Detection of Antibiotic Resistance, Virulence Gene, and Drug Resistance Gene of Staphylococcus aureus Isolates from Bovine Mastitis.

Antimicrobial therapy plays an important role in mastitis control caused by Staphylococcus aureus but has become less effective due to widespread drug resistance. The purpose of this study was to detect antibiotic resistance, drug resistance gene, and virulence gene of S. aureus strains. In this study, 2,962 milk samples were collected from 43 dairy farms located in 16 provinces of China and cultured for isolation of S. aureus. Antibiotic resistance, capsular polysaccharide, spa typing, virulence genes, and drug resistance genes of the strains were analyzed. Of 2,962 samples, 298 strains were isolated and identified as S. aureus. The strains exhibited high percentages of resistance to penicillin G (91.95%). Moreover, all strains showed resistance to more than one antimicrobial agent but were sensitive to nitrofurantoin and sulfamethoxazole/trimethoprim. The results indicate that type 8 was the dominant capsular polysaccharide serotype and t459 was the dominant spa type. The most prevalent virulence gene was clfA (98%). The resistance genes of several antibiotics were detected, among which the blaZ gene (92.95%) was the highest. In conclusion, we present the antimicrobial resistance and virulence genes of S. aureus in this study which are of importance for mastitis control. IMPORTANCE Bovine mastitis is a serious disease associated with both high incidence and economic loss, posing a major challenge to the dairy industry worldwide. Staphylococcus aureus is one of the most common pathogens to cause bovine mastitis, and antimicrobial therapy plays an important role in mastitis control caused by S. aureus but has become less effective due to widespread drug resistance. The purpose of this study was to detect antibiotic resistance, drug resistance gene, and virulence gene of S. aureus strains, which would be helpful to mastitis control.

Antimicrobial Resistance and Virulence Factor of Streptococcus dysgalactiae Isolated from Clinical Bovine Mastitis Cases in Northwest China.

OBJECTIVE: Streptococcus dysgalactiae is a major pathogen in bovine mastitis. The purpose of this study was to survey the prevalence, antimicrobial resistance, as well as the spread of resistance and virulence-associated gene of S. dysgalactiae. METHODS: A total of 60 S. dysgalactiae strains were obtained from 830 milk samples from Holstein cows with clinical mastitis. Antimicrobial resistance was examined by the disk diffusion method. Antimicrobial resistance and virulence genes were investigated by PCR, agarose gel electrophoresis and 16S rRNA gene sequencing. RESULTS: All isolates were resistant to tetracycline and showed a high level of resistance to aminoglycoside antibiotics, where 81.67% of the strains were multi-resistant to these ten sorts of antibiotics. In addition, the most prevalent resistance gene in S. dysgalactiae was aphA-1 (98.33%), followed by blaTEM (96.67%), ermB (83.3%), aadA1/aadA2 (78.33%) and tetL (73.33%). Totally, seven virulence genes with 25 combination patterns were detected in these isolates, and each isolates harbored at least one virulence gene. 21.67% of the isolates carried three or more virulence genes, while one strain with seven virulence-related genes and belonged to cfb+lmb+eno+napr+bca+scpB+cyl. CONCLUSION: These findings indicate that S. dysgalactiae isolated from clinical bovine mastitis cases in Northwest China show a variety of molecular ecology and are highly resistant to antibiotics commonly used in dairy farms. This research will help investigators better understand the pathophysiology S. dysgalactiae in bovine mastitis and choose the appropriate antibiotics to treat mastitis.

Steady and Robust CNTs-Based Electric Heating Membrane Fabricated by Addition of Nanocellulose and Hot-Press Encapsulation.

Herein, a type of biomass-based electric heating membrane (EHM) with excellent stability was fabricated; this was achieved by incorporating carbon nanotubes (CNTs) into the nanofibrillated cellulose (NFC) as a natural dispersant and a biological substrate, as well as via the control of ultrasonic dispersion, grammage, and encapsulation using poly(dimethylsiloxane) (PDMS) with hot pressing. NFC entangles with CNTs in the form of an intertwined network and non-covalent interactions to fabricate a flexible EHM with steady electric heating performance; this formation is attributed to not only their similar morphology and surface-active groups but also the use of NFC that avoids additional disturbances in the overlapped interface among CNTs as far as possible. The obtained steady resistance varies as low as 5.1% under energized operation. In the encapsulated EHM (EM), PDMS was anchored on its surface by using hot pressing and an intertwined structure to enhance flexibility and robustness. The encapsulated membrane can be used in low-voltage applications, which require flexibility, waterproofing, and insulation.

Performance of the highly sensitive humidity sensor constructed with nanofibrillated cellulose/graphene oxide/polydimethylsiloxane aerogel via freeze drying.

A kind of capacitive humidity sensor with high sensitivity constructed with nanofibrillated cellulose (NFC), graphene oxide (GO) and polydimethylsiloxane (PDMS) is presented in this work, via a simple ultrasonic dispersion and freeze drying technology. The NFC and GO with a strong adsorption for water molecules were used as a substrate for the promotion of capacitive response of the humidity sensor. Moreover, anhydrous ethanol was added to inhibit the generation of big cracks in the humidity sensor in the freeze drying process, so as to obtain a regular network porous structure, then providing a great deal of conduction channels and active sites for molecular water. Also, the addition of PDMS can effectively enhance the flexibility and stability of its porous structure. The results confirmed that the humidity sensor with 30 wt% GO showed an excellent humidity sensitivity (6576.41 pF/% RH), remarkable reproducibility, low humidity hysteresis characteristic in 11-97% relative humidity (RH) at 25 °C, and short response/recovery times (57 s/2 s). In addition, the presented sensor exhibited small relative deviation of the measured relative humidity value compared with the commercial hygrometer. The realization of the high sensitivity can be attributed to the theories about interaction of the hydrophilic group, proton transfer of water molecules and the three-dimensional network transport structure model. Therefore, the NFC/GO/PDMS humidity sensor finally realizes stable, reproducible and fast humidity sensing via an eco-friendly process, exhibiting promising potential for wide practical application.

