Concentrations Of Streptomycin Research Articles

Effects of Three Commonly Used Herbicides on Bacterial Antibiotic Resistance

The spread of antibiotic resistance has become a serious threat to global public health. Recently, several studies have found that non-antibiotic chemicals can promote the generation and spread of bacterial antibiotic resistance. However, the effects of herbicides on the antibiotic resistance of bacteria remain unclear. In this study, Escherichia coli DH5α was used as the model strain to explore the effects of three commonly used herbicides (glyphosate, glufosinate, and dicamba) on the antibiotic resistance under soil environmental concentrations. The results showed that herbicide exposure affected the sensitivity of E. coli DH5α to antibiotics and significantly improved the resistance of E. coli DH5α to gentamicin (glyphosate > dicamba > glufosinate). After 30 d of herbicide exposure, the E. coli mutant strains enhanced the resistance to tetracycline, chloramphenicol, and aminoglycoside antibiotics, and the minimum inhibitory concentration of streptomycin was increased by 19.8 times. The whole-genome sequencing results illustrated that herbicides induced several previously well-characterized mutations associated with membrane proteins (ompF and papC), fimbriae proteins (yraH), and ribosomes (rpsL) related to antibiotic resistance. Together, the results showed that herbicides can enhance the antibiotic resistance of bacteria via inducing genetic mutations, thereby promoting the potential risk of the spread of antibiotic resistance genes in the environment.

Endophytic fungus Diaporthe caatingaensis MT192326 from Buchanania axillaris: An indicator to produce biocontrol agents in plant protection

The study aims at the Isolation, screening and antibacterial evaluation of Camptothecin (CPT) and its derivatives, an anticancer molecule from endophytic fungus Diaporthe caatingaensis MT192326 of the medicinal plant, Buchanania axillaris. Plant parts were collected from Sathyamangalam Tiger Reserve forest, Tamil Nadu. The fungus was isolated using DEKM07 medium was used as the screening medium for the presence of CPT. The strain with the highest yield of CPT was identified at the molecular level by 18S rDNA sequencing. CPT was isolated and analyzed by UV–Vis spectrophotometry, Thin layer chromatography, High-Performance Liquid Chromatography, Fourier Transform Infrared spectroscopy, and Electron spray ionization-mass spectrometry. The compounds identified by ESI-MS from the fungal extract were studied for their antibacterial assays against procured MTCC bacterial pathogens. The maximum yield of 0.681 mg/L of CPT was produced by the fungus D.caatingaensis. CPT derivatives were identified at m/z of 305, 348 and 389 through ESI-MS analysis. Antibacterial studies revealed that the endophytic fungal extract compounds were studied for antibacterial activities of disc diffusion assay, exhibiting a growth inhibition range of 15–22 mm in nutrient agar plate medium. The Minimum Inhibitory Concentration revealed the antibacterial potential at a lower concentration of 12.5–25 μg/ml with all bacteria studied. The relatively lower antimicrobial efficacy of partially purified bio-metabolites than the positive control streptomycin (3.125) concentration could be due to the presence of derivatives of the compounds that hinder the activity of the biometabolite. This is the first initiative to screen, isolate and analyze the antibacterial assays of CPT and derivatives from endophytic fungus D.caatingaensis of ethnopharmacologically important B.axillaris plant from STRF.

Fourier transform‐infrared assessment of cholesterol effect on antibiotic resistance of Salmonella Typhimurium

In this study, the effect of cholesterol on antibiotic resistance of Salmonella Typhimurium was investigated. Antibiotic resistance patterns revealed that the bacterium was susceptible to ampicillin, streptomycin, sulfamethoxazole/trimethoprim, ciprofloxacin, tetracycline, chloramphenicol, and gentamicin and resistant to penicillin, erythromycin, and vancomycin. The minimum inhibitory concentrations (MICs) of ampicillin, streptomycin, ciprofloxacin, and sulfamethoxazole/ trimethoprim antibiotics were found as 16, 128, 0.25, and 16 mg/L, respectively. When the effect of cholesterol on antibiotic resistivity was examined, it was found that MICs increased in cholesterol medium than in non-cholesterol medium. The increase in MICs and decrement in inhibition zones was considered as the decreasing effect of cholesterol on the sensitivity of Salmonella Typhimurium. The effect of cholesterol on the antibiotic sensitivity of Salmonella Typhimurium was also assessed by Fourier transformed infrared (FT-IR) spectroscopy, and the results indicated that new functional groups were observed at different wavelengths in the presence of cholesterol. Practical applications Antibiotic resistance is a global phenomenon resulting in the emergence of pathogens with resistance to clinically important antibiotics. Antibiotic resistance in foodborne pathogens such as Salmonella is a major concern for public health safety. Significant increase in bacterial resistance makes it increasingly necessary to develop new drugs and antibiotic activity modifiers and effective techniques for treatment. Fourier transformed infrared (FT-IR) can be used as a rapid and precise method for the assessment of cholesterol effect on antibiotic resistance pattern of Salmonella Typhimurium.

