Histamine and biogenic amine production by Morganella morganii isolated from temperature-abused albacore

Histamine-producing bacteria and their role in gastrointestinal disorders

INTRODUCTION

Gut microbiota produces thousands of metabolites, which have a huge impact on the host health. Specific microbial strains are able to synthesize histamine, a molecule with a crucial role in many physiologic and pathologic mechanisms of the host. This function is mediated by the histidine decarboxylase enzyme (HDC) that converts the amino acid histidine to histamine.

AREAS COVERED

This review summarizes the emerging data on histamine production by gut microbiota, and the effect of bacterial-derived histamine in different clinical contexts, including cancer, irritable bowel syndrome, and other gastrointestinal and extraintestinal pathologies. This review will also outline the impact of histamine on the immune system and the effect of probiotics that can secrete histamine. Search methodology: we searched the literature on PubMed up to February 2023.

EXPERT OPINION

The potential of modulating gut microbiota to influence histamine production is a promising area of research, and although our knowledge of histamine-secreting bacteria is still limited, recent advances are exploring their diagnostic and therapeutical potential. Diet, probiotics, and pharmacological treatments directed to the modulation of histamine-secreting bacteria may in the future potentially be employed in the prevention and management of several gastrointestinal and extraintestinal disorders.

Detection, Identification, and Inactivation of Histamine-forming Bacteria in Seafood: A Mini-review

Seafood is one of the essential sources of nutrients for the human diet. However, they can be subject to contamination and can cause foodborne illnesses, including scombroid fish poisoning caused by histamine. Many microorganisms can produce enzymes that eventually decompose endogenous histidine to histamine in postmortem fish muscles and tissues. One of these is histamine-forming bacteria (HFB), primarily found in the gills, gut, and skin of fishes. Previous studies linked a plethora of Gram-negative HFB including Morganella spp. and Photobacterium spp. to scombroid fish poisoning from many types of seafood, especially the Scombridae family. These bacteria possess the hdc gene to produce histidine decarboxylase enzyme. It was reported that Gram-negative HFB produced 6345 ppm in tuna and 1223 ppm in Spanish mackerel. Interestingly, Gram-positive HFB have been isolated in the seafood samples with lower histamine levels. It suggests that Gram-negative HFB are the major contributor to the accumulation of histamine in seafood. Several analytical methods are available to detect and identify HFB and their histamine metabolites from seafood substrates. Rapid test kits can be used in food production settings for early detection of histamine to avoid food intoxication. Furthermore, high hydrostatic pressure and irradiation treatment could prevent the proliferation of HFB and inactivate the existing histidine decarboxylase (HDC) activity. As demonstrated in different seafood model systems, the HDC activity was deactivated at a maximum high hydrostatic pressure level of 400 MPa. The complete inactivation of HFB was achieved by gamma irradiation at a dose of 4.0 kGy. Other postharvest treatments, like enzymatic degradation and electrolyzed oxidizing water, were studied as sustainable methods for bacterial growth prevention and enzyme inactivation. However, other HFB react differently to these treatment conditions, and further studies are recommended.

Influence of polyamine production and proteolytic activities of co-cultivated bacteria on histamine production by Morganiella morganii

Consumption of temperature-abused marine fish containing elevated levels of histamine results in histamine poisoning. Histamine is a biogenic amine produced in fish by the action of certain groups of bacteria which are capable of producing an exogenous enzyme called histidine decarboxylase (HDC). Morganella morganii is one of the major causative organisms of histamine poisoning. In this study, the histamine forming potential of M. morganii (BSS142) was evaluated when it was co-incubated with proteolytic as well as polyamine forming bacteria. This experiment was designed to examine whether biotic factors such as proteolysis and the presence of other amines influenced histamine forming ability of BSS142. The study showed that the proteolytic activity of Aeromonas hydrophila as well as Pseudomonas aeruginosa greatly enhanced the histamine forming ability of M. morganii. Psychrobacter sangunis, a non proteolytic polyamine producer, negatively influenced histamine production by M. morganii.

Molecular Mechanisms of Scombroid Food Poisoning

Scombroid food poisoning (SFP) is a foodborne disease that develops after consumption of fresh fish and, rarely, seafood that has fine organoleptic characteristics but contains a large amount of exogenous histamine. SFP, like other food pseudo-allergic reactions (FPA), is a disorder that is clinically identical to allergic reactions type I, but there are many differences in their pathogenesis. To date, SFP has been widespread throughout the world and is an urgent problem, although exact epidemiological data on incidence varies greatly. The need to distinguish SFP from true IgE-associated allergy to fish and seafood is one of the most difficult examples of the differential diagnosis of allergic conditions. The most important difference is the absence of an IgE response in SFP. The pathogenesis of SFP includes a complex system of interactions between the body and chemical triggers such as exogenous histamine, other biogenic amines, cis-urocanic acid, salicylates, and other histamine liberators. Because of the wide range of molecular pathways involved in this process, it is critical to understand their differences. This may help predict and prevent poor outcomes in patients and contribute to the development of adequate hygienic rules and regulations for seafood product safety. Despite the vast and lengthy history of research on SFP mechanisms, there are still many blank spots in our understanding of this condition. The goals of this review are to differentiate various molecular mechanisms of SFP and describe methods of hygienic regulation of some biogenic amines that influence the concentration of histamine in the human body and play an important role in the mechanism of SFP.

