Biofilm formation by Propionibacterium acnes is a characteristic of invasive isolates

Comprehensive lipidomic analysis of the genus Cutibacterium

Cutibacterium are part of the human skin microbiota and are opportunistic microorganisms that become pathogenic in immunodeficient states. These lipophilic bacteria willingly inhabit areas of the skin where sebaceous glands are abundant; hence, there is a need to thoroughly understand their metabolism. Lipids are no longer considered only structural elements but also serve as signaling molecules and may have antigenic properties. Lipidomics remains a major research challenge, mainly due to the diverse physicochemical properties of lipids. Therefore, this study aimed to perform a large comparative lipidomic analysis of eight representatives of the Cutibacterium genus, including four phylotypes of C. acnes and two strains of C. granulosum, C. avidum, and C. namnetense. Lipidomic analysis was performed by liquid chromatography‒mass spectrometry (LC-MS) in both positive and negative ion modes, allowing the detection of the widest range of metabolites. Fatty acid analysis by gas chromatography‒mass spectrometry (GC-MS) corroborated the lipidomic data. As a result, 128 lipids were identified, among which it was possible to select marker compounds, some of which were characteristic even of individual C. acnes phylotypes. These include phosphatidylcholine PC 30:0, sphingomyelins (SM 33:1, SM 35:1), and phosphatidylglycerol with an alkyl ether substituent PG O-32:0. Moreover, cardiolipins and fatty acid amides were identified in Cutibacterium spp. for the first time. This comparative characterization of the cutibacterial lipidome with the search for specific molecular markers reveals its diagnostic potential for clinical microbiology.

IMPORTANCE

Cutibacterium (previously Propionibacterium) represents an important part of the human skin microbiota, and its role in clinical microbiology is growing due to opportunistic infections. Lipidomics, apart from protein profiling, has the potential to prove to be a useful tool for defining the cellular fingerprint, allowing for precise differentiation of microorganisms. In this work, we presented a comparative analysis of lipids found in eight strains of the genus Cutibacterium, including a few C. acnes phylotypes. Our results are one of the first large-scale comprehensive studies regarding the bacterial lipidome, which also enabled the selection of C. acnes phylotype-specific lipid markers. The increased role of lipids not only as structural components but also as diagnostic markers or potential antigens has led to new lipid markers that can be used as diagnostic tools for clinical microbiology. We believe that the findings in our paper will appeal to a wide range of researchers.

Whole-Genome Sequencing and Phenotypic Analysis of Streptococcus equi subsp. zooepidemicus Sequence Type 147 Isolated from China

Streptococcus equi subsp. zooepidemicus (S. zooepidemicus) is one of the important zoonotic and opportunistic pathogens. In recent years, there has been growing evidence that supports the potential role of S. zooepidemicus in severe diseases in horses and other animals, including humans. Furthermore, the clinical isolation and drug resistance rates of S. zooepidemicus have been increasing yearly, leading to interest in its in-depth genomic analysis. In order to deepen the understanding of the S. zooepidemicus characteristics and genomic features, we investigated the genomic islands, mobile genetic elements, virulence and resistance genes, and phenotype of S. zooepidemicus strain ZHZ 211 (ST147), isolated from an equine farm in China. We obtained a 2.18 Mb, high-quality chromosome and found eight genomic islands. According to a comparative genomic investigation with other reference strains, ZHZ 211 has more virulence factors, like an iron uptake system, adherence, exoenzymes, and antiphagocytosis. More interestingly, ZHZ 211 has acquired a mobile genetic element (MGE), prophage Ph01, which was found to be in the chromosome of this strain and included two hyaluronidase (hyl) genes, important virulence factors of the strain. Moreover, two transposons and two virulence (virD4) genes were found to be located in the same genome island of ZHZ 211. In vitro phenotypic results showed that ZHZ 211 grows faster and is resistant to clarithromycin, enrofloxacin, and sulfonamides. The higher biofilm-forming capabilities of ZHZ 211 may provide a competitive advantage for survival in its niche. The results expand our understanding of the genomic, pathogenicity, and resistance characterization of Streptococcus zooepidemicus and facilitate further exploration of its molecular pathogenic mechanism.

Biofilm tolerance, resistance and infections increasing threat of public health

Microbial biofilms can cause chronic infection. In the clinical setting, the biofilm-related infections usually persist and reoccur; the main reason is the increased antibiotic resistance of biofilms. Traditional antibiotic therapy is not effective and might increase the threat of antibiotic resistance to public health. Therefore, it is urgent to study the tolerance and resistance mechanism of biofilms to antibiotics and find effective therapies for biofilm-related infections. The tolerance mechanism and host reaction of biofilm to antibiotics are reviewed, and bacterial biofilm related diseases formed by human pathogens are discussed thoroughly. The review also explored the role of biofilms in the development of bacterial resistance mechanisms and proposed therapeutic intervention strategies for biofilm related diseases.

Late-Onset Prosthetic Endocarditis with Paraaortic Abscess Caused by Cutibacterium acnes

Cutibacterium acnes, an integral component of the skin's customary bacterial flora, represents a Gram-positive anaerobic bacterium characterized by its low virulence. Despite its low virulence, the pathogen can cause profound-seated infections as well as infections linked to medical devices. We report a case study of a prosthesis endocarditis accompanied by a paraaortic abscess caused by C. acnes, a development occurring five years prior to composite aortic root and valve replacement. At the point of admission, the patient presented with a combination of symptoms hinting at a subacute progression, such as weight loss, chest pain, and limitations of cardiopulmonary functionality. An anaerobic pathogen, namely C. acnes, was detected in a singular blood culture vial. Since first-line imaging modalities such as echocardiography did not reveal any signs of inflammation, and in the case of a suspected diagnosis for IE, did not show high pretest probability, further diagnostic imaging such as 18F-FDG PET CT was put to use. Here, a highly elevated glucose metabolism around the aortic valve ring was detected, pointing to an inflammatory process. The patient received adjusted intravenous antibiotic therapy over a course of six weeks; he then underwent surgical therapy via re-replacement of the aortic root and valve using a composite conduit. Advanced microbiological analyses, including the amplification of PCR and valve sequencing via 16S rDNA, mainly detected one pathogen: C. acnes. Delayed onset with mild symptoms and laboratory findings is characteristic of infective endocarditis by C. acnes. Due to its high rate of complications, mortality, and morbidity, an infection should not be disregarded as contamination. Recommendations from different studies underline a combination of a positive blood culture and microbiological evidence to differentiate between contamination and true infection in the case of an infection involving C. acnes. Serial blood cultures with prolonged incubation, advanced microbiological analyses, and modified Duke criteria including second-line imaging techniques should be utilized for further evaluation.

Antimicrobial activity of thermophilin 110 against the opportunistic pathogen Cutibacterium acnes

OBJECTIVE

Thermophilin 110, a bacteriocin produced by Streptococcus thermophilus B59671, inhibited planktonic growth and biofilm formation of Cutibacterium acnes, a commensal skin bacterium associated with the inflammatory disease, acne vulgaris, and more invasive deep tissue infections.

RESULTS

Thermophilin 110 prevented planktonic growth of C. acnes at a concentration ≥ 160 AU mL-1; while concentrations ≥ 640 AU mL-1 resulted in a > 5 log reduction in viable planktonic cell counts and inhibited biofilm formation. Arabinoxylan (AX) and sodium alginate (SA) hydrogels were shown to encapsulate thermophilin 110, but as currently formulated, the encapsulated bacteriocin was unable to diffuse out of the gel and inhibit the growth of C. acnes. Hydrogels were also used to encapsulate S. thermophilus B59671, and inhibition zones were observed against C. acnes around intact SA gels, or S. thermophilus colonies that were released from AX gels.

CONCLUSIONS

Thermophilin 110 has potential as an antimicrobial for preventing C. acnes infections and further optimization of SA and AX gel formulations could allow them to serve as delivery systems for bacteriocins or bacteriocin-producing probiotics.

Oxygen Exposure and Tolerance Shapes the Cell Wall-Associated Lipids of the Skin Commensal Cutibacterium acnes

Cutibacterium acnes is one of the most abundant bacteria on the skin. Being exposed to oxygen and oxic stress, the secretion of the bacterial antioxidant protein RoxP ensures an endogenous antioxidant system for the preservation of skin health. To investigate the impact of the antioxidant RoxP on oxidation of the bacteria, wildtype and an isogenic roxp mutant were cultured in anaerobic and oxic conditions. The carbonylated status of proteins were recorded, as were the most significant modifications in a relative intensity of free fatty acids (FFA) and lipids containing fatty acids (FA), such as di- (DG) and triglycerides (TG), di- (DGDG) and sulfoquinozyldiacylglycerol (SQDG) and ceramides. Concerning the fatty acid types, it was observed that the free fatty acids contained mainly C12:0-C26:0 in hydroxy and acylated forms, the DG contained mainly C29:0-C37:0, the TG contained mainly C19:0-C33:0, and the DGDG/SQDGs contained very long fatty acids (C29:0-C37:0) demonstrating the interdependence of de novo synthesis of lipids and RoxP. The area of DGDG peaks (924.52, 929.56 and 930.58) were affected by bacterial growth conditions, with the exception of m/z 910.61. Moreover, the FFA unsaturation is wider in the SQDG species (C30:0 to C36:6) than in DG, TG or free FFA species. It could be concluded that both environmental oxidative statuses, as well as the prevalence of bacterial antioxidant systems, significantly shape the lipidome of C. acnes.

