Violet-Blue Light Arrays at 405 Nanometers Exert Enhanced Antimicrobial Activity for Photodisinfection of Monomicrobial Nosocomial Biofilms.

Light-emitting diodes (LEDs) demonstrate therapeutic effects for a range of biomedical applications, including photodisinfection. Bands of specific wavelengths (centered at 405 nm) are reported to be the most antimicrobial; however, there remains no consensus on the most effective irradiation parameters for optimal photodisinfection. The aim of this study was to assess decontamination efficiency by direct photodisinfection of monomicrobial biofilms using a violet-blue light (VBL) single-wavelength array (SWA) and multiwavelength array (MWA). Mature biofilms of nosocomial bacteria (Acinetobacter baumannii, Pseudomonas aeruginosa, Escherichia coli, and Staphylococcus aureus) were grown on 96-well polypropylene PCR plates. The biofilms were then exposed to VBL for 2,700 s (SWA) and 1,170 s (MWA) to deliver 0 to 670 J/cm2, and the antibacterial activity of VBL was assessed by comparing the seeding of the irradiated and the nonirradiated biofilms. Nonirradiated groups were used as controls. The VBL arrays were characterized optically (spectral irradiance and beam profile) and thermally. The SWA delivered 401-nm VBL and the MWA delivered between 379-nm and 452-nm VBL, albeit at different irradiances and with different beam profiles. In both arrays, the irradiated groups were exposed to increased temperatures compared to the nonirradiated controls. All bacterial isolates were susceptible to VBL and demonstrated reductions in the seeding of exposed biofilms compared with the nonirradiated controls. VBL at 405 nm exerted the most antimicrobial activity, exhibiting reductions in seeding of up to 94%. Decontamination efficiency is dependent on the irradiation parameters, bacterial species and strain, and experimental conditions. Controlled experiments that ameliorate the heating effects and improve the optical properties are required to optimize the dosing parameters to advance the successful clinical translation of this technology.IMPORTANCE This study reports the efficacy of VBL and blue light (BL) and their antimicrobial activity against mature biofilms of a range of important nosocomial pathogens. While this study investigated the antibacterial activity of a range of wavelengths of between 375 and 450 nm and identified a specific wavelength region (∼405 nm) with increased antibacterial activity, decontamination was dependent on the bacterial species, strain, irradiation parameters, and experimental conditions. Further research with controlled experiments that ameliorate the heating effects and improve the optical properties are required to optimize the dosing parameters to advance the successful clinical translation of this technology.

Use of an engineered honey to eradicate preformed biofilms of important wound pathogens: an in vitro study.

OBJECTIVE: We previously reported on the ability of SurgihoneyRO (SHRO), an engineered honey, to prevent biofilm formation in vitro, but data were lacking regarding the activity against preformed biofilms. This study aims to assess whether SHRO has any antibacterial activity against mature, preformed biofilms and whether there is any evidence to support the observed clinical effectiveness when SHRO has been used anecdotally on acute and chronic wounds where biofilm is most likely present. METHOD: We tested the in vitro antibacterial activity of SHRO against the mature biofilms of 16 clinically relevant wound pathogens, in terms of impacts on biofilm seeding and biofilm biomass. The honey was serially double diluted from 1:3 down to 1:6144, and the lowest dilution achieving a statistically significant reduction in biomass of ≥50%, compared with untreated controls, was recorded. RESULTS: All 16 bacterial isolates were susceptible to SHRO, with reduced biofilm seeding observed for all, and percentage reductions ranging from 58% (ACI_C59) to 94.3% (MDR_B) for the strongest concentration of honey (1:3). Furthermore at this concentration, biofilm seeding of the test biofilm was reduced by 80-94.3% (when compared with the positive control) for 12/16 isolates. We additionally demonstrated that SHRO has antibiofilm impacts, with the 24 hour exposure resulting in disruption of the biofilm, reduced seeding and reduced biomass. CONCLUSION: SHRO is effective at reducing seeding of preformed biofilms of clinically important wound pathogens in vitro, and also has antibiofilm activity. This supports the anecdotal clinical data for antibiofilm efficacy, and supports the use of SHRO as a promising topical wound care agent.

