Salmonella Closes New Bolton Center

Reprinted from
An outbreak of multidrug-resistant salmonella has occurred at the University of Pennsylvania's New Bolton Center and was reported to have caused an unknown number of animal deaths.

The Center and its Widener Hospital closed on Monday, May 10, so that appropriate decontamination procedures for the entire facility can be performed. This procedure will take about eight weeks.

According to Helma Weeks, director of communications for the university's School of Veterinary Medicine, "At this point all services are closed and no patients are being seen by any service. The hospital will be re-opened after we have instituted appropriate bio-security measures to protect our patients. We have notified our referring veterinarians of the situation."

Salmonella is often found in equine hospitals since stress can cause shedding in animals harboring the organism.

Salmonella species cause a multitude of diseases in horses, including diarrhea, abscesses, septicemia, and other ailments, according to information from Dr. Roberta Dwyer, of the University of Kentucky's Gluck Equine Research Center in the Equine Disease Quarterly. More than 2,200 serotypes of salmonellae are known and can be identified at the National Veterinary Services Laboratories (NVSL) in Ames, Iowa. With the exception of S. typhi, which only affects humans, all other salmonellae are zoonotic--meaning they can be transmitted from animals to people.

Routine, rigorous disinfection of stalls with chemicals known to be effective against salmonellae in the presence of organic matter is essential, both in hospitals and on farms, Dwyer noted. Since no commercially available vaccine exists against salmonella, disinfection and biosecurity are the primary preventive measures that must be undertaken. Horse owners need to be aware of the zoonotic potential of any Salmonella-positive horse and take proper precautions (isolation techniques, use of protective clothing, washing hands, etc.).

These measures are critical because of the zoonotic potential for any Salmonella species, which can be deadly in immunocompromised individuals and dangerous to pregnant women. Of considerable concern to the human and veterinary medical professions is the emergence of multidrug-resistant strains of bacteria. In a report from the Centers for Disease Control and Prevention (June 28, 2002), multidrug-resistant S. newport isolates were reported from New York, Michigan, Pennsylvania, Ohio, and Connecticut.

Shedding of Salmonella
In a report from the 2001 American Association of Equine Practitioners convention on Salmonellosis Spread and Antibiotic Resistance, veterinarians noted Salmonella shedding is a concern in veterinary hospitals and on farms. One study found that out of 246 colic patients, 9% shed Salmonella at some point during their hospital stay. They were more likely to shed the bacterium if:

-- They had diarrhea; 
-- The hospital stay was more than eight days long; 
-- Nasogastric intubation was abnormal (possibly a reflux situation); 
-- Leukopenia (a reduced number of circulating white blood cells) was present; 
-- The patient traveled more than one hour to reach the hospital (possibly causing transport stress).

Further study showed that environmental cultures were usually negative, leading the researchers to think that the sources of Salmonella in hospitals were usually the patients. Therefore, good hygiene practices and disinfection of stalls between patients become major concerns.
Bleach was found to be the most effective disinfectant against Salmonella when used in a 1:32 diluted solution. However, bleach in this concentration is very hard on equipment, and it is readily inactivated by organic material. Therefore, areas to be disinfected should be cleaned of as much organic material as possible, and one might consider a more equipment-friendly disinfectant if disinfection will be done very often. Bleach could then be used on a less frequent basis for more powerful disinfection.

Not only is disinfection a concern, but antibiotic resistance has become a problem. Roughly 24.6 million pounds of antibiotics are given to animals for non-therapeutic use annually, compared with only two million pounds for therapy. Three million pounds go to human treatment each year. Widespread non-therapeutic use of antibiotics leads many to think that we are exposing too many pathogens to low levels of antibiotics that promote "tough" strains to survive. Thus, we might be inadvertently selecting for more resistant pathogens. For example, Salmonella type 104, which has been identified as a cause of salmonellosis in Ontario, Canada, has demonstrated resistance to 12 types of antibiotics.

Human food supplies are presenting the same problem. A survey of beef and chicken purchased from supermarkets showed that 20% contained Salmonella and 82.3% had Enterococcus. High percentages of both contained antibiotic-resistant bacteria, furthering the concern about genetically transmitted antibiotic-resistant genes becoming increasingly problematic.