Bubonic Form Research Articles

A novel sORF gene mutant strain of Yersinia pestis vaccine EV76 offers enhanced safety and improved protection against plague.

We recently identified two virulence-associated small open reading frames (sORF) of Yersinia pestis, named yp1 and yp2, and null mutants of each individual genes were highly attenuated in virulence. Plague vaccine strain EV76 is known for strong reactogenicity, making it not suitable for use in humans. To improve the immune safety of EV76, three mutant strains of EV76, Δyp1, Δyp2, and Δyp1&yp2 were constructed and their virulence attenuation, immunogenicity, and protective efficacy in mice were evaluated. All mutant strains were attenuated by the subcutaneous (s.c.) route and exhibited more rapid clearance in tissues than the parental strain EV76. Under iron overload conditions, only the mice infected with EV76Δyp1 survived, accompanied by less draining lymph nodes damage than those infected by EV76. Analysis of cytokines secreted by splenocytes of immunized mice found that EV76Δyp2 induced higher secretion of multiple cytokines including TNF-α, IL-2, and IL-12p70 than EV76. On day 42, EV76Δyp2 or EV76Δyp1&yp2 immunized mice exhibited similar protective efficacy as EV76 when exposed to Y. pestis 201, both via s.c. or intranasal (i.n.) routes of administration. Moreover, when exposed to 200-400 LD50 Y. pestis strain 201Δcaf1 (non-encapsulated Y. pestis), EV76Δyp2 or EV76Δyp1&yp2 are able to afford about 50% protection to i.n. challenges, significantly better than the protection afforded by EV76. On 120 day, mice immunized with EV76Δyp2 or EV76Δyp1&yp2 cleared the i.n. challenge of Y. pestis 201-lux as quickly as those immunized with EV76, demonstrating 90-100% protection. Our results demonstrated that deletion of the yp2 gene is an effective strategy to attenuate virulence of Y. pestis EV76 while improving immunogenicity. Furthermore, EV76Δyp2 is a promising candidate for conferring protection against the pneumonic and bubonic forms of plague.

SYSTEMATIC REVIEW: ZOONOSIS ASSOCIATED WITH MOUSE AND RAT

Mouse and rat borne zoonotic diseases refer to illnesses that can be transmitted from rodents such as mice and rats to humans. These animals can carry various pathogens, including bacteria, viruses, and parasites, which can cause diseases in humans through direct contact, inhalation of airborne particles, consumption of contaminated food or water, or via vectors such as ticks and fleas. Here are some common mouse and rat zoonotic diseases: Leptospirosis, Hantavirus Pulmonary Syndrome (HPS), Lymphocytic Choriomeningitis (LCM), Rat-Bite Fever (RBF), Salmonellosis dan Pes. Leptospirosis: This bacterial infection is caused by Leptospira bacteria found in the urine of infected rodents. Humans can contract leptospirosis through contact with contaminated water, soil, or food. Symptoms can range from mild flu-like illness to severe complications involving the kidneys, liver, and other organs. Hantavirus Pulmonary Syndrome (HPS): Hantaviruses are transmitted to humans through contact with rodent urine, droppings, or saliva, primarily from deer mice. Inhalation of aerosolized virus particles is the most common route of transmission. HPS can lead to severe respiratory illness, with symptoms including fever, muscle aches, coughing, and potentially fatal pulmonary edema. Lymphocytic Choriomeningitis (LCM): LCM is caused by the Lymphocytic Choriomeningitis Virus (LCMV), which is carried by house mice. Humans can become infected through exposure to rodent urine, droppings, saliva, or nesting materials. LCM can cause flu-like symptoms initially and may progress to more severe neurological complications, including meningitis and encephalitis. Rat-Bite Fever (RBF): This bacterial infection is caused by Streptobacillus moniliformis (commonly associated with rat bites) or Spirillum minus (associated with exposure to rat feces or urine). RBF can result from a bite or scratch from an infected rodent or handling of contaminated materials. Symptoms include fever, rash, joint pain, and in severe cases, endocarditis or meningitis. Salmonellosis: Salmonella bacteria can be carried by rodents, particularly in their feces. Humans can contract salmonellosis through the ingestion of contaminated food or water, as well as through direct contact with rodents or their habitats. Symptoms typically include diarrhea, abdominal cramps, fever, and vomiting. Pes: While commonly associated with fleas that infest rodents like rats, plague bacteria (Yersinia pestis) can also be transmitted directly through contact with infected rodents or their bodily fluids. Plague can manifest as bubonic (swollen lymph nodes), septicemic, or pneumonic forms, with symptoms ranging from fever and chills to respiratory distress and organ failure. Preventing mouse and rat zoonotic diseases involves maintaining good hygiene practices, such as proper food storage, waste disposal, and rodent-proofing buildings. Additionally, avoiding contact with wild rodents and seeking prompt medical attention if exposed to rodents or experiencing symptoms of illness are crucial preventive measures.

