Photobacterium histaminum Okuzumi et al. 1994 is a later subjective synonym of Photobacterium damselae subsp. damselae (Love et al. 1981) Smith et al. 1991

Potential for Scombroid Poisoning from Ingestion of Selar crumenophthalmus Due to Increased Histamine Levels in Grenada, West Indies

ABSTRACT

In scombroid poisoning, a seafood-associated disease, consumption of fish that contains high levels of histamine results in allergy-like symptoms that range from mild to occasionally severe. To date, there is no published information on scombroid poisoning from Selar crumenophthalmus on the Caribbean island of Grenada, West Indies. S. crumenophthalmus is of particular interest because it is a common and heavily consumed fish that has been implicated in scombroid poisoning in Hawaii. Preliminary data on S. crumenophthalmus in Grenada have demonstrated the presence of Photobacterium damselae, a bacterium associated with scombroid poisoning. The present study further tested S. crumenophthalmus purchased in Grenada for factors that would indicate the potential for scombroid poisoning, including increased histamine levels in fish muscle and DNA evidence of bacteria associated with scombroid poisoning. Histamine levels between 7,160 and 66,688 ppm were found after temperature abuse at 37°C for 19 h; this far exceeds the acceptable limit for the United States (50 ppm) and the European Union (100 to 200 ppm). Even after 4 h of incubation at ambient temperature (28.9°C) during a time-point study, histamine levels exceeded U.S. acceptable limits (>50 ppm), and five samples used for temperature-abuse studies had elevated histamine levels (ranging from 141 to 2,510 ppm) at 0 h. PCR and sequence analysis of bacteria in temperature-abused fish identified P. damselae and Morganella morganii, which are histamine-producing bacteria known to be implicated in scombroid poisoning. These results suggest the potential for scombroid poisoning in Grenada and the need for promoting awareness about this disease.

HIGHLIGHTS

Identification, Growth Profile and Probiotic Properties of Autochthonous Intestinal Bacteria of Sagor catfish (Hexanematichthys sagor)

　The prevalence of antibiotic resistant bacteria in aquaculture has reached alarming proportions and intensified the search for microbe derived antimicrobial compounds. This study isolated bacteria from the intestine of Sagor catfish (Hexanematichthys sagor) and screened it for antagonistic properties. Five out of 334 bacterial isolates inhibited growth of fish pathogens. The 5 bacterial strains included relatives of Shewanella haliotis, Myroides odoratimimus, Vibrio harveyi, Vibrio alginolyticus and Alcaligenes faecalis. The growth profiles and probiotic properties of these bacteria were examined. The results showed that the isolate 9 (3) 7.5.2.1, whose closest relative was S. haliotis exhibited growth and probiotic advantage compared to the other bacterial strains, such as highest doubling time and the ability to survive at all experimental temperatures (18 to 60℃) , and bile concentrations (0.01 to 1.00%) and pH (pH2 to 9) . While the bacteria with probiotic properties were successfully isolated. Further study is necessary to examine the efficiency of the probiotic candidate bacteria in boosting fish immunity against pathogens.

