A novel 23S rRNA mutation in Propionibacterium acnes confers resistance to 14-membered macrolides

In-vitro anti-acne activity of Teucrium oliverianum methanolic extract against Cutibacterium acnes

Background

Acne vulgaris is a skin infection widely seen in adolescents between 10-19 years with males affected more than females. It mainly affects the face but may also affect the back and chest. The symptoms vary with mild acne manifesting as comedones and moderate acne as inflammatory lesions (papulopustular), nodules, and mild scarring while severe acne has the same symptoms that have not subsided within 6 months of treatment. Various treatments including topical medications containing different antibiotics are used to treat acne. Recently, herbal treatments have been shown as better alternatives to conventional treatment. Teucrium oliverianum Ging. ex Benth (Lamiaceae) is traditionally used for skin infections such as wound healing and biofilm formation.

Methodology

Methanolic extract of T. oliverianum was subjected to liquid chromatography-mass spectrometry (LC-MS) analysis, and its antibacterial effect against Cutibacterium acnes. The anti-acne, anti-inflammatory, and antioxidant effects were also assessed using HaCaT cells infected with C. acnes. The cytotoxicity of the extract was evaluated using a neutral red uptake assay, and anti-inflammatory effects were determined by measuring TNF-α, IL-1β, INF-γ, and COX2 inhibition. The antioxidant action was assessed by ROS generation in HaCaT cells infected with C. acnes.

Results

LC-MS analysis of the extract showed the presence of 16 different metabolites with L-carnitine, esculin sesquihydrate, and gamma-linoleic acid as major metabolites. The methanolic extract of T. oliverianum showed an antibacterial effect against C. acnes with an IC50 value of 263.2 μg/mL. The extract attenuated the cytotoxicity of C. acnes on the HaCaT cell and the IC50 was found to be 676.2 μg/mL. It also decreased dose-dependently the expression of TNF-α, IL-1β, INF-γ, and inhibited COX2 in the HaCaT cells infected with C. acnes. It also decreased the generation of reactive oxygen species.

Conclusion

The results support the use of T. oliverianum as an anti-acne agent but it possesses mild antibacterial action. It showed anti-inflammatory effects in HaCaT cells infected with C. acnes. It is also an effective antioxidant and decreased the generation of reactive oxygen species. Comparison of the anti-acne effects and adverse reactions of extract with other treatments will provide more insight into its clinical efficacy and toxicity.

First Report of Plasmid-Mediated Macrolide-Clindamycin-Tetracycline Resistance in a High Virulent Isolate of Cutibacterium acnes ST115

Cutibacterium acnes, a prevalent skin commensal, has emerged as a significant global challenge due to its widespread antibiotic resistance. To investigate the antibiotic resistance mechanisms and clinical characterization of C. acnes in Korea, we collected 22 clinical isolates from diverse patient specimens obtained from the National Culture Collection for Pathogens across Korea. Among the isolates, KB112 isolate was subjected to whole genome sequencing due to high resistance against clindamycin, erythromycin, tetracycline, doxycycline, and minocycline. The whole genome analysis of KB112 isolate revealed a circular chromosome of 2,534,481 base pair with an average G + C content of 60.2% with sequence type (ST) 115, harboring the potential virulent CAMP factor pore-forming toxin 2 (CAMP2), the multidrug resistance ABC transporter ATP-binding protein YknY, and the multidrug efflux protein YfmO. The genomic sequence also showed the existence of a plasmid (30,947 bp) containing the erm(50) and tet(W) gene, which confer resistance to macrolide-clindamycin and tetracycline, respectively. This study reports plasmid-mediated multi-drug resistance of C. acnes for the first time in Korea.

Multidrug Resistance Plasmid pTZC1 Could Be Pooled among Cutibacterium Strains on the Skin Surface

