Emerging Resistance Trends in Viridans Group Streptococci Bloodstream Infections Among Immunocompromised Children Receiving Levofloxacin Prophylaxis

BACKGROUND

Levofloxacin prophylaxis (LVXp) is often used for patients with underlying leukemia and severe neutropenia to reduce the risk of fever and bacteremia. This study evaluated trends in viridans group streptococci (VGS) antibiotic susceptibilities over time and clinical outcomes of children with VGS bloodstream infections (BSIs) during institutional adoption of LVXp.

METHODS

VGS blood culture isolates between 1/1/2010 and 12/31/2021 with susceptibility testing reported were included. Available isolates were re-identified to the species level and additional susceptibility testing was performed. Demographic and clinical data were abstracted from medical records.

RESULTS

A total of 264 VGS BSI isolates were identified in immunocompromised (IC, n = 125) and non-immunocompromised subjects, (non-IC, n = 139). IC subjects had lower rates of VGS isolates susceptible (S) to LVX and higher minimum inhibitory concentration (MICs) to LVX (p = 0.004) and ciprofloxacin (p = 0.0005) compared with non-IC subjects. No other evaluated antibiotic had increased MICs in either group. Fifteen of 19 (74%) LVX not susceptible (NS) isolates occurred in IC subjects, 13 represented breakthrough infections. IC subjects had higher rates of VGS-related shock (p = 0.012), need for pressor support (p = 0.039), and longer duration of hospitalization than non-IC subjects (p < 0.001). Clinical outcomes were comparable between subjects with LVX S and NS VGS BSI isolates.

CONCLUSIONS

VGS with reduced susceptibility to LVX emerged during institutional adoption of LVXp in high-risk children with immunocompromising conditions, but did not result in significant differences in clinical outcomes. Ongoing surveillance and susceptibility testing are critical in weighing the utility of LVXp against emerging antimicrobial resistance in this high-risk population.

2160. Mucosal Antiviral Cytokine Responses Are Impaired in Children and Adolescents with Severe COVID-19

Background

The factors associated with severe COVID-19 in pediatric patients remain poorly understood. We sought to determine whether mucosal innate immunity cytokines were associated with disease severity in children and adolescents with acute COVID-19.

Methods

Single-center, prospective study including children and adolescents &lt; 21 years of age hospitalized because of symptomatic COVID-19 from 3/2020 to 1/2021, and age, sex and race matched pre-pandemic (2016-2019) healthy controls. Nasopharyngeal (NP) samples were obtained at enrollment for measurement of SARS-CoV-2 viral loads by rt-PCR and cytokine concentrations using a 92-plex inflammation/antiviral panel (Olink). Disease severity was assessed by the need for supplemental oxygen or PICU admission, and patients classified as severe and non-severe based on these two parameters. Statistical analyses were performed in R studio and Benjamini-Hochberg applied to adjust for multiple comparisons.

Results

Of the 75 children with acute COVID-19 (median IQR age: 3.4 [0.2-15.3] years), 28 (37%) were classified as severe COVID-19 (19 PICU; 25 supplemental oxygen) and 47 (63%) were non-severe. Children with severe COVID-19 were predominantly male and had an underlying condition more frequently than those with non-severe disease (79% vs 49% respectively; p&lt; 0.01, Table 1). SARS-CoV-2 viral loads were comparable between groups, yet patients with severe COVID-19 had significantly higher concentrations of C-reactive protein (p=0.04), more frequent lymphopenia (p=0.03) and cardiac involvement (p=0.04), and received COVID-19 directed therapies more commonly (p&lt; 0.001). Comparative analyses identified 24 cytokines that were significantly different between children with acute COVID-19 versus 45 healthy controls. Of those, concentrations of IFN-γ (p=0.004), CXCL10 (p=0.01), CXCL11 (p=0.02) and CCL19 (p=0.02) were significantly lower in children with severe versus those with non-severe COVID-19 (Fig 1). Table 1.Demographic and clinical characteristics in children with symptomatic COVID-19*Bolded p-values indicates statistical significance. Abbreviations: N, number. CRP, C-Reactive protein; PICU, pediatric intensive care unit.**Other including the following underlying conditions: prematurity, endocrine conditions, immunocompromising conditions, prematurity, trisomy 21 and complex care. Ł Lymphopenia defined as an ALC of &lt;4,500 cells/μl in infants, and &lt;1,500 cells /μl in children &gt;12 months of age