Description of New and Amended Clades of the Genus Photobacterium

Phylogenetic relationships between species in the genus Photobacterium have been poorly studied despite pathogenic and ecological relevance of some of its members. This is the first phylogenetic study that includes new species of Photobacterium (validated or not) that have not been included in any of the previously described clades, using 16S rRNA sequences and multilocus sequence analysis (MLSA) in concatenated sequences of gyrB, gapA, topA, ftsZ and mreB housekeeping genes. Sequence analysis has been implemented using Maximum-parsimony (MP), Neighbour-joining (NJ) and Maximum likelihood (ML) treeing methods and the predicted evolutionary relationship between the Photobacterium clades was established on the basis of bootstrap values of >75% for 16S rRNA sequences and MLSA. We have grouped 22 species of the genus Photobacterium into the following 5 clades: Phosphoreum (comprises P. aquimaris, “P. carnosum,” P. iliopiscarium, P. kishitanii, P. phosphoreum, “P. piscicola” and “P. toruni”); clade Profundum (composed of P. aestuarii, P. alginatilyticum, P. frigidiphilum, P. indicum, P. jeanii, P. lipolyticum, “P. marinum,” and P. profundum); clade Damselae (two subspecies of P. damselae, damselae and piscicida); and two new clades: clade Ganghwense (includes P. aphoticum, P. aquae, P. galatheae, P. ganghwense, P. halotolerans, P. panuliri and P. proteolyticum); and clade Leiognathi (composed by P. angustum, P. leiognathi subsp. leiognathi and “P. leiognathi subsp. mandapamensis”). Two additional clades, Rosenbergii and Swingsii, were formed using a phylogenetic method based on 16S rRNA gene, although they are not confirmed by any MLSA methods. Only P. aplysiae could not be included in none of the established clade, constituting an orphan clade.

The biology and the importance of Photobacterium species

Photobacterium species are Gram-negative coccobacilli which are distributed in marine habitats worldwide. Some species are unique because of their capability to produce luminescence. Taxonomically, about 23 species and 2 subspecies are validated to date. Genomes from a few Photobacterium spp. have been sequenced and studied. They are considered a special group of bacteria because some species are capable of producing essential polyunsaturated fatty acids, antibacterial compounds, lipases, esterases and asparaginases. They are also used as biosensors in food and environmental monitoring and detectors of drown victim, as well as an important symbiont.

Prevalence and Characterization of High Histamine-Producing Bacteria in Gulf of Mexico Fish Species

Recent developments in detection and enumeration of histamine-producing bacteria (HPB) have created powerful molecular-based tools to better understand the presence of spoilage bacteria and conditions, resulting in increased risk of scombrotoxin fish poisoning. We examined 235 scombrotoxin-forming fish from the Gulf of Mexico for the presence of high HPB. Photobacterium damselae subsp. damselae was the most prevalent HPB (49%), followed by Morganella morganii (14%), Enterobacter aerogenes (4%), and Raoultella planticola (3%). The growth characteristics and histamine production capabilities of the two most prevalent HPB were further examined. M. morganii and P. damselae had optimum growth at 35°C and 30 to 35°C and 0 to 2% and 1 to 3% NaCl, respectively. P. damselae produced significantly (P < 0.001) higher histamine than M. morganii in inoculated mahimahi and Spanish mackerel incubated at 30°C for 24 h, but histamine production was not significantly different between the two HPB in inoculated tuna, possibly due to differences in muscle composition and salt content. Results in this study showed that P. damselae was the most prevalent high HPB in Gulf of Mexico fish. In addition, previously reported results using the traditional Niven's method may underreport the prevalence of P. damselae. Molecular-based methods should be used in addition to culture-based methods to enhance detection and enumeration of HPB.

Photobacterium marinum sp. nov., a marine bacterium isolated from a sediment sample from Palk Bay, India

The novel, cream colored, Gram-staining-negative, rod-shaped, motile bacteria, designated strains AK15(T) and AK18, were isolated from sediment samples collected from Palk Bay, India. Both strains were positive for arginine dihydrolase, lysine decarboxylase, oxidase, nitrate reduction and methyl red test. The major fatty acids were C16:0, C18:1 ω7c, C16:1 ω7c and/or C16:1 ω6c and/or iso-C15:0 2-OH (summed feature 3). Polar lipids content of strains AK15(T) and AK18 were found to bephosphatidylethanolamine (PE), two unidentified phospholipids (PL1 and PL2) and three unidentified lipids (L1-L3). The 16S rRNA gene sequence analysis indicated strains AK15(T) and AK18 as the members of the genus Photobacterium and closely related to the type strain Photobacterium jeanii with pair-wise sequence similarity of 96.7%. DNA-DNA hybridization between strain AK15(T) and AK18 showed a relatedness of 87%. Based on data from the current polyphasic study, strains AK15(T) and AK18 are proposed as novel species of the genus Photobacterium, for which the name Photobacterium marinum sp. nov. is proposed. The type strain of Photobacterium marinum is AK15(T) (=MTCC 11066(T)=DSM 25368(T)).

