Tuning the dynamics of imidazolium-based ionic liquids via hydrogen bonding. I. The viscous regime.

Combining results from impedance spectroscopy and oscillatory shear rheology, the present work focuses on the relation between the mass and charge flows and on how these are affected by the H-bonding in viscous ionic liquids (ILs). In particular, we compare the relaxational behaviors of the paradigmatic IL 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMIM-TFSI) and its OH-functionalized counterpart 1-(2-hydroxyethyl)-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (OHEMIM-TFSI). Our results and their analysis demonstrate that the presence of cationic OH-groups bears a strong impact on the overall dynamics of OHEMIM-TFSI, although no signatures of suprastructural relaxation modes could be identified in their dielectric and mechanical responses. To check whether at the origin of this strong variation is the H-bonding or merely the difference between the corresponding cation sizes (controlling both the hydrodynamic volume and the inter-charge distance), the present study includes 1-propyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (PMIM-TFSI), mixtures of EMIM-TFSI and PMIM-TFSI with lithium bis(trifluoromethylsulfonyl)imide (Li-TFSI), and mixtures of OHEMIM-TFSI with PMIM-TFSI. Their investigation clearly reveals that the dynamical changes induced by H-bonding are significantly larger than those that can be attributed to the change in the ion size. Moreover, in the mixtures of OHEMIM-TFSI with PMIM-TFSI, a dilution of the OH-groups leads to strong deviations from ideal mixing behavior, thus highlighting the common phenomenological ground of hydroxy-functionalized ILs and other H-bonded liquids.

Stability and bactericidal activity of chlorine solutions.

OBJECTIVES: To determine the stability of sodium hypochlorite (diluted household bleach) when stored for 30 days in various types of containers and to determine the efficacy of low concentrations of free available chlorine to inactivate test bacteria. DESIGN: Laboratory-based study. Solutions of standard household bleach were prepared using tap water or sterile distilled water at dilutions of 1:100, 1:50, and 1:5. Chlorine concentrations were measured, and then the solutions were placed into five polyethylene containers and left at room temperature (20 degrees C) under various conditions (translucent containers with light exposure and with or without air; brown opaque container without light or air exposure). Samples for chlorine and pH determinations were taken at time 0 and on days 7, 14, 21, 30, and 40. Bactericidal activity of chlorine solutions was assessed using the Association of Official Analytical Chemists Use-Dilution Method. Test bacteria included Pseudomonas aeruginosa, Staphylococcus aureus, and Salmonella choleraesuis. RESULTS: Chlorine concentrations at 30 days varied from the 40% to 50% range for 1:50 or 1:100 dilutions stored in containers other than closed brown containers to 83% to 85% for the 1:5 dilution stored in closed but non-opaque containers to 97% to 100% for 1:50 or 1:5 solutions stored in closed brown containers. The lowest concentration of sodium hypochlorite solution that reliably inactivated all the test organisms was 100 ppm. CONCLUSIONS: These data suggest that chlorine solutions do not need to be prepared fresh daily, as is recommended currently, and the lowest concentration of chlorine that reliably inactivates S aureus, S choleraesuis, and P aeruginosa is 100 ppm.

Infection risks associated with spirometry.

OBJECTIVES: Spirometry is a widely used pulmonary function test that allows measurement of forced vital capacity and time-related measures of dynamic pulmonary function. This study was designed to identify the risk of cross-transmission associated with two commonly used dryrolling seal spirometers. DESIGN: Using a prospective study design, we examined whether microbial contamination of spirometers occurred following use by patients with a heavily colonized or infected respiratory tract. Prior to spirometry evaluation, a patient's sputum culture and equipment samples (i.e., mouthpiece, proximal tubing, piston surface) were obtained. After patient evaluation, a sterile 2 L ventilation bag and sterile tubing were used to simulate the risk of infection of subsequent patients. Simulation 1 was performed immediately after patient testing and Simulation 2, representing a second patient was conducted approximately 18 hours later. SETTING: This study was conducted at the University of North Carolina Hospitals, a large university teaching facility. PATIENTS: Fourteen patients with underlying pulmonary disease were studied. RESULTS: Our study revealed that the mouthpieces became contaminated with the patients' oral flora and with the associated respiratory pathogen. Fourteen percent of the associated tubing after patient testing contained the respiratory pathogen. All other equipment samples (e.g., interior surfaces of the machine, Simulation 1, Simulation 2 samples) were negative for the respiratory pathogen. CONCLUSIONS: These data suggest that mouthpieces and spirometry tubing may become contaminated with microorganisms and should not be shared between patients. Since there is little or no bacterial contamination of the surfaces inside the spirometers and cross transmission is unlikely, it is unnecessary to routinely clean the interior surfaces of the spirometers.