Acne vulgaris is a chronic inflammatory skin disease that is exacerbated by Cutibacterium acnes. Although antimicrobials such as macrolides, clindamycin, and tetracyclines are used to treat acne caused by C. acnes, the increasing prevalence of antimicrobial-resistant C. acnes strains has become a global concern. In this study, we investigated the mechanism by which interspecies transfer of multidrug-resistant genes can lead to antimicrobial resistance. Specifically, the transfer of pTZC1 between C. acnes and C. granulosum isolated from specimens of patients with acne was investigated. Among the C. acnes and C. granulosum isolated from 10 patients with acne vulgaris, 60.0% and 70.0% of the isolates showed resistance to macrolides and clindamycin, respectively. The multidrug resistance plasmid pTZC1, which codes for macrolide-clindamycin resistance gene erm(50) and tetracycline resistance gene tet(W), was identified in both C. acnes and C. granulosum isolated from the same patient. In addition, whole-genome sequencing revealed that the pTZC1 sequences of C. acnes and C. granulosum showed 100% identity using comparative whole-genome sequencing analysis. Therefore, we hypothesize that the horizontal transfer of pTZC1 between C. acnes and C. granulosum strains may occur on the skin surface. The plasmid transfer test revealed a bidirectional transfer of pTZC1 between C. acnes and C. granulosum, and transconjugants that obtained pTZC1 exhibited multidrug resistance. In conclusion, our results revealed that the multidrug resistance plasmid pTZC1 could be transferred between C. acnes and C. granulosum. Furthermore, since pTZC1 transfer among different species may aid in the prevalence of multidrug resistant strains, antimicrobial resistance genes may have been pooled on the skin surface. IMPORTANCE The emergence of antimicrobial resistance not only in Cutibacterium acnes strain but also other skin bacteria such as Staphylococcus epidermidis is a big concern due to antimicrobial use for the treatment of acne vulgaris. Increased prevalence of macrolides-clindamycin resistant C. acnes relates to the acquisition of exogenous antimicrobial resistance genes. erm(50) is harbored by the multidrug resistance plasmid pTZC1, which has been found in C. acnes and C. granulosum strains isolated from patients with acne vulgaris. In this study, C. acnes and C. granulosum with pTZC1 were found in the same patient, and plasmid transfer between C. acnes and C. granulosum was proved by transconjugation assay. This study showed plasmid transfer between other species and the possibility of further prevalence antimicrobial resistance between Cutibacterium species.

Prevalence of antimicrobial-resistant Cutibacterium isolates and development of multiplex PCR method for Cutibacterium species identification

INTRODUCTION

Cutibacterium species such as C. acnes, C. avidum, and C. granulosum are known anaerobic skin inhabitants and often cause surgical site infections. These species are genetically similar and are difficult to identify rapidly. In addition, their pathogenicity and antimicrobial resistance remain unknown. In this study, antimicrobial resistance in Cutibacterium isolates was studied and a multiplex PCR method for their identification was developed.

METHODS

A total of 497 C. acnes, 71 C. avidum, and 25 C. granulosum strains which were isolated from the acne pustule and infectious regions, were used.

RESULTS

The antimicrobial resistance rates of C. acnes, C. avidum, and C. granulosum strains isolated from patients with acne vulgaris were higher than those of strains isolated from patients with infectious diseases. In particular, macrolide-clindamycin-resistant strains were isolated most frequently from all species. Among the resistant strains, strains with 23S rRNA mutations were the most common in C. acnes (24.3%, 71/292), whereas C. avidum and C. granulosum strains were most frequently found with erm(X). For the first time, a C. granulosum strain carrying pTZC1, which codes erm(50) and tet(W), was isolated from patients with acne vulgaris. Regarding the rapid identification of causative pathogens from infectious regions, three Cutibacterium species were identified with 100% sensitivity and specificity using multiplex PCR method.

CONCLUSIONS

Our data showed that antimicrobial resistance differed among Cutibacterium species. The multiplex PCR method may contribute to the rapid detection of Cutibacterium species and selection of appropriate antimicrobial agents.

Identification of a Transferable Linear Plasmid Carrying the Macrolide-Clindamycin Resistance Gene erm(X) in a Cutibacterium acnes Isolate from a Patient with Acne Vulgaris in Japan

Cutibacterium acnes, one of the common skin bacteria, is known to exacerbate acne vulgaris. Macrolide-clindamycin-resistant C. acnes strains have been reported worldwide. In this study, we found a transferable linear plasmid carrying the macrolide-clindamycin resistance gene erm(X) in a C. acnes strain isolated from a patient with acne vulgaris.

Multidrug-resistant Cutibacterium avidum isolated from patients with acne vulgaris and other infections

OBJECTIVES

Cutibacterium avidum, a human skin bacterium, rarely causes infectious diseases. It has been recently shown that C. acnes, another member of the genus Cutibacterium, acts as an opportunistic pathogen in surgical site infections. However, the antimicrobial susceptibility and pathogenicity of C. avidum remain unknown. Here, we investigated the epidemiological features of C. avidum.

RESULTS

C. avidum strains were isolated from patients with acne vulgaris (29 strains) and patients with other infections (12 strains). Antimicrobial susceptibility testing showed clarithromycin and clindamycin resistance in 65.9% of the tested strains (27/41). In addition, ciprofloxacin resistance was found in 34.1% of the strains (14/41), and 13 of those strains additionally exhibited resistance to both macrolides and clindamycin. Notably, the macrolides-clindamycin resistance gene erm(X) was found on the chromosomes of 92.6% (25/27) of the clindamycin-resistant strains and may be prevalent owing to transmission among C. avidum strains. Ciprofloxacin-resistant strains developed amino acid substitutions in GyrA owing to the use of antimicrobial agents. Pulsed-field gel electrophoresis (PFGE) analysis revealed that only a few strains exhibited 100% similarity. Additionally, no clustering associated with antimicrobial resistance, biofilm-forming ability, and type of infection was observed.

