Infection-associated gene regulation of L-tartrate metabolism in Salmonella enterica serovar Typhimurium

Enteric pathogens such as Salmonella enterica serovar Typhimurium experience spatial and temporal changes to the metabolic landscape throughout infection. Host reactive oxygen and nitrogen species non-enzymatically convert monosaccharides to alpha hydroxy acids, including L-tartrate. Salmonella utilizes L-tartrate early during infection to support fumarate respiration, while L-tartrate utilization ceases at later time points due to the increased availability of exogenous electron acceptors such as tetrathionate, nitrate, and oxygen. It remains unknown how Salmonella regulates its gene expression to metabolically adapt to changing nutritional environments. Here, we investigated how the transcriptional regulation for L-tartrate metabolism in Salmonella is influenced by infection-relevant cues. L-tartrate induces the transcription of ttdBAU, genes involved in L-tartrate utilization. L-tartrate metabolism is negatively regulated by two previously uncharacterized transcriptional regulators TtdV (STM3357) and TtdW (STM3358), and both TtdV and TtdW are required for the sensing of L-tartrate. The electron acceptors nitrate, tetrathionate, and oxygen repress ttdBAU transcription via the two-component system ArcAB. Furthermore, the regulation of L-tartrate metabolism is required for optimal fitness in a mouse model of Salmonella-induced colitis. TtdV, TtdW, and ArcAB allow for the integration of two cues, i.e., substrate availability and availability of exogenous electron acceptors, to control L-tartrate metabolism. Our findings provide novel insights into how Salmonella prioritizes the utilization of different electron acceptors for respiration as it experiences transitional nutrient availability throughout infection.

IMPORTANCE

Bacterial pathogens must adapt their gene expression profiles to cope with diverse environments encountered during infection. This coordinated process is carried out by the integration of cues that the pathogen senses to fine-tune gene expression in a spatiotemporal manner. Many studies have elucidated the regulatory mechanisms of how Salmonella sense metabolites in the gut to activate or repress its virulence program; however, our understanding of how Salmonella coordinates its gene expression to maximize the utilization of carbon and energy sources found in transitional nutrient niches is not well understood. In this study, we discovered how Salmonella integrates two infection-relevant cues, substrate availability and exogenous electron acceptors, to control L-tartrate metabolism. From our experiments, we propose a model for how L-tartrate metabolism is regulated in response to different metabolic cues in addition to characterizing two previously unknown transcriptional regulators. This study expands our understanding of how microbes combine metabolic cues to enhance fitness during infection.

Gene regulation of infection-associated L-tartrate metabolism in Salmonella enterica serovar Typhimurium

Enteric pathogens such as Salmonella enterica serovar Typhimurium experience spatial and temporal changes to the metabolic landscape throughout infection. Host reactive oxygen and nitrogen species non-enzymatically convert monosaccharides to alpha hydroxy acids, including L-tartrate. Salmonella utilizes L-tartrate early during infection to support fumarate respiration, while L-tartrate utilization ceases at later time points due to the increased availability of exogenous electron acceptors such as tetrathionate, nitrate, and oxygen. It remains unknown how Salmonella regulates its gene expression to metabolically adapt to changing nutritional environments. Here, we investigated how the transcriptional regulation for L-tartrate metabolism in Salmonella is influenced by infection-relevant cues. L-tartrate induces the transcription of ttdBAU, genes involved in L-tartrate utilization. L-tartrate metabolism is negatively regulated by two previously uncharacterized transcriptional regulators TtdV (STM3357) and TtdW (STM3358), and both TtdV and TtdW are required for sensing of L-tartrate. The electron acceptors nitrate, tetrathionate, and oxygen repress ttdBAU transcription via the two-component system ArcAB. Furthermore, regulation of L-tartrate metabolism is required for optimal fitness in a mouse model of Salmonella-induced colitis. TtdV, TtdW, and ArcAB allow for the integration of two cues, substrate availability and availability of exogenous electron acceptors, to control L-tartrate metabolism. Our findings provide novel insights into how Salmonella prioritizes utilization of different electron acceptors for respiration as it experiences transitional nutrient availability throughout infection.

