Being prepared: bioterrorism and mass prophylaxis: part I

Yersinia pestis and pneumonic plague: Insight into how a lethal pathogen interfaces with innate immune populations in the lung to cause severe disease

Yersinia pestis is the causative agent of bubonic, septicemic and pneumonic plague. The historical importance and potential of plague to re-emerge as a threat worldwide are indisputable. The most severe manifestion of plague is pneumonic plague, which results in disease that is 100% lethal without treatment. Y. pestis suppresses host immune responses early in the lung to establish infection. The later stages of infection see the rapid onset of hyperinflammatory responses that prove lethal. The study of Y. pestis host/pathogen interactions have largely been investigated during bubonic plague and with attenuated strains in cell culture models. There remains a somewhat limited understanding of the interactions between virulent Y. pestis and immune populations in the lung that drive severe disease. In this review we give a broad overview of the progression of pneumonic plague and highlighting how Y. pestis interfaces with host innate immune populations in the lung to cause lethal disease.

Antitoxin Use in the Prevention and Treatment of Anthrax Disease: A Systematic Review

BACKGROUND

Bacillus anthracis is a high-priority threat agent because of its widespread availability, easy dissemination, and ability to cause substantial morbidity and mortality. Although timely and appropriate antimicrobial therapy can reduce morbidity and mortality, the role of adjunctive therapies continues to be explored.

METHODS

We searched 11 databases for articles that report use of anthrax antitoxins in treatment or prevention of systemic anthrax disease published through July 2019. We identified other data sources through reference search and communication with experts. We included English-language studies on antitoxin products with approval by the US Food and Drug Administration (FDA) for anthrax in humans, nonhuman primates, and rabbits. Two researchers independently reviewed studies for inclusion and abstracted relevant data.

RESULTS

We abstracted data from 12 publications and 2 case reports. All 3 FDA-approved anthrax antitoxins demonstrated significant improvement in survival as monotherapy over placebo in rabbits and nonhuman primates. No study found significant improvement in survival with combination antitoxin and antimicrobial therapy compared to antimicrobial monotherapy. Case reports and case series described 25 patients with systemic anthrax disease treated with antitoxins; 17 survived. Animal studies that used antitoxin monotherapy as postexposure prophylaxis (PEP) demonstrated significant improvement in survival over placebo, with greatest improvements coming with early administration.

CONCLUSIONS

Limited human and animal evidence indicates that adjunctive antitoxin treatment may improve survival from systemic anthrax infection. Antitoxins may also provide an alternative therapy to antimicrobials for treatment or PEP during an intentional anthrax incident that could involve a multidrug-resistant B. anthracis strain.

Yersinia pestis: the Natural History of Plague

The Gram-negative bacterium Yersinia pestis is responsible for deadly plague, a zoonotic disease established in stable foci in the Americas, Africa, and Eurasia. Its persistence in the environment relies on the subtle balance between Y. pestis-contaminated soils, burrowing and nonburrowing mammals exhibiting variable degrees of plague susceptibility, and their associated fleas. Transmission from one host to another relies mainly on infected flea bites, inducing typical painful, enlarged lymph nodes referred to as buboes, followed by septicemic dissemination of the pathogen. In contrast, droplet inhalation after close contact with infected mammals induces primary pneumonic plague. Finally, the rarely reported consumption of contaminated raw meat causes pharyngeal and gastrointestinal plague. Point-of-care diagnosis, early antibiotic treatment, and confinement measures contribute to outbreak control despite residual mortality. Mandatory primary prevention relies on the active surveillance of established plague foci and ectoparasite control. Plague is acknowledged to have infected human populations for at least 5,000 years in Eurasia. Y. pestis genomes recovered from affected archaeological sites have suggested clonal evolution from a common ancestor shared with the closely related enteric pathogen Yersinia pseudotuberculosis and have indicated that ymt gene acquisition during the Bronze Age conferred Y. pestis with ectoparasite transmissibility while maintaining its enteric transmissibility. Three historic pandemics, starting in 541 AD and continuing until today, have been described. At present, the third pandemic has become largely quiescent, with hundreds of human cases being reported mainly in a few impoverished African countries, where zoonotic plague is mostly transmitted to people by rodent-associated flea bites.