A decade of plague in Madagascar: a description of two hotspot districts

BackgroundHuman plague cases, mainly in the bubonic form, occur annually in endemic regions of the central highlands of Madagascar. The aim of this study was to compare the dynamics of the epidemiological features of the human plague in two districts of the central highlands region.MethodsIn Madagascar, all clinically suspected plague cases that meet clinical and epidemiological criteria specified in the World Health Organization (WHO) standard case definition are reported to the national surveillance system. Data on plague cases reported between 2006 and 2015 in the districts of Ambositra and Tsiroanomandidy were analysed. Statistical comparisons between the epidemiological characteristics of the two districts were conducted.ResultsA total of 840 cases of plague were reported over the studied period, including 563 (67%) probable and confirmed cases (P + C). Out of these P + C cases, nearly 86% (488/563) were cases of bubonic plague. Reported clinical forms of plague were significantly different between the districts from 2006 to 2015 (p = 0.001). Plague cases occurred annually in a period of 10 years in the Tsiroanomandidy district. During the same period, the Ambositra district was characterized by a one-year absence of cases.ConclusionThe differences in the epidemiological situation with respect to the plague from 2006 to 2015 in the two central highlands districts may suggest that several factors other than biogeographical factors determine the representation of the plague and its dynamics in this region. Considering the epidemiological situations according to the specific contexts of the districts could improve the results in the fight against the plague in Madagascar.

전염병의 과학은 어떻게 논쟁되는가? - 1911년 만주 폐페스트 발병과 국제페스트컨퍼런스

This paper aims to demonstrate the complexity of medical practices on epidemic diseases and the relationships with the circumstances outside laboratory, by reviewing the pneumonic plague in Manchuria and the International Plague Conference in 1911. First of all, although bubonic plague had been historically rampant and its pathogen(Yersinia pestis) was identified in 1894, pneumonic form was unfamiliar disease in 1911, not only because it had rarely been seen but because its symptoms were quite different from the bubonic form. Medical experts at the conference, despite their acquaintance with bubonic plague, could not conclusively confirm that pneumonic plague was the same disease as the bubonic form. Secondly, at that time the way to inspect new and perplexing diseases, such as pneumonic plague, was not single and homogenous, and a variety of medical practices from traditional patho-anatomic observations to laboratory techniques, for example, bacteriological and histological analyses and animal experiments, had to be involved. While these diverse practices served to aid in the understanding of pneumonic plague to some extent, they were judged by different standards and became the central issue of debate at the conference. Thirdly, Manchuria offered an unstable stage for scientific investigations. Medical examinations of representatives concerning pneumonic plague had been influenced by the political position of powers in Manchuria. Therefore, the conference which aimed to understand and overcome unfamiliar epidemic, had failed to draw an unanimous conclusions. This paper, reviewing the case of Manchuria in 1911, would contribute to understand the complexity of medical practices on COVID19 and its relationships with diverse circumstances outside laboratory.

Biological safety of public events: assessment of external epidemiological threat

Division of infections into the constituting individual and population danger taking into account the territorial and seasonal risks of distribution at their drift is proved in article and the differentiation of the last on threat of emergence of emergency situation of biological character at epidemic manifestations that will allow to optimize algorithms of reaction and the organization of antiepidemic actions. The new relative criterion «orient number of infections from one source» reflecting potential ability of the activator to be transferred in human population is offered. Assessment of risk of distribution and threat of emergence of emergency situation at the drift on the territory of the Russian Federation of some diseases constituting population danger is carried out: plagues (in pulmonary and bubonic forms), cholera, hemorrhagic fevers with the leading contact mechanism of transfer of the activator, especially dangerous the ortopoxvirus and the coronavirus of infections, the Crimean hemorrhagic fever, poliomyelitis.

