Antimicrobial resistance poses a significant challenge for infection control, requiring the development of accurate and high-throughput diagnostic techniques. We expanded and optimized an existing DNA microarray platform for the molecular characterization of vancomycin-resistant Enterococcus (VRE) by incorporating resistance, virulence, species-specific, and typing markers. The enhanced microarray allows for the simultaneous analysis of up to 96 strains, providing detailed genetic profiles of clinical isolates. VRE strains from Romania and Bavaria, Germany, were analyzed, and the results were compared to those obtained using traditional typing methods, such as multilocus sequence typing (MLST). Next-generation sequencing (NGS) was used in parallel to validate the microarray findings and explore genomic relationships. The microarray revealed considerable genetic diversity and potential epidemiological linkages among isolates. A novel hexadecimal-based nomenclature system was introduced for standardized and scalable strain classification. Comparative analysis demonstrated that the array profiles provided greater discriminatory power and practical resolution than MLST. Receiver operating characteristic (ROC) curve analysis of 187 target genes in 220 isolates gave diagnostic sensitivity and specificity of 100%. This integrated approach offers a cost-effective, rapid, and adaptable global VRE surveillance and infection control tool. It provides a practical alternative to conventional typing systems and facilitates early detection of outbreaks and emerging clones.

Citrobacter freundii is a nosocomial pathogen increasingly associated with multidrug resistance and hospital outbreaks. Despite its growing clinical relevance, no standardized core genome multilocus sequence typing (cgMLST) scheme has been available for high-resolution epidemiological analyses. Here, we developed and validated a robust cgMLST scheme for C. freundii comprising 3,250 target loci based on a curated data set of 825 globally distributed genomes representing extensive sequence type and geographic diversity. Validation against published outbreak data sets from hospitals in Finland and Belgium, as well as environmental and patient isolates from two German university hospitals, proved that the scheme possesses high target gene coverage (median 99.6%) and strong discriminatory power. Additionally, we developed a combined cgMLST scheme for C. freundii, C. portucalensis, C. braakii, and C. europaeus, based on 2,307 shared target loci and target gene coverages of ≥99.7%. This scheme proved suitable for cross-species outbreak analysis. Our analyses revealed environments, such as sinks, shower drains, and toilets, as likely reservoirs where Citrobacter species may persist in hospital settings. These findings suggest that environmental sources could play a significant role in transmission events involving patients, while allele-based cluster analyses indicated that direct patient-to-patient transmission was rare. Given the increasing prevalence of multidrug-resistant (MDR) Citrobacter strains, the level of discrimination achieved by these newly developed cgMLST schemes underscores the importance of accurate species identification and environmental screening in understanding the transmission dynamics of opportunistic healthcare-associated pathogens. Ultimately, this makes them valuable tools for genomic surveillance, outbreak investigation, and infection prevention. IMPORTANCE:Accurate identification and high-resolution typing of multidrug-resistant bacteria are essential for understanding their transmission dynamics in hospitals, particularly in light of the global spread of resistant strains and the role of environmental reservoirs. The newly developed cgMLST schemes presented here provide standardized, portable tools for both local and global scientific and clinical communities to conduct fine-scale genomic epidemiology across four Citrobacter species. These schemes support detailed outbreak reconstruction, source attribution, and cross-hospital comparisons, capabilities that are critical in an era of increasing antimicrobial resistance and international patient movement. By enabling consistent, species-specific surveillance and comparative analyses, cgMLST enhances infection control and public health responses, facilitating early detection and targeted intervention.

