Plague Bacilli Research Articles

Yersinia pestis can infect the Pawlowsky glands of human body lice and be transmitted by louse bite.

Yersinia pestis, the causative agent of plague, is a highly lethal vector-borne pathogen responsible for killing large portions of Europe's population during the Black Death of the Middle Ages. In the wild, Y. pestis cycles between fleas and rodents; occasionally spilling over into humans bitten by infectious fleas. For this reason, fleas and the rats harboring them have been considered the main epidemiological drivers of previous plague pandemics. Human ectoparasites, such as the body louse (Pediculus humanus humanus), have largely been discounted due to their reputation as inefficient vectors of plague bacilli. Using a membrane-feeder adapted strain of body lice, we show that the digestive tract of some body lice become chronically infected with Y. pestis at bacteremia as low as 1 × 105 CFU/ml, and these lice routinely defecate Y. pestis. At higher bacteremia (≥1 × 107 CFU/ml), a subset of the lice develop an infection within the Pawlowsky glands (PGs), a pair of putative accessory salivary glands in the louse head. Lice that developed PG infection transmitted Y. pestis more consistently than those with bacteria only in the digestive tract. These glands are thought to secrete lubricant onto the mouthparts, and we hypothesize that when infected, their secretions contaminate the mouthparts prior to feeding, resulting in bite-based transmission of Y. pestis. The body louse's high level of susceptibility to infection by gram-negative bacteria and their potential to transmit plague bacilli by multiple mechanisms supports the hypothesis that they may have played a role in previous human plague pandemics and local outbreaks.

Reorganizing Hospital Space: The 1894 Plague Epidemic in Hong Kong and the Germ Theory.

This paper examined whether the preventive measures taken by the Hong Kong's colonial authorities were legitimate during the 1894 Hong Kong plague epidemic, and illuminated the correlation between the plague epidemic and hospital space in Hong Kong in the late 19th century. The quarantine measures taken by the colonial authorities were neither a clear-cut victory for Western medicine nor for a rational quarantine based on scientific medical knowledge. Hong Kong's medical officials based on the miasma theory, and focused only on house-to-house inspections and forced quarantine or isolation, without encouraging people to wear masks and without conducting disinfection. Even after Hong Kong plague spread, the Hong Kong's colonial authorities were not interested in what plague bacilli were, but in where they were to be found and how to prevent and control an outbreak of the disease. The germ theory brought significant changes to the disease classification system. Until the 1890s, Hong Kong's colonial authority had classified cause of death mainly on the basis of symptoms, infectious diseases, parts of the body and diseases of systems. Microbiological analysis of the cause of death in Hong Kong was started by Hunter, a bacteriologist, in 1902. He used bacteriological tests with a microscope to analyze the cause of death. New disease recognition and medical recognition brought large changes to hospital space as well. In particular, from the 1880s to the early 1900s, Western medical circles witnessed shifts from miasma theory to the germ theory, thereby influencing Hong Kong's hospital spaces. As the germ theory took ground in Hong Kong in 1894, the bacteriological laboratory and isolation ward became inevitable facilities, and hospital space were reorganized accordingly. However, the colonial authorities and local elites' strategy was different. As a government bacteriologist, Hunter established a central facility to unify several laboratories and to manage urban space from ouside the hospital. On the contrary, the Tungwah Hospital tried to transform hospital space with isolation ward and Receiving Ward System as the eclectic form of Chinese and Western medicine. The 1894 Hong Kong plague promoted the introduction of germ theory and the reorganization of hospital space.

Cethromycin-Mediated Protection against the Plague Pathogen Yersinia pestis in a Rat Model of Infection and Comparison with Levofloxacin

