THE POTENTIAL OF SELECTED FLAVONOIDS AGAINST METHICILLIN RESISTANT Staphylococcus aureus

Abstract

As a result of developing resistance the antibiotics became ineffective and the microbes including bacteria, viruses, parasites and fungi became able to counterattack against antibiotics. The basic cause of antibiotic or antimicrobial resistance is because of too much use of antibiotics. The impending post antibiotic period is becoming a threat for the both current and forthcoming advances in medical science. Both the rise in the bacterial resistant strains and insufficient availability of novel antibiotics are the major causes of antibiotic resistance. As a result of which the chances for the treatment of various infections have decreased significantly which have given birth to various complications for the patients. Among the resistant microbes, MRSA is currently a very hot issue globally for the last sixty years. This has been responsible for nosocomial infections and has been known to cause threats to life. The resistance against penicillins belongs to β- lactams antibiotics, started soon after a few years of its discovery. Because of rising issue of MRSA, a study was designed to determine the effect of flavonoids on antibiotics which have developed resistance against methicillin resistant Staphylococcus aureus (MRSA). The flavonoids selected for this research were Rutin (R), Morin (M), Qurecetin (Q) and Luteolin (L). The antibiotics included were AMP, AMO, CEF, CET, VAN, ME, CEPH, ERY, IMP, CIP, LEV and SULP-TRI. In this study about 100 MRSA clinical isolates and MRSA ATCC No. 43300 were used. The flavonoids were used alone, in combinations and along with the selected antibiotics. The concentrations of flavonoids and in combination with antibiotics effective against clinical isolates and standard strain were determined through the antibiotic sensitivity assays. The flavonoids, found effective individually against the clinical isolates and standard strain were Q and L. The combination of flavonoids used which have more pronounced effects than the individual ones were Q+L, R+M and Q+M+R. These flavonoids were then used in combination with all the selected antibiotics. The results revealed the qurecetin and luteolin used alone and in combination along with antibiotics have been found to increase the efficacy of AMP, CET, CEPH, ME and IMP against clinical isolates and the standard strain. All these antibiotics alone were having no effect against MRSA isolates except IMP.M+R used in combination with amoxicillin, ceftriaxone, cephradine, methicillin and imipenem, have positive effect on the antibacterial activity of test antibiotics, however, querecetin-morin-rutin combination was found to have more enhancing effects on the test antibiotics (AMP, AMO, xiv CET, CEPH, ME and IMP) activity against the standard and MRSA clinical isolates than the rutin-morin combination. The minimum inhibitory concentrations (MIC’s) of flavonoids were determined. Then in combination with antibiotics, MIC’s of flavonoids were determined as well. A reduction was observed in the MIC’s of flavonoids when combined with test antibiotics. Similarly MIC’s of antibiotics alone and in combination with flavonoids were also determined. A profound decrease was demonstrated in the minimum inhibitory concentration of antibiotics. The MIC’s reduction of antibiotics and flavonoids in combination with each other proves that both of them were increasing each other activity against the bacteria under study. Fractional inhibitory indices (FICI) were measured to find out whether there was synergism or additive relationship between the antibiotics and flavonoids. The results revealed that in all the cases additive relationship existed between the antibiotics and flavonoids except Q+M+R+CEPH, Q+M+R+CET, Q+M+R+IMP, Q+M+R+MET, Q+L+CET and Q+L+IMP where synergism was observed. Then the interaction mechanism between the flavonoids and antibiotics was also determined by measuring the K+ loss caused by flavonoids, antibiotics and in combination with each other. After that mutagenic effect of flavonoids alone and in combination with antibiotics on MRSA was also detected by PCR and sequencing. No mutations were observed. The resistant antibiotics become active against MRSA when combined with flavonoids. This was proved by determining the MIC’s of flavonoids alone and in combination with antibiotics. This revealed significant reduction in the MIC’s. Similarly, the MIC’s of antibiotics alone and in combination with flavonoids was also determined showing a profound reduction in the MIC’s of antibiotics. This proved that both the flavonoids and antibiotics were increasing each other’s activity. The FICI indicated an additive relationship between them. While the potassium loss measurement was the indicative of cell wall damage, which was greatest when flavonoids and antibiotics were used together.