| Article ID | Journal | Published Year | Pages | File Type |
|---|---|---|---|---|
| 3359481 | International Journal of Antimicrobial Agents | 2010 | 5 Pages |
To evaluate the synergistic activity of erythromycin and human polymorphonuclear cells (PMNs) on the binomial erythromycin-resistant (ERYR) Streptococcus pyogenes/host, the phagocytic and bactericidal activities of PMNs against ERYR streptococcal strains (cMLSB, M, and iMLSB A, B and C phenotypes) were assessed in the presence of the macrolide. The results showed that when erythromycin, PMNs and streptococci [both erythromycin-sensitive (ERYS) and ERYR] were simultaneously present in the culture medium, PMN phagocytic activity was similar to that of drug-free controls. In contrast, the results emphasised a significant high increase in intracellular killing by PMNs in the presence of erythromycin not only for ERYS streptococci but also for ERYRS. pyogenes with high (cMLSB, iMLSB A and iMLSB B phenotypes) and moderate (M and iMLSB C phenotypes) erythromycin resistance compared with controls without drug. From literature data it emerged that, even if intracellularly concentrated, erythromycin is relatively inactive because of its instability. The results indicate that the enhanced intra-PMN streptococcal killing detected is mainly attributable to PMN bactericidal systems that synergise with intracellular erythromycin in eradicating ERYRS. pyogenes strains (both with high and moderate resistance). These data confirm that the antibiotic resistance detected in vitro does not always imply a failure of antimicrobial treatment.