Prevalence of Histamine-Forming Bacteria in Two Kinds of Salted Fish at Town Markets of Guangdong Province of South China

ABSTRACT

Histamine-forming bacteria (HFB) were isolated from the 70 salted fish samples bought from town markets of Guangdong Province of south China. In addition, the histamine-forming ability of HFB was analyzed. There were 31 strains of HFB isolated from 36 salted fish pickled overnight. They were identified as six bacteria species: Vibrio alginolyticus, Vibrio rumoiensis, Staphylococcus saprophyticus, Staphylococcus xylosus, Lactococcus lactis, and Morganella morganii. The rate of confirmation of V. alginolyticus was highest (23 of 31), exceeding 200 mg/kg histamine. In particular, M. morganii produced a histamine amount that exceeded 2,000 mg/kg, although it was only one isolate in this study. In addition, five bacteria species of HFB were isolated from 34 dried salted fish. Among them, S. saprophyticus was dominant in the dried salted fish but produced histamines below 200 mg/kg. However, Enterobacter aerogenes from dried salted fish formed a histamine amount exceeding 200 mg/kg. The study showed that the dominant strain of HFB was different in two kinds of salted fish. Both kinds of salted fish contained HFB whose histamine-forming capacity exceeded 200 mg/kg. As a result, the safety of salted fish should be of concern, especially salted fish pickled overnight.

HIGHLIGHTS

Modelling growth and histamine formation of Klebsiella aerogenes TI24 isolated from Indonesian pindang

Indonesian salted-boiled fish (pindang) is a popular traditional food in Indonesia, which is made from Scombroid fish such as tuna and mackerel. As with other traditionally prepared fish products, pindang has important economic and social values, especially for those living in the coastal areas of Indonesia. However, pindang is a major cause of histamine fish poisoning (HFP) for consumers. Klebsiella aerogenes T124, a relatively high histamine-producing isolate from pindang, was used to describe lag time (λ), growth rate (μ_max), maximum population density (N_max), and histamine production in histidine broth and artificially contaminated Grey mackerel. Broth was adjusted to 1.5, 6, 10 and 20% w/v NaCl; mackerel was treated with 6% w/w NaCl, a level common to Indonesian industry practice, or not treated with additional NaCl. Samples were incubated at 10, 15, 20 and 30 °C. In broth, μ_max and N_max were significantly affected by temperature and NaCl, respectively, with λ influenced by both parameters. In control fish, μ_max was significantly affected by temperature and NaCl, except at 10 and 15 °C; for 6% NaCl treatment, growth was only observed at 20 and 30 °C. Under similar incubation conditions for broth and fish, histamine formation was markedly affected by NaCl concentration. In broth, -5.1 to -6.6 log μg of histamine was produced per CFU, versus -4.6 to -6.6 log μg per CFU in fish. This study demonstrated that mackerel treated with 6% NaCl and stored at 10-15 °C prevents growth of K. aerogenes strain TI24 and formation of toxic levels of histamine.

Effect of organic acids on the formation of biogenic amines in fermented anchovy sauce comprising raw anchovy materials with different levels of freshness

We investigated the effect of different levels of organic acids on the formation of biogenic amines in anchovy fish sauce. Fish sauce samples were prepared with fresh anchovies used immediately after being caught (F), and anchovies left at ambient temperature for 4 h (4 h), 18 h (18 h), or 24 h (24 h). Anchovies from each of the four groups were mixed with salt at a 4:1 ratio and then fermented at ambient temperature for varying periods of time. The F and 4 h anchovies contained higher levels of acetic acid, succinic acid, and lactic acid, and the levels increased during the fermentation process. The histamine content of the fish sauce samples prepared using F anchovies ranged from 44.0 to 9.2 mg/kg at 1 and 24 months of fermentation. The histamine content of fish sauce samples prepared using 4 h, 18 h, and 24 h anchovies was 111.5-37.0 mg/kg (4 h), 780.1-560.3 mg/kg (18 h), and 880.6-675.7 mg/kg (24 h). Our findings indicated that the histamine and other biogenic amine levels were closely associated with the degree of freshness of the raw anchovy material. These findings indicate that lower pH levels resulting from organic acids generated by the fresh raw material can effectively inhibit histamine formation.

Chemical-Based Methodologies to Extend the Shelf Life of Fresh Fish-A Review

Due to its characteristics, fresh fish is a highly perishable food with a very short shelf-life under refrigeration. Several methods have been introduced to slow down its deterioration, such as by means of oxygen depletion of the food package (vacuum packaging), or by changing the natural atmosphere that is in contact with the fresh fish (modified atmosphere packaging), or by the use of chemicals generally recognized as safe: such compounds can be directly applied (by dipping or spraying) or incorporated into packaging materials and slowly migrate to the product, exerting a hurdle effect against microbial development and lipid oxidation (active packaging). This review aims to cover the most recent advances in chemical-based approaches for fresh fish preservation, applied either singly or in combination. Vacuum packaging, modified atmosphere, and active packaging preservation methodologies are presented, along with the inclusion of chemical additives, such as organic acids and natural extracts, and their combination with icing systems. Advantages and disadvantages of these methodologies and their impact on fresh fish quality and shelf-life are discussed, reaching the conclusion that both are positively influenced overall. Indeed, the contribution of chemical-based strategies for fresh fish preservation is undeniable, and is expected to be a research topic of increasing interest in the future.

