Subsequent Methicillin-resistant Staphylococcus Aureus Infection Research Articles

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

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. 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. 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 > 21days (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. 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.

Evaluation of the Negative Predictive Value of Methicillin-Resistant Staphylococcus aureus Nasal Swab Screening in the Medical Intensive Care Units and Its Effect on Antibiotic Duration

BackgroundIn addition to active surveillance of methicillin-resistant Staphylococcus aureus (MRSA) carrier, MRSA nasal screening can be valuable for antibiotic de-escalation. This study aimed to assess the correlations between the MRSA nasal swab and subsequent culture results in patients admitted to medical intensive care units (MICU). The impact of MRSA nasal swab on the antibiotic duration was also evaluated.Materials and MethodsThis retrospective study enrolled patients who received glycopeptides in the MICU of a medical center in 2019. Patients treated with glycopeptides for over 2 days before MICU admission were excluded. The associated data were collected through the electronic medical record system. The negative predictive value (NPV) of MRSA nasal swabs for MRSA infection was calculated, and their influence on empirical glycopeptide treatment duration was analyzed.ResultsOf the 338 patients who met the inclusion criteria, 277 underwent MRSA nasal screening. The NPV of MRSA-negative nasal swab for subsequent MRSA infection was 98.4%. The glycopeptide treatment duration of the patients with and without nasal screening was not significantly different (4.2 ± 2.8 vs 4.4 ± 3.0 days, p = 0.577). Of the 120 patients with MRSA-negative nasal swab and no subsequent MRSA infection, 75 continued empirical glycopeptides therapy. The additional treatment time was 3 days (interquartile range: 2–6 days).ConclusionThe MRSA nasal swabs have high NPV for MRSA infection in critically ill patients. However, it has no impact on the empirical glycopeptide treatment duration. The value of MRSA nasal swabs should be advocated to optimize antibiotic therapy.

Evaluation of the negative predictive value of methicillin-resistant Staphylococcus aureus nasal swab screening in patients with acute myeloid leukemia.

Methicillin-resistant Staphylococcus aureus (MRSA) nasal swabs are utilized to guide the discontinuation of empiric MRSA therapy. In multiple studies, MRSA nasal swabs have been shown to have a negative predictive value (NPV) of ~99% in non-oncology patients with pneumonia and other infections. We evaluated the performance characteristics of a negative MRSA nasal swab in the acute myeloid leukemia (AML) populaion to determine its NPV. Retrospective chart review. This study included adult AML patients with a suspected infection and a MRSA nasal swab collected between 2013 and 2018. MRSA nasal swab and culture-documented infections were identified to determine the sensitivity, specificity, NPV, and positive predictive value of the MRSA nasal swabs. In total, 194 patients were identified, and 484 discrete encounters were analyzed. Overall, 468 (97%) encounters had a negative MRSA nasal swab upon admission with no cultured documented MRSA infection during their hospitalization. However, 3 encounters (0.6%) had a negative MRSA nasal swab with a subsequent cultured documented MRSA infection during their admission. Identified infections were bacteremia (n = 2) and confirmed pneumonia (n = 1). MRSA nasal swab had a sensitivity of 62% (95% CI, 0.24-0.91), specificity of 98% (95% CI, 0.96-0.99), positive predictive value of 38% (95% CI, 0.21-0.6), and NPV of 99% (95% CI, 0.98-1). A negative MRSA nasal swab has a 99% NPV for subsequent MRSA infections in AML patients with no prior history of MRSA colonization or infection. Based on these findings, a negative MRSA nasal swab can help guide de-escalation of empiric MRSA antibiotic therapy.

