Revisiting host identification of bacteriophage Enc34: from biochemical to molecular.

In our 2012 genome announcement (J Virol 86:11403-11404, 2012, https://doi.org/10.1128/JVI.01954-12), we initially identified the host bacterium of bacteriophage Enc34 as Enterobacter cancerogenus using biochemical tests. However, later in-house DNA sequencing revealed that the true host is a strain of Hafnia alvei. Capitalizing on our new DNA-sequencing capabilities, we also refined the genomic termini of Enc34, confirming a 60,496-bp genome with 12-nucleotide 5' cohesive ends. IMPORTANCE: Our correction reflects the evolving landscape of bacterial identification, where molecular methods have supplanted traditional biochemical tests. This case underscores the significance of revisiting past identifications, as seemingly known bacterial strains may yield unexpected discoveries, necessitating essential updates to the scientific record. Despite the host identity correction, our genome announcement retains importance as the first complete genome sequence of a Hafnia alvei bacteriophage.

AHL-differential quorum sensing regulation of amino acid metabolism in Hafnia alvei H4.

Quorum sensing (QS) regulation of functional metabolites is rarely reported but a common trait of some bacteria. In this study, we found that QS promoted the extracellular accumulation of glycine and serine while inhibiting the extracellular accumulation of methionine in Hafnia alvei H4. The correlation analysis of five QS signals with the above three QS-regulated amino acids suggested that these QS signals may have functional differences in amino acid regulation. The exogenous AHL add-back studies on genes involved in glycine, serine, and methionine metabolic pathway highlighted that N-octanoyl-l-homoserine lactone (C8-HSL) downregulated the expression of sdhC/fumA genes involved in the succinate to malate pathway, thereby reducing the metabolic flux of the tricarboxylic acid (TCA) cycle as an amino acid metabolism platform. Further in-depth research revealed that the QS system promoted the conversion of folate to tetrahydrofolate (THF) by positively regulating the expression of folA and folM, thus impairing the ability of folate to promote methionine accumulation. Moreover, folate positively regulated the expression of the QS signal synthesis gene luxI, promoting the synthesis of QS signals, which may further enhance the influence of the QS system on amino acid metabolism. These findings contribute to the understanding of amino acid metabolism regulated by QS and provide new perspectives for accurate control of metabolic regulation caused by QS.IMPORTANCEAs one of the important regulatory mechanisms of microorganisms, quorum sensing (QS) is involved in the regulation of various physiological activities. However, few studies on the regulation of amino acid metabolism by QS are available. This study demonstrated that the LuxI-type QS system of Hafnia alvei H4 was involved in the regulation of multiple amino acid metabolism, and different types of QS signals exhibited different roles in regulating amino acid metabolism. Additionally, the regulatory effects of the QS system on amino acid metabolism were investigated from two important cycles that influence the conversion of amino acids, including the TCA cycle and the folate cycle. These findings provide new ideas on the role of QS system in the regulation of amino acid metabolism in organisms.

Protein Extract of a Probiotic Strain of Hafnia alvei and Bacterial ClpB Protein Improve Glucose Tolerance in Mice.

