Animal and In Vitro Models as Powerful Tools to Decipher the Effects of Enteric Pathogens on the Human Gut Microbiota

Examining the interplay between intestinal pathogens and the gut microbiota is crucial to fully comprehend the pathogenic role of enteropathogens and their broader impact on human health. Valid alternatives to human studies have been introduced in laboratory practice to evaluate the effects of infectious agents on the gut microbiota, thereby exploring their translational implications in intestinal functionality and overall health. Different animal species are currently used as valuable models for intestinal infections. In addition, considering the recent advances in bioengineering, futuristic in vitro models resembling the intestinal environment are also available for this purpose. In this review, the impact of the main human enteropathogens (i.e., Clostridioides difficile, Campylobacter jejuni, diarrheagenic Escherichia coli, non-typhoidal Salmonella enterica, Shigella flexneri and Shigella sonnei, Vibrio cholerae, and Bacillus cereus) on intestinal microbial communities is summarized, with specific emphasis on results derived from investigations employing animal and in vitro models.

A Millifluidic Chamber for Controlled Shear Stress Testing: Application to Microbial Cultures

In vitro platforms such as bioreactors and microfluidic devices are commonly designed to engineer tissue models as well as to replicate the crosstalk between cells and microorganisms hosted in the human body. These systems promote nutrient supply and waste removal through culture medium recirculation; consequently, they intrinsically expose cellular structures to shear stress, be it a desired mechanical stimulus to drive the cell fate or a potential inhibitor for the model maturation. Assessing the impact of shear stress on cellular or microbial cultures thus represents a crucial step to define proper environmental conditions for in vitro models. In this light, the aim of this study was to develop a millifluidic device enabling to generate fully controlled shear stress profiles for quantitatively probing its influence on tissue or bacterial models, overcoming the limitations of previous reports proposing similar devices. Relying on this millifluidic tool, we present a systematic methodology to test how adherent cellular structures react to shear forces, which was applied to the case of microbial biofilms as a proof of concept. The results obtained suggest our approach as a suitable testbench to evaluate culture conditions in terms of shear stress faced by cells or microorganisms.

Development of an In Vitro Model of the Gut Microbiota Enriched in Mucus-Adhering Bacteria

Culturing the gut microbiota in in vitro models that mimic the intestinal environment is increasingly becoming a promising alternative approach to study microbial dynamics and the effect of perturbations on the gut community. Since the mucus-associated microbial populations in the human intestine differ in composition and functions from their luminal counterpart, we attempted to reproduce in vitro the microbial consortia adhering to mucus using an already established three-dimensional model of the human gut microbiota. Electrospun gelatin structures supplemented or not with mucins were inoculated with fecal samples and compared for their ability to support microbial adhesion and growth over time, as well as to shape the composition of the colonizing communities. Both scaffolds allowed the establishment of long-term stable biofilms with comparable total bacterial loads and biodiversity. However, mucin-coated structures harbored microbial consortia especially enriched in Akkermansia, Lactobacillus, and Faecalibacterium, being therefore able to select for microorganisms commonly considered mucosa-associated in vivo. IMPORTANCE These findings highlight the importance of mucins in shaping intestinal microbial communities, even those in artificial gut microbiota systems. We propose our in vitro model based on mucin-coated electrospun gelatin structures as a valid device for studies evaluating the effects of exogenous factors (nutrients, probiotics, infectious agents, and drugs) on mucus-adhering microbial communities.

Impact of Bacillus cereus on the Human Gut Microbiota in a 3D In Vitro Model

In vitro models for culturing complex microbial communities are progressively being used to study the effects of different factors on the modeling of in vitro-cultured microorganisms. In previous work, we validated a 3D in vitro model of the human gut microbiota based on electrospun gelatin scaffolds covered with mucins. The aim of this study was to evaluate the effect of Bacillus cereus, a pathogen responsible for food poisoning diseases in humans, on the gut microbiota grown in the model. Real-time quantitative PCR and 16S ribosomal RNA-gene sequencing were performed to obtain information on microbiota composition after introducing B. cereus ATCC 14579 vegetative cells or culture supernatants. The adhesion of B. cereus to intestinal mucins was also tested. The presence of B. cereus induced important modifications in the intestinal communities. Notably, levels of Proteobacteria (particularly Escherichia coli), Lactobacillus, and Akkermansia were reduced, while abundances of Bifidobacterium and Mitsuokella increased. In addition, B. cereus was able to adhere to mucins. The results obtained from our in vitro model stress the hypothesis that B. cereus is able to colonize the intestinal mucosa by stably adhering to mucins and impacting intestinal microbial communities as an additional pathogenetic mechanism during gastrointestinal infection.

