based phylogeny of the genera Proteus and Cosenzaea and description of Proteus terrae subsp. terrae subsp. nov. and Proteus terrae subsp. cibarius subsp. nov

The genera Proteus and Cosenzaea are closely related members of the family Morganellaceae. The genus Cosenzaea consists of the species Cosenzaea myxofaciens originally separated from the genus Proteus by rpoB gene analysis. Due to the high similarity of the 16S rRNA genes between species of both genera, the taxonomic status is here re-evaluated by a genome-based approach. Based on a core genome phylogeny and genome relatedness indices, it is shown that the taxonomy and nomenclature given for the basonym Proteus myxofaciens is more appropriate. Therefore, we propose to use this name in preference. Furthermore, the species status of Proteus terrae and Proteus cibarius was reassessed. Both species are related at subspecies level by digital DNA-DNA hybridization (dDDH) analysis. Additionally, average amino acid identity (AAI) and average nucleotide identity (ANI) do not support a separate species status, and therefore it is proposed to classify P. cibarius as a subspecies of P. terrae. Consequently, both species are being renamed Proteus terrae subsp. cibarius subsp. nov. and Proteus terrae subsp. terrae subsp. nov., respectively. The genome relatedness indices revealed a close relationship of the Proteus genomospecies 5 with P. terrae subsp. terrae. Thus, it has been assigned to the same subspecies.

Multilocus sequence analysis for the taxonomic updating and identification of the genus Proteus and reclassification of Proteus genospecies 5 O'Hara et al. 2000, Proteus cibarius Hyun et al. 2016 as later heterotypic synonyms of Proteus terrae Behrendt et al. 2015

Background

Members of the genus Proteus are mostly opportunistic pathogens that cause a variety of infections in humans. The molecular evolutionary characteristics and genetic relationships among Proteus species have not been elucidated to date. In this study, we developed a multilocus sequence analysis (MLSA) approach based on five housekeeping genes (HKGs) to delineate phylogenetic relationships of species within the genus Proteus.

Results

Of all 223 Proteus strains collected in the current study, the phylogenetic tree of five concatenated HKGs (dnaJ, mdh, pyrC, recA and rpoD) divided 223 strains into eleven clusters, which were representative of 11 species of Proteus. Meanwhile, the phylogenetic trees of the five individual HKGs also corresponded to that of the concatenated tree, except for recA, which clustered four strains at an independent cluster. The evaluation of inter- and intraspecies distances of HKG concatenation indicated that all interspecies distances were significantly different from intraspecies distances, which revealed that these HKG concatenations can be used as gene markers to distinguish different Proteus species. Further web-based DNA-DNA hybridization estimated by genome of type strains confirmed the validity of the MLSA, and each of eleven clusters was congruent with the most abundant Proteus species. In addition, we used the established MLSA method to identify the randomly collected Proteus and found that P. mirabilis is the most abundant species. However, the second most abundant species is P. terrae but not P. vulgaris. Combined with the genetic, genomic and phenotypic characteristics, these findings indicate that three species, P. terrae, P. cibarius and Proteus genospecies 5, should be regarded as heterotypic synonyms, and the species should be renamed P. terrae, while Proteus genospecies 5 has not been named to date.

Conclusions

This study suggested that MLSA is a powerful method for the discrimination and classification of Proteus at the species level. The MLSA scheme provides a rapid and inexpensive means of identifying Proteus strains. The identification of Proteus species determined by the MLSA approach plays an important role in the clinical diagnosis and treatment of Proteus infection.

Antibiotic Resistance of Gram-Negative Bacteria from Wild Captured Loggerhead Sea Turtles

Sea turtles have been proposed as health indicators of marine habitats and carriers of antibiotic-resistant bacterial strains, for their longevity and migratory lifestyle. Up to now, a few studies evaluated the antibacterial resistant flora of Mediterranean loggerhead sea turtles (Caretta caretta) and most of them were carried out on stranded or recovered animals. In this study, the isolation and the antibiotic resistance profile of 90 Gram negative bacteria from cloacal swabs of 33 Mediterranean wild captured loggerhead sea turtles are described. Among sea turtles found in their foraging sites, 23 were in good health and 10 needed recovery for different health problems (hereafter named weak). Isolated cloacal bacteria belonged mainly to Enterobacteriaceae (59%), Shewanellaceae (31%) and Vibrionaceae families (5%). Although slight differences in the bacterial composition, healthy and weak sea turtles shared antibiotic-resistant strains. In total, 74 strains were endowed with one or multi resistance (up to five different drugs) phenotypes, mainly towards ampicillin (~70%) or sulfamethoxazole/trimethoprim (more than 30%). Hence, our results confirmed the presence of antibiotic-resistant strains also in healthy marine animals and the role of the loggerhead sea turtles in spreading antibiotic-resistant bacteria.

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.

