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Antibiotics, Acne, and
Staphylococcus aureus Colonization
Matthew Fanelli, MD; Eli Kupperman, BA; Ebbing Lautenbach, MD, MPH;
Paul H. Edelstein, MD; David J. Margolis, MD, PhD
Objectives: To determine the frequency of Staphylo- and 7 (19%) had S aureus in both their nose and their
coccus aureus colonization among patients with acne and throat. When patients with acne who were antibiotic us-
to compare the susceptibility patterns between the pa- ers were compared with nonusers, the prevalence odds
tients who are using antibiotics and those who are not ratio for the colonization of S aureus was 0.16 (95% con-
using antibiotics. fidence interval [CI], 0.08-1.37) after 1 to 2 months of
exposure and increased to 0.52 (95% CI, 0.12-2.17) af-
Design: Survey (cross-sectional) study of patients treated ter 2 months of exposure (P =.31). Many of the S aureus
for acne. isolates were resistant to treatment with clindamycin and
erythromycin (40% and 44%, respectively), particularly
Setting: Dermatology outpatient office practice the nasal isolates. Very few showed resistance rates
(⬍10%) to treatment with tetracycline antibiotics.
Participants: The study included 83 patients who were
undergoing treatment and evaluation for acne. Conclusion: Unlike current dogma about the long-
term use of antimicrobial agents, the prolonged use of
Main Outcome Measure: Colonization of the nose tetracycline antibiotics commonly used to treat acne low-
or throat with S aureus. ered the prevalence of colonization by S aureus and did
not increase resistance to the tetracycline antibiotics.
Results: A total of 36 of the 83 participants (43%) were
colonized with S aureus. Two of the 36 patients (6%) had Arch Dermatol. 2011;147(8):917-921.
methicillin-resistant S aureus; 20 (56%) had S aureus solely Published online April 11, 2011.
in their throat; 9 (25%) had S aureus solely in their nose; doi:10.1001/archdermatol.2011.67
S
TAPHYLOCOCCUS AUREUS IS A nized, but, fortunately, in the community,
ubiquitous organism that is MRSA organisms colonize fewer than 5% of
found in both hospital and the population.1 Patients with acne are gen-
community settings.1,2 While erally young and healthy and are often ex-
S aureus colonizes the skin, it posed to antibiotics for extended periods be-
can also be responsible for localized cu- cause long-term antibiotic therapy, oral (eg,
taneous infections and life-threatening sys- tetracycline, erythromycin, trimethoprim-
temic infections.1,2 At one time, it was sen- sulfamethoxazole) and/or topical (eg, clin-
sitive to many antibiotics and antimicrobial damycin or erythromycin), is a standard of
agents. However, because of its ability to care in the treatment of acne.3-5 Some of the
antibiotics used to treat acne are also among
those recommended for the treatment of
See Practice Gaps community-associated MRSA (CA-MRSA)
at end of article infections.1,4,6 According to rates among the
Author Affiliations: general population, approximately one-
Departments of Epidemiology adapt to these therapies and become re- third to one-half of patients with acne are
and Biostatistics (Drs Fanelli, sistant, clinical scenarios now exist in likely to be colonized by S aureus.7 These
Lautenbach, and Margolis and which few therapeutic options remain to patients could therefore become a reser-
Mr Kupperman), Medicine
treat this organism. Therefore, methicillin- voir for CA-MRSA as well as a source of
(Dr Lautenbach), Pathology
(Dr Edelstein), and
resistant S aureus (MRSA) has become non–CA-MRSA antibiotic-resistant S au-
Dermatology (Dr Margolis), commonplace.1,2 reus strains.
University of Pennsylvania Colonization with S aureus in general is One cause of the emergence of MRSA
School of Medicine, relatively widespread, with approximately may be long-term exposure to antibiotics
Philadelphia. 40% to 50% of the population at large colo- and antimicrobial agents. For example,
a Values
The long-term use of oral antibiotics to treat acne is a
other than age are expressed as number (percentage).
