Antibiotic resistance and antibiotic development

Knowledge and Attitude toward Antibiotic Use and Identification of Financially Feasible Options to Curb the Spread of Antibiotics in Environment

A survey on antibiotic literacy in terms of the use and abuse of antibiotics to track and understand antibiotic consumption is crucial to optimize the use of antibiotics and minimizing antimicrobial resistance (AMR). Purposive random sampling, using the snow-ball questionnaire technique, was adopted to ensure that the respondents distributed across India, coming from rural and urban settings, were adolescents as well as adults and had completed at least the higher secondary school level of education. Respondents were divided into five subcategories. The questionnaire was distributed between April 2021 and July 2021, during the second COVID-19 wave in India. The survey questionnaire included 34 questions, comprising multiple-choice and 5-point Likert scale-type questions. This study composed of 972 respondents. Most respondents considered antibiotics safe and frequently failed to discriminate between the symptoms of bacterial and viral infections, most often leading to self-prescription. About 34% of the rural participants and 50% of the urban participants considered antibiotic resistance a serious health concern. Antibiotic prescriptions by the medical or paramedical practitioner were largely empirical. At least 95% of participants acknowledged having heard about antibiotics; nearly 20% of antibiotic consumption came from nonprescription users, while 30% had not completed their antibiotic therapy for a variety of reasons. Sixty-two percent consumed antibiotics to treat cold and flu symptoms. Results from the survey suggest the presence of a crucial gap between the respondents' perception of antibiotics and levels of information regarding antibiotic use and misuse. The present study may serve as a benchmark that strongly recommends a financially feasible policy, which includes educating society regarding the spread of AMR and its severe consequences by incorporating AMR into the curriculum at the levels of senior secondary school and higher education.

Antibiotic Prescribing Practices for Upper Respiratory Tract Infections Among Primary Care Providers: A Descriptive Study

Background

Most antibiotics are prescribed in the ambulatory setting with estimates that up to 50% of use is inappropriate. Understanding factors associated with antibiotic misuse is essential to advancing better stewardship in this setting. We sought to assess the frequency of unnecessary antibiotic use for upper respiratory infections (URIs) among primary care providers and identify patient and provider characteristics associated with misuse.

Methods

Unnecessary antibiotic prescribing was assessed in a descriptive study by using adults ≥18 years seen for common URIs in a large, Upper Midwest, integrated health system, electronic medical records from June 2017 through May 2018. Individual provider rates of unnecessary prescribing were compared for primary care providers practicing in the departments of internal medicine, family medicine, or urgent care. Patient and provider characteristics associated with unnecessary prescribing were identified with a logistic regression model.

Results

A total of 49 463 patient encounters were included. Overall, antibiotics were prescribed unnecessarily for 42.2% (95% confidence interval [CI], 41.7–42.6) of the encounters. Patients with acute bronchitis received unnecessary antibiotics most frequently (74.2%; 95% CI, 73.4–75.0). Males and older patients were more likely to have an unnecessary antibiotic prescription. Provider characteristics associated with higher rates of unnecessary prescribing included being in a rural practice, having more years in practice, and being in higher volume practices such as an urgent care setting. Fifteen percent of providers accounted for half of all unnecessary antibiotic prescriptions.

Conclusions

Although higher-volume practices, a rural setting, or longer time in practice were predictors, unnecessary prescribing was common among all providers.

Biosorption of dicloxacillin from pharmaceutical waste water using tannin from Indian almond leaf: Kinetic and equilibrium studies

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The maximum adsorption capacity was 86.93 %.

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Experimental data were in agreement with pseudo-second-order kinetics.

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Experimental data were followed Langmuir isotherm model.

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Biosorption of dicloxacilin onto T. catappa L. biomass is possible, spontaneous and exothermic process.