A commercial strain of Hafnia alvei (H. alvei) 4597 bacteria was shown to reduce food intake and promote weight loss, effects possibly induced by the bacterial protein ClpB, an antigen-mimetic of the anorexigenic α-melanocyte-stimulating hormone. A decrease in the basal plasma glucose levels was also observed in overweight fasted humans and mice receiving H. alvei. However, it is not known whether H. alvei influences sweet taste preference and whether its protein extract or ClpB are sufficient to increase glucose tolerance; these are the objectives tested in the present study. C57BL/6J male mice were kept under standard diet and were gavaged daily for 17 days with a suspension of H. alvei (4.5 × 107 CFU/animal) or with H. alvei total protein extract (5 µg/animal) or saline as a control. Sweet taste preference was analyzed via a brief-access licking test with sucrose solution. Glucose tolerance tests (GTT) were performed after the intraperitoneal (IP) or intragastric (IG) glucose administration at the 9th and 15th days of gavage, respectively. The expression of regulatory peptides' mRNA levels was assayed in the hypothalamus. In another experiment performed in non-treated C57BL/6J male mice, effects of acute IP administration of recombinant ClpB protein on glucose tolerance were studied by both IP- and IG-GTT. Mice treated with the H. alvei protein extract showed an improved glucose tolerance in IP-GTT but not in IG-GTT. Both groups treated with H. alvei bacteria or protein extract showed a reduction of pancreatic tissue weight but without significant changes to basal plasma insulin. No significant effects of H. alvei bacteria or its total protein extract administration were observed on the sweet taste preference, insulin tolerance and expression of regulatory peptides' mRNA in the hypothalamus. Acute administration of ClpB in non-treated mice increased glucose tolerance during the IP-GTT but not the IG-GTT, and reduced basal plasma glucose levels. We conclude that both the H. alvei protein extract introduced orally and the ClpB protein administered via IP improve glucose tolerance probably by acting at the glucose postabsorptive level. Moreover, H. alvei probiotic does not seem to influence the sweet taste preference. These results justify future testing of both the H. alvei protein extract and ClpB protein in animal models of diabetes.

The impact of Hafnia alvei HA4597™ on weight loss and glycaemic control after bariatric surgery - study protocol for a triple-blinded, blocked randomized, 12-month, parallel-group, placebo-controlled clinical trial.

BACKGROUND: Subjects with obesity exhibit changes in gut microbiota composition and function (i.e. dysbiosis) that contribute to metabolic dysfunction, including appetite impairment. Although bariatric surgery is an effective treatment for obesity with a great impact on weight loss, some subjects show weight regain due to increased energy intake after the surgery. This surgery involves gut microbiota changes that promote appetite control, but it seems insufficient to completely restore the obesity-associated dysbiosis - a possible contributor for weight regain. Thus, modulating gut microbiota with probiotics that could improve appetite regulation as a complementary approach to post-operative diet (i.e. Hafnia alvei HA4597™), may accentuate post-surgery weight loss and insulin sensitivity. METHODS: This is a protocol of a triple-blinded, blocked-randomized, parallel-group, placebo-controlled clinical trial designed to determine the effect of Hafnia alvei HA4597™ supplementation on weight loss and glycaemic control 1 year after bariatric surgery. Patients of Hospital CUF Tejo, Lisbon, that undergo Roux-en-Y gastric bypass are invited to participate in this study. Men and women between 18 and 65 years old, with a BMI ≥ 35 kg/m2 and at least one severe obesity-related comorbidity, or with a BMI ≥ 40 kg/m2, and who are willing to take 2 capsules of Hafnia alvei HA4597™ probiotic supplements (equivalent to 5 × 107 CFU) vs. placebo per day for 90 days are included in this study. Assessments are carried out at baseline, 3, 6, 9, and 12 months after the surgery. Loss of weight in excess and glycated haemoglobin are considered primary outcomes. In addition, changes in other metabolic and inflammatory outcomes, gut microbiota composition and metabolites, as well as gastrointestinal quality of life are also being assessed during the trial. DISCUSSION: The evidence obtained in this study will provide relevant information regarding the profile of the intestinal microbiota of individuals with severe obesity and the identification of the risk/benefit ratio of the use of Hafnia alvei HA4597™ as an adjunctive treatment in the maintenance of metabolic and weight control one year after the surgical intervention. TRIAL REGISTRATION: ClinicalTrials.gov NCT05170867. Registered on 28 December 2021.

Anti-infective properties of the protective culture Hafnia alvei B16 in food and intestinal models against multi-drug resistant Salmonella.

Salmonella enterica is a ubiquitous and multi-host pathogen that causes significant morbidity and mortality worldwide. Outbreaks of foodborne salmonellosis continue to occur, highlighting the need for additional interventions. The present study investigated the potential for the commercial protective culture Hafnia alvei B16 to provide enhanced protection against multi-drug resistant strains of S. enterica serovars Typhimurium and Newport by attenuating their virulence when cocultured in milk (as a model food) and broth, and by protecting intestinal epithelial cells from pathogen infection in vitro. Exposure to HA in milk inhibited the subsequent adhesion of S. Typhimurium by 95.23%, whereas the invasion capacity of both serovars was reduced when cocultured with HA in broth and milk. The inhibition of invasion by S. Typhimurium and S. Newport was greater when cocultured in milk (86.95% and 86.58%, respectively) compared to broth (51.64% and 79.88%, respectively). Exposure to HA in both media decreased the expression of virulence genes in S. Typhimurium and S. Newport. Pre-treatment of Caco-2 cells with HA reduced invasion of S. Newport by 89.68% compared to control. These data demonstrate the potential for HA to enhance food safety by attenuating Salmonella virulence and protecting against pathogen invasion of intestinal epithelial cells.

