Plague outbreak in Libya, 2009, unrelated to plague in Algeria

Cryosphere: a frozen home of microbes and a potential source for drug discovery

The world is concerned about the emergence of pathogens and the occurrence and spread of antibiotic resistance among pathogens. Drug development requires time to combat these issues. Consequently, drug development from natural sources is unavoidable. Cryosphere represents a gigantic source of microbes that could be the bioprospecting source of natural products with unique scaffolds as molecules or drug templates. This review focuses on the novel source of drug discovery and cryospheric environments as a potential source for microbial metabolites having potential medicinal applications. Furthermore, the problems encountered in discovering metabolites from cold-adapted microbes and their resolutions are discussed. By adopting modern practical approaches, the discovery of bioactive compounds might fulfill the demand for new drug development.

A systematic review of the clinical profile of patients with bubonic plague and the outcome measures used in research settings

BACKGROUND

Plague is a zoonotic disease that, despite affecting humans for more than 5000 years, has historically been the subject of limited drug development activity. Drugs that are currently recommended in treatment guidelines have been approved based on animal studies alone-no pivotal clinical trials in humans have yet been completed. As a result of the sparse clinical research attention received, there are a number of methodological challenges that need to be addressed in order to facilitate the collection of clinical trial data that can meaningfully inform clinicians and policy-makers. One such challenge is the identification of clinically-relevant endpoints, which are informed by understanding the clinical characterisation of the disease-how it presents and evolves over time, and important patient outcomes, and how these can be modified by treatment.

METHODOLOGY/PRINCIPAL FINDINGS

This systematic review aims to summarise the clinical profile of 1343 patients with bubonic plague described in 87 publications, identified by searching bibliographic databases for studies that meet pre-defined eligibility criteria. The majority of studies were individual case reports. A diverse group of signs and symptoms were reported at baseline and post-baseline timepoints-the most common of which was presence of a bubo, for which limited descriptive and longitudinal information was available. Death occurred in 15% of patients; although this varied from an average 10% in high-income countries to an average 17% in low- and middle-income countries. The median time to death was 1 day, ranging from 0 to 16 days.

CONCLUSIONS/SIGNIFICANCE

This systematic review elucidates the restrictions that limited disease characterisation places on clinical trials for infectious diseases such as plague, which not only impacts the definition of trial endpoints but has the knock-on effect of challenging the interpretation of a trial's results. For this reason and despite interventional trials for plague having taken place, questions around optimal treatment for plague persist.

Serological evidence of Yersinia pestis infection in rodents and carnivores in Northwestern Iran

BACKGROUND

Plague may recur after several decades in its endemic regions; therefore, the continuous monitoring of wildlife is essential, even when no human cases are reported in the old foci. The present study was conducted to monitor rodents and their ectoparasites as well as carnivores to learn about the epidemiology of plague infection in an old focus of Iran.

METHODOLOGY

The present study was conducted from 2019 to 2020 in Takestan county of Qazvin Province in northwestern Iran. Rodents were caught using live traps, and their fleas were separated. Blood and spleen specimens were taken from the captured rodents. Serum samples were also collected from sheepdogs and wild carnivores. The collected samples were tested by culture, serology (ELISA), and molecular methods to detect Yersinia pestis infection.

FINDINGS

A total of 399 small mammals were caught, of which 68.6% were Meriones persicus. A total of 2438 fleas were collected from the rodents, 95.3% of which were Xenopsylla buxtoni. Overall, 23 out of 377 tested rodents (5.7%, CI 95%, 3.9-9.0) had IgG antibodies against the F1 antigen of Y. pestis, and all the positive samples belonged to M. persicus. Nine (4.8%) out of 186 collected sera from the sheepdogs' serum and one serum from the Canis aureus had specific IgG antibodies against the F1 antigen of Y. pestis. There were no positive cases of Y. pestis in the rodents and fleas based on the culture and real-time PCR.

CONCLUSION

Serological evidence of Y. pestis circulation was observed in rodents and carnivores (sheepdogs and C. aureus). The presence of potential plague vectors and serological evidence of Y. pestis infection in the surveyed animals could probably raise the risk of infection and clinical cases of plague in the studied region. Training health personnel is therefore essential to encourage their detection of possible human cases of the disease.

Lice and lice-borne diseases in humans in Africa: a narrative review

Lice are host-specific insects. Human lice include Pediculus humanus humanus (body lice) which are known to be vectors of serious human bacterial infectious diseases including epidemic typhus, relapsing fever, trench fever and plague; Pediculus humanus capitis (head lice) that frequently affect children; and Pthirus pubis, commonly known as crab lice. In Africa, human infections transmitted by lice remained poorly known and therefore, underestimated, perhaps due to the lack of diagnostic tools and professional knowledge. In this paper we review current knowledge of the microorganisms identified in human lice in the continent of Africa, in order to alert health professionals to the importance of recognising the risk of lice-related diseases.

Cave Microbes as a Potential Source of Drugs Development in the Modern Era

The world is constantly facing threats, including the emergence of new pathogens and antibiotic resistance among extant pathogens, which is a matter of concern. Therefore, the need for natural and effective sources of drugs is inevitable. The ancient and pristine ecosystems of caves contain a unique microbial world and could provide a possible source of antimicrobial metabolites. The association between humans and caves is as old as human history itself. Historically, cave environments have been used to treat patients with respiratory tract infections, which is referred to as speleotherapy. Today, the pristine environment of caves that comprise a poorly explored microbial world is a potential source of antimicrobial and anticancer drugs. Oligotrophic conditions in caves enhance the competition among microbial communities, and unique antimicrobial agents may be used in this competition. This review suggests that the world needs a novel and effective source of drug discovery. Therefore, being the emerging spot of modern human civilization, caves could play a crucial role in the current medical crisis, and cave microorganisms may have the potential to produce novel antimicrobial and anticancer drugs.

