Tetracycline-resistant propionibacteria from acne patients are cross-resistant to doxycycline, but sensitive to minocycline

Antibiotic resistance in acne: changes, consequences and concerns

Antibiotic resistance in acne was first observed in the 1970s and has been a major concern in dermatology since the 1980s. The resistance rates and types of antimicrobials have subsequently shown great variations in regions and countries. Illustrative of this is the resistance to topical erythromycin and clindamycin which continues to be a problem worldwide, while resistance to systemic treatment with tetracyclines has remained low during the past decade. The resistance for the newer macrolides like azithromycin and clarithromycin has been increasing. The results of antibiotic resistance may include treatment failure of acne, disturbance of skin microbiota, induction of opportunistic pathogens locally and systemically, and dissemination of resistant strains to both healthcare personnel and the general population. The ensuing complications, such as aggravated opportunistic infections caused by Propionibacterium acnes and the emergence of multiresistant superbugs, have not yet been confirmed.

Evaluating FMX-101 as a promising therapeutic for the treatment of acne

INTRODUCTION

Oral minocycline is a mainstay of therapy for moderate-to-severe acne; however, systemic side effects which include hepatotoxicity, lupus-like syndrome, drug hypersensitivity syndrome, autoimmune hepatitis, polyarteritis nodosa, gastrointestinal side effects and skin hyperpigmentation are of concern. Topical antibiotics commonly used in acne, such as erythromycin and clindamycin, present high P. acnes resistance rates which has opened the market for new topical antibiotics. FMX-101 is a novel topical minocycline foam that has shown promising results in phase I, II and III trials for the treatment of moderate-to-severe acne with a better safety profile than oral minocycline.

AREAS COVERED

The author provides an overview FMX-101 including its clinical efficacy and safety. The author then provides their expert opinion on this treatment and its potential for the treatment option for acne.

EXPERT OPINION

The topical foam formulation of FMX-101 has been shown to reduce both inflammatory and non-inflammatory lesions and to improve IGA scores in patients with moderate-to-severe acne without significant systemic absorption thus limiting associated side effects. Overall, the proven efficacy and safety profile of FMX-101, together with the low systemic absorption, high skin tolerability and cosmetically acceptable foam formulations render this novel therapy an important addition to the acne treatment armamentarium.

Minocycline: old and new therapeutic uses

Since the introduction of minocycline HCl in the late 1960's, it has been used for disease states that have ranged from typical community-acquired infectious diseases to others that are non-infectious, such as resistant rheumatoid arthritis. Owing to its high penetration characteristics throughout the body, minocycline can be used in the treatment of a wide variety of extracellular and intracellular pathogens. This review examines the known and potential therapeutic uses of minocycline in a clinical setting.

Minocycline for acne vulgaris: efficacy and safety

BACKGROUND

Minocycline is an oral antibiotic used for acne vulgaris. Its use has lessened due to safety concerns (including potentially irreversible pigmentation), a relatively high cost, and no evidence of any greater benefit than other acne treatments. A modified-release version of minocycline is being promoted as having fewer side-effects.

OBJECTIVES

To assess new evidence on the effects of minocycline for acne vulgaris.

SEARCH METHODS

Searches were updated in the following databases to November 2011: the Cochrane Skin Group Specialised Register, CENTRAL in The Cochrane Library, MEDLINE (from 1946), EMBASE (from 1974), and LILACS (from 1982). We also searched trials registers and checked reference lists for further references to relevant randomised controlled trials (RCTs).The Cochrane Skin Group's Trials Search Co-ordinator undertook searches exploring minocycline's adverse effects in EMBASE and MEDLINE in February 2012.

SELECTION CRITERIA

We selected randomised controlled trials (RCTs) comparing minocycline, at any dose, to an active or a placebo control, in participants with inflammatory acne vulgaris. For adverse effects, we selected additional studies that reported the number of adverse effects and the number of participants treated.

DATA COLLECTION AND ANALYSIS

Outcome measures used in the trials included lesion counts, acne grades/severity scores, doctors' and participants' global assessments, adverse effects, and dropout rates. Two authors independently assessed the quality of each study. Effect sizes were calculated, and meta-analyses were undertaken where possible.Sixteen studies met the inclusion criteria for the review of adverse effects.

MAIN RESULTS

We included 12 new RCTs for this update, giving a total of 39 RCTs (6013 participants). These additional 12 RCTs have not changed the original conclusions about the clinical efficacy of minocycline.The identified RCTs were generally small and poor quality. Meta-analysis was rarely possible because of the lack of data and different outcome measures and trial durations. Although minocycline was shown to be an effective treatment for moderate to moderately-severe acne vulgaris, there was no evidence that it is better than any of the other commonly-used acne treatments. One company-sponsored RCT found minocycline to be less effective than combination treatment with topical erythromycin and zinc. No trials have been conducted using minocycline in those participants whose acne is resistant to other therapies. Also, there is no evidence to guide what dose should be used.The adverse effects studies must be interpreted with caution. The evidence suggests that minocycline is associated with more severe adverse effects than doxycycline. Minocycline, but not other tetracyclines, is associated with lupus erythematosus, but the risk is small: 8.8 cases per 100,000 person-years. The risk of autoimmune reactions increases with duration of use. The evidence does not support the conclusion that the more expensive extended-release preparation is safer than standard minocycline preparations.