The Gram-negative plague bacterium, Yersinia pestis, has historically been regarded as one of the deadliest pathogens known to mankind, having caused three major pandemics. After being transmitted by the bite of an infected flea arthropod vector, Y. pestis can cause three forms of human plague: bubonic, septicemic, and pneumonic, with the latter two having very high mortality rates. With increased threats of bioterrorism, it is likely that a multidrug-resistant Y. pestis strain would be employed, and, as such, conventional antibiotics typically used to treat Y. pestis (e.g., streptomycin, tetracycline, and gentamicin) would be ineffective. In this study, cethromycin (a ketolide antibiotic which inhibits bacterial protein synthesis and is currently in clinical trials for respiratory tract infections) was evaluated for antiplague activity in a rat model of pneumonic infection and compared with levofloxacin, which operates via inhibition of bacterial topoisomerase and DNA gyrase. Following a respiratory challenge of 24 to 30 times the 50% lethal dose of the highly virulent Y. pestis CO92 strain, 70 mg of cethromycin per kg of body weight (orally administered twice daily 24 h postinfection for a period of 7 days) provided complete protection to animals against mortality without any toxic effects. Further, no detectable plague bacilli were cultured from infected animals' blood and spleens following cethromycin treatment. The antibiotic was most effective when administered to rats 24 h postinfection, as the animals succumbed to infection if treatment was further delayed. All cethromycin-treated survivors tolerated 2 subsequent exposures to even higher lethal Y. pestis doses without further antibiotic treatment, which was related, in part, to the development of specific antibodies to the capsular and low-calcium-response V antigens of Y. pestis. These data demonstrate that cethromycin is a potent antiplague drug that can be used to treat pneumonic plague.

Ectoparasites of Small Mammals in Western Iowa

We conducted a formal survey of small-mammal ectoparasite diversity in Iowa. We examined 166 small mammals and documented 54 species of parasitic arthropods present on 12 species of mammals. Ectoparasite species richness was greatest for Blarina brevicauda (northern short-tailed shrew), Microtus ochrogaster (prairie vole), Peromyscus maniculatus (deer mouse), and Peromyscus leucopus (white-footed mouse). Immature (larvae and nymphs) Dermacentor variabilis (American dog tick) were collected from P. leucopus, M. ochrogaster, Reithrodontomys megalotis (western harvest mouse), and Zapus hudsonius (meadow jumping mouse). The fleas Epitedia wenmanni and Orchopeas leucopus, potential vectors of sylvatic plague bacilli, were found on Mus musculus (house mouse), white-footed mouse, and deer mouse. We document 21 new ectoparasite host records for North America and 115 new host locality records for ectoparasites in Iowa.

Ectoparasites of Chevrier’s field mouse, Apodemus chevrieri, in a focus of plague in southwest China

Chevrier's field mouse, Apodemus chevrieri Milne-Edwards (Rodentia: Muridae), has been identified as the main wild reservoir of plague in the sylvatic plague focus of Yunnan Province, southwest China. Here, the ectoparasite communities of A. chevrieri and the potential medical and veterinary importance of these ectoparasites are described. A high proportion (66%) of 321 mice were found to be infested with ectoparasites. A total of 81 species of ectoparasite, including 48 species of chigger mite, 25 species of mesostigmatid (gamasid) mite, six species of flea and two species of sucking louse were collected. Most species of ectoparasite were relatively uncommon, but a few were abundant. Within this ectoparasite complex, 16 species have previously been reported to be vectors of human disease agents. Apodemus chevrieri would appear therefore to be a natural reservoir for plague bacilli and epidemic haemorrhagic fever (Korean haemorrhagic fever) viruses.

Modern Japanese medical history and the European influence.

Before the first European visited Japan in 1549, traditional Chinese medicine was mainly employed in Japan. Francisco de Xavier, a missionary of the Society of Jesus, tried to promote the introduction of Christianity by providing a medical service for Japanese citizens. However, Japan implemented a national isolation policy in 1639 and cut off diplomatic relations with the rest of the world, except Holland and China. For over 200 years, until the American admiral Matthew Perry forced Japan to open its doors in 1853, Japan learned about western medicine only from doctors of the Dutch merchants' office or from Dutch medical books. After 1853, Western medicine was rapidly introduced into Japan, and great achievements by Japanese medical doctors soon followed, such as the serum therapy for tetanus, the discovery of the plague and dysentery bacilli, the invention of Salvarsan for the treatment of syphilis, and the demonstration of the neurosyphilis spirochete.

Development, characterisation and diagnostic application of monoclonal antibodies against Yersinia pestis fibrinolysin and coagulase.

