Resistant Enterobacter cloacae in a burn center: the ineffectiveness of silver sulfadiazine

Enterobacter cloacae sepsis was found in 15 burn center patients in 1976, of whom 13 died. Nine of the deaths occurred in the first 60 days. The Burn Center isolates were resistant to silver sulfadiazine (AgSD) in agar cup-plate tests and confirmed by tube dilution tests. Hospital, non-burn isolates of E. cloacae were sensitive to AgSD. All E. cloacae isolates were sensitive to mafenide acetate (MA) in the agar cup-plate tests, but this was not confirmed by the tube dilution tests. The agar cup-plate susceptibility test is a simple, rapid and effective technique for determining resistant and sensitive isolates of E. cloacae. Patients who were changed from AgSD to MA because of resistant E. cloacae infection did not have improved survival. An animal study showed that AgSD was ineffective against this strain of E. cloacae and that MA was more effective than AgSD when applied 24 hr postburn but neither were effective at 48 hr postburn. MA was bacteriostatic but not bactericidal with this E. cloacae strain.