Antimicrobial Susceptibility Testing and Therapy of Pseudomonas, Burkholderia, and Similar Organisms
المؤلف:
Patricia M. Tille, PhD, MLS(ASCP)
المصدر:
Bailey & Scotts Diagnostic Microbiology
الجزء والصفحة:
13th Edition , p343
2025-07-23
522
Many of these organisms grow on the media and under the conditions recommended for testing of the more commonly encountered bacteria; however, the ability to grow under test conditions does not guarantee reliable detection of important antimicrobial resistance. Therefore, even though testing can provide an answer, it poses a substantial risk of erroneous interpretations. Validated susceptibility testing methods are available for a limited number of antibiotics.
Burkholderia spp. and R. pickettii are infrequently encountered in human infections. Potential therapies for B. cepacia and B. pseudomallei are provided, but antimicrobial therapy rarely eradicates B. cepacia, especially from the respiratory tract of patients with cystic fibrosis, and the optimum therapy for melioidosis remains controversial. Burkholderia spp. are capable of expressing resistance to various antibiotics, so devising effective treatment options can be problematic. Establishing the clinical significance of these species is important in the care of the patient.
Among Pseudomonas spp. and Brevundimonas spp., P. aeruginosa is the only species for which valid in vitro susceptibility testing methods exist and for which extensive therapeutic evidence exists (see Table 1). Therapy usually involves the use of a beta-lactam developed for antipseudomonal activity and an aminoglycoside. The particular therapy used depends on several clinical factors and on the laboratory antimicrobial resistance profile for the P. aeruginosa isolate. P. aeruginosa isolated from patients with cystic fibrosis may require extended incubation for up to 24 hours before obtaining a reliable susceptibility pattern. In addition, the organ ism may develop resistance during prolonged therapy with any antimicrobial agent within 3 to 4 days requiring repeat susceptibility testing.
P. aeruginosa is intrinsically resistant to various antimicrobial agents; only those with potential activity are shown in Table 1. However, P. aeruginosa also readily acquires resistance to the potentially active agents listed, necessitating susceptibility testing for each clinically relevant isolate.
Although antimicrobial resistance is also characteristic of the other Pseudomonas spp. and Brevundimonas spp., the fact that these organisms are rarely clinically significant and the lack of validated testing methods prohibit the provision of specific guidelines (see Table 1). Antimicrobial agents used for P. aeruginosa infections are often considered for use against the other species; however, before proceeding with the development of treatment strategies, the first critical step should be to establish the clinical significance of the organism.
Table1. Antimicrobial Therapy and Susceptibility Testing
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