The search for a microbiological inhibition method for the rapid, broad-spectrum and high-throughput screening of six kinds of antibiotic residues in swine urine.

In this study, a microbiological inhibition method for rapidly screening antibiotics in swine urine was established with an easy sample pre-treatment. The microbiological system consisted of an agar medium mixed with nutrients, sensitizers, a test bacterium (Geobacillus stearothermophilus ATCC12980) and pH indicator (bromocresol purple). It was observed that the detection limits of the test kit for twenty-eight common antimicrobial residues in urine, including ß-lactams, aminoglycosides, tetracyclines, sulfonamides, macrolides, and lincosamides, were less than or equal to the maximum residue limits of the kidney, as determined by the EU and China. Moreover, the false negative rate and the false positive rate, along with other performance indexes such as interassay coefficients of variation and shelf life of the kit, all met the standard requirements of the ISO13969:2003 guidelines. Additionally, our results were consistent with those using the gold-standard physical chemistry method, which suggest the proposed method is suitable for screening antibiotic residues.

Collision cross section (CCS) as a complementary parameter to characterize human and veterinary drugs.

In the context of human and veterinary drugs identification, ion mobility spectrometry (IMS) in combination with mass spectrometry (MS) may provide a relevant complementary piece of information to mass-to-charge ratio (m/z), the so-called collision-cross-section (CCS). Up to now, however, the application of CCS as identification parameter has not been fully investigated due to the reduced number of these drugs that have being characterized in terms of CCS. This work proposes a CCS database for 92 human and veterinary drugs, including eighteen benzimidazoles, eleven 5-nitroimidazoles, eleven aminoglycosides, nineteen quinolones, eighteen ß-lactams, ten sulfonamides and five tetracyclines. Among them, 37 drugs have been characterized in terms of CCS for the first time. The CCS values of the other 55 compounds have been compared with those from a recently published database in order to evaluate inter-laboratory reproducibility, which is crucial for the implementation of the CCS as identification parameter. CCS values were measured by traveling wave ion mobility spectrometry (TWIMS) under positive ionization conditions. Nitrogen was used as drift gas in the ion mobility cell. The proposed database covers 173 ions including [M+H]+ and [M+Na]+ species. High correlation between m/z and CCS has been observed for [M+H]+ (R2 = 0.9518, n = 91) and [M+Na]+ (R2 = 0.9135, n = 82) ions. As expected, CCS values for sodium adducts are generally greater than for protonated molecules because they exhibit higher molecular weight. However, sodium adducts of aminoglycosides, ß-lactams, and of several quinolones and benzimidazoles, were characterized as more compact ions than their related protonated molecule. In addition, this work describes the fragmentation pattern observed for the studied molecules. For the first time, the main fragment ions for most of the compounds have also been characterized in terms of CCS, involving a total of 238 ions. As proof of concept, for the application of this database to biological matrices, eleven veterinary drugs in bovine urine samples were characterized in terms of CCS, showing that this parameter was not influenced by the matrix.

Sensitive fluorescence detection of etimicin based on derivatives of formaldehyde and acetylacetone.

A novel fluorescence method for the determination of etimicin is described. Etimicin reacts with acetylacetone and formaldehyde in pH 4.0 Britton-Robinson (B.R.) buffer solution to from a fluorescent substance [I]. Emission spectra of [I] and the reagent blank were overlapped, so the arithmetic emission spectra of the fluorescent substance were obtained by subtracted form the spectra of [I] to the spectra of the reagent blank using the Fluorescence Data Software. There is a linear relationship between the intensity of the arithmetic emission spectra and the concentration of etimicin. Effects of pH, amount of acetylacetone-formaldehyde, and heating time on the determination of etimicin have been examined. Etimicin can be determined over the concentration range of 1.0 to 10.0 µg mL(-1) with a correlation coefficient of 0.9991. The relative standard deviation (RSD) for 11 repetitive determinations of 5.0 µg mL(-1) etimicin is 0.22%. The utility of this method was demonstrated by determining etimicin in commercial samples.