Emerging and Re-emerging Infectious Diseases in the WHO Eastern Mediterranean Region, 2001-2018

BACKGROUND

Countries in the World Health Organization (WHO) Eastern Mediterranean Region (EMR) are predisposed to highly contagious, severe and fatal, emerging infectious diseases (EIDs), and re-emerging infectious diseases (RIDs). This paper reviews the epidemiological situation of EIDs and RIDs of global concern in the EMR between 2001 and 2018.

METHODS

To do a narrative review, a complete list of studies in the field was we prepared following a systematic search approach. Studies that were purposively reviewed were identified to summarize the epidemiological situation of each targeted disease. A comprehensive search of all published studies on EIDs and RIDs between 2001 and 2018 was carried out through search engines including Medline, Web of Science, Scopus, Google Scholar, and ScienceDirect.

RESULTS

Leishmaniasis, hepatitis A virus (HAV) and hepatitis E virus (HEV) are reported from all countries in the region. Chikungunya, Crimean Congo hemorrhagic fever (CCHF), dengue fever, and H5N1 have been increasing in number, frequency, and expanding in their geographic distribution. Middle East respiratory syndrome (MERS), which was reported in this region in 2012 is still a public health concern. There are challenges to control cholera, diphtheria, leishmaniasis, measles, and poliomyelitis in some of the countries. Moreover, Alkhurma hemorrhagic fever (AHF), and Rift Valley fever (RVF) are limited to some countries in the region. Also, there is little information about the real situation of the plague, Q fever, and tularemia.

CONCLUSION

EIDs and RIDs are prevalent in most countries in the region and could further spread within the region. It is crucial to improve regional capacities and capabilities in preventing and responding to disease outbreaks with adequate resources and expertise.

Fleas (Siphonaptera) of domestic and wild animals in extreme northeastern Algeria: first inventory, hosts, and medical and veterinary importance

Fleas are an important member of the North African entomofauna. An understanding of the risks of flea-borne diseases to public and veterinary health can be gained with surveys of their abundance, distribution, and hosts. The aims of this study were to make an initial assessment of flea (Siphonaptera) species collected from a selected number of mammalian hosts in Algeria and debate their medical and veterinary importance. To do so, an entomological survey was conducted on several animal species (goats, dogs, cats, rabbits, hedgehogs, and mongooses) in six localities of El Tarf region located in extreme northeastern Algeria. During the survey, flea specimens were collected from hosts, stored in alcohol, and identified using a taxonomic key. More than 1,200 specimens were collected and identified; including four species: Ctenocephalides felis, Ctenocephalides canis, Pulex irritans, and Archaeopsylla erinacei (s.l.). Goats and dogs were the most infested animals, followed by cats and hedgehogs. Ctenocephalides felis was the most prevalent flea among all infested animals, with 631 collected specimens, followed by Pulex irritans with 433 samples. Overall, this study is an initial assessment of flea species recovered from selected common mammals in northeastern Algeria.

Spatiotemporal Variations of Plague Risk in the Tibetan Plateau from 1954-2016

Plague persists in the plague natural foci today. Although previous studies have found climate drives plague dynamics, quantitative analysis on animal plague risk under climate change remains understudied. Here, we analyzed plague dynamics in the Tibetan Plateau (TP) which is a climate-sensitive area and one of the most severe animal plague areas in China to disentangle variations in marmot plague enzootic foci, diffusion patterns, and their possible links with climate and anthropogenic factors. Specifically, we developed a time-sharing ecological niche modelling framework to identify finer potential plague territories and their temporal epidemic trends. Models were conducted by assembling animal records and multi-source ecophysiological variables with actual ecological effects (both climatic predictors and landscape factors) and driven by matching plague strains to periods corresponding to meteorological datasets. The models identified abundant animal plague territories over the TP and suggested the spatial patterns varied spatiotemporal dimension across the years, undergoing repeated spreading and contractions. Plague risk increased in the 1980s and 2000s, with the risk area increasing by 17.7 and 55.5 thousand km², respectively. The 1990s and 2010s were decades of decreased risk, with reductions of 71.9 and 39.5 thousand km², respectively. Further factor analysis showed that intrinsic conditions (i.e., elevation, soil, and geochemical landscape) provided fundamental niches. In contrast, climatic conditions, especially precipitation, led to niche differentiation and resulted in varied spatial patterns. Additionally, while increased human interference may temporarily reduce plague risks, there is a strong possibility of recurrence. This study reshaped the plague distribution at multiple time scales in the TP and revealed multifactorial synergistic effects on the spreading and contraction of plague foci, confirming that TP plague is increasingly sensitive to climate change. These findings may facilitate groups to take measures to combat the plague threats and prevent potential future human plague from occurring.

