<i>Staphylococcus aureus</i> resistance to topical antimicrobials in atopic dermatitis

Bessa, Giancarlo Rezende; Quinto, Vanessa Petry; Machado, Daiane Corrêa; Lipnharski, Caroline; Weber, Magda Blessmann; Bonamigo, Renan Rangel; D'Azevedo, Pedro Alves

doi:10.1590/abd1806-4841.20164860

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Investigation • An. Bras. Dermatol. 91 (5) • Sep-Oct 2016 • https://doi.org/10.1590/abd1806-4841.20164860 copy

Staphylococcus aureus resistance to topical antimicrobials in atopic dermatitis^* * Work performed at the Outpatient Department of the Dermatology Service of the Universidade Federal de Ciências da Saúde de Porto Alegre (UFCSPA) e Ambulatório de Dermatologia Sanitária do Rio Grande do Sul (ADS) – Porto Alegre (RS), Brazil.

Authorship SCIMAGO INSTITUTIONS RANKINGS

Abstract:

Background:

Topical antimicrobial drugs are indicated for limited superficial pyodermitis treatment, although they are largely used as self-prescribed medication for a variety of inflammatory dermatoses, including atopic dermatitis. Monitoring bacterial susceptibility to these drugs is difficult, given the paucity of laboratory standardization.

Objective:

To evaluate the prevalence of Staphylococcus aureus topical antimicrobial drug resistance in atopic dermatitis patients.

Methods:

We conducted a cross-sectional study of children and adults diagnosed with atopic dermatitis and S. aureus colonization. We used miscellaneous literature reported breakpoints to define S. aureus resistance to mupirocin, fusidic acid, gentamicin, neomycin and bacitracin.

Results:

A total of 91 patients were included and 100 S. aureus isolates were analyzed. All strains were methicillin-susceptible S. aureus. We found a low prevalence of mupirocin and fusidic acid resistance (1.1% and 5.9%, respectively), but high levels of neomycin and bacitracin resistance (42.6% and 100%, respectively). Fusidic acid resistance was associated with more severe atopic dermatitis, demonstrated by higher EASI scores (median 17.8 vs 5.7, p=.009). Our results also corroborate the literature on the absence of cross-resistance between the aminoglycosides neomycin and gentamicin.

Conclusions:

Our data, in a southern Brazilian sample of AD patients, revealed a low prevalence of mupirocin and fusidic acid resistance of S. aureus atopic eczema colonizer strains. However, for neomycin and bacitracin, which are commonly used topical antimicrobial drugs in Brazil, high levels of resistance were identified. Further restrictions on the use of these antimicrobials seem necessary to keep resistance as low as possible.

Keywords:
Anti-infective agents, local; Dermatitis, atopic; Drug resistance, bacterial; Staphylococcus aureus

Antibiotic	MIC50 (µg/ml)	MIC90 (µg/ml)
Neomycin	1.5	17.6
Bacitracin	96	>256
Mupirocin	0.19	0.38
Fusidic acid	0.38	0.75

