Positive Methicillin-resistant Staphylococcus Aureus Culture Research Articles

Case validation of bloodstream infections with an antibiotic-resistant organism

Background: Bloodstream infections (BSIs) are an important cause of morbidity and mortality in severely ill patients, contributing to increased length of hospital stay and higher cost of care. Alberta Health Services Infection Prevention and Control (IPC) conducts inpatient surveillance of new episodes of BSIs with methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant enterococci (VRE) or carbapenemase-producing organisms (CPO) in 112 acute care facilities. A case-finding process was undertaken to verify the accuracy of BSI data entry. Methods: All positive MRSA, VRE or CPO blood cultures in 2021 were linked to the Inpatient Discharge Abstract Database (DAD) and the National Ambulatory Care Reporting System (NACRS) to identify new cases during acute care admissions. The results were then compared to surveillance records captured by infection control professionals (ICPs). Cases with unmatched culture date and/or encounter date and cases not identified by ICPs were screened by the study team with final decision made by ICPs. Results were analyzed by ARO and by % increase in number of surveillance records. Results: The laboratory linkage identified 286 new cases. Comparing to surveillance records (n = 248) captured by ICPs, 137 (57.3%) had matching collection dates and encounter dates, 85 (35.6%) had close matches on collection dates and encounter dates, 17 (7.1%) records had either matching collection dates or encounter dates, and 1 (0.4%) record did not have any matches on dates. There were 46 records identified in the laboratory data that were not in the surveillance system and 8 records that were in the surveillance system but not matched to the laboratory data. After review, 22 Surveillance records had data entry errors (1 CPO BSI, 20 MRSA BSI, and 1 VRE BSI), and there were 14 BSI records found to be missing (13 MRSA BSI, 1 VRE BSI). This represents a 6% increase in MRSA BSI and a 3% increase in VRE BSI identified in 2021 and no increase in CPO BSI. Conclusions: A laboratory validation to determine if BSIs with an ARO were missed during routine IPC surveillance identified a small proportion of missed bloodstream infections. The most common reason for the miss was admission through the emergency department with multiple blood cultures collected during a single admission. These results will be shared with the Infection Control program to facilitate correct BSI capture.

Deep learning model for personalized prediction of positive MRSA culture using time-series electronic health records

Methicillin-resistant Staphylococcus aureus (MRSA) poses significant morbidity and mortality in hospitals. Rapid, accurate risk stratification of MRSA is crucial for optimizing antibiotic therapy. Our study introduced a deep learning model, PyTorch_EHR, which leverages electronic health record (EHR) time-series data, including wide-variety patient specific data, to predict MRSA culture positivity within two weeks. 8,164 MRSA and 22,393 non-MRSA patient events from Memorial Hermann Hospital System, Houston, Texas are used for model development. PyTorch_EHR outperforms logistic regression (LR) and light gradient boost machine (LGBM) models in accuracy (AUROCPyTorch_EHR = 0.911, AUROCLR = 0.857, AUROCLGBM = 0.892). External validation with 393,713 patient events from the Medical Information Mart for Intensive Care (MIMIC)-IV dataset in Boston confirms its superior accuracy (AUROCPyTorch_EHR = 0.859, AUROCLR = 0.816, AUROCLGBM = 0.838). Our model effectively stratifies patients into high-, medium-, and low-risk categories, potentially optimizing antimicrobial therapy and reducing unnecessary MRSA-specific antimicrobials. This highlights the advantage of deep learning models in predicting MRSA positive cultures, surpassing traditional machine learning models and supporting clinicians’ judgments.

Genetic Determinants in MRSA Carriage and Their Association with Decolonization Outcome