This study focused on the use of Indian almond leaf biomass, a local plant widely found in Thailand, on removal of dicloxacillin from pharmaceutical waste water by biosorption. The biosorption characteristics of dicloxacillin were investigated in terms of equilibrium, kinetics and thermodynamics. Optimum biosorption conditions were determined from pH, initial dicloxacillin concentration, biomass dosage, contact time, and temperature. The maximum adsorption capacity was 86.93 % (pH 6.0, 0.1 g/L biomass, dicloxacillin concentration 20 mg/L, contact time 24 h, temperature 283.15 K). The thermodynamic parameters (298.15 K), free energy change, enthalpy change and entropy change were -3475.79 J/mol, −25.36 kJ/mol, and −73.40 J/mol/K, respectively. The best interpretation for the experimental data was given by the Langmuir isotherm with correlation coefficient of 0.965. The results were found to tie in well with pseudo-second-order kinetics. Considering the cost-effectiveness, Indian almond leaf biomass is considered to be suitable to remove dicloxacillin from pharmaceutical waste water.

Antibiotic Pollution in the Environment: From Microbial Ecology to Public Policy

The ability to fight bacterial infections with antibiotics has been a longstanding cornerstone of modern medicine. However, wide-spread overuse and misuse of antibiotics has led to unintended consequences, which in turn require large-scale changes of policy for mitigation. In this review, we address two broad classes of corollaries of antibiotics overuse and misuse. Firstly, we discuss the spread of antibiotic resistance from hotspots of resistance evolution to the environment, with special concerns given to potential vectors of resistance transmission. Secondly, we outline the effects of antibiotic pollution independent of resistance evolution on natural microbial populations, as well as invertebrates and vertebrates. We close with an overview of current regional policies tasked with curbing the effects of antibiotics pollution and outline areas in which such policies are still under development.

Confocal fluorescence imaging to evaluate the effect of antimicrobial photodynamic therapy depth on P. gingivalis and T. denticola biofilms

BACKGROUND

Porphyromonas gingivalis and Treponema denticola are both principally implicated in the incidence of both periodontal disease and peri-implantitis. Recent studies have demonstrated that these bacteria exhibit symbiotic growth in vitro and a synergistic virulence in co-infection of animal models. Found at varying depths throughout the biofilm, these bacteria present a significant challenge to traditional antimicrobial treatment modalities. Antimicrobial photodynamic therapy (aPDT) has yielded high success against bacterial biofilms, namely those found in the oral cavity. Data on the use of aPDT against these particular periodontal pathogens is, however, scarce. Here, we studied the qualitative killing efficacy and depth of drug and laser penetration into defined P. gingivalis and T. denticola biofilms.

METHODS

P. gingivalis and T. denticola were incubated under anaerobic (10%CO2, 10%H2, 80%N2) conditions for two days in diluted TSB with PBS (TYGVS for T. denticola maintenance) to elicit biofilm growth on coverslip-modified polystyrene dishes. Treated biofilms were exposed to a purpurin-based sensitizer (25 μg/mL in DMSO) for 30 min, and then aPDT was carried out using a diode laser at 664 nm. Light doses of 15 and 45 J/cm2 were used. All biofilms were then exposed to Filmtracer™ LIVE/DEAD® Biofilm Viability Kit (Cat No. L10316). Qualitative analysis was performed using a Zeiss LSM 510 Meta NLO Confocal Microscope with attached Zeiss Axioimager Z1 and Axiovert 200 M for visual data collection, and images were processed using the ZEN Digital Imaging for Light Microscopy software suite. Analysis was performed in 2 × 3 stacks to assess the entire depth of both the biofilm and presumed drug/laser penetration.

RESULTS

Initial planktonic studies confirmed that the bacteria in question were present in the grown cultures and susceptible to aPDT exposure. Biofilm control groups were found to have significant levels of surviving bacterial colonies. Both treatment groups featured complete bacterial kill throughout the entirety of the biofilm (average: 23.17 μm; range: 18.13-27.20 μm).

CONCLUSIONS

The efficacy of the purpurin-based PS and aPDT is demonstrated to be effective at both high and low light doses. Bacterial kill was fully efficacious at each visualized biofilm layer (1.01 μm/z-level). This study serves as a proof of concept for future studies that must consider appropriate treatment parameters, including the amount of applied PS, and laser dose. These findings indicate that aPDT is a method that can be used to eliminate microorganisms associated with biofilms implicated in the etiology of peri-implantitis and periodontitis at large.

