Skin Commensal Bacteria Research Articles

Impact of Neonatal Intensive Care Unit Admission on Bacterial Colonization of Donated Human Milk

Unpasteurized human donor milk typically contains a variety of bacteria. The impact of neonatal intensive care unit (NICU) admission of the donor's infant and duration of lactation on bacterial contamination of human milk is unknown. Research aim: This study aimed (a) to describe the frequency/concentration of skin commensal bacteria and pathogens in unpasteurized human donor milk and (b) to assess the impact of NICU admission and (c) the duration of milk expression on bacterial colonization of donated milk. The authors conducted a retrospective cohort study of human milk donated to the Rogers Hixon Ontario Human Milk Bank from January 2013 to June 2014. Milk samples from each donor were cultured every 2 weeks. The study included 198 donor mothers, of whom 63 had infants admitted to the NICU. Of 1,289 cultures obtained, 1,031 (80%) had detectable bacterial growth and 363 (28%) yielded bacterial growth in excess of 107 cfu/L, a local threshold for allowable bacteria prior to pasteurization. The mean (standard deviation) donation period per donor was 13.0 (7.5) weeks. Milk from mothers with NICU exposure had significantly higher concentrations of commensals, but not pathogens, at every time period compared with other mothers. For every 1-month increase in donation from all donors, the odds ratio of presence of any commensal in milk increased by 1.13 (95% confidence interval [1.03, 1.23]) and any pathogen by 1.31 (95% confidence interval [1.20, 1.43]). Commensal bacteria were more abundant in donor milk expressed from mothers exposed to neonatal intensive care. Bacterial contamination increased over the milk donation period.

Air sampling to assess potential generation of aerosolized viable bacteria during flow cytometric analysis of unfixed bacterial suspensions.

This study investigated aerosolized viable bacteria in a university research laboratory during operation of an acoustic-assisted flow cytometer for antimicrobial susceptibility testing by sampling room air before, during and after flow cytometer use. The aim was to assess the risk associated with use of an acoustic-assisted flow cytometer analyzing unfixed bacterial suspensions. Air sampling in a nearby clinical laboratory was conducted during the same period to provide context for the existing background of microorganisms that would be detected in the air. The three species of bacteria undergoing analysis by flow cytometer in the research laboratory were Klebsiella pneumoniae, Burkholderia thailandensis and Streptococcus pneumoniae. None of these was detected from multiple 1000 L air samples acquired in the research laboratory environment. The main cultured bacteria in both locations were skin commensal and environmental bacteria, presumed to have been disturbed or dispersed in laboratory air by personnel movements during routine laboratory activities. The concentrations of bacteria detected in research laboratory air samples were reduced after interventional cleaning measures were introduced and were lower than those in the diagnostic clinical microbiology laboratory. We conclude that our flow cytometric analyses of unfixed suspensions of K. pneumoniae, B. thailandensis and S. pneumoniae do not pose a risk to cytometer operators or other personnel in the laboratory but caution against extrapolation of our results to other bacteria and/or different flow cytometric experimental procedures.

Phylogenomic Based Comparative Studies on Indian and American Commensal Staphylococcus epidermidis Isolates.

Staphylococcus epidermidis is a prominent commensal member of human skin microbiome and an emerging nosocomial pathogen, making it a good model organism to provide genomic insights, correlating its transition between commensalism and pathogenicity. While there are numerous studies to understand differences in commensal and pathogenic isolates, systematic efforts to understand variation and evolutionary pattern in multiple strains isolated from healthy individuals are lacking. In the present study, using whole genome sequencing and analysis, we report presence of diverse lineages of S. epidermidis isolates in healthy individuals from two geographically diverse locations of India and North America. Further, there is distinct pattern in the distribution of candidate gene(s) for pathogenicity and commensalism. The pattern is not only reflected in lineages but is also based on geographic origin of the isolates. This is evident by the fact that North American isolates under this study are more genomically dynamic and harbor pathogenicity markers in higher frequency. On the other hand, isolates of Indian origin are less genomically dynamic, harbor less pathogenicity marker genes and possess two unique antimicrobial peptide gene clusters. This study provides a basis to understand the nature of selection pressure in a key human skin commensal bacterium with implications in its management as an opportunistic pathogen.

