Methicillin-resistant Staphylococcus Aureus Culture Research Articles

Evaluation of Gram Stain-Guided Antibiotic Therapy for Methicillin-Resistant Staphylococcus aureus Pneumonia in Intensive Care Unit Patients.

Background: Despite high negative predictive values (NPVs) seen with methicillin-resistant Staphylococcus aureus (MRSA) nares polymerase chain reaction (PCR) assays, utilization of both respiratory sample Gram stain and MRSA nares PCR in patients with pneumonia may contribute to overuse of laboratory resources. The purpose of this study was to evaluate if a Gram stain demonstrating no Gram-positive organisms from a respiratory sample is sufficient to allow for de-escalation of vancomycin therapy. Methods: This single center study retrospectively identified intensive care unit (ICU) patients started on vancomycin for presumed pneumonia at University of Wisconsin (UW) Health in Madison, WI between August 2022 and March 2023. Patients with respiratory sample demonstrating no Gram-positives on Gram stain met inclusion criteria if the sample was ordered within 24 h of vancomycin initiation. The primary outcome was NPV of respiratory sample Gram stain demonstrating no Gram-positive organisms with respect to MRSA detection of the respiratory culture. Secondary outcomes included the NPV of combined MRSA nares PCR plus respiratory sample Gram stain, and difference in time to event in patients that had both a respiratory sample and MRSA nares PCR ordered. Results: A total of 370 patients were screened for study eligibility; of which 99 patients met inclusion criteria. NPV of respiratory sample Gram stain was 99% for MRSA culture. The combined NPV of respiratory sample Gram stain plus MRSA nares PCR was 98.9% for MRSA culture (n = 88). Respiratory sample was ordered 2.3 h faster compared to MRSA nares PCR (4.3 vs 6.6 h, P = .036). Respiratory sample Gram stain resulted 4.5 h faster compared to MRSA nares PCR (10.7 vs 15.2 h, P = .002). Conclusion: Respiratory sample Gram stains demonstrating no Gram-positive organisms may be used to de-escalate vancomycin and deprioritize the use of MRSA nares PCR.

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.

Nasal Methicillin-Resistant Staphylococcus aureus Culture Screens in the Setting of Universal Decolonization

Introduction The negative predictive value (NPV) of nasal methicillin-resistant Staphylococcus aureus (MRSA) screens has been compromised by universal decolonization practices. We aimed to determine the reliability of the nasal MRSA culture screen to deescalate antibiotic therapy in the setting of decolonization with ethyl alcohol. Methodology A retrospective observational cohort study was conducted using 62% ethanol solution intranasally per protocol. Patients were divided into 2 groups based on whether they received decolonization. Data were analyzed to determine NPV of the nasal MRSA culture screen with and without decolonization. Results A total of 505 cases were screened, and 128 subjects were included. One hundred two received decolonization, whereas 26 did not. Baseline characteristics were well balanced. Overall MRSA infection prevalence was 31.25%. The NPV was 73% in the decolonized group compared with 80% in the group without. Positive predictive value was 63% in the group receiving decolonization compared with 100% in the group without. There was also a higher specificity but lower sensitivity of the nasal MRSA culture screen in the decolonization group. Nine patients in the decolonization group required reescalation of antibiotics compared with nil in the other group. Conclusions Culture-based nasal MRSA screens are less accurate than PCR tests, as ethyl alcohol leads to false-negative results. A lower NPV in the decolonization group predisposes to increased false negative results, leading to inappropriate antibiotic deescalation and often requiring reinitiation. Nasal MRSA culture screen is less reliable if alcohol has already been administered for decolonization and cannot be used as an appropriate tool to guide antibiotic deescalation.