Analysis of the microbial content of probiotic products commercialized worldwide and survivability in conditions mimicking the human gut environment

Introduction

Probiotics are living microorganisms that, when administered in adequate amounts, confer a health benefit on the host. Adequate number of living microbes, the presence of specific microorganisms, and their survival in the gastrointestinal (GI) environment are important to achieve desired health benefits of probiotic products. In this in vitro study, 21 leading probiotic formulations commercialized worldwide were evaluated for their microbial content and survivability in simulated GI conditions.

Methods

Plate-count method was used to determine the amount of living microbes contained in the products. Culture-dependent Matrix-Assisted Laser Desorption/Ionization-Time of Flight Mass Spectrometry and culture-independent metagenomic analysis through 16S and 18S rDNA sequencing were applied in combination for species identification. To estimate the potential survivability of the microorganisms contained in the products in the harsh GI environment, an in vitro model composed of different simulated gastric and intestinal fluids was adopted.

Results

The majority of the tested probiotic products were concordant with the labels in terms of number of viable microbes and contained probiotic species. However, one product included fewer viable microbes than those displayed on the label, one product contained two species that were not declared, and another product lacked one of the labeled probiotic strains. Survivability in simulated acidic and alkaline GI fluids was highly variable depending on the composition of the products. The microorganisms contained in four products survived in both acidic and alkaline environments. For one of these products, microorganisms also appeared to grow in the alkaline environment.

Conclusion

This in vitro study demonstrates that most globally commercialized probiotic products are consistent with the claims described on their labels with respect to the number and species of the contained microbes. Evaluated probiotics generally performed well in survivability tests, although viability of microbes in simulated gastric and intestinal environments showed large variability. Although the results obtained in this study indicate a good quality of the tested formulations, it is important to stress that stringent quality controls of probiotic products should always be performed to provide optimal health benefits for the host.

Prevalence, Virulence Potential, and Growth in Cheese of Bacillus cereus Strains Isolated from Fresh and Short-Ripened Cheeses Sold on the Italian Market

This study investigated B. cereus presence in 122 samples belonging to 34 typologies of fresh or short-ripened cheeses made from cow, sheep, goat, or buffalo pasteurized milk, and sold on the Italian market. B. cereus was isolated at a prevalence of 9.8%, with a marked variability among cheese categories, and at low counts (always below 2.26 Log CFU/g). Twelve isolates were identified by MALDI-TOF analysis and typified by RAPD PCR as belonging to different B. cereus strains. All the strains were tested for the production of hemolysin BL, phosphatidylcholine-specific phospholipase C, proteases, and biofilm formation, and for the presence of chromosomal toxin-encoding genes (sph, plcA, cytK, entFM, bcet, nheA, nheB, nheC). Overall, 92% of strains harbored bcet, 75% the three genes nheA, nheB, and nheC, as well as plcA and sph, 67% entFM, and 33% cytK. All strains showed biofilm-forming ability. A chemical-physical characterization of the cheeses was also performed to show their suitability as substrates for B. cereus growth, showing high heterogeneity in terms of pH, aw, salt content, and concentration of organic acids. Finally, the ability to support spore germination and vegetative cell growth of a selected cheese was investigated in spores-inoculated samples maintained at 10 °C and 15 °C, showing the inhibitory effect of low storage temperatures.

Corrigendum: Compositional quality and potential gastrointestinal behavior of probiotic products commercialized in Italy

[This corrects the article DOI: 10.3389/fmed.2018.00059.].

HPLC-MS-MS quantification of short-chain fatty acids actively secreted by probiotic strains

Introduction

Short-chain fatty acids (SCFAs) are the main by-products of microbial fermentations occurring in the human intestine and are directly involved in the host's physiological balance. As impaired gut concentrations of acetic, propionic, and butyric acids are often associated with systemic disorders, the administration of SCFA-producing microorganisms has been suggested as attractive approach to solve symptoms related to SCFA deficiency.

