gms | German Medical Science

The primary purpose of this thesis, in the context of “One Health,” was to evaluate the risk of transmission of multidrug-resistant bacteria within biotopes shared by humans and animals (hospital and stable), and to propose measures to minimize this risk.

The research included two studies including samples of humans (86), pigs (589), and the stable environment (400), which were screened for livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) and extended-spectrum betalactamases carrying Escherichia coli (ESBL-E). Transmission, resistance dynamics, and epidemiological links were analysed. The results of the three studies are presented in the form of articles.

This thesis had three main research objectives:

• To gain more knowledge about the emergence and transmission of multidrug-resistant bacteria such as MRSA and ESBL-E;
• To assess the decontamination of stables contaminated with MRSA and ESBL-E; and
• To draw up specific proposals for incorporating additional resistance-monitoring procedures into existing inter-farm health management systems.

Samples from pigs in nursery and finishing stages were compared to samples from persons living on farms and working in pig stables, and epidemiological links were sought to identify possible reservoirs and transmission pathways of multidrug-resistant bacteria, particularly MRSA and ESBL in particular. Air samples and nasal and anal swabs from humans and pigs were obtained. All samples were subjected to microbiological analysis and molecular typing.

We discuss the roles of MRSA and ESBL-E as indicator organisms and their importance in both human medicine and agriculture. The experimental studies were inspired by the need to supplement existing inter-farm health monitoring systems with monitoring of resistance. The results of the (molecular) microbiological investigations and resistance screenings, epidemiological links, and derivations are presented in three self-contained chapters, designed for separate publication.

Hotspots in the pig-to-pig and pig-to-human transmission of MRSA and/or ESBL-E were identified: the pig stable air for MRSA, piglets on nursery farms for ESBL-E, and pigs crowded into abattoir waiting areas for both MRSA and ESBL-E. Carcass surfaces were tested and found to be completely free from both MRSA and ESBL-E.

To interrupt the infection chain and eliminate MRSA and ESBL-E, hygiene and sanitation measures are required. Therefore, the second experimental study reports on measures taken by a pig farm where MRSA and ESBL-E was confirmed in pigs of different ages and in persons having contact with the animals through their work in the pig stables.

Monitoring the decontamination measures employed in pig stables contaminated with MRSA and ESBL-E showed that, in principle, MRSA and ESBL-E can be successfully eliminated via hygiene and decontamination measures; however, the reintroduction of MRSA during restocking after disinfection is possible.

The extensive hygiene and eradication measures led to successful elimination of MRSA and ESBL-E from both the pigs and the stable environment. Nonetheless, a new strain of MRSA began to colonize both animals and humans.

Screening and elimination activities during the health-monitoring program improved the health status of pigs and consequently reduced the use of antibiotics.

Thus, all participating farms were categorized by their risk of intra- and inter-farm resistance transfer based on the results gathered in the previous experimental studies.

To present the complex results of on-site audits and measurements of test parameters, risk portfolios were created in the form of four-field panels.

Using these results, three scenarios were designed for the possible incorporation of MRSA and/or ESBL-E monitoring schemes into existing and future health management initiatives:

• Scenario I – supplementing the health status certificate of piglet-producing farms
• Scenario II – supplementing risk-oriented categorization of suppliers to abattoirs
• Scenario III – increasing farmers’ personal responsibility by demonstrating and visualizing successful prevention/combating strategies through training and educational events pursuant to the Protection against Infection Act

The final results generated by the studies highlight the importance of interdisciplinary research at the interface between humans and animals in the context of “One Health.”