Preliminary in vitro tests on inhibitory activity of distinct plant extracts toward bacterial pathogens of fruit and nut trees

The present study was undertaken to test the inhibitory activity of several plant extracts against bacteria causing economically important diseases on fruit and nut trees. Essential oils derived from oregano (Origanum vulgare ssp. hirtum), common sage (Salvia officinalis), savory (Satureja pilosa), monarda (Monarda didyma) and an extract from clove (Syzygium aromaticum) flower buds were tested in vitro for their antibacterial activity towards two different strains each of Agrobacterium tumefaciens (At), strains AT4 and C58, Erwinia amylovora (Ea), strains 659 and 691, Pseudomonas syringae pv. syringae (Pss), strains LMG 1247T and 110, Xanthomonas arboricola pv. corylina (Xac), strains CFBP 1159T and 301, and X. arboricola pv. juglandis (Xaj), strains CFBP 2528T and 510. The plant products expressed selective activity in suppressing bacterial growth. Overall, most efficient appeared the essential oils from monarda (for strains At AT4, Ea 659, Pss LMG 1247T Xac CFBP 1159T and Xaj CFBP 2528T) and oregano (against all strains used). In 100% concentrated form these oils exerted on average 48-63% and 40-55% inhibition, respectively. The inhibitory effects of sage and savory oils varied significantly causing either no or from 20 to 60% inhibition. Clove extract was medium efficient against all pathogens providing 18-30% inhibition. Generally, most of the extracts (except clove extract and in some cases sage and savory oils) showed activity exceeding up to 30-40% compared to the inhibitory effect of the maximum concentration (500 ppm) of the antibiotic streptomycin. Monarda, oregano oils and clove extract were almost equally active in undiluted form and at dilution to 50% whereas sage oil and in part savory oil showed lower activity at 50% dilution. The differences in the response of tested pathogens (that were of different origin) suggested that their sensitivity to applied plant products may be related to the genotype. In support to this assumption are our earlier studies where the genetic diversity of the strains used was proven by analysis of housekeeping genes. The results reported here are preliminary and further work is being undertaken to perspective the observed inhibitory effects by in vivo tests in a larger scale.

Response of anammox granules to the simultaneous exposure to macrolide and aminoglycoside antibiotics: Linking performance to mechanism

Antibiotic pollution is becoming increasingly severe due to its extensive use. The potential application of the anaerobic ammonium oxidation (anammox) process in the treatment of wastewater containing antibiotics has attracted much attention. As common antibiotics, spiramycin (SPM) and streptomycin (STM) are widely used to treat human and animal diseases. However, their combined effects on the anammox process remain unknown. Therefore, this study systematically evaluated the response of the anammox process to both antibiotics. The half maximal inhibitory concentrations of SPM and STM were determined. The continuous-flow anammox system could adapt to SPM and STM at low concentrations, while antibiotics at high concentrations exhibited inhibitory effects. When the concentrations reached 5 mg L−1 SPM and 50 mg L−1 STM, the nitrogen removal efficiency dramatically decreased and then rapidly recovered within 8 days. Correspondingly, the abundances of dominant bacteria and genes also changed with antibiotic concentrations. In general, the anammox process showed a stable performance and a high resistance to SPM and STM, suggesting that acclimatization by elevating the concentrations was beneficial for the anammox process to obtain resistance to different antibiotics with high concentrations. This study provides guidance for the stable operation of anammox-based biological treatment of antibiotics containing wastewater.

