Duration of Colonization with Methicillin-ResistantStaphylococcus aureusAmong Patients in the Intensive Care Unit: Implications for Intervention

Stopping Hospital Infections With Environmental Services (SHINE): A Cluster-randomized Trial of Intensive Monitoring Methods for Terminal Room Cleaning on Rates of Multidrug-resistant Organisms in the Intensive Care Unit

BACKGROUND

Multidrug-resistant organisms (MDROs) frequently contaminate hospital environments. We performed a multicenter, cluster-randomized, crossover trial of 2 methods for monitoring of terminal cleaning effectiveness.

METHODS

Six intensive care units (ICUs) at 3 medical centers received both interventions sequentially, in randomized order. Ten surfaces were surveyed each in 5 rooms weekly, after terminal cleaning, with adenosine triphosphate (ATP) monitoring or an ultraviolet fluorescent marker (UV/F). Results were delivered to environmental services staff in real time with failing surfaces recleaned. We measured monthly rates of MDRO infection or colonization, including methicillin-resistant Staphylococcus aureus, Clostridioides difficile, vancomycin-resistant Enterococcus, and MDR gram-negative bacilli (MDR-GNB) during a 12-month baseline period and sequential 6-month intervention periods, separated by a 2-month washout. Primary analysis compared only the randomized intervention periods, whereas secondary analysis included the baseline.

RESULTS

The ATP method was associated with a reduction in incidence rate of MDRO infection or colonization compared with the UV/F period (incidence rate ratio [IRR] 0.876; 95% confidence interval [CI], 0.807-0.951; P = .002). Including the baseline period, the ATP method was associated with reduced infection with MDROs (IRR 0.924; 95% CI, 0.855-0.998; P = .04), and MDR-GNB infection or colonization (IRR 0.856; 95% CI, 0.825-0.887; P < .001). The UV/F intervention was not associated with a statistically significant impact on these outcomes. Room turnaround time increased by a median of 1 minute with the ATP intervention and 4.5 minutes with UV/F compared with baseline.

CONCLUSIONS

Intensive monitoring of ICU terminal room cleaning with an ATP modality is associated with a reduction of MDRO infection and colonization.

Transmission Dynamics of Clostridioides difficile in 2 High-Acuity Hospital Units

BACKGROUND

The key epidemiological drivers of Clostridioides difficile transmission are not well understood. We estimated epidemiological parameters to characterize variation in C. difficile transmission, while accounting for the imperfect nature of surveillance tests.

METHODS

We conducted a retrospective analysis of C. difficile surveillance tests for patients admitted to a bone marrow transplant (BMT) unit or a solid tumor unit (STU) in a 565-bed tertiary hospital. We constructed a transmission model for estimating key parameters, including admission prevalence, transmission rate, and duration of colonization to understand the potential variation in C. difficile dynamics between these 2 units.

RESULTS

A combined 2425 patients had 5491 admissions into 1 of the 2 units. A total of 3559 surveillance tests were collected from 1394 patients, with 11% of the surveillance tests being positive for C. difficile. We estimate that the transmission rate in the BMT unit was nearly 3-fold higher at 0.29 acquisitions per percentage colonized per 1000 days, compared to our estimate in the STU (0.10). Our model suggests that 20% of individuals admitted into either the STU or BMT unit were colonized with C. difficile at the time of admission. In contrast, the percentage of surveillance tests that were positive within 1 day of admission to either unit for C. difficile was 13.4%, with 15.4% in the STU and 11.6% in the BMT unit.

CONCLUSIONS

Although prevalence was similar between the units, there were important differences in the rates of transmission and clearance. Influential factors may include antimicrobial exposure or other patient-care factors.

Potent and Non-Cytotoxic Antibacterial Compounds Against Methicillin-Resistant Staphylococcus aureus Isolated from Psiloxylon mauritianum, A Medicinal Plant from Reunion Island

With the occurrence of antibiotic-resistant Staphylococcus aureus strains, identification of new anti-staphylococcal drugs has become a necessity. It has long been demonstrated that plants are a large and diverse source of antibacterial compounds. Psiloxylon mauritianum, an endemic medicinal plant from Reunion Island, was chemically investigated for its reported biological activity against S. aureus. Aspidin VB, a phloroglucinol derivative never before described, together with Aspidin BB, were first isolated from the ethyl acetate extract of P. mauritianum leaves. Their structures were elucidated from spectroscopic data. Aspidin VB exhibited strong antibacterial activity against standard and methicillin-resistant S. aureus strains, with a minimal inhibition concentration (MIC) of 0.25 μg/mL, and no cytotoxicity was observed at 10-5 M in MRC5 cells. Due to its biological activities, Aspidin VB appears to be a good natural lead in the fight against S. aureus.

