Antimicrobial Susceptibility Testing and Therapy of Acinetobacter, Stenotrophomonas, and Similar Organisms
المؤلف:
Patricia M. Tille, PhD, MLS(ASCP)
المصدر:
Bailey & Scotts Diagnostic Microbiology
الجزء والصفحة:
13th Edition , p333-334
2025-07-20
423
Acinetobacter spp. and S. maltophilia can exhibit resistance to a wide array of antimicrobial agents, making the selection of agents for optimal therapy difficult (Table 1). In addition, automated methods for determining the minimum inhibitory concentration (MIC) for Acinetobacter spp. does not correlate with disk diffusion methods. This underscores the importance of establishing the clinical significance of individual isolates before antimicrobial testing is performed and results are reported. Failure to do so could lead to inappropriate treatment of patients with expensive and potentially toxic agents. If susceptibility testing must be performed, it is recommended that an overnight MIC method be used.
Table1. Antimicrobial Therapy and Susceptibility Testing
For urinary tract infections caused by Acinetobacter spp., single-drug therapy is usually sufficient. In contrast, more serious infections, such as pneumonia or bacteremia, may require the use of a β-lactam in combination with an aminoglycoside. Tigecycline also has potent activity against these organisms. Because this genus is able to acquire and express resistance to most antimicrobial agents, including imipenem, in vitro testing is recommended for clinically relevant isolates. Methods outlined by the Clinical and Laboratory Standards Institute (CLSI) appear to be suitable for testing Acinetobacter spp., S. maltophilia, and other organisms listed in Table 1.
S. maltophilia is notoriously resistant to most currently available antimicrobial agents, leaving trimethoprim sulfamethoxazole as the primary drug of choice for infections caused by this species. Although a few other agents, such as minocycline, ticarcillin/clavulanic acid, and chloramphenicol, often exhibit in vitro activity, clinical experience with these agents is not extensive. Therefore, trimethoprim-sulfamethoxazole remains the drug of choice.
The other agents should be considered only when trimethoprim-sulfamethoxazole–resistant strains are encountered. Even then, the potential efficacy of these other agents is suspect because of the ability of S. maltophilia to rapidly develop resistance. As indicated in Table 1, CLSI guidelines are available for the testing of several of the organisms listed in this chapter.
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