Chemical screening method for the rapid identification of microbial sources of marine invertebrate-associated metabolites

Marine invertebrates have proven to be a rich source of secondary metabolites. The growing recognition that marine microorganisms associated with invertebrate hosts are involved in the biosynthesis of secondary metabolites offers new alternatives for the discovery and development of marine natural products. However, the discovery of microorganisms producing secondary metabolites previously attributed to an invertebrate host poses a significant challenge. This study describes an efficient chemical screening method utilizing a 96-well plate-based bacterial cultivation strategy to identify and isolate microbial producers of marine invertebrate-associated metabolites.

Phylogeny, genomics, and symbiosis of Photobacterium

Photobacterium comprises several species in Vibrionaceae, a large family of Gram-negative, facultatively aerobic, bacteria that commonly associate with marine animals. Members of the genus are widely distributed in the marine environment and occur in seawater, surfaces, and intestines of marine animals, marine sediments and saline lake water, and light organs of fish. Seven Photobacterium species are luminous via the activity of the lux genes, luxCDABEG. Much recent progress has been made on the phylogeny, genomics, and symbiosis of Photobacterium. Phylogenetic analysis demonstrates a robust separation between Photobacterium and its close relatives, Aliivibrio and Vibrio, and reveals the presence of two well-supported clades. Clade 1 contains luminous and symbiotic species and one species with no luminous members, and Clade 2 contains mostly nonluminous species. The genomes of Photobacterium are similar in size, structure, and organization to other members of Vibrionaceae, with two chromosomes of unequal size and multiple rrn operons. Many species of marine fish form bioluminescent symbioses with three Photobacterium species: Photobacterium kishitanii, Photobacterium leiognathi, and Photobacterium mandapamensis. These associations are highly, but not strictly species specific, and they do not exhibit symbiont-host codivergence. Environmental congruence instead of host selection might explain the patterns of symbiont-host affiliation observed from nature.

Dominance of Mycoplasma in the guts of the Long-Jawed Mudsucker, Gillichthys mirabilis, from five California salt marshes

We analysed the gut microflora of the Long-Jawed Mudsucker, Gillichthys mirabilis by polymerase chain reaction/denaturing gradient gel electrophoresis and cloning and sequencing 16S rRNA gene amplicons. Fish were collected at five sites in northern and southern California, USA. The gut microflora assemblages of all G. mirabilis were similar, very simple and dominated by one or more Mycoplasma ribotypes. Hindguts were dominated by Mycoplasmas that were most similar to a ribotype retrieved from Atlantic salmon guts. A Mycoplasma ribotype that was 95% similar to Mycoplasma mobile was the dominant in the foregut.

Evaluation of PCR-single-strand conformational polymorphism analysis for identification of gram-negative histamine-producing bacteria isolated from fish

In this study, the previously established PCR-single-strand conformation polymorphism (SSCP) system for detecting and identifying gram-negative histamine-producing bacteria was evaluated. This system can detect and identify histamine-producing bacteria directly from seafood by the use of sequence polymorphisms of the histidine decarboxylase gene (hdc). First, we isolated 81 histamine-producing strains of bacteria from fish samples and analyzed the hdc gene by the PCR-SSCP system. The 22 newly obtained SSCP banding patterns were added to our database, and the utility of our modified database was tested in a second experiment consisting of 18 strains of histamine-producing bacteria isolated from 25 fish samples. Approximately 80% of the histamine-producing strains corresponded to those in the new database. Use of the database for PCR-SSCP analysis, including the band patterns newly added in this study, for the hdc gene makes it possible to more accurately identify histamine producers.

