Antibiotic resistance among ocular pathogens: current trends from the ARMOR surveillance study (2009–2016)

Figures & data

Table 1 Cumulative resistance profiles and MICs for S. aureus isolates

Antibiotic	S. aureus
	All				MRSA				MSSA
	N	%S	%R	MIC90	N	%S	%R	MIC90	N	%S	%R	MIC90
Vancomycin	1,695	100	0	1	621	100	0	1	1,074	100	0	1
Besifloxacin	1,695	NAb	NAb	1	621	NAb	NAb	2	1,074	NAb	NAb	0.25
Moxifloxacin	1,695	66.4	33.6	4	621	27.2	72.8	16	1,074	89.0	11	1
Gatifloxacin	1,495	65.9	34.1	8	543	26.7	73.3	16	952	88.2	11.8	1
Ciprofloxacin	1,695	64.3	35.8	128	621	24.5	75.5	256	1,074	87.2	12.8	8
Levofloxacin	1,495	65.7	34.3	32	543	26.2	73.9	128	952	88.2	11.8	4
Ofloxacin	1,495	65.2	34.9	>8	543	25.8	74.2	>8	952	87.6	12.4	8
Azithromycin	1,695	39.4	60.6	>512	621	7.2	92.8	>512	1,074	58.0	42.0	>512
Chloramphenicol	1,495	93.9	6.1	8	543	89.5	10.5	16	952	96.4	3.6	8
Clindamycin	1,695	84.6	15.4	>2	621	69.7	30.3	>2	1,074	93.2	6.8	0.25
Methicillina	1,695	63.4	36.6	>2	621	0	100	>4	1,074	100	0	0.5
Tetracycline	419	95.7	4.3	0.5	103	90.3	9.7	4	316	97.5	2.5	0.5
Tobramycin	1,695	82.6	17.4	128	621	58.9	41.1	256	1,074	96.3	3.7	0.5
Trimethoprim	1,495	95.7	4.4	4	543	94.1	5.9	2	952	96.5	3.5	4

Notes:

a Oxacillin was used as a surrogate for methicillin.

b Clinical and Laboratory Standards Institute interpretive breakpoints are not available.

Abbreviations: MIC_90, minimum inhibitory concentration that inhibits the growth of 90% of indicated isolates (µg/mL); MRSA, methicillin-resistant S. aureus; MSSA, methicillin-susceptible S. aureus; NA, not applicable; %R, percentage of resistant isolates; %S, percentage of susceptible isolates.

Table 3 Cumulative resistance profiles and MICs for P. aeruginosa, H. influenzae, and S. pneumoniae isolates

Antibiotic	P. aeruginosa				H. influenzae				S. pneumoniae
	N	%S	%R	MIC90	N	%S	%R	MIC90	N	%S	%R	MIC90
Besifloxacin	599	NAa	NAa	4	586	NAa	NAa	0.03	474	NAa	NAa	0.06
Moxifloxacin	599	NAa	NAa	4	586	99.8	0.2	0.03	474	99.8	0.2	0.12
Gatifloxacin	499	94.2	5.8	2	513	99.8	0.2	0.015	399	99.8	0.3	0.25
Ciprofloxacin	599	94.0	6.0	0.5	586	99.8	0.2	0.015	474	NAa	NAa	1
Levofloxacin	499	94.8	5.2	1	513	99.8	0.2	0.03	399	100	0	1
Ofloxacin	499	92.6	7.4	2	513	99.8	0.2	0.03	399	99.5	0.5	2
Azithromycin	599	NAa	NAa	512	586	99.5	0.5	2	474	64.1	35.9	>128
Chloramphenicol	599	NAa	NAa	128	586	99.5	0.5	0.5	474	97.5	2.5	4
Penicillin	NT	NT	NT	NT	586	NAa	NAa	>4	474	66.7	33.3	1
Polymyxin B	499	91.4	8.6	2	513	NAa	NAa	2	399	NAa	NAa	>128
Tetracycline	145	NAa	NAa	16	160	97.5	2.5	0.5	92	89.1	10.9	4
Tobramycin	599	97.5	2.5	1	586	NAa	NAa	2	474	NAa	NAa	32

Notes:

a Clinical and Laboratory Standards Institute interpretive breakpoints are not available.

Abbreviations: MIC₉₀, minimum inhibitory concentration that inhibits the growth of 90% of indicated isolates (µg/mL); NA, not applicable; NT, not tested; %R, percentage of resistant isolates; %S, percentage of susceptible isolates.