Neuro-Signals from Gut Microbiota: Perspectives for Brain Glioma

Glioblastoma (GBM) is the most aggressive form of glioma tumor in adult brain. Among the numerous factors responsible for GBM cell proliferation and invasion, neurotransmitters such as dopamine, serotonin and glutamate can play key roles. Studies performed in mice housed in germ-free (GF) conditions demonstrated the relevance of the gut-brain axis in a number of physiological and pathological conditions. The gut-brain communication is made possible by vagal/nervous and blood/lymphatic routes and pave the way for reciprocal modulation of functions. The gut microbiota produces and consumes a wide range of molecules, including neurotransmitters (dopamine, norepinephrine, serotonin, gamma-aminobutyric acid [GABA], and glutamate) that reach their cellular targets through the bloodstream. Growing evidence in animals suggests that modulation of these neurotransmitters by the microbiota impacts host neurophysiology and behavior, and affects neural cell progenitors and glial cells, along with having effects on tumor cell growth. In this review we propose a new perspective connecting neurotransmitter modulation by gut microbiota to glioma progression.

Fresh Fish Degradation and Advances in Preservation Using Physical Emerging Technologies

Fresh fish is a highly perishable food characterized by a short shelf-life, and for this reason, it must be properly handled and stored to slow down its deterioration and to ensure microbial safety and marketable shelf-life. Modern consumers seek fresh-like, minimally processed foods due to the raising concerns regarding the use of preservatives in foods, as is the case of fresh fish. Given this, emergent preservation techniques are being evaluated as a complement or even replacement of conventional preservation methodologies, to assure food safety and extend shelf-life without compromising food safety. This paper reviews the main mechanisms responsible for fish spoilage and the use of conventional physical methodologies to preserve fresh fish, encompassing the main effects of each methodology on microbiological and chemical quality aspects of this highly perishable food. In this sense, conventional storage procedures (refrigeration and freezing) are counterpointed with more recent cold-based storage methodologies, namely chilling and superchilling. In addition, the use of novel food packaging methodologies (edible films and coatings) is also presented and discussed, along with a new storage methodology, hyperbaric storage, that states storage pressure control to hurdle microbial development and slow down organoleptic decay at subzero, refrigeration, and room temperatures.

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

Search for Substances That Inhibit Histamine Production Using Used Tea Leaves

ABSTRACT

As food waste has become a major problem in recent years, measures against food loss have become an urgent issue. When manufacturing or making green tea beverages, large quantities of tea leaves are subsequently disposed of, which results in potential food loss. Moreover, because many of the tea components remain in the used tea leaves, these continue to have value, as these leaves exhibit antibacterial action. Furthermore, histamine is produced from histidine via histidine decarboxylase that is produced by microorganisms, with histamine accumulation potentially causing histamine food poisoning. Although we have been trying to develop a simple method for detecting histamine, there has yet to be a quick detection method established. We examined whether a method using a low concentration of bromocresol indicator in the culture medium was capable of rapidly detecting histamine. Our results demonstrated that when using lower indicator concentrations, there was a faster detection of histamine production, within 4 h. Using this method, we also investigated whether used tea leaf components, which have antibacterial effects, could suppress histamine production. In this study, used leaves from green, oolong, and black teas were analyzed according to different extraction processes. Compared with green tea, oolong and black teas were able to suppress histamine production using lower concentrations, 25 and 12.5% extracts, respectively. In contrast, the inhibitory effect on histamine production by used green tea leaves required a high concentration of 50% used tea leaf extracts. Furthermore, our results suggested that used tea leaves suppress histamine production and that the inhibitory effects vary according to different extracts. Based on these findings, we propose that (i) a more rapid detection method for histamine should be established and (ii) used tea leaf extracts may have applications in the storage and processing of foods associated with an undesirable production of histamine.

HIGHLIGHTS

Characterization of a novel enzyme from Photobacterium phosphoreum with histidine decarboxylase activity

Histamine or scombrotoxin fish poisoning is caused by ingestion of bacterially produced histamine in fish. Histamine-producing bacteria generally contain the histidine decarboxylase gene (hdc). However, some strains of Photobacterium phosphoreum are known to produce significant levels of histamine, although the hdc gene in these strains has not been recognized. The objective of this study was to investigate a previously unidentified mechanism of histamine production by P. phosphoreum. We identified a protein with histidine decarboxylase (HDC) activity comparable to activity of the pyridoxal-5-phosphate (PLP) dependent HDC from P. kishitanii and M. morganii. The newly identified protein (HDC2) in P. phosphoreum and P. kishitanii strains, was approximately 2× longer than the HDC protein from other Gram-negative bacteria and had 12% similarity to previously identified HDCs. In addition, the hdc2 gene cluster in P. phosphoreum was identical to the hdc gene cluster in P. kishitanii. HDC2 had optimal activity at 20-35 °C, at pH 4, and was not affected by 0-8% NaCl concentrations. Compared to the hdc gene from P. kishitanii, expression of the hdc2 gene was constitutive and not affected by pH or excess histidine. This newly identified protein explains possible mechanisms of histamine production in P. phosphoreum. Characterization of this protein will help in designing control measures to prevent or reduce histamine production in fish.

Survival and Histamine Production by Histamine-Forming Bacteria Exposed to Low Doses of Gamma Irradiation

ABSTRACT

Histamine poisoning occurs when fish containing high amount of histamine are consumed. Because histamine is thermally stable, control of histamine-forming bacteria in seafood is an appropriate strategy for preventing the formation of histamine. One prevention method is the use of gamma irradiation on the histamine formers. To understand the effect of gamma irradiation on the histamine-forming bacteria, laboratory isolates of the prolific histamine formers Morganella morganii, Klebsiella variicola, and Proteus vulgaris were exposed to various doses of gamma radiation in nutrient broth and tuna muscle spiked with histamine formers. None of the test bacteria survived in tuna muscle irradiated at 2.0 kGy. K. variicola was highly sensitive to gamma irradiation and was eliminated at a dose of 1.5 kGy. Histamine production also was reduced significantly as the radiation dose increased. These results suggest that gamma irradiation can effectively eliminate histamine-forming bacteria and reduce the threat of histamine poisoning from seafood.

