Effective Approaches to Diagnostic Stewardship of Syndromic Molecular Panels

BACKGROUND

Syndromic molecular panels for the diagnosis of gastroenteritis, meningitis/encephalitis, and pneumonia are becoming routinely used for patient care throughout the world.

CONTENT

These rapid, sample-to-answer assays have great potential to improve patient care, infection control, and antimicrobial stewardship. However, diagnostic stewardship is essential for their optimal use and accuracy, and interventions can be applied at all phases of the diagnostic process.

SUMMARY

The aim of this review article is to describe effective approaches to diagnostic stewardship for syndromic molecular panels to ensure appropriate test utilization and quality assured results.

Clinical Outcomes of Treated and Untreated C. difficile PCR-Positive/Toxin-Negative Adult Hospitalized Patients: a Quasi-Experimental Noninferiority Study

Clostridioides difficile infection (CDI) is routinely diagnosed by PCR, with or without toxin enzyme immunoassay testing. The role of therapy for positive PCR and negative toxin remains unclear. The objective of this study was to determine whether clinical outcomes of PCR+/cycle threshold-based toxin (CT-toxin)- individuals vary by result reporting and treatment strategy. We performed a quasiexperimental noninferiority study comparing clinical outcomes of PCR+/CT-toxin- individuals by reporting PCR result only (most patients treated) with reporting CT-toxin result only (most patients untreated) in a single-center, tertiary academic hospital. The primary outcome was symptomatic PCR+/CT-toxin+ conversion at 8 weeks. Secondary outcomes included 7-day diarrhea resolution, hospital length of stay, and 30-day all-cause mortality. A total of 663 PCR+/CT-toxin- test results were analyzed from 632 individuals with a median age of 61 years (interquartile range [IQR], 44 to 72) and 50.4% immunocompromised. Individuals in the preintervention group were more likely to have received CDI therapy than those in the intervention group (91.5 versus 15.1%; P < 0.001). Symptomatic toxin conversion at 8 weeks and hospital length of stay failed to establish the predefined thresholds for noninferiority. Lack of diarrhea resolution at 7 days and 30-day all-cause mortality was similar and established noninferiority (20.0 versus 13.7%; adjusted odds ratio [aOR], 0.57; 90% confidence interval [CI], 0.32 to 1.01; P = 0.1; and 8.6 versus 6.5%; aOR, 0.46; 90% CI, 0.20 to 1.04; P = 0.12). These data support the safety of withholding antibiotics for selected hospitalized individuals with suspected CDI but negative toxin.

Effect of rapid methicillin-resistant Staphylococcus aureus nasal polymerase chain reaction screening on vancomycin use in the intensive care unit

PURPOSE

To determine the impact of a pharmacist-driven methicillin-resistant Staphylococcus aureus (MRSA) nasal polymerase chain reaction (PCR) screen on vancomycin duration in critically ill patients with suspected pneumonia.

METHODS

This was a retrospective, quasi-experimental study at a 613-bed academic medical center with 67 intensive care beds. Adult patients admitted to the intensive care unit (ICU) between 2017 and 2019 for 24 hours or longer and empirically started on intravenous vancomycin for pneumonia were included. The primary intervention was the implementation of a MRSA nasal PCR screen protocol. The primary outcome was duration of empiric vancomycin therapy. Secondary outcomes included the rate of acute kidney injury (AKI), the number of vancomycin levels obtained, the rate of resumption of vancomycin for treatment of pneumonia, ICU length of stay, hospital length of stay, the rate of ICU readmission, and the rate of in-hospital mortality.

RESULTS

A total of 418 patients were included in the final analysis. The median vancomycin duration was 2.59 days in the preprotocol group and 1.44 days in the postprotocol group, a reduction of approximately 1.00 day (P < 0.01). There were significantly fewer vancomycin levels measured in the postprotocol group than in the preprotocol group. Secondary outcomes were similar between the 2 groups, except that there was lower AKI and fewer vancomycin levels obtained in the postprotocol group (despite implementation of area under the curve-based vancomycin dosing) as compared to the preprotocol group.