Higher-order interactions shape microbial interactions as microbial community complexity increases.

Non-pairwise interactions, or higher-order interactions (HOIs), in microbial communities have been described as significant drivers of emergent features in microbiomes. Yet, the re-organization of microbial interactions between pairwise cultures and larger communities remains largely unexplored from a molecular perspective but is central to our understanding and further manipulation of microbial communities. Here, we used a bottom-up approach to investigate microbial interaction mechanisms from pairwise cultures up to 4-species communities from a simple microbiome (Hafnia alvei, Geotrichum candidum, Pencillium camemberti and Escherichia coli). Specifically, we characterized the interaction landscape for each species combination involving E. coli by identifying E. coli's interaction-associated mutants using an RB-TnSeq-based interaction assay. We observed a deep reorganization of the interaction-associated mutants, with very few 2-species interactions conserved all the way up to a 4-species community and the emergence of multiple HOIs. We further used a quantitative genetics strategy to decipher how 2-species interactions were quantitatively conserved in higher community compositions. Epistasis-based analysis revealed that, of the interactions that are conserved at all levels of complexity, 82% follow an additive pattern. Altogether, we demonstrate the complex architecture of microbial interactions even within a simple microbiome, and provide a mechanistic and molecular explanation of HOIs.

The Molecular Weaponry Produced by the Bacterium Hafnia alvei in Foods.

Hafnia alvei is receiving increasing attention from both a medical and veterinary point of view, but the diversity of molecules it produces has made the interest in this bacterium extend to the field of probiotics, the microbiota, and above all, to its presence and action on consumer foods. The production of Acyl Homoserine Lactones (AHLs), a type of quorum-sensing (QS) signaling molecule, is the most often-studied chemical signaling molecule in Gram-negative bacteria. H. alvei can use this communication mechanism to promote the expression of certain enzymatic activities in fermented foods, where this bacterium is frequently present. H. alvei also produces a series of molecules involved in the modification of the organoleptic properties of different products, especially cheeses, where it shares space with other microorganisms. Although some strains of this species are implicated in infections in humans, many produce antibacterial compounds, such as bacteriocins, that inhibit the growth of true pathogens, so the characterization of these molecules could be very interesting from the point of view of clinical medicine and the food industry. Lastly, in some cases, H. alvei is responsible for the production of biogenic amines or other compounds of special interest in food health. In this article, we will review the most interesting molecules that produce the H. alvei strains and will discuss some of their properties, both from the point of view of their biological activity on other microorganisms and the properties of different food matrices in which this bacterium usually thrives.

Quorum Sensing (QS)-regulated target predictions of Hafnia alvei H4 based on the joint application of genome and STRING database.

In this study, we sequenced and characterized the genome of H. alvei to grasp the genetic basis of its physiological activities, including QS, metabolism, virulence and antibiotic resistance, and then mapped these functional gene clusters obtained from KEGG pathways to the STRING database to predict the QS-regulated targets in these pathways. H. alvei was found to possess 63 QS-related genes, most of which were closely related to amino acid metabolism, especially methionine pathway, but were not directly related to carbon and energy metabolism. Furthermore, the adhesion gene clusters were closely relevant to the QS gene clusters as well as to the infection gene clusters, while only one node (KdsD) was predicted between the QS gene clusters and infection gene clusters, suggesting that QS might influence the infection by regulating adhesion. QS might confer cross-resistance to microorganisms not only by regulating the formation of biofilms but also by affecting the efflux of antibiotics. In addition, the interspecies and intraspecies patterns of absence/presence for QS and its target genes were determined to shed light on the conservation of the QS regulatory mechanism among the phylogenetically related species. Taken together, the proposed methodology could expand the spectrum of possible applications of genome-based analysis to decipher the basic metabolic relationship of a microorganism, especially when studying new isolates.

