Comparative toxicity of oxytetracycline and its semisynthetic derivatives, methacycline and doxycycline

The acute toxicity parameters of oxytetracycline and its semisynthetic derivatives was determined on laboratory animals of various species. The three antibiotics were described as belonging to the group of low toxic compounds according to the classification adopted in industrial toxicology. However, the absolute values of LD50 indicated that doxycycline was 5.6 or 2.8 times more toxic than oxyteyracycline or methacycline respectively. In addition, doxycycline had the most pronounced hepatoxic effect.     

Effects of disodium salt of ethylenediaminetetraacetic acid (Na2EDTA) and tetracyclines on drug resistant bacteria. Studies in vitro

An effect of Na2EDTA and tetracycline (oxytetracycline and doxycycline) resistant strains of Staphylococcus aureus and Pseudomonas aeruginosa was tested. The strains were isolated from clinical specimens. The tests were performed in vitro by serial dilutions of the drugs in liquid medium. MIC for Na2EDTA, tetracyclines and a combination of Na2EDTA and tetracyclines was determined. It was shown that the combination of oxytetracycline or doxycycline with Na2EDTA caused changes in sensitivity of Staphylococcus aureus and Pseudomonas aeruginosa resistant to these antibiotics. After an application of the mixture of various concentrations of tetracycline and Na2EDTA it was observed that, with the reduction of the effective Na2EDTA dose by about half, the lowest concentrations of tetracyclines inhibiting the growth of resistant bacteria were 2-64 times lower than MIC values of antibiotics without Na2EDTA.     

Study of oxytetracycline solubility in an aqueous medium]

Solubility of oxytetracycline dihydrate in aqueous media was studied. It was shown that solubility of the drug in bidistillate at a temperature of 20 degrees was 195 gamma/ml, which was much lower than the requirements of some pharmacopoeia with respect to the drug solubility. Dependence of oxytetracycline dihydrate solubility in the aqueous medium on the values of pH and temperature was found. Indigency of the procedure described in the literature for determination of antibiotic solubility according to the dry weight of the filtrate on addition of large excesses of the solid phase to the system was shown.     

Effect of a high dose of three antibiotics on the reproduction of a parthenogenetic strain of Folsomia candida (Isotomidae: Collembola)

Folsomia candida Willem (Isotomidae: Collembola) is an edaphic parthenogenetic species commonly used in ecotoxicity studies. We exposed F. candida to a high dose of three antibiotics, tylosin, ampicillin, and oxytetracycline, that target different bacterial groups. Possible toxic effects were assessed through egg production, hatching, and body size. All three antibiotics caused toxic effects. Treatment with oxytetracycline proved the most toxic. This group showed the smallest body size and lowest number of eggs laid, likely the result of a combination of antibiotic toxicity and avoidance of the antibiotic spiked food. Active toxin avoidance by F. candida in toxicological assays may play a role in minimizing their exposure to toxic compounds. Despite the administration of high doses of oxytetracycline, F. candida individuals remained infected with the intracellular bacteria Wolbachia indicating that this strain is resistant to this antibiotic or that the host or its gut flora had detoxified the compound. An increase in percent egg hatch with time was seen in the ampicillin and oxytetracycline treatments, indicating a possible accommodation of the host and/or gut-flora to these antibiotics.     

Use of metal chelate affinity chromatography and membrane-based ion-exchange as clean-up procedure for trace residue analysis of tetracyclines in animal tissues and egg

A new and efficient procedure for the clean-up of tetracycline residues in animal tissues and egg prior to reversed-phase high-performance liquid chromatography is described. The principal steps involve homogenization of the tissues in sodium succinate buffer and methanol, followed by centrifugation and clean-up with metal chelate affinity chromatography (MCAC). After further concentration on an Empore extraction membrane with cation-exchange properties, the sample is analysed by HPLC with fluorescence detection. The method was tested on porcine kidney and muscle, bovine liver and whole chicken's egg. The recoveries were determined from spiked tissues for oxytetracycline, tetracycline, chlortetracycline and doxycycline and ranged from 40 to 70%, with repeatabilities below 10% R.S.D.. The analytical responses were linear in the range up to at least 1000 ng/g. The detection limits of the method were estimated at 0.42 ng/g of oxytetracycline, 0.49 ng/g of tetracycline, 0.66 ng/g of chlortetracycline and 1.38 ng/g of doxycycline in porcine muscle, using signal-to-noise ratios of 4:1. Similar detection limits were estimated for kidney, liver and egg. The measured limits of quantification were 2 ng/g for oxytetracycline, 3 ng/g for tetracycline, 4 ng/g for chlortetracycline and 5 ng/g for doxycycline in porcine kidney. The advantage of this method over existing methods is its increased limit of detection.     

