A Case ofLeuconostocVentriculitis with Resistance to Carbapenem Antibiotics

Sir—Leuconostoc is a genus of gram-positive bacteria that has been increasingly recognized as a cause of human infections [1]. The fact that these bacteria display intrinsic high-level glycopeptide resistance has clinical implications for antibiotic selection. Existing reports of the antimicrobial susceptibility of clinical isolates have demonstrated that Leuconostoc species have marginal susceptibility to penicillin and susceptibility to aminoglycosides, tetracyclines, clindamycin, and carbapenems [2]. We recently observed a case of Leuconostoc ventriculitis with resistance to carbapenem antibiotics. A 50-year-old man underwent ventricular shunt placement after embolization of a CNS arteriovenous malformation was complicated by subarachnoid hemorrhage and acute hydrocephalus. Within several days after the procedure, he developed altered mental status, fever, and leukocytosis. Culture of CSF samples obtained on 6 consecutive days yielded Leuconostoc lactis. On initial identification of the organism, the ventricular shunt was removed, and therapy was changed from vancomycin and cefotaxime to linezolid and cefotaxime and, later, to meropenem. The patient showed no clinical improvement while receiving these regimens. Subsequent antimicrobial susceptibility testing performed by the broth microdilution method using lysed horse blood-supplemented Mueller-Hinton broth showed the following MICs: vancomycin, >128 µg/mL; penicillin, 0.5 µg/mL; meropenem, >4 µg/mL; imipenem, 4 µg/mL; ertapenem, >8 µg/mL; cefotaxime, 8 µg/mL; ceftriaxone, 32 µg/mL; levofloxacin, 1 µg/mL; gatifloxacin, 0.12 µg/mL; erythromycin, 0.03 µg/mL; clindamycin, 0.03 µg/mL; quinupristin-dalfopsristin, 0.5 µg/mL; linezolid, 4 µg/mL; doxycycline, 0.5 µg/mL. The patient was treated with gatifloxacin followed by high-dose penicillin G (24 million U per day by continuous infusion) in combination with gatifloxacin for 14 days. The patient made an uneventful recovery from his meningitis. There have been prior reports of CNS infections with Leuconsotoc species [3, 4]. The concern that antibiotics with recognized activity against this organism have poor CNS penetration and/or lack bactericidal activity may lead clinicians to choose a carbapenem for treatment of such an infection, on the basis of previous reports that carbapenems have good in vitro activity [2]. This case illustrates that carbapenem resistance may occur in Leuconostoc species and emphasizes the importance of performing antibiotic susceptibility testing on isolates from each individual patient.