Psychrophilic and psychrotrophic Clostridium spp. associated with meat spoilage
Permanent link to Research Commons versionhttps://hdl.handle.net/10289/14906
Twenty two isolates of psychrophilic and psychrotrophic Clostridium spp. associated with ‘blown pack’ spoilage of vacuum-packed meats were studied with respect to their identification, differentiation and taxonomy, as well as spoilage aetiology. The aetiological study was conducted to establish whether a causal relationship exists between psychrophilic and psychrotrophic clostridia and the production of abundant gas in vacuum-packed chilled meats. The attempt was then made to identify these clostridia using conventional microbiological methods. Genotypic approaches to differentiation of psychrophilic and psychrotrophic clostridia at inter- and intra-species level were evaluated and applied to tracing the ‘blown pack’ spoilage causing clostridia back to their contamination source in the abattoir. Where phenotypic and genotypic characteristics indicated that some isolates of psychrophilic and psychrotrophic clostridia differed from those previously described, taxonomic studies were conducted to determine whether these isolates could be described as new clostridial species. Four clostridial isolates were found to cause premature vacuum pack distension during chilled storage. Conventional phenotype based methods were found to be ineffective for identification of psychrophilic and psychrotrophic clostridia. Although RFLP analysis of the amplified 16S rDNA gene allowed differentiation of psychrophilic and psychrotrophic clostridia at the genotypic species level and below, comparison of PCR-RFLP patterns and 16S rDNA sequences of meat isolates with patterns and sequences of reference strains did not effect ready identification of some of these microorganisms. Consequently, the use of these methods for identification of unknown clostridial isolates needs to be approached carefully. Differentiation of some meat-derived isolates of psychrophilic and psychrotrophic clostridia at intra-species or inter-strain level was achieved with methods based on polymorphism of genomic DNAs and/or the 16S-23S rDNA internal transcribed spacers from these organisms. With the 16S-23S rDNA internal transcribed spacer polymorphism analysis, inter-species differentiation of psychrophilic and psychrotrophic clostridia may be achieved in instances where little inter-strain variation is expected e.g. in typing of isolates from the same meat plant or spoilage incident. Hides and faeces of slaughter animals were identified as an abundant abattoir source of psychrophilic and psychrotrophic clostridia representing many species. Seven isolates of these microorganisms, representing four distinct taxonomic groups, were found to differ in their phenotypic, genotypic and phylogenetic characteristics from known clostridial species. With a polyphasic approach, three new clostridial species, C. frigidicarnis, C. gasigenes and C. algidixylanolyticum have been named and characterised. It is hoped that this study has added to our understanding of the aetiology and causative agents of ‘blown pack’ spoilage and, thus, has advanced the process of developing measures to control this type of spoilage of vacuum packed chilled meats.
The University of Waikato
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