Efficacy of topically delivered moxifloxacin against wound infection by Pseudomonas aeruginosa and methicillin-resistant Staphylococcus aureus.

Wound infection is a common risk for patients with chronic nonhealing wounds, causing high morbidity and mortality. Currently, systemic antibiotic treatment is the therapy of choice, despite often leading to several side effects and the risk of an insufficient tissue penetration due to impaired blood supply. If systemically delivered, moxifloxacin penetrates well into inflammatory blister fluid, muscle, and subcutaneous adipose tissues and might therefore be a possible option for the topical treatment of skin and infected skin wounds. In this study, topical application of moxifloxacin was investigated in comparison to mupirocin, linezolid, and gentamicin using a porcine wound infection and a rat burn infection model. Both animal models were performed either by an inoculation with methicillin-resistant Staphylococcus aureus (MRSA) or Pseudomonas aeruginosa. Wound fluid, tissue, and blood samples were taken, and bacterial counts as well as the moxifloxacin concentration were determined for a 14-day follow-up. A histological comparison of the rat burn wound tissues was performed. Both strains were susceptible to moxifloxacin and gentamicin, whereas mupirocin and linezolid were effective only against MRSA. All antibiotics showed efficient reduction of bacterial counts, and except with MRSA, infected burn wounds reached bacterial counts below 10(5) CFU/g tissue. Additionally, moxifloxacin was observed to promote wound healing as determined by histologic analysis, while no induction of bacterial resistance was observed during the treatment period. The use of topical antibiotics for the treatment of infected wounds confers many benefits. Moxifloxacin is therefore an ideal candidate, due to its broad antibacterial spectrum, its high efficiency, and its potential to promote wound healing.

A novel human skin chamber model to study wound infection ex vivo.

Wound infections with multi-drug resistant bacteria increase morbidity and mortality and have considerable socioeconomic impact. They can lead to impaired wound healing, resulting in rising treatment costs. The aim of this study was to investigate an ex vivo human wound infection model. Human full-thickness skin from the operating room (OR) was placed into the Bo-Drum and cultivated for 7 days in an air-liquid interphase. On day 8, the skin was inoculated with either (1) Pseudomonas aeruginosa, (2) Staphylococcus aureus (10(5) CFU, n = 3) or (3) carrier control. 1, 3 and 7 days after inoculation colony forming units in the tissue/media were determined and cytokine expression was quantified. A reliable and reproducible wound infection could be established for 7 days. At this time point, 1.8 x 10(8) CFU/g tissue of P. aeruginosa and 2 x 10(7) CFU/g tissue of S. aureus were detected. Immunohistochemical analysis demonstrated bacterial infection and epidermolysis in infected skin. RT-PCR analysis exhibited a significant induction of proinflammatory cytokines after infection. The BO-drum is a robust, easy-to-use, sterilizable and reusable ex vivo full-skin culture system. For investigation of wound infection, treatment and healing, the BO-drum presents a convenient model and may help to standardize wound research.

Transient non-viral cutaneous gene delivery in burn wounds.

BACKGROUND: Gene transfer to burn wounds could present an alternative to conventional and often insufficient topical and systemic application of therapeutic agents to aid in wound healing. The goals of this study were to assess and optimize the potential of transient non-viral gene delivery to burn wounds. METHODS: HaCaT cells were transfected with luciferase or beta-galactosidase transgene using either pure plasmid DNA (pDNA) or complexed with Lipofectamine 2000, FuGENE6, or DOTAP-Chol. Expression was determined by bioluminescence and fluorescence. Forty male Sprague-Dawley rats received naked pDNA, lipoplexes, or carrier control intradermally into either unburned skin, superficial, partial, or full-thickness scald burn. Animals were sacrificed after 24 h, 48 h, or 7 days, and transgene expression was assessed. RESULTS: Gene transfer to HaCaT cells showed the overall highest expression for DOTAP/Chol (77.85 ng luciferase/mg protein), followed by Lipofectamine 2000 (33.14 ng luciferase/mg protein). pDNA-derived gene transfer to superficial burn wounds showed the highest expression among burn groups (0.77 ng luciferase/mg protein). However, lipoplex-derived gene transfer to superficial burns and unburned skin failed to show higher expression. CONCLUSIONS: Lipofectamine 2000 and DOTAP/Chol lipoplex showed significantly enhanced gene transfer, whereas no transfection was detectable for naked DNA in vitro. In contrast to the in vitro study, naked DNA was the only agent with which gene delivery was successful in experimental burn wounds. These findings highlight the limited predictability of in vitro analysis for gene delivery as a therapeutic approach.