In vitro characterization of PlyE146, a novel phage lysin that targets Gram-negative bacteria

The recent rise of multidrug-resistant Gram-negative bacteria represents a serious threat to public health and makes the search for novel effective alternatives to antibiotics a compelling need. Bacteriophage (Phage) lysins are enzymes that hydrolyze the cell wall of bacteria and represent a promising alternative to tackle this ever-increasing problem. Despite their use is believed to be restricted to Gram-positive bacteria, recent findings have shown that they can also be used against Gram-negative bacteria. By using a phage genome-based screening approach, we identified and characterized a novel lysin, PlyE146, encoded by an Escherichia coli prophage and with a predicted molecular mass of ca. 17 kDa. PlyE146 is composed of a C-terminal cationic peptide and a N-terminal N-acetylmuramidase domain. Histidine-tagged PlyE146 was overexpressed from a plasmid in Lactococcus lactis NZ9000 and purified by NI-NTA chromatography. PlyE146 exhibited in vitro optimal bactericidal activity against E. coli K12 (3.6 log₁₀ CFU/mL decrease) after 2 h of incubation at 37°C at a concentration of 400 μg/mL in the absence of NaCl and at pH 6.0. Under these conditions, PlyE146 displayed antimicrobial activity towards several other E. coli, Pseudomonas aeruginosa (3 to 3.8-log₁₀ CFU/mL decrease) and Acinetobacter baumannii (4.9 to >5-log₁₀ CFU/mL decrease) strains. Therefore, PlyE146 represents a promising therapeutic agent against E. coli, P. aeruginosa and A. baumannii infections. However, further studies are required to improve the efficacy of PlyE146 under physiological conditions.

Antimicrobial resistance: A global emerging threat to public health systems

Antimicrobial resistance (AMR) became in the last two decades a global threat to public health systems in the world. Since the antibiotic era, with the discovery of the first antibiotics that provided consistent health benefits to human medicine, the misuse and abuse of antimicrobials in veterinary and human medicine have accelerated the growing worldwide phenomenon of AMR. This article presents an extensive overview of the epidemiology of AMR, with a focus on the link between food producing-animals and humans and on the legal framework and policies currently implemented at the EU level and globally. The ways of responding to the AMR challenges foresee an array of measures that include: designing more effective preventive measures at farm level to reduce the use of antimicrobials; development of novel antimicrobials; strengthening of AMR surveillance system in animal and human populations; better knowledge of the ecology of resistant bacteria and resistant genes; increased awareness of stakeholders on the prudent use of antibiotics in animal productions and clinical arena; and the public health and environmental consequences of AMR. Based on the global nature of AMR and considering that bacterial resistance does not recognize barriers and can spread to people and the environment, the article ends with specific recommendations structured around a holistic approach and targeted to different stakeholders.

In Vivo Pharmacokinetics and Pharmacodynamics of ZTI-01 (Fosfomycin for Injection) in the Neutropenic Murine Thigh Infection Model against Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa

Fosfomycin is a broad-spectrum agent with activity against Gram-positive and Gram-negative bacteria, including drug-resistant strains, such as extended-spectrum-beta-lactamase (ESBL)-producing and carbapenem-resistant (CR) Gram-negative rods. In the present study, the pharmacokinetic/pharmacodynamic (PK/PD) activity of ZTI-01 (fosfomycin for injection) was evaluated in the neutropenic murine thigh infection model against 5 Escherichia coli, 3 Klebsiella pneumoniae, and 2 Pseudomonas aeruginosa strains, including a subset with ESBL and CR phenotypes. The pharmacokinetics of ZTI-01 were examined in mice after subcutaneous administration of 3.125, 12.5, 50, 200, 400, and 800 mg/kg of body weight. The half-life ranged from 0.51 to 1.1 h, area under the concentration-time curve (AUC_0-∞) ranged from 1.4 to 87 mg · h/liter, and maximum concentrations ranged from 0.6 to 42.4 mg/liter. Dose fractionation demonstrated the AUC/MIC ratio to be the PK/PD index most closely linked to efficacy (R² = 0.70). Net stasis and bactericidal activity were observed against all strains. Net stasis was observed at 24-h AUC/MIC ratio values of 24, 21, and 15 for E. coli, K., pneumoniae and P. aeruginosa, respectively. For the Enterobacteriaceae group, stasis was noted at mean 24-h AUC/MIC ratio targets of 23 and 1-log kill at 83. Survival in mice infected with E. coli 145 was maximal at 24-h AUC/MIC ratio exposures of 9 to 43, which is comparable to the stasis exposures identified in the PK/PD studies. These results should prove useful for the design of clinical dosing regimens for ZTI-01 in the treatment of serious infections due to Enterobacteriaceae and Pseudomonas.

