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In vitro antimicrobial susceptibility of Propionibacterium acnes isolated from acne patients in northern Mexico Roger Gonza´lez1, MD, Oliverio Welsh1, MD, PhD, Jorge Ocampo1, MD, Rosa M. Hinojosa-Robles2, PhD, Lucio Vera-Cabrera1, Dr.Sc., Mary L. Delaney3, MS, and Minerva Go´mez1, MD
1 Dermatology Department, 2Infectious Diseases Department, University Hospital ‘‘Dr. Jose´ Eleuterio Gonza´lez’’, Monterrey, Me´xico, and 3Brigham and Women’s Hospital, Harvard Medical School, Boston, MA, USA
Abstract Background Antimicrobials are essential in acne therapy. In the last decades, Propionibacterium acnes has become resistant to different antibiotics. Objective To determine antimicrobial susceptibility patterns of P. acnes to frequently used drugs. Materials and methods Cutaneous lesion samples were obtained from 50 patients with
Correspondence Roger Gonza´lez, MD Dermatology Department University Hospital ‘‘Dr. Jose´ Eleuterio Gonza´lez’’ Monterrey Me´xico E-mail:
[email protected] Conflicts of Interest: None. Financial Support: None.
acne vulgaris, which were cultured in anaerobic media to demonstrate the presence of P. acnes. After that, antimicrobial susceptibility tests to tetracycline, minocycline, doxycycline, erythromycin, azithromycin, clindamycin, trimethoprim/sulfamethoxazole (SXT) and levofloxacin were performed. Results In the general study group, resistance to azithromycin was 82%, the most prevalent one (P < 0.05), followed by trimethoprim/sulfamethoxazole (68%) and erythromycin (46%). On the other hand, all strains isolated were susceptible to minocycline. Resistance bias were similar when subgroups with and without the previous antimicrobial therapy were performed, finding a low prevalence of resistance to tetracyclines and levofloxacin in both groups. Conclusions In our region, P. acnes is highly resistant to azithromycin, SXT, erythromycin and clindamycin; and being very susceptible to minocycline, levofloxacin and tetracycline, in vitro in both groups: with and without the previous antibiotic use. To our knowledge, high resistance prevalence to azithromycin and SXT has never been reported.
Background Acne is a disease that involves pilosebaceous units of the face, chest, and back. It usually begins at puberty and affects about 80% of adolescents, as well as a large number of adults.1 Acne therapy is based on controlling etiopathogenic factors which cause acne, by means of anti-comedogenic, anti-inflammatory, and antimicrobial medications.2 Propionibacterium acnes is the target of both topical and systemic antibiotic therapies. However, as P. acnes is part of cutaneous bacterial flora, its presence in healthy patients does not necessarily mean disease. The chronicity of the disease, antimicrobial administration route, the duration of therapy, poor treatment compliance, and easy access to therapeutic agents without medical supervision are factors that have contributed to the development of antibiotic resistance. Until the late 1970s, P. acnes was susceptible to all antimicrobials used, e.g. clindamycin, erythromycin, and ª 2010 The International Society of Dermatology
tetracyclines.1,3 However, these susceptibility trends have gradually changed and may vary from one region to another. The susceptibility pattern of P. acnes to antibiotics in northern Mexico is unknown. The aim of this study was to determine the resistance trends of commonly used antimicrobials for P. acnes strains isolated from patients with acne vulgaris treated at the Dermatology Department of the ‘‘Dr. Jose E. Gonzalez’’ University Hospital in Monterrey, México. Material and Methods We carried out a descriptive, observational, cross sectional study of patients with acne, 16–30 years of age who were not taking antimicrobials for the last 3 months. The patients and tutors, in the case of minors, signed an informed legal consent form. Fifty patients were included in the study. Pregnant women and patients who were on isotretinoin therapy were excluded from the study. Patients who did not come for bacterial skin International Journal of Dermatology 2010, 49, 1003–1007
1003
1004
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P. acnes resistance in Mexico
sampling were eliminated. This work was registered and
sulfamethoxazole was obtained. P. acnes ATCC 6919 was
authorized by the Ethics Committee of the Universidad Auto´noma de Nuevo Leo´n, registration number DE07-017.