1223. Utilizing Multiple Antimicrobial Stewardship Metrics to Trend Vancomycin Use in an Implementation Study

Abstract Background Inpatient IV vancomycin use is often inappropriately prolonged. Methicillin-resistant Staphylococcus aureus (MRSA) polymerase chain reaction (PCR) nares swabs have shown high negative predictive values for many infections and can guide appropriate vancomycin de-escalation. Antibiotic stewardship programs (ASPs) often monitor vancomycin use in days of therapy (DoT) per 1000 patient days present (PDP). This measure can be affected, especially for smaller facilities, by changes in bed capacity and prolonged stays and thus may not accurately reflect vancomycin use. We evaluated whether alternative metrics of vancomycin use would show different impacts during a multi-step ASP intervention to reduce inappropriate vancomycin use at Veterans Affairs Tennessee Valley Healthcare System. Figure 1 Run chart of vancomycin DoT/1000 PDP at the Tennessee Valley Healthcare System (TVHS) in two years prior to intervention. Methods In September 2021, the ASP, with multiple stakeholders, initiated use of MRSA nasal swabs to inform vancomycin de-escalation. From 7/2022 to 3/2023, we performed iterative Plan-Do-Study-Act intervention cycles including educating medicine and surgical divisions on MRSA swab result interpretation, educating nurses on timely swab collection, replacing MRSA culture swabs with PCR swabs, and adding MRSA swab orders to vancomycin order sets. In April 2022, in addition to DoT/1000 PDP, we began measuring mean, median, and mode DoT per vancomycin course initiated by start week. Results Despite multiple interventions beginning July 2022, vancomycin use in DoT/1000 PDP increased to a peak of 106 DoT/1000 PDP in September 2022. In that same period, median and mode DoT per vancomycin initiation remained steady at 2 days and 1 day, respectively. Figure 2 Run chart of vancomycin DoT/1000 PDP at the TVHS from April 2022 to March 2023. Specific ASP interventions are annotated on the dates they occur. Figure 3 Run chart of mean, median, and mode days of vancomycin therapy per vancomycin course initiated at the TVHS from April 2022 to March 2023. Specific ASP interventions are annotated on the dates they occur. Conclusion DoT/1000 PDP may not be the best metric to evaluate efforts to reduce inappropriate vancomycin use. By tracking mean, median, and mode of DoT per individual vancomycin course, we determined that most providers already practice rapid de-escalation, minimizing patient vancomycin exposure. This method also allows us to quickly detect changes in prescribing patterns and determine whether interventions were warranted. More evaluation of antibiotic use metric appropriateness based on desired outcome is needed in ASPs. Disclosures Milner Staub, MD, MPH, Gilead: Stocks/Bonds|Johnson & Johnson: Stocks/Bonds

Comparison of risk factors for Methicillin Resistant Staphylococcus aureus (MRSA) colonization in healthy newborns, born to mothers with and without MRSA colonization.

To compare the risk factors for MRSA colonization in healthy newborns, born of mothers with and without MRSA colonization. This case control study was conducted in post-natal unit of Lady Willingdon Hospital, affiliated with King Edward Medical University/Mayo Hospital, Lahore from January to June 2017. The vaginal and anterior nares swabs for MRSA culture were collected from mothers within six hours before planned delivery and the neonatal anterior nares swabs for MRSA culture were taken within one hour of birth. All the samples were cultured in Paediatric Microbiology laboratory in Mayo Hospital. Data were analyzed through SPSS 20.0 and logistic regression was applied for risk factors analysis. Out of total 80 mothers and their newborns, 15 (18.75%) mothers and 16 neonates (20%) were MRSA colonized. The frequency of MRSA colonization in mothers' anterior nares and vaginal swab was 17.5% and 1.25% respectively. The significant risk factors were prolonged rupture of membranes for >18 hours (p-value 0.02, odds ratio 11.85, 95% CI 1.41-99.3), birth weight <2500 grams (p-value 0.01, odds ratio 5.39, 95% CI 1.35-21.4), history of presence of meconium (p-value 0.006, odds ratio 7.30, 95% CI 1.78-29.8). The non-significant factors were age of mother (p-value 0.682, odds ratio 0.765, 95% CI 1.0.212-2.76), parity (p-value 0.185, odds ratio 3.82, 95% CI 0.46-31.66) , gestation (p-value 0.615, odds ratio 0.797, 95% CI 0.714-0.89) , mode of delivery (p-value 0.576, odds ratio 0.543, 95% CI 0.062-4.76), sex of baby (p-value 0.546, odds ratio 0.683, 95% CI 0.196-2.37) and presentation of baby at birth (p-value 0.47, odds ratio 0.795, 95% CI 0.71-0.89). The presence of meconium, prolonged rupture of membranes and low birth weight were the significant risk factors for MRSA colonization in healthy new-borns, born to mothers with and without MRSA colonization.