Air sampling to assess potential generation of aerosolized viable bacteria during flow cytometric analysis of unfixed bacterial suspensions

This study investigated aerosolized viable bacteria in a university research laboratory during operation of an acoustic-assisted flow cytometer for antimicrobial susceptibility testing by sampling room air before, during and after flow cytometer use. The aim was to assess the risk associated with use of an acoustic-assisted flow cytometer analyzing unfixed bacterial suspensions. Air sampling in a nearby clinical laboratory was conducted during the same period to provide context for the existing background of microorganisms that would be detected in the air. The three species of bacteria undergoing analysis by flow cytometer in the research laboratory were Klebsiella pneumoniae, Burkholderia thailandensis and Streptococcus pneumoniae. None of these was detected from multiple 1000 L air samples acquired in the research laboratory environment. The main cultured bacteria in both locations were skin commensal and environmental bacteria, presumed to have been disturbed or dispersed in laboratory air by personnel movements during routine laboratory activities. The concentrations of bacteria detected in research laboratory air samples were reduced after interventional cleaning measures were introduced and were lower than those in the diagnostic clinical microbiology laboratory. We conclude that our flow cytometric analyses of unfixed suspensions of K. pneumoniae, B. thailandensis and S. pneumoniae do not pose a risk to cytometer operators or other personnel in the laboratory but caution against extrapolation of our results to other bacteria and/or different flow cytometric experimental procedures.

Cutibacterium acnes prosthetic joint infection: Diagnosis and treatment.

Cutibacterium acnes is a commensal skin bacterium, regularly implicated in prosthetic joint infection, particularly of the shoulder. Diagnosis has been improved by progress in bacteriological techniques: longer culture time, liquid medium culture, MALDI-TOF mass spectrography, and universal 16S rRNA PCR, associated by some authors to sonication of ablated implants. C. acnes pathogenicity involves many virulence factors, notably including biofilm formation. C. acnes may lead to infection that is clinically evident or, frequently, relatively asymptomatic. C. acnes is an anaerobic Gram-positive bacterium, susceptible to many antibiotics that are regularly used in bone and joint infection: beta-lactams, quinolone, rifampicin and clindamycin. It shows increasing resistance to clindamycin and natural resistance to metronidazole. Treatment is medical and surgical, associating synovectomy or complete 1- or 2-step revision depending on time to treatment, and antibiotic therapy. Antibiotic therapy is typically for three months with an initial 2-6 weeks' intravenous phase. Prognosis is generally favorable with well-conducted treatment. Late discovery of positive samples after apparently aseptic implant change is an at-risk situation, usually managed by antibiotic therapy, but with late initiation and hence increased risk of failure. Adverse secondary progression requires repeat revision under good conditions.

Air sampling during flow cytometric analysis of unfixed bacterial suspensions; a risk assessment

This study investigated airborne bacteria in a university research laboratory during operation of an acoustic-enhanced flow cytometer for antimicrobial susceptibility testing by sampling room air before, during and after flow cytometer use. Air sampling in a nearby clinical laboratory was conducted for comparison during the same period. The three species of bacteria undergoing analysis by flow cytometry were Klebsiella pneumoniae, Burkholderia thailandensis and Streptococcus pneumoniae. These species were not detected from multiple 1000 L air samples acquired in the confined research laboratory environment. The main cultured bacteria were skin commensal and environmental bacteria, presumed to have been disturbed or dispersed in laboratory air by personnel movements during routine laboratory operation. The concentrations of bacteria detected in air samples were reduced after laboratory cleaning measures were introduced and were lower than those in a diagnostic clinical microbiology laboratory located nearby on the same biomedical campus.

