Stenotrophomonas Species Research Articles

Features Associated With the Presence of Specific Bacterial Strains in Pediatric Tracheostomy.

Tracheostomy bypasses physical barriers that decrease microbial access to the lower airway, which can lead to changes to the lung microbiota. Patients often become chronically colonized with potential pathogens. This study described the incidence and prevalence of specific organisms in a 5-y cohort of children with tracheostomy. This retrospective cohort of children aged 0-18 y with tracheostomy identified associations between microbial species and subject characteristics including reason for tracheostomy, gastrostomy tube (G-tube), fundoplication, and ventilator use using chi-square test or Fisher exact test. Of 113 eligible patients, 79 (57% male) met study inclusion criteria. Reasons for tracheostomy included airway obstruction secondary to craniofacial anomalies in 16 children (20%), upper-airway obstruction in 14 subjects (17.3%), neuromuscular disorder in 19 subjects (24%), bronchopulmonary dysplasia with or without pulmonary hypertension in 17 subjects (21%), and congenital heart disease in 13 subjects (16%). Most (69%) used a ventilator for at least 6 h/d; 63% had a G-tube; 41% also had a Nissen fundoplication. Of the 20% with upper-airway obstruction, one third were ventilator dependent, unlike other diagnoses where 57% used a ventilator. Staphylococcus aureus (52/113), Pseudomonas aeruginosa (43/113), and Stenotrophomonas species (39/113) were the most frequently identified bacterial species. Most microbes identified were not associated with subjects underlying diagnoses, ventilator use, or feeding type. However, there was a significant association between upper-airway obstruction and group B Streptococcus species and G-tube with P. aeruginosa. This retrospective single-site descriptive cohort analysis of pediatric subjects with long-term tracheostomy identified trends in microbial prevalence. The presence of specific bacterial strains was more likely to follow individual subject trajectories than sequential appearance of species. P. aeruginosa was associated with G-tube and Streptococcus species with upper-airway obstruction. Ventilator dependence was not associated with specific microbial profiles.

Identification of Indigenous Bacterial Strains from Thai Agricultural Fields for Potential Bioremediation of Carbofuran

This study explored the bioremediation potential of indigenous soil bacteria for carbofuran-contaminated agricultural areas. Twenty soil samples from regions with a history of pesticide use in Pathum Thani and Nakhon Pathom provinces, Thailand, were collected. Five bacterial strains capable of degrading carbofuran were isolated and subjected to cell morphology and biochemical analyses. Phylogenetic analysis of the 16S rRNA gene sequences identified these strains as related to Pseudomonas and Stenotrophomonas species. High-Performance Liquid Chromatography (HPLC) analysis confirmed the complete degradation of carbofuran within 3 days, reducing its concentration from 0.05 mg/mL to below detectable limits. These bacteria could use carbofuran as their sole carbon source, demonstrating their potential for bioremediation of contaminated soils. Given their resilience and ability to thrive in natural environmental conditions, these indigenous strains are well-suited for in-situ degradation of pollutants. The findings indicate that these isolated soil bacteria present a promising method for reducing the environmental risks associated with carbofuran contamination.

Unveiling Agricultural Biotechnological Prospects: The Draft Genome Sequence of Stenotrophomonas geniculata LGMB417.

Stenotrophomonas species are recognized as rhizobacteria that play a pivotal role in promoting plant growth by making substantial contributions to enhanced soil fertility, nutrient recycling, and phytopathogen control. Employing them as bioinputs constitutes an environmentally sound strategy, particularly within the rhizospheric community. This study revealed the draft genome sequence of Stenotrophomonas geniculata LGMB417, which was originally isolated from root samples of maize (Zea mays L.). This research assessed the potential of a bacterial strain at the molecular level through genome mining, aiming to identify genes with biotechnological significance for promoting plant growth and protection. The assembly findings indicate that strain LGMB417 possesses a genome size of 4,654,011bp, with a G + C content of 66.50%. The draft genome sequence revealed the presence of gene clusters responsible for the synthesis of secondary metabolites and carbohydrate active enzymes (CAZymes), glycoside hydrolases (23), glycosyltransferases (18), carbohydrate esterases (5), polysaccharide lyases (2), carbohydrate-binding modules (2), and auxiliary activities (1). Several genes related to growth promotion were found in the genome, including those associated with phosphate transport and solubilization, nitrogen metabolism, siderophore production and iron transport, hormonal modulation, stress responses (such as to drought, temperature fluctuations, osmotic challenges, and oxidative conditions), and volatile organic compounds (VOCs). Subsequent phases will encompass investigations utilizing gene expression methodologies, with future explorations concentrating on facets pertinent to agricultural production, including comprehensive field studies.

