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Antimicrobial resistant bacteria detected from imported snails and bottom dwelling fish

Date

2024-03-27

Journal Title

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Thesis

Degree Level

Masters

Abstract

Food is an important vehicle for the dissemination of antimicrobial-resistant bacteria and genetic elements conferring resistance to antimicrobials of high importance in human medicine. In Canada, CIPARS is the surveillance system for antimicrobial resistance (AMR) in food. This surveillance system has been an important source of information on the status of AMR in food, and the impact of antimicrobial use in producing food animals. However, imported food products are not well represented in this national surveillance program. The objectives of this study were to identify several foodborne indicator bacteria and zoonotic pathogenic bacteria, and characterize resistant elements from imported snails and bottom dwelling fish available to the public. Imported snail (n = 50) and fish (n = 46) products were purchased from grocery stores in Saskatchewan (Saskatoon and Regina) and Alberta (Edmonton and Calgary). These aquaculture products are not included in the Canadian surveillance program for AMR. In addition, these products were produced in regions of Asia where large volumes of antimicrobials are used. The high antimicrobial use in these areas could be reasonably expected to select for high levels of AMR, with particular concern for resistance to the extended-spectrum cephalosporins and carbapenems. Standard culture techniques were used to grow and isolate for important foodborne bacteria, including Salmonella, Escherichia coli and Staphylococcus aureus. Enterobacterales and non-taxa specific bacteria with potential to be extended-spectrum β-lactamase (ESBL) and/or carbapenamase producers were selected by using selective and differential media. Isolates were screened for resistance to a broad panel of antimicrobials by broth-microdilution using commercially prepared media including the β-lactams, aminoglycosides, quinolones, tetracyclines and sulphonamides. Isolates with ESBL or carbapenamese producing phenotypes were subsequently screened for clinically relevant resistance genes. Several important bacterial pathogens, including E. coli, Enterobacter spp., and S. aureus, were isolated from both snail and fish samples. Escherichia coli was found in 46% of snail samples and 11% of fish samples. BlaCTX-M-55 and blaCTX-M-15 were the most common extended-spectrum β-lactamase genes identified in the E. coli isolates. In Enterobacter spp., genes for CTX-M variants belonging to group 1 and 9 were identified. Plasmid-encoded genes conferring mediated quinolone resistance to quinolone (qnrS, qnrA) were also found to be co-harboured in Enterobacter spp. isolates carrying ESBLs. Several Enterobacter spp. isolates wereobserved to be colistin-resistant, however, a mobilized colistin resistance gene was not identified in this study. All methicillin-resistant S. aureus were isolated from snail samples, and were identified as having multilocus sequence types ST45 and ST188. Methicillin-resistant S. argenteus was also identified from snail samples. Citrobacter spp., Klebsiella pneumoniae and Gram-negative non-fermenters (GNNFs) were isolated from snail samples. The Citrobacter spp. isolates had ESBL phenotypes, but no ESBL genes were identified. A K. pneumoniae isolate with ST1106 obtained from one snail sample carried the blaCTX-M-55 and qnrS genes. Isolated and identified GNNFs with growth on carbapenem-resistant selective media were found to be susceptible to meropenem and several other antimicrobials used as first-line treatments. Salmonella was not detected in any of the snail and fish samples. The results from this study demonstrate that imported snails and fish can be important carriers of antimicrobial resistant bacteria (ARBs) and antimicrobial resistance genes (ARGs) from one country to another. Further study of these food types will be required to recognize the extent of ARBs/ARGs dissemination, and potential link to infections occurring in Canada.

Description

Keywords

Antimicrobial resistance, snail, fish, public health, ESBL

Citation

Degree

Master of Science (M.Sc.)

Department

Veterinary Microbiology

Program

Veterinary Microbiology

Advisor

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DOI

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