2017 Infectious Diseases Society of America Infectious Diarrhea Guidelines: A View From the Clinical Laboratory

Clinical Impact of Multiplex Molecular Diagnostic Testing in Children With Acute Gastroenteritis Presenting to an Emergency Department: A Multicenter Prospective Study

BACKGROUND

Multiplex molecular diagnostic panels have greatly enhanced detection of gastrointestinal pathogens. However, data on the impact of these tests on clinical and patient-centered outcomes are limited.

METHODS

We conducted a prospective, multicenter, stepped-wedge trial to determine the impact of multiplex molecular testing at 5 academic children's hospitals on children presenting to the emergency department with acute gastroenteritis. Caregivers were interviewed on enrollment and 7-10 days after enrollment to determine symptoms, risk factors, subsequent medical visits, and impact on family members. During the pre-intervention period, diagnostic testing was performed at the clinician's discretion . During the intervention period, multiplex molecular testing was performed on all children, with results available to clinicians. The primary outcome was return visits to a healthcare provider within 10 days of enrollment.

RESULTS

Potential pathogens were identified by clinician-ordered tests in 19 of 571 (3.3%) in the pre-intervention period compared with 434 of 586 (74%) in the intervention period; clinically relevant pathogens were detected in 2.1% and 15%, respectively. In the multivariate model, the intervention was associated with a 21% reduction in the odds of any return visit (odds ratio, 0.79; 95% confidence interval, .70-.90) after adjusting for potential confounders. Appropriate treatment was prescribed in 11.3% compared with 19.6% during the intervention period (P = .22).

CONCLUSIONS

Routine molecular multiplex testing for all children who presented to the ED with acute gastroenteritis detected more clinically relevant pathogens and led to a 21% decrease in return visits. Additional research is needed to define patients most likely to benefit from testing. Clinical Trials Registration. NCT02248285.

Relationship between Diagnostic Method and Pathogen Detection, Healthcare Resource Use, and Cost in U.S. Adult Outpatients Treated for Acute Infectious Gastroenteritis

A retrospective observational study was performed to assess the relationship between diagnostic method (traditional work-up [TW], multiplex PCR panel with < 12 target pathogens [PCR < 12], or multiplex PCR panel with ≥ 12 target pathogens [PCR12]), and diagnostic yield, health care resource use (HRU), and cost in adult outpatients visiting U.S. hospitals for acute infectious gastroenteritis (AGE). Using data from PINC AI Healthcare Database during January 1, 2016-June 30, 2021, we analyzed adult patients with an AGE diagnosis and stool testing performed during an outpatient visit. Detection rates for different pathogens were analyzed for those with microbiology data available. Among 36,787 patients, TW was most often performed (57.0%). PCR12 testing was more frequent in patients from large, urban, and teaching hospitals, compared to TW (all P < 0.01). PCR12 was associated with a higher mean index visit cost (by $97) but lower mean 30-day AGE-related follow-up cost (by $117) than TW. Patients with PCR12 had a lower 30-day AGE-related hospitalization risk than TW (1.7% versus 2.7% P < 0.01). Among the 8,451 patients with microbiology data, PCR12 was associated with fewer stool tests per patient (mean 1.61 versus 1.26), faster turnaround time (mean 6.3 versus 25.7 h) and lower likelihood of receiving in-hospital antibiotics (39.4% versus 47.1%, all P < 0.01) than TW. A higher percentage of patients with PCR12 had a target pathogen detected (73.1%) compared to PCR < 12 (63.6%) or TW (45.4%, P < 0.01). Thus, we found that large multiplex PCR panels were associated with lower 30-day AGE-related follow-up cost and risk of AGE-related hospitalization, and increased diagnostic yield compared to TW.

Pivotal Shigella Vaccine Efficacy Trials-Study Design Considerations from a Shigella Vaccine Trial Design Working Group

Vaccine candidates for Shigella are approaching phase 3 clinical trials in the target population of young children living in low- and middle-income countries. Key study design decisions will need to be made to maximize the success of such trials and minimize the time to licensure and implementation. We convened an ad hoc working group to identify the key aspects of trial design that would meet the regulatory requirements to achieve the desired indication of prevention of moderate or severe shigellosis due to strains included in the vaccine. The proposed primary endpoint of pivotal Shigella vaccine trials is the efficacy of the vaccine against the first episode of acute moderate or severe diarrhea caused by the Shigella strains contained within the vaccine. Moderate or severe shigellosis could be defined by a modified Vesikari score with dysentery and molecular detection of vaccine-preventable Shigella strains. This report summarizes the rationale and current data behind these considerations, which will evolve as new data become available and after further review and consultation by global regulators and policymakers.

