Several aromatic and aliphatic ketones were tested for inhibitory activity against Clostridium botulinum spores and cells. Six-tenths mM 3-heptanone, 3-hexanone, or benzophenone delayed spore germination in botulinal assay medium (BAM) broth at 32°C. Sporicidal activity was observed for 1,250 mM 2,3-pentanedione, while 2-octanone, 3-octanone, or benzophenone were effective at 2,500 mM. In general, higher concentrations were required to inhibit vegetative cells than to prevent spore germination. Maximum activity against vegetative cells was observed at 25 mM acetanisole (4′-methoxyacetophenone), 2,3-butanedione, 2,3-pentanedione, 2-pentanone, or benzophenone, and inhibition was independent of pH. Five-tenths mM acetanisole inhibited dipicolinic acid release, 100 mM reduced 20 min 80°C thermal resistance, and 5.0 mM delayed toxigenesis in BAM broth at 32°C. Furthermore, inhibitory activity of acetanisole was comparable to that observed in BAM broth when tested in commercially prepared chicken and beef broths. The spectrum of antibotulinal activity was dependent upon carbon chain length, carbonyl position, number of carbonyls, and aromaticity. The inhibitions observed suggest that aliphatic and aromatic ketones might have potential as novel antimicrobial agents.

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