CONCLUSION

The implementation of a pharmacist-driven MRSA nasal PCR screen was associated with a decrease in vancomycin duration and the number of vancomycin levels obtained in critically ill patients with suspected pneumonia.

Discontinuation Patterns and Cost Avoidance of a Pharmacist-Driven Methicillin-Resistant Staphylococcus aureus Nasal Polymerase Chain Reaction Testing Protocol for De-escalation of Empiric Vancomycin for Suspected Pneumonia

A pharmacist-driven methicillin-resistant Staphylococcus aureus (MRSA) nasal polymerase chain reaction (PCR)-based testing protocol with a 70% acceptance rate for vancomycin discontinuation within 24 hours of negative results significantly reduced unnecessary vancomycin use with an estimated cost avoidance of $40 per vancomycin course. We found high concordance (141 of 147, 96%) of culture-based versus PCR-based MRSA nasal screening.

1530. A Cluster of Disseminated Gonococcal Infections in a Non-Immunocompromised Veteran Population

Background

Disseminated gonococcal infection (DGI) is an uncommon manifestation of N. gonorrhoeae that is estimated to occur in 0.5-3% of cases, with a decreasing incidence that has been attributed to changes in circulating serotypes. At a Veterans Affairs Medical Center (VAMC), 3 cases were identified within 4 months in 2019.

Methods

A case series of patients with DGI between March and July 2019 was conducted at a 399-bed tertiary care VAMC that serves central Virginia. Clinical case data was abstracted from the medical record, and data regarding prior gonorrhea cases at the facility was obtained from the laboratory information system.

Results

In 2019, the rate of DGI was 4.9%, with 3 cases out of 61 reported. All occurred in immunocompetent, African-American males with a mean age of 59 years, and all had female sexual partners (Table 1). All presented with joint symptoms, 2 had skin manifestations, and none had genital symptoms. Two patients had positive synovial fluid cultures and the third had a positive blood culture. All isolates were beta-lactamase negative. Orogenital testing by nucleic acid amplification was only positive in 1 patient. No other sexually transmitted infections were identified. One patient underwent surgical washout of the involved shoulder joint, but the others were managed non-operatively. All received a single dose of azithromycin and a 14-day course of ceftriaxone with full symptom resolution. These were the first positive N. gonorrhoeae isolates from invasive specimens at this VAMC since at least 2016.

Table 1. Clinical History and Laboratory Results at Presentation for Patients with Disseminated Gonococcal Infection

Conclusion

This cluster of DGI cases was unusual given the recent rarity at this VAMC, the age of the patients, and lack of overt risk factors. In Virginia, DGI is reported to the health department no differently than uncomplicated infections, so the actual rate of DGI regionally is unknown. One isolate was preserved and sent to the Centers for Disease Control and Prevention for deidentified whole genome sequencing. More refined reporting is necessary to improve understanding of local gonorrhea epidemiology, as well as coupling with additional methodologies such as serotyping or whole genome sequencing. Clinicians should be aware of the possibility of DGI, even in older patients without classic risk factors.

Disclosures

All Authors: No reported disclosures

174. Impact of Cascade Reporting of Antimicrobial Susceptibility on Antimicrobial Consumption at a Veterans Affairs Medical Center

Background

Cascade reporting (CR) is a strategy of reporting antimicrobial susceptibility test results in which secondary agents are only reported if an organism is resistant to primary, narrow spectrum agents within a drug class. A multidisciplinary team developed CR algorithms for Gram-negative bacteria based on the local antibiogram and infectious diseases practice guidelines.

Methods

CR was implemented at a 399-bed tertiary care VAMC in March 2018. In a quasi-experimental study, antimicrobial use data across 8 inpatient units were extracted from the CDC’s NHSN AU module from April 2017 – March 2019 (12 months pre- and post-implementation of CR), reported as antimicrobial days of therapy (DOT) per 1000 days present (DP). T-tests and linear mixed models accounting for seasonal and random unit effects were used to compare antimicrobial use pre- and post-CR implementation.