OBJECTIVES: To evaluate whether vancomycin-resistant Enterococcus faecium (VRE) blood culture isolates reflect the broader hospital VRE epidemiology and to investigate the population structure of VRE in the context of rising bloodstream infection (BSI) rates at our institution. METHODS: Whole genome sequencing (WGS) of VRE BSI isolates and all VRE first annual patient isolates (screening and clinical specimens) at a university tertiary care hospital from 2018 to 2021 was performed. Isolates were analysed using multi-locus sequence typing (MLST), core-genome (cg) MLST, and cluster analysis based on pairwise allelic differences. RESULTS: From 2018 to 2021, 128 patients had VRE BSI and 218 had VSE (vancomycin-susceptible Enterococcus faecium) BSI, however, VRE became dominant in 2021 (2018: 53 vs. 21; 2021: 42 vs. 48). Concurrently, VRE incidence at our institution rose from 2.7 to 4.3 per 1000 patient days. WGS was performed for 125/128 VRE BSI isolates (97.7%) and 1175/1534 first annual isolates (76.6%). Distribution of complex types (CTs) within VRE blood culture isolates and first annual isolates was generally similar: ST80/CT1065, ST117/CT5130, ST1299/CT1903 and ST117/CT71 were detected most often both in BSI and among first annual isolates (26.5% vs. 26.6%; 14.4% vs. 10.8%; 12.0% vs. 13.5%; 10.4% vs. 13.3%, respectively). Eleven large clusters comprising 10 or more isolates were identified within the representative isolate cohort (a curated dataset including all sequenced blood culture isolates and non-redundant first annual patient isolates), consistent with clonal expansion of successful lineages, likely driven at least in part by in-hospital transmission events, but also possibly by repeated introductions of circulating clones, contributing to the rise in VRE incidence. CONCLUSIONS: Performing WGS on both VRE blood culture and first annual isolates points to several outbreaks as the reason behind the increase in VRE BSI rate. Our results demonstrate that sequencing VRE blood culture isolates alone roughly reflects the distribution of all VRE CTs, making it a pragmatic and resource-efficient approach for obtaining valuable information about the epidemiology of VRE within a hospital. CLINICAL TRIAL: Not applicable.

Introduction Vancomycin-resistant Enterococcus faecium (VREfm) isolates of sequence type (ST)1299 were described recently in south-eastern German hospitals and rapidly expanded from local to cross-border level. Aim We describe the spread of the novel VREfm strain ST1299/vanA on a genetic, geographical and temporal level during the first 5 years after its detection. Methods At University Hospital Regensburg (UHoR), routine VREfm surveillance is whole genome sequencing-based (≥ 1 VREfm per van-genotype, patient and year). In this observational cohort study, we analysed one VREfm ST1299 isolate from our database (2016–2022) per patient and year. Isolates were added from the Hospital of the Merciful Brothers Regensburg (MBR), the National Reference Centre for Staphylococci and Enterococci (NRC), and clinical isolates from Austria. Results We identified 635 VREfm ST1299 isolates (100% vanA), including 504 from Regensburg, and 113 blood cultures. ST1299 isolates were first detected in 2018 simultaneously in Regensburg (n = 2) and southern Bavaria (n = 2), with local (UHoR) and regional numbers increasing rapidly from 2020, shifting to national scale in the same year. Genome data, analysed by cgMLST, showed a predominance of ST1299/CT1903 (315/504 isolates, 62.5%) and ST1299/CT3109 (127/504 isolates, 25.2%) isolates from Regensburg. By 2021, ST1299/CT1903 reached Upper Austria causing hospital outbreaks (n = 5). Phylogeny analysis suggests common ancestors with VREfm ST80, ST18 and ST17. Conclusion Since their emergence in 2018, two highly transmissible subtypes of ST1299/vanA reached national, then cross-border scale. The observed outbreak tendency may explain the rapid and successful spread and the high clonality in our collection.

