Effects of cognitive impairment and assisted peritoneal dialysis on exit-site infection in older patients

BACKGROUND

Elderly peritoneal dialysis (PD) patients required assistance for a variety of PD-related tasks. The usefulness of assisted PD in reducing the peritonitis risk has been reported; however, there is little evidence on the effectiveness of assisted PD in preventing exit-site infections in older patients.

METHODS

This was a single-center, prospective cohort study. Thirty-three patients (mean age: 74.8 ± 5.9 years) on PD were evaluated for cognitive impairment (CI) using the Japanese version of the Montreal Cognitive Assessment. They were also evaluated to determine whether they performed the exit-site care procedure alone or with assistance. Patients were categorized into four groups based on the presence or absence of CI and the presence or absence of exit-site care assistance. They were followed up until the occurrence of peritonitis and exit-site infection at the end of the follow-up.

RESULTS

Altogether, 8, 8, and 17 patients were assigned to the "without CI and without assistance", "without CI and with assistance", and "with CI and with assistance groups", respectively; no patients were assigned to the "with CI and without assistance group". Six and 16 patients experienced peritonitis and exit-site infection during follow-up, respectively. Kaplan-Meier analysis and log-rank tests revealed that the "without CI and without assistance group" was significantly associated with exit-site infection (log-rank < 0.05).

CONCLUSION

Patients who did not receive assistance for exit-site care were at a higher risk of exit-site infections, even in the absence of CI. Caregiver assistance is important for preventing exit-site infections in older patients on PD.

EDTA and Taurolidine Affect Pseudomonas aeruginosa Virulence In Vitro-Impairment of Secretory Profile and Biofilm Production onto Peritoneal Dialysis Catheters

Peritoneal catheter-associated biofilm infection is reported to be the main cause of refractory peritonitis in peritoneal dialysis patients. The application of antimicrobial lock therapy, based on results on central venous catheters, may be a promising option for treatment of biofilm-harboring peritoneal catheters. This study investigated the effects of two lock solutions, EDTA and taurolidine, on an in vitro model of Pseudomonas aeruginosa biofilm-related peritoneal catheter infection. Silicone peritoneal catheters were incubated for 24 h with a bioluminescent strain of P. aeruginosa. Then, serial dilutions of taurolidine and/or EDTA were applied (for 24 h) once or twice onto the contaminated catheters, and P. aeruginosa viability/persistence were evaluated in real time up to 120 h using a Fluoroskan reader. On selected supernatants, high-performance liquid chromatography mass spectrometry (HPLC-MS) analysis was performed to measure the production of autoinducers (AI), phenazines, and pyocyianines. Taurolidine alone or in combination with EDTA caused a significant decrease of bacterial load and biofilm persistence on the contaminated catheters. The treatment did not lead to the sterilization of the devices, yet it resulted in a substantial destructuration of the catheter-associated P. aeruginosa biofilm. HPLC-MS analysis showed that the treatment of biofilm-harboring catheters with taurolidine and EDTA also affected the secretory activity of the pathogen. EDTA and taurolidine affect P. aeruginosa biofilm produced on peritoneal catheters and profoundly compromise the microbial secretory profile. Future studies are needed to establish whether such lock solutions can be used to render peritoneal catheter-related infections more susceptible to antibiotic treatment. IMPORTANCE An in vitro model allows studies on the mechanisms by which the lock solutions exert their antimicrobial effects on catheter-associated biofilm, thus providing a better understanding of the management of devise-associated infections.

