Laboratory induction and clinical occurrence of combined clindamycin and erythromycin resistance in Corynebacterium acnes

Mechanistic basis for the translation inhibition of Cutibacterium acnes by Clindamycin

Inflammation and the Gram-positive anaerobic bacterium Cutibacterium acnes, which is implicated in acne pathogenesis and pilosebaceous unit inflammation, are the main targets of antibiotic-based therapy against acne vulgaris (acne). The most widely used antibiotics in acne therapy are tetracyclines, macrolides, and lincosamides. Unfortunately, C. acnes bacteria over the past several decades have demonstrated increased resistance to these antibiotics, particularly to clindamycin. The precise knowledge of how antibiotics interact with their clinical target is needed to overcome this problem. Toward this goal, we determined the structure of clindamycin in complex with the ribosome of Cutibacterium acnes at 2.53 Å resolution using cryogenic electron microscopy. The galactose sugar moiety of clindamycin interacts with nucleotides of the 23S rRNA directly or through a conserved network of water-mediated interactions. Its propyl pyrrolidinyl group interacts with the 23S rRNA through van der Waals forces. Clindamycin binding to the Cutibacterium acnes ribosome interferes with both: proper orientation of the aminoacyl group of the A-site bound tRNA that is needed for peptide bond formation and with the extension of the nascent peptide. Our data are important for advancing understanding of antibiotic resistance and development of narrow- spectrum antibacterial drugs, which is an urgent need for contemporary antibiotic stewardship.

Is there an association between long-term antibiotics for acne and subsequent infection sequelae and antimicrobial resistance? A systematic review

BACKGROUND

Antimicrobial resistance (AMR) is a global health priority. Acne vulgaris is a common skin condition for which antibiotic use ranges from a few months to years of daily exposure.

AIM

To systemically search for and synthesise evidence on the risk of treatment-resistant infections, and other evidence of AMR, following long-term oral antibiotic use for acne.

DESIGN & SETTING

In this systematic review, a literature search was carried out using the databases Embase, MEDLINE, Cochrane, and Web of Science. They were searched using MeSH, Emtree, or other relevant terms, and followed a pre-registered protocol.

METHOD

Search strategies were developed with a librarian and undertaken in July 2019. All searches date from database inception. The primary outcome was antibiotic treatment failure or infection caused by a resistant organism. Secondary outcomes included detection of resistant organisms without an infection, rate of infection, or changes to flora.

RESULTS

A total of 6996 records were identified. Seventy-three full-text articles were shortlisted for full review, of which five were included. Two investigated rates of infection, and three resistance or changes to microbial flora. Three studies had 35 or fewer participants (range 20-118 496). Three studies had a serious or high risk of bias, one moderate, and one a low risk of bias. Weak evidence was found for an association between antibiotic use for acne and subsequent increased rates of upper respiratory tract infections and pharyngitis.

CONCLUSION

There is a lack of high quality evidence on the relationship between oral antibiotics for acne treatment and subsequent AMR sequelae. This needs to be urgently addressed with rigorously conducted studies.

Antimicrobial Susceptibility, Biotypes and Phylotypes of Clinical Cutibacterium (Formerly Propionibacterium) acnes Strains Isolated from Acne Patients: An Observational Study

INTRODUCTION

The aim of this study was to investigate the distribution of antimicrobial susceptibility, biotypes and phylotypes of clinical Cutibacterium acnes (C. acnes, formerly Propionibacterium acnes) isolates as well as the relationship among demographic factors, C. acnes biotypes and phylotypes.

METHODS

Cutibacterium acnes was collected from the skin lesions of acne patients who visited the dermatologic department of Huashan Hospital in Shanghai from October 2016 to March 2017. The agar dilution method was conducted to determine the minimum inhibitory concentrations (MICs) of C. acnes, the fermentation test to identify biotypes and then multiplex touchdown polymerase chain reaction (PCR) to identify phylotypes.

