Friday, March 14, 2008

Methicillin-Resistant Staphylococcus aureus in a Family and Its Pet Cat

Methicillin-Resistant Staphylococcus aureus in a Family and Its Pet Cat

NEJM Mar 13, 2008

To the Editor: Many isolates of community-acquired methicillin-resistant Staphylococcus aureus (MRSA) produce Panton–Valentine leukocidin (PVL), increasing the virulence of the bacteria, which can cause disseminated deep abscesses and necrotizing pneumonia.1 We report the transmission of PVL-positive MRSA between a symptomatic woman and both her asymptomatic family and their healthy pet cat.

An otherwise healthy woman presented with recurrent multiple deep abscesses. Swabs from several abscesses and nasal cultures grew MRSA that was resistant to both beta-lactam and fusidic acid antibiotics. Polymerase-chain-reaction assays for the PVL genes lukS-PV and lukF-PV were positive. The genotype of the staphylococcal chromosomal cassette was SCCmec type IV. Nasal, axillary, and inguinal cultures from her husband and their two children yielded MRSA on several occasions. Mupirocin nasal ointment and antiseptic washes were recommended for all family members. Although the patient's husband and children became MRSA-negative, the patient remained MRSA-positive. Therefore, her three apparently healthy cats were screened. Pharyngeal culture from one cat grew MRSA with the same antimicrobial resistance pattern as that of the human isolates. The clonal identity of the isolates from the family and the cats was found by typing of the spa gene repeat region and multilocus sequence typing,2,3 which showed spa-type t131 and ST80 in all isolates. This sequence combination does not correspond with that of clone USA300 (reference)

A veterinarian recommended topical decolonization of the MRSA-positive cat with ciprofloxacin and rifampin. Four weeks after the cat's treatment, screening tests of the family were negative for MRSA. Moreover, the patient's deep abscesses completely resolved. Further MRSA screening of the asymptomatic cat was declined by the family.

There is evidence that companion animals, mainly dogs, harbor MRSA,4 and interspecies MRSA transmission has been shown in the members of a family and their dog.5 This case illustrates that MRSA transmission also occurs between humans and cats. The abscesses in our patient cleared only after antibiotic treatment of the cat. It remains unclear whether the cat was the source of the patient's infection or vice versa, although spa-type t131 is extremely rare in humans.2 We conclude that pets should be considered as possible household reservoirs of MRSA that can cause infection or reinfection in humans.

Andreas Sing, M.D. Christian Tuschak, Ph.D. Stefan Hörmansdorfer, Vet.D. Bavarian Food and Health Safety Authority 85764 Oberschleißheim, Germany

New England Journal of Medicine

Woman and Cat Shared 'Super Bug'

By Serena GordonHealthDay Reporter Wed Mar 12, 11:47 PM ET
WEDNESDAY, March 12 (HealthDay News) -- People share their homes, their food and more with their pets, but one thing you probably never thought you could share with your animals is a drug-resistant staph infection.

However, according to a letter in the March 13 issue of the New England Journal of Medicine, a German family appears to have done just that. Doctors were puzzled when a woman was repeatedly treated for methicillin-resistant Staphylococcus aureus (MRSA), yet still kept coming back with the infection.

Eventually, they discovered that the family cat was harboring the dangerous bacteria, sometimes called a "super bug."

"Animals and especially pets or companion animals might serve as reservoirs for human-pathogenic bacteria," said Dr. Andreas Sing, head of the department of infectiology at the Bavarian Food and Health Safety Authority in Germany.

Before you give puss the boot, know that researchers believe it was the woman who probably initially transmitted the bacteria to the cat, not the other way around.

About 25 percent to 30 percent of Americans are colonized with staph bacteria, but only about 1 percent are colonized with MRSA, according to the U.S. Centers for Disease Control and Prevention. Most MRSA infections occur in health-care settings, such as hospitals or nursing homes, but the number of community-acquired infections is growing. According to the CDC, about 12 percent of all MRSA infections are now acquired in the community.

MRSA spreads through skin-to-skin contact with an infected person, but its transmission has also been associated with contaminated surfaces, crowded living conditions and poor hygiene, according to the CDC.

MRSA infections often look like a boil or an inflamed pimple, and may be red, swollen and draining pus, the CDC said.

The German woman was otherwise healthy, but kept getting multiple, deep abscesses. Both the abscesses and nasal swabs tested positive for MRSA. Her family members -- a husband and two children -- were also tested, and they tested positive on several occasions. Nasal ointments and antiseptic washes were prescribed for the family to "decolonize" them.

The family members then tested negative for MRSA, but the woman kept testing positive. Doctors then tested the woman's three cats, and found that one, despite having no symptoms, was carrying the same strain of MRSA. Once the cat was decolonized and both the cat and woman were retreated with antibiotics, all family members -- human and feline -- tested negative for the bacteria.

Sing and his colleagues pointed out that this is the first documented MRSA infection in a cat, although there have been reports of other animals, including dogs, harboring MRSA.

Because this infection is generally community-acquired, Sing thinks it's more likely that the woman initially transmitted the bacteria to her pet, and then the animal passed the infection back to her.

"Cats are social. They like to rub up against people and it's the skin-to-skin contact that passes MRSA," explained Dr. Matthew Sims, director of the infectious disease research program at Beaumont Hospital in Royal Oak, Mich.

But, he added, "People shouldn't start worrying about having pets. They can carry all sorts of things which we've known about forever, but you don't need to get rid of your cats or other animals."

Sims said that if you suspect you might have a MRSA infection, go to your doctor for treatment and let your doctor know if you have other people or pets in your household so your doctor can recommend appropriate treatment or prevention steps for them.

The best way to prevent these infections, Sims said, is to practice good hygiene and wash your hands frequently. If you know you have a MRSA infection, avoid direct contact with other people and animals until you've been treated.
More information

To learn more about MRSA, visit the U.S. Centers for Disease Control and Prevention.

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