Lactobacillus species identification, H2O2 production, and antibiotic resistance and correlation with human clinical status

Abstract

Lactobacilli recovered from the blood, cerebrospinal fluid, respiratory tract, and gut of 20 hospitalized immunocompromised septic patients were analyzed. Biochemical carbohydrate fermentation and total soluble cell protein profiles were used to identify the species. Hydrogen peroxide production was measured. Susceptibility to 19 antibiotics was tested by a diffusion method, and the MICs of benzylpenicillin, amoxicillin, imipenem, erythromycin, vancomycin, gentamicin, and levofloxacin were determined. A small number of species produced H2O2, and antibiotic susceptibilities were species related. Eighteen (90%) of the isolates were L. rhamnosus, one was L. paracasei subsp. paracasei, and one was L. crispatus. L. rhamnosus, L. paracasei subsp. paracasei isolates, and the type strains were neither H2O2 producers nor vancomycin susceptible (MICs, ≥256 μg/ml). L. crispatus, as well as most of the type strains of lactobacilli which belong to the L. acidophilus group, was an H2O2 producer and vancomycin susceptible (MICs, <4 μg/ml).