Manual ventilation bags as a source for bacterial colonization of intubated patients.

A group of 14 intensive care unit (ICU) patients were studied to determine if manual ventilation bags (MVB) could serve as a source of bacterial or fungal pathogens that could colonize the respiratory tract of intubated patients. A total of 51 cultures were simultaneously obtained of patient's sputum, the exterior MVB surface, MVB port, and MVB interior (postexhalation valve). Pathogens colonizing or infecting the respiratory tract of intubated ICU patients were frequently simultaneously present on the exterior surface of the MVB and inside the MVB port used to connect the MVB with the endotracheal tube. In addition, coagulase-negative staphylococci and yeast were frequently present on the exterior surface of the MVB. The interior of the MVB was usually sterile. In three instances pathogens were isolated from the MVB before isolation from the patient's sputum. MVB may serve as a source for colonizing the respiratory tract of intubated ICU patients and/or the hands of medical personnel. The exterior surface and port of MVB should be cleaned of visible debris and disinfected at least once a day.

Clinical significance of Bacillus species isolated from blood cultures.

To determine the clinical significance of blood isolates of Bacillus, we reviewed all blood cultures obtained at North Carolina Memorial Hospital between 1981 and 1985. Over the five-year study period the number of patients (incidence per 10,000 hospital admissions) from whom Bacillus was isolated increased from 4.97 in 1981 to 12.5 in 1985. The incidence per 1,000 blood cultures also increased from 1.12 in 1981 to 2.33 in 1985. Review of the medical records of 78 of the 95 patients (82%) with positive cultures allowed retrospective classification of five isolates (6.4%) as clinically significant, 33 isolates (42.3%) as possibly significant, and 40 isolates (51.3%) as nonsignificant. Underlying diseases in patients with clinically significant Bacillus bacteremia included burn trauma in two, leukemia in one, carcinoma in one, and gastrointestinal hemorrhage in one. All isolates judged to be clinically significant and the majority of possibly significant isolates were B cereus. We conclude that the isolation of Bacillus species from blood cultures is clinically significant in 5% to 10% of cases, that the incidence of Bacillus bacteremia is increasing, and that burn trauma should be added to the list of conditions known to predispose to clinically significant Bacillus bacteremia.

An outbreak of Pseudomonas cepacia bacteremia associated with a contaminated intra-aortic balloon pump.

In January 1983, symptomatic Pseudomonas cepacia bacteremia developed in two patients in the cardiothoracic intensive care unit within 3 days after cardiac operation and insertion of an intra-aortic balloon pump. An epidemiologic and microbiologic investigation revealed that both patients required intra-aortic balloon pumping for circulatory support and that the water reservoir of the intra-aortic balloon pump (SMEC, Inc., Cookeville, Tenn.) contained more than 10(5) Pseudomonas cepacia per milliliter. This organism was also recovered from the purge button and on-off switch of the pump and from the hands of a health care worker who manipulated the water reservoir of the intra-aortic balloon pump. Agarose gel electrophoresis of lysates of Pseudomonas cepacia with rapid methods of deoxyribonucleic acid preparation revealed three identical plasmids of the Pseudomonas cepacia from the water reservoir of the intra-aortic balloon pump and from the infected patients. Transmission from the worker's hands to patients presumably occurred by inoculation of the intravascular lines during management. No additional cases of Pseudomonas cepacia bacteremia were observed after the unit was replaced with a nonwater reservior intra-aortic balloon pump. This report substantiates the ability of Pseudomonas cepacia to multiply in water and to cause epidemic bacteremia, identifies the water reservoir of the SMEC intra-aortic balloon pump as a previously unrecognized hazard for the patient requiring intra-aortic balloon pumping, and documents the value of plasmid analysis in elucidating the mode of transmission of nosocomial Pseudomonas cepacia infections.

In vitro susceptibility of Bacillus spp. to selected antimicrobial agents.

