Pneumonic Plague Research Articles

The mystery of plague in medieval Iceland

ABSTRACTThis article is aimed at encouraging scholars to continue to take critical, interdisciplinary approaches to understanding the cause and scale of historic plague outbreaks. It does this by reinvestigating two recorded outbreaks of plague in Iceland in 1402–4 and 1494–5. It is argued that these were episodes of pneumonic plague, caused by Yersinia pestis, and that the likely mortality was no more than 25% of the population in both cases. This contrasts with the higher rates (50–60% and 30–50%) postulated elsewhere. Although it is recognised there are other explanations for plague in Iceland, greater caution needs to be taken in interpreting the direct and indirect evidence for its demographic effects. A lower mortality rate fits better with a less widespread and more fragmented epidemic. The numbers and types of Icelandic farms which might have been vacant during the fifteenth and early sixteenth centuries are given more detailed consideration than in previous accounts. ‘Farm abandonment’ in the fifteenth century was continually driven by a series of environmental and economic factors and need not be interpreted as a demographic collapse caused solely by the plague. Greater attention is also given to understanding how plague could have reached Iceland and the biological, ecological and sociological factors which might then have sustained it.

Plasminogen Activator – Multifunctional Protein of Plague Pathogen

Yersinia pestis plasminogen activator, a surface protease (Pla) is encoded by species-specific plasmid pPla. This enzyme belongs to outer membrane protein family and has a s-barrel structure. Pla protease interacts complexly with homeostasis system of a hostorganism and is an important factor of plague agent virulence. Represented are the literature data on the part of plasminogen activator in the development of bubonic and pneumonic plague. Described is the role of R-form lipopolysaccharide in protease Pla activity manifestation. Plasminogen activator directly contributes to fibrinolysis by activating plasminogen and inactivating plasminogen-1 activator inhibitor (PAI-1) and ά2-anti-plasmin, as well as promoted by thrombin fibrinolysis inhibitor (TAFI). Pro-coagulant Pla protein activity is caused by the destruction of tissue factor pathway inhibitor (TFPI). In addition, given is the information on non-proteolytic functions of plasminogen activator.

Assessment of Live Plague Vaccine Candidates.

Since its creation in the early twentieth century, live plague vaccine EV has been successfully applied to millions of people without severe complications. This vaccine has been proven to elicit protection against both bubonic and pneumonic plague, and it is still in use in populations at risk mainly in the countries of the former Soviet Union. Despite extensive efforts in developing subunit vaccines, there is a reviving interest in creation of a precisely attenuated strain of Yersinia pestis superior to the EV that can serve as a live plague vaccine with improved characteristics. Here we summarize decades of experience of the Russian anti-plague research in developing a standard protocol for early-stage evaluation of safety and immunogenicity of live plague vaccines. This protocol allows step-by-step comparison of the novel test candidates with the EV vaccine by using subcutaneous immunization and bubonic plague infection models in two animal species, e.g., guinea pigs and mice.

Pathology and Pathogenesis of Yersinia pestis.

Various types of animal models of plague have been developed, including mice, rats, guinea pigs, and nonhuman primates. Studies have indicated that rodent and nonhuman primate models of pneumonic plague closely resemble the human disease and that the pathologic changes that occur during bubonic plague are very similar in rodents, nonhuman primates, and humans. In this section, the pathological changes caused by Y. pestis in different animal models are described. The bacterium Y. pestis causes deadly plague, whereas the other two closely related enteropathogenic Yersinia species merely cause limited gastrointestinal manifestations. Y. pestis has unique virulence mechanisms that enable it to be a successful flea-borne and highly virulent pathogen. Massive gene losses and inactivation play important roles, as well as the gene acquisitions, in the evolution process of this pathogen. Here, we summarized several newly acquired features of Y. pestis, including the unique lipid A modification, biofilm formation ability, and loss of adhesions for enteric colonization that are realized by gene inactivation and plasminogen activator and F1 capsular that are realized by gene acquisition, which contribute to the unique transmission and pathogenesis of Y. pestis.

