Incidence of antibiotic-resistant Klebsiella pneumoniae and Enterobacter species in freshwater wetlands

Rhizospheric Phosphate Solubilizing Bacillus atrophaeus GQJK17 S8 Increases Quinoa Seedling, Withstands Heavy Metals, and Mitigates Salt Stress

Introduction of quinoa (Chenopodium quinoa willd.), a gluten-free nutritious pseudo-cereal, outside its traditional growing areas exposed it to seedling damping-off. Here, we isolated eleven phosphate-solubilizing bacteria from the quinoa rhizosphere and assessed their effect on germination and seedlings growth. All isolates solubilized phosphate, produced indole3-acetic acid, hydrocyanic acid, siderophores, and ammonia. Genotypic analysis revealed that our strains are related to the genus of Bacillus, Pseudomonas, and Enterobacter. Strains Enterobacter asburiae (QD14, QE4, QE6, and QE16), Enterobacter sp. QE3, and Enterobacter hormaechei QE7 withstood 1.5 mg·L−1 of cadmium sulfate, 0.5 mg·mL−1 of nickel nitrate, and 1 mg·mL−1 of copper sulfate. Moreover, all strains solubilized zinc from ZnO; P. Stutzeri QD1 and E. asburiae QD14 did not solubilize Zn3(PO4)2 and CO3Zn, whereas CO3Zn was not solubilized by E. asburiae QE16. Bacillus atrophaeus S8 tolerated 11% NaCl. P. frederiksbergensis S6 and Pseudomonas sp. S7 induced biofilm formation. Anti-fusarium activity was demonstrated for E.asburiae QE16, P. stutzeri QD1, P. frederiksbergensis S6, Pseudomonas sp. S7, and B. atrophaeus S8. Lastly, inoculation of quinoa seeds with B. atrophaeus S8 and E. asburiae QB1 induced the best germination rate and seedling growth, suggesting their potential use as inoculants for salty and heavy metal or zinc contaminated soils.

Isolation and characterization of novel plant growth promoting Micrococcus sp NII-0909 and its interaction with cowpea

A phosphate-solubilizing bacterial strain NII-0909 isolated from the Western ghat forest soil in India was identified as Micrococcus sp on the basis of phenotypic characteristics, carbon source utilization pattern, fatty acid methyl esters analysis, and 16S rRNA gene sequence. The strain exhibited the plant growth-promoting attributes of phosphate solubilization, auxin production, 1-aminocyclopropane-1-carboxylate deaminase activity, and siderophore production. It was able to solubilize (122.4μg of Ca(3)PO(4) ml(-1)), and produce IAA (109μgml(-1)) at 30°C. P-solubilizing activity of the strain NII-0909 was associated with the release of organic acids and a drop in the pH of the NBRIP medium. HPLC analysis detected two organic acids in the course of P-solubilization. A significant increase in the growth of cow pea was recorded for inoculations under controlled conditions. Scanning electron microscopic study revealed the root colonization of strain on cow pea seedlings. These results demonstrate that isolates NII-0909 has the promising PGPR attributes to be develop as a biofertilizer to enhance soil fertility and promote the plant growth.

Changes in the subgingival microbiota and periodontal parameters before and 3 months after bracket placement

INTRODUCTION

Dental plaque is organized in a biofilm complex that provides protection and nutrients for periodontopathic bacteria. Several factors can affect microbial colonization, including restorations and orthodontic brackets. The aim of this study was to investigate changes in subgingival microbiota and clinical parameters before and after bracket placement.

METHODS

Clinical parameters and subgingival microbial samples were collected from 30 patients before and after bracket placement. Thirty additional patients with no orthodontic treatment served as controls. Samples were cultured and analyzed for periodontopathic and superinfecting bacteria. A descriptive analysis was conducted, and chi-square, Student t, Wilcoxon matched, and Mann Whitney rank sum tests were used to test for differences between groups (P < or=.05).

RESULTS

No changes in probing depth or clinical attachment level were observed, but scores for bleeding on probing, plaque index, and gingival index increased after bracket placement (P < or =.05). Porphyromonas gingivalis, Prevotella intermedia/Prevotella nigrescens, Tannerella forsythia, and Fusobacterium species were elevated in the experimental group after bracket placement compared with the control group (P < or =.01). Superinfecting microorganisms such as Enterobacter cloacae, Klebsiella oxytoca, Klebsiella pneumoniae, and Serratia marcescens were also found.

CONCLUSIONS

Bracket placement influences the accumulation of plaque and the colonization of important periodontopathic and superinfecting bacteria, resulting in more inflammation and bleeding. Special attention should be paid to oral hygiene methods in orthodontic patients.

Incidence of antibiotic-resistant Klebsiella pneumoniae and Enterobacter species in freshwater wetlands

AIMS

The aim of this study was to assess the incidence of Enterobacteriaceae (potential human and animal pathogens) in wetlands.

METHODS

Enterobacteriaceae, selected from the sediments and rhizosphere of wetland plant Juncus effusus L., were analysed using classical microbiological methods, API20E, API20NE, fatty acid analyses, and 16S rRNA sequencing. Assessed virulence factors include antibiotic resistance, presence of plasmids and capsules.

RESULTS

Klebsiella pneumoniae, Enterobacter cloacae and Enterobacter asburiae, known human pathogens, were identified. K. pneumoniae 16S rRNA gene sequence showed the significant hit (E < 0.001) with the unculturable bacteria obtained from faeces of elderly individuals (accession number AB099804) when Genbank database was used. Ent. asburiae 16S rRNA gene sequence showed the significant hit with (E < 0.001) with the unculturable bacteria obtained from the pig gastrointestinal tract (accession number AF371852). The rate of antibiotic resistance (<50 microg ml(-1)) was high for ampicillin and cephalosporins for the most strains (75.7%) yet low (>10 to 20 microg ml(-1)) for kanamycin, tetracycline and chloramphenicol for all strains tested. Capsules were detected in all investigated strains. PCR detected membrane protein but not chromosomally encoded beta-lactamase.

SIGNIFICANCE AND IMPACT OF THE STUDY

The antibiotic resistance of tested strains and presence of capsules (protect micro-organisms from phagocytosis) suggest that wetland sediments and rhizosphere present a potential reservoirs for enteric human and animal pathogens.