MRSA PCR improves sensitivity of detection of colonization in neonates

Background: Neonates colonized with methicillin-resistant Staphylococcus aureus (MRSA) are at high risk of developing life-threatening MRSA infection. Due to lack of evidence, national guidelines do not currently recommend a specific methodology for detecting MRSA colonization. We hypothesize that surveillance for MRSA colonization via polymerase chain reaction (PCR) is superior to culture for the detection of colonization. Methods: In this retrospective study, we compared results of MRSA surveillance by 2 methodologies, culture and PCR, after implementation of an MRSA surveillance and decolonization protocol in the Texas Children’s Hospital Pavilion for Women, a 42-bed neonatal intensive care unit. MRSA colonization of 3 body sites via the 2 methodologies was assessed from June 2017 through December 2020. All neonates were screened for MRSA upon admission to the NICU and weekly thereafter until MRSA-positive or discharged. Swab specimens were initially tested by PCR (Xpert MRSA NxG, Cepheid) and when MRSA-positive reflexed to culture to recover the organism for further characterization. This study was approved through the Baylor College of Medicine Institutional Review Board. Results: During the study period, 2,351 neonates were assessed for MRSA colonization by PCR; 81 (3.4%) infants were PCR positive (Fig. 1). Of those 81, 57 (70.4%) had concordant MRSA PCR and culture results, and 24 (29.6%) were MRSA PCR positive but no isolate was recovered in culture. Also, 8 specimens were indeterminate by PCR. However, 1 infant who was negative by culture but was PCR positive developed an MRSA orbital infection. Compared to PCR, the overall sensitivity of MRSA culture was 70.4% (range, 57.7%–80.8%, depending on the year) (Table 1). Conclusions: PCR is more sensitive than culture for detecting MRSA colonization in neonates. Utilizing a PCR method enhances the ability to identify MRSA colonized infants more readily and allows for prompt initiation of infection control interventions including isolation precautions and decolonization strategies. Reflex to culture remains important for strain characterization during outbreak investigations and for additional susceptibility testing. Resource utilization and cost–benefit analyses should be done in future studies to influence changes in national guidelines for the control of Staphylococcus aureus colonization and infection in neonatal intensive care units.Disclosures: None

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 &lt;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 &gt;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

Clinical utility of methicillin-resistant Staphylococcus aureus nasal PCR to streamline antimicrobial use in treatment of diabetic foot infection with or without osteomyelitis

