英国留学thesis-医学INTRODUCTION

INTRODUCTION介绍

 

如今,有很多细菌和其他微生物引起的传染病影响着全世界数以百万计的人。在过去的60年,抗生素被开发用来对抗这些传染病。然而,近年来耐药微生物的病例数已经开始上升。许多常用抗生素对某些疾病治疗效果已经越来越低了。例如伤口感染、淋病、肺结核、肺炎、败血症和儿童耳部感染等疾病用抗生素已经变得收效甚微。这是因为一般来说, 抗生素作为治疗药物，微生物获得抗药性的遗传能力,这导致制药行业出现了问题。因此,开发新的抗菌药物是维护的有效治疗所必须的。

Nowadays, there are numerous of infectious diseases caused by bacteria and other microbes that affect millions of people worldwide. In the past 60 years, antibiotics have been developed to fight against these infectious diseases. However, in recent years it has seen a rise in the number of cases of drug resistant microbial. Many major used antibiotics have become less and less effective against certain illness, for example wound infections, gonorrhoea, tuberculosis, pneumonia, septicaemia and childhood ear infections are just a few of the diseases that have become hard to treat with antibiotics. This is because in general, microorganisms have the genetic ability to acquire multi resistances to antibiotic used as therapeutic agents and this have caused problems to pharmaceutical industries. Therefore, the development of new antimicrobial drugs is necessary to maintain a pool of effective drugs at all time (Todar 2008).

 

However, the development of new synthetic antibiotic has become a public concern. The public nowadays is becoming increasingly aware of the health issues posted by synthetic antibiotics or drugs. Thus, the use of antimicrobial drugs that derived from natural sources, especially plants has accelerated in recent years. World Health Organization (WHO) has indicated that the best source to acquire a variety of drugs would be from medicinal plants. In developed countries, there are about 80% of individuals used traditional medicines that contain compounds derived from medicinal plants (Nascimento et al. 2000). Researcher had found that plants are rich in a wide variety of secondary metabolites, such as volatile oils, tannins, terpenoids, alkaloids, and flavonoids that found in vitro to have antimicrobial properties and allowing these plants to be studied and used for the development of new antimicrobial drugs (Peng et al. 2000; Li et al. 2003; Ren et al. 2008). These phytochemicals compounds serve as plant natural defences mechanisms against predator such as microorganisms, insects, and herbivores (Cowan 1999). These substances found in plant have great effect on bacterial inhibition by different mechanisms than those presently used antibiotics and may have a significant clinical value in treatment of microbial drugs resistant.

 

Among all medicinal plants, Chinese herbal medicine is the oldest form of healthcare in the world. A single herb can contain many different bioactive compounds that are effective against several microorganisms, including those which are resistant to synthetic antibiotics. In China, herbal and tea have been used for many purposes, including medication, nutrition, flavouring, beverages, and fragrance. The development of traditional herbal medicine has increased dramatically. Among the various types of herbs, Aloe Vera is most commonly used in traditional and modern herbal medicine. Clinical tests have shown that Aloe Vera possesses antibacterial and antifungal properties, which inhibit microbes like Staphylococcus spp and Candida spp (Lorenzetti et al. 1964; Stuart et al. 1997).

 

In this study, Lonicera japonica was chosen to determine the antimicrobial activities. Lonicera japonica is a species of honeysuckle native to eastern Asia (Japan, Korea, China, and Taiwan). It has been practiced as a medicinal plant and clinical test shown that Lonicera japonica possesses many biological effects, including hepatoprotective, cytoprotective, antimicrobial, antioxidative, antiviral, and anti-inflammatory activities (Chang et al. 1995). Flowers and buds of Lonicera japonica has been used for the treatment of affection by exopathogenic wind-heat at the early stage, sores, carbuncles, furuncles and swellings for centuries (Xiang and Ning 2007). Lonicera japonica has been reported containing iridoid glycosides and polyphenolic compounds (Kakuda et al. 2000). The primary polyphenolic compounds in Lonicera japonica are chlorogenic acids, caffeic acids, and luteolin (Chang et al. 1995). Besides, the primary components of Lonicera japonica have medicinal properties, such as the flower buds have anticancer, antimicrobial, and anti-inflamatory properties (Zhang et al. 2008); the leaf has antioxidant properties and inhibitors of tyrosinase (Byun et al. 2004); the stem also has inhibitory activities against tyrosinase and xanthine oxidase (Wang and Helliwell 2001). 

 

Since the introduction of antibiotic, it becomes one of the most important weapons in fighting bacterial infections and has greatly benefited the quality of human life. However, drug resistance microbial is emerging as one of the most significant challenges to human health. To improve the antimicrobial effectiveness, synergism activity was performed in this study. Scientist found that synergistic therapy against resistant microorganisms may lead to new way of treating infectious diseases. Report had shown that combining of two or more antibiotic agents with different mechanism of action can help to prevent the development of antibiotic resistance and improve the outcome of the therapy (Betoni et al. 2006). This combination can actually expand the antimicrobial spectrum, overcome the resistant mutants, minimize toxicity and to obtain synergistic antimicrobial effect (Olayinka et al. 2009). In construct, synergism is defined as, “a bactericidal effect of the drug combination significantly more pronounced than the sum of the bactericidal effect of each agent alone in comparison with the effect in untreated animals” (Fantin et al. 1992). 

 

Hence, in this study, efforts were made to investigate the antimicrobial activity from methanolic crude flower extract and its sub-fraction of ethyl-acetate and butanol, using minimum inhibitory concentration (MIC) against potent bacteria. Subsequently, in synergistic test, the MICs of the respective bacteria was used in combination with clinical antibiotic, ampicillin to determine their synergistic mechanism, if any