Infections caused by Gram negative aerobes producing extended spectrum b-lactamases (ESBL) are associated with high morbidity and mortality, especially in the ICU.
ESBLs invalidate b-lactam therapy except for carbapenems and leave few options for alternative treatment. Accurate detection of ESBLs is necessary for therapy selection, infection control and epidemiologic surveillance.
Etest for detection of ESBLs uses both cefotaxime and ceftazidime combined with clavulanic acid. The ESBL strip configuration contains two-sided gradients, i.e. cefotaxime alone and cefotaxime + clavulanic acid (CT/CTL) or ceftazidime alone and ceftazidime + clavulanic acid (TZ/TZL). A reduction of 3 log2 dilutions (MIC ratio 8) for either cefotaxime or ceftazidime in the presence of clavulanic acid confirms the presence of ESBL at a detection sensitivity of 99.1 percent and specificity of 97.4 percent.
Keyword: infection, ESBL