Mongolian Part of the Trans-Boundary Sailugem Natural Plague Focus in 2017. Communication 2. Modern Epidemiological Risks

Objective – to study the current epidemiological risks at plague enzootic frontier territory of the Bayan-Ulgy aimag of Mongolia. Materials and methods. Epidemiological analysis was performed according to the reporting documentation of the National Centre of Zoonotic Infections in Mongolia, results of anonymous questioning of 179 residents of the Bayan-Ulgy aimag of Mongolia, materials of the Department of Health of the Bayan-Ulgy aimag, the Aimag Centre of Zoonotic Infections and the Administration of the Aimag Governor. Results and discussion. Plague was first registered in the Bayan-Ulgy aimag in 1989. The total of 9 patients with plague and 4 lethal outcomes were revealed. In all cases marmots were an infection source, the infection occurred in the process of cutting the carcasses. The majority of the plague patients had bubonic form of plague. All patients were men aged 13 to 34 years. Public inquiry showed that 21,8 % of population considered meat of marmots as a delicacy, 54 % – hunted for the animals, 25,7 % – consumed uncooked organs of marmots as a folk remedy, 19,5 % – participated in cutting of marmot carcasses. Results of the inquiry indicated that a marmot was an object of active hunting for local population. Analysis of epizootic activity of the transboundary Sailugem natural plague focus, modern social and economic conditions in the Bayan-Ulgy aimag has showed that in this territory epidemic risks have shaped and act at present. They can be divided into two groups: epidemic risks capable to cause human sporadic plague cases and epidemic risks leading to anthropozoonotic plague dissemination among the population and exportation of Yersinia pestis beyond the limits of enzootic territories. Effective interaction of anti-epidemic Institutions of Mongolia and Russia and also the Agencies and Institutions of the executive power of all levels permits to counteract these risks.

Characterization of Yersinia pestis Interactions with Human Neutrophils In vitro.

Yersinia pestis is a gram-negative, zoonotic, bacterial pathogen, and the causative agent of plague. The bubonic form of plague occurs subsequent to deposition of bacteria in the skin by the bite of an infected flea. Neutrophils are recruited to the site of infection within the first few hours and interactions between neutrophils and Y. pestis have been demonstrated in vivo. In contrast to macrophages, neutrophils have been considered non-permissive to Y. pestis intracellular survival. Several studies have shown killing of the vast majority of Y. pestis ingested by human neutrophils. However, survival of 10–15% of Y. pestis after phagocytosis by neutrophils is consistently observed. Furthermore, these surviving bacteria eventually replicate within and escape from the neutrophils. We set out to further characterize the interactions between Y. pestis and human neutrophils by (1) determining the effects of known Y. pestis virulence factors on bacterial survival after uptake by neutrophils, (2) examining the mechanisms employed by the neutrophil to kill the majority of intracellular Y. pestis, (3) determining the activation phenotype of Y. pestis-infected neutrophils, and (4) characterizing the Y. pestis-containing phagosome in neutrophils. We infected human neutrophils in vitro with Y. pestis and assayed bacterial survival and uptake. Deletion of the caf1 gene responsible for F1 capsule production resulted in significantly increased uptake of Y. pestis. Surprisingly, while the two-component regulator PhoPQ system is important for survival of Y. pestis within neutrophils, pre-induction of this system prior to infection did not increase bacterial survival. We used an IPTG-inducible mCherry construct to distinguish viable from non-viable intracellular bacteria and determined the association of the Y. pestis-containing phagosome with neutrophil NADPH-oxidase and markers of primary, secondary and tertiary granules. Additionally, we show that inhibition of reactive oxygen species (ROS) production or Src family kinases increased survival of intracellular bacteria indicating that both ROS and granule-phagosome fusion contribute to neutrophil killing of Y. pestis. The data presented here further our understanding of the Y. pestis neutrophil interactions and suggest the existence of still unknown virulence factors involved in Y. pestis survival within neutrophils.

Plague: Clinics, Diagnosis and Treatment.