CONCLUSIONS

Our study revealed that erm(X) may be frequently disseminated in C. avidum, and multidrug-resistant C. avidum strains may colonize the skin of patients with acne vulgaris and patients with other infections. Therefore, the prevalence of multidrug-resistant C. avidum and the use of antimicrobial agents for the treatment of acne vulgaris and other infections associated with C. avidum should be monitored.

Increased prevalence of doxycycline low-susceptible Cutibacterium acnes isolated from acne patients in Japan caused by antimicrobial use and diversification of tetracycline resistance factors

The prevalence of antimicrobial-resistant Cutibacterium acnes is an important concern for the antimicrobial treatment of acne vulgaris. We hypothesized that antimicrobial treatment regimens for acne vulgaris would change following the revisions in the Japanese acne treatment guidelines, which added a statement regarding appropriate antimicrobial usage. Here, we studied the changes in antimicrobial use and antimicrobial-resistant C. acnes isolated from acne patients. A total of 127 C. acnes isolates collected from 212 patients with acne between 2013 and 2018 were used. Roxithromycin and clindamycin resistance rates were approximately 50% and 40%, respectively. In contrast, the prevalence of low doxycycline-susceptible strains (minimum inhibitory concentration [MIC] ≥8 μg/mL) in 2018 (17.4%) was 5.6-fold higher than that in 2013 (3.1%). Although the number of patients with severe and moderate acne did not change, the number of patients with a history of oral tetracycline use increased. The incidence of low doxycycline-susceptible strains was high in patients with a history of oral tetracycline use. The prevalence of strains with a 16S rRNA mutation, which confers reduced susceptibility to tetracyclines, increased by 8.6-fold (12.1%) from 2016 to 2018 in comparison with the previously revised guidelines (1.4%). Furthermore, the prevalence of low susceptibility strains with two resistance factors, 16S rRNA mutation and ribosomal S10 protein substitution, also increased. Approximately 10% of strains had the exogenous resistance gene, tet(W) (2013 to 2015, 10.1%; 2016 to 2018, 8.6%), and these strains showed different susceptibility to doxycycline dependent on the expression of tet(W) (MIC range 0.5-8 μg/mL). Our data show that the antimicrobial resistance pattern in C. acnes changes according to the trend of antimicrobial usage for acne treatment. Therefore, we should pay heed to the rapid dissemination of tetracycline resistance in C. acnes owing to acquisition of 16S rRNA mutation and tet(W).

Transferable Multidrug-Resistance Plasmid Carrying a Novel Macrolide-Clindamycin Resistance Gene, erm(50), in Cutibacterium acnes

Antimicrobial-resistant Cutibacterium acnes strains have emerged and disseminated throughout the world. The 23S rRNA mutation and erm(X) gene are known as the major resistance determinants of macrolides and clindamycin in C. acnes We isolated eight high-level macrolide-clindamycin-resistant C. acnes strains with no known resistance determinants, such as 23S rRNA mutation and erm(X), from different acne patients in 2008 between 2013 and 2015. The aim of this study was to identify the novel mechanisms of resistance in C. acnes Whole-genome sequencing revealed the existence of a plasmid DNA, denoted pTZC1 (length, 31,440 bp), carrying the novel macrolide-clindamycin resistance gene erm(50) and tetracycline resistance gene tet(W). pTZC1 was detected in all C. acnes isolates (eight strains) exhibiting high-level macrolide-clindamycin resistance, with no known resistance determinants (MIC of clarithromycin, ≥256 μg/ml; clindamycin, ≥256 μg/ml). Transconjugation experiments demonstrated that the pTZC1 was horizontally transferred among C. acnes strains and conferred resistance to macrolides, clindamycin, and tetracyclines. Our data showed, for the first time, the existence of a transferable multidrug-resistant plasmid in C. acnes Increased prevalence of this plasmid will be a great threat to antimicrobial therapy for acne vulgaris.

Transconjugation of erm(X) conferring high-level resistance of clindamycin for Cutibacterium acnes

Cutibacterium acnes (C. acnes) can become an exacerbating factor in acne vulgaris. Clindamycin has been most frequently used for the treatment of inflammatory acne vulgaris. We studied clindamycin susceptibility and resistance determinants of C. acnes isolated from acne patients in Japan. The isolation rate of clindamycin-resistant C. acnes had significantly increased from 20.3 % in 2009-2010 to 44.1 % in 2016-2017. Strains carrying erm(X), which confers high-level resistance to clindamycin, had significantly increased from 1.4 to 11.8 %. Sequence analysis of the resistance determinant showed that erm(X) was coded on transposon Tn5432. A transconjugation experiment showed that erm(X) can be transferred between C. acnes strains with high frequency and the transconjugants harboured transposon Tn5432 encoding erm(X). Our data show the transconjugation of erm(X) in C. acnes and strongly suggest that the transmission of erm(X) between C. acnes contributes to the increase and spread of clindamycin-resistant C. acnes strains in acne patients.