It is known that volatile fatty acids can inhibit growth of species of the family Enterobacteriaceae in vitro. However, whether these volatile fatty acids affect bacterial populations in the ceca of chickens is unknown. Therefore, a study was conducted to investigate if changes in volatile fatty acids in ceca of broiler chickens during growth affect bacterial populations. Results showed that members of the Enterobacteriaceae and enterococci are present in large numbers in 3-day-old broilers and start to decrease when broilers grow older. Lactobacilli are present in large numbers as well in 3-day-old broilers, but they remain stable during the growth of broilers. Acetate, butyrate, and propionate increase from undetectable levels in 1-day-old broilers to high concentrations in 15-day-old broilers, after which they stabilize. Significant negative correlations could be calculated between numbers of Enterobacteriaceae and concentrations of undissociated acetate, propionate, and butyrate. Furthermore, pure cultures of Enterobacteriaceae isolated from the ceca were grown in the presence of volatile fatty acids. Growth rates and maximal optical density decreased when these strains grew in the presence of increasing volatile fatty acid concentrations. It is concluded that volatile fatty acids are responsible for the reduction in numbers of Enterobacteriaceae in the ceca of broiler chickens during growth.

On the basis of the comparison of the nucleotide sequences of the histidine decarboxylase genes (hdcA) of Lactobacillus 30A and Clostridium perfringens and the amino acid sequences of these histidine decarboxylases and those of Lactobacillus buchneri and Micrococcus, oligonucleotides unique to the hdcA genes were synthesized and used in PCR. All histidine-decarboxylating lactic acid bacteria gave a signal with primer set JV16HC/JV17HC in PCR. In addition to this primer set, CL1/CL2 and CL1/JV17HC were also useful for the detection of histamine-forming Leuconostoc aenos strains in PCR. The 150 base pair amplification product of the decarboxylating Leuc. aenos strain generated with primer set CL1/CL2 was sequenced. Alignment studies showed a high degree of relatedness among the hdcA gene products of Gram-positive bacteria. The amplification products of the hdcA genes from Lac. buchneri and Leuct. aenos were used to serve as a DNA probe in hybridization studies. All histidine-decarboxylating lactic acid bacteria gave a hybridization signal with the DNA probes. In hybridization only one false-positive signal with a Lactobacillus lindneri strain was observed, which was anticipated to contain a truncated hdcA gene. In addition to these DNA probe tests, a simple and reliable activity test is presented, which can be used during starter selection to test strains for histidine decarboxylase activity.

Discrimination of strains within the species Saccharomyces cerevisiae was demonstrated by the use of four different techniques to type 15 strains isolated from spoiled wine and beer. Random amplified polymorphic DNA with specific oligonucleotides and PCR fingerprinting with the microsatellite oligonucleotide primers (GAC) 5 and (GTG) 5 enabled discrimination between the strains tested. Additionally, restriction enzyme analysis, with TaqI and MseI, of PCR-amplified fragments from the complete internal transcribed spacer and nontranscribed spacer, both present in the rRNA-encoding gene cluster, proved to be suitable for generating intraspecies-specific patterns. Random amplified polymorphic DNA with primers 24 and OPA-11 and PCR fingerprinting with primer (GTG) 5 appeared to generate the highest degree of diversity. However, the results indicated that there was no single PCR-mediated typing technique enabling discrimination on the strain level. Discrimination of each individual strain was nevertheless possible by combining the results obtained with all typing techniques.

Several techniques of DNA analysis were applied to identify chrysanthemum cultivars. Unrelated cultivars could be distinguished by using RAPDs (random amplified polymorphic DNAs), inter-SSR (simple sequence repeat) PCR (polymerase chain reaction), hybridization-based DNA fingerprinting, as well as RFLPs (restriction fragment length polymorphisms). Cultivars with different flower colours and belonging to one family, i.e. vegetatively derived from 1 cultivar, appeared to have the same DNA fragment patterns, whichever technique was applied. The absence of polymorphisms between different accessions of the same cultivar indicated a high stability of the observed patterns.