ID3024 Polymeric nanoparticles display bactericidal effect and selective fermentation for the treatment of acne vulgaris

The use of antibiotics in the treatment of acne in specific group (pregnant women) of patients can lead to serious complications. We have previously demonstrated that the nanoparticles made of block copolymers of poly (ethylene glycol) and poly(e-caprolactone) can inhibit the growth of Propionibacterium acnes (P. acnes), a bacterium highly associated with the progress of acne vulgaris in the human skin [Polymers 2016; 8, 321]. To reduce the amount of antibiotics used in the treatment of skin acne, we have further demonstrated that a bacterium in the human skin microbiome can utilize PEG-based polymers to produce various short-chain fatty acids (SCFAs) which suppressed the growth of P. acnes. PEG-based polymers were chosen as selective fermentation initiators which specifically induced the fermentation of the skin commensal bacterium but not P. acnes. Interestingly, PEG-based polymers can efficiently suppress the growth of P. acnes. An acne ex vivo explant was established by using acne biopsies collected from patients with acne vulgaris at the early and middle stages. The levels of pro-inflammatory interleukin (IL)-8 cytokine in early- and middle-staged acnes were significantly higher than those in healthy skins. Incubation of acne ex vivo explants with sucrose remarkably reduced the level of IL-8 and the number of P. acnes. Results from mouse studies revealed that PEG-based polymer functions as antibiotic adjuvants which can considerably reduce the effective doses of clindamycin, a clinically-used acne antibiotic

612 Specific strains of S. epidermidis suppress UV-induced skin tumor formation by production of 6-N-hydroxyaminopurine, a DNA synthesis inhibitor

Evidence continues to accumulate that specific members of the skin microbiome impart important elements to cutaneous defense. In this study, we sought to understand the mechanism of action of specific strains of Staphylococcus epidermidis that we previously screened from healthy human skin based on capability to kill Staphylococcus aureus. Remarkably, these strains were shown to abundantly produce 6-N-hydroxyaminopurine (6-HAP), a molecule not previously known to be produced in nature. Given the structural similarity of this small molecule to adenine, we tested if it could inhibit DNA synthesis in vitro and noted that 6-HAP was a potent competitive inhibitor of Klenow DNA polymerase by competing with adenosine for DNA extension. 6-HAP also potently inhibited BrdU incorporation and the growth of several tumor lines, such as Pam212 SCC, L5178 lymphoma and B16F10 melanoma. In contrast, 6-HAP did not affect growth of normal keratinocytes (NHEK), indicating selective anti-proliferative activity. The selective resistance of NHEKs to 6-HAP was due to expression of Mitochondrial Amidoxime Reducing Components (mARCs), an enzyme that catalyzes reduction of N-hydroxylated compounds, since NHEKs treated with siRNA for mARC1 lost resistance to 6-HAP. We next explored activity of 6-HAP in several mouse tumor models and observed that I.V. injection with 6-HAP was non-toxic but suppressed tumor size of B16F10 melanoma by 60% (P < 0.01) compared to vehicle control. Furthermore, the skin of SHK-1 hairless mice was treated with DMBA and low-dose UV-B (180mJ/cm2) and then colonized by a S. epidermidis strain producing 6-HAP. These mice had 54% lesser tumor incidence at 10 wks and 26% of the total tumor number at 12 wks (P < 0.001) compared to mice colonized by a similar abundance of control strain. These findings show that some skin commensal bacteria may provide selective resistance against neoplasia.

636 Commensal skin bacteria inhibit the capacity of Staphylococcus aureus to induce epidermal serine protease activity in atopic dermatitis

636 Commensal skin bacteria inhibit the capacity of Staphylococcus aureus to induce epidermal serine protease activity in atopic dermatitis

Microbiome precision editing: Using PEG as a selective fermentation initiator against methicillin-resistant Staphylococcus aureus.