Indices of activity of the nitric oxide system in hemodialysis patients.

Arginine deficiency and/or increased levels of circulating nitric oxide (NO) synthesis (NOS) inhibitors can cause reduced NOS, which may contribute to hypertension in patients with end-stage renal disease (ESRD). To test these hypotheses, NO oxidation products (NO(2) + NO(3) = NO(x)) and cyclic guanosine monophosphate (cGMP), the vasodilatory second messenger of NO, were measured in the blood, urine, and dialysate effluent of hemodialysis (HD) patients and compared with the blood and urine of healthy subjects. The subjects ate a controlled low-nitrate diet (approximately 330 micromol/d) for 48 hours before and during blood, dialysis effluent, and 24-hour urine collection. NO(x) output was significantly reduced in HD patients versus controls (552 +/- 51 v 824 +/- 96 micromol/24 h; P < 0.001), whereas cGMP output was not low versus controls. Plasma arginine level was normal and plasma levels of citrulline and the endogenous NOS inhibitor, asymmetric dimethylarginine (ADMA), were markedly elevated in patients with ESRD versus controls. Systolic blood pressure was greater in HD patients compared with controls despite concurrent antihypertensive therapy in most patients with ESRD. These studies suggest NO production is low in patients with ESRD undergoing HD, possibly because of the increased ratio of plasma ADMA to arginine.

Nitric oxide production is low in end-stage renal disease patients on peritoneal dialysis.

To test the hypothesis that nitric oxide (NO) deficiency occurs in end-stage renal disease (ESRD), NO oxidation products (NO2 + NO3 = NOx) and cGMP were measured in blood, urine, and dialysate effluent of peritoneal dialysis (PD) patients and compared with blood and urine of healthy subjects. All subjects were on a controlled low-nitrate diet (approximately 330 micromol/day). NOx and cGMP outputs were significantly reduced in PD patients (334 +/- 50 micromol/24 h and 55 +/- 13 nmol/24 h, respectively) vs. controls (823 +/- 101 micromol/24 h and 149 +/- 46 nmol/24 h). Plasma arginine was borderline low, plasma citrulline was elevated and plasma levels of the endogenous NO synthase inhibitor asymmetric dimethylarginine were approximately five time higher in PD patients (2.2 +/- 0.3 microM) vs. controls (0.4 +/- 0.1 microM). Although blood pressure (BP) was not different between groups at the time of study, 10 of 11 PD patients were on medication for hypertension. These studies demonstrate that total NO production is low in ESRD, and with appropriate caution, we conclude that this NO deficiency may contribute to the increased BP that occurs in ESRD.

Early referral and its impact on emergent first dialyses, health care costs, and outcome.

Early referral (ER) to nephrologists of patients with chronic renal failure was assessed for its impact on the incidence of emergent first dialyses and choice of dialysis modality (hemodialysis [HD] or peritoneal dialysis [PD]), and survival. We reviewed events preceding first dialyses of 238 patients with end-stage renal disease (ESRD) starting dialysis between January 1990 and April 1997, with follow-up extending through November 1997. Patients referred more than 1 month before needing dialysis (early referral [ER]) were compared with patients presenting within 30 days of needing dialysis (late referral [LR]). The need for emergent HD was significantly less among ER (29%) as compared with LR (90%) (P < 0.0001). Initial modality chosen was similar among ER patients (59% for HD v 41% for PD), a finding that contrasts with national percentages, which approximate 85% and 15%, respectively. Whereas most patients had not changed modality at 4 months, significantly more had changed from HD to PD (36 of 160 or 23%) than from PD to HD (7 of 78 or 9%) (P < 0.0001). Despite starting out on HD, ER and LR patients were amenable to ultimately changing to PD. ER and LR groups had similar numbers of Medicaid patients and patients living 1 hour or more distant to tertiary medical care. Furthermore, no difference was observed in the incidence of emergent HD when ER and LR living more than 1 hour away were compared. LR was not associated with lack of insurance or distance from referral site, although these patients more often required emergent HD, with its higher attendant medical care costs. Controlling for age and cause of ESRD, there was no statistically significant difference in long-term survival when ER patients were compared with LR patients or when patients who had received emergent HD were compared with those who had not. Despite the lack of difference in long-term survival, the financial costs of emergent HD alone merit greater promotion of ER and the psychosocial preparation and modality choice it allows.