RESULTS

Of the 63 C. acnes strains we isolated, 18 (28.6%), 31 (49.2%) and 4 (6.3%) strains were resistant to clindamycin, erythromycin and moxifloxacin, respectively; no strains were resistant to tetracycline, minocycline, fusidic acid or β-lactam, while metronidazole was completely resisted; 3 strains showed multidrug resistance (MDR). Biotype III (BIII) was the major biotype (50.8%) followed by BI and BV (both 15.9%), BII (12.7%) and lastly BIV (4.8%). IA₁ was the predominant phylotype (71.4%) followed by IA₂ (19.0%), II (4.8%), IB (3.2%) and IC (1.6%), while III was not detected. Significant differences were observed in the severity of disease: different degrees of acne severity reflected different biotype and phylotype distributions, and the biotype distribution of mild acne was different from that of moderate acne; the phylotype distribution of moderate acne varies from that of severe acne, too. Additionally, there was no significant difference in the distribution of biotypes or phylotypes between resistant and susceptible strains.

CONCLUSION

Erythromycin and clindamycin resistances are the most common in clinical C. acnes strains; BIII is the predominant biotype and IA₁ is the major phylotype of C. acnes, which are mainly related to disease severity.

Prospects of Phage Application in the Treatment of Acne Caused by Propionibacterium acnes

Propionibacterium acnes is associated with purulent skin infections, and it poses a global problem for both patients and doctors. Acne vulgaris (acne) remains a problem due to its chronic character and difficulty of treatment, as well as its large impact on patients' quality of life. Due to the chronic course of the disease, treatment is long lasting, and often ineffective. Currently there are data regarding isolation of P. acnes phages, and there have been numerous studies on phage killing of P. acnes, but no data are available on phage application specifically in acne treatment. In this review, we have summarized the current knowledge on the phages active against P. acnes described so far and their potential application in the treatment of acne associated with P. acnes. The treatment of acne with phages may be important in order to reduce the overuse of antibiotics, which are currently the main acne treatment. However, more detailed studies are first needed to understand phage functioning in the skin microbiome and the possibility to use phages to combat P. acnes.

The extinction of topical erythromycin therapy for acne vulgaris and concern for the future of topical clindamycin

OBJECTIVE

This study aims to evaluate changes in topical antibiotic prescribing trends for acne.

METHODS

We retrospectively reviewed the National Ambulatory Medical Care Survey data from 1993 to 2012 for all visits in which acne vulgaris was the primary diagnosis.

RESULTS

Acne vulgaris represented an estimated 94.5 million (92.3, 96.8) visits during the 20-year study period. Bivariate analysis showed that over time erythromycin use declined (p < 0.001) and clindamycin use rose (p = 0.10). Multivariate analysis showed that the likelihood of erythromycin use declined to near zero (p < 0.001), whereas clindamycin utilization increased (p < 0.05). PubMed searches of "erythromycin AND resistance" and "clindamycin AND resistance" demonstrated increasing publication frequency by year, fit with sigmoidal functions (erythromycin: R²=0.93 and clindamycin: R²=0.94). Yearly publications consistently exceeded 100 papers for erythromycin and clindamycin resistance in 1983 and 2003, respectively, roughly corresponding to the interval between reports of their utility in acne.

CONCLUSIONS

Our findings suggest topical erythromycin use for acne has essentially ceased. By contrast, clindamycin use is increasing. Current recommendations discourage topical antibiotic monotherapy in favor of combination therapy with benzoyl peroxide and topical retinoids. Our group's previous work demonstrated that this trend is indeed occurring.

Systematic review of antibiotic resistance in acne: an increasing topical and oral threat

Topical and oral antibiotics are routinely used to treat acne. However, antibiotic resistance is increasing, with many countries reporting that more than 50% of Propionibacterium acnes strains are resistant to topical macrolides, making them less effective. We reviewed the current scientific literature to enable proposal of recommendations for antibiotic use in acne treatment. References were identified through PubMed searches for articles published from January, 1954, to March 7, 2015, using four multiword searches. Ideally, benzoyl peroxide in combination with a topical retinoid should be used instead of a topical antibiotic to minimise the impact of resistance. Oral antibiotics still have a role in the treatment of moderate-to-severe acne, but only with a topical retinoid, benzoyl peroxide, or their combination, and ideally for no longer than 3 months. To limit resistance, it is recommended that benzoyl peroxide should always be added when long-term oral antibiotic use is deemed necessary. The benefit-to-risk ratio of long-term antibiotic use should be carefully considered and, in particular, use alone avoided where possible. There is a need to treat acne with effective alternatives to antibiotics to reduce the likelihood of resistance.