Nursing home nurses' and community-dwelling older adults' reported knowledge, attitudes, and behavior toward antibiotic use

BACKGROUND

Antibiotic overuse causes antibiotic resistance, one of the most important threats to human health. Older adults, particularly those in nursing homes, often receive antibiotics when they are not indicated.

METHODS

To understand knowledge, attitudes, and behaviors of nursing home (NH) nurses and community-dwelling older adults towards antibiotic use, especially in clinical situations consistent with antibiotic overuse, we conducted a mixed-method survey in two NHs and one Family Medicine clinic in North Carolina, among English-speaking nurses and community-dwelling, cognitively intact adults aged 65 years or older. Based on the Knowledge-Attitude-Practice model, the survey assessed knowledge, attitudes, and behavior towards antibiotic use, including three vignettes designed to elicit possible antibiotic overuse: asymptomatic bacteriuria (ASB), a viral upper respiratory illness (URI), and a wound from a fall.

RESULTS

Of 31 NH nurses and 66 community-dwelling older adults, 70% reported knowledge of the dangers of taking antibiotics. Nurses more often reported evidence-based attitudes towards antibiotics than older adults, except 39% agreed with the statement "by the time I am sick enough to go to the doctor with a cold, I expect an antibiotic", while only 28% of older adults agreed with it. A majority of nurses did not see the need for antibiotics in any of the three vignettes: 77% for the ASB vignette, 87% for the URI vignette, and 97% for the wound vignette. Among older adults, 50% did not perceive a need for antibiotics in the ASB vignette, 58% in the URI vignette, and 74% in the wound vignette.

CONCLUSIONS

While a substantial minority had no knowledge of the dangers of antibiotic use, non-evidence-based attitudes towards antibiotics, and behaviors indicating inappropriate management of suspected infections, most NH nurses and community-dwelling older adults know the harms of antibiotic use and demonstrate evidence-based attitudes and behaviors. However, more work is needed to improve the knowledge, attitudes and behaviors that may contribute to antibiotic overuse.

TNF-α/IL-10 Ratio Correlates with Burn Severity and May Serve as a Risk Predictor of Increased Susceptibility to Infections

Severe burn injury renders patients susceptible to multiple infection episodes; however, identifying specific patient groups at high risk remains challenging. Burn-induced inflammatory response dramatically modifies the levels of various cytokines. Whether these changes could predict susceptibility to infections remains unknown. The aim of this study was to determine the early changes in the pro- to anti-inflammatory cytokine ratio and investigate its ability to predict susceptibility to repeated infections after severe burn trauma. The patient population consisted of 34 adult patients having early (≤48 h since injury) blood draws following severe (≥20% total burn surface area (TBSA)) burn injury and suffering from a first infection episode at least 1 day after blood collection. Plasma TNF-α and IL-10 levels were measured to explore the association between the TNF-α/IL-10 ratio, hypersusceptibility to infections, burn size (TBSA), and common severity scores (Acute Physiology and Chronic Health Evaluation II (APACHEII), Baux, modified Baux (R-Baux), Ryan Score, and Abbreviated Burn Severity Index (ABSI)). TNF-α/IL10 plasma ratio measured shortly after burn trauma was inversely correlated with burn size and the injury severity scores investigated, and was predictive of repeated infections (≥3 infection episodes) outcome (AUROC [95%CI] of 0.80 [0.63-0.93]). Early measures of circulating TNF-α/IL10 ratio may be a previously unidentified biomarker associated with burn injury severity and predictive of the risk of hypersusceptibility to repeated infections.

Resistance in antimicrobial photodynamic inactivation of bacteria

Antibiotics have increasingly lost their impact to kill bacteria efficiently during the last 10 years. The emergence and dissemination of superbugs with resistance to multiple antibiotic classes have occurred among Gram-positive and Gram-negative strains including Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa and Enterobacter strains. These six superbugs can "escape" more or less any single kind of antibiotic treatment. That means bacteria are very good at developing resistance against antibiotics in a short time. One new approach is called photodynamic antimicrobial chemotherapy (PACT) which already has demonstrated an efficient antimicrobial efficacy among multi-resistant bacteria. Until now it has been questionable if bacteria can develop resistance against PACT. This perspective summarises the current knowledge about the susceptibility of bacteria towards oxidative stress and sheds some light on possible strategies of the development of photodynamic inactivation of bacteria (PACT)-induced oxidative stress resistance by bacteria.

