Penicillins and cephalosporins. Physicochemical properties and analysis in pharmaceutical and biological matrices

Construction of a model of endometritis in domestic rabbits using equine-derived pathogens and evaluation of therapeutic effect of sensitive drugs

Pathogenic bacteria were isolated from the uterine lavage fluid of a mare with endometritis. After identification and purification, the pathogenic bacteria were injected into the uterus of rabbits to induce endometritis. Then, anatomical, blood routine, chemical examination, and histopathological examinations were performed on the rabbits. Rabbit uterus was collected, and quantitative polymerase chain reaction (qPCR) was used to detect the mRNA expression of inflammatory factors including IL-1β, IL-6, and TNF-α in the rabbit uterus. In addition, enzyme-linked immunosorbent assay (ELISA) was used to detect the uterine concentrations of the inflammatory factors IL-1β, IL-6, and TNF-α. Western Blot was used to detect the protein expressions of NF-kB, IkBα, and TNF-α in the NF-kB pathway. An antibiotic treatment group was also set up to verify the accuracy of the results. The clinical examination results showed that there was a significant increase of leukocytes in the blood of the rabbits in the model group (P < 0.01). The uterus was congested, enlarged, and purulent. The integrity of the uterine lining was destroyed, and there was a significant increase of lymphocytes in the uterus (P < 0.01). The qPCR and ELISA results showed that the expressions of the inflammatory factors IL-1β, IL-6, and TNF-α in the uterus of rabbits were significantly increased (P < 0.01). Western blot results showed that the inflammatory factors IL-1β, IL-6, and TNF-α play a role in promoting inflammation through the NF-kB pathway. The results of the test provide a simple, economical, and reliable means of studying the occurrence, development, prevention, and treatment of equine endometritis.

Stability of β-lactam antibiotics in bacterial growth media

Laboratory assays such as MIC tests assume that antibiotic molecules are stable in the chosen growth medium-but rapid degradation has been observed for antibiotics including β-lactams under some conditions in aqueous solution. Degradation rates in bacterial growth medium are less well known. Here, we develop a 'delay time bioassay' that provides a simple way to estimate antibiotic stability in bacterial growth media, using only a plate reader and without the need to measure the antibiotic concentration directly. We use the bioassay to measure degradation half-lives of the β-lactam antibiotics mecillinam, aztreonam and cefotaxime in widely-used bacterial growth media based on MOPS and Luria-Bertani (LB) broth. We find that mecillinam degradation can occur rapidly, with a half-life as short as 2 hours in MOPS medium at 37°C and pH 7.4, and 4-5 hours in LB, but that adjusting the pH and temperature can increase its stability to a half-life around 6 hours without excessively perturbing growth. Aztreonam and cefotaxime were found to have half-lives longer than 6 hours in MOPS medium at 37°C and pH 7.4, but still shorter than the timescale of a typical minimum inhibitory concentration (MIC) assay. Taken together, our results suggest that care is needed in interpreting MIC tests and other laboratory growth assays for β-lactam antibiotics, since there may be significant degradation of the antibiotic during the assay.

Abundance and Antimicrobial Resistance of Three Bacterial Species along a Complete Wastewater Pathway

After consumption, antibiotic residues and exposed bacteria end up via the feces in wastewater, and therefore wastewater is believed to play an important role in the spread of antimicrobial resistance (AMR). We investigated the abundance and AMR profiles of three different species over a complete wastewater pathway during a one-year sampling campaign, as well as including antimicrobial consumption and antimicrobial concentrations analysis. A total of 2886 isolates (997 Escherichia coli, 863 Klebsiella spp., and 1026 Aeromonas spp.) were cultured from the 211 samples collected. The bacterial AMR profiles mirrored the antimicrobial consumption in the respective locations, which were highest in the hospital. However, the contribution of hospital wastewater to AMR found in the wastewater treatment plant (WWTP) was below 10% for all antimicrobials tested. We found high concentrations (7-8 logs CFU/L) of the three bacterial species in all wastewaters, and they survived the wastewater treatment (effluent concentrations were around 5 log CFU/L), showing an increase of E. coli in the receiving river after the WWTP discharge. Although the WWTP had no effect on the proportion of AMR, bacterial species and antimicrobial residues were still measured in the effluent, showing the role of wastewater contamination in the environmental surface water.