Background: Prevention of toilet-to-patient transmission of multidrug-resistant Pseudomonas aeruginosa (MDR PA) poses management-related challenges at many bone marrow transplant units (BMTUs). Aim: To conduct a longitudinal retrospective analysis of the toilet-to-patient transmission rate for MDR PA under existing infection control (IC) measures at a BMTU with persistent MDR PA toilet colonization. Methods: The local IC bundle comprised: (1) patient education regarding IC; (2) routine patient screening; (3) toilet flushing volume of 9 L; (4) bromination of toilet water tanks, and (5) toilet decontamination using hydrogen peroxide. Toilet water was sampled periodically between 2016 and 2021 (minimum every three months: 26 intervals). Upon MDR PA detection, disinfection and re-sampling were repeated until <= 3 cfu/100 mL was reached. Whole-genome sequencing (WGS) was performed retrospectively on all available MDR PA isolates (90 out of 117 positive environmental samples, 10 out of 14 patients, including nine nosocomial). Findings: WGS of patient isolates identified six sequence types (STs), with ST235/CT1352/FIM-1 and ST309/CT3049/no-carbapenemase being predominant (three isolates each). Environmental sampling consistently identified MDR PA ST235 (65.5% ST235/CT1352/FIM-1), showing low genetic diversity (difference of <= 29 alleles by core-genome multi-locus sequence typing (cgMLST)). This indicates that direct toilet-to-patient transmission was infrequent although MDR PA was widespread (detection on 79 occasions, detection in every toilet). Only three MDR PA patient isolates can be attributed to the ST235/CT1352/FIM-1 toilet MRD PA population over six years. Conclusion: Stringent targeted toilet disinfection can reduce the potential risk for MDR PA acquisition by patients. (c) 2024 The Authors. Published by Elsevier Ltd on behalf of The Healthcare Infection Society. This is an open access article under the CC BY -NC -ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Background: Surfaces in close proximity to patients within hospitals may cause healthcare-associated infections. These surfaces are repositories for pathogens facilitating their transmission among staff and patients. Regular cleaning and disinfection of these surfaces provides only a temporary elimination of pathogens with inevitable recontamination. Antimicrobial coatings (AMCs) of such surfaces may additionally reduce the risk of pathogen transmissions. Aim: To evaluate the efficacy of a standard and a novel photodynamic AMC, even at very low light intensities, in a field study conducted in two ICUs at our university hospital. Methods: The microbial burden was determined on three coatings: standard photodynamic AMC (A), a novel photodynamic AMC (B), and an inactive AMC as control (C). The control coating C was identical to standard coating A, but it contained no photosensitizer. During a three-month period, 699 samples were collected from identical surfaces using eSwab and were analysed (cfu/cm2). Findings: Mean values of all surfaces covered with control coating (C) showed a microbial burden of 5.5 + 14.8 cfu/cm2. Photodynamic AMC showed significantly lower mean value of 1.6 + 4.6 cfu/cm2 (coating A; P < 0.001) and 2.7 + 9.6 (coating B; P < 0.001). When considering a benchmark of 2.5 cfu/cm2, the relative risk for higher microbial counts was reduced by 52% (coating A) or 40% (coating B), respectively. Conclusion: Both photodynamic AMCs offer a substantial, permanent risk reduction of microbial counts on near-patient surfaces in ICUs with low light intensities.

Today, there is a continuous worldwide battle against antimicrobial resistance (AMR) and that includes vancomycin-resistant enterococci (VRE). Methods that can adequately and quickly detect transmission chains in outbreaks are needed to trace and manage this problem fast and cost-effectively. In this study, DNA-microarray-based technology was developed for this purpose. It commenced with the bioinformatic design of specific oligonucleotide sequences to obtain amplification primers and hybridization probes. Microarrays were manufactured using these synthesized oligonucleotides. A highly parallel and stringent labeling and hybridization protocol was developed and employed using isolated genomic DNA from previously sequenced (referenced) clinical VRE strains for optimal sensitivity and specificity. Microarray results showed the detection of virulence, resistance, and species-specific genes in the VRE strains. Theoretical predictions of the microarray results were also derived from the sequences of the same VRE strain and were compared to array results while optimizing protocols until the microarray result and theoretical predictions were a match. The study concludes that DNA microarray technology can be used to quickly, accurately, and economically detect specifically and massively parallel target genes in enterococci.