BackgroundDiabetic Foot Infection (DFI) guidelines recommend empiric methicillin-resistant Staphylococcus aureus (MRSA)-targeted therapy in settings where there is high prevalence of MRSA infections or in cases of severe infection; however, they do not provide recommendations for de-escalation. This approach has the potential to increase unnecessary use of broad-spectrum antibiotics; therefore, additional strategies are needed to optimize appropriate antibiotic use. This study evaluates the effect of MRSA nasal PCR testing on MRSA-targeted antibiotic use and clinical outcomes in patients with DFI.MethodsThis was a retrospective quasi-experimental study of patients admitted to South Texas Veterans Health Care System for DFI, with or without osteomyelitis (OM), who had an MRSA nasal PCR and culture data. Eligible patients were identified from the Corporate Data Warehouse and reviewed via electronic health record. Patients were allocated into two groups: PRE (5/1/2019-4/30/2020) and POST (12/1/2020-11/30/2021) protocol implementation for de-escalation or avoidance of MRSA-targeted antibiotics. The primary outcome was median (interquartile range [IQR]) hours of empiric inpatient MRSA-targeted antibiotic therapy. A Wilcoxon Rank Sum test was used to assess the difference between the groups for the primary outcome. Secondary outcomes included the proportion of patients needing MRSA coverage added back for MRSA after de-escalation, hospital readmission, length of hospital stay (LOS), patient mortality, and acute kidney injury.ResultsA total of 151 patients were included (83 PRE; 68 POST). Most patients were male (98% PRE; 97% POST) with a median age of 64 (IQR, 56–72) years. Incidence of MRSA in DFI in the cohort was 14.7% overall (12% PRE and 17.6% POST). MRSA was detected via nasal PCR in 12% of patients 15.7% PRE and 7.4% POST). After protocol implementation, there was a significant decrease in empiric MRSA-targeted antibiotic therapy use, from a median of 72 (IQR, 27–120) hours in the PRE group, to 24 (IQR, 12–72) hours in the POST group (p < 0.01). No significant differences were found for other secondary outcomes.ConclusionThis study of patients presenting to a Veterans Affairs (VA) hospital with DFI identified a statistically significant decrease in median duration of MRSA-targeted antibiotic use post-protocol implementation. This suggests a favorable effect of MRSA nasal PCR for de-escalation or avoidance of MRSA-targeted antibiotics in DFI.

Pathogenic Role and Antibiotic Resistance of Methicillin-Resistant Staphylococcus aureus (MRSA) Strains Causing Severe Community-Acquired Pneumonia in Vietnamese Children.

In recent years, the pathogenic role and antibiotic resistance of methicillin-resistant Staphylococcus aureus (MRSA) strains causing severe community-acquired pneumonia (CAP) have received increasing attention in clinical practice. The aim of this study was to determine the rate of isolates of MRSA strains causing severe CAP in children and to assess their level of antibiotic resistance. The study design was cross-sectional. Children with severe CAP were sampled by nasopharyngeal aspiration for the culture, isolation, and identification of MRSA. Antimicrobial susceptibility testing was performed using the gradient diffusion method to determine the minimum inhibitory concentration (MIC) of antibiotics. Results: MRSA was identified as the second leading cause of severe CAP in Vietnamese children. The rate of isolates of S. aureus was 41/239 (17.5%), of which most were MRSA, at 32/41 (78.0%). MRSA strains were completely non-susceptible to penicillin (100%), more resistant to clindamycin and erythromycin, less sensitive to ciprofloxacin and levofloxacin, and fully susceptible to vancomycin and linezolid, with a 32-fold decreased MIC90 for vancomycin (0.5 mg/L) and a 2-fold decreased MIC90 for linezolid (4 mg/L). Therefore, vancomycin and linezolid may be appropriate options for severe CAP identified by MRSA.

Effects of Discontinuation of Weekly Surveillance Testing on Methicillin-Resistant Staphylococcus aureus in the NICU.

Methicillin-resistant Staphylococcus aureus (MRSA) infection is a major cause of serious morbidity and mortality in the neonatal intensive care unit (NICU). There is no clear consensus on infection control measures. Some approaches to MRSA colonization management may be burdensome with unclear benefits. The objective of this study was to determine if stopping weekly MRSA surveillance with active detection and contact isolation (ADI) was associated with a change in infection rate. This is a retrospective cohort study of infants admitted to two affiliated NICUs. The ADI cohort infants received weekly nasal MRSA cultures and were placed in contact isolation if MRSA colonized for the duration of their hospitalization. The No Surveillance cohort infants were only placed in isolation if there was active MRSA infection or if MRSA colonization was identified incidentally. The rates of infection were determined between the cohorts. There were 8,406 neonates representing 193,684 NICU days in the comparison period. In the ADI cohort, MRSA colonization occurred in 3.4% of infants and infection occurred in 29 infants (0.4%). There were no differences between cohorts in the percent of infants with a MRSA infection at any site (0.5 vs. 0.5%, p = 0.89), rate of MRSA infections per 1,000 patient-days (0.197 vs. 0.201, p = 0.92), rate of bloodstream infections (0.12 vs. 0.26%, p = 0.18), or in the overall mortality rate (3.7 vs. 3.0% p = 0.13). ADI represented an annual cost of $590,000. The rates of MRSA infection did not change when weekly ADI was discontinued and was associated with a decrease in cost and resource utilization. · Placing MRSA-colonized infants in contact isolation is a common practice.. · Data are limited with respect to efficacy in the NICU.. · This study provides evidence that active detection and contact isolation for MRSA colonization may not be beneficial..

