Rate of Staphylococcus aureus nasal carriage in immunocompromised patients receiving haemodialysis treatment

Methicillin-resistant Staphylococcus aureus nasal carriage among patients on haemodialysis with newly inserted central venous catheters

BACKGROUND

Although methicillin-resistant Staphylococcus aureus (MRSA) nasal colonization is common among end-stage kidney disease patients undergoing haemodialysis, few studies were focused on MRSA nasal carriers among haemodialysis patients with central venous catheters (CVCs). The aim of this study is to evaluate the risk factors, various clinical outcomes and effect of decolonization for MRSA nasal colonization among patients on haemodialysis via CVCs.

METHODS

This was a single-centre non-concurrent cohort study of 676 patients who had new haemodialysis CVCs inserted. They were all screened for MRSA colonization via nasal swabs and were categorized into two groups: MRSA carriers and MRSA noncarriers. Potential risk factors and clinical outcomes were analysed in both groups. All MRSA carriers were given decolonization therapy and the effect of decolonization on subsequent MRSA infection was also performed.

RESULTS

Eighty-two patients (12.1%) were MRSA carriers. Multivariate analysis showed that MRSA carrier (OR 5.44; 95% CI 3.02-9.79), long-term care facility resident (OR 4.08; 95% CI 2.07-8.05), history of Staphylococcus aureus infection (OR 3.20; 95% CI 1.42-7.20) and CVC in situ > 21 days (OR 2.12; 95% CI 1.15-3.93) were independent risk factors for MRSA infection. There was no significant difference in all-cause mortality between MRSA carriers and noncarriers. The MRSA infection rates were similar between MRSA carriers with successful decolonization and those who had failed/incomplete decolonization in our subgroup analysis.

CONCLUSION

MRSA nasal colonization is an important cause of MRSA infection among haemodialysis patients with CVCs. However, decolonization therapy may not be effective in reducing MRSA infection.

Intermittent nasal carriage with Staphylococcus aureus within a menstrual cycle: Results from a prospective cohort of healthy carriers

Female sex hormones have been related to nasal Staphylococcus aureus carriage in healthy individuals; however, whether nasal staphylococcal carriage varies by menstrual cycle phase remains unknown.We sampled anterior nares of female healthcare workers twice per week for 6 consecutive menstrual cycles. We used mixed-effects Poisson regression models to determine whether intermittent carriage was associated with cycle phases in a given individual. We also performed recurrent event survival analysis to identify host factors linked to incident carriage status.Overall, we collected 754 nasal swabs over 89 consecutive person-cycles from 14 intermittent carriers. In 84 ovulation-defined menstrual cycles (715 swabs), the period prevalence of staphylococcal carriage was 58.7%, 63.1%, and 64.9% in the follicular, periovulatory, and luteal phases, respectively; these differences were not statistically significant after multivariable adjustment and correction for within-person correlation (adjusted relative risk [RR]-periovulatory 0.92, P: 0.30; luteal 1.00, P: 0.98).Using survival analysis, we identified several host factors that were associated with incident loss, gain of colonization, or both. For example, as compared to women aged 20 to 30 years, those aged 30 to 40 years were less likely to losing carriage (hazard ratio [HR]: 0.26, 95% confidence interval [CI]: 0.09, 0.80) but were as likely to regaining carriage (HR: 0.53, 95% CI: 0.21, 1.34). In comparison, being underweight (body mass index [BMI] <18.5) was significantly associated with a higher risk for regaining (HR: 1.95, 95% CI: 1.34, 1.51) and losing (HR: 1.57, 95% CI: 1.16, 2.12) colonization, indicating the alternating tendency for status changes. Personal hygiene behaviors, such as nostril cleansing habit and methods, differentially affected carriers' risk for losing or regaining staphylococcal colonization.Using an intensive sampling scheme, we found that nasal staphylococcal carriage could vary substantially over time in healthy carriers. Yet, such dynamic intraperson changes in carriage status did not depend on menstrual cycle phases but were associated with host age, BMI, and personal hygiene behavior.

Body site Staphylococcus aureus colonization among maintenance hemodialysis patients

BACKGROUND

Patients on maintenance hemodialysis therapy are at high risk for health care-associated infections. Staphylococcus aureus is a common cause of health care-associated infections among maintenance hemodialysis patients. It is established that S. aureus colonization is associated with an increased risk for subsequent infection in this population. There is an increasing number of reports that extranasal S. aureus colonization is more common than previously believed and in certain body sites even more common than nasal colonization. There are few data describing extranasal colonization among maintenance hemodialysis patients.

METHODS

We surveyed 100 patients at 3 body sites (anterior nares, oropharynx, and inguinal region) for S. aureus colonization. Participants were also administered a standardized survey to assess risk factors for S. aureus colonization.