Synthesis and antibacterial activity of novel 2-(arylimino)thiazolidin-4-one and 2-(benzylidenehydrazono)-3-arylthiazolidin-4-one derivatives

The ongoing spread of multidrug-resistant bacteria demands an intensive search for new antibacterial agents. In the present study, a series of new 1,3-thiazolidin-4-ones has been synthesized and investigated for its in vitro antibacterial activity. The most potent antibacterial compound 4c was found to be active, at low micromolar range, against Staphylococcus aureus, Staphylococcus epidermidis, Enterococcus faecalis and the pneumonic plague causative agent Yersinia pestis with minimum inhibitory concentrations of 5 µM, 2.5 µM, 2.5 µM and 5 µM, respectively. Compound 4c showed the ability to kill E. faecalis JH212 strain with a minimum bactericidal concentration of 5 µM. Furthermore, compounds 9b and 10a inhibited the biofilm formation in S. epidermidis, where they showed 70% to 80% inhibition at a concentration of 40 µM.

A Phase I Safety and Immunogenicity Dose Escalation Trial of Plague Vaccine, Flagellin/F1/V, in Healthy Adult Volunteers (DMID 08-0066)

Abstract Introduction Intentional aerosolization of Yersinia pestis may result in pneumonic plague which is highly fatal if not treated early. Methods We conducted a phase 1 randomized, double blind (within each group), placebo controlled, dose escalation trial to evaluate a plague vaccine, Flagellin/F1/V, in healthy adults aged 8 through 45 years. Vaccine was administered intramuscularly on Days 0 and 28 at a dose of 1, 3, 6 or 10 mcg. Subjects were observed for 4 h after vaccination for cytokine release syndrome. Reactogenicity and adverse events (AE) were collected for 14 and 28 days, respectively, after each vaccination. Serious AE were collected for the entire study. ELISA antibody and cytokines were measured at multiple time points. Subject’s participation lasted 13 months. Results Sixty healthy subjects were enrolled; 52% males, 100% non-Hispanic, 91.7% white and mean age 30.8 years. No severe reactogenicity events occurred; most AE were mild. No serious AE related to vaccine occurred. A dose response effect was observed to F1, V and flagellin. The peak ELISA IgG antibody titers (95% CI) after two 10 mcg doses of vaccine were 260.0 (102.6–659.0) and 983.6 (317.3–3048.8), respectively, against F1 and V antigens. The 6 mcg dose group provided similar titers. Titers were low for the placebo, 1 mcg and 3 mcg recipients. A positive antibody dose response was observed to F1, V and flagellin. Vaccine antigen specific serum IgE was not detected. There were no significant rises in serum or cellular cytokine responses and no significant IgG increase to flagellin after the second dose. Conclusion The Flagellin/F1/V vaccine exhibited a dose dependent increase in immunogenicity and was well tolerated at all doses. Antibody specific responses to F1, V and flagellin increased as dose increased. Given the results from this trial, testing higher doses of the vaccine may be merited.

Inactivation of Peroxiredoxin 6 by the Pla Protease of Yersinia pestis.

Pneumonic plague represents the most severe form of disease caused by Yersinia pestis due to its ease of transmission, rapid progression, and high mortality rate. The Y. pestis outer membrane Pla protease is essential for the development of pneumonic plague; however, the complete repertoire of substrates cleaved by Pla in the lungs is not known. In this study, we describe a proteomic screen to identify host proteins contained within the bronchoalveolar lavage fluid of mice that are cleaved and/or processed by Y. pestis in a Pla-dependent manner. We identified peroxiredoxin 6 (Prdx6), a host factor that contributes to pulmonary surfactant metabolism and lung defense against oxidative stress, as a previously unknown substrate of Pla. Pla cleaves Prdx6 at three distinct sites, and these cleavages disrupt both the peroxidase and phospholipase A2 activities of Prdx6. In addition, we found that infection with wild-type Y. pestis reduces the abundance of extracellular Prdx6 in the lungs compared to that after infection with Δpla Y. pestis, suggesting that Pla cleaves Prdx6 in the pulmonary compartment. However, following infection with either wild-type or Δpla Y. pestis, Prdx6-deficient mice exhibit no differences in bacterial burden, host immune response, or lung damage from wild-type mice. Thus, while Pla is able to disrupt Prdx6 function in vitro and reduce Prdx6 levels in vivo, the cleavage of Prdx6 has little detectable impact on the progression or outcome of pneumonic plague.

