MRSA colonization status as a predictor of clinical infection: A systematic review and meta-analysis

Hospital-acquired bacterial pneumonia in critically ill patients: from research to clinical practice

INTRODUCTION

Hospital-acquired pneumonia (HAP) represents a significant cause of mortality among critically ill patients admitted to Intensive Care Units (ICUs). Timely and precise diagnosis is imperative to enhance therapeutic efficacy and patient outcomes. However, the diagnostic process is challenged by test limitations and a wide-ranging list of differential diagnoses, particularly in patients exhibiting escalating oxygen requirements, leukocytosis, and increased secretions.

AREAS COVERED

This narrative review aims to update diagnostic modalities, facilitating the prompt identification of nosocomial pneumonia while guiding, developing, and assessing therapeutic interventions. A comprehensive literature review was conducted utilizing the MEDLINE/PubMed database from 2013 to April 2024.

EXPERT OPINION

An integrated approach that integrates clinical, microbiological, and imaging tools is paramount. Progress in diagnostic techniques, including novel molecular methods, the expanding utilization and accuracy of bedside ultrasound, and the emergence of Artificial Intelligence, coupled with an improved comprehension of lung microbiota and host-pathogen interactions, continues to enhance our capability to accurately and swiftly identify HAP and its causative agents. This advancement enables the refinement of treatment strategies and facilitates the implementation of precision medicine approaches.

Predictive Value of Methicillin-Resistant Staphylococcus aureus Nasal Swab PCR Assay for MRSA Infection in Critically Ill Pediatric Patients

BACKGROUND

Critically ill pediatric patients are frequently initiated methicillin-resistant Staphylococcus aureus (MRSA) active antibiotics during infection evaluation even though MRSA infections are rare in many patient populations. The MRSA nasal swab polymerase chain reaction assay (MRSA-NS-PCR) is a test that has been shown to have a high negative predictive value (NPV) for MRSA infection in adults. This study evaluated the diagnostic test characteristics of the MRSA-NS-PCR in predicting the presence of MRSA infection in critically ill pediatric patients.

STUDY DESIGN

A retrospective cohort study was performed in a 44-bed pediatric intensive care unit (PICU) between 2013 and 2017. 3860 pediatric patients (54% male, median age 4 years [IQR 1-11 years]) admitted to the PICU who met pediatric systemic inflammatory response syndrome (pSIRS) criteria, were screened with a MRSA-NS-PCR, and had cultures obtained within seven days of MRSA-NS-PCR collection were included. Predictive values and post-test probabilities of the MRSA-NS-PCR for MRSA infection were calculated.

RESULTS

MRSA-NS-PCR was positive in 8.6% of patients. MRSA infection was identified in 40 patients, equaling an incidence rate of 2 per 1000 patient days. The MRSA-NS-PCR demonstrated a positive predictive value (PPV) of 9.7%, a NPV of 99.8%, and a post-test probability for a negative test of 0.2% for MRSA infection.

CONCLUSIONS

The MRSA-NS-PCR has a poor PPV but a high NPV for MRSA infection in PICU patients when the incidence of MRSA infection is low. Creation of protocols to guide antimicrobial selection based on MRSA-NS-PCR results may lead to improved antimicrobial stewardship and significant risk reduction.

Risk factors for prolonged mechanical ventilation in critically ill patients with influenza-related acute respiratory distress syndrome

BACKGROUND

Patients with influenza-related acute respiratory distress syndrome (ARDS) are critically ill and require mechanical ventilation (MV) support. Prolonged mechanical ventilation (PMV) is often seen in these cases and the optimal management strategy is not established. This study aimed to investigate risk factors for PMV and factors related to weaning failure in these patients.

METHODS

This retrospective cohort study was conducted by eight medical centers in Taiwan. All patients in the intensive care unit with virology-proven influenza-related ARDS requiring invasive MV from January 1 to March 31, 2016, were included. Demographic data, critical illness data and clinical outcomes were collected and analyzed. PMV is defined as mechanical ventilation use for more than 21 days.