HIGHLIGHTS

The use of the so-called 'tubs' for transporting and storing fresh fishery products

On-land transport/storage of fresh fishery products (FFP) for up to 3 days in 'tubs' of three-layered poly-ethylene filled with freshwater and ice was compared to the currently authorised practice (fish boxes of high-density poly-ethylene filled with ice). The impact on the survival and growth of biological hazards in fish and the histamine production in fish species associated with a high amount of histidine was assessed. In different modelling scenarios, the FFP are stored on-board in freshwater or seawater/ice (in tubs) and once on-land they are 'handled' (i.e. sorted or gutted and/or filleted) and transferred to either tubs or boxes. The temperature of the FFP was assumed to be the most influential factor affecting relevant hazards. Under reasonably foreseeable 'abusive' scenarios and using a conservative modelling approach, the growth of the relevant hazards (i.e. Listeria monocytogenes, Aeromonas spp. and non-proteolytic Clostridium botulinum), is expected to be < 0.2 log10 units higher in tubs than in boxes after 3 days when the initial temperature of the fish is 0°C ('keeping' process). Starting at 7°C ('cooling-keeping' process), the expected difference in the growth potential is higher (< 1 log10 for A. hydrophila and < 0.5 log10 for the other two hazards) due to the poorer cooling capacity of water and ice (tub) compared with ice (box). The survival of relevant hazards is not or is negligibly impacted. Histamine formation due to growth of Morganella psychrotolerans under the 'keeping' or 'cooling-keeping' process can be up to 0.4 ppm and 1.5 ppm higher, respectively, in tubs as compared to boxes after 3 days, without reaching the legal limit of 100 ppm. The water uptake associated with the storage of the FFP in tubs (which may be up to 6%) does not make a relevant contribution to the differences in microbial growth potential compared to boxes.

Occurrence of Histamine in Canned Fish Samples (Tuna, Sardine, Kilka, and Mackerel) from Markets in Tehran

Food poisoning is one of the most addressed health issues and has raised notable concerns. Histamine is the biogenic amine responsible for scombroid poisoning, which is due to the histidine decarboxylation by bacterial decarboxylases in various types of fish and fish products. The present investigation was conducted to measure the concentration of histamine in canned fish samples of tuna in oil (n = 18), tuna in oil with vegetables (n = 15), tuna in brine (n = 9), kilka in oil (n = 9), sardine in oil (n = 3), and mackerel in oil (n = 6) collected from markets in Tehran, Iran. Histamine concentrations were determined with a high-performance liquid chromatography device equipped with a UV detector. For method validation, the correlation coefficient (R²), recovery percentage, relative standard deviation for repeatability, limit of detection, and limit of quantification were 0.99, 82%, 1.3%, 1.5 mg/kg, and 5 mg/kg, respectively. Histamine was detected in 46.6% of the samples, and 18.3% of samples exceeded the histamine limit stipulated by the U.S. Food and Drug Administration (50 mg/kg). The overall mean histamine concentration was 17.36 ± 15.44 mg/kg, with a range of 0 to 88 mg/kg. A significant difference in histamine concentration was found between canned tuna in oil and canned tuna in brine (P < 0.05). However, no significant difference in histamine concentration was found among samples of canned tuna in brine, canned sardine in oil, canned kilka in oil, and canned mackerel in oil. Because of the high histamine concentrations detected in some brands of Iranian canned tuna, precise control programs, hazard analysis critical control point systems, and good hygiene practices should be implemented.

Phylogeography and Ecological Niche Shape the Cichlid Fish Gut Microbiota in Central American and African Lakes

Cichlid fishes, with their repeated colonization of lakes and subsequent radiations at different scales of phylogenetic and ecological diversification, offer an excellent model system to understand the factors shaping the host-gut microbiota association in nature. Here, we characterized the gut microbiota of the Amphilophus species complex from Central America (known as the Midas cichlid complex), encompassing 158 wild specimens (13 species) collected from seven Nicaraguan lakes, and combined these data with previously published data from two African lakes (spanning 29 species). Our aim was to comprehensively explore trends in microbiota variation and persistence along the large spatial and temporal scales of cichlid diversification (from the oldest radiation in L. Tanganyika, 9-12 My old, to young ones in Nicaraguan crater lakes, <0.5 My old), in allopatry and sympatry (within and across lakes), and across the range of dietary niches (from highly specialized to generalist feeders). Despite their extraordinary diversity, cichlids shared a remarkably conserved microbial taxonomic profile, which argues for a primary role of the host genetics in the assembly and maintenance of these microbial communities. Within this partly constrained microbiota profile, geographic isolation (continent and lake) represented the first level of discrimination. For the Midas cichlid, a partial congruency was found between host microbiota and genetic distances, suggesting that microbial communities have partly diversified along their cichlid phylogeographic history of crater lake colonization. In sympatry (within lakes), the young and poorly ecologically diversified cichlid assemblages of Central American lakes display largely unresolved gut microbiotas (in terms of both alpha and beta diversities), whereas the phylogenetically and ecologically diverse species found in African lakes showed greater microbial interspecific diversity. This pattern largely points to the level of habitat segregation, trophic niche overlap, and reproductive barriers as major modulators of the gut microbiota connectivity among sympatric species.

