Eventos externos e internos da infecção de larvas e ninfas de Rhipicephalus sanguineus por Metarhizium anisopliae / External and internal events of Rhipicephalus sanguineus larvae and nymphs infection by Metarhizium anisopliae

Examinaram-se a adesão, a germinação, a penetração e a colonização de larvas e ninfas de Rhipicephalus sanguineus por Metarhizium anisopliae, assim como as lesões infringidas pelo fungo nas respectivas fases do ciclo de vida do ácaro. Realizaram-se infecções experimentais em 11 grupos contendo 250 larvas e 11 grupos contendo 75 ninfas de R. sanguineus, por meio de banho, durante três minutos sob agitação manual, em suspensão contendo 10(8) conídios/ml do fungo. Nos grupos-controles, o banho foi realizado usando o veículo da suspensão. Larvas e ninfas foram processadas para um estudo histopatológico e de microscopia eletrônica de varredura nos seguintes tempos após a infecção: uma e 18 horas, e um, dois, três, quatro, cinco, seis, sete, nove e 11 dias. A germinação dos conídios ocorreu em até 18 horas pós-inoculação, e o fungo penetrou nas larvas e ninfas através do tegumento, dois e três dias após a infecção, respectivamente. Após penetração, o fungo invadiu o corpo das larvas e ninfas, promovendo uma colonização difusa, sem preferência aparente por tecidos específicos. Lesões significativas não foram observadas. A morte das larvas e ninfas ocorreu no terceiro e quarto dias pós-infecção, e a esporulação do patógeno sobre o cadáver foi iniciada no sexto dia pós-infecção.

The adhesion, germination and colonization of Rhipicephalus sanguineus larvae and nymphs by Metarhizium anisopliae as well as the lesions caused by the fungus were studied. For this purpose, 11 groups of 250 larvae each and 11 groups of 75 nymphs each were bathed during 3 minutes under manual shaking in a 10(8) conidia/ml suspension. Corresponding control groups were bathed only in the suspension vehicle. Ticks were also submitted to both conventional microscopy and scanning eletronmicrocopy analyses at several post-infection periods (1 and 18 hours and 1, 2, 3, 4, 5, 6, 7, 9, and 11 days). Conidial germination occurred in less than 18 hours post-inoculation and the fungus penetration through the tegument into the larvae and nymphs in, respectively, two and three days post-infection. Following penetration, the fungus invaded the body of the ticks and colonized it diffusely without a noticeable predilection for tissue, but no apparent lesions were observed. Death of larvae and nymphs occurred on the 3rd and 4th post-infection days and pathogen sporulation over the dead tick began on the 6th post-infection day.

Pro domain peptide of HGCP-Iv cysteine proteinase inhibits nematode cysteine proteinases

Cysteine proteinases (CPs) are synthesized as zymogens and converted to mature proteinase forms by proteolytic cleavage and release of their pro domain peptides. A cDNA encoding a papain-like CP, called hgcp-Iv, was isolated from a Heterodera glycines J2 cDNA library, expressed and utilized to assess the ability of its propeptide to inhibit proteinase in its active form. The hgcp-Iv cDNA sequence encodes a polypeptide of 374 amino acids with the same domain organization as other cathepsin L-like CPs, including a hydrophobic signal sequence and a pro domain region. HGCP-Iv, produced in Escherichia coli as a fusion protein with thioredoxin, degrades the synthetic peptide benzyloxycarbonyl-Phe-Arg-7-amido-4-methylcoumarin and is inhibited by E-64, a substrate and inhibitor commonly used for functional characterization of CPs. Recombinant propeptides of HGCP-Iv, expressed in E. coli, presented high inhibitory activity in vitro towards its cognate enzyme and proteinase activity of Meloidogyne incognita females, suggesting its usefulness in inhibiting nematode CPs in biological systems. Cysteine proteinases from other species produced no noticeable activity.

Environmental and genetic factors affecting mutability to aminoglycoside antibiotics among Escherichia coli K12 strains

Environmental and genetic factors affecting the in vitro spontaneous mutation frequencies to aminoglycoside resistance in Escherichia coli K12 were investigated. Spontaneous mutation frequencies to kanamycin resistance were at least 100 fold higher on modified Luria agar (L2) plates, when compared to results obtained in experiments carried out with Nutrient agar (NA) plates. In contrast to rifampincin, the increased mutability to kanamycin resistance could not be attributed to a mutator phenotype expressed by DNA repair defective strains. Kanamycin mutant selection windows and mutant preventive concentrations on L2 plates were at least fourfold higher than on NA plates, further demonstrating the role of growth medium composition on the mutability to aminoglycosides. Mutability to kanamycin resistance was increased following addition of sorbitol, suggesting that osmolarity is involved on the spontaneous mutability of E. coli K12 strains to aminoglycosides. The spontaneous mutation rates to kanamycin resistance on both L2 and NA plates were strictly associated with the selective antibiotic concentrations. Moreover, mutants selected at different antibiotic concentrations expressed heterogeneous resistance levels to kanamycin and most of them expressing multiple resistance to all tested aminoglycoside antibiotics (gentamicin, neomycin, amykacin and tobramycin). These results will contribute to a better understanding of the complex nature of aminoglycoside resistance and the emergence of spontaneous resistant mutants among E. coli K12 strains

Miíase vulvar / Vulvar myiasis

A miíase é uma infecção parasitária causada por larvas de diversos tipos de moscas. Embora o reconhecimento e tratamento sejam fáceis, constituem uma infecção pouco freqúente na região vulvar. Este estudo apresenta uma revisão a respeito da patologia por miíase e a descrição do caso de uma adolescente de 19 anos, gestante, portadora de miíase vulvar associada à tricomoníase, candidíase e sífilis, além se ser soropositiva para HIV.