E. Anne Eady

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 subject (P < 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 > P > 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 < 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.

16S rRNA Mutation Associated with Tetracycline Resistance in a Gram-Positive Bacterium

ABSTRACT 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.

Propionibacterium acnes - friend or foe?

Propionibacterium acnes is frequently referred to as a strictly anaerobic skin commensal of low pathogenicity, a description which is misleading. The bacterium is like Dr Jekyll and Mr Hyde, demonstrating both beneficial and harmful effects which are host- and possibly strain-dependent. Although the pilosebaceous follicles of the face and upper trunk are the major habitat of P. acnes, significant populations also exist in the healthy mouth and colon of a minority of individuals. P. acnes can behave as an opportunist pathogen in compromized hosts but the incidence of such infections is low or underestimated. There is considerable evidence that persistence of this phagocytosis-resistant bacterium in a variety of organs and tissues can lead to a chronic inflammatory response with granuloma formation. P. acnes has the capacity to produce enzymes which could contribute to tissue destruction in dental caries and periodontal disease. Whether some strains are more virulent than others or are associated with specific disease syndromes will be ascertained only when an adequate biotyping scheme has been developed. P. acnes should not be dismissed as a culture contaminant without good reason, especially in situations where other bacteria are not recovered. To date, attempts to harness the potent immunomodulating effects of the organism in cancer therapy have been disappointing.

Identification of a chromosomally encoded ABC-transport system with which the staphylococcal erythromycin exporter MsrA may interact

The energy-dependent efflux of erythromycin (Er) in staphylococci is due to the presence of msr A, which encodes an ATP-binding protein. MsrA is related to the multi-component ATP-binding cassette (ABC) transporters which characteristically also contain membrane-spanning domains. Since MsrA functions in a heterologous host in the absence of other plasmid-encoded products, the requirement for a transmembrane (TM) complex might be fulfilled by hijacking a chromosomally encoded protein. Two genes, stpA and smpA, were identified upstream from msrA on the original Staphylococcus epidermidis plasmid, encoding an ATP-binding protein and a hydrophobic TM protein, respectively. Sequences highly similar to stpA and smpA (stpB and smpB) were also found adjacent to a chromosomal copy of msrA in S. hominis. In Southern blots, internal fragments of stpA or smpA hybridized to the chromosome of the Ers S. aureus RN4220. Cloning and sequence analysis of the region identified revealed the presence of two genes, stpC and smpC, related to stpA and smpA. The deduced amino-acid sequences of the gene products showed that StpA and StpC were 85% identical, whereas SmpA and SmpC were 65% identical. A gene similar to msrA was not present in the S. aureus chromosome. There was no further sequence similarity outside these conserved regions. These results indicate that the chromosomes of S. hominis and S. aureus contain sequences encoding a potential TM protein with which MsrA might interact.

Superior antibacterial action and reduced incidence of bacterial resistance in minocycline compared to tetracycline-treated acne patients

Twenty‐five previously untreated acne patients were monitored throughout a 6‐month course of therapy with either tetracycline or minocycline for changes in the numbers of staphylococci, propionibacteria and yeasts of the genus Malessezia on the skin surface. Antibiotic resistant staphylococci and propionibacteria were also counted. Minocycline (50 mg b.d.) produced a 10‐fold greater reduction in propionibacterial numbers compared to tetracycline (500 mg b.d.) after 12 (P < 0.02, t‐test) and 24 weeks (P < 0.05) of therapy. As treatment progressed, propionibacteria were replaced by yeasts, numbers of which were significantly increased by week 12 (P < 0.02) in tetracycline‐treated patients and by week 24 (P < 0.01) in minocycline‐treated patients. This suggests that yeasts have no role in the pathogenesis of acne but may compete with propionibacteria for the same niche. Overgrowth of antibiotic resistant staphylococci prevented any decrease in staphylococcal numbers in tetracycline‐treated patients, but minocycline produced a significant and sustained reduction in staphylococcal numbers after 1 week of therapy (P < 0.001). An increase in the number of multiply resistant ( 3 resistances) staphylococci occurred in 67% of tetracycline‐treated and 33% of minocycline‐treated patients by the end of the treatment period. There was no evidence of propionibacterial resistance in either treatment group. This study shows that minocycline has much greater antibacterial activity in vivo against both staphylococci and propionibacteria and produces less staphylococcal antibiotic resistance than tetracycline.