Description and validation of coupling high performance liquid chromatography with resonance Rayleigh scattering in aminoglycosides determination.

In view of the fact that many substances generally exhibit very little ultraviolet absorbance and the absence of native fluorescence, a new strategy with simple instrumentation and excellent analytical performance combining high performance liquid chromatography (HPLC) with resonance Rayleigh scattering (RRS) was developed. It was validated for the quantification of aminoglycosides (AGs). This fact was also carefully calculated by quantum chemistry. However, the sensitivity was probably limited by the volume of flow-through cell. Therefore, the result calls for a suitable one to ensure optimal RRS signal. Interestingly, when serum or urine samples of analytes were analyzed by this method, they were all well resolved without any interference, which would hold a new perspective to be applied in the determination of substances in biological matrix.

Resonance Rayleigh-scattering spectral method for the determination of some aminoglycoside antibiotics using CdTe quantum dots as a probe.

A novel method is used for the determination of some aminoglycoside antibiotics (AGs) such as etimicin (ETM), isepamicin (ISP) and amikacin (AMK). It is based on the resonance Rayleigh scattering (RRS) intensities enhanced by AGs-induced CdTe quantum dots aggregation. Under the optimum conditions, the increments in RRS intensity were directly proportional to the concentration of AGs in certain ranges. At the same time, the second-order scattering, the frequency-doubling scattering and the frequency-trebling scattering intensities were also enhanced and their increments were proportional to the concentration of AGs. Among them, the RRS method had the highest sensitivity; the linear ranges and detection limits for ETM, ISP and AMK were 0.085-7.2, 0.0067-1.2, 0.017-6.0 and 0.025, 0.0051, 0.0020 µg mL(-1) . This method was applied to the measurement of AGs in human serum and urine with satisfactory results. In addition, the reaction mechanism and the reasons for the enhancement of RRS are discussed using fluorescence, RRS, transmission electron microscope technology and quantum chemistry method.

Tissue distribution and excretion of 125I-lidamycin in mice and rats.

AIM: To investigate the tissue distribution, urinary and fecal excretions of (125)I-lidamycin ((125)I-C-1027) in mice and its biliary excretion in rats. METHODS: The total radioactivity assay (RA method) and the radioactivity assay after precipitation with 200 mL/L trichloroacetic acid (TCA-RA method) were used to determine the tissue distribution, and the urinary and fecal excretions of (125)I-C-1027 in mice and its biliary excretion in rats. RESULTS: Tissue concentrations reached the peak at the fifth minute after administration of (125)I-C-1027 to mice. The highest concentration was in kidney, and the lowest in brain at all test-time points. The organs of the concentrations of (125)I-C-1027 from high to low were kidney, lung, liver, stomach, spleen, uterus, ovary, intestine, muscle, heart, testis, fat, and brain in mice. The accumulative excretion amounts of 0-24 h, and 0-96 h after administration of (125)I-C-1027 were 68.36 and 71.64% in urine, and 2.60 and 3.21% in feces of mice, respectively, and the accumulative excretion amount of 0-24 h was 3.57% in bile in rats. CONCLUSION: Our results reflect the characteristics of the tissue distribution, urinary and fecal excretions of (125)I-C-1027 in mice and the biliary excretion of (125)I-C-1027 and its metabolites in rats, and indicate that (125)I-C-1027 and its metabolites are mainly distributed in kidney, and excreted in urine.

Population pharmacokinetics of arbekacin, vancomycin, and panipenem in neonates.