562. Reducing MRSA Bacteremia in Adult Patients through MRSA Decolonization Bundle

BackgroundPatients colonized with methicillin-resistant Staphylococcus aureus (MRSA) are at an increased risk of developing a subsequent MRSA infection. Moreover, these individuals may serve as an endogenous reservoir to spread the bacteria to other patients. In an attempt to reduce MRSA bacteremia rates, a decolonization protocol was developed and implemented at a tertiary teaching hospital in Detroit, Michigan. In this study, we evaluate the intervention’s impact on community-onset (CO) and hospital onset (HO) MRSA bacteremia rates.MethodsInfection Control developed an MRSA decolonization bundle for adults that consisted of daily Chlorhexidine gluconate (CHG) bathing and twice-daily nasal swabs with 10% Povidone–iodine (PI) or Nozin for individuals with iodine allergies. Patients with known risk factors for developing an MRSA infection, such as patients residing in an intensive care unit and/or undergoing specified procedure, were prescribed the bundle for their length of stay (Figure 1). Countraindications for nasal decolonization included inhalation injuries, CSF leaks, ENT surgeries, and transphenoidal surgeries. A retrospective chart review of high-risk patients was conducted to determine compliance with the elements of the MRSA decolonization bundle. Rates of CO and HO MRSA bacteremia per 1,000 patient-days were graphed against compliance with bundle elements (2 nasal swabs and 1 CHG bath per day). To quantify the correlation, a linear regression model and the Pearson coefficient was used.ResultsApproximately 2,000 and 1,000 opportunities for nasal decolonization and CHG bathing, respectively, were identified between September 2018 and March 2019. The data suggest a strong correlation between compliance with MRSA decolonization elements and rate of HO MRSA bacteremia (R2 = 0.785) and a moderate association between nasal decolonization and rate of CO bacteremia (R2 = 0.322) (Figures 2 and 3).ConclusionThe MRSA decolonization bundle of CHG bathing and nasal swabs appears to be an effective strategy to decrease HO MRSA bacteremia rates with higher bundle compliance being associated with lower rates of infection. Disclosures All authors: No reported disclosures.

Postdischarge MRSA Decolonization to Prevent Infections

Patients who are carriers of methicillin-resistant Staphylococcus aureus (MRSA) are at increased risk for subsequent MRSA infection after

Methicillin-resistant Staphylococcus aureus Colonization and Pre- and Post-hospital Discharge Infection Risk.

The Department of Veterans Affairs implemented an active surveillance program for methicillin-resistant Staphylococcus aureus (MRSA) in 2007 in which acute care inpatients are tested for MRSA carriage on admission, unit-to-unit transfer, and discharge. Using these data, we followed patients longitudinally to estimate the difference in infection rates for those who were not colonized, those who were colonized on admission (importers), and those who acquired MRSA during their stay. We examined MRSA infections that occurred prior to discharge and at 30, 90, 180, and 365 days after discharge. We constructed a dataset of 985626 first admissions from January 2008 through December 2015 who had surveillance tests performed for MRSA carriage. We performed multivariable Cox proportional hazards and logistic regression models to examine the relationship between MRSA colonization status and infection. The MRSA infection rate across the predischarge and 180-day postdischarge time period was 5.5% in importers and 7.0% in acquirers without a direct admission to the intensive care unit (ICU) and 11.4% in importers and 11.7% in acquirers who were admitted directly to the ICU. The predischarge hazard ratio for MRSA infection was 29.6 (95% confidence interval [CI], 26.5-32.9) for importers and 28.8 (95% CI, 23.5-35.3) for acquirers compared to those not colonized. Fully 63.9% of all MRSA pre- and postdischarge infections among importers and 61.2% among acquirers occurred within 180 days after discharge. MRSA colonization significantly increases the risk of subsequent MRSA infection. In addition, a substantial proportion of MRSA infections occur after discharge from the hospital.

The Role of Negative Methicillin-Resistant Staphylococcus aureus Nasal Surveillance Swabs in Predicting the Need for Empiric Vancomycin Therapy in Intensive Care Unit Patients.

OBJECTIVES The role of methicillin-resistant Staphylococcus aureus (MRSA) nasal surveillance swabs (nasal swabs) in guiding decisions about prescribing vancomycin is unclear. We aimed to determine the likelihood that patients with negative MRSA nasal swabs develop subsequent MRSA infections; to assess avoidable vancomycin days for patients with negative nasal swabs; and to identify risk factors for having a negative nasal swab and developing a MRSA infection during the intensive care unit (ICU) stay. METHODS This retrospective cohort study was conducted in 6 ICUs at a tertiary-care hospital from December 2013 through June 2015. The negative predictive value (NPV), defined as the ability of a negative nasal swab to predict no subsequent MRSA infection, was calculated. Days of vancomycin continued or restarted after 3 days from the collection time of the first negative nasal swab were determined. A matched case-control study identified risk factors for having a negative nasal swab and developing MRSA infection. RESULTS Of 11,441 patients with MRSA-negative nasal swabs, the rate of subsequent MRSA infection was 0.22%. A negative nasal swab had a NPV of 99.4% (95% confidence interval [CI], 99.1%-99.6%). Vancomycin was continued or started after nasal swab results were available in 1,431 patients, translating to 7,364 vancomycin days. No risk factors associated with MRSA infection were identified. CONCLUSIONS In our hospital with a low prevalence of MRSA transmission, a negative MRSA nasal swab was helpful in identifying patients with low risk of MRSA infection in whom empiric vancomycin therapy could be stopped and in whom the subsequent initiation of vancomycin therapy during an ICU admission could be avoided. Infect Control Hosp Epidemiol 2018;39:290-296.