Epidemiology, management, and prevention of exit site infections in peritoneal dialysis patients

Exit site infection (ESI) is a leading complication of peritoneal dialysis (PD), at an incidence of 0.6 episodes per year in the United States, and a major risk factor for catheter removal and peritonitis. An estimated 20% of all peritonitis cases are preceded by an ESI, with up to 50% of Staphylococcus aureus peritonitis associated with ESI. Gram-negative ESIs are less associated with succeeding peritonitis than their gram-positive counterparts, though when present, are associated with a lower peritonitis cure rate. The rate of catheter removal for refractory ESI is relatively highest in ESI due to mycobacteria (up to 40%), S. aureus (35%), Pseudomonas aeruginosa (28%), followed by Corynebacterium, Serratia, and fungi. In review of relevant literature, we found no prophylactic benefit of dressings over nondressings, specific antiseptics over normal saline, or topical honey over topical antibiotic prophylaxis, and thus recommend individualized exit site hygiene. We found topical gentamicin effective for prevention of most ESIs, including gram-negative ESIs, and thus recommend consideration of prophylactic topical gentamicin in areas of high gram-negative peritonitis incidence. With long-term use, observational studies detect up to 25% of gram-positive and 14% of gram-negative ESIs may be mupirocin and gentamicin resistant, respectively. We review empiric and targeted ESI management, including indications for ultrasound, anti-VMRSA, anti-Pseudomonal, and anti-mycobacterial antibiotic use, and catheter removal. We recommend further investigation into the earlier use of second-line treatment agents and the utility of treating post-infectious exit site colonization as avenues to decrease refractory and repeat ESI.

A New Titanium Fiber Mesh-Cuffed Peritoneal Dialysis Catheter: Evaluation and Comparison with a Dacron-Cuffed Tenckhoff Catheter in Goats

Objective

We report the development of a new peritoneal dialysis catheter. The purpose of the current study was to evaluate tissue response to this catheter.

Design

In our catheter design, the catheter's cuffs are made from sintered titanium fiber mesh instead of the common Dacron material. The catheters were implanted in goats. During the study period, the catheter exit sites were observed once every 2 weeks. After 14 weeks, the catheters and surrounding tissues were processed for histology and analyzed.

Results

We observed that catheters with titanium cuffs performed significantly better, compared with a commercial catheter design. Histology showed that titanium fibers evoked a lesser inflammatory response compared with Dacron fibers. In addition, the capsule surrounding the titanium cuff was significantly thinner.

Conclusions

Supported by the obtained results, we conclude that the use of Dacron velour for anchorage of percutaneous catheters has to be reconsidered. Titanium fiber mesh has a great potential for application in percutaneous catheters.

Colonization-Resistant Antimicrobial-Coated Peritoneal Dialysis Catheters: Evaluation in a Newly Developed Rat Model of Persistent Pseudomonas Aeruginosa Peritonitis

Objective

Development of a rat model of persistent peritonitis and evaluation of the ability of liposomal ciprofloxacin hydrogel-coated silicone to resist colonization.

Design

A newly developed model of persistent Pseudomonas aeruginosa peritonitis to compare the ability of liposomal ciprofloxacin hydrogel (LCH)-coated silicone versus plain silicone for resistance to bacterial colonization.

Animals

Male Sprague–Dawley rats.

Results

Inoculating the peritoneum of rats with 1 mL 0.5% agar containing 106 colony-forming units (cfu)/mL P. aeruginosa in the presence of a plain silicone coupon resulted in persistent peritonitis for at least 7 days. Plain silicone coupons in all 40 rats were colonized (median 2.54 × 103 cfu/cm2; range 5.0 × 101 – 1.0 × 106 cfu/cm2) and peritoneal washings were consistently culture-positive. In contrast, the LCH coupons removed after 7 days from the 40 test rats were sterile, as were the peritoneal washings, and there was no evidence of peritonitis. Blood cultures were negative in both groups.

Conclusions

Liposomal ciprofloxacin hydrogel-coated silicone resists colonization in this rat model of persistent P. aeruginosa peritonitis.

Peritoneal Microbiome in End-Stage Renal Disease Patients and the Impact of Peritoneal Dialysis Therapy