Peroxidase activity and glutathione content in the human first-trimester placenta and decidua.

OBJECTIVE: Recently, a novel pathway of xenobiotic oxidation by peroxidase in the placenta at term was described. Herein, we aim to determine the potential of the first-trimester placenta and decidua to activate carcinogens and mutagens by peroxidase and to scavenge free radicals by glutathione. METHODS: Placental and decidual peroxidase activity was measured using a sensitive, quantitative colorimetric kinetic assay, with O-phenylenediamine dihydrochloride (OPD) as substrate and H2O2 as co-substrate. Glutathione levels were measured using a colorimetric assay. RESULTS: Peroxidase activity in cytosolic and CaCl2-extracted (membrane-bound) fractions was inhibited by a specific inhibitor, NaN3. The membrane-bound peroxidase activity was maximal at 12 weeks of gestation while cytosolic peroxidase activity did not change. Placental glutathione content remained unchanged during the first trimester. Decidual and placental peroxidase activities were similar; however decidual glutathione content was 15-fold lower, resulting in a higher decidual peroxidase activity/glutathione ratio (p < 0.03). CONCLUSIONS: We report for the first time that peroxidase may be an important pathway for xenobiotic activation at the maternal-embryonal interface. It remains to be established whether the low glutathione content limits the ability of the decidua but not placenta to protect against genomic damage induced through xenobiotic oxidation.

Stopping dialysis of an incompetent patient over the family's objection: is it ever ethical and legal?

Decisions to stop dialysis or other life-sustaining treatments for incompetent patients are among the most difficult ethical problems faced by physicians and families. This observation is verified by the large number of court cases and the increasing frequency of ethics consultations on these issues. In such instances, in the absence of an advance directive, the usual practice for physicians is to turn to the patient's family for direction on whether to start, continue, or withdraw the treatment. They do so on the presumption that the family best represents the patient's interests. This presumption may not always be correct. A case is presented in which the family's insistence on continued dialysis was contrary to the patient's previously expressed wishes and the treating physician's assessment of the patient's best interests. It is asserted that, in such situations, after thorough conversation with the family, consultation, documentation, and an unsuccessful attempt to transfer the patient's care to another physician, nephrologists have an ethical obligation and legal right to override the family's decision and to stop dialysis. The ethical obligation is supported by the principles of respect for persons, beneficence, and nonmaleficence. The legal right is grounded in common law and state statutes.

Is ultrasonography useful in predicting catheter loss?

Exit-site infections (ESI) and/or tunnel infections (TI) are common causes of peritoneal catheter loss. Catheter-related infection can be characterized by ultrasonographic examination (UE) of the exit site and the tunnel. This study was done to determine if the UE is useful in predicting catheter loss. Records from 1990 to 1992 of all continuous ambulatory peritoneal dialysis (CAPD) patients with an ESI or TI who had an UE performed were reviewed for causative organism, loss of catheter, and infection resolution. ESI was defined as redness or induration of exit site with or without the presence of drainage. TI was defined as induration or redness along tunnel or incision site with or without the presence of drainage. The presence of a pericatheter sonolucent fluid collection was considered a positive (+) UE, and the absence of fluid a negative (-) UE. Eleven CAPD patients had 12 UE performed within a week of starting antibiotic therapy. Ten were (+) and 2 (-); 7 catheters were removed, all with (+) UE. Of those removed, 6 were due to S. aureus, and 1 due to mycobacterial infection. Of the 3 (+) catheters not removed, 2 infections resolved clinically: both reverted to (-) UE after treatment. We conclude that a (+) UE is a useful predictor of catheter loss.

The effect of body weight on CAPD related infections and catheter loss.

