Table 4.

Change in log₁₀ CFU/thigh (and lung) after 24 h of therapy with ceftolozane alone or in combination with tazobactam at ratios of 2:1, 4:1, and 8:1 against Enterobacteriaceae producing various ESBLs in neutropenic mice^a

Organism	Control	Ceftolozane dose (mg/kg)	Change in log10 CFU/thigh after 24 h of therapy
			Ceftolozane	Ceftolozane + TZB (2:1)	Ceftolozane + TZB (4:1)	Ceftolozane + TZB (8:1)
E. coli 6042	2.22 ± 0.17	400	–0.32 ± 0.56	–1.91 ± 0.63	–1.31 ± 0.21	–1.15 ± 0.37
K. pneumoniae 4105	3.07 ± 0.10	400	1.76 ± 0.30	–0.21 ± 0.30	0.58 ± 0.35	1.28 ± 0.10
	2.63 ± 0.37	800	0.87 ± 0.77	–1.44 ± 0.40	–1.01 ± 0.25	0.53 ± 0.82
Lung	2.22 ± 0.50	400	1.09 ± 0.85	–0.60 ± 0.45	–0.09 ± 0.22	0.41 ± 0.81
K. pneumoniae 4110	1.82 ± 0.10	400	1.05 ± 0.07	1.03 ± 0.04	0.91 ± 0.08	1.01 ± 0.05
	1.57 ± 0.24	800	0.29 ± 0.12	–0.53 ± 0.10	–0.41 ± 0.23	0.33 ± 0.92
K. pneumoniae 81-1260A	3.15 ± 0.07	400	–0.87 ± 0.41	–2.33 ± 0.50	–1.59 ± 0.86	–1.08 ± 0.57
E. cloacae 81-1291A	2.04 ± 0.09	400	–1.06 ± 0.30	–3.05 ± 0.37	–3.29 ± 0.57	–2.78 ± 0.30

^aValues are expressed as means ± the standard error of the mean where applicable.