Immature renal function in neonates requires antibiotic dosage adjustment. Population pharmacokinetic studies were performed to determine the optimal dosage regimens for three types of antibiotics: an aminoglycoside, arbekacin; a glycopeptide, vancomycin; and a carbapenem, panipenem. Eighty-three neonates received arbekacin (n = 41), vancomycin (n = 19), or panipenem (n = 23). The postconceptional ages (PCAs) were 24.1 to 48.4 weeks, and the body weights (BWs) ranged from 458 to 5,200 g. A one-compartment open model with first-order elimination was applied and evaluated with a nonlinear mixed-effect model for population pharmacokinetic analysis. In the fitting process, the fixed effects significantly related to clearance (CL) were PCA, postnatal age, gestational age, BW, and serum creatinine level; and the fixed effect significantly related to the volume of distribution (V) was BW. The final formulas for the population pharmacokinetic parameters are as follows: CL(arbekacin) = 0.0238 x BW/serum creatinine level for PCAs of <33 weeks and CL(arbekacin) = 0.0367 x BW/serum creatinine level for PCAs of > or = 33 weeks, V(arbekacin) = 0.54 liters/kg, CL(vancomycin) = 0.0250 x BW/serum creatinine level for PCAs of <34 weeks and CL(vancomycin) = 0.0323 x BW/serum creatinine level for PCAs of > or = 34 weeks, V(vancomycin) = 0.66 liters/kg, CL(panipenem) = 0.0832 for PCAs of <33 weeks and CL(panipenem) = 0.179 x BW for PCAs of > or = 33 weeks, and V(panipenem) = 0.53 liters/kg. When the CL of each drug was evaluated by the nonlinear mixed-effect model, we found that the mean CL for subjects with PCAs of <33 to 34 weeks was significantly smaller than those with PCAs of > or = 33 to 34 weeks, and CL showed an exponential increase with PCA. Many antibiotics are excreted by glomerular filtration, and maturation of glomerular filtration is the most important factor for estimation of antibiotic clearance. Clinicians should consider PCA, serum creatinine level, BW, and chemical features when determining the initial antibiotic dosing regimen for neonates.

Analysis of antibiotics by capillary electrophoresis.

Recent developments in the characterization of antibiotics are reviewed. Many capillary electrophoretic techniques have been utilized in their analyses, addressing various aspects of quantifying, profiling, and monitoring. Laser-induced fluorescence detection systems demonstrated their usefulness in clinical settings and in the monitoring of residue levels in food matrices. Different sample introduction methods have been explored, enhancing detection sensitivity, or reducing or eliminating sample manipulation prior to injection.

Effects of compound injection of Pyrola rotundifolia L and Astragalus membranaceus Bge on experimental guinea pigs' gentamicin ototoxicity.

In attempting to find drugs effective in preventing and remedying ototoxic injury caused by aminoglycoside antibiotics, we relied on the theory that the induction of ototoxic injury by aminoglycoside antibiotics is related to a decrease of cyclic adenosine monophosphate and RNA content in the cochlea or a dysfunction of the kidney. We selected Pyrola rotundifolia L and Astragalus membranaceus Bge from traditional Chinese herbal medicine, made a compound injection of them, and observed the effect on the pattern of gentamicin ototoxicity in guinea pigs. By electrocochleography and morphology by scanning electron microscopy, the experimental results indicated that the Chinese herbal compound possessed the definite effect of protecting the guinea pig cochlea. The determination of blood urea nitrogen, urinary N-acetyl-D-aminoglucosidase, and urinary protein and observation of renal morphology showed that it also protected the kidney against nephrotoxic nephritis of gentamicin. The conjecture that protection of the kidney by the Chinese herbs may be one of the important factors in preventing ototoxicity supports some explanations of ototoxic mechanisms induced by aminoglycoside antibiotics.

Systemic absorption of endotracheally administered aminoglycosides in seriously ill patients with pneumonia.