Continuous variables displayed as medians and 25%-75% interquartile ranges (IQR), Mann-Whitney test was used to determine differences between two groups; Kruskal-Wallis & Dunn’s multiple test correction was used to determine differences between three groups (p-values*). Categorical data expressed as numbers and proportions (in parenthesis) and analyzed by Fisher’s exact test or Chi square test. Figure 1.Nasal mucosal concentrations of antiviral/regulatory cytokines in children with symptomatic COVID-19 according to disease severity

Conclusion

Mucosal concentrations of antiviral/regulatory cytokines were decreased in children with severe COVID-19. These findings suggest that impaired mucosal innate immune responses might favor SARS-CoV-2 disease progression and severity in children.

Disclosures

Amy Leber, PhD, BioFire: Advisor/Consultant|BioFire: Grant/Research Support|Biorad: Advisor/Consultant|Cepheid: Grant/Research Support Octavio Ramilo, MD, Adagio: Advisor/Consultant|Bill & Melinda Gates Foundation: Grant/Research Support|Janssen: Advisor/Consultant|Janssen: Grant/Research Support|Lilly: Advisor/Consultant|Merck: Advisor/Consultant|Merck: Grant/Research Support|NIH: Grant/Research Support|Pfizer: Advisor/Consultant|Pfizer: Honoraria|Sanofi: Advisor/Consultant|Sanofi: Honoraria Asuncion Mejias, MD, PhD, MsCS, AstraZeneca: Honoraria|Janssen: Advisor/Consultant|Janssen: Grant/Research Support|Merck: Advisor/Consultant|Merck: Grant/Research Support|Roche: Advisor/Consultant|Sanofi-Pasteur: Advisor/Consultant|Sanofi-Pasteur: Honoraria.

Corrigendum to: 204. Mucosal Cytokine Profiles in Children with COVID-19

[This corrects the article DOI: 10.1093/ofid/ofab466.000.].

Myeloid-Derived Suppressor Cells and Clinical Outcomes in Children With COVID-19

BACKGROUND

Although children with COVID-19 account for fewer hospitalizations than adults, many develop severe disease requiring intensive care treatment. Critical illness due to COVID-19 has been associated with lymphopenia and functional immune suppression. Myeloid-derived suppressor cells (MDSCs) potently suppress T cells and are significantly increased in adults with severe COVID-19. The role of MDSCs in the immune response of children with COVID-19 is unknown.

AIMS

We hypothesized that children with severe COVID-19 will have expansion of MDSC populations compared to those with milder disease, and that higher proportions of MDSCs will correlate with clinical outcomes.

METHODS

We conducted a prospective, observational study on a convenience sample of children hospitalized with PCR-confirmed COVID-19 and pre-pandemic, uninfected healthy controls (HC). Blood samples were obtained within 48 h of admission and analyzed for MDSCs, T cells, and natural killer (NK) cells by flow cytometry. Demographic information and clinical outcomes were obtained from the electronic medical record and a dedicated survey built for this study.

RESULTS

Fifty children admitted to the hospital were enrolled; 28 diagnosed with symptomatic COVID-19 (10 requiring ICU admission) and 22 detected by universal screening (6 requiring ICU admission). We found that children with severe COVID-19 had a significantly higher percentage of MDSCs than those admitted to the ward and uninfected healthy controls. Increased percentages of MDSCs in peripheral blood mononuclear cells (PBMC) were associated with CD4+ T cell lymphopenia. MDSC expansion was associated with longer hospitalizations and need for respiratory support in children admitted with acute COVID-19.

CONCLUSION

These findings suggest that MDSCs are part of the dysregulated immune responses observed in children with severe COVID-19 and may play a role in disease pathogenesis. Future mechanistic studies are required to further understand the function of MDSCs in the setting of SARS-CoV-2 infection in children.

