Staphylococcus aureus colonization and infection in patients on continuous ambulatory peritoneal dialysis

Recurrent peritonitis relapse in a patient with atrial septal defect undergoing peritoneal dialysis: a case report

BACKGROUND

Peritonitis is the most common complication in patients undergoing peritoneal dialysis (PD). Most patients recover with appropriate antibiotic treatment; however, when peritonitis repeatedly relapses, the cause of recurrence must be explored. The relationship between atrial septal defect (ASD), infective endocarditis (IE), and peritonitis is rarely reported. Here, we present a case of recurrent peritonitis due to Staphylococcus aureus in a patient with ASD and IE undergoing PD.

CASE PRESENTATION

A 46-year-old woman with chronic renal failure secondary to chronic glomerulonephritis experienced three episodes of peritonitis within 80 days of starting PD. The patient had a history of untreated ASD without symptoms. After undergoing PD for approximately 35 days, the patient was admitted to our hospital on April 5, 2016, due to abdominal pain and fever for 1 week (maximum temperature of 38.5 °C) accompanied by chills and shivering. The PD effluent from the time of her admission was positive for S. aureus. Thereafter, peritonitis recurred each month. When the third episode of peritonitis occurred, transthoracic echocardiography was performed, and a vegetation measuring 9.5 × 6.4 mm attached to the surface of the right ventricle around the ventricular septal membrane was identified. Finally, the patient was diagnosed with IE. Then, ASD repair surgery was successfully performed after the infection was controlled. The patient was followed up for 5 years, with no further episodes of recurrence.

CONCLUSIONS

When a patient with ASD undergoing PD develops peritonitis, especially relapsing peritonitis, the possibility of IE is significantly increased. ASD repair surgery may be an important contributing factor to prevent peritonitis recurrence.

Phagocytosis and Killing of Suspended and Adhered Bacteria by Peritoneal Cells after Dialysis

Objective

To determine the effect of dialysis fluid containing various glucose concentrations on the phagocytosis and killing of Staphylococcus aureus by rat peritoneal cells under conditions mimicking the in vivo situation.

Design

Phagocytosis and killing were evaluated by quantitation of the killing capacity of macrophages after in vivo phagocytosis of the bacteria as well as by an in vitro flow cytometric assay of the phagocytosis and killing of adhered bacteria by peritoneal cells.

Animals

Male Wistar rats.

Main Outcome Measure

It was expected that the intraperitoneal administration of dialysis fluid would im pair the capacity of peritoneal cells to eliminate bacteria.

Results

The first test revealed no effects of glucose concentration or dwell time on the killing of phagocytosed bacteria by macrophages, median percentages ranging between 29% and 64%. In the second series of experiments no effect of glucose concentration on the phagocytosis and killing of adhered bacteria was found either; however, longer dwell times significantly enhanced both the phagocytosis (at a dwell time of 1 hour, under 20%; at dwell times of 4 or 18 hours, above 20%, p < 0.02) and the killing (at a dwell time of 1 hour, under 53%; at dwell times of 4 and 18 hours, above 70%, p < 0.01).

Conclusions

Glucose concentration has no effect on the phagocytosis and killing of Staphylococcus aureus, whereas the dwell time significantly enhances both of these functional capacities of peritoneal cells if the bacteria are adhered to surfaces.

Staphylococcus Aureus Carriage in Adult Peritoneal Dialysis Patients and Their Spouses

Objective

We hypothesized that carriage of Staphylococcus aureus among continuous ambulatory peritoneal dialysis (CAPD) patients was influenced by their spouses. Furthermore, this carrier status was compared to previous Staph. aureus peritonitis episodes in order to identify the influence of Staph. aureuscarriage on peritonitis rate.

Design

A combined prospective surveillance study (Staph. aureus carriage) and retrospective chart review (Staph. aureus peritonitis).

Setting

A single peritoneal dialysis unit in a county hospital.

Patients and methods

Cultures from patients (n = 32) and spouses (n = 16) were obtained twice, with a 1-month interval, from the anterior nares, the umbilical, and one groin area. All positive cultures were phage typed. Retrospective chart review of all episodes of Staph. aureus peritonitis among the patients was carried out.

Results

Twelve of 32 patients (37.5%) and 5 of 16 spouses (31 %)evaluated were carriers. Half of the spouses of patients who were Staph. aureus carriers, were also carriers, as opposed to 20% of spouses of non carrier patients (p = 0.30). Patients and spouses always shared the same phage type. Among patients, Staph. aureus was found in the nose only (n = 9), in all three regions (n = 2), and extranasally only (n = 1). If only one nasal culture was used to establish carriage, the sensitivity and negative predictive value would be 92% and 95%, respectively. A trend toward a higher incidence (p = 0.062) of Staph. aureus peritonitis was found among carriers (patients), 0.37 versus 0.28 peritonitis episode/dialysis -year.

