Predictive factors of outcome following staphylococcal peritonitis in continuous ambulatory peritoneal dialysis

BACKGROUND AND AIMS: Staphylococcus epidermidis and other coagulase-negative staphylococci (CoNS) are the most common agents of continuous ambulatory peritoneal dialysis (CAPD) peritonitis. Episodes caused by Staphylococcus aureus evolve with a high method failure rate while CoNS peritonitis is generally benign. The purpose of this study was to compare episodes of peritonitis caused by CoNS species and S. aureus to evaluate the microbiological and host factors that affect outcome. MATERIAL AND METHODS: Microbiological and clinical data were retrospectively studied from 86 new episodes of peritonitis caused by staphylococci species between January 1996 and December 2000 in a university dialysis center. The influence of microbiological and host factors (age, sex, diabetes, use of vancomycin, exchange system and treatment time on CAPD) was analyzed by logistic regression model. The clinical outcome was classified into two results (resolution and non-resolution). RESULTS: The odds of peritonitis resolution were not influenced by host factors. Oxacillin susceptibility was present in 30 of 35 S. aureus lineages and 22 of 51 CoNS (p = 0.001). There were 32 of 52 (61.5%) episodes caused by oxacillin-susceptible and 20 of 34 (58.8%) by oxacillin-resistant lineages resolved (p = 0.9713). Of the 35 cases caused by S. aureus, 17 (48.6%) resolved and among 51 CoNS episodes 40 (78.4%) resolved. Resolution odds were 7.1 times higher for S. epidermidis than S. aureus (p = 0.0278), while other CoNS had 7.6 times higher odds resolution than S. epidermidis cases (p = 0.052). Episodes caused by S. haemolyticus had similar resolution odds to S. epidermidis (p = 0.859). CONCLUSIONS: S. aureus etiology is an independent factor associated with peritonitis non-resolution in CAPD, while S. epidermidis and S. haemolyticus have a lower resolution rate than other CoNS. Possibly the aggressive nature of these agents, particularly S. aureus, can be explained by their recognized pathogenic factors, more than antibiotic resistance.     

Use of pulsed-field gel electrophoresis in the analysis of recurrent Staphylococcus aureus infections in patients on continuous ambulatory peritoneal dialysis

BACKGROUND/AIM: The purpose of this study was to evaluate pulsed-field gel electrophoresis (PFGE) for distinguishing between relapse and reinfection of Staphylococcus aureus infections in patients on continuous ambulatory peritoneal dialysis (CAPD). METHODS: Between July 1993 and May 1997, 4 patients with recurrent CAPD-associated infections caused by S. aureus we enrolled in this study. There were nine episodes of peritonitis, one episode of temporary double lumen catheter infection, and one episode of Hickman catheter infection. A total of eleven S. aureus isolates were collected from peritoneal fluid (n = 9) and blood (n = 2). PFGE typing was applied. RESULTS: In our study, from PFGE typing, the 11 S. aureus isolates were classified into seven patterns. Antibiogram profiling classified only four patterns. Patient A had a reinfection by another strain of S. aureus, and patient B had three episodes of peritonitis caused by the same strain of S. aureus due to exit site infections. Patient C had two episodes of CAPD peritonitis caused by two different strains, respectively. Patient D had four episodes of S. aureus infection (three CAPD peritonitis and one bacteremia); the first two episodes of peritonitis were caused by an identical strain of S. aureus, whereas the subsequent two infections were caused by other organisms. CONCLUSION: PFGE has a high discriminatory power and can be an assistant method to antibiogram profiling for distinguishing relapse from reinfection in CAPD-associated peritonitis.     

Renal histology for the diagnosis of primary hyperoxaluria in patients with end-stage renal disease

In patients utilizing continuous ambulatory peritoneal dialysis (CAPD), Staphylococcus epidermidis is the most prevalent organism isolated from peritoneal and exit site infections [1] although clinically significant systemic infection is unusual. We report 2 patients undergoing CAPD who developed generalized lymphadenopathy following peritonitis and exit site infection with S. epidermidis isolated from the excised lymph nodes. We conclude that catheter-related S. epidermidis infection may result in generalized lymphadenopathy due to dissemination of the infective focus.     

Peritoneal drainage: an important element in host defence against staphylococcal peritonitis in patients on CAPD.

