Use of an enzyme-linked immunosorbent assay to assess penetration of amoxicillin into lung secretions

Increased RNA Transcription of Energy Source Transporters in Circulating White Blood Cells of Aged Mice

Circulating white blood cells (WBC) contribute toward maintenance of cerebral metabolism and brain function. Recently, we showed that during aging, transcription of metabolism related genes, including energy source transports, in the brain significantly decreased at the hippocampus resulting in impaired neurological functions. In this article, we investigated the changes in RNA transcription of metabolism related genes (glucose transporter 1 [Glut1], Glut3, monocarboxylate transporter 4 [MCT4], hypoxia inducible factor 1-α [Hif1-α], prolyl hydroxylase 3 [PHD3] and pyruvate dehydrogenase kinase 1 [PDK1]) in circulating WBC and correlated these with brain function in mice. Contrary to our expectations, most of these metabolism related genes in circulating WBC significantly increased in aged mice, and correlation between their increased RNA transcription and impaired neurological functions was observed. Bone marrow mononuclear transplantation into aged mice decreased metabolism related genes in WBC with accelerated neurogenesis in the hippocampus. In vitro analysis revealed that cell-cell interaction between WBC and endothelial cells via gap junction is impaired with aging, and blockade of the interaction increased their transcription in WBC. Our findings indicate that gross analysis of RNA transcription of metabolism related genes in circulating WBC has the potential to provide significant information relating to impaired cell-cell interaction between WBC and endothelial cells of aged mice. Additionally, this can serve as a tool to evaluate the change of the cell-cell interaction caused by various treatments or diseases.

Determination of amoxicillin and cotrimoxazole concentrations in sputum of patients with cystic fibrosis

In the management of cystic fibrosis, treatments against Staphylococcus aureus and Haemophilus influenzae such as amoxicillin or cotrimoxazole have to be prescribed and the antibiotherapy's efficacy may be linked to the concentration that reaches the infected site. As cystic fibrosis patients present disturbed pharmacokinetics parameters, drug monitoring would be relevant to assess the lung distribution of antibiotics and to optimize dosing regimens. In this context, the aim of the study was to develop and validate HPLC-based methods for the determination of both antibiotics in bronchial sputum from cystic fibrosis patients, in order to assess the distribution of the drugs into the lungs. Plasma proteins were precipitated by acetonitrile and amoxicillin concentrations in sputum were determined by HPLC coupled with tandem-mass spectrometry. Following liquid extraction with ethyl acetate, cotrimoxazole was quantified by HPLC using ultraviolet detection. Both methods were rapid, specific, accurate and reproducible. The method was applied to patient samples. In three treated patients, concentrations of amoxicillin in sputum were similar and below the lower limit of quantification (0.1 μg/g) and in six patients, sputum concentrations up to 11.1 and 6.4 μg/g were measured for sulfamethoxazole and trimethoprim, respectively.

Pitfalls in the Immunochemical Determination of β-Lactam Antibiotics in Water

Contamination of waters with pharmaceuticals is an alarming problem as it may support the evolution of antimicrobial resistance. Therefore, fast and cost-effective analytical methods for potential on-site analysis are desired in order to control the water quality and assure the safety of its use as a source of drinking water. Antibody-based methods, such as the enzyme-linked immunosorbent assay (ELISA), can be helpful in this regard but can also have certain pitfalls in store, depending on the analyte. As shown here for the class of β-lactam antibiotics, hydrolysis of the β-lactam ring is a key factor in the immunochemical analysis as it influences antibody recognition. With the antibody used in this study, the limit of detection (LOD) in the immunoassay could be significantly reduced by hydrolysis for the five tested penicillins, with the lowest LOD for carbenicillin (0.2 nmol/L) and the greatest impact on penicillins G and V (reduction by 85%). In addition to enhanced quantification, our strategy also provides access to information about the degree of hydrolysis in water samples as shown for the most abundant penicillin amoxicillin.