Background In most of Europe and especially in Germany, there is currently a concerning rise in the number of hospital-acquired infections due to vancomycin-resistant Enterococcus faecium (VREfm). Therefore, there is a need to improve our understanding of the way VREfm spreads in hospitals. In this study, we investigated the molecular epidemiology of VREfm isolates from the first appearance at our university hospital in 2004 until 2010. There is only very scarce information about the molecular epidemiology of VREfm from this early time in Germany. Methods Our analysis includes all available first VREfm isolates of each patient at our tertiary care center collected during the years 2004–2010. If available, additional consecutive VREfm isolates from some patients were analyzed. We used multilocus sequence typing (MLST) and core genome multilocus sequence typing (cgMLST) for the analysis and description of nosocomial transmission pathways as well as the detection of outbreaks. Results VREfm isolates from 158 patients and 76 additional subsequent patient isolates were included in the analysis. Until 2006, detections of VREfm remained singular cases, followed by a peak in the number of VREfm cases in 2007 and 2008 with a subsequent decline to baseline in 2010. MLST and cgMLST analysis show significant changes in the dominant sequence types (STs) and complex types (CTs) over the study period, with ST192 and ST17 being responsible for the peak in VREfm cases in 2007 and 2008. The four largest clusters detected during the study period are comprised of these two STs. Cluster analysis shows a focus on specific wards and departments for each cluster. In the early years of this study (2004–2006), all analyzed VREfm stemmed from clinical specimens, whereas since 2007, approximately half of the VREfm were detected by screening. Of the 234 VREfm isolates analyzed, 96% had a vanB and only 4% had a vanA resistance genotype. Conclusions This retrospective study contributes significant knowledge about regional VREfm epidemiology from this early VREfm period in Germany. One remarkable finding is the striking dominance of vanB -positive VREfm isolates over the entire study period, which is in contrast with countrywide data. Analysis of cgMLST shows the transition from sporadic VRE cases at our institution to a sharp increase in VRE numbers triggered by oligoclonal spread and specific outbreak clusters with the dominance of ST192 and ST17.

The colonization of skin with pathogenic, partially antibiotic‐resistant bacteria is frequently a severe problem in dermatological therapies. For instance, skin colonization with Staphylococcus aureus is even a disease‐promoting factor in atopic dermatitis. The photodynamic inactivation (PDI) of bacteria could be a new antibacterial procedure. Upon irradiation with visible light, a special photosensitizer exclusively generates singlet oxygen. This reactive oxygen species kills bacteria via oxidation independent of species or strain and their antibiotic resistance profile causing no bacterial resistance on its part.

The photodynamic inactivation (PDI) uses molecules (photosensitizers) that absorb visible light (385-450 nm) energy, transfer it to adjacent molecular oxygen and thereby generating the biocidal singlet oxygen and other reactive oxygen species in situ. Efficacy of PDI was tested against Listeria monocytogenes and Salmonella enterica in three ways. Firstly, by adding the photosensitizer to bacterial suspensions. Secondly, bacteria were placed on inanimate surfaces and then sprayed with a photosensitizer suspension. Thirdly, bacteria were placed on coated inanimate surfaces, where the photosensitizer was permanently fixed in this coating (antimicrobial coating, AMC). Experiments were performed without and with soiling (albumin, sheep erythrocytes). In suspension, PDI reduced the number of viable Listeria monocytogenes and Salmonella enterica by more than 6 Log CFU/mL within seconds of light exposure. Photosensitizer spray suspension reduced the bacterial burden on surfaces with up to about 6 Log CFU/mL (5 s light exposure). PDI, even in the presence of high soiling, achieved a reduction of up to 5.1 +/- 1.2 Log CFU/mL. The AMC showed a bacterial reduction that decreased from 5.1 to 0.7 Log CFU/mL with increasing soiling. Depending on the soiling and the respective bacteria, the spray suspension or AMC achieved a bacterial reduction on the running conveyor belt demonstrator ranging from 2.9 to 5.3 or 0.5 to 4.5 Log CFU/mL, respectively. PDI used visible light, phenalene-1-one and curcumin photosensitizers, and oxygen from ambient air to reduce the bioburden on typical surfaces in food processing. The AMC acts slower than the spray suspension but enables a permanent, self-sanitizing effect.

