Properties and production characteristics of vomiting, diarrheal, and necrotizing toxins of Bacillus cereus. (1/18)

Evidence is provided that the enterotoxin of Bacillus cereus variously described in the literature as diarrheagenic toxin, diarrheal agent, fluid accumulation factor, vascular permeability factor, dermonecrotic toxin, and intestinonecrotic toxin is a single relatively unstable protein of molecular weight approximately 50,000 and isoelectric point of the order of 4.9. It is presumed to be the enterotoxin responsible for the diarrheal-type B. cereus food poisoning syndrome and it may also be the pyogenic and pyrogenic factor in nongastrointestinal B. cereus infections of man and animals. The enterotoxin is a vegetative growth metabolite produced to one degree or another by almost all B. cereus strains and is readily separated from phospholipase and heat-labile cereolysin but less readily differentiated from a heat-stable hemolysin. It is lethal to mice but may also be separable from another mouse lethal factor by electrofocusing. The emetic toxin responsible for the vomiting-type B. cereus food poisoning syndrome is clearly distinguishable from the diarrheal and other toxic factors and appears to be a highly stable compound of molecular size less than 5000.  (+info)

Isolation of dermatoxin from frog skin, an antibacterial peptide encoded by a novel member of the dermaseptin genes family. (2/18)

A 32-residue peptide, named dermatoxin, has been extracted from the skin of a single specimen of the tree frog Phyllomedusa bicolor, and purified to homogeneity using a four-step protocol. Mass spectral analysis and sequencing of the purified peptide, as well as chemical synthesis and cDNA analysis were consistent with the structure: SLGSFLKGVGTTLASVGKVVSDQF GKLLQAGQ. This peptide proved to be bactericidal towards mollicutes (wall-less eubacteria) and Gram-positive eubacteria, and also, though to a lesser extent, towards Gram-negative eubacteria. Measurement of the bacterial membrane potential revealed that the plasma membrane is the primary target of dermatoxin. Observation of bacterial cells using reflected light fluorescence microscopy after DNA-staining was consistent with a mechanism of cell killing based upon the alteration of membrane permeability rather than membrane solubilization, very likely by forming ion-conducting channels through the plasma membrane. CD spectroscopy and secondary structure predictions indicated that dermatoxin assumes an amphipathic alpha-helical conformation in low polarity media which mimic the lipophilicity of the membrane of target microorganisms. PCR analysis coupled with cDNA cloning and sequencing revealed that dermatoxin is expressed in the skin, the intestine and the brain. Preprodermatoxin from the brain and the intestine have the same sequence as the skin preproform except for two amino-acid substitutions in the preproregion of the brain precursor. The dermatoxin precursor displayed the characteristic features of preprodermaseptins, a family of peptide precursors found in the skin of Phyllomedusa ssp. Precursors of this family have a common N-terminal preproregion followed by markedly different C-terminal domains that give rise to 19-34-residue peptide antibiotics named dermaseptins B and phylloxin, and to the D-amino-acid-containing opioid heptapeptides dermorphins and deltorphins. Because the structures and cidal mechanisms of dermatoxin, dermaseptins B and phylloxin are very different, dermatoxin extends the repertoire of structurally and functionally diverse peptides derived from the rapidly evolving C-terminal domains of precursors of the dermaseptins family.  (+info)

Oro-facial gangrene (noma/cancrum oris): pathogenetic mechanisms. (3/18)

Cancrum oris (Noma) is a devastating infectious disease which destroys the soft and hard tissues of the oral and para-oral structures. The dehumanizing oro-facial gangrenous lesion affects predominantly children ages 2 to 16 years, particularly in sub-Saharan Africa, where the estimated frequency in some communities varies from 1 to 7 cases per 1000 population. The risk factors are poverty, malnutrition, poor oral hygiene, residential proximity to livestock in unsanitary environments, and infectious diseases, particularly measles and those due to the herpesviridae. Infections and malnutrition impair the immune system, and this is the common denominator for the occurrence of noma. Acute necrotizing gingivitis (ANG) and oral herpetic ulcers are considered the antecedent lesions, and ongoing studies suggest that the rapid progression of these precursor lesions to noma requires infection by a consortium of micro-organisms, with Fusobacterium necrophorum (Fn) and Prevotella intermedia (Pi) as the suspected key players. Additional to production of a growth-stimulating factor for Pi, Fn displays a classic endotoxin, a dermonecrotic toxin, a cytoplasmic toxin, and a hemolysin. Without appropriate treatment, the mortality rate from noma is 70-90%. Survivors suffer the two-fold afflictions of oro-facial mutilation and functional impairment, which require a time-consuming, financially prohibitive surgical reconstruction.  (+info)