AUTHORS' CONCLUSIONS

Minocycline is an effective treatment for moderate to moderately-severe inflammatory acne vulgaris, but there is still no evidence that it is superior to other commonly-used therapies. This review found no reliable evidence to justify the reinstatement of its first-line use, even though the price-differential is less than it was 10 years ago. Concerns remain about its safety compared to other tetracyclines.

Antibiotic resistance of microbial strains isolated from Korean acne patients

Over several decades, topical and systemic antibiotics have been the mainstay of treatment for acne vulgaris. The widespread and long-term use of antibiotics in the treatment of acne has resulted in the spread of resistant bacterial strains and treatment failure. We aimed to examine the bacteriology of acne vulgaris and to evaluate its susceptibility to the antibiotics widely used for acne in Korea. We examined the species of bacteria aerobically and anaerobically isolated from 100 Korean acne patients. Among the bacteria isolated, Staphylococcus epidermidis (36 patients) was the most common, followed by Propionibacterium acnes (30 patients). Eleven strains of P. acnes (36.7%) and 25 strains of S. epidermidis (69.4%) were resistant to one or other of the antibiotics tested. A higher proportion of P. acnes isolates were resistant to clindamycin (30%) and erythromycin (26.7%), than to any other antibiotics tested (P = 0.0003). Some S. epidermidis isolates were resistant to tetracycline and doxycycline in addition to clindamycin and erythromycin. In the previous studies, few strains of P. acnes were found to be resistant to any of the antibiotics, but this study shows that antibiotic-resistant strains have been increasing in Korea acne patients.

Minocycline in acne vulgaris: benefits and risks

Minocycline is a semi-synthetic, second-generation tetracycline. It was introduced in 1972 and has both antibacterial and anti-inflammatory properties. Minocycline is used for a variety of infectious diseases and in acne. Even today, new indications beyond the antibacterial indications are being investigated such as its use in neurologic diseases. Formerly, minocycline was thought to have a superior efficacy in the treatment of inflammatory acne, especially with respect to antibacterial-resistant Propionibacterium acnes. A thorough review of the literature, however, shows that minocycline is not more effective in acne than other tetracyclines. Compared with first-generation tetracyclines, minocycline has a better pharmacokinetic profile, and compared with doxycycline it is not phototoxic. However, minocycline has an increased risk of severe adverse effects compared with other tetracyclines. It may induce hypersensitivity reactions affecting the liver, lung, kidneys, or multiple organs (Drug Reaction with Eosinophilia and Systemic Symptoms [DRESS] syndrome) in the first weeks of treatment and, with long-term treatment, may cause autoimmune reactions (systemic lupus erythematosus, autoimmune hepatitis). In addition, CNS symptoms, such as dizziness, are more frequent compared with other tetracyclines. Long-term treatment may induce hyperpigmentation of the skin or other organs. Resistance of P. acnes to minocycline also occurs, dependent on the prescribing behavior. Considering the aspects of efficacy, its adverse effect profile, resistance, price, and alternatives, minocycline is no longer considered the first-line antibacterial in the treatment of acne.

The role of tetracyclines in rosacea

There is a great deal of evidence to support the use of tetracycline and doxycycline in the treatment of papulopustular rosacea. Nevertheless, these agents have shared and unique adverse effects and relative contraindications. Recently, subantimicrobial-dose doxycycline was demonstrated to be an effective treatment for rosacea, due to its inherent anti-inflammatory properties. Furthermore, subantimicrobial-dose doxycycline has a more preferable tolerability profile and a lower occurrence of bacterial resistance than traditional-dose doxycycline. To further elucidate the role of tetracycline agents in rosacea, clinical trials that compare these agents with each other as well as with other effective rosacea treatments are called for. Adherence studies comparing oral tetracycline treatment with topical metronidazole treatment may also enhance clinical decision making.

The tetracycline resistome

Resistance to tetracycline emerged soon after its discovery six decades ago. Extensive clinical and non-clinical uses of this class of antibiotic over the years have combined to select for a large number of resistant determinants, collectively termed the tetracycline resistome. In order to impart resistance, microbes use different molecular mechanisms including target protection, active efflux, and enzymatic degradation. A deeper understanding of the structure, mechanism, and regulation of the genes and proteins associated with tetracycline resistance will contribute to the development of tetracycline derivatives that overcome resistance. Newer generations of tetracyclines derived from engineering of biosynthetic genetic programs, semi-synthesis, and in particular recent developments in their chemical synthesis, together with a growing understanding of resistance, will serve to retain this class of antibiotic to combat pathogens.