Plague still poses a significant threat to human health and as a reemerging infection is unfamiliar to the majority of the modern medical doctors. In this chapter, the plague is described according to Dr. Nikiforov's experiences in the diagnosis and treatment of patients, and also a review of the relevant literature on this subject is provided. The main modern methods and criteria for laboratory diagnosis of plague are briefly described. The clinical presentations include the bubonic and pneumonic form, septicemia, rarely pharyngitis, and meningitis. Early diagnosis and the prompt initiation of treatment reduce the mortality rate associated with bubonic plague and septicemic plague to 5-50 %; although a delay of more than 24 h in the administration of antibiotics and antishock treatment can be fatal for plague patients. Most human cases can successfully be treated with antibiotics.

Human plague and pneumonic plague : pathogenicity, epidemiology, clinical presentations and therapy

Yersinia pestis is a highly pathogenic gram-negative bacterium and the causative agent of human plague. In the last 1500 years and during three dreaded pandemics, millions of people became victims of Justinian's plague, the Black Death, or modern plague. Today, Y. pestis is endemic in natural foci of Asian, African and American countries. Due to its broad dissemination in mammal species and fleas, eradication of the pathogen will not be possible in the near future. In fact, plague is currently classified as a "re-emerging disease". Infection may occur after the bite of an infected flea, but also after oral ingestion or inhalation of the pathogen. The clinical presentations comprise the bubonic and pneumonic form, septicemia, rarely pharyngitis, and meningitis. Most human cases can successfully be treated with antibiotics. However, the high transmission rate and lethality of pneumonic plague require international and mandatory case notification and quarantine of patients. Rapid diagnosis, therapy and barrier nursing are not only crucial for the individual patient but also for the prevention of further spread of the pathogen or of epidemics. Therefore, WHO emergency schedules demand the isolation of cases, identification and surveillance of contacts as well as control of zoonotic reservoir animals and vectors. These sanctions and effective antibiotic treatment usually allow a rapid containment of outbreaks. However, multiple antibiotic resistant strains of Y. pestis have been isolated from patients in the past. So far, no outbreaks with such strains have been reported.

Deep comparative genomics among Chlamydia trachomatis lymphogranuloma venereum isolates highlights genes potentially involved in pathoadaptation

Lymphogranuloma venereum (LGV) is a human sexually transmitted disease caused by the obligate intracellular bacterium Chlamydia trachomatis (serovars L1–L3). LGV clinical manifestations range from severe ulcerative proctitis (anorectal syndrome), primarily caused by the epidemic L2b strains, to painful inguinal lymphadenopathy (the typical LGV bubonic form). Besides potential host-related factors, the differential disease severity and tissue tropism among LGV strains is likely a function of the genetic backbone of the strains. We aimed to characterize the genetic variability among LGV strains as strain- or serovar-specific mutations may underlie phenotypic signatures, and to investigate the mutational events that occurred throughout the pathoadaptation of the epidemic L2b lineage. By analyzing 20 previously published genomes from L1, L2, L2b and L3 strains and two new genomes from L2b strains, we detected 1497 variant sites and about 100 indels, affecting 453 genes and 144 intergenic regions, with 34 genes displaying a clear overrepresentation of nonsynonymous mutations. Effectors and/or type III secretion substrates (almost all of those described in the literature) and inclusion membrane proteins showed amino acid changes that were about fivefold more frequent than silent changes. More than 120 variant sites occurred in plasmid-regulated virulence genes, and 66% yielded amino acid changes. The identified serovar-specific variant sites revealed that the L2b-specific mutations are likely associated with higher fitness and pointed out potential targets for future highly discriminatory diagnostic/typing tests. By evaluating the evolutionary pathway beyond the L2b clonal radiation, we observed that 90.2% of the intra-L2b variant sites occurring in coding regions involve nonsynonymous mutations, where CT456/tarp has been the main target. Considering the progress on C. trachomatis genetic manipulation, this study may constitute an important contribution for prioritizing study targets for functional genomics aiming to dissect the impact of the identified intra-LGV polymorphisms on virulence or tropism dissimilarities among LGV strains.

Subtle genetic modifications transformed an enteropathogen into a flea-borne pathogen.