A study was performed with 10 hospitalized patients to determine the percentage of an aminoglycoside dose (tobramycin or gentamicin) that is absorbed systemically after being instilled into the endotracheal tube at steady state. All patients were on respirators, had indwelling urinary catheters, and had creatinine clearances estimated to be greater than or equal to 40 ml/min. Tobramycin or gentamicin (40 mg) was instilled every 4 h directly into the endotracheal tube. Nine patients also received systemically a different aminoglycoside from that administered through the endotracheal tube. Urine was collected over a 4-h dosing interval at steady state (after at least 5 doses of the drug). The amount of aminoglycoside excreted over the 4-h interval was measured and expressed as percentage of the dose administered over that period. The range of percentage of dose absorbed was 1.5 to 34%, with a mean of 16.7 +/- 11.4% standard deviation and a median of 16.5%. The coefficient of variation was 68%. Levels of the endotracheally administered aminoglycoside in serum were measured, and all were less than 1.0 microgram/ml. While a large degree of variability in absorption was observed in this study, significant amounts of aminoglycosides could be absorbed in some patients. However, levels apparently did not accumulate in sera of patients with adequate renal function, and an empirical dosage reduction in intravenous aminoglycoside should not be necessary with the addition of endotracheally instilled aminoglycoside in patients with creatinine clearances greater than 40 ml/min.

[Pharmacokinetics of arbekacin in dogs. I. Serum concentration and urinary excretion].

A new aminoglycoside antibiotic, arbekacin (HBK) was intramuscularly and intravenously administered to dogs in order to study its pharmacokinetics in comparison to amikacin (AMK). The results obtained are summarized as follows. Serum concentrations of HBK were well correlated with dose levels. The dose-serum concentration relationship with HBK was similar to other aminoglycoside antibiotics. Biological half-lives of HBK and AMK were both about 1 hour in dogs. This was also similar to other aminoglycoside antibiotics. There was no significant difference in peak serum concentrations between 1 hour intravenous infusion and intramuscular injection of HBK at 2 mg/kg in dogs. Repetitive administration of HBK to dogs at 2 mg/kg twice a day for 14 days did not affect its serum concentration and biological half-life. Urinary excretion of HBK in dogs in 24 hours after administration accounted for about 80-90%.

Study on pulmonary, prostatic and renal (medulla and cortex) distribution of sagamicin at different time intervals.

In order to assess the therapeutic activity of an antibiotic, not only its serum kinetics but also its kinetics in the peripheral tissues must be determined, thus evaluating the specific power of penetration of the drug. Sagamicin is an aminoglycosidic basic antibiotic closely related to gentamicin and its penetration rate into lungs, kidney and prostate, together with its serum concentrations time-course, were investigated. The findings obtained showed that this antibiotic attained a good distribution in the peripheral tissues, where it easily reached therapeutic levels.

Renal disposition of gentamicin, dibekacin, tobramycin, netilmicin, and amikacin in humans.

The tubular disposition of five aminoglycosides was studied in humans to establish a possible relationship between tubular reabsorption and the nephrotoxicity that has been described in the literature. Thirty-three healthy male volunteers received a continuous intravenous infusion of isotonic saline with inulin, followed 1 h later by inulin plus gentamicin, dibekacin, tobramycin, netilmicin, or amikacin (1 mg/kg per h) or amikacin (4 mg/kg per h) over a period of 2 h. Brain-stem-evoked response audiometry was performed both before and at the end of each infusion. The latency of wave V remained constant whichever antibiotic was considered. The glomerular filtration rate did not vary significantly during the infusion of each drug. The percent fractional excretion was 79 +/- 6, 81 +/- 22, 85 +/- 5, and 99 +/- 9 for gentamicin, dibekacin, tobramycin, and netilmicin, respectively, and 83 +/- 4 and 124 +/- 13 for amikacin at concentrations of 1 and 4 mg/kg per h, respectively. Net balance and renal clearance were similar for the five aminoglycosides when administered at a rate of 1 mg/kg per h. With gentamicin only, fractional excretion was correlated with the urinary flow rate. We can conclude that (i) gentamicin, generally considered the most nephrotoxic agent, had the highest degree of net reabsorption; (ii) netilmicin exhibited a net zero tubular balance; (iii) amikacin had different patterns of tubular disposition according to the dose, i.e., reabsorption at 1 mg/kg per h and secretion at 4 mg/kg per h, raising the hypothesis of a saturable process of reabsorption; and (iv) these differences in tubular reabsorption could account at least in part for the known different nephrotoxic potentials of these five aminoglycosides in humans.