Subantimicrobial Dose Doxycycline for Acne and Rosacea

Acne vulgaris and rosacea present therapeutic challenges due to their chronicity, potential for disfigurement, and psychosocial impact. Although pathophysiologically distinct, both conditions have major inflammatory components. Consequently, topical and systemic antimicrobial agents are routinely prescribed for extended periods. Emergence of resistant strains of Propionibacterium acnes, adverse events, and compliance issues associated with chronic systemic tetracycline use have led to new treatment approaches. At subantimicrobial doses, tetracyclines reduce inflammation via anticollagenolytic, antimatrix-degrading metalloproteinase, and cytokine down-regulating properties. Subantimicrobial dose (SD) doxycycline (Periostat 20 mg) has clinical utility in periodontitis and has been investigated in a double-blind, placebo-controlled trial in the treatment of moderate facial acne as well as in an open label study in the treatment of rosacea. The results of subantimicrobial dose doxycycline treatment in early trials support its benefits and further investigation in acne and rosacea.

Development potential of rifalazil and other benzoxazinorifamycins

Rifalazil and other benzoxazinorifamycins (new chemical entities [NCEs]) are rifamycins that contain a distinct planar benzoxazine ring. Rifalazil has excellent antibacterial activity, high intracellular levels and high tissue penetration, which are attributes that favour its use in treating diseases caused by the obligate intracellular pathogens of the genus Chlamydia. Recent studies have shown that rifalazil has efficacy in the treatment of human sexually transmitted disease caused by Chlamydia trachomatis. The extraordinary potency of rifalazil and other NCEs, such as ABI-0043, extends to the related microorganism, C. pneumoniae, a respiratory pathogen that can disseminate and persist chronically in the vasculature, resulting in increased plaque formation in animal studies. A pivotal clinical trial with rifalazil has been initiated for the treatment of peripheral arterial disease. Other opportunities include gastric ulcer disease caused by Helicobacter pylori and antibiotic-associated colitis caused by infection with Clostridium difficile in the colon. The NCEs could prove to be valuable as follow-on compounds in these indications, as rifampin replacements in antibacterial combination therapy or as stand-alone topical antibacterials (e.g., to treat acne). Neither rifalazil nor NCEs appear to induce the cytochrome P450 3A4, an attribute of rifampin that can result in adverse events due to drug-drug interactions.

Acne vulgaris: a review of antibiotic therapy

Antibiotic therapy has been integral to the management of inflammatory acne vulgaris for many years. Systemic antibiotics work via antibacterial, anti-inflammatory and immunomodulatory modes of action, and have been found to be useful in managing moderate-to-severe acne. Commonly prescribed antibiotics include tetracyclines, erythromycin and trimethoprim, with or without sulfamethoxazole. In selecting the appropriate antibiotic for patients needing to receive topical or systemic antibiotic therapy, the clinician should take into account the severity of the acne, cost-effectiveness, the safety profile of the drug and the potential for development of resistance. The widespread and long-term use of antibiotics over the years has unfortunately led to the emergence of resistant bacteria. The global increase in the antibiotic resistance of Propionibacterium acnes may be a significant contributing factor in treatment failures. It is therefore essential that clinicians prescribing antibiotics for the treatment of acne adopt strategies to minimise further development of bacterial resistance. This includes addressing compliance issues, using combination therapies, avoiding prolonged antibiotic treatment, and avoiding concomitant topical and oral antibiotics with chemically dissimilar antibiotics.

A review on the treatment of acne vulgaris

The following article reviews treatment for acne vulgaris. Selection of therapy should be based on clinical appearance taking into account lesion type and severity, as well as identification of acne scarring and the psychosocial disability caused by the disease.

A guide to antibiotic resistance in bacterial skin infections

The emergence of bacterial resistance to commonly used antibiotics is not new. In this review we have tried to cover the ever increasing problems facing the treatment and containment of bacterial skin infections. We have tried to give an overview of the varied mechanisms by which bacteria gain and spread antimicrobial resistance, whilst dealing with the patterns of resistance exhibited by some of the commonly encountered organisms. Where there is evidence, we have formulated an approach on how to tackle antibiotic resistance. Where there is a lack of evidence we have formulated what we perceive to be appropriate guidelines.

Defensins and acne

Acne a disease of the pilosebaceous unit is characterised by hypercornification and hyperkeratosis of outer root sheath (ORS) and sebaceous duct and perilesional infiltrate. Lesions may be characterised as "non"-inflammatory versus inflammatory. Hypercornification of the distal ORS and the pilosebaceous duct in concert with increased sebum production and abnormalities of the microbial flora are considered to be major factors in the pathogenesis of acne vulgaris. However, the basic mechanisms involved in the development of inflammation during acne vulgaris remain unclear. We have investigated the expression patterns of two antimicrobial peptides, human beta-defensin 1 (hBD1) and human beta-defensin 2 (hBD2) in healthy human hair follicles as well as in peri- and intralesional skin of acne vulgaris lesions such as comedones, papules and pustules. Strong hBD1 and hBD2 immunoreactivity was found in all suprabasal layers of the epidermis, and all permanent compartments of the hair follicle including the distal ORS of the hair follicle and the pilosebaceous duct. Moreover, marked hBD1 and hBD2 expression was also detected in the hair follicle stem cell compartment. In contrast, the proximal follicle bulb which undergoes apoptotic regression and is also able to regenerate following injury did not express hBD1 or hBD2. The majority of acne biopsies displayed a marked upregulation of hBD2 IR in the lesional and perilesional epithelium; in particular in pustules, and a less marked upregulation of hBD1 IR. The upregulation of beta-defensins expression in acne vulgaris lesions when compared to controls suggests that beta-defensins may be involved in the pathogenesis of acne vulgaris.

