Propionibacterium acnes resistance: a worldwide problem

Antibiotic therapy directed against Propionibacterium acnes has been a mainstay of treatment for more than 40 years. Despite years of widespread use of systemic tetracyclines and erythromycin, change in P. acnes sensitivity to antibiotics was not seen until the early 1980s. The first clinically relevant changes in P. acnes antibiotic sensitivity were found in the USA shortly after the introduction of topical formulations of erythromycin and clindamycin. By the late 1980s, P. acnes strains with very high MIC levels for erythromycin and elevated MICs for tetracycline were increasingly found in the UK and the USA. Mutations in the genes encoding the 23S and 16S subunits of ribosomal RNA were first identified in the UK and also seen in a recent survey from clinics in Europe, Japan, Australia and the USA. In addition, strains were found in which these known mutations could not be identified, indicating that as yet unidentified resistance mechanisms have evolved. These findings indicate the need to develop strategies to minimize the use of antibiotics in acne therapy.

Antibiotic resistance of Propionibacterium acnes in acne vulgaris

Acne vulgaris is a common skin disease affecting all ages. Antibiotics remain the most common prescribed agent for the treatment of acne. Improper use of antibiotics in the dermatological setting needs to be evaluated to prevent the increasing prevalence of antibiotic resistance.

Inhibition of lipase activity in antibiotic-resistant propionibacterium acnes strains

BACKGROUND AND OBJECTIVE

Erythromycin-sensitive and/or clindamycin-sensitive strains of Propionibacterium acnes show a reduced lipase production at levels below the minimal growth-inhibitory concentration (MIC). The objective of this study was to determine whether erythromycin and clindamycin concentrations far below the MIC inhibit lipase production in P. acnes strains resistant to these antibiotics.

METHODS

Of 42 P. acnes strains, 10 showed an MIC >256 micro g/ml for erythromycin. Two strains showed MICs of 0.19 and 0.25 micro g/ml, while the MIC of the remaining strains was <or=0.016 micro g/ml. Lipase activity was determined up to a concentration of 192 micro g/ml by cultivation on spirit blue agar + lipase reagent. The 10 strains whose erythromycin MIC was >256 micro g/ml were also tested for lipase inhibition by clindamycin. While this method fails to differentiate between inhibition of lipase production and inhibition of lipase activity, the absence of inhibition of lipase activity rules out inhibition of lipase production.

RESULTS

Inhibition of lipolysis by sub-MIC concentrations was demonstrated only for clindamycin in 3 P. acnes strains. However, lipase inhibition was seen only at the dilution level immediately below the MIC.

CONCLUSIONS

Resistant P. acnes strains with high erythromycin and/or clindamycin MICs can be ruled out to show in vitro inhibition of lipase production at antibiotic concentrations far below the MIC.

Proton magic angle spinning NMR reveals new features in photodynamically treated bacteria

The bacterium Propionibacterium acnes is light-sensitive due to porphyrin-induced photosensitization. The light sensitivity increases with incubation of 5-aminolevulinic acid, ALA. For the first time, 1H magic angle spinning NMR spectroscopy is used to describe the photoinduced changes in the bacterium after ALA incubation. Successful photosensitization was performed with light-emitting diodes in the blue and red regions (430 and 654 nm, respectively). The irradiation setup, suitable for irradiation of bacterium suspensions in petri dishes is described. For NMR studies blue light diodes with about 90 micromol/m2s were chosen. After blue light irradiation, the endogenous glycine betaine, proline, glutamate and choline levels in P. acnes decreased with increasing irradiation time. For sublethal light doses (50% survival fraction), the endogenous glycine betaine level decreased 80% on average. The corresponding percentages for proline, choline and glutamate were about 40, 25 and 10, respectively. It is hypothesized that the irradiation, inducing porphyrin photosensitization amplified by ALA incubation, leads to elimination of the osmolyte glycine betaine and possibly also proline by so-called regulatory volume decrease (RVD) mechanisms. These mechanisms are known to be active in several prokaryotic and eukaryotic cells when exposed to hypotonic stress. They are also known to be present in several eukaryotic cells during photodynamic therapy (PDT) exposure leading to hypotonoc stress. The findings contribute to the knowledge of the inactivation mechanisms of P. acnes in photosensitization, and could therefore be of interest in the efforts to use PDT as treatment of the acne disease.