In vitro effect of new penicillins and aminoglycosides on tests for glycosuria.

The effect of newer penicillins (azlocillin, mezlocillin, cyclacillin, and piperacillin) a 6 beta-amidinopenicillanic acid derivative (amdinocillin), and newer aminoglycosides (netilmicin and sisomicin) on the accuracy of tests for glycosuria was studied. Solutions of each of the drugs were prepared in urine in a range of clinically obtainable drug concentrations. In addition, urine solutions were prepared that contained the same drug concentrations and 0.5, 1, and 2% glucose. All solutions were tested in triplicate using the five-drop Clinitest method and two glucose oxidase methods (Diastix and Tes-Tape). Falsely elevated Clinitest readings of approximately 0.25% were obtained with the penicillins. These readings were influenced by the concentration of the penicillins and of glucose. Neither amdinocillin nor the aminoglycosides had an effect on Clinitest determinations. None of the drugs interfered with Diastix or Tes-Tape readings. Because the Clinitest-penicillin interaction is unpredictable, Clinitest results should be rechecked using one of the qualitative glucose oxidase tests when Clinitest is used as a quantitative test for glycosuria in patients receiving penicillins. All three tests studied can be used to test for glycosuria in patients receiving amdinocillin or one of the aminoglycosides.

[Pharmacokinetic studies on micronomicin in dogs. Comparison of intramuscular and drip intravenous administration models].

The pharmacokinetics of micronomicin (MCR) were studied in dogs after intramuscular (i.m.) and drip intravenous (d.i.v., 0.5, 1 and 2 hours) administration (10 mg/kg). After i.m. administration, the plasma levels of MCR followed a one-compartment open model, and after d.i.v. administration it followed a two-compartment open model. The peak plasma levels of MCR after i.m., 0.5, 1 and 2 hours d.i.v. administration were 28.7 +/- 6.5, 36.7 +/- 3.6, 30.2 +/- 5.1 and 20.3 +/- 2.3 mcg/ml, respectively. The pharmacokinetic parameters (T1/2, AUC, Kel, Vd and Cl) of MCR except Cmax and Tmax were not differentiated by the route of administration. Urinary recovery of MCR after d.i.v. administration was equal to that of MCR after i.m. administration.

[Pharmacokinetic studies of micronomicin using a continuous intravenous infusion method].

The basic pharmacokinetics of micronomicin (MCR) were studied in 4 healthy adult volunteers. MCR 60 and 120 mg were intravenously administered in 30 and 60 minutes at constant rates by means of continuous infusion apparatus. The same dosages were also tested by intramuscular route. The concentrations of MCR in serum and urine were determined by HPLC and analyzed following the two-compartment open model after intravenous treatment and following the one-compartment open model after intramuscular treatment. When MCR was given by intramuscular route, the mean serum concentration of 4 subjects reached a peak of 3.98 micrograms/ml at 30 minutes after a dose of 60 mg and 6.7 micrograms/ml at 30 minutes after that of 120 mg. The peak concentration was achieved at the end of intravenous infusion and was dose-related, since it was 6.1 and 10.5 micrograms/ml after a 30-minute infusion of 60 and 120 mg, respectively, and 4.85 and 9.43 micrograms/ml after a 60-minute infusion of 60 and 120 mg, respectively. At 8 hours, concentrations dropped to less than 0.1 microgram/ml and to 0.2 microgram/ml or less after 60 and 120 mg, respectively, regardless of the route and rate of administration. The mean urinary recovery up to 8 hours ranged 84 to 92% of the dose. There were no appreciable differences in pharmacokinetic parameters among 4 modes of intravenous infusion, with a T1/2(beta) of 1.43 approximately 2.02 hours. In the case of intramuscular treatment, parameters analyzed following the one-compartment open model were on similar levels to corresponding values found after intravenous treatment and the T1/2 was 1.39 hours after 60 mg and 1.43 hours after 120 mg.(ABSTRACT TRUNCATED AT 250 WORDS)