Methods

In this research, nine probiotic strains (Bacillus clausii NR, OC, SIN, and T, Bacillus coagulans ATCC 7050, Bifidobacterium breve DSM 16604, Limosilactobacillus reuteri DSM 17938, Lacticaseibacillus rhamnosus ATCC 53103, and Saccharomyces boulardii CNCM I-745) commonly included in commercial formulations were tested for their ability to secrete SCFAs by using an improved protocol in high-performance liquid chromatography coupled to tandem mass spectrometry (HPLC-MS-MS).

Results

The developed method was highly sensitive and specific, showing excellent limits of detection and quantification of secreted SCFAs. All tested microorganisms were shown to secrete acetic acid, with only B. clausii and S. boulardii additionally able to produce propionic and butyric acids. Quantitative differences in the secretion of SCFAs were also evidenced.

Discussion

The experimental approach described in this study may contribute to the characterization of probiotics as SCFA-producing organisms, a crucial stage toward their application to improve SCFA deficiency.

The administration of Enterococcus faecium SF68 counteracts compositional shifts in the gut microbiota of diet-induced obese mice

Microorganisms with probiotic properties are eliciting an increasing interest as coadjuvants in the prevention and treatment of obesity through modulation of the gut microbiota. In this study, a probiotic formulation based on Enterococcus faecium SF68 was administered to mice fed with a high-fat diet (HFD) to evaluate its efficacy in reducing body mass gain and in modulating the intestinal bacterial composition. Both stool and ileum samples were collected from untreated and treated mice and absolute abundances of specific taxa constituting the gut microbial consortium were evaluated. SF68 administration significantly reduced the HFD-induced weight gain. In these animals, the microbial gut composition shifted toward an enrichment in microbes positively correlated with mucus thickness, lower inflammation, lower glycemia levels, and SCFA production (i.e., Bifidobacterium, Akkermansia, and Faecalibacterium), as well as a depletion in bacterial phyla having a key role in obesity (i.e., Firmicutes, Proteobacteria). Our results demonstrate the efficacy of E. faecium SF68 in adjusting the composition of the dysbiotic microbiota of HFD-fed animals, thus ameliorating clinical conditions and exerting anti-obesity effects.

In vitro assessment of probiotic attributes for strains contained in commercial formulations

Although probiotics are often indiscriminately prescribed, they are not equal and their effects on the host may profoundly differ. In vitro determination of the attributes of probiotics should be a primary concern and be performed even before clinical studies are designed. In fact, knowledge on the biological properties a microbe possesses is crucial for selecting the most suitable bacteriotherapy for each individual. Herein, nine strains (Bacillus clausii NR, OC, SIN, T, Bacillus coagulans ATCC 7050, Bifidobacterium breve DSM 16604, Limosilactobacillus reuteri DSM 17938, Lacticaseibacillus rhamnosus ATCC 53103, and Saccharomyces boulardii CNCM I-745) declared to be contained in six commercial formulations were tested for their ability to tolerate simulated intestinal conditions, adhere to mucins, and produce β-galactosidase, antioxidant enzymes, riboflavin, and D-lactate. With the exception of B. breve, all microbes survived in simulated intestinal fluid. L. rhamnosus was unable to adhere to mucins and differences in mucin adhesion were evidenced for L. reuteri and S. boulardii depending on oxygen levels. All microorganisms produced antioxidant enzymes, but only B. clausii, B. coagulans, B. breve, and L. reuteri synthesize β-galactosidase. Riboflavin secretion was observed for Bacillus species and L. rhamnosus, while D-lactate production was restricted to L. reuteri and L. rhamnosus. Our findings indicate that the analyzed strains possess different in vitro biological properties, thus highlighting the usefulness of in vitro tests as prelude for clinical research.

Characterization of a Bacillus cereus strain associated with a large feed-related outbreak of severe infection in pigs

Aims

Bacillus cereus is often responsible for foodborne diseases and both local and systemic infections in humans. Cases of infection in other mammals are rather rare. In this study, we report a B. cereus feed‐related outbreak that caused the death of 6234 pigs in Italy.