The Microbiota-Gut-Brain Axis

The importance of the gut-brain axis in maintaining homeostasis has long been appreciated. However, the past 15 yr have seen the emergence of the microbiota (the trillions of microorganisms within and on our bodies) as one of the key regulators of gut-brain function and has led to the appreciation of the importance of a distinct microbiota-gut-brain axis. This axis is gaining ever more traction in fields investigating the biological and physiological basis of psychiatric, neurodevelopmental, age-related, and neurodegenerative disorders. The microbiota and the brain communicate with each other via various routes including the immune system, tryptophan metabolism, the vagus nerve and the enteric nervous system, involving microbial metabolites such as short-chain fatty acids, branched chain amino acids, and peptidoglycans. Many factors can influence microbiota composition in early life, including infection, mode of birth delivery, use of antibiotic medications, the nature of nutritional provision, environmental stressors, and host genetics. At the other extreme of life, microbial diversity diminishes with aging. Stress, in particular, can significantly impact the microbiota-gut-brain axis at all stages of life. Much recent work has implicated the gut microbiota in many conditions including autism, anxiety, obesity, schizophrenia, Parkinson’s disease, and Alzheimer’s disease. Animal models have been paramount in linking the regulation of fundamental neural processes, such as neurogenesis and myelination, to microbiome activation of microglia. Moreover, translational human studies are ongoing and will greatly enhance the field. Future studies will focus on understanding the mechanisms underlying the microbiota-gut-brain axis and attempt to elucidate microbial-based intervention and therapeutic strategies for neuropsychiatric disorders.

A Forward Chemical Genetic Screen Reveals Gut Microbiota Metabolites That Modulate Host Physiology

The intestinal microbiota produces tens of thousands of metabolites. Here, we used host sensing of small molecules by G-protein coupled receptors (GPCRs) as a lens to illuminate bioactive microbial metabolites that impact host physiology. We screened 144 human gut bacteria against the non-olfactory GPCRome and identified dozens of bacteria that activated both well-characterized and orphan GPCRs, including strains that converted dietary histidine into histamine and shaped colonic motility; a prolific producer of the essential amino acid L-Phe, which we identified as an agonist for GPR56 and GPR97; and a species that converted L-Phe into the potent psychoactive trace amine phenethylamine, which crosses the blood-brain barrier and triggers lethal phenethylamine poisoning after monoamine oxidase inhibitor administration. These studies establish an orthogonal approach for parsing the microbiota metabolome and uncover multiple biologically relevant host-microbiota metabolome interactions.

Histamine Content in Rennet Ripening Cheeses During Storage at Different Temperatures and Times

Introduction

In recent years, there has been a great interest in biogenic amines such histamine, as they are associated with the quality and safety of some kinds of fermented foods. The aim of this study was to evaluate the effect of temperature and storage time on the content of histamine in cheeses.

Material and Methods

Samples of mould and hard cheeses were examined with RP-HPLC with an organic-aqueous mobile phase containing acidic buffer and chaotropic salt. The samples were stored either at 22 ± 2°C for 42 days (mould and hard cheeses) or at 4 ± 2°C for 112 days (mould cheeses) and 133 days (hard cheeses).

Results

The mean total histamine content in cheeses stored at 22°C was higher than the content in those stored at 4°C, with the highest concentrations found in Gorgonzola Piccante cheese (730.47 mg/kg). Histamine concentration in some types of cheeses exceeded the toxic threshold dose, indicating that after long or inadequately cool storage they may not be safe for consumers.

Conclusion

To protect cheeses from contamination with histamine-producing bacteria and to safeguard consumers from poisoning, factors conducive to this amine's formation should be minimised during cheese processing. Suitable temperature and time during storage of cheeses are recommended to avoid the intoxication. Monitoring of this toxin in food is necessary to ensure safety of consumers.

Histamine content in rennet ripening cheeses during storage at different temperatures and times

Introduction

In recent years, there has been a great interest in biogenic amines such histamine, as they are associated with the quality and safety of some kinds of fermented foods. The aim of this study was to evaluate the effect of temperature and storage time on the content of histamine in cheeses.

Material and Methods

Samples of mould and hard cheeses were examined with RP-HPLC with an organic-aqueous mobile phase containing acidic buffer and chaotropic salt. The samples were stored either at 22 ± 2°C for 42 days (mould and hard cheeses) or at 4 ± 2°C for 112 days (mould cheeses) and 133 days (hard cheeses).

Results

The mean total histamine content in cheeses stored at 22°C was higher than the content in those stored at 4°C, with the highest concentrations found in Gorgonzola Piccante cheese (730.47 mg/kg). Histamine concentration in some types of cheeses exceeded the toxic threshold dose, indicating that after long or inadequately cool storage they may not be safe for consumers.

Conclusion

To protect cheeses from contamination with histamine-producing bacteria and to safeguard consumers from poisoning, factors conducive to this amine’s formation should be minimised during cheese processing. Suitable temperature and time during storage of cheeses are recommended to avoid the intoxication. Monitoring of this toxin in food is necessary to ensure safety of consumers.