Methicillin-Resistant Staphylococcus aureus in a Trauma Population: Does Decolonization Prevent Infection?

The purpose of this study was to determine if a decolonization regimen reduces the frequency of methicillin-resistant Staphylococcus aureus (MRSA) infections and if colonization isolates are genetically related to subsequent infectious strains. Trauma patients admitted to the intensive care unit with positive MRSA nasal swabs were randomized to either daily chlorhexidine gluconate (CHG) baths and mupirocin (MUP) ointment to the nares or soap and water baths and placebo ointment for five days. Nasal swabs performed at the end of treatment and invasive MRSA infections during the remaining hospitalization were compared with the original nasal isolate via polymerase chain reaction for genetic relatedness as well as CHG and MUP resistance genes. Six hundred and seventy-eight intensive care unit admissions were screened, and 92 (13.6%) had positive (+) MRSA nasal swabs over a 22-month period ending in 3/2014. After the five day treatment period, there were 13 (59.1%) +MRSA second nasal swabs for CHG + MUP and 9 (90%) for soap and water baths and placebo, P = 0.114. No isolates tested positive for the MUP or CHG resistance genes mupA and qacA/B but 7 of 20 (35%) contained smr. There were seven (31.8%) MRSA infections in the CHG group and six (60%) for soap, P = 0.244. All 13 patients with MRSA infections had the same MRSA isolate present in the original nasal swab. There was no difference in all-cause Gram-negative or positive infections for CHG versus soap, 12 (54.5%) versus 7 (70%), P = 0.467. CHG + MUP are ineffective in eradicating MRSA from the anterior nares but may reduce the incidence of infection. Subsequent invasive MRSA infections are typically caused by the endogenous colonization strain.

Comparison of subsequent infection in methicillin-resistant Staphylococcus aureus nasal carriers between ST72 community-genotype and hospital genotypes: a retrospective cohort study

BackgroundCarriage of methicillin-resistant Staphylococcus aureus (MRSA) is an important risk factor of subsequent infection. The purpose of our study was to compare the rates of subsequent infection among newly-admitted patients carrying MRSA between community-genotype and hospital-genotypesMethodsIn this retrospective cohort study, we compared the rates of subsequent MRSA infection, time to subsequent infection and mortality in the following 6 months between the community-genotype ST72 MRSA cohort and the hospital-genotypes ST5 / ST239 MRSA cohort.ResultsWe identified 198 patients carrying ST72 and 156 patients carrying ST5 or ST239. There was no difference in the rates of subsequent infection between ST72 cohort and ST5 / ST239 cohort (13.1% vs. 12.8%; P = 0.931). The median time to development of subsequent infection was not significantly different (27 days vs. 88 days; P = 0.0877). The Kaplan-Meier method showed no difference in the cumulative rate of being free of subsequent infection between the cohorts (P = 0.9209). Overall mortality rates at 6 months did not differ (1.5% vs. 1.9%; P = 1.000)ConclusionsWe found no evidence that rates of subsequent MRSA infection were different between newly-admitted patients carrying community-genotype ST72 MRSA and those whom carrying hospital-genotypes ST5 or ST239 MRSA.

Risk factors for the development of active methicillin-resistant Staphylococcus aureus (MRSA) infection in patients colonized with MRSA at hospital admission.