Clinical Characteristics and Microbial Profiles of Paediatric Patients with Methicillin-Resistant Staphylococcus aureus Pneumonia in China

Background: Staphylococcus aureus can cause fatal pneumonia. The evolution of bacteria and the overuse of antibiotics have enhanced the drug resistance of methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-sensitive Staphylococcus aureus (MSSA). Objectives: This study aimed to recapitulate the microbiological profile and clinical characteristics of paediatric patients with MRSA. Methods: This retrospective study was conducted to investigate 1372 paediatric patients with S. aureus pneumonia from January 2017 to December 2021. Sputum specimens were collected and processed for performing bacterial culture and drug sensitivity tests. Medical records of patients were reviewed for clinical characteristics and laboratory examination results. Results: The MRSA and MSSA pneumonia mainly occurred in infants; however, comparisons of sex, age, and sampling time between patients with MRSA and MSSA pneumonia showed no significant differences (P &gt; 0.05). The results of drug sensitivity in sputum culture revealed that all MRSA and MSSA isolates were susceptible to vancomycin, tigecycline, linezolid, teicoplanin, and ceftaroline. Methicillin-sensitive Staphylococcus aureus was completely sensitive to rifampicin and oxacillin. Methicillin-resistant Staphylococcus aureus was completely resistant to penicillin and oxacillin, while MSSA was less sensitive to penicillin. Methicillin-resistant Staphylococcus aureus and MSSA both maintained high sensitivity rates to gentamicin, sulfamethoxazole-trimethoprim, levofloxacin, and moxifloxacin, with the exception of clindamycin and erythromycin. According to our results, moreover, the sensitivity of MRSA to gentamicin and sulfamethoxazole-trimethoprim was significantly higher than that of MSSA (P &lt; 0.05). The common symptoms of patients with S. aureus pneumonia were fever, cough, and wheezing. patients with MRSA pneumonia had significantly higher counts of white blood cells (WBCs), C-reactive protein (CRP), and procalcitonin (PCT) than patients with MSSA pneumonia (P &lt; 0.05). Conclusions: The results of antimicrobial sensitivity test in sputum culture of MRSA and MSSA isolates can reflect the sensitivity of antibiotics and guide the use of clinical antibiotics. Infectious biomarkers can reflect the severity of infection and guide prognosis.

Use of nares swab to de-escalate vancomycin for patients with suspected methicillin-resistant Staphylococcus aureus.

According to the US Center for Disease Control and Prevention, 30%-50% of antibiotic use in hospitals is unnecessary or inappropriate. The coronavirus disease 2019 pandemic further complicates antibiotic use leading to greater initiation of empiric antibiotics. The result is antibiotic overuse and increased duration of unnecessary therapy. Vancomycin is a drug of last resort, primarily relegated to the treatment of Methicillin-Resistant Staphylococcus aureus (MRSA). De-escalating vancomycin can mean waiting on MRSA culture results, which may take up to 96 h. Nares screening for MRSA is shown to possess high negative predictive value for ruling out suspected MRSA pneumonia, intra-abdominal infections, and bacteremia. This before-and-after study examines the impact of vancomycin therapy de-escalation due to absence of MRSA colonization detected via PCR assay of nares swabs. An intervention with providers using SMART goals was designed to increase nasal swabbing for MRSA and ultimately decrease vancomycin use at a large, tertiary-care urban hospital. There was a significant increase in use of vancomycin nares swabs (28/150 vs 48/100, p = 0.040) in the immediate pre/postintervention period, and significant decreases in vancomycin usage days/1,000 patient days of 2.34% per month (p = 0.039) over a two year period after the intervention. An intervention using PCR nares swabs to detect MRSA led to significant, lasting decreases in vancomycin usage at this hospital. Similar interventions should be planned at hospitals experiencing overuse of this antibiotic.