Histamina e rastreamento de pescado: revisão de literatura

A preocupação com a qualidade do pescado sempre foi um tema recorrente, visto que é um alimento de alto valor nutricional para toda população, porém com grande susceptibilidade à deterioração e formação de substâncias prejudiciais ao homem, caso não sejam obedecidas as condições de conservação. Um exemplo de substância formada é a histamina, uma diamina biogênica primária e heterocíclica, não volátil, termoestável, originada pela descarboxilação da L-histidina, quando as condições de manuseio e estocagem são inadequadas, favorecendo a multiplicação da microbiota natural do pescado. A histamina possui potencial alergênico, podendo causar um quadro de intoxicação no ser humano e, em casos graves, levar à morte. Para tal problema, um sistema de rastreabilidade poderia ser a solução. Seu objetivo é garantir ao consumidor um produto seguro e saudável por meio do controle de todas as fases da produção, industrialização, distribuição e comercialização, possibilitando uma perfeita correlação entre o produto final e a matéria-prima que lhe deu origem. Em diversos países existem atualmente sistemas de rastreabilidade controlando a cadeia de pescado. No Brasil, vários entraves podem ser apontados para a não obrigatoriedade da rastreabilidade em pescado. A divisão de regulamentação do setor entre diferentes órgãos, tais como Ministério da Pesca e Aquicultura (MPA), Ministério da Agricultura, Pecuária e Abastecimento (MAPA) e a Agência Nacional de Vigilância Sanitária (ANVISA), a falta de articulação entre esses órgãos fiscalizadores, a baixa capacitação de mão de obra e a desvalorização dos produtos da pesca, o que trazem a descapitalização da base da cadeia produtiva. De tal maneira, pode-se afirmar que há uma série de desafios para que ocorra a implantação de um sistema de rastreabilidade em território nacional. De acordo com o exposto, este estudo objetivou, através de uma revisão bibliográfica sistemática da literatura, informar a situação atual da escombrotoxicose e da rastreabilidade da histamina em pescado.

Storage Time and Temperature Effects on Histamine Production in Tuna Salad Preparations

Scombrotoxin fish poisoning (SFP), also known as histamine (Hst) poisoning, has been associated with consumption of scombroid-type fish, including tuna and tuna fish products. Preparation of commercial tuna salad contaminated with Hstproducing bacteria (HPB), combined with time-temperature abuse, can present a food safety hazard. A potential source of HPB is raw ingredients, such as celery and onions. The objectives of this study were to determine whether raw ingredients can be a source of HPB and to ascertain the effects of storage time (up to 4 days or 4 weeks) and temperature (4, 10, 18, 25, 30°C) on growth and Hst production by high-HPB (>1,000 ppm of Hst) in tuna salad preparations. Pantoea-Erwinia, Erwinia persicinus, Erwinia spp., and Enterobacter pyrinus isolated from celery in this study were used to inoculate tuna salad and tuna salad with celery or onion. HPB numbers were 0.7 to 4.3 log most probable number per g higher in the presence of celery or onion versus plain tuna salad (3:1 tuna:mayonnaise). E. pyrinus-inoculated plain tuna salad and tuna salad with celery and onion had >500 ppm of Hst after 2 days at 30°C and 4 days at 25°C. E. pyrinus-inoculated salad with celery and onion had >500 ppm of Hst after 4 days at 18°C and 2 weeks at 10°C. Raw celery can introduce HPB into tuna salad, which can cause SFP if the product is time-temperature abused. Tuna salad products must be refrigerated at ≤4°C to prevent growth and Hst production by the HPB used in this study, to protect consumers from potential SFP.

Heat resistance of histamine-producing bacteria in irradiated tuna loins

Consumption of foods high in biogenic amines leads to an illness known as histamine, or scombrotoxin, poisoning. The illness is commonly associated with consumption of fish with high levels of histamine ( $ 500 ppm). The objective of this study was to determine and compare the heat resistance of five histamine-producing bacteria in irradiated albacore tuna loins. Heat-resistance parameters (D- and z-values) were determined for Morganella morganii, Raoultella planticola, Hafnia alvei, and Enterobacter aerogenes. D- or z-values were not determined for Photobacterium damselae, which was the most heat-sensitive organism in this study. P. damselae declined > 5.9 log CFU/g after a heat treatment of 50°C for 10 min, 54°C for 3 min, and 56°C for 0.5 min. M. morganii was the most heat-resistant histamine-producing bacteria in albacore tuna loins, followed by E. aerogenes, H. alvei, and R. planticola. M. morganii and E. aerogenes had the highest D(50°C), 49.7 ± 17.57 and 51.8 ± 17.38 min, respectively. In addition, M. morganii had the highest D-values for all other temperatures (54, 56, and 58°C) tested. D- and zvalues were also determined for M. morganii in skipjack tuna. While no significant (P > 0.05) difference was observed between D(54°C) and D(56°C) of M. morganii in either albacore or skipjack tuna, the D(58°C) (0.4 ± 0.17 min) was significantly lower (P < 0.05) in skipjack than in albacore (0.9 ± 0.24 min). The z-values for all organisms tested were in the range of 3.2 to 3.8°C. This study suggests that heat treatment designed to control M. morganii in tuna loins is sufficient for controlling histamine-producing bacteria in canned-tuna processing environments.