Methicillin-resistant Staphylococcus aureus nasal colonization and infection in an intensive care unit of a university hospital in China

Objective This study was performed to determine the prevalence and risk factors associated with nasal methicillin-resistant Staphylococcus aureus (MRSA) colonization upon intensive care unit (ICU) admission and during the ICU stay in mainland China. Methods A prospective observational study was performed in a 50-bed general ICU of a 4300-bed teaching hospital in China from 2011 to 2013. Nasal swabs for MRSA detection were obtained upon ICU admission and at discharge for patients having stayed in the ICU for longer than 3 days. Results In total, 115 patients (4.1%; 95% confidence interval [CI], 3.4-4.9) were already colonized with MRSA on ICU admission, and another 185 patients (10.7%; 95% CI, 9.3-12.2) acquired MRSA during their ICU stay. Development of an MRSA infection was significantly more likely in patients with than without MRSA colonization on ICU admission (odds ratio [OR], 2.8; 95% CI, 1.1-7.3). Patients who acquired MRSA had significantly prolonged lengths of stay in the ICU (23.3 days) and higher hospital bills (135,171 RMB; about 19,590 USD) than those who tested negative for MRSA. Conclusion The MRSA colonization rate among ICU patients in mainland China is high. Patients with MRSA-positive nasal swabs are more likely to develop MRSA infections.

A Dynamic Transmission Model to Evaluate the Effectiveness of Infection Control Strategies

BACKGROUND

The advancement of knowledge about control of antibiotic resistance depends on the rigorous evaluation of alternative intervention strategies. The STAR*ICU trial examined the effects of active surveillance and expanded barrier precautions on acquisition of methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococcus (VRE) in intensive care units. We report a reanalyses of the STAR*ICU trial using a Bayesian transmission modeling framework.

METHODS

The data included admission and discharge times and surveillance test times and results. Markov chain Monte Carlo stochastic integration was used to estimate the transmission rate, importation, false negativity, and clearance separately for MRSA and VRE. The primary outcome was the intervention effect, which when less than (or greater than) zero, indicated a decreased (or increased) transmission rate attributable to the intervention.

RESULTS

The transmission rate increased in both arms from pre- to postintervention (by 20% and 26% for MRSA and VRE). The estimated intervention effect was 0.00 (95% confidence interval [CI], -0.57 to 0.56) for MRSA and 0.05 (95% CI, -0.39 to 0.48) for VRE. Compared with MRSA, VRE had a higher transmission rate (preintervention, 0.0069 vs 0.0039; postintervention, 0.0087 vs 0.0046), higher importation probability (0.22 vs 0.17), and a lower clearance rate per colonized patient-day (0.016 vs 0.035).

CONCLUSIONS

Transmission rates in the 2 treatment arms were statistically indistinguishable from the pre- to postintervention phase, consistent with the original analysis of the STAR*ICU trial. Our statistical framework was able to disentangle transmission from importation and account for imperfect testing. Epidemiological differences between VRE and MRSA were revealed.

Cost-effectiveness of strategies to prevent methicillin-resistant Staphylococcus aureus transmission and infection in an intensive care unit

OBJECTIVE To create a national policy model to evaluate the projected cost-effectiveness of multiple hospital-based strategies to prevent methicillin-resistant Staphylococcus aureus (MRSA) transmission and infection. DESIGN Cost-effectiveness analysis using a Markov microsimulation model that simulates the natural history of MRSA acquisition and infection. PATIENTS AND SETTING Hypothetical cohort of 10,000 adult patients admitted to a US intensive care unit. METHODS We compared 7 strategies to standard precautions using a hospital perspective: (1) active surveillance cultures; (2) active surveillance cultures plus selective decolonization; (3) universal contact precautions (UCP); (4) universal chlorhexidine gluconate baths; (5) universal decolonization; (6) UCP + chlorhexidine gluconate baths; and (7) UCP+decolonization. For each strategy, both efficacy and compliance were considered. Outcomes of interest were: (1) MRSA colonization averted; (2) MRSA infection averted; (3) incremental cost per colonization averted; (4) incremental cost per infection averted. RESULTS A total of 1989 cases of colonization and 544 MRSA invasive infections occurred under standard precautions per 10,000 patients. Universal decolonization was the least expensive strategy and was more effective compared with all strategies except UCP+decolonization and UCP+chlorhexidine gluconate. UCP+decolonization was more effective than universal decolonization but would cost $2469 per colonization averted and $9007 per infection averted. If MRSA colonization prevalence decreases from 12% to 5%, active surveillance cultures plus selective decolonization becomes the least expensive strategy. CONCLUSIONS Universal decolonization is cost-saving, preventing 44% of cases of MRSA colonization and 45% of cases of MRSA infection. Our model provides useful guidance for decision makers choosing between multiple available hospital-based strategies to prevent MRSA transmission.

