Antimicrobial Susceptibility Testing and Therapy of Neisseria and Moraxella catarrhalis
المؤلف:
Patricia M. Tille, PhD, MLS(ASCP)
المصدر:
Bailey & Scotts Diagnostic Microbiology
الجزء والصفحة:
13th Edition , p455
2025-08-21
544
Although beta-lactamase production is common among M. catarrhalis isolates, many beta-lactam antibiotics maintain activity. Because several other agents are also effective, susceptibility testing to guide therapy is not routinely required (Table 1).
Table1. Antimicrobial Therapy and Susceptibility Testing
Standard methods have been established for performing in vitro susceptibility testing with N. gonorrhoeae and N. meningitidis. The Clinical and Laboratory Standards Institute (CLSI) recommends the use of agar dilution for minimum inhibitory concentration (MIC) measurements and GC agar containing 1% growth supplement for N. gonorrhoeae disk diffusion methods.
In addition, various agents can be considered for testing and therapeutic use. Quinolones were widely used to treat gonorrhea; however, resistance to these agents has emerged (i.e., quinolone-resistant N. gonorrhoeae [QRNG]), and they are no longer recommended for treatment of gonorrhea.
The Gonococcal Isolate Surveillance Project (GISP) has identified six categories of antibiotic susceptibility patterns for the characterization of isolates: PPNG (plasmid-mediated beta-lactamase positive); TRNG (plasmid-mediated tetracycline resistance, MIC ≥ 16 µg/ mL); PPNG-TRNG; Penr; Tetr (MIC = 2-8 µg/mL) (chromosomal-mediated resistance patterns); and CMRNG (Penr combined with Tetr).
Because of the increase in QRNG and PPNG isolates, broad-spectrum cephalosporins have become the treatment of choice for N. gonorrhoeae. However, treatment failures have been associated with the use of broad spectrum cephalosporins. Oral and intravenous regimens are recommended, depending on the severity and location of the infection.
Beta-lactamase production in N. meningitidis is extremely rare, although decreased susceptibility to penicillin, mediated by altered penicillin-binding proteins, is emerging. Optimum laboratory methods for detecting this relatively low level of resistance have not yet been established, and the impact of this resistance on the clinical efficacy of penicillin is not known. The CLSI recommends that susceptibility testing be performed by disk diffusion on Mueller-Hinton agar or using cation-adjusted Mueller-Hinton broth in microdilution.
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