In a patient with MRSA cellulitis, what is the most appropriate antibiotic in addition to vancomycin?

In the context of treating a patient with MRSA cellulitis, the selection of rifampicin in addition to vancomycin is appropriate due to its ability to enhance the effectiveness of the treatment, particularly in cases where deeper tissue or persistent infections are suspected.

Rifampicin is a potent antibiotic that acts by inhibiting bacterial RNA synthesis. When used in conjunction with vancomycin, which is effective against methicillin-resistant Staphylococcus aureus (MRSA), rifampicin can provide a synergistic effect, particularly in complicated infections where the likelihood of biofilm formation or bacterial persistence is high. This combination can help improve treatment outcomes in more severe or refractory infections.

As for the other options, amoxicillin is not effective against MRSA, azithromycin, while it has some Gram-positive coverage, is not a first-line agent for MRSA, and flucloxacillin is ineffective against MRSA since it is a penicillinase-resistant penicillin, primarily effective against MSSA. Thus, rifampicin stands out as the appropriate adjunct therapy in managing MRSA cellulitis alongside vancomycin.