Guidelines for the management of acne vulgaris in adolescents

This article reviews the treatment of acne in adolescents. The choice of therapy should be principally based on the type of lesion and the severity of the acne, but psychosocial disability relating to the disease and the presence of scarring may also influence the approach to treatment.Mild acne generally requires topical treatment only. Benzoyl peroxide, azelaic acid, and antibacterials are generally used for inflammatory lesions. Topical retinoids are particularly effective for noninflamed lesions, and combination therapies are useful for mixed lesions. Moderately severe acne generally requires oral antibacterials. Tetracyclines/oxytetracycline and erythromycin are usually the first-line antibacterials. Second-generation tetracyclines, such as lymecycline, doxycycline, and minocycline, show improved absorption. Minocycline has the advantage of being rarely associated with Propionibacterium acnes antibacterial resistance, but can occasionally lead to potentially serious adverse effects. Trimethoprim is a useful third-line antibacterial therapy for patients resistant to other antibacterial therapies. Benzoyl peroxide should generally be used in combination with oral antibacterials as this has been shown to reduce the development of antibacterial resistance. For severe nodular acne, isotretinoin is the treatment of choice. In addition, over recent years dermatologists have increasingly used this drug to treat patients with moderate acne which has not responded to other systemic therapies, particularly when associated with scarring or significant psychological disability. However, this use is outside the current license of the drug. Isotretinoin is associated with a number of serious adverse effects and careful monitoring of patients during therapy is required.Physical therapies for the treatment of acne nodules and macrocomedones are also important adjuncts to drug therapies.

Antibacterial therapy for acne: a guide to selection and use of systemic agents

Acne vulgaris is a very common disorder, affecting virtually every adolescent at some point in time. Systemic antibacterials have been used in the treatment of acne for many years, and there are several commonly used antibacterials which have established efficacy and safety records. In recent years, the issue of antibacterials resistance has become more prominent, especially with concerns that Propionibacterium acnes can transfer antibacterials resistance to other bacteria within the resident skin flora. Commonly used antibacterials include tetracycline, doxycycline, minocycline, erythromycin (and other macrolides) and trimethoprim/sulfamethoxazole (cotrimoxazole). The choice of antibacterial should take into account efficacy, cost-effectiveness, benefit-risk ratios, patient acceptability and the potential for the development of resistance. Poor clinical response can be the result of poor compliance, inadequate duration of therapy, development of gram-negative folliculitis, resistance of P. acnes to the antibacterial(s) administered, or a high sebum excretion rate. In order to help prevent the development of resistance a number of measures should be undertaken: antibacterials are prescribed for an average of 6 months; if retreatment is required, utilize the same antibacterial; generally, antibacterials should be given for at least 2 months before considering switching due to poor therapeutic response; concomitant use of oral and topical chemically-dissimilar antibacterials should be avoided (try benzoyl peroxide and/or retinoids instead) and systemic isotretinoin should be considered if several antibacterials have been tried without success.

Minocycline for acne vulgaris: efficacy and safety

BACKGROUND

Minocycline is a tetracycline antibiotic that is commonly used in the treatment of moderate to severe acne vulgaris. Although it is more convenient for patients to take than first-generation tetracyclines, as it only needs to be taken once or twice a day and can be taken with food, it is more expensive. Concerns have also been expressed over its safety following the deaths of two patients taking the drug. There is a lack of consensus among dermatologists over the relative risks and benefits of minocycline. As most acne prescribing is undertaken by general practitioners, it is important that guidelines issued to them are based on the best available evidence rather than personal judgements.

OBJECTIVES

To collate and evaluate the evidence on the clinical efficacy of minocycline in the treatment of inflammatory acne vulgaris. Specific objectives were to compare the efficacy of minocycline with other drug treatments for acne and to collate information on the incidence of adverse drug reactions.

SEARCH STRATEGY

Randomised controlled trials (RCTs) of minocycline for acne vulgaris were identified by searching the following electronic databases; MEDLINE, EMBASE, Biosis, Biological Abstracts, International Pharmaceutical Abstracts, Cochrane Skin Group's Trial Register, Theses Online, BIDS ISI Science Citation Index, National Research Register, Current Controlled Trials and Bids Index to Scientific and Technical Proceedings. Other strategies used were scanning the references of articles retrieved, hand-searching of major dermatology journals and personal communication with trialists and drug companies.

SELECTION CRITERIA

To be eligible for the review, studies had to be RCTs comparing the efficacy of minocycline at any dose to active or placebo control, in subjects with inflammatory acne vulgaris. Diagnoses of papulo-pustular, polymorphic and nodular acne were also accepted. Trials were not excluded on the basis of language.

