Prospective evaluation of the Amplidiag® CarbaR+VRE assay for direct screening of carbapenemase producing gram-negative bacilli from rectal swabs

Performance of two methods of carbapenem-resistant Enterobacterales surveillance on a kidney transplant ward: selective culture of and real-time PCR directly from rectal swabs

BACKGROUND

Infection with carbapenem-resistant Enterobacterales (CRE) is associated with a high mortality rate in kidney transplant recipients, and colonization with CRE is one of the major risk factors for CRE infection. There is, therefore, a need to improve the capacity to detect colonization with CRE among inpatients.

METHODS

In this prospective study, we compared the performance of real-time PCR for carbapenemase directly from rectal swabs with that of conventional CRE surveillance culture in all patients admitted to a kidney transplant ward between February 2019 and March 2020. Surveillance culture and real-time PCR were performed at admission and weekly until hospital discharge. Two perineum-rectal swabs were collected: one for culture and one for PCR.

RESULTS

We collected 905 paired samples for CRE surveillance from 399 patients, of whom 347 (87.0%) were kidney transplant recipients and 52 were waiting list patients. CRE was detected by culture and/or PCR in 75 patients (18.8%). Positivity for CRE was identified by PCR in 62 (15.5%) of the 399 patients and by culture in 55 (13.8%); 20 (5.0%) of the patients tested positive only on PCR, and 13 (3.3%) tested positive only on culture. The most common carbapenemase and species were, respectively, bla_KPC (in 85.5%) and Klebsiella pneumoniae (in 80.0%). Infection with CRE occurred in 21.6% of the colonized patients, those cases occurred only among kidney transplant recipients. None of the patients who tested negative on culture developed CRE infection.

CONCLUSION

In conclusion, the two methods are complementary and could be useful in a scenario of high CRE prevalence.

Evaluation of three molecular carbapenemase tests: Eazyplex SuperBug complete B, Novodiag CarbaR+, and Amplidiag CarbaR+MCR

BACKGROUND

Carbapenemase-producing Gram-negative bacilli, i.e., Enterobacterales, Pseudomonas aeruginosa, and Acinetobacter, are of increased concern for the public health around the world. There is urgent need for rapid and accurate tests in order to provide correct treatment and to prevent bacterial spread in healthcare settings.

METHODS

The aim of this study was to evaluate three commercial multiplex carbapenemase tests with CE-IVD marking: Eazyplex SuperBug complete B (AmplexDiagnostics), Novodiag CarbaR+ (Mobidiag), and Amplidiag CarbaR+MCR (Mobidiag). All these tests recognize KPC, NDM, OXA-48/181 group, VIM, OXA-23 group, and OXA-24/40 group, and Novodiag CarbaR+ and Amplidiag CarbaR+MCR additionally recognize IMP, OXA-51 group (with promoter located within ISAbaI), OXA-58 group, and MCR, and Amplidiag CarbaR+MCR further recognizes GES (carbapenemase-type only).

RESULTS

The sensitivities and specificities of these tests with bacterial isolates were 100%. The sensitivity directly from clinical samples was 100%, but the specificity was lower, which is simply explained by the higher sensitivity of the molecular methods compared with culture method.

CONCLUSIONS

Overall, these CE-IVD marked tests provide a good alternative in the detection of carbapenemase-producing organisms.