COVID-19 and Corticosteroids: Unfamiliar but Potentially Fatal Infections That Can Arise following Short-Course Steroid Treatment

Corticosteroid use is increasing worldwide as recent studies confer survival benefit of corticosteroids in the management of patients with severe COVID-19. Strongyloides and amebic infections are neglected diseases that can progress to catastrophic complications in patients exposed to corticosteroids, even with short treatment courses. To prevent lethal outcomes, clinicians should be aware of the threat these two parasitic infections pose to at-risk patients receiving corticosteroids, especially in the era of COVID-19.

Shigella sonnei: virulence and antibiotic resistance

Shigella sonnei is the emerging pathogen globally, as it is the second common infectious species of shigellosis (bloody diarrhoea) in low- and middle-income countries (LMICs) and the leading one in developed world. The multifactorial processes and novel mechanisms have been identified in S. sonnei, that are collectively playing apart a substantial role in increasing its prevalence, while replacing the S. flexneri and other Gram-negative gut pathogens niche occupancy. Recently, studies suggest that due to improvement in sanitation S. sonnei has reduced cross-immunization from Plesiomonas shigelliodes (having same O-antigen as S. sonnei) and also found to outcompete the two major species of Enterobacteriaceae family (Shigella flexneri and Escherichia coli), due to encoding of type VI secretion system (T6SS). This review aimed to highlight S. sonnei as an emerging pathogen in the light of recent research with pondering aspects on its epidemiology, transmission, and pathogenic mechanisms. Additionally, this paper aimed to review S. sonnei disease pattern and related complications, symptoms, and laboratory diagnostic techniques. Furthermore, the available treatment reigns and antibiotic-resistance patterns of S. sonnei are also discussed, as the ciprofloxacin and fluoroquinolone-resistant S. sonnei has already intensified the global spread and burden of antimicrobial resistance. In last, prevention and controlling strategies are briefed to limit and tackle S. sonnei and possible future areas are also explored that needed more research to unravel the hidden mysteries surrounding S. sonnei.

Clinical Yield of a Molecular Diagnostic Panel for Enteric Pathogens in Adult Outpatients With Diarrhea and Validation of Guidelines-Based Criteria for Testing

Background

Molecular diagnostic panels for enteric pathogens offer increased sensitivity and reduced turnaround time. However, many pathogen detections do not change clinical management, and the cost is substantial.

Methods

We performed a retrospective chart review of adult outpatients with diarrhea at the University of Virginia who had samples tested by the FilmArray Gastrointestinal Panel (BioFire Diagnostics, Salt Lake City, UT) to identify the clinical yield and to validate the clinical criteria for testing recommended in the 2017 Infectious Diseases Society of America (IDSA) guidelines.

Results

We analyzed 629 tests sent from adult outpatients with diarrhea between March 23, 2015, and July 18, 2016. A pathogen was detected in 127 of 629 specimens (20.2%). The most common pathogens were enteropathogenic Escherichia coli (47, 7.5%), norovirus (24, 3.8%), enteroaggregative E. coli (14, 2.2%), Campylobacter (9, 1.4%), and Salmonella (9; 1.4%). The clinical yield of testing was low, with antimicrobial treatment clearly indicated for only 18 subjects (2.9%) and any change in clinical management indicated for 33 subjects (5.2%). Following the clinical criteria for diagnostic testing from the 2017 IDSA guidelines, which suggest diagnostic testing for patients with fever, abdominal pain, blood in stool, or an immunocompromising condition, would have reduced testing by 32.3% without significantly reducing the clinical yield (sensitivity, 97.0%; 95% confidence interval [CI], 84.2%-99.9%; negative predictive value, 99.5%; 95% CI, 97.3%-100.0%).

Conclusions

The clinical yield of molecular diagnostic testing in this population was low. Compliance with IDSA guidelines in adult outpatients with diarrhea could reduce testing by approximately one-third.

