Prevention and management of internal cerebrospinal fluid shunt infections.

Cerebrospinal fluid (CSF) shunt infection is a serious and potentially devastating complication of CSF shunt placement. Younger age, previous CSF shunt infection or revision, and the type of the shunt are important risk factors for shunt infection. More than half of the cases are caused by Staphylococcus aureus and coagulase-negative staphylococci. The biofilm plays a central role in its pathogenesis. CSF cultures remain the gold standard for diagnosis of CSF shunt infection. The most effective way to prevent CSF shunt infection is optimization of sterile protocols and use of proper and timely antibiotic prophylaxis. Management of CSF shunt infection frequently requires removal of all shunt components, placement of a temporary external device, and administration of intravenous antibiotics, followed by reshunting at a later time. This review summarizes and analyses the results of previous reports of CSF shunt infection and assesses the prevention and management of this important entity.

Spinal and paraspinal pneumococcal infections-a review.

Spinal and paraspinal infections caused by Streptococcus pneumoniae remain a rare event. We present two cases from our institution, discuss the pathophysiology, and present a literature review of an additional 50 cases of spinal pneumococcal infections. Spinal epidural abscess and vertebral osteomyelitis as well as paraspinal abscesses caused by pneumococcus were included in the analysis. As has been reported for spinal infections due to other bacteria, persistent localized back pain with an elevation in inflammatory markers was almost universal. The lumbar spine was the most commonly involved. Pneumococcus was most frequently isolated from material obtained at the site of the infection; blood cultures were a less common source. The majority of patients with neurologic deficits had spinal epidural abscess or phlegmon, and had a higher mortality. Most patients were treated with 6 weeks of parenteral antimicrobials, and surgical intervention was not associated with a mortality benefit.

Efficacy of trypsin in enhancing assessment of bacterial colonisation of vascular catheters.

Since the number of organisms isolated from a medical device is crucial in assessing the likelihood of device-associated infection, we examined whether incubation of catheters in trypsin before sonication can increase the yield of superficially colonised vascular catheters in vitro and those removed from patients. Polyurethane and silicone catheters were individually colonised in vitro with individual clinical isolates including Staphylococcus aureus and Escherichia coli. Equal numbers of 1 cm segments of colonised catheters were then individually incubated either in a trypsin-containing solution or a control solution without trypsin. Each solution containing the segment was then sonicated and cultured quantitatively. In the clinical arm, indwelling catheters removed from patients were also cut into 1 cm segments that were equally suspended in the trypsin-containing or control solution and then sonicated and cultured quantitatively. Trypsin-based sonication enhanced the detection of S. aureus on colonised polyurethane and silicone catheters in vitro by 14- and 30-fold, respectively (P = 0.03 and P = 0.04), and the detection of E. coli on colonised polyurethane and silicone catheters by 3- and 6-fold, respectively (P = 0.04 and P = 0.05). Compared with sonication alone, trypsin followed by sonication resulted in 10% increase in the detectability of significant colonisation of indwelling catheters removed from patients and 11% increase in the mean colony counts of colonising organisms (P = 0.04). Exposure of catheters to trypsin before sonication improves the sensitivity of sonication and enhances the accuracy of assessing significant catheter colonisation.

A bacterial interference strategy for prevention of UTI in persons practicing intermittent catheterization.

STUDY DESIGN: Non-randomized pilot trial. OBJECTIVES: To determine whether Escherichia coli 83972-coated urinary catheters in persons with spinal cord injury (SCI) practicing an intermittent catheterization program (ICP) could (1) achieve bladder colonization with this benign organism and (2) decrease the rate of symptomatic urinary tract infection (UTI). SETTING: Outpatient SCI clinic in a Veterans Affairs hospital (USA). METHODS: Participants had neurogenic bladders secondary to SCI, were practicing ICP, had experienced at least one UTI and had documented bacteruria within the past year. All participants received a urinary catheter that had been pre-inoculated with E. coli 83972. The catheter was left in place for 3 days and then removed. Participants were followed with urine cultures and telephone calls weekly for 28 days and then monthly until E. coli 83972 was lost from the urine. Outcome measures were (1) the rate of successful bladder colonization, defined as the detection (>or=10(2) cfu ml(-1)) of E. coli 83972 in urine cultures for >3 days after catheter removal and (2) the rate of symptomatic UTI during colonization with E. coli 83972. RESULTS: Thirteen participants underwent 19 insertions of study catheters. Eight participants (62%) became successfully colonized for >3 days after catheter removal. In these 8 participants, the rate of UTI during colonization was 0.77 per patient-year, in comparison with the rate of 2.27 UTI per patient-year before enrollment. CONCLUSIONS: E. coli 83972-coated urinary catheters are a viable means of achieving bladder colonization with this potentially protective strain in persons practicing ICP.