The updates and implications of cutaneous microbiota in acne

Acne is a chronic inflammatory skin disorder that profoundly impacts the quality of life of patients worldwide. While it is predominantly observed in adolescents, it can affect individuals across all age groups. Acne pathogenesis is believed to be a result of various endogenous and exogenous factors, but the precise mechanisms remain elusive. Recent studies suggest that dysbiosis of the skin microbiota significantly contributes to acne development. Specifically, Cutibacterium acnes, the dominant resident bacterial species implicated in acne, plays a critical role in disease progression. Various treatments, including topical benzoyl peroxide, systemic antibiotics, and photodynamic therapy, have demonstrated beneficial effects on the skin microbiota composition in acne patients. Of particular interest is the therapeutic potential of probiotics in acne, given its direct influence on the skin microbiota. This review summarizes the alterations in skin microbiota associated with acne, provides insight into its pathogenic role in acne, and emphasizes the potential of therapeutic interventions aimed at restoring microbial homeostasis for acne management.

Genomics of Invasive Cutibacterium acnes Isolates from Deep-Seated Infections

Cutibacterium acnes, formerly known as Propionibacterium acnes, is a commensal of the human pilosebaceous unit but also causes deep-seated infection, especially in the context of orthopedic and neurosurgical foreign materials. Interestingly, little is known about the role of specific pathogenicity factors for infection establishment. Here, 86 infection-associated and 103 commensalism-associated isolates of C. acnes were collected from three independent microbiology laboratories. We sequenced the whole genomes of the isolates for genotyping and a genome-wide association study (GWAS). We found that C. acnes subsp. acnes IA1 was the most significant phylotype among the infection isolates (48.3% of all infection isolates; odds ratio [OR] = 1.98 for infection). Among the commensal isolates, C. acnes subsp. acnes IB was the most significant phylotype (40.8% of all commensal isolates; OR = 0.5 for infection). Interestingly, C. acnes subsp. elongatum (III) was rare overall and did not occur at all in infection. The open reading frame-based GWAS (ORF-GWAS) did not show any loci with a strong signal for infection association (no P values of ≤0.05 after adjustment for multiple testing; no logarithmic OR [logOR] of ≥|2|). We concluded that all subspecies and phylotypes of C. acnes, possibly with the exception of C. acnes subsp. elongatum, are able to cause deep-seated infection given favorable conditions, most importantly related to inserted foreign material. Genetic content appears to have a small effect on the likelihood of infection establishment, and functional studies are needed to understand the individual factors contributing to deep-seated infections caused by C. acnes. IMPORTANCE Opportunistic infections emerging from human skin microbiota are of ever-increasing importance. Cutibacterium acnes, being abundant on the human skin, may cause deep-seated infections (e.g., device-associated infections). Differentiation between invasive (i.e., clinically significant) C. acnes isolates and sole contaminants is often difficult. Identification of genetic markers associated with invasiveness not only would strengthen our knowledge related to pathogenesis but also could open ways to selectively categorize invasive and contaminating isolates in the clinical microbiology lab. We show that in contrast to other opportunistic pathogens (e.g., Staphylococcus epidermidis), invasiveness is apparently a broadly distributed ability across almost all C. acnes subspecies and phylotypes. Thus, our work strongly supports an approach in which clinical significance is judged from clinical context rather than by detecting specific genetic traits.

C.acnes in the joint, is it all just a false positive?

BACKGROUND

Cutibacterium Acnes (C.acnes) has been linked to several shoulder pathologies. An alternative hypothesis suggests it only occurs in the joint secondary to previous instrumentation. Our hypothesis was patients with previous instrumentation would have C.acnes in their joint if it was in skin.

MATERIALS AND METHODS

Sixty-six patients undergoing arthroscopic shoulder surgery had biopsies taken from the affected joint at the time of surgery, along with control biopsies of subdermal fat. The extended culture results were assessed and correlated to previous intervention.

RESULTS

35% tested positive for C.acnes in their joint. 78% were male. 53% had absence of C.acnes in both skin and joint and 29% had presence in both (p = 0.0001). 15% with previous surgery had C.acnes. 53% with previous injection had C.acnes. 25% of patients with virgin joints had C.acnes. There was no statistical difference in the presence of C.acnes in the joint between those with previous instrumentation and without.

CONCLUSION

The significant factors for joint C.acnes were male sex and the presence of the bacteria in the fat. Previous instrumentation was not correlated with C.acnes in the joint. This raises the question of whether the process of biopsy itself may lead to inoculation of the joint.

A Case of Coccidioidal Meningitis With Biofilm Obstructing VP Shunt Due to Cutibacterium acnes

Herein described is a case of biofilm obstructing ventriculoperitoneal shunt due to Cutibacteirum acnes infection in a patient with coccidioidal meningitis. Cutibacterium acnes infects and obstructs cerebral shunts by the production of biofilm; however, diagnosis is usually missed by routine aerobic cultures. Obtaining anaerobic cultures routinely in patients with foreign body implants leading to central nervous system infections could prevent a missed diagnosis of this pathogen. Penicillin G is the first-line treatment.

His-Ala-Phe-Lys peptide from Burkholderia arboris possesses antifungal activity

Burkholderia arboris, which belongs to the Burkholderia cepacia complex, has been shown to possess antifungal activity against several plant fungal pathogens; however, the antifungal compounds are yet to be identified. Here, we identified the antifungal compounds produced by B. arboris using genetic and metabolomic approaches. We generated a Tn5 transposon mutation library of 3,000 B. arboris mutants and isolated three mutants with reduced antifungal activity against the plant fungal pathogen Fusarium oxysporum. Among the mutants, the M464 mutant exhibited the weakest antifungal activity. In the M464 genome, the transposon was inserted into the cobA gene, encoding uroporphyrin-III methyltransferase. Deletion of the cobA gene also resulted in reduced antifungal activity, indicating that the cobA gene contributed to the antifungal activity of B. arboris. Furthermore, a comparison of the differential metabolites between wild type B. arboris and the ∆cobA mutant showed a significantly decreased level of tetrapeptide His-Ala-Phe-Lys (Hafk) in the ∆cobA mutant. Therefore, a Hafk peptide with D-amino acid residues was synthesized and its antifungal activity was evaluated. Notably, the Hafk peptide displayed significant antifungal activity against F. oxysporum and Botrytis cinerea, two plant pathogens that cause destructive fungal diseases. Overall, a novel antifungal compound (Hafk) that can be used for the biocontrol of fungal diseases in plants was identified in B. arboris.

An avirulent Ralstonia solanacearum strain FJAT1458 outcompetes with virulent strain and induces tomato plant resistance against bacterial wilt

BACKGROUND

Bacterial wilt (BW) caused by Ralstonia solanacearum (RS) is considered as one of the most destructive plant diseases. An avirulent strain of RS, FJAT1458, is a potential biocontrol agent of BW. In this study, the mechanism of FJAT1458 against BW was evaluated.

RESULTS

FJAT1458 was tagged with the red fluorescent protein gene, and the resulting strain was named as FJAT1458-RFP. When FJAT1458-RFP and FJAT91-GFP (a virulent strain of RS labelled with the green fluorescent protein gene), were co-inoculated in potted tomato plants, the colonization of FJAT91-GFP reached an almost undetectable level at 7 days post-inoculation (dpi) in the roots and at 9 dpi in rhizosphere soil. When they were co-inoculated in a hydroponic tomato growing system, numbers of the two strains were similar at 3 dpi in the root tissues; however, FJAT91-GFP was not detected at 9 dpi while FJAT1458-RFP maintained 1.77 × 10⁵  CFU g^-1 . The inoculation of FJAT1458-RFP alone or combination with FJAT91-GFP significantly increased tomato root activity. Moreover, expression levels of the defense-related genes PR-1a, GLUA, and CHI3 in tomato roots were significantly up-regulated by FJAT1458-RFP and co-inoculation of FJAT1458-RFP and FJAT91-GFP at 5 dpi, compared to the control (water, CK) treatment. Noteworthy, expression levels of GLUA in the treatments of FJAT1458-RFP and FJAT1458-RFP + FJAT91-GFP were 12.22- and 12.05-fold higher than that in the CK at 5 dpi, respectively.

