Reservoirs and Transmission Pathways of Resistant Indicator Bacteria in the Biotope Pig Stable and along the Food Chain: A Review from a One Health Perspective

Abstract

The holistic approach of “One Health” includes the consideration of possible links between animals, humans, and the environment. In this review, an effort was made to highlight knowledge gaps and various factors that contribute to the transmission of antibiotic-resistant bacteria between these three reservoirs. Due to the broad scope of this topic, we focused on pig production and selected “indicator bacteria”. In this context, the role of the bacteria livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) and extended spectrum beta-lactamases carrying Escherichia coli (ESBL-E) along the pig production was particularly addressed. Hotspots of their prevalence and transmission are, for example, pig stable air for MRSA, or wastewater and manure for ESBL-E, or even humans as vectors in close contact to pigs (farmers and veterinarians). Thus, this review focuses on the biotope “stable environment” where humans and animals are both affected, but also where the end of the food chain is not neglected. We provide basic background information about antibiotics in livestock, MRSA, and ESBL-bacteria. We further present studies (predominantly European studies) in tabular form regarding the risk potentials for the transmission of resistant bacteria for humans, animals, and meat differentiated according to biotopes. However, we cannot guarantee completeness as this was only intended to give a broad superficial overview. We point out sustainable biotope approaches to try to contribute to policy management as critical assessment points in pig housing conditions, environmental care, animal health, and food product safety and quality as well as consumer acceptance have already been defined.

Extended Spectrum β-Lactamase (ESBL) Producing Escherichia coli in Pigs and Pork Meat in the European Union

“…Some of the initial phases where pigs can be colonized by ESBL-producing E. coli is at trading places, livestock transport vehicles, through introduction of new animals into herds, or at lairage in the slaughterhouse [ 20 ]. As drinking water [ 80 ], surface water [ 81 ] and wastewater [ 82 ], all can be contaminated with ESBL-producing E. coli , a possible transmission of ESBLs from the environment to pigs can occur.…”

“…According to the reports of the European Food Safety Authority (EFSA) the prevalence of presumptive ESBL producing E. coli in fattening pigs and pork meat varies a lot within the EU countries [ 18 , 19 ]. It is worth noting that there are several steps within the pork production chain where pigs are exposed to ESBL producing bacteria and can become carriers of them, such as trading places, where new animals are mixed with older animals within the same herd, or slaughterhouse waiting areas [ 20 ]. In addition, cross-contamination in slaughterhouses, especially at evisceration, poses a risk of carcass contamination with ESBL producing Enterobacteriaceae [ 21 , 22 ].…”

Achieving Environmentally Sustainable Livestock Production

“…Another major issue related to animal health is antibiotic resistance, and this has also links to the environmental impacts of livestock production. In their comprehensive review, Schmithausen et al [20] highlight knowledge gaps and various factors that contribute to the transmission of antibiotic-resistant bacteria between animals, humans, and the environment in pig production, following a holistic "One Health" approach.…”

Bioaerosol measurements over a fattening period in a pig barn focused on the presence of Staphylococcus spp.

“…as indicator bacteria for investigations of contaminated barn materials. Nevertheless, only a small percentage of the cultivable airborne Gram-negative bacteria survive in the environment (Zucker et al 2000;Schmithausen et al 2018).…”