Antibiotic Therapy of Plague: A Review

Plague-a deadly disease caused by the bacterium Yersinia pestis-is still an international public health concern. There are three main clinical forms: bubonic plague, septicemic plague, and pulmonary plague. In all three forms, the symptoms appear suddenly and progress very rapidly. Early antibiotic therapy is essential for countering the disease. Several classes of antibiotics (e.g., tetracyclines, fluoroquinolones, aminoglycosides, sulfonamides, chloramphenicol, rifamycin, and β-lactams) are active in vitro against the majority of Y. pestis strains and have demonstrated efficacy in various animal models. However, some discrepancies have been reported. Hence, health authorities have approved and recommended several drugs for prophylactic or curative use. Only monotherapy is currently recommended; combination therapy has not shown any benefits in preclinical studies or case reports. Concerns about the emergence of multidrug-resistant strains of Y. pestis have led to the development of new classes of antibiotics and other therapeutics (e.g., LpxC inhibitors, cationic peptides, antivirulence drugs, predatory bacteria, phages, immunotherapy, host-directed therapy, and nutritional immunity). It is difficult to know which of the currently available treatments or therapeutics in development will be most effective for a given form of plague. This is due to the lack of standardization in preclinical studies, conflicting data from case reports, and the small number of clinical trials performed to date.

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.

Fleas and flea-borne diseases of North Africa

North Africa has an interesting and rich wildlife including hematophagous arthropods, and specifically fleas, which constitute a large part of the North African fauna, and are recognised vectors of several zoonotic bacteria. Flea-borne organisms are widely distributed throughout the world in endemic disease foci, where components of the enzootic cycle are present. Furthermore, flea-borne diseases could re-emerge in epidemic form because of changes in the vector-host ecology due to environmental and human behaviour modifications. We need to know the real incidences of flea-borne diseases in the world due to this incidence could be much greater than are generally recognized by physicians and health authorities. As a result, diagnosis and treatment are often delayed by health care professionals who are unaware of the presence of these infections and thus do not take them into consideration when attempting to determine the cause of a patient's illness. In this context, this bibliographic review aims to summarise the main species of fleas present in North Africa, their geographical distribution, flea-borne diseases, and their possible re-emergence.

Human plague: An old scourge that needs new answers

Yersinia pestis, the bacterial causative agent of plague, remains an important threat to human health. Plague is a rodent-borne disease that has historically shown an outstanding ability to colonize and persist across different species, habitats, and environments while provoking sporadic cases, outbreaks, and deadly global epidemics among humans. Between September and November 2017, an outbreak of urban pneumonic plague was declared in Madagascar, which refocused the attention of the scientific community on this ancient human scourge. Given recent trends and plague's resilience to control in the wild, its high fatality rate in humans without early treatment, and its capacity to disrupt social and healthcare systems, human plague should be considered as a neglected threat. A workshop was held in Paris in July 2018 to review current knowledge about plague and to identify the scientific research priorities to eradicate plague as a human threat. It was concluded that an urgent commitment is needed to develop and fund a strong research agenda aiming to fill the current knowledge gaps structured around 4 main axes: (i) an improved understanding of the ecological interactions among the reservoir, vector, pathogen, and environment; (ii) human and societal responses; (iii) improved diagnostic tools and case management; and (iv) vaccine development. These axes should be cross-cutting, translational, and focused on delivering context-specific strategies. Results of this research should feed a global control and prevention strategy within a "One Health" approach.

Rapid diagnostic tests for plague

BACKGROUND

Plague is a severe disease associated with high mortality. Late diagnosis leads to advance stage of the disease with worse outcomes and higher risk of spread of the disease. A rapid diagnostic test (RDT) could help in establishing a prompt diagnosis of plague. This would improve patient care and help appropriate public health response.

OBJECTIVES

To determine the diagnostic accuracy of the RDT based on the antigen F1 (F1RDT) for detecting plague in people with suspected disease.

SEARCH METHODS

We searched the CENTRAL, Embase, Science Citation Index, Google Scholar, the World Health Organization International Clinical Trials Registry Platform and ClinicalTrials.gov up to 15 May 2019, and PubMed (MEDLINE) up to 27 August 2019, regardless of language, publication status, or publication date. We handsearched the reference lists of relevant papers and contacted researchers working in the field.

SELECTION CRITERIA

We included cross-sectional studies that assessed the accuracy of the F1RDT for diagnosing plague, where participants were tested with both the F1RDT and at least one reference standard. The reference standards were bacterial isolation by culture, polymerase chain reaction (PCR), and paired serology (this is a four-fold difference in F1 antibody titres between two samples from acute and convalescent phases).

DATA COLLECTION AND ANALYSIS

Two review authors independently selected studies and extracted data. We appraised the methodological quality of each selected studies and applicability by using the Quality Assessment of Diagnostic Accuracy Studies (QUADAS-2) tool. When meta-analysis was appropriate, we used the bivariate model to obtain pooled estimates of sensitivity and specificity. We stratified all analyses by the reference standard used and presented disaggregated data for forms of plague. We assessed the certainty of the evidence using GRADE.

