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Cases of heterosexual transmission of CA-MRSA recently reported
Clinicians should consider the diagnosis of MRSA when a patient presents with a vaginal, groin or pubic abscess.
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Although several modes of transmission of community-associated methicillin-resistant Staphylococcus aureus infection have been reported, heterosexual activity has not previously been identified as a means of transmission. Recently, however, in northern Manhattan, three cases of heterosexual transmission of community-associated methicillin-resistant Staphylococcus aureus have been identified.
“Normally healthy people with no other known or identifiable risk factors are becoming infected with CA-MRSA; heterosexual activity is one possible means of transmission of MRSA to those outside of the traditional risk groups. This has not previously nor seriously been considered, but it should be after the identification of these three cases,” said Heather A. Cook, MPH, of the department of medicine, division of infectious diseases of the College of Physicians and Surgeons at Columbia University in New York City.
Cook and her colleagues of the Columbia University Medical Center conducted a prospective, community-based study that included patients with positive cultures for MRSA. Between April 2004 and September 2006, MRSA-positive patients who agreed to participate were interviewed. The researchers collected sociodemographic and medical information and data regarding potential risk factors for CA-MRSA infection for the presenting patient as well as for all household members.
Additionally, all consenting adult household members provided nasal samples, axillary samples and self-administered vaginal and genital swabs, which were cultured for S. aureus. Visible skin lesions were also cultured.
The researchers identified three cases of possible heterosexual transmission of CA-MRSA, and in each case, sexual partners described a history of recurrent CA-MRSA infection that often involved the pubic, vaginal or perineal area. The three case reports were recently published in Clinical Infectious Diseases.
Three cases
The first household was identified when a 3-year-old girl presented to the Columbia University Medical Center emergency department with an MRSA-positive abscess in the pubic area. During an interview, the girl’s mother reported having tiny pimples in her groin area. The pimples had first appeared six months earlier, when she had five different male sex partners, one of which was her husband.
According to the woman, all of her partners except her husband had used condoms, and her husband and one other partner had pimples similar to hers in the groin area. Additionally, the woman shaved her pubic area and had received a diagnosis of vaginal herpes soon after her initial vaginal cultures were positive for CA-MRSA.
Although the husband’s and the wife’s nasal cultures were negative for CA-MRSA, the wife’s vaginal swab sample and the husband’s groin sample were both positive for CA-MRSA. The woman’s vaginal sample and the husband’s groin sample both contained isolates that were staphylococcal chromosomal cassette (SCC) mec type IV and were identical by pulsed field gel electrophoresis (PFGE).
The second household was identified when a woman presented to the Columbia University Medical Center emergency department with a buttock abscess that was MRSA-positive. The abscess resolved after incision and drainage and treatment with trimethoprim-sulfamethoxazole. However, two months later, the woman’s husband developed boils and a full-body rash that were culture-positive for CA-MRSA, and the woman developed boils in her groin area. The woman was treated with clindamycin, trimethoprim-sulfamethoxazole and mupirocin ointment, but the abscesses failed to resolve, and she eventually underwent incision and drainage. The woman and her husband were sexually active with each other during this time.
The woman’s nasal samples were repeatedly negative for MRSA, but her husband’s nasal samples were positive for MRSA (SCC mec type IV). Additionally, the woman’s vaginal swab sample and her husband’s groin swab sample were both positive for MRSA SCC mec type IV. The samples were identical by PFGE.
The third case was identified when a woman reported multiple episodes of MRSA-positive abscesses during a three-month period. The woman’s boyfriend was in the military, and his unit had experienced an MRSA outbreak. Her episodes of MRSA-positive abscesses always followed visits from her boyfriend. He had boils on his face and groin, which were treated with antibiotics and incision and drainage.
The woman, who regularly shaved her pubic area, had abscesses on her legs, groin and buttocks, and they were also treated with antibiotics and incision and drainage. Her symptoms would resolve until the next visit from her boyfriend, after which the abscesses would return. Although the woman’s nasal cultures were persistently negative for MRSA, the isolate obtained from her groin samples was SCC mec type IV.
Implications for clinicians
“We have evidence that MRSA is presenting in a context that hasn’t previously been recognized, and, therefore, clinicians need to consider the diagnosis of MRSA and not just other sexually transmitted infections when a patient has a vaginal, groin or pubic abscess,” Cook said.
She noted that effective treatment starts with the proper diagnosis, which includes obtaining an antibiogram. After diagnosis, clinicians can prescribe the proper medications and/or hygiene practices. In addition to treating the index case, as with other STI, the case’s partner(s) also need to be treated.
“If both partners aren’t treated concurrently, the infection can ping-pong between people as well as persist. Also, we believe that there are underestimates of MRSA pubic infections because people are identified with disease more commonly at other infection sites first,” she said. – by Michelle Stephenson
For more information:
- Cook HA, Furuya EY, Larson E, et al. Heterosexual transmission of community-associated methicillin-resistant Staphylococcus aureus. Clin Infect Dis. 2007;44:410-413.