Comparison of the modified hodge test and the carba NP Test for detection of carbapenemases in enterobacteriaceae isolates Enterobacteriaceae izolatlarinda Karbapenemazlarin Saptanmasinda Modifiye Hodge Testi ve Carba NP Testlerinin Karşilaştirilmasi

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Mikrobiyoloji Bulteni, vol.50, no.1, pp.1-10, 2016 (Journal Indexed in SCI Expanded) identifier identifier identifier

  • Publication Type: Article / Article
  • Volume: 50 Issue: 1
  • Publication Date: 2016
  • Doi Number: 10.5578/mb.10861
  • Title of Journal : Mikrobiyoloji Bulteni
  • Page Numbers: pp.1-10


A rapid, pra:tical, and accurate identification of carbapenemase-producing Enterobacteriaceoe isolates is crucial for the implementation of appropriate infection control measures and proper treatment of the infection:.. For this purpose, a large number of phenotypic test methods havi been developed, although none has 100% sensitivity and specificity. Variations in sensitivity and speci icity of these tests based on the tyf>e of beta-lactamase enzymes carried by that isolates might result in deferences between regions and countries. The aim of this study was to compare the performances of wic'ely used modified Hodge test (MHT) and Carbapenemase Nordmann-Poirel (Carba NP) test in the dc cction of carbap- enemases in Enlerobacteriaceae family members. A total of 65 Enterobacteriaceoe isol ites (43 blaOX4.8, 10 blaVLM 9 blaMb, 1 blaNDM-1,1 blaKPC-2and 1 blaOZA-48+blaVLMcarrying strains) that showed decreased sensitivity to at least one carbapenem (ertapenem, imipenem or meropenem), and carriage of carbapenemase gene confirmed by polymerase chain reaction (PCR), were included in the sti dy. Seventy-eight isolates showing decreased susceptibility to carbapenems but lacking carbapenemase genes were used as controls. All isolates were identified by using conventional methods as well as autor lated BD Phoenix System (Becton Dickinson, USA). The antimicrobial susceptibility testing was performed using the same automated system, and was confirmed by disk diffusion method. Results were evaluated according to the CLSI criteria. MHT was performed in accordance with the CLSI guideline, and Carba NP test was carried out by a modified protocol. Instead of imipenem monohydrate, which was used in the original protocol, 6 mg/ml imipenem/cilastatin was used in the modified protocol. In the study, MHT Identified 90.8% (59/65) of carbapenemase-producing isolates, while 93.9% (61/65) of the isolates were identified by Carba HP test. With MHT, four Klebsiella pneumoniae producing OXA-48, one Escherichia coli producing IMP, .ind one K.pneumoniae producing NDM-1, and with Carba NP test, One E-colli and one K.pneumoniae producing OXA-48, one E.coli producing IMP, and one Enterobacter cloacae producing VIM could not dc detected. Three OXA-48-producing isolates (two K.pneumoniae and one E.coli) yielded late and weak positive results with Carba NP test MHT had false positivity for 31 isol ites, while Carba NP test showed no false positivity. In comparison of the sensitivity and specificity of the two tests, sensitivities were found to be similar although the Carba NP has a slightly higher sensitiv ty than the MHT (93.9% versus 9C.8%, respectively; p= 0.754), Carba NP was found more specific (10C% versus 60.3%, respectively; p< 0.0001). With Carba NP test, 26% of the isolates (n= 16) were positive within 15 minutes, and 85% (n= 52) were positive within the first hour. It was concluded that, Carb.: NP test showed high sensitivity and specificity than the MHT and the results can be obtained more rapicly for the presence of carbapeneniases in Enterobacteriaceoe. The use of MHT alone is not recommendc d to confirm the presence of carbapenemases produced by Enterobacteriaceae. On the other hand Carba NP test can be used for this purpose, however molecular analysis should be considered for suspicious negative results.