MAIN RESULTS

We included eight manuscripts reporting seven studies. Studies were conducted in three countries in Africa among adults and children with any form of plague. All studies except one assessed the F1RDT produced at the Institut Pasteur of Madagascar (F1RDT-IPM) and one study assessed a F1RDT produced by New Horizons (F1RDT-NH), utilized by the US Centers for Disease Control and Prevention. We could not pool the findings from the F1RDT-NH in meta-analyses due to a lack of raw data and a threshold of the test for positivity different from the F1RDT-IPM. Risk of bias was high for participant selection (retrospective studies, recruitment of participants not consecutive or random, unclear exclusion criteria), low or unclear for index test (blinding of F1RDT interpretation unknown), low for reference standards, and high or unclear for flow and timing (time of sample transportation was longer than seven days, which can lead to decreased viability of the pathogen and overgrowth of contaminating bacteria, with subsequent false-negative results and misclassification of the target condition). F1RDT for diagnosing all forms of plague F1RDT-IPM pooled sensitivity against culture was 100% (95% confidence interval (CI) 82 to 100; 4 studies, 1692 participants; very low certainty evidence) and pooled specificity was 70.3% (95% CI 65 to 75; 4 studies, 2004 participants; very low-certainty evidence). The performance of F1RDT-IPM against PCR was calculated from a single study in participants with bubonic plague (see below). There were limited data on the performance of F1RDT against paired serology. F1RDT for diagnosing pneumonic plague Performed in sputum, F1RDT-IPM pooled sensitivity against culture was 100% (95% CI 0 to 100; 2 studies, 56 participants; very low-certainty evidence) and pooled specificity was 71% (95% CI 59 to 80; 2 studies, 297 participants; very low-certainty evidence). There were limited data on the performance of F1RDT against PCR or against paired serology for diagnosing pneumonic plague. F1RDT for diagnosing bubonic plague Performed in bubo aspirate, F1RDT-IPM pooled sensitivity against culture was 100% (95% CI not calculable; 2 studies, 1454 participants; low-certainty evidence) and pooled specificity was 67% (95% CI 65 to 70; 2 studies, 1198 participants; very low-certainty evidence). Performed in bubo aspirate, F1RDT-IPM pooled sensitivity against PCR for the caf1 gene was 95% (95% CI 89 to 99; 1 study, 88 participants; very low-certainty evidence) and pooled specificity was 93% (95% CI 84 to 98; 1 study, 61 participants; very low-certainty evidence). There were no data providing data on both F1RDT and paired serology for diagnosing bubonic plague.

AUTHORS' CONCLUSIONS

Against culture, the F1RDT appeared highly sensitive for diagnosing either pneumonic or bubonic plague, and can help detect plague in remote areas to assure management and enable a public health response. False positive results mean culture or PCR confirmation may be needed. F1RDT does not replace culture, which provides additional information on resistance to antibiotics and bacterial strains.

Trends of Human Plague, Madagascar, 1998-2016

Madagascar is more seriously affected by plague, a zoonosis caused by Yersinia pestis, than any other country. The Plague National Control Program was established in 1993 and includes human surveillance. During 1998-2016, a total of 13,234 suspected cases were recorded, mainly from the central highlands; 27% were confirmed cases, and 17% were presumptive cases. Patients with bubonic plague (median age 13 years) represented 93% of confirmed and presumptive cases, and patients with pneumonic plague (median age 29 years) represented 7%. Deaths were associated with delay of consultation, pneumonic form, contact with other cases, occurrence after 2009, and not reporting dead rats. A seasonal pattern was observed with recrudescence during September-March. Annual cases peaked in 2004 and decreased to the lowest incidence in 2016. This overall reduction occurred primarily for suspected cases and might be caused by improved adherence to case criteria during widespread implementation of the F1 rapid diagnostic test in 2002.

A Review of Zoonotic Pathogens of Dromedary Camels

Dromedary, or one-humped, camels Camelus dromedarius are an almost exclusively domesticated species that are common in arid areas as both beasts of burden and production animals for meat and milk. Currently, there are approximately 30 million dromedary camels, with highest numbers in Africa and the Middle East. The hardiness of camels in arid regions has made humans more dependent on them, especially as a stable protein source. Camels also carry and may transmit disease-causing agents to humans and other animals. The ability for camels to act as a point source or vector for disease is a concern due to increasing human demands for meat, lack of biosafety and biosecurity protocols in many regions, and a growth in the interface with wildlife as camel herds become sympatric with non-domestic species. We conducted a literature review of camel-borne zoonotic diseases and found that the majority of publications (65%) focused on Middle East respiratory syndrome (MERS), brucellosis, Echinococcus granulosus, and Rift Valley fever. The high fatality from MERS outbreaks during 2012-2016 elicited an immediate response from the research community as demonstrated by a surge of MERS-related publications. However, we contend that other camel-borne diseases such as Yersinia pestis, Coxiella burnetii, and Crimean-Congo hemorrhagic fever are just as important to include in surveillance efforts. Camel populations, particularly in sub-Saharan Africa, are increasing exponentially in response to prolonged droughts, and thus, the risk of zoonoses increases as well. In this review, we provide an overview of the major zoonotic diseases present in dromedary camels, their risk to humans, and recommendations to minimize spillover events.

Quantification of low abundance Yersinia pestis markers in dried blood spots by immuno-capture and quantitative high-resolution targeted mass spectrometry

Plague, caused by the bacterium Yersinia pestis, is still present in several countries worldwide. Besides, Y. pestis has been designated as Tier 1 agent, the highest rank of bioterrorism agents. In this context, reliable diagnostic methods are of great importance. Here, we have developed an original workflow based upon dried blood spot for simplified sampling of clinical specimens, and specific immuno-mass spectrometry monitoring of Y. pestis biomarkers. Targeted proteins were selectively enriched from dried blood spot extracts by multiplex immunocapture using antibody-coated magnetic beads. After accelerated on-beads digestion, proteotypic peptides were monitored by multiplex LC-MS/MS through the parallel reaction monitoring mode. The DBS-IC-MS assay was designed to quantify both F1 and LcrV antigens, although 10-fold lower sensitivity was observed with LcrV. The assay was successfully validated for F1 with a lower limit of quantification at 5 ng·mL^-1 in spiked blood, corresponding to only 0.1 ng on spots. In vivo quantification of F1 in blood and organ samples was demonstrated in the mouse model of pneumonic plague. The new assay could help to simplify the laboratory confirmation of positive point of care F1 dipstick.