Histidine decarboxylases and their role in accumulation of histamine in tuna and dried saury

Histamine-producing bacteria (HPB) such as Photobacterium phosphoreum and Raoultella planticola possess histidine decarboxylase (HDC), which converts histidine into histamine. Histamine fish poisoning (HFP) is attributable to the ingestion of fish containing high levels of histamine produced by HPB. Because freezing greatly decreases the histamine-producing ability of HPB, especially of P. phosphoreum, it has been speculated that HFP is caused by HDC itself from HPB cells autolyzing during frozen storage, even when HPB survive frozen storage. Here we constructed recombinant HDCs of P. phosphoreum, Photobacterium damselae, R. planticola, and Morganella morganii and investigated the ability of HDCs to produce sufficient histamine to cause HFP. To elucidate the character of these HDCs, we examined the specific activity of each recombinant HDC at various temperatures, pH levels, and NaCl concentrations. Further, we also investigated the stability of each HDC under different conditions (in reaction buffer, tuna, and dried saury) at various temperatures. P. damselae HDC readily produced sufficient histamine to cause HFP in fish samples. We consider that if HDC is implicated as an independent cause of HFP in frozen-thawed fish, the most likely causative agent is HDC of P. damselae.

Simultaneous detection of marine fish pathogens by using multiplex PCR and a DNA microarray

We coupled multiplex PCR and a DNA microarray to construct an assay suitable for the simultaneous detection of five important marine fish pathogens (Vibrio vulnificus, Listonella anguillarum, Photobacterium damselae subsp. damselae, Aeromonas salmonicida subsp. salmonicida, and Vibrio parahaemolyticus). The array was composed of nine short oligonucleotide probes (25-mer) complementary to seven chromosomal loci (cyt, rpoN, gyrB, toxR, ureC, dly, and vapA) and two plasmid-borne loci (fatA and A.sal). Nine primer sets were designed to amplify short fragments of these loci (100 to 177 bp) in a multiplex PCR. PCR products were subsequently labeled by nick translation and hybridized to the microarray. All strains of the five target species (n = 1 to 21) hybridized to at least one species-specific probe. Assay sensitivities ranged from 100% for seven probes to 83 and 67% for the two remaining probes. Multiplex PCR did not produce any nonspecific amplification products when tested against 23 related species of bacteria (n = 40 strains; 100% specificity). Using purified genomic DNA, we were able to detect PCR products with < 20 fg of genomic DNA per reaction (equivalent to four or five cells), and the array was at least fourfold more sensitive than agarose gel electrophoresis for detecting PCR products. In addition, our method allowed the tentative identification of virulent strains of L. anguillarum serotype O1 based on the presence of the fatA gene (67% sensitivity and 100% specificity). This assay is a sensitive and specific tool for the simultaneous detection of multiple pathogenic bacteria that cause disease in fish and humans.

Photobacterium phosphoreum caused a histamine fish poisoning incident

An incident of histamine fish poisoning (HFP) occurred due to the consumption of iwashi maruboshi (dried sardine) in Osaka, Japan in March 2002. A histamine-producing bacterial strain, YS4-7, was isolated from iwashi maruboshi that contained 1700 mg of histamine per kilogram. This strain was identified as Photobacterium phosphoreum by biochemical examinations and partial sequencing of 16S rDNA. P. phosphoreum YS4-7 showed greater capability as a histamine producer at 4 and 12 degrees C than Morganella morganii JCM 1672. Strain YS4-7 produced 546 mg of histamine per kilogram in a sardine homogenate stored for 12 h at 20 degrees C. M. morganii, Raoultella planticola and Hafnia alvei have been isolated from fish implicated in HFP incidents, whereas this is the first report of P. phosphoreum being the causative bacterium in a sporadic case of histamine food poisoning.

