CDC Guidelines for the Prevention and Treatment of Anthrax, 2023

In Vivo Comparison of Branched vs Linear Pegylation of a Capsule-Degrading Enzyme for Treatment of Anthrax

Polymers of d-glutamic acid (PDGA) form capsules of virulent strains of Bacillus anthracis. PDGA is antiphagocytic and weakly immunogenic; it enables the bacteria to evade innate immune responses. Capsule depolymerase (CapD) catalyzes the covalent anchoring of PDGA to the cell wall. There has been interest in developing CapD as a therapeutic to treat antibiotic-resistant anthrax infections. We previously showed that a His-tagged and circularly permuted (CP) CapD modified with a branched 3-prong polyethylene glycol (PEG) molecule termed PEG-CapDS334C-CP could protect mice with 80% survival against a 5 LD50 challenge with virulent B. anthracis. In the current study, we compare the efficacy of tag-free CapDS334C-CP modified by either the branched 3-prong or a linear 1-prong PEG. Pharmacokinetic studies in mice showed the branched 3-prong PEG-CapDS334C-CP has a slightly higher, but not statistically different, total exposure in animals than the linear 1-prong PEG variant. The T max of the 1-prong PEG-CapDS334C-CP was 8 times shorter than the 3-prong. Mice infected with spore doses of 10 and 100 LD50, treated 24 h after infection every 8 h for 7 days, were protected by both the 3-prong (10 LD50: p = 0.0051; 100 LD50: p = 0.0463, log-rank analysis) and 1-prong (10 LD50: p = 0.0009; 100 LD50: p < 0.0001, log-rank analysis) PEG-CapDS334C-CP when compared with control animals. A second iteration similarly showed statistically significant protection by both variants at both challenge doses, and the combined data from both experiments showed no significant difference in efficacy between the 1- and 3-prong enzymes confirming that tag-free PEG-CapDS334C-CP is protective against experimental anthrax infection.

Review of category A bioweapons with cutaneous features: Epidemiology, clinical presentation, and contemporary management strategies

Major health organizations recognize various pathogens as potential bioweapons. Category A bioweapons (anthrax, plague, smallpox, tularemia, and viral hemorrhagic fevers) are the highest priority due to their ease of spread and high mortality rates. As these conditions have cutaneous manifestations, dermatologists may have an important role as front-line responders to indolent or bioterrorism threats. Few dermatologists are adequately prepared to approach the diagnosis and management of these conditions if encountered. Furthermore, despite improvements made in identifying, diagnosing, and treating these conditions over the past 10 years, there persists an absence of a synthesized distribution of these updates customized to adequately equip dermatologists. In this paper, we review the epidemiology, transmission, and dermatologic signs and symptoms of the category A bioweapons listed above. We also offer an overview of the evidence-based strategies for diagnosis and management and provide access to each states' guidelines for reporting these conditions.

Vaccines in Pregnancy: An Update on Recommendations From CDC's Advisory Committee on Immunization Practices

Vaccinations in pregnancy are an essential part of prenatal care and play a critical role in protecting both pregnant persons and their infants from certain infectious diseases. In the United States, recommendations for vaccines are made through a comprehensive review of currently available scientific literature, including clinical trials and post-marketing surveillance data, by the Advisory Committee on Immunization Practices (ACIP). The ACIP is an advisory committee to the US Centers for Disease Control and Prevention (CDC), comprised of medical and public health experts who develop evidence-based recommendations and guidelines for vaccinations, including for pregnant persons. The ACIP has several work groups that review scientific evidence on an ongoing basis, and full-committee public meetings are held at least three times a year. As more data regarding the safety and efficacy of vaccines in pregnancy become available, these recommendations continue to evolve. To develop these recommendations, the ACIP carefully considers the risks of exposure to infectious agents against the potential risks of vaccination. We review here current ACIP recommendations for vaccinations and their use in pregnant persons. Recommendations are divided into four categories: vaccines recommended during pregnancy, vaccines recommended during pregnancy under certain circumstances, vaccines not recommended or contraindicated during pregnancy, and vaccines without specific ACIP recommendations. To ensure optimal care during pregnancy, healthcare providers who care for pregnant persons need to be familiar with these recommendations.