Roles of diversifying selection and coordinated evolution in the evolution of amphibian antimicrobial peptides. (4/18)

Antimicrobial peptides are expressed in the skin of amphibians and are used to prevent infection by microorganisms. Frog species store distinct collections of antimicrobial peptides that show variation in size, charge, conformation, and bactericidal activity, and so the evolution of antimicrobial peptide gene families may reflect the adaptive diversification of these loci. We examined the molecular evolution of antimicrobial peptide transcripts from hylid and ranid frog species. Our results show that after the gene family arose in the common ancestor of the Hylidae and Ranidae, before the divergence of these families in the Mesozoic, it subsequently diversified within these groups with numerous duplication events and divergence of loci. Moreover, we provide evidence that suggests that members of the antimicrobial peptide gene family have been subject to diversifying selection within both propiece and mature domains of hylids and solely within the mature domain of ranids. Finally, our results suggest that coordinated and compensatory amino acid replacements have occurred within the acidic propiece and cationic mature domain of hylid antimicrobial peptide precursors, as has been observed for mammalian defensin genes, but not among those of ranid precursors.  (+info)

Enhanced adherence of Pasteurella multocida to porcine tracheal rings preinfected with Bordetella bronchiseptica. (5/18)

Adherence of 25 isolates of Pasteurella multocida to porcine tracheal rings was evaluated. Results indicated that adherence was not related to the isolate's origin, capsular or somatic types, dermonecrotoxin production or hemagglutination activity. The effect of a preinfection with Bordetella bronchiseptica on the colonization by P. multocida was then studied. On rings infected with P. multocida alone, bacteria initially adhered to the epithelium, but within a few hours, the level of colonization decreased progressively. On rings preinfected with B. bronchiseptica, or pretreated with a cell-free B. bronchiseptica culture supernate (or filtrate), a high level of P. multocida colonization was maintained for at least 24 hours. Results indicate that B. bronchiseptica appears to facilitate upper respiratory tract colonization by P. multocida by a process which involves a low molecular weight (less than or equal to 1000) heat-stable substance, possibly the tracheal cytotoxin.  (+info)

Use of ELISA to detect toxigenic Pasteurella multocida in atrophic rhinitis in swine. (6/18)

The use of an enzyme-linked immunosorbent assay (ELISA) as a means of detecting dermonecrotoxin-producing strains of Pasteurella multocida was investigated. The assay was evaluated as a means to identify toxigenic P. multocida isolates recovered from nasal secretions of swine with atrophic rhinitis. The sensitivity and specificity of the ELISA for detecting dermonecrotoxin-producing P. multocida strains were compared to those of mouse-inoculation and cytotoxicity assays. The ELISA was highly sensitive and more specific than animal inoculation or tissue culture assay and is thus a more effective method for screening swine herds for the presence of toxigenic strains of P. multocida. The ELISA is a rapid, effective, economical way to identify toxigenic P. multocida isolates.  (+info)

Lateral gene transfer of a dermonecrotic toxin between spiders and bacteria. (7/18)

MOTIVATION: Spiders in the genus Loxosceles, including the notoriously toxic brown recluse, cause severe necrotic skin lesions owing to the presence of a venom enzyme called sphingomyelinase D (SMaseD). This enzyme activity is unknown elsewhere in the animal kingdom but is shared with strains of pathogenic Corynebacteria that cause various illnesses in farm animals. The presence of the same toxic activity only in distantly related organisms poses an interesting and medically important question in molecular evolution. RESULTS: We use superpositions of recently determined structures and sequence comparisons to infer that both bacterial and spider SMaseDs originated from a common, broadly conserved domain family, the glycerophosphoryl diester phosphodiesterases. We also identify a unique sequence/structure motif present in both SMaseDs but not in the ancestral family, supporting SMaseD origin through a single divergence event in either bacteria or spiders, followed by lateral gene transfer from one lineage to the other.  (+info)

Effects of purified Pasteurella multocida dermonecrotoxin on the nasal ventral turbinates of fattening pigs: histological observations. (8/18)

Fattening specific pathogen-free derived pigs were injected intramuscularly with dermonecrotoxin of Pasteurella multocida, capsular type D. Ten days later, the nasal ventral turbinates and liver were examined histologically. A moderate turbinate atrophy was observed due to an increased number of osteoclasts and the absence of intramembranous bone apposition. Liver lesions were limited to some hepatocyte necrosis, sinusoid neutrophil infiltration and Kupffer cell hypertrophy. This study demonstrated that adult pigs are sensitive to P. multocida dermonecrotoxin.  (+info)

• 1
• 2
• 3