Biography
Thanyaluck Siriyong is a PhD candidate in Microbiology from Prince of Songkla University, Thailand. She has completed her BSc and MSc in Thai Traditional Medicine from Prince of Songkla University. She is currently a Visiting Doctoral Researcher at the University of St Andrews, Scotland, UK. Her project is supported by the Thailand Research Fund through the Royal Golden Jubilee PhD Program co-funded by the British Council through Newton Fund
Abstract
The Pseudomonas aeruginosa MexAB-OprM, MexXY-OprM, MexCD-OprJ and MexEF-OprN are well characterized efflux systems of the resistance-nodulation-cell division (RND) family and are able to export a wide variety of structurally diverse compounds, including many clinically administered antibiotics. The pumps are expressed upon exposure to antibiotics and mutations in local or global regulator genes can occur, leading to overexpression of these efflux pumps and to multidrug resistance (MDR) phenotypes. To overcome MDR, efflux pump inhibitors are a potential solution. Efflux pump inhibitors from natural products have been extensively explored as potential sources because of fewer adverse effects, low cost and traditional medicine. Many plant alkaloids have been previously reported as efflux pump inhibitors such as curcumin, reserpine, capsaicin and piperine. This study has determined the effects of steroidal alkaloids from Holarrhena antidysenterica and its major steroidal alkaloid conessine as efflux pump inhibitors against P. aeruginosa. Steroidal alkaloids and conessine combined with various antibiotics were investigated for synergistic activity against P. aeruginosa PAM1020 (WT), P. aeruginosa PAM1032 (nalB), P. aeruginosa PAM1033 (nfxB), P. aeruginosa PAM1034 (nfxC) and P. aeruginosa PAM1626 (∆mex). Conessine (32 mg/L) reduced MICs of piperacillin, meropenem and levofloxacin in MexEF-OprN overexpressed strain (P. aeruginosa PAM1034). However, synergistic activity obtained from steroidal alkaloids at 1024 mg/L demonstrated less effects than conessine. The results suggested that conessine could be applied as an efflux pump inhibitor to restore antibiotic activity by inhibiting efflux pump system in P. aeruginosa
Biography
Baodong Ling has completed his MD from West China Medical University and worked as a Visiting Scholar in University of Zurich in 1996. He is a distinguished Professor in Pharmacology. He is also the Director of Small Molecule Drugs Key Laboratory of Sichuan Province and Institute of Materia Medica. He has published more than 60 papers in reputed journals and has been serving as an Editorial Board Member of Chinese Journal of Antibiotics and World Notes on Antibiotics.
Abstract
Nosocomial infections caused by quinolone-resistant Acinetobacter baumannii (QRAB) have been increasing in recent years, posing a threat to public health. In this study, we aimed to determine the mechanisms of quinolone resistance in A. baumannii isolates and investigate the occurrence of carbapenem resistance gene blaOXA-23 and aminoglycoside resistance gene armA among these QRAB. Totally, 101 A. baumannii isolates were collected from one university hospital in western China between 2011 and 2012. All isolates were identified and confirmed by sequencing analysis of 16S rRNA internal transcribed spacer and recA. The minimal inhibitory concentrations (MICs) of ciprofloxacin and levofloxacin were determined by agar dilution. Plasmid-mediated quinolone resistance determinants (PMQRs) were performed with PCR assay, whilst gyrA and parC genes of QRAB were amplified and sequenced. The results showed that 77 QRAB harbored mutations of gyrA and parC, whereas PMQRs were not detected. Additionally, 41 isolates had resistance to aminoglycosides and carbapenems due to the expression of a 16S rRNA methylase armA (with high level resistance) and acquisition of OXA-type carbapenemase OXA-23. Obviously, most of sequence types belonged to clonal complex 92 in these 41 isolates, which demonstrated that these isolates had a common origin and caused nosocomial infection. An A. baumannii clone producing OXA-23, armA along with mutations of quinolone resistance-determining regions (QRDRs) has been identified as an emerging and rapidly spreading pathogen. To our knowledge, this is the first report of hospital dissemination of A. baumannii carrying blaOXA-23, armA and mutations of QRDRs in QRAB in western China