Anthrax: Transmission, Pathogenesis, Prevention and Treatment

Bacillus anthracis is a deadly pathogen that under unfavourable conditions forms highly resistant spores which enable them to survive for a long period of time. Spores of B. anthracis are transmitted through the contaminated soil or animal products and enter to the host through the skin, lungs or oral route and can cause cutaneous, injection, inhalation and gastrointestinal anthrax, respectively. The disease is caused by the toxin which is produced by them once they germinate within the host cell. Anthrax toxin is the major virulence factor which has the ability to kill the host cell. The role of protein kinases and phosphatases of B. anthracis in toxin production and other virulence related properties have also been reported. There are two vaccines, BioThrax and CYFENDUSTM, which are approved by the FDA-USA to prevent anthrax disease. Recently, anthrax toxin has also been shown to be a potential candidate for cancer therapeutics. Through present review, we aim to provide insights into sporulation, transmission and pathogenesis of B. anthracis as well as the current state of its prevention, treatment, vaccines and possible therapeutic uses in cancer.

Anthrax meningoencephalitis: A case report

The present study describes the case of a patient with anthrax meningoencephalitis with the aim of providing a scientific basis for the control of this disease. The cerebrospinal fluid and blood of the patient were tested for genes and Bacillus anthracis was detected. The patient's meningitis was cured following treatment. Tracing the route of infection, anthrax was detected on the chopping board of the rural cattle and sheep butcher shop where the patient had purchased meat. In 2018, the patient complained of intermittent nasal discharge for 11 days after brain injury and came to the Second People's Hospital of Liaocheng (Linqing, China). Considering the existence of cerebrospinal fluid rhinorrhea, the patient's cerebrospinal fluid biochemistry was assessed and showed low sugar and high protein levels, resulting in a diagnosis of bacterial encephalitis. This encephalitis was considered to be related to bacterial retrograde infection after cerebrospinal fluid rhinorrhea. It is required to strengthen the training of medical personnel according to guidelines and laws and improve the level of early detection, reporting and diagnosis, as well as timely treatment at medical institutions. There is an urgent need to intensify the education of the population regarding the awareness and prevention of the disease. For individuals involved in the breeding, slaughtering and processing of livestock, multiple measures need to be taken to comprehensively intervene and to enhance occupational protection awareness and disease prevention capabilities.

In-depth exploration of cutaneous anthrax: clinical and pathological manifestations of a case report

Anthrax is an acute infectious disease caused by Bacillus anthracis, which can infect various animals and humans. Cutaneous anthrax primarily presents as infiltrative, edematous erythema, surface vesicles, hemorrhagic vesicles, and necrotic eschar; some patients may also experience systemic symptoms such as fever and leukocytosis. With economic development and improvements in public health conditions, naturally occurring cases of cutaneous anthrax have significantly decreased, leading to limited reports on the pathological manifestations of this disease. This article reports a case of a patient with cutaneous anthrax diagnosed and treated in our hospital, aiming to explore the laboratory examinations, imaging, pathological features, and clinical treatment methods of the disease. The goal is to enhance understanding of anthrax and increase vigilance in clinical practice to avoid misdiagnosis and missed diagnosis. The described diagnostic and therapeutic processes are accurate and reliable, with no modifications or exaggerations. It is important to note that the patient's treatment may have been influenced by local social, economic, health, and epidemiological conditions, which introduces certain limitations. We hope that our colleagues will approach this study with an objective mindset for learning and reference.