Methicillin-resistant Staphylococcus aureus (MRSA) colonization increases the risk of infection. Response to decolonization treatment is highly variable and determinants for successful decolonization or failure of eradication treatment are largely unknown. Insight into genetic predictors of eradication failure is potentially useful in clinical practice. The aim of this study was to explore genetic characteristics that are associated with MRSA decolonization failure. This cohort study was performed in a tertiary care hospital in the Netherlands. Patients with ≥ 1 positive MRSA culture from any site and with available whole -genome sequencing data of the MRSA isolate between 2017 and 2022 were included. Lineages, resistance, and virulence factors were stratified by MRSA decolonization outcome. In total, 56 patients were included: 12/56 (21%) with treatment failure and 44/56 (79%) with successful decolonization (with or without preceding treatment). A significant association was found between ciprofloxacin-resistant lineages and failure of eradication (OR 4.20, 95%CI 1.11–15.96, P = 0.04). Furthermore, livestock-associated MRSA and the major community-associated MRSA lineages ST6-t304 and ST8-t008 were associated with successful eradication treatment or spontaneous clearance. In conclusion, this explorative study showed a higher eradication failure rate in complicated MRSA carriers with ciprofloxacin-resistant MRSA lineages, which are predominantly healthcare-associated. Further studies are warranted to confirm the higher eradication failure risk of ciprofloxacin-resistant lineages, and identify the underlying mechanisms.

Prevalence of Methicillin Resistant Staphylococcus aureus Colonisation in Patients undergoing Total Joint Arthroplasty: A Retrospective Observational Study

Introduction: Methicillin Resistant Staphylococcus aureus (MRSA) presents a significant, yet preventable, complication in Total Joint Arthroplasties (TJAs). Surgical Site Infections (SSIs) of prosthetic joints resulting from MRSA lead to substantial patient morbidity, mortality, and impose a significant burden on healthcare budgets. One method to mitigate these risks is to screen for MRSA colonisation prior to elective surgeries. The prevalence of MRSA colonisation in nasal mucosa ranges from 0.18-7.2% in different patient populations, with a nosocomial prevalence of 1.7%. Aim: To determine the prevalence of MRSA colonisation in all patients undergoing elective TJA, including Total Hip Replacement (THR) or Total Knee Replacement (TKR). Materials and Methods: A retrospective observational study was conducted on a total of 407 patients scheduled for elective TJAs. Data from 407 patients who underwent elective TJA between January 2020 and December 2022 (a period of three years) were selected for the study. Data compilation and analysis of the study subjects were performed retrospectively until March 2023 at the Sanjay Gandhi Institute of Trauma and Orthopaedics, a tertiary care Orthopaedic centre in Bengaluru, Karnataka, India. The study subjects were screened for MRSA colonisation through nasal swab culture and sensitivity. Patients with positive MRSA culture results were treated with decolonisation therapy, which involved the local application of 2% mupirocin and chlorhexidine body wash for five days. Descriptive data analytics were employed in the study, and tables were generated using Microsoft Word 2010 and Microsoft Excel 2010 (Microsoft Corp, Redmond, WA, USA). Results: The prevalence rates of MRSA nasal colonisation were n1=8 (8.42%), n2=2 (2%), and n3=16 (7.55%) for the years 2020 (n1), 2021 (n2), and 2022 (n3), respectively, at the centre. The period prevalence rate of MRSA colonisation in the nasal mucosa over three years was N=26 (6.4%). Conclusion: The present study revealed a high period prevalence of MRSA colonisation (6.4%) in patients undergoing TJAs. Therefore, all elective TJAs should undergo MRSA screening and decolonisation using 2% intranasal mupirocin and daily chlorhexidine body wash for five days as a successful treatment modality for all patients with MRSA-positive nasal colonisation. This approach helps prevent postoperative SSIs caused by MRSA.

Fear of missing organisms (FOMO): Diabetic foot and osteomyelitis management opportunities