Although often dismissed as contaminants when isolated from blood cultures, Bacillus spp. are increasingly recognized as capable of causing serious systemic infections. As part of a clinical-microbiological study, 89 strains of Bacillus spp. isolated from clinical blood cultures between 1981 and 1985 had their species determined and were tested for antimicrobial agent susceptibility to 18 antibiotics. Species of isolates were determined by the API 50CH and API 20E systems. Bacillus cereus (54 strains) was the most common species isolated, followed by B. megaterium (13 strains), B. polymyxa (5 strains), B. pumilus (4 strains), B. subtilis (4 strains), B. circulans (3 strains), B. amyloliquefaciens (2 strains), B. licheniformis (1 strain), and Bacillus spp. (3 strains). Microdilution MIC susceptibility tests revealed all B. cereus strains to be susceptible to imipenem, vancomycin, chloramphenicol, gentamicin, and ciprofloxacin. Non-B. cereus strains were most susceptible to imipenem, vancomycin, LY146032, and ciprofloxacin. Disk susceptibility testing suggested that B. cereus was rarely susceptible to penicillins, semisynthetic penicillins, or cephalosporins with the exception of mezlocillin. In contrast, many non-B. cereus strains were susceptible to penicillins, semisynthetic penicillins, and cephalosporins, but marked variability was noted among species.

Outbreak of wound infections following outpatient podiatric surgery due to contaminated bone drills.

An outbreak of podiatric infections due to an uncommon strain of Proteus mirabilis occurred following outpatient podiatric surgery. An evaluation of the operating room environment failed to reveal the strain of P. mirabilis from any site other than three bone drills. Thus the drills served as the reservoir for the organism that was subsequently inoculated onto the hands of the surgeon or directly to a patient during bone drilling. The gas sterilization procedure that was used to sterilize the drills was found deficient. No additional cases of P. mirabilis infection have been observed since the elimination of the contaminated drills.

Serious postoperative infections caused by coagulase-negative staphylococci: an epidemiological and clinical study.

We have reviewed all 3577 nosocomial infections occurring at our institution over a 49-month period and found coagulase-negative staphylococci (CNS) associated with 297. Seventy-eight of 193 CNS tested for antibiotic sensitivity were multiple-drug resistant (MR-CNS). There were 19 well-documented serious postoperative CNS infections including nine ventricular, seven bloodstream and three peritoneal infections. Each was associated with an indwelling device and 11 of the infections involved MR-CNS. Antibiotic therapy with or without removal of the device resulted in cure of all patients. Air samples taken during various surgical procedures frequently were positive for CNS but rarely revealed MR-CNS. Our results cause concern regarding current antibiotic prophylaxis regimens.

Plaster-associated Bacillus cereus wound infection. A case report.

Plaster of Paris and nonsterile cast padding have previously been implicated in wound infections. The observation of three pin site infections with Bacillus cereus following pin placement and plaster fixation of an open forearm fracture led to an epidemiologic investigation. Two hundred sixty-one bacterial cultures were taken from materials in the Steinmann pin application and plaster fixation procedures. B. cereus with a similar antibiogram and biotype as was identified in the pin site cultures was recovered from three of the 22 (14%) plaster-impregnated gauze rolls and six of seven (81%) tapwater samples. The Bacillus sp contamination rate of plaster when dry or wetted with sterile water or tapwater was 58%, 25% and 40% respectively. All cultures of plaster samples were negative after steam or gas sterilization. These results suggest that the patient may have acquired the infection from the plaster-impregnated gauze wetted in tapwater. In this case, the Steinmann pins may have facilitated infection by guiding the plaster-associated bacteria to the pin insertion site. The use of gas sterilized plaster materials should be considered in certain circumstances.

Infections associated with subclavian Uldall catheters.

During a 12-month period, the use of a subclavian vein Uldall catheter (UC) for hemodialysis or plasmapheresis in 27 patients was studied prospectively. Ten patients had ten UC site infections. Organisms associated with these infections included Staphylococcus epidermidis (five), Staphylococcus aureus (four), Proteus mirabilis (two), and Enterococcus (one). The four S aureus infections occurred 1, 2, 4, and 9 days after UC insertion, whereas the five S epidermidis infections occurred 6, 17, 17, 26, and 97 days after insertion. Five patients had associated bacteremias; in one of these patients, the bacteremia was the major cause of death. The incidence of UC site infection and bacteremia based was higher than the incidence of infection reported with any other type of vascular access for hemodialysis. Further studies are necessary to define whether the UC should be routinely employed for temporary vascular access.