Genomic and functional characterization of fecal sample strains of Proteus cibarius carrying two floR antibiotic resistance genes and a multiresistance plasmid-encoded cfr gene

The objective of this study was to investigate the molecular characteristics and horizontal transfer of florfenicol resistance gene-related sequences in Proteus strains isolated from animals. A total of six Proteus strains isolated from three farms between 2015 and 2016 were screened by polymerase chain reaction (PCR) for known florfenicol resistance genes. Proteus cibarius G11, isolated from the fecal material of a goose, was found to harbor both cfr and floR genes. Whole genome sequencing revealed that the strain harbored two copies of the floR gene: one was located on the chromosome and the other was located on a plasmid named pG11-152. Two floR-containing fragments 4028 bp in length were identical and showed transposon-like structures. The cfr gene was found on a plasmid named pG11-51 and flanked by a pair of IS26s. Thus, mobile genetic elements played an important role in floR replication and horizontal resistance gene transfer. Therefore, increasing attention should be paid to monitoring the spread of resistance genes and resistance in real time.

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.

An Update on the Novel Genera and Species and Revised Taxonomic Status of Bacterial Organisms Described in 2016 and 2017

Recognition and acknowledgment of novel bacterial taxonomy and nomenclature revisions can impact clinical practice, disease epidemiology, and routine clinical microbiology laboratory operations. The Journal of Clinical Microbiology (JCM) herein presents its biannual report summarizing such changes published in the years 2016 and 2017, as published and added by the International Journal of Systematic and Evolutionary Microbiology Noteworthy discussion centers around descriptions of novel Corynebacteriaceae and an anaerobic mycolic acid-producing bacterium in the suborder Corynebacterineae; revisions within the Propionibacterium, Clostridium, Borrelia, and Enterobacter genera; and a major reorganization of the family Enterobacteriaceae. JCM intends to sustain this series of reports as advancements in molecular genetics, whole-genome sequencing, and studies of the human microbiome continue to produce novel taxa and clearer understandings of bacterial relatedness.

Proteus faecis sp. nov., and Proteus cibi sp. nov., two new species isolated from food and clinical samples in China

Eight swarming motile bacteria were isolated from food and clinical samples in China. Cells were Gram-stain-negative, facultatively anaerobic and rod-shaped (0.5-0.8×1.0-3.0 μm) with hairlike pili and flagella. The 16S rRNA and partial rpoB housekeeping gene sequence analyses indicated that the strains belong to the genus Proteusin the family Enterobacteriaceae. Of the eight strains studied, seven and a single isolate formed two separate clades in the phylogeny of Proteusspecies, indicating two separate species. Both the in silico DNA-DNA hybridization and the average nucleotide identity values between these two groups and to the type strains of the genus Proteuswere below the recommended threshold for signifying their candidature as two separate species. The DNA G+C contents of strains TJ1636^T and FJ2001126-3^T were 37.8 and 38.1 mol%, respectively. The major cellular fatty acids of the two novel type strains were C16:0, cyclo C17:0, summed feature 3 and summed feature 8. The results supported that the strains belong to different taxonomic positions in the genus Proteus. The isolates were named Proteus faecis sp. nov., with type strain TJ1636^T (=DSM 106180^T=GDMCC 1.1245^T), and Proteuscibi sp. nov., with type strain FJ2001126-3^T (=DSM 106178^T =GDMCC 1.1244^T).

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.

Proteus spp. as Putative Gastrointestinal Pathogens

Proteus species, members of the Enterobacteriaceae family, are usually considered commensals in the gut and are most commonly recognized clinically as a cause of urinary tract infections. However, the recent identification of Proteus spp. as potential pathogens in Crohn's disease recurrence after intestinal resection serves as a stimulus to examine their potential role as gut pathogens. Proteus species possess many virulence factors potentially relevant to gastrointestinal pathogenicity, including motility; adherence; the production of urease, hemolysins, and IgA proteases; and the ability to acquire antibiotic resistance. Gastrointestinal conditions that have been linked to Proteus include gastroenteritis (spontaneous and foodborne), nosocomial infections, appendicitis, colonization of devices such as nasogastric tubes, and Crohn's disease. The association of Proteus species with Crohn's disease was particularly strong. Proteus species are low-abundance commensals of the human gut that harbor significant pathogenic potential; further investigation is needed.

Proteus alimentorum sp. nov., isolated from pork and lobster in Ma'anshan city, China

Two strains of Gram-stain-negative, facultatively anaerobic short-rod bacteria were recovered from two different food samples in Ma'anshan city, Anhui province, China in 2008. The bacteria were characterized in a polyphasic taxonomic study that included phenotypic, phylogenetic and genotypic methodologies. Phylogenetic analysis of the 16S rRNA gene demonstrated that the two strains belonged to the genus Proteus and were most similar to Proteus vulgaris ATCC 29905^T with a score of 99.7 %. Phylogenetic analysis of the rpoB gene placed the two strains into a cluster with a distinctly interspecies phylogenetic branch that was clearly separated from six type strains of the genus Proteus, with the most closely related species being Proteus mirabilis ATCC 29906^T. In silico genomic comparisons, including in silico DNA-DNA hybridization (isDDH) and average nucleotide identity (ANI) analysis showed that the representative strain, 08MAS0041^T, and all six Proteus species share less than 70 % isDDH and have a 95 % ANI cutoff level, supporting the designation of the two strains as a novel species of the genus Proteus. The predominant cellular fatty acids of strain 08MAS0041^T were C16 : 0 (24.8 %), C16 : 1ω7c/16 : 1ω6c (16.5 %), C18 : 1ω6c/C18 : 1ω7c (14.5 %), C17 : 0 cyclo (12.6 %) and C16 : 1iso I/C14 : 0 3-OH (10.6 %). The analysis of biochemical, phylogenetic and genomic data confirmed that the two strains were clearly different from all recognized species of the genus Proteus and represent a novel Proteus species, for which the name Proteus alimentorum sp. nov. is proposed. The type strain is 08MAS0041^T (=DSM 104685^T=CGMCC 1.15939^T).

