Rapid Detection of Bacillus anthracis Bloodstream Infections by Use of a Novel Assay in the GeneXpert System

A simple and sensitive test for Candida auris colonization, surveillance, and infection control suitable for near patient use

Candida auris is a multidrug-resistant fungal pathogen with a propensity to colonize humans and persist on environmental surfaces. C. auris invasive fungal disease is being increasingly identified in acute and long-term care settings. We have developed a prototype cartridge-based C. auris surveillance assay (CaurisSurV cartridge; "research use only") that includes integrated sample processing and nucleic acid amplification to detect C. auris from surveillance skin swabs in the GeneXpert instrument and is designed for point-of-care use. The assay limit of detection (LoD) in the skin swab matrix was 10.5 and 14.8 CFU/mL for non-aggregative (AR0388) and aggregative (AR0382) strains of C. auris, respectively. All five known clades of C. auris were detected at 2-3-5× (31.5-52.5 CFU/mL) the LoD. The assay was validated using a total of 85 clinical swab samples banked at two different institutions (University of California Los Angeles, CA and Wadsworth Center, NY). Compared to culture, sensitivity was 96.8% (30/31) and 100% (10/10) in the UCLA and Wadsworth cohorts, respectively, providing a combined sensitivity of 97.5% (40/41), and compared to PCR, the combined sensitivity was 92% (46/50). Specificity was 100% with both clinical (C. auris negative matrix, N = 31) and analytical (non-C. auris strains, N = 32) samples. An additional blinded study with N = 60 samples from Wadsworth Center, NY yielded 97% (29/30) sensitivity and 100% (28/28) specificity. We have developed a completely integrated, sensitive, specific, and 58-min prototype test, which can be used for routine surveillance of C. auris and might help prevent colonization and outbreaks in acute and chronic healthcare settings.

IMPORTANCE

This study has the potential to offer a better solution to healthcare providers at hospitals and long-term care facilities in their ongoing efforts for effective and timely control of Candida auris infection and hence quicker response for any potential future outbreaks.

The Biosafety Research Road Map: The Search for Evidence to Support Practices in the Laboratory-Bacillus anthracis and Brucella melitensis

Introduction

Brucella melitensis and Bacillus anthracis are zoonoses transmitted from animals and animal products. Scientific information is provided in this article to support biosafety precautions necessary to protect laboratory workers and individuals who are potentially exposed to these pathogens in the workplace or other settings, and gaps in information are also reported. There is a lack of information on the appropriate effective concentration for many chemical disinfectants for this agent. Controversies related to B. anthracis include infectious dose for skin and gastrointestinal infections, proper use of personal protective equipment (PPE) during the slaughter of infected animals, and handling of contaminated materials. B. melitensis is reported to have the highest number of laboratory-acquired infections (LAIs) to date in laboratory workers.

Methods

A literature search was conducted to identify potential gaps in biosafety and focused on five main sections including the route of inoculation/modes of transmission, infectious dose, LAIs, containment releases, and disinfection and decontamination strategies.

Results

Scientific literature currently lacks information on the effective concentration of many chemical disinfectants for this agent and in the variety of matrices where it may be found. Controversies related to B. anthracis include infectious dose for skin and gastrointestinal infections, proper use of PPE during the slaughter of infected animals, and handling contaminated materials.

Discussion

Clarified vulnerabilities based on specific scientific evidence will contribute to the prevention of unwanted and unpredictable infections, improving the biosafety processes and procedures for laboratory staff and other professionals such as veterinarians, individuals associated with the agricultural industry, and those working with susceptible wildlife species.

Rapid Capsular Antigen Immunoassay for Diagnosis of Inhalational Anthrax: Preclinical Studies and Evaluation in a Nonhuman Primate Model

Inhalational anthrax is a fatal infectious disease. Rapid and effective treatment is critically dependent on early and accurate diagnosis. Blood culture followed by identification and confirmation may take days to provide clinically relevant information. In contrast, immunoassay for a shed antigen, the capsular polypeptide gamma-d-polyglutamate (γDPGA), can provide rapid results at the point of care. In this study, a lateral flow immunoassay for γDPGA was evaluated in a robust nonhuman primate model of inhalational anthrax. The results showed that the time to a positive result with the rapid test using either serum or blood as a clinical specimen was similar to the time after infection when a blood culture became positive. In vitro testing showed that the test was equally sensitive with cultures of the three major clades of Bacillus anthracis. Cultures from other Bacillus spp. that are known to produce γDPGA also produced positive results. The test was negative with human sera from 200 normal subjects and 45 subjects with culture-confirmed nonanthrax bacterial or fungal sepsis. Taken together, the results showed that immunoassay for γDPGA is an effective surrogate for blood culture in a relevant cynomolgus monkey model of inhalational anthrax. The test would be a valuable aid in early diagnosis of anthrax, which is critical for rapid intervention and a positive outcome. Use of the test could facilitate triage of patients with signs and symptoms of anthrax in a mass-exposure incident and in low-resource settings where laboratory resources are not readily available. IMPORTANCE Patient outcome in anthrax is critically dependent on early diagnosis followed by effective treatment. We describe a rapid lateral flow immunoassay that detects capsular antigen of Bacillus anthracis that is shed into blood during infection. The test was evaluated in a robust cynomolgus monkey model of inhalational anthrax. Rapid detection of capsular antigen is an effective surrogate for the time-consuming and laboratory-intensive diagnosis by blood culture, direct fluorescent antibody staining, or other molecular testing. The test can be performed at the point of patient contact, is rapid and inexpensive, and can be used by individuals with minimal training.

