Use of Antimicrobial Susceptibility Testing for Epidemiology and the Selection of Oral, Parenteral and Topical Regimens for Control of CAPD-AssociatedStaphylococcus aureusInfection

Publisher Website
Google Scholar
Abstract
Staphylococcus aureus is an important cause of peritonitis in patients undergoing continuous ambulatory peritoneal dialysis (CAPD). Using standard broth microdilution and disk diffusion methodology, we evaluated the in vitro activity of selected antimicrobial agents against S. aureus strains isolated from CAPD patients to assess candidate regimens for 1) topical agent control of colonization, 2) oral chemotherapy of CAPD infectious complications, and 3) parenteral treatment of serious CAPD-associated staphylococcal infections. A total of 34 isolates (31 patients) of S. aureus were available for testing, including 29 isolates (29 patients) from pericatheter skin, four isolates (four patients) from the nares, and one isolate from an episode of peritonitis. Six of the isolates were oxacillin-resistant (ORSA). The antimicrobial agents tested by broth microdilution included 17 different quinolones, 10 cephalosporins, six glycopeptides, two aminoglycosides, and imipenem. A total of eight potential topical agents, including the antistaphylococcal agent mupirocin, were tested by disk diffusion. All of the quinolones, with the exception of nalidixic acid (MIC90 > 16 μg/ml), had excellent activity against both ORSA and oxacillin-susceptible S. aureus (OSSA) with the most active agent being WIN57273 (MIC90 ≤ 0.015 μg/ml). Imipenem and the cephalosporins, with the exception of cefixime, ceftazidime, and E-1040, possessed good activity against OSSA. None of the beta-lactam agents tested were active against ORSA. Likewise, the aminoglycosides, amikacin and gentamicin, exhibited good activity against OSSA strains but no activity against ORSA strains. All glycopeptides tested demonstrated excellent activity against ORSA strains. Of the topical antimicrobial agents tested only bacitracin, mupirocin, and nitrofurantoin were active against all OSSA and ORSA strains tested. The 34 strains tested revealed 18 distinct restriction endonuclease profiles of plasmid DNA (REAP). Isolates with the same REAP profiles could be further delineated by the use of neomycin, novobiocin, or norfloxacin tests. These findings suggest that clinical trials for prophylaxis and treatment of S. aureus infections in CAPD patients utilizing the new fluoroquinolones, glycopeptides, and mupirocin may be warranted. Furthermore, selected use of the phenotypic antimicrobial agent resistance pattern can supplement REAP and other molecular typing techniques in epidemiological studies.