In Vivo Antimicrobial Activity of Garlic Against Staphylococci Infection

Objectives: To observe the effect of garlic extract alone or with amoxicillin on the staphylococcal infection induced with penicillin-sensible (PSSA) or methicillin-resistant (MRSA) strains, in rats.
Methods: Aqueous and hydroalcoholic extracts of garlic bulbs (Allium sativum) were chemically analyzed by GC/MS. A PSSA Staphylococcus aureus (ATCC 25923) and a MRSA strain (ATCC 33592) were used in the in vitro and in vivo models. Minimal inhibitory (MIC) and bactericidal (MBC) concentrations were obtained. 205 rats received four sterilized polyurethane sponge discs subcutaneously in their back. After 14 days, PSSA or MRSA was injected into the granulation tissues. After 24 hours of infection, the animals were submitted to one of the following treatments: Group 1 (Control) – 0.5 mL of NaCl 0.9%/daily; Group 2 - A. sativum 400mg/kg/daily; and Group 3 – amoxicillin suspension 50 mg/kg/mL; and Group 4 - A. sativum 400mg/kg/mL + amoxicillin suspension 50 mg/kg/mL. All treatments were administered p.o., every 6 hours, and the animals were killed right after the first administration (t=0) and after 6, 12 and 24 hours. Infected tissue samples were dispersed and spread (10 µL) on salt mannitol agar. Colonies were counted 18h after incubation at 37^oC. Results were submitted to Kruskal-Wallis (Dunn) test, with significant level set at 5%.
Results: MIC of garlic and amoxicillin against the penicillin-sensible strain was 2 mg/mL and 0.1 µg/mL, respectively, and MBC was 4mg/mL and 2 µg/mL, respectively. MIC and MBC of amoxicillin against MRSA were 2048 µg/mL and 8192 µg/mL, respectively. A. sativum MIC and MBC against MRSA were 16 mg/mL and 64 mg/mL, respectively. Amoxicillin decreased the PSSA counts from 6 to 12 hours and A. sativum 400 mg/kg from 6 to 24 hours. No differences were observed between amoxicillin and garlic extract against PSSA. No significant effect against MRSA was observed along the time in any group.
Conclusions: Thus, A. sativum was able to reduce PSSA infection, but not MRSA infection