Methods and Results

Massive doses of a Gram‐positive, spore‐forming bacterium were recovered from the animal feed, faeces of survived pigs and intestinal content of dead ones. The B. cereus MM1 strain was identified by MALDI‐TOF MS and typified by RAPD‐PCR. The isolate was tested for the production of PC‐PLC, proteases, hemolysins and biofilm, for motility, as well as for the presence of genes encoding tissue‐degrading enzymes and toxins. Antimicrobial resistance and pathogenicity in Galleria mellonella larvae were also investigated. Our results show that the isolated B. cereus strain is swimming‐proficient, produces PC‐PLC, proteases, hemolysins, biofilm and carries many virulence genes. The strain shows high pathogenicity in G. mellonella larvae.

Conclusions

The isolated B. cereus strain demonstrates an aggressive profile of pathogenicity and virulence, being able to produce a wide range of determinants potentially hazardous to pigs' health.

Significance and Impact of Study

This study highlights the proficiency of B. cereus to behave as a devastating pathogen in swine if ingested at high doses and underlines that more stringent quality controls are needed for livestock feeds and supplements.

Study of the Adhesion of the Human Gut Microbiota on Electrospun Structures

Although the adhesion of bacteria on surfaces is a widely studied process, to date, most of the works focus on a single species of microorganisms and are aimed at evaluating the antimicrobial properties of biomaterials. Here, we describe how a complex microbial community, i.e., the human gut microbiota, adheres to a surface to form stable biofilms. Two electrospun structures made of natural, i.e., gelatin, and synthetic, i.e., polycaprolactone, polymers were used to study their ability to both promote the adhesion of the human gut microbiota and support microbial growth in vitro. Due to the different wettabilities of the two surfaces, a mucin coating was also added to the structures to decouple the effect of bulk and surface properties on microbial adhesion. The developed biofilm was quantified and monitored using live/dead imaging and scanning electron microscopy. The results indicated that the electrospun gelatin structure without the mucin coating was the optimal choice for developing a 3D in vitro model of the human gut microbiota.

Delivery Mode Shapes the Composition of the Lower Airways Microbiota in Newborns

Radical alterations in the human microbiota composition are well-known to be associated with many pathological conditions. If these aberrations are established at the time of birth, the risk of developing correlated pathologies throughout life is significantly increased. For this reason, all newborns should begin their lives with a proper microbiota in each body district. The present study aimed at demonstrating a correlation between the mode of delivery and the development of a well-balanced microbiota in the lower airways of newborns. 44 pregnant women were enrolled in this study. Microbiological comparative analysis was carried out on tracheobronchial secretions of babies born through vaginal delivery (VD) or caesarean section (CS). All samples showed the presence of bacterial DNA, regardless of the mode of delivery. No viable cultivable bacteria were isolated from the CS samples. On the contrary, VD allowed colonization of the lower airways by alive cultivable bacteria. The identification of bacterial species revealed that Lactobacillus spp. and Bacteroides vulgatus were the most common microorganisms in the lower airways of vaginally-delivered newborns. Data obtained from quantitative PCRs showed a significantly higher total bacterial load, as well as Firmicutes and Lactobacillus spp. amount, in VD samples than CS ones, while no statistically significant difference was found in Torque Teno Virus (TTV) load between samples. Taken together, our findings confirm the hypothesis that passage through the maternal vaginal canal determines more beneficial colonization of the lower airways in newborns.

Microbiological Quality and Resistance to an Artificial Gut Environment of Two Probiotic Formulations

The quality control of probiotic products is the focus of numerous organizations worldwide. Several studies have highlighted the poor microbiological quality of many commercial probiotic formulations in terms of the identity of the contained microorganisms, viability, and purity, thus precluding the expected health benefits and representing a potential health risk for consumers. In this paper, we analyzed the contents of two probiotic formulations, one composed of an encapsulated mixture of lactobacilli and bifidobacteria, and one by a lyophilized yeast. The microorganisms contained in the products were quantified and identified using up-to-date methodologies, such as MALDI-TOF MS and metagenomic analysis. Moreover, as acid and bile tolerance is included among the criteria used to select probiotic microorganisms, in vitro tests were performed to evaluate the behavior of the formulations in conditions mimicking the harsh gastric environment and the intestinal fluids. Our results indicate the high quality of the formulations in terms of the enumeration and identification of the contained organisms, as well as the absence of contaminants. Moreover, both products tolerated the acidic conditions well, with encapsulation providing further protection for the microorganisms. A good tolerance to the simulated artificial intestinal conditions was also evidenced for both preparations.