DATA COLLECTION AND ANALYSIS

27 randomised controlled trials met the inclusion criteria and were included in this review. The comparators used were placebo (2 studies), oxytetracycline (1), tetracycline (6), doxycycline (7), lymecycline (2), topical clindamycin (3), topical erythromycin/zinc (1), cyproterone acetate/ ethinyloestradiol (1), oral isotretinoin (2), topical fusidic acid (1) and there was one dose response study. Two studies are ongoing and it remains to be clarified whether one further study is a RCT. Major outcome measures used in the trials included lesion counts, acne grades/severity scores, doctors' and patients' global assessments, adverse drug reactions and drop out rates. The quality of each study was assessed independently by two assessors and an effect size calculated where possible. An additional three RCTs and three safety studies were identified by searches conducted in November 2002; these will be reviewed for a major update in early 2003 when it is anticipated that the results of the two ongoing studies will be available.

MAIN RESULTS

The trials were generally small and of poor quality and in many cases the published reports were inadequate for our purpose. Pooling of the studies was not attempted due to the lack of common outcome measures and endpoints and the unavailability of some primary data. Although minocycline was shown to be an effective treatment for acne vulgaris, in only two studies was it found to be superior to other tetracyclines. Both of these were conducted under open conditions and had serious methodological problems. A third study showed it to be more effective than 2% fusidic acid, applied topically, against inflammatory lesions in mild to moderate acne. Differences in the way adverse drug reactions were identified could have accounted for the wide variation between studies in numbers of events reported. This meant that no overall evaluation could be made of incidence rates of adverse events associated with minocycline therapy. No RCT evidence was found to support the benefits of minocycline in acne resistant to other therapies and the dose response has only been evaluated up to eight weeks of therapy.

REVIEWER'S CONCLUSIONS

Minocycline is likely to be an effective treatment for moderate acne vulgaris, but this review found no reliable RCT evidence to justify its continued use first-line, especially given the price differential and the concerns that still remain about its safety. Its efficacy relative to other acne therapies could not be reliably determined due to the poor methodological quality of the trials and lack of consistent choice of outcome measures. Similarly the relative risk of adverse drug reactions could not be ascertained reliably and no recommendations can be made concerning the appropriate dose that should be used. It is hoped that this review will highlight the inadequacy of acne trials in general and encourage improvements in methodological quality and standards of reporting.

Is antibiotic resistance in cutaneous propionibacteria clinically relevant? : implications of resistance for acne patients and prescribers

It is well recognized that some patients with acne do not respond adequately to antibiotic therapy. It is important to distinguish antibiotic recalcitrant acne which we would suggest represents acne that shows a diminished response to treatment irrespective of the cause as opposed to 'antibiotic-resistant acne' which is acne that is less responsive to treatment as a direct consequence of skin colonization with resistant propionibacteria. Here we show that antibiotic-resistant acne is not just a theoretical possibility but a real phenomenon that could have important consequences for patients and prescribers. The relationship between skin colonization by antibiotic-resistant propionibacteria and treatment outcomes is a complex one that is explained at the follicular level by physiological differences affecting local drug concentrations. A systematic review of the literature on antibiotic-resistant propionibacteria revealed methodological shortcomings in studies of their prevalence and a paucity of evidence on their clinical significance. Despite the elucidation of resistance mechanisms in cutaneous propionibacteria, our continuing inability to distinguish between strains of Propionibacterium acnes means that we still do not fully understand how resistance spreads, although person-to-person transfer is most likely. Finally, we present a decision tree for acne management in an era of prudent antimicrobial prescribing that provides an alternative to existing treatment algorithms by placing topical retinoids and not antibiotics at the cornerstone of acne management.

Human beta defensin-1 and -2 expression in human pilosebaceous units: upregulation in acne vulgaris lesions

A rich residential microflora is harboured by the distal outer root sheath of the hair follicle and the hair canal - normally without causing skin diseases. Although the basic mechanisms involved in the development of inflammation during acne vulgaris remain unclear, microbial agents might play an important role in this process. In this study we have analyzed by in situ hybridization and immunohistochemistry the expression patterns of two antimicrobial peptides, human beta defensin-1 and human beta defensin-2, in healthy human hair follicles as well as in perilesional and intralesional skin of acne vulgaris lesions such as comedones, papules, and pustules. Strong defensin-1 and defensin-2 immunoreactivity was found in all suprabasal layers of the epidermis, the distal outer root sheath of the hair follicle, and the pilosebaceous duct. Marked defensin-1 and defensin-2 immunoreactivity was also found in the sebaceous gland and in the basal layer of the central outer root sheath including the bulge region. The majority of acne biopsies displayed a marked upregulation of defensin-2 immunoreactivity in the lesional and perilesional epithelium - in particular in pustules - and a less marked upregulation of defensin-1 immunoreactivity. The upregulation of beta-defensin expression in acne vulgaris lesions compared to controls suggests that beta-defensins may be involved in the pathogenesis of acne vulgaris.

