Deng Hua, McShan Danielle, Zhang Ying, Sinha Sudarson S, Arslan Zikri, Ray Paresh C, Yu Hongtao
Department of Chemistry and Biochemistry, Jackson State University , Jackson, Mississippi 39217, United States.
Environ Sci Technol. 2016 Aug 16;50(16):8840-8. doi: 10.1021/acs.est.6b00998. Epub 2016 Jul 26.
A combination of silver nanoparticles (AgNPs) and an antibiotic can synergistically inhibit bacterial growth, especially against the drug-resistant bacteria Salmonella typhimurium. However, the mechanism for the synergistic activity is not known. This study chooses four classes of antibiotics, β-lactam (ampicillin and penicillin), quinolone (enoxacin), aminoglycoside (kanamycin and neomycin), and polykeptide (tetracycline) to explore their synergistic mechanism when combined with AgNPs against the multidrug-resistant bacterium Salmonella typhimurium DT 104. Enoxacin, kanamycin, neomycin, and tetracycline show synergistic growth inhibition against the Salmonella bacteria when combined with AgNPs, while ampicillin and penicillin do not. UV-vis and Raman spectroscopy studies reveal that all these four synergistic antibiotics can form complexes with AgNPs, while ampicillin and penicillin do not. The presence of tetracycline enhances the binding of Ag to Salmonella by 21% and Ag(+) release by 26% in comparison to that without tetracycline, while the presence of penicillin does not enhance the binding of Ag or Ag(+) release. This means that AgNPs first form a complex with tetracycline. The tetracycline-AgNPs complex interacts more strongly with the Salmonella cells and causes more Ag(+) release, thus creating a temporal high concentration of Ag(+) near the bacteria cell wall that leads to growth inhibition of the bacteria. These findings agree with the recent findings that Ag(+) release from AgNPs is the agent causing toxicity.
银纳米颗粒（AgNPs）与抗生素联合使用可协同抑制细菌生长，尤其是对耐药性鼠伤寒沙门氏菌。然而，这种协同活性的机制尚不清楚。本研究选择了四类抗生素，即β-内酰胺类（氨苄青霉素和青霉素）、喹诺酮类（依诺沙星）、氨基糖苷类（卡那霉素和新霉素）和多肽类（四环素），以探究它们与AgNPs联合使用时对多重耐药性鼠伤寒沙门氏菌DT 104的协同作用机制。依诺沙星、卡那霉素、新霉素和四环素与AgNPs联合使用时对沙门氏菌显示出协同生长抑制作用，而氨苄青霉素和青霉素则没有。紫外可见光谱和拉曼光谱研究表明，这四种具有协同作用的抗生素都能与AgNPs形成复合物，而氨苄青霉素和青霉素则不能。与不存在四环素的情况相比，四环素的存在使Ag与沙门氏菌的结合增加了21%，Ag(+)释放增加了26%，而青霉素的存在并没有增强Ag的结合或Ag(+)的释放。这意味着AgNPs首先与四环素形成复合物。四环素-AgNPs复合物与沙门氏菌细胞的相互作用更强，并导致更多的Ag(+)释放，从而在细菌细胞壁附近形成暂时的高浓度Ag(+)，导致细菌生长受到抑制。这些发现与最近关于AgNPs释放的Ag(+)是导致毒性的因素的研究结果一致。
