Radar is up for new multidrug-resistant MRSA

A multidrug-resistant variant of community-acquired methicillin-resistant Staphylococcus aureus (MRSA) bacteria is emerging in cities on both coasts of the United States, according to data from a new California-led study.1

The research is based on information collected from MRSA cases from nine of 10 medical centers serving San Francisco and medical records from outpatients with MRSA infections who were treated in an HIV clinic in San Francisco and a clinic serving a predominantly lesbian/gay/bisexual/transgender population in Boston.

The research suggests that men who have sex with men were at higher risk for infection with a multidrug-resistant variant of the MRSA USA300 bacteria. In the current study, specific sexual behaviors were not assessed or documented in clinic charts, so researchers cannot comment on the association between multidrug-resistant USA300 infection and specific male-male sexual practices, says Binh Diep, PhD, a University of California at San Francisco (UCSF) postdoctoral scientist and lead author of the report.

"We are currently conducting several prospective studies to identify if any specific sexual behaviors may be correlated with multidrug-resistant USA300," says Diep.

MRSA is a common cause of skin infections throughout the United States, according to the Centers for Disease Control and Prevention (CDC). These infections occur in men, women, adults, children, and persons of all races and sexual orientations, and they are known to be transmitted by close skin-to-skin contact.

Concern has arisen concerning drug-resistant strains of MRSA. While evidence of the USA300 strain was not seen before 2000, it is now widely disseminated in 38 U.S. states, Canada, and nine European Union countries.1 This strain can cause unusually severe human diseases, including necrotizing fasciitis, sepsis, endocarditis, and pneumonia.1 The spread of this multidrug-resistant MRSA into communities was first reported by the UCSF team in 2006.2

Is it an STD?

Can this strain of MRSA be considered a sexually transmitted disease (STD)? Evidence is not available to determine whether S. aureus, including MRSA, is a sexually transmitted infection as judged by the classic criteria of sex as a predominant mode of transmission and transmission through genital, anal, or oral mucosal contact, notes an accompanying commentary to the current paper.3

The Staphylococcus aureus bacterium is transmitted primarily by direct skin-to-skin contact, which includes skin-to-skin contact during sexual activity. While the buttocks and groin area can be a site for MRSA infection, it does not imply sexual transmission, notes Kim Workowski, MD, chief of the guidelines unit in the epidemiology and surveillance branch of the CDC's Division of STD Prevention and a commentary co-author. While contact of these infected areas of skin during sexual activity could result in cutaneous transmission, scientists do not yet know if the mucosal contact that can occur with specific sexual practices imparts an independent risk for transmission, she states.

MRSA is resistant to the antibiotic methicillin and closely related drugs, while the variant studied in the new research is resistant to several other antibiotics, which makes it more difficult to treat. While CDC's monitoring of invasive MRSA indicates that such drug-resistant strains are rare, the agency continues to check resistance patterns and strain characteristics in MRSA isolates submitted to the CDC for a variety of investigations.

How can clinicians help in stemming the spread of infection? Provide the following educational tips to patients to help prevent spreading staph or MRSA skin infections:

  • Cover your wound. Keep wounds that are draining or have pus covered with clean, dry bandages.
  • Follow instructions on proper care of the wound. Pus from infected wounds can contain staph and MRSA, so keeping wounds covered will help prevent the spread to others. Bandages or tape can be discarded with the regular trash.
  • Wash your hands. You, your family, and others in close contact should wash their hands frequently with soap and warm water or use an alcohol-based hand sanitizer, especially after changing the bandage or touching the infected wounds.
  • Do not share personal items. Avoid sharing personal items such as towels, washcloths, razors, clothing, or uniforms that may have had contact with infected wounds or bandages. Wash sheets, towels, and clothes that become soiled with water and laundry detergent. Drying clothes in a hot dryer, rather than air-drying, also helps kill bacteria in clothes.
  • Tell any health care providers who treat you that you have or had a staph or MRSA skin infection.4

References

  1. Diep BA, Chambers HF, Graber CJ, et al. Emergence of multidrug-resistant, community-associated, methicillin-resistant Staphylococcus aureus clone USA300 in men who have sex with men. Ann Intern Med 2008; 148:249-257.
  2. Diep BA, Gill S, Chang R, et al. Complete genome sequence of USA300, an epidemic clone of community-acquired methicillin-resistant Staphylococcus aureus. Lancet 2006; 367:731-739.
  3. Gorwitz R, Fridkin SK, Workowski KA. More challenges in the prevention and management of community-associated, methicillin-resistant Staphylococcus aureus skin disease. Ann Intern Med 2008; 148:310-312.
  4. Centers for Disease Control and Prevention. CDC Statement on MRSA in Men Who Have Sex with Men. Press release. Jan. 16, 2008. Accessed at: www.cdc.gov.