RESULTS

There were 263 patients with influenza-related ARDS requiring invasive MV enrolled during the study period. Seventy-eight patients had PMV. The final weaning rate was 68.8% during 60 days of observation. The mortality rate in PMV group was 39.7%. Risk factors for PMV were body mass index (BMI) > 25 (kg/m2) [odds ratio (OR) 2.087; 95% confidence interval (CI) 1.006-4.329], extracorporeal membrane oxygenation (ECMO) use (OR 6.181; 95% CI 2.338-16.336), combined bacterial pneumonia (OR 4.115; 95% CI 2.002-8.456) and neuromuscular blockade use over 48 h (OR 2.8; 95% CI 1.334-5.879). In addition, risk factors for weaning failure in PMV patients were ECMO (OR 5.05; 95% CI 1.75-14.58) use and bacteremia (OR 3.91; 95% CI 1.20-12.69).

CONCLUSIONS

Patients with influenza-related ARDS and PMV have a high mortality rate. Risk factors for PMV include BMI > 25, ECMO use, combined bacterial pneumonia and neuromuscular blockade use over 48 h. In addition, ECMO use and bacteremia predict unsuccessful weaning in PMV patients.

Profiling of serum factors associated with Staphylococcus aureus skin and soft tissue infections as a foundation for biomarker identification

Background

People living in close quarters, such as military trainees, are at increased risk for skin and soft tissue infections (SSTI), especially those caused by methicillin-resistant Staphylococcus aureus (MRSA). The serum immune factors associated with the onset of SSTI are not well understood.

Methods

We conducted a longitudinal study of SSTIs, enrolling US Army trainees before starting military training and following up for 14 weeks. Samples were collected on Day 0, 56, and 90. Serum chemokines and cytokines among 16 SSTI cases and 51 healthy controls were evaluated using an electro-chemiluminescence based multiplex assay platform.

Results

Of 54 tested cytokines, 12 were significantly higher among SSTI cases as compared to controls. Among the cases, there were correlations between factors associated with vascular injury (i.e., VCAM-1, ICAM-1, and Flt1), the angiogenetic factor VEGF, and IL-10. Unsupervised machine learning (Principal Component Analysis) revealed that IL10, IL17A, C-reactive protein, ICAM1, VCAM1, SAA, Flt1, and VGEF were indicative of SSTI.

Conclusion

The study demonstrates the power of immunoprofiling for identifying factors predictive of pre-illness state of SSTI thereby identifying early stages of an infection and individuals susceptible to SSTI.

Effectiveness of a low trough serum concentration of vancomycin on acute kidney injury in infants and toddlers in the paediatric intensive care unit

OBJECTIVE

This study aimed to assess the effectiveness of a low trough serum concentration of vancomycin on acute kidney injury in infants and toddlers in the paediatric intensive care unit (PICU).

METHODS

A retrospective cohort study was performed of 126 infants and toddlers (aged between 29 days and 3 years) from the PICU of a tertiary care hospital who were administered intravenous vancomycin between January 2019 and December 2022. Information about their demographic factors, duration of PICU stay, time of administration and trough levels of vancomycin were retrieved. Descriptive statistics were used for demographic factors and multivariable logistic regression analyses were conducted to assess the determining factors.

RESULTS

Based on the trough concentration of vancomycin, the participants were divided into three groups as follows: 4-5 mg/L, 5-15 mg/L and >15 mg/L. The serum vancomycin concentration was significantly related to body weight, albumin, cystatin C, urea nitrogen in serum, serum creatinine and creatinine clearance (p<0.05) in these patients. Multivariate analysis showed that body weight, albumin, cystatin C, urea nitrogen in serum and creatinine clearance were independent contributors to the trough vancomycin concentration. There was no difference in the effectiveness of different trough concentrations on patients (p=0.241). The cumulative incidence of acute kidney injury was highest in the group with a trough concentration of vancomycin >15 mg/L (p<0.01).