Structural Characterisation of FabG from Yersinia pestis, a Key Component of Bacterial Fatty Acid Synthesis.

Ketoacyl-acyl carrier protein reductases (FabG) are ubiquitously expressed enzymes that catalyse the reduction of acyl carrier protein (ACP) linked thioesters within the bacterial type II fatty acid synthesis (FASII) pathway. The products of these enzymes, saturated and unsaturated fatty acids, are essential components of the bacterial cell envelope. The FASII reductase enoyl-ACP reductase (FabI) has been the focus of numerous drug discovery efforts, some of which have led to clinical trials, yet few studies have focused on FabG. Like FabI, FabG appears to be essential for survival in many bacteria, similarly indicating the potential of this enzyme as a drug target. FabG enzymes are members of the short-chain alcohol dehydrogenase/reductase (SDR) family, and like other SDRs, exhibit highly conserved secondary and tertiary structures, and contain a number of conserved sequence motifs. Here we describe the crystal structures of FabG from Yersinia pestis (YpFabG), the causative agent of bubonic, pneumonic, and septicaemic plague, and three human pandemics. Y. pestis remains endemic in many parts of North America, South America, Southeast Asia, and Africa, and a threat to human health. YpFabG shares a high degree of structural similarity with bacterial homologues, and the ketoreductase domain of the mammalian fatty acid synthase from both Homo sapiens and Sus scrofa. Structural characterisation of YpFabG, and comparison with other bacterial FabGs and the mammalian fatty acid synthase, provides a strong platform for virtual screening of potential inhibitors, rational drug design, and the development of new antimicrobial agents to combat Y. pestis infections.

Complete Protection against Pneumonic and Bubonic Plague after a Single Oral Vaccination

BackgroundNo efficient vaccine against plague is currently available. We previously showed that a genetically attenuated Yersinia pseudotuberculosis producing the Yersinia pestis F1 antigen was an efficient live oral vaccine against pneumonic plague. This candidate vaccine however failed to confer full protection against bubonic plague and did not produce F1 stably.Methodology/Principal FindingsThe caf operon encoding F1 was inserted into the chromosome of a genetically attenuated Y. pseudotuberculosis, yielding the VTnF1 strain, which stably produced the F1 capsule. Given orally to mice, VTnF1 persisted two weeks in the mouse gut and induced a high humoral response targeting both F1 and other Y. pestis antigens. The strong cellular response elicited was directed mostly against targets other than F1, but also against F1. It involved cells with a Th1—Th17 effector profile, producing IFNγ, IL-17, and IL-10. A single oral dose (108 CFU) of VTnF1 conferred 100% protection against pneumonic plague using a high-dose challenge (3,300 LD50) caused by the fully virulent Y. pestis CO92. Moreover, vaccination protected 100% of mice from bubonic plague caused by a challenge with 100 LD50 Y. pestis and 93% against a high-dose infection (10,000 LD50). Protection involved fast-acting mechanisms controlling Y. pestis spread out of the injection site, and the protection provided was long-lasting, with 93% and 50% of mice surviving bubonic and pneumonic plague respectively, six months after vaccination. Vaccinated mice also survived bubonic and pneumonic plague caused by a high-dose of non-encapsulated (F1-) Y. pestis.SignificanceVTnF1 is an easy-to-produce, genetically stable plague vaccine candidate, providing a highly efficient and long-lasting protection against both bubonic and pneumonic plague caused by wild type or un-encapsulated (F1-negative) Y. pestis. To our knowledge, VTnF1 is the only plague vaccine ever reported that could provide high and durable protection against the two forms of plague after a single oral administration.

Structural Characterisation of the Beta-Ketoacyl-Acyl Carrier Protein Synthases, FabF and FabH, of Yersinia pestis.

