The nightmare begins - CA MRSA that resists vancomycin

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

The high incidence of multidrug-resistant USA300 among men who have sex with men has major implications for empirical treatment of skin infections among these patients. Several important antimicrobial classes for treatment of MRSA infections or eradication of colonization, including clindamycin, tetracycline, and mupirocin, may not be effective in this population. Resistance to trimethoprim–sulfamethoxazole and rifampin remains rare among USA300 isolates and was not seen in multidrug-resistant USA300 in our study (Table 1). However, prophylactic antimicrobial use has selected for the emergence of trimethoprim–sulfamethoxazole resistance in subclones genetically related to the USA300 lineage in patients from San Francisco and New York City who were infected with HIV (50–52). Prudent use of these antimicrobial agents for suspected MRSA disease in men who have sex with men is advisable to slow the emergence of even more resistant community-associated MRSA. The pUSA03 plasmid that determines multidrug resistance in multidrug-resistant USA300 belongs to a highly promiscuous class of conjugative plasmids that could readily accept transposons encoding resistance to aminoglycosides, trimethoprim, vancomycin, and other antimicrobials, potentiating the emergence of even more resistant community-associated MRSA (28, 53).