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.

Methicillin-Resistant Staphylococcus aureus Membrane Vesicles Inhibit the Proliferation and Induce the Apoptosis of Epithelial Cells.

Staphylococcus aureus, or methicillin-resistant Staphylococcus aureus (MRSA), is the predominant pathogen in skin and soft tissue infections (SSTIs), and MRSA membrane vesicles (MVs) play a pivotal role in bacterial pathogenesis and the modulation of the host immune response. We aimed to investigate the interaction between MRSA MVs and epithelial cells. In this study, MVs were isolated from an MRSA culture supernatant using the ELD method, comprising an electrophoretic technique used in combination with a 300 kDa cut-off dialysis bag. The proteomic analysis of the MRSA MVs via mass spectrometry showed that shared and distinct proteins exist in the MVs from clinical MRSA isolates with different genetic backgrounds, such as health-care-associated MRSA (HA-MRSA) and community-associated MRSA (CA-MRSA). These MRSA MVs were found to suppress the proliferation and increase the apoptosis of HaCaT cells. We conducted qPCR array, quantitative real-time PCR (qRT-PCR), and Western blotting (WB) analyses, and the results indicated that BCL2 antagonist/killer 1 (Bak1) may be involved in the apoptosis of HaCaT epithelial cells. Our findings suggest that MRSA MVs inhibit the proliferation and induce the apoptosis of epithelial cells.

Wound swabs versus biopsies to detect methicillin resistant Staphylococcus aureus in experimental equine wounds.

To compare: (1) the load and diversity of cultivatable bacterial species isolated from tissue biopsies with cultures from surface swabs, and (2) the ability of each technique to detect methicillin-resistant Staphylococcus aureus (MRSA) in a model of MRSA-infected equine wounds. Experimental in vivo study. Three light-breed adult horses. Four 2.5 × 2.5cm full-thickness skin wounds were created on the dorsolateral aspect of each forelimb. Five days later, each wound was inoculated with a pure culture of MRSA (ATCC 43300). One hundred microlitres of 0, 5 × 108 , 5 × 109 or 5 × 1010 colony forming units (CFU)/ml was used to inoculate each wound. Surface swabs (Levine technique) and tissue biopsy samples (3 mm punch biopsy) were obtained at 2, 7, 14, and 21 days after inoculation. Quantitative aerobic culture was performed using routine clinical techniques. A similar bacterial profile was identified from the culture of each wound-sampling technique and there was moderate correlation (R=0.49, P < .001) between the bacterial bioburdens. Agreement was fair (κ=0.31; 95% CI, 0.129-0.505) between the sampling techniques in identification of MRSA. Methicillin-resistant Staphylococcus aureus was isolated more frequently (P=.016) from cultures of tissue biopsies (79%; 76/96) than from surface swabs (62%; 60/96). Bacterial load and diversity did not differ between sampling techniques but MRSA was detected more often from the cultures of tissue biopsies. Tissue biopsy should be preferred to culture swab in wounds where MRSA is suspected.

18β-Glycyrrhetinic Acid Induces Metabolic Changes and Reduces Staphylococcus aureus Bacterial Cell-to-Cell Interactions.

