title: Lactobacillus bacteremia, species identification, and antimicrobial susceptibility of 85 blood isolates.
abstract: BACKGROUND
  Data regarding antimicrobial susceptibility of clinical Lactobacillus isolates are scarce, and appropriate interpretation criteria for susceptibility tests are not available.
  
  
  METHODS
  We examined 85 cases of Lactobacillus bacteremia, of which 47 cases have been included in our previous studies. Overall, 14 antimicrobial agents were evaluated by the E-test method, and these results were compared with disk diffusion test findings. The clinical outcomes of the patients and their antimicrobial treatments were registered.
  
  
  RESULTS
  The antimicrobial susceptibility of Lactobacillus strains was species dependent. The considerable number of Lactobacillus rhamnosus (n=46), Lactobacillus fermentum (n=12), and Lactobacillus casei (n=12) strains available for testing made it possible to compare the susceptibilities within 1 species, as well. Of the 46 L. rhamnosus isolates, 22 were identified as L. rhamnosus GG type by pulsed-field gel electrophoresis. All Lactobacillus isolates demonstrated low minimum inhibitory concentrations (MICs) of imipenem, piperacillin-tazobactam, erythromycin, and clindamycin. MICs of vancomycin were high (>256 microg/mL) for all other species except Lactobacillus gasseri and Lactobacillus jensenii. Disk diffusion and E-test results were concordant. The MICs of cephalosporins varied; cefuroxime demonstrated a higher level of activity than did ceftriaxone. Benzylpenicillin and ampicillin MICs had variable ranges between different species. Combination therapy was given to 83% of the patients, but, in 54% of them, therapy included only 1 microbiologically active agent, according to results of the susceptibility tests. Mortality at 1 week was 12% among patients who presumably were receiving adequate treatment and 27% among patients who were receiving inadequate treatment (P=.131, by E-test).
  
  
  CONCLUSIONS
  Most clinical Lactobacillus blood isolates demonstrated low MICs of imipenem, piperacillin-tazobactam, erythromycin, and clindamycin, but they had variable susceptibility to penicillin and cephalosporins.
authors.affiliation: Division of Infectious Diseases, Department of Medicine, Helsinki University Central Hospital, Helsinki, Finland. minna.salminen@hus.fi
authors.forename: M K
authors.initials: MK
authors.lastname: Salminen
authors.forename: H
authors.initials: H
authors.lastname: Rautelin
authors.forename: S
authors.initials: S
authors.lastname: Tynkkynen
authors.forename: T
authors.initials: T
authors.lastname: Poussa
authors.forename: M
authors.initials: M
authors.lastname: Saxelin
authors.forename: V
authors.initials: V
authors.lastname: Valtonen
authors.forename: A
authors.initials: A
authors.lastname: Järvinen
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D016470:Bacteremia / Q000188:drug therapy / Q000382:microbiology*; D024881:Drug Resistance, Bacterial; D006801:Humans; D007778:Lactobacillus / Q000187:drug effects*; D008826:Microbial Sensitivity Tests; D013045:Species Specificity
chemical_list: D000900:Anti-Bacterial Agents