Spotlight on the Compositional Quality of Probiotic Formulations Marketed Worldwide

On the worldwide market, a great number of probiotic formulations are available to consumers as drugs, dietary supplements, and functional foods. For exerting their beneficial effects on host health, these preparations should contain a sufficient amount of the indicated living microbes and be pathogen-free to be safe. Therefore, the contained microbial species and their amount until product expiry are required to be accurately reported on the labels. While commercial formulations licensed as drugs are subjected to rigorous quality controls, less stringent regulations are generally applied to preparations categorized as dietary supplements and functional foods. Many reports indicated that the content of several probiotic formulations does not always correspond to the label claims in terms of microbial identification, number of living organisms, and purity, highlighting the requirement for more stringent quality controls by manufacturers. The main focus of this review is to provide an in-depth overview of the microbiological quality of probiotic formulations commercialized worldwide. Many incongruences in the compositional quality of some probiotic formulations available on the worldwide market were highlighted. Even if manufacturers carry at least some of the responsibility for these inconsistencies, studies that analyze probiotic products should be conducted following recommended and up-to-date methodologies.

Antivirulence Properties of a Low-Molecular-Weight Quaternized Chitosan Derivative against Pseudomonas aeruginosa

The co-occurrence of increasing rates of resistance to current antibiotics and the paucity of novel antibiotics pose major challenges for the treatment of bacterial infections. In this scenario, treatments targeting bacterial virulence have gained considerable interest as they are expected to exert a weaker selection for resistance than conventional antibiotics. In a previous study, we demonstrated that a low-molecular-weight quaternized chitosan derivative, named QAL, displays antibiofilm activity against the major pathogen Pseudomonas aeruginosa at subinhibitory concentrations. The aim of this study was to investigate whether QAL was able to inhibit the production of relevant virulence factors of P. aeruginosa. When tested in vitro at subinhibiting concentrations (0.31-0.62 mg/mL), QAL markedly reduced the production of pyocyanin, pyoverdin, proteases, and LasA, as well as inhibited the swarming motility of three out of four P. aeruginosa strains tested. Furthermore, quantitative reverse transcription PCR (qRT-PCR) analyses demonstrated that expression of lasI and rhlI, two QS-related genes, was highly downregulated in a representative P. aeruginosa strain. Confocal scanning laser microscopy analysis suggested that FITC-labelled QAL accumulates intracellularly following incubation with P. aeruginosa. In contrast, the reduced production of virulence factors was not evidenced when QAL was used as the main polymeric component of polyelectrolyte-based nanoparticles. Additionally, combination of sub-MIC concentrations of QAL and tobramycin significantly reduced biofilm formation of P. aeruginosa, likely due to a synergistic activity towards planktonic bacteria. Overall, the results obtained demonstrated an antivirulence activity of QAL, possibly due to polymer intracellular localization and QS-inhibition, and its ability to inhibit P. aeruginosa growth synergizing with tobramycin.

A novel 3D in vitro model of the human gut microbiota

Clinical trials and animal studies on the gut microbiota are often limited by the difficult access to the gut, restricted possibility of in vivo monitoring, and ethical issues. An easily accessible and monitorable in vitro model of the gut microbiota represents a valid tool for a wider comprehension of the mechanisms by which microbes interact with the host and with each other. Herein, we present a novel and reliable system for culturing the human gut microbiota in vitro. An electrospun gelatin structure was biofabricated as scaffold for microbial growth. The efficiency of this structure in supporting microbial proliferation and biofilm formation was initially assessed for five microbes commonly inhabiting the human gut. The human fecal microbiota was then cultured on the scaffolds and microbial biofilms monitored by confocal laser and scanning electron microscopy and quantified over time. Metagenomic analyses and Real-Time qPCRs were performed to evaluate the stability of the cultured microbiota in terms of qualitative and quantitative composition. Our results reveal the three-dimensionality of the scaffold-adhered microbial consortia that maintain the bacterial biodiversity and richness found in the original sample. These findings demonstrate the validity of the developed electrospun gelatin-based system for in vitro culturing the human gut microbiota.