used as reference strain. All minimum inhibitory concentrations (MIC) were tabulated in lg/ml and comparisons of each antimicrobial susceptibility index
Skin sampling Skin sampling was performed according to Palma-Ramos et al.4 and modified by our team. The sample area was cleansed with a 60 alcohol-embebbed cotton swab. To sample the open comedos (blackheads), a sterile comedo extractor was used. In the case of closed comedos (whiteheads), the lesion was punctured with a (25 · 35 mm) hypodermic needle and the sample was subsequently obtained with the comedo extractor. For patients with inflammatory lesions such as papules and pustules, the lesion was first punctured with a hypodermic needle and its contents were collected with the comedo extractor.
were made for each isolated strain (Table 1). Resistance breakpoints for antimicrobials were defined according to CLSI (NCCLS Document M11-A7)8: clindamycin, ‡8 lg/ml, erythromycin, ‡2 lg/ml, tetracycline ‡16 lg/ml, minocycline ‡16 lg/ml, doxycycline, ‡4 lg/ml, levofloxacin ‡8 lg/ml; breakpoints for azithromycin against anaerobes have not been established, so Haemophilus breakpoint of 0.05). In the general study group (n = 49), 37 patients (75.52%) were resistant to at least one of the antimicrobials tested. Only 12 strains (24.48%) were sensitive to
Table 1 Minimum inhibitory concentrations (MICs) of several antimicrobials against Propionibacterium acnes isolates No. isolates inhibited at an MIC (lg/ml) of: Antimicrobial
£0.03
0.06
0.125
0.25
0.5
Clindamycin Erythromycin Azithromycin Tetracycline Minocycline Doxycycline SXT Levofloxacin
2 1
2 2 1
2 2 2
13
9 4 1 9 10 11 3 29
6 1 2 2
2 9 3 5 8
1
2
4
11
2 6
10 8 4 5 4
7 12 8 2 1
2 8 3 12 3
8
16
1
1
5 7 1 7
9 1
3
1
2
32
2 6
64
1
128
‡256
MIC50
MIC90
Total
1
16 23 24 1
0.5 2.0 64.0 2.0 0.5 2.0 ‡256 0.5
‡256 ‡256 ‡256 32.0 2.0 8.0 ‡256 8.0
49 49 49 49 49 49 49 49
1 29 1
SXT = trimethoprim/sulfamethoxazole. International Journal of Dermatology 2010, 49, 1003–1007
ª 2010 The International Society of Dermatology
Gonza´lez et al.
P. acnes resistance in Mexico
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Figure 1 General prevalence of antimicrobial resistance. y-axis shows percentage of resistant strains. CLI, clindamycin; ERY, erythromycin; AZM, azithromycin; TET, tetracycline; MIN, minocycline; DOX, doxycycline; SXT, trimethoprim/sulfamethoxazole, LVX, levofloxacin
all the antimicrobials. General prevalence of antimicrobial resistance of P. acnes is shown in Fig. 1. Both subgroups showed the same distribution pattern of resistant P. acnes strains; however, they differ in frequency from one subgroup to another. Subgroup 1 (Previously untreated group)
In this subgroup (n = 22), despite nonspecific previous therapy for acne vulgaris, it was observed that azithromycin was the antibiotic with the highest resistance rate (72.7%), followed by SXT and erythromycin (59% and 31.8%, respectively). Subgroup 2 (Previously treated group)
This group (n = 27), shares the same distribution antimicrobial resistance pattern with subgroup 1; however, the frequency of resistant strains is higher than subgroup 1. The most relevant percentages of resistance are to azithromycin (92.5%), SXT (77.7%), and erythromycin (59.2%); doxycicline showed the highest rate of resistant strains within the tetracyclines antimicrobials (33%). Prevalence of resistant strains of P. acnes in subgroups is detailed in Fig. 2. A comparison of the rate of resistance was made between each antimicrobial tested. The following comparisons are
relevant, resistance to clindamycin is statistically greater than that of tetracycline, minocycline, and levofloxacin, (P = 0.0002,
