Rapid Blue-Carba test: reduction in the detection time of carbapenemases performed from a 4-hour bacterial lawn

Abstract

The increase in carbapenem-resistant gram-negative bacteria is a matter of concern due to the limited therapeutic options available. In severe infections caused by these isolates, the rapid detection of the mechanisms of resistance is vital. We described a slightly modified version of the Blue-Carba test, rapid Blue-Carba test, which allows the detection of carbapenemases at 4 h of incubation from a haze of bacterial growth obtained from a positive blood culture. It was able to detect carbapenemase-producing isolates (Enterobacteriaceae, Pseudomonas aeruginosa and Acinetobacter baumannii) with a sensitivity and specificity of 98.1 and 100%, respectively. It is a rapid, easy-to-perform and an inexpensive technique that can be applied to routine laboratories, together with the simultaneous identification by mass spectrometry which would help to screen non-enzymatic carbapenem resistance; this method allows the detection of clinically relevant multidrug-resistant bacteria and the early implementation of accurate therapeutic interventions.

Evaluation of Blue-Carba Test and ISOPLEX CRE-ART-LAMP assay for rapid screening and characterization of Carbapenemases producing Enterobacteriaceae.Sudan

“…The BCT proved to be fast (detection observed ≤2 hours), highly sensitive, specific with accuracy up to 95.8%, and very cheap. These findings are in agreement with previous reports (9,10,14). The percentages of agreement between the BCT and multiplex PCR for carbapenemase genes methods for each species were comparatively good, the lowest one recorded for, 86.28%, and the highest for 95.15% as mentioned before emphasizing that BCT was able to characterize the CPE in a simple, rapidly and accessible way, and it can be implemented in clinical laboratories and hospitals with the advantage of having the affordability, accuracy and mainly speed to obtain results when compared traditional methods and molecular techniques for the detection of carbapenemase genes are costly, slow and are limited by the targets included (18).…”

Phenotypic screening and molecular characterization of carbapenemase-producing Gram-negative bacilli recovered from febrile neutropenic pediatric cancer patients in Egypt

“…The plates were incubated at 37°C for 2 hours and carbapenemase activity was determined when test and negative control solution were respectively, yellow versus blue, yellow versus green and green versus blue. Non CPs failed to change color of indicator and both solution remained either blue or green[ 16 – 18 ]. Blue carba test was done in duplicate on the promising CPs isolates after plasmid extraction.…”

Direct β-Lactam Inactivation Method: a New Low-Cost Assay for Rapid Detection of Carbapenemase- or Extended-Spectrum-β-Lactamase-Producing Enterobacterales Directly from Positive Blood Culture Bottles

“…An interesting finding was the decreased diagnostic sensitivity for the detection of VIM activity in anaerobic versus aerobic bottles (53.6% and 100%, respectively), raising the hypothesis that this enzyme may be downregulated, inactivated, or rapidly degraded in anaerobic bottles. Previous studies have shown high sensitivity values when metallo-␤-lactamases are detected directly from BCs by colorimetric methods (8)(9)(10)(11), immunochromatographic tests (14,16), or MALDI-TOF-based hydrolysis assays (17,18), even though these screening were performed only on spiked aerobic BC bottles. More recently, Cointe et al have reported the low reproducibility of the RESIST-4 O.K.N.V.…”

“…Although a number of genotypic diagnostic methods for the detection of ␤-lactamase-encoding genes in blood cultures (BCs) are currently available, they are expensive procedures requiring skilled personnel and are not able to identify all ESBL-or carbapenemase-encoding genes (6). Thus, during the last decade, several phenotype-based assays have been developed to detect ESBL or carbapenemase production in BCs, including colorimetric methods (7)(8)(9)(10)(11)(12)(13), immunochromatogenic assays (14)(15)(16), and ␤-lactam hydrolysis assays combined with matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) (17)(18)(19)(20).…”