Prevention of infections associated with vascular catheters.

The expanding use of vascular catheters has increased the need to prevent hazardous infectious complications. Since bloodstream infection is the most common serious complication of indwelling vascular catheters, the proof that a potentially preventive approach is truly protective against clinical infection requires a significant reduction in the incidence of this infectious complication.Although catheter colonization is a prelude to infection, most colonized catheters do not result in catheter-related infection and, therefore, a mere reduction in catheter colonization does not, in and by itself, confirm protection against clinical infection. Adherence to optimal infection control guidelines is the primary measure for preventing infection, but in most instances the level of adherence to guidelines drops subsequent to the initial surge that follows the institutional adoption of educational programs. This explains the need to assess the potential clinical protection afforded by anti-infective technologies. In addition to improving patient care, a clinically protective anti-infective approach can also bring tremendous cost savings.

Antimicrobial coating of devices for prevention of infection: principles and protection.

Device-associated infections are responsible for about half of nosocomial infections and can cause major medical and economical sequelae. Despite adherence to basic infection control measures, which constitute the mainstay for preventing infection, infections associated with certain devices continue to exist at unacceptably high rates. Potentially-preventive, antimicrobial-utilizing strategies include systemic antibiotic prophylaxis and local administration of antimicrobial agents (antibiotics or antiseptics), which includes antimicrobial irrigation of the surgical field, placement of antimicrobial carriers, antiseptic cleansing of the skin, dipping of surgical implants in antimicrobial solutions, and inserting antimicrobial-coated implants. Since bacterial colonization of the indwelling device is a prelude to infection, prevention of device colonization may lead to a lower rate of clinical infection. Different approaches for antimicrobial coating of devices have been variably successful in preventing device-associated infections. Optimal characteristics of antimicrobial coating can help predict the likelihood and degree of clinical protection against infection. This review addresses the impact of device-related infection, antimicrobial-utilizing approaches for preventing infection, clinical protection afforded by different types of antimicrobial coating, characteristics that predict the ability of antimicrobial coating of devices to prevent clinical infection, and future directions of antimicrobial coating.

Proteus bacteriuria is associated with significant morbidity in spinal cord injury.

STUDY DESIGN: Retrospective chart review. OBJECTIVES: We investigated the morbidity associated with Proteus bacteriuria in a spinal cord injured (SCI) population. SETTING: Michael E DeBakey Veterans Affairs Medical Center in Houston, Texas, USA. METHODS: We reviewed the medical records of all veterans with SCI who received care in our medical center during the past 3 years. Proteus bacteriuria was defined as the growth of Proteus species in any urine culture during the study period. Urinary stones were defined as either renal or bladder calculi. RESULTS: During the study period, 71 of the 501 subjects (14%) had Proteus and 90 (18%) had urinary stones. Twenty-seven percent of the subjects with Proteus had stones, and the association of Proteus with stones was significant (P<0.05). Proteus bacteriuria was likewise associated with complete injury, hospitalization, decubitus ulcers, and history of stones (P<0.001). Subjects using indwelling catheters, either transurethral or suprapubic, were significantly more likely to have Proteus, whereas subjects practising spontaneous voiding and clean intermittent catheterization were significantly less likely to have Proteus. In the 90 patients with stones, Proteus was associated with requiring treatment for stones and having multiple stones (P<0.01). Twenty-five of the 90 patients with stones (28%) required treatment, most often with lithotripsy, and 6 (7%) developed urosepsis. CONCLUSIONS: In persons with SCI, Proteus was found in subjects with a greater degree of impairment who were more likely to be hospitalized, to have decubiti, and to use indwelling catheters. Bacteriuria with Proteus predicted urologic complications in persons with SCI. STATEMENT OF ETHICS: All applicable institutional and governmental regulations concerning the ethical use of human volunteers were followed during the course of this research.

Antifungal activity of antimicrobial-impregnated devices.

