Tetracycline and penicillin resistant Clostridium perfringens isolated from the fangs and venom glands of Loxosceles laeta: its implications in loxoscelism treatment.

The venom of Loxosceles spiders produces severe dermonecrotic damage, intravascular hemolysis, systemic alterations and risk of death. Clostridium perfringens is present in the microbial flora of the fangs and venom glands of Loxosceles intermedia. Its inoculation with the venom may infect the wound site and exacerbate the dermonecrotic damage. This anaerobic bacterium is widely distributed in nature and capable of damage with similar characteristics and severity to the spider venom. In this study we isolated and characterized species of Clostridium from the fangs and venom glands of Loxosceles laeta, including C. perfringens. The sensitivity patterns of different isolates of C. perfringens were evaluated by minimum inhibitory concentration against penicillin, ampicillin, erythromycin, gentamicin, chloramphenicol, clindamycin and tetracycline, under anaerobic conditions, using the method of microdilution in broth. Strain C. perfringens H28 showed resistance to penicillin, ampicillin, tetracycline and chloramphenicol. Resistance to penicillin and ampicillin was mediated by beta-lactamase. In vivo evaluation of dermonecrosis in rabbits using L. laeta venom co-inoculated with isolate C. perfringens H28 produced an increase in the area of dermonecrotic lesions in the presence of penicillin and tetracycline, but not with gentamicin. Antibiotic therapy Loxosceles poisoning should be re-evaluated, considering the existence of multi-resistant strains of C. perfringens.