Legislative Mandates for Use of Active Surveillance Cultures to Screen for Methicillin-ResistantStaphylococcus aureusand Vancomycin-Resistant Enterococci: Position Statement From the Joint SHEA and APIC Task Force

Legislation aimed at controlling antimicrobial-resistant pathogens through the use of active surveillance cultures to screen hospitalized patients has been introduced in at least 2 US states. In response to the proposed legislation, the Society for Healthcare Epidemiology of America (SHEA) and the Association of Professionals in Infection Control and Epidemiology (APIC) have developed this joint position statement. Both organizations are dedicated to combating healthcare-associated infections with a wide array of methods, including the use of active surveillance cultures in appropriate circumstances. This position statement reviews the proposed legislation and the rationale for use of active surveillance cultures, examines the scientific evidence supporting the use of this strategy, and discusses a number of unresolved issues surrounding legislation mandating use of active surveillance cultures. The following 5 consensus points are offered. (1) Although reducing the burden of antimicrobial-resistant pathogens, including methicillin-resistantStaphylococcus aureus(MRSA) and vancomycin-resistant enterococci (VRE), is of preeminent importance, APIC and SHEA do not support legislation to mandate use of active surveillance cultures to screen for MRSA, VRE, or other antimicrobial-resistant pathogens. (2) SHEA and APIC support the continued development, validation, and application of efficacious and cost-effective strategies for the prevention of infections caused by MRSA, VRE, and other antimicrobial-resistant and antimicrobial-susceptible pathogens. (3) APIC and SHEA welcome efforts by healthcare consumers, together with private, local, state, and federal policy makers, to focus attention on and formulate solutions for the growing problem of antimicrobial resistance and healthcare-associated infections. (4) SHEA and APIC support ongoing additional research to determine and optimize the appropriateness, utility, feasibility, and cost-effectiveness of using active surveillance cultures to screen both lower-risk and high-risk populations. (5) APIC and SHEA support stronger collaboration between state and local public health authorities and institutional infection prevention and control experts.

Active Surveillance to Determine the Impact of Methicillin-Resistant Staphylococcus aureus Colonization on Patients in Intensive Care Units of a Veterans Affairs Medical Center

Objective.

The impact of methicillin-resistant Staphylococcus aureus (MRSA) colonization on mortality has not been well characterized. We sought to describe the impact of MRSA colonization on patients admitted to intensive care units (ICUs) in the Birmingham Veterans Affairs Medical Center (VAMC).

Methods.

We conducted a retrospective cohort study of ICU patients at the Birmingham VAMC during 2005 to evaluate the predictors of MRSA colonization and determine its effect on clinical outcomes. Surveillance cultures for MRSA were performed on admission to the ICU and weekly thereafter. Clinical findings, the incidence of MRSA infection, and mortality within 3 months after ICU admission were recorded. Predictors of mortality and S. aureus colonization were determined using multivariable models.

Results.

S. aureus colonization was present in 97 (23.3%) of 416 patients screened, of whom 67 (16.1%) were colonized with methicillin-susceptible S. aureus (MSSA) and 30 (7.2%) with MRSA. All-cause mortality at 3 months among MRSA-colonized patients was significantly greater than that among MSSA-colonized patients (46.7% vs 19.4%; P = .009). MRSA colonization was an independent predictor of death (adjusted odds ratio [OR] ,3.7 [95% confidence interval {CI}, 1.5–8.9]; P = .003) and onset of MRSA infection after hospital discharge (adjusted OR, 7.6 [95% CI, 2.48–23.2]; P < .001). Risk factors for MRSA colonization included recent antibiotic use (adjusted OR, 4.8 [95% CI, 1.9–12.2]; P = .001) and dialysis (adjusted OR, 18.9 [95% CI, 2.1–167.8]; P = .008).

Conclusions.

Among ICU patients, MRSA colonization is associated with subsequent MRSA infection and an all-cause mortality that is greater than that for MSSA colonization. Active surveillance for MRSA colonization may identify individuals at risk for these adverse outcomes. Prospective studies of outcomes in MRSA-colonized patients may better define the role of programs for active MRSA surveillance.