Background: Hospitalizations for diabetic foot infections and lower-extremity osteomyelitis are common. Use of empiric antibiotic therapy for methicillin-resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa is also common. Guidelines recommend antibiotic therapy based on severity of illness, risk factors for MRSA and P. aeruginosa, and local prevalence. We evaluated the concordance between empiric antibiotic therapy and both culture results and definitive antibiotic therapy with a focus on MRSA and P. aeruginosa. We also evaluated how well MRSA and pseudomonal risk factors were predictive of culture results with these organisms. Methods: We conducted a cohort study of all patients admitted to our hospital system in 2021 with a diagnosis of a diabetic foot infection or lower-extremity osteomyelitis. Patients were included if they had an International Classification of Disease, Tenth Revision (ICD-10) diagnosis code of M86, E10.621, E11.621, or E08.621. Patients were excluded if antibiotics were for another indication or if they were aged <18 years. In patients with multiple hospitalizations only the first hospitalization was included. Empiric antibiotic therapy included antibiotics started by the admitting team. Definitive antibiotic therapy included the final antibiotic course either completed during admission or prescribed at the time of discharge. MRSA risk factors included prior positive culture with MRSA within the last year, hospitalization with IV antibiotics within 90 days, intravenous drug use, or hemodialysis. Pseudomonal risk factors included prior positive culture with P. aeruginosa within the last year or hospitalization with IV antibiotics within 90 days. Results: In 2021, 260 unique patients were admitted with suspected diabetic foot infections or lower-extremity osteomyelitis. 68 patients had >1 admission. Empiric anti-MRSA and antipseudomonal therapy was administered to 224 (86%) and 214 (82%) patients, respectively. Definitive anti-MRSA and antipseudomonal therapy was administered to 76 (30%) and 51 (20%) patients, respectively. Of the 195 patients who had wound cultures, 29 (15%) and 18 (9%) had positive cultures for MRSA and P. aeruginosa respectively (Fig.). The negative predictive value of MRSA risk factors for predicting a negative culture with MRSA was 91%. The negative predictive value of pseudomonal risk factors for predicting a negative culture with P. aeruginosa was 95%. Conclusions: Our data suggest an opportunity for substantial reductions in empiric anti-MRSA and antipseudomonal therapy for diabetic foot infection and lower-extremity osteomyelitis. The absence of MRSA and pseudomonal risk factors was reasonably good at predicting the absence of a positive culture with these organisms.Disclosure: None

1287: METHICILLIN-RESISTANT STAPHYLOCOCCUS AUREUS NARES SCREEN LEADS TO VANCOMYCIN DE-ESCALATION IN TRAUMA

Introduction: Methicillin-resistant Staphylococcus aureus (MRSA) polymerase chain reaction (PCR) nares swab is a proven screening tool to de-escalate vancomycin therapy due to its high negative predictive value in pneumonia and other infections. However, data are lacking on the utility of this test in the critically ill trauma population, which is at high risk for hospital-acquired infections. This study evaluated the impact of empiric MRSA PCR nares screening on de-escalation of vancomycin therapy in critically ill trauma patients. Methods: This is a single center, pre-post observational cohort study conducted at an academic, level I trauma center. Adult patients who were admitted for trauma and received empiric vancomycin therapy for suspected infection in the trauma intensive care unit were included. Patients were grouped by whether they were included 6 months before (pre-cohort) and 6 months after (post-cohort) the implementation of empiric rapid MRSA PCR nares screening in September 2021. The primary outcome was duration of vancomycin therapy. Secondary outcomes included rate of acute kidney injury (AKI), positive MRSA screen or cultures, ICU length of stay (LOS), hospital LOS, and mortality. Results: One-hundred fifty-eight patients were included: 82 in the pre-cohort group and 76 in the post-cohort group. Ninety vancomycin initiation orders were observed in the pre-cohort versus 80 orders in the post-cohort. Baseline demographics were similar between groups. There was a significantly higher rate of MRSA PCR orders in the post-cohort group (75%) compared to (21%) in the pre-cohort (p< 0.001). The pre-cohort group had higher rates of positive MRSA screens (26 vs. 13%, p=0.18) and MRSA positive cultures (17 vs. 9%, p=0.22) compared to post-cohort. There were no reported instances of positive MRSA cultures with a negative PCR. Vancomycin duration was significantly shorter in the post-cohort group (2.55 days vs. 3.5, p=0.02). Hospital and ICU LOS, rates of AKI, and mortality were not different between groups. Conclusions: Implementation of empiric rapid MRSA nares screening led to a shorter overall duration of vancomycin therapy by nearly one day in critically ill trauma patients. Further study is required to evaluate the potential cost savings of empiric MRSA screening in critically ill trauma patients.

Eleven-Year surveillance of methicillin-resistant Staphylococcus aureus infections at an Academic Health Centre.

