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The filamentous bacteriophage M13KO7 (M13) is the most used in phage display (PD) technology and, like other phages, has been applied in several areas of medicine, agriculture, and in the food industry. One of the advantages is that they can modulate the immune response in the presence of pathogenic microorganisms, such as bacteria and viruses. This study evaluated the use of phage M13 in the chicken embryos model. We inoculated 13-day-old chicken embryos with Salmonella Pullorum (SP) and then evaluated survival for the presence of phage M13 or E. coli ER2738 (ECR) infected with M13. We found that the ECR bacterium inhibits SP multiplication in 0.32 (M13-infected ECR) or 0.44 log UFC/mL (M13-uninfected ECR) and that the ECR-free phage M13 from the PD library can be used in chicken embryo models. This work provides the use of the chicken embryo as a model to study systemic infection and can be employed as an analysis tool for various peptides that M13 can express from PD selection. KEY POINTS: • SP-infected chicken embryo can be a helpful model of systemic infection for different tests. • Phage M13 does not lead to embryonic mortality or cause serious injury to embryos. • Phage M13 from the PD library can be used in chicken embryo model tests.

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Two well characterized tick-borne rickettsioses occur in Brazil. Rickettsia rickettsii caused spotted-fever, transmitted by Amblyomma sculptum and Amblyomma aureolatum, is a severe disease with a high case-fatality rate in the southeastern region of the country. Rickettsia parkeri strain Atlantic rainforest infections transmitted by adult Amblyomma ovale ticks cause a milder non-lethal febrile disease with an eschar (necrosis) at the tick bite site. Clinical diagnosis of rickettsiosis is challenging, particularly during the early stages of the illness when signs and symptoms are non-specific. Since eschar at the tick bite site has emerged as the main clinical feature of mild R. parkeri infections and used to differentiate it from severe R. rickettsii infection, its proper recognition, distinction from other tick bite lesions, and boundaries as a clinical tool must be highlighted. Of importance, eschars induced by Rickettsia must be differentiated from dermatoses caused by other tick-borne skin infections as well from lesions caused by the tick bite itself. We herein highlight information on eschar in rickettsial diseases in Brazil and discuss the need for further research on its clinical relevance and application in the diagnosis of spotted fever caused by R. parkeri strain Atlantic rainforest. In particular, we draw attention to diagnosis of other febrile diseases in the presence of concomitant tick bites.

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An amendment to this paper has been published and can be accessed via a link at the top of the paper.

RESUMO

Brazilian spotted fever (BSF), caused by Rickettsia rickettsii, is the most lethal tick-borne disease in the western hemisphere. In Brazil, Amblyomma sculptum ticks are the main vector. Capybaras (Hydrochoerus hydrochaeris), the largest living rodents of the world (adults weighing up to 100 Kg), have been recognized as amplifying hosts of R. rickettsii for A. sculptum in BSF-endemic areas; i.e., once primarily infected, capybaras develop bacteremia for a few days, when feeding ticks acquire rickettsial infection. We conducted experimental infections of five capybaras with an A. sculptum-derived strain of R. rickettsii and performed clinical and bacteremia evaluation during primary and subsequent infections. Bacteremia was detected in all capybaras during primary infection, but not in subsequent infections. All animals seroconverted to R. rickettsii (titres range: 64-32,768), and remained seropositive throughout the study. Primary infection resulted in clinical spotted fever illness in four capybaras, of which two had a fatal outcome. Subsequent infections in seropositive capybaras resulted in no clinical signs. Capybaras developed a sustained immune response that prevented a second bacteremia. This condition may imply a high reproduction rate of capybaras in BSF-endemic areas, in order to continuously generate capybaras susceptible to bacteremia during primary infection.

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A Ehrlichia é uma bactéria gram-negativa pleomórfica, intracelular obrigatória de células hematopoiéticas maduras ou imaturas, especialmente do sistema fagocitário mononuclear, tais como monócitos e macrófagos. A erliquiose canina ocorre principalmente em regiões tropicais e subtropicais, devido a maior distribuição de seu principal vetor, o Rhipicephalus sanguineus. A doença ocorre em três fases, a aguda, a subclínica e a fase crônica, caracterizadas principalmente pela trombocitopenia. O tratamento é feito com tetraciclinas e seus derivados, principalmente a doxiciclina, tetraciclina, oxitetraciclina e minociclina. Estudos da doença são importantes, visto que a erliquiose canina pode ser patogênica para seres humanos, sendo os organismos causadores de erliquiose humana virtualmente indistinguíveis das espécies que acometem os animais, com homologia de 98,2% e mortalidade de 5% dos pacientes humanos com erliquiose monocítica.(AU)