The effect of soil moisture on the response by fungi and bacteria to nitrogen additions for N2O production

In addition to bacteria, the contribution of fungi to nitrous oxide (N2O) production has been recognized but the responses of these two broad and unrelated groups of microorganisms to global environmental changes, atmospheric nitrogen (N) deposition, and precipitation in terms of N2O production are unclear. We studied how these two microbial-mediated N2O production pathways responded to soil moisture conditions and to N addition in an N-limited temperate forest. Soils from a long-term N addition experiment in Changbai Mountain, northeastern China were incubated. Varied concentrations of cycloheximide and streptomycin, both inhibitors of fungal and bacterial activity, were used to determine the contributions of both to N2O production in 66%, 98% and 130% water-filled pore spaces (WFPS). The results showed that N2O production decreased significantly with increasing cycloheximide concentration whereas streptomycin was only inhibiting N2O emissions at 98% and 130% WFPS. The bacterial pathway of N2O production in N-addition (Nadd) soil was significantly more dominant than that in untreated (Namb) soil. The difference in the fungal pathway of N2O production between the soil with nitrogen addition and the untreated soil was not significant. Net N2O emissions increased with increasing soil moisture, especially at 130% WFPS, a completely flooded condition. Bacteria dominated carbon dioxide (CO2) and N2O emissions in Nadd soil and at 130% WFPS regardless of N status, while fungi dominated CO2 and N2O emissions in soil without N addition at 66% and 98% WFPS. The results suggest that flooded soil is an important source of N2O emissions and that bacteria might be better adapted to compete in fertile soils under anoxic conditions.

The Development of a Turbidimetric Method for the Quantitative Determination of Antibiotics of the Aminoglycoside Group in Medications

A method for the quantitative determination of streptomycin sulfate in medicines by the turbidimetric method has been developedand validated. Based on the results of the experiments, it was found that the metrological characteristics of such validation parameters of the method as linearity, precision, and correctness do not exceed the validation criteria. Linearity was noted in the range of streptomycin concentrations from 3.75 to 8.43 μg/ml. The results of validation tests of the method for the quantitative determination of streptomycin indicate the prospects and feasibility of introducing the turbidimetric method into the domestic system for standardization and quality assessment of aminoglycoside antibiotics.

Antimicrobial activities and mechanism of action of Cymbopogon khasianus (Munro ex Hackel) Bor essential oil

BackgroundDue to concerns regarding the safety of the chemical control measures, the trend is shifting globally towards the use of natural compounds as antimicrobial agent especially, plant essential oils.ResultsThis study presented the antibacterial potential of Cymbopogon khasianus essential oil (CKEO) against human pathogens: Pseudomonas aeruginosa, Salmonella typhimurium, Escherichia coli, Klebsiella pneumoniae, Bacillus subtilis, Staphylococcus aureus and Candida albicans with MIC ranging from 20 to 100 μg/mL. CKEO, in comparison to its major constituent, geraniol, showed better MICs against tested pathogens. In combination studies, the effective concentrations of CKEO and streptomycin were reduced from 20 to 5 μg/mL and 11 to 0.7 ng/mL against E. coli. This suggests their synergistic action. However, CKEO showed partial synergy with ciprofloxacin. To understand the efficacy of CKEO, time-kill kinetics was performed. CKEO took the half time to show the bactericidal effect in comparison to streptomycin at their 2x MICs (double the MIC), while their combination took only 30 min for this. Fluorescence and surface electron microscopic and protein estimation studies suggested the multi-target action of CKEO-streptomycin combination against E. coli. Further, CKEO alone/in combination exhibited less than 10% haemolytic activity at its MIC.ConclusionThese results indicate that CKEO is a potentially safe alternative for the treatment of various pathogenic bacterial strains. It could be used for a variety of applications including human health, food storage, aquaculture, etc.

Resistance Patterns of Mycobacterium tuberculosis to First-Line Anti-TB Drugs in Kaduna State, North-Western Nigeria

