Herbal Extracts with Anti-MRSA and Quorum Sensor Neutralization Activities HUSSEIN El Haj Ahmad SUNIL Maharjan RATISH S. Pillai

MRSA causes infections: In hospitals including: –Catheter-associated bacteraemia –Surgical site infections –Ventillator-associated pneumonia (VAP) In community –patients who lack traditional MRSA risk factors Alp and Voss (2006); HPA (2007); CDC (2007).

High Global MRSA Prevalence Canada 2.3% USA 55% UK 44% Australia 26% China 39% Japan 74% Hong Kong 80% Singapore 63% South Africa 49% Nigeria 21% Latin America 29% Germany 25% France 27% Spain 27% Romania 61% Cyprus 56% Netherlands 1% Alpesh and Batts (2006); EARSS (2005); PHAC (1997); Collignon et al (2005).

UK MRSA Prevalence in UK Between 1990 and 2005 HPA (2007); EARSS (2005).

UK MRSA Deaths in UK National Statistics online (February 2007). This increase may be related to improved levels of reporting on death certificates.

MRSA Resistance MSRA is resistant to several classes of antibiotics. Emerging problem: formation of tolerant biofilm –causing chronic and recurrent nosocomial device-related infections Increased demand for new anti-infectives and novel strategies to control MRSA infections Alpesh and Batts (2006); Rice (2006); Costerton et al., (1999); Donlan and Costerton (2002); Lewis (2001).

–Downregulation of microbial virulence factors –Inhibition of biofilm formation Those agents are known as QSI. Crude extract and toluene extract of garlic showed –QSI activity against Pseudomonas aeruginosa –Synergism with some conventional antibiotics at sublethal concentration Until now garlic extract and allicin activities against MRSA biofilms are not studied. Antipathogenic Agents Watnick and Kotler (1999); Davies et al. (1998); Rasmussen (2005).

MRSA Market MRSA market of five antibiotics had increased from 570 million USD in 2002 to 1.5 billion USD in To have a share in this growing market, some pharmaceutical companies are developing newer anti-MRSA agents in their pipelines. –Arpida (iclaprim) –GlaxoSmithKline (pleuromitilin) –Astra-Zeneca (AZD1279) Why not to have a share in this market?

Aim This research aims to study whether: Allicin alone, allicin mixed with toluene, toluene-, ethanol-, and chloroform- extracts of garlic can prevent or not MRSA biofilm formation.

Materials and Methods Clinical isolates –Clinical MRSA isolates, MRSA control strain, Pseudomonas aeruginosa positive control strain. Chemicals –Aqueous extract of allicin, allicin + toluene, toleuene extract of garlic, ethanol-extract of garlic, and chloroform-extract of garlic. MIC and MBC –MIC & MBC of planktonic bacteria and those in biofilms will be determined according to BSAC guidelines.

Materials and Methods Biofilm formation –Plasma method –MBEC TM -HTP Assay in Calgary Biofilm Device Measurement of microbial count, viability and killing in MRSA biofilms –Microbial viable count will be determined on real- time basis by plate count and luminometry.

Summary Global increase in MRSA prevalence MRSA grows in biofilms thus increasing its resistance Any agent interfering with QS will inhibit biofilm formation and decrease microbial pathogenicity. If allicin inhibits MRSA biofilm formation: –it may act as QSI –proven antimicrobial activity, promising natural agent against serious MRSA infections.

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