In vitro activity of an engineered honey, medical-grade honeys, and antimicrobial wound dressings against biofilm-producing clinical bacterial isolates.

OBJECTIVE: Honey is recognised to be a good topical wound care agent owing to a broad-spectrum of antimicrobial activity combined with healing properties. Surgihoney RO (SH1) is a product based on honey that is engineered to produce enhanced reactive oxygen species (ROS) and has been reported to be highly antimicrobial. The objective was to investigate the ability of the engineered honey and its comparators to prevent biofilm formation in vitro. METHOD: We tested the ability of three medical-grade honeys SH1, Activon manuka honey (MH) and Medihoney manuka honey (Med), alongside five antimicrobial dressings (AMDs) to prevent the formation of biofilms by 16 isolates. Honeys were serially double diluted from 1:3 down to 1:6144 and the lowest dilution achieving a statistically significant reduction in biomass of at least 50%, compared with untreated controls, was recorded. RESULTS: Although all the honeys were antibacterial and were able to prevent the formation of biofilms, SH1 was the most potent, with efficacy at lower dilutions than the medical honeys for five isolates, and equivalent dilutions for a further six. Additionally, SH1 was superior in antibacterial potency to three commercially available AMDs that contain honey. CONCLUSION: SH1 is effective at preventing bioflms from forming and is superior to medical honeys and AMDs in in vitro tests. DECLARATION OF INTEREST: Surgihoney RO was provided free of charge for testing by Matoke Holdings, UK and the hospital pharmacy provided the other honeys and dressings. This paper presents independent research funded by the National Institute for Health Research (NIHR). The views expressed are those of the authors and not necessarily those of the NHS, the NIHR or the Department of Health.

Whole genome sequencing of toxigenic Clostridium difficile in asymptomatic carriers: insights into possible role in transmission.

BACKGROUND: Estimates of the prevalence of asymptomatically carried Clostridium difficile in elderly patients in long-term care range from 0% to 51%. Asymptomatic carriage is possibly a risk factor for the development of infection, and there is ongoing debate surrounding the role of asymptomatic carriage in transmission. AIM: To investigate the prevalence of asymptomatic carriage amongst patients residing in intermediate care (bedded) facilities (ICBFs), and to investigate whether asymptomatically carried C. difficile strains contribute to nosocomial C. difficile infection (CDI). METHODS: Stools were collected from eligible asymptomatic patients in ICBFs, and a subset was also processed from symptomatic patients accessing primary or secondary care outside of ICBFs. All samples were cultured for C. difficile, and resulting colonies were processed through whole genome sequencing. FINDINGS: In total, 151 asymptomatic patients were sampled, 22 of which were positive for C. difficile through stool culture, representing a carriage rate of 14.6%. Sequencing of these isolates, alongside 14 C. difficile polymerase chain reaction and culture-positive isolates from symptomatic individuals, revealed that all asymptomatic patients were carrying toxigenic C. difficile, and these strains were genetically similar to those from symptomatic patients. CONCLUSION: This small study of asymptomatic carriage revealed a rectal asymptomatic carriage rate of 14.6% in patients nursed in ICBFs, and a high level of genetic similarity of these strains to those recovered from symptomatic patients. As such, asymptomatic carriers may be important for the transmission of symptomatic CDI, although it is acknowledged that this study was small, and many other factors govern whether C. difficile is carried asymptomatically or causes symptoms.

Top research priorities in healthcare-associated infection in the UK.

BACKGROUND: There is a mismatch between research questions which are considered to be important by patients, carers and healthcare professionals and the research performed in many fields of medicine. No relevant studies which have assessed research priorities in healthcare-associated infection (HCAI) that have involved patients' and carers' opinions were identified in the literature. AIM: The Healthcare-Associated Infections Priority Setting Partnership was established to identify the top research priorities in the prevention, diagnosis and treatment of HCAI in the UK, considering the opinions of all these groups. METHODS: The methods broadly followed the principles of the James Lind Alliance (JLA) priority setting activity. FINDINGS: In total, 259 unique valid research questions were identified from 221 valid responses to a consultation of patients, carers and healthcare professionals after seeking their opinions for research priorities. The steering committee of the priority setting partnership rationalized these to 50 unique questions. A literature review established that for these questions there were no recent high-quality systematic reviews, high-quality systematic reviews which concluded that further studies were necessary, or the steering committee considered that further research was required despite the conclusions of recent systematic reviews. An interim survey ranked the 50 questions, and the 10 main research priorities were identified from the top 32 questions by consensus at a final priority setting workshop of patients, carers and healthcare professionals using group discussions. CONCLUSIONS: A priority setting process using JLA methods and principles involving patients, carers and healthcare professionals was used to identify the top 10 priority areas for research related to HCAI. Basic, translational, clinical and public health research would be required to address these uncertainties.

