Methods: Perianal swabs were collected weekly from HSCT recipients between Dec. 2013-Apr. 2015 and plated onto HardyCHROM™ ESBL and CRE agar. Swabs that yielded a ceftriaxone-resistant Enterobacteriaceae (CTX-R-E) and their corresponding CTX-R-E isolated from chromogenic agar were subjected to molecular testing (PCR/sequencing). For each positive swab, we also analyzed a swab from the same day that did not yield a CTX-R-E. A panel of target-specific molecular beacon probes in a real time PCR assay (MB-PCR) was used to rapidly identify ESBLs (CTX-M, TEM and SHV ESBLs) and carbapenemases (NDM, VIM, IMP, OXA-48 and KPC). The results of MB-PCR directly from the perianal swab were compared to the genotyping results from CTX-R-E isolates identified on chromogenic agar.
Results: CTX-R-E were recovered on chromogenic agar from 50 swabs. The most common CTX-R-E recovered from swabs were E. coli (35), E. cloacae (4), multiple species (4), and K. pneumoniae (3). The MB-PCR identified CTX-M in 30 of the 31 swabs that yielded a CTX-M-producing Enterobacteriaceae by culture (97% sensitivity) and identified KPC in 9 of the 10 swabs that yielded a KPC-producing Enterobacteriaceae (90% sensitivity). CTX-M was detected from 4 of the 69 swabs that did not yield a CTX-M-producing Enterobacteriaceae (94% specificity) and KPC was not detected from the 90 swabs that did not yield a KPC-producing Enterobacteriaceae (100% specificity).
Conclusion: Multiplex MB-PCR assay is a sensitive and specific tool for detection of colonization by ESBLs and CRE directly from perianal swabs in HSCT recipients. This assay, with a turnaround time of <6 hrs, if implemented in real-time, could rapidly identify colonized patients, limit nosocomial transmission, and guide empirical antibacterial therapy.
K. D. Chavda,
L. Chen, None
C. Manca, None
S. G. Jenkins, None
T. J. Walsh, None
B. N. Kreiswirth, None