Treatment of tetracycline antibiotics by laccase in the presence of 1-hydroxybenzotriazole

Tetracycline antibiotics are widely used in human and veterinary medicine; however, residual amounts of these antibiotics in the environment are of concern since they could contribute to selection of resistant bacteria. In this study, tetracycline (TC), chlortetracycline (CTC), doxycycline (DC) and oxytetracycline (OTC) were treated with laccase from the white rot fungus Trametes versicolor in the presence of the redox mediator 1-hydroxybenzotriazole (HBT). High performance liquid chromatography demonstrated that DC and CTC were completely eliminated after 15 min, while TC and CTC were eliminated after 1 h. This system also resulted in a complete loss of inhibition of growth of Escherichia coli and Bacillus subtilis and the green alga Pseudokirchneriella subcapitata with decreasing tetracycline antibiotic concentration. These results suggest that the laccase-HBT system is effective in eliminating tetracycline antibiotics and removing their ecotoxicity.     

Tetracycline resistance determinants from groups A to D vary in their ability to confer decreased accumulation of tetracycline derivatives by Escherichia coli

The ability of four genetically distinct plasmid-located tetracycline resistance determinants (TetA, B, C and D) to confer decreased accumulation of tetracycline and some of its analogues by Escherichia coli K12 was examined. Accumulation of oxytetracycline, tetracycline, demethylchlorotetracycline, 6-demethyl-6-deoxy-5-hydroxy-6-methylene-tetracycline, chlorotetracycline, doxycycline and 6-demethyl-6-deoxytetracycline was examined by fluorescence spectroscopy. The determinants varied in their ability to promote decreased accumulation of tetracyclines, defined as an R+/R- fluorescence ratio of less than 0.85. Plasmid pIP7 (TetA) caused reduced accumulation of only oxytetracycline, tetracycline and chlorotetracycline, but plasmid pDU301 (TetB) promoted reduced accumulation of all the compounds tested except 6-demethyl-6-deoxytetracycline. The TetC determinant of pBR322 caused decreased uptake of five derivatives, but not doxycycline or 6-demethyl-6-deoxytetracycline. Plasmid RA1 (TetD) encoded reduced accumulation of oxytetracycline, tetracycline, 6-demethyl-6-deoxy-5-hydroxy-6-methylenetetracycline and chlorotetracycline. In general, the resistance determinants were more efficient in promoting decreased accumulation of hydrophilic tetracyclines. These accumulation studies provide a satisfactory method for the phenotypic identification of Tet resistance determinants.     

土霉素暴露对小麦根际抗生素抗性细菌及土壤酶活性的影响

通过培养的方法研究了土霉素暴露和小麦根际抗性细菌的数量、种类、分布特征及土壤酶活性之间的剂量效应关系。结果表明,土霉素暴露下小麦根际单一抗生素抗性细菌数量和抗土霉素—链霉素双重抗性细菌数都明显增加,且与暴露剂量呈正效应关系;同时,土壤磷酸酶、脱氢酶活性下降,但与土霉素的剂量效应关系不明显。从土霉素暴露的土壤中分离到50株抗性细菌,经形态观察、RFLP分组和16S rDNA序列测定与分析,将它们聚集在Actinobacteria、Bacilli、Alphaproteobacteria、Gammaproteobacteria 和Sphingobacteria类群。其中放线菌最多（15株）,占抗性菌总数的30 %;其次是Bacillus属细菌（9株）和Pseudomonas属细菌（8株）,分别占18 %和16 %。同时,具有抗性的人类机会致病菌Pseudomonas、Sphingomonas和Stenotrophomonas属细菌在土霉素暴露的样品中均被分离到,分别占抗性菌株总数的16 %、8 %和4 %。值得注意的是,随着土霉素暴露剂量的增加,小麦根际优势促生菌Bacillus属细菌的抗性检出率逐步降低;但具有抗生素抗性的人类机会致病菌Pseudomonas、Sphingomonas和Stenotrophomonas属细菌的检出率却明显增加,提示可能会进一步增大其机会致病性。     