CONCLUSIONS

Patients with a vancomycin trough concentration of 4-5 mg/L in the PICU had a high cure rate (79.4%) and a low incidence of acute kidney injury (HR 18.3, 95% CI 5.135 to 87.621; p<0.001). Therefore, the serum trough concentration should be considered but it should also be combined with the treatment effect to achieve individualised administration for the clinical application of vancomycin.

Comparison of Methicillin-Resistant Staphylococcus aureus Nasal Screening Predictive Value in the Intensive Care Unit and General Ward

BACKGROUND

The clinical utility of methicillin-resistant Staphylococcus aureus (MRSA) nasal screening appears promising for antimicrobial stewardship programs. However, a paucity of data remains on the diagnostic performance of culture-based MRSA screen in the intensive care unit (ICU) for pneumonia and bacteremia.

OBJECTIVE

The objective of this study was to compare the predictive value of culture-based MRSA nasal screening for pneumonia and bacteremia in ICU and general ward patients.

METHODS

This multicenter, retrospective study was conducted over a 23-month period. Adult patients with MRSA nasal screening ≤48 hours of collecting a respiratory and/or blood culture with concurrent initiation of anti-MRSA therapy were included. The primary endpoint was to compare the negative predictive value (NPV) associated with culture-based MRSA nasal screening between ICU and general ward patients with suspected pneumonia.

RESULTS

A total of 5106 patients representing the ICU (n = 2515) and general ward (n = 2591) were evaluated. The NPV of the MRSA nares for suspected pneumonia was not significantly different between ICU and general ward patient populations (98.3% and 97.6%, respectively; P = 0.41). The MRSA nares screening tool also had a high NPV for suspected bacteremia in ICU (99.8%) and general ward groups (99.7%) (P = 0.56). The overall positive MRSA nares rates in the ICU and general ward patient populations were 9.1% and 8.2%, respectively (P = 0.283). Moreover, MRSA-positive respiratory and blood cultures among ICU patients were 5.8% and 0.8%, respectively.

CONCLUSION AND RELEVANCE

Our findings support the routine use of MRSA nasal screening using the culture-based method in ICU patients with pneumonia. Further research on the clinical performance for MRSA bacteremia in the ICU is warranted.

Defining the Roles of Pyruvate Oxidation, TCA Cycle, and Mannitol Metabolism in Methicillin-Resistant Staphylococcus aureus Catheter-Associated Urinary Tract Infection

Methicillin-resistant Staphylococcus aureus (MRSA) is an important cause of complicated urinary tract infection (UTI) associated with the use of indwelling urinary catheters. Previous reports have revealed host and pathogen effectors critical for MRSA uropathogenesis. Here, we sought to determine the significance of specific metabolic pathways during MRSA UTI. First, we identified four mutants from the Nebraska transposon mutant library in the MRSA JE2 background that grew normally in rich medium but displayed significantly reduced growth in pooled human urine (HU). This prompted us to transduce the uropathogenic MRSA 1369 strain with the transposon mutants in sucD and fumC (tricarboxylic acid [TCA] cycle), mtlD (mannitol metabolism), and lpdA (pyruvate oxidation). Notably, sucD, fumC, and mtlD were also significantly upregulated in the MRSA 1369 strain upon exposure to HU. Compared to the WT, the MRSA 1369 lpdA mutant was significantly defective for (i) growth in HU, and (ii) colonization of the urinary tract and dissemination to the kidneys and the spleen in the mouse model of catheter-associated UTI (CAUTI), which may be attributed to its increased membrane hydrophobicity and higher susceptibility to killing by human blood. In contrast to their counterparts in the JE2 background, the sucD, fumC, and mtlD mutants in the MRSA 1369 background grew normally in HU; however, they displayed significant fitness defects in the CAUTI mouse model. Overall, identification of novel metabolic pathways important for the urinary fitness and survival of MRSA can be used for the development of novel therapeutics. IMPORTANCE While Staphylococcus aureus has historically not been considered a uropathogen, S. aureus urinary tract infection (UTI) is clinically significant in certain patient populations, including those with chronic indwelling urinary catheters. Moreover, most S. aureus strains causing catheter-associated UTI (CAUTI) are methicillin-resistant S. aureus (MRSA). MRSA is difficult to treat due to limited treatment options and the potential to deteriorate into life-threatening bacteremia, urosepsis, and shock. In this study, we found that pathways involved in pyruvate oxidation, TCA cycle, and mannitol metabolism are important for MRSA fitness and survival in the urinary tract. Improved understanding of the metabolic needs of MRSA in the urinary tract may help us develop novel inhibitors of MRSA metabolism that can be used to treat MRSA-CAUTI more effectively.