A randomized controlled study for the treatment of acne vulgaris using high-intensity 414 nm solid state diode arrays

The treatment of acne vulgaris poses a challenge to the dermatologist, and the disease causes emotional anxiety for the patient. The treatment of acne vulgaris may be well-suited to home-use applications, where sufferers may be too embarrassed to seek medical treatment. This randomized controlled study is designed to quantify the effectiveness of using a blue light device in a therapy combined with proprietary creams, in the investigation of a self-treatment regimen. A total of 41 adults with mild-to-moderate facial inflammatory acne were recruited. The subjects were randomly assigned to combination blue light therapy (n = 26) or control (n = 15). Photography was used for qualitative assessment of lesion counts, at weeks 1, 2, 4, 8, and 12. All subjects in the treatment cohort achieved a reduction in their inflammatory lesion counts after 12 weeks. The mean inflammatory lesion counts reduced by 50.02% in the treatment cohort, and increased by 2.45% in the control cohort. The reduction in inflammatory lesions was typically observable at week-3, and maximal between weeks 8 and 12. The treatment is free of pain and side-effects. The blue light device offers a valuable alternative to antibiotics and potentially irritating topical treatments. Blue light phototherapy, using a narrow-band LED light source, appears to be a safe and effective additional therapy for mild to moderate acne.

Propionibacterium acnes: from commensal to opportunistic biofilm-associated implant pathogen

Propionibacterium acnes is known primarily as a skin commensal. However, it can present as an opportunistic pathogen via bacterial seeding to cause invasive infections such as implant-associated infections. These infections have gained more attention due to improved diagnostic procedures, such as sonication of explanted foreign materials and prolonged cultivation time of up to 14 days for periprosthetic biopsy specimens, and improved molecular methods, such as broad-range 16S rRNA gene PCR. Implant-associated infections caused by P. acnes are most often described for shoulder prosthetic joint infections as well as cerebrovascular shunt infections, fibrosis of breast implants, and infections of cardiovascular devices. P. acnes causes disease through a number of virulence factors, such as biofilm formation. P. acnes is highly susceptible to a wide range of antibiotics, including beta-lactams, quinolones, clindamycin, and rifampin, although resistance to clindamycin is increasing. Treatment requires a combination of surgery and a prolonged antibiotic treatment regimen to successfully eliminate the remaining bacteria. Most authors suggest a course of 3 to 6 months of antibiotic treatment, including 2 to 6 weeks of intravenous treatment with a beta-lactam. While recently reported data showed a good efficacy of rifampin against P. acnes biofilms, prospective, randomized, controlled studies are needed to confirm evidence for combination treatment with rifampin, as has been performed for staphylococcal implant-associated infections.

Antibiotic resistance of P. acnes in the treatment of acne. Ways for solving the problem

The author describes the reasons and frequency of antibiotic resistance of P. acnes in acne patients. He reviews the strategy and methods for doctors to inhibit the prevalence of antibiotic resistance of P. acnes. The article discusses the important role of benzoyl peroxide and synergistic effect of the combination of adapalene and benzoyl peroxide in the finished form to overcome the antibiotic resistance of P. acnes and ensure the treatment efficacy.

Thiazolidinedione derivatives as novel agents against Propionibacterium acnes biofilms

AIMS

The aim of the present study was to determine the effect of two thiazolidinedione derivatives on Propionibacterium acnes biofilm formation in vitro and to assess their effect on the susceptibility of P. acnes biofilms towards antimicrobials.

METHODS AND RESULTS

The compounds were shown to have a moderate to strong antibiofilm activity when used in subinhibitory concentrations. These compounds do not affect P. acnes attachment but lead to increased dispersal of biofilm cells. This dispersal results in an increased killing of the P. acnes biofilm cells by conventional antimicrobials.

CONCLUSION

The antibiofilm effect and the effect on biofilm susceptibility of the thiazolidinedione-derived quorum sensing inhibitors were clearly demonstrated.

SIGNIFICANCE AND IMPACT OF THE STUDY

Propionibacterium acnes infections are difficult to treat due to the presence of biofilms at the infection site and the associated resistance towards conventional antimicrobials. Our results indicate that these thiazolidinedione derivatives can be promising leads used for the treatment of P. acnes infections and as anti-acne drugs.