A novel pathogenic species of genus Stenotrophomonas: Stenotrophomonas pigmentata sp. nov.

Stenotrophomonas is a prominent genus owing to its dual nature. Species of this genus have many applications in industry and agriculture as plant growth-promoting rhizobacteria and microbial biological control agents, whereas species such as Stenotrophomonas maltophilia are considered one of the leading gram-negative multi-drug-resistant bacterial pathogens because of their high contribution to the increase in crude mortality and significant clinical challenge. Pathogenic Stenotrophomonas species and most clinical isolates belong to the Stenotrophomonas maltophilia complex (SMc). However, a strain highly homologous to S. terrae was isolated from a patient with pulmonary tuberculosis (TB), which aroused our interest, as S. terrae belongs to a relatively distant clade from SMc and there have been no human association reports. The pathogenicity, immunological and biochemical characteristics of 610A2T were systematically evaluated. 610A2T is a new species of genus Stenotrophomonas, which is named as Stenotrophomonas pigmentata sp. nov. for its obvious brown water-soluble pigment. 610A2T is pathogenic and caused significant weight loss, pulmonary congestion, and blood transmission in mice because it has multiple virulence factors, haemolysis, and strong biofilm formation abilities. In addition, the cytokine response induced by this strain was similar to that observed in patients with TB, and the strain was resistant to half of the anti-TB drugs. The pathogenicity of 610A2T may not be weaker than that of S. maltophilia. Its isolation extended the opportunistic pathogenic species to all 3 major clades of the genus Stenotrophomonas, indicating that the clinical importance of species of Stenotrophomonas other than S. maltophilia and potential risks to biological safety associated with the use of Stenotrophomonas require more attention.

Relationships among bacterial cell size, diversity, and taxonomy in rumen.

The rumen microbial community plays a crucial role in the digestion and metabolic processes of ruminants. Although sequencing-based studies have helped reveal the diversity and functions of bacteria in the rumen, their physiological and biochemical characteristics, as well as their dynamic regulation along the digestion process in the rumen, remain poorly understood. Addressing these gaps requires pure culture studies to demystify the intricate mechanisms at play. Bacteria exhibit morphological differentiation associated with different species. Based on the difference in size or shape of microorganisms, size fractionation by filters with various pore sizes can be used to separate them. In this study, we used polyvinylidene difluoride filters with pore sizes of 300, 120, 80, 40, 20, 8, 6, 2.1, and 0.6 μm. Bacterial suspensions were successively passed through these filters for the analysis of microbial population distribution using 16S rRNA gene sequences. We found that bacteria from the different pore sizes were clustered into four branches (> 120 μm, 40-120 μm, 6-20 μm, 20-40 μm, and < 0.6 μm), indicating that size fractionation had effects on enriching specific groups but could not effectively separate dominant groups by cell size alone. The species of unclassified Flavobacterium, unclassified Chryseobacterium, unclassified Delftia, Methylotenera mobilis, unclassified Caulobacteraceae, unclassified Oligella, unclassified Sphingomonas, unclassified Stenotrophomonas, unclassified Shuttleworthia, unclassified Sutterella, unclassified Alphaproteobacteria, and unclassified SR1 can be efficiently enriched or separated by size fractionation. In this study, we investigated the diversity of sorted bacteria populations in the rumen for preliminary investigations of the relationship between the size and classification of rumen bacteria that have the potential to improve our ability to isolate and culture bacteria from the rumen in the future.

Stenotrophomonas riyadhensis sp. nov., isolated from a hospital floor swab.

