Effects of tigecycline, linezolid and vancomycin on biofilms of viridans streptococci isolates from patients with endocarditis.

BACKGROUND: Endocarditis, and prosthetic valve endocarditis in particular, is a serious disease with high morbidity and mortality. We investigate the effects of tigecycline, linezolid and vancomycin on biofilms of viridans group streptococci (VGS) isolated from patients with definite native or prosthetic valve endocarditis. METHODS AND RESULTS: Ten of 20 VGS blood stream isolates from patients with endocarditis formed biofilms in the microtiter plate biofilm model. The minimal inhibitory concentrations (MIC) for tigecycline, linezolid and vancomycin were determined using the microdilution broth method. Biofilms were grown for 24 hours and were incubated with tigecycline, linezolid and vancomycin at increasing concentrations from 1-128x MIC of the isolate being tested. Biofilm thickness was quantified by measuring the optical density (OD) after dyeing it with crystal violet. The incubation of the biofilms with tigecycline, linezolid or vancomycin resulted in a significant reduction of OD compared to the control biofilm without antibiotic (p<0.05). The optical density ratio (Odr) decreased significantly at 2x MIC for tigecycline, and at 8x MIC for linezolid and vancomycin (p<0.05). Although biofilms persisted even at the highest antibiotic concentrations of 128x MIC, bacterial growth was eradicated starting at concentrations of 16x MIC for vancomycin and of 32x MIC for linezolid, but not for tigecycline, up to a concentration of 128x MIC. CONCLUSIONS: In the present study on viridans streptococci isolated from patients with endocarditis, tigecycline and linezolid reduced the density of the biofilms as effectively as vancomycin. However, linezolid and vancomycin were bactericidal at higher concentrations. Linezolid and vancomycin at very high doses may be useful in the treatment of biofilm-associated diseases caused by VGS infections.

Viridans streptococci in endocarditis and neutropenic sepsis: biofilm formation and effects of antibiotics.

OBJECTIVES: Viridans group streptococci (VGS) are a frequent cause of bacterial endocarditis or sepsis in patients with neutropenia. Endocarditis in particular, is associated with plaque formation on the endocardium and valve leaflets whereas VGS septicaemia in neutropenic patients is caused by the influx of oral flora bacteria through mucositic lesions. This study examined the in vitro potency for biofilm formation of clinical VGS bloodstream isolates, and the effects of antibiotics on these biofilms. METHODS: During the years 1998-2000, 40 VGS bloodstream isolates from 18 patients with endocarditis and 22 patients with severe sepsis and neutropenia were collected. The MICs of penicillin, teicoplanin and moxifloxacin were determined using the microdilution broth method according to NCCLS criteria. Biofilms were grown in microtitre plates, dyed with Crystal Violet, and the mean optical density (OD) was used for quantification. Biofilms were incubated with penicillin, teicoplanin and moxifloxacin at various concentrations starting with the MICs for the respective isolates tested. RESULTS: Isolates from eight out of 18 patients with endocarditis and six out of 22 patients with neutropenia formed biofilms (not significant). For the 14 isolates, the MIC(90)s (range) of penicillin, teicoplanin and moxifloxacin were 0.5 mg/L (0.001-0.5), 0.125 mg/L (0.025-0.125) and 0.5 mg/L (0.05-0.5), respectively. Generally, biofilms persisted although incubated with the antibiotics up to concentrations of 128 x MIC. However, the ODs of biofilms after incubation with an antibiotic were significantly lower than the ODs of biofilms without antibiotic (P<0.05). A significant decrease in the biofilms with increasing antibiotic concentrations was observed for teicoplanin and moxifloxacin, but not for penicillin G. CONCLUSIONS: VGS isolated from patients with endocarditis and patients with sepsis and neutropenia form biofilms. Biofilms persist even when exposed to antibiotics at concentrations up to 128 x MIC. Nevertheless, teicoplanin and moxifloxacin reduced the density of the biofilms at concentrations >/=16 x MIC. Thus, testing the effects of antibiotics on biofilms may supply useful information in addition to standard in vitro testing, particularly in diseases where biofilm formation is involved in the pathogenesis.

The mediating effect of eating self-efficacy on the relationship between emotional arousal and overeating in the treatment-seeking obese.

In this study, we tested the proposition that the emotion-based eating of obese individuals is mediated by the effects of emotional arousal tendencies on brittle dieting self-restraint. Our indices of emotion-aroused eating, overeating, and brittle restraint were derived from a set of measures administered to 632 female and 254 male participants in a residential weight control and lifestyle change program. Mediation analyses indicated that (a) the relationship between positive emotion and overeating was entirely mediated by restraint tendencies and (b) the relationship between negative emotion eating and overeating was only partially mediated by brittle restraint. These findings held for both males and females. The results are discussed in relation to the viability of the psychosomatic hypothesis for understanding the relationship between emotions and overeating.