Conclusions

Only one positive nasal culture was necessary when carriage of Staph. aureus was to be established. Staph. aureuscarriage was found more often in patients who had previously suffered from Staph. aureus peritonitis. The phage types isolated remained fairly constant, and the patients and spouses often had the same carrier state and shared the same phage types, although transmission does not always take place.

Sources of Staphylococcus Aureus for Patients on Continuous Ambulatory Peritoneal Dialysis

← Objective

This study was designed to determine whether family members and health care workers are a source of Staphylococcus aureus for patients on peritoneal dialysis.

← Design

Over 36 months, cultures were obtained from the nares of patients, family members that cared for the patients’ catheters, and health care workers in a dialysis unit. Pulsed-field gel electrophoresis was performed on all S. aureus isolates.

← Setting

A university-based peritoneal dialysis program.

← Participants

74 patients, 32 family members, and 17 health care workers.

← Interventions

None.

← Main Outcome Measures

The number of patients that acquired S. aureusstrains during the study period.

← Results

Of the 48 patients whose initial nares cultures were negative, 7 (15%) acquired S. aureus strains. Overall, 24 of 53 (45%) patients that had 2 or more cultures obtained during the study gained strains. Potential sources were not identified for strains gained by 11 (46%) patients. Five patients appeared to acquire their strains from family members; however, other patients also shared related strains; 8 patients acquired strains shared by other patients.

← Conclusions

Family members and other patients appeared to be important sources of S. aureus for patients on peritoneal dialysis. Health care workers that carry S. aureus transiently may be important intermediaries. Good hand hygiene is essential to prevent transmission of S. aureus to these susceptible patients.

Nasal Carriage and Peritonitis by Staphylococcus Aureus in Patients on Continuous Ambulatory Peritoneal Dialysis: A Prospective Study

Objective

To establish whether or not patients on continuous ambulatory peritoneal dialysis (CAPD) using current infection control measures who are nasal carriers of Staphylococcus aureus are at risk for the development of S. aureus peritonitis.

Design

A prospective 22-month study analyzing nasal and ski nlnasal (i.e., nasal and/orexit-site)carrier status for S. aureusand peritonitis episodes. Nasal swab cultures for S. aureus were taken with 1 to 3-month intervals; swab cultures from the catheter exit site were taken only when infection was suspected.

Setting

Renal unit, tertiary-care center.

Patients

All patients on CAPD at our center that could be observed during at least 2 months.

Interventions

None.

Main Outcome Measures

Nasal and skinlnasal carrier status, occurrence of peritonitis.

Results

Of 54 enrolled patients, 31 (57%) were nasal carriers for S. aureus: 6 of these 31 developed S. aureus peritonitis as opposed to none of 23 non-carriers (p = 0.03). The S. aureus peritonitis rate in 28 skin/nasal carriers was increased when compared to non-carriers (p = 0.02), but there was no difference between chronic and intermittent skin/nasal carriers (p = 0.63).

Conclusions

In our population, nasal carriers are at increas ed risk for the development of S. aureusperitonitis. Further studies should evaluate the effect of eradication of nasal carriage of S. aureus and the effect of additional preventive hygienic measures on the occurrence of peritonitis by S. aureus.

Recommendations for Treatment of Exit-Site P a Thology

Good local care including measures to prevent trauma keeps healthy exit sites free of infection. Acute infection can be cured with aggressive therapy. Chronic infection may progress to cuff infection, which even when treated, may progress to peritonitis. Cuff and tunnel infections require deroofing, cuff shaving, and/or catheter removal. Therapy may prolong the life of a catheter. An equivocal exit site requires aggressive therapy in order to achieve cure. Local care of the exit should include measures to prevent trauma. Should trauma occur, aggressive therapy that includes a systemic antibiotic should be instituted immediately. Aggressive therapy is particularly indicated during the healing period. Prophylactic antibiotics, systemic or topical, are indicated in trauma, recurrent infection, and may be beneficial during the healing period.

Significance, Epidemiology, and Prevention of Peritoneal Dialysis Catheter Infections

Catheter infections are a major cause of morbidity, catheter loss, and transfer to hemodialysis. These infections are mainly due to S. aureus. To date, treatment is less than optimal. Therefore, the primary goal should be prevention of catheter infections. Prevention is based on improving catheter design and implantation technique while using careful exit-site care. Prophylaxis with antimicrobials such as intranasal mupirocin or the use of silverimpregnated catheters appears promising as a way to reduce the risk of developing S. aureus infections. To optimize patient outcome, one must focus on these preventive measures.

Peritonitis in Latin America

Peritoneal dialysis has a high acceptance rate in Latin America, thus the knowledge concerning complication patterns is of great relevance. This work reviews Latin American data on peritonitis, the most serious complication of peritoneal dialysis.

