Evidence for a close phylogenetic relationship between Melissococcus pluton, the causative agent of European foulbrood disease, and the genus Enterococcus

Tracing the Enterococci from Paleozoic Origins to the Hospital

We examined the evolutionary history of leading multidrug resistant hospital pathogens, the enterococci, to their origin hundreds of millions of years ago. Our goal was to understand why, among the vast diversity of gut flora, enterococci are so well adapted to the modern hospital environment. Molecular clock estimation, together with analysis of their environmental distribution, phenotypic diversity, and concordance with host fossil records, place the origins of the enterococci around the time of animal terrestrialization, 425-500 mya. Speciation appears to parallel the diversification of hosts, including the rapid emergence of new enterococcal species following the End Permian Extinction. Major drivers of speciation include changing carbohydrate availability in the host gut. Life on land would have selected for the precise traits that now allow pathogenic enterococci to survive desiccation, starvation, and disinfection in the modern hospital, foreordaining their emergence as leading hospital pathogens.

Honey bee pathology: current threats to honey bees and beekeeping

Managed honey bees are the most important commercial pollinators of those crops which depend on animal pollination for reproduction and which account for 35% of the global food production. Hence, they are vital for an economic, sustainable agriculture and for food security. In addition, honey bees also pollinate a variety of wild flowers and, therefore, contribute to the biodiversity of many ecosystems. Honey and other hive products are, at least economically and ecologically rather, by-products of beekeeping. Due to this outstanding role of honey bees, severe and inexplicable honey bee colony losses, which have been reported recently to be steadily increasing, have attracted much attention and stimulated many research activities. Although the phenomenon "decline of honey bees" is far from being finally solved, consensus exists that pests and pathogens are the single most important cause of otherwise inexplicable colony losses. This review will focus on selected bee pathogens and parasites which have been demonstrated to be involved in colony losses in different regions of the world and which, therefore, are considered current threats to honey bees and beekeeping.

European foulbrood in honey bees

European foulbrood (EFB) is a severe bacterial brood disease caused by the Gram-positive bacterium Melissocccus plutonius. The disease has a worldwide distribution and is an increasing problem in some areas. Although the causative agent of EFB was described almost a century ago, many basic aspects of its pathogenesis are still unknown. This review presents both historical results and recent molecular data to synthesize present knowledge of this enigmatic honey bee disease.

A nested array of rRNA targeted probes for the detection and identification of enterococci by reverse hybridization

Complete 23S and almost complete 16S rRNA gene sequences were determined for the type strains of the validly described Enterococcus species, Melissococcus pluton and Tetragenococcus halophilus. A comprehensive set of rRNA targeted specific oligonucleotide hybridization probes was designed according to the multiple probe concept. In silico probe design and evaluation was performed using the respective tools of the ARB program package in combination with the ARB databases comprising the currently available 16S as well as 23S rRNA primary structures. The probes were optimized with respect to their application for reverse hybridization in microplate format. The target comprising 16S and 23S rDNA was amplified and labeled by PCR (polymerase chain reaction) using general primers targeting a wide spectrum of bacteria. Alternatively, amplification of two adjacent rDNA fragments of enterococci was performed by using specific primers. In vitro evaluation of the probe set was done including all Enterococcus type strains, and a selection of other representatives of the gram-positive bacteria with a low genomic DNA G+C content. The optimized probe set was used to analyze enriched drinking water samples as well as original samples from waste water treatment plants.

Identification and characterization of Enterococcus species isolated from forage crops and their influence on silage fermentation

Forty-eight strains of lactic acid bacteria were isolated from forage crops, and their identification, characterization and influence on silage fermentation were studied. All isolates were Gram-positive, short-chain-forming, catalase-negative, and facultatively anaerobic cocci that did not produce gas from glucose, only formed L-lactic acid, and were able to grow at pH 9.6%, in 6.5% NaCl, or with 40% bile, but not below pH 4.5. These isolates were commonly isolated from forage crops, and they were divided into four groups (A, B, C, and D) according to sugar fermentation characteristics. Selected strains of FA 5, FA 27, FA 45, and FA 57 were identified as Enterococcus hirae, E. faecalis, E. casseliflavus, and E. mundtii, respectively, on the basis of DNA-DNA homology, Strains FA 5, FA 27, FA 45, and FA 57 and two strains from commercial inoculants, LC 10 (Lactobacillus casei) and LP 15 (L. plantarum), were used as additives to alfalfa and guinea grass silages. Alphalfa and guinea grass silages inoculated with LC 10, LP 15, FA 5 + LC 10, and FA 5 + LP 15-treatments in alfalfa and guinea grass silages had significantly lower pH values, contents of butyric acid and ammonia nitrogen, gas production, and dry matter losses compared with the control silage after 60 d of fermentation. However, the E. hirae FA 5, E. faecalis FA 27, E. casseliflavus FA 45, and E. mundtii FA 57-inoculated silages gave similar values to the control in both types of silage. The FA 27 + LC 10 and FA 27 + LP 15-inoculated silages did not differ in fermentation quality from LC 10 and LP 15-inoculated silages alone. The results confirmed that Enterococcus species were not able to improve silage quality.