The growth of Staphylococcus aureus and coagulase-negative staphylococci were studied in fresh and effluent peritoneal dialysate from patients on continuous ambulatory peritoneal dialysis (CAPD). Peritoneal drainage during CAPD removes bacterial contaminants from the peritoneal cavity with an efficiency that depends upon the volume of peritoneal fluid remaining after drainage (residual volume). Combination of our data on the growth of coagulase-negative staphylococci in dialysate with a mathematical model of peritoneal drainage during CAPD shows that a residual volume of less than 800 ml (normal = approximately 400 ml) will prevent survival in the peritoneal fluid. A residual volume of less than 200 ml is required to eliminate S. aureus because of its faster rate of growth in dialysate. Previous work has shown that numbers of macrophages are too few to influence bacterial growth in the peritoneal dialysate. Coagulase-negative staphylococci adhere poorly to mesothelial cells in culture. Survival within the peritoneal cavity during CAPD probably depends on colonization of the PD catheter. Coagulase-negative staphylococcal peritonitis is likely to be localized to areas of the peritoneal membrane in close contact with the PD catheter. S. aureus is able to multiply in the peritoneal dialysate during CAPD and thereby causes generalized peritonitis.     

Staphylococcus aureus skin carriage and development of peritonitis in patients on continuous ambulatory peritoneal dialysis

We conducted a 15-month prospective study to investigate the skin carriage of Staphylococcus aureus and the development of peritonitis in 43 patients undergoing continuous ambulatory peritoneal dialysis (CAPD). Sixteen of 43 patients (37%) were chronic carriers of S. aureus in the anterior nares and/or in the exit-site of the catheter; 12 patients (28%) were intermittent carriers, and 15 (35%) were noncarriers. Fifty episodes of peritonitis occurred during a total of 422 patient-months of observation. S. aureus was responsible for 16 episodes of peritonitis diagnosed in 15 patients. All episodes of S. aureus peritonitis occurred in chronic and intermittent carriers. Phage typing was performed on isolates from 8 patients with S. aureus peritonitis, and they were found to have the same phage type as that previously carried in the skin. We conclude that CAPD patients who are chronic or intermittent carriers of S. aureus are at higher risk of development of peritonitis than noncarriers.     

Methicillin-resistant staphylococcal infections in an outpatient peritoneal dialysis program

In view of the increasing concern about hospital-acquired methicillin resistance, we examined the sensitivities and outcome of staphylococcal infections related to outpatient peritoneal dialysis over a 5-year period. Data on all episodes of peritonitis (n = 360) and catheter infections (n = 507) were gathered prospectively from January 1984 to December 1988. The numbers of patients on peritoneal dialysis each year ranged from 136 in 1984 to 109 in 1987. Fifteen methicillin-resistant staphylococcal infections (MRSI) related to outpatient peritoneal dialysis occurred. Three were due to methicillin-resistant Staphylococcus aureus found in infected exit sites (2.3% of all S aureus catheter infections). Two of these infections occurred in a continuous ambulatory peritoneal dialysis (CAPD) patient who carried methicillin-resistant S aureus in his nares. The other 12 methicillin-resistant organisms were coagulase-negative staphylococci that caused peritonitis. There was a significant increase in the percentage of episodes of coagulase-negative staphylococci peritonitis caused by methicillin-resistant organisms; from 5% (3/57) in 1984 through 1986 to 28% (9/32) in 1987 through 1988 (P less than 0.005). In view of the high percentage of coagulase-negative staphylococci peritonitis that is methicillin-resistant, vancomycin rather than cephalosporins should be used for initial treatment.     

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.     

Exit-site and tunnel infections in continuous ambulatory peritoneal dialysis patients

One hundred two exit-site infections (ESI) were diagnosed in 63 of 163 (38.6%) patients, with an incidence of one episode every 23.7 patient-months in patients with a history of ESI, whereas in the overall continuous ambulatory peritoneal dialysis (CAPD) population the incidence was one episode every 48.7 patient-months. In diminishing order of frequency, the bacteria isolated were Staphylococcus aureus, Staphylococcus epidermidis, Pseudomonas aeruginosa, and Escherichia coli. The probability of remaining free of ESI was 72% at 1 year and 45% at 5 years. The ESI that led to catheter removal were due to S aureus and gram-negative rods. In 13 (48%) of 27 S aureus ESI unresponsive to antibiotics and local care, deroofing and outer cuff shaving completely resolved the ESI. Despite this treatment, the catheters of the remaining 14 patients had to be removed because of peritonitis associated with the tunnel infection. In conclusion, ESI is a major cause of CAPD failure. In our series, shaving the cuff as a rescue treatment was effective for almost 50% of the patients with antibiotic-resistant S aureus ESI.     