CONCLUSIONS

The results suggested that the avirulent strain FJAT1458-RFP could suppress colonization of the virulent strain in tomato roots, and induce tomato plant resistance against BW. © 2022 Society of Chemical Industry.

Microbiological Characterization of Cutibacterium acnes Strains Isolated from Prosthetic Joint Infections

Aims: This study aimed to characterize 79 Cutibacterium acnes strains isolated from prosthetic joint infections (PJIs) originated from eight European hospitals. Methods: Isolates were phylotyped according to the single-locus sequence typing (SLST) scheme. We evaluated the ability of the biofilm formation of C. acnes strains isolated from PJIs and 84 isolates recovered from healthy skin. Antibiotic susceptibility testing of planktonic and biofilm cells of PJI isolates and skin isolates was performed. Results: Most of the isolates from PJIs belonged to the SLST class H/phylotype IB (34.2%), followed by class D/phylotype IA1 (21.5%), class A/phylotype IA1 (18.9%), and class K/phylotype II (13.9%). All tested isolates were biofilm producers; no difference in biofilm formation was observed between the healthy skin group and the PJI group of strains. Planktonic and sessile cells of C. acnes remained highly susceptible to a broad spectrum of antibiotics, including beta-lactams, clindamycin, fluoroquinolones, linezolid, rifampin, and vancomycin. The minimal inhibitory concentrations (MICs) for planktonic and biofilm states coincided in most cases. However, the minimal biofilm eradication concentration (MBEC) was high for all antimicrobial drugs tested (>32 mg/L), except for rifampin (2 mg/L). Conclusions: C. acnes strains isolated from healthy skin were able to produce biofilm to the same extent as isolates recovered from PJIs. All C. acnes strains in planktonic and sessile states were susceptible to most antibiotics commonly used for PJI treatment, although rifampin was the only antimicrobial agent able to eradicate C. acnes embedded in biofilm.

Acne, Microbiome, and Probiotics: The Gut–Skin Axis

The objective of this narrative review was to check the influence of the human microbiota in the pathogenesis of acne and how the treatment with probiotics as adjuvant or alternative therapy affects the evolution of acne vulgaris. Acne is a chronic inflammatory skin disease involving the pilosebaceous units. The pathogenesis of acne is complex and multifactorial involving genetic, metabolic, and hormonal factors in which both skin and gut microbiota are implicated. Numerous studies have shown the bidirectionality between the intestinal microbiota and skin homeostasis, a communication mainly established by modifying the immune system. Increased data on the mechanisms of action regarding the relevance of Cutibacterium acnes, as well as the importance of the gut–skin axis, are becoming known. Diverse and varied in vitro studies have shown the potential beneficial effects of probiotics in this context. Clinical trials with both topical and oral probiotics are scarce, although they have shown positive results, especially with oral probiotics through the modulation of the intestinal microbiota, generating an anti-inflammatory response and restoring intestinal integrity, or through metabolic pathways involving insulin-like growth factor I (IGF-1). Given the aggressiveness of some standard acne treatments, probiotics should continue to be investigated as an alternative or adjuvant therapy.

True infection or contamination in patients with positive Cutibacterium blood cultures-a retrospective cohort study

Cutibacterium is a genus often considered a contaminant when present in blood cultures, but it can also cause severe infections, especially related to implanted foreign materials. We investigated the incidence and features of patients with true Cutibacterium infection. Patients with positive Cutibacterium blood cultures between the years 2015-2020 in southern Sweden were identified through microbiology records and medical records were studied retrospectively. Cutibacterium isolates were species determined using MALDI-TOF MS. Patients were classified as having true infection or contamination according to a definition considering both clinical and microbiological features and these groups were compared. A total of 313 episodes of positive Cutibacterium blood cultures were identified in 312 patients. Of these, 49 (16%, corresponding to an incidence of 6 cases per million inhabitants per year) were classified as true infections. The most common species was Cutibacterium acnes (87%), and the majority were elderly men with comorbidities. Patients with true Cutibacterium infection often had an unknown focus of infection (n = 21) or a focus in the respiratory tract (n = 18). We identified one episode of ventriculo-peritoneal shunt infection, three episodes of aortic stent-graft infection, and one episode of infective endocarditis. Two patients, where Cutibacterium was isolated at the site of infection, had only one positive blood culture. The finding of positive Cutibacterium blood cultures should not always be considered contamination. Definitions of true Cutibacterium bacteremia with a demand that more than one blood culture must be positive may miss true infections.

Clindamycin Efficacy for Cutibacterium acnes Shoulder Device-Related Infections

Clindamycin is an antibiotic with high bioavailability and appropriate bone diffusion, often proposed as an alternative in guidelines for C. acnes prosthetic joint infections. We aimed to evaluate the efficacy of clindamycin in the treatment of C. acnes shoulder implant joint infections (SIJI). Methods: A retrospective analysis was conducted at the University Hospital of Nice (France) between 2010 and 2019. We included patients with one shoulder implant surgical procedure and at least one C. acnes positive sample. We selected the C. acnes SIJI according to French and international recommendations. The primary endpoint was favorable outcome of C. acnes SIJI treatment after at least 1-year follow-up in the clindamycin group compared to another therapeutic group. Results: Forty-eight SIJI were identified and 33 were treated with clindamycin, among which 25 were treated with monotherapy. The median duration of clindamycin antibiotherapy was 6 weeks. The average follow-up was 45 months; one patient was lost to follow-up. Twenty-seven patients out of 33 (82%) were cured with clindamycin, compared to 9/12 (75%) with other antibiotics. The rate of favorable outcomes increased to 27/31 (87%) with clindamycin and to 9/10 (90%) for other antibiotics when no septic revision strategies were excluded (P = 1.00). Conclusions: The therapeutic strategy based on one- or two-stage revision associated with 6 weeks of clindamycin seems to be effective.

Pectolinarin Inhibits the Bacterial Biofilm Formation and Thereby Reduces Bacterial Pathogenicity

Bacterial biofilms are a growing problem as it is a major cause of nosocomial infection from urinary catheters to chronic tissue infections and provide resistance to a variety of antibiotics and the host’s immune system. The effect of pectolinarin on the biofilm formation in Enterococcus faecalis, Enterococcus faecium, Escherichia coli, Streptococcus mutans, Streptococcus sobrinus, Staphylococcus aureus, Pseudomonas aeruginosa, Cutibacterium acnes, and Porphyromonas gingivalis was studied in TSBg (tryptic soy broth supplemented with 1% glucose). Pectolinarin inhibited biofilm formation of E. faecalis (IC₅₀ = 0.39 μg/mL), E. faecium (IC₅₀ = 0.19 μg/mL), E. coli (IC₅₀ = 0.25 μg/mL), S. mutans (IC₅₀ = 1.2 μg/mL), S. sobrinus (IC₅₀ = 1.4 μg/mL), S. aureus (IC₅₀ = 0.39 μg/mL), P. aeruginosa (IC₅₀ = 0.9 μg/mL), P. acnes (IC₅₀ = 12.5 μg/mL), and P. gingivalis (IC₅₀ = 9.0 μg/mL) without inhibiting the bacterial growth. Pectolinarin also showed increased susceptibility of antibacterial activity with commercially available antibiotics including ampicillin, vancomycin, streptomycin, and oxytetracyclin against E. faecalis and E. faecium. Finally, pectolinarin dose-dependently reduced the expression of genes including cytolysin genes (cylLS, cylR2 and cylM), quorum sensing (QS) genes (fsrB, fsrC, gelE, ebpA, ebpB, acm, scm and bps), and biofilm virulence genes (esp) of E. faecalis and E. faecium. Pectolinarin reduced the bacterial biofilm formation, activated the antibacterial susceptibility, and reduced the bacterial adherence. These results suggest that bacterial biofilm formation is a good target to develop the antibacterial agents against biofilm-related infections.

The role of synovial fluid aspiration in shoulder joint infections

BACKGROUND

Joint aspiration with analysis of synovial fluid white blood cell count (WBC) and microbiological culture is a widely established aspect in the diagnosis of shoulder joint infections (SJI). In case of a two stage revision for SJI, joint aspiration before re-/implantation of a total shoulder arthroplasty (TSA) was used to rule out persistent infection for years but its value is under debate. Shoulder specific data on all aspects is rare. The current study aims to answer the following research questions: Does joint aspiration have an insufficient predictive value in the diagnosis of SJI in (1) initial workup and (2) before definite arthroplasty with polymethylmethacrylate (PMMA)-Spacer in place?

