Massive empyema due to Citrobacter diversus.

Citrobacter diversus is a gram-negative rod member of the Enterobacteriacease family. A patient is described from whom this organism was isolated twice in pure culture from empyema fluid. Our isolates of Citrobacter diversus were resistant to ampicillin and carbenicillin and sensitive to cephalothin. Citrobacter diversus should be distinguished from Citrobacter freundii, Enterobacter cloacae and Klebsiella pneumoniae. This organism joins Streptococcus pyogenes, bacteroids species, anaerobic streptococci and Escherichia coli as a cause of slight pneumonia with extensive empyema.