Closing the Gaps: Testing the Efficacy of Carbapenem and Cephalosporin Treatments of Late-Stage Anthrax in Rabbits

Anthrax is a fatal zoonotic disease caused by exposure to Bacillus anthracis spores. The CDC's guidelines divide anthrax treatment into three categories according to disease progression: post-exposure prophylaxis (PEP), systemic, and systemic with a suspicion of CNS infection. While the prognosis for PEP or the early treatment of systemic anthrax is very good, ingress of the bacteria into the CNS poses a substantial clinical challenge. Here, we use rabbits to test the efficacy of a combined treatment of meropenem and doxycycline, which is the first choice in the CDC recommendations for treating systemic patients with an indication of CNS infection. In addition, we test the efficacy of the first-generation cephalosporin, cefazolin, in treating different stages of the disease. We found that the combination of doxycycline and meropenem is highly effective in treating rabbits in our inhalation model. Cefazolin was efficient only for PEP or systemic-stage treatment and not for CNS-infected animals. Our findings support the CDC recommendation of using a combination of doxycycline and meropenem for systemic patients with or without indications of CNS infection. We found that cefazolin is a decent choice for PEP or early-stage systemic disease but recommend considering using this antibiotic only if all other options are not available.

Determination of Dipicolinic Acid through the Antenna Effect of Eu(III) Coordination Polymer

Bacillus anthracis is a Gram-positive bacterium that can cause acute infection and anthracnose, which is a serious concern for human health. Determining Bacillus anthracis through its spore biomarker dipicolinic acid (DPA) is crucial, and there is a strong need for a method that is rapid, sensitive, and selective. Here, we created Eu(III)-coordination polymers (Eu-CPs) with surfaces that have abundant carboxyl and hydroxyl groups. This was achieved by using citric acid and europium nitrate hexahydrate as precursors in a straightforward one-pot hydrothermal process. These Eu-CPs were then successfully utilized for highly sensitive DPA determination. The fluorescence (FL) emission of Eu-CPs, which is typically weak due to the coordination of Eu(III) with water molecules, was significantly enhanced in the presence of DPA. This enhancement is attributed to the competitive binding between DPA's carboxyl or hydroxyl groups and water molecules. As a result, the absorbed energy of DPA, when excited by 280 nm ultraviolet light, is transferred to Eu-CPs through an antenna effect. This leads to the emission of the characteristic red fluorescence of Eu3+ at 618 nm. A strong linear relationship was observed between the enhanced FL intensity and DPA concentration in the range of 0.5-80 μM. This relationship allowed for a limit of detection (LOD) of 15.23 nM. Furthermore, the Eu-CPs we constructed can effectively monitor the release of DPA from Bacillus subtilis spores, thereby further demonstrating the potential significance of this strategy in the monitoring and management of anthrax risk. This highlights the novelty of this approach in practical applications, provides a valuable determination technique for Bacillus anthracis, and offers insights into the development cycle of microorganisms.

Omadacycline is active in vitro and in vivo against ciprofloxacin-resistant Bacillus anthracis

Bacillus anthracis, the causative agent of anthrax, is among the most likely bacterial pathogens to be used in a biological attack. Inhalation anthrax is a serious, life-threatening form of infection, and the mortality from acute inhaled anthrax can approach 100% if not treated early and aggressively. Food and Drug Administration-approved antibiotics indicated for post-exposure prophylaxis (PEP) or treatment of anthrax are limited. This study assessed the in vitro activity and in vivo efficacy of omadacycline and comparators against clinical isolates of B. anthracis, including a ciprofloxacin-resistant isolate. Minimum inhibitory concentrations (MICs) of omadacycline, ciprofloxacin, and doxycycline were determined against animal and human clinical isolates of B. anthracis, including the ciprofloxacin-resistant Ames strain BACr4-2. Mice were challenged with aerosolized BACr4-2 spores, and survival was monitored for 28 days post-challenge. Treatment was initiated 24 h after aerosol challenge and administered for 14 days. Omadacycline demonstrated in vitro activity against 53 B. anthracis isolates with an MIC range of ≤0.008-0.25 µg/mL, and an MIC50/MIC90 of 0.015/0.03 µg/mL. Consistent with this, omadacycline demonstrated in vivo efficacy in a PEP mouse model of inhalation anthrax caused by the Ames BACr4-2 ciprofloxacin-resistant B. anthracis isolate. Omadacycline treatment significantly increased survival compared with the vehicle control group and the ciprofloxacin treatment group. As antibiotic resistance rates continue to rise worldwide, omadacycline may offer an alternative PEP or treatment option against inhalation anthrax, including anthrax caused by antibiotic-resistant B. anthracis.