A library of monoclonal antibodies (MAbs) which recognised different epitopes of Yersinia pestis fibrinolysin (Fib) was developed. These MAbs were species-specific and demonstrated no cross-reaction in indirect immunofluorescence tests (IIFT) with other gram-negative bacteria possessing plasminogen activator activity. All the MAbs provided equally high levels of immunofluorescence with pPst+ Y. pestis strains cultivated at 37 degrees C and at 28 degrees C. In all cases, the MAbs inhibited both fibrinolytic and coagulase (Coag) activities of Y. pestis in Fib-activity inhibition and coagulase-activity inhibition reactions, and reacted with 35- and 37-kDa proteins of Y. pestis in immunoblotting, demonstrating bifunctional activity possibly similar to the properties of MAbs produced by hybrid hybridomas. On the basis of these and earlier studies, the immunochemical identity of Fib and Coag, two distinct subunits of a bifunctional fusion protein whose specific functional activity depends upon the temperature factor, was established. A new rapid, cheap, strictly specific and safe dot-ELISA based on the use of MAb against Y. pestis Fib (MAb-Fib) for reliable identification of Y. pestis strains was developed. This technique has great advantages over monoclonal diagnostic kits based on the use of MAb against Y. pestis fraction I (FI) because it allows detection of plague bacilli grown at 37 degrees C as well as at 28 degrees C. This dot-ELISA will be valuable as a clinical diagnostic tool and might be applicable to field studies and plague surveillance.

Role of the Yersinia pestis Hemin Storage ( hms ) Locus in the Transmission of Plague by Fleas

Yersinia pestis, the cause of bubonic plague, is transmitted by the bites of infected fleas. Biological transmission of plague depends on blockage of the foregut of the flea by a mass of plague bacilli. Blockage was found to be dependent on the hemin storage (hms) locus. Yersinia pestis hms mutants established long-term infection of the flea's midgut but failed to colonize the proventriculus, the site in the foregut where blockage normally develops. Thus, the hms locus markedly alters the course of Y. pestis infection in its insect vector, leading to a change in blood-feeding behavior and to efficient transmission of plague.

Mutation in the pla gene of Yersinia pestis alters the course of the plague bacillus-flea (Siphonaptera: Ceratophyllidae) interaction.

Yersinia pestis possesses a unique gene (pla) encoding coagulase and fibrinolysin which is implicated in the transmission of plague by fleas. This gene is encoded on the highly conserved but poorly characterized 'pesticin' plasmid pKYP1. The role of the pKYP1-encoded gene, pla, in plague transmission was addressed by feeding fleas on blood containing avirulent Y. pestis strain EV76-6 and three derivatives of this strain (K10-2, K10-3, and K10-5) carrying Tn801 insertions in pKYP1. One of these mutant strains, K10-5, contains an insertion within the pla gene that eliminates both coagulase and fibrinolysin activities, whereas strains K10-3 and K10-2 retain both pla-associated phenotypes. After feeding, it was found that flea mortality at 4 d after infection associated with strain K10-5 (26%) was significantly lower than the mortality observed with other strains (53-64%). These results suggest that expression of the pla gene product may contribute to the deleterious effects of plague bacilli on fleas that have been associated with flea blockage and plague transmission. This increased mortality is not caused simply by an increased bacterial load in fleas containing pla+ bacteria because fleas ingesting pla+ strains contained no more bacteria by flea blot hybridization analysis than did those that ingested the pla- strain K10-5. It is anticipated that further work in this area will clarify the mechanism by which pla acts and will reveal additional genetic loci in the plague bacillus which are required for transmission by fleas.

A Yersinia pestis‐specific DNA fragment encodes temperature‐dependent coagulase and fibrinolysin associated phenotypes

The effect of temperature on coagulase and fibrinolysin expression (Pla) by Yersinia pestis has been implicated in the transmission of plague by fleas. In an attempt to improve our understanding of this process, we have cloned, sequenced and characterized the gene encoding the Pla phenotypes in Y. pestis, and examined its temperature-dependent regulation. The coding region for this gene overlaps a 900bp Y. pestis-specific DNA fragment that we have previously shown to be capable of detecting plague bacilli in fleas. The pla gene contains a single open reading frame encoding 312 amino acids with a predicted molecular weight of 34.7 kD and a putative signal sequence of 20 amino acids. This coding region appears to be sufficient for both coagulase and fibrinolytic activities. In Y. pestis, modulation between coagulase and fibrinolytic activities is temperature-dependent: coagulase activity is most evident at temperatures below 30 degrees C but fibrinolytic activity increases with higher temperatures (greater than 30 degrees C), regardless of the temperature at which the bacteria are grown. Our results lead us to believe that this regulation occurs post-translationally. It is possible that the alternative forms of the Pla protein are essential to 'flea blockage' and subsequent transmission of the plague bacillus to animals.

