Acta clinica Croatica, Vol. 57. No. 4., 2018.
Original scientific paper
https://doi.org/10.20471/acc.2018.57.04.02
Comparison of Two Different Methods for Tigecycline Susceptibility Testing in Acinetobacter Baumannii
Branka Bedenić
orcid.org/0000-0002-5946-7997
; Department of Microbiology, School of Medicine, University of Zagreb, Zagreb, Croatia; Department of Clinical and Molecular Microbiology, Zagreb University Hospital Centre, Zagreb, Croatia
Gordana Cavrić
; Department of Intensive Care, Merkur University Hospital, Zagreb, Croatia
Mirna Vranić-Ladavac
; Department of Microbiology, Public Health Institute of Istria County, Pula, Croatia
Nada Barišić
; Department of Microbiology, Karlovac General Hospital, Karlovac, Croatia
Natalie Karčić
; Department of Microbiology, Public Health Institute of Istria County, Pula, Croatia
Tatjana Tot
orcid.org/0000-0003-4056-7880
; Department of Microbiology, Karlovac General Hospital, Karlovac, Croatia
Aleksandra Presečki-Stanko
; Department of Clinical and Molecular Microbiology, Zagreb University Hospital Centre, Zagreb, Croatia
Amarela Lukić-Grlić
; Department of Microbiology, School of Medicine, University of Zagreb, Zagreb, Croatia; Department of Clinical Microbiology, Zagreb Children’s Hospital, Zagreb, Croatia
Sonja Frančula-Zaninović
orcid.org/0000-0002-7726-0500
; Zagreb Health Centre, Zagreb, Croatia
Katherina Bernadette Sreter
; Department of Clinical Immunology, Pulmonology and Rheumatology, Sestre milosrdnice University Hospital Centre, Zagreb, Croatia
Abstract
Tigecycline susceptibility testing (TST) presents a tremendous challenge for clinical microbiologists. Previous studies have shown that the Epsilometer test (E-test) and Vitek 2 automated system significantly overestimate the minimum inhibitory concentrations for tigecycline resistance compared to the broth microdilution method (BMM). This leads to very major errors or false susceptibility (i.e. the isolate is called susceptible when it is actually resistant). The aim of this study was to compare E-test against BMM for TST in carbapenem-resistant and carbapenem-susceptible Acinetobacter (A.) baumannii and to analyze changes in tigecycline susceptibility between two time periods (2009-2012 and 2013-2014), with BMM as the gold standard. Using the EUCAST criteria, the rate of resistance to tigecycline for the OXA-23 MBL-positive, OXA-23 MBL-negative and carbapenemase-negative strains for BMM was 54.5% (6/11), 29.4% (5/17) and 2.7% (1/37), respectively; the OXA-24/40 and OXA-58 producing organisms did not exhibit any resistance. With E-test, all OXA-23 MBL-positive organisms (11/11), 23.5% (4/17) of OXA-23 MBL-negative, and 4.1% of OXA-24/40 (3/74) strains displayed tigecycline resistance; there were no resistant strains among the OXA-58 and carbapenemase-negative isolates. Resistance emerged in the bacterial isolates from 2013 to 2014. Although tigecycline does not display cross-resistance, the highest rates of resistant A. baumannii isolates were observed among those producing VIM MBL, regardless of the testing method. These findings suggest that the commercial E-test does not provide reliable results for TST of A. baumannii. Further confirmation with the dilution method should be recommended, particularly in cases of serious infections.
Keywords
Tigecycline; Disk diffusion, antimicrobial tests; Microbial sensitivity tests; Acinetobacter baumannii; Drug resistance, microbial
Hrčak ID:
217797
URI
Publication date:
1.12.2018.
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