185. Trends in Clinical Presentation and Antibiotic Resistance of Viridans Group Streptococci Bloodstream Infections in Immunocompromised Children

Background

Levofloxacin prophylaxis (LVXp) is recommended in children with severe neutropenia from underlying malignancy or hematopoietic cell transplantation (HCT). The impact of LVXp on the epidemiology of viridans group streptococcus bloodstream infections (VGS-BSI) is unknown. At our center, LVXp was prescribed to high-risk children with expected prolonged neutropenia (ANC < 100, > 7 days) as part of a clinical trial (2013-17) and routinely since November 2018. We aim to describe our local epidemiology, antibiotic susceptibilities, and clinical outcomes of VGS-BSI over time.

Methods

VGS-BSI from 1/1/10-1/31/21 were identified via the laboratory database. Clinical data of patients followed at NCH with underlying malignancy, severe neutropenia, or HCT were extracted from the electronic health record. Available VGS isolates were subcultured, species identification confirmed by MALDI-ToF or 16s rDNA sequencing and susceptibility to penicillin (PCN), cefepime (CEF), vancomycin (VAN), and LVX performed via Etest per CLSI M100 guidelines. Non-parametric descriptive statistics were applied.

Results

Over a 10-yr period, 111 VGS-BSI occurred in 93 patients (Table 1); 15 (16%) patients had ≥ 2 VGS-BSI. 80 (86%) patients had fever and neutropenia (F&N); 26 (28%) required ICU care for vasopressors (N=17, 18%) or mechanical ventilation (N=10, 11%). Most VGS isolates were S. mitis/oralis group. In total, 15 (16%) patients received LVXp ≤ 6 months before VGS-BSI; 9 (10%) had breakthrough VGS-BSI while receiving LVXp and all isolates were LVX resistant. Figure 1 shows susceptibilities: overall, 24% of isolates had frank resistance to PCN, 19% CEF, 13% LVX; all were VAN susceptible. When evaluating for changes in susceptibilities over time, there was a significant difference in the proportion of LVX-resistant isolates (p=0.009, Cochran-Armitage χ ²), but not CEF (p=0.08) or PCN (p=0.86).

Table 1. Demographic and Clinical Characteristics of Immunocompromised Children with Viridans Group Streptococci Bloodstream Infections (VGS-BSI)

Figure 1. Antimicrobial Susceptibility Profile of Viridans Group Streptococci Bloodstream Isolates from Immunocompromised children, 2010-2021. Of 111 VGS-BSI reported during the study period from immunocompromised children, 83 (75%) were available for further testing. Antimicrobial susceptibility testing was performed by Etest and interpreted per CLSI M100. Susceptibility profiles to penicillin (PCN), cefepime (CEP) and, levofloxacin (LVX) are shown. Abbreviations: S—susceptible, I—intermediate, R—resistant.

Conclusion

Breakthrough, LVX-resistant VGS-BSI occurred in 10% of patients, most frequently in children with AML or HCT. Over time, there was a trend towards increased LVX resistance in the cohort. Routine antimicrobial testing and ongoing monitoring for emergence of resistance are warranted to inform local prophylaxis and empirical antibiotic strategies for high-risk children with F&N.

Disclosures

Monica I. Ardura, DO, MSCS, Shire (Grant/Research Support)

Renal length z-score for the detection of dysfunction in children with solitary functioning kidney

AIM

To evaluate whether renal length z-scores predict renal dysfunction in children with a solitary functioning kidney (SFK).

METHODS

In a single-centre retrospective cohort of children with SFK, we correlated body mass index z-scores, extracellular volume and lean body mass to renal length z-scores. We grouped these z-scores to other markers of renal dysfunction (proteinuria, hypertension, extracellular volume and abnormal estimated glomerular function rate [eGFR]) and analysed renal length z-score with multivariate analysis, receiver-operated characteristics (ROC) plots and Youden's index to determine an appropriate cut-off.

