In vitro inhibition activity of different bacteriocin-producing Escherichia coli against Salmonella strains isolated from clinical cases.

AIMS: To compare in vitro the inhibitory activity of four bacteriocin-producing Escherichia coli to a well-characterized panel of Salmonella strains, recently isolated from clinical cases in Switzerland. METHODS AND RESULTS: A panel of 68 nontyphoidal Salmonella strains was characterized by pulsed-field gel electrophoresis analysis and susceptibility to antibiotics. The majority of tested strains were genetically different, with 40% resistant to at least one antibiotic. E. coli Mcc24 showed highest in vitro activity against Salmonella (100%, microcin 24), followed by E. coli L1000 (94%, microcin B17), E. coli 53 (49%, colicin H) and E. coli 52 (21%, colicin G) as revealed using a cross-streak activity assay. CONCLUSIONS: Escherichia coli Mcc24, a genetically modified organism producing microcin 24, and E. coli L1000, a natural strain isolated from human faeces carrying the mcb-operon for microcin B17-production, were the most effective strains in inhibiting in vitro both antibiotic resistant and sensitive Salmonella isolates. SIGNIFICANCE AND IMPACT OF THE STUDY: Due to an increasing prevalence of antibiotic resistant Salmonella strains, alternative strategies to fight these foodborne pathogens are needed. E. coli L1000 appears to be a promising candidate in view of developing biotechnological alternatives to antibiotics against Salmonella infections.

Technique to improve surveying in confined areas.

Current surveying instrumentation precludes the thorough analysis of some areas of cast topography. The use of readily available, supplemental instrumentation when casts are surveyed will enhance removable partial denture therapy. In particular, facial embrasures and rest seats can be advantageously studied with this modified technique.