Multidrug-resistant Infections in Veterinary Clinics

July 27, 2016
Laurie Anne Walden, DVM, ELS

Dr. Walden received her doctorate in veterinary medicine from North Carolina State University. She is a practicing veterinarian and a certified editor in the life sciences (ELS). She owns Walden Medical Writing, LLC, and writes and edits materials for healthcare professionals and the general public.

Multidrug-resistant infections associated with veterinary facilities pose a risk to both animal patients and humans.

Multidrug-resistant infections associated with veterinary facilities pose a risk to both animal patients and humans, according to a review recently published in Veterinary Microbiology. More than 80% of US veterinary teaching hospitals have reported outbreaks of nosocomial infection.

“In modern veterinary medicine [healthcare-associated infections] represent an urgent but largely unresolved issue, and infection control remains in its infancy,” write the authors. “Multidrug-resistant pathogens…pose a significant challenge due to the apparent spread of these pathogens within veterinary environments.” Because infections acquired in the hospital may be drug resistant and are often transmissible between humans and nonhuman animals, they represent a risk for patients, owners, and hospital staff.

The most common veterinary healthcare-associated infections are surgical site infections, wound infections, central line—associated blood infections, and catheter-associated urinary tract infections. Companion species most often affected are dogs, cats, and horses. Pathogens of special concern are methicillin-resistant staphylococci (Staphylococcus aureus [MRSA] and S pseudintermedius [MRSP]), extended-spectrum beta-lactamase (ESBL)—producing Escherichia coli, and multidrug-resistant Salmonella.

Methicillin-resistant Staphylococci

Outbreaks of MRSA in horses were first reported in the late 1990s in Japan and the United States. In a German study published in 2014, between 41% and 63% of S aureus isolates from wound swabs of dogs, cats, and horses were methicillin resistant. MRSA does not appear to be host specific, and infection in dogs and cats could represent “spill-over” from human infections.

Epidemiological data on MRSP outbreaks is somewhat limited, but environmental exposure in veterinary hospitals is a probable source of infection, as illustrated by an outbreak in a veterinary teaching hospital in Finland. Because treatment options for MRSP are limited, infected veterinary patients may face euthanasia out of concern for their welfare.

Extended-spectrum Beta-lactamase—producing E coli

Many E coli produce beta-lactamases, enzymes that confer resistance to beta-lactam antibiotics (eg, penicillins and cephalosporins). ESBL-producing bacteria, which are resistant to additional antibiotic classes, were identified in humans in the 1980s. Infections with ESBL-producing E coli have been reported in dogs, cats, and horses since the late 1990s.

Multidrug-resistant Salmonella

Salmonella infection is an ongoing problem in food animals, and infections with serovars resistant to multiple drugs have also been reported in dogs, horses, and humans. Animal feed containing meat and human food from livestock sources have been implicated in outbreaks.

Risk Factors for Veterinary Hospital—acquired Infections

Not all animals (or humans) exposed to drug-resistant bacteria become clinically ill. Veterinary clinics contaminated with these organisms can be a source of infection for animals and people who may then become asymptomatic carriers. Observations regarding veterinary risk factors include the following:

  • Introduction of multidrug-resistant organisms is more likely at referral centers than at primary care practices.
  • Studies have shown environmental contamination with ESBL-producing E coli near a veterinary hospital (from dog feces), increased MSRA risk in dogs belonging to veterinary students, and shedding of drug-resistant E coli by horses after hospital discharge. These reports underline the potential for veterinary clinics to become sources of spread of these organisms to the community.
  • In horses, the risk of becoming carriers of drug-resistant organisms increases with hospitalization for more than 6 days or administration of certain antibiotics (such as aminoglycosides, cephalosporins, and metronidazole).
  • MRSA infections in dogs have been associated with intravenous catheterization, treatment with antibiotics such as beta-lactams and fluoroquinolones, the number of employees working at a veterinary clinic, and surgical site infections. Decontamination and hygiene practices reduced the risk.
  • Living or working with animals increases the risk of acquiring pathogens. Studies have demonstrated that owners and veterinarians of dogs and horses with drug-resistant infections have an increased risk of being colonized with the same bacteria.

Reducing the Risk for Veterinary Hospital—acquired Infections

The following practices can reduce the risk of hospital-acquired infections:

  • Monitoring the rate of nosocomial infection in a facility
  • Implementing infection control practices that reflect the structural characteristics of the facility and the needs of the animal patients
  • Providing education and practical training for personnel

“With the exception of very basic hygiene measures…the strategies, concepts and approaches evolved to overcome and/or limit the spread of nosocomial pathogens within human hospital settings cannot always be directly transferred to veterinary clinics,” write the authors. “Thus, a balanced holistic hygiene management is needed which respects both animal needs and welfare, and effective hygiene procedures.” Limiting the spread of multidrug-resistant organisms in veterinary clinics is necessary to safeguard the health of both humans and animals.