Yersinia pestis is the etiological agent of plague, one of the most devastating diseases in human history. Because of the identification of the plague bacillus, the understanding of its epidemiological cycle, and the advent of efficient antibiotic therapies, the death toll due to the plague has dramatically decreased over the last 100 y. However, this disease has never been eradicated, and because of its rodent reservoir, it will not be eradicated in the near future. On the contrary, human plague cases have been reported since the 1990s in countries where the disease was thought to be extinct for decades, and therefore, the plague is now categorized as a reemerging disease. Y. pestis has two characteristics that distinguish it from most other bacterial pathogens. One is its exceptional pathogenicity for humans, with a mortality rate of 40–70% in ∼1 wk for the bubonic form and close to 100% in around 3 d for pneumonic plague. The other characteristic of Y. pestis is its transmission from rodent to rodent and from rodent to human by an infectious fleabite. These two characteristics are probably linked (see below), and therefore deciphering the mechanisms that explain the peculiar mode of transmission of Y. pestis by fleas is a key step in the understanding of pathogen evolution and gain of virulence. In PNAS, Chouikha and Hinnebusch identify a fundamental event in the adaptation of the plague bacillus to its flea vector (1).

Selectivity in IgG Subclass Response to Live Plague Vaccine in Humans

Attenuated Yersinia pestis strain EV NIIEG is a licensed live plague vaccine (LPV) for human use in Russia that can elicit protection against both the bubonic and pneumonic forms of disease. However, little is known about the mechanisms underlying the formation of immunity to Y. pestis provided by this vaccine. Our recent study reported a prevalence of specific IgG antibodies to the capsular antigen F1 and the type three secretion system (T3SS) structural subunit YscF in humans immunized with live plague vaccine. In this study, IgG subclasses of antibodies to the plague antigens F1 and YscF in the sera of vaccinees were determined by using an enzyme-linked immunosorbent assay (ELISA) with monoclonal antibodies. IgG subclass antibodies to F1 antigen were predominantly IgG1, although IgG2 and IgG4 subclasses were detectable. The IgG1 titers were markedly higher in donors who received multiple annual injections, while the IgG2 and IgG4 titers showed no increase and stayed low in all donors. The IgG1 anti-F1 remained detectable even 20 years post-vaccination, suggesting a long-term immunity. Sera of YscF-positive donors also contained predominantly IgG1-specific antibodies. The IgG2 and IgG4 titers to YscF were undetectable in all donors, including those who received multiple vaccinations. In conclusion, we describe for the first time that IgG1 is a dominating isotype for both F1 and YscF antigens in humans immunized with live plague vaccine.

Evaluation of Protective Potential of Yersinia pestis Outer Membrane Protein Antigens as Possible Candidates for a New-Generation Recombinant Plague Vaccine

Plague caused by Yersinia pestis manifests itself in bubonic, septicemic, and pneumonic forms. Although the U.S. Food and Drug Administration recently approved levofloxacin, there is no approved human vaccine against plague. The capsular antigen F1 and the low-calcium-response V antigen (LcrV) of Y. pestis represent excellent vaccine candidates; however, the inability of the immune responses to F1 and LcrV to provide protection against Y. pestis F1(-) strains or those which harbor variants of LcrV is a significant concern. Here, we show that the passive transfer of hyperimmune sera from rats infected with the plague bacterium and rescued by levofloxacin protected naive animals against pneumonic plague. Furthermore, 10 to 12 protein bands from wild-type (WT) Y. pestis CO92 reacted with the aforementioned hyperimmune sera upon Western blot analysis. Based on mass spectrometric analysis, four of these proteins were identified as attachment invasion locus (Ail/OmpX), plasminogen-activating protease (Pla), outer membrane protein A (OmpA), and F1. The genes encoding these proteins were cloned, and the recombinant proteins purified from Escherichia coli for immunization purposes before challenging mice and rats with either the F1(-) mutant or WT CO92 in bubonic and pneumonic plague models. Although antibodies to Ail and OmpA protected mice against bubonic plague when challenged with the F1(-) CO92 strain, Pla antibodies were protective against pneumonic plague. In the rat model, antibodies to Ail provided protection only against pneumonic plague after WT CO92 challenge. Together, the addition of Y. pestis outer membrane proteins to a new-generation recombinant vaccine could provide protection against a wide variety of Y. pestis strains.

