Research Article: Infection prevention and control interventions in the first outbreak of methicillin-resistant Staphylococcus aureus infections in an equine hospital in Sweden

Date Published: March 8, 2012

Publisher: BioMed Central

Author(s): Karin Bergström, Görel Nyman, Stefan Widgren, Christopher Johnston, Ulrika Grönlund-Andersson, Ulrika Ransjö.


The first outbreak of methicillin-resistant Staphylococcus aureus (MRSA) infection in horses in Sweden occurred in 2008 at the University Animal Hospital and highlighted the need for improved infection prevention and control. The present study describes interventions and infection prevention control in an equine hospital setting July 2008 – April 2010.

This descriptive study of interventions is based on examination of policy documents, medical records, notes from meetings and cost estimates. MRSA cases were identified through clinical sampling and telephone enquiries about horses post-surgery. Prospective sampling in the hospital environment with culture for MRSA and genotyping of isolates by spa-typing and pulsed-field gel electrophoresis (PFGE) were performed.

Interventions focused on interruption of indirect contact spread of MRSA between horses via staff and equipment and included: Temporary suspension of elective surgery; and identification and isolation of MRSA-infected horses; collaboration was initiated between authorities in animal and human public health, human medicine infection control and the veterinary hospital; extensive cleaning and disinfection was performed; basic hygiene and cleaning policies, staff training, equipment modification and interior renovation were implemented over seven months.

Collaboration between relevant authorities and the veterinary hospital and formation of an infection control committee with an executive working group were required to move the intervention process forward. Support from hospital management and the dedication of staff were essential for the development and implementation of new, improved routines. Demonstration of the outbreak strain in the environment was useful for interventions such as improvement of cleaning routines and interior design, and increased compliance with basic hygienic precautions. The interventions led to a reduction in MRSA-positive samples and the outbreak was considered curbed as no new cases occurred for over a year.

Partial Text

A worldwide, steady increase in nosocomial and community-acquired infections due to methicillin-resistant Staphylococcus aureus (MRSA) is apparent in humans. Carriage and infections in animals are also reported by many authors [1-7]. The first reported findings of MRSA in equines were in broodmares with endometritis [8,9], but surgical site and traumatic wound infections have been most frequently described [4,10-12]. A special sequence type (ST), 398, has emerged in livestock and horses in European countries [5,7,12-16]. ST398 has also become relatively frequent among MRSA isolates in the human community in some European countries [15-17]. The frequency of MRSA in animals in Sweden is still considered low. MRSA was first detected in Sweden in dogs in 2006 [18] and the first positive horse in Sweden was one nasal carrier found in a MRSA screening study of 300 healthy horses in 2007 [18]. In a recent (2010-2011) screening study of 284 horses, none tested positive for MRSA [19].

The University Animal Hospital offers highly qualified surgery and medicine and some patients are immunocompromised. Consequently, the usage of antimicrobials might be relatively high. Since antimicrobial usage has been described as a risk for equine MRSA colonisation [11,42] effective infection prevention and control are essential in such settings. Success in short-term eradication by sectioning, improved infection control and repeated MRSA testing without using antimicrobials in two Canadian farms with MRSA-colonised horses has been reported [43]. The main interventions in the present study were aimed at improved infection prevention and control, supported by environmental sampling.

Joint efforts by hospital management, microbiology and infection control, with support from local and national authorities, curbed the MRSA outbreak studied here. The occurrence of single horses infected by the same strain and subsequent findings of the MRSA strain in the hospital and the surrounding region show the need for continuous awareness and improvement of infection prevention and control measures.

The authors declare that they have no competing interests.

KB initiated and wrote the study together with UR and GN. KB designed the protocol for sampling in the environment. UR was the infection control expert who led the work at the UDS. CJ was the contact at the hospital, providing the information and records and adding editorial comments to the manuscript. SW designed Figure 1 and provided information from the process at the time of the outbreak. UGA contributed the authority view to the manuscript. All authors have discussed, read and agreed the final manuscript.