Genetic determinants of antimicrobial resistance in three multi-drug resistant strains of Cutibacterium acnes isolated from patients with acne: a predictive in silico study

Comparative efficacy of essential oils against Cutibacterium acnes: Effect upon strains from phylotypes with different virulence patterns

OBJECTIVES

Despite being a commensal of human skin, Cutibacterium acnes plays an important role in the pathogenesis of Acne vulgaris, with the loss of bacterial phylotype diversity being related to disease progression. This study evaluated differences in the virulence profile of C. acnes strains from different phylotypes and investigated the possible phylotype-selective efficacy of essential oils (EOs) from Thymus x citriodorus (TC), Thymus mastichina, and Cistus ladanifer compared to Melaleuca alternifolia (tea tree), focusing on both planktonic and biofilm growth forms, the latter being related with pathogenesis and treatment resistance.

METHODS

One collection strain and seven clinical isolates were classified into phylotypes using multiplex-touchdown PCR. Virulence trait differences across phylotypes were evaluated by studying antibiotic resistance, biofilm formation, porphyrin production, and lipase activity. EOs were tested for minimum inhibitory/bactericidal concentrations (MIC/MBC) and effects on biofilm biomass and metabolic activity.

RESULTS

Strains from phylotype IA1 were higher biofilm and lipase producers than phylotype II strains. Regarding EO's efficacy, TC EO presented lower planktonic MIC values for all strains compared to the other EOs, presenting a smaller difference in MIC values across phylotypes. TC EO was able to similarly reduce biofilm biomass and metabolic activity in phylotype IA1 clinical strains, being effective at lower concentrations compared with the remaining EOs.

CONCLUSIONS

Not all virulence traits were phylotype-related, highlighting the multifactorial nature of the disease. TC EO showed a relevant anti-acne potential, outperforming tea tree EO (a species with a commercial claim for Acne vulgaris) against both planktonic and biofilm growth forms of C. acnes.

Prevalence of antibiotic-resistant Cutibacterium acnes (formerly Propionibacterium acnes) isolates, a systematic review and meta-analysis

OBJECTIVE

This study aimed to assess the overall antibiotic susceptibility of Cutibacterium acnes (C. acnes), a bacterium implicated in acne vulgaris, with a particular focus on clindamycin and fluoroquinolones, which are commonly used in inflammatory acne treatment.

METHODS

A systematic search of Scopus, PubMed, Web of Science and EMBASE databases was conducted to identify relevant studies. Pooled prevalence estimates were calculated using a random-effects model, and additional analyses included quality assessment, evaluation of publication bias, meta-regression and subgroup analyses based on antimicrobial susceptibility methods and year of publication.

RESULTS

The analysis incorporated a total of 39 studies. The random-effects model revealed that the proportion of clindamycin-resistant isolates was 0.031 (95% CI: 0.014-0.071). Additionally, macrolides, including erythromycin (0.366; 95% CI: 0.302-0.434) and azithromycin (0.149; 95% CI: 0.061-0.322), exhibited distinct prevalence rates. Tetracyclines, including doxycycline (0.079; 95% CI: 0.014-0.071), tetracycline (0.062; 95% CI: 0.036-0.107) and minocycline (0.025; 95% CI: 0.012-0.051), displayed varying prevalence estimates. Fluoroquinolones, including ciprofloxacin (0.050; 95% CI: 0.017-0.140) and levofloxacin (0.061; 95% CI: 0.015-0.217), demonstrated unique prevalence rates. Additionally, the prevalence of the combination antibiotic trimethoprim/sulfamethoxazole (SXT) was estimated to be 0.087 (95% CI: 0.033-0.208).

CONCLUSION

The study findings highlight a concerning increase in antimicrobial-resistant C. acnes with the use of antibiotics in acne treatment. The strategic utilization of appropriate antimicrobials has emerged as a crucial measure to mitigate the emergence of antimicrobial-resistant skin bacteria in acne management.