The Ehrlichia is a gram-negative pleomorphic obligatory intracellular mature or immature hematopoietic cells, especially of the mononuclear phagocyte system, such as monocytes and macrophages. Canine's ehrtichiosis occurs mainly in tropical and subtropical regions, due to greater distribution of its main vector, the Rhipicephalus sanguineus. The disease occurs in three phases, the acute, the subclinical and chronic phase, mainly characterized by thrombocytopenia. Treatment is with tetracyclines and their derivatives, especially doxycycline, tetracycline, oxytetracycline and minocycline. Studies of the disease is important, since the canine ehrlichiosis may be pathogenic for humans, causing organisms and human ehrlichiosis virtually indistinguishable species that affect animals, homology of 98.2% and 5% mortality of human patients with monocytic ehrlichiosis.(AU)

La Ehrlichia es una bacteria gram-negativa pleomórfica, intracelular obligatoria de células hematopoyéticas maduras o inmaduras, especialmente del sistema fagocitário mononuclear, tales como monocitos y macrófagos. La erliquiosis canina ocurre principalmente en regiones tropicales y subtropicales, debido a la mayor distribución de su principal vector, Rhipicephalus sanguineus. La enfermedad se desarrolla en tres fases: aguda, subclínica y crónica,caracterizadas principalmente por una trombocitopenia. El tratamiento se realiza con tetraciclinas e sus derivados,principalmente la doxiciclina, tetraciclina, oxitetraciclina y minociclina. Estudios de la enfermedad son muy importantes,puesto que la erliquiosis canina puede ser patógena para seres humanos, siendo los organismos causadores de la erliquiosis humana virtualmente indistinguibles de las especies que acometen los animales, con homología de 98,2% y mortalidad del 5% de los pacientes humanos con erliquiosis monocítica.(AU)

Assuntos

RESUMO

A Ehrlichia é uma bactéria gram-negativa pleomórfica, intracelular obrigatória de células hematopoiéticas maduras ou imaturas, especialmente do sistema fagocitário mononuclear, tais como monócitos e macrófagos. A erliquiose canina ocorre principalmente em regiões tropicais e subtropicais, devido a maior distribuição de seu principal vetor, o Rhipicephalus sanguineus. A doença ocorre em três fases, a aguda, a subclínica e a fase crônica, caracterizadas principalmente pela trombocitopenia. O tratamento é feito com tetraciclinas e seus derivados, principalmente a doxiciclina, tetraciclina, oxitetraciclina e minociclina. Estudos da doença são importantes, visto que a erliquiose canina pode ser patogênica para seres humanos, sendo os organismos causadores de erliquiose humana virtualmente indistinguíveis das espécies que acometem os animais, com homologia de 98,2% e mortalidade de 5% dos pacientes humanos com erliquiose monocítica.

The Ehrlichia is a gram-negative pleomorphic obligatory intracellular mature or immature hematopoietic cells, especially of the mononuclear phagocyte system, such as monocytes and macrophages. Canine's ehrtichiosis occurs mainly in tropical and subtropical regions, due to greater distribution of its main vector, the Rhipicephalus sanguineus. The disease occurs in three phases, the acute, the subclinical and chronic phase, mainly characterized by thrombocytopenia. Treatment is with tetracyclines and their derivatives, especially doxycycline, tetracycline, oxytetracycline and minocycline. Studies of the disease is important, since the canine ehrlichiosis may be pathogenic for humans, causing organisms and human ehrlichiosis virtually indistinguishable species that affect animals, homology of 98.2% and 5% mortality of human patients with monocytic ehrlichiosis.

La Ehrlichia es una bacteria gram-negativa pleomórfica, intracelular obligatoria de células hematopoyéticas maduras o inmaduras, especialmente del sistema fagocitário mononuclear, tales como monocitos y macrófagos. La erliquiosis canina ocurre principalmente en regiones tropicales y subtropicales, debido a la mayor distribución de su principal vector, Rhipicephalus sanguineus. La enfermedad se desarrolla en tres fases: aguda, subclínica y crónica,caracterizadas principalmente por una trombocitopenia. El tratamiento se realiza con tetraciclinas e sus derivados,principalmente la doxiciclina, tetraciclina, oxitetraciclina y minociclina. Estudios de la enfermedad son muy importantes,puesto que la erliquiosis canina puede ser patógena para seres humanos, siendo los organismos causadores de la erliquiosis humana virtualmente indistinguibles de las especies que acometen los animales, con homología de 98,2% y mortalidad del 5% de los pacientes humanos con erliquiosis monocítica.

Assuntos