Screening for Carriage of Methicillin-Resistant Staphylococcus aureus Shortly After Exposure May Lead to False-Negative Results

We evaluated a double screening strategy for carriage of methicillin-resistant Staphylococcus aureus (MRSA) in patients exposed to a newly detected MRSA carrier. If the first screening of the exposed patient yielded negative results, screening was repeated 4 days later. This strategy detected 12 (28%) of the 43 new MRSA carriers identified during the study period. The results suggest that there is an incubation period before MRSA carriage is detectable.

The prevalence and significance of methicillin-resistant Staphylococcus aureus colonization at admission in the general ICU Setting: a meta-analysis of published studies

OBJECTIVE

To estimate the prevalence and significance of nasal methicillin-resistant Staphylococcus aureus colonization in the ICU and its predictive value for development of methicillin-resistant S. aureus infection.

DATA SOURCES

MEDLINE and EMBASE and reference lists of all eligible articles.

STUDY SELECTION

Studies providing raw data on nasal methicillin-resistant S. aureus colonization at ICU admission, published up to February 2013. Analyses were restricted in the general ICU setting. Medical, surgical, and interdisciplinary ICUs were eligible. ICU studies referring solely on highly specialized ICUs populations and reports on methicillin-resistant S. aureus outbreaks were excluded.

DATA EXTRACTION

Two authors independently assessed study eligibility and extrapolated data in a blinded fashion. The two outcomes of interest were the prevalence estimate of methicillin-resistant S. aureus nasal colonization at admission in the ICU and the sensitivity/specificity of colonization in predicting methicillin-resistant S. aureus-associated infections.

DATA SYNTHESIS

Meta-analysis, using a random-effect model, and meta-regression were performed. Pooled data extracted from 63,740 evaluable ICU patients provided an estimated prevalence of methicillin-resistant S. aureus nasal colonization at admission of 7.0% (95% CI, 5.8-8.3). Prevalence was higher for North American studies (8.9%; 95% CI, 7.1-10.7) and for patients screened using polymerase chain reaction (14.0%; 95% CI, 9.6-19). A significant per year increase in methicillin-resistant S. aureus colonization was also noted. In 17,738 evaluable patients, methicillin-resistant S. aureus infections (4.1%; 95% CI, 2.0-6.8) developed in 589 patients. The relative risk for colonized patients was 8.33 (95% CI, 3.61-19.20). Methicillin-resistant S. aureus nasal carriage had a high specificity (0.96; 95% CI, 0.90-0.98) but low sensitivity (0.32; 95% CI, 0.20-0.48) to predict methicillin-resistant S. aureus-associated infections, with corresponding positive and negative predictive values at 0.25 (95% CI, 0.11-0.39) and 0.97 (95% CI, 0.83-1.00), respectively.

CONCLUSIONS

Among ICU patients, 5.8-8.3% of patients are colonized by methicillin-resistant S. aureus at admission, with a significant upward trend. Methicillin-resistant S. aureus colonization is associated with a more than eight-fold increase in the risk of associated infections during ICU stay, and methicillin-resistant S. aureus infection develops in one fourth of patients who are colonized with methicillin-resistant S. aureus at admission to the ICU.

Risk factors for and impact of methicillin-resistant Staphylococcus aureus nasal colonization in patients in a medical intensive care unit

This retrospective cohort study investigated the impact and predictive factors of methicillin-resistant Staphylococcus aureus (MRSA) nasal colonization in 180 patients admitted to a medical intensive care unit between July 2009 and June 2010. No significant associations between MRSA nasal colonization and the incidence of health care-associated multidrug-resistant-related infections, intensive care unit length of stay, or inpatient mortality were found. Significant risk factors for MRSA colonization included previous medical history of diabetes mellitus and congestive heart failure.

Multiple site surveillance cultures as a predictor of methicillin-resistant Staphylococcus aureus infections

OBJECTIVE

To determine the relationship between methicillin-resistant Staphylococcus aureus (MRSA) colonization density, colonization site, and probability of infection in a frequently screened cohort of intensive care unit (ICU) patients.

METHODS

Patients had swab samples tested for MRSA at admission to the ICU, discharge from the ICU, and twice weekly during their ICU stay, and they were followed up for development of MRSA infection. Swab test results were analyzed to determine the proportion of patients colonized and the proportion colonized at each screening site. Hazard of MRSA infection (rate of infection per day at risk) was calculated using a Cox proportional hazards analysis, and risk factors for MRSA infection, including presence of MRSA, degree of colonization, and pattern of colonization were determined.