Cloning and sequencing of the histidine decarboxylase genes of gram-negative, histamine-producing bacteria and their application in detection and identification of these organisms in fish

The use of molecular tools for early and rapid detection of gram-negative histamine-producing bacteria is important for preventing the accumulation of histamine in fish products. To date, no molecular detection or identification system for gram-negative histamine-producing bacteria has been developed. A molecular method that allows the rapid detection of gram-negative histamine producers by PCR and simultaneous differentiation by single-strand conformation polymorphism (SSCP) analysis using the amplification product of the histidine decarboxylase genes (hdc) was developed. A collection of 37 strains of histamine-producing bacteria (8 reference strains from culture collections and 29 isolates from fish) and 470 strains of non-histamine-producing bacteria isolated from fish were tested. Histamine production of bacteria was determined by paper chromatography and confirmed by high-performance liquid chromatography. Among 37 strains of histamine-producing bacteria, all histidine-decarboxylating gram-negative bacteria produced a PCR product, except for a strain of Citrobacter braakii. In contrast, none of the non-histamine-producing strains (470 strains) produced an amplification product. Specificity of the amplification was further confirmed by sequencing the 0.7-kbp amplification product. A phylogenetic tree of the isolates constructed using newly determined sequences of partial hdc was similar to the phylogenetic tree generated from 16S ribosomal DNA sequences. Histamine accumulation occurred when PCR amplification of hdc was positive in all of fish samples tested and the presence of powerful histamine producers was confirmed by subsequent SSCP identification. The potential application of the PCR-SSCP method as a rapid monitoring tool is discussed.

Amplified fragment length polymorphism (AFLP) and biochemical typing of Photobacterium damselae subsp. damselae

AIMS

The aim of the present study was to characterize subspecifically Photobacterium damselae subsp. damselae strains isolated from cultured Sparus aurata and Dicentrarchus labrax by means of phenotypic and molecular typing techniques (amplified fragment length polymorphism, AFLP).

METHODS AND RESULTS

Seventy-one strains of P. damselae subsp. damselae were isolated from 38 cultured fishes at different fish farms located on the Mediterranean coast near Valencia, Spain. Most fish studied were asymptomatic and some were recovered during infectious outbreaks. Phenotypic characterization revealed a considerable degree of variability within the subspecies, including some characters, such as production of urease, which are used to differentiate P. damselae subsp. damselae from P. damselae subsp. piscicida. Genetic characterization was conducted on a selection of 33 strains, including two reference strains. Dice coefficient (Sd) and the unweighted pair group method with average linkage (UPGMA) were used for numerical analysis of banding patterns. AFLP type was defined on the basis of 100% similarity in the dendrogram obtained, yielding 24 distinct AFLP profiles. At 70% similarity, 13 clusters were defined, thus confirming the great variability observed for the phenotypic traits.

CONCLUSIONS

The AFLP variability shown by the isolates was high enough to discriminate between different strains which colonize the same fish. However, closely related AFLP types were usually derived from strains isolated at the same fish farm, indicating an epidemiological relationship.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study has confirmed that the AFLP technique allows discrimination of individual strains within P. damselae subsp. damselae for epidemiological studies, and that this subspecies exhibits greater variability than that described for subspecies piscicida.

Purification and properties of a histidine decarboxylase from Tetragenococcus muriaticus, a halophilic lactic acid bacterium

AIMS

A histidine decarboxylase from Tetragenococcus muriaticus, a halophilic histamine-producing bacterium isolated from Japanese fermented squid liver sauce, was purified to homogeneity, for the first time.

METHODS AND RESULTS

The enzyme was purified 16-fold from cell-free extract by ammonium sulphate precipitation, anion exchange chromatography and hydroxyapatite chromatography. The pure enzyme consisted of two polypeptide chains with molecular mass of 28.8 and 13.4 kDa. The N-terminal amino acid sequences of these polypeptides highly correlated with those of the alpha- and beta-chains of other Gram-positive bacterial histidine decarboxylases. The optimum and stable pH for the enzyme was 4.5-7.0 and 4.0-7.0, respectively. This enzyme did not decarboxylate lysine, arginine, tyrosine, tryptophan and ornithine. The enzyme activity decreased with the addition of NaCl. At pH 4.8, the Vmax and Km values were 16.8 micromol histamine min-1 mg-1 and 0.74 mmol l-1, respectively.

