Transcript--What you should know about people, pets, MRSA, and bite wounds

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Community-acquired methicillin-resistant Staphylococcus aureus, or MRSA, strains have become more prevalent over the last 10 years. Several clinical reports have suggested that people are likely the source of infection in pets, since dogs and cats are more frequently colonized by Staphylococcus intermedius, not S. aureus. This is one of the findings in an article in The Lancet Infectious Diseases that reviewed the human and veterinary literature to determine transmission patterns of MRSA in pets and people.

Additional findings indicate that pets may become bacterial reservoirs, causing reinfection cycles throughout a household or a facility such as a nursing home. The advent of bacterial DNA fingerprinting techniques has allowed further documentation of the transmission of MRSA strains between people and pets, and a 2007 analysis suggested that pets may play a role in transmitting fluoroquinolone-resistant MRSA strains to people.

The review points out that scientific reports regarding the clinical signs of MRSA infections in dogs and cats are uncommon. Luckily, contact with asymptomatic pets is not a risk factor for immunocompromised people for acquiring S. aureus, because most household pets are unlikely to harbor MRSA. Furthermore, MRSA strains are generally susceptible to antibiotics apart from beta-lactams, and treating both pets and people can eliminate the infection and stop the reinfection cycle.

Another aspect of the article reviewed common infectious pathogens that people acquire from dog and cat bite wounds. The literature search revealed that such bites usually transmit a mixture of aerobic and anaerobic bacteria from the victim’s skin and the animal’s oral cavity, including Streptococcus, Staphylococcus (MRSA included), Pasteurella, Fusobacterium, Bacteroides, and Capnocytophaga species. Infection can set in after only eight hours. And in a few cases, bacteria can be transmitted to a person by an animal licking that person’s broken skin.

In about 20% of bite wounds, severe infection such as sepsis can occur. The most vulnerable area is the hand, where about 30% to 40% of dog and cat bite wounds result in infection and can cause disabling damage. And although cat bites occur less frequently than dog bites do, they are more likely to become infected. Abscesses, osteomyelitis, and septic arthritis are more likely to develop with cat bites because a cat’s teeth cause deep but narrow puncture wounds, restricting drainage and creating an ideal nidus of infection.

This review article underscores the importance of veterinarians advising owners and staff members who have been bitten to seek medical attention to avoid infection and possible complications such as sepsis. In this review, physicians are advised that immediately irrigating a bite wound with tap water or saline helps dislodge bacteria and foreign material from the wound and can reduce rabies virus transmission. Débriding devitalized tissues and exploring a wound for embedded teeth or fragments is also advised, as is obtaining a radiograph of the injured area to identify a foreign body or bone trauma.

Prophylactic antibiotic therapy is recommended unless the bite is superficial and easily cleaned, and tetanus vaccination status should be addressed. Orthopedic surgery, plastic surgery, or neurosurgery consultation may be needed, and physicians are also encouraged to contact local public-health officials in cases of serious domestic pet bites or bites involving strays, unprovoked attacks, an animal that can’t be found, or an animal with unknown rabies vaccination status. And rabies prophylaxis for the bite victim is considered based on the exposure risk and local epidemiologic data.

In conclusion, this review emphasizes the critical role all health care providers play in protecting the relationships people have with their pets and in promoting loving pet ownership while being aware of the diseases that may occur and helping to prevent them through simple precautions, education, and recognition.

Oehler RL, Velez AP, Mizrachi M, et al. Bite-related and septic syndromes caused by cats and dogs. Lancet Infect Dis 2009;9(7):439-447.