Amoxicillin concentrations in relation to beta-lactamase activity in sputum during exacerbations of chronic obstructive pulmonary disease

Background

Acute exacerbations of chronic obstructive pulmonary disease (COPD) are often treated with antibiotics. Theoretically, to be maximally effective, the antibiotic concentration at sites of infection should exceed the minimum inhibitory concentration at which 90% of the growth of potential pathogens is inhibited (MIC₉₀). A previous study showed that most hospitalized COPD patients had sputum amoxicillin concentrations <LMIC₉₀ when treated with amoxicillin/clavulanic acid. Those with adequate sputum concentrations had better clinical outcomes. Low amoxicillin concentrations can be caused by beta-lactamase activity in the lungs. This study investigated whether patients with sputum amoxicillin concentrations <MIC₉₀ had higher beta-lactamase activity in sputum than patients with a concentration ≥MIC₉₀.

Methods

In total, 23 patients hospitalized for acute exacerbations of COPD and treated with amoxicillin/clavulanic acid were included. Sputum and serum samples were collected at day 3 of treatment to determine beta-lactamase activity in sputum and amoxicillin concentrations in both sputum and serum.

Results

We found no difference in beta-lactamase activity between patients with sputum amoxicillin concentrations <MIC₉₀ and ≥MIC₉₀ (P=0.79). Multivariate logistic regression analysis showed no significant relationship between beta-lactamase activity and sputum amoxicillin concentrations <MIC₉₀ or ≥MIC₉₀ (odds ratio 0.53; 95% confidence interval 0.23–1.2; P=0.13). Amoxicillin concentrations were <MIC₉₀ in 78% of sputum samples and in 30% of serum samples.

Conclusion

In patients treated with amoxicillin/clavulanic acid for an acute exacerbation of COPD, sputum beta-lactamase activity did not differ between those with sputum amoxicillin concentrations <MIC₉₀ or ≥MIC₉₀. The finding that the majority of patients had sputum amoxicillin concentrations <MIC₉₀ suggests that current treatment with antibiotics for acute exacerbations of COPD should be optimized.

Preparation and identification of monoclonal antibodies against ω-conotoxin MVIIA

ω-Conotoxins MVIIA (ω-CTX MVIIA) is a peptide with 25 amino acid residues. It is a selective and reversible N-type voltage-gated calcium channel blocker, which could be used as an analgesic for pain. To date, there are no monoclonal antibodies (MAb) for immunoassay against ω-conotoxin MVIIA. In this study, an MAb against ω-conotoxin MVIIA was prepared. The conotoxin-coding DNA sequence was chemically synthesized and cloned into expression vector pGEX-6p-1 and pET32a (+), respectively. The fusion protein GST-CTX was expressed and purified, and was used to immunize BALB/c mice for preparing the anti-CTX antibody. The spleen cells were fused with SP2/0 myeloma cells after the titer of antiserum was detected and qualified. After being screened by indirect ELISA and cloned by limiting dilution, a hybridoma named 4A12, which produces monoclonal antibody specifically against ω-CTX MVIIA, was successfully obtained. It was found that there are 102 chromosomes in the 4A12 cell, and the subclass for the MAb is IgM. The MAb affinity against ω-CTX MVIIA was 7.33×10(9) L/mol, and the cross-reaction test showed that the MAb specifically bound ω-CTX MVIIA. The MAb could be used as a specific antagonist for ω-CTX MVIIA in the physiological study on the CaV channels in the nervous system.

