Development and performance of a multiplex PCR assay for the detection of bacteria in sterile body fluids

Detection of bacterial pathogens directly from synovial fluids using digital PCR: A proof of concept study

Diagnosis of joint infections is often challenging due to low specimen volumes, low sensitivity of Gram stains and long incubation times of cultures. Digital PCR (dPCR) is a molecular tool that can detect nucleic acid targets with high sensitivity and resistance to inhibition. A 3 hour dPCR assay targeting the 16S gene was performed on archived synovial fluids. The assay detected the 16S gene directly from 4 µL of joint fluid without nucleic acid extraction. In 43 culture positive neat synovial fluids, the dPCR instrument detected 31 (72%) as positive, and 12 (28%) as indeterminate. In 49 culture negative specimens, dPCR was negative for 34 (69%), indeterminate for 14 (29%). The detection of bacteria was similar to real-time PCR performed on extracted specimens and demonstrated superior sensitivity to Gram stain. This technique shows potential as a rapid detection method for bacterial pathogens in synovial fluids, with optimization to improve specificity.

Increased Incidence and Severity of Group A Streptococcal Infections in Children in Southeast Texas From June 2022 to May 2023

BACKGROUND

Group A Streptococcus (GAS) infections can cause a range of disease manifestations and severity, including invasive infections that can lead to death. In 2022-2023, there was an increased number of cases of invasive GAS in the United States following a decline in 2020-2022.

METHODS

We investigated this surge at a 3-hospital system of children's hospitals in Southeast Texas. Cases of invasive GAS (n = 252) were retrospectively reviewed from peak periods of infection, beginning June 2019-May 2020 and continuing each successive year until May 2023. Cases were analyzed based on patient demographics, disease manifestations, coinfections, and hospital course. Isolates grown in culture were sequenced, and the emm types and genes associated with virulence were analyzed.

RESULTS

Compared with previous years, June 2022-May 2023 had the largest number of invasive GAS cases (n = 154, 2022-2023; 34, 2021-2022; 12, 2020-2021; 52, 2019-2020). Compared with the previous 3 years, patients from 2022 to 2023 were more likely to present with complicated pneumonia (23.4% vs. 7.1%; P = 0.0009), require respiratory support (34.4% vs. 14.3%; P < 0.001), be admitted to the intensive care unit (29.2% vs. 16.3; P = 0.0235), and be infected with emm type 12 isolates (40.6% vs. 10.3%; P = 0.0030).

CONCLUSIONS

In June 2022-May 2023, there was a 5-fold surge of invasive GAS infection cases in children at Texas Children's Hospital compared with the previous 3 years. These cases required greater intensive care unit hospitalization and respiratory support requirements due to higher rates of complicated pneumonia.

Clinical Impact of Pleural Fluid Streptococcus pneumoniae Polymerase Chain Reaction Testing in Children With Complicated Pneumonia

BACKGROUND

While Streptococcus pneumoniae (Spn) is the leading cause of pediatric complicated community-acquired pneumonia (cCAP), it is infrequently recovered by culture-based methods. We studied the real-world clinical impact of an Spn polymerase chain reaction (PCR) assay for pleural fluid.

METHODS

This pre-post quasi-experimental cohort study compared pathogen detection, antibiotic usage, and outcomes in children hospitalized with cCAP requiring pleural effusion or empyema drainage at Children's Hospital Colorado between 2016 and 2023. Patients were compared across 2 diagnostic periods: pre-Spn PCR and post-Spn PCR. Cox proportional hazard models compared time from admission to pathogen detection, optimal therapy (narrowest pathogen-directed or guideline-recommended empiric therapy), and methicillin-resistant Staphylococcus aureus (MRSA) therapy discontinuation between periods.

RESULTS

Compared to the pre-Spn PCR cohort (n = 149), the post-Spn PCR cohort (n = 79) was more likely to have a pathogen detected (73.4% post-PCR vs 38.9% pre-PCR, P < .001), driven by more Spn detections (45.6% vs 14.1%, P < .001). Time to pathogen detection during hospitalization was shorter in the post-Spn PCR period (P < .001). The post-PCR cohort was more likely to receive optimal therapy (84.8% vs 53.0%, P < .001), with shorter median times to optimal antibiotics (4.9 vs 10.0 days, P < .001) and MRSA therapy discontinuation (1.5 vs 2.5 days, P = .03). There were no differences in hospital length of stay or readmissions.