The problem of tuberculosis (TB) in Nigeria has been made worse by the issues of drug resistant Mycobacterium tuberculosis. Resistance associated with treatment failures has become a common occurrence worldwide. Of particular concern is the increasing prevalence of multi drug resistant M. tuberculosis; organisms resistant to isoniazid and rifampicin, the two drugs that form the backbone of modern short-course therapy. Susceptibility of forty (40) M. tuberculosis isolates to isoniazid (INH), rifampicin (RIF), streptomycin (SM) and ethambutol (EMB) was determined by the proportion method on Lowenstein Jensen egg based slopes containing critical concentrations of INH, RIF, SM and EMB (0.2 μg/ml, 40 μg/ml, 4.0 μg/ml and 2.0 μg/ml respectively). Overall drug resistance was found in 21 (52.5%) isolates. Mono-drug resistance was seen in 9 (22.5%) of the isolates tested and was against streptomycin. Two (5.0%) isolates were found to be MDR. Five (12.5%) were poly-drug resistant. One isolate showed poly-drug resistance to SM and INH, 2 (5%) were poly-drug resistant to SM and EMB, 1 (2.5%) was resistant to INH and EMB. Poly resistance to SM, INH and EMB was found in only 1 isolate. No poly-resistance to RIF and EMB, RIF and SM or RIF/SM/EMB was observed.

New Determinants of Aminoglycoside Resistance and Their Association with the Class 1 Integron Gene Cassettes in Trueperella pyogenes.

Trueperella pyogenes is an important opportunistic animal pathogen. Different antimicrobials, including aminoglycosides, are used to treat T. pyogenes infections. The aim of the present study was to evaluate aminoglycoside susceptibility and to detect aminoglycoside resistance determinants in 86 T. pyogenes isolates of different origin. Minimum inhibitory concentration of gentamicin, streptomycin, and kanamycin was determined using a standard broth microdilution method. Genetic elements associated with aminoglycoside resistance were investigated by PCR and DNA sequencing. All studied isolates were susceptible to gentamicin, but 32.6% and 11.6% of them were classified as resistant to streptomycin and kanamycin, respectively. A total of 30 (34.9%) isolates contained class 1 integrons. Class 1 integron gene cassettes carrying aminoglycoside resistance genes, aadA11 and aadA9, were found in seven and two isolates, respectively. Additionally, the aadA9 gene found in six isolates was not associated with mobile genetic elements. Moreover, other, not carried by gene cassettes, aminoglycoside resistance genes, strA-strB and aph(3’)-IIIa, were also detected. Most importantly, this is the first description of all reported genes in T. pyogenes. Nevertheless, the relevance of the resistance phenotype to genotype was not perfectly matched in 14 isolates. Therefore, further investigations are needed to fully explain aminoglycoside resistance mechanisms in T. pyogenes.

Minimum influent concentrations of oxytetracycline, streptomycin and spiramycin in selecting antibiotic resistance in biofilm type wastewater treatment systems

It has been demonstrated that antibiotic resistance could be induced and selected under high antibiotic concentrations in biological wastewater treatment systems. However, little is available regarding the minimum concentrations of antibiotics for selecting antibiotic resistance during wastewater treatment. Herein, the minimum influent concentrations of oxytetracycline, streptomycin, and spiramycin in selecting antibiotic resistance in biofilm type wastewater treatment systems were investigated by spiking respective antibiotic into wastewater with an antibiotic dose increasing from 0 to 0.1, 1, 5, 25, 50 mg/L stepwise over a period of 606 days. Significant increase (p < .01) in the total abundance of antibiotic resistance genes was observed for both streptomycin and oxytetracycline at a dose of 0.1 mg/L according to metagenomic sequencing, while the concentration levels leading to significant increases (p < .05) in resistant bacteria ratio were higher: 5 mg/L for streptomycin and 25 mg/L for oxytetracycline. Although resistome abundance increased with the increase of spiramycin dose, neither the corresponding Macrolide-Lincosamide-Streptogramin (MLS) resistance genes nor the resistant bacteria ratio showed perceptible increase. Partial canonical correspondence analysis showed that both bacterial community shift and mobile genetic elements alteration contributed to the enrichment of resistomes under the presence of streptomycin and oxytetracycline. Regarding spiramycin which is mainly targeting on Gram-positive bacteria, the dominance of the intrinsically resisting Gram-negative bacteria in the biofilm microbiota might be responsible for the vague change of MLS resistant determinants under the spiramycin stress. The results demonstrated that it is possible to prevent the development of antibiotic resistance during wastewater treatment by controlling the influent streptomycin and oxytetracyline concentrations below 0.1 mg/L. This work proposed an actionable approach for the management of antibiotic production wastewater.