GTP-Dependent FlhF Homodimer Supports Secretion of a Hemolysin in Bacillus cereus

The multidomain (B-NG) protein FlhF, a flagellar biogenesis regulator in several bacteria, is the third paralog of the signal recognition particle (SRP)-GTPases Ffh and FtsY, which are known to drive protein-delivery to the plasma membrane. Previously, we showed that FlhF is required for Bacillus cereus pathogenicity in an insect model of infection, being essential for physiological peritrichous flagellation, for motility, and for the secretion of virulence proteins. Among these proteins, we found that the L₂ component of hemolysin BL, one of the most powerful toxins B. cereus produces, was drastically reduced by the FlhF depletion. Herein, we demonstrate that B. cereus FlhF forms GTP-dependent homodimers in vivo since the replacement of residues critical for their GTP-dependent homodimerization alters this ability. The protein directly or indirectly controls flagellation by affecting flagellin-gene transcription and its overproduction leads to a hyperflagellated phenotype. On the other hand, FlhF does not affect the expression of the L₂-encoding gene (hblC), but physically binds L₂ when in its homodimeric form, recruiting the protein to the plasma membrane for secretion. We additionally show that FlhF overproduction increases L₂ secretion and that the FlhF/L₂ interaction requires the NG domain of FlhF. Our findings demonstrate the peculiar behavior of B. cereus FlhF, which is required for the correct flagellar pattern and acts as SRP-GTPase in the secretion of a bacterial toxin subunit.

Identification of Bacillus species: Implication on the quality of probiotic formulations

Spores of several Bacillus species have long history of consumption and safe use as probiotics and a variety of formulations containing these organisms are available in the global market. Considering the difficulties in the identification of Bacillus species and the poor microbiological quality of many probiotic formulations, we used three up-to-date methodological approaches for analyzing the content of ten formulations marketed in Italy and labeled to contain Bacillus spores. We compared the performance of biochemical tests based on the BCL Vitek2 card and MALDI-TOF mass spectrometry, using 16S rDNA sequencing as the reference technique. The BCL card performed well in identifying all Bacillus probiotic strains as well as the Bruker’s MALDI Biotyper. Nevertheless, the MALDI score values were sometimes lower than those indicated by the manufacturer for correct species identification. Contaminant bacteria (Lysinibacillus fusiformis, Acinetobacter baumannii, Bacillus cereus, Brevibacillus choshinensis, Bacillus licheniformis, Bacillus badius) were detected in some formulations. Characterization of the B. cereus contaminant showed the potential pathogenicity of this strain. Microbial enumeration performed by the plate count method revealed that the number of viable cells contained in many of the analyzed products differed from the labeled amount. Overall, our data show that only two of the ten analyzed formulations qualitatively and quantitatively respect what is on the label. Since probiotic properties are most often strain specific, molecular typing of isolates of the two most common Bacillus species, B. clausii and B. coagulans, was also performed. In conclusion, the majority of the analyzed products do not comply with quality requirements, most likely leading to reduced/absent efficacy of the preparation and representing a potential infective risk for consumers.

Compositional Quality and Potential Gastrointestinal Behavior of Probiotic Products Commercialized in Italy

Recent guidelines indicate that oral probiotics, living microorganisms able to confer a health benefit on the host, should be safe for human consumption, when administered in a sufficient amount, and resist acid and bile to exert their beneficial effects (e.g., metabolic, immunomodulatory, anti-inflammatory, competitive). This study evaluated quantitative and qualitative aspects and the viability in simulated gastric and intestinal juices of commercial probiotic formulations available in Italy. Plate counting and MALDI-TOF mass spectrometry were used to enumerate and identify the contained organisms. In vitro studies with two artificial gastric juices and pancreatin-bile salt solution were performed to gain information on the gastric tolerance and bile resistance of the probiotic formulations. Most preparations satisfied the requirements for probiotics and no contaminants were found. Acid resistance and viability in bile were extremely variable depending on the composition of the formulations in terms of contained species and strains. In conclusion, this study indicates good microbiological quality but striking differences in the behavior in the presence of acids and bile for probiotic formulations marketed in Italy.

