Screening swabs surpass traditional risk factors as predictors of MRSA bacteremia

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.

Randomized controlled trial of chlorhexidine gluconate, intranasal mupirocin, rifampin, and doxycycline versus chlorhexidine gluconate and intranasal mupirocin alone for the eradication of methicillin-resistant Staphylococcus aureus (MRSA) colonization

BACKGROUND

Several decolonization regimens have been studied to prevent recurrent methicillin-resistant Staphylococcus aureus (MRSA) infections. Clinical equipoise remains with regard to the role of MRSA decolonization. We compared initial MRSA clearance and subsequent MRSA recolonization rates over a 12-month period after standard decolonization (using topical chlorhexidine gluconate, and intranasal mupirocin) or systemic decolonization (using topical chlorhexidine gluconate, intranasal mupirocin, oral rifampin, and oral doxycycline).

METHODS

MRSA-colonized patients were randomized to receive either standard or systemic decolonization. Follow-up with MRSA screening was obtained at approximately 3, 6, and 12 months after completion of therapy. Kaplan-Meier survival curves were calculated and assessed for significant differences using log-rank tests.

RESULTS

Of 98 enrolled patients (25 standard decolonization, 73 systemic decolonization), 24 patients (7 standard decolonization, 17 systemic decolonization) did not complete the study. Univariate analysis showed a marginally significant difference in the probability of remaining MRSA-negative post-treatment (p = 0.043); patients who received standard decolonization had a 31.9% chance of remaining MRSA-negative compared with a 49.9% chance among those who received systemic decolonization. With multivariate analysis, there was no difference in the probability of remaining MRSA-negative between systemic and standard decolonization (p = 0.165). Initial MRSA clearance was more readily achieved with systemic decolonization (79.1%; 95% CI 32.4% to 71.6%) than with standard decolonization (52.0%; 95% CI 69.4% to 88.8%; p = 0.0102).

CONCLUSIONS

Initial MRSA clearance is more readily achieved with systemic decolonization than with standard decolonization. There is no significant difference in the probability of sustained MRSA clearance.

Emerging drugs for treating methicillin-resistant Staphylococcus aureus

Introduction: In clinical practice, methicillin-resistant Staphylococcus aureus (MRSA) represents a major threat and has been associated with high rates of inadequate antibiotic treatment and significant increases in morbidity, mortality, and overall healthcare costs. The association between the prescription of an inappropriate or delayed antibiotic and impaired clinical outcomes has been widely described. Areas covered: To address the threat of MRSA, many new therapeutic options with a peculiar activity against MRSA have been recently developed and approved. New agents are characterized by specific issues in terms of spectrum of activity, pharmacokinetics, risk of drug-drug interactions, and toxicity, with potential advantages that should be considered in everyday clinical practice. Expert opinion: The most attractive characteristic of new drugs is represented by the broad spectrum of activity against multidrug-resistant pathogens; moreover, new compounds in most cases are characterized by favorable toxicity profiles compared with old drugs currently used in clinical practice. Some of the new antimicrobials will be also available as oral formulations, with the potential for oral switch, even in infections due to resistant pathogens. In particular conditions/populations (e.g. liver failure, renal disease, pregnancy, diabetic, children, and elderly), novel antibiotics with reduced toxicity could be an important option, including after hospital discharge.

Machine learning in infection management using routine electronic health records: tools, techniques, and reporting of future technologies

BACKGROUND

Machine learning (ML) is increasingly being used in many areas of health care. Its use in infection management is catching up as identified in a recent review in this journal. We present here a complementary review to this work.

OBJECTIVES

To support clinicians and researchers in navigating through the methodological aspects of ML approaches in the field of infection management.

SOURCES

A Medline search was performed with the keywords artificial intelligence, machine learning, infection∗, and infectious disease∗ for the years 2014-2019. Studies using routinely available electronic hospital record data from an inpatient setting with a focus on bacterial and fungal infections were included.

CONTENT

Fifty-two studies were included and divided into six groups based on their focus. These studies covered detection/prediction of sepsis (n = 19), hospital-acquired infections (n = 11), surgical site infections and other postoperative infections (n = 11), microbiological test results (n = 4), infections in general (n = 2), musculoskeletal infections (n = 2), and other topics (urinary tract infections, deep fungal infections, antimicrobial prescriptions; n = 1 each). In total, 35 different ML techniques were used. Logistic regression was applied in 18 studies followed by random forest, support vector machines, and artificial neural networks in 18, 12, and seven studies, respectively. Overall, the studies were very heterogeneous in their approach and their reporting. Detailed information on data handling and software code was often missing. Validation on new datasets and/or in other institutions was rarely done. Clinical studies on the impact of ML in infection management were lacking.

IMPLICATIONS

Promising approaches for ML use in infectious diseases were identified. But building trust in these new technologies will require improved reporting. Explainability and interpretability of the models used were rarely addressed and should be further explored. Independent model validation and clinical studies evaluating the added value of ML approaches are needed.

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.

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

BACKGROUND

Vancomycin is often used as empiric therapy for methicillin-resistant Staphylococcus aureus (MRSA), but can be associated with clinically important adverse events including renal failure. MRSA colonization swabs are primarily used for infection control; their use as a diagnostic test to inform the decision to add empiric vancomycin therapy has not been well elucidated.

METHODS

We performed a Medline and Embase systematic review for peer-reviewed studies reporting the diagnostic accuracy of using MRSA colonization status to predict MRSA infections. Meta-analysis was performed using Cochrane guidelines. Grey literature was excluded.

FINDINGS

29 studies were included involving 24225 patients. In cases where the pathogen is not known to be S. aureus, specificities were greater than 85% for bacteremia, lower respiratory tract infections, skin and soft tissue infections (SSTI), and all infections pooled together. Sensitivities ranged between 54.0% and 77.5%. In cases where the pathogen is known to be S. aureus, we found studies on bacteremia and SSTI and arrived at pooled estimates of sensitivities ranging between 56.6% and 56.9%, and of specificities greater than 91%. Most importantly, for most infections in settings where the prevalence of MRSA as a causative organism is below 15%, the negative predictive value of a negative MRSA colonization swab exceeds 90%.

INTERPRETATIONS

In settings of low-moderate MRSA prevalence, negative MRSA screening swabs may prevent unnecessary vancomycin use. More research is needed to assess if this strategy can mitigate the cost of screening in areas with a low MRSA colonization rate.