Recent creation of a Unified Microbiome Initiative (UMI) has the aim of understanding how microbes interact with each other and with us. When pathogenic Staphylococcus aureus infects the skin, the interplay between S. aureus and skin commensal bacteria occurs. Our previous data revealed that skin commensal bacteria can mediate fermentation against the growth of USA300, a community-acquired methicillin-resistant S. aureus MRSA. By using a fermentation process with solid media on a small scale, we define poly(ethylene glycol) dimethacrylate (PEG-DMA) as a selective fermentation initiator which can specifically intensify the probiotic ability of skin commensal Staphylococcus epidermidis bacteria. At least five short-chain fatty acids including acetic, butyric and propionic acids with anti-USA300 activities are produced by PEG-DMA fermentation of S. epidermidis. Furthermore, the S. epidermidis-laden PEG-DMA hydrogels effectively decolonized USA300 in skin wounds in mice. The PEG-DMA and its derivatives may become novel biomaterials to specifically tailor the human skin microbiome against invading pathogens.

Staphylococcus lugdunensis cutaneous infection with sporotrichoid distribution

We report the occurrence of Staphylococcus lugdunensis cutaneous infection with sporotrichoid distribution of the left lower limb of a 60-year-old man. Recent studies have confirmed that Staphylococcus lugdunensis is a significant pathogen in causing skin and soft tissue infections that usually manifest in abscesses, surgical wound infections, and cellulitis. It used to be considered a skin commensal bacteria, but if unrecognized it can lead to fulminant endocarditis, meningitis, skin abscesses, peritonitis, and spondylodiscitis.

Establishing Tolerance to Commensal Skin Bacteria: Timing Is Everything.

Commensal bacteria live intimately and in constant dialogue with skin immune cells. Regulating our immune response to these bacteria is critical for skin homeostasis. Using a new murine model to track Staphylococcus epidermidis-specific T cells, we found that colonization during neonatal but not adult life led to S.epidermidis-specific immune tolerance. This tolerance protected against skin inflammation and was mediated by a wave of regulatory T cells entering neonatal skin. These findings provide new insight into how we establish a healthy symbiosis with commensal microbes and highlight avenues for future research to identify novel therapies for inflammatory skin disease.

The Skin as a Route of Allergen Exposure: Part II. Allergens and Role of the Microbiome and Environmental Exposures.

This second part of the article aims to highlight recent contributions in the literature that enhance our understanding of the cutaneous immune response to allergen. Several properties of allergens facilitate barrier disruption and cutaneous sensitization. There is a strong epidemiologic relationship between the microbiome, both the gut and skin, and atopic dermatitis (AD). The mechanisms connecting these two entities remain enigmatic; however, recent murine models show that commensal skin bacteria play an active role in supporting skin barrier homeostasis and defense against microbial penetration. Likewise, the association between the lack of colonization with Staph species and AD development suggests a potentially functional role for these organisms in regulating the skin barrier and response to environmental allergens. In undisrupted skin, evidence suggests that the cutaneous route may promote allergen tolerance. Properties of environmental allergens and commensal bacteria add to the complex landscape of skin immunity. Further investigation is needed to elucidate how these properties regulate the cutaneous immune response to allergen.

Induction of Pulmonary Granuloma Formation by Propionibacterium acnes Is Regulated by MyD88 and Nox2.