FlhF Is Required for Swarming Motility and Full Pathogenicity of Bacillus cereus

Besides sporulation, Bacillus cereus can undergo a differentiation process in which short swimmer cells become elongated and hyperflagellated swarmer cells that favor migration of the bacterial community on a surface. The functionally enigmatic flagellar protein FlhF, which is the third paralog of the signal recognition particle (SRP) GTPases Ffh and FtsY, is required for swarming in many bacteria. Previous data showed that FlhF is involved in the control of the number and positioning of flagella in B. cereus. In this study, in silico analysis of B. cereus FlhF revealed that this protein presents conserved domains that are typical of SRPs in many organisms and a peculiar N-terminal basic domain. By proteomic analysis, a significant effect of FlhF depletion on the amount of secreted proteins was found with some proteins increased (e.g., B component of the non-hemolytic enterotoxin, cereolysin O, enolase) and others reduced (e.g., flagellin, L₂ component of hemolysin BL, bacillolysin, sphingomyelinase, PC-PLC, PI-PLC, cytotoxin K) in the extracellular proteome of a ΔflhF mutant. Deprivation of FlhF also resulted in significant attenuation in the pathogenicity of this strain in an experimental model of infection in Galleria mellonella larvae. Our work highlights the multifunctional role of FlhF in B. cereus, being this protein involved in bacterial flagellation, swarming, protein secretion, and pathogenicity.

Prolonged prophylaxis with unfractioned heparin is effective to reduce delayed deep vein thrombosis in total hip replacement

The aim of this study was to assess the incidence of deep vein thrombosis (DVT) and pulmonary embolism (PE) until 45 days after elective total hip replacement (THR) and the efficacy of prolonged unfractioned heparin (UH) prophylaxis up to postoperative day 30. To this end 79 of 96 patients admitted consecutively to the University Hospital of Pisa for THR were randomly assigned to short- or long-term UH prophylaxis. Sixty-one patients completed the study: 28 of them received short-term prophylaxis (subcutaneous UH 15,000 IU/24 h for 15 days) and 33 prolonged prophylaxis (subcutaneous UH 15,000 IU/24 h for 30 days). Lower limb phlebography was performed in all patients on day 45 after THR. DVT was demonstrated in 10 (16.3%) cases after hospital discharge. Among them, 2 patients also had symptomatic PE. The incidence of DVT was 21.4% in short- and 12.1% in long-term UH-treated patients. The incidence of only proximal DVT was 17.8% in short- and 3.0% in long-term UH-treated patients; although the difference was only close to significance (p = 0.085), the relative risk of developing proximal DVT was about six times greater in the former group of patients. We concluded that the risk for thromboembolism persists at least until 45 days after surgery in patients subjected to THR. Prophylaxis with UH given up to postoperative day 30 appears more effective and safer in reducing the delayed thromboembolic risk compared to prophylaxis with UH given up to discharge only.

Computerized impedance plethysmography in the diagnosis of delayed deep vein thrombosis after total hip replacement

Although noninvasive techniques have been extensively evaluated in the diagnosis of deep vein thrombosis (DVT), few data exist about the role of computerized impedance plethysmography (CIP) in the diagnosis of delayed DVT after surgery, when patients are at home and the risk of DVT is still high. The aim of this study was to evaluate the reliability of CIP in the diagnosis of proximal and distal delayed DVT in both symptomatic and asymptomatic patients who had undergone elective total hip replacement (THR). Bilateral CIP of lower limbs was performed in 61 patients on days 5, 9, 15 and 45 after THR; for comparison, ascending phlebography was performed on days 45 after THR in all patients on the operated limb or on the limb with positive results on CIP. The overall rate of DVT diagnosed by phlebography was 16.3% (10/61). The sensitivity and specificity of CIP for all DVT were 20% and 98%, respectively, while the accuracy was 85%. The results were not influenced by the presence of symptoms or signs of the lower limbs. Similar results were obtained when considering proximal DVT only. In conclusion, the low sensitivity of computerized impedance plethysmography means that it cannot be used in screening for delayed deep vein thrombosis after total hip replacement, in both symptomatic and asymptomatic patients. However, because of its high specificity, when the results of computerized impedance plethysmography are positive phlebography should be performed to confirm the diagnosis of deep vein thrombosis.