RESULTS

We found that 42% (95% CI 32-52) of patients were S. aureus colonized in >1 body site. Extranasal colonization was found among 32% (95% CI 23-41). There were trends suggestive of an association between S. aureus colonization and younger age (OR 0.97, 95% CI 0.94-1.001, p = 0.06) and not having been hospitalized in the previous 12 months (OR 0.44, 95% CI 0.19-1.06, p = 0.14).

CONCLUSION

Extranasal S. aureus colonization is common among maintenance hemodialysis patients with a prevalence of approximately one third. Future S. aureus decolonization efforts may need to consider not just nasal decolonization but also decolonization of the skin and oropharynx.

Epidemiology and prevention of Staphylococcus aureus nasal carriage in hemodialyzed patients

Nasal carriage of Staphylococcus aureus may be responsible for some serious infections among hemodialyzed patients. Its pathogenic potential and commensal nature allows for an easy transmission both in and out of hospital environment.

PURPOSE

This study was to assess the prevalence of S. aureus nasal carriage, to determine its frequency and nature in hemodialyzed patients of the Rabat Ibn Sina University hospital, in Morocco.

PATIENT AND METHOD

The study began in March 2008 according to the following protocol: screening of nasal carriage with five samplings, performed once a month three times, then once a month two times again after an interruption period of three months. Screening was performed weekly during the first month in hemodialyzed patients treated with mupirocin (Bactroban(®) 2%), and then monthly, to monitor the kinetics of S. aureus eradication.

RESULTS

The study included 54 hemodialyzed patients with a mean 44.16±14 years of age, sex ratio of 0.54, and mean hemodialysis duration of 118.7±67 months. Permanent and intermittent S. aureus carriage was found in respectively 18.52% and 25.92% of patients. Eighty-one strains of S. aureus were identified, 14.81% of which were methicillin resistant. Eradication was sustained beyond 20 months in patients treated with mupirocin.

CONCLUSION

This investigation allowed us to identify hemodialyzed patients at risk, so as to implement the rules of individual and collective hygiene, and to extend mupirocin antibiotic prophylaxis in our hemodialysis unit.

Novel Technology to study co-evolution of humans and Staphylococcus aureus: consequences for interpreting the biology of colonisation and infection

Human nasal carriage of Staphylococcus aureus is a textbook example of an apparently neutral interaction between humans and a bacterial species that can still lead to (severe) opportunistic infections. The co-evolutionary aspects of this interaction are slowly surfacing, facilitated by the emergence of a diversity of diagnostic, epidemiological and molecular research tools. Basic microbiology has helped define persistent vs. non-carriage and the genotype of both host and guest has been explored in search of genetic markers for bacterial persistence. This chapter summarises the current state of affairs relating to artificial human colonisation studies with S. aureus, large-scale human cohort studies and innovative assessment of the humoral immune status of (non-)nasal carriers. These experimental approaches have recently assisted in identifying bacterial and human determinants and risk factors for staphylococcal carriage. Further refinement of the model by describing the interactions between S. aureus and its human host in molecular detail is important since it may pinpoint novel anti-infectious strategies.

Nasal carriage of methicillin-resistant Staphylococcus aureus is associated with higher all-cause mortality in hemodialysis patients

BACKGROUND AND OBJECTIVES

Methicillin-resistant Staphylococcus aureus (MRSA) nasal carriage is a recognized risk factor for subsequent endogenous infections. However, the association between MRSA carriage and patient survival in hemodialysis patients has not been established.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

In March 2007, this prospective cohort study enrolled 306 outpatients under maintenance hemodialysis from a hospital-based dialysis center in Taiwan. They received two consecutive weekly nasal swab cultures at the beginning of the study. Patients having at least one positive culture of MRSA were defined as MRSA carriers. Subjects were followed up until December 31, 2008. The primary outcome was all-cause mortality. Main secondary outcomes were infection-related mortality and morbidity.

RESULTS

We identified 29 MRSA carriers (9.48%) at study entry. After a median of 613 days of follow-up, Kaplan-Meier analysis showed significant survival differences between MRSA carriers and noncarriers (log-rank P = 0.02). Compared with noncarriers, MRSA carriers had a 2.46-fold increased risk of dying from any cause, after adjusting for covariates at the start of follow-up. The adjusted hazard ratios of infection-related mortality and occurrence of subsequent S. aureus infection in carriers were 4.99 and 4.31, respectively.

CONCLUSIONS

A major limitation is the relatively small sample size of MRSA carriers. Nevertheless, we demonstrated that there may be an association between MRSA nasal carriage and poor clinical outcomes in an outpatient hemodialysis population. This underscores the need for routine surveillance of MRSA nasal carriage and should alert the physicians of a group at high risk of morbidity and mortality.