CAPD related infections and catheter loss continue to be the major problems facing the peritoneal dialysis patient. Few risk factors for infections and catheter loss have been identified. We hypothesized that overweight and underweight patients may be at increased risk for infections and catheter related problems. We examined the effect of the patient's weight at the start of peritoneal dialysis on the subsequent peritonitis and catheter infection rates, as well as catheter loss. Weight was expressed as a percentage of ideal body weight (IBW). Those patients who were more than 110% of IBW were considered to be overweight, 90 to 110% of IBW normal and less than 90%, underweight. An equivalent percentage of patients were overweight and underweight at the initiation of peritoneal dialysis (55/228, 24% for both groups). Overweight, normal, and underweight patients had peritonitis rates of 1.0, 0.9, and 0.8 episodes/y and catheter infection rates of 1.1, 1.2, and 0.8 episodes/y, respectively. Despite these similar rates, catheter loss due to infectious complications was greatest in the overweight group and least in the underweight group (p less than 0.05). No obvious explanation for the difference in catheter loss rate was found. Neither S. aureus nor P. aeruginosa infections occurred more frequently in the overweight patients. However, S. aureus infections more often led to catheter loss in the overweight patients. Catheter loss due to catheter leaks and failure to drain was similar in the three groups of patients. We conclude that deviation from ideal body weight at the initiation of dialysis is not a risk factor for CAPD related infections.(ABSTRACT TRUNCATED AT 250 WORDS)

Initiatives in peritoneal dialysis: where do we go from here?

In 1989, a conference was held to discuss the current status of technique survival for patients treated with continuous ambulatory peritoneal dialysis (CAPD). Major reasons for patient drop-out from CAPD-peritonitis, inadequate dialysis, catheter-related problems and psychosocial factors-were reviewed, as were constructive techniques for dealing with these problems and areas for future investigation.

The effect of the Y-set on catheter infection rates in continuous ambulatory peritoneal dialysis patients.

We hypothesized that catheter infections in continuous ambulatory peritoneal dialysis (CAPD) patients may be reduced with a disconnect system. We examined this theory in 116 CAPD patients over a 2-year period. In CAPD patients who switched to the Y-set (n = 22), the catheter infection rate decreased from one per 13 patient-months to one per 26 patient-months (P = 0.05), whereas the catheter infection rate in matched controls (n = 22) remained unchanged. Patients who began CAPD using the Y-set (n = 36) had catheter infection rates of one per 14 patient-months versus one per 8 patient-months in matched controls (n = 36, P = 0.05). Staphylococcus aureus was the most common cause of catheter infections in both groups of patients. However, Pseudomonas aeruginosa replaced Staphylococcus epidermidis as the second most common cause of catheter infections in the patients using the Y-set. The number of catheters that had to be removed due to catheter infections, mainly those due to S aureus or P aeruginosa, was the same in the Y-set and control groups. We conclude that the Y-set system is associated with reduced numbers of catheter infections, but that catheter loss from catheter infections remains a serious problem.

Glucocorticoids and control of glomerular filtration rate.

Glucocorticoids given acutely or chronically at physiological/pharmacological doses increase GFR in both experimental animals and humans. Glomerular micropuncture studies have shown that in the normal rat kidney, glucocorticoids vasodilate both the preglomerular and efferent resistances and result in an increase in glomerular plasma flow, which is the sole factor responsible for the increase in GFR. However, the mechanism(s) initiating these alterations in the glomerular microcirculation remain obscure. The glucocorticoid-induced increase in GFR does not appear to be due to volume expansion or alteration in tubulo-glomerular feedback activity. Chronic glucocorticoid administration has been shown to increase renal prostaglandin synthesis in some but not all species; however, a link between increased prostaglandin production and glucocorticoid-induced increase in GFR has not been established. A number of studies have examined glucocorticoid-induced alterations in renal vascular reactivity to vasoconstrictor agonists and the data have been conflicting. The suggestion that glucocorticoid-stimulated ANP production evokes the increase in GFR is unlikely to be correct based on substantial differences in the glomerular hemodynamic changes seen with ANP or glucocorticoids. An interesting proposal that appears well worth exploring is that glucocorticoids may increase GFR through their effects on catabolism of proteins to increase production of amino acids. Amino acid infusion markedly elevates GFR and has a similar glomerular hemodynamic profile as that of glucocorticoids. By virtue of their action to increase GFR, glucocorticoids increase the rate of electrolyte and water delivery into the nephron. Therefore, glucocorticoid-induced alterations in electrolyte and water excretion may be secondary to an elevation in GFR, in addition to direct actions of glucocorticoids on the tubule. Also, by determining the hemodynamic state of the kidney, and hence, rate of fluid delivery through the nephron, glucocorticoids may influence the sensitivity of the nephron to regulatory influences. Glucocorticoids have their most profound effect (especially clinically) by modifying the immunological or cellular mechanisms responsible for glomerular injury. Less important is their ability to increase GFR. In view of some evidence that suggests increasing glomerular pressure accelerates the progression of established renal disease, some might speculate that glucocorticoids actually increase glomerular damage under certain conditions.