Plague: The Disease,Yersinia pestisand its Genome

Plague is a highly virulent, vector-borne disease of ancient antecedents, transmitted from members of the family Rodentia, through the bites of infected fleas. The disease, caused by the bacterium Yersinia pestis, presents itself in septicaemic, bubonic and pneumonic forms. The rat flea Xenopsylla cheopis is most often implicated in transmission. The plague remains one of the most dreaded infectious diseases, which has raised its head in western, northern and southern regions in the last few decades, being a category ‘A’ critical agent with a significant threat to public health and national security. Rapid antigen detection or nucleic acid-based molecular tests for plague are not widely available. Modern immunoprophylactic regimes for pre- and postgeneration vaccination are needed. Complete genome sequences unveiled for all four biotypes and other strains/isolates recently will help scientists gain insights into the genomic rearrangement and pathogenicity of the organism.

Role of the Yersinia pestis Yersiniabactin Iron Acquisition System in the Incidence of Flea-Borne Plague

Plague is a flea-borne zoonosis caused by the bacterium Yersinia pestis. Y. pestis mutants lacking the yersiniabactin (Ybt) siderophore-based iron transport system are avirulent when inoculated intradermally but fully virulent when inoculated intravenously in mice. Presumably, Ybt is required to provide sufficient iron at the peripheral injection site, suggesting that Ybt would be an essential virulence factor for flea-borne plague. Here, using a flea-to-mouse transmission model, we show that a Y. pestis strain lacking the Ybt system causes fatal plague at low incidence when transmitted by fleas. Bacteriology and histology analyses revealed that a Ybt-negative strain caused only primary septicemic plague and atypical bubonic plague instead of the typical bubonic form of disease. The results provide new evidence that primary septicemic plague is a distinct clinical entity and suggest that unusual forms of plague may be caused by atypical Y. pestis strains.

Lymphogranuloma venereum proctocolitis: a silent endemic disease in men who have sex with men in industrialised countries

Lymphogranuloma venereum (LGV) is a sexually transmitted disease (STD) caused by serovars L1-L3 of Chlamydia trachomatis. Rare in the western world prior to 2003, different outbreaks or clusters of LGV have been reported in Europe, North America and Australia among men who have sex with men (MSM) over the past few years. The majority were HIV infected MSM with high-risk sexual behaviour and a high rate of concomitant STD, including hepatitis C. Most of them presented with a proctitis syndrome and only a few with the classical bubonic form. A previously non-described serovar, L2b, has been identified as the main causative agent of the epidemic. A delay in diagnosis has been the rule because of the misleading symptomatology of LGV proctitis, the unfamiliarity of the disease to physicians, and the lack of a routine diagnostic test for LGV serovars. It is crucial to increase the awareness of the disease among physicians for prompt diagnosis and treatment, to avoid complications, and to stop ongoing transmission. It has additional public health implications since LGV may facilitate the transmission and acquisition of HIV and other STD.

Yersinia pestiswith Regulated Delayed Attenuation as a Vaccine Candidate To Induce Protective Immunity against Plague

Two mutant strains of Yersinia pestis KIM5+, a Deltacrp mutant and a mutant with arabinose-dependent regulated delayed-shutoff crp expression (araC P(BAD) crp), were constructed, characterized in vitro, and evaluated for virulence, immunogenicity, and protective efficacy in mice. Both strains were highly attenuated by the subcutaneous (s.c.) route. The 50% lethal doses (LD(50)s) of the Deltacrp and araC P(BAD) crp mutants were approximately 1,000,000-fold and 10,000-fold higher than those of Y. pestis KIM5+, respectively, indicating that both strains were highly attenuated. Mice vaccinated s.c. with 3.8 x 10(7) CFU of the Deltacrp mutant developed high anti-Y. pestis and anti-LcrV serum IgG titers, both with a strong Th2 bias, and induced protective immunity against subcutaneous challenge with virulent Y. pestis (80% survival) but no protection against pulmonary challenge. Mice vaccinated with 3.0 x 10(4) CFU of the araC P(BAD) crp mutant also developed high anti-Y. pestis and anti-LcrV serum IgG titers but with a more balanced Th1/Th2 response. This strain induced complete protection against s.c. challenge and partial protection (70% survival) against pulmonary challenge. Our results demonstrate that arabinose-dependent regulated crp expression is an effective strategy to attenuate Y. pestis while retaining strong immunogenicity, leading to protection against the pneumonic and bubonic forms of plague.