Comparative analysis of antimicrobial susceptibility among organisms from France, Germany, Italy, Spain and the UK as part of the tigecycline evaluation and surveillance trial.

As part of the tigecycline evaluation and surveillance trial (TEST), bacterial isolates were collected from 39 centres in France, Germany, Italy, Spain and the UK between January 2004 and August 2006. Antimicrobial susceptibilities were determined according to CLSI guidelines. Italy had the highest rate of methicillin-resistant Staphylococcus aureus (36.4%), and was the only country to report vancomycin-resistant Enterococcus faecalis (8.6%). Tigecycline was the only agent to which all Gram-positive isolates were susceptible. For many of the Gram-negative organisms collected, antimicrobial susceptibilities were lowest among isolates from Italy and highest among isolates from Spain. The notable exception was Acinetobacter baumannii, where the poorest susceptibility profile was among isolates from Spain. For A. baumannii, MIC(90)s of imipenem varied from 1 mg/L for isolates in France and Germany to > or =32 mg/L for isolates from Italy and Spain. Tigecycline was the only agent to maintain an MIC(90) of < or =1 mg/L against isolates from all five countries. The in-vitro activity of tigecycline against both Gram-positive and Gram-negative isolates may make it valuable in the treatment of hospital infections, including those caused by otherwise antimicrobial-resistant organisms.

Rapid recontamination with MRSA of the environment of an intensive care unit after decontamination with hydrogen peroxide vapour.

Meticillin-resistant Staphylococcus aureus (MRSA) persists in the hospital environment and conventional cleaning procedures do not necessarily eliminate contamination. A prospective study was conducted on an intensive care unit to establish the level of environmental contamination with MRSA, assess the effectiveness of hydrogen peroxide vapour (HPV) decontamination and determine the rate of environmental recontamination. MRSA was isolated from 11.2% of environmental sites in the three months preceding the use of HPV and epidemiological typing revealed that the types circulating within the environment were similar to those colonising patients. After patient discharge and terminal cleaning using conventional methods, MRSA was isolated from five sites (17.2%). After HPV decontamination but before the readmission of patients, MRSA was not isolated from the environment. Twenty-four hours after readmitting patients, including two colonized with MRSA, the organism was isolated from five sites. The strains were indistinguishable from a strain with which a patient was colonized but were not all confined to the immediate vicinity of the colonized patient. In the eight weeks after the use of HPV, the environment was sampled on a weekly basis and MRSA was isolated from 16.3% sites. Hydrogen peroxide vapour is effective in eliminating bacteria from the environment but the rapid rate of recontamination suggests that it is not an effective means of maintaining low levels of environmental contamination in an open-plan intensive care unit.

Continued transmission of Pseudomonas aeruginosa from a wash hand basin tap in a critical care unit.

Pseudomonas aeruginosa is an important nosocomial pathogen, colonizing hospital water supplies including taps and sinks. We report a cluster of P. aeruginosa acquisitions during a period of five months from tap water to patients occupying the same burns single room in a critical care unit. Pseudomonas aeruginosa cultured from clinical isolates from four different patients was indistinguishable from water strains by pulsed-field gel electrophoresis. Water outlets in critical care may be a source of P. aeruginosa despite following the national guidance, and updated guidance and improved control measures are needed to reduce the risks of transmission to patients.

Viridans streptococcal bacteraemia in patients with haematological and solid malignancies.