European multi-centre study to establish MIC and zone diameter epidemiological cut-off values for Bacillusanthracis

OBJECTIVES

Bacillus anthracis clinical breakpoints, representing a systematic approach to guide clinicians in selecting the most appropriate antimicrobial treatments, are not part of the guidance from the European Committee on Antimicrobial Susceptibility Testing (EUCAST). This is because defined distributions of MIC values and of epidemiological cut-off values (ECOFFs) have been lacking. In this study, a Europe-wide network of laboratories in collaboration with EUCAST, aimed at establishing standardized antimicrobial susceptibility testing methods, wild-type MIC distributions, and ECOFFs for ten therapeutically relevant antimicrobials.

METHODS

About 335 B. anthracis isolates were tested by broth microdilution and disc diffusion methodologies. MIC and inhibition zone diameters were curated according to EUCAST SOP 10.2 and the results were submitted to EUCAST for ECOFFs and clinical breakpoint determination.

RESULTS

Broth microdilution and disc diffusion data distributions revealed putative wild-type distributions for the tested agents. For each antimicrobial agent, ECOFFs were defined. Three highly resistant strains with MIC values of 32 mg/L benzylpenicillin were found. MIC values slightly above the defined ECOFFs were observed in a few isolates, indicating the presence of resistance mechanisms to doxycycline, tetracycline, and amoxicillin.

DISCUSSION

B. anthracis antimicrobial susceptibility testing results were used by EUCAST to determine ECOFFs for ten antimicrobial agents. The MIC distributions were used in the process of determining clinical breakpoints. The ECOFFs can be used for the sensitive detection of isolates with resistance mechanisms, and for monitoring resistance development. Genetic changes causing phenotypic shifts in isolates displaying slightly elevated MICs remain to be investigated.

Postexposure prophylaxis for occupational exposure to selected pathogens for healthcare personnel

PURPOSE OF REVIEW

Timely postexposure prophylaxis is important after an occupational exposure. Here we review select organisms, exposure opportunities in the healthcare setting, and postexposure prophylaxis regimens.

RECENT FINDINGS

Needlestick injuries pose a risk of exposure to bloodborne pathogens, such as HIV, Hepatitis B, and Hepatitis C. Risk mitigation strategies should be reexamined in light of newer vaccines and therapeutics. Increased vaccine hesitancy and vaccine denialisms may foster the re-emergence of some infections that have become extremely uncommon because of effective vaccines. With increasing occurrences of zoonotic infections and the ease of global spread as evidenced by COVID-19 and mpox, healthcare exposures must also consider risks related to emerging and re-emerging infectious diseases.

SUMMARY

Early recognition and reporting of occupational exposures to pathogens with available postexposure prophylaxis is key to mitigating the risk of transmission. Providers should be able to evaluate the exposure and associated risks to provide prompt and appropriate postexposure prophylaxis.

Antimicrobial Resistance Profile, Whole-Genome Sequencing and Core Genome Multilocus Sequence Typing of B. anthracis Isolates in Croatia from 2001 to 2022