Classification and characterization of lactic acid bacteria isolated from the intestines of common carp and freshwater prawns

Fifty-four isolates of lactic acid bacteria were obtained from the intestines of the common carp (Cyprinus carpio) and freshwater prawns (Macrobrachium rosenbergii) in Nakorn-Pathom Province, Thailand. All isolates were Gram-positive and catalase-negative cocci that did not produce gas from glucose and formed dl or L(+) lactic acid only. Most isolates were able to grow in broth at pH 9.6, in 6.5% NaCl (w/v) and 40% (w/v) bile. These isolates were divided into six groups (A-F) by sugar fermentation patterns. Strains in the groups A, B, C, and D showed intergroup DNA homology values of above 73.8%, indicating that these groups were composed of a single species. Following phylogenetic analysis, strains E 1, E 7, and E 26 from groups A, E, and F were placed in the clusters of the genera Lactococcus, Pediococcus, and Enterococcus, respectively. The type strains of Lactococcus garvieae, Pediococcus acidilactici, and Enterococcus faecium were the most closely related species with E 1, E 7, and E 26 in the phylogenetic tree, respectively. The DNA-DNA hybridization results indicated that strains in groups A (including groups B, C, and D), E, and F could be identified as belonging to the species Lactococcus garvieae, Pediococcus acidilactici, and Enterococcus faecium, respectively. Lactococcus garvieae was the dominant member of the population, accounting for 90.7% of the isolates.

Characterization and identification of Pediococcus species isolated from forage crops and their application for silage preparation

Pediococcus species isolated from forage crops were characterized, and their application to silage preparation was studied. Most isolates were distributed on forage crops at low frequency. These isolates could be divided into three (A, B, and C) groups by their sugar fermentation patterns. Strains LA 3, LA 35, and LS 5 are representative isolates from groups A, B, and C, respectively. Strains LA 3 and LA 35 had intragroup DNA homology values above 93.6%, showing that they belong to the species Pediococcus acidilactici. Strain LS 5 belonged to Pediococcus pentosaceus on the basis of DNA-DNA relatedness. All three of these strains and strain SL 1 (Lactobacillus casei, isolated from a commercial inoculant) were used as additives to alfalfa and Italian ryegrass silage preparation at two temperatures (25 and 48 degrees C). When stored at 25 degrees C, all of the inoculated silages were well preserved and exhibited significantly (P < 0.05) reduced fermentation losses compared to that of their control in alfalfa and Italian ryegrass silages. When stored at 48 degrees C, silages inoculated with strains LA 3 and LA 35 were also well preserved, with a significantly (P < 0.05) lower pH, butyric acid and ammonia-nitrogen content, gas production, and dry matter loss and significantly (P < 0.05) higher lactate content than the control, but silages inoculated with LS 5 and SL 1 were of poor quality. P. acidilactici LA 3 and LA 35 are considered suitable as potential silage inoculants.

A PCR detection method for rapid identification of Melissococcus pluton in honeybee larvae

Melissococcus pluton is the causative agent of European foulbrood, a disease of honeybee larvae. This bacterium is particularly difficult to isolate because of its stringent growth requirements and competition from other bacteria. PCR was used selectively to amplify specific rRNA gene sequences of M. pluton from pure culture, from crude cell lysates, and directly from infected bee larvae. The PCR primers were designed from M. pluton 16S rRNA sequence data. The PCR products were visualized by agarose gel electrophoresis and confirmed as originating from M. pluton by sequencing in both directions. Detection was highly specific, and the probes did not hybridize with DNA from other bacterial species tested. This method enabled the rapid and specific detection and identification of M. pluton from pure cultures and infected bee larvae.

Lactic acid bacteria of foods and their current taxonomy

Application of molecular genetic techniques to determine the relatedness of food-associated lactic acid bacteria has resulted in significant changes in their taxonomic classification. During the 1980s the genus Streptococcus was separated into the three genera Enterococcus, Lactococcus and Streptococcus. The lactic acid bacteria associated with foods now include species of the genera Carnobacterium, Enterococcus, Lactobacillus, Lactococcus, Leuconostoc, Oenococcus, Pediococcus, Streptococcus, Tetragenococcus, Vagococcus and Weissella. The genus Lactobacillus remains heterogeneous with over 60 species (ymol% G+C content ranging from 33 to 55), of which about one-third are strictly heterofermentative. However, many changes have been made and reorganization of the genus along lines that do not follow previous morphological or phenotypic differentiation from Leuconostoc and Pediococcus is being studied. Phylogenetically belonging to the Actinomyces branch of the bacteria, Lactobacillus bifidus has been moved to the genus Bifidobacterium also on account of its greater than 50 mol% G+C content. It is therefore no longer considered one of the lactic acid bacteria senso strictu, which form part of the Clostridium branch of the bacteria. The new genus Weissella has been established to include one member of the genus Leuconostoc (Leuc, paramesenteroides) and heterofermentative lactobacilli with unusual interpeptide bridges in the peptidoglycan. Contrary to the clear-cut division of the streptococci, morphological and physiological features of Weissella do not directly support this grouping which now incorporates species that produce D(-)- as well as DL-lactate. The new genus Carnobacterium is morphologically similar to the lactobacilli, but it shares some physiological similarities (e.g. growth at pH 9.5) and a common phylogenetic branch with the genus Enterococcus. The review includes information on the taxonomic changes and the relationship of the bacteria of food fermentation and spoilage.