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Published on: October 9, 2017
Oxytetracycline-resistant Paenibacillus larvae identified in commercial beekeeping operations in Saskatchewan using
Oleksii Obshta1, Michael W Zabrodski2, Tayab Soomro1
1Departments of Veterinary Pathology, University of Saskatchewan, SK, Canada.
Abstract:
American foulbrood (AFB) is an infectious disease of honey bee brood caused by the endospore-forming bacterium Paenibacillus larvae. P. larvae spores are resilient in the environment, thus colonies with clinical signs of AFB are often destroyed by burning to eradicate the causative agent. To prevent outbreaks of AFB, oxytetracycline metaphylaxis is widely used in North America, resulting in sustained selective pressure for oxytetracycline resistance in P. larvae. To determine if antimicrobial resistance (AMR) is present among P. larvae isolates from commercial beekeeping operations in Saskatchewan, Canada, we performed antimicrobial susceptibility testing of 718 P. larvae samples cultured from pooled, extracted honey collected from 52 beekeepers over a 2-y period, 2019 and 2020. We found that 65 of 718 (9%) P. larvae samples collected from 8 beekeepers were resistant to oxytetracycline with minimum inhibitory concentration (MIC) values of 64-256 µg/mL. Eight of 718 (1%) samples from 4 beekeepers had intermediate resistance to oxytetracycline (MIC: 4-8 µg/mL). Susceptibility testing for tylosin and lincomycin indicated that P. larvae in Saskatchewan continue to be susceptible to these antimicrobials (tylosin MIC: <1 µg/mL, lincomycin MIC: ≤2 µg/mL). Most oxytetracycline-resistant P. larvae samples were identified in northeastern Saskatchewan. Whole-genome sequence analysis identified the P. larvae-specific plasmid pMA67 with tetracycline-resistance gene tet(L) in 9 of 11 oxytetracycline-resistant P. larvae isolates sequenced. Our results highlight the advantage of using pooled, extracted honey as a surveillance tool for monitoring AMR in P. larvae.
Insights
Nine percent of honey bee samples in Saskatchewan showed resistance to oxytetracycline, a common antibiotic. This study monitored antimicrobial resistance (AMR) in Paenibacillus larvae, the cause of American foulbrood disease.
Area of Science:
- Veterinary Microbiology
- Apiculture Science
- Antimicrobial Resistance
Background:
- American foulbrood (AFB) is a significant honey bee brood disease caused by *Paenibacillus larvae*.
- Oxytetracycline use for AFB prevention exerts selective pressure, potentially leading to antimicrobial resistance (AMR).
- Monitoring AMR in *P. larvae* is crucial for effective disease management in beekeeping operations.
Purpose of the Study:
- To determine the prevalence of antimicrobial resistance in *Paenibacillus larvae* isolates from commercial beekeepers in Saskatchewan, Canada.
- To assess the susceptibility of *P. larvae* to oxytetracycline, tylosin, and lincomycin.
- To identify potential genetic mechanisms conferring oxytetracycline resistance.
Main Methods:
- Antimicrobial susceptibility testing was performed on 718 *P. larvae* samples cultured from pooled honey.
- Samples were collected from 52 beekeepers in Saskatchewan over two years (2019-2020).
- Whole-genome sequencing was used to identify resistance genes in oxytetracycline-resistant isolates.
Main Results:
- Nine percent (65/718) of *P. larvae* samples exhibited oxytetracycline resistance (MIC: 64-256 µg/mL).
- One percent (8/718) of samples showed intermediate oxytetracycline resistance (MIC: 4-8 µg/mL).
- All isolates remained susceptible to tylosin and lincomycin; oxytetracycline resistance was linked to the *tet*(L) gene on plasmid *pMA67*.
Conclusions:
- A significant proportion of *P. larvae* in Saskatchewan exhibit oxytetracycline resistance.
- Pooled honey analysis is an effective surveillance method for monitoring AMR in honey bee pathogens.
- Continued monitoring and judicious use of antimicrobials are essential to preserve treatment efficacy.