The photodynamic inactivation (PDI) uses molecules (photosensitizers) that absorb visible light energy, transfer it to adjacent molecular oxygen and thereby generating the biocidal singlet oxygen in situ . PDI was tested against Listeria monocytogenes and Salmonella enterica in suspensions, on inoculated surfaces using spray suspensions and antimicrobial coatings (AMC), without and with soiling. In suspension, PDI reduced the number of viable Listeria monocytogenes and Salmonella enterica with more than 6 log 10 steps within seconds or minutes of light exposure. The use of a photosensitizer spray suspension and five second light exposure reduced the bacterial burden on surfaces with up to about 6 log 10 steps, which was still more than 3 log 10 steps in the presence of high soiling. The AMC showed a bacterial reduction in a range of 0.7 to 5.1 log 10 steps depending on the soiling concentration using 10 minutes light exposure. PDI was also effective on a running conveyor belt demonstrator.PDI uses visible light, harmless photosensitizers and oxygen from ambient air to reduce effectively the bioburden on typical surfaces in food processing. The AMC acts a little slower but enables a permanent, self-sanitizing effect. Noteworthy, PDI is a modality that does not trigger resistance in bacteria.

The antibiotic crisis increasingly threatens the health systems world-wide. Especially as there is an innovation gap in the development of novel antibiotics, treatment options for bacterial infections become fewer. The photodynamic inactivation (PDI) of bacteria appears to be a potent, new technology that may support the treatment of colonized or infected skin. In photodynamic inactivation, a dye – called photosensitizer – absorbs light and generates reactive singlet oxygen. This singlet oxygen is then capable of killing bacteria independent of species or strain and their antibiotic resistance profile. In order to provide a practical application for the skin surface, the photosensitizer was included in an aqueous hydrogel (photodynamically active hydrogel). The efficacy of this gel was initially tested on an inanimate surface and then on the human skin ex vivo . NBTC staining and TUNEL assays were carried out on skin biopsies to investigate potential harmful effects of the surface PDI to the underlying skin cells. The photosensitizer in the gel sufficiently produced singlet oxygen while showing only little photobleaching. On inanimate surfaces as well as on the human skin, the number of viable bacteria was reduced by over or nearly up to 4 log10 steps, equal to 99.99% reduction or even more. Furthermore, histological staining showed no harmful effects of the gel towards the tissue. The application of this hydrogel represents a valuable method in decolonizing human skin including the potential to act against superficial skin infections. The presented results are promising and should lead to further investigation in a clinical study to check the effectivity of the photodynamically active hydrogel on patients.

Photodynamic inactivation of microorganisms (PDI) finds use in a variety of applications. Several studies report on substances enhancing or inhibiting PDI. In this study, we analyzed the inhibitory potential of ubiquitous salts like CaCl2 and MgCl2 on PDI against Staphylococcus aureus and Pseudomonas aeruginosa cells using five cationic photosensitizers methylene blue, TMPyP, SAPYR, FLASH-02a and FLASH-06a. TMPyP changed its molecular structure when exposed to MgCl2, most likely due to complexation. CaCl2 substantially affected singlet oxygen generation by MB at small concentrations. Elevated concentrations of CaCl2 and MgCl2 impaired PDI up to a total loss of bacterial reduction, whereas CaCl2 is more detrimental for PDI than MgCl2. Binding assays cannot not explain the differences of PDI efficacy. It is assumed that divalent ions tightly bind to bacterial cells hindering close binding of the photosensitizers to the membranes. Consequently, photosensitizer binding might be shifted to outer compartments like teichoic acids in Gram-positives or outer sugar moieties of the LPS in Gram-negatives, attenuating the oxidative damage of susceptible cellular structures. In conclusion, CaCl2 and MgCl2 have an inhibitory potential at different phases in PDI. These effects should be considered when using PDI in an environment that contains such salts like in tap water or different fields of food industry.