O2- photogenerated from aqueous solutions of tetracycline antibiotics (pH 7.3) as evidenced by DMPO spin trapping and cytochrome c reduction

UV-irradiation of several tetracycline antibiotics in aqueous buffer (pH 7.3) resulted in the generation of the superoxide anion radical (O2-) which was detected by cytochrome c reduction and by spin trapping with 5,5-dimethyl-1-pyrroline-N-oxide and was inhibited by superoxide dismutase. A comparison of the O2- yields from the tetracyclines examined showed the trend chlortetracycline (CTC) greater than oxytetracycline (OXY) greater than demeclocycline (DEM) much greater than (doxycycline (DOXY) = tetracycline (TC) = minocycline (MINO) = 0). This trend is in reasonable agreement with clinical reports that CTC, OXY and DEM are potent photosensitizers, TC is only weakly phototoxic whereas MINO is not. These findings suggest that the O2- production may be involved in tetracycline-induced phototoxicity. While the two methods for O2- detection gave comparable results for most of the tetracyclines, the spin trapping technique was clearly superior for DOXY which reduced cytochrome c in the dark.     

Factors Which Influence Synergism by Neomycin and Oxytetracycline

Six strains of enteropathogenic gram-negative bacteria were tested for susceptibility to neomycin or oxytetracycline alone and combined in fixed ratios. The minimal inhibitory concentration for the combination was less than one-half of that expected if the antibiotic activities were simply additive. Neomycin alone was more effective against bacteria multiplying in the presence of abundant oxygen, whereas oxytetracycline alone was more effective against bacteria multiplying in relatively anaerobic environments; when combined, the antibiotics complemented each other by their opposing optima for activity. Oxygen concentration, pH, and neomycin activity are related, and the depression of acid production by oxytetracycline is believed to be partially responsible for the synergistic activity of this pair of antibiotics.     

Synthesis and anti Methicillin resistant Staphylococcus aureus activity of substituted chalcones alone and in combination with non-beta-lactam antibiotics

A total of 30 chalcone analogues was synthesized via a base catalyzed Claisen Schmidt condensation and screened for their in vitro antibacterial activity against Methicillin-sensitive Staphylococcus aureus (MSSA) and Methicillin-resistant Staphylococcus aureus (MRSA) alone or in combination with non beta-lactam antibiotics namely ciprofloxacin, chloramphenicol, erythromycin, vancomycin, doxycycline and gentamicin. In the checkerboard technique, fractional inhibitory concentration indices (FICI) show that the following combinations like ciprofloxacin with 25 (4'-bromo-2-hydroxychalcone); doxycycline with 21 (4-hydroxychalcone); doxycycline with 25; and doxycycline with 4 (2',2-dihydroxychalcone) were synergistic against MRSA. In term SAR study, the relationship between chalcone structure and their antibacterial activity against S. aureus and synergy with tested antibiotics were discussed. Possible mechanisms for antibacterial activity of chalcones alone as well as the synergistic effect in combinations were proposed by molecular modeling studies, respectively. Combinations of chalcones with conventional antibiotics could be an effective alternative in the treatment of infection caused by MRSA.     

Simultaneous determination of selected veterinary antibiotics in gilthead seabream (Sparus Aurata) by liquid chromatography-mass spectrometry

A method was optimised and validated for simultaneous monitoring of several drugs of different classes of antibiotics such as quinolones (oxilinic acid and flumequine), tetracyclines (oxytetracycline), sulfonamides (sulfadiazine) and trimethoprim in fish muscle and skin. The method is based on solid-liquid extraction without further sample clean up followed by liquid chromatography-mass spectrometry (LC-MS) determination with electrospray ion source (ESI) in positive mode. The limits of quantification (LOQs) were lower than 20 microg/kg for all compounds and repeatability, expressed as relative standard deviations (RSD), were lower than 15%. Therefore, the LC-MS method was successfully applied for the quantitative determination of antibiotics in gilthead sea bream muscle and skin and oxytetracycline in medicated fishes.     