Bacillus anthracis, the causative agent of anthrax disease, is a worldwide threat to livestock, wildlife and public health. It is also considered one of the most important pathogens of bioterrorism. Rapid and reliable diagnosis and administration of antimicrobials are essential for effective anthrax treatment. In this study, we determined the in vitro susceptibilities of 40 isolates of B. anthracis isolated in Croatia over the recent two decades to 18 antimicrobials. Whole-genome sequencing was performed, and bioinformatics tools were used to determine virulence factors and antimicrobial resistance genes. Core genome-based multilocus sequence typing was used for isolate comparison and phylogenetic analysis. All isolates were susceptible to all antimicrobials recommended for post-exposure prophylaxis or anthrax therapy. Susceptibility was found to all other tested antimicrobials that are an alternative for primary therapy. We found two beta-lactamase genes, but their expression is not sufficient to confer resistance. In all isolates used in this study, we found 21 virulence genes, 8 of which are responsible for toxin and capsule production. As far as phylogenetic analysis is concerned, the B. anthracis isolates from Croatia are categorised into two clades. The first is clade A, subclade Trans Eurasia, and the other is clade B, subclade B2.

Central Nervous System Antimicrobial Exposure and Proposed Dosing for Anthrax Meningitis

BACKGROUND

The high mortality of systemic anthrax is likely a consequence of the severe central nervous system inflammation that occurs in anthrax meningitis. Effective treatment of such infections requires, at a minimum, adequate cerebrospinal fluid (CSF) antimicrobial concentrations.

METHODS

We reviewed English medical literature and regulatory documents to extract information on serum and CSF exposures for antimicrobials with in vitro activity against Bacillus anthracis. Using CSF pharmacokinetic exposures and in vitro B. anthracis susceptibility data, we used population pharmacokinetic modeling and Monte Carlo simulations to determine whether a specific antimicrobial dosage would likely achieve effective CSF antimicrobial activity in patients with normal to inflamed meninges (ie, an intact to markedly disrupted blood-brain barrier).

RESULTS

The probability of microbiologic success at achievable antimicrobial dosages was high (≥95%) for ciprofloxacin, levofloxacin (500 mg every 12 hours), meropenem, imipenem/cilastatin, penicillin G, ampicillin, ampicillin/sulbactam, doxycycline, and minocycline; acceptable (90%-95%) for piperacillin/tazobactam and levofloxacin (750 mg every 24 hours); and low (<90%) for vancomycin, amikacin, clindamycin, and linezolid.

CONCLUSIONS

Prompt empiric antimicrobial therapy of patients with suspected or confirmed anthrax meningitis may reduce the high morbidity and mortality. Our data support using several β-lactam-, fluoroquinolone-, and tetracycline-class antimicrobials as first-line and alternative agents for treatment of patients with anthrax meningitis; all should achieve effective microbiologic exposures. Our data suggest antimicrobials that should not be relied on to treat suspected or documented anthrax meningitis. Furthermore, the protein synthesis inhibitors clindamycin and linezolid can decrease toxin production and may be useful components of combination therapy.

Doxycycline, levofloxacin, and moxifloxacin are superior to ciprofloxacin in treating anthrax meningitis in rabbits and NHP

Efficient treatment of anthrax-related meningitis in patients poses a significant therapeutic challenge. Previously, we demonstrated in our anthrax meningitis rabbit model that ciprofloxacin treatment is ineffective with most of the treated animals succumbing to the infection. Herein we tested the efficacy of doxycycline in our rabbit model and found it highly effective. Since all of our findings are based on a rabbit model, we test the efficacy of ciprofloxacin or doxycycline in a specific central nervous system (CNS) model developed in non-human primates (NHPs). Similar to rabbits, ciprofloxacin treatment was ineffective, while doxycycline protected the infected rhesus macaques (n = 2) from the lethal CNS Bacillus anthracis infection. To test whether the low efficacy of Ciprofloxacin is an example of low efficacy of all fluoroquinolones or only this substance, we treated rabbits that were inoculated intracisterna magna (ICM) with levofloxacin or moxifloxacin. We found that in contrast to ciprofloxacin, levofloxacin and moxifloxacin were highly efficacious in treating lethal anthrax-related meningitis in rabbits and NHP (levofloxacin). We demonstrated (in naïve rabbits) that this difference probably results from variances in blood-brain-barrier penetration of the different fluoroquinolones. The combined treatment of doxycycline and any one of the tested fluoroquinolones was highly effective in the rabbit CNS infection model. The combined treatment of doxycycline and levofloxacin was effective in an inhalation rabbit model, as good as the doxycycline mono-therapy. These findings imply that while ciprofloxacin is highly effective as a post-exposure prophylactic drug, using this drug to treat symptomatic patients should be reconsidered.