Stenseth N. The Third Plague Pandemic in Europe

Plague has a long history on the European continent, with evidence of the disease dating back to the Stone Age. Plague epidemics in Europe during the First and Second Pandemics, including the Black Death, are infamous for their widespread mortality and lasting social and economic impact. Yet, Europe still experienced plague outbreaks during the Third Pandemic, which began in China and spread globally at the end of the nineteenth century. The digitization of international records of notifiable diseases, including plague, has enabled us to retrace the introductions of the disease to Europe from the earliest reported cases in 1899, to its disappearance in the 1940s. Using supplemental literature, we summarize the potential sources of plague in Europe and the transmission of the disease, including the role of rats. Finally, we discuss the international efforts aimed at prevention and intervention measures, namely improved hygiene and sanitation, that ultimately led to the disappearance of plague in Europe.

Plague: A Millenary Infectious Disease Reemerging in the XXI Century

Plague, in the Middle Ages known as Black Death, continues to occur at permanent foci in many countries, in Africa, Asia, South America, and even the USA. During the last years outbreaks were reported from at least 3 geographical areas, in all cases after tens of years without reported cases. The recent human plague outbreaks in Libya and Algeria suggest that climatic and other environmental changes in Northern Africa may be favourable for Y. pestis epidemiologic cycle. If so, other Northern Africa countries with plague foci also may be at risk for outbreaks in the near future. It is important to remember that the danger of plague reoccurrence is not limited to the known natural foci, for example, those of Algeria, Angola, and Madagascar. In a general context, it is important that governments know the dangerous impact that this disease may have and that the health and medical community be familiar with the epidemiology, symptoms, treatment, and control of plague, so an appropriated and timely response can be delivered should the worst case happen. Plague can be used as a potential agent of bioterrorism. We have concluded that plague is without a doubt a reemerging infectious disease.

Curative Treatment of Severe Gram-Negative Bacterial Infections by a New Class of Antibiotics Targeting LpxC

The infectious diseases caused by multidrug-resistant bacteria pose serious threats to humankind. It has been suggested that an antibiotic targeting LpxC of the lipid A biosynthetic pathway in Gram-negative bacteria is a promising strategy for curing Gram-negative bacterial infections. However, experimental proof of this concept is lacking. Here, we describe our discovery and characterization of a biphenylacetylene-based inhibitor of LpxC, an essential enzyme in the biosynthesis of the lipid A component of the outer membrane of Gram-negative bacteria. The compound LPC-069 has no known adverse effects in mice and is effective in vitro against a broad panel of Gram-negative clinical isolates, including several multiresistant and extremely drug-resistant strains involved in nosocomial infections. Furthermore, LPC-069 is curative in a murine model of one of the most severe human diseases, bubonic plague, which is caused by the Gram-negative bacterium Yersinia pestis. Our results demonstrate the safety and efficacy of LpxC inhibitors as a new class of antibiotic against fatal infections caused by extremely virulent pathogens. The present findings also highlight the potential of LpxC inhibitors for clinical development as therapeutics for infections caused by multidrug-resistant bacteria.

The rapid spread of antimicrobial resistance among Gram-negative bacilli highlights the urgent need for new antibiotics. Here, we describe a new class of antibiotics lacking cross-resistance with conventional antibiotics. The compounds inhibit LpxC, a key enzyme in the lipid A biosynthetic pathway in Gram-negative bacteria, and are active in vitro against a broad panel of clinical isolates of Gram-negative bacilli involved in nosocomial and community infections. The present study also constitutes the first demonstration of the curative treatment of bubonic plague by a novel, broad-spectrum antibiotic targeting LpxC. Hence, the data highlight the therapeutic potential of LpxC inhibitors against a wide variety of Gram-negative bacterial infections, including the most severe ones caused by Y. pestis and by multidrug-resistant and extensively drug-resistant carbapenemase-producing strains.

Yersinia pestis Resists Predation by Acanthamoeba castellanii and Exhibits Prolonged Intracellular Survival