common practice, which may have some untoward con-
sequences.11,12 Concern has been noted in the lay press
[52%]) (pOR, 0.26; 95% CI, 0.09-0.79). Overall, those about the long-term use of antibiotics and the creation
who used topical antibiotics to treat their acne were of multidrug-resistant microbes.13 In our study, we found
also less likely to be colonized by S aureus (pOR, 0.30; that the overall colonization rates for both S aureus (43%)
95% CI, 0.11-0.82). Overall, the use of any antibiotics and CA-MRSA (2%) were similar to previous esti-
(oral or topical) to treat acne was associated with a mates.7,14 Long-term use of antibiotics decreased the preva-
decreased risk of S aureus colonization (pOR, 0.31; lence of S aureus colonization by nearly 70% (pOR, 0.31;
95% CI, 0.12-0.79). 95% CI, 0.12-0.79). A decreased rate of colonization was
Individual variables were selected a priori to test for noted with the use of both oral and topical antibiotics.
confounding. None of the variables added (age, sex, His- Fewer than 10% of the isolates of S aureus were resistant
panic lineage, grade of acne severity, or race/ethnicity) to tetracyclines, the most commonly used antibiotic fam-
had a direct relationship with the colonization rates of S ily to treat acne. Resistance to erythromycin and clinda-
aureus (ie, any change in the effect estimate between an- mycin was mostly prevalent among our isolates and was
tibiotic exposure and the presence of S aureus was less noted in the patients who did and did not use antibiot-
than 15%). We therefore report only our unadjusted es- ics. Finally, the ability to identify patients who are colo-
timates. As a secondary analysis, we looked at how long nized by S aureus is enhanced by culturing from 2 sites.
the patients had been using oral antibiotics and how that Colonization with S aureus in general is relatively com-
related to S aureus colonization. The duration of cur- mon in that approximately 40% to 50% of people will be
rent exposure was dichotomized as oral antibiotic use for colonized.1,14,15 However, MRSA colonizes fewer than 5%
2 or fewer months or for more than 2 months. Of 7 pa- of patients, and colonization with CA-MRSA is depen-
tients who were using oral antibiotics for fewer than 2 dent on geographic location and comorbidities.1,2,16 Prior
months, only 1 (14%) was colonized with S aureus. Of investigations by Levy et al7,17 looked at the coloniza-
10 patients who were using oral antibiotics for more than tion rates of S aureus in young, healthy populations simi-
2 months, 3 (30%) were colonized with S aureus. When lar to our study population. They looked at both acne
patients with acne who were users were compared with and nonacne populations but obtained cultures from the
nonusers, the pOR for the colonization of S aureus was oropharynx only. Our observed oropharyngeal coloni-
0.16 (95% CI, 0.08-1.37) after 1 to 2 months of expo- zation rate of 30% is similar to their findings, as they found
sure and increased to 0.52 (95% CI, 0.12-2.17) after 2 a 29% S aureus colonization rate in patients with acne
months of exposure. A test for trend was not statisti- and a 26.2% rate in patients without acne, but because
cally significant (P = .31). Many of the S aureus isolates they failed to sample the nares, their overall coloniza-
were resistant to clindamycin and erythromycin (39.5% tion rate was lower.17 Levy and colleagues also investi-
and 44.2%, respectively), especially nasal isolates. Low gated the difference between antibiotic users and non-
antimicrobial resistance rates (⬍10%) were detected for users in patients with acne and, indeed, found that
all other antibiotics tested (Table 3). antibiotic users had a lower colonization rate (22% vs
In previous studies, we observed an association be- 29%), but their results were not statistically significant,
tween oral antibiotic use for acne and the self-report of possibly because they sampled only the orophar-
a “sore throat” in the 30 days prior to the survey.10,11 We ynx.15,18-20 In one study by Levy et al,7 as well as our cur-
did note a pOR of 1.57 (95% CI, 0.50-4.90) for sore throat rent study, the use of antibiotics for the treatment of acne,
among patients exposed to oral antibiotics. This finding whether oral or topical, was associated with a decreased
was not statistically significant, but the effect estimate S aureus colonization rate. In our study, the use of oral
was similar to that in our previous studies. Interest- antibiotics showed the strongest negative association for
S aureus colonization, with a pOR of 0.26 (P =.02; 95% et al7 were able to determine the true carriage rates in their
CI, 0.09-0.79). study population. Had we swabbed for S aureus solely
Assuming that antibiotic resistance is acquired over in 1 location, our results could have been significantly
time, we evaluated the association of time of exposure different. The sensitivity of combined nares and throat
to the use of oral antibiotics on colonization status. We cultures for MRSA colonization was previously shown
hypothesized that the rates of S aureus colonization would to be 90%.15 Further studies are needed to evaluate the
be higher among patients who were receiving longer- importance of culturing from more than 2 sites.