Acne therapy: clinical pearls

Several classes of medications successfully treat acne. Systemic and topical retinoids, systemic and topical antimicrobials, and systemic hormonal therapy are the major categories. Failure of therapy may result from drug interactions, antibiotic resistance, or coexisting conditions; therefore, a detailed history including these points should be used to decide which therapy is appropriate for each patient. Furthermore, one must consider the potential side effects of each treatment and make sure that (1) the benefits outweigh the risks of the treatment, (2) the side effects can be avoided by adding another agent, or (3) the side effects can be safely treated.

The risk of liver damage associated with minocycline: a comparative study

Using the General Practice Research Database, the authors performed (1) a cohort analysis comparing the incidence of liver dysfunction in new users of minocycline with new users of oxytetracycline/tetracycline and (2) a case control study assessing antibiotic exposure in new cases of liver dysfunction and controls without liver dysfunction. In new users, the incidence of liver dysfunction in those exposed to minocycline was 1.04 cases/10,000 exposed person months (EPM) and 0.69 cases/10,000 EPM in those exposed to oxytetracycline/tetracycline (relative risk 1.51 [CI95: 0.63, 3.65]). The risk in both groups was greatest in the first month of use. The adjusted odds ratio (ORadj) of liver dysfunction associated with exposure to minocycline compared with nonuse was 2.10 (CI95: 1.30, 3.40); for oxytetracycline/tetracycline, the ORadj was 1.46 (CI95: 0.81, 2.64); and for exposure to erythromycin, the ORadj was 1.64 (CI95: 0.71, 3.80). The authors thus support a weak association between the use of oral antibiotics and liver dysfunction in patients with acne. The risk associated with exposure to minocycline appears to be very small. The cohort analysis demonstrated that any risk associated with minocycline was not significantly greater than that associated with oxytetracycline/tetracycline exposure.

Phenotypic and genotypic characterization of antibiotic-resistant Propionibacterium acnes isolated from acne patients attending dermatology clinics in Europe, the U.S.A., Japan and Australia

BACKGROUND

Propionibacterium acnes is the target of antimicrobial treatments for acne vulgaris. Acquired resistance to erythromycin, clindamycin and tetracyclines has been reported in strains from diverse geographical loci, but the molecular basis of resistance, via mutations in genes encoding 23S and 16S rRNA, respectively, has so far only been elucidated for isolates from the U.K.

OBJECTIVES

To determine whether similar or different resistance mechanisms occur in resistant P. acnes isolates from outside the U.K.

METHODS

The phenotypes and genotypes of 73 antibiotic-resistant strains of P. acnes obtained from the skin of acne patients in the U.K., U.S.A., France, Germany, Australia and Japan were compared. Antibiotic susceptibilities were determined by minimum inhibitory concentration (MIC) measurements, and polymerase chain reaction and DNA sequencing were used to identify mutations in genes encoding rRNA.

RESULTS

Most erythromycin-resistant isolates (MIC(90) > or = 512 microg mL(-1)) were cross-resistant to clindamycin but at a much lower level (MIC(90) > or = 64 microg mL(-1)). As in the U.K., resistance to erythromycin was associated with point mutations in 23S rRNA in 49 of 58 strains. An A-->G transition at Escherichia coli equivalent base 2058 was present in 24 strains. This gave a unique cross-resistance phenotype against a panel of macrolide, lincosamide and type B streptogramin antibiotics. Two further point mutations (at E. coli equivalent bases 2057 and 2059) were identified (in three and 22 isolates, respectively) and these were also associated with specific cross-resistance patterns originally identified in isolates from the U.K. However, nine of 10 erythromycin resistant-strains from Germany did not exhibit any of the three base mutations identified and, in six cases, cross-resistance patterns were atypical. Consistent with previous U.K. data, 34 of 38 tetracycline-resistant strains carried a base mutation at E. coli 16S rRNA equivalent base 1058. Tetracycline-resistant isolates displayed varying degrees of cross-resistance to doxycycline and minocycline, but isolates from the U.S.A. had higher MICs for minocycline (4--16 microg mL(-1)) than isolates from other countries and, in particular, Australia. All the P. acnes isolates resistant to one or more of the commonly used antiacne antibiotics were sensitive to penicillin, fusidic acid, chloramphenicol and the fluoroquinolone, nadifloxacin. All but one isolate (from the U.K.) were sensitive to trimethoprim.

CONCLUSIONS

This study shows that 23S and 16S mutations identified in the U.K. conferring antibiotic resistance in P. acnes are distributed widely. However, resistant strains were isolated in which mutations could not be identified, suggesting that as yet uncharacterized resistance mechanisms have evolved. This is the first report of high-level resistance to minocycline and is of concern as these strains are predicted to be clinically resistant and are unlikely to remain confined to the U.S.A. Epidemiological studies are urgently required to monitor how resistant strains are selected, how they spread and to ascertain whether the prevalence of resistance correlates with antibiotic usage patterns in the different countries.