A Nanofibrillated Cellulose-Based Electrothermal Aerogel Constructed with Carbon Nanotubes and Graphene.

Nanofibrillated cellulose (NFC) as an environmentally friendly substrate material has superiority for flexible electrothermal composite, while there is currently no research on porous NFC based electrothermal aerogel. Therefore, this work used NFC as a skeleton, combined with multi-walled carbon nanotubes (MWCNTs) and graphene (GP), to prepare NFC/MWCNTs/GP aerogel (CCGA) via a simple and economic freeze-drying method. The electrothermal CCGA was finally assembled after connecting CCGA with electrodes. The results show that when the concentration of the NFC/MWCNTs/GP suspension was 5 mg mL-1 and NFC amount was 80 wt.%, the maximum steady-state temperature rise of electrothermal CCGA at 3000 W m-2 and 2000 W m-2 was of about 62.0 °C and 40.4 °C, respectively. The resistance change rate of the CCGA was nearly 15% at the concentration of 7 mg mL-1 under the power density of 2000 W m-2. The formed three-dimensional porous structure is conducive to the heat exchange. Consequently, the electrothermal CCGA can be used as a potential lightweight substrate for efficient electrothermal devices.

The use of nanofibrillated cellulose to fabricate a homogeneous and flexible graphene-based electric heating membrane.

Nanofibrillated cellulose (NFC) as a natural macromolecule, binder, dispersant, enhancer, was utilized to facilitate the assembly of graphene sheets, imparting a steady stacked structure by the sheets to the electric heating membrane with flexibility and uniform heating performance. Strong interface bonding formed in the membrane, which combined graphene sheets to be a steady conductive network structure for electric heating. The membrane attained an equilibrium temperature rise to 60°C in 3min under 2000Wm-2, which increased linearly with increasing power density and graphene content. Decreased resistance between two electrodes was caused by electric-heat coupling effect which led to a decrease in the membrane's oxygen-containing groups as conducting electrification. The temperature distributing on membrane surface, and that as bent and distorted to different angles even simultaneously at the electric heating status, were all characterized by infrared thermal imaging to indicate the uniform distribution and well bonding performance between NFC and graphene, as well as the great flexibility in the biomass membrane. This study would further broaden the utilization of the natural nanocellulose-graphene biomass composites.

Whole-Genome Sequence of Streptococcus parauberis Strain SP-llh, Isolated from Cows with Mastitis in Western China.

Streptococcus parauberis strain SP-llh was isolated from cows with mastitis in western China in 2015. The 2,522,235-bp genome sequence consists of 46 large contigs in 14 scaffolds and contains 2,620 predicted protein-coding genes, with a G+C content of 35.3%.

Determination and pharmacokinetic study of chlorogenic acid in rat dosed with Yin-Huang granules by RP-HPLC.

A reversed-phase high-performance liquid chromatographic (RP-HPLC) method was described for the determination of chlorogenic acid (CGA) in rat plasma using protocatechuic acid as internal standard (IS). CGA in plasma was extracted with acetonitrile, which also acted as deproteinization agent. Chromatographic separation was performed on a Kromasil C18 column with methanol-0.2 m acetic acid (pH 3.0, 25:75, v/v) as mobile phase at a flow-rate of 1.0 mL/min with an operating temperature of 30 degrees C and UV detection at 300 nm. The standard curve was found to be linear over the concentration ranges of 0.4-2.5 microg/mL and 2.5-40 microg/mL, and the limit of quantification (LOQ) was 0.4 microg/mL. The analytical precision and accuracy were validated by relative standard deviation (RSD) and relative error, which were in ranges 3.14-10.78% and -2.20-5.00%, respectively. The average recovery of CGA was 87.59%. The method was successfully applied to the pharmacokinetic study of CGA in Yin-Huang granules.

Simultaneous determination of chlorogenic acid, caffeic acid, ferulic acid, protocatechuic acid and protocatechuic aldehyde in Chinese herbal preparation by RP-HPLC.

In the present study, a reversed phase high performance liquid chromatographic (RP-HPLC) method was established for simultaneous determination of chlorogenic acid, caffeic acid, ferulic acid, protocatechuic acid and protocatechuic aldehyde in a Chinese herbal preparation (Fufang-Pugongying-Mixture). The separation was performed on a Hypersil ODS-2 column by isocratic elution with methanol and 0.2 M acetate buffer (pH 3.6) (15 : 85, v/v) as the mobile phase at the flow-rate of 1.0 ml/min with operating temperature of 30 degrees C, and detection wavelength of 300 nm. A good linear regression relationship between peak-areas and concentrations was obtained over the range of 2-200 microg/ml for the five marker compounds mentioned above. The spike recoveries were within 96.72-104.07%. The variation coefficient (CV) values of the precision were in the range of 0.89-4.50%. Moreover the developed method has reference value for quantitative analysis of Taraxacum, Lonicera and Angelica.