Visual Assay for Methicillin-Resistant Staphylococcus aureus Based on Rolling Circular Amplification Triggering G-Quadruplex/Hemin DNAzyme Proximity Assembly

Nowadays, infections caused by methicillin-resistant Staphylococcus aureus (MRSA) have constituted a new challenge for anti-infective treatment. Precise identification and rapid clinical diagnostics of MRSA from other methicillin-sensitive strains entail assays with robust diagnostic efficiency and simple operation steps. Sensitive detection of MecA gene is promising to indicate MRSA infection, but it is challenged by the lack of isothermal and simple strategies. A visual assay based on isothermal rolling circular amplification and G-quadruplex/hemin (G4/hemin) DNAzyme proximity assembly was proposed for the immediate, efficient, and cost-effective detection of MecA in simple operation steps and in a single tube. The presence of MecA specifically drove the formation of circular templates, which further triggered isothermal amplification. The amplified product offered abundant binding sites for DNA-grafted hemin probes to form a novel proximity-assembled G4/hemin DNAzyme structure for colorimetric changing diagnosis. This tandem-repeated novel DNAzyme possessed higher catalytic activity and a lower background signal than traditional G4/hemin DNAzyme, ensuring sensitive discrimination of MRSA (limit of detection: 9.6 pM). Assay stability and antimatrix interference capability enable clinical application, which shows compared diagnostic ability with classic methods (100% sensitivity and 100% specificity) but possesses more simplified procedures and shorter turnaround time (<6 h). This colorimetric strategy in a nonsite-specific and hypersensitive manner holds foreseeable prospects in clinical diagnostic and research applications.

Should a MRSA Nasal Swab Guide Empiric Antibiotic Treatment?

MRSA Nasal Swab and Empiric Antibiotic TreatmentMRSA nasal screening has emerged as a potential antimicrobial stewardship tool to guide empiric use of anti-MRSA therapy. The authors address diagnostic considerations when performing MRSA nasal screening and clinical situations in which its results may be used to guide empiric antibiotic therapy in hospitalized patients.

Impact of Nares Swabs in the Operative Management of Distal Lower Extremity Infections

Associations between nares surveillance cultures and lower extremity wound cultures remains a topic of discussion in the literature and in clinical practice. Reports are limited due to the questionable accuracy of bedside foot cultures. A retrospective review of our institution's lower extremity wounds requiring surgical management distal to the tibial tuberosity was conducted. Deep intraoperative tissue cultures collected in a sterile operating field were referenced against nares cultures from the same hospitalization. Accuracy, sensitivity, and specificity of nares cultures for predicting methicillin-resistant Staphylococcus aureus (MRSA) infection were determined. Four hundred and forty unique patients with both nares and wound cultures met inclusion criteria. Comorbid diagnoses revealed 66.82%, 30.68%, and 32.27% of patients had diabetes mellitus, chronic kidney disease, and/or peripheral arterial disease, respectively. Sensitivity and specificity were found to be 53.13% and 96.13%, respectively. Prevalence of MRSA in a lower extremity wound was 14.9%, and accuracy of nares culture was 90.04% (CI: 86.91%-92.65%). A review of 30 false negative cases was conducted. Using exclusion criteria of a hospital admission within 60 days of presentation, history of MRSA infection, and/or presentation from a long-term care facility, negative predictive value of MRSA nares colonization was 99.51%. A case of necrotizing fasciitis accounted for one outlier. This data demonstrates that nares surveillance swabs have excellent diagnostic performance in ruling out MRSA infections in foot and ankle wounds. Further analysis is required to determine whether this performance is improved in specialized subgroups or dependent on temporal proximity.