Bacterial superantigen TSST-1 attenuates suppressive efficacy of glucocorticoids and calcineurin inhibitors against blastogenesis of peripheral blood mononuclear cells from patients with chronic renal failure on hemodialysis treatment

BACKGROUND

Many cases of patients with chronic renal failure (CRF) on hemodialysis are known to be infected with Staphylococcus aureus (S. aureus) from the sites of blood vessel puncture for hemodialysis and the custody of the vascular access catheter. S. aureus produces superantigens, such as toxic shock syndrome toxin-1 (TSST-1), which may influence the sensitivity of peripheral-blood mononuclear cells (PBMCs) to immunosuppressive drugs after they are received postrenal transplantation.

METHODS

We examined the drug-sensitivities of PBMCs stimulated with TSST-1 in 18 CRF patients on hemodialysis. PBMCs were isolated from venous blood before hemodialysis, and were cultured in the presence of concanavalin A (ConA) or TSST-1 and serial concentrations of the drugs. In vitro drug concentrations giving 50% inhibition (IC(50)) of PBMC blastogenesis were calculated. INF-gamma and IL-4 in supernatants of cultured PBMCs were measured with ELISA.

RESULTS

The median (range) IC(50) values (ng/ml) for four drugs; tacrolimus, cyclosporine, methylprednisolone, and prednisolone, evaluated in ConA-stimulated PBMCs of CRF patients were 0.04 ng/ml (0.03-0.21), 3.0 (0.1-15.1), 3.0 (1-104), and 16.2 (5.9-35.4), respectively. The values for the four drugs evaluated in TSST-1-stimulated PBMCs were 0.22 (0.08-0.36), 18.9 (5.1-38.2), 328.3 (1.9-1000), and 150.9 (94.7-880), respectively, which were significantly higher than those evaluated in the ConA-stimulated PBMCs (p=0.003-0.023). Amounts of INF-gamma and IL-4 produced from cells were not significantly different between the ConA-or TSST-1-stimulated PBMCs in the presence or absence of immunosuppressive drugs.

CONCLUSION

These observations raise the possibility that TSST-1 induced by S. aureus infection attenuates the clinical efficacy of glucocorticoids and calcineurin inhibitors in CRF patients after renal transplantation. Furthermore, INF-gamma and IL-4 related pathways appear not to play major roles in the TSST-1-induced attenuation of the drug sensitivities.

The investigation of Staphylococcus aureus and coagulase-negative staphylococci nasal carriage among patients undergoing haemodialysis

The frequency of nasal staphylococcal colonization among haemodialysed patients was investigated. The swabs were collected in 1998 and 2004 from 28 and 43 patients, respectively. Staphylococcus aureus colonization rates were 57.1% and 27.9% in 1998 and 2004, respectively. Twenty-six coagulase-negative staphylococci (CNS) isolates were cultured: S. epidermidis (21), S. lugdunensis (2), single S. haemolyticus, S. warneri, and S. capitits isolates. One S. aureus and 10 CNS isolates were methicillin resistant. The methicillin-resistant S. aureus (MRSA) was resistant to beta-lactams, tetracycline, and harbored the pvl gene encoding the Panton-Valentine leukocidin. The decrease in S. aureus colonization at 6-year interval was observed. The presence of the pvl gene and a favorable antibiotic susceptibility pattern of the MRSA suggest that the isolate was a member of community-acquired MRSA (CA-MRSA). Concluding, screening of haemodialysed patients for staphylococcal colonization accompanied by characterization of cultured isolates is important to understand its epidemiology and to develop infection prevention measures and treatment strategies.

Nasal carriage of Staphylococcus aureus on admission to intensive care: incidence and prognostic significance

We retrospectively studied the prevalence of the nasal carriage of methicillin-sensitive Staphylococcus aureus (MSSA) and methicillin-resistant Staphylococcus aureus (MRSA) on admission to a medical surgical intensive care unit (ICU). We also compared the intensive care survival of MSSA carriers with non-carriers. Records of 678 patients admitted over a 24-month period were retrospectively reviewed. Nasal swabs were taken from 565 patients on admission to the ICU. MSSA was isolated from the anterior nares of 126 (22%) patients, MRSA was isolated in 16 (3%) patients and 423 (75%) patients had no nasal carriage identified. MSSA carriers were more likely to have been admitted to the ICU after less than 24 h hospital stay (28% non-carriers, 44% MSSA carriers) and were significantly younger (mean age of 50 years) than non-carriers (mean age 55 years). The median survival (with confidence intervals (CI)) was 29 days (CI 14-44) in non-carriers, 16 days (CI 10-22) in MSSA carriers and 6 days (CI 4-8) for the MRSA carriers. This difference was significant when MSSA carriers were compared with non-carriers ( p=0.003). The ICU mortality was also significantly higher ( p=0.004) in MSSA carriers (88 of the 423 (21%) non-carriers and 40 of 126 (32%) MSSA carriers died prior to ICU discharge).