Plague is a flea-borne rodent-associated zoonotic disease caused by Yersinia pestis The disease is characterized by epizootics with high rodent mortalities, punctuated by interepizootic periods when the bacterium persists in an unknown reservoir. This study investigates the interaction between Y. pestis and the ubiquitous soil free-living amoeba (FLA) Acanthamoeba castellanii to assess if the bacterium can survive within soil amoebae and whether intracellular mechanisms are conserved between infection of mammalian macrophages and soil amoebae. The results demonstrate that during coculture with amoebae, representative Y. pestis strains of epidemic biovars Medievalis, Orientalis, and Antiqua are phagocytized and able to survive within amoebae for at least 5 days. Key Y. pestis determinants of the intracellular interaction of Y. pestis and phagocytic macrophages, PhoP and the type three secretion system (T3SS), were then tested for their roles in the Y. pestis-amoeba interaction. Consistent with a requirement for the PhoP transcriptional activator in the intracellular survival of Y. pestis in macrophages, a PhoP mutant is unable to survive when cocultured with amoebae. Additionally, induction of the T3SS blocks phagocytic uptake of Y. pestis by amoebae, similar to that which occurs during macrophage infection. Electron microscopy revealed that in A. castellanii, Y. pestis resides intact within spacious vacuoles which were characterized using lysosomal trackers as being separated from the lysosomal compartment. This evidence for prolonged survival and subversion of intracellular digestion of Y. pestis within FLA suggests that protozoa may serve as a protective soil reservoir for Y. pestisIMPORTANCEYersinia pestis is a reemerging flea-borne zoonotic disease. Sylvatic plague cycles are characterized by an epizootic period during which the disease spreads rapidly, causing high rodent mortality, and an interepizootic period when the bacterium quiescently persists in an unknown reservoir. An understanding of the ecology of Y. pestis in the context of its persistence in the environment and its reactivation to initiate a new epizootic cycle is key to implementing novel surveillance strategies to more effectively predict and prevent new disease outbreaks. Here, we demonstrate prolonged survival and subversion of intracellular digestion of Y. pestis within a soil free-living amoeba. This suggests the potential role for protozoa as a protective soil reservoir for Y. pestis, which may help explain the recrudescence of plague epizootics.

Yersinia pestis halotolerance illuminates plague reservoirs

The plague agent Yersinia pestis persists for years in the soil. Two millennia after swiping over Europe and North Africa, plague established permanent foci in North Africa but not in neighboring Europe. Mapping human plague foci reported in North Africa for 70 years indicated a significant location at <3 kilometers from the Mediterranean seashore or the edge of salted lakes named chotts. In Algeria, culturing 352 environmental specimens naturally containing 0.5 to 70 g/L NaCl yielded one Y. pestis Orientalis biotype isolate in a 40 g/L NaCl chott soil specimen. Core genome SNP analysis placed this isolate within the Y. pestis branch 1, Orientalis biovar. Culturing Y. pestis in broth steadily enriched in NaCl indicated survival up to 150 g/L NaCl as L-form variants exhibiting a distinctive matrix assisted laser desorption-ionization time-of-flight mass spectrometry peptide profile. Further transcriptomic analyses found the upregulation of several outer-membrane proteins including TolC efflux pump and OmpF porin implied in osmotic pressure regulation. Salt tolerance of Y. pestis L-form may play a role in the maintenance of natural plague foci in North Africa and beyond, as these geographical correlations could be extended to 31 plague foci in the northern hemisphere (from 15°N to 50°N).

Plague in Iran: its history and current status

OBJECTIVES:

Plague remains a public health concern worldwide, particularly in old foci. Multiple epidemics of this disease have been recorded throughout the history of Iran. Despite the long-standing history of human plague in Iran, it remains difficult to obtain an accurate overview of the history and current status of plague in Iran.

METHODS:

In this review, available data and reports on cases and outbreaks of human plague in the past and present in Iran and in neighboring countries were collected, and information was compiled regarding when, where, and how many cases occurred.

RESULTS:

This paper considers the history of plague in Persia (the predecessor of today’s Iran) and has a brief review of plague in countries in the World Health Organization Eastern Mediterranean Region, including a range of countries in the Middle East and North Africa.

CONCLUSIONS:

Since Iran has experienced outbreaks of plague for several centuries, neighboring countries have reported the disease in recent years, the disease can be silent for decades, and the circulation of Yersinia pestis has been reported among rodents and dogs in western Iran, more attention should be paid to disease monitoring in areas with previously reported human cases and in high-risk regions with previous epizootic and enzootic activity.

Plague in Arab Maghreb, 1940-2015: A Review

We reviewed the epidemiology of 49 plague outbreaks that resulted in about 7,612 cases in 30 localities in the Arabic Maghreb (Mauritania, Morocco, Algeria, Tunisia, Libya, and Egypt) over 75 years. Between 1940 and 1950, most cases recorded in Morocco (75%) and Egypt (20%), resulted from plague imported to Mediterranean harbors and transmitted by rat ectoparasites. By contrast, the re-emergence of plague in the southern part of Western Sahara in 1953 and in northeast Libya in 1976 was traced to direct contact between nomadic populations and infected goats and camels in natural foci, including the consumption of contaminated meat, illustrating this neglected oral route of contamination. Further familial outbreaks were traced to human ectoparasite transmission. Efforts to identify the factors contributing to natural foci may guide where to focus the surveillance of sentinel animals in order to eradicate human plague, if not Yersinia pestis from the Arab Maghreb.

A review of methods for subtyping Yersinia pestis: From phenotypes to whole genome sequencing

Numerous subtyping methods have been applied to Yersinia pestis with varying success. Here, we review the various subtyping methods that have been applied to Y. pestis and their capacity for answering questions regarding the population genetics, phylogeography, and molecular epidemiology of this important human pathogen. Methods are evaluated in terms of expense, difficulty, transferability among laboratories, discriminatory power, usefulness for different study questions, and current applicability in light of the advent of whole genome sequencing.

Epidemiology of Tropical Neglected Diseases in Ecuador in the Last 20 Years

Background

Tropical and zoonotic diseases are major problems in developing countries like Ecuador. Poorly designed houses, the high proportion of isolated indigenous population and under developed infrastructure represent a fertile environment for vectors to proliferate. Control campaigns in Ecuador over the years have had varying success, depending on the disease and vectors targeted.