Assessment of antibiotic resistance in starter and non-starter lactobacilli of food origin

The absence of acquired resistance to antimicrobials has become an important criterion in evaluation of the biosafety of lactobacilli used as industrial starter or probiotic cultures. The aim of this study was to assess antibiotic resistance in starter and non-starter lactobacilli of food origin. Minimal inhibitory concentrations of ampicillin, chloramphenicol, clindamycin, erythromycin, gentamicin, kanamycin, streptomycin, tetracycline and vancomycin were established in 81 strains of lactobacilli (L. acidophilus, L. animalis, L. brevis, L. curvatus, L. delbrueckii, L. fermentum, L. helveticus, L. paracasei, L. plantarum, L. rhamnosus and L. sakei) by the microdilution method. The strains were classified as susceptible or resistant to antimicrobials based on the cut-off values according to the EFSA guideline. Sixty-two strains (77% food isolates, 76% starter or adjunct cultures) were resistant to at least one antimicrobial agent (the most frequently to aminoglycosides). Adjunct cultures showed a higher antibiotic resistance (80%) than starters (60%). Four multiresistant strains (3 food isolates, 1 adjunct culture) were analyzed by whole genome sequencing. One potentially transferable aadE gene (responsible for streptomycin resistance) was detected only in one multi-drug resistant strain of L. animalis originating from an adjunct culture. Thus, there is a risk of horizontal transmission of this gene. It is necessary to eliminate such strains from use in the food industry. This study provides relevant data concerning the use of lactobacilli in safe food production. To ensure food safety, detailed characterization of resistance to antimicrobials is necessary not only in starter strains but also in non-starter lactic acid bacteria isolated from food products.

In vitro study of Nano Hydroxyapatite/Streptomycin -Gelatin-Based Injectable Bone Substitute Associated- 3D printed Bone Scaffold for Spinal Tuberculosis Case

According to WHO (2018) Indonesia was placed in the third ranked of the highest number of TB sufferers worldwide. TB was caused by the Mycobacterium tuberculosis. This bacterial infection not only could affect the lungs, but also bone tissue, especially the spine, which then called as spinal tuberculosis. There had been many alternatives to overcome this case. One of them was by using Injectable Bone Substitutes (IBS) based on nano Hydroxyapatite (nanoHA), gelatin and streptomycin. The severe sponal tuberculosis case might cause the bone defect. Due to this bone defect, IBS alone would not be able to handle this issue. Thus, scaffold was needed to replace and support the infected bone. Besides, the combination between IBS paste and bone scaffold could help the bone tissue regeneration. The nanoHA and gelatin contents of the IBS paste provided the mineral which was need for bone tissue regeneration. While the bone scaffold would support those contents by providing the extracellular matrix for the new bone tissue attachment. The IBS associated- scaffold could be an alternative to deliver spinal tuberculosis’ drug locally. This study aimed to evaluate the performance of this combination through antibacterial study and drug release test using UVVis spectrophotometer. As well as the cytotoxicity test to know the risk of these two materials within the body. The IBS was synthesized by mixing nano hydroxyapatite and 20 w/v% gelatin with ratio of 65:35 and 10% streptomycin addition as antibiotic agent. The mixture was added by hydroxypropyl methylcellulose as suspending agent. FTIR test showed that there was a chemical reaction occurred in the mixture. The performance of this combination showed that the released- streptomycin, qualitatively, could kill the Staphylococcus aureus trough the antibacterial test. Furthermore, it also had been proven that the IBS associated- scaffold could release an increasing streptomycin concentration over time. In addition, the combination showed a good result in cytotoxicity test where the cell viability was more than 50%. According to the results mentioned before, the IBS paste associated- scaffold was a promising breakthrough to overcome spinal tuberculosis case as a local drug deliver.

Streptomycin mediated biofilm inhibition and suppression of virulence properties in Pseudomonas aeruginosa PAO1.

Pseudomonas aeruginosa is known as an opportunistic pathogen whose one of the antibiotic resistance mechanisms includes biofilm formation and virulence factor production. The present study showed that the sub-minimum inhibitory concentration (sub-MIC) of streptomycin inhibited the formation of biofilm and eradicated the established mature biofilm. Streptomycin at sub-MIC was also capable of inhibiting biofilm formation on the urinary catheters. In addition, the sub-MIC of streptomycin attenuated the bacterial virulence properties as confirmed by both phenotypic and gene expression studies. The optimal conditions for streptomycin to perform anti-biofilm and anti-virulence activities were proposed as alkaline TSB media (pH 7.9) at 35°C. However, sub-MIC of streptomycin also exhibited a comparative anti-biofilm efficacy in LB media at similar pH level and temperature. Furthermore, this condition also improved the biofilm inhibition and eradication properties of streptomycin, tobramycin and tetracycline towards the biofilm formed by a clinical isolate of P. aeruginosa. Findings from the present study provide an important insight for further studies on the mechanisms of biofilm inhibition and dispersion of pre-existing biofilm by streptomycin as well as tobramycin and tetracycline under a specific culture environment.