During the analysis of a collection of Pseudomonas strains linked to an outbreak in an intensive care unit at King Faisal Specialist Hospital and Research Center in 2019, one isolate (CFS3442T) was identified phenotypically as Pseudomonas aeruginosa. However, whole-genome sequencing revealed its true identity as a member of the genus Stenotrophomonas, distinct from both P. aeruginosa and Stenotrophomonas maltophilia. The isolate demonstrated: (i) a significant phylogenetic distance from P. aeruginosa; (ii) considerable genomic differences from several S. maltophilia reference strains and other Stenotrophomonas species; and (iii) unique phenotypic characteristics. Based on the combined geno- and phenotypic data, we propose that this isolate represents a novel species within the genus Stenotrophomonas, for which the name Stenotrophomonas riyadhensis sp. nov. is proposed. The type strain is CFS3442T (=NCTC 14921T=LMG 33162T).

Optimization of cultural parameters for lipase production by indigenous stenotrophomonas sp. And pseudomonas aeruginosa isolated from lipid-rich environments

The present study aims to identify prospective lipase-producing bacteria and optimize different culture parameters to produce maximum lipase. A total of 37 lipase-positive bacteria were isolated from lipid-rich environments. Among them, strains S1N-2 and S10P-1 were found to have potential and were molecularly identified as Stenotrophomonas species ICMM10 and Pseudomonas aeruginosa BA7823, respectively. For maximum lipase production, the optimum pH was 7 and the temperature was 37ºC. Using these conditions, the isolates were grown on media with additional carbon and nitrogen sources along with different inoculum concentrations. The maximum amount of lipase produced by Stenotrophomonas sp. ICMM10 was 136.47 ± 1.63 U/ml, which is 5-fold higher than before. Pseudomonas aeruginosa BA7823 produced a maximum lipase of 96.33 ± 0.21 U/ml, which was about 9-fold higher than before. These results would provide useful information about lipase production by indigenous isolates, which may be employed as a potential bacterial lipase source of biotechnological interest. Bangladesh J. Bot. 52(4): 979-988, 2023 (December)

Characteristics of Stenotrophomonas rhizophila Lipopolysaccharide, a Representative of Antarctica

Characteristics of Stenotrophomonas rhizophila Lipopolysaccharide, a Representative of Antarctica

Respiratory infectious burden in a cohort of antibody deficiency patients treated with immunoglobulin replacement therapy: The impact of lung pathology and gastroesophageal reflux disease.

Antibody deficiencies result from reduced immunoglobulin levels and function, increasing susceptibility to, primarily, bacterial infection. Primary antibody deficiencies comprise intrinsic defects in B-cell physiology, often due to inherited errors. Hematological malignancies or B-cell suppressive therapy are major causes of secondary antibody deficiency. Although immunoglobulin replacement therapy (IGRT) reduces infectious burden in antibody deficiency patients, respiratory tract infections remain a significant health burden. We hypothesize that lung pathology and gastroesophageal reflux disease (GORD) increase the risk of pneumonia in antibody deficiency patients, as in the general population. For our cohort of patients with primary antibody deficiency and secondary antibody deficiency, we reviewed their respiratory infectious burden and the impact of lung pathologies and GORD. The medical records of 231 patients on IGRT at a tertiary referral center, from October 26, 2014, to February 19, 2021, were reviewed to determine microbial isolates from sputum samples and prevalence of common lung pathologies and GORD. Haemophilus and Pseudomonas species represent a large infectious burden, being identified in 30.2% and 21.4% of sputum samples demonstrating growth, respectively; filamentous fungal and mycobacterial infections were rare. Diagnosed lung pathology increased the proportion of patients with Pseudomonas, Klebsiella, Stenotrophomonas, and Candida species isolated in their sputum, and diagnosed GORD increased the proportion with Enterobacter and Candida species isolated. Bacterial respiratory infectious burden remains in primary antibody deficiency and secondary antibody deficiency despite IGRT. Lung pathologies encourage growth of species less susceptible to IGRT, so specialist respiratory medicine input and additional treatments such as inhaled antibiotics are indicated to optimize respiratory outcomes.

