CA-MRSA, HPV vaccine spark debate

February 1, 2008

Recent studies document a high prevalence of community-acquired infections caused by methicillin-resistant Staphylococcus aureus and show the causative pathogen is often resistant to empirically prescribed antimicrobial treatment. The availability of the quadrivalent human papilloma virus vaccine has stimulated debate over its role and economic impact.

Key Points

New York - Community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) infection and use of the human papilloma virus (HPV) vaccine stand out as two of the current "hot topics" in dermatologic infectious disease, says Gary Goldenberg, assistant professor of dermatology and associate director, dermatopathology laboratory, University of Maryland School of Medicine, Baltimore.

Study findings

A recently published study in the New England Journal of Medicine underscores that CA-MRSA infections are a growing and serious problem.

They determined there were 1,647 cases of CA-MRSA. Across the three areas, the CA-MRSA infections represented between 8 percent and 20 percent of all MRSA infections.

Additional analyses determined that the annual CA-MRSA infection incidence was higher among children younger than 2 years of age, compared to older patients.

In addition, more than three-fourths of the CA-MRSA infections involved the skin and soft tissue, and an alarming 73 percent were resistant to prescribed antimicrobial agents.

Almost one-fourth of the patients with CA-MRSA infections required hospitalization.

Corroborating those findings were the results of another study appearing subsequently in the same journal, in which the investigators prospectively identified MRSA in adult patients who presented to 11 university-affiliated emergency departments with acute, purulent skin and soft-tissue infections.

In the month of August 2004, 422 patients were enrolled, and Staphylococcus aureus was isolated from 320 (76 percent) patients. MRSA accounted for 59 percent of all isolates, and therefore, the vast majority of all Staphylococcus aureus infections.

Microbiological testing showed the CA-MRSA isolates were all susceptible to rifampin and trimethoprim-sulfamethoxazole, and clindamycin and tetracycline also maintained good activity.

However, only 60 percent of the MRSA isolates were susceptible to fluoroquinolones and almost all of the MRSA isolates (94 percent) were resistant to erythromycin.

"Antibiotic therapy was not concordant with the results of susceptibility testing in 57 percent of patients treated with an antimicrobial agent. That finding underlines the importance of obtaining specimens for in vitro sensitivity testing to guide appropriate therapy,"Dr. Goldenberg tells Dermatology Times.

Alternative therapy

In the area of therapy for CA-MRSA, a recent study suggests a possible role for topical tea tree oil preparations for clearing MRSA colonization in hospitalized patients.

The study included 224 hospitalized patients with MRSA carriage, and compared a standard topical regimen consisting of mupirocin 2 percent nasal ointment, chlorhexidine gluconate 4 percent soap and silver sulfadiazine 1 percent cream against tea tree 10 percent cream and 5 percent body wash.

Overall, MRSA clearance rate for the standard regimen was slightly higher than for the tea tree oil therapy, 49 vs. 41 percent, but the difference between the two rates was not significantly different.

Looking at specific sites, mupirocin was more effective than tea tree oil at clearing nasal carriage of MRSA, 78 percent vs. 47 percent.

However, rates of MRSA eradication from superficial skin sites and skin lesions were higher among patients treated with the tea tree oil regimen.

The biggest difference was seen in the groin, where clearance rates were 80 percent for the tea tree oil group and 29 percent for patients in the standard regimen arm.

However, the MRSA eradication rate was also superior for the tea tree oil regimen patients, compared with those treated with the standard regimen for comparisons of the axilla, 57 percent vs. 50 percent, and skin lesions, 47 percent vs. 31 percent.

Economics of HPV vaccination

In 2007, the Advisory Committee on Immunization Practices issued recommendations on use of the quadrivalent HPV vaccine (Gardasil, Merck) to females. Vaccination was recommended in females at 11 to 12 years of age, but girls as young as 9 years of age could be considered eligible. It was also recommended that older females, ages 13 to 26 years old, should be given a "catch-up" vaccination if they were not previously vaccinated. Similar recommendations emerged from the American Cancer Society, except that organization endorsed catch-up vaccination only for females up to age 18.

"The vaccine itself is expensive, but the economic burden of HPV is high, being estimated at $4 billion or more in direct costs based on 2004 U.S. dollars. Those costs include $200 million for management of genital warts and another $300 to $400 million for management of invasive cervical cancer.

"The remaining costs derive from routine cervical cancer screening, follow-up in women with an abnormal Pap test and treatment of pre-invasive cervical cancer," Dr. Goldenberg says.

"While the vaccine is safe and effective, routine prophylactic vaccination is still a very expensive venture and an enormous debate is continuing," he says.

Disclosure: Dr. Goldenberg has no financial interest in any of the subject matter he discussed.