METHODS

This retrospective evaluation investigates 35 patients that were treated for SJI with a two staged implantation of a TSA after debridement and implantation of an PMMA-Spacer. Joint aspirations were performed preoperatively (PA) and before re-/implantation of the prosthesis while spacer was in place (interstage aspiration, IA). Samples were taken for microbiological culture and analysis of WBC. Sensitivity and specificity were calculated with reference to intraoperative microbiological samples. Receiver Operating Characteristic (ROC), Area-Under-Curve analysis (AUC) and calculation of the Youden index were performed to find optimum cut-off for WBC.

RESULTS

The sensitivity of microbiological cultures from PA was 58.3% and the specificity was 88.9%. The mean WBC was 27,800 leucocytes/mm³ (range 400-96,300). The maximum Youden index (0.857) was a cut-off of 2600 leucocytes/mm³ with a sensitivity of 85.7% and a specificity of 100.0%. The sensitivity and specificity of IA were 0.0% and 88.5%, respectively.

CONCLUSIONS

Preoperative aspiration is likely to miss Cutibacteria spp. and CoNS and cannot rule out infection for sure. However, we recommend it for its advantages of targeted antibiotic therapy in case of germ identification. Empiric antibiotic therapy should cover Cutibacteria and CoNS even if aspiration showed negative microbiological cultures. In contrast, the diagnostic value of interstage aspiration does not qualify for its routine use.

Silver carboxylate-doped titanium dioxide-polydimethylsiloxane coating decreases Cutibacterium acnes adherence and biofilm formation on polyether ether ketone

BACKGROUND CONTEXT

Cutibacterium acnes (C. acnes) is a gram-positive facultative anaerobe found in the deep sebaceous follicles of the skin on the shoulder and back. C. acnes has been increasingly recognized as a pathogen in spinal surgical site infection (SSI) especially in the presence of instrumentation.

PURPOSE

This study assesses whether a silver carboxylate-doped titanium dioxide-polydimethylsiloxane (TiO₂-PDMS) coating can decrease C. acnes adherence and biofilm formation on PEEK and four other commonly used spinal implant materials, stainless steel, cobalt chromium, titanium, and titanium alloy.

STUDY DESIGN

We compared the adherence of C. acnes over 24 hours between uncoated, 95:5 TiO₂ to PDMS ratio with 10× silver carboxylate coating and a 100% silver carboxylate coating on each implant material, which were uniformly saw cut and sterilized. Implants were then subjected to scanning electron microscopy (SEM) and confocal scanning laser microscopy (CSLM).

METHODS

Samples were coated using 95:5 TiO₂-PDMS 10× silver carboxylate, 100% silver carboxylate, or left uncoated. C. acnes was applied onto the samples and allowed to adhere for periods of 4, 8, 12, 16, or 20 hours. Nonadherent bacteria were then washed from the samples. These samples were then allowed to continue incubating for a total of 24 hours. SEM and confocal laser scanning microscope were used to visualize all samples for the presence of biofilm and quantification of C. acnes adherence at each time point.

RESULTS

The 95:5 TiO₂-PDMS 10× silver carboxylate coating was able to significantly decrease C. acnes adherence on PEEK after 8, 12, 16, and 20 hours of adherence. No statistical difference was found between the 95:5 TiO₂-PDMS 10× silver carboxylate coating and the 100% silver carboxylate positive control. We previously observed extensive C. acnes biofilm formation on uncoated PEEK, but none on PEEK coated with either the 95:5 TiO₂-PDMS 10× silver carboxylate or 100% Ag coating . Furthermore, no biofilm formation was observed on stainless steel, cobalt chromium, titanium, and titanium alloy coated with 95:5 TiO₂-PDMS 10× silver carboxylate or 100% Ag coating.

CONCLUSION

A 95:5 TiO₂-PDMS 10× silver carboxylate coating decreases C. acnes adhesion and prevents biofilm formation on PEEK and other common orthopedic implant materials.

CLINICAL SIGNIFICANCE

A 95:5 TiO₂-PDMS 10× silver carboxylate coating may help decrease spinal SSI due to C. acnes, especially in procedures with instrumentation.

Cutibacterium recovered from deep specimens at the time of revision shoulder arthroplasty samples has increased biofilm-forming capacity and hemolytic activity compared with Cutibacterium skin isolates from normal subjects

BACKGROUND

Biofilm formation and hemolytic activity are factors that may correlate with the virulence of Cutibacterium. We sought to compare the prevalence of these potential markers of pathogenicity between Cutibacterium recovered from deep specimens obtained at the time of surgical revision for failed shoulder arthroplasty and Cutibacterium recovered from skin samples from normal subjects.

METHODS

We compared 42 deep-tissue or explant isolates with 43 control Cutibacterium samples obtained from skin isolates from normal subjects. Subtyping information was available for all isolates. Biofilm-forming capacity was measured by inoculating a normalized amount of each isolate onto a 96-well plate. Planktonic bacteria were removed, the remaining adherent bacteria were stained with crystal violet, the crystal violet was re-solubilized in ethyl alcohol, and biofilm-forming capacity was quantitated by optical density (OD). Hemolytic activity was measured by plating a normalized amount of isolate onto agar plates. The area of the colony and the surrounding area of blood lysis were measured and reported as minimal, moderate, or severe hemolysis.

RESULTS

Biofilm-forming capacity was significantly higher in the tissue and explant samples compared with the control skin samples (OD of 0.34 ± 0.30 for deep tissue vs. 0.20 ± 0.28 for skin, P = .002). Hemolytic activity was also significantly higher in the tissue and explant samples than in the control skin samples (P < .0001). Samples with hemolytic activity had significantly higher biofilm-forming capacity compared with samples without hemolytic activity (OD of 0.27 ± 0.29 vs. 0.12 ± 0.15, P = .015). No difference in biofilm-forming capacity or hemolytic activity was found between subtypes.

CONCLUSIONS

Cutibacterium obtained from deep specimens at the time of revision shoulder arthroplasty has higher biofilm-forming capacity and hemolytic activity than Cutibacterium recovered from the skin of normal subjects. These data add support for the view that Cutibacterium harvested from deep tissues may have clinically significant virulence characteristics. The lack of correlation between these clinically relevant phenotypes and subtypes indicates that additional study is needed to identify genotypic markers that better correlate with biofilm and hemolytic activity.

Real-time monitoring of Ralstonia solanacearum infection progress in tomato and Arabidopsis using bioluminescence imaging technology

BACKGROUND

Ralstonia solanacearum, one of the most devastating bacterial plant pathogens, is the causal agent of bacterial wilt. Recently, several studies on resistance to bacterial wilt have been conducted using the Arabidopsis-R. solanacearum system. However, the progress of R. solanacearum infection in Arabidopsis is still unclear.

RESULTS

We generated a bioluminescent R. solanacearum by expressing plasmid-based luxCDABE. Expression of luxCDABE did not alter the bacterial growth and pathogenicity. The light intensity of bioluminescent R. solanacearum was linearly related to bacterial concentrations from 104 to 108 CFU·mL-1. After root inoculation with bioluminescent R. solanacearum strain, light signals in tomato and Arabidopsis were found to be transported from roots to stems via the vasculature. Quantification of light intensity from the bioluminescent strain accurately reported the difference in disease resistance between Arabidopsis wild type and resistant mutants.

CONCLUSIONS

Bioluminescent R. solanacearum strain spatially and quantitatively measured bacterial growth in tomato and Arabidopsis, and offered a tool for the high-throughput study of R. solanacearum-Arabidopsis interaction in the future.

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.

Bone marrow mesenchymal stem cells offer an immune-privileged niche to Cutibacterium acnes in case of implant-associated osteomyelitis

Considered as some of the most devastating complications, Cutibacterium acnes (C. acnes)-related osteomyelitis are among the hardest infections to diagnose and treat. Mesenchymal stem cells (MSCs) secrete number of immunomodulatory and antimicrobial soluble factors, making them an attractive treatment for bacterial infection. In this study, we examined MSCs/C. acnes interaction and analyzed the subsequent MSCs and bacteria's behaviors. Human bone marrow-derived MSCs were infected by C. acnes clinical strain harvested from non-infected bone site. Following 3 h of interaction, around 4% of bacteria were found in the intracellular compartment. Infected MSCs increased the secretion of prostaglandin E2 and indolamine 2,3 dioxygenase immunomodulatory mediators. Viable intracellular bacteria analyzed by infrared spectroscopy and atomic force microscopy revealed deep modifications in the wall features. In comparison with unchallenged bacteria, the viable intracellular bacteria showed (i) an increase in biofilm formation on orthopaedical-based materials, (ii) an increase in the invasiveness of osteoblasts and (iii) persistence in macrophage, suggesting the acquisition of virulence factors. Overall, these results showed a direct impact of C. acnes on bone marrow-derived MSCs, suggesting that blocking the C. acnes/MSCs interactions may represent an important new approach to manage chronic osteomyelitis infections. STATEMENT OF SIGNIFICANCE: The interaction of bone commensal C. acnes with bone marrow mesenchymal stem cells induces modifications in C. acnes wall characteristics. These bacteria increased (i) the biofilm formation on orthopaedical-based materials, (ii) the invasiveness of bone forming cells and (iii) the resistance to macrophage clearance through the modification of the wall nano-features and/or the increase in catalase production.