Thirty-three episodes of septicaemia caused by viridans streptococci are reported in 32 adults under treatment for malignant diseases. The underlying diseases were acute leukaemia (17), lymphoma (4), myeloma (1), small cell carcinoma of the bronchus (6), carcinoma of the breast (2) and carcinoma of the stomach (2). Important predisposing factors included severe neutropenia and oral mucositis due to intensive chemotherapeutic regimens. There was a poor response to standard empirical antibiotics and a mortality of 12%. A role for prophylactic penicillin in high risk groups is suggested.

Dynamic hepatobiliary SPECT: a method for tomography of a changing radioactivity distribution.

Dynamic single photon emission computed tomography (SPECT) of a changing radioactivity distribution can be performed with a rotating scintillation camera by acquiring several 360 degree studies and generating a new 360 degree study for which the acquisition time for every image is shifted to a single selected time. Following suppression of gallbladder filling with a fatty meal, dynamic SPECT of the hepatobiliary system was carried out by acquiring two successive studies with each head of a dual-headed camera within a 35-min period following injection of technetium-99m DISIDA. Each of the four acquired studies consisted of 60 images acquired at 6 degree intervals, spanning 360 degrees. Time-shifted studies, each consisting of 60 images over 360 degrees, were generated for times 9, 17, and 26 min postinjection. Transverse, sagittal, and coronal images were generated for each study. These images were artifact-free and demonstrated physiologic shifting of the radioactivity distribution over time. When gallbladder filling was not suppressed gross artifacts were obtained. This procedure permits examination of regional liver function and provides improved visualization of the biliary tree.

Uniformity correction for SPECT using a mapped cobalt-57 sheet source.

As little as 1% nonuniformity of the scintillation camera can produce disturbing artifacts in SPECT images. To correct for nonuniformity, acquired images must be divided by the flood-field image of a uniform sheet source. The refillable 99mTc sheet source requires meticulous preparation before each use, and is subject to spillage. We propose the use of a permanent 57Co solid sheet source in conjunction with a map of the radioactivity distribution in the source. The flood-field image of the cobalt source is converted by the map into the equivalent of a flood-field image of an almost perfectly uniform source. An accurate and reproducible method is described for generating a map of the cobalt sheet source from images of it made in multiple positions with the scintillation camera. The mapping process is independent of sensitivity variations across the face of the camera.

Functional renal imaging through factor analysis.

Functional images tend to be noisy, since they are formed from parameter values estimated from noisy time-activity curves. Factor analysis provides a rapid method for fitting smooth curves to these noisy curves. Noise in functional images is reduced by estimating parameter values from the smooth curves. The method is illustrated for three parameters: TMAX (time to maximum value), RISE (increase from first to maximum value), and RISMX (maximum increase between successive values). When curve-fitting through factor analysis is used to generate functional renal images from clinical studies or to estimate parameter values for simulated noisy renogram curves, noise is reduced for the TMAX and RISMX parameters and accuracy is improved for the RISE parameter.

An automated method for the alignment of image pairs.

The computer comparison of two images of the same organ requires proper alignment of the images before further computer processing. This alignment can be achieved by (a) fixing patient position during the study, (b) alignment methods using analytical transformations, or (c) operator interaction. We propose an automated method based upon the cross-correlation between projections of the images. With fast Fourier transforms, the algorithm becomes computationally cheap.

Direct comparison of fluorine-18-FDG SPECT, fluorine-18-FDG PET and rest thallium-201 SPECT for detection of myocardial viability.

UNLABELLED: Twenty consecutive patients were evaluated for presumptive myocardial viability using rest TI-SPECT, FDG-PET and FDG-SPECT. The FDG studies were performed after rest TI-SPECT to guide intervention or medical management. METHODS: Twenty patients with proven coronary artery disease, either known or suspected to have previous myocardial infarction and persistent perfusion defects shown by rest reinjection TI-SPECT, underwent FDG-PET and subsequent FDG-SPECT with a three-detector SPECT camera. FDG-PET and SPECT images were compared by five observers to determine if any fixed thallium segments were visualized by either FDG imaging method. RESULTS: Thirteen of 60 fixed segments were shown probably viable by FDG-SPECT (8 of 20 patients) and 14 of 60 by FDG PET (7 of 20 patients). Two patients had fixed thallium segments found probably viable with FDG by SPECT alone and one by PET alone. CONCLUSION: FDG is shown to provide additional information about myocardial viability. Both SPECT, using a three-detector camera, and PET with a specialized instrument are equally effective for imaging FDG in this application.

