Time-Kill Effect of Crude Extracts of Garcinia kola Seeds on Methicillin-Resistant Staphylococcus aureus from the Anterior Nares of Healthcare Workers at a Tertiary Hospital in Nigeria

Aims: This study investigated the time-kill effects of crude methanol and aqueous extracts of Garcinia kola (Bitter kola) against isolates of Staphylococcus aureus obtained from the anterior nares of healthcare workers in a tertiary hospital in Nigeria.

Study Design: This was a cross-sectional study.

Place and Duration of Study: Lagos University Teaching Hospital (LUTH), Lagos, Nigeria between June 2013 and January 2014.

Methodology: Nasal swab samples were aseptically collected from two hundred and fifty (250) health workers using sterile swab sticks and analyzed using standard microbiological techniques. The isolates were identified using standard techniques and subjected to susceptibility testing that categorized them into oxacillin-resistant, β-lactamase producing and oxacillin-sensitive strains. The isolates were further subjected to agar well dilution to determine the minimum inhibitory concentration (MIC) and time-kill assays of the extracts.

Results: The overall carriage rate of 35.6% (89 of 250) was observed and out of the 89 Staphylococcus aureus isolates recovered, 26 were from laboratory workers and 16 from those in labour ward. Also, 34 (38.2%) of the isolates were oxacillin-resistant (MRSA), 32 (36%) were oxacillin-sensitive (MSSA) while the remaining 23 (25.8%) were β-lactamase producers. The overall MRSA presence among the healthcare workers was 13.6%. Both the methanol and aqueous extracts of Garcinia kola seeds showed intense activity with complete inhibition of most strains at 25 μg/ml (including all β-lactamase strains). However, thirty-two out of the thirty-four of the oxacillin-resistant (MRSA) strains showed sensitivity to the extracts at higher minimum inhibitory concentrations (MIC) of 50 μg/ml while most strains that were oxacillin-sensitive (including S. aureus ATCC 25923) were sensitive at lower MIC of 12.5 μg/ml. At 200 μg/ml of the extracts, all isolates under study were killed within 4 minutes whereas 100 μg/ml killed (oxacillin-sensitive and β-lactamase producers) within 10 minutes and MRSA within 30 minutes.

Conclusion: Extracts of Garcinia kola seeds possessed good antibacterial activity against isolates of Staphylococcus aureus. Therefore, using this plant extract as an ointment for nasal decolonization will go a long way in reducing the transmission of staphylococcal infections from health workers to patients. The study also reveals that nasal decolonization using these extracts greatly depend on concentration and contact time. Abiding by standard infection control methods and judicious use of antibiotics could greatly reduce transmission and antimicrobial resistance respectively among health workers.