Factors influencing the occurrence of peritoneal dialysis (PD)-related infections are still far from fully understood. Recent studies described the existence of specific microbiomes in body sites previously considered microbiome-free, unravelling new microbial pathways in the human body. In the present study, we analyzed the peritoneum of end-stage kidney disease (ESKD) patients to determine if they harbored a specific microbiome and if it is altered in patients on PD therapy. We conducted a cross-sectional study where the peritoneal microbiomes from ESKD patients with intact peritoneal cavities (ESKD non-PD, n = 11) and ESKD patients undergoing PD therapy (ESKD PD, n = 9) were analyzed with a 16S rRNA approach. Peritoneal tissue of ESKD patients contained characteristically low-abundance microbiomes dominated by Proteobacteria, Firmicutes, Actinobacteria, and Bacteroidetes. Patients undergoing PD therapy presented lower species richness, with dominance by the Pseudomonadaceae and Prevotelaceae families. This study provides the first characterization of the peritoneal microbiome in ESKD patients, bringing new insight to the human microbiome. Additionally, PD therapy may induce changes in this unique microbiome. The clinical relevance of these observations should be further explored to uncover the role of the peritoneal microbiome as a key element in the onset or aggravation of infection in ESKD patients, especially those undergoing PD.

A Case of Relapsing Peritoneal Dialysis-Associated Peritonitis by Dokdonella koreensis

Peritonitis is a common and serious complication of peritoneal dialysis (PD) with significant morbidity. We report the first case of relapsing Dokdonella koreensis peritonitis in a patient on peritoneal dialysis. A 63-year-old Chinese man, with history of renal failure on continuous ambulatory peritoneal dialysis, presented with cloudy peritoneal effluent and abdominal pain. There was no sign or symptom suggestive of exit-site/tunnel tract infection. Peritoneal effluent cultures yielded Dokdonella koreensis which was initially misidentified as Weeksella virosa and Brevundimonas species by the API® 20 NE and VITEK® 2 GN ID card, respectively. He was treated with intraperitoneal amikacin, but the infection relapsed within a few days upon completing each antibiotic course. He eventually required removal of catheter and was transferred to hemodialysis. Infections due to unusual organisms may pose a diagnostic issue as currently available commercial tests will not be able to identify them. There is a role for using 16S rRNA sequencing to help identify these organisms and guide patient management.

Pharmacodynamics of ceftazidime/avibactam against extracellular and intracellular forms of Pseudomonas aeruginosa

Objectives

When tested in broth, avibactam reverses ceftazidime resistance in many Pseudomonas aeruginosa that express ESBLs. We examined whether similar reversal is observed against intracellular forms of P. aeruginosa .

Methods

Strains: reference strains; two engineered strains with basal non-inducible expression of AmpC and their isogenic mutants with stably derepressed AmpC; and clinical isolates with complete, partial or no resistance to reversion with avibactam. Pharmacodynamic model: 24 h concentration-response to ceftazidime [0.01-200 mg/L alone or with avibactam (4 mg/L)] of bacteria in broth or bacteria phagocytosed by THP-1 monocytes, with calculation of ceftazidime relative potency ( C s : concentration yielding a static effect) and maximal relative effect [ E max : cfu decrease at infinitely large antibiotic concentrations (efficacy in the model)] using the Hill equation. Cellular content of avibactam: quantification by LC-MS/MS.

Results

For both extracellular and intracellular bacteria, ceftazidime C s was always close to its MIC. For ceftazidime-resistant strains, avibactam addition shifted ceftazidime C s to values close to the MIC of the combination in broth. E max was systematically below the detection limit (-5 log 10 ) for extracellular bacteria, but limited to -1.3 log 10 for intracellular bacteria (except for two isolates) with no effect of avibactam. The cellular concentration of avibactam reflected extracellular concentration and was not influenced by ceftazidime (0-160 mg/L).

Conclusions

The potential for avibactam to inhibit β-lactamases does not differ for extracellular and intracellular forms of P. aeruginosa , denoting an unhindered access to its target in both situations. The loss of maximal relative efficacy of ceftazidime against intracellular P. aeruginosa was unrelated to resistance via avibactam-inhibitable β-lactamases.