Aims

In our study we analyse the current situation of some neglected diseases in Ecuador and the efficiency of the control campaigns (by measuring changes in numbers of cases reported) that the Ecuadorian government has been running to limit the spread of these infectious and parasitic diseases.

Results

Our study reveals that Brucellosis, Chagas Disease, Rabies and Onchocerciasis have been controlled, but small outbreaks are still detected in endemic areas. Leptospirosis and Echinococcosis have been increasing steadily in recent years in Ecuador since the first records. The same increase has been reported world-wide also. Better diagnosis has resulted in a higher number of cases being identified, particularly with regard to the linking of outdoor activities and contact with farm animals as contributing vectors. Improvements in diagnosis are due to regular professional training, implementation of automatized systems, establishing diagnosis protocols and the creation of an epidemiological vigilance network that acts as soon as a case is reported.

Conclusion

Control campaigns performed in Ecuador have been successful in recent years, although natural phenomena limit their efficiency. Leptospirosis and Echinococcosis infections remain a growing problem in Ecuador as it is worldwide.

Plague in Egypt: Disease biology, history and contemporary analysis: A minireview

Plague is a zoonotic disease with a high mortality rate in humans. Unfortunately, it is still endemic in some parts of the world. Also, natural foci of the disease are still found in some countries. Thus, there may be a risk of global plague re-emergence. This work reviews plague biology, history of major outbreaks, and threats of disease re-emergence in Egypt. Based on the suspected presence of potential natural foci in the country, the global climate change, and the threat posed by some neighbouring countries disease re-emergence in Egypt should not be excluded. The country is in need for implementation of some preventive measures.

Structural and functional characterization of TesB from Yersinia pestis reveals a unique octameric arrangement of hotdog domains

Acyl-CoA thioesterases catalyse the hydrolysis of the thioester bonds present within a wide range of acyl-CoA substrates, releasing free CoASH and the corresponding fatty-acyl conjugate. The TesB-type thioesterases are members of the TE4 thioesterase family, one of 25 thioesterase enzyme families characterized to date, and contain two fused hotdog domains in both prokaryote and eukaryote homologues. Only two structures have been elucidated within this enzyme family, and much of the current understanding of the TesB thioesterases has been based on the Escherichia coli structure. Yersinia pestis, a highly virulent bacterium, encodes only one TesB-type thioesterase in its genome; here, the structural and functional characterization of this enzyme are reported, revealing unique elements both within the protomer and quaternary arrangements of the hotdog domains which have not been reported previously in any thioesterase family. The quaternary structure, confirmed using a range of structural and biophysical techniques including crystallography, small-angle X-ray scattering, analytical ultracentrifugation and size-exclusion chromatography, exhibits a unique octameric arrangement of hotdog domains. Interestingly, the same biological unit appears to be present in both TesB structures solved to date, and is likely to be a conserved and distinguishing feature of TesB-type thioesterases. Analysis of the Y. pestis TesB thioesterase activity revealed a strong preference for octanoyl-CoA and this is supported by structural analysis of the active site. Overall, the results provide novel insights into the structure of TesB thioesterases which are likely to be conserved and distinguishing features of the TE4 thioesterase family.

YersiniaBase: a genomic resource and analysis platform for comparative analysis of Yersinia

BACKGROUND

Yersinia is a Gram-negative bacteria that includes serious pathogens such as the Yersinia pestis, which causes plague, Yersinia pseudotuberculosis, Yersinia enterocolitica. The remaining species are generally considered non-pathogenic to humans, although there is evidence that at least some of these species can cause occasional infections using distinct mechanisms from the more pathogenic species. With the advances in sequencing technologies, many genomes of Yersinia have been sequenced. However, there is currently no specialized platform to hold the rapidly-growing Yersinia genomic data and to provide analysis tools particularly for comparative analyses, which are required to provide improved insights into their biology, evolution and pathogenicity.

DESCRIPTION

To facilitate the ongoing and future research of Yersinia, especially those generally considered non-pathogenic species, a well-defined repository and analysis platform is needed to hold the Yersinia genomic data and analysis tools for the Yersinia research community. Hence, we have developed the YersiniaBase, a robust and user-friendly Yersinia resource and analysis platform for the analysis of Yersinia genomic data. YersiniaBase has a total of twelve species and 232 genome sequences, of which the majority are Yersinia pestis. In order to smooth the process of searching genomic data in a large database, we implemented an Asynchronous JavaScript and XML (AJAX)-based real-time searching system in YersiniaBase. Besides incorporating existing tools, which include JavaScript-based genome browser (JBrowse) and Basic Local Alignment Search Tool (BLAST), YersiniaBase also has in-house developed tools: (1) Pairwise Genome Comparison tool (PGC) for comparing two user-selected genomes; (2) Pathogenomics Profiling Tool (PathoProT) for comparative pathogenomics analysis of Yersinia genomes; (3) YersiniaTree for constructing phylogenetic tree of Yersinia. We ran analyses based on the tools and genomic data in YersiniaBase and the preliminary results showed differences in virulence genes found in Yersinia pestis and Yersinia pseudotuberculosis compared to other Yersinia species, and differences between Yersinia enterocolitica subsp. enterocolitica and Yersinia enterocolitica subsp. palearctica.

CONCLUSIONS

YersiniaBase offers free access to wide range of genomic data and analysis tools for the analysis of Yersinia. YersiniaBase can be accessed at http://yersinia.um.edu.my .