Evaluation of phenotypical and genotypical methods for the identification and typing of Stenotrophomonas maltophilia isolated from a pharmaceutical facility.

Evaluate methods for identification and typing of Stenotrophomonas maltophilia isolated from a pharmaceutical facility. From 270 S. maltophilia strains identified by VITEK®2, 40 were selected and submitted to MALDI TOF-MS, 16S and 23S rRNA gene analysis, ERIC-PCR, and antimicrobial susceptibility profile. 16S rRNA sequencing was able to identify 39 (97.5%) strains as Stenotrophomonas spp. and one (2.5%) as Luteimonas huabeiensis. MALDI TOF-MS identified 37 (92.5%) strains as S. maltophilia, and three (7.5%) were not identified. PCR targeting 23S rRNA yielded a positive result for 39 (97.5%) strains. However, after sequencing, two strains were identified as Stenotrophomonas rhizophila, showing false-positive results. The confirmed S. maltophilia strains (n=37) showed 35 distinct ERIC-PCR profiles and exhibited sensitivity to minocycline and levofloxacin, and six (16.3%) showed intermediate resistance to sulfamethoxazole-trimethoprim. MALDI-TOF MS was a satisfactory methodology for the identification of S. maltophilia, but expansion of the database is necessary for the identification of other species. 16S rDNA sequencing showed low resolution for Stenotrophomonas species differentiation. PCR targeting 23S rRNA could not differentiate S. maltophilia from S. rhizophila. ERIC-PCR was shown to be a useful tool for the microbial source tracking of S. maltophilia.

Diversity of blaL1-like genes in Stenotrophomonas species: insights from genome analysis of publicly available genome sequences.

L1 metallo-β-lactamases produced by Stenotrophomonas maltophilia exhibit high diversity. Here, we characterized the genomes of Stenotrophomonas species harboring blaL1-like genes using publicly available genome sequences. Our findings provide evidence that Stenotrophomonas species with blaL1-like genes constitute a complex comprising many species with high genetic diversity, and similarities between blaL1-like genes are lower than those of the genome. This suggests that the diversity of blaL1-like is attributable to species diversity in Stenotrophomonas species harboring blaL1-like and the rapid evolutionary changes in blaL1-like genes.

Reduction of hexavalent chromium using sulphonated polyether ether ketone as proton exchange membrane in microbial fuel cells

AbstractHexavalent chromium (Cr(VI)) is a major source of environmental pollutants from tannery effluents. Reduction of hexavalent chromium was performed in a 500 mL working volume dual chamber microbial fuel cell (MFC). Synthetic wastewater containing Cr(VI) was used as anolyte and substrate for mixed microbial consortia to release electrons. The ions produced were transferred to cathodic chamber via a Proton Exchange Membrane (PEM). In this study, sulphonated polyether ether ketone (SPEEK) was used as PEM and compared with Nafion 117 for Cr(VI) reduction. The microbial consortia that aided the treatment were isolated and identified to belong to Enterobacter, Acinetobacter, Stenotrophomonas and Pseudomonas species. The Cr(VI) reduction observed were 14.4% and 51% for MFCs with Nafion 117 and SPEEK as PEM, respectively. The wastewater analysis also showed improved percentage removal for SPEEK than for Nafion 117. The cost analysis shows that Nafion was 2 times higher than SPEEK to be used as PEM. This study highlights that SPEEK as PEM in MFC will be an efficient method for reduction of Cr(VI) from tannery effluents.

Monitoring the degradation of total petroleum hydrocarbon in hydrocarbon impacted site using a consortium of hydrocarbon utilizing bacteria