Deciphering the Contribution of Biofilm to the Pathogenesis of Peritoneal Dialysis Infections: Characterization and Microbial Behaviour on Dialysis Fluids

Infections are major complications in peritoneal dialysis (PD) with a multifactorial etiology that comprises patient, microbial and dialytic factors. This study aimed at investigating the contribution of microbial biofilms on PD catheters to recalcitrant infections and their interplay with PD related-factors. A prospective observational study was performed on 47 patients attending Centro Hospitalar of Porto and Vila Nova de Gaia/Espinho to whom the catheter was removed due to infectious (n = 16) and non-infectious causes (n = 31). Microbial density on the catheter was assessed by culture methods and the isolated microorganisms identified by matrix-assisted laser desorption/ionization time-of-flight intact cell mass spectrometry. The effect of conventional and three biocompatible PD solutions on 16 Coagulase Negative Staphylococci (CNS) and 10 Pseudomonas aeruginosa strains planktonic growth and biofilm formation was evaluated. Cultures were positive in 87.5% of the catheters removed due infectious and 90.3% removed due to non-infectious causes. However, microbial yields were higher on the cuffs of catheters removed due to infection vs. non-infection. Staphylococci (CNS and Staphylococcus aureus) and P. aeruginosa were the predominant species: 32% and 20% in the infection and 43.3% and 22.7% in the non-infection group, respectively. In general, PD solutions had a detrimental effect on planktonic CNS and P. aeruginosa strains growth. All strains formed biofilms in the presence of PD solutions. The solutions had a more detrimental effect on P. aeruginosa than CNS strains. No major differences were observed between conventional and biocompatible solutions, although in icodextrin solution biofilm biomass was lower than in bicarbonate/lactate solution. Overall, we show that microbial biofilm is universal in PD catheters with the subclinical menace of Staphylococci and P. aeruginosa. Cuffs colonization may significantly contribute to infection. PD solutions differentially impact microbial species. This knowledge is important for the development of infection diagnosis, treatment and preventive strategies.

Exit-Site Dressing and Infection in Peritoneal Dialysis: A Randomized Controlled Pilot Trial

♦

OBJECTIVE

Peritoneal dialysis (PD)-related infection is a common cause of catheter loss and the main reason for PD drop-out. Exit-site infection (ESI) is a pathway to developing tunnel infection and peritonitis, hence rigorous exit-site care has always been emphasized in PD therapy. The aim of this study was to evaluate the effect of exit-site dressing vs non-dressing on the rate of PD-related infection. ♦

METHODS

A prospective randomized controlled study was conducted in prevalent PD patients at the Hospital Tuanku Jaafar Seremban, Negeri Sembilan, Malaysia, from April 2011 until April 2013. All patients were required to perform daily washing of the exit site with antibacterial soap during a shower. In the dressing group (n = 54), patients were required to clean their exit site using povidone-iodine after drying, followed by topical mupirocin antibiotic application to the exit site. The exit site was then covered with a sterile gauze dressing and the catheter immobilized with tape. In the non-dressing group (n = 54), patients were not required to do any further dressing after drying. They were only required to apply mupirocin cream to the exit site and then left the exit site uncovered. The catheter was immobilized with tape. The primary outcome was ESI. The secondary outcomes were evidence of tunnel infection or peritonitis. ♦

RESULTS

A total of 97 patients completed the study. There were a total of 12 ESI episodes: 4 episodes in 4 patients in the dressing group vs 8 episodes in 4 patients in the non-dressing group. This corresponds to 1 episode per 241.3 patient-months vs 1 episode per 111.1 patient-months in the dressing and non-dressing groups respectively. Median time to first ESI episode was shorter in the non-dressing than in the dressing group, but not significant (p = 0.25). The incidence of gram-positive ESI in both groups was similar. There were no gram-negative ESI in the non-dressing group compared with 2 in the dressing group. The peritonitis rate was 1 per 37.1 patient-month in the dressing group and 1 per 44.4 patient-months in the non-dressing group. Median time to first peritonitis episode was significantly shorter in the dressing group compared to non-dressing (p = 0.03). There was no impact of dressing disruptions in the occurrence of major PD catheter-related infection. ♦

CONCLUSION

Use of a non-dressing technique with only prophylactic topical mupirocin cream application is effective in preventing PD-related infection. The non-dressing technique is more cost-effective and convenient for PD patients, with fewer disposables.