Chronic infections in laboratory rodents from inoculation of nonencapsulated plague bacilli (Yersinia pestis).

Infections with nonencapsulated Y. pestis persisted for 9 weeks in mice and 56 weeks in rats after experimental inoculation. Mice succumbed with bacteremia. Rats developed chronic lesions containing nonencapsulated plague bacilli.

Atypical plague bacilli isolated from rodents, fleas, and man.

Atypical plague bacilli isolated from rodents, fleas, and man.

Detection and differentiation of iron-responsive avirulent mutants on Congo red agar

Agar medium containing Congo red dye differentiates virulent and avirulent colonies of Shigella, Vibrio cholerae, Escherichia coli, and Neisseria meningitidis. Like virulent plague bacilli, wild-type cells of these species absorb the dye and produce red colonies. Mutants or colonial variants have been isolated that fail to absorb the dye and produce colorless colonies. These mutants exhibit reduced virulence in the chicken embryo model, but their virulence is enhanced by supplementation with iron. Of those species tested, only Neisseria gonorrhoeae isolates failed to grow in the presence of this dye. Inhibition of growth by Congo red may thus provide a simple means for differentiating gonococci from other Neisseria.

Famine, mortality, and epidemic disease: a comment.

R John D. Post's article 'Famine, Mortality, and Epidemic Disease in D Process of Modernization' is a valuable addition to our limited knowledge of interaction between epidemic disease and a wide variety of environmental factors, including nutrition, housing, hygiene, and public health programmes. His article raises certain questions that perhaps can benefit from further elaboration. The following remarks are intended as comment, not as criticism, in hope that they may clarify some of points at issue in these complex environmental-medical relationships and point way for further research within this relatively new field of historical inquiry. Dr Post characterized as extreme position-which he attributes to Dr N. L. Tranter-that the decline in mortality [in later eighteenth century] resulted from an increase in natural immunity of human populations long exposed to contagion.3 Further on, Dr Post says that low case-fatality rate in typhus epidemic of I8I 7-I 8 may, indeed, be explained by growing human resistance to disease.4 He rejects, however, possibility that human beings acquired any resistance to bubonic plague bacilli, quite rightly noting that-so far as we can tell-plague in humans did not decline in virulence over time. He adds that plague is dependent on animal and insect vectors which can be controlled by quarantine, improved housing, and better hygiene.5 Let us try to separate these seemingly contradictory observations about increased human resistance to some diseases but not to others. Prof. Rene Dubos has suggested that there is a tendency towards ecological equilibrium-a search for a modus vivendi-between microbes responsible for disease and hosts on which they prey. It is not too much to say that it is in interest of microbes to reach such an equilibrium because if they are too virulent, they kill their host, which in turn means that they, too, die. Far better for them to be less virulent and keep their hosts alive. Of course, any decrease in virulence is not arrived at by conscious choice of microbes but rather by mutation to a less virulent form which has a better chance to survive than deadly form which tends to eliminate itself. The same blind process works in development of resistance in host: hosts with least resistance die, often before they have offspring, while those with resistance live to pass their resistance on to their offspring. This tendency towards accommodation-on part of both microbes and hosts-has been observed in changing patterns of disease in both animals and 1 DrJohn D. Post has indicated that he does not wish to make any reply.-Eds. 2 Economic History Review, 2nd ser. xxix (1976), I4-37. 3 Ibid. I5. 4 Ibid. 31. 5 Ibid. 34-5.

Chemical and Biological Warfare

Why should the world be more averse to chemical and biological warfare (CBW) than to other forms of war, repeatedly attempting to ban such warfare by means of international law? Is there some objective difference between poison gas or plague bacilli on one hand, and steel bullets, or B-52 high explosive bombs, or nuclear weapons on the other? Or does CBW instead illustrate the faddishness and superficiality of disarmament campaigns in general? The Allied Powers after 1919 may indeed have condemned chemical warfare simply to reinforce the impression that Germany was morally culpable in World War I. The Germans supposedly had initiated the of gas warfare (although the first use here might really have to be pinned on France instead); if Germans had used such weapons first, such must have been evil. Perhaps instead the aversion to gas reflected the horrors of such warfare for the soldier exposed to it, although casualty statistics suggest that fewer soldiers died or were permanently maimed after being incapacitated by gas, as compared with those stricken by other means. Perhaps instead the techniques of chemistry and biology have seemed unclean and unmanly, the products of odd-ball scientists ensconced in laboratories, reflecting perverted scientific ingenuity rather than the bravery of cold steel. The

Antibody and resistance to infection with Yersinia pestis in the progeny of immunized rats.