猪粪和土霉素对不同肥力土壤微生物数量及活性的影响

在不施肥和施用猪粪两种情况下,采用培养试验研究了不同浓度土霉素污染(0、0.1、1、10、100和1000 mg·kg^-1)对土壤细菌丰度、酶活性和NO₃-N浓度等的影响.试验培养温度为25 ℃,培养时间为30 d,取样分析时间分别为1、4和30 d.结果表明：在不施肥条件下,土霉素污染对土壤细菌数量及微生物活性的影响较小,土壤S₁、S₂和S₃细菌数量、呼吸强度、酶活性和NO₃-N浓度下降10%时土霉素的剂量（EC₁₀）分别为36～1000 mg·kg^-1、20～1000 mg·kg^-1和4～1000 mg·kg^-1;而在施用猪粪的情况下,对应的数值分别为2～656 mg·kg^-1、2～81 mg·kg^-1和1～42 mg·kg^-1.添加土霉素对土壤细菌及酶活性的影响随土壤肥力的提高而增大,且其对土壤细菌数量和呼吸强度的影响大于对酶活性和NO₃-N浓度的影响.土霉素污染对土壤微生物数量和活性的影响随时间变化而变化,一般在培养4 d时的影响最为明显.土霉素对土壤微生物的影响总体上表现为抑制作用.     

Rapid determination of tetracycline antibiotics in serum by reversed-phase high-performance liquid chromatography with fluorescence detection

A rapid and accurate determination of tetracycline antibiotics in human serum by reversed-phase high-performance liquid chromatography with fluorescence detection has been developed, based on protein precipitation in serum. Various reagents for precipitation were investigated, and 24% trichloroacetic acid in methanolic solution gave the maximum recovery (at least 94.3%) and interference-free chromatograms of different three tetracyclines. At a concentration of 0.5 μg/ml, the precision (relative standard deviation) ranged from 1.12 to 1.94%. In the range 0.04–10.0 μg/ml for oxytetracycline and chlorotetracycline and 0.01–10.0 μg/ml for tetracycline, linear responses were observed. The detection limits of this method were 10–35 ng/ml for all three antibiotics. The proposed method was applied to the determination of serum concentrations in subjects receiving tetracycline antibiotics.     

蝇蛆肠道微生物菌群对猪粪残留抗生素的降解及抗性基因的影响

【目的】过度使用抗生素作为动物饲料添加剂,导致畜禽粪便已成为抗生素抗性基因的主要蓄积库,为了研究蝇蛆(Musca domestica)对猪粪中残留抗生素及抗性基因的影响,本文动态采集了实际农场条件下蝇蛆转化过程中猪粪堆体及虫体样本。【方法】利用q PCR、液相色谱-电喷雾质谱、同位素内标法、Illumina高通量测序以及局部相似性研究蝇蛆生物转化过程中残留抗生素降解效能及相关抗性基因组变化的微生物生态机制。【结果】6 d周期内,猪粪中四环素、土霉素、金霉素、强力霉素、磺胺嘧啶、诺氟沙星、氧氟沙星、环丙沙星以及恩诺沙星等9种残留抗生素含量显著下降,累积减量为34.3%–58.1%,每日减量百分比介于7.8%–57.4%之间。猪粪中共检测到的158种抗性基因,其中有118种大幅衰减,衰减量平均达79.3%;23种抗性基因存在富集现象,富集倍数平均为3.48。在蝇蛆肠道的作用下,粪源微生物群落中Bacteroidetes相对丰度下降,Proteobacteria相对丰度增加,尤其是Ignatzschineria增幅最大。网络分析发现,抗性基因的增减与微生物群落的变化显著相关,与抗性基因衰减相关的微生物主要属于Clostridiales和Bacteroidales,而与抗性基因富集相关的微生物主要为Alcaligenaceae、[Weeksellaceae]及Bacillales。【结论】蝇蛆可有效削减猪粪中的残留抗生素及防控抗性基因向环境扩散。     

Genetic and physiological characterization of oxytetracycline-resistant bacteria from giant prawn farms

Four hundred and thirteen oxytetracycline-resistant bacteria were recovered from six freshwater giant prawn farms with a history of oxytetracycline use. Most oxytetracyclineresistant isolates were Gram-negative bacteria. Six groups of oxytetracycline-resistant bacteria were classified using cluster analysis based on a comparison of levels of oxytetracycline resistance. Complex fingerprint patterns were obtained for 71 isolates studied. In general, the band patterns of isolates from different ponds were very similar, and the data indicated that the isolates were closely related. The exploration for crossresistance found that most of the 71 oxytetracycline-resistant isolates were also resistant to tetracycline and chlortetracycline, but had a relatively low resistance to doxycycline. Many isolates showed higher chlortetracycline resistance than oxytetracycline resistance. Additionally, the oxytetracyclineresistant isolates were examined for the presence of tetracycline resistance (tet) genes. Fifty percent of the isolates carried one of the 14 known tet genes examined. The most common determinants were TetA and TetD. However, TetB, TetC, TetE, TetK, TetL, and TetM were also found with various frequencies.     

