Photodamage to multidrug-resistant gram-positive and gram-negative bacteria by 870 nm/930 nm light potentiates erythromycin, tetracycline and ciprofloxacin

Flagellar rotational features of an optically confined bacterium at high frequency and temporal resolution reveal the microorganism's response to changes in the fluid environment

Rotations of the flagella control the movement of a peritrichous (multiflagellar) bacterium in fluids, the run and tumble events being caused through modulations in the flagella's collective rotation speed and pattern. Observing such modulations is a challenge in free swimming bacteria. In this work, we present a setup to measure the collective flagellar rotational features of an optically confined Bacillus subtilis bacterium. We adopt a Continuous Wavelet Technique (CWT) while monitoring the rotational patterns in frequency and time, thus achieving optimal resolution in both the domains. This enables in marking the events wherein subtle changes in the flagellar rotational pattern occur. These studies unravel a fact, hitherto unknown, that variations in swimming speed that are seen in pure run sequences are also caused by modulations in the rotating flagella. Further, we have monitored the flagellar rotation for durations over a minute and observe a gradual slowing down of the rotation before ceasing completely due to the trapping laser induced photodamage. We have observed a significant alteration in the rate of rotational fall off in real time with changes in pH or the nutrient concentration in the fluid. This work serves to demonstrate the advantage of optical confinement of a bacterium in its pristine form for carrying out such studies and can serve as a marker for work that assesses membrane photodamage in active matter. Details on the role of flagella in propulsion and on other factors influencing the rotations, can be of significance in the design of artificial microswimmers.

Identification of bacteria by poly-aromatic hydrocarbon biosensors

Human health is consistently threatened by different species of pathogenic bacteria. To fight the spread of diseases, it is important to develop rapid methods for bacterial identification. Over the years, different kinds of biosensors were developed for this cause. Another environmental risk is poly-aromatic hydrocarbons (PAHs) that may be emitted from industrial facilities and pollute environmental water and soil. One of the methods for their purification is conducted by the addition of bacteria that can degrade the PAHs, while the bacteria can be filtrated at the end of the process. Although many studies reported monitoring of the PAHs degradation by fluorescence, not much attention was dedicated to studying the influence of the PAHs on the intrinsic fluorescence of the degrading bacteria. In this work, we apply synchronous fluorescence (SF) measurements to study the ability of the 5 PAHs: 9-Antracene carboxylic acid (9ACA), Pyrene, Perylene, Pentacene, and Chrysene to interact with bacteria and change its fluorescence spectra. We show that upon incubation of each PAH with the bacterium E. coli, only the 2 PAHs 9ACA and Perylene cause an intensity decrease in the emission at λ = 300-375 nm, which derives from the emission of tyrosine and tryptophan (TT). Also, we show that upon incubation of 9ACA and Perylene with 5 different pathogenic bacteria, the intensity increase or decrease in the TT emission is unique to each bacterial species. Based on this observation, we suggest that the PAHs 9ACA and Perylene can be utilized as biosensors for bacterial identification.

Fast label-free identification of bacteria by synchronous fluorescence of amino acids

Fast identification of pathogenic bacteria is an essential need for patient's diagnostic in hospitals and environmental monitoring of water and air quality. Bacterial cells consist of a very high amount of biological molecules whose content changes in response to different environmental conditions. The similarity between the molecular compositions of different bacterial cells limits the possibility to find unique markers to enable differentiation among species. Although many biological molecules in the cells absorb at the UV-Vis region, only a few of them can be detected in whole cells by their intrinsic fluorescence. Among these molecules are the amino acids phenylalanine, tyrosine, and tryptophan. In this work, we develop a rapid method for bacterial identification by synchronous fluorescence. We show that we can quantify the concentration for the 3 amino acids without any significant interference from other fluorophores in the cells and that we can differentiate among 6 pathogenic bacterial species by using the concentrations of their amino acids as a bacterial fingerprint. Fluorescent amino acids exist in all living cells. Therefore, this method has the potential to be applicative for the rapid identification of cells from all kinds of organisms.