Role of epaQ, a Previously Uncharacterized Enterococcus faecalis Gene, in Biofilm Development and Antimicrobial Resistance

Enterococcus faecalis is a commensal of the human gastrointestinal tract; it is also an opportunistic pathogen and one of the leading causes of hospital-acquired infections. E. faecalis produces biofilms that are highly resistant to antibiotics, and it has been previously reported that certain genes of the epa operon contribute to biofilm-associated antibiotic resistance. Despite several studies examining the epa operon, many gene products of this operon remain annotated as hypothetical proteins. Here, we further explore the epa operon; we identified epaQ, currently annotated as encoding a hypothetical membrane protein, as being important for biofilm formation in the presence of the antibiotic daptomycin. Mutants with disruptions of epaQ were more susceptible to daptomycin relative to the wild type, suggesting its importance in biofilm-associated antibiotic resistance. Furthermore, the ΔepaQ mutant exhibited an altered biofilm architectural arrangement and formed small aggregates in liquid cultures. Our cumulative data show that epa mutations result in altered polysaccharide content, increased cell surface hydrophobicity, and decreased membrane potential. Surprisingly, several epa mutations significantly increased resistance to the antibiotic ceftriaxone, indicating that the way in which the epa operon impacts antibiotic resistance is antibiotic dependent. These results further define the key role of epa in antibiotic resistance in biofilms and in biofilm architecture.IMPORTANCE E. faecalis is a common cause of nosocomial infection, has a high level of antibiotic resistance, and forms robust biofilms. Biofilm formation is associated with increased antibiotic resistance. Therefore, a thorough understanding of biofilm-associated antibiotic resistance is important for combating resistance. Several genes from the epa operon have previously been implicated in biofilm-associated antibiotic resistance, pathogenesis, and competitive fitness in the GI tract, but most genes in this locus remain uncharacterized. Here, we examine epaQ, which has not been characterized functionally. We show that the ΔepaQ mutant exhibits reduced biofilm formation in the presence of daptomycin, altered biofilm architecture, and increased resistance to ceftriaxone, further expanding our understanding of the contribution of this operon to intrinsic enterococcal antibiotic resistance and biofilm growth.

Activation of Aflatoxin Biosynthesis Alleviates Total ROS in Aspergillus parasiticus

An aspect of mycotoxin biosynthesis that remains unclear is its relationship with the cellular management of reactive oxygen species (ROS). Here we conduct a comparative study of the total ROS production in the wild-type strain (SU-1) of the plant pathogen and aflatoxin producer, Aspergillus parasiticus, and its mutant strain, AFS10, in which the aflatoxin biosynthesis pathway is blocked by disruption of its pathway regulator, aflR. We show that SU-1 demonstrates a significantly faster decrease in total ROS than AFS10 between 24 h to 48 h, a time window within which aflatoxin synthesis is activated and reaches peak levels in SU-1. The impact of aflatoxin synthesis in alleviation of ROS correlated well with the transcriptional activation of five superoxide dismutases (SOD), a group of enzymes that protect cells from elevated levels of a class of ROS, the superoxide radicals (O₂^-). Finally, we show that aflatoxin supplementation to AFS10 growth medium results in a significant reduction of total ROS only in 24 h cultures, without resulting in significant changes in SOD gene expression. Our findings show that the activation of aflatoxin biosynthesis in A. parasiticus alleviates ROS generation, which in turn, can be both aflR dependent and aflatoxin dependent.