CONCLUSIONS

Spn molecular testing of pleural fluid in children with cCAP resulted in significantly more microbiologic diagnoses and was associated with the optimization of antibiotics and decreased exposure to MRSA therapy, suggesting its clinical impact for pediatric complicated pneumonia.

Acute Hematogenous Osteomyelitis of the Pelvis in Children

BACKGROUND

Pelvic involvement has been reported in 3%-14% of acute hematogenous osteomyelitis (AHO) cases in children. One guideline suggests need for a longer antibiotic course in pelvic AHO, however, recent data are lacking. We describe the clinical course of children with pelvic AHO and compare it to nonpelvic AHO.

METHODS

A retrospective review of patients with a diagnosis of AHO admitted to Texas Children's Hospital from January 2012 to December 2020 was conducted. Patients 6 months-<19 years old and with ≤14 days of symptoms at admission were eligible. Patients with sickle cell disease or immunocompromised were excluded. Wilcoxon rank-sum test assessed for differences between continuous variables and Fisher exact for categorical variables using STATA 17.

RESULTS

We compared 104 cases of pelvic AHO to 314 cases of nonpelvic AHO. Patients had similar microbiology, length of stay and length of antibiotic therapy. Patients with pelvic AHO had pyomyositis identified by magnetic resonance imaging more often (28.8 vs. 9.4%, P < 0.001) and bone abscess less often (22.1 vs. 46.5%, P < 0.001). Rates of chronic complications were comparable between patients with pelvic AHO and nonpelvic AHO (8.4% vs. 15.1%, P = 0.1). Nineteen patients (18.3%) with pelvic AHO received ≤30 antibiotic days without complications, but they had less need for intensive care or bone abscesses than patients treated longer.

CONCLUSIONS

Pelvic AHO in children may be more frequent than previously reported but is not associated with more complications. Four weeks of therapy may be sufficient in selected patients. Prospective studies to compare outcomes with different lengths of therapy are needed.

DIAGNOSTIC PERFORMANCE OF CENTRAL NERVOUS SYSTEM INFECTIONS IN PATIENTS WITH NEUROSURGICAL INTENSIVE CARE USING METAGENOMIC NEXT-GENERATION SEQUENCING: A PROSPECTIVE OBSERVATIONAL STUDY

ABSTRACT

Background. Identifying the causative pathogens of central nervous system infections (CNSIs) is crucial, but the low detection rate of traditional culture methods in cerebrospinal fluid (CSF) has made the pathogenic diagnosis of CNSIs a longstanding challenge. Patients with CNSIs after neurosurgery often overlap with inflammatory and bleeding. Metagenomic next-generation sequencing (mNGS) has shown some benefits in pathogen detection. This study aimed to investigate the diagnostic performance of mNGS in the etiological diagnosis of CNSIs in patients after neurosurgery. Methods. In this prospective observational study, we enrolled patients with suspected CNSIs after neurosurgical operations who were admitted to the intensive care unit of Beijing Tiantan Hospital. All enrolled patients' CSF was tested using mNGS and pathogen culture. According to comprehensive clinical diagnosis, the enrolled patients were divided into CNSIs group and non-CNSIs group to compare the diagnostic efficiency of mNGS and pathogen culture. Results. From December 2021 to March 2023, 139 patients were enrolled while 66 in CNSIs group and 73 in non-CNSIs. The mNGS exceeded culture in the variety and quantity of pathogens detected. The mNGS outperformed traditional pathogen culture in terms of positive percent agreement (63.63%), accuracy (82.01%), and negative predictive value (75.00%), with statistically significant differences ( P < 0.05) for traditional pathogen culture. The mNGS also detected bacterial spectrum and antimicrobial resistance genes. Conclusions. Metagenomics has the potential to assist in the diagnosis of patients with CNSIs who have a negative culture.

Invasive Group A Streptococcus in Infants Less Than 1-year of Age From 2012 to 2022: A Single-Center Experience

The incidence of invasive Group A Streptococcus (iGAS) has varied throughout the COVID-19 pandemic. We reviewed iGAS infections in infants ≤1 year from 2012 to 2022. Twenty-five percent of cases occurred in the last quarter of 2022. Pneumonia (21.8%) was the most common presentation. Twenty-one patients (65.6%) were successfully transitioned to oral antibiotics.