Addition of benzylpenicillin to antibiotic prophylaxis reduces deep sternal wound infection after cardiac surgery

Objectives

In Sweden, cloxacillin is recommended as the sole antibiotic prophylaxis for prevention of surgical site infections after cardiac surgery. Cutibacterium acnes, formerly Propionibacterium acnes, has been shown to be present in the surgical wound. Formerly an overlooked pathogen, there are increasing reports that C acnes can cause surgical site infections, including sternal wound infections. Cloxacillin may not be optimal for prevention of C acnes infection, therefore benzylpenicillin was added to our routine intraoperative prophylaxis in 2015. The aim of this study was to investigate the effect of benzylpenicillin on incidence of sternal wound infection.

Methods

We included 3920 consecutive patients that underwent cardiac surgery via median sternotomy at our centre from 2009 thru 2018. All patients were followed up two months postoperatively. The rate of sternal wound infection before and after 2015 were compared. Logistic multivariable analysis was used to adjust for potential confounders.

Results

The mean incidence of sternal wound infection that required surgical revision decreased from 4.7% to 1.7% after addition of benzylpenicillin (p < 0.001). Significant decrease was seen in sternal wound infections caused by Coagulase negative staphylococci, either alone (p<0.001) or concomitant with C acnes (p=0.008). Addition of benzylpenicillin remained independently associated with the reduction of sternal wound infections in the multivariable analysis (OR=0.36 CI=0.23–0.56, p<0.001).

Conclusions

Addition of benzylpenicillin was associated with a reduction in surgically treated infections and might be effective against infection caused by CoNS with and without co-infection by C acnes, although the exact underlying mechanism is unknown.

Cutibacterium acnes phylogenetic type IC and II isolated from patients with non-acne diseases exhibit high-level biofilm formation

Cutibacterium (formerly Propionibacterium) acnes is an important for not only exacerbating factor of acne vulgaris but also pathogen of surgical site infections (SSIs) in orthopedics and plastic surgery. Although biofilm-forming (BF) C. acnes are associated with intractable SSI, characteristics of these strains were still unknown. Here, we explored detailed molecular epidemiological features of BF C. acnes isolated as causative pathogen of infectious diseases. Phylogenetic types of 205 C. acnes strains isolated between 2013 and 2018 from 18 clinical departments of a university hospital in Japan were determined by single-locus sequence type (SLST). Clade H (traditional type IC) and K (type II) which are less relevant with healthy skin and acne vulgaris, were detected in 26.8% (55/205) and 16.1% (33/205) of the strains, respectively. The incidence of them was significantly higher than that of acne patients (H and K, each 2.9%, P < 0.05). In addition, SLST distribution of C. acnes strains differed by each department and isolation site. When biofilm formation was quantified, 51 strains (24.9%) were defined as high-BF strains. Notably, most high-BF strains were classified into the strains of clade H (56.4%, 31/55) and clade K (54.4%, 18/33), and these strains were frequently found in the strains isolated from patients of medical emergency center and plastic surgery. Similarly, high-BF strains were frequently found among the isolates from blood (35.7%) and catheters (30.0%), with a high proportion belonging to clades H and K. Compared to C. acnes strains isolated from acne patients, antimicrobial-resistant strains were less identified in non-acne patients. Our findings showed that pathogenicity of C. acnes strains differs by their phylogenetic types. Furthermore, we showed clade H and K have the ability of high biofilm formation and suggest that these strains have potential to become a risk factor for SSI.

Comparison of Two Cutibacterium acnes Biofilm Models

The study of biofilms in vitro is complex and often limited by technical problems due to simplified models. Here, we compared C. acnes biofilm formation, from species involved in bone and prosthesis infection, in a static model with a dynamic model. Using similar parameters, the percentage of live bacteria within the biofilm was higher in dynamic than in static approach. In both models, bacterial internalization in osteoblast-like cells, playing the role of stress factor, affected this proportion but in opposite ways: increase of live bacteria proportion in the static model (×2.04 ± 0.53) and of dead bacteria proportion (×3.5 ± 1.03) in the dynamic model. This work highlights the huge importance in the selection of a relevant biofilm model in accordance with the environmental or clinical context to effectively improve the understanding of biofilms and the development of better antibiofilm strategies.

Growth Suppression of a Gingivitis and Skin Pathogen Cutibacterium (Propionibacterium) acnes by Medicinal Plant Extracts

Propionibacterium acnes, newly reclassified as Cutibacterium acnes, is an anaerobic Gram-positive bacterium causing acne, found mainly on the skin. In addition, P. acnes is responsible for inflammation of the gums (gingivitis) and blood vessels, consequently leading to various diseases in the human body. In recent years, the evolution of microorganisms, such as P. acnes, that have become resistant to many commercial antibiotics due to the widespread use of antimicrobial drugs in the treatment of infectious diseases has emerged as a major clinical problem. We here analyzed the potential use of 37 medicinal plant extracts as plausible candidates for treating P. acnes, in terms of total phenolic and flavonoid contents, antioxidants scavenging and antimicrobial activity. Consequently, methanol extracts from 14 medicinal plants showed promising antimicrobial activities against P. acnes. In particular, as the extracts from Chrysosplenium flagelliferum F. and Thuja orientalis L. exhibited distinct antimicrobial activities in both the broth dilution and disc diffusion assay, they could be effectively used as active ingredients for preventing or treating inflammatory periodontal diseases, such as periodontitis.

Effects of Ulva sp. Extracts on the Growth, Biofilm Production, and Virulence of Skin Bacteria Microbiota: Staphylococcus aureus, Staphylococcus epidermidis, and Cutibacterium acnes Strains

Ulva sp. is known to be a source of bioactive compounds such as ulvans, but to date, their biological activity on skin commensal and/or opportunistic pathogen bacteria has not been reported. In this study, the effects of poly- and oligosaccharide fractions produced by enzyme-assisted extraction and depolymerization were investigated, for the first time in vitro, on cutaneous bacteria: Staphylococcus aureus, Staphylococcus epidermidis, and Cutibacterium acnes. At 1000 μg/mL, poly- and oligosaccharide fractions did not affect the growth of the bacteria regarding their generation time. Polysaccharide Ulva sp. fractions at 1000 μg/mL did not alter the bacterial biofilm formation, while oligosaccharide fractions modified S. epidermidis and C. acnes biofilm structures. None of the fractions at 1000 μg/mL significantly modified the cytotoxic potential of S. epidermidis and S. aureus towards keratinocytes. However, poly- and oligosaccharide fractions at 1000 μg/mL induced a decrease in the inflammatory potential of both acneic and non-acneic C. acnes strains on keratinocytes of up to 39.8%; the strongest and most significant effect occurred when the bacteria were grown in the presence of polysaccharide fractions. Our research shows that poly- and oligosaccharide Ulva sp. fractions present notable biological activities on cutaneous bacteria, especially towards C. acnes acneic and non-acneic strains, which supports their potential use for dermo-cosmetic applications.

Recurrent Cutibacterium acnes prosthetic valve endocarditis

A 29-year-old man with a history of congenital aortic stenosis and mechanical aortic valve replacement with previous Cutibacterium acnes prosthetic valve endocarditis (PVE) presented with a 2-week history of fevers and night sweats. Transoesophageal echocardiogram revealed a 0.6 cm×0.5 cm vegetation on the mechanical aortic valve. An anaerobic blood culture became positive for C. acnes 6 days after the blood cultures were obtained. He did not have any surgical intervention. He was successfully treated with 6 weeks of ceftriaxone, followed by chronic suppression with oral doxycycline. Despite its low virulence, a growing number of C. acnes PVE cases have been reported, owing to its biofilm production. When clinical suspicion is high, extending culture incubation duration beyond the standard 5 days might be helpful. Most cases are treated with surgical repair or replacement in conjunction with antibiotics, but medical therapy alone has been documented as being successful.