A prospective evaluation of blood culture versus standard plate techniques for diagnosing peritonitis in continuous ambulatory peritoneal dialysis

Peritonitis remains a major cause of morbidity in patients treated with continuous ambulatory peritoneal dialysis (CAPD). Culture-negative episodes of peritonitis occur at rates of up to 20%, and in part may reflect inadequate culturing techniques of peritoneal effluent. Through a large, prospective study, the improved sensitivity of a blood culture system, when compared with a standard plate technique (P = 0.001), for the detection of bacterial growth in 67 episodes of CAPD peritonitis is demonstrated. Improved recognition of infections caused by gram-positive organisms, primarily Staphylococcus epidermidis, was especially significant using the blood culture system (P = 0.0001). Because of improved sensitivity and a decreased time to organism identification, particularly with infections caused by S epidermidis, the most common cause of bacterial peritonitis in CAPD patients, we suggest that a blood culture system be the standard means of culturing peritoneal fluid in CAPD patients with peritonitis. The lysis-centrifugation system of culturing peritoneal fluid is also discussed in comparison with the blood culture system.     

Staphylococci as uropathogens-frequency of isolation in hospitalized patients and sensitivity to antimicrobial agents

For a period of 24 months (1997-1999) were isolated 266 clinically significant staphylococcal strains, S. aureus, 36 (13.5%) and 230 (86.5%) coagulase negative staphylococci (CNS) from urines of hospitalised patients (over 14 years) with UTI. The most frequently isolated strains from CNS was S. haemolyicus, 110 (47.8) strains, followed by S. saprophyticus 47 (20.4%) strains and S. epidermidis 18 (7.8%). The susceptibility of the isolates to 13 antimicrobial agents was determined by agar dilution method (NCCLS). From the isolated 36 strains S. aureus, 24 were sensitive and 12 were resistant to methicillin. From 230 CNS, 105 strains showed sensitivity and 125 strains resistance to methicillin. All staphylococci were sensitive to vancomycin and most of them (over 95%) to amikacin and rifampin. It was established a considerable difference between the sensitivity of methicillin-sensitive and methicillin-resistant staphylococci. The established resistance accompanied with high rate percentage methicillin resistance requires careful consideration to antimicrobial therapy of staphylococcal urinary tract infections (UTI).     

Vancomycin pharmacokinetics in continuous ambulatory peritoneal dialysis patients with peritonitis

Peritonitis has proven to be the major deterrent to the further growth of continuous ambulatory peritoneal dialysis (CAPD) as a treatment strategy for end-stage renal disease. The correct treatment of peritonitis remains unsettled as evidenced by the presence of advocates for oral, intravenous or intraperitoneal antibiotic administration. This study examines the pharmacokinetic parameters of intravenous vancomycin when employed in the therapy of peritonitis. One gram of intravenous vancomycin was administered during 7 episodes of peritonitis in 5 patients. Plasma and end-of-dwell dialysate levels were maintained above the minimum inhibitory concentration for Staphylococcus aureus and S. epidermidis for 7 days following this single dose of vancomycin. These data establish the existence of sustained intraperitoneal entry of intravenous vancomycin during peritonitis and raise for speculation its use as the sole therapy in most episodes of gram-positive peritonitis.     

A five-year study of the microbiologic results of exit site infections and peritonitis in continuous ambulatory peritoneal dialysis

We studied the culture results from 321 continuous ambulatory peritoneal dialysis (CAPD) related infections (exit site, tunnel infections, and peritonitis) in 137 patients over a 5-year period to determine the contribution of exit site and tunnel infections to peritonitis and catheter loss. Seventeen percent of peritonitis episodes were associated temporally and by microbiologic results with exit site or tunnel infections. Twenty-one percent of exit site and tunnel infections and 20% of peritonitis episodes resulted in catheter loss. Peritonitis due to Staphylococcus aureus was more likely to be associated with an exit site or tunnel infection and was more likely to result in loss of the catheter than peritonitis due to Staphylococcus epidermidis. Peritonitis and exit site infections due to Pseudomonas sp also frequently resulted in catheter removal. We found that exit site infections cause significant morbidity in CAPD patients. Further studies in this area are needed.     