Psychological symptoms are greater among weight cycling women with severe binge eating behavior.

OBJECTIVE: To identify psychological characteristics and eating behaviors associated with weight cycling and binge eating behaviors in overweight women (body mass index > 27.3). DESIGN: Questionnaires measuring self-esteem, self-efficacy, coping strategies, psychological symptoms, depression, binge eating, restrained eating, disinhibition, and hunger were administered to female weight cyclers who were overweight. Psychological characteristics were compared between subjects grouped by binge eating disorder classification and by binge eating severity. SUBJECTS: A convenience sample of 62 female weight cyclers who were overweight was recruited from the Chicago, Ill, area. Questionnaires were administered individually or in small groups in subjects' homes or other private settings. STATISTICAL ANALYSES: Student's t tests or Mann-Whitney U tests were used to assess differences in psychological characteristics. RESULTS: Thirty-six weight cyclers (58%) met the criteria for binge eating disorder and 26 (42%) did not. Weight cyclers with binge eating disorder reported greater severity of binge eating (P < .0005) and disinhibition (P < .0005) and poorer eating self-efficacy (P < .0005) than weight cyclers without binge eating disorder. Weight cyclers with severe binge eating behaviors reported greater psychological distress (P < .0005) and depression (P < .005) and lower self-esteem (P = .0001) and used less healthful coping strategies (P = .0027) than weight cyclers with no binge eating to moderate binge eating problems. Weight cyclers with severe binge eating behavior also reported more hunger (P < .0005) and used less cognitive restraint (P = .0024) than those with no binge eating to moderate binge eating problems. APPLICATIONS: Operational definitions of weight cycling and binge eating are needed to facilitate research on effective weight-loss treatments. Persons seeking to lose weight (especially weight cyclers) should be assessed for binge eating severity, problematic eating behaviors, and psychological symptoms.

Cerebral symptoms after whiplash injury of the neck: a prospective clinical and neuropsychological study of whiplash injury.

Twenty one unselected patients with an acute whiplash injury of the neck had neurological and neuropsychological assessment, cervical x rays, EEG, BAEP, MRI, and an otoneurological examination within two weeks of the injury. Subjectively, 13 patients reported concentration deficits, 18 reported sleep disturbances, 9 had symptoms of depression, and 7 female patients told of menstrual irregularities. Neuropsychological examination revealed significantly lower performance in tests related to attention and concentration compared to sex, age and educational matched control subjects. Otoneurological examination showed abnormalities in 9 of 17 whiplash subjects. EEG showed questionable changes in 8 of 18 recordings. MRI and BAEP were normal in all patients. Repeat neuropsychological testing in 15 patients at three months showed that attention deficits had improved but were still shown in 12 of 14 and the concentration deficits in 8 of 13 patients. At one year all patients had returned to work, 16 to full and 5 to part time employment. In 4, cognitive dysfunction remained the only significant problem. These findings are discussed as being compatible with possible damage to basal frontal and upper brain stem structures after whiplash injury of the neck.

Film quality in image intensifier photofluorography.

Three films of different sensitivity and grain size were tested in 70 mm image intensifier photofluorography. The radiographic exposure was kept constant, adaptation to the different film speeds being achieved by different settings of the camera diaphragm. Reduced film speed implied a greater number of object details being recorded.

Receptor saturation in roentgen films.

Roentgen-film recording of small object details of low attenuation differences (e.g. pulmonary vessels) is regularly seen to be impaired when the film is exposed to yield high values of optical density (D). The high-density failure is due to receptor saturation, which implies that at high exposure values most silver halide grains of the film are made developable, leaving few grains available to receive additional informative photons. The receptor saturation is analysed by means of a mathematical model of a non-screen film yielding Dmax = 2.0. Optimum recording, defined by maximum signal-to-noise ratio in the image, is found at D = 0.64, corresponding to, on an average, 1.6 photons absorbed per grain. On the other hand, maximum contrast occurs at D approximately 1.4, where, on the average, 3.6 photons are absorbed per grain. The detective quantum efficiency of the film, i.e. the fraction of the photons actually contributing to the information content of the image, drops from 41 per cent at maximum signal-to-noise ratio to a mere 10 per cent at maximum contrast. Receptor saturation does not manifest itself as 'mottle' in the image--it is therefore easily overlooked. The importance of adequate removal of secondary radiation is emphasised by these results.

Storage and display of information in roentgen films.