Yersinia pestis, the causative agent of bubonic, pneumonic, and septicaemic plague, remains a major public health threat, with outbreaks of disease occurring in China, Madagascar, and Peru in the last five years. The existence of multidrug resistant Y. pestis and the potential of this bacterium as a bioterrorism agent illustrates the need for new antimicrobials. The β-ketoacyl-acyl carrier protein synthases, FabB, FabF, and FabH, catalyse the elongation of fatty acids as part of the type II fatty acid biosynthesis (FASII) system, to synthesise components of lipoproteins, phospholipids, and lipopolysaccharides essential for bacterial growth and survival. As such, these enzymes are promising targets for the development of novel therapeutic agents. We have determined the crystal structures of the Y. pestis β-ketoacyl-acyl carrier protein synthases FabF and FabH, and compared these with the unpublished, deposited structure of Y. pestis FabB. Comparison of FabB, FabF, and FabH provides insights into the substrate specificities of these enzymes, and investigation of possible interactions with known β-ketoacyl-acyl carrier protein synthase inhibitors suggests FabB, FabF and FabH may be targeted simultaneously to prevent synthesis of the fatty acids necessary for growth and survival.

Spatially Distinct Neutrophil Responses within the Inflammatory Lesions of Pneumonic Plague

ABSTRACTDuring pneumonic plague, the bacterium Yersinia pestis elicits the development of inflammatory lung lesions that continue to expand throughout infection. This lesion development and persistence are poorly understood. Here, we examine spatially distinct regions of lung lesions using laser capture microdissection and transcriptome sequencing (RNA-seq) analysis to identify transcriptional differences between lesion microenvironments. We show that cellular pathways involved in leukocyte migration and apoptosis are downregulated in the center of lung lesions compared to the periphery. Probing for the bacterial factor(s) important for the alteration in neutrophil survival, we show both in vitro and in vivo that Y. pestis increases neutrophil survival in a manner that is dependent on the type III secretion system effector YopM. This research explores the complexity of spatially distinct host-microbe interactions and emphasizes the importance of cell relevance in assays in order to fully understand Y. pestis virulence.

Intramuscular Immunization of Mice with a Live-Attenuated Triple Mutant of Yersinia pestis CO92 Induces Robust Humoral and Cell-Mediated Immunity To Completely Protect Animals against Pneumonic Plague.

Earlier, we showed that the Δlpp ΔmsbB Δail triple mutant of Yersinia pestis CO92 with deleted genes encoding Braun lipoprotein (Lpp), an acyltransferase (MsbB), and the attachment invasion locus (Ail), respectively, was avirulent in a mouse model of pneumonic plague. In this study, we further evaluated the immunogenic potential of the Δlpp ΔmsbB Δail triple mutant and its derivative by different routes of vaccination. Mice were immunized via the subcutaneous (s.c.) or the intramuscular (i.m.) route with two doses (2 × 10(6) CFU/dose) of the above-mentioned triple mutant with 100% survivability of the animals. Upon subsequent pneumonic challenge with 70 to 92 50% lethal doses (LD(50)) of wild-type (WT) strain CO92, all of the mice survived when immunization occurred by the i.m. route. Since Ail has virulence and immunogenic potential, a mutated version of Ail devoid of its virulence properties was created, and the genetically modified ail replaced the native ail gene on the chromosome of the Δlpp ΔmsbB double mutant, creating a Δlpp ΔmsbB::ailL2 vaccine strain. This newly generated mutant was attenuated similarly to the Δlpp ΔmsbB Δail triple mutant when administered by the i.m. route and provided 100% protection to animals against subsequent pneumonic challenge. Not only were the two above-mentioned mutants cleared rapidly from the initial i.m. site of injection in animals with no histopathological lesions, the immunized mice did not exhibit any disease symptoms during immunization or after subsequent exposure to WT CO92. These two mutants triggered balanced Th1- and Th2-based antibody responses and cell-mediated immunity. A substantial increase in interleukin-17 (IL-17) from the T cells of vaccinated mice, a cytokine of the Th17 cells, further augmented their vaccine potential. Thus, the Δlpp ΔmsbB Δail and Δlpp ΔmsbB::ailL2 mutants represent excellent vaccine candidates for plague, with the latter mutant still retaining Ail immunogenicity but with a much diminished virulence potential.

Impact of the Pla protease substrate α2-antiplasmin on the progression of primary pneumonic plague.