In vitro antibiotic susceptibility of bacteria isolated from EUS-affected fishes in India

AIMS: Twelve antibiotics were evaluated for in vitro sensitivity against 16 bacterial strains isolated from surface lesions of fishes affected with epizootic ulcerative syndrome (EUS). METHODS AND RESULTS: Disc diffusion assay in Mueller-Hinton agar showed that the pseudomonads and aeromonads were mainly resistant to penicillin, ampicillin and erythromycin. Additionally, some were resistant to gentamycin and amoxycillin. However, resistance towards antibiotics previously recommended for EUS treatment, such as oxytetracycline and chloramphenicol, was not observed. Four aeromonads and two pseudomonads were found to induce ulcers when injected intramuscularly in healthy Anabas testudineus. CONCLUSIONS: All six pathogenic isolates were sensitive towards oxytetracycline, chloramphenicol and nalidixic acid. Oxytetracycline seems to be an effective antibiotic, and further investigations to determine the mode of treatment and dose appear to be worthwhile.     

Interference of Iron with the Absorption of Tetracylines in Man

Ferrous sulphate administered together with tetracycline and three of its derivatives—oxytetracycline, methacycline, and doxycycline—was found seriously to impair the absorption of these antibiotics. Thus even small doses of iron taken simultaneously should be avoided during tetracycline treatment.     

Characterization of the superoxide anion radical scavenging activity by tetracycline antibiotics in aprotic media

The tetracycline family antibiotics are widely used as human and veterinary treatments. The drugs are effective as antibiotics and also show antimicrobial and non‐microbial action. However, the antioxidant properties of tetracyclines have not been characterized in aprotic media. To better understand their biological functions, the in vitro superoxide anion radical () scavenging activities of tetracycline, chlortetracycline, oxytetracycline, doxycycline and methacycline were characterized, along with a very efficient scavenger, tiron, in dimethyl sulphoxide (DMSO), using ultra‐weak chemiluminescence (CL). We found that tetracycline, chlortetracycline and doxycycline efficiently inhibited CL from the ‐generating system at concentration levels of 0.02–1.0 mmol/L. Methacycline and oxytetracycline were the scavengers at concentration levels of 0.01–0.1 mmol/L, whereas when their concentration was lowered the drugs were capable of generating , leading to CL enhancement. For all the data obtained in this study, the scavenging activity for the compounds tested decreased in the following order: tetracycline > doxycycline > chlortetracycline > tiron methacycline > oxytetracycline. These results indicate that the tetracycline drugs directly alter redox chemistry in aprotic media. Copyright © 2011 John Wiley & Sons, Ltd.     

Metallic ion content and damage to the DNA in oral mucosa cells of children with fixed orthodontic appliances

Although the metal devices used in orthodontic treatments are manufactured highly resistance to corrosion, they may still suffer some localized corrosion resulting from the oral cavity conditions. The corrosion causes the release of metals from the alloys used for their manufacture. In this report, we evaluated the in vivo metal ions release of three alloys (stainless steel, titanium and nickel-free) usually used in the orthodontics treatments and its genotoxicity. We applied to 15 patients, between 12 and 16 years, 4 tubes and 20 brackets. Samples from oral mucosa were taken before the treatment and 30 days later. The concentration of the titanium, chromium, manganese, cobalt, nickel, molybdenum and iron were detected using inductively coupled plasma mass spectrometry (ICP-MS). The genotoxicity was measured with a comet assay (Olive moment). The oral mucosa cells in contact with the stainless steel alloy displayed the greatest titanium and manganese concentrations and those in contact with the nickel-free alloy presented the greatest concentration of chromium and iron. Both alloys, stainless steel and nickel-free, induced a higher DNA damage in the oral mucosa cells than the titanium alloy, in which the Olive moment was similar to controls. Based on the results of our study, we can conclude that titanium brackets and tubes are the most biocompatible of the three alloys.