Detection Of Streptomycin Residues In Sheep Carcasses In Duhok Province, Kurdistan Region, Iraq

In general, the Iraqi farmers of breeding and fattening of sheep using a broad-spectrum antibiotics like tetracycline and aminoglycosides family for treatment and prophylaxis without considering to the withdrawal periods of these drugs before slaughtering the animals. The aim of the present study was to determine the residues of streptomycin (member of aminoglycosides group) in sheep meat and edible tissues using enzyme linked immunosorbent assay (ELISA) method. A total of 88 samples including longissimus dorsi, diaphragmatic muscles, liver and kidney were collected from 22 sheep carcasses slaughtered in Duhok abattoir, Kurdistan, Iraq. The result revealed that streptomycin residues were found in 12 samples (54.5%) of the sheep carcasses distributed as following 36.36 %, 45.45 %, 22.72 % and 50 % of Longissimus dorsi, diaphragm muscle, liver and kidney samples., respectively. The minimal streptomycin concentration in ovine meat samples was 3.001 ppb and the maximum concentration was 690.307 ppb. The results of this study show that sheep meat, which is sold in Dohuk governorate, often contains the residues of antibiotics due to slaughtered animals might have been treated with veterinary drugs and the proper withdrawal period was not respected before slaughtering.

Streptomycin Pharmaceutical Wastewater affects the T-AOC and CAT activity of Zebrafish

Streptomycin is increasingly being used to treat human diseases. Recently, its toxic effects on aquatic organisms have attracted global attention. The aim of this study was to investigate the toxic effects of streptomycin on zebrafish by measuring T-AOC and CAT activity. Zebrafish were exposed to four different volume concentrations of streptomycin wastewater and their T-AOC and CAT activities were measured at 3, 6, 9, 12 and 15 days. T-AOC activity shows an inverted “N” trend, and T-AOC activity reached the maximum (1.90U·mgprot−1) on the 12th days. Furthermore, The CAT activity shows “M” tendency, and concentrations of streptomycin can affect CAT activity. Streptomycin wastewater induced oxidative stress in Zebrafish muscle tissue.

Symbiotic effectiveness and ecologically adaptive traits of native rhizobial symbionts of Bambara groundnut (Vigna subterranea L. Verdc.) in Africa and their relationship with phylogeny

Bambara groundnut (Vigna subterranea L. Verdc.) is an indigenous, drought-tolerant, underutilized African food legume, with the ability to fix atmospheric N2 in symbiosis with soil bacteria called rhizobia. The aim of this study was to assess the morpho-physiological, symbiotic and phylogenetic characteristics of rhizobia nodulating Bambara groundnut in Ghana, Mali and South Africa. The morpho-physiologically diverse isolates tested were also found to exhibit differences in functional efficiency and phylogenetic positions. Based on Enterobacterial Repetitive Intergenic Consensus (ERIC)-PCR banding patterns, the isolates were grouped into eight major clusters. The concentrations of Ca, Na and K in soils had a significant (p ≤ 0.01) effect on the distribution of rhizobia. Though many isolates were symbiotically very effective, the effectiveness index varied markedly (p ≤ 0.05) among them. Moreover, the isolates also exhibited tolerance to a wide range of NaCl (0.5–7%), streptomycin (50–500 µg.ml−1), and kanamycin (25–150 µg.ml−1) concentrations. Additionally, these isolates could produce 0.02 to 69.71 µg.ml−1 of indole-3-acetic acid (IAA) in tryptophan-supplemented medium, as well as solubilize tri-calcium phosphate. Phylogenetic analysis of these rhizobial isolates using 16S rRNA, atpD, glnII, gyrB, recA and symbiotic (nifH and nodC) gene sequences revealed distinct and novel evolutionary lineages related to the genus Bradyrhizobium, with some of them being very close to Bradyrhizobium vignae, B. kavangense, B. subterraneum, B. elkanii and B. pachyrhizi.