The Gram-Negative Bacilli Isolated from Caves-Sphingomonas paucimobilis and Hafnia alvei and a Review of Their Involvement in Human Infections.

The opportunistic infections with Gram-negative bacilli are frequently reported. The clinical studies are focused on the course of human infectious and very often the source of infection remain unclear. We aim to see if the Gram-negative bacilli isolated from a non-contaminated environment-the caves-are reported in human infections. Eleven samples were collected from six Romanian caves. We used the standard procedure used in our clinical laboratory for bacterial identification and for antibiotic susceptibility testing of the cave isolates. Out of the 14 bacterial strains, three isolates are Gram-negative bacilli-one isolate belong to Hafnia alvei and two strains belong to Sphingomonas paucimobilis. We screened for the published studies-full-text original articles or review articles-that reported human infections with S. paucimobilis and H. alvei. Data sources-PubMed and Cochrane library. We retrieved 447 cases from 49 references-262 cases (58.61%) are S. paucimobilis infections and 185 cases (41.39%) are H. alvei infections. The types of infections are diverse but there are some infections more frequent; there are 116 cases (44.27%) and many infections of the bloodstream with S. paucimobilius (116 cases) and 121 cases (65.41%) are urinary tract infections with H. alvei. The acquired source of the bloodstream infections is reported for 93 of S. paucimobilis bloodstream infections-50 cases (43%) are hospital-acquired, and 40 cases (37%) are community-acquired. Most of the infections are reported in patients with different underlying conditions. There are 80 cases (17.9%) are reported of previously healthy persons. Out of the 72 cases of pediatric infections, 62 cases (86.11%) are caused by S. paucimobilis. There are ten death casualties-three are H. alvei infections, and seven are S. paucimobilis infections.

Specific Strains of Honeybee Gut Lactobacillus Stimulate Host Immune System to Protect against Pathogenic Hafnia alvei.

Honeybee gut microbiota plays an important role in host physiology and metabolism. Recent studies have shown that the influence of the resident microorganisms in the regulation of honeybee immune system is profound, which protects against the pathogen Serratia marcescens. However, only few of the core gut members in the regulation of immune functions have been studied. Here, we explored how different bee gut bacterial species aided in the clearance of the pathogenic Hafnia alvei, which causes bee septicemia with a high mortality rate. We found that both Gilliamella apicola W8136 and Lactobacillus apis W8172 protect honeybees from the opportunistic pathogen, while two other strains from Gilliamella and Lactobacillus did not affect the invasion of H. alvei. Transcriptomic analysis revealed that gut species induced different expression profiles in the gut. Specifically, two regulator genes from the Toll pathway, PGRP-S3 recognizing Gram-positive and Spätzle that bind to the Toll protein for the downstream signal transduction, were elevated by L. apis. Correspondingly, multiple genes encoding antibacterial proteins were also stimulated by L. apis. Interestingly, we found an increased expression of apidaecin, which also exhibited a high in vitro inhibitory effect on H. alvei. To elucidate the difference of strains in the host's immune regulation, comparative genomic analyses indicate that the S-layer proteins unique to L. apis are potentially involved in honeybee Toll signaling and the activation of antibacterial protein production. IMPORTANCE Honeybees are essential pollinators supporting global agricultural economies and food supplies. Recent honeybee decline has been linked to several factors, while pathogen infection is considered one of the most significant contributing factors. Although a limited number of bacterial pathogens have been identified, Hafnia alvei is one of the pathogens causing septicemia in adult bees. In this study, we showed that two bee gut members, Gilliamella and Lactobacillus, can clear H. alvei from invasion. Mono-colonization of specific strains can stimulate the host Toll signaling pathway and the downstream expression of AMPs. Specifically, apidaecin upregulated by the gut symbionts is more effective against the pathogen. Moreover, our genomic analysis suggests that the surface-layer proteins specific to Lactobacillus strains are an important driver of Toll signaling, highlighting the variation of bee gut strains in regulating the host immune system.

