Retrospective analysis of Vitek®2 performance compared to manual broth micro-dilution for colistin susceptibility testing of Acinetobacter baumannii complex isolates in South Africa

Vuyolwethu Fadana; Teena Thomas; Nina von Knorring

doi:10.4102/ajlm.v11i1.1597

Retrospective analysis of Vitek^®2 performance compared to manual broth micro-dilution for colistin susceptibility testing of Acinetobacter baumannii complex isolates in South Africa

Afr J Lab Med. 2022 Feb 28;11(1):1597. doi: 10.4102/ajlm.v11i1.1597. eCollection 2022.

Authors

Vuyolwethu Fadana^{1

2}, Teena Thomas^{1

3}, Nina von Knorring^{1

4}

Affiliations

¹ School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa.
² Department Pathology, National Health Laboratory Services, Johannesburg, South Africa.
³ Infectious Control Services Laboratory, National Health Laboratory Services, Johannesburg, South Africa.
⁴ Mycobacteriology Referral Laboratory, National Health Laboratory Service, Johannesburg, South Africa.

Abstract

The manual broth micro-dilution (mBMD) is the recommended reference method for colistin minimum inhibitory concentration determination; however, it is not as readily available in South Africa as the Vitek^®2. This retrospective study compared the performance of Vitek^®2 against mBMD in determining the colistin minimum inhibitory concentration of 337 extensively drug-resistant Acinetobacter baumannii complex isolates. Vitek^®2 yielded a categorical agreement of 89%, an essential agreement of 56%, a major error rate of 8% and a very major error rate of 55%. The Vitek^®2 is not an alternative to mBMD for colistin susceptibility testing.

Keywords: Acinetobacter; Vitek®2; antimicrobial susceptibility testing; broth micro-dilution; colistin.