1.1 Background of the study

It is charming to observe how different cultures have never come into contact with one another came to the same conclusion about the role of garlic in health and disease. Some of the earliest references to this medicinal and culinary plant are found on Sumerian clay tablets dating from 2600–2100 BC. Garlic was an important medicine to the ancient Egyptians listed in the medical text Codex Ebers (ca. 1550 BC) especially for the working class involved inheavy labor Lawson et al., 1998; Moyers et al., 1996). There is evidence that during the earliest Olympics in Greece, garlic was fed to the athletes for increasing stamina (Lawson et al., 1998).

The great herbalists and physicians of the ancient world record garlic historical use. “Garlic has powerful properties and is of great benefit against changes of water and of residence,” wrote Pliny the elder, the first century Roman naturalist (23-79 AD) (Foster, 1996; Koch and Lawson, 1995). Garlic has been used from the time when ancient times in India and China for a valuable effect on the heart and circulation, cardiovascular disease (KrisEtherton et al., 2002; Koscielny et al., 1999; Yu-Yan and Liu, 2001; Gardner et al., 2003), and regular use of garlic may help to prevent cancer, to treat malaria, and to raise immunity. Garlic has also proposed to treat asthma, candidiasis, colds, diabetes, and antibacterial effect against food borne pathogens like Salmonella, Shigella and S. aureus (Teferi and Hahn, 2002).

S. aureus are characterised by the formation of biofilms on biomaterials,  damaged  tissues,  and  most  commonly  on indwelling medical devices, causing biofilm-associated infections (Otto, 2008; Makino et al., 2013). These infections are becoming  more  common  and  occur  widely,  reflecting  the increased use of indwelling medical devices over the past few decades (Crnich and Maki, 2002). In clinical settings, these organisms persist in sessile environments, such as in biofilms, resulting in chronic infections (Gowrishankar et al., 2012). Over a half of S. aureus, including MRSA, have the ability of biofilm formation in various levels (Indrawattana et al., 2013; Rezaei et al., 2013). Furthermore, S. aureus also gain increased resistance to antimicrobial agents through biofilm formation  as  a  bacterial  survival  strategy  (Donlan  and Costerton,  2002;  Hall-Stoodley  et  al.,  2004).  In  addition, nosocomial MRSA infection is based on non-specific mechanism of resistance, which biofilm formation is involved (Otto, 2008).  Consequently,  biofilms  formed  by  MRSA  might become more resistant to most available antimicrobial agents, resulting in treatment failures.

Therapeutic use of garlic has been recognized as a potential medicinal value for thousands of years to different microorganisms. For example; antifungal, antiviral, antibacterial antihelmantic, antiseptic and antiinflammatory properties of garlic are well documented. Moreover, garlic extracts exhibited activity against both gram negative (E. coli, Salmonella sp. and Citrobacter enterobacter, Pseudomona kilabsella) and gram positive (S. aureus, S. pneumonia Group A streptococcus and Bacillus anthrax) all of which are cause of morbidity worldwide. This study will focus on recent research on protective effects of garlic against Staphylococcus aureus.

Garlic (Allium sativum L.) and garlic extracts have been previously demonstrated as effective in inhibiting the growth of different bacterial pathogens, including Staphylococci and MRSA (Tsao and Yin, 2001; Tsao et al., 2003; Rattanachaikunsopon and Phumkhachorn, 2009; Houshmand et al., 2013). Chemical analysis of garlic oil extract showed that  54.5%  of  the  total  sulphides  comprise  diallyl  monosulphide, diallyl disulphide, diallyl trisulphide and diallyl tetrasulphide, and the minimum inhibitory concentration of whole garlic oil extract against MRSA was 32 ìl/ml, whereas the MICs for the individuals sulphide compounds were 32, 12, 8 and 2 l/ml, respectively (Lawson et al., 1991). Allicin, the active compound in fresh garlic extract, also inhibited the proliferation of MRSA in a dose-dependent manner (Cutler and Wilson, 2004).

There is extensive literature on the antibacterial effects of fresh garlic juice, aqueous and alcoholic extracts, lyophilized  powders, steam distilled oil and other commercial preparations of garlic. Fenwick and Hanely (1985) understood a thorough review of the antibacterial effects of garlic and other allium vegetables up to mid-1984; more recently, the antibacterial effects of garlic have been studied by Reuter et al. (1996). The present study tested an aqueous extract of dried garlic in vitro for its antibacterial activity against Staphylococcus aureus.