Description
A-54556A is an acyldepsipeptide (ADEP) antibiotic that has been found in Streptomyces hawaiiensis. It is active against B. subtilis, S. pyogenes, and E. faecalis, as well as penicillin-resistant S. pneumoniae, vancomycin-resistant E. faecium, and methicillin-resistant S. aureus (MRSA; IC50s = 0.2, 0.4, 0.4, 1.6, 0.4, and 6.3 μg/ml, respectively). It binds to and activates caseinolytic protease P (ClpP), inducing degradation of β-casein by the B. subtilis ClpP in an ATPase-independent manner when used at concentrations of 2.5 and 5 μg/ml.
Uses
A 54556A is an unusual depsipeptide isolated from Streptomyces hawaiiensis by researchers at Eli Lilly in 1985, featuring a trienone side chain. A 54556A is potently active against Gram positive and Gram negative bacteria, including MRSA. A 54556A was the original lead structure of the recently re-discovered acyldepsipeptide (ADEP) antibiotics that act by activating and disregulating Clp-family proteins. ADEPs are considered important leads in the development of new generations of antibiotics against resistant bacteria.
in vitro
previous study found that the treatment of b. subtilis with 1.6 mg/ml of a-54556a reduced the number of viable cells by 2 log units. in addition, the biosynthesis of dna, rna, protein, cell wall and fatty acid proceeded unhindered for 1 h at 2 mg/ml a-54556a, whereas classical antibiotics were clearly distinguished by preferential inhibition of their target pathway. microscopic examination showed that after addition of a-54556a at concentrations as low as 0.4 mg/ml, b. subtilis started to form filaments [1].
in vivo
two a-54556a analogs, adep 2 and adep 4, were proven to be active in the treatment of bacterial infections in rodents. when mice were challenged with a lethal systemic infection of e. faecalis, 1 mg/kg adep 2 or 0.5 mg/kg adep 4 were sufficient for 100% survival. in lethal sepsis caused by s. aureus, 12.5 mg/kg adep 4 rescued 80% of the mice and reduced the bacterial loads in liver, spleen and lung by 2–3 log units compared to an untreated control [1].
IC 50
0.2 μg/ml for bacillus subtilis 168
References
[1] h. brtz-oesterhelt, d. beyer, h. p. kroll, et al. dysregulation of bacterial proteolytic machinery by a new class of antibiotics. nature medicine 11(10), 1082-1087 (2005).