Haptoglobin-Conjugated Gold Nanoclusters as a Nanoantibiotic to Combat Bacteremia

Gold nanoclusters have revealed great potential as nanoantibiotics due to their superior chemical and physical characteristics. In this study, a peptide with 83 amino acids derived from haptoglobin was utilized as a surface ligand to synthesize gold nanoclusters via a facile hydrothermal approach. Characterization of the structural and optical properties demonstrated the successful synthesis of derived haptoglobin-conjugated gold nanoclusters. The spherical derived haptoglobin-conjugated gold nanoclusters exhibited a (111) plane of cubic gold and an ultra-small size of 3.6 ± 0.1 nm. The optical properties such as ultraviolet-visible absorption spectra, X-ray photoelectron spectroscopy spectra, fluorescence spectra, and Fourier transform infrared spectra also validated the successful conjugation between the derived haptoglobin peptide and the gold nanoclusters surface. The antibacterial activity, reactive oxygen species production, and antibacterial mechanisms of derived haptoglobin-conjugated gold nanoclusters were confirmed by culturing the bacterium Escherichia coli with hemoglobin to simulate bacteremia. The surface ligand of the derived haptoglobin peptide of derived haptoglobin-conjugated gold nanoclusters was able to conjugate with hemoglobin to inhibit the growth of Escherichia coli. The derived haptoglobin-conjugated gold nanoclusters with an ultra-small size also induced reactive oxygen species production, which resulted in the death of Escherichia coli. The superior antibacterial activity of derived haptoglobin-conjugated gold nanoclusters can be attributed to the synergistic effect of the surface ligand of the derived haptoglobin peptide and the ultra-small size. Our work demonstrated derived haptoglobin-conjugated gold nanoclusters as a promising nanoantibiotic for combating bacteremia.

Antimicrobial stewardship

PURPOSE OF REVIEW

The optimal use of antimicrobials is necessary to slow resistance development and improve patient outcomes. Antimicrobial stewardship (AMS) is a bundle of interventions aimed at promoting the responsible use of antiinfectives. The ICU is an important field of activity for AMS because of high rates of antimicrobial use, high prevalence of resistant pathogens and complex pharmacology. This review discusses aims and interventions of AMS with special emphasis on the ICU.

RECENT FINDINGS

AMS-interventions can improve the quality and quantity of antimicrobial prescribing in the ICU without compromising patient outcomes. The de-escalation of empiric therapy according to microbiology results and the limitation of treatment duration are important steps to reduce resistance pressure. Owing to the complex nature of critical illness, the pharmacological optimization of antimicrobial therapy is an important goal in the ICU. AMS-objectives and strategies are also applicable to patients with sepsis. This is reflected in the most recent guidelines by the Surviving Sepsis Campaign. AMS-interventions need to be adapted to their respective setting and be mindful of local prescribing cultures and prescribers' attitudes.

SUMMARY

AMS in the ICU is effective and safe. Intensivists should be actively involved in AMS-programs and propagate responsible use of antimicrobials.

Ventilator-Associated Pneumonia Due to MRSA vs. MSSA: What Should Guide Empiric Therapy?

The guidelines on ventilator-associated pneumonia (VAP) recommend an empiric therapy against methicillin-resistant Staphylococcus aureus (MRSA) according to its prevalence rate. Considering the MRSA and MSSA VAP prevalence over the last 9 years in our tertiary care hospital, we assessed the clinical value of the MRSA nasal-swab screening in either predicting or ruling out MRSA VAP. We extracted the data of 1461 patients with positive bronchoalveolar lavage (BAL). Regarding the MRSA nasal-swab screening, 170 patients were positive for MRSA or MSSA. Overall, MRSA had a high prevalence in our ICU. Despite the COVID-19 pandemic, there was a significant downward trend in MRSA prevalence, while MSSA remained steady over time. Having VAP due to MRSA did not have any impact on LOS and mortality. Finally, the MRSA nasal-swab testing demonstrated a very high negative predictive value for MRSA VAP. Our results suggested the potential value of a patient-centered approach to improve antibiotic stewardship.