Mechanism of berberine hydrochloride interfering with biofilm formation of Hafnia alvei.

The mechanism of berberine hydrochloride (BBH) inhibiting the biofilm formation of Hafnia alvei was investigated in this study. The antibiofilm potential of BBH was evaluated by confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM) as well as crystal violet staining. The quorum-sensing (QS) inhibition was revealed by determination of QS-related genes expression and related signal molecules production using real-time quantitative PCR (RT-qPCR) and high performance liquid chromatography (HPLC). The binding of BBH to receptor proteins was simulated by molecular docking and molecular dynamics simulations. It was found that BBH at sub-minimum inhibitory concentrations (sub-MICs) significantly reduced the biofilm formation of H. alvei in a dose dependent manner. BBH inhibited the bacterial swimming motility, decreased the transcription of halI and halR genes, and reduced the production of signal molecule C14-HSL. It bound to HalR protein mainly through Van der Waals force and electrostatic interaction force. Based on these results, it was concluded that BBH inhibits the biofilm formation of H. alvei and the mechanism is related to its interference with QS through down-regulating the expression of halI and halR genes.

[Rare Cause of Lung Tumour - Pulmonary Infection with Hafnia alvei: A Case Report]. / Seltene Ursache eines Lungentumors ­ Fallbericht einer pulmonalen Infektion mit Hafnia alvei.

If a malignant disease is suspected, rapid diagnosis of suspicious pulmonary masses is required. In the presented case, malignancy was repeatedly not proven. Only the test-appropriate antibiotic treatment of an intestinal germ that was initially assessed as an impurity brought the therapeutic success with total remission. In our case the treatment with broad-spectrum penicillin piperacillin/tazobactam was ineffective and only the gyrase inhibitors ciprofloxacin and levofloxacin brought therapeutic success.

The Probiotic Strain H. alvei HA4597® Improves Weight Loss in Overweight Subjects under Moderate Hypocaloric Diet: A Proof-of-Concept, Multicenter Randomized, Double-Blind Placebo-Controlled Study.

Background: Increasing evidence supports the role of the gut microbiota in the control of body weight and feeding behavior. Moreover, recent studies have reported that the probiotic strain Hafnia alvei HA4597® (HA), which produces the satietogenic peptide ClpB mimicking the effect of alpha-MSH, reduced weight gain and adiposity in rodent models of obesity. Methods: To investigate the clinical efficacy of HA, 236 overweight subjects were included, after written informed consent, in a 12-week prospective, double-blind, randomized study. All subjects received standardized counselling for a -20% hypocaloric diet and were asked to maintain their usual physical activity. Subjects of the HA group received two capsules per day providing 100 billion bacteria per day and subjects in the Placebo (P) group received two placebo capsules. The primary endpoint was the percentage of subjects achieving a weight loss of at least 3% after 12 weeks. Intention-to-treat statistical analysis was performed using exact-Fischer, Mann-Whitney and paired-Wilcoxon tests as appropriate. Results: In the HA group, significantly more subjects (+33%) met the primary endpoint than in the P group (54.9 vs. 41.4%, p = 0.048). In the HA group, an increased feeling of fullness (p = 0.009) and a greater loss of hip circumference (p < 0.001) at 12 weeks were also observed. Fasting glycemia at 12 weeks was significantly lower (p < 0.05) in the HA compared to P group. Clinical and biological tolerance was good in both groups. Conclusions: A 12-week treatment with the probiotic strain H. alvei HA4597® significantly improves weight loss, feeling of fullness and reduction of hip circumference in overweight subjects following moderate hypocaloric diet. These data support the use of H. alvei HA4597® in the global management of excess weight.

Generation of phytase chimeras with low sequence identities and improved thermal stability.