SummaryIntroductionMethicillin-resistant Staphylococcus aureus (MRSA) is an important human pathogen associated with nosocomial and community infections. There is a continual focus on the epidemiology of this public health threat owing to the increase in its spread and rapid development of resistance.AimWe aimed to demonstrate the time trend of antibiotic resistance by describing the epidemiology of MRSA infections at an academic health centre.MethodologyWe retrospectively reviewed cases during an 11-year period (from January 2009 to December 2019) with positive cultures for MRSA from various clinical sites in King Fahad Hospital of the University, to understand their clinical and microbiological profiles. Screening and colonisation samples were excluded.ResultsA total of 1338 MRSA isolates were identified, with an increasing trend from 5.2% to 14.5% during 2009-2019. Skin and soft tissue samples were the most common source (52.4%) of MRSA infections. Vancomycin activity remained stable against MRSA, and only one isolate showed resistance to linezolid (< 1%). A significant reduction in susceptibility to clindamycin (p = 0.003), trimethoprim-sulfamethoxazole (p = 0.001), and rifampin (p < 0.0001) was detected over the study period.ConclusionsMRSA infections still represent a significant burden on healthcare systems. Our data support the need for constant local and regional surveillance to devise relevant protocols to manage MRSA infections. Empirical therapy needs to consider the changing antimicrobial susceptibility trends among MRSA isolates.

Evaluation of the Association between Trough and Area Under the Curve to Minimum Inhibitory Concentration Ratio (AUC24/MIC) of Vancomycin in Infected Patients with Methicillin Resistant Staphylococcus aureus (MRSA)

Background: The recent studies emphasized on the correlation of vancomycin antibacterial effect with pharmacokinetics properties such as the area under the curve/minimum inhibitory concentration (AUC24/MIC) ≥400 and serum trough level 15-20 mg /L in the patients with severe infection with methicillin-resistant Staphylococcus aureus (MRSA). The purpose is to assay the vancomycin pharmacokinetic properties in our population and evaluates the correlation between AUC24/MIC and trough serum level of vancomycin in given patients. Methods: The patients with a positive MRSA culture, treated with vancomycin, were enrolled in this cross-sectional study. Three plasma samples were obtained during the study including 30 min before fourth and the fifth dose as trough levels and 1 hour after the fourth dose as peak level to determine AUC24. E-TEST determined the MIC of vancomycin. Results: Thirty-eight patients with an average age of 48.33±16.44 were enrolled in this study. The mean ± SD of MIC was 0.99±0.30 mg/L. Thirty-four patients reached the adequate therapeutic range of AUC24/MIC ≥ 400 due to the standard vancomycin dosing method. In comparison, only 7 and 10 patients had the first and second trough levels in target intervals of 15-20 mg/L, respectively. Due to the receiver operating characteristic curve test (ROC test), the trough level after the fourth dose had a strong correlation with target AUC24/MIC with a sensitivity of 94.1%and specificity of 75.0%. Conclusion: This study concluded using only a trough level is not appropriate for therapeutic drug monitoring (TDM) of vancomycin. In our population, target AUC24/MIC (≥ 400) had a reasonably strong correlation with the trough level before the fifth dose which achieved with trough level ≥10.81 mg/L and MIC&lt; 1 mg/L.

Octenidine Body Wash and Nasal Gel Reduces MRSA Bacteremia

Background: Methicillin-resistant Staphylococcus aureus (MRSA) is highly prevalent in Singapore hospitals. The Ministry of Health (MOH) has set a reduction of MRSA bacteremia as a key performance indicator for publicly funded hospitals, resulting in the adoption of various strategies to achieve this goal. Decolonization regimens have been implemented in different institutions with variable outcomes. In Tan Tock Seng hospital (TTSH), octenidine was chosen instead of chlorhexidine for its gentler action on the skin, and nasal octenidine was chosen instead of mupirocin (which has a high resistance rate) for nasal decolonization. Methods: All patients admitted to TTSH are screened for MRSA on admission. Patients who are either colonized or infected with MRSA are either placed in isolation rooms (when available) or are placed in cohorts in MRSA wards. The Department of Infection Prevention and Control (IPC) keeps a database of all patients with positive cultures for MRSA, including bacteremia. We used this database to implement and evaluate targeted strategies in such MRSA wards. In January 2018 we began a pilot project in 1 ward, whereby all patients had intranasal octenidine gel applied twice a day for 5 days, as well as daily octenisan baths throughout their stay in the ward. The outcome of interest was MRSA bacteremia occurring ≥3 days after admission. This quasi-experimental before-and-after study was conducted from January 2016 to September 2019 with January 2018 excluded as a washout month. Results: In total, 44 observational months (24 months before the intervention 20 months after the intervention) and 4,309 patients were included. In the preintervention period, 12 bacteremia cases occurred among 2,333 patients (0.5%); in the postintervention period, 4 MRSA bacteremia cases occurred in 1,976 patients (0.2%): RR, 0.49 (95% CI, 0.13–1.22), 1-sided P = .07. The rate of MRSA bacteremia was halved, but it did not reach statistical significance due to the small number of cases overall. The products were well tolerated by patients and staff who applied them to nonambulant patients. Conclusions: Octenidine baths and nasal gel reduced risk of MRSA bacteremia in a cohort of MRSA-positive patients, and this strategy may be preferable to the universal use of antiseptic baths.Funding: NoneDisclosures: None