A small peptide with therapeutic potential for inflammatory acne vulgaris

A designed peptide named LZ1 with 15 amino acid residues containing strong antimicrobial activity against bacteria pathogens of acne vulgaris including Propionibacterium acnes, Staphylococcus epidermidis and S. aureus. Especially, it exerted strong anti-P. acnes ability. The minimal inhibitory concentration against three strains of P. acnes was only 0.6 µg/ml, which is 4 times lower than that of clindamycin. In experimental mice skin colonization model, LZ1 significantly reduced the number of P. acnes colonized on the ear, P. acnes-induced ear swelling, and inflammatory cell infiltration. It ameliorated inflammation induced by P. acnes by inhibiting the secretion of inflammatory factors including tumor necrosis factor-α (TNF-α) and interleukin (IL)-1β. LZ1 showed little cytotoxicity on human keratinocyte and hemolytic activity on human blood red cells. Furthermore, LZ1 was very stable in human plasma. Combined with its potential bactericidal and anti-inflammatory properties, simple structure and high stability, LZ1 might be an ideal candidate for the treatment of acne.

About local administration of antibacterial drugs for acne therapy

The review summarizes and systematizes data accumulated in the world research literature, which are related to the role of P. acnes in the pathogenesis of acne, its microbiology and antibacterial resistance; it also examines antibacterial drugs for the external therapy of acne and recommendations for their use.

Trends in prescription of acne medication in the US: Shift from antibiotic to non‐antibiotic treatment

AIM

To describe trends in the prescription of medication for acne vulgaris in the USA from 1990 to 2002 with particular reference to the shift from antibiotic to non-antibiotic treatment.

METHODS

Retrospective cross-sectional observational study which analysed the data from the 4922 patient visits for acne vulgaris from the 1990-2002 National Ambulatory Medical Care Survey (NAMCS) to assess medications mentioned or prescribed at office visits for acne vulgaris. We specifically analysed visits for benzoyl peroxide or combination benzoyl peroxide products, topical retinoids, clindamycin, erythromycin, tetracycline group antibiotics and isotretinoin. A priori predictions were made for changes in physician behaviour over time, and were tested by regression. Multivariate regression also assessed the impact of demographic variables such as patient age, gender, race and type of physician seen on prescribing behaviour.

RESULTS

From 1990 to 2002 there were significant declines (p<0.01) in the likelihood of use of several drug classes that are reliant on antimicrobial mechanisms for acne including the following: benzoyl peroxide, topical clindamycin, oral erythromycin and tetracycline group antibiotics. There were significant increases in likelihood of utilization for agents not reliant on antimicrobial mechanisms including topical retinoids and oral isotretinoin during this period. These changes in utilization were not affected by controlling for demographic factors in multivariate analysis.

CONCLUSION

There has been a shift towards non-antibiotic treatment in acne management. Growing awareness of antibiotic-resistant Propionibacterium species may contribute to increased use of topical and systemic retinoid agents.

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.

Laser therapy for acne

Considered the most common skin disorder, acne affects millions of people every year. This multifactorial condition of the pilosebaceous follicle is a combination of at least four different primary pathogeneses. In recent years, acne therapies have been improving, becoming more effective, and targeting one or more of these causes. Many current therapies have drawbacks involving patient compliance, systemic toxicities, and bacterial resistance. Lasers are now established options in the armamentarium to treat acne. The 532-nm potassium titanyl phosphate laser, 585- and 595-nm pulsed dye lasers, 1450-nm diode laser, and 1540-nm erbium glass laser have been used with variable efficacy. Lasers may be best used in combination with other therapies to enhance their results. Photodynamic therapy has been successful with substances such as 5-aminolevulinic acid and indocyanine green. Lasers remain viable alternatives for people who may not desire or be able to use topical or systemic formulations. Drawbacks associated with lasers include potential pain, skin discoloration, and cost of treatment. Typically, multiple sessions are required to achieve the desired results, with future maintenance treatments possible to maintain the outcomes. With additional clinical trials underway, laser treatment of acne will surely advance and continue to be optimized in the future.

Topical antibacterial treatments for acne vulgaris : comparative review and guide to selection

