45692513
Sphingobacterium sp. strain PM2-P1-29 harbours a functional tet(X) gene encoding for the degradation of tetracycline.
AIMS
The tet(X) gene has previously been found in obligate anaerobic Bacteroides spp., which is curious because tet(X) encodes for a NADP-dependent monooxygenase that requires oxygen to degrade tetracycline. In this study, we characterized a tetracycline resistant, aerobic, Gram-negative Sphingobacterium sp. strain PM2-P1-29 that harbours a tet(X) gene.


METHODS AND RESULTS
Sphingobacterium sp. PM2-P1-29 demonstrated the ability to transform tetracycline compared with killed controls. The presence of the tet(X) gene was verified by PCR and nucleotide sequence analysis. Additional nucleotide sequence analysis of regions flanking the tet(X) gene revealed a mobilizable transposon-like element (Tn6031) that shared organizational features and genes with the previously described Bacteroides conjugative transposon CTnDOT. A circular transposition intermediate of the tet(X) region, characteristic of mobilizable transposons, was detected. However, we could not demonstrate the conjugal transfer of the tet(X) gene using three different recipient strains and numerous experimental conditions.


CONCLUSIONS
This study suggests that Sphingobacterium sp. PM2-P1-29 or a related bacterium may be an ancestral source of the tet(X) gene.


