The flora of renal haemodialysis shunt sites

The role of nasal carriage in Staphylococcus aureus infections

Staphylococcus aureus is a frequent cause of infections in both the community and hospital. Worldwide, the increasing resistance of this pathogen to various antibiotics complicates treatment of S aureus infections. Effective measures to prevent S aureus infections are therefore urgently needed. It has been shown that nasal carriers of S aureus have an increased risk of acquiring an infection with this pathogen. The nose is the main ecological niche where S aureus resides in human beings, but the determinants of the carrier state are incompletely understood. Eradication of S aureus from nasal carriers prevents infection in specific patient categories-eg, haemodialysis and general surgery patients. However, recent randomised clinical trials in orthopaedic and non-surgical patients failed to show the efficacy of eliminating S aureus from the nose to prevent subsequent infection. Thus we must elucidate the mechanisms behind S aureus nasal carriage and infection to be able to develop new preventive strategies. We present an overview of the current knowledge of the determinants (both human and bacterial) and risks of S aureus nasal carriage. Studies on the population dynamics of S aureus are also summarised.

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.

Staphylococcus aureus carriage and infections among patients in four haemo- and peritoneal-dialysis centres in Denmark. The Danish Study Group of Peritonitis in Dialysis (DASPID)

A three-month prospective surveillance study was undertaken in four dialysis centres to establish the prevalence of Staphylococcus aureus carriage in a Danish population of patients on haemodialysis (HD) or on continuous ambulatory peritoneal dialysis (CAPD). General data such as sex, age, diagnosis, number of months in dialysis, hospital and ward were registered on a precoded form. Standardized nose and four skin swabs (axillae, groins, perineum) were performed on the first day of the survey. After one and two months, nose swabs were collected. Infections were registered and cultures were sent for phage-typing together with the S. aureus strains isolated from the swabs; 59.5% of HD patients and 51.2% of CAPD patients carried S. aureus. Permanent carriage was most frequent (P < 0.00009), primarily in the nose (44.0 and 34.9%, respectively in HD and CAPD). Skin carriage alone was rare (2.4 and 4.7%). Approximately one third (36.6 and 40.7%) of infections were caused by S. aureus. Although diabetics were not significantly more frequent carriers (60.5%) than non-diabetics (55.0%), the incidence of infection was much higher (26.3% vs. 10.3%, P = 0.004). In CAPD, peritonitis and tunnel/exit-site infections predominated (81.4%), often caused by S. aureus (34.8%). More than two thirds of the infections in HD patients were related to intravascular catheterization. The most serious infection was septicaemia, in all cases due to S. aureus. S aureus infections occurred significantly more frequently among carriers (P = 0.005), and more than half the patients were infected by the same or possibly the same strain as they carried in the nose or on skin. Different regimens for the elimination of S. aureus carriage in dialysis patients are discussed. A policy for risk assessment of patients should be developed, and the elimination of S. aureus carriage before dialysis should be encouraged. Controlled trials comparing the cost-effectiveness of recommended regimens to eliminate carriage in HD/CAPD patients are needed. Nose swabs are reliable indicators of carriage in dialysis patients.

The efficacy of mupirocin ointment and chlorhexidine body scrubs in the eradication of nasal carriage of Staphylococcus aureus among patients undergoing long-term hemodialysis

BACKGROUND

Patients undergoing long-term hemodialysis have a high prevalence of Staphylococcus aureus nasal carriage, which may lead to serious infections. Mupirocin ointment has been used intranasally to eradicate S. aureus carriage in health human volunteers and health care workers. Chlorhexidine, an antiseptic with excellent antistaphylococcal activity, is widely used for handwashing and skin cleansing.

METHODS

Anterior nares cultures were obtained from patients older than 18 years who were undergoing long-term hemodialysis. Patients with S. aureus nasal carriage were enrolled in the study. Axillae and groins were cultured. Patients were given mupirocin ointment intranasally twice per day for 7 days and chlorhexidine body scrubs daily for the first 3 days. Follow-up cultures were obtained from anterior nares, axillae, and groins at 1 day, and 1, 4, 8 and 12 weeks after treatment.

RESULTS

One day after completion of treatment nasal carriage was eradicated in 83% of patients (15/18). After 12 weeks, 69% of patients (11/16) were free of nasal carriage.

CONCLUSIONS

Success rates of eradication were excellent compared with those in other published reports. This simple and effective regimen had no major side effects.

