Hydrogen Peroxide, Povidone-Iodine and Chlorhexidine Fail to Eradicate Staphylococcus aureus Biofilm from Infected Implant Materials

Hydrogen peroxide, povidone-iodine, and chlorhexidine are antiseptics that are commonly added to irrigants to either prevent or treat infection. There are little clinical data available that demonstrate efficacy of adding antiseptics to irrigants in the treatment of periprosthetic joint infection after biofilm establishment. The objective of the study was to assess the bactericidal activity of the antiseptics on S. aureus planktonic and biofilm. For planktonic irrigation, S. aureus was exposed to different concentrations of antiseptics. S. aureus biofilm was developed by submerging a Kirschner wire into normalized bacteria and allowing it to grow for forty-eight hours. The Kirschner wire was then treated with irrigation solutions and plated for CFU analysis. Hydrogen peroxide, povidone-iodine, and chlorhexidine were bactericidal against planktonic bacteria with over a 3 log reduction (p < 0.0001). Unlike cefazolin, the antiseptics were not bactericidal (less than 3 log reduction) against biofilm bacteria but did have a statistical reduction in biofilm as compared to the initial time point (p < 0.0001). As compared to cefazolin treatment alone, the addition of hydrogen peroxide or povidone-iodine to cefazolin treatment only additionally reduced the biofilm burden by less than 1 log. The antiseptics demonstrated bactericidal properties with planktonic S. aureus; however, when used to irrigate S. aureus biofilms, these antiseptics were unable to decrease biofilm mass below a 3 log reduction, suggesting that S. aureus biofilm has a tolerance to antiseptics. This information should be considered when considering antibiotic tolerance in established S. aureus biofilm treatment

Self-assembled monolayers of thiophenol on gold as a novel substrate for surface-enhanced infrared absorption

A unique method of obtaining surface-enhanced infrared absorption (SEIRA) spectra for chemicals that will not chemically attach to a metal surface has been investigated. Surface enhancements are greatest for molecules that bind to metals. In order to achieve greater enhancement for those analytes that do not bind to SEIRA metals, we have investigated self-assembled monolayers as a means of linking analytes to a gold substrate. Monolayers of thiophenol were formed onto sputter-coated gold-silicon substrates. Analytes were deposited onto the thiophenol-coated gold-silicon wafers, and external reflection SEIRA spectra were then measured. Enhancement factors as high as 30-fold compared to those for conventional SEIRA substrates are demonstrated. The self-assembled monolayers on gold substrates are shown to change both relative intensities and band positions of the adsorbed analyte. These intensity changes and frequency shifts show strong interaction of selected analytes with the self-assembled monolayer. This study of phthalates and nitro-substituted aromatic compounds demonstrates the usefulness of the technique. Spectral changes evident through the use of the thiophenol monolayer are discussed

Photoacoustic discrimination of antibiotic-resistant and sensitive Staphylococcus aureus isolates

Objectives: Bacteremia is a serious and potentially lethal condition. Staphylococcus aureus is a leading cause of bacteremia and methicillin-resistant S. aureus (MRSA) accounts for more than a third of the cases. Compared to methicillin-sensitive S. aureus, MRSA is more than twice as likely to be fatal. Furthermore, subpopulations of seemingly isogenic bacteria may exhibit a range of susceptibilities, often called heterogenous resistance. These heterogeneous antibiotic-resistant infections are often misdiagnosed as hospital-acquired secondary infections because there are no clinically used tests that can differentiate between homogeneous and heterogeneous antibiotic resistance. We describe the development and proof of concept of rapid bacterial identification using photoacoustic flow cytometry and labeled bacteriophages with the characterization and differentiation of heterogeneous antibiotic-resistant bacterial infections. Methods: In photoacoustic flow cytometry, pulsed laser light is delivered to a sample flowing past a focused transducer and particles that absorb laser light create an acoustic response. Optically labeled bacteriophage are added to a bacterial mixture that flows through the photoacoustic chamber. The presence of target bacteria is determined by bound labeled phage which are detected photoacoustically. Incubation of bacterial samples in the presence and absence of the antibiotic daptomycin creates a difference in bacterial cell numbers that is quantified using photoacoustic flow cytometry. Results: Four clinical isolates were tested in the presence and absence of daptomycin. Photoacoustic events for each isolate were recorded and compared to growth curves. Samples treated with daptomycin fell into three categories: resistant, susceptible, and heterogeneous resistant. Conclusions: Here we show a method to determine the presence of bacteria as a marker for bloodstream infection level and antibiotic sensitivity in less than 4 hours. Additionally, these results show an ability to identify heterogeneous resistant strains that are often misidentified

