Epsilon Archive for Student Projects

Abstract

Antibiotics have been used in human and animal treatment for many years and revolutionized the modern medicine. Overconsumption and misuse have led to a global problem with antibiotic resistance. Sweden is among the countries in the European union with the lowest usage of antibiotic for livestock. Development and spread of antibiotic resistant bacteria in humans can occur through consumption of foods. The objective of this pilot study aimed to investigate the occurrence of antibiotic resistant bacteria in unpasteurized milk and Swedish dairy products (pasteurized milk, fresh cheese, ripened hard cheese and fermented milk) available on Swedish market. Culturing and isolation of bacteria was performed along with taxonomic identification using MALDI-TOF MS. Nine antibiotics were used for the investigation of bacterial resistance. These antibiotics belong to some of the most important antibiotic classes used in human and veterinary medicine. Eleven antibiotic resistant bacteria species were identified. Antibiotic resistant bacteria were found in unpasteurized milk and in all the dairy products. The bacteria species were resistant towards eight antibiotics included in the investigation. Greatest diversity of antibiotic resistant bacteria species was identified in unpasteurized milk and fermented milk. Antibiotic resistant lactic acid bacteria were found in ripened hard cheese, fermented milk and unpasteurized milk. This study used a single batch of each investigated product. Further research that includes more batches from each product is required in order to elucidate how frequently occurring antibiotic resistant bacteria are in Swedish dairy products.