Detection of Rickettsia felis, Rickettsia typhi, Bartonella Species and Yersinia pestis in Fleas (Siphonaptera) from Africa

Little is known about the presence/absence and prevalence of Rickettsia spp, Bartonella spp. and Yersinia pestis in domestic and urban flea populations in tropical and subtropical African countries.

METHODOLOGY/PRINCIPAL FINDINGS

Fleas collected in Benin, the United Republic of Tanzania and the Democratic Republic of the Congo were investigated for the presence and identity of Rickettsia spp., Bartonella spp. and Yersinia pestis using two qPCR systems or qPCR and standard PCR. In Xenopsylla cheopis fleas collected from Cotonou (Benin), Rickettsia typhi was detected in 1% (2/199), and an uncultured Bartonella sp. was detected in 34.7% (69/199). In the Lushoto district (United Republic of Tanzania), R. typhi DNA was detected in 10% (2/20) of Xenopsylla brasiliensis, and Rickettsia felis was detected in 65% (13/20) of Ctenocephalides felis strongylus, 71.4% (5/7) of Ctenocephalides canis and 25% (5/20) of Ctenophthalmus calceatus calceatus. In the Democratic Republic of the Congo, R. felis was detected in 56.5% (13/23) of Ct. f. felis from Kinshasa, in 26.3% (10/38) of Ct. f. felis and 9% (1/11) of Leptopsylla aethiopica aethiopica from Ituri district and in 19.2% (5/26) of Ct. f. strongylus and 4.7% (1/21) of Echidnophaga gallinacea. Bartonella sp. was also detected in 36.3% (4/11) of L. a. aethiopica. Finally, in Ituri, Y. pestis DNA was detected in 3.8% (1/26) of Ct. f. strongylus and 10% (3/30) of Pulex irritans from the villages of Wanyale and Zaa.

CONCLUSION

Most flea-borne infections are neglected diseases which should be monitored systematically in domestic rural and urban human populations to assess their epidemiological and clinical relevance. Finally, the presence of Y. pestis DNA in fleas captured in households was unexpected and raises a series of questions regarding the role of free fleas in the transmission of plague in rural Africa, especially in remote areas where the flea density in houses is high.

Typing and clustering of Yersinia pseudotuberculosis isolates by restriction fragment length polymorphism analysis using insertion sequences

Yersinia pseudotuberculosis is an enteropathogen that has an animal reservoir and causes human infections, mostly in temperate and cold countries. Most of the methods previously used to subdivide Y. pseudotuberculosis were performed on small numbers of isolates from a specific geographical area. One aim of this study was to evaluate the typing efficiency of restriction fragment length polymorphism of insertion sequence hybridization patterns (IS-RFLP) compared to other typing methods, such as serotyping, ribotyping, and multilocus sequence typing (MLST), on the same set of 80 strains of Y. pseudotuberculosis of global origin. We found that IS100 was not adequate for IS-RFLP but that both IS285 and IS1541 efficiently subtyped Y. pseudotuberculosis. The discriminatory index (DI) of IS1541-RFLP (0.980) was superior to those of IS285-RFLP (0.939), ribotyping (0.944), MLST (0.861), and serotyping (0.857). The combination of the two IS (2IS-RFLP) further increased the DI to 0.998. Thus, IS-RFLP is a powerful tool for the molecular typing of Y. pseudotuberculosis and has the advantage of exhibiting well-resolved banding patterns that allow for a reliable comparison of strains of worldwide origin. The other aim of this study was to assess the clustering power of IS-RFLP. We found that 2IS-RFLP had a remarkable capacity to group strains with similar genotypic and phenotypic markers, thus identifying robust populations within Y. pseudotuberculosis. Our study thus demonstrates that 2IS- and even IS1541-RFLP alone might be valuable tools for the molecular typing of global isolates of Y. pseudotuberculosis and for the analysis of the population structure of this species.

Plague gives surprises in the first decade of the 21st century in the United States and worldwide

Plague is an ancient disease caused by the bacterium Yersinia pestis and transmitted by rodent flea bites that continues to surprise us with first-ever events. This review documents plague in human cases in the 1st decade of the 21st century and updates our knowledge of clinical manifestations, transmission during outbreaks, diagnostic testing, antimicrobial treatment, and vaccine development. In the United States, 57 persons were reported to have the disease, of which seven died. Worldwide, 21,725 persons were affected with 1,612 deaths, for a case-fatality rate of 7.4%. The Congo reported more cases than any other country, including two large outbreaks of pneumonic plague, surpassing Madagascar, which had the most cases in the previous decade. Two United States scientists suffered fatal accidental exposures: a wildlife biologist, who carried out an autopsy on a mountain lion in Arizona in 2007, and a geneticist with subclinical hemochromatosis in Chicago, who was handling an avirulent strain of Y. pestis in 2009. Antimicrobial drugs given early after the onset of symptoms prevented many deaths; those recommended for treatment and prophylaxis included gentamicin, doxycycline, and fluoroquinolones, although fluoroquinolones have not been adequately tested in humans. Fleas that do not have their guts blocked by clotted blood meals were shown to be better transmitters of plague than blocked fleas. Under development for protection against bioterrorist use, a subunit vaccine containing F1 and V antigens of Y. pestis was administered to human volunteers eliciting antibodies without any serious side effects. These events, although showing progress, suggest that plague will persist in rodent reservoirs mostly in African countries burdened by poverty and civil unrest, causing death when patients fail to receive prompt antimicrobial treatment.