Measurement of ceftazidime concentration in human plasma by ultra-performance liquid chromatography-tandem mass spectrometry. Application to critically ill patients and patients with osteoarticular infections

Ceftazidime is an antibiotic belonging to the third generation of the cephalosporin family. It is indicated in the treatment of serious, simple or mixed bacterial infections, and its administration in continuous or intermittent infusion allows optimization of the concentration of antibiotic to keep it above the minimum inhibitory concentration. We developed and validated a chromatographic method by ultra-performance liquid chromatography-tandem mass spectrometry to measure ceftazidime concentration in human plasma. Following extraction with acetonitrile and 1,2-dichloroethane, the chromatographic separation was achieved using an Acquity ® UPLC ® BEH(TM) (2.1 × 100 mm i.d., 1.7 µm) reverse-phase C18 column, with a water-acetonitrile linear gradient containing 0.1% formic acid at a 0.4 mL/min flow rate. Ceftazidime and its internal standard (cefotaxime) were detected by electrospray ionization mass spectrometry in positive ion multiple reaction monitoring mode using mass-to-charge transitions of 547.0 → 467.9/396.1 and 456.0 → 395.8/324.1, respectively. The limit of quantification was 0.58 mg/L and linearity was observed in the range 0.58-160 mg/L. Coefficients of variation and absolute relative biases were <9.8 and 8.4%. The mean recovery for ceftazidime was 74.4 ± 8.1%. Evaluation of the matrix effect showed ion enhancement, and no carry-over was observed. The validated method could be applied to daily clinical laboratory practice to measure the concentration of ceftazidime in plasma.

Pharmaceutical impurities--a mini-review

The control of pharmaceutical impurities is currently a critical issue to the pharmaceutical industry. The International Conference on Harmonization (ICH) has formulated a workable guideline regarding the control of impurities. In this review, a description of different types and origins of impurities in relation to ICH guidelines and, degradation routes, including specific examples, are presented. The article further discusses measures regarding the control of impurities in pharmaceuticals.

Stability and compatibility of ceftazidime administered by continuous infusion to intensive care patients

The stability and compatibility of ceftazidime have been examined in the context of its potential use in concentrated solutions for continuous infusion in patients suffering from severe nosocomial pneumonia and receiving other intravenous medications by the same route. Ceftazidime stability in 4 to 12% solutions was found satisfactory (<10% degradation) for 24 h if kept at a temperature of 25 degrees C (77 degrees F) maximum. Studies mimicking the simultaneous administration of ceftazidime and other drugs as done in clinics showed physical incompatibilities with vancomycin, nicardipine, midazolam, and propofol and a chemical incompatibility with N-acetylcystein. Concentrated solutions (50 mg/ml) of erythromycin or clarithromycin caused the appearance of a precipitate, whereas gentamicin, tobramycin, amikacin, isepamicin, fluconazole, ketamine, sufentanil, valproic acid, furosemide, uradipil, and a standard amino acid solution were physically and chemically compatible.

Characterization of partitioning behavior of cephalosporins using microemulsion and micellar electrokinetic chromatography

Electrokinetic chromatography (EKC) was introduced to determine the partitioning behavior of various cephalosporins (cefpim, cefpirom, cefaloridin, cefaclor, cephalexin, cefuroxim, cefotaxim) in microemulsions (ME) and micellar (MC) systems. The partitioning behavior of cephalosporins in microemulsions was characterized calculating the capacity factor. The required parameters for the determination of the capacity factor (micro(aq) and micro-me are the electrophoretic mobilities of the solutes in the aqueous phase and the microemulsion phase, micro(eff) is the effective mobility in the microemulsion solution) were measured by EKC using cationic and anionic microemulsion systems consisting of the surfactants/n-heptane/1-butanol/10 mM phosphate buffer solution, pH 7.0. Electrokinetic chromatography was shown to be a useful method to quantify the partitioning behavior of drugs in oil/water microemulsion. The logarithm of the capacity factor was correlated with the logarithm of the 1-octanol/water partitioning coefficients.

