Resistance Trends in Antimicrobial Susceptibility of Anaerobic Bacteria, Part II

Despite the suggestions of both the Clinical and Laboratory Standards Institute (CLSI) and the American Society for Microbiology (ASM) Manual of Clinical Microbiology that hospitals should test individual patient isolates to assist in their care, periodically establish patterns of resistance for certain anaerobes, and include these data in the hospital antibiogram, anaerobic susceptibility studies are performed in only a minority of clinical laboratories and their patterns of susceptibility are obtainable mostly from published surveys conducted by a small number of research centers scattered worldwide. The Bacteroides fragilis group species, the most frequently studied anaerobes, have been reported to vary in their frequencies of resistance to all antimicrobial agents worldwide. Limited data exist about the resistance patterns of other genera and species. Part I of this two-part article reviewed the methods used for anaerobic susceptibility testing and the correlation of in vitro susceptibility test results with clinical outcome, and antimicrobial resistance that has been reported for gram-negative and gram-positive anaerobes. Part II of this article reviews mechanisms of resistance among anaerobes to commonly used antimicrobial agents.