The in-vitro and in-vivo efficacy against Candida albicans and Candida krusei of devices impregnated with chlorhexidine and chloroxylenol was examined. The impregnated devices produced large zones of inhibition against both organisms (mean size, 39 mm and 38 mm, respectively). In a rabbit model in which segments of silicone catheters were placed percutaneously, non-impregnated devices were twice as likely as impregnated devices to become colonised with either C. albicans or C. krusei. Impregnated devices also had significantly lower colony counts of C. albicans (58 vs. 1361 CFU; p 0.008) and C. krusei (19 vs. 764 CFU; p 0.008).

Dalbavancin compared with vancomycin for prevention of Staphylococcus aureus colonization of devices in vivo.

OBJECTIVES: Although active against free-floating bacteria, vancomycin displays a poor activity against organisms embedded within the biofilm surrounding implanted devices. Dalbavancin is a novel glycopeptide antibiotic with strong activity against staphylococci and a long half-life that allows for once-a-week dosing. The objective of this animal study was to examine the ability of dalbavancin and vancomycin to prevent Staphylococcus aureus colonization of devices. METHODS: Twelve rabbits were randomized, in three groups of four each, to receive intravenous injections of dalbavancin, vancomycin or normal saline (control). Eight polyurethane catheter segments were subcutaneously implanted in the back of each rabbit, then inoculated with S. aureus. Rabbits were sacrificed a week later and explanted devices were cultured. RESULTS: The rates of device colonization were comparable in the vancomycin (53%) and control (47%) groups, whereas only 28% of devices in the dalbavancin group became colonized. There was a trend (although not statistically significant) toward a lower rate of device colonization following receipt of dalbavancin vs. vancomycin (P = 0.07) or saline (P = 0.02). CONCLUSIONS: The demonstrated efficacy of dalbavancin in this animal study suggest that this novel antibiotic may have an important role in the prevention and treatment of device-related infection.

Comparison of adherence of Candida albicans and Candida parapsilosis to silicone catheters in vitro and in vivo.

OBJECTIVE: Although Candida parapsilosis has been associated with device-related infections in the clinical settings, factors that contribute to this association have not been previously examined. The objectives of this study were to compare in vitro and in vivo the adherence to silicone catheters of: (1) Candida albicans vs. C. parapsilosis, and (2) invasive vs. colonizing isolates of C. albicans and C. parapsilosis. METHODS: The records of 840 patients who had had Candida species isolated at three teaching hospitals during a three-month period were reviewed. A total of 20 clinical isolates of each of C. parapsilosis and C. albicans were examined for their adherence to silicone catheters in vitro and in a rabbit model of percutaneously placed catheters. For each Candida species, ten invasive isolates that had caused clinical device-related infection and 10 colonizing isolates that had caused only device colonization were studied. RESULTS: Candida parapsilosis accounted for <5% of yeast isolates from all sites, while three-quarters were C. albicans. Candida parapsilosis was isolated proportionately more often from blood and/or devices than C. albicans (34.3% vs. 8.5%, respectively, P < 0.0001). There were no significant differences in the degrees of adherence in vitro and in vivo between C. albicans and C. parapsilosis or between invasive and colonizing Candida. CONCLUSION: Although C. parapsilosis was isolated proportionately more often from blood and/or devices than C. albicans in our studied population, there was no significant difference in the adherence of the two Candida species to silicone, nor between invasive and colonizing Candida in our in vitro and in vivo models. Factors other than microbial adherence may help explain the observed association of C. parapsilosis with device-related infections.

Diagnosis of catheter-related bloodstream infections: is it necessary to culture the subcutaneous catheter segment?

In order to determine the diagnostic usefulness of culturing the subcutaneous catheter segment, an analysis was performed using data derived from two prospective, randomized studies that included 479 patients with central venous catheters and 13 episodes of catheter-related bacteremia. The results indicate that quantitative culture, using the roll-plate and sonication methods, of the subcutaneous catheter segment did not add to the diagnostic yield (sensitivity, 83-100%; specificity, 82-97%; negative predictive value, 100%) of semiquantitative and quantitative catheter-tip cultures or aid in identifying catheter-related bloodstream infections.

Device-associated infections: a macroproblem that starts with microadherence.