The incidence of peritonitis has been reduced over time, concomitantly with the incorporation of safer exchange systems and the use of prophylactic measurements. Today, rates lower than 1 episode per 24 patient-months are commonly reported. Furthermore, changes in causative organisms have been observed, with predominance of Staphylococcus aureus up through the mid-1990s, as well as increases in coagulase-negative staphylococcus and participation of gram negatives. However, the prevalence of S. aureus is still high, due possibly to climatic conditions and the elevated prevalence of carriers. Resolution rate varies from 55% to 78%, transfer to hemodialysis from 10.9% to 15.4%, and death in 3% to 9.9% of cases. Outcome is worse in S. aureus episodes compared to those with coagulase-negative staphylococcus, despite the higher percentage of oxacillin-resistant strains among the former. In general, despite socioeconomic or climatic conditions, our results are similar to those in developed countries, perhaps as a consequence of technological improvements and/or center expertise.

Prevention of Catheter Related Infections in Patients on CAPD

Catheter-related infections remain a serious problem for patients on peritoneal dialysis. Such infections can be reduced by careful patient selection and training, by the use of the best connection technology and screening and treating nasal carriage. To date, treatment is less than optimal and therefore, the primary goal should be prevention of catheter-related infections. Prevention is based on improving catheter design and implantation technique, while providing careful exit-site care. Regardless of how it is implemented, we must aggressively pursue the prevention of catheter-related infections by eradicating S.aureus exit-site carriage in PD patients. Based on its effectiveness in adult PD patients, its low rate of adverse effects, and its reasonable cost-effectiveness, application of mupirocin ointment at the exit-site is the current method of choice for preventing PD catheter infections caused byS. aureus. In addition to reducing S. aureus exit-site infections, mupirocin seems to reduce the rates of staphylococcal peritonitis and PD catheter loss. Whether the ointment should be applied in the nares, to the exit-site or both, and whether it should be used only in staphylococcal nasal carriers or all PD patients requires further study.

Prophylactic treatment of chronic renal disease in patients undergoing peritoneal dialysis and colonized by Staphylococcus aureus: a systematic review and meta-analysis

BACKGROUND

This study was performed to evaluate the clinical effectiveness of alternative strategies for the prevention and treatment of patients with chronic kidney disease undergoing peritoneal dialysis and colonized by Staphylococcus aureus.

METHODS

A systematic review and meta-analysis were performed. The literature search involved the following databases: the Cochrane Controlled Trials Register, Embase, LILACS, CINAHL, SciELO, and PubMed/Medline. The descriptors were "Staphylococcus aureus," "MRSA," "MSSA," "treatment," "decolonization," "nasal carrier," "colonization," "chronic kidney disease," "dialysis," and "peritoneal dialysis." Randomized controlled trials that exhibited agreement among reviewers as shown by a kappa value of >0.80 were included in the study; methodological quality was evaluated using the STROBE statement. Patients who received various antibiotic treatments (antibiotic group) or topical mupirocin (mupirocin group) were compared with those who received either no treatment or placebo (control group). Patients in the antibiotic group were also compared with those in the mupirocin group.

RESULTS

In total, nine studies involving 839 patients were included in the analysis, 187 (22.3 %) of whom were nasal carriers of S. aureus. The probability of S. aureus infection at the catheter site for peritoneal dialysis was 74 % lower in the mupirocin than control group (odds ratio [OR], 0.26; 95 % confidence interval [CI], 0.14-0.46; p < 0.001), 56 % lower in the antibiotic than control group (OR, 0.44; 95 % CI, 0.19-0.99; p = 0.048), and 52 % lower in the mupirocin than antibiotic group (OR, 0.48; 95 % CI, 0.21-1.10; p = 0.084). The difference in the probability of S. aureus peritonitis in patients undergoing peritoneal dialysis was not statistically significant among the three groups.

CONCLUSIONS

Mupirocin and topical antibiotics were effective for reduction of S. aureus catheter site infection in patients undergoing peritoneal dialysis when compared with no treatment or placebo. However, evidence was insufficient to identify the optimal agent, route, or duration of antibiotics to treat peritonitis.

Staphylococcus aureus: Immunopathogenesis and Human Immunity

Considering a large number of pathogen factors that enable high virulence of a microorganism such as Staphylococcus aureus (S. aureus), it is essential to see them through the continuous adaptation to the newly acquired mechanisms of the host immune response and efforts to overcome these, allowing the bacteria a perfect ecological niche for growth, reproduction, and location of new hosts. Past efforts to create a vaccine that would provide effective protection against infections caused by S. aureus remained without success. The reasons for this stem from the outstanding adaptability skills of this microorganism to almost all environmental conditions, the existence of a numerous virulence factors whose mechanisms of action are not well known, as well as insufficient knowledge of the immune response to S. aureus infections. This review article deals with this issue from another perspective and emphasizes actual knowledge on virulence factors and immune response to S. aureus.