Analysis of the causative pathogens in uncomplicated CAPD-associated peritonitis: duration of therapy, relapses, and prognosis

We analyzed the frequency with which certain bacteria caused uncomplicated peritonitis in an adult continuous ambulatory peritoneal dialysis (CAPD) program that continued patients on this modality of therapy despite frequent infections. All infections were treated with a commonly employed 10- to 14-day course of narrow spectrum intraperitoneal antibiotics. Although the distribution of bacterial pathogens was similar to previous reports (coagulase-negative staphylococci, 43%; Staphylococcus aureus, 13%), we observed no episodes of fungal peritonitis. Twenty percent of our infections were associated with either "no specimens obtained" or "no growth," a finding similar to the CAPD registry. When the data were available, two thirds of all infections were caused by the same pathogen (genus and species) as in the most immediately preceding infection. Twenty-two of 96 episodes of uncomplicated peritonitis occurred within three weeks of a preceding infection. In all 11 cases where organisms were isolated from both paired episodes, the infecting agent was the same as in the preceding infection and was a staphylococcus. This high rate of apparent relapse and the absence of fungal infections may relate to our treatment protocol and possible explanations are discussed. Lastly, the occurrence of coagulase-negative staphylococcal peritonitis is a harbinger of future episodes of peritonitis caused by a variety of organisms.     

Infection in total joint replacements. Why we screen MRSA when MRSE is the problem?

A retrospective review of MRSA screening showed that of a total of 8911 patients screened pre-operatively between May 1996 and February 2001, 83 (0.9%) had MRSA isolated from one source or another. During the same period, 115 (13.6%) of 844 positive tissue samples taken during surgery grew Staphylococcus aureus. Of these only 1 (0.01%) was reported to be methicillin-resistant (MRSA). However, a total of 366 (43.4%) isolates from tissue samples were reported as coagulase-negative staphylococci (C-NS). Of these, 312 samples were tested for methicillin sensitivity, of which 172 (55.1%) were found to be resistant. Staphylococcus epidermidis is the most prevalent and persistent species found on most skin and mucous membranes, constituting 65% to 90% of all staphylococci. Most isolates in tissue samples were found to be methicillin-resistant coagulase-negative staphylococcus (55.1%). Hence, it may be appropriate to undertake screening for methicillin-resistant Staphylococcus epidermidis in addition to that for MRSA.     

Peritoneal dialysis-associated peritonitis in Scotland (1999-2002).

BACKGROUND: Peritonitis is a major complication of peritoneal dialysis (PD). We have performed a national study of all patients on PD in Scotland over a 3.5 year period examining the causes of technique failure, rates of peritonitis, causative organisms, clinical outcomes and differences between automated peritoneal dialysis (APD) and continuous ambulatory peritoneal dialysis (CAPD). METHODS: All 10 adult renal units in Scotland participated in the study and the data include all 1205 patients who were on PD in Scotland from January 1999 to June 2002. The data were collected prospectively by the PD nurses and reported to the Scottish Renal Registry every 6 months. RESULTS: Refractory or recurrent peritonitis was the cause of technique failure in 167 patients (42.6% of all cases of technique failure). There were 928 cases of peritonitis in 1487 patient-years, which equates to an overall peritonitis rate of one episode every 19.2 months. The peritonitis rates for APD and CAPD were similar at one episode every 20.3 months and one episode every 18.6 months, respectively. These results include 88 cases of peritonitis due to relapse or re-infection. There was a statistically significant difference (P = 0.012) in peritonitis rates between units using nasal mupiricin (one episode every 21.9 months) and those that did not (one episode every 18.3 months). Coagulase-negative Staphylococcus was the most common cause of peritonitis (29%), although this rate is lower than in historic studies. The overall initial cure rate was 75%. The initial cure rate for APD was 77.2% and for CAPD was 73.7%. No causative organism was isolated in 17% of cases. CONCLUSION: PD-associated peritonitis is the leading cause of technique failure in Scotland. We validate previous studies showing a decrease in the proportion of peritonitis episodes that are caused by coagulase-negative staphylococci. APD peritonitis rates are not significantly better than CAPD peritonitis rates in Scotland, and the initial cure rates for APD and CAPD are similar.     

