Piet J. Jooste

A polyphasic taxonomic study of Chryseobacterium strains isolated from dairy sources.

A polyphasic taxonomic study, employing protein electrophoresis (SDS-PAGE), gas chromatographic analysis of cellular fatty acids (FAME), mol% G+C determination and DNA-DNA hybridizations, was undertaken on 103 dairy isolates shown to belong to Chryseobacterium. Reference strains of the Chryseobacterium species, CDC group IIb and Embedobacter brevis were included. SDS-PAGE analysis yielded good differentiation between the investigated species. About half of the strains could be clustered into nine major groups while the other half occupied a separate position. With FAME analysis no clear differentiation of the Chryseobacterium species (except C. meningosepticum) and SDS-PAGE groups could be achieved. FAME analysis, however, gave good differentiation between the Chryseobacterium and Empedobacter strains. The mol% G+C of the isolates tested, ranged between 36.4 and 39.0. The combination of SDS-PAGE and DNA-DNA hybridization identified a large group of dairy isolates as C. indologenes, one isolate as C. gleum and two new genotypic groups, comprising five and 15 dairy isolates respectively, emerged from the polyphasic study. Another large part of strains have a separate or uncertain position in Chryseobacterium and remained classified as Chryseobacterium species CDC group IIb.

Relative gene expression in acid-adapted Escherichia coli O157:H7 during lactoperoxidase and lactic acid challenge in Tryptone Soy Broth.

Cross-protection of acid-adapted Escherichia coli O157:H7 against inimical stresses is mediated by the glucose-repressed sigma factor RpoS. However, many food systems in which E. coli O157:H7 occurs are complex and contain glucose. This study was aimed at investigating the contribution of acid and lactoperoxidase (LP)-inducible genes to cross-protection of E. coli O157:H7 against LP system and lactic acid (LA) in Tryptone Soy Broth (TSB). Acid-adapted and non-adapted E. coli O157:H7 were challenged to activated LP and LA at pH 4.0 and 5.0 in TSB for 6h at 25°C followed by expression of acid and LP-inducible genes. Acid-adapted E. coli showed cross-protection against activated LP and LA. All the acid-inducible genes tested were repressed at pH 4.0 with or without activated LP system. At pH 7.4, gadA, ompC and ompF were induced in acid-adapted cells. Induction of corA occurred in non-adapted cells but was repressed in acid-adapted cells. Although acid-inducible genes were repressed at pH 4.0, high resistance of acid-adapted cells indicates that expression of acid-inducible genes occurred during acid adaptation and not the actual challenge. Repression of rpoS indicates that RpoS-independent systems contribute to cross-protection in acid-adapted E. coli O157:H7.

Chryseobacterium carnipullorum sp. nov., isolated from raw chicken

Three Gram-staining-negative, rod-shaped, non-spore-forming, non-motile, oxidase-positive, yellow pigmented and aerobic bacterial isolates designated 8_R23573, 9_R23581(T) and 10_R23577 were isolated from raw chicken at a broiler processing plant in Bloemfontein, South Africa. A polyphasic taxonomic approach was used to determine their exact taxonomic identities. Phylogenetic analysis of the 16S rRNA gene sequences showed that the three strains belonged to the genus Chryseobacterium, exhibiting the highest similarities to Chryseobacterium shigense DSM 17126(T) (98.6-99.2%) and Chryseobacterium luteum DSM 18605(T) (98.3-98.7%). The most abundant quinone was menaquinone MK-6 and the predominant cellular fatty acids were iso-15:0, iso-17:1ω9c, iso-17:0 3-OH and summed feature 3 (iso-16:1ω7c and/or iso-15:0 2-OH), which supported the affiliation of the strains to the genus Chryseobacterium. The DNA G+C contents of the strains were 36.9, 36.7 and 36.6 mol% respectively. The DNA-DNA hybridization results gave relatedness values ranging from 78.8 to 87.2% among the three strains and 23.4 to 56.1% to the two nearest phylogenetic neighbours C. shigense DSM 17126(T) and C. luteum LMG 23785(T). On the basis of the data from this polyphasic study, the three strains are concluded to represent a novel species of the genus Chryseobacterium for which the name Chryseobacterium carnipullorum sp. nov. is proposed. The type strain is 9_R23581(T) ( = LMG 26732(T) =DSM 25581(T)).

Wildlife-associated zoonotic diseases in some southern African countries in relation to game meat safety: A review

With on-going changes in land use practices from conventional livestock farming to commercial, wildlife-based activities, the interface or interaction between livestock and wildlife is increasing. As part of the wildlife-based activities of ecotourism, breeding and hunting, game farmers are also exploring the utilisation of meat from hunted or harvested game. The expanding interface or increased interaction between livestock and wildlife increases the risk of disease incidence and the emergence of new diseases or the re-emergence of previously diagnosed diseases. The risk is not only related to domestic and wild animal health, but also to the occupational hazards that it poses to animal handlers and the consumers of game meat. This review endeavours to highlight the role that game plays in the spreading of zoonotic diseases to other animals and humans. Examples of zoonotic diseases that have occurred in wild animals in the past, their relevance and risk have been summarised and should function as a quick reference guide for wildlife veterinarians, ecologists, farmers, hunters, slaughter staff, processors and public health professionals.