Predictive Value of MRSA Nares Colonization in Diabetic Foot Infections: A Systematic Review and Bivariate Random Effects Meta-Analysis

The primary objective of this study was to assess the negative predictive value of methicillin-resistant Staphylococcus aureus (MRSA) nasal swabs in MRSA diabetic foot infections. MEDLINE and Cochrane Library were searched from inception to May 1, 2020. The following search string was used: (methicillin-resistant S. aureus OR MRSA) AND (nasal OR nares) AND (diabetic OR foot OR diabetic foot infections). All studies that contained data comparing MRSA nasal swab positivity to wound cultures from diabetic foot infections and met the inclusion criteria were included. Among the 86 relevant studies, 6 studies with 8706 diabetic patients were included. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses guideline extension for Diagnostic Test Accuracy reviews was followed. The primary meta-analysis outcomes were the negative and positive predictive values of MRSA nasal swabs for MRSA diabetic foot infections. The pooled specificity and pooled sensitivity were determined by generating hierarchical summary receiver characteristic operating curves. In the bivariate meta-analysis, involving the 6 studies, pooled sensitivity and specificity was 41.7% (95% confidence interval = 32.9, 51) and 94.1% (95% confidence interval = 89.5, 96.8), respectively. In low-moderate MRSA prevalence levels (<15%), negative predictive value of MRSA nasal swab was >90% and positive predictive value was <55%. This meta-analysis suggests that in patients with diabetic foot infections, the nasal swab MRSA screen has a poor positive predictive value but an excellent negative predictive value in regions of low to moderate prevalence of MRSA diabetic foot infections.

Metal nanoparticles functionalized with nutraceutical Kaempferitrin from edible Crotalaria juncea, exert potent antimicrobial and antibiofilm effects against Methicillin-resistant Staphylococcus aureus

Kaempferitrin (KF), a flavonol glycoside, was isolated from the edible plant Crotalaria juncea. Optimization for the synthesis of silver (AgNPs) and copper (CuNPs) nanoparticles using C. juncea extract and kaempferitrin were attempted for the first time. A detailed study on size and stability analysis have been reported. Efficacy of KF@AgNPs and KF@CuNPs against biofilm formation and planktonic mode of growth on methicillin-resistant Staphylococcus aureus (MRSA) along with possible mechanisms has been explored. Release of Cu(II) upon prolonged treatment with KF@CuNPs in the presence of MRSA was quantified through Alizarin red test, indicating the antibacterial effect is initiated by the CuNPs itself. Time kill curve depicted both the NPs have similar kill kinetics to curtail the pathogen and imaging with Crystal violet assay, Fluorescent live dead imaging and SEM analysis revealed a 60% reduction in biofilm formation at the Sub-MIC concentration of KF@AgNPs and KF@CuNPs. Furthermore, the membrane permeability and cell surface hydrophobicity were altered in the presence of both the NPs. The colony count from the in vivo infection zebrafish model in the treatment group showed a decline of > 1.8 fold for KF@AgNPs and > two fold for KF@CuNPs. Toxicity studies did not reveal any abnormality in liver and brain enzyme levels. Liver morphology images show no severe cytological alterations when treated with KF@AgNPs and were almost similar to the normal liver. Thus, KF@AgNPs was nontoxic and caused significant reduction in biofilm formation in MRSA, also reduced bacterial bioburden in the infected zebrafish, which has the potential to be explored in higher animal models.

