Comparative In vitro antibacterial activity of nemonoxacin and other fluoroquinolones in correlation with resistant mechanisms in contemporary methicillin-resistant Staphylococcus aureus blood isolates in Taiwan

Table 2 Comparisons of nemonoxacin minimum inhibitory concentration (MIC) distributions by moxifloxacin susceptibility and sequence types of 501 methicillin–resistant Staphylococcus aureus blood isolates

	MIC (µg/mL)
	≤ 0.008	0.015	0.03	0.06	0.12	0.25	0.5^a	1^a	2	4	8	16	32	MIC₅₀/MIC₉₀	GM
Total (n = 501)	0	7	84	83	16	4	93	164	42	6	2	0	0	0.5/1	0.291
Moxifloxacin non-susceptible^b
Subtotal (n = 313)	0	0	3	3	1	1	92	163	42	6	2	0	0	1/2	0.867
ST8 (n = 155)	0	0	0	0	0	0	58	76	17	4	0	0	0	1/2	0.863
ST239 (n = 63)	0	0	0	0	0	0	0	49	11	2	1	0	0	1/2	1.219
ST59 (n = 15)	0	0	2	2	1	0	5	4	1	0	0	0	0	0.5/1	0.031
CC45 (n = 42)	0	0	1	1	0	1	22	15	1	0	1	0	0	0.5/1	0.618
Other STs (n = 38)	0	0	0	0	0	0	7	19	12	0	0	0	0	1/2	1.095
Moxifloxacin susceptible
Subtotal (n = 188)	0	7	81	80	15	3	1	1	0	0	0	0	0	0.06/0.12	0.047
ST8 (n = 2)	0	0	1	1	0	0	0	0	0	0	0	0	0	–^c/–^c	–^c
ST239 (n = 1)	0	0	1	0	0	0	0	0	0	0	0	0	0	–^c/–^c	–^c
ST59 (n = 93)	0	5	49	29	9	1	0	0	0	0	0	0	0	0.03/0.12	0.042
CC45 (n = 21)	0	2	17	1	0	0	1	0	0	0	0	0	0	0.03/0.03	0.033
Other STs (n = 71)	0	0	13	49	6	2	0	1	0	0	0	0	0	0.06/0.12	0.061

MIC minimum inhibitory concentration, MIC₅₀/MIC₉₀ the lowest concentration of the antibiotics at which 50% and 90% of the isolates were inhibited, respectively, GM geometric means, ST sequence type, CC clonal complex; –, not applicable
^aTentative S. aureus clinical breakpoints are 0.5 & 1 µg/mL for IV 500 mg & IV 750 mg nemonoxacin
^bAll 313 isolates had moxifloxacin MICs of ≥ 2 µg/mL, except one isolate with moxifloxacin MIC of 1 µg/mL, categorized as intermediate by CLSI clinical breakpoint criteria
^cOnly 2 ST8 isolates and 1 ST239 isolate were susceptible to moxifloxacin. Accordingly, we didn’t calculate nemonoxacin MIC₅₀/MIC₉₀ and MIC GM

ISSN: 1476-0711