A novel chimeric peptide with antimicrobial activity

Beta-lactamase-mediated bacterial drug resistance exacerbates the prognosis of infectious diseases, which are sometimes treated with co-administration of beta-lactam type antibiotics and beta-lactamase inhibitors. Antimicrobial peptides are promising broad-spectrum alternatives to conventional antibiotics in this era of evolving bacterial resistance. Peptides based on the Ala46-Tyr51 beta-hairpin loop of beta-lactamase inhibitory protein (BLIP) have been previously shown to inhibit beta-lactamase. Here, our goal was to modify this peptide for improved beta-lactamase inhibition and cellular uptake. Motivated by the cell-penetrating pVEC sequence, which includes a hydrophobic stretch at its N-terminus, our approach involved the addition of LLIIL residues to the inhibitory peptide N-terminus to facilitate uptake. Activity measurements of the peptide based on the 45-53 loop of BLIP for enhanced inhibition verified that the peptide was a competitive beta-lactamase inhibitor with a K(i) value of 58 μM. Incubation of beta-lactam-resistant cells with peptide decreased the number of viable cells, while it had no effect on beta-lactamase-free cells, indicating that this peptide had antimicrobial activity via beta-lactamase inhibition. To elucidate the molecular mechanism by which this peptide moves across the membrane, steered molecular dynamics simulations were carried out. We propose that addition of hydrophobic residues to the N-terminus of the peptide affords a promising strategy in the design of novel antimicrobial peptides not only against beta-lactamase but also for other intracellular targets.

In vivo pharmacokinetics and pharmacodynamics of the lantibiotic NAI-107 in a neutropenic murine thigh infection model

NAI-107 is a novel lantibiotic compound with potent in vitro activity against Gram-positive bacteria, including methicillin-resistant Staphylococcus aureus (MRSA). The purpose of this study was to examine the activity of NAI-107 against S. aureus strains, including MRSA, in the neutropenic murine thigh infection model. Serum pharmacokinetics were determined and time-kill studies were performed following administration of single subcutaneous doses of 5, 20, and 80 mg/kg body weight. The dose fractionation included total doses ranging from 1.56 to 400 mg/kg/72 h, divided into 1, 2, 3, or 6 doses. Studies of treatment effects against 9 S. aureus strains (4 methicillin-susceptible Staphylococcus aureus [MSSA] and 5 MRSA) using a 12-h dosing interval and total dose range of 1.56 to 400 mg/kg/72 h were also performed. A maximum effect (Emax) model was used to determine the pharmacokinetic/pharmacodynamic (PK/PD) index that best described the dose-response data and to estimate the doses required to achieve a net bacteriostatic dose (SD) and a 1-log reduction in CFU/thigh. The pharmacokinetic studies demonstrated an area under the concentration-time curve (AUC) range of 26.8 to 276 mg·h/liter and half-lives of 4.2 to 8.2 h. MICs ranged from 0.125 to 0.5 μg/ml. The 2 highest single doses produced more than a 2-log kill and prolonged postantibiotic effects (PAEs) ranging from 36 to >72 h. The dose fractionation-response curves were similar, and the AUC/MIC ratio was the most predictive PD index (AUC/MIC, coefficient of determination [R2]=0.89; maximum concentration of drug in serum [Cmax]/MIC, R2=0.79; time [T]>MIC, R2=0.63). A ≥2-log kill was observed against all 9 S. aureus strains. The total drug 24-h AUC/MIC values associated with stasis and a 1-log kill for the 9 S. aureus strains were 371±130 and 510±227, respectively. NAI-107 demonstrated concentration-dependent killing and prolonged PAEs. The AUC/MIC ratio was the predictive PD index. Extensive killing was observed for S. aureus organisms, independent of the MRSA status. The AUC/MIC target should be useful for the design of clinical dosing regimens.

