Evaluation of Modified Hodge Test as a Non-molecular Assay for Accurate Detection of KPC-producing Klebsiella pneumoniae

Abstract

A b s t r a c tKlebsiella pneumoniae carbapenemase (KPC) have become a major therapeutic challenge because of its increasingly fast dissemination throughout the world. Accurate detection of KPC is essential for optimal treatment. The Clinical and Laboratory Standards Institutes (CLSI) for fast detection of KPC producers currently recommend Modified Hodge Test (MHT) and Carba NP test. MHT can directly detect carbapenemase production in Enterobacteriaceae isolates. The current study was conducted to evaluate the capacity of MHT with two carbapenem disks for accurate detection of KPC. MHT was performed according to guidelines of CLSI to identify isolates with carbapenem resistance. In doing so, two substrates of MHT were assigned into two groups for examination: meropenem and ertapenem groups. A total of 96 non-repetitive clinical isolates of Klebsiella pneumoniae were tested. The presence of the bla KPC gene in each MHT-positive isolate was examined by PCR. A total of 54 isolates exhibited reduced susceptibility or resistance to carbapenems. Sensitivity of MHT with two carbapenem disks was similar. Specificity of the MHT with meropenem disk was 64% and with ertapenem disk was 53%. Detection of KPC by MHT with meropenem disk was found to be more effective than with ertapenem disk. Based on our results, the presence of KPC does not in itself influence the categorization of resistance. Therefore, the use of MHT with ertapenem disk for the rapid detection of KPC among K. pneumoniae for infection control should not be recommended.K e y w o r d s: Klebsiella pneumoniae, carbapenem disks, detection method, Modified Hodge Test, KPC Ghasemnejad A. et al.

The role of the bla KPC gene in antimicrobial resistance of Klebsiella pneumoniae

“…Ninety-six K. pneumoniae isolates were isolated from the following departments: intensive care unit (34.38%), emergency ward (17.71%), outpatient unit (15.63%), surgery ward (9.38%), rheumatology and nephrology unit (5.21%), neonatal intensive care unit (4.17%), neurology unit (3.13%), gynecology ward (3.13%), neonatal unit (2.08%), orthopedics (1.04%), laparoscopy unit (1.04%), ear-throat-nose unit (1.04%), Radiology (1.04%), and unknown units (1.04%). Overall, 59 (61.5%) patients were male, and 37 (38.5%) patients were female (20).…”

“…K. pneumoniae isolates were collected from Al-Zahra hospital, Isfahan, Iran between February and June 2016. The clinical specimens included urine samples, wound swabs, peritoneal fluid sample, blood samples, respiratory secretions, and others (20).…”

“…The cycling conditions were as follows; 10 min at 94°C, followed by 35 cycles of 30 s at 94°C, 20 s at 57°C, and 20 s at 72°C, then 10 min hold at 72°C. Ten microliter of the product was detected by 1% (w/v) agarose gel electrophoresis in 1X TAE buffer (20, 21).…”

“…According to the CLSI guidelines, MHT was performed for the detection of carbapenemases. Due to the low specificity of MHT method, both meropenem and ertapenem discs were used separately as the substrates for MHT (20, 22).…”

“…Initial denaturation at 95°C for 5 min, followed by 35 cycles of denaturation at 95°C for 60 s, annealing at 53°C for 30 s, elongation at 72°C for 90 s, and a final extension at 72°C for 10 min. The amplification product was approximately 819 bp in length (20).…”