Bacteria (Hydrocarbon utilizing Bacteria) are ever present in natural history, and they make use of these blends as the origin of carbon and energy, however bacteria with such potential are frequently utilized for bioremediation of fossil fuel polluted earth, and have develop corrective measures against petroleum contaminants, by improving the bonding capacity of their cells changing their exterior mechanism and secreting surface active biomolecule materials to augment contact to objective hydrocarbon substrates. The essence of the study is to examine the degradation of total petroleum hydrocarbon in fossil oil polluted soil matrix using consortium of bacteria in three concentrations. (10%, 1.0% 0.1%. for 16 weeks). Consortium of bacteria used is Bacillus thuringiensis, Bacillus velezensis and Stenotrophomonas species. However result from the Gas chromatography flame induction detector (GC-FID) analysis showed the extent of degradation 10% (948.46±0.07 mg/kg and 2.97±0.01 mg/kg), 1.0% (110.07±0.10 mg/kg and 21.95±0.08 mg/kg) and 0.1% (99.99±0.01 mg/kg and 13.88±0.04), at the initial and final stage of exposure respectively. The study specifies that, augmenting biodegradation prospective via the application of bacterial consortia with several catabolic genes, is practical and possible approach for facilitating the elimination competence of petroleum hydrocarbons from contaminated environments.

Characterization of three Stenotrophomonas strains isolated from different ecosystems and proposal of Stenotrophomonas mori sp. nov. and Stenotrophomonas lacuserhaii sp. nov.

Members of the genus Stenotrophomonas, and particularly Stenotrophomonas maltophilia, are opportunistic human pathogens, but not enough research has evaluated the identification of environmental Stenotrophomonas spp. However, most Stenotrophomonas spp. serves as plant-probiotic bacteria.In this study, we obtained and characterized three Stenotrophomonas strains from different ecosystems. Based on phenotypic differences, chemotaxonomic properties, ANI and dDDH identity values, and phylogenetic analyses, two novel Stenotrophomonas species are proposed for the strains identified here. The encoding genes related to plant-growth promotion in the genomes of the newly recovered Stenotrophomonas spp. were retrieved. Follow-on experiments confirmed that these strains produced the important plant hormone IAA. Thus, these Stenotrophomonas spp. could considerably contribute to shaping and maintaining ecological stability in plant-associated environments, particularly while acting as plant-probiotic microorganisms.

Assessment of bioremediation potential of petroleum-contaminated soils from the shanbei oilfield of China revealed by qPCR and high throughput sequencing

With the crude oil exploration activities in the Shanbei oilfield of China, the risk of soil contamination with crude oil spills has become a major concern. This study aimed at assessing the bioremediation potential of the petroleum polluted soils by investigating the expression of key functional genes decoding alkane and aromatic component degradation using an array of primers and real-time quantitative PCR (qPCR), and the functional microbiomes were determined using a combination of substrate-induced metabolic responses and high throughput sequencing. The results showed that the species that were more inclined to degrade aliphatic fraction of crude oil included Acinetobacter, Stenotrophomonas, Neorhizobium and Olivebacter. And Pseudomonas genus was a highly specific keystone species with the potential to degrade PAH fraction. Both aliphatic and PAH-degrading genes were upregulated when the soil petroleum contents were less than 10,000 mg/kg but downregulated when the oil contents were over 10,000 mg/kg. Bioremediation potential could be feasible for medium pollution with petroleum contents of less than 10,000 mg/kg. Optimization of the niche of Acinetobacter, Stenotrophomonas, Pseudomonas, Neorhizobium and Olivebacter species was beneficial to the biodegradation of refractory hydrocarbon components in the Shanbei plateau oilfield.

Zoo animal manure as an overlooked reservoir of antibiotic resistance genes and multidrug-resistant bacteria.

Animal fecal samples collected in the summer and winter from 11 herbivorous animals, including sable antelope (SA), long-tailed goral (LTG), and common eland (CE), at a public zoo were examined for the presence of antibiotic resistance genes (ARGs). Seven antibiotics, including meropenem and azithromycin, were used to isolate culturable multidrug-resistant (MDR) strains. The manures from three animals (SA, LTG, and CE) contained 104-fold higher culturable MDR bacteria, including Chryseobacterium, Sphingobacterium, and Stenotrophomonas species, while fewer MDR bacteria were isolated from manure from water buffalo, rhinoceros, and elephant against all tested antibiotics. Three MDR bacteria-rich samples along with composite samples were further analyzed using nanopore-based technology. ARGs including lnu(C), tet(Q), and mef(A) were common and often associated with transposons in all tested samples, suggesting that transposons carrying ARGs may play an important role for the dissemination of ARGs in our tested animals. Although several copies of ARGs such as aph(3')-IIc, blaL1, blaIND-3, and tet(42) were found in the sequenced genomes of the nine MDR bacteria, the numbers and types of ARGs appeared to be less than expected in zoo animal manure, suggesting that MDR bacteria in the gut of the tested animals had intrinsic resistant phenotypes in the absence of ARGs.