Decolonization in Prevention of Health Care-Associated Infections

Colonization with health care-associated pathogens such as Staphylococcus aureus, enterococci, Gram-negative organisms, and Clostridium difficile is associated with increased risk of infection. Decolonization is an evidence-based intervention that can be used to prevent health care-associated infections (HAIs). This review evaluates agents used for nasal topical decolonization, topical (e.g., skin) decolonization, oral decolonization, and selective digestive or oropharyngeal decontamination. Although the majority of studies performed to date have focused on S. aureus decolonization, there is increasing interest in how to apply decolonization strategies to reduce infections due to Gram-negative organisms, especially those that are multidrug resistant. Nasal topical decolonization agents reviewed include mupirocin, bacitracin, retapamulin, povidone-iodine, alcohol-based nasal antiseptic, tea tree oil, photodynamic therapy, omiganan pentahydrochloride, and lysostaphin. Mupirocin is still the gold standard agent for S. aureus nasal decolonization, but there is concern about mupirocin resistance, and alternative agents are needed. Of the other nasal decolonization agents, large clinical trials are still needed to evaluate the effectiveness of retapamulin, povidone-iodine, alcohol-based nasal antiseptic, tea tree oil, omiganan pentahydrochloride, and lysostaphin. Given inferior outcomes and increased risk of allergic dermatitis, the use of bacitracin-containing compounds cannot be recommended as a decolonization strategy. Topical decolonization agents reviewed included chlorhexidine gluconate (CHG), hexachlorophane, povidone-iodine, triclosan, and sodium hypochlorite. Of these, CHG is the skin decolonization agent that has the strongest evidence base, and sodium hypochlorite can also be recommended. CHG is associated with prevention of infections due to Gram-positive and Gram-negative organisms as well as Candida. Conversely, triclosan use is discouraged, and topical decolonization with hexachlorophane and povidone-iodine cannot be recommended at this time. There is also evidence to support use of selective digestive decontamination and selective oropharyngeal decontamination, but additional studies are needed to assess resistance to these agents, especially selection for resistance among Gram-negative organisms. The strongest evidence for decolonization is for use among surgical patients as a strategy to prevent surgical site infections.

Laser-assisted nasal decolonization of Staphylococcus aureus, including methicillin-resistant Staphylococcus aureus

OBJECTIVES

Methicillin-sensitive Staphylococcus aureus (MSSA) and methicillin-resistant S aureus (MRSA) contribute to 25% of nosocomial infections, increasing complications, health care cost, and growing antibiotic resistance. Nasal decolonization (ND) can reduce the staphylococcal infection rate. A new method of laser therapy (LT) MRSA ND was tested.

STUDY DESIGN

This is a prospective, nonrandomized study.

METHODS

Following institutional review board approvals, 25 patients colonized with MSSA/MRSA were allocated to 4 treatment arms; low-power, dual-wavelength 870-/930-nm laser alone (GR1); low-power, dual-wavelength laser followed by erythromycin (E-mycin) cream (GR2); low-power, dual-wavelength laser followed by peroxide irrigation (GR3); and high-power 940-nm laser alone (GR4). Quantitative cultures were obtained before and after in all arms. Laser therapy was performed via a laser fiber diffuser, delivering 200 to 600 J/cm² to each naris circumferentially. Patient's distribution was 3 in GR1, 14 in GR2, 4 in GR3, and 4 in GR4 (last 10 recruited to GR4).

RESULTS

Nasal decolonization for GR1, GR2, GR3, and GR4 was 1 of 3, 13 of 14, 2 of 4, and 4 of 4, respectively. Because LT + E-mycin cleared all first 3 patients of MRSA and MSSA, all remaining patients were treated with LT + Er with over 90% of patients clearing. No adverse events or discomfort were reported.

CONCLUSIONS

First human study using LT and topical E-mycin in ND is presented. Laser therapy can eradicate MRSA and potentially resensitization of bacteria to the antimicrobial effect of erythromycin. Although decolonization was maintained at 4 weeks posttreatment, further studies can determine the LT long-term effect.

Strategies to potentiate antimicrobial photoinactivation by overcoming resistant phenotypes

Conventional antimicrobial strategies have become increasingly ineffective due to the emergence of multidrug resistance among pathogenic microorganisms. The need to overcome these deficiencies has triggered the exploration of alternative treatments and unconventional approaches towards controlling microbial infections. Photodynamic therapy (PDT) was originally established as an anticancer modality and is currently used in the treatment of age-related macular degeneration. The concept of photodynamic inactivation requires cell exposure to light energy, typically wavelengths in the visible region that causes the excitation of photosensitizer molecules either exogenous or endogenous, which results in the production of reactive oxygen species (ROS). ROS produce cell inactivation and death through modification of intracellular components. The versatile characteristics of PDT prompted its investigation as an anti-infective discovery platform. Advances in understanding of microbial physiology have shed light on a series of pathways, and phenotypes that serve as putative targets for antimicrobial drug discovery. Investigations of these phenotypic elements in concert with PDT have been reported focused on multidrug efflux systems, biofilms, virulence and pathogenesis determinants. In many instances the results are promising but only preliminary and require further investigation. This review discusses the different antimicrobial PDT strategies and highlights the need for highly informative and comprehensive discovery approaches.