The effects of living distantly from peritoneal dialysis units on peritonitis risk, microbiology, treatment and outcomes: a multi-centre registry study

Background

The aim of the study was to determine whether distance between residence and peritoneal dialysis (PD) unit influenced peritonitis occurrence, microbiology, treatment and outcomes.

Methods

The study included all patients receiving PD between 1/10/2003 and 31/12/2008, using ANZDATA Registry data.

Results

365 (6%) patients lived ≥100 km from their nearest PD unit (distant group), while 6183 (94%) lived <100 km (local group). Median time to first peritonitis in distant patients (1.34 years, 95% CI 1.07-1.61) was significantly shorter than in local patients (1.68 years, 95% CI 1.59-1.77, p = 0.001), whilst overall peritonitis rates were higher in distant patients (incidence rate ratio 1.32, 95% CI 1.20-1.46). Living ≥100 km away from a PD unit was independently associated with a higher risk of S. aureus peritonitis (adjusted odds ratio [OR] 1.64, 95% CI 1.09-2.47). Distant patients with first peritonitis episodes were less likely to be hospitalised (64% vs 73%, p = 0.008) and receive antifungal prophylaxis (4% vs 10%, p = 0.01), but more likely to receive vancomycin-based antibiotic regimens (52% vs 42%, p < 0.001). Using multivariable logistic regression analysis of peritonitis outcomes, distant patients were more likely to be cured with antibiotics alone (OR 1.55, 95% CI 1.03-2.24). All other outcomes were comparable between the two groups.

Conclusions

Living ≥100 km away from a PD unit was associated with increased risk of S. aureus peritonitis, modified approaches to peritonitis treatment and peritonitis outcomes that were comparable to, or better than patients living closer to a PD unit. Staphylococcal decolonisation should receive particular consideration in remote living patients.

Surveillance programs for detection and characterization of emergent pathogens and antimicrobial resistance: results from the Division of Infectious Diseases, UNIFESP

Several epidemiological changes have occurred in the pattern of nosocomial and community acquired infectious diseases during the past 25 years. Social and demographic changes possibly related to this phenomenon include a rapid population growth, the increase in urban migration and movement across international borders by tourists and immigrants, alterations in the habitats of animals and arthropods that transmit disease, as well as the raise of patients with impaired host defense abilities. Continuous surveillance programs of emergent pathogens and antimicrobial resistance are warranted for detecting in real time new pathogens, as well as to characterize molecular mechanisms of resistance. In order to become more effective, surveillance programs of emergent pathogens should be organized as a multicenter laboratory network connected to the main public and private infection control centers. Microbiological data should be integrated to guide therapy, adapting therapy to local ecology and resistance patterns. This paper presents an overview of data generated by the Division of Infectious Diseases, Federal University of São Paulo, along with its participation in different surveillance programs of nosocomial and community acquired infectious diseases.

Staphylococcus aureusPeritonitis Complicates Peritoneal Dialysis: Review of 245 Consecutive Cases

Peritonitis that is caused by Staphylococcus aureus is a serious complication in peritoneal dialysis (PD), but the clinical course of PD-related S. aureus peritonitis remains unclear. All of the S. aureus peritonitis in a dialysis unit from 1994 to 2005 were reviewed. During this period, 2065 episodes of peritonitis were recorded; 245 (11.9%) episodes in 152 patients were caused by S. aureus and 45 (18.4%) episodes were caused by methicillin-resistant S. aureus (MRSA). Patients with a history of recent hospitalization had a higher risk for isolation of MRSA than the others (30.6 versus 14.2%; P = 0.004). The overall primary response rate was 87.8%; the complete cure rate was 74.3%. However, 21 (8.6%) episodes developed relapse and 59 (24.1%) developed repeat S. aureus peritonitis. Episodes that were caused by MRSA had a lower primary response rate (64.4 versus 93.0%; P < 0.001) and complete cure rate (60.0 versus 77.5%; P = 0.023) than the others. Episodes that were treated initially with vancomycin had better primary response rate than those that were treated with cefazolin (98.0 versus 85.2%; P = 0.001), but the complete cure rate was similar. Adjuvant rifampicin treatment was associated with a significantly lower risk for relapse or repeat S. aureus peritonitis than was treatment without rifampicin (21.4 versus 42.8%; P = 0.004). In contrast, initial antibiotic regimen (cefazolin versus vancomycin) and concomitant exit-site infection did not have any effect on the risk for relapse or repeat peritonitis. S. aureus peritonitis is a serious complication of PD. Recent hospitalization is a major risk factor of methicillin resistance in the bacterial isolate. Rifampicin is a valuable adjunct in preventing relapse and repeat S. aureus peritonitis after the index episode.

