Detección de aislados clínicos de Escherichia coli y Klebsiella spp. productoras de β-lactamasas de espectro extendido mediante el sistema DIRAMIC

Abstract

In the past few years there has been an increasing interest about extended-spectrum betalactamase
(ESBL) producing Enterobacteriaceae. The organisms of this phenotype develop the ability to hydrolyze many classes
of antibiotics, including third generation cephalosporins and aztreonam. They confer variable level of resistance to
oxyimino-betalactams, it is shown to increase in minimum inhibitory concentration (MIC) value, remaining sensitive
in vitro. These enzymes could be undetected in the laboratory, but it does affect the patient, because there is no activity
of the drug and therefore, can cause therapeutic failure. Hence, the accurate laboratory detection is very important. For
this research the DIRAMIC system was compared with the modified double-disc synergy test (DDD) for the detection of
ESBL. A total of 175 clinical isolates, 132 Escherichia coli and 43 Klebsiella spp., from three hospitals of the Havana city,
during the period June 2008 - June 2009, were studied. In 42 (24 %) positive isolates for ESBL detected by DDD, 39 (22.3
%) isolates were identified by the DIRAMIC system. In three isolates, the ESBL phenotype was only detected by DDD,
DIRAMIC reported as false negative. The 72.6 % of the isolates (127) were negative for both methods. Both tests had the
similar performance, shown in 92.85 % of correspondence. The DIRAMIC system exhibited 92.85 % sensitivity and 95.48
% specificity for ESBL detection compared to DDD