Molecular diversity of live-attenuated prototypic vaccine strains and clinical isolates of Staphylococcus aureus.

Bovine mastitis Staphylococcus aureus isolates and prototypic live-attenuated vaccine strains were analyzed by SmaI pulsed-field gel electrophoresis (PFGE) typing and automated ribotyping. The discriminatory index of these methods was 0.91 and 0.69, respectively. SmaI PFGE typing assigned all laboratory strains into cluster Q, which shared 49% similarity with clusters A and B, and 35% similarity with cluster C. Automated ribotyping placed laboratory strains within ribogroups different from those of bovine isolates. These methods have 70% concordance and permitted identification of the prototypic vaccine background from those of clinical isolates. This information is required before conducting field trials with the vaccine.

Comparison of enteric-coated capsules and liquid formulation of Ty21a typhoid vaccine in randomised controlled field trial.

In a randomised, double-blind, controlled field trial in Santiago, Chile, 81,621 schoolchildren aged 5-19 years received three doses, within a week, of attenuated Salmonella typhi oral vaccine Ty21a in enteric-coated capsules or in a new liquid suspension, or placebo. Over 36 months of surveillance, the liquid formulation (76.9% vaccine efficacy) was significantly superior to the enteric-coated capsules (33.2% vaccine efficacy). The liquid formulation protected young children (5-9 years) (efficacy 82.3%) as well as older children (efficacy 69.3%), whereas the capsules significantly protected only older children. The liquid suspension was easy to prepare by mixing lyophilised vaccine with buffer in water and was easily administered, even to the youngest children. Thus, the liquid formulation of Ty21a is preferable to enteric-coated capsules.