Genetic basis of clarithromycin resistance in Bacillus anthracis

The high-consequence pathogen Bacillus anthracis causes human anthrax and often results in lethal infections without the rapid administration of effective antimicrobial treatment. Antimicrobial resistance profiling is therefore critical to inform post-exposure prophylaxis and treatment decisions, especially during emergencies such as outbreaks or where intentional release is suspected. Whole-genome sequencing using a rapid long-read sequencer can uncover antimicrobial resistance patterns if genetic markers of resistance are known. To identify genomic markers associated with antimicrobial resistance, we isolated B. anthracis derived from the avirulent Sterne strain with elevated minimal inhibitory concentrations to clarithromycin. Mutants were characterized both phenotypically through broth microdilution susceptibility testing and observations during culturing, as well as genotypically with whole-genome sequencing. We identified two different in-frame insertions in the L22 ribosomal protein-encoding gene rplV, which were subsequently confirmed to be involved in clarithromycin resistance through the reversion of the mutant gene to the parent (drug-susceptible) sequence. Detection of the rplV insertions was possible with rapid long-read sequencing, with a time-to-answer within 3 h. The mutations associated with clarithromycin resistance described here will be used in conjunction with known genetic markers of resistance for other antimicrobials to strengthen the prediction of antimicrobial resistance in B. anthracis.IMPORTANCEThe disease anthrax, caused by the pathogen Bacillus anthracis, is extremely deadly if not treated quickly and appropriately. Clarithromycin is an antibiotic recommended for the treatment and post-exposure prophylaxis of anthrax by the Centers for Disease Control and Prevention; however, little is known about the ability of B. anthracis to develop resistance to clarithromycin or the mechanism of that resistance. The characterization of clarithromycin-resistant isolates presented here provides valuable information for researchers and clinicians in the event of a release of the resistant strain. Additionally, knowledge of the genetic basis of resistance provides a foundation for susceptibility prediction through rapid genome sequencing to inform timely treatment decisions.

A case study on anthrax in an eight-month old infant at Kyrgyz Republic

Anthrax remains a threat, especially in countries like Kyrgyzstan with developed livestock farming. Despite preventive efforts, sporadic outbreaks endure on an annual basis, transmitted from infected animals to humans. Here, we report a severe anthrax case in an 8-month-old child known to be caused when a sick calf was slaughtered in the neighborhood without proper protocols, resulting in intra-family infection. This underscores the importance of swift diagnosis, treatment, preventive measures, and awareness of zoonotic infections, animal vaccination and adherence to sanitary and veterinary protocols.

The second cutaneous anthrax infection diagnosed by metagenomic next-generation sequencing: A case report

RATIONALE

Anthrax is a severe zoonotic infectious disease caused by Bacillus anthracis. Most reported cases were traditionally diagnosed through culture and microscopy. We reported here the second case of cutaneous anthrax diagnosed by metagenomic next-generation sequencing (mNGS).

PATIENT CONCERNS

A 63-year-old man had a history of contact with an unwell sheep, developing local redness and swelling on wrist. The dorsal side of the left hand and forearm, with tension blisters on the back of the left.

DIAGNOSIS

B anthracis was detected from culturing and mNGS of tension blisters.

INTERVENTIONS

On the second day of admission, the patient was administered 3.2 million units of penicillin every 6 hours, and isolated and closely observed.

OUTCOMES

The patient improves and is discharged.

LESSONS

Traditional bacterial cultures are time-consuming, while mNGS offers the advantage of accurate, quick, high-throughput, unbiased sequencing of all genetic material in a sample, which is a good technical tool for assisting in the diagnosis of rare pathogen infections.