Patients who present to Veterans Affairs hospitals are screened for methicillin-resistant Staphylococcus aureus (MRSA) colonization. Those who test positive are isolated during their hospital stay. However, it is unknown which of these patients are most likely to subsequently develop active MRSA infections. This retrospective case-control study characterized risk factors for active MRSA infection among patients colonized with MRSA at hospital admission. Potential demographic and clinical risk factors were identified using electronic queries and manual chart abstraction; data were compared by standard statistical tests, and variables with P ≤ .05 in bivariable analysis were entered into a multivariable logistic regression model. There were 71 cases and 213 controls. Risk factors associated with MRSA infection included diabetes mellitus with or without end organ damage (26% vs 14%, P = .02), hemiplegia (9% vs 2%, P = .01), chronic kidney disease (33% vs 20%, P = .03), postcolonization inpatient admission within 90 days (44% vs 29%, P = .03), surgery (41% vs 9%, P < .01), and dialysis (10% vs 3%, P = .02). On multivariable analysis, surgery during follow-up, dialysis during follow-up, and hemiplegia remained significant. Among patients with MRSA colonization, surgery or dialysis during follow-up and history of hemiplegia were associated with subsequent MRSA infection. Knowledge of these risk factors may allow for future targeted interventions to prevent MRSA infections among colonized patients.

Colonization With Methicillin-resistant Staphylococcus aureus and Risk for Infection Among Asymptomatic Athletes: A Systematic Review and Metaanalysis.

Athletes are a vulnerable population for methicillin-resistant Staphylococcus aureus (MRSA) infection. Our aim was to determine MRSA colonization in asymptomatic athletes and estimate the risk for subsequent MRSA infection. We searched the PubMed and EMBASE (through 29 October 2015) for studies on MRSA colonization among asymptomatic athletes. The pooled prevalence of MRSA colonization among athletes was 6% (95% confidence interval [CI], 1,13), and it was higher in the United States (8%; 95% CI, 2,17). USA300 was the most common strain detected (22%), and 62% and 36% of isolates were resistant to clindamycin and trimethoprim/sulfamethoxazole, respectively. The prevalence of MRSA colonization among collegiate athletes reached 13% (95% CI, 4,25). Sports with the highest prevalence among collegiate athletes were wrestling (22%; 95% CI, 0,85), football (8%; 95% CI, 3,15) and basketball (8%; 95% CI, 0,28). The risk for MRSA skin and soft tissue infection within 3 months after documented colonization among MRSA-colonized athletes was significantly higher than for noncolonized athletes (relative risk = 7.37, 95% CI, [2.47,21.94]). Decolonization treatment among colonized athletes decreased significantly the risk for infection (relative risk reduction = 0.33; 95% CI, .03,4.28). The prevalence of MRSA colonization among asymptomatic athletes is comparable to that among individuals with chronic illness, it is higher among collegiate athletes and can be twice that for patients in intensive care units. Importantly, colonization is associated with a >7-fold increase in the incidence of subsequent MRSA infection. Infection control and decontamination protocols for this population need to be studied and implemented with urgency.

Risk Factors of Methicillin-Resistant Staphylococcus aureus Infection and Correlation With Nasal Colonization Based on Molecular Genotyping in Medical Intensive Care Units: A Prospective Observational Study.

Methicillin-resistant Staphylococcus aureus (MRSA) is a common and important cause of colonization and infection in medical intensive care units (ICU). The aim of this study was to assess association factors between MRSA nasal colonization and subsequent infections in medical ICU patients by clinical investigation and molecular genotyping.A prospective cohort observational analysis of consecutive patients admitted to medical ICUs between November 2008 and May 2010 at a tertiary teaching hospital were included. To detect MRSA colonization, the specimens from the nares were obtained within 3 days of admission to the ICU and again 1 week following admission to the ICU. Genetic relatedness for colonized and clinical isolates from each study patient with MRSA infection were analyzed and compared.A total of 1266 patients were enrolled after excluding 195 patients with already present MRSA infections. Subsequent MRSA infection rates were higher in patients with nasal colonization than in those without (39.1% versus 14.7%, respectively). Multivariate Poisson regression analysis demonstrated that nasal MRSA colonization (relative risk [RR]: 2.50; 95% confidence interval [CI]: 1.90–3.27; P < 0.001) was independent predictors for subsequent MRSA infections. History of tracheostomy, however, was a protective predictor in all patients (RR: 0.38; 95% CI: 0.18–0.79; P = 0.010) and in patients with MRSA nasal colonization (RR: 0.22; 95% CI: 0.55–0.91; P = 0.037). Molecular genetics studies revealed that most MRSA isolates were healthcare-associated clones and that nasal and clinical isolates exhibited up to 75% shared identity.Methicillin-resistant S. aureus nasal colonization was significantly associated with subsequent MRSA infection among medical ICU patients. Previous MRSA infection was associated with subsequent MRSA infections, and history of tracheostomy associated with reducing this risk. Most MRSA isolates were healthcare-associated strains that were significantly correlated between nasal and clinical isolates.