Eradication of Propionibacterium acnes by its endogenic porphyrins after illumination with high intensity blue light

Propionibacterium acnes is a Gram-positive, microaerophilic bacterium that causes skin wounds. It is known to naturally produce high amounts of intracellular porphyrins. The results of the present study confirm that the investigated strain of P. acnes is capable of producing endogenic porphyrins with no need for any trigger molecules. Extracts from growing cultures have demonstrated emission peaks around 612 nm when excited at 405 nm, which are characteristic for porphyrins. Endogenic porphyrins were determined and quantified after their extraction from the bacterial cells by fluorescence intensity and by elution retention time on high-performance liquid chromatography (HPLC). The porphyrins produced by P. acnes are mostly coproporphyrin, as shown by the HPLC elution patterns. Addition of delta-aminolevulinic acid (ALA) enhanced intracellular porphyrin synthesis and higher amounts of coproporphyrin have been found. Eradication of P. acnes by its endogenic porphyrins was examined after illumination with intense blue light at 407-420 nm. The viability of 24 h cultures grown anaerobically in liquid medium was reduced by less than two orders of magnitude when illuminated once with a light dose of 75 J cm(-2). Better photodynamic effects were obtained when cultures were illuminated twice or three times consecutively with a light dose of 75 J cm(-2) and an interval of 24 h between illuminations. The viability of the culture under these conditions decreased by four orders of magnitude after two illuminations and by five orders of magnitude after three illuminations. When ALA-triggered cultures were illuminated with intense blue light at a light dose of 75 J cm(-2) the viability of the treated cultures decreased by seven orders of magnitude. This decrease in viability can occur even after a single exposure of illumination for the indicated light intensity. X-ray microanalysis and transmission electron microscopy revealed structural damages to membranes in the illuminated P. acnes. Illumination of the endogenous coproporphyrin with blue light (407-420 nm) apparently plays a major role in P. acnes photoinactivation. A treatment protocol with a series of several illuminations or illumination after application of ALA may be suitable for curing acne. Treatment by both pathways may overcome the resistance of P. acnes to antibiotic treatment.

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.

Comparison of chloroxylenol 0.5% plus salicylic acid 2% cream and benzoyl peroxide 5% gel in the treatment of acne vulgaris: a randomized double-blind study

A 12-week double-blind randomized study was performed to compare benzoyl peroxide 5% (BP) gel and chloroxylenol 0.5% plus salicylic acid 2% (PCMX + SA) cream (Nisal cream) for efficacy and adverse reactions. Thirty-seven volunteers participated in the study, 19 in the BP group and 18 in the PCMX + SA group. The patients applied the medication twice daily to the entire face. Clinical evaluation and lesion counts were obtained at 0, 3, 6, 9 and 12 weeks. At week 12 both groups showed a marked improvement in both inflammatory and noninflammatory lesions (60% and 54% for the BP group and 62% and 56% for and 56% for the PCMX + SA group, respectively). Although PCMX + SA showed a slightly stronger keratolytic effect throughout the study period, there was no statistically significant difference in the reduction of the papulopustules or comedones between the two groups. Adverse effects such as erythema and photosensitivity were significantly fewer in the PCMX + SA group at week 12 (p = 0.0002 and p = 0.05, respectively). These results suggest that PCMX + SA cream is as effective as BP gel in the treatment of papulopustular and comedonal acne and that it is better tolerated.

Effect of lipase activities of Propionibacterium granulosum and Propionibacterium acnes

We studied the lipase activities of Propionibacterium granulosum, P. acnes and the suppression of these activities by Jumi-haidoku-to (JHT). Lipase activity of P. acnes biotype III (BIII) was strongest, while that of P. granulosum was faintly expressed. Compared with the control medium, the production of propionic and butyric acids was suppressed by all the tested mediums combined with JHT. The decrease in these acids produced by JHT was significantly higher in P. granulosum than in P. acnes. Although P. acnes BIII may produce a strong effect on acne, the presence of P. granulosum should not be ignored. Further research is required on the correlation between P. acnes and P. granulosum.

Anti-inflammatory effects of erythromycin and tetracycline on Propionibacterium acnes induced production of chemotactic factors and reactive oxygen species by human neutrophils

