Monique da Silva Neves

Vaccination of cattle with a recombinant bivalent toxoid against botulism serotypes C and D

Cattle botulism is a fatal intoxication caused by botulinum neurotoxins (BoNTs) produced by Clostridium botulinum serotypes C and D resulting in economic losses. Vaccination is the most effective way to control botulism. However, the commercially available vaccines are difficult and hazardous to produce. Neutralizing antibodies against the C-terminal fragment of the BoNT heavy chain (HC) are known to protect against lethal doses of BoNTs. We report the vaccination of cattle with a previously tested recombinant chimera consisting of Escherichia coli heat-labile enterotoxin B subunit and the HC of BoNTs C and D. Vaccinated animals produced neutralizing antibodies against serotypes C and D averaging 5±0 and 6.14±1.06IU/mL, respectively. For BoNT D, the titers were greater than those measured for the commercial vaccine, which induced titers of 5±0 and 2.85±1.35 against the respective serotypes, suggesting that this chimera is effective against cattle botulism.

Evaluation of three enzyme immunoassays and a nucleic acid amplification test for the diagnosis of Clostridium difficile-associated diarrhea at a university hospital in Brazil

INTRODUCTION Despite the known importance of Clostridium difficile as a nosocomial pathogen, few studies regarding Clostridium difficile infection (CDI) in Brazil have been conducted. To date, the diagnostic tests that are available on the Brazilian market for the diagnosis of CDI have not been evaluated. The aim of this study was to compare the performances of four commercial methods for the diagnosis of CDI in patients from a university hospital in Brazil. METHODS Three enzyme immunoassays (EIAs) and one nucleic acid amplification test (NAAT) were evaluated against a cytotoxicity assay (CTA) and toxigenic culture (TC). Stool samples from 92 patients with suspected CDI were used in this study. RESULTS Twenty-five (27.2%) of 92 samples were positive according to the CTA, and 23 (25%) were positive according to the TC. All EIAs and the NAAT test demonstrated sensitivities between 59 and 68% and specificities greater than 91%. CONCLUSIONS All four methods exhibited low sensitivities for the diagnosis of CDI, which could lead to a large number of false-negative results, an increased risk of cross-infection to other patients, and overtreatment with empirical antibiotics.