Many pathogens usurp the host hemostatic system during infection to promote pathogenesis. Yersinia pestis, the causative agent of plague, expresses the plasminogen activator protease Pla, which has been shown in vitro to target and cleave multiple proteins within the fibrinolytic pathway, including the plasmin inhibitor α2-antiplasmin (A2AP). It is not known, however, if Pla inactivates A2AP in vivo; the role of A2AP during respiratory Y. pestis infection is not known either. Here, we show that Y. pestis does not appreciably cleave A2AP in a Pla-dependent manner in the lungs during experimental pneumonic plague. Furthermore, following intranasal infection with Y. pestis, A2AP-deficient mice exhibit no difference in survival time, bacterial burden in the lungs, or dissemination from wild-type mice. Instead, we found that in the absence of Pla, A2AP contributes to the control of the pulmonary inflammatory response during infection by reducing neutrophil recruitment and cytokine production, resulting in altered immunopathology of the lungs compared to A2AP-deficient mice. Thus, our data demonstrate that A2AP is not significantly affected by the Pla protease during pneumonic plague, and although A2AP participates in immune modulation in the lungs, it has limited impact on the course or ultimate outcome of the infection.

Importation of rare but life-threatening and highly contagious diseases. Current situation and outlook

ZusammenfassungAls Internist muss man damit rechnen, Erstbehandler eines Patienten mit selten importierter hochkontagiöser, lebensbedrohlicher Erkrankung zu sein. Dies kommt sicherlich nur äußerst selten vor, hat aber enorme Konsequenzen. Man sollte daher grundsätzlich die viralen hämorrhagischen Fieber kennen: Filoviren verursachen das Ebola- und Marburg-Fieber, Arenaviren das Lassa-Fieber und südamerikanische hämorrhagische Fieber, die Bunya-Viren u. a. das hämorrhagische Krim-Kongo-Fieber. Weiterhin sollte man einige hochkontagiöse respiratorische Infektionen wie das „hantavirus pulmonary syndrome“, die Lungenpest und das „Middle East respiratory syndrome“ kennen.

Characterization of a Cynomolgus Macaque Model of Pneumonic Plague for Evaluation of Vaccine Efficacy.

The efficacy of a recombinant plague vaccine (rF1V) was evaluated in cynomolgus macaques (CMs) to establish the relationship among vaccine doses, antibody titers, and survival following an aerosol challenge with a lethal dose of Yersinia pestis strain Colorado 92. CMs were vaccinated with a range of rF1V doses on a three-dose schedule (days 0, 56, and 121) to provide a range of survival outcomes. The humoral immune response following vaccination was evaluated with anti-rF1, anti-rV, and anti-rF1V bridge enzyme-linked immunosorbent assays (ELISAs). Animals were challenged via aerosol exposure on day 149. Vaccine doses and antibody responses were each significantly associated with the probability of CM survival (P < 0.0001). Vaccination also decreased signs of pneumonic plague in a dose-dependent manner. There were statistically significant correlations between the vaccine dose and the time to onset of fever (P < 0.0001), the time from onset of fever to death (P < 0.0001), the time to onset of elevated respiratory rate (P = 0.0003), and the time to onset of decreased activity (P = 0.0251) postinfection in animals exhibiting these clinical signs. Delays in the onset of these clinical signs of disease were associated with larger doses of rF1V. Immunization with ≥ 12 μg of rF1V resulted in 100% CM survival. Since both the vaccine dose and anti-rF1V antibody titers correlate with survival, rF1V bridge ELISA titers can be used as a correlate of protection.

Resistance to Innate Immunity Contributes to Colonization of the Insect Gut by Yersinia pestis.

Yersinia pestis, the causative agent of bubonic and pneumonic plague, is typically a zoonotic vector-borne disease of wild rodents. Bacterial biofilm formation in the proventriculus of the flea contributes to chronic infection of fleas and facilitates efficient disease transmission. However prior to biofilm formation, ingested bacteria must survive within the flea midgut, and yet little is known about vector-pathogen interactions that are required for flea gut colonization. Here we establish a Drosophila melanogaster model system to gain insight into Y. pestis colonization of the insect vector. We show that Y. pestis establishes a stable infection in the anterior midgut of fly larvae, and we used this model system to study the roles of genes involved in biofilm production and/or resistance to gut immunity stressors. We find that PhoP and GmhA both contribute to colonization and resistance to antimicrobial peptides in flies, and furthermore, the data suggest biofilm formation may afford protection against antimicrobial peptides. Production of reactive oxygen species in the fly gut, as in fleas, also serves to limit bacterial infection, and OxyR mediates Y. pestis survival in both insect models. Overall, our data establish the fruit fly as an informative model to elucidate the relationship between Y. pestis and its flea vector.