Consumer acceptability of a synbiotic version of the maize beverage mageu

This study examined the possibility of converting mageu, a fermented maize beverage popular throughout southern Africa, into a health-promoting and affordable alternative to probiotic dairy products. A range of probiotic Lactobacillus species was compared with a control species traditionally used to prepare mageu. Prebiotic oligosaccharide (soluble fibre), which enhances the growth of beneficial bacteria, was also included. The resulting beverages were compared in two ways: sensory attributes were determined by a trained panel using quantitative descriptive analysis (QDA), and consumer acceptability was assessed by 53 untrained volunteers. The QDA results suggest that mageu fermented by Lb. acidophilus or Lb. rhamnosus was most similar to the control mageu, while Lb. paracasei mageu and Lb. casei mageu were least similar. The consumer acceptability data confirmed that Lb. acidophilus or Lb. rhamnosus mageu did not differ significantly from the control, suggesting that either of these is suitable for commercial production of probiotic mageu.

The hygiene practices of three systems of game meat production in South Africa in terms of animal class and health compliance

Three game meat production systems used on game ranches in South Africa are reported on. System one is applied in the game export market and conforms to the hygiene requirements of the European Union (EU). System two and three entail game meat available on the local market not subjected to any regulation. System 2 however, implemented basic meat hygiene values. Measurements of pH, temperature, Aerobic Plate Count (APC), E. coli, Salmonella and S. aureus were subjected to a 3×2 factorial analysis of variance with factors that involve 3 system compliances in 2 classes of game animals in a completely randomised design. The measured bacteriological and quality differences between the three systems do not justify EU standards application on the local market but results indicated a significant compliance×class interaction.

Anticandidal activity of cell extracts from 13 probiotic Lactobacillus strains and characterisation of lactic acid and a novel fatty acid derivative from one strain

This study investigated the anti-Candida activity of methanol extracts from freeze-dried probiotic cells and the isolation of some constituents in the extracts. The MIC values of the probiotic methanol cell extracts against Candida albicans ranged between 1.25 and 5mg/ml after 48 h of incubation. However, Lactococcus latics subsp. lactis strain X and Lactobacillus casei strain B extracts had an MIC of 10mg/ml after 48 h of incubation. The extracts had fungistatic rather than fungicidal activity. These extracts had a much higher antifungal activity than antifungal compounds isolated from the growth medium by many other authors. This indicates that probiotics may also release antifungal compounds in their cells that could contribute to a therapeutic effect. Lactic acid (1) and 6-O-(α-D-glucopyranosyl)-1,6-di-O-pentadecanoyl-α-D-glucopyranose a novel fatty acid derivative (2) were isolated from methanol probiotic extracts and the structure of these compounds were elucidated using NMR (1 and 2D) and mass spectrometry (MS).

Chapter 22:Culture Media for Food-associated Genera in the Family Flavobacteriaceae

The taxonomy of the flavobacteria has undergone many changes over the past 10 years and has rapidly expanded in the past five years. This may lead to confusion when deciding on culture media for this group of bacteria. This chapter is organised so that it orientates the reader in terms of the taxonomy of the family and then deals with the media that can be suggested for the isolation, cultivation, maintenance and differentiation of the members of the Flavobacteriaceae family that may be of significance to the food microbiologist. The most useful isolation media for this group of bacteria are nutrient agar, standard plate count agar, trypticase soy agar, Reasoners 2A medium, marine agar and Anacker and Ordal agar.

Comparison of rpoA and pheS Gene Sequencing to 16S rRNA Gene Sequencing in Identification and Phylogenetic Analysis of LAB from Probiotic Food Products and Supplements

An investigation of the relevance of sequenced protein-coding genes in comparison with 16S rRNA gene sequences to correctly delineate and discriminate between closely related Lactobacillus isolates is presented. These reportedly probiotic Lactobacillus strains were obtained from probiotic supplements and food products. Probiotic Lactobacillus species have been found to have several potential health benefits and technological properties which may be strain-dependent. It was deemed necessary to investigate molecular techniques for the identification and discrimination between closely related isolates. The 16S rRNA, pheS, and rpoA genes were amplified in a polymerase chain reaction using the oligonucleotide pairs 27F/1492R, pheS-21-F/pheS-23-R, and rpoA-21-F/rpoA-23-R. The PCR amplicons were separated using gel agarose electrophoresis and observed by the Bio-Rad Gel DocTM XR+ Imaging system transilluminator. Sequencing of the PCR amplicons was done in an ABI PRISMTM 3100 genetic analyzer. MEGA 5.05 software was employed in doing the phylogenetic analysis. Identification by 16S rRNA gene sequencing was confirmed by pheS and rpoA gene sequencing. Subsequent phylogenetic analysis and concatenation showed that interspecies and intraspecies degrees of diversity and similarity were better enabled by pheS and rpoA primers. Overall, findings revealed cases of inaccurate identification of Lactobacillus strains in probiotic supplements on the market, highlighting the relevance of the multigenic approach in more accurately identifying Lactobacillus strains. Supplemental materials are available for this article; see the publishers online edition of Food Biotechnology to view the supplemental file.

Chapter 21 Culture media for genera in the family flavobacteriaceae

The taxonomy of the flavobacteria has undergone many changes over the past 10 years. This fact may lead to confusion when seeking culture media for this group of bacteria. This chapter is organised in such a way that it orientates the reader in terms of the taxonomy of the family and the deals with the isolation, cultivation and maintenance media that can be used for members of the Flavobacteriaceae family that are of significance for the food microbiologist.