Figure 1A. Cascade reporting algorithm for antimicrobial susceptibility reporting for Enterobacteriaceae

Figure 1B. Cascade reporting algorithm for antimicrobial susceptibility reporting for Pseudomonas aeruginosa

Results

Following CR implementation, mean monthly meropenem (p=0.005) and piperacillin/tazobactam (p=0.002) use decreased, while cefepime use increased (p< 0.001). The slope of ciprofloxacin use decreased by 2.16 DOTs/1,000 DP per month (SE=0.25, p< 0.001). The slope of cefpodoxime and moxifloxacin use decreased by 18% (p< 0.001), and 7% (p< 0.001), respectively. The slope of cephalexin use decreased by 0.55 DOTs/1,000 DP (SE=0.26, p< 0.001). The slope of ceftriaxone and cefepime use increased by 1.51 (SE=0.59, p=0.011) and 1.06 (SE=.32, p=0.002) DOTs/1000 DP per month, respectively. There were no significant changes in the slope of amoxicillin/clavulanate, levofloxacin, or meropenem consumption. Rates of Clostridioides difficile infection did not significantly change.

Figure 2A. Average monthly use of oral antibiotics across all units in average days of therapy (DOTs) per 1000 days present. CR = Cascade reporting. *For Cefpodoxime and moxifloxacin medians were reported as data was not normally distributed.

Figure 2B. Average monthly use of intravenous antibiotics across all units in average days of therapy (DOTs) per 1000 days present. CR = Cascade reporting.

Table 1. Slope of Antimicrobial Utilization Pre and Post-Cascade Reporting Implementation.

Conclusion

After implementation of CR, the slope of ciprofloxacin use decreased and mean monthly meropenem use decreased. CR is a valuable tool that can be employed by ASPs to encourage optimal use of antibiotics.

Disclosures

All Authors: No reported disclosures

1489. Safety and Performance of a Pharmacist-Driven Nasal MRSA PCR Protocol for De-escalation of Empiric Vancomycin for Suspected Pneumonia at an Academic Medical Center

Background

Limited published data supports the de-escalation of empiric anti-methicillin resistant Staphylococcus aureus (MRSA) antibiotics for suspected pneumonia upon negative nasal MRSA screening. Besides limited sample sizes, special populations, such as those who are immunocompromised and/or critically ill, have been underrepresented in these reports. We describe real-world efficacy and safety of a pharmacist-driven nasal MRSA PCR testing protocol implemented at Stanford Health Care in May 2018 across a diverse patient population.

Methods

This was an observational cohort study of adult patients who received vancomycin for empiric pneumonia before (PRE) vs after (POST) implementation of a pharmacist-driven nasal MRSA PCR testing protocol (between 05/01/2017 - 08/31/2017 (PRE) and 5/7/2018 - 12/31/2019 (POST). The primary outcome measure was duration of vancomycin administration. Secondary outcomes included time to vancomycin discontinuation, frequency of restarting vancomycin for empiric pneumonia within 7 days, acute kidney injury (defined as “risk” by RIFLE criteria), and MRSA respiratory cultures. Statistical methods are described in Figure A.

Figure A. Statistical methods

Results

Total of 610 patients were included in this study with 116 in the PRE group and 494 in the POST group. Over 40% were critically ill and approximately 37% were immunocompromised in both groups (Table 1). For the primary outcome, median vancomycin duration was significantly shorter in the POST group (1.29 days; 95% CI 1.13-1.45) vs. PRE group (1.98 days; 95% CI 1.49-2.46) (p < 0.0005), a 34.8% reduction (Figure 1). Median vancomycin duration was lower in patients with a negative vs positive nasal MRSA PCR (1.20 days [95% CI 1.08-1.33] vs 2.53 days [95% CI 1.77-3.29], p < 0.0005), a 52.6% reduction (Figure 2). MRSA was recovered in respiratory cultures in 1.7% vs 1.4% in the PRE vs POST groups. One (0.002%) patient had a negative nasal MRSA PCR but culture-confirmed MRSA pneumonia and recovered after completing a treatment course. Secondary safety outcomes were similar between groups (Table 2).