Molecular characterization of methicillin-resistant Staphylococcus aureus (MRSA) nasal colonization and infection isolates in a Veterans Affairs hospital.

BackgroundNasal colonization with methicillin-resistant Staphylococcus aureus (MRSA) is associated with increased infection risk, yet colonization and infection isolates are rarely compared within the same study. The objectives of this study were to compare colonization and infection isolates from a Veterans Administration hospital in Iowa, and to determine the prevalence of livestock-associated MRSA (LA-MRSA) colonization and infection in a state with high livestock density.MethodsAll patients with available MRSA isolates collected through routine nasal screening (73%; n = 397) and from infections (27%; n = 148) between December 2010 and August 2012 were included and tested for spa type and presence of PVL and mecA genes. Clinical isolates were tested for antibiotic resistance patterns. Paired colonization and infection isolates were compared for genetic and phenotypic congruity.ResultsThe most common spa types were t002 (and other CC5-associated strains; 65%) and t008 (and other CC8-associated strains; 20%). No classic LA-MRSA spa types were identified. CC5-associated strains were less likely to be associated with infections (22%; 77/353) compared with CC8-associated strains (49%; 53/109). MRSA colonization was more common among patients with infections (71%) compared with the general screening population (7%). In most cases (82%; 28/34), paired colonization and infection isolates were genetically and phenotypically indistinguishable.ConclusionsOur data demonstrate a direct link between antecedent nasal colonization and subsequent MRSA infection. Further, our data indicate variability in colonization and infection efficiency among MRSA genotypes, which points to the need to define the molecular determinants underlying emergence of S. aureus strains in the community and nosocomial setting.

Effect of mupirocin decolonization on subsequent methicillin-resistant Staphylococcus aureus infection in infants in neonatal intensive care units.

To evaluate whether topical mupirocin treatment can effectively decolonize methicillin-resistant Staphylococcus aureus (MRSA) carriage and reduce subsequent MRSA infection in neonates. During a 1-year period, the infants admitted to our neonatal intensive care units (NICUs)-1 and NICU-2 were included, and specimens from the nares and umbilicus were obtained within 24 hours, and specimen collection was repeated weekly for 2 weeks. Mupirocin was administered for 5 days to the infants with MRSA colonization in NICU-1 during the first half of the year and then switched to those in NICU-2 during the second half of the year. A total of 525 infants were recruited: 257 infants in the treatment group and 268 in the control group. MRSA colonization was detected in 130 infants (25%) during NICU stay, which is a similar rate in both groups. Twenty-two (4.2%) episodes of MRSA infection were identified. The rate of MRSA infection was significantly higher in infants with prior colonization than in those without (10.2% vs. 2.3%, P<0.001). Among the infants with prior colonization, the rate of MRSA infection in the treatment group was significantly lower than that in the control group (3.2% vs. 16%, P=0.014), and the rate in the treatment group was comparable to that in those without colonization (P=0.7804). Of the 15 infants with both clinical and colonizing isolates, indistinguishable strains between the paired isolates from the same infant by molecular methods were identified in 14 infants (93%). Administering mupirocin topical therapy to MRSA-colonized infants in NICUs might reduce subsequent MRSA infections during hospitalization in these infants. A large-scale study should be conducted.

Active surveillance of the trachea or throat for MRSA is more sensitive than nasal surveillance and a better predictor of MRSA infections among patients in intensive care.

BackgroundMethicillin-resistant Staphylococcus aureus (MRSA) is one of the most common causes of infection in the intensive care unit (ICU). Although surveillance culture for MRSA is recommended for ICU patients, no comparative study investigating the optimal sites and frequency of culture has been performed in this population.MethodsA prospective observational cohort study was performed in an 18-bed emergency intensive care unit (EICU) in a tertiary teaching hospital. A total of 282 patients were included. Samples for MRSA detection were obtained at the time of admission, 48 h after admission, and then weekly thereafter. All subjects were routinely monitored for the development of MRSA infection during their stay in the ICU.ResultsMRSA colonization was detected in 129 (46%) patients over the course of the study. The sensitivity of MRSA surveillance culture was significantly higher in throat or tracheal aspirates (82%; 106/129) than in anterior nares (47%; 61/129) (P<0.001). The sensitivity of MRSA surveillance culture for subsequent MRSA infection and MRSA pneumonia was also higher in the throat/trachea (69 and 93%, respectively) than in the anterior nares (48 and 50%, respectively). The area under the curve for subsequent MRSA infection was higher in trachea/throat (0.675) than in the anterior nares (0.648); however, this difference was not significant (P>0.05). The area under the curve for MRSA pneumonia was significantly higher in trachea/throat (0.791; 95% CI, 0.739-0.837) than anterior nares (0.649; 95% CI, 0.590-0.705) (P = 0.044).ConclusionMRSA colonization was more common in the trachea/throat than in the anterior nares in ICU patients. Cultures from throat or tracheal aspirates were more sensitive and predictive of subsequent MRSA pneumonia than cultures from the anterior nares in this population.