Superior vena cava syndrome due to subclavian hemodialysis catheters.

The widespread use of subclavian dialysis catheters has revealed a high incidence of venous thrombosis and exposed their potential to cause major obstructive complications that may compromise permanent vascular access. We describe for the first time a patient who developed superior vena cava syndrome secondary to central vein stenosis caused by multiple uses of subclavian dialysis catheters. Central vein stenosis in our patient probably caused the failure of permanent vascular accesses in the upper extremities and rendered both arms useless for any further temporary or permanent vascular access. In view of these late vascular complications, use of subclavian dialysis catheters should be kept to a minimum by creating an early permanent vascular access.

An intraperitoneal insulin regimen for diabetics on continuous cyclic peritoneal dialysis.

Intraperitoneal insulin requirements were evaluated in six diabetic patients who were switched from continuous ambulatory peritoneal dialysis to continuous cyclic peritoneal dialysis. The mean total daily intraperitoneal insulin dose on continuous cyclic peritoneal dialysis was 85% of the mean dose on continuous ambulatory peritoneal dialysis (66 +/- 33 vs. 78 +/- 47 units/day, respectively, not significant), with comparable glycemic control. Twenty-five to 58% (mean value, 41%) of the total daily intraperitoneal insulin was administered in the diurnal exchange of the patients on continuous cyclic peritoneal dialysis. The ratio of the total intraperitoneal insulin dose on continuous cyclic peritoneal dialysis to the subcutaneous insulin dose predialysis was between 1.2 and 2.4 (mean value, 1.9). As guidelines for converting intraperitoneal insulin doses for patients switched from continuous ambulatory peritoneal dialysis to continuous cyclic peritoneal dialysis, we recommend starting continuous cyclic peritoneal dialysis with a total daily insulin dose 15% less than the continuous ambulatory peritoneal dialysis dose and giving approximately 40% of the total daily insulin dose in the diurnal exchange.

Catheter infections as a factor in the transfer of continuous ambulatory peritoneal dialysis patients to hemodialysis.

The effect of peritoneal catheter infections on the transfer of continuous ambulatory peritoneal dialysis (CAPD) patients to hemodialysis over a 9-year period were examined. Twenty-seven percent (68/247) of all patients were transferred permanently to hemodialysis after a mean of 15 +/- 14 months of CAPD. An additional 29% transferred temporarily one or more times during the study period (mean time of peritoneal dialysis, 35 +/- 23 months). The reasons for permanent transfer to hemodialysis were catheter infections (15/68, 22%), peritonitis (13/68, 19%), catheter infections associated with peritonitis (10/68, 15%), patient preference (9/68, 13%), mechanical problems (4/68, 6%), noncompliance (7/68, 10%), inadequate clearance or ultrafiltration (6/68, 9%), with other reasons for the remainder (4/68, 6%). Temporary transfers to hemodialysis were also mainly due to catheter infections (32%), peritonitis (23%), and simultaneous catheter infections and peritonitis (24%). Catheter infection rates were much higher in the groups that permanently and temporarily were transferred to hemodialysis in comparison with those patients who remained on peritoneal dialysis. We conclude that catheter infections are a leading cause of both temporary and permanent transfer of CAPD patients to hemodialysis.

Exit-site location does not influence peritoneal catheter infection rate.

Peritoneal catheter infections are a cause of peritonitis, catheter loss, and permanent transfer of continuous ambulatory peritoneal dialysis (CAPD) patients to hemodialysis. Risk factors for catheter infections have not been delineated. We investigated the location of the peritoneal exit-site location as a risk factor for catheter infection and loss. There was no relationship between catheter infection rates and exit location. Catheters exiting on the beltline had a median infection rate of 0.5 episodes/year, as opposed to 1.2 episodes/year for catheters exiting above the beltline and 0.9 episodes/year for catheters exiting below the beltline (ns). The percentage of catheters that became infected and required removal was the same for catheters exiting above, below, or on the beltline. Although we recommend avoiding the beltline for patient comfort, exit-site location is not an important determinant of infection rates or catheter outcome.