Microbial efflux pump inhibition: tactics and strategies

Traditional antimicrobials are increasingly suffering from the emergence of multidrug resistance among pathogenic microorganisms. To overcome these deficiencies, a range of novel approaches to control microbial infections are under investigation as potential alternative treatments. Multidrug efflux is a key target of these efforts. Efflux mechanisms are broadly recognized as major components of resistance to many classes of chemotherapeutic agents as well as antimicrobials. Efflux occurs due to the activity of membrane transporter proteins widely known as Multidrug Efflux Systems (MES). They are implicated in a variety of physiological roles other than efflux and identifying natural substrates and inhibitors is an active and expanding research discipline. One plausible alternative is the combination of conventional antimicrobial agents/antibiotics with small molecules that block MES known as multidrug efflux pump inhibitors (EPIs). An array of approaches in academic and industrial research settings, varying from high-throughput screening (HTS) ventures to bioassay guided purification and determination, have yielded a number of promising EPIs in a series of pathogenic systems. This synergistic discovery platform has been exploited in translational directions beyond the potentiation of conventional antimicrobial treatments. This venture attempts to highlight different tactical elements of this platform, identifying the need for highly informative and comprehensive EPI-discovery strategies. Advances in assay development genomics, proteomics as well as the accumulation of bioactivity and structural information regarding MES facilitates the basis for a new discovery era. This platform is expanding drastically. A combination of chemogenomics and chemoinformatics approaches will integrate data mining with virtual and physical HTS ventures and populate the chemical-biological interface with a plethora of novel chemotypes. This comprehensive step will expedite the preclinical development of lead EPIs.

All you need is light: antimicrobial photoinactivation as an evolving and emerging discovery strategy against infectious disease

The story of prevention and control of infectious diseases remains open and a series of highly virulent pathogens are emerging both in and beyond the hospital setting. Antibiotics were an absolute success story for a previous era. The academic and industrial biomedical communities have now come together to formulate consensus beliefs regarding the pursuit of novel and effective alternative anti-infective countermeasures. Photodynamic therapy was established and remains a successful modality for malignancies but photodynamic inactivation has been transformed recently to an antimicrobial discovery and development platform. The concept of photodynamic inactivation is quite straightforward and requires microbial exposure to visible light energy, typically wavelengths in the visible region, that causes the excitation of photosensitizer molecules (either exogenous or endogenous), which results in the production of singlet oxygen and other reactive oxygen species that react with intracellular components, and consequently produce cell inactivation. It is an area of increasing interest, as research is advancing i) to identify the photochemical and photophysical mechanisms involved in inactivation; ii) to develop potent and clinically compatible photosensitizer; iii) to understand how photoinactivation is affected by key microbial phenotypic elements (multidrug resistance and efflux, virulence and pathogenesis determinants, biofilms); iv) to explore novel delivery platforms inspired by current trends in pharmacology and nanotechnology; and v) to identify photoinactivation applications beyond the clinical setting such as environmental disinfectants.

Effects of metal and the phytyl chain on chlorophyll derivatives: physicochemical evaluation for photodynamic inactivation of microorganisms

Chlorophyll compounds and their derivatives containing metal or phytyl chain can be used as photosensitizer in photodynamic inactivation of microorganisms (PDI). So, the physicochemical properties and antimicrobial effect of chlorophyll derivatives were investigated: Mg-chlorophyll (Mg-Chl), Zn-chlorophyll (Zn-Chl), Zn-chlorophyllide (Zn-Chlde), Cu-chlorophyll (Cu-Chl), pheophytin (Pheo) and pheophorbide (Pheid). The photobleaching experiments showed photostability according to Cu-Chl > Pheo ∼ Pheid ≫ Zn-Chl ∼ Zn-Chlde > Mg-Chl. This order was discussed in terms of metal and the phytyl chain presences. Pheid and Zn-Chl in aqueous Tween 80 solution exhibited highest singlet oxygen yield compared with the other derivatives. Chlorophyll derivatives (CD) with phytyl chain was limited by the self-aggregation phenomenon at high concentrations, even in micellar systems (Tween 80 and P-123). The antimicrobial effect of CD derivatives was investigated against Staphylococcus aureus, Escherichia coli, Candida albicans and Artemia salina. Pheid showed the best results against all organisms tested, Zn-Chlde was an excellent bactericide in the dark and Cu-Chl had no PDI effect. No correlation with CD uptake by microorganisms and darkness cytotoxicity was found. The physicochemical properties allied to bioassays results indicate that Mg-Chl, Pheo, Zn-Chl and Pheid are good candidates for PDI.