Early emergence of Yersinia pestis as a severe respiratory pathogen.

Yersinia pestis causes the fatal respiratory disease pneumonic plague. Y. pestis recently evolved from the gastrointestinal pathogen Y. pseudotuberculosis; however, it is not known at what point Y. pestis gained the ability to induce a fulminant pneumonia. Here we show that the acquisition of a single gene encoding the protease Pla was sufficient for the most ancestral, deeply rooted strains of Y. pestis to cause pneumonic plague, indicating that Y. pestis was primed to infect the lungs at a very early stage in its evolution. As Y. pestis further evolved, modern strains acquired a single amino-acid modification within Pla that optimizes protease activity. While this modification is unnecessary to cause pneumonic plague, the substitution is instead needed to efficiently induce the invasive infection associated with bubonic plague. These findings indicate that Y. pestis was capable of causing pneumonic plague before it evolved to optimally cause invasive infections in mammals.

Impact Assessment of the Response Measures to Local Epidemics Induced by the Agents of Particularly Dangerous Infections: Isolation

The paper discusses the opportunities of using universal model of local, evolving within a closed population, epidemics/outbreaks, developed at the premises of SRC VB “Vector”, for investigations and assessment of the impact of various resource limitations on the countermeasure effectiveness, and in particular isolation of a patient and contact tracing and isolation. Based on the epidemic dynamics analysis for a number of infections such as smallpox, anthrax, pneumonic and bubonic plague, hemorrhagic Ebola, Marburg, Lassa, Crimean-Congo fevers, it is demonstrated that occurrence of resource limitations of isolation can have a significant impact on the scale of epidemic aftermaths. Moreover, the outset of response measures takes a severe effect, as one of the important for localization of arthropod-borne infection factors is quarantine, alongside with isolation. The computer based software model is available at http://vector-epimod.ru

Circumventing Y. pestis Virulence by Early Recruitment of Neutrophils to the Lungs during Pneumonic Plague

Pneumonic plague is a fatal disease caused by Yersinia pestis that is associated with a delayed immune response in the lungs. Because neutrophils are the first immune cells recruited to sites of infection, we investigated the mechanisms responsible for their delayed homing to the lung. During the first 24 hr after pulmonary infection with a fully virulent Y. pestis strain, no significant changes were observed in the lungs in the levels of neutrophils infiltrate, expression of adhesion molecules, or the expression of the major neutrophil chemoattractants keratinocyte cell-derived chemokine (KC), macrophage inflammatory protein 2 (MIP-2) and granulocyte colony stimulating factor (G-CSF). In contrast, early induction of chemokines, rapid neutrophil infiltration and a reduced bacterial burden were observed in the lungs of mice infected with an avirulent Y. pestis strain. In vitro infection of lung-derived cell-lines with a YopJ mutant revealed the involvement of YopJ in the inhibition of chemoattractants expression. However, the recruitment of neutrophils to the lungs of mice infected with the mutant was still delayed and associated with rapid bacterial propagation and mortality. Interestingly, whereas KC, MIP-2 and G-CSF mRNA levels in the lungs were up-regulated early after infection with the mutant, their protein levels remained constant, suggesting that Y. pestis may employ additional mechanisms to suppress early chemoattractants induction in the lung. It therefore seems that prevention of the early influx of neutrophils to the lungs is of major importance for Y. pestis virulence. Indeed, pulmonary instillation of KC and MIP-2 to G-CSF-treated mice infected with Y. pestis led to rapid homing of neutrophils to the lung followed by a reduction in bacterial counts at 24 hr post-infection and improved survival rates. These observations shed new light on the virulence mechanisms of Y. pestis during pneumonic plague, and have implications for the development of novel therapies against this pathogen.

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.