Antibiotic Resistance of Azotobacter Isolated from Mercury-Contaminated Area

Nitrogen-fixing Azotobacter is a renewable source of biofertilizer for plant growth. Increased of antibiotic level in soil due to intensive used manure is believed to induce bacterial sensitivity to antaibiotic. An antibiotic sensitivity test has been carried out to study the inhibition effect of ampicillin, streptomycin, tetracycline and chloramphenicol on Azotobacter isolated from mercury-contaminated taling. The resistance test was performend by using disc plate method in Nitrogen-free Ashby’s agar with and without mercury. The results showed that the presence of 20 mg/L mercury in plate agar totally inhibited Azotobater growth. In the absence of mercury chloride, all isolates showed different sensitivity to antibiotics. Growth of Azotobacter buru1 was only inhibited by tetracycline. Azotobacter buru2 was susceptible to high and low concentration of tetracycline and streptomycin but they were resistance to low concentration of chloramphenicol as well as ampicillin; while Azotobacter bd3a were sensitive to all tested antibiotic. In conclusion, order of Azotobacter resistance to antibiotics in the absence of mercury was Bd3a&lt;Buru2&lt;Buru1. This research have not revealed the resistance of Azotobacter to antibiotic in the presence of mercury.

Antibiotic susceptibility trend before and after long-term use of selective digestive decontamination: a 16 year ecological study.

The aim of this study was to compare antimicrobial susceptibility rates in a Spanish ICU before and after the introduction of selective digestive decontamination (SDD) and also to compare these with susceptibility data from other Spanish ICUs without SDD. We performed a retrospective study in the ICU of the University Hospital of Alava, where SDD was implemented in 2002. The SDD protocol consisted of a 2% mixture of gentamicin, colistin and amphotericin B applied on the buccal mucosa and a suspension of the same drugs in the gastrointestinal tract; additionally, for the first 3 days, systemic ceftriaxone was administered. From 1998 to 2013 we analysed the susceptibility rates for 48 antimicrobial/organism combinations. Interrupted time series using a linear dynamic model with SDD as an intervention was used. Data from other ICUs were obtained from the ENVIN-HELICS national registry. Only amoxicillin/clavulanic acid against Escherichia coli and Proteus mirabilis, and a high concentration of gentamicin against Enterococcus faecalis, resulted in a significant decrease in the susceptibility rate after the implementation of SDD, with a drop of 20%, 27% and 32%, respectively. Compared with other Spanish ICUs without SDD, the susceptibility rate was higher in the ICU of our hospital in most cases. When it was lower, differences were <10%, except for a high concentration of streptomycin against Enterococcus faecium, for which the difference was 19%. No relevant changes in the overall susceptibility rate after the implementation of SDD were detected. Susceptibility rates were not lower than those in the Spanish ICUs without SDD.

Characterization and Antibacterial Activity of Streptomycin Antibiotic Loaded Organo-Kaolinite

Antibiotics are medicines used against bacterial infection. In spite of its significance to kill bacteria, it also shows a problem with antibiotics resistance that makes it less effective to kill bacteria. Therefore, an improvement for the antibacterial agent is needed to inhibit bacteria growth and infections. Organo-kaolinite was selected in this study to act as a carrier system to improve antibacterial agent immobilization and increase the effectiveness of the antibiotic activity. Organo-kaolinite was prepared using cationic surfactant hexadecyltrimethylammonium (HDTMA) and it was adsorbed with different concentrations of streptomycin. The organo-kaolinite and streptomycin-organo-kaolinite were characterized by Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD). The characterization results showed that the attachment of cationic surfactant molecules and the adsorption of streptomycin on kaolinite surfaces did not affect the structure and the original morphology of the kaolinite. The antibacterial assay of the samples was carried out against Gram negative bacteria (Escherichia coli ATCC 11229) and Gram-positive bacteria (Enterococcus faecalis ATCC 29212) through disk diffusion technique (DDT). Based on the antibacterial assay results, streptomycin-organo-kaolinite showed better antibacterial activity compared to organo-kaolinite. This study revealed that the adsorption of streptomycin on organo-kaolinite showed a significant effect on killing bacteria and significantly increased its antibacterial activity compared to organo-kaolinite.