Demographic data	All patients	Gentamicin^* * defined by disk diffusion technique;			Neomycin^ defined by MIC breakpoints. R: resistant; S: sensible; SD: standard deviation; IQR: interquartile range (the values between the 75th percentile and the 25th percentile).			Fusidic acid^ defined by MIC breakpoints. R: resistant; S: sensible; SD: standard deviation; IQR: interquartile range (the values between the 75th percentile and the 25th percentile).
Demographic data	n=91	R (n=10)	S (n=58)	p	R (n=29)	S (n=39)	p	R (n=4)	S (n=64)	p
Male Sex – n(%)	48 (52,7)	5 (50,0)	33 (56,9)	0,740^‡ ‡ Fisher's Exact Test; £ asymmetric variable;	15 (51,7)	23 (59,0)	0,625^¶ ¶ Pearson's Chi-square Test with continuity correction;	2 (50,0)	36 (56,3)	1,000^‡ ‡ Fisher's Exact Test; £ asymmetric variable;
Age (years)				0,674^§ § Mann Whitney Test;			0,312^§ § Mann Whitney Test;			0,900^§ § Mann Whitney Test;
Range	0,3 -30
Mean ± SD	7,0±5,2	6,6±2,2	7,4±5,9		8,1±5,9	6,7±5,3		7,0±3,8	7,4±5,7
Median (IQR)	6,0	7,0	6,0		7,0	6,0		8,0	6,5
	(2,6-10,0)	(0,5-10,0)	(0,5-30,0)		(0,5-30,0)	(0,6-26,0)		(2,0-10,0)	(0,5-30,0)
Topical antibiotic use – n(%)	9,0 (9,9)	0 (0,0)	8 (13,8)	0,593^‡ ‡ Fisher's Exact Test; £ asymmetric variable;	3 (10,3)	5 (12,8)	1,000^‡ ‡ Fisher's Exact Test; £ asymmetric variable;	0 (0,0)	8 (12,5)	0,975^‡ ‡ Fisher's Exact Test; £ asymmetric variable;
Previous skin infection – n(%)	30 (33,0)	4 (40,0)	20 (34,5)	0,733^‡ ‡ Fisher's Exact Test; £ asymmetric variable;	12 (41,4)	12 (30,8)	0,516^¶ ¶ Pearson's Chi-square Test with continuity correction;	0 (0,0)	24 (37,5)	0,289^‡ ‡ Fisher's Exact Test; £ asymmetric variable;
Recurrent infections– n(%)	24 (26,4)	3 (30,0)	16 (27,6)	1,000^‡ ‡ Fisher's Exact Test; £ asymmetric variable;	10 (34,5)	9 (23,1)	0,445^¶ ¶ Pearson's Chi-square Test with continuity correction;	0 (0,0)	19 (29,7)	0,570^‡ ‡ Fisher's Exact Test; £ asymmetric variable;
Systemic antibiotic use – n(%)	27 (29,7)	2 (20,0)	19 (32,8)	0,250^‡ ‡ Fisher's Exact Test; £ asymmetric variable;	9 (31,0)	12 (30,8)	1,000	2 (50,0)	19 (29,7)	0,658^‡ ‡ Fisher's Exact Test; £ asymmetric variable;
Hospitalization	– n(%) 7 (7,7)	1 (10,0)	5 (8,6)	1,000^‡ ‡ Fisher's Exact Test; £ asymmetric variable;	2 (6,9)	4 (10,3)	1,000^‡ ‡ Fisher's Exact Test; £ asymmetric variable;	1 (25,0)	5 (7,8)	0,315^‡ ‡ Fisher's Exact Test; £ asymmetric variable;
Disease duration (years) £				0,896^§ § Mann Whitney Test;			0,121^§ § Mann Whitney Test;			0,444^§ § Mann Whitney Test;
range	(0,1–30,0)
mean ± SD	4,7 ± 4,7	5,2±2,7	4,9±5,4		6,1±6,2	4,1±3,8		6,8±4,0	4,8±5,1
median (IQR)	3,0	5,6	3,0		5,0	2,5		8,0	4,0
	(1,5 – 6,3)	(0,5-10,0)	(0,3-30,0)		(0,3-30,0)	(0,3-1,7)		(1,5-10,0)	(0,3-30,0)
EASI score £				0,965^§ § Mann Whitney Test;			0,437^§ § Mann Whitney Test;			0,009^§ § Mann Whitney Test;
range	(0,4–40,5)
mean ± SD	7,8 ± 8,1	9,1±11,3	9,0±8,3		9,9±8,1	8,3±9,2		20,5±17,1	8,3±7,6
median (IQR)	5,4	5,7	6,2		7,3	4,9		17,8	5,7
	(2,0 – 9,9)	(1,2-40,5)	(0,6-32,2)		(0,6-32,2)	(0,6-40,5)		(6,0-40,5)	(0,6-32,2)

Independent variables	Gentamicin resistant
	Coefficient B	SE	Risk		P
	Coefficient B	SE	OR	IC95%	P
Factor
Neomycin MIC	1,18	0,89	1,19	0,87-2,93	0,258
Covariables
Male Sex	0,77	0,82	2,15	0,43-10,81	0,352
Female Sex	0,31	0,12	0,87	0,11-2,11	0,352
Age (years)	0,16	0,17	0,12	0,84-1,66	0,334
Topical antibiotics use	19,5	14,62	0,99	0,21-3,03	0,999
Previous skin Infection	-0,15	1,12	0,86	0,09-7,71	0,894
Recurrent cutaneous infections	-0,40	1,29	0,67	0,053-8,427	0,757
Systemic antibiotics use	2,15	1,54	3,29	0,88-18,54	0,214
Hospitalization	0,88	1,37	2,41	0,16-35,31	0,520
Disease duration (years) £	-0,121	0,17	0,88	0,63-1,24	0,483
EASI score (points) £	-0,01	0,04	0,99	0,91-1,01	0,828

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[1] Mailing address: Giancarlo Rezende Bessa, Ambulatório do Serviço de Dermatologia da UFCSPA, Rua Capitão Montanha, 27 Centro, 90010-040 Porto Alegre, RS. E-mail: gianmed@yahoo.com