The presence of HA antibody to the Fraction I antigen of Yersinia pestis was examined in sera of neonatal, suckling, and newly weaned Rattus norvegicus. Newborn rats from immunized dams possessed antibody at birth, before suckling. Antibody declined or disappeared in suckling rats nursed by unimmunized dams, while antibody appeared in sera of rats born of unimmunized dams and fostered by immunized dams. Antibody also appeared in suckling young of dams inoculated with antiserum to Y. pestis prepared in rabbits. Offspring of immunized dams usually had titers of HA antibody at weaning equal to 25%-50% of the dams' titers. Most one-week-old rats and many six-week-old rats that had been nursed by immunized dams survived inoculation with about 1,000 virulent plague bacilli, and all young rats that possessed HA antibody titers of > 64 at the time of inoculation survived. The significance of passively acquired antibody and protection in the epidemiology and the ecology of plague was considered.

Plague in Vietnam. Clinical observations and treatment with kanamycin.

Twenty-three Montagnard tribesmen had plague infections and were hospitalized in the central highlands of Vietnam; their clinical appearances, diagnostic techniques, and kanamycin sulfate therapy were evaluated. Severely ill patients were categorized as When contrasted with patients having bubonic plague, patients with bubonic-septicemic plague had delirium, a higher pulse rate, and a higher white blood cell count and plague bacilli on methylene-blue smears of unspun venous blood. Bacterial staining of lymph-node material and peripheral blood smears was essential for early diagnosis of plague. Results of treatment with kanamycin in 18 patients were similar to those reported with streptomycin sulfate therapy.

Plague in Vietnam

Twenty-three Montagnard tribesmen had plague infections and were hospitalized in the central highlands of Vietnam; their clinical appearances, diagnostic techniques, and kanamycin sulfate therapy were evaluated. Severely ill patients were categorized as "bubonic-septicemic plague." When contrasted with patients having bubonic plague, patients with bubonic-septicemic plague had delirium, a higher pulse rate, and a higher white blood cell count and plague bacilli on methylene-blue smears of unspun venous blood. Bacterial staining of lymph-node material and peripheral blood smears was essential for early diagnosis of plague. Results of treatment with kanamycin in 18 patients were similar to those reported with streptomycin sulfate therapy.

The rate of formation of phage resistant mutants in the cell population of virulent strains of plague bacilli

The rate of formation of phage resistant mutants in the cell population of virulent strains of plaque bacilli.

Efficacy of fluorescent antibody methods for detection of Pasteurella pestis in carcasses of albino laboratory mice stored for various periods.

Fluorescent antibody techniques were used for detection of plague antigens in infected mouse carcasses stored at 4°–5° C., 20°–25° C. (room temperature) and 370° C. for periods as long as 340 days in certain cases. Tissues of two guinea-pigs infected withPasteurella pestiswere examined after 7 years storage at room temperature. The efficacy of the fluorescent antibody test was compared with blood agar plate culture and animal inoculation during periods in which viable plague bacilli were presumed to be present, and compared with Larson's modified Ascoli test for the presence of soluble plague antigens during periods in which plague bacteria were presumed to be non-viable.Fluorescent antibody tests were superior to animal inoculation or cultural methods in detection ofP. pestisantigens in mouse carcasses stored for 4 days or longer at 37° C., for 8 days or longer at 20°–25° C. (room temperature), and for 34 days or longer at 4°–5° C. Upon examination of specimens presumed to lack viable plague organisms the fluorescent antibody test and precipitin tests were approximately equal in efficiency for detection of plague antigens in carcasses stored for 16–82 days at 37° C. and for 16–82 days at 20°–25° C. Ten of 21 mice stored for longer periods (140 and 340 days) at 4°–5° C. were negative by precipitin tests, whereas 19 of the same 21 rodents were positive by fluorescent antibody tests. In addition, after 7 years storage at room temperature tissues of two plague-infected guinea-pigs were negative by Larson's modified Ascoli test but positive by the fluorescent antibody test.