Staphylococcus aureus nasal carriage and infection in patients on continuous ambulatory peritoneal dialysis

We studied 140 consecutive patients beginning continuous ambulatory peritoneal dialysis (CAPD) at one of seven hospitals to assess the relation of the nasal carriage of Staphylococcus aureus to subsequent catheter-exit-site infection or peritonitis. Shortly before the implantation of the catheters, the patients' anterior nares were cultured for the presence of S. aureus. Antibiotics were not prescribed for the S. aureus carriers, but all the patients were monitored for signs of catheter infection (median follow-up, 10.4 months). At the initiation of CAPD, 63 patients (45 percent) carried S. aureus in the nares. Nasal carriage was more frequent among the 30 patients with diabetes (77 percent) than among the 110 without the disease (36 percent). The carriers of S. aureus had a significantly higher rate of exit-site infection than the noncarriers (0.40 vs. 0.10 episode per year; P = 0.012). Of these episodes, 24 of 34 were caused by S. aureus. The rates of peritonitis of all bacterial types did not differ significantly between the groups, but all 11 episodes of peritonitis caused by S. aureus occurred among the carriers. In 85 percent of the patients with clinical S. aureus infections, the strain from the nares and the strain causing the infection were similar in phage type and antibiotic profile. We conclude that in patients beginning ambulatory peritoneal dialysis, the nasal carriage of S. aureus is associated with an increased risk of catheter-exit-site infection and that the performance of nasal cultures before the implantation of the catheter can identify patients at high risk of subsequent morbidity.

Staphylococcus aureus nasal carriage and infection in patients on hemodialysis. Efficacy of antibiotic prophylaxis

We conducted a five-year prospective controlled study of prophylaxis of Staphylococcus aureus nasal carriage and infection among patients in a hemodialysis unit. Carriers tended to have chronic colonization with a single phage type. S. aureus infections occurred significantly more frequently in carriers than in noncarriers and, in 93 percent of the infected carriers, were caused by the same phage type as that carried in the nares. Neither intravenous vancomycin nor topical bacitracin was found to be efficacious in eradicating nasal carriage. However, oral rifampin given for five days decreased S. aureus carriage over a one-month follow-up period, but within three months colonization of the nares recurred in most carriers, often with an S. aureus of the original phage type. Carriers were then randomly assigned to receive either rifampin or no prophylaxis. Rifampin was readministered at three-month intervals if culture of the anterior nares yielded S. aureus. Infections with S. aureus occurred significantly more frequently in carriers given no prophylaxis than in those given a full course of rifampin. S. aureus resistant to rifampin was isolated from the anterior nares of four patients, but these isolates were not implicated in any infections. The incidence of infection at the dialysis access site, skin, and soft tissue of patients on hemodialysis can be decreased by interventions directed at nasal carriage of S. aureus.

Comparison of 4% chlorhexidine gluconate in a detergent base (Hibiclens) and povidone-iodine (Betadine) for the skin preparation of hemodialysis patients and personnel

The abnormal cutaneous flora of hemodialysis (HD) patients might contribute to their frequent septic complications. We compared the effects of 13 wk of Betadine and 13 wk of Hibiclens on the skin flora of HD patients and personnel. Skin cultures were obtained weekly immediately prior to the disinfection, preceding each triweekly HD treatment, and monthly, at 2 and 4 hr postdisinfection. Total bacterial counts from predisinfection cultures were not significantly altered over either 13-wk treatment period. Hibiclens reduced total bacterial counts (p less than 0.01) and eradicated cutaneous staphylococci (p = 0.032) at both 2 and 4 hr postdisinfection significantly more than did Betadine. No reduction of staphylococcal sensitivity to either germicidal agent could be demonstrated. Neither agent was associated with severe adverse reactions and Hibiclens could not be detected in the blood. Hibiclens appears to offer short-term advantages over Betadine in the HD setting because of significantly longer duration of antibacterial activity.

Nasal and cutaneous flora among hemodialysis patients and personnel: quantitative and qualitative characterization and patterns of Staphylococcal carriage

Staphylococcal sepsis is a leading cause of morbidity and mortality among chronic hemodialysis (HD) patients. We studied nasal and cutaneous flora of HD patients and personnel and their patterns of staphylococcal carriage. HD patients had significantly increased cutaneous total bacterial colony counts (p less than 0.01) as well as both nasal (p less than 0.0001) and cutaneous (p less than 0.0001) carriage of Staphylococcus aureus compared to personnel. Cutaneous staphylococcal carriage could be significantly correlated with nasal carriage (p less than 0.01). Cutaneous streptococcal species and gram-negative bacilli were not different between patients and personnel. Staphylococcal phage typing of nasal isolates from staphylococcal carriers revealed a mean of 90% of isolates from each subject belonging to a predominant phage type. Predominant nasal staphylococcal phage types corresponded with respective predominant cutaneous phage types in 93% of HD patients carriers. These studies substantiate autoinoculation of S. aureus from the nasal vestibule to the skin overlying the vascular access site.

Staphylococcal septicaemia, endocarditis, and osteomyelitis in dialysis and renal transplant patients

Septicaemia is a common and potentially lethal hazard of haemodialysis and renal transplantation; it is usually caused by Staphylococcus pyogenes. In 6 patients with S. pyogenes septicaemia, fatal endocarditis and spinal osteomyelitis have each occurred once, and 3 patients have had recurrent episodes of septicaemia. The management of septicaemia in these patients must include a search for metastatic infection, and prolonged therapy with 2 antistaphylococcal agents is necessary to ensure eradication of infection. Access site infection in dialysis patients must be treated vigorously, and recognized as potentially hazardous by patients. The risk of sepsis in dialysis and transplant patients cannot be excluded, but devastating consequences may be avoided by simple measures.