Being able to recombine more than two genes with four or more crossover points in a sequence independent manner is still a challenge in protein engineering and limits our capabilities in tailoring enzymes for industrial applications. By computational analysis employing multiple sequence alignments and homology modeling, five fragments of six phytase genes (sequence identities 31-64 %) were identified and efficiently recombined through phosphorothioate-based cloning using the PTRec method. By combinatorial recombination, functional phytase chimeras containing fragments of up to four phytases were obtained. Two variants (PTRec 74 and PTRec 77) with up to 32 % improved residual activity (90 °C, 60 min) and retained specific activities of > 1100 U/mg were identified. Both variants are composed of fragments from the phytases of Citrobacter braakii, Hafnia alvei and Yersinia mollaretii. They exhibit sequence identities of ≤ 80 % to their parental enzymes, highlighting the great potential of DNA recombination strategies to generate new enzymes with low sequences identities that offer opportunities for property right claims.

COVID-19 influences lung microbiota dynamics and favors the emergence of rare infectious diseases: A case report of Hafnia Alvei pneumonia.

The coronavirus disease 2019 causes a wide degree of organ dysfunction and is associated with bacterial secondary infections. We reported lung microbiota dynamics in a critically ill patient with coronavirus disease 2019, who developed severe Hafnia alvei ventilator-associated pneumonia and required extracorporeal membrane oxygenation support.

The complete genome sequence of Hafnia alvei A23BA; a potential antibiotic-producing rhizobacterium.

OBJECTIVES: The urgent need for novel antibiotics cannot be overemphasized. Hafnia alvei A23BA was isolated from plant rhizosphere as part of an effort to recover novel antibiotic-producing bacterial strains from soil samples. The genome of the isolate was sequenced to facilitate mining for potential antibiotic-encoding biosynthetic gene clusters and to gain insights into how these gene clusters could be activated. DATA DESCRIPTION: Here, we report the complete genome sequence of H. alvei A23BA obtained from the hybrid assembly of Illumina HiSeq and GridION reads. The genome, consisting of a circular chromosome and a circular plasmid, is 4.77 Mb in size with a GC content of 48.77%. The assembly is 99.5% complete with genomic features including 4,217 CDSs, 125 RNAs, and 30 pseudogenes. Thiopeptide, beta-lactone, siderophore, and homoserine lactone biosynthetic gene clusters were also identified. Other gene clusters of interest include those associated with bioremediation, biocontrol, and plant growth promotion- all of which are reported for H. alvei for the first time. This dataset serves to expedite the exploration of the biosynthetic and metabolic potentials of the species. Furthermore, being the first published genome sequence of a soil isolate, this dataset enriches the comparative genomics study of H. alvei strains.

Effect of quorum sensing and quorum sensing inhibitors on the expression of serine protease gene in Hafnia alvei H4.

The serp gene codes for a protease that is considered to be an important factor associated with quorum sensing (QS)-based food spoilage caused by microorganisms. In this study, we evaluated the effect of temperature (4-37 °C) and QS inhibitors on the production of N-acyl-L-homoserine lactones (AHLs) and relative expression of the luxR/I, as well as serp in Hafnia alvei H4. Production of AHLs and expression of luxR/I were found to reach maximum levels at 10 °C, suggesting that the QS system of H. alvei H4 might have higher activity at low temperatures; similar result was also obtained for serp expression. Mutants of H. alvei H4 deficient in QS were used to identify the regulation of QS on serp expression. Significant reduction (P < 0.05) in serp expression was found in the mutants ∆luxR, ∆luxI, and ∆luxR/I, with ∆luxI and ∆luxR/I showing greater reduction than ∆luxR. Minimum inhibition concentrations (MIC) of Benzyl isothiocyanate and 3-Methylthiopropyl isothiocyanate for H. alvei H4 were determined to be 7.813 and 15.625 mM, respectively. Furthermore, the expression of serp, as well as that of luxR and luxI, was significantly repressed (P < 0.05) by the two QS inhibitors at 1/8 MIC and 1/16 MIC, indicating that these inhibitors might repress serp expression through affecting luxR and luxI expression in H. alvei H4. The findings of this study, therefore, suggested that food spoilage caused by H. alvei could be controlled through the application of QS inhibitors.

The effect of protective cultures on Staphylococcus aureus growth and enterotoxin production.