Evaluation of post-contamination survival and persistence of applied attenuated E. coli O157:H7 and naturally-contaminating E. coli O157:H7 on spinach under field conditions and following postharvest handling

This study determined the variability in population uniformity of an applied mixture of attenuated E. coli O157:H7 (attEcO157) on spinach leaves as impacted by sampling mass and detection technique over spatial and temporal conditions. Opportunistically, the survival and distribution of naturally contaminating pathogenic E. coli O157:H7 (EcO157), in a single packaged lot following commercial postharvest handling and washing, was also evaluated. From the main study outcomes, differences in the applied inoculum dose of 100-fold, resulted in indistinguishable population densities of approximately Log 1.1 CFU g^-1 by 14 days post-inoculation (DPI). Composite leaf samples of 150 g and the inclusion of the spinach petiole resulted in the greatest numerical sensitivity of detection of attEcO157 when compared to 25 and 150 g samples without petioles (P < 0.05). Differences in population density and protected-site survival and potential leaf internalization were observed between growing seasons and locations in California (P < 0.05). A Double Weibull model best described and identified two distinct populations with different inactivation rates of the inoculated attEcO157. Linear die-off rates varied between 0.14 and 0.29 Log/Day irrespective of location. Detection of EcO157- stx1-negative and stx2-positive, resulting from a natural contamination event, was observed in 11 of 26 quarantined commercial units of washed spinach by applying the 150 g sample mass protocol. The capacity to detect EcO157 varied between commercial test kits and non-commercial qPCR. Our findings suggest the need for modifications to routine pathogen sampling protocols employed for lot acceptance of spinach and other leafy greens.

Diagnostic Stewardship: Opportunity for a Laboratory-Infectious Diseases Partnership

Recent advances in microbial diagnostics are providing clinicians with information about microbes causing infections and their resistance to antimicrobial agents more rapidly than ever before. Diagnostic stewardship refers to the appropriate use of laboratory testing to guide patient management, including treatment, in order to optimize clinical outcomes and limit the spread of antimicrobial resistance. Fulfilling the promise of diagnostic stewardship requires a seamless partnership between clinical laboratories, pharmacists, and infectious diseases clinicians, so that appropriate tests are ordered and diagnostic information is translated into appropriate management in real time.

Bacterial diarrhea in hospitalized children: Pathogen distribution and drug resistance

AIM

To study the pathogen distribution and drug resistance in hospitalized children with bacterial diarrhea to guide the selection of appropriate antimicrobial drug regimen for the clinical treatment of bacterial diarrhea in children.

METHODS

A total of 1107 children with bacterial diarrhea treated at our hospital from May 2012 to October 2017 were retrospectively analyzed. According to the clinical data of all children (including medical records, laboratory examination results, fecal pathogen detection results, and drug susceptibility test results), the distribution and composition of pathogenic bacteria, clinical symptoms, the drug resistance of main pathogenic bacteria, therapeutic effects, and prognosis were analyzed.

RESULTS

In feces from 1107 children with bacterial diarrhea, 206 strains of pathogenic bacteria were isolated, including 39 cases of Gram-positive bacteria (such as Staphylococcus aureus) and 167 cases of Gram-negative bacteria (such as shigella, pathogenic Escherichia coli, and salmonella). The detection rate of pathogenic bacteria in the feces was the highest in children aged < 1 year, and the detection rate decreased with the increase of age. Pathogenic bacteria were detected throughout the year, especially in summer. There was a statistically significant difference (P < 0.05) in clinical symptoms (such as fever, abdominal pain, defecation, and rehydration) between bacterial diarrhea caused by Escherichia coli and Staphylococcus aureus. The rate of resistance of main Gram-positive bacteria to antimicrobial drugs moxifloxacin, vancomycin, and linezolid was less than 30%, and the rate of resistance of Gram-negative bacteria to antibiotics ceftazidime, trimethoprim/sulfamethoxazole, meropenem, and imipenem was less than 30%. The cure rate of bacterial diarrhea was 96.48% (1068/1107) after one week of treatment with antibiotics and selective antibacterial agents.

CONCLUSION

The pathogen distribution in children with bacterial diarrhea is complex, and clinicians should select antimicrobial drugs with a resistance rate less than 30% based on drug susceptibility test results.

Syndromic Panel-Based Testing in Clinical Microbiology

The recent development of commercial panel-based molecular diagnostics for the rapid detection of pathogens in positive blood culture bottles, respiratory specimens, stool, and cerebrospinal fluid has resulted in a paradigm shift in clinical microbiology and clinical practice. This review focuses on U.S. Food and Drug Administration (FDA)-approved/cleared multiplex molecular panels with more than five targets designed to assist in the diagnosis of bloodstream, respiratory tract, gastrointestinal, or central nervous system infections. While these panel-based assays have the clear advantages of a rapid turnaround time and the detection of a large number of microorganisms and promise to improve health care, they present certain challenges, including cost and the definition of ideal test utilization strategies (i.e., optimal ordering) and test interpretation.