Staphylococcus epidermidis Biofilms Have a High Tolerance to Antibiotics in Periprosthetic Joint Infection

Both Staphylococcus aureus and Staphylococcus epidermidis are commonly associated with periprosthetic joint infections (PJIs). The treatment of PJI can be challenging because biofilms are assumed to have an increased intolerance to antibiotics. This makes the treatment of PJI challenging from a clinical perspective. Although S. aureus has been previously demonstrated to have increased biofilm antibiotic tolerance, this has not been well established with Staphylococcus epidermidis. A prospective registry of PJI S. epidermidis isolates was developed. The efficacy of clinically relevant antibiotics was quantified against these isolates. S. epidermidis planktonic minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were collected using clinical laboratory standard index (CLSI) assays for eight antibiotics (doxycycline, vancomycin, daptomycin, clindamycin, rifampin, nafcillin, and trimethoprim/sulfamethoxazole). Mature biofilms were grown in vitro, after which minimum biofilm inhibitory concentration (MBIC) and minimum biofilm bactericidal concentration (MBBC) were quantified. Only rifampin and doxycycline had a measurable MBIC across all tested isolates. Based on MBBC, 64% of S. epidermidis biofilms could be eliminated by rifampin, whereas only 18% by doxycycline. S. epidermidis biofilm was observed to have a high tolerance to antibiotics as compared to planktonic culture. Isolate biofilm antibiotic tolerance varied to a larger degree than was seen in planktonic cultures

Hydrogen Peroxide, Povidone-Iodine and Chlorhexidine Fail to Eradicate <i>Staphylococcus aureus</i> Biofilm from Infected Implant Materials

Hydrogen peroxide, povidone-iodine, and chlorhexidine are antiseptics that are commonly added to irrigants to either prevent or treat infection. There are little clinical data available that demonstrate efficacy of adding antiseptics to irrigants in the treatment of periprosthetic joint infection after biofilm establishment. The objective of the study was to assess the bactericidal activity of the antiseptics on S. aureus planktonic and biofilm. For planktonic irrigation, S. aureus was exposed to different concentrations of antiseptics. S. aureus biofilm was developed by submerging a Kirschner wire into normalized bacteria and allowing it to grow for forty-eight hours. The Kirschner wire was then treated with irrigation solutions and plated for CFU analysis. Hydrogen peroxide, povidone-iodine, and chlorhexidine were bactericidal against planktonic bacteria with over a 3 log reduction (p p S. aureus; however, when used to irrigate S. aureus biofilms, these antiseptics were unable to decrease biofilm mass below a 3 log reduction, suggesting that S. aureus biofilm has a tolerance to antiseptics. This information should be considered when considering antibiotic tolerance in established S. aureus biofilm treatment

Hydroelectric power potential, Woonsocket Falls Dam, Woonsocket, Rhode Island

The feasibility of developing a hydroelectric power plant at an existing flood control dam of the city of Woonsocket, RI was examined considering environmental, economic, technical and engineering factors. It was concluded that the City should proceed with plans to develop a hydro plant. (LCL

A high-rate fastbus silicon strip readout system

This paper describes a synchronous silicon S ~rePado ut system capable of zero deadtime readout at average trigger rates in excess of 1 MHz. The system is implemented in FASTBUS, uses pipelining techniques, and includes p6nt-Wpoint fiberoptic data links to transmit detector digital data. Semi-custom ASIC chips are used to amplify, discriminate, and logically combine track data before encoding. This paper describes the overall system, each major FASTBUS module, and the functional aspects of the ASIC chips

A high-rate fastbus silicon strip readout system

This paper describes a synchronous silicon S ~rePado ut system capable of zero deadtime readout at average trigger rates in excess of 1 MHz. The system is implemented in FASTBUS, uses pipelining techniques, and includes p6nt-Wpoint fiberoptic data links to transmit detector digital data. Semi-custom ASIC chips are used to amplify, discriminate, and logically combine track data before encoding. This paper describes the overall system, each major FASTBUS module, and the functional aspects of the ASIC chips