Preventing amikacin related ototoxicity with N-acetylcysteine in patients undergoing peritoneal dialysis

Amikacin is a frequently used antibiotic in the treatment of peritoneal dialysis (PD)-related peritonitis. Ototoxicity is a well-known complication of amikacin for which increased oxidative stress and free oxygen radicals are thought to be responsible. In this study, the effect of N-acetyl-cysteine (NAC) on cochlear function and oxidant situation in the amikacin related ototoxicity in PD-related peritonitis patients are investigated. Forty-six patients who had their first PD-related peritonitis attacks receiving empirical amikacin treatment were enrolled in the study. The patients were randomized into two groups; the first group (n = 23) as NAC receiving and the second group (n = 23) as a placebo receiving, control group. Otoacoustic emissions were measured before, 1 week after and 4 weeks after the treatment. Oxidative stress measurements were performed concurrently in order to evaluate the effectiveness of NAC. The results of screening with otoacoustic emission testing after amikacin treatment showed that cochlear function is protected especially in higher frequencies in NAC group when compared with the control group. Evaluation of the antioxidant status of the two groups showed no differences in the basal values, but at the first week there was an increase in the NAC group compared with the control group, and this increase became significant at the fourth week. NAC is found to be safe and effective in amikacin-related ototoxicity in patients with PD-related peritonitis. We suggest a close monitoring of the patients receiving amikacin containing treatment protocols and if amikacin is administrated supplementing the treatment with NAC.

Update on the challenging role of biofilms in peritoneal dialysis

Biofilms are commonly associated with an increased risk of patient infection. In peritoneal dialysis (PD), catheter associated infection, especially peritonitis, remains a clinically relevant problem. Although the presence of a biofilm is recognized in relapsing, repeat, and catheter-related peritonitis, it remains poorly characterized. In this review, an update on the role of biofilms in PD infections is presented. The emerging concept that host cells and tissue associated biofilms, in addition to the biofilms on the catheters themselves, contribute to the recalcitrance of infections is discussed. Furthermore, the evidence of biofilms on PD catheters, their developmental stages, and the possible influence of the PD environment are reviewed. The focus is given to ex vivo and in vitro studies that contribute to the elucidation of the interplay between host, microbial, and dialysis factors. The key issues that are still to be answered and the challenges to clinical practice are discussed.

Prevention of peritoneal dialysis catheter infections in Saudi peritoneal dialysis patients: the emergence of high-level mupirocin resistance

PURPOSE

Exit-site infection (ESI) and peritonitis remain the major causes of morbidity and mortality in peritoneal dialysis (PD) patients. This study compared the effectiveness of local mupirocin ointment and gentamicin cream in preventing both gram-positive and gram-negative bacterial infections in PD patients.

METHODS

Patients from two centers (n = 203) were assigned to daily mupirocin ointment or gentamicin cream application. Infections were tracked prospectively by organisms and expressed as episodes per patient-year for both ESI and peritonitis.

RESULTS

The rate of gram-positive ESI was 0.31/episode/patient-year and 0.22 episodes/patient-year (p<0.05), whereas the rate of gram-negative ESI was 0.28 episode/patient-year and 0.11 episode/patient-year (p<0.01) in the mupirocin group and gentamicin group, respectively. Gram-positive ESI occurred in 17.1% vs 10.2% of patients (p<0.05), whereas 20% of and 5.1% of patients (p<0.001) had gram-negative ESI in the 2 groups respectively. S.aureus was cultured at exit-site in the mupirocin group in 27.8% patients, 60% (16.7% of the total Gram-positive isolates) of them being with high-level mupirocin-resistance. Pseudomonas aeruginosa was cultured in 21.8% of ESI in the mupirocin group, and in only 6.7% in the gentamicin group (p<0.01). Peritonitis rates were lower using gentamicin cream, 0.17 episode/patient-year compared with mupirocin, 0.39 episode/patient-year (p<0.01). With multivariate analysis, only gentamicin exit-site use was a significant predictor for lower catheter infection rate.

CONCLUSION

Prolonged use of mupirocin for ESI-prophylaxis is associated with the emergence of mupirocin-resistant S. aureus. Gentamicin cream is superior to mupirocin ointment in the prevention of PD catheter infections.

