SULBACTAM TREATMENT OF A SERRATIA-MARCESC ENS BACTEREMIA

The authors report a case of bacteremia caused by cephalosporinase-pro ducing Serratia marcescens, and successfully strictly treated by conco mitant administration of sulbactam (Sulb) with combined cefepime (CF) and amikacin (Akn). The data was collected by determining the speed of bactericidal effect. The patient was a 52-year-old man, presenting co lectasia and nosocomial bacteremia caused by cephalosporinase-producin g S. marcescens. Combined antibiotic treatment with imipenem (IPM) and Akn was given from D1 to D7. At D7, IPM was replaced by CF (4 g/d). B lood cultures remained positive for the same bacteria from D1 to D8. T he dosage of CF was increased to 6 g/d (D9) and the patient's catheter s chan,oed (D11), without improvement. The same strain of Serratia was isolated from the central catheter (D11) and from stool cultures (D9 and D14). Sulb was given on D14 without modifying the other medication . From D15, fever dropped (t degrees < 38 degrees C), and was followed by definitive apyrexia. No further Serratia was isolated after D14. C ombined CF-Sulb treatment was maintained until D38, and the patient wa s discharged on D46. Microbiology: the strain of S. marcescens involve d (API 20E panel) is resistant to ticarcillin + clavulanic acid (MIG = 128 mg/l), piperacillin (PIP) (MIG = 64 mg/l), PIP + tazobactam, cefo taxime (MIG = 16 mg/l), and fluoroquinolones. It is susceptible to cef tazidime (CAZ) (MIC = 1 mg/l), cefepime (MIG mg/l), cefpirome (MIG = 0 .25 mg/l), imipenem (MIG = 0.25 mg/l) and amikacin (MIG = 1 mg/l) (MIG determined by dilution test in agar). The speed of bactericidal effec t against S. marcescens was determined for Sulb alone, CF alone, and c ombined CF-Akn and CF-Akn-Sulb. A decrease of 4 log10 units was taken to indicate bactericidal activity. The results were as follows: sulb w as inactive at a concentration of 32 mg/l, a fall of 2 log10 units at t = 6 h with renewed growth of bacteria was recorded at CF concentrati ons of 2 to 16 mg/l, fall of 2 log10 units at t = 6 h followed by bact eriostasis was recorded for the combination CF (4 mg/l)-Sulb (16 mg/l) , bactericidal effects of CF (4 mg/l)-Akn (2 mg/l) after 5 h 30 min., bactericidal effects of CF (4 mg/l)-Akn (2 mg/l)-Sulb after 3 h 30 min . Conclusion: the failure of IPM-Akn and CF-Akn combinations was neith er due to inadequate dose nor to deep-lying infection. Inactivation of cefpirome and CF by cephalosporinases was low, and they were conseque ntly active against Enterobacteriaceae that produce high levels of cep halosporinase. Nevertheless, the determination of the speed of bacteri cidal activity showed that in this case, CF alone exhibited no bacteri cidal activity, even at a concentration 16 times greater than the MIG, whereas combined use of Akn conferred bactericidal activity, which wa s enhanced by Sulb. This correlates to the therapeutic outcome.