Antimicrobial Spectrum of Titroleane™: A New Potent Anti-Infective Agent

Tea Tree oil (TTO) is well known for its numerous good properties but might be also irritating or toxic when used topically or ingested, thus limiting the number of possible applications in Humans. The aim of the study was to characterize the antimicrobial spectrum as well as the toxicity of Titroleane™, a new anti-infective agent obtained from TTO but cleared of its toxic monoterpenes part. The susceptibility to Titroleane™ of various pathogens (bacteria and fungi) encountered in animal and human health was studied in comparison with that of TTO. Antimicrobial screening was carried out using the broth microdilution method. Activities against aerobic, anaerobic, fastidious and non-fastidious microorganisms were performed. For all microorganisms tested, the MIC values for Titroleane™ ranged from 0.08% to 2.5%, except for Campylobacter jejuni, and Aspergillus niger. In particular, Titroleane™ showed good efficacy against skin and soft tissue infection pathogens, such as methicillin resistant Staphylococcus aureus (MRSA), intra-abdominal infections and oral pathogens, as well as fish farming pathogens. Toxicity testing showed little and similar cytotoxicities between TTO and Titroleane™ of 37% and 23%, respectively at a concentration of 0.025% (v/v). Finally, we demonstrated that the antimicrobial activity of Titroleane™ is similar to that of TTO.

Crystal structure of UDP-glucose pyrophosphorylase from Yersinia pestis, a potential therapeutic target against plague

Yersinia pestis, the causative agent of bubonic plague, is one of the most lethal pathogens in recorded human history. Today, the concern is the possible misuse of Y. pestis as an agent in bioweapons and bioterrorism. Current therapies for the treatment of plague include the use of a small number of antibiotics, but clinical cases of antibiotic resistance have been reported in some areas of the world. Therefore, the discovery of new drugs is required to combat potential Y. pestis infection. Here, the crystal structure of the Y. pestis UDP-glucose pyrophosphorylase (UGP), a metabolic enzyme implicated in the survival of Y. pestis in mouse macrophages, is described at 2.17 Å resolution. The structure provides a foundation that may enable the rational design of inhibitors and open new avenues for the development of antiplague therapeutics.

Influence of pH on the activity of finafloxacin against extracellular and intracellular Burkholderia thailandensis, Yersinia pseudotuberculosis and Francisella philomiragia and on its cellular pharmacokinetics in THP-1 monocytes

OBJECTIVES

Burkholderia pseudomallei, Yersinia pestis and Francisella tularensis are facultative intracellular bacteria causing life-threatening infections. We have (a) compared the activity of finafloxacin (a fluoroquinolone in development showing improved activity at acidic pH) with that of ciprofloxacin, levofloxacin and imipenem against the extracellular and intracellular (THP-1 monocytes) forms of infection by attenuated surrogates of these species (B. thailandensis, Y. pseudotuberculosis, F. philomiragia) and (b) assessed finafloxacin cellular pharmacokinetics (accumulation, distribution, efflux).

METHODS

Bacteria in broth or in infected monocytes were exposed to antibiotics at pH 7.4 or 5.5 for 24 hr. Maximal relative efficacies (E_max) and static concentrations (C_s) were calculated using the Hill equation (concentration-response curves). Finafloxacin pharmacokinetics in cells at pH 7.4 or 5.5 was investigated using ¹⁴C-labelled drug.

RESULTS

Extracellularly, all drugs sterilized the cultures, with finafloxacin being two to six times more potent at acidic pH. Intracellularly, E_max reached the limit of detection (4-5 log₁₀ cfu decrease) for finafloxacin against all species, but only against B. thailandensis and F. philomiragia for ciprofloxacin and levofloxacin, while imipenem caused less than 2 log₁₀ cfu decrease for all species. At acid pH, C_s shifted to two to five times lower values for finafloxacin and to one to four times higher values for the other drugs. Finafloxacin accumulated in THP-1 cells by approximately fivefold at pH 7.4 but up to 20-fold at pH 5.5, and distributed in the cytosol.

CONCLUSIONS

Fluoroquinolones have proven to be effective in reducing the intracellular reservoirs of B. thailandensis, Y. pseudotuberculosis and F. philomiragia, with finafloxacin demonstrating an additional advantage in acidic environments.

The Assessment of Knowledge of Organisational - Administrative Procedures in the Case of a Bioterrorist Threat in Selected Environmental Populations

In the past we have seen numerous cases of the purposeful utilisation of micro-organisms and toxins. This situation forced us to undertake actions aimed at a limitation of the production and storage of biological weapons. Unfortunately, despite the signing of the Convention on Biological and Chemical Weapons, many countries are still involved in research into the use of biological agents as a military resource.

The objective of the work was to perform an assessment of the knowledge of threats connected with bioterrorism as well as of the procedures in the case of a bioterrorist attack in two different urban populations - i.e. of below 50 thousand and above 500 thousand inhabitants.

The study was conducted in two towns, Nysa and Łódź. A self-designed questionnaire included 100 persons from each town, both men and women aged between 18 and 65 years. Despite the small differences between the researched populations, the knowledge of respondents concerning bioterrorist threats and procedures during an attack is insufficient.

On the basis of the obtained results we may conclude that there is a need to educate the entire society, irrespective of the place of residence, in order to raise an awareness with regard to the potential threat and procedures in the event of a bioterrorist attack.