Antibiotics, lactam synergy

In some cases, catechins can also act in synergistic mode when used in association with currently used antibiotic molecules (Table 2). EGCG exhibited synergy with /3-lactams. Sudano Roccaro et al. [73] found that this compound is able to reverse tetracycline resistance in Staphylococcus epidermidis and S. aureus isolates. This synergistic interaction has been explained by inhibition of tetracycline efflux pump activity in microbial cells resulting in an... 

These data are consistent with a second possible mechanism of action of daptomycin inhibition of YycG function in S. aureus and perhaps in some other low G + C Gram-positive bacteria, but not in E. coli or other Gramnegative bacteria which lack this target. This model is also consistent with the early studies showing that daptomycin inhibits cell wall biosynthesis at an unspecified early step(s).24 This partial mechanism of action is consistent with daptomycin synergy with gentamicin and certain (1-lactam antibiotics (see below). 

There are several other examples in which berberine is combined with other substances to potentiate its antibacterial activity. Flavones, chrysosplenol-D, and chrysoplenetm from Artemisia annua L. (Asteraceae), which possess very weak antibacterial action by themselves, produce potent combinations with berberine resulting in very effective inhibition of Staphylococcus aureus growth. The combination of amphotericin B and berberine can reduce by approximately 75 % the amphotericin B dose in the treatment of candidiasis in mice, implying that berberine indeed has synergy with amphotericin B against C. albicans [104]. Another example is methicillin-resistant Staphylococcus aureus (MRSA) bacteria, which are responsible for substantial morbidity and mortality in hospitals. According to Yu et al., berberine is able to restore the effectiveness of / -lactam antibiotics... 

They essentially show a dual mechanism of action firstly, the antibiotic penetrates cells by active transport, altering the permeability of the membrane (which explains the synergy with P-lactams). Secondly, once it is present into the cell cytoplasm, it binds to the 30 S ribosomal subunit inhibiting protein synthesis. 

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