Liver damage associated with minocycline use in acne: a systematic review of the published literature and pharmacovigilance data

OBJECTIVE

Minocycline is an antibacterial drug used in the treatment of acne. Concern has been expressed over the possibility of severe adverse reactions to minocycline, including hepatitis. This study set out to identify and characterise reported cases of hepatotoxicity associated with the use of minocycline.

METHODS

A systematic review of the literature including a search of computerised databases and analysis of data from the Uppsala Monitoring Centre (WHO Collaborating Centre for International Drug Monitoring) was conducted. The review involved a search for original case reports involving liver damage in people using minocycline. Patients taking minocycline for reasons other than acne or those given intravenous minocycline were excluded. The search strategy involved an enquiry of computerised databases and a search for secondary references. Cases were then classified appropriately.

RESULTS

65 reported cases of hepatitis or liver damage in association with minocycline from either case reports or case series were identified from the literature review. 58% of cases occurred in females and 94% were aged under 40 years. For 20 case reports there was insufficient information to classify the type of event, but for the remaining 45, 2 types of hepatic reaction were recognised: autoimmune hepatitis associated with lupus-like symptoms occurring after a median duration of exposure to minocycline of 365 days in females (n = 20) and 730 days in males (n = 9), hypersensitivity reaction associated with eosinophilia and exfoliative dermatitis occurring within 35 days of therapy (n = 16). Reports to the WHO of hepatic adverse drug reactions associated with minocycline accounted for 6% (493) of all minocycline-related adverse drug reactions (8025). The pattern of distribution in relation to exposure demonstrated 2 groups, similar to that described by the case reports.

CONCLUSIONS

Severe cases of minocycline-associated hepatotoxicity appear to be a hypersensitivity reaction and occur within a few weeks of commencing therapy. An autoimmune hepatitis usually presents after exposure to minocycline of a year or more, is more common in women and is sometimes associated with lupus-like symptoms.

In-vitro and in-vivo efficacy of zinc acetate against propionibacteria alone and in combination with erythromycin

Some studies have been published about the in vitro activity of zinc acetate (ZA), erythromycin (E) and their combination (ZA/E) against Propionibacterium spp., especially erythromycin resistant strains. The efficacy of topical ZA/E combination has been reported as well, but a comparison to ZA monotherapy is missing. Therefore, the MIC values of ZA, E and the ZA/E combination were determined for 15 erythromycin-resistant and 12 erythromycin-sensitive Propionibacterium strains using the agar dilution method and the checkerboard technique. Furthermore, the antimicrobial efficacy of ZA (1.2%) vs. the ZA/E (1.2%/4%) combination in an alcoholic solution was tested in a 7-day treatment administered to 32 acne patients. The MIC 100 for ZA was 1024 micrograms ZA/ml for both, erythromycin resistant and erythromycin sensitive Propionibacterium strains. The ZA, as well as the ZA/E solution showed efficacy reducing both the Propionibacterium spp., and the Micrococcaceae in the sebaceous gland infundibula of acne patients. There was no significant difference between the two treatments. As the MIC 100 of ZA/E was equal to the MIC 100 of ZA, the decrease of the erythromycin MIC of the ZA/E combination in erythromycin-resistant strains may be partly attributed to the addition of ZA to E. The in vivo antibacterial efficacy on 32 acne patients supports the hypothesis that the antibacterial effect of ZA/E in short-term treatment can be mostly attributed to ZA.

In Vitro activity of 6 antimicrobials against propionibacteria isolates from untreated acne papulopustulosa

In the present study, MIC values of 6 antibiotics were determined for 70 Propionibacterium acnes and 13 P.granulosum strains from 71 untreated acne patients using the agar dilution method. The interpretation of in vitro results is difficult because there are only poor data about the concentrations of antibiotics achievable in the sebaceous gland infundibulum. Based on breakpoint concentrations according to DIN 58,944, no resistance was found against chlortetracycline, doxycycline, minocycline, and chloramphenicol. In contrast, 11% of the P.acnes and 31% of the P.granulosum strains were not susceptible in vitro to erythromycin at a breakpoint concentration of 4 micrograms/ml. The present study shows that these strains are not suppressed even at higher erythromycin concentrations up to 256 micrograms/ml. Data from the literature reporting ineffective treatment of patients carrying erythromycin-resistant P.acnes strains may be explained by our study. Concerning clindamycin, resistance was found in only 6.8% of P.acnes and in 0% of the P.granulosum strains. Since sensitivity was seen in 100% of the strains already at a concentration of 16 micrograms/ml, a therapeutic effect may be possible.

Azithromycin compared with minocycline in the treatment of acne comedonica and papulo-pustulosa

This open study was conducted in 72 outpatients with acne vulgaris, to compare the clinical efficacy and tolerability of azithromycin and minocycline. Azithromycin was administered as a single oral dose (500 mg/day) for 4 days in four cycles every 10 days and minocycline was administered 100 mg daily for 6 weeks. Improvement was assessed 6 weeks after initiation of treatment with a four-graded scale. A satisfactory clinical response was observed in 75.8% of the patients treated with azithromycin and in 70.5% of those treated with minocycline. There were no significant differences between these two acne treatments in terms of reduction of the number of lesions (p> 0.05). Both agents were well tolerated and mild side effects were reported in 10.3% of azithromycin and 11.7% of minocycline treated patients. We conclude that azithromycin is at least as clinically effective and well tolerated as minocycline as treatment of facial comedonic and papulopustular acne.

