Epidemiology of antimicrobial-resistant bacteria in food and humans

This thesis describes different aspects around the central topic if food could be a source of resistant bacteria for humans. Extended-spectrum beta-lactamase-producing E. coli (ESBL-EC) are bacteria that are resistant to different antimicrobials which are frequently used in Dutch hospitals. Chicken meat was known to frequently be contaminated with ESBL-EC. This thesis shows a decline in contamination rate of chicken meat in Dutch supermarkets from 68.3% in 2014 to 44.6% in 2015. Also, free-range chicken meat is less frequently contaminated than conventional chicken meat. The latest research, not from this thesis, shows that the contamination rate has further declined to 7.6% in 2020. The genetics of ESBL-EC cultured from humans and chicken meat were compared. A small group of ESBL-EC cultured from humans could not genetically be distinguished from ESBL-EC cultured from chicken meat, suggesting potential transfer between chicken meat and humans.
In this thesis a relatively novel potential source for ESBL-EC is described, bean sprouts. Nine-teen percent of bean sprouts samples from Dutch shops were contaminated with ESBL-E. Bean sprouts have the potential to more easily transmit bacteria to humans as they are often consumed raw or only lightly cooked.
Bacteria from the gut that are acquired through food must pass the gastric-acid barrier. It was investigated whether proton-pump inhibitors, medication that decreases the acidity of the stomach, increase the risk of carriage with ESBL-producing Enterobacteriaceae. This was confirmed by our research and has since the publication been re-confirmed multiple times including by a large meta-analysis on this specific topic. Based on microbiological data it should be reevaluated if proton-pump inhibitors should be purchasable over the counter without a prescription.