Development of Antibiotic Resistance in Herbal Drug-sensitized Staphylococcus aureus Isolate

Background: Herbal remedies are locally produced drugs usually made from plant sources. Due to their inexpensive nature, low-income individuals prefer them over modern antibiotics in the treatment of infections.

Aims: The purpose of the current study was to determine the ability of a herbal drug called Goko Alcoholic Bitters (GAB) to induce resistance in opportunistic pathogens such as Staphylococcus aureus.

Methods: To evaluate the antimicrobial efficacy of GAB on S. aureus, Disc diffusion method was employed to observe the zones of clearance by GAB. Overnight cultures of S. aureus grown in Tryptone Soy Broth (TSB) at an optical density of 0.5 were serially diluted to 109. Five (5) different concentrations of GAB (0.018 g/ml, 0.006 g/ml, 0.002 g/ml, 0.0007 g/ml and 0.0002 g/ml) were added to the serially diluted culture. The growth responses of these different dilutions were checked against S. aureus isolate in vitro. The experiment was monitored for 24 and 48 hrs conditions using two different growth determination methods; turbidity and colony forming unit counting methods. The five (5) different conditions were further analyzed by plating 200 µl of bacterial broth on Tryptic Soy Agar (TSA) and antibiotic sensitivity discs were embedded onto the agar. 200 µl of control bacterial Tryptone Soy broth containing S. aureus not exposed to the herbal drug was also performed alongside for comparison. This was repeated for both 24 and 48 hrs exposure to GAB.

Results: The efficacy of GAB showed some levels of antimicrobial activity, however, were significantly lower compared to Ampicillin (10 µg). The growth response analysis showed gradual reduction but not complete elimination with the highest concentration of GAB. GAB-sensitized S. aureus showed resistance seen in the reduced zones of clearance to some Septrin 10 µg (SEP), Ampicillin 10 µg (AMP) and Nalidixic acid 10 µg (NA) which were effective against untreated S. aureus (control).

Conclusion: GAB has some levels of antimicrobial efficacy but antibiotic resistance gets induced in the case of surviving GAB-pretreated S. aureus.