Examining the Evidence
Is MRSA a common isolate from vulvar abscesses?
This study directs our attention to a common clinical problem in obstetrics and gynecology: the vulvar abscess. Extensive use of antibiotics has fostered the emergence of resistant microorganisms—and MRSA is one of the most common and virulent.
The vulva is especially susceptible to colonization by MRSA owing to its proximity to the rectum and to trauma caused by shaving, waxing, sexual contact, and use of personal hygiene products.
Moreover, obese and disabled women may have difficulty cleaning the vulva adequately; poor hygiene is also associated with MRSA colonization.
MRSA wasn’t the only pathogen identified
Gram-negative organisms, such as Proteus mirabilis and Escherichia coli, and gram-positive organisms, such as Enterococcus and group B Streptococcus also were isolated from patients in this study.
Although most of the vulvar abscesses in this study were colonized with MRSA, that fact was not apparent until specimens were cultured. No presenting signs or symptoms distinguished patients who had MRSA from those who did not.
Nor were women with MRSA more likely to require hospitalization or experience complications from treatment. Rather, hospitalization was more likely in women who had such comorbidities as:
- an initial serum glucose level above 200 mg/dL
- a larger abscess (mean, 5.2 cm in diameter)
- an elevated white blood cell count (≥12×103/µL).
The overall complication rate was 7.4%, with one case of sepsis and one death.
Management of MRSA-colonized vulvar abscess primarily involved incision and drainage. Most inpatients also received intravenous vancomycin or clindamycin. Among outpatients, trimethoprim-sulfamethoxazole, an antibiotic regimen known to be eff ective against MRSA, was given in selected cases.
Limitations of this study
This study was conducted in a large county hospital in San Antonio that served primarily low-income Hispanic patients. Findings may therefore apply only to this population or geographic region.
Several variables were either not presented or inadequately discussed in the published study. For example, 26 of the subjects were pregnant. Should they have been included in the overall analysis? Does pregnancy alter the immune system—thereby becoming a risk factor for MRSA-colonized vulvar abscess? Was antibiotic selection different for pregnant patients than it was for nonpregnant patients?
The article also fails to provide much information on the prevalence of sexually transmitted infections (STI) in this population. Only 41% of the 133 women who had their abscess cultured were screened for STI. If these patients were infected with HIV (AIDS-defined), Chlamydia trachomatis, gonorrhea, genital herpes, or other STI pathogen, how would this have changed the data and outcomes?
Last, it is unclear whether the 10 cases of recurrent vulvar abscess identified in this study came from the inpatient or outpatient group.
WHAT THIS EVIDENCE MEANS FOR PRACTICE
A number of practice points can be gleaned from this study:
- When any patient has a vulvar abscess, culture it for aerobic and anaerobic microorganisms, including MRSA
- Because highly resistant organisms are becoming increasingly common in the community as well as the hospital, it is critical that you be familiar with your hospital’s antibiotic biogram, which delineates the organisms that are causing infection as well as susceptibility patterns
- Incision and drainage are the mainstay of management of MRSA-colonized vulvar abscess
- When deciding whether to treat a patient as an inpatient, consider medical conditions such as diabetes, HIV infection, obesity, and other conditions that compromise the immune system
- When selecting an antibiotic, choose one that includes coverage of MRSA as well as gram-negative enteric and other gram-positive organisms
- To prevent the spread of MRSA, incorporate proper hand washing and other infection-control measures into routine procedures. Also, decontaminate areas in which patients undergo incision and drainage to prevent transmission of MRSA to staff and other patients.—DAVID A. BAKER, MD