Scombroid poisoning: a review

Scombroid poisoning, also called histamine fish poisoning, is an allergy-like form of food poisoning that continues to be a major problem in seafood safety. The exact role of histamine in scombroid poisoning is not straightforward. Deviations from the expected dose-response have led to the advancement of various possible mechanisms of toxicity, none of them proven. Histamine action levels are used in regulation until more is known about the mechanism of scombroid poisoning. Scombroid poisoning and histamine are correlated but complicated. Victims of scombroid poisoning respond well to antihistamines, and chemical analyses of fish implicated in scombroid poisoning generally reveal elevated levels of histamine. Scombroid poisoning is unique among the seafood toxins since it results from product mishandling rather than contamination from other trophic levels. Inadequate cooling following harvest promotes bacterial histamine production, and can result in outbreaks of scombroid poisoning. Fish with high levels of free histidine, the enzyme substrate converted to histamine by bacterial histidine decarboxylase, are those most often implicated in scombroid poisoning. Laboratory methods and screening methods for detecting histamine are available in abundance, but need to be compared and validated to harmonize testing. Successful field testing, including dockside or on-board testing needed to augment HACCP efforts will have to integrate rapid and simplified detection methods with simplified and rapid sampling and extraction. Otherwise, time-consuming sample preparation reduces the impact of gains in detection speed on the overall analysis time.

Histamine, cadaverine, and putrescine produced in vitro by enterobacteriaceae and pseudomonadaceae isolated from spinach

A total of 364 bacterial isolates, obtained from spinach leaves, were assayed in a decarboxylase broth containing histidine, lysine, and ornithine to check their ability to produce biogenic amines, and then quantified by high-performance liquid chromatography. Among these isolates, 240 formed cadaverine, 208 formed putrescine, and 196 formed histamine, in widely varying amounts. They frequently produced more than one biogenic amine. Klebsiella pneumoniae subsp. pneumoniae and Morganella morganii were the main histamine producers, with mean values of 1,600 and 2,440 mg/liter, respectively, followed by Pantoea spp. 3 (1,710 mg/liter) and Hafnia alvei (2,500 mg/liter). Enterobacter amnigenus and Enterobacter cloacae produced particularly high amounts of putrescine, with mean values of 2,340 and 2,890 mg/liter, respectively. The strongest cadaverine formation was shown by Serratia liquefaciens (3,300 mg/liter), Serratia marcescens (3,280 mg/liter), and Stenotrophomonas maltophilia (1,000 mg/liter).

Growth, inactivation and histamine formation of Morganella psychrotolerans and Morganella morganii - development and evaluation of predictive models

Mathematical models for growth, heat inactivation and histamine formation by Morganella psychrotolerans and Morganella morganii were studied to evaluate the importance of these bacteria in seafood. Curves for growth and histamine formation by M. psychrotolerans in broth and seafood were generated at constant and changing storage temperatures (n=12). Observed and predicted times to formation of 100, 500 and 2000 ppm histamine were used for evaluation of an existing M. psychrotolerans histamine formation model [Emborg, J., Dalgaard, P., 2008-this issue-this issue. Modelling and predicting the growth and histamine formation by Morganella psychrotolerans. International Journal of Food Microbiology. doi:10.1016/j.ijfoodmicro.2008.08.016] Growth rates for M. psychrotolerans and M. morganii were determined at different constant temperatures from 0 degrees C to 42.5 degrees C whereas heat inactivation was studied between 37.5 degrees C and 60 degrees C. A M. morganii growth and histamine formation model was developed by combining these new data (growth rate model) and data from the existing literature (maximum population density and yield factor for histamine formation). The developed M. morganii model was evaluated by comparison of predicted growth and histamine formation with data from the existing literature. Observed and predicted growth rates for M. psychrotolerans, at constant temperatures, were similar with bias- and accuracy factor values of 1.15 and 1.45, respectively (n=11). On average times to formation of critical concentrations of histamine by M. psychrotolerans were acceptably predicted but the model was not highly accurate. Nevertheless, predictions seemed useful to support decisions concerning safe shelf-life in relation to formulation, storage and distribution of chilled seafood. Parameters for the effect of temperature on growth and inactivation of M. psychrotolerans and M. morganii differed markedly with Tmin of -8.3 to -5.9 degrees C vs. 0.3 to 2.8 degrees C, Topt of 26.0 to 27.0 degrees C vs. 35.9 to 37.2 degrees C and Tmax 32.0 to 33.3 degrees C vs. 44.0 to 47.4 degrees C, D(50 degrees C) of 5.3 min vs. 13.1 min and z-values of 6.8 degrees C and 7.2 degrees C. At temperatures above approximately 15 degrees C M. morganii grew faster than M. psychrotolerans. Bias- and accuracy factor-values of 1.41 and 2.44 (n=93) showed the predicted growth of M. morganii to be faster than previously observed in fresh fish and broth. In agreement with this, predicted times to formation of critical histamine concentrations by M. morganii were on average shorter than observed in fresh fish. A combined model was suggested to predict histamine formation by both psychrotolerant and mesophilic Morganella during storage of fresh fish between 0 degrees C and 37 degrees C.

Changes in histamine and microbiological analyses in fresh and frozen tuna muscle during temperature abuse

Temperature abuse of tuna (Thunnus alalunga) was carried out in order to assess the histamine buildup in fish-processing facilities where fish can be exposed to high temperatures for short periods of time. Histamine production was studied in tuna loins under different storage and abuse conditions. Tuna was stored at 0-2 degrees C, 3-4 degrees C, and 6-7 degrees C, and abused for 2 h daily at 20 degrees C and 30 degrees C for 7-12 days. Loins abused at 30 degrees C for 2 h daily contained potentially toxic histamine concentrations (67-382 mg kg(-1)) when stored at a low refrigeration temperature (0-2 degrees C), whereas when stored at 6-7 degrees C, the loins contained highly toxic histamine concentrations (544.5-4156.6 mg kg(-1)). Lower histamine concentrations (23-48 mg kg(-1) in loins stored at 0-2 degrees C and 124.7-2435.8 mg kg(-1) in loins stored at 6-7 degrees C) were observed in temperature-abused loins that were initially frozen. An increase over time was observed in most microbial counts tested. Bacteria isolated from the temperature-abused loins showed a varied ability of histamine production, with Morganella morganii, Klebsiella oxytoca, Staphylococcus hominis, and Enterococcus hirae being the most active histamine-producing bacteria.