Tables 1 and 2: Baseline Characteristics and Secondary Outcomes

Figure 1. Primary Outcome: Kaplan–Meier Estimates of Cumulative Active Vancomycin Therapy Before and After Implementation of Nasal MRSA PCR protocol

Figure 2. Secondary Outcome: Figure 2. Kaplan–Meier Estimates of Cumulative Active Vancomycin Therapy in Patients with Negative vs Positive Nasal MRSA PCR

Conclusion

Pharmacist-driven nasal MRSA PCR testing is effective and safe in early de-escalation of empiric vancomycin used for pneumonia treatment in a diverse population including critically ill and immunocompromised patients.

Disclosures

All Authors: No reported disclosures

Dual Reporting of Clostridioides difficile PCR and Predicted Toxin Result Based on PCR Cycle Threshold Reduces Treatment of Toxin-Negative Patients without Increases in Adverse Outcomes

Nucleic acid amplification tests are commonly used to diagnose Clostridioides difficile infection (CDI). Two-step testing with a toxin enzyme immunoassay is recommended to discriminate between infection and colonization but requires additional resources. Prior studies showed that PCR cycle threshold (CT ) can predict toxin positivity with high negative predictive value. Starting in October 2016, the predicted toxin result (CT-toxin) based on a validated cutoff was routinely reported at our facility. To evaluate the clinical efficacy of this reporting, all adult patients with positive GeneXpert PCR results from October 2016 through October 2017 underwent a chart review to measure the recurrence of or conversion to a CT-toxin+ result and 30-day all-cause mortality. There were 482 positive PCR tests in 430 unique patients, 282 CT-toxin+ and 200 CT-toxin- Patient characteristics were similar at testing, though CT-toxin+ patients had higher white blood cell (WBC) counts (12.5 × 103 versus 9.3 × 103 cells/μl; P = 0.001). All cases (n = 21) of fulminant CDI had a CT-toxin+ result. Index CT-toxin+ patients were significantly more likely to have a CT-toxin+ result within 90 days than CT-toxin- patients (17.4% [n = 49] versus 8.0% [n = 16], respectively; P = 0.003). Thirty-day all-cause mortality was higher in CT-toxin- patients (11.1% versus 6.8%; P = 0.1), though no deaths in CT-toxin- patients were directly attributable to CDI. Of the 200 CT-toxin- patients, 51.5% (n = 103) were treated for CDI. The rates of conversion to a CT-toxin+ result (8.8% versus 7.2%; P = 0.8) and all-cause mortality (8.8% versus 13.4%; P = 0.3) were similar between treated and untreated CT-toxin- patients, respectively. CT -based toxin prediction may identify patients at higher risk for CDI-related complications and reduce treatment among CT-toxin- patients.

Reproducibility of positive results for rare pathogens on the FilmArray GI Panel

Though the FilmArray GI Panel has a reported aggregate specificity and reproducibility of >97% and > 99%, respectively, the reproducibility is less understood in clinical practice. We measured the reproducibility of positive results for low-prevalence pathogens. Samples with positive results for selected targets were repeated using a different FilmArray module. Overall, 331 of 373 (89%) results were reproducible. Giardia lamblia (57/57, 100%), Cryptosporidium spp. (61/63, 97%), Cyclospora cayetanensis (34/35, 97%), Plesiomonas shigelloides (17/18, 94%), and Rotavirus A (76/77, 99%) were highly reproducible, while Adenovirus F40/41 (38/54, 70%), Vibrio spp. (8/10, 80%), V. cholerae (3/8, 37.5%), and Yersinia enterocolitica (36/50, 72%) were poorly reproducible. Review of 38 patients with nonreproducible results showed that 19 (50%) had evidence of gastroenteritis and only 6 (16%) had possible infection with the organism that showed a nonreproducible result. Higher false-positive rates with certain targets on FAGP emphasize the need for diagnostic stewardship.