Effects of colistin and tigecycline on multidrug-resistant Acinetobacter baumannii biofilms: advantages and disadvantages of their combination

Yoshinori Sato,Yasuo Ono,Yusuke Yoshino,Tsuneyuki Ubagai,Shigeru Tansho-Nagakawa

doi:10.1038/s41598-021-90732-3

Yoshinori Sato, Yasuo Ono + Show 3 more

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https://doi.org/10.1038/s41598-021-90732-3

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Journal: Scientific Reports	Publication Date: Jun 3, 2021
Citations: 14	License type: open-access

Affiliation: Teikyo University

Abstract

We investigated the antimicrobial effects of colistin (CST) and tigecycline (TGC), either alone or in combination, on biofilm-dispersed and biofilm-embedded multidrug-resistant Acinetobacter baumannii (MDRAB) strains R1 and R2. The bacterial growth of biofilm-dispersed MDRAB was inhibited by CST or TGC. However, the inhibitory effects were attenuated by a combination of CST and low concentrations of TGC. The bactericidal effects of CST, but not TGC, were observed on biofilm-dispersed MDRAB. Notably, the bactericidal effects increased with a combination of CST and high concentrations of TGC, whereas they were attenuated with the combination of CST and low concentrations of TGC. Although biofilm formation by MDRAB decreased with increasing concentrations of CST or TGC, there was no complete disruption of the biofilms. Additionally, the biofilms increased with a combination of 1–2 μg/mL CST and TGC at 2 μg/mL and 2–4 μg/mL for strains R1 and R2, respectively. Biofilm-embedded MDRAB was eradicated with CST, but not TGC. Notably, the eradication effects increased with a combination of CST and high concentrations of TGC, whereas attenuation happened with the combination of CST and low concentrations of TGC. These results provide information on the combined effects of CST and TGC in the treatment of biofilm-associated MDRAB infection.

Highlights

We investigated the antimicrobial effects of colistin (CST) and tigecycline (TGC), either alone or in combination, on biofilm-dispersed and biofilm-embedded multidrug-resistant Acinetobacter baumannii (MDRAB) strains R1 and R2
These results suggest that CST at 32 μg/mL has antibiotic effects for biofilm-dispersed and for biofilm-embedded MDRAB, whereas TGC is an effective antibiotic for the inhibition of bacterial growth of biofilm-dispersed but not biofilm-embedded MDRAB
The inhibitory effects were slightly attenuated by the combination of CST at 8 and 16 μg/mL and TGC at 0.25–1 μg/mL (Table 3). These results suggest that the inhibitory effects of CST on the bacterial growth of biofilm-dispersed MDRAB were attenuated when used in combination with low concentrations of TGC

Summary

Introduction

We investigated the antimicrobial effects of colistin (CST) and tigecycline (TGC), either alone or in combination, on biofilm-dispersed and biofilm-embedded multidrug-resistant Acinetobacter baumannii (MDRAB) strains R1 and R2. The eradication effects increased with a combination of CST and high concentrations of TGC, whereas attenuation happened with the combination of CST and low concentrations of TGC These results provide information on the combined effects of CST and TGC in the treatment of biofilm-associated MDRAB infection. We have reported that clinical isolates of MDRAB showed different degrees of biofilm formation in the presence of sub-minimum inhibitory concentrations (sub-MICs) of CST and TGC17, suggesting that A. baumannii is emerging as a highly pathogenic bacterium and that the characteristics of A. baumannii vary under different environmental stress conditions, such as in the presence of multiple antimicrobial agents. We analyzed the combined effects of CST and TGC on biofilms formed by MDRAB

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