Staphylococcus aureus carriage patterns and the risk of infections associated with continuous peritoneal dialysis

The epidemiology and risks of Staphylococcus aureus carriage in continuous peritoneal dialysis (CPD) patients was studied in a single tertiary-care institution. On outpatient visits samples for culture were routinely taken prospectively from the CPD catheter exit site and the vestibulum nasi. Seventy-five patients with at least one culture positive for S. aureus in this period were included: 43 had genotypically identical S. aureus strains in over 80% of the cultures and were classified as persistent carriers; 32 were intermittent carriers. Persistent carriage was associated with a threefold higher risk for CPD-related infections and sixfold higher rates of vancomycin consumption compared to those for the intermittent carriers. No methicillin or vancomycin resistance was detected.

Staphylococcus aureus colonization and nosocomial infections: Implications for prevention

Colonization with Staphylococcus aureus is a risk factor for invasive S. aureus infections. Intranasal mupirocin has effectively eradicated S. aureus colonization and appears to prevent S. aureus nosocomial infections in some patient populations. In hospitals and communities where mupirocin use has been widespread, resistance to the drug has emerged. New strategies and agents are needed if we want to significantly decrease the risk of S. aureus infections.

Peritoneal catheter exit-site infections: predisposing factors, prevention and treatment

Catheter-related infections, exit-site-tunnel infections and peritonitis remain the Achilles heel of peritoneal dialysis. Although the overall incidence of peritoneal-dialysis-related infectious complications has been reduced since the introduction of the Y-set and double bag system, approximately one-fifth of peritonitis episodes are associated with catheter exit-site and tunnel infections. Since its development in 1968, the Tenckhoff catheter has become one of the most widely used peritoneal catheters, and many have proposed that a number of modifications have made it a better choice. Controversies concerning the effect on exit-site infections of catheter(s) with one or two cuffs, with straight, coiled, Swan-Neck, or other modifications led to the randomized controlled studies that are reviewed in this paper. Several studies have confirmed that mupirocin, applied at the exit-site as part of regular exit-site care, reduces the risk of S. aureus exit-site and tunnel infections. Recently, the emergence on a world-wide basis of mupirocin-resistant S. aureus (MuRSA) in peritoneal dialysis patients has brought this prophylactic strategy into question. However the low frequency of resistant organisms after four years of mupirocin prophylaxis suggests that we can continue its use with annual surveillance. Once established, exit-site infections may respond to appropriate treatment, but if not the only option may be catheter removal and replacement. Although peritonitis risk has decreased over the past decade, mainly due to improvements in connection technology, exit-site and tunnel infections have not. An exit-site infection that does not respond to treatment may lead to tunnel infection and to persistent peritonitis, which may require catheter removal and occasionally discontinuation of the peritoneal dialysis. Therefore it is important to be familiar with these factors that predispose to exit-site infection and to know how to prevent and to treat such infections. This review will discuss factors that predispose to catheter-related exit-site infections, techniques of exit-site care, and ways to prevent exit-site infection, with emphasis on S. aureus infections and their treatment.

Peritoneal dialysis catheter removal for acute peritonitis: a retrospective analysis of factors associated with catheter removal and prolonged postoperative hospitalization

BACKGROUND

Most patients with acute peritoneal dialysis (PD) peritonitis respond to antibiotic therapy, but a significant minority of patients require surgical catheter removal to eradicate the infection. These patients may experience an adverse postsurgical course.

METHODS

We retrospectively analyzed 64 episodes of acute peritonitis requiring PD catheter removal in comparison to 426 episodes treated with antibiotics alone.

RESULTS

There were no differences between patients who required PD catheter removal and medically treated patients in sex (62% versus 60% men; P > 0.05), PD modality (31% versus 27% automated PD; P > 0.05), time spent on PD therapy (35 versus 26 months; P > 0.05), or cause of end-stage renal failure. Catheter removal was more likely to occur in elderly (mean age, 61 versus 54 years; P = 0.023) and South Asian patients (38% versus 22%; P = 0.020) and after peritonitis caused by Escherichia coli (16% versus 4%; P = 0.0005), Enterobacter species (5% versus 0.7%; P = 0.031), and Pseudomonas species (5% versus 0.7%; P = 0.031). The most significant correlation with requirement for surgical catheter removal was duration of peritonitis (mean, 7.5 versus 2.8 days; P = 1.3 x 10(-6)). Fifty-three percent of catheter removals resulted in postoperative hospitalization longer than 10 days. Delayed discharges were caused by multiple reasons. Compared with discharges within 10 days, prolonged hospitalization was associated with increased age (mean, 64 versus 58 years; P = 0.028) and delay in time to catheter removal (mean, 7.9 versus 5.3 days; P = 0.027). After catheter removal, only 4% of patients successfully returned to maintenance PD therapy.