MRSA nares swab is a more accurate predictor of MRSA wound infection compared with clinical risk factors in emergency department patients with skin and soft tissue infections

ObjectivesSkin and soft tissue infections (SSTI) caused by methicillin-resistant Staphylococcus aureus (MRSA) are prevalent in the emergency department (ED). We determined whether MRSA nasal carriage better identifies patients with MRSA...

Subgroup Analysis of Antibiotic Treatment for Skin Abscesses

Two large randomized trials recently demonstrated efficacy of methicillin-resistant Staphylococcus aureus (MRSA)-active antibiotics for drained skin abscesses. We determine whether outcome advantages observed in one trial exist across lesion sizes and among subgroups with and without guideline-recommended antibiotic indications. We conducted a planned subgroup analysis of a double-blind, randomized trial at 5 US emergency departments, demonstrating superiority of trimethoprim-sulfamethoxazole (320/1,600 mg twice daily for 7 days) compared with placebo for patients older than 12 years with a drained skin abscess. We determined between-group differences in rates of clinical (no new antibiotics) and composite cure (no new antibiotics or drainage) through 7 to 14 and 42 to 56 days after treatment among subgroups with and without abscess cavity or erythema diameter greater than or equal to 5 cm, history of MRSA, fever, diabetes, and comorbidities. We also evaluated treatment effect by lesion size and culture result. Among 1,057 mostly adult participants, median abscess cavity and erythema diameters were 2.5 cm (range0.1 to 16.0 cm) and 6.5 cm (range 1.0 to 38.5), respectively; 44.3% grew MRSA. Overall, for trimethoprim-sulfamethoxazole and placebo groups, clinical cure rate at 7 to 14 days was 92.9% and 85.7%; composite cure rate at 7 to 14 days was 86.5% and 74.3%, and at 42 to 56 days, it was 82.4% and 70.2%. For all outcomes, across lesion sizes and among subgroups with and without guideline antibiotic criteria, trimethoprim-sulfamethoxazole was associated with improved outcomes. Treatment effect was greatest with history of MRSA infection, fever, and positive MRSA culture. Treatment with trimethoprim-sulfamethoxazole was associated with improved outcomes regardless of lesion size or guideline antibiotic criteria.

Differences in Pre- and Post-dischcarge Methicillin-resistant Staphylococcus aureus (MRSA) infection rates by colonization status in US Department of Veterans Affairs (VA) hospitals

BackgroundLittle is known about how MRSA infection rates differ between patients who are colonized on admission compared with those who acquire colonization during an inpatient stay. In addition, most studies focus on MRSA infections that are diagnosed prior to discharge while ignoring those that are identified post-discharge. The VA implemented an active surveillance program for MRSA in 2007 in which all inpatients are tested for MRSA on admission. This surveillance data along with the ability to follow patients longitudinally allowed us to estimate the difference in infection rates for those who import vs. those who acquire MRSA colonization during their stay and to characterize post-discharge MRSA infections.MethodsWe constructed a dataset of 3,659,911 acute care inpatient admissions to 125 VA hospitals nationwide between January 1, 2008 and December 31/2015 who had surveillance tests performed for MRSA carriage. Admissions were restricted to individuals with at least 365 days of VA activity prior to admission. We categorized these admissions into 3 groups: no colonization, importation, and acquisition based on MRSA test results throughout the admission. We then captured MRSA infections in these individuals prior to discharge and at 30 and 90 days post-discharge. Infections were defined as positive MRSA cultures taken from sterile sites (including blood, catheter site, or bone).ResultsDuring the 8-year period, we identified 4,037 total pre-discharge MRSA infections, 2,793 MRSA infections at 30 days post-discharge, and 7,018 infections at 90 days post-discharge. During the pre-discharge time period, patients who acquired MRSA carriage were more likely to progress to an infection prior to discharge than those who imported the pathogen (RR = 2.6, P < 0.001). For patients who acquired MRSA carriage, the percentage who progressed to infection prior to discharge decreased from 2.0% in 2010 to 1.4% in 2015. The results from our analyses can be found in Figures 1–3.ConclusionWe found that roughly half of post-discharge infections were in patients who acquired the organism pre-discharge. These may be preventable with optimal infection control. In addition, there were nearly twice as many post-discharge MRSA infections at 90 days than during the pre-discharge period.Disclosures All authors: No reported disclosures.