Medical devices are responsible for a large portion of nosocomial infections, particularly in critically ill patients. Device-associated infections can cause major medical and economic sequelae. Bacterial colonization of the indwelling device can be a prelude to both infection and malfunction of the device. The pathogenesis of device-associated infection centers around the multifaceted interaction among the bacteria, the device, and the host. Bacterial factors are probably the most important in pathogenesis of infection, whereas device factors are the most amenable to modification with the objective of preventing infection. Some, but not all, of the studied bacterial receptors satisfy the proposed "adherence/infection" version of Koch's postulates. Traditional surface-modifying preventive approaches have largely focused on antimicrobial coating of devices and resulted in variable clinical success in preventing device-associated infections. The potential protective role of newer innovative approaches, such as biofilm modification and bacterial interference, ought to be further investigated.

Pilot trial of bacterial interference for preventing urinary tract infection.

OBJECTIVES: To examine the safety and efficacy of bacterial interference in preventing symptomatic urinary tract infection (UTI). METHODS: A prospective, nonrandomized, pilot clinical trial was conducted in patients with spinal cord injury who had neurogenic bladder and had frequent episodes of symptomatic UTI. The bladder of patients was inoculated with a nonpathogenic prototype of Escherichia coli 83972. The rate of symptomatic UTI in successfully colonized patients while colonized with E. coli 83972 was compared with (a) their own baseline prestudy rate and (b) the rate of symptomatic UTI in patients who were not successfully colonized. RESULTS: Of 44 inoculated patients, 30 (68%) became colonized with E. coli 83972 for 1 month or longer. Only two episodes of symptomatic UTI occurred in the group of 30 patients while colonized with E. coli 83972 (a total of 34 patient-years), and none was attributed to E. coli 83972. The group of 30 patients experienced a 63-fold reduction in the rate of symptomatic UTI while colonized with E. coli 83972 versus their baseline prestudy period (mean 0.06 versus 3.77 episodes of symptomatic UTI/patient-year, P <0.001). The rate of symptomatic UTI was also 33-fold lower in this group of 30 patients while colonized with E. coli 83972 than in the well-matched group of 14 patients who were not successfully colonized (mean 0.06 versus 1.80 episodes of symptomatic UTI/patient-year, P <0.001). CONCLUSIONS: The results of this pilot study indicate that bacterial interference using E. coli 83972 may be safe and effective in preventing UTI.

Tuberculous pericarditis: optimal diagnosis and management.

Pericarditis is a rare manifestation of tuberculous disease. The appropriate diagnostic workup and optimal therapeutic management are not well defined. We present 10 new cases of tuberculous pericarditis and review the relevant literature. The specific topics addressed are (1) the importance of tissue for diagnosis, (2) the optimal surgical management, (3) the role of corticosteroids, and (4) the impact of human immunodeficiency virus (HIV) on the management of this disease. The cases and the literature suggest that the optimal management includes an open pericardial window with biopsy, both for diagnosis and to prevent reaccumulation of fluid. Corticosteroids probably offer some benefit in preventing fluid reaccumulation as well. The data are inconclusive regarding whether open drainage or corticosteroid use prevents progression to constrictive pericarditis. No studies have addressed these issues specifically in HIV-positive patients, but the 3 HIV-positive patients in our series had an excellent response to drainage and antituberculous therapy.

Characterization of a fish antimicrobial peptide: gene expression, subcellular localization, and spectrum of activity.

Antimicrobial peptides are proposed to act as the first line of mucosal host defense by exerting broad-spectrum microbicidal activity against pathogenic microbes. Pleurocidin, a new 25-residue linear antimicrobial peptide, was recently isolated from the skin secretions of winter flounder (Pleuronectes americanus). The present study identifies the cDNA and gene encoding pleurocidin. The pleurocidin gene comprises four exons. Its upstream region demonstrates consensus binding sequences for transcription factors found in host defense genes in mammals, including sequences identical to the NF-IL6 and alpha and gamma interferon response elements. Pleurocidin is predicted to exist as a 68-residue prepropeptide that undergoes proteolytic cleavage of its amino-terminal signal and carboxy-terminal anionic propiece to form the active, mature peptide. Transmission electron microscopy localized pleurocidin to the mucin granules of skin and intestinal goblet cells. Significant synergy was shown to occur between pleurocidin and D-cycloserine targeting Mycobacterium smegmatis. Pleurocidin was functionally active at physiologic concentrations of magnesium and calcium; however, high concentrations of these divalent cations ablated pleurocidin's activity against a standard test strain, Escherichia coli D31. Pleurocidin was tested against bacterial and fungal clinical isolates and showed broad-spectrum antimicrobial activity. Together, these data support the hypothesis that pleurocidin participates in innate mucosal immunity, and it may prove to be a beneficial therapeutic agent.

