ENHANCEMENT OF ANTIBIOTIC SUSCEPTIBILITY AND SUPPRESSION OF MYCOBACTERIUM-AVIUM COMPLEX GROWTH BY POLOXAMER-331

The resistance of Mycobacterium avium complex (MAC) to antibiotics is thought to be enhanced by its outer glycolipid layer, which protects t he organisms from antibiotics and host defense mechanisms, We hypothes ized that surfactants which disrupt the lipid barrier might be of ther apeutic value, We evaluated the ability of 10 poloxamer surfactants to inhibit the growth of R/IAC organisms and to potentiate antimycobacte rial drug activity in broth culture using a radiometric assay, Very la rge, small, or hydrophilic poloxamers had little or no effect. However , certain hydrophobic poloxamers, especially P331, retarded the growth of most isolates of MAC and produced a synergistic effect with rifamp in, The MIC of rifampin required to inhibit the growth of MAC was redu ced from a mean of 14.6 mu g/ml (range, 4 to >32 mu g/ml) to 1.4 mu g/ ml (range, <1.125 to 4 mu g/ml) by 1.0 mg of P331 per mi (P < 0.01). E nhancement of antibiotic susceptibility was observed with concentratio ns of poloxamer as low as 10 mu g/ml. These studies suggest that P331 might be useful in increasing the effectiveness of antibiotic therapy of MAC infections.