Document Type : Original Article
Authors
1
Department of Biology, College of Science, King Abdulaziz University, Jeddah, Saudi Arabia.
2
Department of Biology, College of Science, King Abdulaziz University, Jeddah, Saudi Arabia. -Department of Botany and Microbiology, Faculty of Science, Kafrelsheikh University, Kafrelsheikh, Egypt.
3
Department of Microbiology, King Faisal Medical Complex, Taif, Makkah, Saudi Arabia
Abstract
Carbapenem resistance Gram-Negative bacteria (CR-GNB) impose life-threatening infections with limited treatment options. Rapid detection of CR-GNB-associated infections is usually associated with proper treatment and better disease prognosis. The aim of this study was to evaluate the efficacy of the Phoenix automated system, Modified Hodge Test (MHT) and X΄pert Carba-R assay for the detection of CR-GNB. A panel of 167 non-repetitive CR-GNB with reduced susceptibility to carbapenems which was identified by the Kirby-Bauer method was analyzed by means of 1) Phoenix automated system, 2) MHT, and 3) X΄pert Carba-R assay. The most accurate identification of resistance determinants was obtained with the Phoenix automated system that diagnosed and confirmed all carbapenem-resistant isolates (n=167/167, 100%). Just 57% of CR-GNB were identified by X΄pert Carba-R Assay whereas seventy-nine (n=79/99, 79.8%) of CR Klebsiella spp., (n=5/23, 21.7%) of CR Pseudomonas spp., (n=10/32, 31.25%) of CR Acinetobacter baumannii, and (n=4/13, 30.8%) of CR other bacteria were identified. MHT correctly identified 56/99 (56.6%) strains of CR Klebsiella spp., 12/23 (52.2%) strains of CR Pseudomonas spp., 18/32 (56.25%) strains of CR A. baumannii, and 2/13 (15.4%) strains of other CR bacteria. While according to carbapenemase producers' genes, MHT most successfully identified blaNDM+blaOXA pattern of carbapenem resistance strains (n=25/26, 96.2%), then sensitivity lowered when testing blaOXA positive strain with (n=17/30, 56.7%), and less than half blaNDM positive samples were recognized by MHT with (n=19/42, 45.2%), sensitivity and specificity of MHT to detect carbapenemase producers' bacteria were 69.3% and 60.9%, respectively. Phoenix automated system diagnosed all the carbapenemase producers' bacteria in all genetic patterns as carbapenem resistance isolates with one hundred percent sensitivity but without any specificity to carbapenmase mechanism among other CR mechanisms. In conclusion, to detect and control the spread of CR-GNB with complicated resistance mechanisms, phenotypic automated assays are recommended in the routine diagnostic of clinical laboratories, but genotypic assays are recommended in nosocomial infection control to detect carbapenemase producers.
Keywords
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