ABSTRACT Many studies show that photodynamic inactivation (PDI) is a powerful tool for the fight against pathogenic, multiresistant bacteria and the closing of hygiene gaps. However, PDI studies have been frequently performed under standardized in vitro conditions comprising artificial laboratory settings. Under real‐life conditions, however, PDI encounters substances like ions, proteins, amino acids and fatty acids, potentially hampering the efficacy of PDI to an unpredictable extent. Thus, we investigated PDI with the phenalene‐1‐one‐based photosensitizer SAPYR against Escherichia coli and Staphylococcus aureus in the presence of calcium or magnesium ions, which are ubiquitous in potential fields of PDI applications like in tap water or on tissue surfaces. The addition of citrate should elucidate the potential as a chelator. The results indicate that PDI is clearly affected by such ubiquitous ions depending on its concentration and the type of bacteria. The application of citrate enhanced PDI, especially for Gram‐negative bacteria at certain ionic concentrations ( e.g. CaCl 2 or MgCl 2 : 7.5 to 75 mmol L −1 ). Citrate also improved PDI efficacy in tap water (especially for Gram‐negative bacteria) and synthetic sweat solution (especially for Gram‐positive bacteria). In conclusion, the use of chelating agents like citrate may facilitate the application of PDI under real‐life conditions.

Photodynamic inactivation (PDI) of pathogenic bacteria is a promising technology in different applications. Thereby, a photosensitizer (PS) absorbs visible light and transfers the energy to oxygen yielding reactive oxygen species (ROS). The produced ROS are then capable of killing microorganisms via oxidative damage of cellular constituents. Among other PS, some flavins are capable of producing ROS and cationic flavins are already successfully applied in PDI. When PDI is used for example on tap water, PS like flavins will encounter various ions and other small organic molecules which might hamper the efficacy of PDI. Thus, the impact of carbonate and phosphate ions on PDI using two different cationic flavins (FLASH-02a, FLASH-06a) was investigated using Staphylococcus aureus and Pseudomonas aeruginosa as model organisms. Both were inactivated in vitro at a low light exposure of 0.72 J cm - 2 . Upon irradiation, FLASH-02a reacts to single substances in the presence of carbonate or phosphate, whereas the photochemical reaction for FLASH-06a was more unspecific. DPBF-assays indicated that carbonate and phosphate ions decreased the generation of singlet oxygen of both flavins. Both microorganisms could be easily inactivated by at least one PS with up to 6 log 10 steps of cell counts in low ion concentrations. Using the constant radiation exposure of 0.72 J cm -2 , the inactivation efficacy decreased somewhat at medium ion concentrations but reached almost zero for high ion concentrations. Depending on the application of PDI, the presence of carbonate and phosphate ions is unavoidable. Only upon light irradiation such ions may attack the PS molecule and reduce the efficacy of PDI. Our results indicate concentrations for carbonate and phosphate, in which PDI can still lead to efficient reduction of bacterial cells when using flavin based PS.

Background Near-patient surfaces are recognized as a source for hospital-acquired infections. Such surfaces act as reservoirs for microbial contamination by which pathogens can be transmitted from colonized or infected patients to susceptible patients. Routine disinfection of surfaces only results in a temporal elimination of pathogens, and recontamination inevitably occurs shortly between disinfections. Aim A novel antimicrobial coating based on photodynamics was tested under laboratory conditions and subsequently in a field study in two hospitals under real-life conditions. Methods Identical surfaces received a photodynamic or control coating. Bacterial counts [colony-forming units (cfu)/cm2) were assessed regularly for up to 6 months. Findings The laboratory study revealed a mean reduction of several human pathogens of up to 4.0 ± 0.3 log10. The field study in near-patient environments demonstrated mean bacterial values of 6.1 ± 24.7 cfu/cm2 on all control coatings. Photodynamic coatings showed a significantly lower mean value of 1.9 ± 2.8 cfu/cm2 (P<0.001). When considering benchmarks of 2.5 cfu/cm2 or 5 cfu/cm2, the relative risk for high bacterial counts on surfaces was reduced by 48% (odds ratio 0.38, P<0.001) or 67% (odds ratio 0.27, P<0.001), respectively. Conclusion Photodynamic coatings provide a significant and lasting reduction of bacterial counts on near-patient surfaces, particularly for high bacterial loads, in addition to routine hygiene. The promising results of this proof-of-concept study highlight the need for further studies to determine how this novel technology is correlated with the frequency of hospital-acquired infections.