Sarcoidosis is characterized by noncaseating granulomas with an unknown cause that present primarily in the lung. Propionibacterium acnes, an immunogenic commensal skin bacterium involved in acne vulgaris, has been implicated as a possible causative agent of sarcoidosis. Here, we demonstrate that a viable strain of P. acnes isolated from a patient with sarcoidosis and instilled intratracheally into wild-type mice can generate pulmonary granulomas similar to those observed in patients with sarcoidosis. The formation of these granulomas is dependent on the administration of viable P. acnes. We also found that mice deficient in the innate immunity adapter protein MyD88 had a greater number and a larger area of granuloma lesions compared with wild-type mice administered P. acnes. Early after P. acnes administration, wild-type mice produced proinflammatory mediators and recruited neutrophils into the lung, a response that is dependent on MyD88. In addition, there was an increase in granuloma number and size after instillation with P. acnes in mice deficient in CybB, a critical component of nicotinamide adenine dinucleotide phosphate oxidase required for the production of reactive oxygen species in the phagosome. Myd88-/- or Cybb-/- mice both had increased persistence of P. acnes in the lung, together with enhanced granuloma formation. In conclusion, we have generated a mouse model of early granuloma formation induced by a clinically relevant strain of P. acnes isolated from a patient with sarcoidosis, and, using this model, we have shown that a deficiency in MyD88 or CybB is associated with impaired bacterial clearance and increased granuloma formation in the lung.

The Short-Chain Fatty Acid Sodium Butyrate Functions as a Regulator of the Skin Immune System

There is evidence that gut commensal microbes affect the mucosal immune system via expansion of regulatory T cells (Tregs) in the colon. This is mediated via short-chain fatty acids, bacterial metabolites generated during fiber fermentation, which include butyrate, propionate, and acetate. We postulated that short-chain fatty acids produced by commensal skin bacteria may also activate resident skin Tregs, the activity of which is diminished in certain inflammatory dermatoses. Sodium butyrate (SB) either injected subcutaneously or applied topically onto the ears of hapten-sensitized mice significantly reduced the contact hypersensitivity reaction. This effect was histone acetylation-dependent because suppression was abrogated by anacardic acid, a histone acetyltransferase inhibitor. The genes encoding for the Treg-specific transcription factor foxp3 and for IL-10 were up-regulated upon treatment with sodium butyrate, as determined by quantitative real-time reverse transcription-PCR. Immunofluorescence analysis showed enhanced numbers of Foxp3-positive cells in sodium butyrate-treated skin. Additionally, CD4+CD25- nonregulatory human T cells exerted suppressive features upon incubation with sodium butyrate. This indicates that Tregs can be induced by short-chain fatty acids, suggesting (i) that resident skin microbes may prevent exaggerated inflammatory responses by exerting a down-regulatory function and thereby maintaining a stable state under physiologic conditions and (ii) that short-chain fatty acids may be used therapeutically to mitigate inflammatory skin reactions.

Analysis of the effectiveness of Sodium Hypochlorite decontamination of cadaveric human tissues at retrieval.

Bacterial contamination of tissues retrieved from cadaveric donors is a common feature worldwide, and every tissue bank, albeit using different methods, conducts decontamination to guarantee safe tissues suitable for clinical use. The effectiveness of the methods used to eradicate pathogens differs. In order to reduce the tissue bioburden at retrieval, we have introduced a new method involving rinsing tissues in a sodium hypochlorite solution. To test its effectiveness we analyzed two comparable groups of tissues: Group A: 1881 tissues, all rinsed with isotonic saline solution after retrieval, and Group B: 1968 tissues immersed in an isotonic saline solution containing sodium hypochlorite (final concentration 0.1 %) for different lengths of time and subsequently rinsed with isotonic saline. The rinsing solution of each tissue was then sampled for microbiological cultures in both groups. The resultant overall contamination rate was 40.5 % for Group A and 6.7 % for Group B, with an 82.8 % difference in the reduction of contamination between the two groups. This was especially the case for commensal skin bacteria in musculoskeletal tissue, which accounted for over half the overall contamination. Our data highlighted that decontamination with sodium hypochlorite was helpful in reducing the bacterial bioburden in tissues retrieved from cadaveric donors.