Symptom-limited arm exercise increases detection of ischemia during dipyridamole tomographic thallium stress testing in patients with coronary artery disease.

Exercise combined with dipyridamole during thallium stress testing in patients with coronary artery disease (CAD) increases the frequency of angina and ischemic ST changes in the electrocardiogram. Evidence for an increase in thallium abnormalities has been inconclusive. We prospectively examined 54 consecutive patients who underwent coronary angiography and tomographic thallium with dipyridamole (0.57 mg/kg) alone and combined with symptom-limited dynamic arm exercise. Most patients presented with a history of chest pain and 49 had angiographic evidence of significant coronary stenosis (50% diameter narrowing). Thallium abnormalities were scored blindly by consensus. The number of abnormal segments (total and ischemic) and indexes of left ventricular dysfunction, such as increased lung uptake or ischemic dilation, were compared in the 49 patients with CAD. During arm exercise more patients had evidence of ischemia (39 vs 30; p < 0.001), and the number of ischemic segments increased significantly from 1.3 +/- 1.5 to 2.5 +/- 2.2 (p < 0.001). There was also a significant increase in the indexes of left ventricular dysfunction, ischemic dilation (10 vs 4 patients; p < 0.03) and increased lung uptake (16 vs 5 patients; p < 0.001). Patients who exercised had increased thallium evidence of extent and severity of ischemia and more frequent indexes of left ventricular dysfunction. Thus, symptom-limited arm exercise improves detection of extent and severity of ischemia in patients with CAD undergoing dipyridamole thallium stress testing.

Computer-assisted radiology resident rotation scheduling.

The author developed a method for computer-assisted scheduling of resident rotations in which the chief resident determines the most desirable set of rotations for each resident, disregarding specific month assignments except as required or requested, and the computer generates the schedule by assigning months to rotations. The computer uses an efficient search algorithm to find a schedule that satisfies all requirements. The method satisfies training goals, staffing needs, and residents' desires more effectively than manual scheduling. Although fixed staffing levels for every rotation are required, flexibility is achieved through "dummy" assignments of rotations to residents.

Screening for cytomegalovirus (CMV) infection in allogeneic bone marrow transplantation using a quantitative whole blood polymerase chain reaction (PCR) method: analysis of potential risk factors for CMV infection.

Potential risk factors for CMV infection and the use of quantitative CMV PCR screening to guide pre-emptive anti-CMV therapy were reviewed retrospectively in 32 allogeneic bone marrow transplant patients accrued over a 2-year period. Significant CMV PCR positivity (an indicator of CMV infection) developed in 34% of patients. When analysed by recipient CMV IgG serostatus, 69% of seropositive recipients developed significant CMV PCR positivity while none of the seronegative recipients did so (P = 0.00007). Considering only the seropositive recipients, 100% of those who received the low intensity campath-1H/fludarabine/melphalan 'mini-allograft' conditioning regimen developed significant CMV PCR positivity, while only 44% of those who had received cyclophosphamide/TBI did so (P = 0.0337). The mean time to first episode of significant CMV PCR positivity for those who had received campath/fludarabine/melphalan was 25 days while for those who had received cyclophosphamide/TBI, this was 66 days (P = 0.0372). For the first episode of significant CMV PCR positivity, the mean index and peak CMV PCR counts for those who had received campath/fludarabine/melphalan were 4.54 and 5.22 log copies/ml respectively, while for cyclophosphamide/TBI, the corresponding figures were 3.85 and 4.12 log copies/ml respectively (P = 0.2986 and P = 0.0472 for index and peak values). 85% of those who had significant CMV PCR positivity with the campath/fludarabine/melphalan regimen developed more than one such episode, while 50% of those receiving cyclophosphamide/TBI regimen did so (P = 0.491). Significant CMV PCR positivity was associated with symptoms in a proportion of patients (pyrexia 45%, cough 18%, rise in AST 72%). No patient developed overt CMV disease. CMV PCR is useful for guiding pre-emptive anti-CMV therapy and for monitoring response.