Effects of topical erythromycin on ecology of aerobic cutaneous bacterial flora

Abstract

We have demonstrated previously that application of topical erythromycin, an antibiotic commonly used for the treatment of acne, results in an increased density of cutaneous erythromycin-resistant (Emr) coagulase-negative staphylococci; however, it is unknown if this increase results in an overall higher density of total cutaneous staphylococci or if upon cessation of erythromycin use, Emr coagulase-negative staphylococci remain at an increased density compared with the pretreatment density. To investigate this, 2% erythromycin or vehicle was applied to each subject's forehead (n = 225) twice a day by laboratory personnel for a period of 6 weeks. Samples were obtained for culture from the forehead, anterior nares, and back of the subjects at baseline and at weeks 6, 9, and 12 of the study. Cultures were performed on differential media. Plates into which erythromycin was incorporated (8 micrograms/ml) were used to identify Emr coagulase-negative staphylococci. The species of all Emr coagulase-negative staphylococci were determined, and an antibiogram for 16 antibiotics was obtained. The baseline prevalence of Emr coagulase-negative staphylococci on the forehead and nose was about 80% at the two study sites, whereas that on the back was 50%. The baseline density of Emr coagulase-negative staphylococci on the forehead, nose, and back was approximately 20% of the total flora. Following 6 weeks of erythromycin treatment, the prevalence of Emr coagulase-negative staphylococci on the forehead and nose was nearly 100% and the densities were 73 and 62%, respectively; the prevalence and density for the back were 78 and 42%, respectively. The most prevalent erythromycin resistance gene expressed by the Emr coagulase-negative staphylococci was ermC. There was no increase in the numbers of Staphylococcus aureus, gram-negative rods, or yeasts, nor was there increased resistance to any other antibiotic except clindamycin. The density of total aerobic organisms also remained static. There were no changes in the prevalence or density of Emr coagulase-negative staphylococci in the vehicle group. A statistically significant decrease in the prevalence and density of Emr coagulase-negative staphylococci in the erythromycin group was observed within 3 weeks posttreatment and by 6 weeks posttreatment, the prevalence and density returned to baseline values. These data demonstrate that the increased prevalence and density of Emr coagulase-negative staphylococci as a result of topical 2% erythromycin use are transient on both population and individual levels.

Clinical implications of antibiotic resistance: risk of systemic infection fromStaphylococcusandStreptococcus

“…This finding did not reach statistical significance. Similar effects on nasal S. aureus had been seen in prior studies (21).…”

“…The first possible explanation involves the direct transfer of antibiotics and/or bacterial organisms to the oropharynx via a person's fingers or by devices such as eating utensils. This theory is supported by the findings of several studies, which demonstrated an increase in erythromycin-resistant coagulase-negative staphylococci at sites (back and anterior nares) where antibiotic was not directly applied (21,31). An alternative less likely (blood levels so low) mechanism is systemic absorption of topically applied antibiotic, leading to hematogenous spread of drug to noncutaneous sites such as the oropharynx.…”

Topical antibiotics

“…In fact, changes in cutaneous flora have been reported with both topical and oral antibiotic use (6,(17)(18)(19)(20)(21)(22)(23). In fact, changes in cutaneous flora have been reported with both topical and oral antibiotic use (6,(17)(18)(19)(20)(21)(22)(23).…”

“…Potential issues of concern that have been raised in the literature include increased prevalence of P. acnes strains less responsive to antibiotics, alterations in cutaneous flora, decreased therapeutic responsiveness to antibiotic therapy, and promotion of other clinical infections among treated patients and/or their close contacts (6,17,18,(21)(22)(23)(24)26,27). Potential issues of concern that have been raised in the literature include increased prevalence of P. acnes strains less responsive to antibiotics, alterations in cutaneous flora, decreased therapeutic responsiveness to antibiotic therapy, and promotion of other clinical infections among treated patients and/or their close contacts (6,17,18,(21)(22)(23)(24)26,27).…”

Optimizing Non-Antibiotic Treatments for Patients with Acne: A Review

“…Both systemic and topical antibiotics are capable of changing the antibiotic-resistance patterns in bacteria. Topical erythromycin has been shown to produce overgrowth of antibiotic resistance bacteria both locally and at distant sites [10, 11]. Similar resistance trends are also likely to result from topical clindamycin monotherapy.…”