CONCLUSIONS

The very similar physiological properties of this enzyme and almost identical N-terminal amino acid sequences to those from other Gram-positive bacteria indicated that this enzyme may be evolutionally highly conserved among Gram-positive bacteria.

SIGNIFICANCE AND IMPACT OF THE STUDY

Information on this enzyme could be useful for studying the mechanism of histamine accumulation in salted foods. In addition, the N-terminal amino acid sequence can be utilized to design oligonucleotide probes, which may prove valuable in the rapid monitoring of halophilic histamine producers in salted products.

Genomic diversity amongst Vibrio isolates from different sources determined by fluorescent amplified fragment length polymorphism

The genomic diversity among 506 strains of the family Vibrionaceae was analysed using Fluorescent Amplified Fragments Length Polymorphisms (FAFLP). Isolates were from different sources (e.g. fish, mollusc, shrimp, rotifers, artemia, and their culture water) in different countries, mainly from the aquacultural environment. Clustering of the FAFLP band patterns resulted in 69 clusters. A majority of the actually known species of the family Vibrionaceae formed separate clusters. Certain species e.g. V. alginolyticus, V. cholerae, V. cincinnatiensis, V. diabolicus, V. diazotrophicus, V. harveyi, V. logei, V. natriegens, V. nereis, V. splendidus and V. tubiashii were found to be ubiquitous, whereas V. halioticoli, V. ichthyoenteri, V. pectenicida and V. wodanis appear to be exclusively associated with a particular host or geographical region. Three main categories of isolates could be distinguished: (1) isolates with genomes related (i.e. with > or =45% FAFLP pattern similarity) to one of the known type strains; (2) isolates clustering (> or =45% pattern similarity) with more than one type strain; (3) isolates with genomes unrelated (<45% pattern similarity) to any of the type strains. The latter group consisted of 236 isolates distributed in 31 clusters indicating that many culturable taxa of the Vibrionaceae remain as yet to be described.

Histamine formation by Tetragenococcus muriaticus, a halophilic lactic acid bacterium isolated from fish sauce

We examined histamine formation in cultures of Tetragenococcus muriaticus, a halophilic lactic acid bacterium isolated from fish sauce. T. muriaticus formed histamine in low acidity (pH 5.8), O2 limiting conditions with optimal NaCl and glucose concentrations of 5-7% (w/v) and above 1%, respectively. Histamine formation could not be prevented even at 20% (w/v) NaCl, indicating that NaCl could not prevent histamine formation by this bacterium. A conspicuous amount of histamine accumulated only during the late stationary phase regardless of the growth conditions. Studies of cell suspension experiments confirmed the results obtained from cultured cells.

The effect of biogenic amine production by single bacterial cultures and metabiosis on cold-smoked salmon

AIM

Biogenic amines are important indicators of spoilage in vacuum-packed cold-smoked salmon. It is the aim of this study to identify bacteria responsible for biogenic amine production in cold-smoked salmon.

METHODS AND RESULTS

The present study identified spoilage microflora from cold-smoked salmon and determined biogenic amine production of single and co-cultures growing in cold-smoked salmon. Photobacterium phosphoreum was the only species that produced histamine when inoculated on sterile cold-smoked salmon. Production of putrescine was enhanced 10-15 times when cultures of Serratia liquefaciens or Hafnia alvei were grown with Carnobacterium divergens or Lactobacillus sakei subsp. carnosus. This phenomenon was explained by interspecies microbial metabolism of arginine, i.e., metabiosis.

CONCLUSIONS

The amounts of biogenic amines produced by single and co-cultures corresponded to those observed during spoilage of naturally-contaminated cold-smoked salmon. Photobacterium phosphoreum and Lact. curvatus were identified as the specific spoilage organisms in cold-smoked salmon.

SIGNIFICANCE AND IMPACT OF THE STUDY

Determination of the specific spoilage organism is needed before a model can be developed for shelf-life predictions of cold-smoked salmon.