Intraspecific variation in the venom electrophoretic profile of recently captured Crotalus durissus terrificus (Laurenti, 1768) snakes

EVALUATION OF THE ANTIBACTERIAL ACTIVITY OF Crotalus durissus terrificus CRUDE VENOM

Abstract Snake venoms are recognized as a promising source of pharmacologically active substances and are potentially useful for the development of new antimicrobial drugs. This study aimed to investigate the antimicrobial activity of the venom from the rattlesnake Crotalus durissus terrificus against several bacteria. Antibacterial activity was determined by using the plate microdilution method and the activity on the bacterial envelope structure was screened by using the crystal violet assay. The proteins in crude venom were separated by electrophoresis and characterized regarding their proteolytic activity. C. d. terrificus venom exhibited antimicrobial action against gram-positive and gram-negative bacteria. MIC values were defined for Pseudomonas aeruginosa ATCC 27853 (62.5 µg/mL), Staphylococcus aureus ATCC 25923 (125 µg/mL), and Micrococcus luteus ATCC 9341 (≤500 µg/mL). For Salmonella enterica serovar typhimurium ATCC 14028 and Corynebacterium glutamicum ATCC 13032, the decrease in bacterial growth was not detected visually, but was statistically significant. The crystal violet assay demonstrated that the crude venom increased bacterial cell permeability and the secreted protein profile agreed with previous reports. The results suggest that the proteins with lytic activity against bacteria in C. d. terrificus venom deserve further characterization as they may offer reinforcements to the weak therapeutic arsenal used to fight microbial multidrug resistance.

Aspectos clínico-patológicos e laboratoriais do envenenamento crotálico experimental em bovinos

Reproduziu-se experimentalmente o envenenamento crotálico, através da inoculação, por via subcutânea, do veneno de Crotalus durissus terrificus (cascavel sul-americana) em dez bovinos mestiços. Dois animais foram utilizados como controle. O bovino que recebeu dose de 0,03mg/kg de peso corporal, morreu 7h40min após a inoculação. A dose de 0,015mg/kg causou a morte em quatro de sete bovinos inoculados, enquanto os dois animais que receberam 0,0075mg/kg adoeceram discretamente e se recuperaram. Os sintomas tiveram início entre 1h30min e 13h45min após a inoculação. A evolução oscilou entre 5h25min e 45h para os animais que morreram e entre 33h15min e 17 dias entre os animais que se recuperaram. Os principais sinais nervosos observados foram diminuição da resposta aos estímulos externos, reflexos hipotônicos, arrastar dos cascos no solo, aparente apatia, paralisia do globo ocular e da língua, decúbito esternal e lateral. Verificaram-se também adipsia e, por vezes, petéquias nas mucosas vaginal e conjuntival. Houve discreto a moderado aumento do tempo de sangramento e moderado aumento do tempo de tromboplastina parcial ativada. Houve moderada leucocitose com neutrofilia, linfopenia relativa, eosinopenia, monocitose e discreto aumento do número de bastões. Foi evidenciado significativo aumento dos níveis séricos de creatinaquinase, contudo, não foram observadas alterações significativas através da urinálise. À necropsia constataram-se edema quase imperceptível no local da inoculação, discretas petéquias e sufusões no epicárdio, omento, vesícula biliar e mucosa da bexiga em alguns dos animais envenenados experimentalmente. Os exames histopatológicos revelaram necrose (hialinização) de grupos de miócitos ou em miócitos isolados em dez diferentes músculos esqueléticos examinados, próximos ou distantes do local de inoculação em todos os animais necropsiados. Concluí-se que o envenenamento por Crotalus Sul-americanas em bovinos não cursa com mioglobinúria e que o quadro marcado de paralisia flácida mimetiza o observado no botulismo. Adicionalmente foram feitas observações sobre o diagnóstico do envenenamento crotálico e sua diferenciação com enfermidades que cursam com paralisia e necrose muscular em bovinos do Brasil.

A comparative study of biological activities of crotoxin and CB fraction of venoms from Crotalus durissus terrificus, Crotalus durissus cascavella and Crotalus durissus collilineatus

In Brazil, the Crotalus durissus terrificus subspecie is the most studied, particularly concerning its crotoxin. Crotoxin is the major toxic component of the South American rattlesnake Crotalus durissus venom. It is composed of two different subunits, CA called crotapotin and CB weakly toxic phospholipase A2 with high enzymatic activity. In this paper, we decided to make a study of the main toxic characteristics of crotoxin (CTX) and CB fraction from the other subspecies, Crotalus durissus cascavella and of Crotalus durissus collilineatus, in comparison with those of C. d. terrificus. Ours results have shown that the venoms presented similar chromatographic profiles and the purified fractions were free of contaminants. Regarding the toxic activities, the DL50 of the crotoxins showed no significant differences between the subspecies. The smaller toxicity of CB indicated that the toxicity of the crotoxin complex depends on the interaction between CA and CB. CTX and fraction CB of the three species of Crotalus showed negligible proteolytic activity. C. d. terrificus CTX presented higher PLA2 activity when compared with the others two subspecies. The oedema induced by CB developed later than the CTX and reached its peak 3 h after the injection. The myotoxic activity was determined by assaying serum CK levels. Mice injected with CTX of C. d. terrificus presented greater myotoxic activity compared to the others. The myotoxic activity of CB from the three subspecies was lower than the activity of the crotoxin, reinforcing the idea that the fraction CA increases the toxicity of CB.