Characterization of Stenotrophomonas maltophilia phage AXL1 as a member of the genus Pamexvirus encoding resistance to trimethoprim–sulfamethoxazole

Stenotrophomonas maltophilia is a ubiquitous environmental bacterium capable of causing disease in humans. Antibiotics are largely ineffective against this pathogen due to numerous chromosomally encoded antibiotic resistance mechanisms. An alternative treatment option is phage therapy, the use of bacteriophages to selectively kill target bacteria that are causing infection. To this aim, we isolated the Siphoviridae bacteriophage AXL1 (vB_SmaS-AXL_1) from soil and herein describe its characterization. Host range analysis on a panel of 30 clinical S. maltophilia strains reveals a moderate tropism that includes cross-species infection of Xanthomonas, with AXL1 using the type IV pilus as its host surface receptor for infection. Complete genome sequencing and analysis revealed a 63,962 bp genome encoding 83 putative proteins. Comparative genomics place AXL1 in the genus Pamexvirus, along with seven other phages that infect one of Stenotrophomonas, Pseudomonas or Xanthomonas species. Functional genomic analyses identified an AXL1-encoded dihydrofolate reductase enzyme that provides additional resistance to the antibiotic combination trimethoprim–sulfamethoxazole, the current recommended treatment option for S. maltophilia infections. This research characterizes the sixth type IV pilus-binding phage of S. maltophilia and is an example of phage-encoded antibiotic resistance.

Taxonomic position, antibiotic resistance and virulence factor production by Stenotrophomonas isolates from patients with cystic fibrosis and other chronic respiratory infections

BackgroundThe potential pathogenic role of Stenotrophomonas maltophilia in lung disease and in particular in cystic fibrosis is unclear. To develop further understanding of the biology of this taxa, the taxonomic position, antibiotic resistance and virulence factors of S. maltophilia isolates from patients with chronic lung disease were studied.ResultsA total of 111 isolates recovered between 2003 and 2016 from respiratory samples from patients in five different countries were included. Based on a cut-off of 95%, analysis of average nucleotide identity by BLAST (ANIb) showed that the 111 isolates identified as S. maltophilia by Matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF/MS) belonged to S. maltophilia (n = 65), S. pavanii (n = 6) and 13 putative novel species (n = 40), which each included 1–5 isolates; these groupings coincided with the results of the 16S rDNA analysis, and the L1 and L2 ß-lactamase Neighbor-Joining phylogeny. Chromosomally encoded aminoglycoside resistance was identified in all S. maltophilia and S. pavani isolates, while acquired antibiotic resistance genes were present in only a few isolates. Nevertheless, phenotypic resistance levels against commonly used antibiotics, determined by standard broth microbroth dilution, were high. Although putative virulence genes were present in all isolates, the percentage of positive isolates varied. The Xps II secretion system responsible for the secretion of the StmPr1–3 proteases was mainly limited to isolates identified as S. maltophilia based on ANIb, but no correlation with phenotypic expression of protease activity was found. The RPF two-component quorum sensing system involved in virulence and antibiotic resistance expression has two main variants with one variant lacking 190 amino acids in the sensing region.ConclusionsThe putative novel Stenotrophomonas species recovered from patient samples and identified by MALDI-TOF/MS as S. maltophilia, differed from S. maltophilia in resistance and virulence genes, and therefore possibly in pathogenicity. Revision of the Stenotrophomonas taxonomy is needed in order to reliably identify strains within the genus and elucidate the role of the different species in disease.

First report of Stenotrophomonas maltophilia causing root soft rot of Sanqi (Panax notoginseng) in China.

