Table 1

MICs of antimicrobials in bacterial keratitis

Organism	Fluoroquinolone	Systemic breakpoint (mg/L)	MIC₉₀ keratitis isolates (mg/L)	MIC₉₀ systemic isolates (mg/L)	References
Staphylococcus aureus*	Ciprofloxacin	1.00	0.25–128	>32	12 30 79 87 88
	Ofloxacin	NA	0.5 to >8	1 to >8	12 30 87–89
	Levofloxacin	1.00	0.38–16	>16	12 30 87 90
	Moxifloxacin	0.25	0.09–4	8	12 30 79 87 88
Streptococci†	Ciprofloxacin	NA	1–4	1–64	12 30 63 79 87 88
	Ofloxacin	NA	1.5–4	2–4	12 30 87–89
	Levofloxacin	2.00	1–1.5	64	12 30 79 87
	Moxifloxacin	0.50	0.12–0.38	0.25–4	12 30 79 87 88
Pseudomonas aeruginosa	Ciprofloxacin	0.50	0.25–0.5	0.5	12 30 79 87 88
	Ofloxacin	NA	1.5–2	>8	12 30 87–89
	Levofloxacin	1.00	0.52–1	2	12 30 79 87
	Moxifloxacin	N/A	1–4	4	12 30 79 87 91
CoNS‡	Ciprofloxacin	1.00	0.38–64	1 to >8	12 30 87–89
	Ofloxacin	NA	0.75–32	1 to >8	12 30 87–89
	Levofloxacin	1.00	0.25–128	8–16	12 30 92 93
	Moxifloxacin	0.25	0.06–16	0.12	12 30 88 93 94
Enterobacteriaceae	Ciprofloxacin	0.50	0.12	0.12–16	30 79 87 89
	Ofloxacin	0.50	0.38	0.25 to >8	30 89 93 95
	Levofloxacin	1.00	0.19	0.06–64	30 87 96
	Moxifloxacin	0.25	0.25–1.37	0.12–128	30 79 88 91 93

Systemic breakpoints, with MIC₉₀ values, for systemic and bacterial keratitis isolates for the FQs currently in ophthalmic use. The MIC₉₀ for both systemic and keratitis isolates are provided for comparison. If the MIC of the bacteria is much less than the lower quartile concentration, then it is likely that the bacteria will be clinically susceptible to that antimicrobial. If the MIC exceeds the lower quartile MIC consider modifying treatment (e.g increasing the frequency or changing route), combining antimicrobials or changing antimicrobials.
*Includes MRSA and MSSA
†Includes α-haemolytic streptococci, β-haemolytic streptococci and S. pneumoniae
‡Includes MRCoNS and MSCoNS
MICs, minimum inhibitory concentrations; NA, not available.