Annals of Clinical Microbiology, The official Journal of the Korean Society of Clinical Microbiology

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pISSN 2288-0585 eISSN 2288-6850

Assessment of Efflux Activity Using H33342 Accumulation in Tigecycline-Resistant Acinetobacter baumannii Clinical Isolates

Original article

Annals of Clinical Microbiology (Ann Clin Microbiol) 2017 December, Volume 20, Issue 4, pages 90-96.

https://doi.org/10.5145/ACM.2017.20.4.90

Assessment of Efflux Activity Using H33342 Accumulation in Tigecycline-Resistant Acinetobacter baumannii Clinical Isolates

Choon-Mee Kim1*, In Sun Choi2*, Sook Jin Jang2, Na-Ra Yun3, Dong-Min Kim3, Donghoon Lim4, Young-Joon Ahn5, Seong Ho Kang2, Geon Park2, Dae Soo Moon2
1Premedical Science, College of Medicine, Chosun University, Departments of 2Laboratory Medicine, 3Internal Medicine, 4Urology, 5Medical Education, College of Medicine, Chosun University, Gwangju, Korea

Abstract

Background: Tigecycline resistance has emerged recently and has shown diverse mechanisms. The aim of this study was to assess the role of efflux activity in tigecycline resistance in 120 clinical isolates of A. baumannii using two

methods: the H33342 accumulation assay and adeB real-time reverse transcriptase polymerase chain reaction. In addition, we analyzed the correlation between the expression level of adeB and H33342 accumulation level. Methods: A. baumannii clinical isolates was divided into tigecycline-resistant (49 strains), intermediate (40 strains), and susceptible (31 strains) groups. The H33342 accumulation was measured in the absence or presence of the efflux pump inhibitor carbonyl cyanide 3-chlorophenylhydrazone (CCCP). Real-time RT- PCR was performed to determine the relative expression of the adeB gene in A. baumannii clinical isolates.

Results: The level of H33342 accumulation in the resistant group was relatively lower than those in the other groups. The addition of CCCP caused a significantly increased fold change in H33342 accumulation in the tigecycline-resistant group. Significant difference in the fold change level in H33342 accumulation was found between tigecycline-susceptible and resistant isolates. Those findings support the role of efflux pumps of which substrates are H33342 in the resistance of tigecycline. Significant differences in the relative expression levels of adeB were shown between tigecycline-susceptible and resistant groups also.

Conclusion: The results showed that several efflux pumps of which substrates were H33342 can contribute to tigecycline resistance. The adeB overexpression can also contribute to tigecycline resistance. It is possible that efflux pumps other than adeB efflux pumps contribute to tigecycline resistance because there was no correlation between fold change level in H33342 accumulation and adeB expression level. (Ann Clin Microbiol 2017;20:90-96)

Keywords

Acinetobacter baumannii, Efflux pump inhibitor, Tigecycline