Long-term survival in primary amyloidosis of the laryngotracheobronchial tract by treating complications only

Primary amyloidosis limited to the laryngotracheobronchial tract is relatively uncommon; therefore, knowledge of survival in these patients is poor and consensus regarding appropriate therapy unreached. The case is reported of a patient affected by primary amyloidosis limited to the laryngotracheobronchial tract who had a long survival and a good quality of life after only medical and neodymium-yttrium aluminium garnet (Nd-YAG) laser therapy. The patient had amyloidosis first detected in the larynx, which, 4 yrs later, progressed to involve the tracheobronchial tract, without pulmonary involvement. The patient was treated three times with Nd-YAG laser to obtain the recanalization of obstructed bronchi, with evident improvement of symptoms and pulmonary function. In conclusion, laryngotracheobronchial amyloidosis survival may be lengthened and quality of life made more acceptable by treating potential complications only.

Value of thrombin-antithrombin III complexes in major orthopedic surgery: relation to the onset of venous thromboembolism

This study evaluated (a) the possible changes of plasma levels of thrombin-antithrombin III complexes during hospitalization to predict venous thromboembolism in patients undergoing elective total hip replacement and (b) the sensitivity and specificity of thrombin-antithrombin III complexes in the late incidence of deep vein thrombosis when these patients are discharged from the hospital. In 50 consecutive patients (18 men, mean age = 63 +/- 8 years) a venous blood sample was obtained from each patient before surgery and postsurgery on days 5 +/- 2, 9 +/- 2, and 45 to evaluate the thrombin-antithrombin III complexes by the enzyme-linked immunosorbent assay as a part of a larger surveillance program. Six of 50 patients developed deep vein thrombosis, diagnosed by phlebography on the 45th day postsurgery. From the day before until the ninth day after surgery, mean values of the thrombin-antithrombin III complexes increased to a greater extent in patients with deep vein thrombosis than in those without, although the differences were not significant (from 14.8 +/- 11.2 ng/mL to 36.2 +/- 19.1 ng/mL in the former group and from 13.6 +/- 3.3 ng/mL to 22.4 +/- 5.1 ng/mL in the latter, p = NS). On the 45th day after surgery the mean value of the thrombin-antithrombin III complexes reduced less in patients with deep vein thrombosis (up to 9.9 +/- 1.9 ng/mL and to 25.2 +/- 17.2 ng/mL, respectively, p = NS). In addition, thrombin-antithrombin III complexes remained over the level reached on the fifth day only in the patients who developed deep vein thrombosis. On the 45th day after surgery, thrombin-antithrombin III complexes exhibited a sensitivity of 17%, a specificity of 86%, and an accuracy of 78% in differentiating the presence and absence of deep vein thrombosis as compared with phlebography. We conclude that after total hip replacement (a) serial measurement of the thrombin-antithrombin III complexes does not appear helpful in predicting venous thromboembolism during hospitalization, and (b) measurement of thrombin-antithrombin III complexes has a low diagnostic accuracy in diagnosing delayed deep vein thrombosis. However, the greater and persistent increase of thrombin-antithrombin III complexes level in patients who developed deep vein thrombosis may deserve further investigations.

Resolution of pulmonary embolism: effect of therapy and putative age of emboli

The purpose of this study was to evaluate functional and scintigraphic improvement in patients with pulmonary embolism (PE) according to the kind of treatment and the putative age of the emboli. The study includes 20 patients with both scintigraphic and angiographic diagnosis of PE enrolled in Pisa as a part of two previous multicenter trials: PAIMS 2 and BAPE. All patients were admitted to the Pulmonary Unit of the University of Pisa and treated with recombinant tissue-type plasminogen activator (rt-PA) plus heparin (H) (n = 10) or with H alone (n = 10). Results confirmed previous data, namely that perfusion damage decreases significantly from embolization to 7 days later in both patients treated with rt-PA + H and H alone (p < 0.001), although patients treated with rt-PA + H have a significantly higher perfusion restoration (p < 0.001) and a standard PaO2 increase (p < 0.01). Interestingly, our data also showed that the putative age of the emboli does not influence the efficacy of rt-PA + H treatment, while it does influence that of H treatment alone; in other words, rt-PA + H therapy may act efficaciously not only in fresh, but also in old pulmonary emboli.