Emergence of cefotaxime resistance in Citrobacter freundii causing necrotizing fasciitis and osteomyelitis

We present a diabetic patient with necrotizing fasciitis caused by Citrobacter freundii associated with an injury from the fish fin. Two isolates recovered six days after cefotaxime treatment had a cefotaxime minimum inhibitory concentration (MIC) of 0.12 and 256 mg/L, respectively, and a cefepime MIC of 0.03 and 0.25 mg/L, respectively. The two isolates both possessed bla(CMY-2) gene. The patient responded unsatisfactorily to cefotaxime and cefepime therapy and surgical debridement but recovered completely after ertapenem treatment for 42 days.