CONCLUSION

Increased age and duration of peritonitis are associated with both requirement for PD catheter removal and prolonged postoperative hospitalization.

Infections associated with uremia and dialysis

Patients with chronic renal failure are predisposed to infections. Infections in end-stage renal disease patients are caused by immunosuppressive effects of uremia. Patients with renal failure on dialysis have impaired host defenses and may develop infections related to vascular access. This article reviews the infectious complications related to chronic renal failure in dialysis.

Peritoneal dialysis. Prevention and control of infection

In spite of the reduction in peritonitis and catheter-related infection rates in patients undergoing peritoneal dialysis, these infections remain major sources of morbidity and transfer to haemodialysis. Touch contamination at the time of doing the exchanges is still a major cause of peritonitis and leads to Gram-positive organisms (coagulation-negative staphylococcus) being the most common pathogens. Newer exchange techniques have reduced this incidence but the more serious pathogens (Staphylococcal aureus, pseudomonas and fungi) remain a major problem. Treatment has to be immediate, and hence empirical, giving adequate cover for both Gram-positive and Gram-negative organisms. The use of vancomycin as an initial antibacterial has been discontinued because of the problem of vancomycin-resistant enterococcus. Recent guidelines advocate the use of a first generation cephalosporin combined with ceftazidime (if the urine output is >100 ml/day) or an aminoglycoside in anuric patients. Subsequent therapy changes are made upon bacterial isolation and sensitivities. Vancomycin is reserved for methicillin-resistant staphylococcus. Peritoneal catheter-related infections (exit site and tunnel) are predominantly caused by S. aureus and pseudomonal organisms and can be difficult to eradicate. Tunnel infections invariably involve the catheter dacron cuffs and therefore are more likely to lead to peritonitis; in this situation catheter removal is the treatment of choice. Treatment of exit-site infections is with oral antibacterials (penicillinase-resistant penicillins, cefalexin). Vancomycin is avoided if possible. The identification that nasal carriage of S. aureus predisposes to exit-site and tunnel infections has led to prophylactic regimens to combat this problem. Mupirocin applied at the exit site leads to a reduction in catheter-related infections and peritonitis.

Head-injured patients who are nasal carriers of Staphylococcus aureus are at high risk for Staphylococcus aureus pneumonia

OBJECTIVE

To determine if head-injured patients with premorbid nasal colonization with Staphylococcus aureus are at increased risk for S. aureus infection.

DESIGN

Patients admitted over a 2-yr period were enrolled if they met the following criteria: Injury Severity Score > or = 9, intensive care unit (ICU) admission, hospitalization in another hospital < 24 hrs, no recent use of antibiotics.

SETTING

Acute care trauma facility.

PATIENTS

Any patient sustaining acute, blunt, or penetrating injury and meeting the enrollement criteria were eligible.

INTERVENTIONS

Swab cultures of both internal nares were performed within 72 hrs of readmission and cultured for S. Aureus. Patients were prospectively monitored for S. Aureus infections until discharge.

MEASUREMENTS AND MAIN RESULTS

Admission nasal cultures were positive (NC+) for S. aureus in 144 of the 776 patients cultured. Forty of the 144 NC+ patients had isolated head (37) or high cervical spine (3) injury, and 11 of that group (27.5%) developed S. aureus infections. The remaining 104 patients positive for S. aureus on admission had no head injury (74) or head combined with torso and extremity injuries (30). S. aureus infection was diagnosed in 11 of the 104 patients (10.6%). The difference in incidence of infections is significant (p <.01), as is the difference in incidence of pneumonia (20% vs. 3.8%, respectively [p <.01]). Organisms causing pneumonia were often the same organisms isolated from the nares on admission.

CONCLUSIONS

Nasal colonization with S. aureus at the time of severe head injury increases the risk of S. aureus pneumonia during hospitalization. Prophylactic measures against S. aureus pneumonia may help reduce the length and cost of hospitalization.

Reduction of Staphylococcus aureus nasal carriage and infection in dialysis patients

Numerous studies conducted in different countries and in different populations of patients on dialysis have consistently documented that a large proportion of such patients carry Staphylococcus aureus in their nares and that the risk of them becoming infected with their own strains is quite high. Furthermore, S. aureus infections can cause considerable morbidity and mortality in these patients. Thus, decolonization of the nares may prevent S. aureus infections and the attendant complications. The published data that support the use of rifampicin, intranasal mupirocin and povidone-iodine to prevent S. aureus infections in patients on dialysis are reviewed in detail.