Propionibacterium acnes (P. acnes), an anaerobic pathogen, plays an important role in the pathogenesis of acne and seems to initiate the inflammatory process by producing neutrophil chemotactic factors (NCF). Once neutrophils attracted by bacterial chemoattractants reach the inflamed site, they release inflammatory mediators such as lysosomal enzymes and reactive oxygen species (ROS). Previously, it has been shown that antibiotics may affect acne by means other than their anti-bacterial effects. Thus, we investigated the effect of subminimal inhibitory concentration (sub-MIC) of tetracycline and erythromycin on production of NCF and ROS. NCF was tested in vivo in a mouse model and ROS was estimated on human PMNL in vitro, by nitroblue tetrazolium dye reduction test (NBT) and cytochrome-C reduction test. Tetracycline (CS-T) and Erythromycin (CS-E) treated cultures showed a significant reduction of 35.8% and 58.3% in NCF production respectively, as compared to P. acnes stimulated cultures. Tetracycline and erythromycin at their sub-MIC also significantly inhibited release of ROS from human PMNL. Thus, tetracycline and erythromycin, besides having antibacterial activity, also have an anti-inflammatory action. These antibiotics reduce the capacity of P. acnes to produce NCF, as well decrease its ability to induce ROS from PMNL.

Effects of Roxithromycin on the production of lipase and neutrophil chemotactic factor by Propionibacterium acnes

BACKGROUND

The macrolide antibiotic roxithromycin is effective against acne associated with inflammation, but the mechanism by which this is achieved has not been clarified.

OBJECTIVE

We studied the effects of roxithromycin on the production of lipase and neutrophil chemotactic factor by Propionibacterium acnes in vitro.

RESULTS

Roxithromycin significantly inhibited the production of lipase and neutrophil chemotactic factor by P. acnes at a concentration one eighth of the MIC, at which the growth curve of P. acnes is not affected.

CONCLUSION

One mechanism of the effectiveness of roxithromycin in acne therapy is thought to be the inhibition of bacterial lipase and neutrophil chemotactic factor production by P. acnes.

Comparative efficacy of clindamycin and benzoyl peroxide for in vivo suppression of Propionibacterium acnes

BACKGROUND

Benzoyl peroxide and clindamycin are the two most widely prescribed topical antimicrobials in the treatment of acne.

AIM

To compare the antimicrobial efficacy, in vivo, of benzoyl peroxide and clindamycin against Propionibacterium acnes.

METHODS

Two groups of 10 subjects each, with comparable mean P. acnes baseline counts of log 5.75 to 5.85, underwent twice daily application of benzoyl peroxide or clindamycin for 14 days.

RESULTS

The results of quantitatively sampling P. acnes after 3, 7 and 14 days of treatment showed that Triaz 6% benzoyl peroxide special gel produced faster and significantly greater reductions in P. acnes than did the 1% clindamycin phosphate in Cleocin-T lotion (p < 0.01). These results were paralleled by the greater reductions produced by Triaz versus Cleocin (p < 0.05) in P. acnes fluorescence.

CONCLUSION

Benzoyl peroxide formulations suppress the follicular population of P. acnes more rapidly and to a greater degree than topical antibiotics such as clindamycin.

Current issues in antimicrobial therapy for the treatment of acne

This review summarizes current information regarding the use of antimicrobial agents for the treatment of patients with inflammatory acne. A number of drugs have been used effectively as topical or systemic therapy, often in combination with benzoyl peroxide or a retinoid. Propionibacterium acnes exhibits high in vitro sensitivity to a wide range of antimicrobials, including ampicillin, clindamycin, erythromycin, tetracycline, doxycycline, nadifloxacin, ofloxacin, minocycline, cephalexin, and gentamycin. However, not all of these drugs are equally effective in penetrating the lipid-filled microcomedo and reducing numbers of P. acnes in the skin. Antimicrobial therapy, particularly systemic treatment, may be complicated by the potential for drug-drug interactions. Historically, the potential for antimicrobials to reduce the effectiveness of oral contraceptives has been a concern in the treatment of acne. However, there is evidence to suggest that such an interaction does not take place in patients being treated with the antimicrobials most often used in dermatological practice. Antimicrobial therapy for acne has also been complicated by the emergence of antibiotic-resistant strains of P. acnes. Increasing P. acnes resistance can be combated by judicious use of retinoids in combination with antibiotics to reduce inflammation and infection, and employment of retinoids for maintenance therapy.

A randomized, double-blind comparison of a clindamycin phosphate/benzoyl peroxide gel formulation and a matching clindamycin gel with respect to microbiologic activity and clinical efficacy in the topical treatment of acne vulgaris

BACKGROUND

One approach to suppressing the overgrowth of antibiotic-resistant bacteria is to develop combination products composed of active constituents with complementary but distinct mechanisms of antibacterial action.

OBJECTIVE

The purpose of this study was to compare the antimicrobial and clinical efficacy and tolerability of clindamycin phosphate 1%/benzoyl peroxide 5% gel formulation with matching clindamycin 1% gel in the treatment of acne vulgaris.