Endocarditis infecciosa derecha como primera manifestación de leucemia linfoblástica aguda en niños

IntroductionRight-sided infective endocarditis, represents from 5% to 10% of infective endocarditis in adults, which is less frequent in children. Case Series: Case 1A 12 year-old girl with fever and a history a left hip injury due to a fall. She developed breathing difficulties, shock, bilateral pneumonia, and cellulitis in the left hip. The blood cultures were positive for methicillin resistant Staphylococcus aureus (MRSA), as such that the echocardiogram showed growth in the tricuspid valve. Due to persistent bicytopenia, a bone marrow aspirate was performed, with acute lymphocytic leukaemia being diagnosed. She received vancomycin for six weeks and chemotherapy was subsequently started. Case 2A 5 year-old girl, with fever, breathing difficulties, a leukemoid reaction, and bicytopenia, developed shock with bilateral pneumonia, and hepato-splenomegaly, as well as positive blood cultures for MRSA. The echocardiogram showed growth in the tricuspid valve, and the bone marrow aspirate performed helped diagnose an acute lymphocytic leukaemia. The patient died. ConclusionRight-sided infective endocarditis, concomitant with MRSA, is reported in patients with acute lymphocytic leukaemia, a disease with a low reported incidence.

Attributable Mortality of Healthcare-Associated Infections Due to Multidrug-Resistant Gram-Negative Bacteria and Methicillin-Resistant Staphylococcus Aureus

OBJECTIVE The purpose of this study was to quantify the effect of multidrug-resistant (MDR) gram-negative bacteria and methicillin-resistant Staphylococcus aureus (MRSA) healthcare-associated infections (HAIs) on mortality following infection, regardless of patient location. METHODS We conducted a retrospective cohort study of patients with an inpatient admission in the US Department of Veterans Affairs (VA) system between October 1, 2007, and November 30, 2010. We constructed multivariate log-binomial regressions to assess the impact of a positive culture on mortality in the 30- and 90-day periods following the first positive culture, using a propensity-score-matched subsample. RESULTS Patients identified with positive cultures due to MDR Acinetobacter (n=218), MDR Pseudomonas aeruginosa (n=1,026), and MDR Enterobacteriaceae (n=3,498) were propensity-score matched to 14,591 patients without positive cultures due to these organisms. In addition, 3,471 patients with positive cultures due to MRSA were propensity-score matched to 12,499 patients without positive MRSA cultures. Multidrug-resistant gram-negative bacteria were associated with a significantly elevated risk of mortality both for invasive (RR, 2.32; 95% CI, 1.85-2.92) and noninvasive cultures (RR, 1.33; 95% CI, 1.22-1.44) during the 30-day period. Similarly, patients with MRSA HAIs (RR, 2.77; 95% CI, 2.39-3.21) and colonizations (RR, 1.32; 95% CI, 1.22-1.50) had an increased risk of death at 30 days. CONCLUSIONS We found that HAIs due to gram-negative bacteria and MRSA conferred significantly elevated 30- and 90-day risks of mortality. This finding held true both for invasive cultures, which are likely to be true infections, and noninvasive infections, which are possibly colonizations. Infect Control Hosp Epidemiol 2017;38:848-856.