Nafcillin enhances innate immune-mediated killing of methicillin-resistant Staphylococcus aureus

Based on in vitro synergy studies, the addition of nafcillin to daptomycin was used to treat refractory methicillin-resistant Staphylococcus aureus (MRSA) bacteremia. Daptomycin is a de facto cationic antimicrobial peptide in vivo, with antistaphylococcal mechanisms reminiscent of innate host defense peptides (HDPs). In this study, the effects of nafcillin on HDP activity against MRSA were examined in vitro and in vivo. Exposures to β-lactam antimicrobials in general, and nafcillin in particular, significantly increased killing of S. aureus by selected HDPs from keratinocytes, neutrophils, and platelets. This finding correlated with enhanced killing of MRSA by whole blood, neutrophils, and keratinocytes after growth in nafcillin. Finally, nafcillin pretreatment ex vivo reduced MRSA virulence in a murine subcutaneous infection model. Despite the lack of direct activity against MRSA, these studies show potent, consistent, and generalized nafcillin-mediated "sensitization" to increased killing of MRSA by various components of the innate host response. The use of nafcillin as adjunctive therapy in MRSA bacteremia merits further study and should be considered in cases refractory to standard therapy.

KEY MESSAGES

Nafcillin has been used as adjunctive therapy to clear persistent MRSA bacteremia. Nafcillin enhances killing of MRSA by a cadre of innate host defense peptides. Nafcillin increases binding of human cathelicidin LL-37 to the MRSA membrane. Nafcillin enhances killing of MRSA by neutrophils. Nafcillin reduces virulence of MRSA in a murine subcutaneous infection model.

Antibiotic-resistant bacteria: a challenge for the food industry

Antibiotic-resistant bacteria were first described in the 1940s, but whereas new antibiotics were being discovered at a steady rate, the consequences of this phenomenon were slow to be appreciated. At present, the paucity of new antimicrobials coming into the market has led to the problem of antibiotic resistance fast escalating into a global health crisis. Although the selective pressure exerted by the use of antibiotics (particularly overuse or misuse) has been deemed the major factor in the emergence of bacterial resistance to these antimicrobials, concerns about the role of the food industry have been growing in recent years and have been raised at both national and international levels. The selective pressure exerted by the use of antibiotics (primary production) and biocides (e.g., disinfectants, food and feed preservatives, or decontaminants) is the main driving force behind the selection and spread of antimicrobial resistance throughout the food chain. Genetically modified (GM) crops with antibiotic resistance marker genes, microorganisms added intentionally to the food chain (probiotic or technological) with potentially transferable antimicrobial resistance genes, and food processing technologies used at sub-lethal doses (e.g., alternative non-thermal treatments) are also issues for concern. This paper presents the main trends in antibiotic resistance and antibiotic development in recent decades, as well as their economic and health consequences, current knowledge concerning the generation, dissemination, and mechanisms of antibacterial resistance, progress to date on the possible routes for emergence of resistance throughout the food chain and the role of foods as a vehicle for antibiotic-resistant bacteria. The main approaches to prevention and control of the development, selection, and spread of antibacterial resistance in the food industry are also addressed.

Photodynamic inactivation of multi-resistant bacteria (PIB) - a new approach to treat superficial infections in the 21st century

The increasing resistance of bacteria against antibiotics is one of the most important clinical challenges of the 21(st) century. Within the gram-positive bacteria the methicillin-resistant Staphylococcus aureus and Enterococcus faecium represent the major obstacle to successful therapy. Apart from the development of new antibiotics it requires additional differently constituted approaches, like photodynamic inactivation in order to have further effective treatment options against bacteria available. Certain dyes, termed photosensitizers, are able to store the absorbed energy in long-lived electronic states upon light activation with appropriate wavelengths and thus make these states available for chemical activation of the immediate surroundings. The interaction with molecular oxygen, which leads to different, very reactive and thus cytotoxic oxygen species, is highlighted. In this review the application of the photodynamic inactivation of bacteria will be discussed regarding the possible indications in dermatology, like localized skin and wound infections or the reduction of nosocomial colonization with multi-resistant bacteria on the skin. The crucial advantage of the local application of photosensitizers followed by irradiation of the area of interest is the fact that independent of the resistance pattern of a bacterium a direct inactivation takes place similarly as with an antiseptic. In this review the physical-chemical and biological basics of photo-dynamic inactivation of bacteria (PIB) will be discussed as well as the possible dermatological indications.