SIGNIFICANCE AND IMPACT OF THE STUDY
This study demonstrates the importance of environmental bacteria and lateral gene transfer in the dissemination and proliferation of antibiotic resistance among bacteria.
12219567
Application of rbcL based molecular diversity analysis to algae in wastewater treatment plants.
The molecular diversity of algae in the final clarifier or denitrification filter outfall from three wastewater treatment plants (WWTPs) with activated sludge based treatment was analyzed using the rbcL gene as a phylogenetic marker. The rbcL gene encodes the large subunit of the CO(2) fixing enzyme RuBisCO. Among algae identified at the WWTPs were diatoms, green algae, cyanobacteria, Eustigmatophyceae, and unknown heterokonts. A high level of diversity was observed within WWTPs with 19-24 unique rbcL sequences detected at each plant. Algae composition also varied between treatment plants. Our results show that the rbcL gene can be used as a phylogenetic marker for algae diversity analysis in a wastewater treatment context.
21394365
Chlorinated phenols control the expression of the multidrug resistance efflux pump MexAB-OprM in Pseudomonas aeruginosa by interacting with NalC.
NalC is a TetR type regulator that represses the multidrug efflux pump MexAB-OprM in Pseudomonas aeruginosa. Here we explain the mechanism of NalC-mediated regulation of MexAB-OprM. We show that NalC non-covalently binds chlorinated phenols and chemicals containing chlorophenol side-chains such as triclosan. NalC-chlorinated phenol binding results in its dissociation from promoter DNA and upregulation of NalC's downstream targets, including the MexR antirepressor ArmR. ArmR upregulation and MexR-ArmR complex formation have previously been shown to upregulate MexAB-OprM. In vivo mexB and armR expression analyses were used to corroborate in vitro NalC-chlorinated phenol binding. We also show that the interaction between chlorinated phenols and NalC is reversible, such that removal of these chemicals restored NalC promoter DNA binding. Thus, the NalC-chlorinated phenol interaction is likely a pertinent physiological mechanism that P. aeruginosa uses to control expression of the MexAB-OprM efflux pump.
2929379
The effects of subtherapeutic antibiotic use in farm animals on the proliferation and persistence of antibiotic resistance among soil bacteria
The use of antibiotics at subtherapeutic concentrations for agricultural applications is believed to be an important factor in the proliferation of antibiotic-resistant bacteria. The goal of this study was to determine if the application of manure onto agricultural land would result in the proliferation of antibiotic resistance among soil bacteria. Chlortetracycline-resistant bacteria were enumerated and characterized from soils exposed to the manure of animals fed subtherapeutic concentrations of antibiotics and compared to the chlortetracycline-resistant bacteria from soils at farms with restricted antibiotic use (dairy farms) and from non-agricultural soils. No significant differences were observed at nine different study sites with respect to the numbers and types of cultivated chlortetracycline-resistant bacteria. Genes encoding for tetracycline resistance were rarely detected in the resistant bacteria from these sites. In contrast, soils collected from a tenth farm, which allowed manure to indiscriminately accumulate outside the animal pen, had significantly higher chlortetracycline-resistance levels. These resistant bacteria frequently harbored one of 14 different genes encoding for tetracycline resistance, many of which (especially tet(A) and tet(L)) were detected in numerous different bacterial species. Subsequent bacterial enumerations at this site, following the cessation of farming activity, suggested that this farm remained a hotspot for antibiotic resistance. In conclusion, we speculate that excessive application of animal manure leads to the spread of resistance to soil bacteria (potentially by lateral gene transfer), which then serve as persistent reservoir of antibiotic resistance.
24499740
Molecular characterization of full-length genomic segment 2 of a bovine picobirnavirus (PBV) strain: evidence for high genetic diversity with genogroup I PBVs.
We report here the molecular characterization of a bovine genogroup I picobirnavirus strain RUBV-P detected from a 1-month-old diarrhoeic calf in eastern India. Sequence comparisons and phylogenetic analysis of a short stretch of gene segment 2 of RUBV-P revealed low nucleotide identities (51.2-64.9%) with and distant genetic relatedness to other genogroup I picobirnaviruses. The complete gene segment 2 sequence of RUBV-P was obtained by the single primer amplification method with modifications. Gene segment 2 of RUBV-P was 1758 bp long, encoded a predicted protein of 554 aa and exhibited low nucleotide (58.1-58.8%) and amino acid (51.3-55.4%) identities with genogroup I human strains Hy005102 and 1-CHN-97. The 5'- and 3'-end nucleotide sequences, and the three motifs of RNA-dependent RNA polymerases of double-stranded RNA viruses, were conserved among these strains. Our findings suggested that bovine strain RUBV-P might be distinct from genogroup I picobirnaviruses of humans and other animals.
7845617
Molecular characterization of rare bovine group A rotavirus G15P[11] and G15P[21] strains from eastern India: identification of simian SA11-like VP6 genes in G15P[21] strains
During a surveillance study (November 2001–March 2005), one rare G15P[11] and two rare G15P[21] bovine group A rotavirus strains were detected in diarrhoeic calves in Eastern India. Sequence analysis of the VP8*, VP6, NSP4 and NSP5 genes of the G15P[11] strain confirmed its bovine origin. Although the NSP4 and NSP5 genes of the two G15P[21] strains were of bovine origin, their VP6 genes shared higher nucleotide and amino acid identities with simian strain SA11 (92.5–93.1% and 98.5–98.7%) than bovine strains (88.5–88.9% and 97–97.2%), and by phylogenetic analysis, exhibited clustering with SA11, distantly related to bovine strains. All these pointed towards a possible reassortment event of VP6 gene between bovine and simian (SA11-like) strains. Therefore, the present study provided molecular evidence for bovine origin of G15 strains and revealed a rare instance of genetic diversity in the bovine VP6 gene, otherwise conserved in group A rotavirus strains from cattle.
20902543
Fatal Morganella morganii bacteraemia in a diabetic patient with gas gangrene.
We report a case of a 60-year-old lady with a history of a heel ulcer that had not responded to antibiotic therapy. This progressed to involve the right leg, which was swollen and erythematous. Radiological imaging revealed the presence of gas within the fascial planes. Blood cultures on admission yielded Morganella morganii. Due to the extent of the gas gangrene and her co-morbidities the patient was not suitable for surgical intervention and was treated conservatively with antibiotics. She deteriorated and died within 72 h of presentation. Non-clostridial gas gangrene is relatively rare, and diagnosis is frequently delayed and often missed. Early aggressive surgical intervention combined with appropriate antibiotic therapy is essential. Bacterial species other than Clostridium should be considered in all cases of gas gangrene.
22990361
Cell density is a critical determinant of aromatase expression in adipose stromal cells
Obesity is associated with an increased risk of breast cancer among postmenopausal women. This is at least partly due to excessive estrogen production in adipose tissue of obese women. Aromatase, the key enzyme in estrogen biosynthesis, is an important target in endocrine therapy for estrogen receptor (ER)-positive postmenopausal breast cancer. In this study we show that high confluency of human adipose stromal cells (ASCs) cultured in vitro can significantly stimulate aromatase gene expression and reduce the expression of breast tumor suppressor BRCA1 and members of the NR4A orphan nuclear family. Furthermore, small interfering RNA (siRNA)-mediated knockdown of Nurr1, a member of the NR4A family, substantially increased aromatase expression. Lastly, we found that the cell density-triggered inducibility of aromatase expression varies in ASCs isolated from different disease-free individuals. Our finding highlights the impact of increased cell number on estrogen biosynthesis as in the case of excessive adiposity.
1771625
Correlation of macular thickness and posterior hyaloid change following bevacizumab and triamcinolone in diffuse diabetic macular edema in middle-aged patients
To compare changes in posterior vitreous detachment (PVD) following intravitreal injection of bevacizumab and triamcinolone in diffuse diabetic macular edema in middle-aged type 2 diabetes patients and to correlate this change with change in central macular thickness (CMT). Design: cross sectional study. Fifteen consecutive patients treated by intravitreal bevacizumab (group A) and ten patients treated by intravitreal triamcinolone (group B). Institutional study carried out by retrospective analysis of patient registers including serial optical coherence tomography (OCT) images at baseline, and after 1 and 4 months. A central macular thickness (CMT) and vitreomacular relationship was noted on OCT. PVD was graded on a linear scale (0–4). Change in grade of PVD was correlated with change in CMT at each follow-up. At month 4, the decrease in mean CMT from baseline was 51.2 μ (P = 0.000) and 45 μ (P = 0.022) in group A and group B, respectively, with no significant difference between the two groups (P = 0.874). A change in grades of PVD from baseline to month 4 was significant in both group A (P = 0.001) and group B (P = 0.004) with no significant difference between the two groups (P = 0.906). A significant correlation between change in PVD and reduction of CMT was observed in group A (P = 0.011) but not in group B (P = 0.315). Both bevacizumab and triamcinolone caused a significant reduction in macular thickness and a significant change in grade of PVD. Change in PVD played an influential role in the reduction of macular thickness following bevacizumab.