Systematic review of Propionibacterium acnes resistance to systemic antibiotics

OBJECTIVE

To document changes in the prevalence of resistance of Propionibacterium acnes to antibiotics used for treating acne.

DATA SOURCES

MEDLINE and EMBASE were searched for publications on P. acnes resistance to systemic antibiotics. The search strategy mapped "acne" or "acne vulgaris" with the terms "antibiotic resistance" or "drug resistance, microbial". Only papers published in English during 1976 to 1997 were included in the search.

STUDY SELECTION

53 publications met the search criteria. The search output was refined by selecting papers that specifically addressed P. acnes resistance patterns. Additional studies (not included in the search output) were identified from review articles and references of the retrieved articles. Twelve articles were reviewed.

DATA EXTRACTION

Data on the prevalence of antibiotic-resistant propionibacteria, the incidence of individual resistance phenotypes, mixed resistance, and correlation between poor therapeutic response and resistant propionibacteria were extracted.

DATA SYNTHESIS

Research since 1978 has suggested an association between poor therapeutic response and antibiotic-resistant propionibacteria. The overall incidence of P. acnes antibiotic resistance has increased from 20% in 1978 to 62% in 1996. Resistance to specific antibiotics varied and was most commonly reported with erythromycin and clindamycin, tetracycline and doxcycline, and trimethoprim. Resistance to minocycline is rare.

CONCLUSIONS

In many patients with acne, continued treatment with antibiotics can be inappropriate or ineffective. It is important to recognise therapeutic failure and alter treatment accordingly. The use of long-term rotational antibiotics is outdated and will only exacerbate antibiotic resistance.

16S rRNA mutation associated with tetracycline resistance in a gram-positive bacterium

A genetic basis for tetracycline resistance in cutaneous propionibacteria was suggested by comparing the nucleotide sequences of the 16S rRNA genes from 16 susceptible and 21 resistant clinical isolates and 6 laboratory-selected tetracycline-resistant mutants of a susceptible strain. Fifteen clinical isolates resistant to tetracycline were found to have cytosine instead of guanine at a position cognate with Escherichia coli 16S rRNA base 1058 in a region important for peptide chain termination and translational accuracy known as helix 34. Cytosine at base 1058 was not detected in the laboratory mutants or the tetracycline-susceptible strains. The apparent mutation was recreated by site-directed mutagenesis in the cloned E. coli ribosomal operon, rrnB, encoded by pKK3535.E. coli strains carrying the mutant plasmid were more resistant to tetracycline than those carrying the wild-type plasmid both in MIC determinations and when grown in tetracycline-containing liquid medium. These data are consistent with a role for the single 16S rRNA base mutation in clinical tetracycline resistance in cutaneous propionibacteria.

Dispelling myths about acne

Virtually no one escapes adolescence and early adulthood unscathed by acne. However, advanced methods of therapy are now available to deal with all but the most recalcitrant forms of the condition. Unfortunately, stereotypical notions about causes and treatments still persist, and as Dr Landow points out, patient education to dispell these myths is an important part of management.

Molecular study of persistence of Nocardia asteroides and Nocardia otitidiscaviarum strains in patients with long-term nocardiosis

Three Nocardia asteroides and five Nocardia otitidiscaviarum isolates recovered from three patients with long-term nocardiosis were compared by random amplification of polymorphic DNA fingerprinting, antibiotic susceptibility testing, and enzymatic characterization. Results obtained with primer DKU49 (P. Palittapongarnpim, S. Chomyc, A. Fanning, and D. Kunimoto, J. Infect. Dis. 167:975-978, 1993) provide evidence that patient A was infected by two N. asteroides strains during a single episode of nocardiosis and that patients B and C remained infected by the same strain, respectively. Resistance to minocycline that was present in the first isolate recovered from patient B reverted to intermediate resistance in the second isolate and reverted to susceptibility in the third isolate. Resistance to penicillin G and beta-lactams was acquired by the second isolate obtained from patient C.

Acne. An overview of clinical research findings

Although acne represents the most common chronic skin condition seen by dermatologists, there are still many unanswered questions regarding its pathophysiology, and patients are still in need of more effective therapies, particularly those aimed at the hormonal aspects of acne. Recent clinical research has led to advances in our understanding of factors such as cytokines in follicular hyperkeratinization and the role of androgens in acne, the emergence and significance of antibiotic resistance of P. acnes, the long-term safety and efficacy of isotretinoin, and the safety and efficacy of new topical retinoids, such as tazarotene and adapalene. Fruitful interactions between basic scientists and clinical researchers within medicine and the pharmaceutical industry will, it is hoped, provide for future advances in this area.

Dermatologic therapy: 1993

This article reviews some therapeutic results reported in the English-language literature during 1993. Readers should review the original article in full before attempting any experimental or controversial therapy.