BackgroundAmpicillin-resistant S. aureus (ARSA) now poses a serious problem for hospitalized patients, and their care providers. Plant-derived antibacterial that can reverse the resistance to well-tried agents which have lost their original effectiveness are the research objectives of far reaching importance. To this aim, the present study investigated antibacterial and synergistic activities of Stephania suberosa extracts (SSE) against ARSA when used singly and in combination with ampicillin.ResultsThe majority chemical compounds of SSE were alkaloid (526.27 ± 47.27 mg/1 g of dried extract). The Minimum inhibitory concentration (MICs) for ampicillin and SSE against all ARSA strains were >512 μg/ml and 4 mg/ml, respectively. Checkerboard assay revealed synergistic activity in the combination of ampicillin (0.15 μg/ml) and SSE (2 mg/ml) at fractional inhibitory concentration index (FICI) <0.5. The killing curve assay had confirmed that the viability of ARSA was dramatically reduced from 5x105 cfu/ml to 103 cfu/ml within 6 h after exposure to SSE (2 mg/ml) plus ampicillin (0.15 μg/ml) combination. Electron microscopic study clearly revealed that these ARSA cells treated with this combination caused marked morphological damage, peptidoglycan and cytoplasmic membrane damage, and average cell areas significant smaller than control. Obviously, Immunofluorescence staining and confocal microscopic images confirmed that the peptidoglycan of these cells were undoubtedly disrupted by this combination. Furthermore, the CM permeability of ARSA was also increased by this combination. Enzyme assay demonstrated that SSE had an inhibitory activity against β-lactamase in concentrations manner.ConclusionsSo, these findings provide evidence that SSE has the high potential to reverse bacterial resistance to originate traditional drug susceptibility of it and may relate to three modes of actions of SSE: (1) inhibits peptidoglycan synthesis, resulting in morphological damage, (2) inhibits β-lactamases activity, and (3) increases CM permeability. It is widely recognized that many types of drugs are derived from alkaloids. So, this SSE offers the prominent potential to develop a novel adjunct phytopharmaceutical to ampicillin for the treatment of ARSA. Further active ingredients study, toxicity of it, and the synergistic effect on blood and tissue should be performed and confirmed in an animal test or in humans.

Abstract:Dissemination of antibiotic resistance in Enterobacteriaceae mediated by AmpC, ESBL and MBL β-lactamases is clinically significant. A simple, rapid method for the detection of these resistance phenotypes would greatly improve chemotherapeutic recommendation. This technology would provide valuable input in our surveillance of resistance on a global stage, particularly if the methodology could be applicable to resource poor settings. A resazurin microtitre plate (RMP) assay incorporating cloxacillin (CX), clavulanic acid (CA), and EDTA for the rapid phenotypic identification of AmpC, ESBL, MBL and the co-existence of β-lactamases has been developed. A total of 44 molecularly characterised Enterobacteriaceae clinical isolates producing AmpCs, ESBLs, co-producers of ESBL and AmpC, MBLs, and co-producers of ESBL and MBL were phenotypically examined using the RMP assay. The ceftazidime (CAZ)-based and cefotaxime (CTX)-based RMP assay successfully detected all 15 AmpC, 12 ESBL, 9 MBL producers, 6 ESBL-AmpC co-producers, and 2 ESBL-MBL co-producers without false positive results. The CAZ-based assay was more reliable in detecting AmpC alone, while the CTX-based assay performed better in identifying co-producers of ESBL and AmpC. There was no difference in detection of ESBL and MBL producers. The findings of the present study suggest that use of the RMP assay with particular β-lactamase inhibitors explicitly detects three different β-lactamases, as well as coexistence of β-lactamases within 6 h. This assay is applicable to carry out in any laboratory, is cost-effective and easy to interpret. It could be implemented in screening patients, controlling infection and for surveillance purposes. Powered by Editorial Manager® and ProduXion Manager® from Aries Systems Corporation