Staphylococcus aureus nasal colonization in HIV-seropositive and HIV-seronegative drug users

Nasal colonization plays an important role in the pathogenesis of Staphylococcus aureus infections. To identify characteristics associated with colonization, we studied a cross-section of a well-described cohort of HIV-seropositive and -seronegative active and former drug users considered at risk for staphylococcal infections. Sixty percent of the 217 subjects were Hispanic, 36% were women, 25% actively used injection drugs, 23% actively used inhalational drugs, 23% received antibiotics, and 35% were HIV-seropositive. Forty-one percent of subjects had positive nasal cultures for S. aureus. The antibiotic susceptibility patterns were similar to the local hospital's outpatient isolates and no dominant strain was identified by arbitrarily primed polymerase chain reaction (AB-PCR). Variables significantly and independently associated with colonization included antibiotic use (odds ratio [OR] = 0.37; confidence interval [CI] = 0.18-0.77), active inhalational drug use within the HIV-seropositive population (OR = 2.36; CI = 1.10-5.10) and female gender (OR = 1.97; CI = 1.09-3.57). Characteristics not independently associated included injection drug use, HIV status, and CD4 count. The association with active inhalational drug use, a novel finding, may reflect alterations in the integrity of the nasal mucosa. The lack of association between HIV infection and S. aureus colonization, which is contrary to most previous studies, could be explained by our rigorous control for confounding variables or by a limited statistical power due to the sample sizes.

Nasal carriage of Staphylococcus aureus: epidemiology, underlying mechanisms, and associated risks

Staphylococcus aureus has long been recognized as an important pathogen in human disease. Due to an increasing number of infections caused by methicillin-resistant S. aureus (MRSA) strains, therapy has become problematic. Therefore, prevention of staphylococcal infections has become more important. Carriage of S. aureus appears to play a key role in the epidemiology and pathogenesis of infection. The ecological niches of S. aureus are the anterior nares. In healthy subjects, over time, three patterns of carriage can be distinguished: about 20% of people are persistent carriers, 60% are intermittent carriers, and approximately 20% almost never carry S. aureus. The molecular basis of the carrier state remains to be elucidated. In patients who repeatedly puncture the skin (e.g., hemodialysis or continuous ambulatory peritoneal dialysis [CAPD] patients and intravenous drug addicts) and patients with human immunodeficiency virus (HIV) infection, increased carriage rates are found. Carriage has been identified as an important risk factor for infection in patients undergoing surgery, those on hemodialysis or CAPD, those with HIV infection and AIDS, those with intravascular devices, and those colonized with MRSA. Elimination of carriage has been found to reduce the infection rates in surgical patients and those on hemodialysis and CAPD. Elimination of carriage appears to be an attractive preventive strategy in patients at risk. Further studies are needed to optimize this strategy and to define the groups at risk.

Effect of rifampin on Staphylococcus aureus colonization in children on chronic peritoneal dialysis

The efficacy of rifampin in eliminating Staphylococcus aureus colonization was evaluated in a pediatric peritoneal dialysis population. Six children with documented nasal colonization were treated for 7 days with rifampin and cloxacillin. Although antimicrobial therapy eliminated nasal carriage in all patients, recolonization occurred in 66%. Exit site colonization proved difficult to eradicate with negative cultures documented in only 3 of 5 children after rifampin/cloxacillin therapy. Although S. aureus carriage is a risk factor for S. aureus infections, efforts to eradicate carriage with rifampin are hindered by rapid recolonization.

Effect of glucose in dialysis fluid on antibacterial defence in the peritoneal cavity

To study the effect of glucose concentration and dwell time of dialysis fluid on peritoneal antibacterial defence, an experimental infection with Staphylococcus aureus was induced in rats. For this purpose rats were inoculated intraperitoneally with Staphylococcus aureus at different intervals after the administration of various dialysis fluids. Twenty-four hours later the numbers of bacteria and cells in the peritoneal cavity were determined. The number of bacteria was correlated positively with the glucose concentration. Furthermore, an inverse correlation between dwell time and the number of bacteria was observed. Neither finding could be attributed to a glucose-dependent growth of the bacteria or disruption of the killing capacity of peritoneal cells in vitro. A glucose-dependent increase in the volume of the peritoneal fluid could partially explain the differences found in vivo. It is concluded that the glucose in dialysis fluid impairs antibacterial defence in the peritoneal cavity and that longer dwell times enhance this defence.

