A peptide based on homologous sequences of the ß-barrel assembly machinery component BamD potentiates antibiotic susceptibility of Pseudomonas aeruginosa.

OBJECTIVES: The ß-barrel assembly machinery (BAM) complex plays a critical role in outer membrane protein (OMP) biogenesis. The outer membrane (OM) of Pseudomonas aeruginosa is centrally involved in mechanisms of antibiotic resistance. This study aimed to identify effects of a synthetic peptide based on conserved sequences in the putative BamA-binding region of BamD, focusing on antibiotic susceptibility and OMP characteristics in P. aeruginosa. METHODS: We synthesized a peptide FIRL (Phe-Ile-Arg-Leu-CONH(2)) with a sequence related to that of the BamD protein. We assessed antibiotic susceptibility of P. aeruginosa PAO1 using the chequerboard method and a time-kill assay. Changes in OMPs and in OM permeability were examined using SDS-PAGE, western blot analysis and nitrocefin assays. The combined effects of the peptide and antibiotics were investigated using a mouse pneumonia model. RESULTS: Although the peptide alone exerted no antimicrobial effect, it reduced the MICs of colistin, levofloxacin, erythromycin, vancomycin and rifampicin for P. aeruginosa PAO1 by 4-fold or more. Time-kill tests revealed bacterial numbers were significantly reduced after 2 h of incubation with the peptide plus colistin or levofloxacin. Moreover, in the presence of the peptide, expression of OprM was reduced by a third, and OM permeability was increased. The combination of the peptide (2.08 mg/kg) and colistin (1.25 mg/kg) significantly reduced P. aeruginosa by more than 1 log cfu/mL in a mouse pneumonia model. CONCLUSIONS: We show, for the first time, that a synthetic peptide based on homologous sequences of BamD can potentiate antibiotic susceptibility of P. aeruginosa.

Development of an enzyme-linked immunosorbent assay system to determine the presence of antibodies specific for taxane structures.

Taxanes, which are widely used in treatment of numerous cancer types, are well-known to induce hypersensitivity reactions (HSR), especially in the case of paclitaxel. Although the cause of the HSR is commonly thought to be a non-immunological direct effect of the diluent which is used to dissolve paclitaxel, some reports suggest the possibility of the presence of an immunological reaction to the common taxane structure. The aim of this study was to establish a method to determine the presence of anti-taxane antibodies in body fluids of patients who have previously received paclitaxel, in order to estimate the risk of the occurrence of HSR to other taxane compounds, such as docetaxel. To prepare an enzyme-linked immunosorbent assay (ELISA) plate for determining taxanes, 10-deacetylbaccatin III (DAB) was first succinylated by use of dimethylaminopyridine and succinic anhydride in dried pyridine. After the succinylation reaction, three different products were obtained, and these were confirmed as 7-succinoyl DAB (7-DAB), 10-succinoyl DAB (10-DAB), and 7,10-disuccinoyl DAB (7,10-DAB) by (1)H-NMR analysis. Each of these three products was conjugated with bovine serum albumin (BSA), and adsorbed on an ELISA plate. By using a commercially available anti-taxane monoclonal antibody as a model antibody, the detection limit of the anti-taxane antibodies on the 7-DAB-BSA-, 10-DAB-BSA-, and 7,10-DAB-BSA-conjugated ELISA plate was estimated as 0.3, 1 and 10 ng/ml, respectively. The ELISA system established in this study may therefore be useful for estimating the risk of HSR to taxanes in a patient prior to the use of these drugs.