Different Propionibacterium acnes Phylotypes Induce Distinct Immune Responses and Express Unique Surface and Secreted Proteomes

Propionibacterium acnes is a skin commensal bacterium that contributes to the development of acne vulgaris and other infections. Recent work revealed that P.acnes clinical isolates can be classified into distinct phylotypes, several of which have associations with healthy skin or acne. We sought to determine if these phylotypes induce different immunological responses and express protein factors that may contribute to their disease associations. We found that acne-associated P.acnes phylotypes induced 2- to 3-fold higher levels of IFN-γ and IL-17 in peripheral blood mononuclear cells compared with healthy phylotypes. On the other hand, P.acnes phylotypes associated with healthy skin induced 2- to 4-fold higher levels of IL-10. Comparative proteomic analysis of P.acnes phylotypes revealed a differential expression of several proteins, including an adhesion protein that was expressed at least 10-fold higher in acne-associated phylotypes and a cell surface hydrolase expressed in all phylotypes except those associated with healthy skin. Taken together, our data provide insight into how specific P.acnes phylotypes influence immune responses and the pathogenesis of acne.

Structure Elucidation Of Ursene And Oleanene Derivatives From Castanea Sativa (European Chestnut) That Inhibit Staphylococcus Aureus Virulence And Pathogenesis

Alarming trends in the spread of antibiotic resistance among pathogens, including Staphylococcus aureus, have pushed mankind toward what has been coined as the “post-antibiotic era.” Therefore, an indirect therapy is proposed, quorum quenching. Investigation of botanical folk medicines used in the Mediterranean for the treatment of skin and soft tissue infections identified Castanea sativa (European Chestnut) for its potential antibacterial activity. This work demonstrates the quorum sensing inhibitory activity of a methanolic C. sativa leaf extract against all S. aureus accessory gene regulator (agr) alleles (IC50 1.56 – 25 µg mL-1). The extract is nontoxic to human keratinocytes and does not inhibit the growth of S. aureus or skin commensal bacteria. The bioactivity guided fractionation identified several compounds with ursene (1) and oleanene (2) backbones as the active compounds. The isolation and complete structure elucidation was performed using LC FT-MS and a suite of 1D and 2D NMR experiments.

The mPEG-PCL Copolymer for Selective Fermentation of Staphylococcus lugdunensis Against Candida parapsilosis in the Human Microbiome.

Many human skin diseases, such as seborrheic dermatitis, potentially occur due to the over-growth of fungi. It remains a challenge to develop fungicides with a lower risk of generating resistant fungi and non-specifically killing commensal microbes. Our probiotic approaches using a selective fermentation initiator of skin commensal bacteria, fermentation metabolites or their derivatives provide novel therapeutics to rein in the over-growth of fungi. Staphylococcus lugdunensis (S. lugdunensis) bacteria and Candida parapsilosis (C. parapsilosis) fungi coexist in the scalp microbiome. S. lugdunensis interfered with the growth of C. parapsilosis via fermentation. A methoxy poly(ethylene glycol)-b-poly(ε-caprolactone) (mPEG-PCL) copolymer functioned as a selective fermentation initiator of S. lugdunensis, selectively triggering the S. lugdunensis fermentation to produce acetic and isovaleric acids. The acetic acid and its pro-drug diethyleneglycol diacetate (Ac-DEG-Ac) effectively suppressed the growth of C. parapsilosis in vitro and impeded the fungal expansion in the human dandruff. We demonstrate for the first time that S. lugdunensis is a skin probiotic bacterium that can exploit mPEG-PCL to yield fungicidal short-chain fatty acids (SCFAs). The concept of bacterial fermentation as a part of skin immunity to re-balance the dysbiotic microbiome warrants a novel avenue for studying the probiotic function of the skin microbiome in promoting health.

Tolerating Staphylococcus Epidermidis

Why do some bacteria on the skin elicit inflammation and an immune reaction while others don't? Investigators hypothesized that the adaptive immune system plays a role in mediating tolerance to skin commensal bacteria. They developed a model system to study antigen-specific responses to the skin commensal bacterium Staphylococcus epidermidis . To allow for standardization of relative antigen expression, they …