Biodefence research two decades on: worth the investment?

For the past 20 years, the notion of bioterror has been a source of considerable fear and panic worldwide. In response to the terror attacks of 2001 in the USA, extensive research funding was awarded to investigate bioterror-related pathogens. The global scientific legacy of this funding has extended into the present day, highlighted by the ongoing COVID-19 pandemic. Unsurprisingly, the surge in biodefence-related research and preparedness has been met with considerable apprehension and opposition. Here, we briefly outline the history of modern bioterror threats and biodefence research, describe the scientific legacy of biodefence research by highlighting advances pertaining to specific bacterial and viral pathogens, and summarise the future of biodefence research and its relevance today. We sought to address the sizeable question: have the past 20 years of investment into biodefence research and preparedness been worth it? The legacy of modern biodefence funding includes advancements in biosecurity, biosurveillence, diagnostics, medical countermeasures, and vaccines. In summary, we feel that these advances justify the substantial biodefence funding trend of the past two decades and set a precedent for future funding.

Clinically Important Toxins in Bacterial Infection: Utility of Laboratory Detection

The elaboration of proteins that damage host cells is fundamental to the pathogenesis of many bacterial pathogens. The clinical significance of many bacterial toxins is well recognized, and routine detection is necessary to confirm definitive diagnosis for some types of infectious diseases. Determining the clinical significance of a toxin involves many factors, including the toxin's prevalence, virulence, and role in disease pathogenesis. While essential from a diagnostic perspective, toxin detection has the potential to be important for patient management decision making, as well as infection prevention and control measures. This review focuses on the history, epidemiology, pathogenesis, clinical presentation, and management of infections associated with well-defined, clinically important toxins (such as Shiga toxin-producing Escherichia coli), as well as those that are less well defined (such as Staphylococcus aureus' Panton-Valentine leukocidin) where detection may yield clinically important information.

Multiplex Detection of Three Select Agents Directly from Blood by Use of the GeneXpert System

Francisella tularensis, Bacillus anthracis, and Yersinia pestis are tier 1 select agents with the potential to rapidly cause severe disease. Rapid detection of these bacteria from patient samples at the point of care could contribute to improved clinical outcomes in the event of a bioterrorism attack. A multiplex nested PCR assay for detection of F. tularensis, B. anthracis, and Y. pestis directly from patient blood samples was developed using the GeneXpert system. The multiplex GeneXpert cartridge-based assay includes all necessary sample processing and amplification reagents. Blood samples spiked with different numbers of CFU were used to measure the analytical limit of detection (LOD) and dynamic range. Sensitivity was determined by testing spiked blood samples and negative-control blood in a blind manner. Specificity was determined by testing against nontarget pathogens and blood samples from clinical patients. The assay LOD was 8.5 CFU/ml for F. tularensis, 10 CFU/ml for B. anthracis, and 4.5 CFU/ml for Y. pestis The sensitivity was 100% at the LOD for all three select agent bacteria in spiked patient blood samples. The assay specificity was 100% when it was tested against both nontarget pathogens and clinical patient blood samples. The total assay time was approximately 100 min. This automated assay, which is suitable for use at the point of care, identifies three select agents directly in blood without the need for enrichment with a high sensitivity within 100 min. This assay may enable rapid detection and treatment of patients infected with the target organisms in the event of a bioterrorism attack.

Advances in Molecular Diagnostic Approaches for Biothreat Agents

The advancement in Molecular techniques has been implicated in the development of sophisticated, high-end diagnostic platform and point-of-care (POC) devices for the detection of biothreat agents. Different molecular and immunological approaches such as Immunochromatographic and lateral flow assays, Enzyme-linked Immunosorbent assays (ELISA), Biosensors, Isothermal amplification assays, Nucleic acid amplification tests (NAATs), Next Generation Sequencers (NGS), Microarrays and Microfluidics have been used for a long time as detection strategies of the biothreat agents. In addition, several point of care (POC) devices have been approved by FDA and commercialized in markets. The high-end molecular platforms like NGS and Microarray are time-consuming, costly, and produce huge amount of data. Therefore, the future prospects of molecular based technique should focus on developing quick, user-friendly, cost-effective and portable devices against biological attacks and surveillance programs.

Confronting the threat of bioterrorism: realities, challenges, and defensive strategies

Global terrorism is a rapidly growing threat to world security, and increases the risk of bioterrorism. In this Review, we discuss the potential threat of bioterrorism, agents that could be exploited, and recent developments in technologies and policy for detecting and controlling epidemics that have been initiated intentionally. The local and international response to infectious disease epidemics, such as the severe acute respiratory syndrome and west African Ebola virus epidemic, revealed serious shortcomings which bioterrorists might exploit when intentionally initiating an epidemic. Development of new vaccines and antimicrobial therapies remains a priority, including the need to expedite clinical trials using new methodologies. Better means to protect health-care workers operating in dangerous environments are also needed, particularly in areas with poor infrastructure. New and improved approaches should be developed for surveillance, early detection, response, effective isolation of patients, control of the movement of potentially infected people, and risk communication. Access to dangerous pathogens should be appropriately regulated, without reducing progress in the development of countermeasures. We conclude that preparedness for intentional outbreaks has the important added value of strengthening preparedness for natural epidemics, and vice versa.