Topical antibacterial agents are an essential part of the armamentarium for treating acne vulgaris. They are indicated for mild-to-moderate acne, and are a useful alternative for patients who cannot take systemic antibacterials. Topical antibacterials such as clindamycin, erythromycin, and tetracycline are bacteriostatic for Propionibacterium acnes, and have also been demonstrated to have anti-inflammatory activities through inhibition of lipase production by P. acnes, as well as inhibition of leukocyte chemotaxis. Benzoyl peroxide is a non-antibiotic antibacterial agent that is bactericidal against P. acnes and has the distinct advantage that thus far, no resistance has been detected against it. Combined agents such as erythromycin/zinc, erythromycin/tretinoin, erythromycin/isotretinoin, erythromycin/benzoyl peroxide, and clindamycin/benzoyl peroxide are increasingly being used and have been proven to be effective. They generally demonstrate good overall tolerability and are useful in reducing the development of antibacterial resistance in P. acnes. The selection of a topical antibacterial agent should be tailored for specific patients by choosing an agent that matches the patient's skin characteristics and acne type. Topical antibacterial agents should generally not be used for extended periods beyond 3 months, and topical antibacterials should ideally not be combined with systemic antibacterial therapy for acne; in particular, the use of topical and systemic antibacterials is to be avoided as far as possible.

Systemic therapy for acne vulgaris

There are three main groups of systemic therapies available for the treatment of acne vulgaris: systemic antibiotics, hormonal therapy (for females) and oral isotretinoin. This article outlines when these treatments should be prescribed for the treatment of acne, considers the impact of therapy on aetiology, and advises on dosage regimens, potential adverse effects and expected efficacy.

Pulsed-dye laser treatment for inflammatory acne vulgaris: randomised controlled trial

BACKGROUND

Low-fluence (low irradiation energy density) pulsed-dye lasers (PDLs) have been used for atrophic acne scarring, and anecdotal experience suggests that long-term improvements in inflammatory acne can be seen after one PDL treatment. Our aim was to compare the efficacy and tolerability of such PDL treatment with sham treatment in patients with facial inflammatory acne in a double-blind, randomised controlled trial.

METHODS

We recruited 41 adults with mild-to-moderate facial inflammatory acne. We randomly assigned patients to PDL (n=31) or sham treatment (n=10). Treatment was given at baseline and patients were seen after 2, 4, 8, and 12 weeks. Assessors and participants were unaware of treatment allocations. Primary outcome measures were acne severity after 12 weeks and adverse events at any time. Secondary measures were change in lesion counts after 12 weeks and change in acne severity with time. Analysis was by intention-to-treat.

FINDINGS

After 12 weeks, acne severity (measured by Leeds revised grading system) was reduced from 3.8 (SD 1.5) to 1.9 (1.5) in the PDL group and 3.6 (1.8) to 3.5 (1.9) in the sham group (p=0.007). Treatment was well tolerated. Total lesion counts fell by 53% (IQR 19 to 64) in PDL patients and 9% (-16 to 38) in controls (p=0.023), and inflammatory lesion counts reduced by 49% (30 to 75) in PDL patients and 10% (-8 to 49) in controls (p=0.024). The most rapid improvements were seen in the first 4 weeks after treatment.

INTERPRETATION

PDL therapy improves inflammatory facial acne 12 weeks after one treatment with no serious adverse effects.

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.

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.

Prevalence of antibiotic-resistant propionibacteria on the skin of acne patients: 10-year surveillance data and snapshot distribution study

BACKGROUND

Cutaneous propionibacteria are implicated in acne pathogenesis, although their exact role in the genesis of inflammation is still poorly understood. Agents, including antibiotics, that reduce the numbers of propionibacteria on skin are therapeutic. Resistance in the target organism is a well-recognized consequence of antibiotic therapy for acne but formal prevalence and distribution data are lacking.

OBJECTIVES

To monitor the prevalence of skin colonization by antibiotic-resistant propionibacteria in acne patients attending the dermatology out-patient clinic at Leeds General Infirmary over a 10-year period beginning in 1991, and to examine the distribution of resistant strains on acne-prone skin and in the nares.

METHODS

Propionibacterial samples were obtained from the skin surface of the worst affected site (usually the face) of 4274 acne patients using a moistened swab. The swab was used to inoculate agar plates with and without selective antibiotics. After anaerobic incubation at 37 degrees C for 7 days, the amount of growth in the presence of each antibiotic was scored on a scale from 0 to 5+. A small number of patients (72) were selected for more detailed quantitative sampling at six different sites to examine the distribution of resistant propionibacteria on acne-prone skin and in the anterior nares.

RESULTS

The proportion of patients carrying strains resistant to one or more commonly used antiacne antibiotics rose steadily from 34.5% in 1991 to a peak of 64% in 1997. The prevalence dropped to 50.5% during 1999 and then rose again to 55.5% in 2000. Resistance to erythromycin was the most common and the majority of erythromycin-resistant strains were cross-resistant to clindamycin. Resistance to tetracyclines was less common in all years and with little increase over time. The more detailed quantitative study in 72 patients showed that population densities of resistant propionibacteria varied considerably between sites and between individuals. Almost invariably, patients were colonized with resistant strains at multiple sites, including the nares.

