Staphylococcal micrococcins. III. Antibacterial and therapeutic properties

Micrococcin M, micrococcin M1 and eight micrococcin M derivatives, and two peptide antibiotics produced by micrococci and staphylococci were investigated for their antibacterial activity and therapeutic value. These antibiotics appeared to act solely on Gram-positive bacteria, especially on staphylococci and streptococci, in quite low concentrations in vitro and exerting both bacteriostatic and bactericidal effects. Gram-negative bacteria were virtually not susceptible. Resistance to micrococcins developed very rapidly, due to existence of numerous primarily resistant cells in sensitive populations. Complete cross-resistance resulted from acquiring resistance to one of the micrococcin antibiotics. Therapeutic effects are poor, as micrococcins are not absorbed from the injection site or from the intestinal tract after peroral administration. Importance of micrococcins in nature may be high, especially when ecology of normal bacterial flora and carriage of staphylococci and streptococci are concerned.