Development of a 3D Bioartificial Shoulder Joint Implant Mimetic of Periprosthetic Joint Infection

Post-surgical infections of the shoulder joint involving Cutibacterium acnes are difficult to diagnose and manage. Despite the devastating clinical complications and costly healthcare burden of joint infections, the scarcity of joint infection models was identified as an unmet need by the 2019 International Consensus on Orthopedic Infections. In this study, we have developed a novel 3D shoulder joint implant mimetic (S-JIM) that includes a surgical metal surface and supports a co-culture of C. acnes and patient-derived shoulder capsule fibroblasts. Our findings indicate the S-JIM can generate a near anaerobic interior environment that allows for C. acnes proliferation and elicit fibroblast cell lysis responses that are consistent with clinical reports of tissue necrosis. Using the S-JIM, we provided proof-of-concept for the use of mass spectrometry in real-time detection of C. acnes joint infections during surgery. The S-JIM is the first in vitro cell culture-based biomimetic of periprosthetic joint infection that provides a preclinical method for the rapid and reliable testing of novel anti-PJI interventions.

A Janus-Faced Bacterium: Host-Beneficial and -Detrimental Roles of Cutibacterium acnes

The bacterial species Cutibacterium acnes (formerly known as Propionibacterium acnes) is tightly associated with humans. It is the dominant bacterium in sebaceous regions of the human skin, where it preferentially colonizes the pilosebaceous unit. Multiple strains of C. acnes that belong to phylogenetically distinct types can co-exist. In this review we summarize and discuss the current knowledge of C. acnes regarding bacterial properties and traits that allow host colonization and play major roles in host-bacterium interactions and also regarding the host responses that C. acnes can trigger. These responses can have beneficial or detrimental consequences for the host. In the first part of the review, we highlight and critically review disease associations of C. acnes, in particular acne vulgaris, implant-associated infections and native infections. Here, we also analyse the current evidence for a direct or indirect role of a C. acnes-related dysbiosis in disease development or progression, i.e., reduced C. acnes strain diversity and/or the predominance of a certain phylotype. In the second part of the review, we highlight historical and recent findings demonstrating beneficial aspects of colonization by C. acnes such as colonization resistance, immune system interactions, and oxidant protection, and discuss the molecular mechanisms behind these effects. This new insight led to efforts in skin microbiota manipulation, such as the use of C. acnes strains as probiotic options to treat skin disorders.

Recurrent strokes in an occult case of recurrent Cutibacterium acnes prosthetic valve infective endocarditis: a case report

Background

Infective endocarditis (IE) is a known but uncommon cause of cardioembolic stroke and there are rare but recognized cases of IE without an inflammatory response. Cutibacterium acnes is an increasingly recognized source of invasive infections, including IE, but diagnosis is challenging due to its low virulence and fastidious nature.

Case summary

A 47-year-old man presented with a multi-focal stroke suggestive of a cardioembolic source. Outpatient transoesophageal echocardiography (TOE) was concerning for vegetation or thrombus associated with his previous mitral valve repair. He remained clinically well, with no evidence of an inflammatory response and sterile blood cultures. Computed tomography–positron emission tomography (CT-PET) corroborated the TOE findings, however, given the atypical presentation, he was treated for valvular thrombus. Following discharge, he quickly re-presented with further embolic phenomena and underwent emergency mitral valve replacement. Intraoperative findings were consistent with prosthetic valve IE (PVE) and a 6-week course of antibiotics commenced. C. acnes was identified on molecular testing. Eighteen months later, he re-presented with further neurological symptoms. Early TOE and CT–PET were consistent with IE. Blood cultures grew C. acnes after prolonged incubation. Given the absence of surgical indications, he was managed medically, and the vegetation resolved without valvular dysfunction. He continues to be followed up in an outpatient setting.

Discussion

In patients presenting with multi-territory stroke, IE should be considered despite sterile blood cultures and absent inflammatory response. C. acnes is an increasingly recognized cause of PVE in this context, often requiring surgical intervention. A high index of suspicion and collaboration with an Endocarditis Team is therefore essential to diagnose and treat.

Is Propionibacterium acnes becoming the most common bacteria in delayed infections following adolescent idiopathic scoliosis surgery?

STUDY DESIGN

Retrospective review of hospital charts.

OBJECTIVE

(1) To determine the microbiological profile of patients with surgical site infections following posterior spinal fusion surgery (PSF) for Adolescent Idiopathic scoliosis (AIS). (2) To study the treatment outcome of patients with surgical site infections (SSI) following surgery for AIS. (3) To identify the key differences in presentation and management of acute and delayed SSI following AIS surgery. There has been increasing evidence of the role of P. acnes in deep surgical site infections. Literature related to this is abundant in relation to shoulder arthroplasty; however, it is sparse in relation to spine surgery.

METHODS

We conducted a retrospective review of all patients treated for AIS during a 5-year period (2010-2014) at our institution, with a minimum of 2-year follow-up after the index surgery. Patients with a postoperative infection following their index surgery were included. Charts of AIS patients with post-op infections were reviewed for details of the index surgery, time to presentation of the infection, presenting signs/symptoms, microbiology details, details of surgical and antibiotic treatment, and outcomes.

RESULTS

Nine (2.8%) post-op infections were identified out of 315 cases for AIS during this period. Seven (2.2%) involved P. acnes. Two (0.6%) involved MSSA. The average time for cultures to show growth was 6.1 days (range 5-8 days) in P. acnes group and 2-3 days in MSSA group. Patients with P. acnes infections were treated with implant removal, debridement and antibiotics. All patients achieved solid fusion except two patients from the P. acnes group had pseudoarthrosis and had to undergo revision fusion.

CONCLUSION

Propionibacterium acnes was the single most common bacteria isolated from delayed surgical site infection following PSF in AIS patients. Optimal treatment consists of debridement, implant removal and antibiotics. These patients have high incidence of pseudoarthrosis.

LEVEL OF EVIDENCE

Level IV.

Combining Visible Light and Non-Focused Ultrasound Significantly Reduces Propionibacterium acnes Biofilm While Having Limited Effect on Host Cells

Bacterial biofilms are highly resistant to antibiotics and have been implicated in the etiology of 60%–80% of chronic microbial infections. We tested a novel combination of low intensity ultrasound and blue light against biofilm and planktonic bacteria. A laboratory prototype was built which produced both energies uniformly and coincidently from a single treatment head, impinging upon a 4.45 cm² target. To demonstrate proof of concept, Propionibacterium acnes biofilms were cultured on Millicell hanging inserts in 6-well plates. Hanging inserts with biofilms were treated in a custom exposure chamber designed to minimize unwanted ultrasound reflections. Coincident delivery of both energies demonstrated synergy over either alone, killing both stationary planktonic and biofilm cultures of P. acnes. Reduction in biofilm bacteria was dose dependent on exposure time (i.e., energy delivered). P. acnes biofilms were significantly reduced by dual energy treatment (p < 0.0001), with a >1 log₁₀ reduction after a 5 min (9 J/cm²) and >3 log₁₀ reduction after a 30 min (54 J/cm²) treatment (p < 0.05). Mammalian cells were found to be unaffected by the treatment. Both the light and the ultrasound energies are at levels previously cleared by the FDA. Therefore, this combination treatment could be used as a safe, efficacious method to treat biofilm related syndromes.

Cutibacterium acnes Central Nervous System Catheter Infection Induces Long-Term Changes in the Cerebrospinal Fluid Proteome

Cutibacterium acnes is the third most common cause of cerebrospinal fluid (CSF) shunt infection and is likely underdiagnosed due to the difficulty in culturing this pathogen. Shunt infections lead to grave neurologic morbidity for patients especially when there is a delay in diagnosis. Currently, the gold standard for identifying CSF shunt infections is microbiologic culture. However, C. acnes infection often results in falsely negative cultures; therefore, new diagnostic methods are needed. To investigate potential CSF biomarkers of C. acnes CSF shunt infection we adapted a rat model of CSF catheter infection to C. acnes. We found elevated levels of interleukin-1β (IL-1β), IL-6, chemokine ligand 2, and IL-10 in the CSF and brain tissues of animals implanted with C. acnes-infected catheters compared to sterile controls at day 1 postinfection. This coincided with modest increases in neutrophils in the CSF and, to a greater extent, in the brain tissues of animals with C. acnes infection, which closely mirrors the clinical findings in patients with C. acnes shunt infection. Mass spectrometry revealed that the CSF proteome is altered during C. acnes shunt infection and changes over the course of disease, typified at day 1 postinfection by an acute-phase and pathogen neutralization response evolving to a response consistent with wound resolution at day 28 compared to a sterile catheter placement. Collectively, these results demonstrate that it is possible to distinguish C. acnes infection from sterile postoperative inflammation and that CSF proteins could be useful in a diagnostic strategy for this pathogen that is difficult to diagnose.

