Impact of prolonged treatment with linezolid on the human gut flora

A 79-year-old male was treated for 6 months with linezolid for prosthetic knee joint osteomyelitis. At the end of this 6-month period, quantitative stool cultures revealed partial loss of the normal gut flora and concomitant colonization by opportunistic pathogens such as Pseudomonas aeruginosa and other Gram-negatives. Follow-up cultures at 6 weeks after antibiotic discontinuation revealed restoration of the normal flora. Prolonged linezolid administration may lead to replacement of normal gut flora by pathogenic microorganisms, which under certain conditions might cause systemic infections.