Biocides and antibiotics are commonly used in Irish agriculture. This could lead to accumulation at sublethal levels in water and resistance development. The risk of this has earlier been assessed as non-existent. However, resistant strains have been found in Irish farm waste water. Due to possible horizontal gene transfer between bacterial populations the risk may be higher. Antibiotic resistance mechanisms have worked against certain biocides and antibiotic resistant strains have in certain cases showed reduced biocidal susceptibility. The aim of this project was to characterise bacterial populations from Irish aquatic samples and investigate their susceptibility to agriculturally common biocides and relevant antibiotics. Isolates from Dublin Bay water samples (n=15) were characterised using basic techniques. Minimum inhibitory concentration (MIC) tests with a broth microdilution method were performed with eight biocides and complimentary minimum bactericidal concentration (MBC) tests. Antibiotic disc diffusions were performed with eight antibiotics. The samples contained gram-negative isolates (n=3), Staphylococcus aureus (n=1) and Bacillus spp. (n=8) isolates. All isolates were on average resistant towards methylated spirits and iodine at the 2% v/v starting concentration. MIC values for Tri Scrub and the generic biocide were high. All MBC values were on average higher than the corresponding MIC values. A significant amount of the Bacillus spp. isolates were resistant towards β-lactams. As there is statistical uncertainty around the results, further investigations are needed. In conclusion, a trend of both high MIC and MBC values while showing resistance towards the largest number of antibiotics could be seen in Bacillus spp. isolates.
| Identifer | oai:union.ndltd.org:UPSALLA1/oai:DiVA.org:uu-530648 |
| Date | January 2024 |
| Creators | Ezelius, Andreas |
| Publisher | Uppsala universitet, Institutionen för medicinsk cellbiologi |
| Source Sets | DiVA Archive at Upsalla University |
| Language | English |
| Detected Language | English |
| Type | Student thesis, info:eu-repo/semantics/bachelorThesis, text |
| Format | application/pdf |
| Rights | info:eu-repo/semantics/openAccess |
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