term oral antibiotics (⬎2 months of exposure for their Our study does have some limitations. It focused on
acne treatment) because of antibiotic resistance. A patients who were seen in a dermatology clinic for acne,
2-month period was chosen to differentiate between short- so our results may not be generalizable to all individu-
and long-term exposure to the antibiotics; however, no als. We also cannot be certain that we identified all of
statistically significant difference was shown (P =.31). A the patients who were colonized with S aureus because
trend may have been established in that 14% of patients we swabbed only the oropharynx and the anterior na-
who were on an oral regimen of antibiotics for 2 months res. We did not examine all time points after commenc-
or less were colonized vs 30% of patients who were on ing antibiotic therapy so it is possible that we did not see
an oral regimen of antibiotics for more than 2 months. a time-dependent association that truly exists. We rec-
However, contrary to what might have been expected ommend a prospective study that would start before the
based on concerns that microbial resistance increases af- onset of antibiotic use for acne treatment, with continu-
ter long-term antibiotic exposure, at no time was the rate ous culture attempts at weekly intervals.
of colonization with S aureus greater in patients who were In conclusion, this cross-sectional study looked at the
receiving antibiotic therapy than in those who were not prevalence of S aureus in a healthy population of indi-
receiving antibiotic therapy. viduals with acne. With respect to the use of tetracy-
The mechanism responsible for the decreased coloni- cline antibiotics, it contradicts previous ideologies that
zation of S aureus noted in this study is likely straightfor- long-term prescribing of antibiotics causes increased
ward (eg, tetracycline antibiotics are active against both S prevalence of and resistance to S aureus. Specifically, in
aureus and MRSA, and resistance is poorly acquired). An our study, the prolonged use of antibiotics from the tet-
increasing trend in colonization rates was noted over time, racycline class that are commonly used to treat acne low-
but this trend was not statistically significant. The S au- ered the prevalence of colonization by S aureus and did
reus isolates were often resistant to treatment with clinda- not increase resistance to the tetracycline antibiotics. Fu-
mycin and erythromycin. These isolates were more likely ture research should be conducted with respect to other
obtained from the patients who were using antibiotics to organisms and antibiotics.
treat their acne.14 However, there was no evidence of high
levels of resistance to the other antibiotics tested, such as Accepted for Publication: February 2, 2011.
the tetracylines and trimethoprim-sulfamethoxazole. Over- Published Online: April 11, 2011. doi:10.1001
all, the patients who were using antibiotics to treat their /archdermatol.2011.67
acne were less likely to be colonized. In the future, pro- Correspondence: David J. Margolis, MD, PhD, Depart-
spective studies looking at the colonization status of S au- ment of Epidemiology and Biostatistics, University of
reus immediately after the initiation of antibiotic therapy Pennsylvania School of Medicine, 815 Blockley Hall, 423
on a weekly basis may help to further elucidate whether Guardian Dr, Philadelphia, PA 19104 (dmargoli@cceb
there is a point past which S aureus colonization is in- .med.upenn.edu).
creased with longer duration of use. Author Contributions: All authors had full access to all
It is necessary to evaluate multiple anatomical loca- the data in the study and take responsibility for the in-
tions for the presence of S aureus. As in other recent stud- tegrity of the data and the accuracy of the data analysis.
ies, S aureus colonization was found just in the orophar- Study concept and design: Edelstein and Margolis. Acqui-
ynx and not in the anterior nares in more than half of sition of data: Fanelli, Edelstein, and Margolis. Analysis
the patients in our study.15,18,19 It was found in the ante- and interpretation of data: Fanelli, Kupperman, Lauten-
rior nares but not in the oropharynx in one-fourth of our bach, and Margolis. Drafting of the manuscript: Fanelli,
patients, leaving fewer than 20% of S aureus–positive pa- Kupperman, Edelstein, and Margolis. Critical revision of
tients with colonization in both the anterior nares and the manuscript for important intellectual content: Fanelli,
the oropharynx. This finding deviates from a recent study Kupperman, Lautenbach, Edelstein, and Margolis. Sta-
by Nakamura et al,21 who found that 55.7% of S aureus tistical analysis: Fanelli, Kupperman, Lautenbach, and
carriers in a pediatric intensive care unit were colonized Margolis. Obtained funding: Margolis. Administrative, tech-
in both locations. This importance of culturing from both nical, and material support: Edelstein and Margolis. Study
the nares and the throat begs the question of whether Levy supervision: Edelstein and Margolis.
PRACTICE GAPS