The influence of storage conditions of tuna viscera before fermentation on the chemical, physical and microbiological changes in fish sauce during fermentation

Effect of storage condition of tuna viscera on chemical, physical and microbiological changes of its sauce were monitored. Results based on microbial counts, protein degradation products, total volatile base (TVB), and trimethylamine (TMA) contents, showed that tuna viscera stored at room temperature underwent more deterioration than that kept in ice, especially with increasing storage time. As a result, fish sauce obtained from tuna viscera stored at room temperature for a longer time rendered the greater amino nitrogen, TVB, TMA contents as well as browning intensity. However, storage conditions had no marked effect on overall changes in chemical, physical and microbiological characteristics of sauce generated during fermentation. Additionally, fish sauce produced from tuna viscera kept at room temperature comprised lower histamine content than that prepared from fresh or ice-stored viscera. Therefore, tuna viscera stored at room temperature for up to 8h could be used for the production of fish sauce with no detrimental effect on the quality.

Detection and identification of histamine-producing bacteria associated with harvesting and processing mahimahi and yellowfin tuna

Histamine poisoning is one of the most common chemically induced seafoodborne illnesses reported in the United States today. The causative agents are biogenic amines, commonly produced by gram-negative bacteria. The purpose of this study was to detect and identify histamine-producing bacteria associated with standard industry practices during the harvesting, receiving, and processing of mahimahi and yellowfin tuna in North Carolina. Twenty-nine composite samples were obtained from 18 mahimahi and 11 yellowfin tuna and analyzed for their histamine content. No sample analyzed exceeded 2 ppm histamine, the lower detection limit. Composite fish muscle and environmental samples were screened (n = 386) for the presence of histamine-producing bacteria. Twenty-six percent (145) of 549 isolates selected on the basis of their morphological characteristics tested positive on Niven's media. Sixty-three Niven-positive isolates were gram negative, and 58 were gram positive. Of the 43 isolates tested further, 5 were confirmed as histamine producers, and all 5 produced at low levels (< 250 ppm in 48 h at > 15 degrees C). Three gram-negative and two gram-positive isolates were identified as Enterobacter cloacae and Staphylococcus kloosii, respectively. This study revealed that gram-negative bacteria might not be solely responsible for histamine production in at-risk fish. The confirmation of histamine-producing bacteria demonstrates the potential risk for histamine production. However, no detectable levels were found in the composite fish muscle samples analyzed even though 60% of the yellowfin tuna harvested did not meet the U.S. Food and Drug Administration's regulatory hazard analysis critical control point guidelines for temperature reduction. Therefore, no seafood safety risks were found under the standard industry practices observed in this study.

Multiplex PCR for colony direct detection of Gram-positive histamine- and tyramine-producing bacteria

Formation of biogenic amines (BA) may occur in fermented foods and beverages due to the amino acid decarboxylase activities of Gram-positive bacteria. These compounds may cause food poisoning and therefore could imply food exportation problems. A set of consensual primers based on histidine decarboxylase gene (hdc) sequences of different bacteria was designed for the detection of histamine-producing Gram-positive bacteria. A multiplex PCR based on these hdc primers and recently designed primers targeting the tyrosine decarboxylase (tyrdc) gene was created. A third set of primers targeting the 16S rRNA gene of eubacteria was also used as an internal control. This multiplex PCR was performed on extracted DNA as well as directly on cell colonies. The results obtained show that this new molecular tool allowed for the detection of Gram-positive histamine- and/or tyramine-producing bacteria. The use of this molecular tool for early and rapid detection of Gram-positive BA-producing bacteria is of interest in evaluating the potential of cultured indigenous strains to produce biogenic amines in a fermented food product as well as to validate the innocuity of potential starter strains in the food industry.

Detection of Morganella morganii, a prolific histamine former, by the polymerase chain reaction assay with 16S rDNA-targeted primers

A polymerase chain reaction (PCR) assay for the rapid and sensitive detection of the most prolific histamine former, Morganella morganii, was developed. 16S rDNA targeted PCR primers were designed, and the primer specificity and sensitivity of the PCR assay were evaluated. The 16S rDNA sequence (1,503 bp) for M. morganii showed 95% identity to those for enteric bacteria, i.e., Enterobacter spp., Klebsiella spp., Citrobacter spp., Hafnia alvei, Proteus spp., and Providencia spp. The unique primers for M. morganii were designed on the basis of the variable regions in the 16S rDNA sequence. The primers showed positive reactions with all M. morganii strains tested. However, PCR amplification was not detected when the primers were tested with other enteric or marine bacteria. When the sensitivity of the assay was evaluated, M. morganii was detected at levels ranging from 10(6) to 10(8) CFU/ml in albacore homogenate after the PCR amplification. The sensitivity of the assay was greatly improved with the enrichment of samples, and 9 CFU of M. morganii per ml of albacore homogenate was detected after 6 h of enrichment at 37 degrees C.

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.