MRSA 300 presents unique challenges, new treatments

Among methicillin-resistant Staphylococcus aureus (MRSA) strains, MRSA 300 is proving particularly widespread and hardy, an expert says. Fortunately, he adds, recently approved intravenous (IV) antibiotics for MRSA require fewer doses than their predecessors.

MRSA 300 has grown particularly problematic in the United States, says Theodore Rosen, M.D., professor of dermatology at Baylor College of Medicine. Typically presenting as abscesses and cellulitis, it is the most common MRSA strain found in the general population, as well as in athletes, soldiers, IV drug users, the homeless and men who have sex with men.

"Unlike hospital-acquired MRSA," Dr. Rosen adds, "MRSA 300 is uniquely capable of colonizing extra-nasal sites such as the oropharyngeal and anogenital areas, and of surviving on fromites." MRSA 300 is also increasingly drug (including mupirocin) resistant, he says. Sources of contamination range from raw meats – often derived from animals given unnecessary antibiotics – to frequently handled household objects such as landline phones, bathroom fixtures and hair brushes.

Clinicians should consider MRSA 300 particularly if infections occur in areas such as the groin, buttocks, penis, vulva and suprapubic skin, Dr. Rosen says. Fortunately, he adds, the IV antibiotics oritavancin, dalbavancin and tedizolid earned Food and Drug Administration approval for MRSA in 2014. The longer half-life of these drugs means that they require fewer administrations per course than previously available IV antibiotics, he says. Dosing recommendations are as follows:

• Oritavancin – single 1,200 mg dose

• Dalbavancin – 1,000 mg; 500 mg one week later

• Tedizolid – 200 mg QD.

Disclosure: Dr. Rosen reports no relevant financial interests.

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