Growth in a biofilm sensitizes Cutibacterium acnes to nanosecond pulsed electric fields

The Gram-positive anaerobic bacterium Cutibacterium acnes (C. acnes) is a commensal of the human skin, but also an opportunistic pathogen that contributes to the pathophysiology of the skin disease acne vulgaris. C. acnes can form biofilms; cells in biofilms are more resilient to antimicrobial stresses. Acne therapeutic options such as topical or systemic antimicrobial treatments often show incomplete responses. In this study we measured the efficacy of nanosecond pulsed electric fields (nsPEF), a new promising cell and tissue ablation technology, to inactivate C. acnes. Our results show that all tested nsPEF doses (250 to 2000 pulses, 280 ns pulses, 28 kV/cm, 5 Hz; 0.5 to 4 kJ/ml) failed to inactivate planktonic C. acnes and that pretreatment with lysozyme, a naturally occurring cell-wall-weakening enzyme, increased C. acnes vulnerability to nsPEF. Surprisingly, growth in a biofilm appears to sensitize C. acnes to nsPEF-induced stress, as C. acnes biofilm-derived cells showed increased cell death after nsPEF treatments that did not affect planktonic cells. Biofilm inactivation by nsPEF was confirmed by treating intact biofilms grown on glass coverslips with an indium oxide conductive layer. Altogether our results show that, contrary to other antimicrobial agents, nsPEF kill more efficiently bacteria in biofilms than planktonic cells.

Low-Grade Infection and Implant Failure Following Spinal Instrumentation: A Prospective Comparative Study

BACKGROUND

Spinal instrumentation can be associated with complications, including implant loosening. Hitherto, implant loosening has mainly been attributed to mechanical overload.

OBJECTIVE

To examine the role of low-grade infections as the cause of implant failure in suspected aseptic implant loosening following spinal instrumentation.

METHODS

A prospective single center observational study was performed. All patients who had revision surgery following spinal instrumentation between August 2015 and February 2018 were screened. Patients with revision surgery due to screw loosening on the computed tomograhy scan constituted the study group. Patients in which the screws where not loosened but removal was performed for other reasons formed the comparison group. Intraoperative swabs were taken and sonication was performed with the explanted material. Results of microbiological cultivation were analyzed.

RESULTS

A total of 59 patients were included in the study group and 34 in the comparison group. In the study group in 42.4% of the cultures a bacterium was detected, while in the comparison group only in 17.6%. 84%, and 83.3% of these germs were detected by sonication in the study and comparison group, respectively. The rate of positive cultures was significantly higher in the study group compared to the comparison group (P = .001). The most frequent bacterium cultivated in both groups was Propionibacterium acnes, followed by Staphylococcus species.

CONCLUSION

For patients with screw loosening a high level of suspicion for a low-grade infection should be raised. Cultures should be performed from the sonication fluid of the explanted devices in all patients with symptomatic screw loosening.

Interaction of implant infection-related commensal bacteria with mesenchymal stem cells: a comparison between Cutibacterium acnes and Staphylococcus aureus

Staphylococcus aureus and Cutibacterium acnes are involved in several tissue infections and can encounter mesenchymal stem cells (MSCs) during their role in tissue regenerative process. C. acnes and S. aureus internalization by three types of MSCs derived from bone marrow, dental pulp and Wharton's jelly; and bacterial biofilm production were compared. Internalization rates ranged between 1.7-6.3% and 0.8-2.7% for C. acnes and S. aureus, respectively. While C. acnes strains exhibited limited cytotoxic effect on MSCs, S. aureus were more virulent with marked effect starting after only 3 h of interaction. Both bacteria were able to produce biofilms with respectively aggregated and monolayered structures for C. acnes and S. aureus. The increase in C. acnes capacity to develop biofilm following MSCs' internalization was not linked to the significant increase in number of live bacteria, except for bone marrow-MSCs/C. acnes CIP 53.117 with 79% live bacteria compared to the 36% before internalization. On the other hand, internalization of S. aureus had no impact on its ability to form biofilms composed mainly of living bacteria. The present study underlined the complexity of MSCs-bacteria cross-interaction and brought insights into understanding the MSCs behavior in response to bacterial infection in tissue regeneration context.

Biofilms by bacterial human pathogens: Clinical relevance - development, composition and regulation - therapeutical strategies

Notably, bacterial biofilm formation is increasingly recognized as a passive virulence factor facilitating many infectious disease processes. In this review we will focus on bacterial biofilms formed by human pathogens and highlight their relevance for diverse diseases. Along biofilm composition and regulation emphasis is laid on the intensively studied biofilms of Vibrio cholerae, Pseudomonas aeruginosa and Staphylococcus spp., which are commonly used as biofilm model organisms and therefore contribute to our general understanding of bacterial biofilm (patho-)physiology. Finally, therapeutical intervention strategies targeting biofilms will be discussed.

Biofilm Formation among Stenotrophomonas maltophilia Isolates Has Clinical Relevance: The ANSELM Prospective Multicenter Study

The ability to form biofilms is a recognized trait of Stenotrophomonas maltophilia, but the extent of its clinical relevance is still unclear. The present multicenter prospective study (ANSELM) aims at investigating the association between biofilm formation and clinical outcomes of S. maltophilia infections. One hundred and nine isolates were collected from various geographical origins and stratified according to their clinical relevance. Biofilm formation was evaluated by the microtiter plate assay and correlated with microbiological and clinical data from the associated strains. Antibiotic susceptibility of the planktonic cells was tested by the disk diffusion technique, while antibiotic activity against mature biofilms was spectrophotometrically assessed. Most strains (91.7%) were able to form biofilm, although bloodborne strains produced biofilm amounts significantly higher than strains causing hospital- rather than community-acquired infections, and those recognized as “definite” pathogens. Biofilm formation efficiency was positively correlated with mechanical ventilation (p = 0.032), whereas a negative relationship was found with antibiotic resistance (r² = 0.107; p < 0.001), specifically in the case of the pathogenic strains. Mature S. maltophilia biofilms were markedly more resistant (up to 128 times) to cotrimoxazole and levofloxacin compared with their planktonic counterparts, especially in the case of bloodborne strains. Our findings indicate that biofilm formation by S. maltophilia is obviously a contributing factor in the pathogenesis of infections, especially in deep ones, thus warranting additional studies with larger cohort of patients and isolates.

Noninflammatory comedones have greater diversity in microbiome and are more prone to biofilm formation than inflammatory lesions of acne vulgaris

BACKGROUND

The ability of Cutibacterium acnes strains to form biofilms has been correlated with their virulence.

OBJECTIVE

This study examined biofilm and skin microbiota in acne patients in order to understand their role in the development of acne lesions.

METHODS

Thin sections of punch biopsy specimens of (i) uninflamed comedones, (ii) inflammatory lesions, and (iii) uninvolved adjacent skin of acne patients were examined. Epiflourescence and confocal laser scanning microscopy were used for biofilm detection, and pyrosequencing with taxonomic classification of 16s rRNA gene amplicons was used for microbiota analysis.

RESULTS

Of the 39 skin specimens from patients with mild-moderate acne (n = 13) that were studied, nine (23%) contained biofilm. Among these specimens, biofilm was most frequently detected in comedones (55.6%) and less frequently in inflammatory papules (22.2%) and uninvolved skin (22.2%). Comedones demonstrated the highest mean alpha diversity of all the lesion subtypes. The relative abundance of Staphylococcus was significantly higher in comedones (11.400% ± 12.242%) compared to uninvolved skin (0.073% ± 0.185%, P = 0.024).

CONCLUSIONS

The microenvironment of the comedone differs from that of inflammatory lesions and unaffected skin. The increased frequency of biofilm in comedones may account for the lack of host inflammatory response to these lesions.

The In Vitro Efficacy of Doxycycline over Vancomycin and Penicillin in the Elimination of Cutibacterium Acnes Biofilm

Cutibacterium acnes (formerly Propionibacterium acnes) is a significant pathogen in periprosthetic joint infections (PJIs) in total shoulder arthroplasty. Poor outcomes seen in PJIs are due to the established C. acnes bacterial biofilms. The prolonged nature of C. acnes infections makes them difficult to treat with antibiotics. The goal of this study was to determine the relative efficacy of vancomycin compared with penicillin and doxycycline against planktonic and mature biofilms. Clinical isolates from PJI patients as well as a laboratory strain of C. acnes were tested. Planktonic minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) were obtained using modified clinical laboratory standard index assays. Biofilm MICs and MBCs were also obtained. The MIC was determined for both using the PrestoBlue viability stain. The MBC was determined using differential reinforced clostridial medium agar plates for colony-forming unit analysis. Using the PrestoBlue viability reagent, the planktonic MIC values for vancomycin were significantly higher than doxycycline. Across 10 strains of C. acnes, all three antibiotics had decreased efficacy when comparing planktonic and biofilm cultures. Although effective antibiotic doses ranged from 1 to 1,000 μg/mL, only doxycycline achieved inhibitory and bactericidal concentrations in all tested strains. Penicillin failed to achieve the minimum biofilm inhibitory concentration (MBIC) in 60% of tested strains, whereas vancomycin failed in 80% of tested strains. Penicillin, doxycycline, and vancomycin have similar abilities in inhibiting C. acnes growth planktonically. The MBIC for doxycycline was within the clinical dosing range, suggesting C. acnes biofilm offers minimal tolerance to these antibiotics. The MBIC for penicillin was within clinical dosing ranges in only 60% of trials, suggesting the relative tolerance of C. acnes to penicillin. The minimum biofilm bactericidal concentration (MBBC) of doxycycline showed efficacy in 90% of trials, whereas penicillin and vancomycin achieved MBBC in 15% of samples.