Novel spore-forming species exhibiting intrinsic resistance to third- and fourth-generation cephalosporins and description of Tigheibacillus jepli gen. nov., sp. nov

A comprehensive microbial surveillance was conducted at NASA's Mars 2020 spacecraft assembly facility (SAF), where whole-genome sequencing (WGS) of 110 bacterial strains was performed. One isolate, designated 179-BFC-A-HST, exhibited less than 80% average nucleotide identity (ANI) to known species, suggesting a novel organism. This strain demonstrated high-level resistance [minimum inhibitory concentration (MIC) >256 mg/L] to third-generation cephalosporins, including ceftazidime, cefpodoxime, combination ceftazidime/avibactam, and the fourth-generation cephalosporin cefepime. The results of a comparative genomic analysis revealed that 179-BFC-A-HST is most closely related to Virgibacillus halophilus 5B73CT, sharing an ANI of 78.7% and a digital DNA-DNA hybridization (dDDH) value of 23.5%, while their 16S rRNA gene sequences shared 97.7% nucleotide identity. Based on these results and the recent recognition that the genus Virgibacillus is polyphyletic, strain 179-BFC-A-HST is proposed as a novel species of a novel genus, Tigheibacillus jepli gen. nov., sp. nov (type strain 179-BFC-A-HST = DSM 115946T = NRRL B-65666T), and its closest neighbor, V. halophilus, is proposed to be reassigned to this genus as Tigheibacillus halophilus comb. nov. (type strain 5B73CT = DSM 21623T = JCM 21758T = KCTC 13935T). It was also necessary to reclassify its second closest neighbor Virgibacillus soli, as a member of a novel genus Paracerasibacillus, reflecting its phylogenetic position relative to the genus Cerasibacillus, for which we propose Paracerasibacillus soli comb. nov. (type strain CC-YMP-6T = DSM 22952T = CCM 7714T). Within Amphibacillaceae (n = 64), P. soli exhibited 11 antibiotic resistance genes (ARG), while T. jepli encoded for 3, lacking any known β-lactamases, suggesting resistance from variant penicillin-binding proteins, disrupting cephalosporin efficacy. P. soli was highly resistant to azithromycin (MIC >64 mg/L) yet susceptible to cephalosporins and penicillins.

IMPORTANCE

The significance of this research extends to understanding microbial survival and adaptation in oligotrophic environments, such as those found in SAF. Whole-genome sequencing of several strains isolated from Mars 2020 mission assembly cleanroom facilities, including the discovery of the novel species Tigheibacillus jepli, highlights the resilience and antimicrobial resistance (AMR) in clinically relevant antibiotic classes of microbes in nutrient-scarce settings. The study also redefines the taxonomic classifications within the Amphibacillaceae family, aligning genetic identities with phylogenetic data. Investigating ARG and virulence factors (VF) across these strains illuminates the microbial capability for resistance under resource-limited conditions while emphasizing the role of human-associated VF in microbial survival, informing sterilization practices and microbial management in similar oligotrophic settings beyond spacecraft assembly cleanrooms such as pharmaceutical and medical industry cleanrooms.

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.

Medical Astro-Microbiology: Current Role and Future Challenges

The second and third decades of the twenty-first century are marked by a flourishing of space technology which may soon realise human aspirations of a permanent multiplanetary presence. The prevention, control and management of infection with microbial pathogens is likely to play a key role in how successful human space aspirations will become. This review considers the emerging field of medical astro-microbiology. It examines the current evidence regarding the risk of infection during spaceflight via host susceptibility, alterations to the host's microbiome as well as exposure to other crew members and spacecraft's microbiomes. It also considers the relevance of the hygiene hypothesis in this regard. It then reviews the current evidence related to infection risk associated with microbial adaptability in spaceflight conditions. There is a particular focus on the International Space Station (ISS), as one of the only two  crewed objects in low Earth orbit. It discusses the effects of spaceflight related stressors on viruses and the infection risks associated with latent viral reactivation and increased viral shedding during spaceflight. It then examines the effects of the same stressors on bacteria, particularly in relation to changes in virulence and drug resistance. It also considers our current understanding of fungal adaptability in spaceflight. The global public health and environmental risks associated with a possible re-introduction to Earth of invasive species are also briefly discussed. Finally, this review examines the largely unknown microbiology and infection implications of celestial body habitation with an emphasis placed on Mars. Overall, this review summarises much of our current understanding of medical astro-microbiology and identifies significant knowledge gaps.

Graphical Abstract