Risk factors affecting nasal colonization of methicillin-resistant Staphylococcus aureus when admitted in intensive care unit

Background Colonization with methicillin-resistant Staphylococcus aureus (MRSA) is a risk factor for subsequent invasive MRSA infection, particularly in patients admitted for critical care. The purpose of this study was to investigate the risk factors affecting nasal colonization of MRSA in patients admitted to intensive care units (ICU). Methods Between August 1, 2011 and June 30, 2012, we screened for MRSA nasal colonization in 350 patients by Real-time PCR within 24 hours of admission by means of swab samples taken from the anterior nares. According to the results of PCR, the patients were divided into 2 groups: the positive group with nasal MRSA colonization and the negative group without nasal MRSA colonization. The 31 (8.86%) patients were MRSA positive. The risk factors evaluated included thirteen variables, which were analyzed by t test for continuous variables and χ 2 test for discrete variables. The variables with significance (P &lt;0.05) were analyzed with stepwise Logistic regression. Results There were differences (P &lt;0.05) in four variables between two groups. The duration of stay in hospital prior to ICU admission in the positive group was (35.7±16.1) days, vs. (4.5±3.1) days in the negative group. The average blood albumin level was (28.4±2.9) g/L in the positive group, vs. (30.5±4.3) g/L in the negative group. Of 31 patients in the positive group, seven had been treated with antibiotics longer than seven days vs. 34 of 319 patients in the negative group. In the positive group, four of 31 patients received treatment with more than two classes of antibiotics prior to admission in ICU, contrasted to 13 of 319 patients in the negative group. Furthermore, stepwise Logistic regression analysis for these four variables indicates that the duration of stay in hospital prior to ICU admission may be an independent risk factor. Conclusions MRSA colonization in ICU admission may be related to many factors. The duration of stay in hospital prior to ICU admission is an independent risk factor.

Meta-Analysis of Methicillin-Resistant Staphylococcus aureus Colonization and Risk of Infection in Dialysis Patients

Patients undergoing dialysis are particularly vulnerable to methicillin-resistant Staphylococcus aureus (MRSA) infections. We performed a meta-analysis of published studies to estimate the prevalence of MRSA colonization in dialysis patients, time trends, and long-term risk of subsequent MRSA infections. Our search of the PubMed and Embase databases returned 5743 nonduplicate citations, from which we identified 38 relevant studies that included data on 5596 dialysis patients. The estimated prevalence of MRSA colonization was 6.2% (95% confidence interval [95% CI], 4.2% to 8.5%). The prevalence increased over time but remained stable after 2000. Stratification of patients according to dialysis modality and setting revealed that 7.2% (95% CI, 4.9% to 9.9%) of patients on hemodialysis were colonized with MRSA compared with 1.3% (95% CI, 0.5% to 2.4%) of patients on peritoneal dialysis (P=0.01), and that a statistically significant difference existed in the percentage of colonized inpatients and outpatients (14.2% [95% CI, 8.0% to 21.8%] versus 5.4% [95% CI, 3.5% to 7.7%], respectively; P=0.04). Notably, the risk of developing MRSA infections increased among colonized hemodialysis patients compared with noncolonized patients (relative risk, 11.5 [95% CI, 4.7 to 28.0]). The long-term (6-20 months) probability of developing a MRSA infection was 19% among colonized hemodialysis patients compared with only 2% among noncolonized patients. In summary, 6.2% of dialysis patients are MRSA colonized, and the average prevalence of colonization has remained stable since 2000. Colonization in hemodialysis patients is associated with increased risk of MRSA infection.