Roentgen images of high density, without actually being overexposed, tend to leave small details of low contrast unrecorded. Still, these details may be reproduced by the same film if the density is lower, even if the gamma value is kept constant. The present report is concerned with how information is stored in the film and the information stored is displayed to the inspecting eye. It appears that films of high density contain information which is invisible, so that the disappearance of image details to a certain extent reflects a defect of display.

Influence of radiation dose on image quality.

When the speed of a recording medium is doubled the background quantum mottle is increased by a factor square root 2. However, the signal/noise ratio is changed not in proportion to the square root of the exposure, but in a linear fashion, i.e. by a factor 2. The change in the depiction of objects with a very high attenuation difference in relation to its surroundings appears not to be linear, but proportional to the square root of the exposure. Such objects (metal wire meshes, lead bar grids) should thus be avoided in routine evaluation of image quality since they give incomplete information as to image impairment when high-speed recording media are used.

Choice of screens in high-speed angiography.

In phantom experiments a number of intensifying screens were tested as regards their usefulness for angiography. Film speed was adjusted so as to make possible a constant radiographic exposure despite screen speeds varying by a factor of 3. Thus, screen unsharpness varied considerably. However, it was of no practical importance as long as the radiographic exposure was kept constant. This observation indicates that the modulation transfer function is of limited value in differentiating between screens for high-speed angiography. Likewise, film contrast was of little significance for image quality, as compared with radiographic exposure to the intensifying screens.

Visual evaluation of microscopic mottle.

According to Rose the resolution of an imaging system is under certain conditions limited by noise rather than by the finite geometric response as expressed by the modulation transfer function. In order to investigate whether this applies to clinical radiography as well, a technique for magnification of roentgen films has been devised, making possible visual evaluation of microscopic noise.

Relevance of radiographic resolution capacity.

Resolution capacity is traditionally evaluated by radiography of metal objects (lead bar grids or fine slits). These objects yield high image contrast. Resolution, then, is limited by the sideways spread of information as expressed by the MTF. However, biologic objects of fine dimensions give rise to much less image contrast than the test objects of metal. Since the amplitude of the signals thus becomes reduced the signal/noise ratio in fact limits resolution capacity much more effectively than does the sideways spread of information. Thus, the MTF expresses a property of the radiographic system which appears only rarely to affect the information capacity of clinical radiographic images.

Influence of microscopic mottle on the definition of small image details.

By a special technique of enlarging films, a microscopic mottle caused by quantum fluctuations was demonstrated. It was found to affect depiction of small details in such a way as to suggest that it would be of importance for determining resolution capacity, especially in high-speed radiography. Thus, the modulation transfer function appears not to be the only factor determining radiographic resolution. The resolution of high-speed screens may be improved if the film speed is reduced, which leads to a diminished microscopic mottle.

Optimised tomography for clinical use.

A technique elaborated by the present authors (1974) for the establishment of optimum tomographic movements was applied to ear tomography in order to design a movement that is not too complex, but yielding good tomographic depiction. Such a movement was found to consist of a spiral of 5 revolutions. Modern engineering appears to allow such complex movements to be carried out with satisfactory stability within a reasonable exposure time.

Tomographic localization of motion axes.

Localization of motion axes within joints and junctures in living humans has been carried out by means of roentgen stereophotogrammetry. Another technique is presented here, in which the localization of the axis is carried out by means of tomography. The field of application for this technique has been examined in a series of phantom experiments. It may be employed in certain situations where roentgen stereophotogrammetry is not useful. No other equipment is needed than a pluridirectional tomograph and conventional dark-room facilities.

Quantity of tomographic blurring.

A spiral tomographic movement gives rise to a lower quantity of blurring than does a circular movement with the same tomographic angle since in the former the focus comes nearer to the central point. It has been demonstrated that the transfer function may be used to express the quantity of blurring for different tomographic movements. For the sake of convenience the blurring quantity for every type of spiral movement may be expressed in terms of the tomographic angle of a circular movement giving rise to the same transfer function.

Testing of roentgen film quality.

Evaluation of film quality is often based upon the film's characteristic curve. A practical test method implying radiography of sandpaper sheets has been devised, yielding crucial information about the quality, which cannot be derived from the characteristic curve. Since this test appears to give more valid information about film quality than conventional sensitometry, it is suggested that the test procedure should be standardised and used by the manufacturers.

Medichrome film as an alternative to silver-free recording systems.

A shortage of silver is forcing film manufacturers to lower the silver content of radiographic films. No further lowering seems possible without film quality being adversely affected. Various ways to solve the silver problem in the future are discussed and colour radiography is regarded as one solution since it makes possible a high degree of immediate recovery of silver. The feasibility and proper use of the only colour film available, Medichrome, is discussed. Suitable screens in order to compensate for the low sensitivity of the film without loss of image quality and a strong light source containing a monochromatic sodium lamp for inspection of dense areas are recommended.