Bacterial interference for prevention of urinary tract infection: an overview.

Urinary tract infection (UTI) is the most common infection in patients with spinal cord injury (SCI) and is a major cause of morbidity and mortality in this population. The bladders of patients with SCI, particularly those with indwelling bladder catheters, can become colonized by a variety of organisms, including those that may, and others that may not, cause symptoms of infection. The latter group of bacteria, so-called benign colonizers, are often left untreated because they may provide some protection against symptomatic infection with more pathogenic bacteria. In recent years, deliberate urogenital tract colonization with benign bacterial strains was studied with the objective of offering some protection against invasion by uropathogenic strains. When well-characterized strains of Lactobacillus sp. were used to colonize the vagina of women prone to frequent UTI, a moderate reduction in the rate of recurrent UTI was observed. In other studies, a non-pathogenic prototype of Escherichia coli (strain 83,972) causing asymptomatic bacteriuria was used for deliberate bladder colonization. These preliminary observations encourage the examination of the safety and preventive efficacy of this approach in human subjects.

Infection-resistant alloplasts.

Prosthesis-related infection accounts for nearly half of nosocomial infections, resulting in significant morbidity, mortality, prolonged hospitalization, and higher healthcare costs. Although numerous antimicrobial-coated surfaces have been suggested to guard against prosthesis-related infection, only a few, such as minocylcine plus rifampin, are clinically protective. The differences in clinical efficacy can be attributed at least in part to differences in the magnitude of leaching of the antimicrobial agent off the surface. There is a pressing need to explore the clinical efficacy of antimicrobial surfaces suitable for use in devices intended for long-term use.

Direct confocal microscopy studies of the bacterial colonization in vitro of a silver-coated heart valve sewing cuff.

The antimicrobial coating of prosthetic heart valve sewing cuffs has been considered a potentially effective method for preventing prosthetic valve endocarditis. Although traditional in vitro bacterial adherence studies are often useful as screening tools, they can be inadequate in examining the antiinfective efficacy of antimicrobial-coated devices. We conducted a pilot in vitro study to directly assess the antimicrobial activity of a silver-coated sewing cuff versus uncoated cuff using confocal scanning laser microscopy. Staphylococcus epidermidis adhered more to the surfaces of the silver-coated sewing cuff compared with the uncoated cuff. These pilot in vitro results cast a doubt on the antiinfective efficacy of silver-coated prosthetic heart valve sewing cuffs and suggest further assessment should be carried out using animal studies.

Efficacy of antimicrobial-impregnated bladder catheters in reducing catheter-associated bacteriuria: a prospective, randomized, multicenter clinical trial.

OBJECTIVES: To examine the efficacy of bladder catheters impregnated with minocycline and rifampin in reducing catheter-associated bacteriuria. METHODS: A prospective, randomized clinical trial was conducted at five academic medical centers. Patients undergoing radical prostatectomy were randomized to receive intraoperatively either regular silicone bladder catheters (control catheters) or silicone bladder catheters impregnated with minocycline and rifampin (antimicrobial-impregnated catheters). Catheters remained in place for a mean of 2 weeks. Urine cultures were obtained at about 3, 7, and 14 days after catheter insertion. Bacteriuria was defined as the growth of organism(s) in urine at a concentration of 10(4) colony-forming units per milliliter or greater. RESULTS: Kaplan-Meier analysis demonstrated that it took significantly longer for patients (n = 56) who received the antimicrobial-impregnated catheters to develop bacteriuria than those (n = 68) who received the control catheters (P = 0.006 by the log-rank test). Patients who received the antimicrobial-impregnated catheters had significantly lower rates of bacteriuria than those in the control group both at day 7 (15.2% versus 39.7%) and at day 14 (58.5% versus 83.5%) after catheter insertion. Patients who received the antimicrobial-impregnated catheters had significantly lower rates of gram-positive bacteriuria than the control group (7.1% versus 38.2%; P <0.001) but similar rates of gram-negative bacteriuria (46.4% versus 47.1%) and candiduria (3.6% versus 2.9%). The antimicrobial-impregnated catheters provided zones of inhibition against Enterococcus faecalis and Escherichia coli, both at baseline and on removal. CONCLUSIONS: Bladder catheters impregnated with minocycline and rifampin significantly reduced the rate of gram-positive catheter-associated bacteriuria up to 2 weeks after catheter insertion.