RESULTS

Among the 4,194 patient episodes, 238 (5.7%) had screening results that were positive for MRSA, and there were 34 cases of MRSA infection. The hazard ratio (HR) for developing an infection increased as more sites were colonized (HR, 3.4 for being colonized at more than 1 site compared with colonization at 1 site [95% confidence interval, 1.2-9.9]). Colonization site was predictive of developing infection (HR for nose or throat colonization compared with no colonization, 168 [95% confidence interval, 69-407]).

CONCLUSION

This study demonstrated that the hazard of developing an infection was higher when more sites were colonized and that certain sites were more predictive of infection than others. These results may be useful for predicting infection in ICU patients and may influence treatment.

Randomized comparison of 2 protocols to prevent acquisition of methicillin-resistant Staphylococcus aureus: results of a 2-center study involving 500 patients

OBJECTIVE

To compare an interventional protocol with a standard protocol for preventing the acquisition of methicillin-resistant Staphylococcus aureus (MRSA) in the intensive care unit (ICU).

DESIGN

Prospective, randomized, controlled, parallel-group, nonblinded clinical trial.

SETTING

Medical ICUs of 2 French university hospitals.

PARTICIPANTS

Five hundred adults with an expected length of stay in the ICU greater than 48 hours.

INTERVENTIONS

For the intervention group, the protocol required repeated MRSA screening, contact and droplet isolation precautions for patients at risk for MRSA at ICU admission and for MRSA-positive patients, and decontamination with nasal mupirocin and chlorhexidine body wash for MRSA-positive patients. For the standard group, the standard precautions protocol was used, and the results of repeated MRSA screening in the standard group were not communicated to investigators.

MAIN OUTCOME MEASURE

MRSA acquisition rate in the ICU. An audit was conducted to assess compliance with hygiene and isolation precautions.

RESULTS

In the intent-to-treat analysis ([Formula: see text]), the MRSA acquisition rate in the ICU was similar in the standard (13 [5.3%] of 243) and intervention (16 [6.5%] of 245) groups ([Formula: see text]). The audit showed that the overall compliance rate was 85.5% in the standard group and 84.1% in the intervention group ([Formula: see text]), although compliance was higher when isolation precautions were absent than when they were in place (88.2% vs 79.1%; [Formula: see text]). MRSA incidence rates were higher without isolation precautions (7.57‰) than with isolation precautions (2.36‰; [Formula: see text]).

CONCLUSIONS

Individual allocation to MRSA screening, isolation precautions, and decontamination do not provide individual benefit in reducing MRSA acquisition, compared with standard precautions, although the collective risk was lower during the periods of isolation.

TRIAL REGISTRATION

Clinicaltrials.gov identifier: NCT00151606.

Nasal swabs collected routinely to screen for colonization by methicillin-resistant Staphylococcus aureus in intensive care units are a sensitive screening test for the organism in clinical cultures

BACKGROUND

Many hospitals screen patients for methicillin-resistant Staphylococcus aureus (MRSA) on admission to the intensive care unit (ICU). We hypothesized that this screening information could be used to assist with empiric antibiotic decisions.

METHODS

The medical records of patients admitted to a university-affiliated community hospital as well as a tertiary-care university hospital were reviewed. Patients admitted to the ICU were screened for MRSA colonization with a nasal swab that was analyzed with either chromogenic medium (hospital 1) or polymerase chain reaction (PCR) (hospital 2). The results of the nasal swab were compared with clinical culture results.

RESULTS

There were 141 patients, and 167 cultures were obtained. The majority of the cultures (70%) were performed on sputum specimens in an effort to diagnose pneumonia. The remaining cultures were performed on blood (10.1%), incisions (21.5%), and urine (3.4%). The overall sensitivity of nasal swab results was 69.5%. However, the sensitivity was significantly higher for nasal swab screening performed within six days of clinical cultures compared with screening performed seven days or more before cultures were obtained. (79% vs. 46%; p < 0.0001). Sensitivity also differed significantly depending on the surveillance method, being significantly higher among patients screened with PCR within six days of developing an infection than in patients screened with chromogenic medium (88% vs. 65.5%; p = 0.006).

CONCLUSION

Screening with PCR analysis of nasal swab specimens is a highly sensitive test for MRSA in clinical cultures. Clinicians may be able to use the swab results to tailor more appropriate empiric antimicrobial regimens. The results with chromogenic medium screening are markedly poorer, which suggests that clinicians should view them with caution.