Background To prevent infections that arise from the skin surface it is necessary to decolonize human skin prior to any proposed treatment or surgical intervention. Photodynamic inactivation of bacteria (PIB) uses cationic photosensitizers that attach to the surface of bacteria, generate reactive oxygen species on light irradiation and thereby kill bacteria via oxidative mechanisms. Objectives To evaluate the potential and the safety of PIB for decolonization of bacteria from skin. Methods PIB with the new photosensitizer SAPYR [2-((4-pyridinyl)methyl)-1H-phenalen-1-one chloride] was initially tested against different bacterial species in vitro. Then, ex vivo porcine skin samples were used as a model for decolonization of different bacteria species. The numbers of viable bacteria were quantified and the mitochondrial activity of skin cells was histologically analysed (using nitroblue tetrazolium chloride, NBTC). The same procedure was performed for human skin and meticillin-resistant Staphylococcus aureus (MRSA). Results The in vitro studies showed a 5 log(10) reduction of all tested bacterial species. On ex vivo porcine skin samples, PIB reduced the viability of all tested bacterial species by at least 3 log(10) steps. On human skin samples ex vivo, PIB reduced the number of viable MRSA by maximal 4 center dot 4 log(10) steps (1000 mu mol L-1 SAPYR, incubation time 10 min, 60 J cm(-2)). NBTC staining showed normal mitochondrial activity in skin cells after all PIB modalities. Conclusions The results of this study show that PIB can effectively and safely kill bacteria like MRSA on the skin surface and might have the potential of skin decolonization in vivo.

One of the sources of infections in hospitals is the presence of potentially harmful bacteria on the skin surface (carriage) of a patient without the development of an infection, but which can spread to other people under certain conditions. Bacteria living on the skin surface can also contribute to worsening of eczema. The current methods of ridding the skin of these microbes (bacteria) involves giving the patient either topical (on the skin) or oral (by mouth) antibiotics, a strategy which, over time, is thought to have caused antibiotic resistance, meaning the antibiotics can no longer kill the bacteria. The study described in this paper was carried out by a group from the University of Regensburg in Germany. They used excised pig and human skin samples to which they had added drug resistant bacteria, such as methicillin resistant staphylococci or MRSA, and then treated the skin with a chemical in solution that acts by increasing sensitivity to light. Skin samples were then exposed to a source of light, a process known as photodynamic activation. They found that this technique led to a large reduction in the numbers of bacteria, without damage to skin cells. The authors suggest that this process should now be investigated as a safer method of reducing surface bacterial carriage without increasing the risk of bacterial resistance and without damaging the skin.

作为医院感染的来源之一, 患者皮肤表面(载体)存在潜在有害细菌, 它们不会产生感染, 但在某些条件下可能传播给其他人。皮肤表面生活的细菌也会导致湿疹恶化。目前去除这些微生物(细菌)皮肤的方法包括给患者使用局部抗生素(皮肤上的)或口服抗生素(口服),但随着时间的推移, 这种策略被认为导致了抗生素耐药性, 这意味着抗生素不再能杀死细菌。本文中描述的是由德国雷根斯堡大学的一个小组进行的研究。他们使用切掉的猪和人体皮肤样本, 在样本中加入耐药细菌,如耐甲氧西林葡萄球菌或 MRSA, 然后用一种化学溶液对皮肤进行处理, 这种化学溶液的作用是增加对光的敏感性。皮肤样本随后暴露在光源下,这一过程被称为光动力激活。他们发现这种技术可以在不损害皮肤细胞的情况下, 大量减少细菌的数量。作者建议,这一过程现在应该作为一种更安全的方法来研究, 以减少表面细菌运输, 而不增加细菌耐药性的风险,也不损害皮肤。