Changes in the lipopolysaccharide of Proteus mirabilis 9B-m (O11a) clinical strain in response to planktonic or biofilm type of growth

The impact of planktonic and biofilm lifestyles of the clinical isolate Proteus mirabilis 9B-m on its lipopolysaccharide (O-polysaccharide, core region, and lipid A) was evaluated. Proteus mirabilis bacteria are able to form biofilm and lipopolysaccharide is one of the factors involved in the biofilm formation. Lipopolysaccharide was isolated from planktonic and biofilm cells of the investigated strain and analyzed by SDS–PAGE with silver staining, Western blotting and ELISA, as well as NMR and matrix-assisted laser desorption ionization time-of-flight mass spectrometry techniques. Chemical and NMR spectroscopic analyses revealed that the structure of the O-polysaccharide of P. mirabilis 9B-m strain did not depend on the form of cell growth, but the full-length chains of the O-antigen were reduced when bacteria grew in biofilm. The study also revealed structural modifications of the core region in the lipopolysaccharide of biofilm-associated cells—peaks assigned to compounds absent in cells from the planktonic culture and not previously detected in any of the known Proteus core oligosaccharides. No differences in the lipid A structure were observed. In summary, our study demonstrated for the first time that changes in the lifestyle of P. mirabilis bacteria leads to the modifications of their important virulence factor—lipopolysaccharide.

Proteus columbae sp. nov., isolated from a pigeon in Ma'anshan, China

A Gram-negative, facultatively anaerobic bacillus, strain 08MAS2615^T, was isolated from the flesh of a pigeon specimen collected in Ma'anshan, Anhui province, China. Phylogenetic analysis of 16S rRNA gene sequences confirmed that strain 08MAS2615^T belonged to the genus Proteus, and formed an independent branch which was clearly separated from the other six known species of Proteus. Strain 08MAS2615^T was more closely related to Proteus vulgaris ATCC 29905^T and Proteus penneri NCTC 12737^T than other Proteus species. Similar independent phylogenetic results were obtained using rpoB gene sequence analysis, whereas strain 08MAS2615^T clustered near the species of Proteus cibarius JS9^T and Proteus terrae N5/687^T. Furthermore, the genome-wide core-single nucleotide polymorphism-based phylogenetic tree confirmed that strain 08MAS2615^T formed a monophyletic and robust clade. Based on whole-genome sequences, the range of in silico DNA-DNA hybridization and average nucleotide identity between strain 08MAS2615^T and the six Proteus species were 25.5-48.8 % and 82.8-92.9 %, respectively, less than the proposed cutoff level for species delineation, i.e. 70 and 95 %. In addition, the major cellular fatty acid profile of strain 08MAS2615^T was C14 : 0 (12.4 %), C16 : 0 (23.8 %), C17 : 0cyclo (14.4 %), summed feature 2 (C16 : 1iso I/C14 : 0 3-OH) (11.0 %), summed feature 3 (C16 : 1ω7c/16 : 1ω6c) (18.5 %) and summed feature 8 (C18 : 1ω6c) (18.6 %). On the basis of these results, strain 08MAS2615^T represents a novel species of the genus Proteus, for which the name Proteuscolumbae sp. nov. is proposed with strain 08MAS2615^T (=DSM 104686^T=CGMCC 1.15982^T) designated as the species type strain.

Genetic diversity of the O antigens of Proteus species and the development of a suspension array for molecular serotyping

Proteus species are well-known opportunistic pathogens frequently associated with skin wound and urinary tract infections in humans and animals. O antigen diversity is important for bacteria to adapt to different hosts and environments, and has been used to identify serotypes of Proteus isolates. At present, 80 Proteus O-serotypes have been reported. Although the O antigen structures of most Proteus serotypes have been identified, the genetic features of these O antigens have not been well characterized. The O antigen gene clusters of Proteus species are located between the cpxA and secB genes. In this study, we identified 55 O antigen gene clusters of different Proteus serotypes. All clusters contain both the wzx and wzy genes and exhibit a high degree of heterogeneity. Potential functions of O antigen-related genes were proposed based on their similarity to genes in available databases. The O antigen gene clusters and structures were compared, and a number of glycosyltransferases were assigned to glycosidic linkages. In addition, an O serotype-specific suspension array was developed for detecting 31 Proteus serotypes frequently isolated from clinical specimens. To our knowledge, this is the first comprehensive report to describe the genetic features of Proteus O antigens and to develop a molecular technique to identify different Proteus serotypes.