Correlation between hearing loss and peritonitis frequency and administration of ototoxic intraperitoneal antibiotics in patients with CAPD

AIM

Aminoglycosides have been used in the treatment of CAPD peritonitis despite their potential risk for ototoxicity. The ototoxicity risk of intraperitoneally administered aminoglycosides has been investigated by a number of studies. However, their results are somewhat conflicting. The aim of the present study was to examine the frequency of hearing loss and the correlation between the repeated doses of aminoglycosides and hearing loss in CAPD peritonitis therapy.

METHODS

Hearing functions of the CAPD patients who had developed peritonitis and had been treated with various antibiotics including aminoglycosides were compared with those CAPD patients who had never developed peritonitis. Threshold values for hearing were determined through "pure tone audiometry" measurements.

RESULTS

Hearing threshold levels of the patients with history of peritonitis were found to be significantly higher in both lower [pure tone averages - 1 (PTA-1)] and higher [pure tone averages - 2 (PTA-2)] frequencies, when compared to the ones with no history of peritonitis (p values were 0.001 and 0.007, respectively).

CONCLUSION

The present study showed that intraperitoneal aminoglycoside administration in CAPD patients is associated with the development of hearing loss. The severity of hearing loss may range from mild hearing loss to profound deafness. A remarkable correlation exists between the severity of the hearing loss and the repeated and total aminoglycoside dose received.

Peritonitis due to Lactococcus lactis in a CAPD patient

Lactococcus lactis is a gram-positive bacterium, commonly used in the dairy industry. Although Lactococcus lactis is known to be non-pathogenic for humans, it can cause infection in immunocompromised patients. We report a case of peritonitis due to L. lactis in a continuous ambulatory peritoneal dialysis patient, which is the second reported case in the literature.

Determinants of Catheter Loss following Continuous Ambulatory Peritoneal Dialysis Peritonitis

Background

Few patients are able to resume peritoneal dialysis (PD) therapy after an episode of peritonitis that requires catheter removal. PD catheter loss is therefore regarded as an important index of patient morbidity. The aim of the present study was to evaluate factors influencing catheter loss in patients suffering from continuous ambulatory PD (CAPD) peritonitis.

Patients and Methods

We retrospectively reviewed 579 episodes of CAPD peritonitis from 1999 to 2006 in a tertiary-care referral hospital. Demographic, biochemical, and microbiological characteristics were recorded. Episodes resulting in PD catheter removal ( n = 68; 12%) were compared by both univariate and multivariate analyses with those in which PD catheters were preserved.

Results

The incidence of PD catheter loss increased as the number of organisms cultured increased ( p = 0.001). Also, PD catheter removal was more likely to occur after peritonitis episodes with low serum albumin level ( p = 0.004), those with long duration of PD effluent leukocyte count remaining above 100/μL ( p < 0.001), those with concomitant tunnel infection ( p < 0.001), those with concomitant exit-site infection ( p = 0.005), and those with presence of catastrophic intra-abdominal visceral events ( p < 0.001). Duration on PD preceding the peritonitis episode was of borderline significance ( p = 0.080). On the contrary, initial PD effluent leukocyte count and serum level of C-reactive protein were not predictive of PD catheter loss. Micro-organisms of the Enterobacteriaceae family were the major pathogens responsible for PD catheter loss following polymicrobial peritonitis. Furthermore, we found that there was no association between polymicrobial peritonitis and the catastrophic intra-abdominal visceral event, although both resulted in a greater incidence of PD catheter loss. Among the single-organism group in our population, the microbiological determinants of PD catheter loss included fungi ( p < 0.001), anaerobes ( p = 0.018), and Pseudomonas sp (borderline significance: p = 0.095).

Conclusion

PD catheter loss as a consequence of peritonitis is related primarily to hypoalbuminemia, longer duration of PD effluent leukocyte count remaining above 100/μL, the etiologic source of the infection, and the organism causing the infection. Peritonitis associated with concomitant tunnel or exit-site infections and abdominal catastrophes were more likely to proceed to PD catheter loss. The microbiological determinants of PD catheter loss in the present study included polymicrobial infections caused by Enterobacteriaceae as well as monomicrobial pseudomonal, anaerobic, and fungal infections.