Methicillin-resistant Staphylococcus aureus Screening PCR adapted to locally emerging variants—Evaluation of novel SCCmec primers

Infections with multi-resistant bacteria, such as Methicillin-resistant Staphylococcus aureus (MRSA), represent a world-wide health-care problem. The original MRSA Screening TaqMan PCR was based on the detection of the SCCmec-orfX-junction as described by the group of Huletsky in 2004. In the recent years, this assay increasingly failed to detect new MRSA variants in swab specimens. In this work, we analyzed the usefulness of 17 additional SCCmec primers to increase PCR sensitivity by testing 290 collected samples with negative PCR results and positive MRSA culture in a retrospective analysis, and 380 samples of the daily routine diagnostics. Sequencing of the PCR products revealed that locally new MRSA variants became detectable by nine of these forward primers. Four primers were solely responsible for the detection of 85.4% (117/123) of the PCR products: F13 (n=76), F11 (n=6), F14 (n=15) and F25 (n=8). These four primers were integrated in the Screening PCR and the novel primer collection was validated by testing 71 MRSA isolates, which covered SCCmec types I to VI, 50 MSSA isolates and 100 swab specimens. The sensitivity of MRSA Screening PCR increased from 93% to 98.6% without affecting the detection of the common MRSA strains. Phylogenetic analysis of the PCR products suggests that the adapted MRSA Screening PCR is able to detect SCCmec types I–X, including CA- and LA-MRSA variants by the SCCmec primers F11 and F25.

Evaluation of clinical outcome in children and adolescents receiving vancomycin for invasive infections due to methicillin-resistant Staphylococcus aureus: impact of increasing vancomycin MICs.

Vancomycin is the preferred drug for the treatment of methicillin-resistant Staphylococcus aureus (MRSA) infections in children. In adults, treatment failure with vancomycin has been associated with an area under the curve/24 hrs /MIC (AUC24/MIC) ratio of ≤400 and high minimum inhibitory concentrations (MIC ≥1.0 mg/L). Vancomycin dosing information to ensure optimal AUC24/MIC in the pediatric population remains limited. A retrospective chart review from August 2008 to 2011 and a prospective study from September 2011 to October 2013 was conducted on all pediatric patients at two hospitals in Brooklyn, NY with positive cultures for MRSA who received vancomycin. Treatment failure was defined as persistent positive cultures (≥5 days) or persistence of clinical symptoms. Vancomycin AUC24/MICs were calculated. Twenty-three children with MRSA infection, 0-18 years of age, were identified; 18 of 23 (78.3%) were community acquired. MICs of 91% of the isolates were ≥1.5 µg/mL and 9 had MICs of 2 µg/mL. Treatment failure was seen in 12 (52%) patients with MICs of 1.5 µg/mL and above. Vancomycin trough levels >15 µg/mL and AUC24/MIC >400 were achieved in only 18% and 0% of patients, respectively. High treatment failure rates with vancomycin was associated with MIC ≥1.5 µg/mL. Current recommended vancomycin dosing in children did not achieve a trough concentration of >15 µg/mL in majority of the patients and none achieved an AUC24/MIC>400.

Healthcare-associated pneumonia with positive respiratory methicillin-resistant Staphylococcus aureus culture: Predictors of the true pathogenicity.

Although methicillin-resistant Staphylococcus aureus (MRSA) is commonly isolated from respiratory specimens in healthcare-associated pneumonia (HCAP), it is difficult to determine the causative pathogen because of the possibilities of contamination/colonization. The present study aimed to identify clinical predictors of the true pathogenicity of MRSA in HCAP. Patients with HCAP with positive MRSA cultures in the sputum or endotracheal aspirates who were admitted to Seirei Mikatahara General Hospital, Hamamatsu, Japan, from 2009 to 2014 were enrolled. According to the administered drugs and the treatment outcomes, patients with true MRSA pneumonia (MP) and those with contamination/colonization of MRSA (false MP) were identified. Baseline characteristics were compared between groups, and clinical predictors of true MP were evaluated by logistic regression analyses. A total of 93 patients (mean age 78.7 ± 12.6 years) were identified and classified into the true MP (n = 16) or false MP (n = 77) groups. Although baseline characteristics were broadly similar between groups, the true MP group had significantly more patients with PaO2 ≤ 60 Torr/pulse oximetry saturation ≤90% and those with MRSA single cultivation. Both variables were significant predictors of true MP in multivariate analysis (odds ratio of PaO2 ≤ 60 Torr/pulse oximetry saturation ≤90%: 5.64, 95% confidence interval 1.17-27.32; odds ratio of MRSA single cultivation: 4.76, 95% confidence interval 1.22-18.60). Poor oxygenation and MRSA single cultivation imply the true pathogenicity of MRSA in HCAP with positive respiratory MRSA cultures. The present results might be helpful for the proper use of anti-MRSA drugs in this population. Geriatr Gerontol Int 2017; 17: 456-462.