How colonization factors are linked to outbreaks of methicillin-resistant Staphylococcus aureus: the roles of SasX and ACME.

Methicillin-resistant Staphylococcus aureus (MRSA) is the most frequent cause of hospital-associated morbidity and mortality. One reason why MRSA has remained a serious threat to public health is that new clones of MRSA constantly keep re-emerging. These new clones are better adapted to thrive in the hospital environment or even the community than their predecessors because they have developed increased and diversified antibiotic resistance and/or enhanced virulence. In addition, non-symptomatic colonization has been identified as a risk factor for subsequent MRSA infection; therefore, acquisition of factors promoting colonization has gained increased attention regarding the surge of MRSA outbreak clones. Two specific genes or genetic loci, namely sasX and the arginine catabolic mobile element (ACME), could recently be linked to the epidemiological success of MRSA clones, supporting the notion that colonization factors play a crucial role in MRSA outbreaks. SasX is a surface protein that enhances nasal colonization. ACME contains an arc arginine deiminase gene cluster promoting the survival of MRSA in the acidic skin environment, in addition to a polyamine resistance gene that deals with the increased production of toxic polyamines by the host that is prompted by arc. Notably, a better understanding of MRSA colonization on the molecular level may lead to eradication strategies based on vaccination or bacterial interference, with great promise to decrease MRSA infection rates.

Risk factors for development of methicillin-resistant Staphylococcus aureus infection among colonized patients

This study was conducted to identify clinical factors associated with development of infection caused by methicillin-resistant Staphylococcus aureus (MRSA) among hospitalized patients with nasal MRSA colonization. We conducted a prospective cohort with nested case-control study at a 672-bed, public, academic hospital in Dallas, Texas. The study duration was from January 1, 2008, to July 28, 2009. From the cohort of patients who had presence of nasal colonization with MRSA at admission, we identified patients who developed subsequent infection with MRSA during a 3-month period. We compared these patients (cases) with colonized patients who remained uninfected (controls; 2 controls per case). We collected demographic and clinical data and performed statistical analyses. During the 19-month study period, 426 patients were found to have nasal colonization with MRSA. Of these, 36 (8.5%) developed a subsequent infection with MRSA within 3 months. When these 36 cases were compared with 72 controls, the factors independently associated with the development of subsequent infection were development of pressure ulcer during hospital stay (adjusted odds ratio, 5.82; 95% confidence interval: 2.21-15.31; P value=.000) and preadmission steroid therapy (adjusted odds ratio, 13.2; 95% confidence interval: 2.44-70.97; P value=.003). History of steroid therapy prior to admission and development of pressure ulcer are associated with increased risk of subsequent MRSA infection in patients nasally colonized with MRSA.

Long-Term Risk for Readmission, Methicillin-Resistant Staphylococcus aureus (MRSA) Infection, and Death among MRSA-Colonized Veterans

While numerous studies have assessed the outcomes of methicillin-resistant S. aureus (MRSA) colonization over the short term, little is known about longer-term outcomes after discharge. An assessment of long-term outcomes could provide information about the utility of various MRSA prevention approaches. A matched-cohort study was performed among Veterans Affairs (VA) patients screened for MRSA colonization between the years 2007 and 2009 and followed to evaluate outcomes until 2010. Cox proportional-hazard models were used to evaluate the association between MRSA colonization and long-term outcomes, such as infection-related readmission and crude mortality. A total of 404 veterans were included, 206 of whom were MRSA carriers and 198 of whom were noncarriers. There were no culture-proven MRSA infections on readmission among the noncarriers, but 13% of MRSA carriers were readmitted with culture-proven MRSA infections on readmission (P < 0.01). MRSA carriers were significantly more likely to be readmitted, to be readmitted more than once due to proven or probable MRSA infections, and to be readmitted within 90 days of discharge than noncarriers (P < 0.05). Infection-related readmission (adjusted hazard ratio [HR] = 4.07; 95% confidence interval [CI], 2.16 to 7.67) and mortality (adjusted HR = 2.71; 95% CI, 1.87 to 3.91) were significantly higher among MRSA carriers than among noncarriers after statistically adjusting for potential confounders. Among a cohort of VA patients, MRSA carriers are at high risk of infection-related readmission, MRSA infection, and mortality compared to noncarriers. Noncarriers are at very low risk of subsequent MRSA infection. Future studies should address whether interventions such as nasal or skin decolonization could result in improved outcomes for MRSA carriers.