Staphylococcus epidermidis and Cutibacterium acnes: Two Major Sentinels of Skin Microbiota and the Influence of Cosmetics

Dermatological and cosmetics fields have recently started to focus on the human skin microbiome and microbiota, since the skin microbiota is involved in the health and dysbiosis of the skin ecosystem. Amongst the skin microorganisms, Staphylococcus epidermidis and Cutibacterium acnes, both commensal bacteria, appear as skin microbiota sentinels. These sentinels have a key role in the skin ecosystem since they protect and prevent microbiota disequilibrium by fighting pathogens and participate in skin homeostasis through the production of beneficial bacterial metabolites. These bacteria adapt to changing skin microenvironments and can shift to being opportunistic pathogens, forming biofilms, and thus are involved in common skin dysbiosis, such as acne or atopic dermatitis. The current evaluation methods for cosmetic active ingredient development are discussed targeting these two sentinels with their assets and limits. After identification of these objectives, research of the active cosmetic ingredients and products that maintain and promote these commensal metabolisms, or reduce their pathogenic forms, are now the new challenges of the skincare industry in correlation with the constant development of adapted evaluation methods.

Incidence of Cutibacterium acnes from shoulder arthroplasties in Asians: ethnic differences should be considered

BACKGROUND

Most studies on Cutibacterium acnes in shoulder surgery have been conducted in the Western population, and studies on Asians are rare. We evaluated the incidence and risk factors of C acnes in shoulder arthroplasty in Asians.

METHODS

We retrospectively analyzed 154 patients between January 2017 and May 2019 who underwent shoulder arthroplasty. Swabs were taken after skin preparation from the skin surface of the anterior acromion, axilla, and joint fluid to study the incidence of C acnes. Before skin preparation we also collected swabs from the anterior acromion, axilla, and thigh from 59 of the 154 patients.

RESULTS

Eight of 154 patients after and 6 of 59 patients before skin preparation were positive for C acnes. C acnes were found in 2 patients at the anterior acromion and in 6 at the synovial joint after skin preparation and in 1 patient at the axilla, in 5 at the anterior acromion, and in 3 at the thigh before preparation. History of steroid injection and number of steroid injections were significantly associated with C acnes isolation (P = .039 and P = .006, respectively), whereas age, sex, body mass index, shoulder surgery history, hypertension, diabetes, and cerebrovascular disease were not, as were serum inflammatory markers, including white blood cell count, C-reactive protein level, and erythrocyte sedimentation rate.

CONCLUSION

A total of 5.2% of the patients after skin preparation and 10.2% of patients before skin preparation were found to be positive for C acnes. The incidence of C acnes in patients who underwent shoulder arthroplasties in Asia was low and, thus, ethnic differences should be considered for C acnes. The history and number of steroid injections were associated with isolation of C acnes.

Cutibacterium acnes Biofilm Study during Bone Cells Interaction

Cutibacterium acnes is an opportunistic pathogen involved in Bone and Prosthesis Infections (BPIs). In this study, we observed the behavior of commensal and BPI C. acnes strains in the bone environment through bacterial internalization by osteoblast-like cells and biofilm formation. For the commensal strains, less than 1% of the bacteria were internalized; among them, about 32.7 ± 3.9% persisted intracellularly for up to 48 h. C. acnes infection seems to have no cytotoxic effect on bone cells as detected by LDH assay. Interestingly, commensal C. acnes showed a significant increase in biofilm formation after osteoblast-like internalization for 50% of the strains (2.8-fold increase). This phenomenon is exacerbated on a titanium support, a material used for medical devices. For the BPI clinical strains, we did not notice any increase in biofilm formation after internalization despite a similar internalization rate by the osteoblast-like cells. Furthermore, fluorescent staining revealed more live bacteria within the biofilm after osteoblast-like cell interaction, for all strains (BPIs and commensal). The genomic study did not reveal any link between their clinical origin and phylotype. In conclusion, we have shown for the first time the possible influence of internalization by osteoblast-like cells on commensal C. acnes.

Early adherence and biofilm formation of Cutibacterium acnes (formerly Propionibacterium acnes) on spinal implant materials

BACKGROUND

Cutibacterium acnes (C. acnes) is associated with infection following shoulder and spine surgery due to follicular pore concentrations in these anatomic regions. It has been established that it can form biofilms on surgical implant materials, which may contribute to its role in perioperative infection, but its behavior of early colonization on those materials is not yet well understood.

PURPOSE

The purpose of this study was to evaluate the time to adherence and subsequent biofilm formation of C. acnes in the first 24 hours on implant materials commonly used in spinal surgery.

STUDY DESIGN

We compared the colonization and behavior of C. acnes over time when applied to five commonly used spine implant materials - polyether ether ketone (PEEK), cobalt chromium (CC), stainless steel (SS), titanium, and titanium alloy.

METHODS

C. acnes was applied onto the samples of PEEK, CC, SS, titanium, and titanium alloy, and allowed to adhere for periods of 4, 8, 12, 16, and 20 hours. Nonadherent bacteria were then washed from the samples. These samples were then allowed to continue incubating for a total 24 hours. Scanning electron microscopy and confocal laser scanning microscopy were used to visualize all samples for the presence and quantification of C. acnes adherence at each time period. Subsequent transition to biofilm formation on these samples was assessed via scanning electron microscopy at each time period.

RESULTS

The PEEK specimens exhibited the highest amount of surface biological burden in the first 24 hours compared with the other materials, which displayed little or no adherence. Rapid biofilm formation first observed at 8 hours of allowed adhesion on PEEK, whereas no significant biofilm formation was seen on the other materials during the observed time period.

CONCLUSIONS

Although C. acnes is known to have a slow proliferation rate, the results of this investigation demonstrate that it can rapidly adhere to and form a biofilm on PEEK. These data suggest that the use of PEEK implants placed during spinal surgery may facilitate early intraoperative colonization, and subsequent infection, compared with metallic implants.

CLINICAL SIGNIFICANCE

The findings of this study suggest that PEEK may prove to be problematic as a choice of implant material in cases were C. acnes infection is a possibility.

Factors predictive of Cutibacterium periprosthetic shoulder infections: a retrospective study of 342 prosthetic revisions

BACKGROUND

Cutibacterium are the most common cause of periprosthetic shoulder infections, as defined by ≥2 deep cultures. Established Cutibacterium periprosthetic infections cannot be resolved without prosthesis removal. However, the decision for implant removal must be made from an assessment of infection risk before the results of intraoperative cultures are finalized. We hypothesized that the risk for a Cutibacterium infection is associated with characteristics that are available at the time of revision arthroplasty.

METHODS

In a retrospective review of 342 patients having prosthetic revisions between 2006 and 2018 for whom definitive deep culture results were available, we used univariate and multivariate analyses to compare the preoperative and intraoperative characteristics of 101 revisions with Cutibacterium periprosthetic infections to the characteristics of 241 concurrent revisions not meeting the definition of infection.

RESULTS

Patients with definite Cutibacterium periprosthetic infections were younger (59 ± 10 vs. 64 ± 12, P < .001), were more likely to be male (91% vs. 44%, P < .001), were more likely to have had their index procedure performed for primary osteoarthritis (54% vs. 39%, P = .007), were more likely to be taking testosterone supplements (8% vs. 2%, P = .02), had lower American Society of Anesthesiologists scores (1.9 ± 0.7 vs. 2.3 ± 0.7, P < .001), and had lower body mass indices (29 ± 5 vs. 31 ± 7, P = .005). Patients with definite Cutibacterium periprosthetic infections also had significantly higher preoperative loads of Cutibacterium on their unprepared skin surface (1.7 ± 0.9 vs. 0.4 ± 0.8, P < .001) and were more likely to have the surgical finding of synovitis (41% vs. 16%, P < .001).

CONCLUSIONS

The risk of definite Cutibacterium periprosthetic infections is associated with observations that can be made before or at the time of revision arthroplasty.