Impact of Nasal Swabs on Empiric Treatment of Respiratory Tract Infections (INSERT-RTI)

Methicillin-resistant Staphylococcusaureus (MRSA) polymerase-chain-reaction nasal swabs (PCRNS) are a rapid diagnostic tool with a high negative predictive value. A PCRNS plus education “bundle” was implemented to inform clinicians on the utility of PCRNS for anti-MRSA therapy de-escalation in respiratory tract infections (RTI). The study included patients started on vancomycin with a PCRNS order three months before and after bundle implementation. The primary objective was the difference in duration of anti-MRSA therapy (DOT) for RTI. Secondary objectives included hospital length of stay (LOS), anti-MRSA therapy reinitiation, 30-day readmission, in-hospital mortality, and cost. We analyzed 62 of 110 patients screened, 20 in the preintervention and 42 in the postintervention arms. Mean DOT decreased after bundle implementation by 30.3 h (p = 0.039); mean DOT for patients with a negative PCRNS decreased by 39.7 h (p = 0.014). Median cost was lower after intervention [USD$51.69 versus USD$75.30 (p < 0.01)]. No significant difference in LOS, mortality, or readmission existed. The bundle implementation decreased vancomycin therapy and cost without negatively impacting patient outcomes.

The effect of body mass index and creatinine clearance on serum trough concentration of vancomycin in adult patients

Background

The aim of this study was to evaluate the influence of patient body mass index (BMI) and estimated creatinine clearance (CrCl) on serum vancomycin concentrations to define a possible optimal dosage regimen in overweight patients based on data obtained during therapeutic drug monitoring.

Methods

This retrospective study used data collected from January 2017 to January 2019. Adult patients (n = 204) received vancomycin treatment at a dose of 1000 mg every 12 h and underwent serum monitoring. Data collected included patient disease category, sex, age, height, weight, vancomycin concentrations, and serum creatinine. The CrCl values were estimated using the Cockcroft-Gault formula. In this study, statistical comparisons were performed on the results of patients according to serum vancomycin concentration.

Results

Serum vancomycin concentration was significantly related to BMI (P <  0.001) and CrCl (P <  0.05) in adult patients. Furthermore, the trough serum vancomycin concentration showed a logarithmic correlation with BMI (R = − 0.5108, 95% CI: − 0.6082 to − 0.3982, P <  0.001) and CrCl (R = − 0.5739, 95% CI: − 0.6616 to − 0.4707, P <  0.001). The multivariate analysis showed that BMI and CrCl are independent contributors to the trough vancomycin concentration. Moreover, some of the patients with higher BMI (≥ 24 kg/m²) met the goal trough concentration after an adjustment from 1000 mg every 12 h to 1000 mg every 8 h.

Conclusions

Serum vancomycin concentration decreases progressively with increasing BMI and the augmentation in CrCl in adult patients. The trough concentration of vancomycin should be continuously monitored for patients with a BMI ≥ 24 kg/m², and the dosage regimen should be adjusted to reach the target trough concentration in these patients to reduce the impact of BMI.

Positive nasal Staphylococcus aureus polymerase chain reaction assay is not sensitive in predicting concurrent or subsequent Staphylococcus aureus infection in critically ill patients

Staphylococcal infection is associated with significant morbidity and mortality in critically ill patients. Using data from 16,681 patients who had a nasal Staphylococcus aureus polymerase chain reaction (PCR) assay on admission to the intensive care unit (ICU) of Royal Perth Hospital between March 2006 and September 2016, this retrospective cohort study assessed whether nasal S. aureus colonisation on admission to an ICU was predictive of concurrent or subsequent S. aureus infections. Culture-proven S. aureus infections were identified using the hospital microbiology database. Of the 16,681 patients included, 565 (3.4%) had a positive methicillin-resistant S. aureus (MRSA) assay, 146 (0.9%) had a positive methicillin-sensitive S. aureus (MSSA) assay and eight (0.05%) had both positive MRSA and MSSA assays. Of those 565 patients with a positive MRSA PCR assay, 79 (13.8%) had concurrent or subsequent MRSA infections. Of those 146 patients with a positive MSSA PCR assay, only 5 (3.4%) had MSSA infection. The sensitivity and specificity for the MRSA PCR assay in predicting concurrent or subsequent MRSA infection were 72.7% (95% confidence intervals (CI) 63.4%-80.8%) and 97.0% (95% CI 96.8%-97.3%), respectively. The sensitivity and specificity for the MSSA PCR assay in predicting concurrent or subsequent MSSA infection were 3.3% (95% CI 1.1%-7.6%) and 99.1% (95% CI 98.9%-99.2%), respectively. Both nasal MRSA and MSSA PCR assays had a high specificity and negative predictive value in predicting MRSA and MSSA infections, respectively, suggesting that in centres without endemic S. aureus infections, a negative nasal MRSA or MSSA PCR assay may be useful to reduce unnecessary empirical antibiotic therapy against S. aureus.