RESULTS

111 children had a median follow-up 5.08 years, eGFR 80.8 mL/min/1.73 m² , and age at last follow-up 7.4 (3.8-13.4 years). The median renal length z-scores of those without any renal dysfunction (n = 37, 25.1%) were greater (+3.66, interquartile range 3.02-4.47) than those with renal dysfunction (median 3.11, interquartile range 1.76-4.11, P = .0107, Mann-Whitney test). Using a cut-off of z-score of >+1.911, the odds ratio for having no renal dysfunction was 0.07 (95% CI 0.002-0.459, P = .0010). However, accuracy of the renal length z-score was poor (ROC curve 0.6488).

CONCLUSION

In this cohort of children with SKF, using the renal length z-score as a biomarker of renal dysfunction at 7 years of age is not recommended.

Detection of insulitis by pancreatic scintigraphy with 99mTc-labeled IL-2 and MRI in patients with LADA (Action LADA 10)

OBJECTIVE

Pancreatic scintigraphy with interleukin-2 radiolabeled with (99m)Tc ((99m)Tc-IL-2) is a technique used to image chronic inflammatory-mediated disorders. We used this method to detect a signal consistent with the presence of insulitis in patients with autoimmune diabetes. Positive and negative controls (patients with pancreatic carcinoma and type 2 diabetes, respectively) also were studied.

RESEARCH DESIGN AND METHODS

We examined 25 patients with autoimmune diabetes (16 with recently diagnosed type 1 diabetes, 9 with latent autoimmune diabetes in adults [LADA]), 6 with type 2 diabetes, and 7 with pancreatic carcinoma (the latter two groups were used as negative and positive controls, respectively). All patients underwent (99m)Tc-IL-2 scintigraphy and contrast-enhanced MRI of the pancreas. To validate positive controls, samples were taken from patients with pancreatic carcinoma during surgery for histological and immunohistochemical investigations.

RESULTS

Pancreatic accumulation of (99m)Tc-IL-2 was detected in patients with autoimmune diabetes (61% positive) and, notably, in 6 of 9 patients with LADA; semiquantitative evaluation of pancreatic uptake of (99m)Tc-IL-2 showed higher values in patients with autoimmune diabetes (both childhood and LADA) and pancreatic carcinoma than in those with type 2 diabetes (4.45 ± 1.99, 4.79 ± 1.1, and 4.54 ± 1.62 vs. 2.81 ± 0.63; P = 0.06, P = 0.01, and P = 0.04, respectively). In patients with pancreatic carcinoma, pancreatic interleukin-2 receptor expression correlated with pancreatic (99m)Tc-IL-2 uptake (r = 0.8; P = 0.01). In patients with LADA, (99m)Tc-IL-2 uptake inversely correlated with duration of disease (r = 0.7; P = 0.03).

CONCLUSIONS

Autoimmune diabetes in adults is associated with increased pancreatic (99m)Tc-IL-2 uptake, indicating the presence of insulitis, particularly within 1 year of the beginning of insulin therapy, similar to type 1 diabetes at diagnosis.

Imaging of β-cell mass and insulitis in insulin-dependent (Type 1) diabetes mellitus

Insulin-dependent (type 1) diabetes mellitus is a metabolic disease with a complex multifactorial etiology and a poorly understood pathogenesis. Genetic and environmental factors cause an autoimmune reaction against pancreatic β-cells, called insulitis, confirmed in pancreatic samples obtained at autopsy. The possibility to noninvasively quantify β-cell mass in vivo would provide important biological insights and facilitate aspects of diagnosis and therapy, including follow-up of islet cell transplantation. Moreover, the availability of a noninvasive tool to quantify the extent and severity of pancreatic insulitis could be useful for understanding the natural history of human insulin-dependent (type 1) diabetes mellitus, to early diagnose children at risk to develop overt diabetes, and to select patients to be treated with immunotherapies aimed at blocking the insulitis and monitoring the efficacy of these therapies. In this review, we outline the imaging techniques currently available for in vivo, noninvasive detection of β-cell mass and insulitis. These imaging techniques include magnetic resonance imaging, ultrasound, computed tomography, bioluminescence and fluorescence imaging, and the nuclear medicine techniques positron emission tomography and single-photon emission computed tomography. Several approaches and radiopharmaceuticals for imaging β-cells and lymphocytic insulitis are reviewed in detail.