Patterns of triclosan resistance in Vibrionaceae.

Keri A Lydon,Erin K Lipp,Megan J Robertson

doi:10.7717/peerj.5170

Abstract

The antimicrobial additive triclosan has been used in personal care products widely across the globe for decades. Triclosan resistance has been noted among Vibrio spp., but reports have been anecdotal and the extent of phenotypic triclosan resistance across the Vibrionaceae family has not been established. Here, triclosan resistance was determined for Vibrionaceae strains across nine distinct clades. Minimum inhibitory concentrations (MIC) were determined for 70 isolates from clinical (n = 6) and environmental sources (n = 64); only two were susceptible to triclosan. The mean MIC for all resistant Vibrionaceae was 53 µg mL−1 (range 3.1–550 µg mL−1), but was significantly different between clades (p < 0.001). The highest mean triclosan MIC was observed in the Splendidus clade (200 µg mL−1; n = 3). Triclosan mean MICs were 68.8 µg mL−1 in the Damselae clade and 45.3 µg mL−1 in the Harveyi clade. The lowest mean MIC was observed in the Cholerae clade with 14.4 µg mL−1, which was primarily represented by clinical strains. There were no significant differences in triclosan MIC among individual species or among environmental strains isolated from different locations. Overall, phenotypic triclosan resistance appears to be widespread across multiple clades of Vibrionaceae.

Highlights

The bacterial Family Vibrionaceae is made up of seven genera and 142 species, grouped into 23 distinct clades (Sawabe, Kita-Tsukamoto & Thompson, 2007; Sawabe et al, 2013)
The mean triclosan Minimum inhibitory concentrations (MIC) observed for all Vibrionaceae isolates (n = 70) was 53 μg mL−1 with a range of 3.1–550 μg mL−1
Triclosan resistance was previously documented in V. cholerae (Massengo-Tiasse & Cronan, 2008) and was suspected in unidentified Vibrio spp. from the estuarine environment (DeLorenzo et al, 2016), but resistance had not been systematically examined across a wide range of Vibrionaceae

Summary

Introduction

The bacterial Family Vibrionaceae is made up of seven genera and 142 species, grouped into 23 distinct clades (Sawabe, Kita-Tsukamoto & Thompson, 2007; Sawabe et al, 2013) These aquatic bacteria exhibit high amounts of gene exchange (Polz et al, 2006), and act as opportunistic pathogens to both humans and marine organisms. Common pathogenic species in humans include Vibrio cholerae, Vibrio vulnificus, Vibrio parahaemolyticus, Vibrio alginolyticus, and Photobacterium damselae; any member of the Vibrionaceae associated with clinical disease is nationally reportable in the U.S under the Cholera and Other Vibrio Illness Surveillance (COVIS) program (US Centers for Disease Control and Prevention (CDC), 2017) In some cases, these infections may lead to severe outcomes including fatal bouts of diarrhea due to dehydration or fatal septicemia in patients with compromised immune systems (Hlady & Klontz, 1996; Guerrant, Carneiro & Dillingham, 2003; Menon et al, 2014). The role of antibiotic resistance in these bacteria has been investigated in environmental and retail oysters (Han et al, 2007), with some studies

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