Multicenter Observational Study on Factors and Outcomes Associated with Various Methicillin-Resistant Staphylococcus aureus Types in Children with Cystic Fibrosis.

Methicillin-resistant Staphylococcus aureus (MRSA) prevalence continues to increase in patients with cystic fibrosis (CF) in the United States, reaching 26.5% in 2012. Approximately 30% of strains are SCCmec (staphylococcal cassette chromosome mec) IV type, frequently USA300, which in the general population have different genotypic and phenotypic features than SCCmec II type. We hypothesized that risk factors for acquisition and outcomes in patients with CF differed for "health care-associated" (SCCmec II) versus "community-associated" (SCCmec IV) MRSA strains. To determine the role of SCCmec type and Panton-Valentine leukocidin (PVL), MRSA isolates from patients not more than 18 years old at seven CF centers were typed and the association of potential risk factors and subsequent clinical course was assessed, using data provided by the CF Patient Registry. Participants with chronic MRSA (295) had typeable isolates and clinical data; 205 (69.5%) had SCCmec II PVL(-), 39 (13.2%) had SCCmec IV PVL(-), and 51 (17.3%) had SCCmec IV PVL(+) strains. SCCmec IV, compared with SCCmec II, increased during the study period, 1996-2010 (P = 0.03). SCCmec II was associated with Pseudomonas aeruginosa-positive cultures and three or more clinic visits in the 6 months preceding the first positive MRSA culture (adjusted odds ratio, 2.05; 95% confidence interval, 1.13-3.74; P = 0.019). Lung function and anthropometrics remained unchanged in the 6 months after initial MRSA detection compared with the 6 months prior. Although CF care increased for participants in both groups in the 6 months after MRSA detection, inhaled antibiotics were prescribed more frequently in those with SCCmec II strains and increased hospitalizations occurred in those with SCCmec IV PVL(-) strains compared with those with PVL(+) strains (adjusted difference, 34.10%; 95% confidence interval, 7.58-60.61; P = 0.012). Participants in both groups had an increase in CF care in the 2 years after MRSA detection compared with the 2 years prior. Increased exposure to CF clinics and P. aeruginosa may constitute risk factors for acquisition of SCCmec II MRSA strains. Clinical interventions increased 6 months and 2 years after initial MRSA detection regardless of SCCmec type.

The impact of healthcare-associated methicillin-resistant Staphylococcus aureus infections on post-discharge healthcare costs and utilization.

Healthcare-associated methicillin-resistant Staphylococcus aureus (MRSA) infections are a major cause of morbidity, mortality, and cost among hospitalized patients. Little is known about their impact on post-discharge resource utilization. The purpose of this study was to estimate post-discharge healthcare costs and utilization attributable to positive MRSA cultures during a hospitalization. Our study cohort consisted of patients with an inpatient admission lasting longer than 48 hours within the US Department of Veterans Affairs (VA) system between October 1, 2007, and November 30, 2010. Of these patients, we identified those with a positive MRSA culture from microbiology reports in the VA electronic medical record. We used propensity score matching and multivariable regression models to assess the impact of positive culture on post-discharge outpatient, inpatient, and pharmacy costs and utilization in the 365 days following discharge. Our full cohort included 369,743 inpatients, of whom, 3,599 (1.0%) had positive MRSA cultures. Our final analysis sample included 3,592 matched patients with and without positive cultures. We found that, in the 12 months following hospital discharge, having a positive culture resulted in increases in post-discharge pharmacy costs ($776, P<.0001) and inpatient costs ($12,167, P<.0001). Likewise, having a positive culture increased the risk of a readmission (odds ratio [OR]=1.396, P<.0001), the number of prescriptions (incidence rate ratio [IRR], 1.138; P<.0001) and the number of inpatient days (IRR, 1.204; P<.0001,) but decreased the number of subsequent outpatient encounters (IRR, 0.941; P<.008). The results of this study indicate that MRSA infections are associated with higher levels of post-discharge healthcare cost and utilization. These findings indicate that financial benefits resulting from infection prevention efforts may extend beyond the initial hospital stay.

Duration of Colonization With Methicillin-Resistant Staphylococcus aureus: A Question With Many Answers

Duration of Colonization With Methicillin-Resistant Staphylococcus aureus: A Question With Many Answers