Degradation pathways of ampicillin in alkaline solutions

Ampicillin trihydrate, sodium salt, in aqueous solution has a pH of about 8. No complete degradation pathway has been proposed to explain the degradation of ampicillin under alkaline conditions and the information available explains the formation of only certain products. The present work was carried out with the aim of providing this information. The formation of degradation products of ampicillin trihydrate, sodium salt, produced in aqueous solutions (pH 12 and 37 degrees C) have been studied as an accelerated form of the possible degradation that may occur in aqueous solutions at pH 8. Some of the degradation products formed under these conditions were then obtained either by synthesis or by degradation of ampicillin sodium followed by isolation using semi-preparative HPLC. These compounds were characterized by 1H NMR spectroscopy. The information obtained from the experiments by HPLC and NMR spectroscopy made it possible to propose a degradation pathway for ampicillin under the conditions described above. 5R-penicilloic acid is the first degradation product of ampicillin and subsequently undergoes epimerization at C-5 to form the 5S isomer via the imine tautomer. Mechanisms for the formation of compounds previously believed to form only under acidic conditions are proposed, i.e. ampicillin penilloic acid and 2-hydroxy-3-phenylpyrazine. The formation of ampicillin polymers was detected in dilute solutions (1% w/v) within a few hours of dissolution. The presence of ampicillin penicillenic acid and ampicillin penamaldic acid was detected by 1H NMR and their main spectroscopic features determined.

Dissolution studies on ampicillin embonate and amoxycillin embonate

The dissolution behaviour of slightly water-soluble embonic acid salts of ampicillin and amoxycillin was studied quantitatively as a function of solution pH (1.15-8.00) using the rotating disk method combined with reversed-phase high-performance liquid chromatography. The dissolution rate of ampicillin embonate was greater than that of amoxycillin embonate at all pH values investigated. The graphs of pH-intrinsic rate of dissolution of the antibiotics from the salts were U-shaped, the minimum being close to the respective isoelectric points of the parent antibiotics. Embonic acid was not detectable below pH 5; above pH 5 the dissolution rate of embonic acid increased as a function of pH.

A study of the metal complexation behaviour of some penicillins, cephalosporins and their derivatives

The metal complexation behaviour of several beta-lactam antibiotics and derivatives is explained, based on the results of potentiometric titrations. The (organo)metal ions used were (organic derivatives of) transition elements and elements with a filled d-subshell. The emphatic class b (organo)metal ions Ag(I), Hg(II) and C6H5Hg(I) form the most stable complexes with the studied ligands: Hg(II) is the most suited ion. The alkaline degradation products and hydroxamic acid derivatives of penicillins and cephalosporins are very similar to penicillamine in their complexation behaviour. This emphasizes the dominant role of the thiol group as site of complexation. A scheme for stepwise complex formation with Hg(II) and Ag(I) is presented. The availability of the thiol group is used to explain small differences in complexation behaviour between penicillin derivatives on the one hand, and cephalosporin derivatives and penicillamine on the other.

Micromethod for determination of ceftriaxone in plasma and urine by high-performance liquid chromatography

A sensitive and rapid high-performance liquid chromatographic method for the determination of ceftriaxone in human plasma and urine is described. A C18 reversed phase column is used; the mobile phase comprises water-methanol-triethylamine (750:250:4v/v/v) adjusted to pH 3 with orthophosphoric acid. Quantitation is performed at 270 nm with cefazolin as the internal standard. This method involves precipitation of proteins from fluids with acetonitrile followed by extraction of endogenous compounds with chloroform and injection of the upper aqueous phase on to the chromatograph. Relative standard deviations for between-day and within-day assays are 6.2%. The detection limit is 0.5 microg(-1) in plasma and urine. Studies of drug stability during sample storage, sample pretreatment and chromatography showed no degradation of ceftriaxone or of the internal standard. The method is convenient for clinical monitoring and for pharmacokinetic studies.