Resistant bacteria heterosexually transmitted

By Megan Rauscher

NEW YORK (Reuters Health) - Doctors in New York have identified three households in which there was clinical, microbiological, and molecular evidence of heterosexual transmission of community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA).

Until now, heterosexual transmission of CA-MRSA has not been documented, the Columbia University-based team notes in the current issue of the journal Clinical Infectious Diseases.

MRSA is most often found in the hospital setting and has typically affected very ill, elderly patients and those with poorly functioning immune systems. Infection can pose a serious problem because it is susceptible to few antibiotics.

While homosexual transmission of CA-MRSA has been documented among HIV-positive men, heterosexual transmission "poses a far greater risk of dissemination in the community," Dr. Franklin D. Lowy and colleagues point out.

According to their report, in the first household, a woman reported that she noticed "tiny pimples" in the groin area, which appeared 6 months earlier after she was sexually active with five different men, including her husband. Both her husband and another partner also had similar "pimples" in the groin. The woman's vaginal swab sample and husband's groin sample were both positive for CA-MRSA and the isolated bacteria were identical.

In household two, a woman who was sexually active with her husband sought treatment for a MRSA-positive buttock abscess. Two months later, her husband developed an extensive rash and boils that were tested positive for CA-MRSA. At the same time, the woman developed boils in her pubic area. The vaginal swab from the wife and groin swab from husband were both MRSA-positive.

In household three, a woman reported multiple episodes of MRSA-positive abscesses over 90 days and these episodes always followed visits from her boyfriend who was a member of a military unit that had been experiencing an outbreak of MRSA infection. A sample obtained from the woman was positive for MRSA, but a sample from the boyfriend was unavailable.

The vaginal and groin samples obtained from the sexual partners in these households were all USA 300, the predominant CA-MRSA type found in the United States, the authors note.

Lowy told Reuters Health: "I think the take-home message is that spread of CA-MRSA via heterosexual activity is an underappreciated means of transmission. It may account for the ability of these strains to become resident in communities where other risk factors are not present."

SOURCE: Clinical Infectious Diseases, February 1, 2007.