MDR CA-MRSA in MSM*

Blogging on Peer-Reviewed Research Methicillin-resistant Staphylococcus aureus (MRSA) has taken up residence in sport teams, prisons, schools, the military, and even swine. A new article in the Annals of Internal Medicine shows that, at least in Boston and San Francisco, it’s also causing a lot of infections in men who have sex with men; more after the jump.

To examine this, the authors looked at MRSA infections from a variety of health care settings: medical centers, community health clinics, HIV clinics, and emergency rooms. These were examined in separate analyses. For example, for the medical centers they looked at in San Francisco, they were able to estimate overall incidence of infection for the city, and for each ZIP code within the city–and they found this incidence to be quite variable. They grouped several contiguous ZIP codes together, and found that the highest-incidence areas averaged an incidence rate of 59 cases of a specific multidrug-resistant (MDR) strain of community-associated MRSA (dubbed USA300) per 100,000, while the other areas averaged only 4 cases/100,000. The areas with highest incidence corresponded to areas that also had the highest proportion of male same-sex couples. For instance, in the Castro district, roughly 26% of the households are male same-sex couples, and their incidence for MDR USA300 was 170 cases per 100,000.

The authors looked at a number of different variables that may play a role in infection, including HIV status, prior MRSA infection, and antibiotic use. They found that, while HIV status was a risk factor for acquisition of the MDR USA300 strain, men having sex with men was an independent risk factor–so men having sex with men who were HIV negative still had a greatly increased risk of acquiring the MDR USA300 strain of MRSA.

They also noted that of the MDR USA300 infections, a high proportion of them involved the buttocks, genitals, or perineum–suggesting transmission during sex. Though Staph aureus is typically carried in the nose or on the skin, it can also be carried rectally (though this is less common)–so there are a number of ways parters could infect each other during sexual activity.

A big limitation of this research is that, while incidence of disease can be calculated, we don’t know anything about prevalence of infection with this strain in the community at large. It’s likely to be low based on what they found in their emergency department studies in 11 cities around the U.S. (only 2 out of 212 MRSA isolates were MDR USA300), but do the incidence rates they found in the current article accurately reflect carriage rates in MSM or other populations?

[EDIT TO ADD: see also Mike's post on this topic]

Reference

Diep, BA et al. 2008. Emergence of Multidrug-Resistant, Community-Associated, Methicillin-Resistant Staphylococcus aureus Clone USA300 in Men Who Have Sex with Men. Annals of Internal Medicine, in press. Link.

Comments

  1. #1 Eric
    January 17, 2008

    I’ve also seen fairly substantial outbreaks of Gonorrhea in young gay males. We’re seeing a new generation arise for whom HIV/AIDS is something you live with, not something that has killed everyone you know.

    I wonder if we’ll see more of this in the future.

  2. #2 Tom Smith
    January 22, 2008

    1. In the quoted NEJM paper Bellevue ER rates of MRSA are so out of sync with all the other sites and the number of patients is so small (20), that I cannot help but question the validity of data collection/case identification at that study site.

    2. Though generally safe, hypersensitivity to bactrim is not as rare as one may hope. Bellevue’s MRSA (at least hospital isolates for which we have data) seems to be sensitive to tetracyclines more than 90% of the time. Any comment on using these drugs for PO management?

    3. Since diabetics are probably not at high risk for community MRSA and since DM wound infection is not a typical presentation of the bug, why not simply use PO dicloxacillin or Augmentin in a stable patient while waiting for the cultures?

    4. I am personally not a big fan of new Abx as long as older once retain activity. I have a serious mental block even considering either Linezolid or daptomycin in patients without contraindications to vancomycin.

  3. #3 William Daley
    February 8, 2008

    My name is William Daley. I am a graduate student at The Sage Colleges and my final assignment is to work with Mr. Ed Dombroski from the NYS Department of Health and study Community-Associated Methicillin-Resistant Staphylococcus aureus (CA-MRSA). Then I must develop some guidelines or recommendations for school athletic departments to reduce the risk of CA-MRSA among athletes.

    I am looking for two types of information:
    1–Information pertaining to established guidelines that your school has in place to prevent and/or contain the outbreak of CA-MRSA.
    2–Survey information your school may have obtained through a third party or first hand.
    These surveys would have been any information with the knowledge or protocols currently in place regarding CA-MRSA.

    If you cannot provide any information could you please offer any persons to contact that may be able to help me out?

    Thank you and I look forward to hearing from you,

    William Daley

    daleyw@sage.edu
    (518) 274-4822 Home
    (518) 209-7066 Cell