Ultrastructural Studies of
            <i>Rickettsia prowazeki</i>
            From Louse Midgut Cells to Feces: Search For “Dormant” Forms

Silverman, David J.; Boese, Jack L.; Wisseman, Charles L.

doi:10.1128/iai.10.1.257-263.1974

Cited by 22 publications

(8 citation statements)

References 14 publications

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“…The presence of the halo or microcapsule described by Silverman et a1. 12 was confirmed in some of our preparations. Some of these structures may well represent some type of capsular material that is not preserved in the thinsectioned specimens.…”

Section: Discussionsupporting

confidence: 76%

Murine Typhus Rickettsiae in the Oriental Rat Flea*

Ito

Vinson

McGuire

1975

Annals of the New York Academy of Sciences

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INTRODUCTIONRickettsia rnooseri. the etiologic agent of murine typhus, is transmitted from its natural rodent host to man by the oriental rat flea, Xenopsylla cheopis.' When these rickettsiae are imbibed in an infectious blood meal, they propagate in the midgut epithelium of the flea and are excreted in the feces, which thus becomes the actual vehicle of infection.'-' A similar sequence of events occurs in the transmission of epidemic typhus rickettsiae by the infected human body louse. Adult rat fleas may under normal circumstances live for many months. Infection of the flea with R . tnooseri can occur only during the parasitic adult stage, and the life-span of the flea is not shortened by the infection.5Although electron microscopic features of the infection of the body louse by Rickettsiae prowazeki have been examined in several studies,5-12 no comparable investigations have been made of rickettsia1 infection in oriental rat fleas. Indeed, ultrastructural studies on the flea midgut epithelium have so far been limited to a short report by Reinhardt et aI.l3 on the midgut of the oriental rat flea and two other species and to an earlier description by Richards and Richards I ' of a novel beaded layer that forms the basement lamina that underlies the midgut epithelium of the flea, Ctenophthalmus.Herein, we intend to provide further information on normal midgut epithelium of X. cheopis and to elucidate some of the ultrastructural features of the infection of this species by murine typhus rickettsiae. MATERIALS AND METHODSThe Wilmington strain l5 of R. tnooseri used in the present study represents the eighth passage in the yolk sacs of developing chick embryos since it was received in this laboratory in 1946. The stock pool of this strain was a 50% suspension of infected yolk sac in sucrose-PG,13 aliquots of which were stored at -70" C.Our colony of Xenopsylla cheopis, originally obtained from the United States

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Section: Discussionsupporting

confidence: 76%

Murine Typhus Rickettsiae in the Oriental Rat Flea*

Ito

Vinson

McGuire

1975

Annals of the New York Academy of Sciences

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“…They displayed differences in size and ultrastructure that were consistent with those of certain other bacteria in comparable growth phases (3,7,8,11,16,19). Of particular interest is the restriction of the vacuoles, presumably representing storage granules or inclusions that have been noted previously (2,14), to organisms in the later phases of growth. Moreover, the RLB/PFU ratio of the late or stationary-phase seed was greater by an order of magnitude than that of the log-phase seed, suggesting that the former contained a large proportion of dead or nonin-fectious organisms.…”

Section: Discussionmentioning

confidence: 52%

In vitro studies on Rickettsia-host cell interactions: lag phase in intracellular growth cycle as a function of stage of growth of infecting Rickettsia prowazeki, with preliminary observations on inhibition of rickettsial uptake by host cell fragments