Staphylococcus aureus induces caspase-independent cell death in human peritoneal mesothelial cells

Bacterial peritonitis remains a serious complication of peritoneal dialysis. Although Staphylococcus epidermidis is the most common pathogen involved, infections with Staphylococcus aureus lead to severe peritoneal damage and are often associated with a dramatic loss of mesothelial cells. Induction of cell death appears to be involved in peritoneal damage and mesothelial cell loss during bacterial infections. Using cultured human peritoneal mesothelial cells (HMCs), we investigated the ability of different S. epidermidis and S. aureus strains to damage the HMC monolayer and to trigger cell death. We show that only a subgroup of live S. aureus isolates, characterized by an invasive and alpha-hemolysin-producing phenotype, induces cell death. None of the tested S. epidermidis strains, which were not invasive or hemolytic, had a cytotoxic effect. After host cell invasion, S. aureus resided within phagocytic vacuoles, and HMCs were apparently able to degrade staphylococci. However, even after prolonged infection, a high percentage of S. aureus remained alive within HMCs and might be released after host cell death. Cell death induced by S. aureus was accompanied by apoptotic alterations, such as DNA fragmentation, but was independent of endogenous FasL and tumor necrosis factor-alpha death ligand expression. Moreover, caspases were not involved in S. aureus-induced mesothelial cell death. In conclusion, our data indicate that mesothelial cell death might represent a major mechanism of S. aureus-induced damage of the peritoneum during bacterial peritonitis.

Pseudomonas aeruginosa protease IV: a corneal virulence factor of low immunogenicity

PURPOSE

To study antibody production to Pseudomonas aeruginosa protease IV (PIV) for immunoassay development and to assess the possible role of antibody in arresting corneal damage.

METHODS

Rabbits were immunized with PIV, urea-soluble recombinant PIV (rPIV), or precipitated rPIV. Antibody was analyzed by ELISA and Western blotting. Antibody-mediated inhibition of PIV activity was tested by colorimetric assay and during keratitis by slit-lamp examination of infected eyes.

RESULTS

Antibody was not produced after PIV immunization but was induced by rPIV. Rabbits immunized first with soluble and then precipitated rPIV produced high titers (log(10)) to rPIV (4.28 +/- 0.09) and significantly higher titers to PIV (3.90 +/- 0.06) compared to the other immunized groups. Antibody to rPIV reacted with PIV, but neither neutralized enzyme activity in vitro nor protected infected rabbits in vivo.

CONCLUSIONS

The present study demonstrates that PIV is a virulence factor which can escape a protective immune response.

Randomized, double-blind trial of antibiotic exit site cream for prevention of exit site infection in peritoneal dialysis patients

Infection is the Achilles heel of peritoneal dialysis. Exit site mupirocin prevents Staphylococcus aureus peritoneal dialysis (PD) infections but does not reduce Pseudomonas aeruginosa or other Gram-negative infections, which are associated with considerable morbidity and sometimes death. Patients from three centers (53% incident to PD and 47% prevalent) were randomized in a double-blinded manner to daily mupirocin or gentamicin cream to the catheter exit site. Infections were tracked prospectively by organism and expressed as episodes per dialysis-year at risk. A total of 133 patients were randomized, 67 to gentamicin and 66 to mupirocin cream. Catheter infection rates were 0.23/yr with gentamicin cream versus 0.54/yr with mupirocin (P = 0.005). Time to first catheter infection was longer using gentamicin (P = 0.03). There were no P. aeruginosa catheter infections using gentamicin compared with 0.11/yr using mupirocin (P < 0.003). S. aureus exit site infections were infrequent in both groups (0.06 and 0.08/yr; P = 0.44). Peritonitis rates were 0.34/yr versus 0.52/yr (P = 0.03), with a striking decrease in Gram-negative peritonitis (0.02/yr versus 0.15/yr; P = 0.003) using gentamicin compared with mupirocin cream, respectively. Gentamicin use was a significant predictor of lower peritonitis rates (relative risk, 0.52; 95% confidence interval, 0.29 to 0.93; P < 0.03), controlling for center and incident versus prevalent patients. Gentamicin cream applied daily to the peritoneal catheter exit site reduced P. aeruginosa and other Gram-negative catheter infections and reduced peritonitis by 35%, particularly Gram-negative organisms. Gentamicin cream was as effective as mupirocin in preventing S. aureus infections. Daily gentamicin cream at the exit site should be the prophylaxis of choice for PD patients.

