Effects of triclosan on bacterial community composition and Vibrio populations in natural seawater microcosms

Abstract

Pharmaceuticals and personal care products, including antimicrobials, can be found at trace levels in treated wastewater effluent. Impacts of chemical contaminants on coastal aquatic microbial community structure and pathogen abundance are unknown despite the potential for selection through antimicrobial resistance. In particular, Vibrio, a marine bacterial genus that includes several human pathogens, displays resistance to the ubiquitous antimicrobial compound triclosan. Here we demonstrated through use of natural seawater microcosms that triclosan (at a concentration of ~5 ppm) can induce a significant Vibrio growth response (68–1,700 fold increases) in comparison with no treatment controls for three distinct coastal ecosystems: Looe Key Reef (Florida Keys National Marine Sanctuary), Doctors Arm Canal (Big Pine Key, FL), and Clam Bank Landing (North Inlet Estuary, Georgetown, SC). Additionally, microbial community analysis by 16 S rRNA gene sequencing for Looe Key Reef showed distinct changes in microbial community structure with exposure to 5 ppm triclosan, with increases observed in the relative abundance of Vibrionaceae (17-fold), Pseudoalteromonadaceae (65-fold), Alteromonadaceae (108-fold), Colwelliaceae (430-fold), and Oceanospirillaceae (1,494-fold). While the triclosan doses tested were above concentrations typically observed in coastal surface waters, results identify bacterial families that are potentially resistant to triclosan and/or adapted to use triclosan as a carbon source. The results further suggest the potential for selection of Vibrio in coastal environments, especially sediments, where triclosan may accumulate at high levels.

Biodegradation of Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) Plastic under Anaerobic Sludge and Aerobic Seawater Conditions: Gas Evolution and Microbial Diversity

“…Extracted DNA was quantified (NanoDrop 1000, Thermo Scientific, Wilmington, DE) and diluted 1:10 before being subjected to PCR amplification of the 16S rRNA gene (primers 515 F /806R) . Two rounds of amplification were used to amplify, then subsequently tag, the V4 16S RNA gene region as previously described. , Custom Illumina adaptors with barcode sequences were added during a second round of amplification (Table S2). Amplicons were purified using equal volume SPRI magnetic beads (Sera-Mag SpeedBeads, Thermo Scientific, Freemont, CA) with 96 well magnetic plate (Promega MagnaBot II) and quantified with a Qubit Fluorometer (Thermo Fisher Scientific, Grand Island, NY) before storage at −20 °C.…”

Patterns of triclosan resistance in Vibrionaceae

“…Results suggest that members of Vibrionaceae are broadly resistant to triclosan across three genera ( Vibrio, Allivibrio , and Photobacterium ), nine clades (Cholerae, Coralliilyticus, Damselae, Fischeri, Halioticoli, Harveyi, Orientalis, Splendidus, and Vulnificus), and 15 species ( Aliivibrio fischeri , V. alginolyticus, Vibrio brasiliensis, V. campbellii , V. cholerae , Vibrio coralliilyticus , Vibrio furnissii , V. harveyi , Vibrio mimicus , V. parahaemolyticus , Vibrio pelgaius, Vibrio rotiferianus, Vibrio splendidus , V. vulnificus, and P. damselae ). Furthermore, these included known pathogens (e.g., clinical strains from established culture collections), as well as recently collected environmental isolates from distinctly different ecosystems with variable amounts of anthropogenic impacts ( Lydon et al, 2017 ).…”

“…There is growing evidence that Vibrio could be enriched in coastal waters by pharmaceutical wastes and antimicrobial agents in personal care products ( Peele et al, 1981 ; Grimes, Singleton & Colwell, 1984 ; DeLorenzo et al, 2016 ; Lydon et al, 2017 ). Triclosan resistance has specifically been hypothesized as a potential factor leading to increased abundance of Vibrio bacteria after exposure of seawater or marine organisms to triclosan ( DeLorenzo et al, 2016 ; Lydon et al, 2017 ). V. alginolyticus demonstrated MICs up to 200 µg mL −1 and are an emerging cause of vibriosis cases in the US, with infections increasing by 12-fold from 1996 to 2012, the highest rate of any Vibrio ( Slifka, Newton & Mahon, 2017 ).…”

“…Members of clades represented are common human pathogens and include seven isolates of clinical origin. In addition, 54 presumptive Vibrionaceae isolates were collected from coastal surface waters on thiosulfate-citrate-bile salts-sucrose (TCBS) agar plates during a previous study ( Lydon et al, 2017 ). Isolates were obtained from three coastal sites in the southeast U.S. between July and September 2014.…”

“…The final station was Clam Bank Landing in North Inlet Estuary (Georgetown, SC; 33.333933 N 79.192913 W). Triclosan concentrations at the time of sampling for these locations were 103, 362, and 18 ng L −1 , for Looe Key Reef, Doctors Arm Canal, and Clam Bank Landing, respectively ( Lydon et al, 2017 ).…”