Polyphosphate and omptins: novel bacterial procoagulant agents

Derangement of the blood clotting system contributes strongly to multiple organ failure in severe sepsis. In this review, we examine two microbial modulators of the clotting system: polyphosphates and omptins. Polyphosphates are linear polymers of inorganic phosphate that are abundant in the acidocalcisomes of prokaryotes and unicellular organisms as well as in the dense granules of human platelets. Polyphosphates modulate haemostasis by: (1) triggering clotting via the contact pathway; (2) accelerating the activation of coagulation factor V (a key cofactor in blood clotting) and (3) causing fibrin to form clots whose fibrils are thicker and more resistant to fibrinolysis. While polyphosphates are found in all prokaryotes, omptins have a more limited distribution among certain Gram-negative species. Omptins are outer membrane aspartyl proteases which were recently found to proteolytically inactivate tissue factor pathway inhibitor (TFPI), the main inhibitor of the initiation phase of blood clotting. Omptin activity against TFPI requires lipopolysaccharide without O-antigen (rough LPS) such as is found on the surface of Yersinia pestis, the etiologic agent of plague. Interestingly, expression of Pla, the Yersinia pestis omptin, has a demonstrated virulence role in converting plasminogen into the fibrinolytic enzyme plasmin, which would seemingly antagonize any procoagulant effect of TFPI inactivation. However, since the rate of TFPI inactivation is much higher than the rate of plasminogen activation, we suggest that Pla may have a dual function in supporting the bubonic form of plague which is unique to Yersinia pestis.

Direct Transcriptional Control of the Plasminogen Activator Gene of Yersinia pestis by the Cyclic AMP Receptor Protein

Horizontal gene transfer events followed by proper regulatory integration of a gene drive rapid evolution of bacterial pathogens. A key event in the evolution of the highly virulent plague bacterium Yersinia pestis was the acquisition of plasmid pPCP1, which carries the plasminogen activator gene, pla. This promoted the bubonic form of the disease by increasing bacterial dissemination from flea bite sites and incidentally enhanced replication in respiratory airways during pneumonic infection. We determined that expression of pla is controlled by the global regulator cyclic AMP (cAMP) receptor protein (Crp). This transcription factor is well conserved among distantly related bacteria, where it acts as a soluble receptor for the ubiquitous signaling molecule cAMP and controls a global network of metabolic and stress-protective genes. Crp has a similar physiological role in Y. pestis since loss of its function resulted in an inability to metabolize a variety of nonglucose substrates. Activation of pla expression requires a transcription activation element of the pla promoter that serves as a Crp binding site. Crp interaction with this site was demonstrated to occur only in the presence of cAMP. Alteration of the Crp binding site nucleotide sequence prevented in vitro formation of Crp-DNA complexes and inhibited in vivo expression of pla. The placement of pla under direct regulatory control of Crp highlights how highly adapted pathogens integrate laterally acquired genes to coordinate virulence factor expression with global gene networks to maintain homeostasis through the infectious life cycle.

Epidemiological trends for human plague in Madagascar during the second half of the 20th century: a survey of 20 900 notified cases

To describe the principal characteristics and epidemiological trends for human plague in modern times based on the largest reported series of cases from the highly active Malagasy focus. We used a file of 20,900 notified cases of suspected plague, 4,473 of which were confirmed or probable, to carry out a statistical analysis of incidence and mortality rates and associated factors for 5-year periods from 1957 to 2001. Our analysis of trends showed (1) an increase in the incidence rate and the number of districts affected, (2) an increase in the proportion of bubonic forms (64.8-96.8%) at the expense of the pneumonic forms (35.2-3.2%) more frequent in elderly subjects and (3) a decrease in case fatality rate (CFR, 55.7-20.9%) associated with five factors: clinical form, season, province, urban/rural and period considered. The median age of patients was 14 years and more men than women were affected. Since the end of the 1980s, the incidence of plague in Madagascar has increased in both rural and urban areas, because of multiple socioeconomic and environmental factors. However, the plague mortality rate has tended to decrease, together with the frequency of pneumonic forms, because of the strengthening of control measures. Making dipstick tests for the rapid diagnosis of human cases and epizootics in rats available for health structures should make it possible to raise the alarm and to react rapidly, thereby further decreasing morbidity and CFR.