CONCLUSIONS

Skin colonization with antibiotic-resistant propionibacteria is much more common now than a decade ago. Resistant propionibacteria are widely distributed on acne-prone skin and in the nares. This suggests that they will be very difficult to eradicate using existing therapeutic regimens, especially from the nasal reservoir.

The evolving role of Propionibacterium acnes in acne

Propionibacterium acnes is a member of the resident cutaneous flora. Sebaceous follicles involved in acne are characterized by the accumulation of abnormally desquamated corneocytes and excess sebum-the microcomedo. This environment provides ideal growth conditions for P acnes. Several orders of magnitude level of P acnes are found in microcomedos. P acnes produces a variety of chemotactic factors and proinflammatory molecules that are responsible for the inflammatory phase of acne. Antibiotic therapy works by reducing the viable number of P acnes as well as by reducing the production of inflammatory stimuli. Antibiotic therapy has been a mainstay of treatment for more than 30 years. In the last decade, decreased sensitivity to antibiotics has developed and clinical resistance has been described. This development threatens the usefulness of antibiotic therapy in the future.

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.

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.

Clinical resistance to erythromycin and clindamycin in cutaneous propionibacteria isolated from acne patients is associated with mutations in 23S rRNA

The genetic basis of erythromycin resistance in cutaneous propionibacteria was determined by comparing the nucleotide sequences of the peptidyl transferase region in the 23S rRNAs from 9 susceptible and 26 resistant clinical isolates as well as 4 laboratory-selected erythromycin-resistant mutants of a susceptible strain. In 13 isolates and the 4 laboratory mutants, cross-resistance to macrolides, lincosamides, and B-type streptogramins was associated with an A-->G transition at a position cognate with Escherichia coli 23S rRNA base 2058. These strains were resistant to > or = 512 microg of erythromycin per ml. Two other mutations were identified, an A-->G transition at base 2059 in seven strains, associated with high-level resistance to all macrolides, and a G-->A transition at base 2057 in six strains, associated with low-level resistance to erythromycin. These mutations correspond to three of four phenotypic classes previously identified by using MIC determinations.

The short-term treatment of acne vulgaris with benzoyl peroxide: effects on the surface and follicular cutaneous microflora

A 28-day treatment regimen was undertaken by 12 volunteers, in which 5% (w/v) benzoyl peroxide (BP) in an aqueous gel was applied daily to the entire face. Clinical efficacy of the treatment was assessed after 2, 4, 9, 14 and 28 days, and the surface and follicular microbial populations were enumerated using established techniques. Viable counts were obtained for propionibacteria and Micrococcaceae. Mean numbers of propionibacteria recovered from the skin surface and follicular casts were significantly reduced after 2 days' treatment (P < 0.01), and the population was maintained at a significantly lower level throughout the study (P < 0.01), with mean values approaching the lower detection limit of the assay. Significant reductions in the surface and follicular Micrococcaceae were observed after 2 days' treatment, and at all subsequent visits (P < 0.05). After 2 days' treatment, only slight reductions in mean acne grade and mean inflamed lesion count were observed. However, at all subsequent visits the mean acne grade was significantly reduced (P < 0.05) compared with T0. The mean non-inflamed lesion count was lower than the pretreatment level at all visits, although the results were variable. The results indicate that significant reductions in surface and follicular microorganisms may be obtained after 48 h treatment with BP. Therefore, the non-specific antibacterial action of BP may be utilized in short intervening courses to reduce the carriage of antibiotic-resistant micro-organisms and thus improve the long-term efficacy of antibiotic acne treatments.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of benzoyl peroxide and erythromycin alone and in combination against antibiotic-sensitive and -resistant skin bacteria from acne patients

Topical formulations of erythromycin and benzoyl peroxide are popular and effective treatments for mild to moderate acne vulgaris. Use of the former is associated with resistance gain in both skin propionibacteria and coagulase-negative staphylococci, whereas use of the latter is not. We evaluated the efficacy of a combination of erythromycin and benzoyl peroxide against a total of 40 erythromycin-sensitive and -resistant strains of Staphylococcus epidermidis and skin propionibacteria in vitro. Using the checkerboard technique, five erythromycin resistant strains of Propionibacterium acnes were inhibited synergistically or additively by the combination. Complete mutual indifference was exhibited between the drugs against the remaining 35 strains. However, erythromycin resistant staphylococci and propionibacteria were inhibited by the same concentration of benzoyl peroxide as erythromycin-sensitive strains. These results suggest that, although the combination of erythromycin and benzoyl peroxide is not synergistic against the majority of erythromycin-resistant staphylococci and propionibacteria, the concomitant therapeutic use of both drugs should counteract the selection of erythromycin-resistant variants and reduce the number of pre-existing resistant organisms on the skin of acne patients.