Staphylococcus aureus is the causative agent of staphylococcal food poisoning and is a common contaminant in milk. Despite efforts to control S. aureus, recalls and outbreaks continue to occur, highlighting the need for additional interventions. This study determined the potential for protective cultures (PC) that are commercially available to producers to control S. aureus growth in raw milk and attenuate virulence by impeding staphylococcal enterotoxin (SE) production in raw milk and laboratory medium. Cultures of Hafnia alvei and Lactococcus lactis effectively inhibited S. aureus growth in raw milk to counts ~5 log CFU/mL lower than control when cocultured following a cheesemaking time and temperature profile; two cultures of Lactobacillus plantarum inhibited growth to ~1.5 log CFU/mL less than control. Cocultures of S. aureus with Lc. lactis, H. alvei and Lb. plantarum in raw milk reduced SE levels by 24.9%, 62.4%, and 76%, respectively. Lc. lactis also decreased SE production in raw milk in the absence of PC-mediated growth inhibition. Significant reductions in SE production in the absence of pathogen growth inhibition were also achieved in laboratory medium. Together, these results demonstrate the potential for PCs to inhibit S. aureus growth and impede SE production in the absence of growth inhibition.

Microbiology of Hafnia alvei. / Microbiología de Hafnia alvei.

Hafnia alvei is a Gram-negative facultatively anaerobic bacillus that constitutes part of the human gut flora. Until recently, H. alvei strains could be mistakenly identified by conventional methods, miniaturisation or automatic systems as members of the Serratia, Escherichia, Citrobacter, Yokenella, Obesumbacterium or Salmonella genera. Consequently, molecular techniques were required for their definitive identification in the clinical laboratory. In addition, a new Hafnia species, H. paralvei, has recently appeared, which undoubtedly includes many of the strains reported in the literature as H. alvei. Alrhough H. alvei isolation from human clinical specimens remains uncommon, the development of drug resistance due to this species is emerging and it is likely that this organism will gain increasing importance in the future. Moreover, although H. alvei shares some virulence mechanisms with other Gram-negative enteropathogens, little is known about the factors that contribute to its pathogenesis in humans. The present article reviews the current identification methods, antimicrobial resistance and virulence factors of this bacterium.

Commensal Hafnia alvei strain reduces food intake and fat mass in obese mice-a new potential probiotic for appetite and body weight management.

BACKGROUND/OBJECTIVES: Based on the recent identification of E.coli heat shock protein ClpB as a mimetic of the anorexigenic α-melanocyte stimulating hormone (α-MSH), the objective of this study was to preclinically validate Hafnia alvei, a ClpB-producing commensal bacterium as a potential probiotic for appetite and body weight management in overweight and obesity. METHODS: The involvement of enterobacterial ClpB in the putative anti-obesity effects was studied using ClpB-deficient E.coli. A food-grade H. alvei HA4597 strain synthetizing the ClpB protein with an α-MSH-like motif was selected as a candidate probiotic to be tested in ob/ob and high-fat diet (HFD)-fed obese and overweight mice. The relevance of the enterobacterial ClpB gene to human obesity was studied by in silico analysis of fecal metagenomes of 569 healthy individuals from the "MetaHIT" database. RESULTS: Chronic per os administration of native but not ClpB-deficient E.coli strain reduced body weight gain (p < 0.05) and daily meal frequency (p < 0.001) in ob/ob mice. Oral gavage of H.alvei for 18 and 46 days in ob/ob and HFD-fed obese mice, respectively, was well tolerated, reduced body weight gain and fat mass in both obesity models (p < 0.05) and decreased food intake in hyperphagic ob/ob mice (p < 0.001). Elevated fat tissue levels of phosphorylated hormone-sensitive lipase were detected in H.alvei -treated ob/ob mice (p < 0.01). Enterobacterial ClpB gene richness was lower in obese vs. non-obese humans (p < 0.0001) and correlated negatively with BMI in genera of Enterobacter, Klebsiella and Hafnia. CONCLUSIONS: H.alvei HA4597 strain reduces food intake, body weight and fat mass gain in hyperphagic and obese mice. These data combined with low enterobacterial ClpB gene abundance in the microbiota of obese humans provide the rationale for using H.alvei as a probiotic for appetite and body weight management in overweight and obesity.