MINIMAL FUNCTIONAL SYSTEM REQUIRED FOR EXPRESSION OF ERYTHROMYCIN RESISTANCE BY MSRA IN STAPHYLOCOCCUS AUREUS RN4220

Previous studies have suggested that inducible erythromycin (Er) resistance in staphylococci mediated by the plasmid-borne ABC-transporter msrA is dependent on additional unidentified chromosomally encoded transmembrane (TM) domains. The requirement for two S. aureus candidate sequences, stpC and smpC, highly similar to sequences adjacent to msrA on the original S. epidermidis plasmid was investigated. Deletion of the sequences by allelic replacement was accomplished by electroporation of S. aureus RN4220 with a nonreplicating suicide vector. S. aureus strains carrying a delta(stpC-smpC) mutation showed an identical ErR phenotype to those arising from single crossover events and unmutated RN4220 containing msrA. This proves that neither stpC nor smpC is required for ErR. To further define the minimal functional unit required for MSR, the control region within the leader sequence of msrA was deleted. This resulted in constitutive resistance to Er and type B streptogramins (Sg), proving that SgR does not require the presence of Er. Deletion constructs containing the N- or C-terminal ABC regions of MsrA did not confer ErR in RN4220 singly or in combination.

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 propionibac teria compared with only 5% of untreated controls. There was a significant association between erythromycin therapy and the isolation of erythromycin resistant propionibacteria (P < 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 < 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.

Is acne an infection of blocked pilosebaceous follicles? Implications for antimicrobial treatment.

A model is proposed which is based on the assumption that acne is due to infection of functionally blocked pilosebaceous follicles by propionibacteria. Noninflamed lesions, which are first visible during the adrenarche in acne-prone individuals, do not contain propionibacteria. Comedogenesis appears to be independent of bacterial infection and may be driven by high levels of bioactive interleukin-1α derived from ductal hyperkeratinocytes. The stimulus which triggers interleukin-1α production is unknown. Formalin killed Propionibacterium acnes failed to stimulate production of the cytokine by cultured human keratinocytes in vitro.Inflamed lesions are thought to arise from microcomedones, but the initiating events are unknown. Evidence that propionibacteria are involved in the generation of inflammatory lesions is inconclusive. The cellular infiltrate is consistent with a type IV hypersensitivity response to one or more persistent lesional antigens, not necessarily bacterial. The potent adjuvant activity of P. acnes would up-regulate the immune response to any antigen which came into contact with the mononuclear cell infiltrate.Antibiotics are widely used in the treatment of acne, and their effects in selecting a predominantly resistant commensal population are well recognized. Although they reduce numbers of propionibacteria on the skin, other modes of action may contribute to or explain their therapeutic efficacy. At a time when there is global concern that antibiotic resistance rates in common bacterial pathogens may threaten our future ability to control bacterial infections, practices which promote the spread of antibiotic-resistant bacteria must be fully justified. A thorough reappraisal of the role of propionibacteria in acne is overdue. It is likely that further experimental work is needed to confirm or refute that P. acnes is aptly named.

IL-17: A Key Player in the P. acnes Inflammatory Cascade?

Recent advances in our understanding of inflammatory skin diseases now afford an opportunity to delve deeper into microbial/host interactions in acne. Agak et al. report that Propionibacterium acnes induces IL-17 expression in peripheral blood mononuclear cells and present new evidence that IL-17+ cells are found in the perifollicular infiltrate of comedones. Additional studies are needed to assess the clinical relevance of IL-17 in acne.

Identifying acne treatment uncertainties via a James Lind Alliance Priority Setting Partnership

Objectives The Acne Priority Setting Partnership (PSP) was set up to identify and rank treatment uncertainties by bringing together people with acne, and professionals providing care within and beyond the National Health Service (NHS). Setting The UK with international participation. Participants Teenagers and adults with acne, parents, partners, nurses, clinicians, pharmacists, private practitioners. Methods Treatment uncertainties were collected via separate online harvesting surveys, embedded within the PSP website, for patients and professionals. A wide variety of approaches were used to promote the surveys to stakeholder groups with a particular emphasis on teenagers and young adults. Survey submissions were collated using keywords and verified as uncertainties by appraising existing evidence. The 30 most popular themes were ranked via weighted scores from an online vote. At a priority setting workshop, patients and professionals discussed the 18 highest-scoring questions from the vote, and reached consensus on the top 10. Results In the harvesting survey, 2310 people, including 652 professionals and 1456 patients (58% aged 24 y or younger), made submissions containing at least one research question. After checking for relevance and rephrasing, a total of 6255 questions were collated into themes. Valid votes ranking the 30 most common themes were obtained from 2807 participants. The top 10 uncertainties prioritised at the workshop were largely focused on management strategies, optimum use of common prescription medications and the role of non-drug based interventions. More female than male patients took part in the harvesting surveys and vote. A wider range of uncertainties were provided by patients compared to professionals. Conclusions Engaging teenagers and young adults in priority setting is achievable using a variety of promotional methods. The top 10 uncertainties reveal an extensive knowledge gap about widely used interventions and the relative merits of drug versus non-drug based treatments in acne management.