Antibiotic — ziracin
The emergence of an increasingly wide range of bacterial pathogens resistant to the antibiotics in current use is becoming a worldwide problem, as is the rise in the incidence of community-acquired pneumonia caused by Streptococcus pneumoniae. Intense efforts are now being made to discover new and more effective antibacterial agents. The oligosaccharide ziracin is a potentially valuable compound. It is one of the everinomicin antibiotics obtained from cultures of Microspora carbonaceae, and appears to be capable of inhibiting the growth of many Gram-positive organisms.1
Laboratory studies involving over 1,000 clinical isolates of penicillin-susceptible S. pneumoniae (PSSP) and penicillin-resistant S. pneumoniae (PRSP) showed ziracin was effective in low concentrations against both strains.2 Animal studies showed good correlation between in vitro and in vivo concentration of ziracin, and indicated that the antibiotic had a marked, rapid and extended antibacterial action on both PSSP and PRSP-induced pneumonia.3 In lung infections, the penetration of an antibiotic into the pulmonary tissues may be modified by changes in cell permeability and the infiltration of leucocytes, or possibly by its local inactivation.
Ziracin has the advantage of a long half-life of about 9hr, associated with high peak concentrations of the drug, which are not affected by pulmonary inflammation or infection. The good penetration of ziracin was associated with a high clearance of bacteria from the blood, an important factor in reducing the risks of septicaemia, as in toxic pneumonia the survival rate after ziracin treatment is high.
The mechanism of action of ziracin is not yet clear, but may be linked with the inhibition of protein synthesis. If that is the case, the target of ziracin activity may be different from that of other antibiotics that also inhibit protein synthesis. Ziracin may prove an effective alternative treatment in the control of infections caused by Gram-positive organisms, and clinical trials are now in progress to assess its value in infections resistant to other forms of therapy.