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.

Active surveillance testing and decontamination strategies in intensive care units to reduce methicillin-resistant Staphylococcus aureus infections

BACKGROUND

Active surveillance testing (AST) and decontamination strategies (DS) using a topical methicillin-resistant Staphylococcus aureus (MRSA) cleansing agent was introduced in July 2007 in a medical intensive care unit (MICU) and a surgical ICU (SICU) of a tertiary care hospital to reduce the incidence of MRSA infection.

METHODS

Data on ICU admissions between July 1, 2007, and June 30, 2008, was analyzed. All subjects, excluding known MRSA status, had an ICU length of stay (LOS) of more than 24 hours and nasal swabs performed on ICU admission, every 7 days during the ICU stay, and on discharge. MICU and SICU specimens were sent for culture and in-house real-time polymerase chain reaction, respectively. MRSA-colonized (MRSAc) patients were subjected to contact isolation precautions and DS for 5 days or until ICU discharge. Data recorded included demographics, LOS, and antibiotic use. Results were analyzed using SPSS. Control charts were used to determine special cause variation.

RESULTS

Of 653 eligible patients admitted to the ICU, 85 (13%) were determined to be MRSAc on ICU admission. A further 15% (52 of 351) were determined to be MRSAc during the ICU stay or at discharge. Thus, AST detected MRSA in at least 137 of the 653 patients (21.0%). In contrast, clinical cultures for MRSA were positive in only 12 patients (1.8%). Compared with noncolonized patients, MRSAc patients at any screening point had a longer pre-ICU LOS (P =.001), received more antibiotics (P = .004), and had a longer ICU LOS (P = .003). Compared with the preintervention period of July 2006 to June 2007, there was no significant reduction in mean MRSA infection incidence rate in both ICUs (3.8 to 3.0 per 1000 patient-days [P = .057] in the SICU and 1.4 to 1.7 per 1000 patient-days in the MICU) following intervention.

CONCLUSIONS

In ICUs, AST detected 11 times more MRSA than clinical cultures. The lack of reduction in MRSA infection rates in the ICUs does not negate the roles of AST and DS, but does argue for better study design and outcome measures like MRSA transmission incidence, which perhaps would have demonstrated a true benefit of AST and DS.

Nasal colonization with methicillin-resistant Staphylococcus aureus: clinical implications and treatment

Methicillin-resistant Staphylococcus aureus (MRSA) has become an increasingly important pathogen during the past 30 years, and infections due to MRSA are associated with substantial morbidity and mortality. Despite intensive infection control measures, the prevalence of MRSA has increased significantly, and the organism has become endemic in many hospitals worldwide. Asymptomatic nasal carriage of MRSA has been identified as a major risk factor for subsequent S. aureus infection in multiple settings and populations. As a result, considerable interest exists in developing decolonization strategies, with the ultimate goal of reducing the incidence of MRSA infection. Approaches to decolonization have included the use of systemic and inhalation anti-biotics, antiseptic washes, and topical antimicrobials.

Spectra MRSA, a new chromogenic agar medium to screen for methicillin-resistant Staphylococcus aureus

A novel chromogenic medium, Spectra MRSA (Remel, Lenexa, KS), was designed to detect methicillin-resistant Staphylococcus aureus (MRSA) rapidly and more efficiently than traditional media (i.e., tryptic soy agar with 5% sheep blood [SBA] and mannitol salt agar [MSA]). A multicenter study (including four clinical trial sites and the Medical College of Wisconsin [MCW] Milwaukee, WI) compared the performance characteristics of Spectra MRSA to those of the traditional media for the detection of MRSA. For this study, 767 nasal swab specimens from the multicenter study (traditional medium used, SBA) and 667 nasal swab specimens from MCW (traditional medium used, MSA) were plated on each test medium and examined after 24 and 48 h of incubation. At 24 h, the sensitivity and the specificity of each medium were as follows: in the multicenter study, 95.4% and 99.7%, respectively, for Spectra MRSA and 93.6% and 100%, respectively, for SBA; at MCW, 95.2% and 99.5%, respectively, for Spectra MRSA and 88.7% and 94.0%, respectively, for MSA. The positive predictive values of each medium at 24 h were as follows: in the multicenter study, 98.1% for Spectra MRSA and 100% for SBA; at MCW, 95.2% for Spectra MRSA and 60.4% for MSA. In our evaluation, we found that Spectra MRSA was able to rapidly identify and differentiate methicillin-resistant S. aureus from methicillin-susceptible S. aureus on the basis of the utilization of chromogens that result in denim blue colonies, thus eliminating the need for biochemical analysis and antimicrobial susceptibility testing. Extending the incubation beyond 24 h did not significantly improve the recovery of MRSA and resulted in decreased specificity.

