Detection and Control of a Nosocomial Outbreak Caused by Salmonella Newport at a Large Animal Hospital

Abstract

Background: Nosocomial salmonellosis is often assumed to occur because infection control and surveillance practices are inadequate, but published evidence is lacking to support the related contention that rigorous application of these practices can impact the severity of outbreaks. Objective: Describe active surveillance, early recognition, and intensive mitigation efforts used in an effort to control an outbreak of nosocomial Salmonella enterica serotype Newport infections without hospital closure. Animals: Large animals hospitalized at a referral hospital. Methods: This prospective outbreak investigation was initiated when Salmonella Newport infections were detected among hospitalized animals by active surveillance. Data were analyzed to identify temporal and spatial patterns for epidemic spread of Salmonella in the hospital. Mitigation efforts were aggressively adjusted in response to surveillance data. Genetic relatedness of isolates was investigated by pulsed‐field gel electrophoresis. Results: Of 145 large animals sampled, 8 (5.6%) were infected with the Salmonella strain associated with this outbreak, and all but 1 shed Salmonella in the absence of or before the onset of disease. This strain was recovered from 14.2% (42/295) of environmental samples (ENV samples), indicating that widespread environmental contamination had occurred. Isolates of Salmonella Newport obtained from infected animals and the environment were genetically indistinguishable, confirming clonal dissemination. Conclusions and Clinical Importance: Active surveillance allowed early detection of nosocomial Salmonella transmission and hospital contamination. Use of aggressive interventions was followed by cessation of transmission. Active surveillance can allow earlier recognition and mitigation compared with programs by only sampling of clinically affected animals.

Nosocomial Infections and their Surveillance in Veterinary Hospitals

“…Even though loads of recommendations for prevention and control of nosocomial infection is available out of the lesson learnt from previous experiences (Hartmann et al, 1996;Wright et al, 2005;Dallap et al, 2010;Goehring et al, 2010;Steneroden et al, 2010). Presently there is no recognized or published principles or standards for surveillance and control of infection in veterinary hospitals, which makes the system weak to determine rates and fraction of nosocomial and preventable infections respectively (Morley, 2002(Morley, , 2004Benedict et al, 2008;Morley and Weese, 2008).…”

“…Studies have reported 1% to 5% prevalence of the sub-clinical shedding of Salmonella by horses entering veterinary clinics (Roberts and O'Boyle, 1981). Persistence of Salmonella in the hospital environment has been often reported to be associated with nosocomial outbreaks (Steneroden et al, 2010;) and environmental contamination with S. enterica in veterinary hospitals are identified as a hazard related to the nosocomial infections (Pandya et al, 2009;). In fact, many nosocomial outbreaks recorded in equine veterinary hospitals have been associated with multi drug resistant strains (Table 1).…”

“…Many outbreaks of nosocomial salmonellosis have been reported from different large animal hospitals especially among horses (Steneroden et al, 2010;Tillotson et al, 1997;Dallap et al, 2010;). In horses Salmonella spp.…”

“…In 2008, Benedict et al (2008) conducted a study in US veterinary teaching hospitals and reported that 53% of hospitals are collecting samples for detecting the specific pathogen and it is their one of the element of infection control practices. One of the specific contagious pathogen often encountered in veterinary nosocomial outbreaks and also incorporated in hospital surveillance is Salmonella Cherry et al, 2004;Benedict et al, 2008;Steneroden et al, 2010). Patient who are under greater risk of shedding Salmonella are included in the surveillance (Morley, 2002(Morley, , 2004Morley and Weese, 2008;Ekiri et al, 2010).…”

“…Prevalence studies have shown that 4-9% patients endure from a nosocomial infection (Mielke, 2010). The occurrence of nosocomial infections in veterinary hospitals has not been well established and in nascent stage (Boerlin et al, 2001;Johnson, 2002;Morley, 2004;Smith, 2004;Traub-Dargatz et al, 2004;Morley and Weese, 2008), even though the nosocomial infections are of immense significance in the field of veterinary medicine since quite a lot of March 2015 | Volume 3 | Special issue 2 | Page 2 nosocomial outbreaks of different etiologies in veterinary hospitals has been documented (Castor et al, 1989;Madewell et al, 1995;Hartmann et al, 1996;Konkle et al, 1997;Tillotson et al, 1997;Seguin et al, 1999;Weese and Armstrong, 2003;Cherry et al, 2004;Wright et al, 2005;Weese et al, 2006a;Dallap et al, 2010;Goehring et al, 2010;Steneroden et al, 2010). Six of those outbreaks had evidence of zoonotic infection (Konkle et al, 1997;Seguin et al, 1999;Cherry et al, 2004;Wright et al, 2005;Weese et al, 2006a).…”