Relation between amoxicillin concentration in sputum of COPD patients and length of hospitalization

Amoxicillin is a widely used antibiotic in COPD. Little is known about the transfer of amoxicillin into sputum of COPD patients. The objective was to investigate the relationship between the concentration of amoxicillin in sputum in hospitalized COPD patients and length of hospitalization. To be effective against bacterial pathogens, the amoxicillin concentration in target tissues should be higher than the Minimal Inhibiting Concentration (MIC) of 2 mg/l. Therefore, this was also used as the cut-off value for the amoxicillin concentration in sputum, as a marker for lung tissue concentration. Fifty-two COPD in-patients with an exacerbation, treated with amoxicillin clavulanic acid, were included in this cohort study. Of these patients 7 also had pneumonia. Patients were divided in patients with an amoxicillin sputum concentration ≥ 2 mg/l and < 2 mg/l. Furthermore, inflammation markers in sputum and serum and clinical parameters were obtained. Of the 33 patients with usable sputum, 11 had a concentration in sputum ≥ 2 mg/l. The mean length of hospitalization for patients with concentrations below the MIC90 to common respiratory pathogens was 11.0 days, while for patients with concentrations at or above the MIC90 this was 7.0 days (p = 0.005). COPD patients admitted for an acute exacerbation of COPD, with a sputum concentration of amoxicillin ≥ 2 mg/l had a markedly reduced length of hospitalization compared to patients with a concentration < 2 mg/l. It is worthwhile testing whether individualized treatment based on sputum amoxicillin concentrations of patients during hospitalization for acute exacerbations can effectively reduce hospital stay.

Development of amoxicillin enzyme-linked immunosorbent assay and measurements of tissue amoxicillin concentrations in a pigeon microdialysis model

A sensitive ELISA was developed for the detection of amoxicillin (AMX) in serum, urine, and milk. The ELISA used an indirect competitive method produced by coating the plate with ovalbumin conjugated with AMX hapten. Antibodies against AMX-BSA were detected by a goat-antirabbit antibody conjugated with peroxidase. Calibration standard curves ranged from 1.28 ng/mL to 20 microg/mL [IC(50) (inhibition concentration 50%) = 100 ng/mL], and the limits of detection were 1.3, 2.7, and 4.8 ng/mL for urine, milk, and serum, respectively. The intra- and interassay variations were less than 4 and 9.6%. The antibody produced against AMX cross-reacted highly with penicillin G (77%); cross-reacted moderately with ampicillin, oxacillin, and cloxacillin (56.9, 51.4, and 48.8%, respectively); but was considered non-cross-reactive with dicloxacillin (7.4%), cefadroxil (<1%), and cefazolin (<1%). Concentrations of AMX were measured simultaneously in venous blood and muscles by using the developed AMX ELISA in an in vivo microdialysis model designed for pigeons. Following i.m. injection (25 mg/kg), AMX attained a peak blood level of 4.74 +/-0.30 mu g/mL and decreased with a half-life of 2.38 +/-0.16 h. In contrast, measurements in pectoral and femoral muscles exhibited delayed appearances, reduced peak concentrations, and prolonged half-lives of 4.07 +/-0.48 (pectoral) and 3.01 +/-0.26 (femoral) that were significantly different from each other and those in the blood (P < 0.05). Blood protein binding was calculated to be 27.9 +/-5.7%. This study demonstrated the semiquantitative application of a selective AMX ELISA in the first microdialysis procedure for continuous monitoring of drug levels in specific tissues of pigeons and maybe useful for related studies in other poultry species.

A direct correlation between nicotinamide N-methyltransferase activity and protein levels in human liver cytosol

Phenotypic differences in nicotinamide N-methyltransferase (NNMT, E. C. 2.1.1.1) activity may be due to a genetic polymorphism. We report the characterisation of the hepatic NNMT activity in cytosol from normal human livers, enzyme protein levels determined by Western blotting and ELISA and mRNA levels determined by SDS-PAGE/Northern blotting. Subjects with high NNMT activity had high levels of NNMT protein and NNMT mRNA levels in hepatic cytosol and the converse was true for individuals with low NNMT activity. No differences in sequences were seen when cDNAs of individuals with high and low NNMT activity were compared. Thus phenotypic differences in the general population are due to differences in steady-state mRNA levels and not because of a polymorphism in the coding region of the NNMT gene.