METHODS

This 16-week, single-center, double-blind, randomized, parallel-group study compared the combination gel with clindamycin monotherapy applied BID in patients 13 to 30 years of age with mild to moderate acne and facial Propionibacterium acnes counts > or = 10(4) colony-forming units per square centimeter of skin.

RESULTS

Seventy-nine patients were enrolled and randomly assigned to receive the combination gel (n = 40) or clindamycin monotherapy (n = 39). Seventy patients (50 males, 20 females; mean age, 18.2 years) were included in the intent-to-treat group. The combination gel treatment produced significantly greater reductions (P < or = 0.046) from baseline in total lesion counts and in numbers of inflammatory lesions and comedones compared with clindamycin monotherapy. Greater reductions in the severity of acne also were observed in the physician's and patient's Clinical Global Improvement scale scores and in other secondary efficacy measurements. Reductions in clindamycin-resistant P acnes counts were observed relative to baseline in the combination gel group; in contrast, P acnes counts increased by >1,600% in the clindamycin monotherapy group at week 16 (P = 0.018 vs combination gel). Reductions in inflammatory (r2 = 0.31; P = 0.016) and total (r2 = 0.28; P = 0.027) lesions were correlated with decreases in clindamycin-resistant bacteria. Also, significant correlations were observed between the percent change from baseline in total lesion counts (r2 = 0.44; P < 0.001) and comedo counts (r2 = 0.50; P < 0.001) and the log10 change from baseline in total P acnes counts.

CONCLUSIONS

The total P acnes count (P = 0.002) and the clindamycin-resistant P acnes count (P = 0.018) were significantly reduced after 16 weeks of treatment with combination gel compared with clindamycin monotherapy. These reductions in total P acnes and clindamycin-resistant P acnes counts correlated with reductions in total acne lesions.

Effect of topical benzoyl peroxide/clindamycin versus topical clindamycin and vehicle in the reduction of Propionibacterium acnes

Propionibacterium acnes is one of the primary factors involved in the pathogenesis of acne vulgaris; proliferation of this bacteria is present in all patients with inflammatory lesions. Combination topical therapy with agents that have different but complementary antimicrobial mechanisms of action has the potential to increase efficacy and to prevent the emergence of resistant organisms. The onset of action and effectiveness of 3 topical preparations (benzoyl peroxide 5%/clindamycin phosphate 1% gel, clindamycin phosphate 1% solution, and vehicle gel) in reducing P acnes were compared in a randomized, open-label, evaluator-blinded, comparative trial involving 60 healthy volunteers who were free of acne but had high levels of facial P acnes. Treatment with benzoyl peroxide 5%/clindamycin phosphate 1% gel significantly (P<.001) reduced P acnes levels by >1 log10/cm2 from baseline (91% inhibition) 24 hours after application. Progressive declines were observed throughout the 2-week study period, with a 3 log10/cm2 reduction (99.9% inhibition) from baseline in P acnes at the end of the 2-week treatment period. In contrast, significant (P<.05) reductions from baseline in P acnes levels following treatment with clindamycin phosphate 1% solution were only observed at the last assessment period (2 weeks), with an average reduction of 0.64 log10/cm2 (77% inhibition). Patients receiving vehicle gel had no measurable reductions in P acnes from baseline. These results demonstrate that topical benzoyl peroxide 5%/clindamycin phosphate 1% gel produces rapid and clinically relevant reductions in P acnes greater than those produced by single-agent therapy. This activity is likely responsible for the quick onset of clinical efficacy produced by this combination regimen.

[General antibiotic therapy in acne]

The primary indication for systemic antibiotics is acute therapy for moderate-to-severe inflammatory acne. The preferred agents include tetracyclines and derivatives; macrolides, co-trimoxazole, and trimethoprim may represent acceptable alternatives. Antibiotics act mainly on inflammatory lesions (papules and pustules) and are only slightly comedolytic. Oral antibiotics reduce the number of Propionibacterium acnes. In addition, they have an anti-inflammatory activity. The side effects associated with oral antibiotics for acne depend on the drug; however, severe side effects are not common. Resistant strains of Propionibacterium acnes to antibiotics are increasing. Thus, general guidelines are useful when utilizing oral antibiotic therapy in acne.

Lymecycline and minocycline in inflammatory acne: a randomized, double-blind intent-to-treat study on clinical and in vivo antibacterial efficacy

BACKGROUND

Some antibiotics represent a mainstay in acne treatment. However, studies comparing their efficacies are rare.

AIM

To evaluate the clinical and in vivo antibacterial effect of lymecycline and minocycline at different dosages.

