Role of inoculum and mutant frequency on fosfomycin MIC discrepancies by agar dilution and broth microdilution methods in Enterobacteriaceae  M. Ballestero-Téllez, F. Docobo-Pérez, J.M. Rodríguez-Martínez, M.C. Conejo, M.S. Ramos-Guelfo, J. Blázquez, J. Rodríguez-Baño, A. Pascual  Clinical Microbiology and Infection  Volume 23, Issue 5, Pages 325-331 (May 2017) DOI: 10.1016/j.cmi.2016.12.022 Copyright © 2016 European Society of Clinical Microbiology and Infectious Diseases Terms and Conditions

Fig. 1 Bland–Altman analysis of agreement between agar dilution (104 CFU/spot) and broth microdilution performed with (a) low inoculum (105 CFU/mL, i.e. 104 CFU/well) similar to the agar dilution method or (b) standard inoculum (2 × 105 to 8 × 105 CFU/mL, i.e. 2 × 104 to 8 × 104 CFU/well). The differences of the log2-transformed MICs obtained by agar dilution and broth microdilution are plotted against their mean MIC values. The solid line represents the mean of the differences, the dotted lines indicate the lower and upper limits of the 95% CI. Clinical Microbiology and Infection 2017 23, 325-331DOI: (10.1016/j.cmi.2016.12.022) Copyright © 2016 European Society of Clinical Microbiology and Infectious Diseases Terms and Conditions

Fig. 2 Fosfomycin mutant frequency at different concentrations of 21 Escherichia coli (MIC=1mg/L) and 21 Klebsiella pneumoniae (MIC=16mg/L) clinical isolates. Horizontal bars and whiskers represent the mean and SD, respectively. Open grey circles denote each independent result. Clinical Microbiology and Infection 2017 23, 325-331DOI: (10.1016/j.cmi.2016.12.022) Copyright © 2016 European Society of Clinical Microbiology and Infectious Diseases Terms and Conditions

Fig. 3 Subpopulation growth monitoring over time, at different initial bacterial inocula. Total bacterial population (no fosfomycin) is shown by red lines. Resistant subpopulations able to grow at 4 mg/L (blue lines) and 8 mg/L (green lines) of fosfomycin (4×and 8×MIC) are shown for Ec42, Ec148, Ec162, Ec271, Ec2974 and Escherichia coli ATCC 25922 strains (all with MIC=1mg/L). Each line represents the growth of a single experiment. Experiments were carried out in quadruplicate using the same overnight inoculum. Clinical Microbiology and Infection 2017 23, 325-331DOI: (10.1016/j.cmi.2016.12.022) Copyright © 2016 European Society of Clinical Microbiology and Infectious Diseases Terms and Conditions