A review of Staphylococcus aureus exit-site and tunnel infections in peritoneal dialysis patients

Staphylococcus aureus peritoneal exit-site and tunnel infections are a source of considerable morbidity for peritoneal dialysis patients. These infections are difficult to resolve, can lead to peritonitis, and often require removal of the peritoneal catheter. Staphylococcal nasal carriage is the major risk factor for S aureus exit-site infections and peritonitis episodes. In the future, the identification of patients who are S aureus nasal carriers and then treatment of the carriage state with rifampin may prove to be a means of decreasing infection rates. The best treatment for S aureus exit-site and tunnel infections has not been established. Treatment regimens in general use include oral antibiotics or intraperitoneal vancomycin. The optimal length of therapy is also unclear. Since the development of the disconnect peritoneal dialysis system, S aureus, rather than the Staphylococcus epidermidis, is the leading cause of peritonitis. To further decrease peritonitis rates, attention must now be directed at catheter-related peritonitis episodes, with S aureus the most common cause of such episodes. Controlled, prospective studies designed to investigate methods of preventing and treating S aureus exit-site infections in peritoneal dialysis patients are needed.     

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.     

Specific opsonic activity for staphylococci in peritoneal dialysis effluent during continuous ambulatory peritoneal dialysis.

In a prospective study of intraperitoneal opsonins in 30 patients undergoing continuous ambulatory peritoneal dialysis (CAPD), the IgG concentration, the fibronectin concentration, the specific antistaphylococcal antibody level, and the opsonic activity against Staphylococcus epidermidis were measured in peritoneal dialysis effluent from the initiation of CAPD and monthly for 6 months. Significant correlation was found between the four assays, but the interindividual and intraindividual variations were considerable. No statistically significant correlation was observed between susceptibility of the patients to CAPD-related infectious peritonitis and any of the above-mentioned parameters of humoral defense. We conclude that at the present time it is not feasible to use these assays for the establishment of prognosis with regard to peritonitis in CAPD.     

Antimicrobial susceptibility of coagulase-negative staphylococci on tissue allografts and isolates from orthopedic patients.

Allograft infection occurs at a rate not different from that of similar procedures with large allografts or sterilized prosthetic devices and is usually caused by coagulase-negative staphylococci (CNS). CNS are feared for their limited antimicrobial susceptibility. We aimed at investigating this risk. CNS were isolated from 260 of 1461 allograft tissue grafts and compared with 384 consecutive clinical isolates from a general orthopedic population (258 patients). The CNS were identified and examined for their susceptibility to nine antibiotics used in routine practice. Staphylococcus epidermidis was the most commonly identified (35%) and the most resistant species of the allograft isolates. Comparing the overall antibiotic susceptibility patterns, clinical pathogens were significantly more resistant to six of the nine antibiotics (p < 0.01), namely penicillin, oxacillin, erythromycin, clindamycin, ofloxacin, and gentamicin. In conclusion, massive allograft infection is a well-known life-threatening surgical risk. However, we did demonstrate that allograft-related in contrast to orthopedic clinics-related CNS, are susceptible to commonly used first and second line antibiotics.     

Changes of microbial flora and wound colonization in burned patients

To determine time related changes of microbial colonization of burn wounds and body flora of burned patients, a prospective study was carried out. Fifty-one patients who were hospitalized at least 3 weeks were enrolled in the study. Periodic swabs were taken from burn wound, nasal, axillary, inguinal, and umbilical regions of the patients on admission and 7th, 14th, and 21st days of hospitalization. The mean body surface area burned was 22.9%. A total of 1098 microbial isolates were detected during the study period. Coagulase-negative staphylococci (CNS, 63.0%) and Staphylococcus aureus (19.7%) were the most prevalent isolates in admission cultures. There was a gradual decrease in the number of isolates of CNS and a marked increase in the numbers of S. aureus and Pseudomonas aeruginosa from admission to 21st day. At the 21st day, the most frequent organisms were S. aureus (37.6%), CNS (34.7%), and P. aeruginosa (16.2%). Methicillin resistance of staphylococci strains were increased constantly in study period. While 35.3% of burn wounds were sterile on admission, microbial colonization reached 86.3% within the first week. Nasal carriage of methicillin resistant S. aureus increased from 3.9% to 62.7% at 21st day. The nature of microbial wound colonization and flora changes should be taken into consideration in empirical antimicrobial therapy of burned patients.