Comparison of Broth Microdilution, Etest, and Agar Disk Diffusion Methods for Antimicrobial Susceptibility Testing of Lactobacillus acidophilus Group Members

Abstract

In recent years, the absence of acquired antimicrobial resistance has become an important criterion to evaluate the biosafety of lactobacilli used as industrial starter or probiotic cultures. At present, however, standards for susceptibility testing of Lactobacillus strains or approved guidelines for interpreting the test results are not available. Hence, this study was carried out to contribute to the establishment of a standardized procedure for antimicrobial susceptibility testing of lactobacilli. The results obtained by testing 104 strains of the Lactobacillus acidophilus group were compared based on broth microdilution, disk diffusion, and Etest. Except for some specific agent-related effects, agreement between MICs resulting from the broth microdilution method and the Etest was good. In addition, inhibition zone diameters determined with disk diffusion correlated well with MICs from Etest and broth microdilution.

Intra- and Interlaboratory Performances of Two Commercial Antimicrobial Susceptibility Testing Methods for Bifidobacteria and Nonenterococcal Lactic Acid Bacteria

“…Unlike the participants in the present study, other researchers (3,24) have observed ingrowth of resistant microcolonies in elliptical inhibition zones during Etest analyses of NELAB. Possibly, this may be due to the high rate of spontaneous mutation after prolonged (Ͼ24-to 48-h) incubation with subinhibitory antibiotic concentrations.…”

“…In a recent study of Lb. acidophilus group members in which VetMIC was compared to the agar-based disk diffusion and Etest methods, a minor satisfying level of agreement was specifically found for results of susceptibility testing with bacteriostatic agents such as clindamycin (24). In the present study, VetMIC and Etest were compared to broth microdilution as a noncommercial reference method, and MICs of tetracycline, streptomycin, gentamicin, and ampicillin determined by the two assays were in good agreement with those determined by the reference method.…”

“…(when supplemented with 0.03% cysteine) and minimizes potential antagonism between medium components and tested antimicrobials. So far, LSM and related mixedmedium formulations, all containing IST broth as the basic component, have been successfully used to determine MICs for members of the genera Bifidobacterium, Lactobacillus, Lactococcus, Pediococcus, and Streptococcus by microdilution and Etest methods (2,5,7,8,17,18,(20)(21)(22)(23)(24)32).…”

Curd Lactobacilli with Probiotic Potentiality

“…The lack of acquisition of antibiotic resistance has been an important criterion in assessing the safety profile of lactobacilli to be used as probiotics [34], since acquisition of such resistances and their plausible dissemination to the human pathogenic bacteria in the intestine are of great concern [35]. Therefore, it is important to determine the effect on the growth of lactobacilli of antibiotics.…”

Determination of FICI of Ethanolic Extract of Aloe Vera Skin Leaves (Aloe vera (L.) Burm.f.) and Gentamicin Sulphate againts Staphylococcus aureus

“…Metode disk difusi merupakan salah metode yang direkomendasikan oleh CLSI dalam penentuan nilai konsentrasi minimum. Menurut Mayrhofer et al, (2008) zona hambat yang diperoleh dari metode difusi berkorelasi baik dengan nilai MIC yang diperoleh dari metode dilusi dan E-test. Menurut Singh et al, (2015) metode disk difusi dan makrodilusi juga berkorelasi dengan baik dalam penentuan MIC.…”