Synergistic Activity of Colistin/Fosfomycin Combination against Carbapenemase-Producing Klebsiella pneumoniae in an In Vitro Pharmacokinetic/Pharmacodynamic Model

Table 3

Log changes at 4, 8, 12, 16, 20, and 24 h at an inoculum of 10⁸ CFU/mL with colistin and/or fosfomycin against K. pneumoniae.

Isolate	Time; (h)	log change [log10(CFUt) − log10(CFU0)]
		Col 0.5 mg/L	Col 2 mg/L	Col 5 mg/L	Fos 100 mg/L	Col 0.5 mg/L; +; Fos 100 mg/L	Col 2 mg/L; +; Fos 100 mg/L	Col 5 mg/L; +; Fos 100 mg/L
Kp47	4	−3.23	−5.00	−5.24	−3.00	−6.30	−5.30	−8.13
	8	−0.80	−3.63	−4.57	−0.08	−4.17	−4.87	−5.27
	12	0.73	−2.58	−3.75	0.70	−4.60	−6.34	−6.73
	16	0.74	0.08	−1.23	0.87	−6.78	−4.62	−8.13
	20	0.78	0.52	−0.81	0.66	−5.83	−3.46	−6.73
	24	0.83	1.11	0.56	0.84	−5.32	−3.50	−4.59
Kp79	4	1.10	−4.29	−5.07	0.60	0.63	−4.32	−4.97
	8	1.16	−3.42	−5.38	0.66	1.16	−3.43	−5.33
	12	1.03	−3.40	−3.94	0.27	0.41	−3.19	−5.01
	16	0.85	−1.83	−1.30	0.55	0.94	−3.46	−4.71
	20	0.66	−1.10	−0.69	0.31	0.58	−3.37	−4.01
	24	0.97	−0.21	−0.01	0.38	0.32	−3.00	−2.97
Kp42	4	0.93	−6.14	−5.20	0.79	−2.20	−5.44	−5.80
	8	0.97	−4.53	−5.53	0.78	−1.47	−5.44	−3.51
	12	0.87	−3.52	−5.10	0.50	−1.18	−6.22	−4
	16	0.81	−2.94	−3.80	0.47	0.58	−3.43	−4.98
	20	0.69	−3.08	−4.10	0.31	0.75	−3.65	−4.60
	24	0.76	−2.29	−3.70	0.32	0.71	−3.44	−3.72
Kp11	4	0.26	−4.58	−3.79	0.24	−3.76	−5.15	−5.99
	8	1.07	−3.73	−4.35	0.46	−3.77	−4.17	−4.92
	12	0.87	−3.85	−5.12	0.01	−3.57	−4.16	−4.83
	16	0.70	−4.06	−5.48	0.36	−3.66	−4.65	− 5
	20	0.67	−3.02	−5.74	0.10	−3.54	−4.74	−5.21
	24	0.56	−2.26	−3.46	0.29	−2.18	−3.97	−4.62

The italic font indicates activity (a reduction of ≥1 log₁₀CFU/mL below the initial inoculum); bold font indicates synergy (a decrease of ≥2 log₁₀ in the number of CFU/mL between the combination and its most active component); bold italic font indicates additivity (a decrease of 1.0 to <2 log₁₀ in the number of CFU/mL between the combination and its most active component).