Persistent and Transient Airborne MRSA Colonization of Piglets in a Newly Established Animal Model.

Kerstin Rosen,Uwe Roesler,Roswitha Merle,Anika Friese

doi:10.3389/fmicb.2018.01542

Abstract

Livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) was first found in 2005 and is up to date widespread in animal husbandry reservoir – focusing on pig farming. The regular detectability of MRSA in the air of pigsties as well as in exhaust air of pig farms (mean count: 102 cfu/m3) poses the question whether an airborne spread and, therefore, a MRSA colonization of animals via the airborne route exists. To answer this question, we exposed three groups of nine MRSA-negative tested piglets each to a defined airborne MRSA concentration (102, 104, and 106 cfu/m3) in our aerosol chamber for 24 h. In the following observation period of 21 days, the MRSA status of the piglets was monitored by taking different swab samples (nasal, pharyngeal, skin, conjunctival, and rectal swab). At the end of the experiment, we euthanized the piglets and investigated different tissues and organs for the spread of MRSA. The data of our study imply the presence of an airborne MRSA colonization route: the animals exposed to 106 cfu/m3 MRSA in the air were persistent colonized. The piglets exposed to an airborne MRSA concentration of 104 cfu/m3 were transient, and the piglets exposed to an airborne MRSA concentration of 102 cfu/m3 were not colonized. Consequently, a colonization via the airborne route was proven.

Highlights

For more than a decade, it is known that the occurrence of methicillin-resistant Staphylococcus aureus (MRSA) is no longer restricted to the well-known hospital-acquired MRSA (HA-MRSA) and community-acquired MRSA (CA-MRSA)
The results of the air samplings during the animal exposure of all three groups are included. It shows that the targeted MRSA concentrations in the air were reproducible and that all three groups were exposed to the defined MRSA concentration in the air during the different experiments
Our study aimed to identify the required dose for a successful MRSA colonization of piglets via the airborne transmission route

Summary

Introduction

For more than a decade, it is known that the occurrence of methicillin-resistant Staphylococcus aureus (MRSA) is no longer restricted to the well-known hospital-acquired MRSA (HA-MRSA) and community-acquired MRSA (CA-MRSA). Livestock – and of outstanding importance – pig farming is a reservoir where MRSA was first described in 2005 (Voss et al, 2005). To distinguish it from the already known MRSA, these variants were referred as livestock-associated MRSA (LAMRSA). Most of the LA-MRSA isolates are assigned to the clonal complex (CC) 398 and the sequence type (ST) 398 with the predominant spa type t011. There was an increase of MRSA isolates associated to livestock in hospitals of rural areas (Becker et al, 2017)

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Conclusion