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Brief Report

Antimicrobial Drug-Resistant Gram-Negative Saprophytic Bacteria Isolated from Ambient, Near-Shore Sediments of an Urbanized Estuary: Absence of β-Lactamase Drug-Resistance Genes

1
School of Public Health, University of California, Berkeley, CA 94720, USA
2
Department of Environmental Sciences, Southern Illinois University, Edwardsville, IL 62026, USA
*
Author to whom correspondence should be addressed.
Antibiotics 2020, 9(7), 400; https://doi.org/10.3390/antibiotics9070400
Received: 11 June 2020 / Revised: 5 July 2020 / Accepted: 7 July 2020 / Published: 10 July 2020
(This article belongs to the Special Issue Antimicrobial Resistance and Virulence Mechanisms)
We assessed the prevalence of antimicrobial resistance and screened for clinically relevant β-lactamase resistance determinants in Gram-negative bacteria from a large urbanized estuary. In contrast to the broad literature documenting potentially hazardous resistance determinants near wastewater treatment discharge points and other local sources of aquatic pollution, we employed a probabilistic survey design to examine ambient, near-shore sediments. We plated environmental samples from 40 intertidal and shallow subtidal areas around San Francisco Bay (California, USA) on drug-supplemented MacConkey agar, and we tested isolates for antimicrobial resistance and presence of clinically relevant β-lactamase resistance determinants. Of the 74 isolates identified, the most frequently recovered taxa were Vibrio spp. (40%), Shewanella spp. (36%), Pseudomonas spp. (11%), and Aeromonas spp. (4%). Of the 55 isolates tested for antimicrobial resistance, the Vibrio spp. showed the most notable resistance profiles. Most (96%) were resistant to ampicillin, and two isolates showed multidrug-resistant phenotypes: V. alginolyticus (cefotaxime, ampicillin, gentamicin, cefoxitin) and V. fluvialis (cefotaxime, ampicillin, cefoxitin). Targeted testing for class 1 integrons and presence of β-lactam-resistance gene variants TEM, SHV, OXA, CTX-M, and Klebsiella pneumonia carbapenemase (KPC) did not reveal any isolates harboring these resistance determinants. Thus, while drug-resistant, Gram-negative bacteria were recovered from ambient sediments, neither clinically relevant strains nor mobile β-lactam resistance determinants were found. This suggests that Gram-negative bacteria in this well-managed, urbanized estuary are unlikely to constitute a major human exposure hazard at this time. View Full-Text
Keywords: antibiotic resistance; aquatic contamination; probabilistic sampling; San Francisco Estuary; coast; Pseudomonas; Shewanella algae; Vibrio parahaemolyticus antibiotic resistance; aquatic contamination; probabilistic sampling; San Francisco Estuary; coast; Pseudomonas; Shewanella algae; Vibrio parahaemolyticus
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MDPI and ACS Style

Moritz, C.F.; Snyder, R.E.; Riley, L.W.; Immke, D.W.; Greenfield, B.K. Antimicrobial Drug-Resistant Gram-Negative Saprophytic Bacteria Isolated from Ambient, Near-Shore Sediments of an Urbanized Estuary: Absence of β-Lactamase Drug-Resistance Genes. Antibiotics 2020, 9, 400. https://doi.org/10.3390/antibiotics9070400

AMA Style

Moritz CF, Snyder RE, Riley LW, Immke DW, Greenfield BK. Antimicrobial Drug-Resistant Gram-Negative Saprophytic Bacteria Isolated from Ambient, Near-Shore Sediments of an Urbanized Estuary: Absence of β-Lactamase Drug-Resistance Genes. Antibiotics. 2020; 9(7):400. https://doi.org/10.3390/antibiotics9070400

Chicago/Turabian Style

Moritz, Charles F., Robert E. Snyder, Lee W. Riley, Devin W. Immke, and Ben K. Greenfield. 2020. "Antimicrobial Drug-Resistant Gram-Negative Saprophytic Bacteria Isolated from Ambient, Near-Shore Sediments of an Urbanized Estuary: Absence of β-Lactamase Drug-Resistance Genes" Antibiotics 9, no. 7: 400. https://doi.org/10.3390/antibiotics9070400

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