The rise in bacterial resistance to common antibiotics has raised an increased need for alternative treatment strategies. The natural antibacterial product, 18β-glycyrrhetinic acid (GRA) has shown efficacy against community-associated methicillin-resistant Staphylococcus aureus (MRSA), although its interactions against planktonic and biofilm modes of growth remain poorly understood. This investigation utilized biochemical and metabolic approaches to further elucidate the effects of GRA on MRSA. Prolonged exposure of planktonic MRSA cell cultures to GRA resulted in increased production of staphyloxanthin, a pigment known to exhibit antioxidant and membrane-stabilizing functions. Then, 1D 1H NMR analyses of intracellular metabolite extracts from MRSA treated with GRA revealed significant changes in intracellular polar metabolite profiles, including increased levels of succinate and citrate, and significant reductions in several amino acids, including branch chain amino acids. These changes reflect the MRSA response to GRA exposure, including potentially altering its membrane composition, which consumes branched chain amino acids and leads to significant energy expenditure. Although GRA itself had no significant effect of biofilm viability, it seems to be an effective biofilm disruptor. This may be related to interference with cell–cell aggregation, as treatment of planktonic MRSA cultures with GRA leads to a significant reduction in micro-aggregation. The dispersive nature of GRA on MRSA biofilms may prove valuable for treatment of such infections and could be used to increase susceptibility to complementary antibiotic therapeutics.

Prospective surveillance of colonization and disease by methicillin-resistant Staphylococcus aureus (MRSA) at a European pediatric cancer center

PurposeChildren and adolescents undergoing treatment for cancer or allogeneic hematopoietic cell transplantation are at increased risk for methicillin-resistant Staphylococcus aureus (MRSA). We therefore examined the occurrence and outcome of MRSA colonization and infection in patients of a large European pediatric cancer center.MethodsIn a prospective observational cohort study conducted between 2007 and 2018, nasopharyngeal swabs for culture of MRSA were obtained from all admitted patients. The primary endpoint of the study was the colonization rate over time. Secondary endpoints included genetic relatedness of isolates, time burden of isolation measures, and results of decolonization efforts.ResultsDuring the study period, MRSA screening identified 34 colonized patients (median age: 10 years; range: 0–21) without trends over time. MRSA colonization was associated with the presence of classical risk factors. There was no molecular evidence of patient-to-patient transmission. A standard MRSA eradication regimen led to a lasting eradication of the organism in 26 of 34 patients. MRSA infection occurred in two patients with no associated fatalities.ConclusionProspective monitoring revealed low rates of MRSA colonization and infection at our center. These low rates and the absence of patient-to-patient transmission support the effectiveness of the management bundle of MRSA identification, isolation, and decolonization.

Antimicrobial Effect of Syzygium cumini Extract Against Methicillin Non-Susceptible Staphylococcus aureus

Background: Methicillin-resistant Staphylococcus aureus (MRSA) is a leading cause of infections in Community- Associated (CA) as well as Hospital-Associated (HA) settings. Identification of new antibacterial agents from natural sources takes the forefront in research. Objectives: The aim of the present study was to identify the resistance pattern of S. aureus in the clinical samples causing disease in Dhaka city, molecular typing of the methicillin non-susceptible S. aureus isolates and identifying new herbal components with anti-microbial effect against S. aureus. Methods: We screened total of 78 clinical specimen of various nature (pus, urine, tracheal aspirate, conjunctiva and wound swab) with confirm S. aureus infection between March 2018 to October 2018. The specimen were cultured on mannitol salt agar to isolate S. aurues, which were later tested for antibiotic resistance according to disc diffusion method. The MRSA isolates were confirmed with PCR and typed for SCCmec element to know the distribution of hospital-associated and community-associated strains. Finally, the MRSA isolates were cultured in the presence of leaf extract and fruit extract of Syzygium cumini for observing the antibacterial potential. Result: A total of 12 isolates of S. aureus were found to be non-susceptible to methicillin, 34%, 25%, 17% out of these were from pus, blood and urine respectively and 8% isolates were from wound swab, conjunctiva and tracheal aspirates each. Out of methicillin non-susceptible isolates, 25% and 16% were HA-MRSA and CAMRSA respectively, as seen from PCR analysis of the SCCmec gene cassette of the S. aureus genome. The rest of the 59% of the isolates were untypable. Overall, higher concentration of leaf and fruit extract reduced the optical density of MRSA culture and reduced bacterial growth in drop plate significantly. Conclusion: Dhaka population has S. aureus with varying sensitivity against methicillin, which needs further characterization by molecular epidemiology methods. Bangladesh Med Res Counc Bull 2021; 47(1): 82-89