METHOD

Eighty-six patients with moderate to severe acne were enrolled in a randomized, double-blind, intent-to-treat study comparing in three parallel groups the effect of (1) lymecycline 300 mg daily for 12 weeks, (2) minocycline 50 mg daily for 12 weeks and (3) minocycline 100 mg daily for 4 weeks followed by 50 mg daily for 8 weeks. Evaluations were made at the screening visit and at five on-treatment visits. They consisted of clinical counts of acne lesions and evaluations of bacterial viability using dual flow cytometry performed on microorganisms collected from sebaceous infundibula by cyanoacrylate strippings.

RESULTS

Patients receiving minocycline 100/50 mg had the best clinical outcome, particularly in the reduction of the number of papules. By the end of the trial, the microbial response to minocycline 100/ 50 mg was also superior to either of the other two treatments. There were less live and more dead bacteria.

CONCLUSION

In this trial, minocycline 100/50 mg was superior for the treatment of inflammatory acne when compared to lymecycline 300 mg and minocycline 50 mg.

The combination formulation of clindamycin 1% plus benzoyl peroxide 5% versus 3 different formulations of topical clindamycin alone in the reduction of Propionibacterium acnes. An in vivo comparative study

BACKGROUND

Isolates of Propionibacterium acnes resistant to one or more anti-acne antibiotics (most commonly erythromycin) are being increasingly reported, and the emergence of resistant strains can be associated with therapeutic failure of topical treatment.

OBJECTIVE

Comparison of the in vivo effectiveness of the combination of clindamycin 1% plus benzoyl peroxide 5% in a gel formulation to that of each of 3 clindamycin 1% preparations (gel, lotion, and solution) with respect to reduction in counts of P. acnes cultured from the foreheads of healthy volunteers.

METHODS

The effects of treatment with the 4 study drugs were compared in an open-label study. Cultures were collected before, after 1 week and after 2 weeks of treatment.

RESULTS

Treatment with the combination formulation resulted in a 99.8% (> 2 logs) reduction in total propionibacterial numbers after 1 week of therapy compared with 30 to 62% (< 1 log) decreases for the different formulations of topical clindamycin alone. By the end of week 2, the combination had decreased P. acnes counts by more than 99.9% (> 3 logs) relative to reductions of from 88 to 95% (< or > 1 log) for the single agent formulations.

CONCLUSIONS

Under the conditions of the present study, the combination of clindamycin 1% plus benzoyl peroxide 5% gel produced more rapid and highly significant reductions in P. acnes compared with formulations containing clindamycin alone.

[Mechanisms behind the development of antibiotic resistant bacteria]

BACKGROUND

Bacterial resistance to antibiotics is an increasing threat to the successful treatment of hospital and community-acquired infections.

MATERIAL AND METHODS

Based on relevant literature, this article focuses on some of the essential resistance problems caused by pathogens such as pneumococci, staphylocci, enterococci and gram-negative rods, and provides a review of the genetic and molecular basis of bacterial resistance, as well as of the global trends in bacterial resistance.

RESULTS

Mechanisms of resistance continue to evolve and disseminate among gram-negative as well as gram-positive pathogens. New problems are developing, such as glycopeptide resistance in Staphylococcus aureus. Bacteria have become resistant to antibiotics as a result of chromosomal changes or the exchange of genetic material via plasmids and transposons. The emergence of multiresistant bacteria e.g. S. aureus, enterococci and Mycobacterium tuberculosis, has made many currently available antibiotics ineffective.

INTERPRETATION

The introduction of new antibiotics has always been followed by development of resistance.

Activation of clindamycin phosphate by human skin

AIMS

To investigate the relative antimicrobial activity of clindamycin phosphate (CP) and clindamycin (Cly) and to examine the effect of skin homogenates on the activity of CP.

METHODS AND RESULTS

Minimum inhibitory concentrations (MIC) were determined against dermally relevant organisms and bactericidal activity was studied using time-kill methodology. The effect of skin homogenates on the antimicrobial activity of CP was studied by well-diffusion assay. The MIC of Cly was substantially lower than that of CP in all susceptible organisms. Clindamycin also showed greater bactericidal activity (rate of kill) than CP. Phosphatases in skin homogenates activated CP at pH 4-8 with a maximal activation at pH 4.

CONCLUSION

Phosphatases within the skin have been shown to convert CP to the more potent form Cly.

SIGNIFICANCE AND IMPACT OF THE STUDY

Conversion to Cly is a major determinant of antimicrobial activity in the skin layers following topical application of CP.