Predicting clearance of colonization with vancomycin-resistant Enterococci and methicillin-resistant Staphylococcus aureus by use of weekly surveillance cultures

We analyzed surveillance cultures for vancomycin-resistant enterococci (VRE) and methicillin-resistant Staphylococcus aureus (MRSA) collected during a multicenter trial to determine if three negative cultures collected at weekly intervals would predict clearance of VRE or MRSA from colonized patients. Seventy-two percent of VRE-colonized patients and 94% of MRSA-colonized patients were culture negative after three consecutive negative cultures.

Which patients are most at risk of methicillin resistant Staphylococcus aureus: a review of admissions to a regional maxillofacial ward between 2001 and 2005

This study aimed to identify all Staphylococcus aureus (MRSA) cases on a Regional Maxillofacial ward, to estimate incidence and to ascertain who were most at risk. The study also explored clinical and demographic factors associated with MRSA in a subset of consecutive patients managed by primary surgery for previously untreated oral and oropharyngeal squamous cell carcinoma (OOSCC) over the same time period. Patients admitted from 1st April 2001 to 31st March 2006 to the Regional Maxillofacial Unit ward, Liverpool were identified by a retrospective review of the hospital MRSA database and there were 10109 patient admissions. MRSA (1.1%) occurred in 115 patient episodes involving 97 patients. There were 84 patients having a single episode and 13 more than one. There were no cases of mortality due to MRSA. Of the MFU patients 73 were oncology and 7 trauma. In the oncology group the commonest primary sites were wound (41) and sputum (11). Of new patients admitted for definitive treatment for OOSCC, 14% had MRSA and the two main risk factors were stage of cancer (P<0.001) and free flap (P<0.001). The risk of MRSA infection on our maxillofacial ward is low though MRSA infection is more prevalent among oncology patients particularly those requiring free tissue transfer. Careful adherence to infection prevention and control precautions is essential and practical methods to reduce MRSA need further evaluation.

A randomized Phase I study of Atuna racemosa: a potential new anti-MRSA natural product extract

AIM

We previously reported significant antimicrobial activity against Gram-positive bacteria from the extract of the Atun tree (Atuna racemosa), identified through rapid digital bioprospecting of a 400-year-old historic herbal text. Toxicity studies in human cell lines showing safety, combined with the ethnomedical descriptions of botanical use, suggested that this extract might be clinically useful against topical Gram-positive bacteria infections.

MATERIALS AND METHODS

Using a minimal inhibitory concentration assay, we examined the susceptibility of methicillin-resistant Staphylococcus aureus (MRSA) to an extract of the kernel of the Atun tree (Atuna racemosa). Additionally, a maximum tolerated topical application of the extract was determined in a randomized, double-blind, placebo-controlled pilot clinical trial.

RESULTS

Here we report that the effectiveness of this Atuna racemosa extract against MRSA (MIC=16-32microg/mL) is on par with currently available last-line antibiotics, while it remains well tolerated in short-term topical applications of 10 times the minimally inhibitory concentration.

CONCLUSIONS

Although further studies are needed to determine safety and clinical efficacy, this effective extract, identified in a 400-year-old historic herbal text, may prove to be clinically useful in the treatment of MRSA.

Staphylococcus aureus poststernotomy mediastinitis: description of two distinct acquisition pathways with different potential preventive approaches

OBJECTIVE

Determining the acquisition routes of infection is crucial to designing specific preventive approaches against Staphylococcus aureus poststernotomy mediastinitis.

METHODS

From 2002 to 2004, a nasal sample was obtained from patients before cardiac surgery. We collected clinical and microbiologic data of all episodes of S aureus poststernotomy mediastinitis. A case-control study (3:1) was performed to confirm the role of previous preoperative nasal colonization by S aureus as a risk factor for S aureus poststernotomy mediastinitis. Pulsed field gel electrophoresis molecular analysis of nasal and surgical site S aureus isolates was performed to analyze their relatedness in each patient with poststernotomy mediastinitis and with other patients of the study cohort.