Wisseman¹,

Waddell²,

Silverman³

1976

Infect Immun

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Two Rickettsia prowazeki seeds, an "early" seed in the logarithmic or exponential growth phase and a "late" seed in the stationary or possibly early decline phase, were prepared in chicken embryo (CE) cell cultures and compared with respect to morphology and infection cycle in CE cells in culture. Differences in size and ultrastructure of the organisms in the two seeds were similar to those seen in other gram-negative bacteria at comparable stages of growth. Vacuolar structures, rare in log-phase organisms, were common in stationary-phase organisms. Minute spherical forms reminiscent of minicells were seen in the stationary-phase preparations. In quantitative uptake experiments, organisms, typical in size and morphology of each preparation, had comparable capacity per plaque-forming unit to penetrate into CE cells in suspension when the seeds had been depleted of host cell membrane fragments and other debris. This suggests that host cell fragments, presumably of membrane origin, competitively inhibit rickettsial uptake by intact CE cells. Organisms of the log-phase seed, upon entry into a host cell, entered the logarithmic or exponential phase of intracellular growth without a measurable lag phase, whereas stationary-phase organisms displayed a lag phase of about 7.5 h, during which they enlarged and increased in intensity of staining, before entering the log phase of growth. R This equation is in fact a modification of the one given by Lodge and Hinshelwood (9), simply making use of the information contained in the equation for INFECT. IMMUN. on July 15, 2020 by guest http://iai.asm.org/ Downloaded from

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“…Our results demonstrate efficient exchange of R. felis between infected donor cat fleas and uninfected recipient cat fleas (intraspecific transmission) and rat fleas (interspecific transmission), respectively, through cofeeding transmission on an uninfected vertebrate host. In contrast to R. felis, horizontal transmission of other insect-borne rickettsial pathogens, such as R. typhi and Rickettsia prowazekii (the agent of louse-borne epidemic typhus), occurs primarily through infected insect faeces (Silverman et al 1974;Azad 1990). In addition, both horizontal transmission via flea bite and vertical transmission via transovarial and transstadial mechanisms are reported for R. typhi, although at a lower rate compared to faecal transmission (Azad 1990).…”

Section: Discussionmentioning

confidence: 99%

Cofeeding intra‐ and interspecific transmission of an emerging insect‐borne rickettsial pathogen

et al. 2015

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Cat fleas (Ctenocephalides felis) are known as the primary vector and reservoir of Rickettsia felis, the causative agent of flea‐borne spotted fever; however, field surveys regularly report molecular detection of this infectious agent from other blood‐feeding arthropods. The presence of R. felis in additional arthropods may be the result of chance consumption of an infectious bloodmeal, but isolation of viable rickettsiae circulating in the blood of suspected vertebrate reservoirs has not been demonstrated. Successful transmission of pathogens between actively blood‐feeding arthropods in the absence of a disseminated vertebrate infection has been verified, referred to as cofeeding transmission. Therefore, the principal route from systemically infected vertebrates to uninfected arthropods may not be applicable to the R. felis transmission cycle. Here, we show both intra‐ and interspecific transmission of R. felis between cofeeding arthropods on a vertebrate host. Analyses revealed that infected cat fleas transmitted R. felis to naïve cat fleas and rat fleas (Xenopsylla cheopis) via fleabite on a nonrickettsemic vertebrate host. Also, cat fleas infected by cofeeding were infectious to newly emerged uninfected cat fleas in an artificial system. Furthermore, we utilized a stochastic model to demonstrate that cofeeding is sufficient to explain the enzootic spread of R. felis amongst populations of the biological vector. Our results implicate cat fleas in the spread of R. felis amongst different vectors, and the demonstration of cofeeding transmission of R. felis through a vertebrate host represents a novel transmission paradigm for insect‐borne Rickettsia and furthers our understanding of this emerging rickettsiosis.

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Ultrastructural Studies of Rickettsia prowazeki From Louse Midgut Cells to Feces: Search For “Dormant” Forms

Cited by 22 publications

References 14 publications

Murine Typhus Rickettsiae in the Oriental Rat Flea*

Murine Typhus Rickettsiae in the Oriental Rat Flea*

In vitro studies on Rickettsia-host cell interactions: lag phase in intracellular growth cycle as a function of stage of growth of infecting Rickettsia prowazeki, with preliminary observations on inhibition of rickettsial uptake by host cell fragments

Cofeeding intra‐ and interspecific transmission of an emerging insect‐borne rickettsial pathogen

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