Resumen

Introduction: Delay in appropriate treatment in patients with bacteraemia can increase morbidity, mortality, and health expenditures. We compared the Rapid Direct Test (RDT) designed to detect ESBL-producing gram-negative bacteria (GNB) directly from positive blood cultures bottles, with two conventional ESBL detection tests: Screening and Confirmatory Disk Diffusion Assay (SC-DDA) and an MIC Screening and ESBL E-test (MIC/ET). Material and methods: We screened all blood cultures in a tertiary care facility from August to December 2005. We only included one positive bottle per patient in which GNB were observed. RDT: Blood from each bottle was inoculated on Mueller-Hinton agar. Ceftazidime and cefotaxime disks with and without clavulanic acid were added and incubated at 35ºC + 2ºC for 24 h. Results were interpreted according to CLSI recommendations for the SC-DDA and MIC/ET. All methods were performed simultaneously. Time for reporting as an ESBL-producer and cost of the tests were recorded. Results: We isolated 124 GNB in 114 episodes of bacteraemia, 10 of them (8.8%) polymicrobial; 79 (63.7%) of the GNB were enteric bacteria, 44 (35.5%) glucose non-fermenter GNB and one Haemophilus influenzae. The most common microorganism was Escherichia coli in 56 episodes (45.2%), followed by Pseudomonas aeruginosa in 24 (19.3%), and Klebsiella pneumoniae in 13 (10.5%). Of the 114 episodes, 41 (36%) had at least one GNB resistant to 3rd generation cephalosporins, and 25 (21.9%) were caused by an ESBL-producing GNB. Sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) for the RDT were 96%, 98.9%, 96% and 98.9%, respectively. Agreement by kappa index between RDT and SC-DDA was 0.95 and between the RDT and MIC/ET was 0.92. The RDT detected 24/25 ESBL-producing bacteria. The mean time to detect an isolate as an ESBL producer after a positive blood culture bottle signal was 1.02 + 0.19 days when using the RDT, and 3.40 + 0.59 days when using any other method. The difference in reporting time was 2.38 + 0.63 days (p < 0.0001). Our estimated cost per test was $1.54 for RDT, $2.32 for screening/confirmatory SC-DDA, and $49.65 for MIC screening and MIC/ET. Conclusions: The RDT is a rapid, reliable and easy analysis to perform, as well as cost-effective.

Palabras clave: Bacteraemia gram-negative rods ESBL-detection rapid methods.

2009-12-17   |   833 visitas   |   Evalua este artículo 0 valoraciones

Vol. 61 Núm.4. Julio-Agosto 2009 Pags. 306-312 Rev Invest Clin 2009; 61(4-ENGLISH)