Using VRE screening tests to predict vancomycin resistance in enterococcal bacteremia

BACKGROUND AND OBJECTIVE

Enterococcus causes clinically significant bloodstream infections (BSIs). In centers with a higher prevalence of vancomycin resistant enterococcus (VRE) colonization, a common clinical question is whether empiric treatment directed against VRE should be initiated in the setting of a suspected enterococcal BSI. Unfortunately, VRE treatment options are limited, and relatively expensive, and subject patients to the risk of adverse reactions. We hypothesized that the results of VRE colonization screening could predict vancomycin resistance in enterococcal BSI.

METHODS

We reviewed 370 consecutive cases of enterococcal BSI over a 7-year period at 2 tertiary-care hospitals to determine whether vancomycin-resistant BSIs could be predicted based on known colonization status (ie, patients with swabs performed within 30 days, more remotely, or never tested). We calculated sensitivity and specificity, and we plotted negative predictives values (NPVs) and positive predictive values (PPVs) as a function of prevalence.

RESULTS

A negative screening swab within 30 days of infection yielded NPVs of 90% and 95% in settings where <27.0% and 15.0% of enterococcal BSI are resistant to vancomycin, respectively. In patients with known VRE colonization, the PPV for VRE in enterococcal BSI was >50% at any prevalence exceeding 25%.

CONCLUSIONS

The results of a negative VRE screening test result performed within 30 days can help eliminate unnecessary empiric therapy in patients with suspected enterococcal BSI. Conversely, patients with positive VRE screening swabs require careful consideration of empiric VRE-directed therapy when enterococcal BSI appears likely.

The novel use of oral antibiotic monotherapy in prosthetic valve endocarditis caused by Finegoldia magna: a case study

Background

Finegoldia magna, a Gram-positive anaerobic coccus, is part of the human normal microbiota as a commensal of mucocutaneous surfaces. However, it remains an uncommon pathogen in infective endocarditis, with only eight clinical cases previously reported in the literature.

Currently, infective endocarditis is routinely treated with prolonged intravenous antibiotic therapy. However, recent research has found that switching patients to oral antibiotics is non-inferior to prolonged parenteral antibiotic treatment, challenging the current guidelines for the treatment of infective endocarditis.

Case presentation

This case report focuses on a 52-year-old gentleman, who presented with initially culture-negative infective endocarditis following bioprosthetic aortic valve replacement. Blood cultures later grew Finegoldia magna. Following initial intravenous antibiotic therapy and re-do surgical replacement of the prosthetic aortic valve, the patient was successfully switched to oral antibiotic monotherapy, an unusual strategy in the treatment of infective endocarditis inspired by the recent publication of the POET trial. He made excellent progress on an eight-week course of oral antibiotics and was successfully discharged from surgical follow-up.

Conclusions

This case is the 9th reported case of Finegoldia magna infective endocarditis in the literature. Our case also raises the possibility of a more patient-friendly and cost-effective means of providing long-term antibiotic therapy in suitable patients with prosthetic valve endocarditis and suggests that the principles highlighted in the POET trial can also be applicable to post-operative patients after cardiac surgery.