~~The major outer membrane (OM) proteins of 23 enterobacterial strains (principally clinical isolates) and five non-Enterobacteriaceae species were investigated by the sodium dodecyl sulphate-polyacrylamide gel immunoperoxidase (SGIP) technique to evaluate antigenic cross-reactivity among these proteins. All enterobacterial strains contained one or more peptidoglycan-associated major OM proteins, cross-reactive with the peptidoglycan-bound protein I of Escherichia coli, and one non-peptidoglycan-bound heat-modifiable protein, cross-reactive with protein 11" of E. coli. Results indicated that antigenic cross-reactivity of the major OM proteins is a general phenomenon in the family Enterobacteriaceae, independent of any molecular weight variation of the corresponding proteins in different bacterial strains. SGIP experiments carried out with OM preparations of other species showed no cross-reactivity of any of their OM proteins with enterobacterial major OM proteins. The significance of the immunological relatedness of OM proteins for the classification of some Enterobacteriaceae is discussed.

293The protein constituents in the outer membrane (OM) of several serotypes of Escherichia coli and some other Enterobacteriaceae cross-reacted antigenically. Solubilized OM preparations of these bacteria were applied in interfacial precipitin tests to antisera elicited in rabbits against whole bacterial cells, absorbed with their appropriate lipopolysaccharide before testing. The resulting immunecomplexes were analysed on polyacrylamide gels. Protein profiles of the imrnunoprecipitates showed a considerable antigenic cross-reactivity of outer membrane proteins between most E. coli serotypes. Cross-reactivity, though substantially lower, was also found with OM from three other Enterobacteriaceae species, but was not detectable with Pseudomonas aeruginosa OM. When OM preparations were solubilized at room temperature, the peptidoglycan-bound proteins in the molecular weight range 37000 to 41000 predominated in the protein profiles of the immunecomplexes. In profiles of immunecomplexes obtained with boiled OM preparations, a heat-modifiable protein (mol. wt 33000) predominated. The major OM proteins of the Gram-negative bacterium may therefore play a role as common surface antigens of the family of Enterobacteriaceae.

An outbreak of Campylobacter upsaliensis in four Brussels day care centers (A, B-1, B-2, and C) affected 44 children. Diarrhea was the major symptom. From January 1991 to June 1992, the outbreak strain was isolated from 3, 1, and 21 (of 68) children in centers A, B-1, and B-2, respectively, and from 19 of 22 children in center C, IgG, IgM, and IgA antibodies were detected by Western blotting of serum specimens of 9 of 10 and 13 of 16 children in centers B-2 and C, respectively. Strains were typed by biotyping, DNA restriction-based and antibiotic susceptibility typing, whole cell protein and plasmid analysis, restriction fragment length polymorphism (RFLP), and polymerase chain reaction (PCR). On the basis of RFLP and PCR typing, the strains could be divided into two strongly related clonal variants: One was isolated only from the children of center A and the second only from children in the other day care centers.

The random amplified polymorphic DNA (RAPD) assay and the restriction enzyme analysis of PCR amplified rDNA are compared for the identification of the common spoilage yeasts Zygosaccharomyces bailii, Z. rouxii, Saccharomyces cerevisiae, Candida valida and C. lipolytica. Both techniques proved to be adequate tools for yeast identification. Since the RAPD does provide less stable patterns than restriction enzyme analysis of PCR amplified rDNA, and a large amount of data had to be compared without data reduction, Principal Component Analysis (PCA) was applied successfully for clustering the RAPD patterns. The success of PCA is highly influenced by the primer used in RAPD and the amount of reference samples. A large amount of reference samples improves the performance of clustering in PCA. The primer of choice was shown to be important with respect to the discriminatory power of the RAPD method. Some primers used enabled discrimination on the subspecies level. The results collected with both typing methods justify the conclusion that the present typing system can be applied for taxonomical purposes.