The effect of zinc and erythromycin on the growth of erythromycin-resistant and erythromycin-sensitive isolates of Propionibacterium acnes: an in-vitro study

The effect of zinc and erythromycin on cultures inoculated with mixtures of different ratios of erythromycin sensitive (ES) and resistant (ER) Propionibacterium acnes cells was studied in vitro. Propionibacterium acnes ES outgrew P. acnes ER in the absence of erythromycin and zinc. At low levels of erythromycin ES outgrew ER, whilst the addition of 600 pg/ml zinc further reduced the growth of ER compared to ES. Growth of ER and ES were similar at levels of erythromycin near the minimum inhibitory concentration (MIC) of ES cells. Concentrations above the MIC for ES cells inhibited ES but not ER cells. At the higher concentrations of erythromycin, the addition of 96 ng/ml zinc delayed the growth of ER cells, whilst the addition of 300 micrograms/ml zinc prevented the growth of ER cells. The combination of erythromycin and zinc, at appropriate concentrations, inhibits both ES and ER.

Erythromycin resistant propionibacteria in antibiotic treated acne patients: association with therapeutic failure

Erythromycin resistant (EmR) propionibacteria were isolated from the skin surface of 51% of patients treated with oral erythromycin and 42% of patients treated with topical clindamycin compared with 3% of untreated control subjects (P less than 0.001). Amongst the topical clindamycin-treated patients, there was a higher incidence of EmR propionibacterial carriage in those patients who had previously been treated with oral erythromycin (64%) than in patients with no known previous exposure to erythromycin (20%; 0.01 greater than P greater than 0.001). Patients responding to oral erythromycin treatment carried EmR propionibacteria less frequently (24%) than patients who were not responding or who had relapsed (70%; P less than 0.001). These observations suggest that the use of oral erythromycin and/or topical clindamycin encourages the development of resistant propionibacteria and that the emergence of resistant strains is associated with therapeutic failure in erythromycin-treated patients. In total 63 resistant isolates were obtained from 52 subjects. There were 42 strains of Propionibacterium acnes, 16 strains of Propionibacterium granulosum and five strains of Propionibacterium avidum. The majority of isolates were inducibly or constitutively resistant to macrolide (e.g. erythromycin), lincosamide (e.g. clindamycin) and streptogramin B type antibiotics. Therefore, the isolates are phenotypically indistinguishable from the majority of EmR bacteria in which resistance is due to methylation of 23S ribosomal RNA.

Recalcitrant acne vulgaris. Clinical, biochemical and microbiological investigation of patients not responding to antibiotic treatment

A small, but clinically significant proportion of acne patients fail to respond adequately to antibiotic therapy. All non-responding acne patients attending the Leeds General Infirmary between September 1985 and April 1986 (49 out of a total of 610 patients; 8%) were investigated with respect to changes in their acne grade, microbial flora and sebum excretion rate. They were compared with 22 age and sex matched untreated control subjects. It was found that in 65% of non-responding patients there was no microbiological abnormality, in 16% there was evidence of Gram-negative folliculitis and 20% carried predominantly antibiotic resistant propionibacteria compared with only 5% of untreated controls. There was a significant association between erythromycin therapy and the isolation of erythromycin resistant propionibacteria (P less than 0.001). A causal link, however, has yet to be established between carriage of antibiotic resistant propionibacteria and failure to respond to antibiotic therapy. Our results show that for most patients with recalcitrant acne a non-microbiological explanation must be sought for the lack of therapeutic success. The mean sebum excretion rate (SER) of the non-responding patients was significantly higher than that of matched untreated acne patients (P less than 0.001). A majority of non-responders (69%) had an SER above the upper 95% confidence limit of the control mean. The SER may affect treatment efficacy by influencing the antibiotic concentration within the pilosebaceous ducts.