Table 3.
MBC of S. hillii leaf extracts on screened bacterial strains.
| Bacterial Strain | Tested Concentration of the Standard Antibiotic (mg/mL) |
MBC of S. hillii Extracts (mg/mL) | |
|---|---|---|---|
| Methanol | Ethanol | ||
| Gram-positive bacteria | |||
| Bacillus cereus (ATCC 14579) | 1.0 | 15.0 | 20.0 |
| MSSA (NCTC 6571) | 1.0 | 5.0 | 5.0 |
| MRSA (ATCC 33591) | 1.0 | 7.5 | 7.5 |
| MRSA (QUT 1113) | 1.0 | 7.5 | 5.0 |
| Bacillus subtilis (QUT 0535) | 1.0 | 15.0 | 15.0 |
| Staphylococcus epidermidis (QUT 0613) | 1.0 | 5.0 | 5.0 |
| Enterococcus faecalis (QUT 1105) | 1.0 | >20.0 | >20.0 |
| Enterococcus faecium (QUT 1101) | 1.0 | >20.0 | >20.0 |
| Enterococcus gallinarum (ATCC 13048) | 1.0 | >20.0 | >20.0 |
| Enterococcus casseliflavus (ATCC 25788) | 1.0 | >20.0 | >20.0 |
| Staphylococcus saprophyticus (QUT 0703) | 1.0 | 5.0 | 5.0 |
| Gram-negative Bacteria | |||
| Proteus vulgaris (ATCC 7002) | 1.0 | >20.0 | >20.0 |
| Proteus mirabilis (ATCC 6380) | 1.0 | >20.0 | >20.0 |
| Acinetobacter baumannii (ATCC 19606) | 1.0 | >20.0 | >20.0 |
| Enterobacter cloacae (ATCC 13047) | 1.0 | >20.0 | >20.0 |
Staphylococcal species exhibited the greatest susceptibility to all the S. hillii extracts. Gram-negative strains exhibited resistance to methanol and ethanol S. hillii extracts at 20.0 mg/mL. MBC values were defined as the lowest concentration that ceased bacterial growth on the Mueller–Hinton agar/tryptic soy agar and are expressed as the mean of triplicates. SXT: trimethoprim + sulfamethoxazole. MSSA: methicillin-sensitive Staphylococcus aureus. MRSA: methicillin-resistant Staphylococcus aureus. ND: not determined. Standard antibiotics were used as positive controls, whereby trimethoprim (1.25 μg) + sulfamethoxazole (23.75 μg) acted as the control for both MRSA isolates, S. epidermidis, S. saprophyticus, P. vulgaris, and P. mirabilis; penicillin G (10 μg) for MSSA; erythromycin (15 μg) for B. cereus and B. subtilis; gentamicin (10 μg) for A. baumannii and E. clocae; teicoplanin (30 μg) for E. faecalis, E. casseliflavus, and E. gallinarum; and linezolid (30 μg) was used for E. faecium. Test performed in triplicate and repeated three times (n = 3).