Variation and persistence of methicillin-resistant Staphylococcus aureus strains among individual patients over extended periods of time

To determine the strain variation and persistence among isolates of methicillin-resistant Staphylococcus aureus (MRSA) cultured from patients with colonization over extended time spans, pulsed-field gel electrophoresis was used to analyze the isolates from 47 patients for whom at least two mecA-positive isolates collected a minimum of six months apart were available. For 22 (47%) patients, the isolates represented multiple distinct strains of Staphylococcus aureus, while 20 (43%) patients had only a single strain detected; five (11%) patients had similar, genetically related isolates. MRSA were frequently associated with mucocutaneous abnormalities; 29 (62%) patients had focal cutaneous defects, and ten (21%) had chronic dermatitis. Multiple strains of MRSA were detected more frequently than single strains among patients in whom the initial focus of MRSA resolved clinically and another mucocutaneous defect subsequently developed compared to patients with clinically persistent foci (11/15 versus 9/23, respectively; p = 0.05, Fisher's exact test). Among the 21 patients in this series for whom isolates cultured within a two-month time span were available, there were seven (33%) patients with multiple strains of MRSA, including one patient with polyclonal bacteremia. In summary, patients with long-term MRSA colonization often have several different strains of MRSA, which typically change overtime in association with removal or resolution of a colonized focus and the recurrence of mucocutaneous defects.

Managing Staphylococcus aureus catheter infection in continuous ambulatory peritoneal dialysis patients

A case of Staphylococcus aureus catheter infection in a patient on peritoneal dialysis is presented and discussed by nephrologists, a social worker, a nurse specializing in the care of peritoneal dialysis patients, and the patient involved. The focus of the multidisciplinary case discussion concerns the management of S aureus catheter infections, including catheter removal, psychosocial issues and the patient's response to the need for catheter removal, the risk factors and prevention of S aureus catheter infections in peritoneal dialysis patients, and exit site care practices.

Association between Staphylococcus aureus nasopharyngeal colonization and septicemia in patients infected with the human immunodeficiency virus

In an attempt to identify risk factors for Staphylococcus aureus septicemia, 136 consecutive HIV-infected patients were investigated for the presence of nasopharyngeal colonization with Staphylococcus aureus and subsequent Staphylococcus aureus infection. Sixty of 136 (44.1%) HIV-infected patients had staphylococci which were detected in the nasopharynx on initial culture compared to 12 of 39 (30.8%) patients with chronic diseases and 11 of 47 (23.4%) healthy hospital staff. Another 12 HIV-infected subjects proved to be Staphylococcus aureus carriers on follow-up cultures. Patients with full-blown AIDS had a higher carriage rate compared to subjects who were only HIV-positive (p < 0.05), indicating that Staphylococcus aureus colonized patients were more severely ill. Eight patients with Staphylococcus aureus septicemia were observed, all of whom were carriers; no septicemia occurred in the non-colonized patients (p < 0.01). Colonized patients with neutropenia (< 1000/microliters) were significantly more likely to develop septicemia (p < 0.01). Nasopharyngeal colonization with Staphylococcus aureus and the presence of an indwelling catheter were established to be factors that help identify patients at risk of acquiring subsequent Staphylococcus aureus infection.

Carriage of methicillin-resistant Staphylococcus aureus by non-hospitalized subjects in Israel

The prevalence of methicillin-resistant Staphylococcus aureus (MRSA) in the anterior nares and axilla was studied in 920 non-hospitalized subjects: 350 drug addicts, 350 individuals presenting at a hospital emergency room for various reasons, and 220 hospital health care workers. S. aureus was isolated from 105 (11.4%) subjects, in six (6.3%) of whom the isolates were methicillin-resistant. The isolation rate of the organism and the prevalence of resistant strains in the different subgroups were, respectively: drug-addicts, n = 32 (9.1%), n = 2 (6.9%); emergency room patients, n = 36 (10.2%), n = 1 (3.2%); and hospital health care workers, n = 37 (16.8%), n = 3 (8.5%). Our findings suggest that MRSA remains uncommon in the community, while the prevalence of S. aureus carriage (including methicillin-resistant strains) in hospital personnel is quite similar in divergent geographical areas.

Application of restriction endonuclease analysis of chromosomal DNA in the study of Staphylococcus aureus colonization in continuous ambulatory peritoneal dialysis patients

The relationship between nasal and skin colonization with Staphylococcus aureus and subsequent infection in continuous ambulatory peritoneal dialysis (CAPD) patients in Brazil has been documented by restriction endonuclease analysis of plasmid DNA. However, S. aureus strains without detectable plasmids have been identified. Using restriction endonuclease analysis of chromosomal DNA hybridized with an rRNA gene probe, we document the diversity of S. aureus strains without detectable plasmids colonizing CAPD patients. Ten paired strains without detectable plasmids from five patients were studied by restriction endonuclease analysis of chromosomal DNA and by phage typing. Five different profiles were obtained by restriction endonuclease analysis of chromosomal DNA. Although four of the ten paired isolates were nontypeable by phage typing, all were discriminated by restriction endonuclease analysis of chromosomal DNA. These results demonstrate that restriction endonuclease analysis of chromosomal DNA is a useful epidemiologic tool and complements the restriction endonuclease analysis of plasmid DNA of S. aureus by providing a means of typing strains without detectable plasmids.