Evaluation of an antimicrobial-impregnated continuous ambulatory peritoneal dialysis catheter for infection control in rats

Infection is the most serious complication arising in long-term continuous ambulatory peritoneal dialysis (CAPD), specifically peritonitis and exit-site infection. The initial weeks after implantation is the crucial period during which bacterial colonization of the catheter results in maximal morbidity, with Staphylococcus aureus being the most virulent organism. We developed an antimicrobial-impregnated CAPD catheter by impregnating the cuff and tubing with chlorhexidine, silver sulfadiazine, and triclosan in a polymer matrix. The antimicrobial spectrum and duration were shown by measuring zones of inhibition to various bacteria and fungi over the course of 5 to 10 days. Activity also was assessed subsequent to soaking in trypticase soy broth containing 20% bovine serum over the course of 1, 3, and 7 days. Significant antimicrobial activity was shown against all organisms tested for, with particular efficacy against gram-positive bacteria. Catheters were implanted in rats followed by inoculation of the exit site with S aureus. Seven days postimplantation, 0% of the impregnated catheters were colonized intraperitoneally compared with 100% of the control catheters. Similarly, 12.5% of the impregnated catheters were colonized at the exit site, whereas 100% of the controls were colonized. Histologic analysis showed that this combination and concentration of antimicrobials did not retard healing or cause increased inflammation compared with control catheters after 3, 10, and 24 days postimplantation in noninoculated rats.

Infections associated with dialysis and transplantation

Infection within the abdominal wall and peritonitis are still important causes of morbidity which ultimately limit the use of peritoneal dialysis in end-stage renal failure. Similarly disastrous complications resulting in loss of access can follow infection in venous cannulae and artificial arteriovenous fistulae, particularly in synthetic vascular grafts. Important publications continue to underline the mechanism of reduced resistance to infection by uraemic patients. After renal transplantation bacterial infection is common and predictable. However, immunosuppressed recipients are particularly susceptible to viral and fungal infection. Arguably infection of all types can induce organ rejection.

Staphylococcus aureus infections in dialysis patients: focus on prevention

Staphylococcus aureus infections are a major cause of morbidity and hospitalization in dialysis patients. The risk of infection relates to the type of access. Patients with acute hemodialysis (HD) catheters are at the greatest risk of S. aureus bacteremia, followed by tunneled HD catheters, and grafts. Patients with a fistula have a rate similar to that of peritoneal (PD) patients. In PD patients, however, S. aureus is the second most common cause of peritonitis, is often associated with a catheter infection, and frequently requires catheter removal for resolution. S. aureus infections in dialysis patients are much more common in nasal carriers. S. aureus moves from the nasal reservoir to the hands and skin, and from there to infect the access. Therefore, prevention of infection can be aimed at treating the carriage or in applying antibiotics at the catheter exit site, thus preventing colonization and subsequent infection of the catheter. For HD patients with a permanent access (either fistula or graft), intranasal mupirocin, twice a day for 5 days followed by a once weekly application, is effective in reducing the risk of S. aureus bacteremia. Cost analysis indicates that treating all patients would result in more cost savings than treating just carriers. For patients with acute HD catheters, exit site mupirocin applied as part of routine care during each HD treatment, reduces the risk of S. aureus exit site infection and bacteremia. For PD patients, S. aureus infections can be diminished by using mupirocin at the exit site as part of daily exit site care. Prophylaxis against S. aureus is under utilized in dialysis patients and, if implemented, could lower the rate of these serious infections.