RESULTS

S aureus nasal cultures were positive in 228 (15.9%) of 1432 patients: methicillin-susceptible S aureus in 222 (15.5%) and meticillin-resistant S aureus in 6 (0.4%). S aureus poststernotomy mediastinitis was diagnosed in 17 (1.2%) of 1432 patients: 9 (3.95%) of 228 in colonized patients versus 8 (0.66%) of 1204 in noncolonized patients (P < .0001). Seven of 9 patients (1.2%) with methicillin-susceptible S aureus had an identical isolate by pulsed field gel electrophoresis in preoperative nasal and surgical-site cultures, but no clonal relatedness was shown among the isolates from these 9 patients. None of the 8 patients with methicillin-resistant S aureus poststernotomy mediastinitis had an identical isolate by pulsed field gel electrophoresis in preoperative nasal and surgical-site cultures, and the same clone of methicillin-resistant S aureus was responsible for all these cases.

CONCLUSIONS

Endogenous [corrected] nasal colonization often precedes methicillin-resistant S aureus poststernotomy mediastinitis, which suggests that preoperative [corrected] decontamination is adequate for preventing methicillin-susceptible [corrected] S aureus poststernotomy mediastinitis, whereas hospital infection control measures seem to be the major factor for preventing methicillin-resistant S aureus poststernotomy mediastinitis.

Selective use of intranasal mupirocin and chlorhexidine bathing and the incidence of methicillin-resistant Staphylococcus aureus colonization and infection among intensive care unit patients

OBJECTIVE

To determine whether the use of chlorhexidine bathing and intranasal mupirocin therapy among patients colonized with methicillin-resistant Staphylococcus aureus (MRSA) would decrease the incidence of MRSA colonization and infection among intensive care unit (ICU) patients.

METHODS

After a 9-month baseline period (January 13, 2003, through October 12, 2003) during which all incident cases of MRSA colonization or infection were identified through the use of active-surveillance cultures in a combined medical-coronary ICU, all patients colonized with MRSA were treated with intranasal mupirocin and underwent daily chlorhexidine bathing.

RESULTS

After the intervention, incident cases of MRSA colonization or infection decreased 52% (incidence density, 8.45 vs 4.05 cases per 1,000 patient-days; P=.048). All MRSA isolates remained susceptible to chlorhexidine; the overall rate of mupirocin resistance was low (4.4%) among isolates identified by surveillance cultures and did not increase during the intervention period.

CONCLUSIONS

We conclude that the selective use of intranasal mupirocin and daily chlorhexidine bathing for patients colonized with MRSA reduced the incidence of MRSA colonization and infection and contributed to reductions identified by active-surveillance cultures. This finding suggests that additional strategies to reduce the incidence of MRSA infection and colonization--beyond expanded surveillance--may be needed.

Legislative mandates for use of active surveillance cultures to screen for methicillin-resistant Staphylococcus aureus and vancomycin-resistant enterococci: Position statement from the Joint SHEA and APIC Task Force

Legislation aimed at controlling antimicrobial-resistant pathogens through the use of active surveillance cultures to screen hospitalized patients has been introduced in at least 2 US states. In response to the proposed legislation, the Society for Healthcare Epidemiology of America (SHEA) and the Association for Professionals in Infection Control and Epidemiology, Inc., (APIC) have developed this joint position statement. Both organizations are dedicated to combating health care-associated infections with a wide array of methods, including the use of active surveillance cultures in appropriate circumstances. This position statement reviews the proposed legislation and the rationale for use of active surveillance cultures, examines the scientific evidence supporting the use of this strategy, and discusses a number of unresolved issues surrounding legislation mandating use of active surveillance cultures. The following 5 consensus points are offered. (1) Although reducing the burden of antimicrobial-resistant pathogens, including methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant enterococci (VRE), is of preeminent importance, the APIC and the SHEA do not support legislation to mandate use of active surveillance cultures to screen for MRSA, VRE, or other antimicrobial-resistant pathogens. (2) The SHEA and the APIC support the continued development, validation, and application of efficacious and cost-effective strategies for the prevention of infections caused by MRSA, VRE, and other antimicrobial-resistant and antimicrobial-susceptible pathogens. (3) The APIC and the SHEA welcome efforts by health care consumers, together with private, local, state, and federal policy makers, to focus attention on and formulate solutions for the growing problem of antimicrobial resistance and health care-associated infections. (4) The SHEA and the APIC support ongoing additional research to determine and optimize the appropriateness, utility, feasibility, and cost-effectiveness of using active surveillance cultures to screen both lower-risk and high-risk populations. (5) The APIC and the SHEA support stronger collaboration between state and local public health authorities and institutional infection prevention and control experts.