Sanqi (Panax notoginseng (Burk.) F. H. Chen) is a traditional Chinese medicinal plant with a long planting cycle of 2-3 years that makes it vulnerable to root diseases caused by several pathogens, including Fusarium solani, Alternaria panax, Phytophthoracactorum, and Pseudomonas sp. In April 2019, root soft rot samples of Sanqi were collected from a plantation site in Songming, southwest of China. Typical symptoms included root softening and necrosis, yellow leaf, and stem wilting. Ten diseased roots samples were collected and sterilized with 0.1% HgCl2 for 1 min, 75% ethanol for 2min, and then rinsed thrice with sterile water. Sterilized roots were cut into small pieces of 5 × 5 mm and cultured on the nutrient agar (NA) medium for 48 h at 28°C. From the root cultures, a total of thirteen bacterial strains were obtained. Three strains, SM 2-5, SM 2-13, and SM 2-14 were selected for further study. These three strains were gram-negative, short rod-shaped (1～2×0.5～1μm), non-spore-forming and had polar tufted flagella as observed under a transmission electron microscope (TEM). Also, the strains were positive for oxidase, beta-galactosidase, arginine dihydrolase, and lysine decarboxylase while negative for amylase and urease tested by biochemical methods (Wang 2017). To further determine the pathogenic species, genomic DNA of these three strains was extracted using a Genomic DNA Kit (Tsing Ke, Beijing, China), to PCR amplify 16S rDNA using universal primers 27F/1492R (Wang et al. 2017). Also, S. maltophilia 23S rDNA specific primers SM1/SM4 (Whitby et al. 2000) were used for PCR amplification to confirm the species. 16S rDNA sequence analysis showed that SM 2-5 (GenBank Accession No. MW555227), SM 2-13 (GenBank Accession No. MW555228), and SM 2-14 (GenBank Accession No. MW555229) shared the highest identity (>99.9%) with the S. maltophilia strains (GenBank Accession No. MT323142, MH669295, MN826555). Furthermore, 23S rDNA sequence analysis of SM 2-5 (GenBank Accession No. MZ707732), SM 2-13 (GenBank Accession No. MZ645941) and SM 2-14 (GenBank Accession No. MZ707733) revealed their high identity (>99.8%) with the S. maltophilia species. 16S and 23S rDNA phylogenetic analysis (Mega6.06) using the neighbor-joining (NJ) method with 1,000 bootstrap replicates revealed the three strains clustering with the other S. maltophilia strains. Therefore, based on morphology, metabolic profile, and sequence analysis, the three strains were identified as Stenotrophomonas maltophilia. To test pathogenicity, the strains were grown in the nutrient broth (NB) medium for 48h at 28°C until bacterial suspension reached to OD600≈1.0 (2.0×109CFU/mL). Then, healthy roots of one-year-old Sanqi plants, pre-washed with sterilized water and -poked with a sterilized needle, were soaked in bacterial suspension (2.0×109CFU/mL) of the three strains separately for inoculation 10min. Sterilized water treatment was used as a control. Subsequently, bacteria-inoculated plants were planted in sterile soil pots and cultured in a greenhouse at 28°C with shading rate of 70%. Each treatment group included 3 plants with 3 replicates. Ten days post inoculation, symptoms similar to the ones in natural conditions were observed in the bacteria-inoculated plants. Based on the disease index (Li et al. 2020), we found that among the three strains, SM 2-13 displayed the highest virulence, while no symptoms were observed in the control plants. The same bacterial strains were re-isolated from these inoculated roots and identified by the methods described above. Previous studies showed that some Stenotrophomonas species cause plant diseases such as rice white stripe (Singh et al. 2001), strawberry leaf black spot (Wang et al. 2017), Cyclobalanopsis patelliformis leaf spot (Bian et al. 2020), and Jatropha curcas L. seed borne and stem necrosis (Wang et al. 2018). To our knowledge, this is the first report confirming Stenotrophomonas maltophilia causing root soft rot of Panax notoginseng in China.

Incidence of Stenotrophomonas Species in Milk and Some Dairy Products in Beni-Suef Province, Egypt

Incidence of Stenotrophomonas Species in Milk and Some Dairy Products in Beni-Suef Province, Egypt