Table 2 Cumulative resistance profiles and MICs for CoNS isolates

Antibiotic	CoNS
	All				MRCoNS				MSCoNS
	N	%S	%R	MIC90	N	%S	%R	MIC90	N	%S	%R	MIC90
Vancomycin	1,475	100	0	2	717	100	0	2	758	100	0	2
Besifloxacin	1,475	NAb	NAb	2	717	NAb	NAb	4	758	NAb	NAb	0.25
Moxifloxacin	1,475	68.9	31.1	16	717	48.5	51.5	32	758	88.1	11.9	1
Gatifloxacin	1,331	66.9	33.1	16	641	44.2	55.9	32	690	88.1	11.9	1
Ciprofloxacin	1,475	65.1	34.9	64	717	42.0	58.0	64	758	86.9	13.1	4
Levofloxacin	1,331	66.6	33.4	128	641	43.4	56.6	128	690	88.1	11.9	4
Ofloxacin	1,331	66.2	33.8	>8	641	43.1	56.9	16	690	87.7	12.3	8
Azithromycin	1,475	38.8	61.2	>512	717	21.8	78.2	>512	758	54.9	45.1	>512
Chloramphenicol	1,331	98.8	1.2	8	641	98.4	1.6	8	690	99.1	0.9	4
Clindamycin	1,475	73.9	26.1	>2	717	63.9	36.1	>16	758	83.4	16.6	2
Methicillina	1,445	51.4	48.6	>2	717	0	100	>2	758	100	0	0.25
Tetracycline	381	86.1	13.9	>16	176	82.4	17.6	>16	205	89.3	10.7	8
Tobramycin	1,475	83.1	17.0	8	717	72.3	27.8	32	758	93.3	6.7	4
Trimethoprim	1,331	72.1	28.0	>128	641	58.4	41.7	256	690	84.8	15.2	128

Notes:

a Oxacillin was used as a surrogate for methicillin.

b Clinical and Laboratory Standards Institute interpretive breakpoints are not available.

Abbreviations: CoNS, coagulase-negative staphylococci; MIC₉₀, minimum inhibitory concentration that inhibits the growth of 90% of indicated isolates (µg/mL); MRCoNS, methicillin-resistant coagulase-negative staphylococci; MSCoNS, methicillin-susceptible coagulase-negative staphylococci; NA, not applicable; %R, percentage of resistant isolates; %S, percentage of susceptible isolates.

Figure 1 Multidrug resistance in staphylococci.

Notes: Isolates were tested against azithromycin, chloramphenicol, ciprofloxacin, clindamycin, oxacillin (methicillin), tetracycline, tobramycin, trimethoprim, and vancomycin.
Abbreviations: CoNS, coagulase-negative staphylococci; MDR, multidrug resistance; MRCoNS, methicillin-resistant coagulase-negative staphylococci; MRSA, methicillin-resistant S. aureus; MSCoNS, methicillin-susceptible coagulase-negative staphylococci; MSSA, methicillin-susceptible S. aureus.

Figure 2 Methicillin resistance in staphylococci by patient age.

Notes: Methicillin resistance among staphylococci was evaluated by patient decade of life. Significant differences in mean percent methicillin resistance were found, with higher rates of resistance observed in older patients (P<0.0001 for both S. aureus and CoNS).
Abbreviation: CoNS, coagulase-negative staphylococci.

Figure 3 Trends in methicillin resistance over time (ARMOR, 2009–2016) in staphylococci.

Notes: Methicillin resistance rates among staphylococci over the course of the ARMOR study are shown. A decrease in methicillin resistance over time was observed among S. aureus isolates (P<0.0001, bold font) but not among CoNS isolates.
Abbreviations: ARMOR, Antibiotic Resistance Monitoring in Ocular micRoorganisms; CoNS, coagulase-negative staphylococci.

Figure 4 Trends in antibiotic resistance over time (ARMOR, 2009–2016).

Notes: Trends in antibiotic resistance over 8 years of ARMOR are shown for representative antibiotics for which systemic breakpoints were available. Significant changes (P<0.05, bold font) in antibiotic resistance trends over time were observed.
Abbreviations: ARMOR, Antibiotic Resistance Monitoring in Ocular micRoorganisms; CoNS, coagulase-negative staphylococci; MRCoNS, methicillin-resistant coagulase-negative staphylococci; MRSA, methicillin-resistant S. aureus.