Byproducts of inflammatory radical metabolism provide transient nutrient niches for microbes in the inflamed gut

Louis Pasteur's experiments on tartaric acid laid the foundation for our understanding of molecular chirality, but major questions remain. By comparing the optical activity of naturally-occurring tartaric acid with chemically-synthesized paratartaric acid, Pasteur realized that naturally-occurring tartaric acid contained only L-tartaric acid while paratartaric acid consisted of a racemic mixture of D- and L-tartaric acid. Curiously, D-tartaric acid has no known natural source, yet several gut bacteria specifically degrade D-tartaric acid. Here, we investigated the oxidation of monosaccharides by inflammatory reactive oxygen and nitrogen species. We found that this reaction yields an array of alpha hydroxy carboxylic acids, including tartaric acid isomers. Utilization of inflammation- derived D- and L-tartaric acid enhanced colonization by Salmonella Typhimurium and E. coli in murine models of gut inflammation. Our findings suggest that byproducts of inflammatory radical metabolism, such as tartrate and other alpha hydroxy carboxylic acids, create transient nutrient niches for enteric pathogens and other potentially harmful bacteria. Furthermore, this work illustrates that inflammatory radicals generate a zoo of molecules, some of which may erroneously presumed to be xenobiotics.

Iron acquisition by a commensal bacterium modifies host nutritional immunity during Salmonella infection

During intestinal inflammation, host nutritional immunity starves microbes of essential micronutrients, such as iron. Pathogens scavenge iron using siderophores, including enterobactin; however, this strategy is counteracted by host protein lipocalin-2, which sequesters iron-laden enterobactin. Although this iron competition occurs in the presence of gut bacteria, the roles of commensals in nutritional immunity involving iron remain unexplored. Here, we report that the gut commensal Bacteroides thetaiotaomicron acquires iron and sustains its resilience in the inflamed gut by utilizing siderophores produced by other bacteria, including Salmonella, via a secreted siderophore-binding lipoprotein XusB. Notably, XusB-bound enterobactin is less accessible to host sequestration by lipocalin-2 but can be "re-acquired" by Salmonella, allowing the pathogen to evade nutritional immunity. Because the host and pathogen have been the focus of studies of nutritional immunity, this work adds commensal iron metabolism as a previously unrecognized mechanism modulating the host-pathogen interactions and nutritional immunity.

Formate oxidation in the intestinal mucus layer enhances fitness of Salmonella enterica serovar Typhimurium

Salmonella enterica serovar Typhimurium induces intestinal inflammation to create a niche that fosters the outgrowth of the pathogen over the gut microbiota. Under inflammatory conditions, Salmonella utilizes terminal electron acceptors generated as byproducts of intestinal inflammation to generate cellular energy through respiration. However, the electron donating reactions in these electron transport chains are poorly understood. Here, we investigated how formate utilization through the respiratory formate dehydrogenase-N (FdnGHI) and formate dehydrogenase-O (FdoGHI) contribute to gut colonization of Salmonella. Both enzymes fulfilled redundant roles in enhancing fitness in a mouse model of Salmonella-induced colitis, and coupled to tetrathionate, nitrate, and oxygen respiration. The formic acid utilized by Salmonella during infection was generated by its own pyruvate-formate lyase as well as the gut microbiota. Transcription of formate dehydrogenases and pyruvate-formate lyase was significantly higher in bacteria residing in the mucus layer compared to the lumen. Furthermore, formate utilization conferred a more pronounced fitness advantage in the mucus, indicating that formate production and degradation occurred predominantly in the mucus layer. Our results provide new insights into how Salmonella adapts its energy metabolism to the local microenvironment in the gut. IMPORTANCE Bacterial pathogens must not only evade immune responses but also adapt their metabolism to successfully colonize their host. The microenvironments encountered by enteric pathogens differ based on anatomical location, such as small versus large intestine, spatial stratification by host factors, such as mucus layer and antimicrobial peptides, and distinct commensal microbial communities that inhabit these microenvironments. Our understanding of how Salmonella populations adapt its metabolism to different environments in the gut is incomplete. In the current study, we discovered that Salmonella utilizes formate as an electron donor to support respiration, and that formate oxidation predominantly occurs in the mucus layer. Our experiments suggest that spatially distinct Salmonella populations in the mucus layer and the lumen differ in their energy metabolism. Our findings enhance our understanding of the spatial nature of microbial metabolism and may have implications for other enteric pathogens as well as commensal host-associated microbial communities.

Iron acquisition by a commensal bacterium modifies host nutritional immunity during Salmonella infection

During intestinal inflammation, host nutritional immunity starves microbes of essential micronutrients such as iron. Pathogens scavenge iron using siderophores, which is counteracted by the host using lipocalin-2, a protein that sequesters iron-laden siderophores, including enterobactin. Although the host and pathogens compete for iron in the presence of gut commensal bacteria, the roles of commensals in nutritional immunity involving iron remain unexplored. Here, we report that the gut commensal Bacteroides thetaiotaomicron acquires iron in the inflamed gut by utilizing siderophores produced by other bacteria including Salmonella, via a secreted siderophore-binding lipoprotein termed XusB. Notably, XusB-bound siderophores are less accessible to host sequestration by lipocalin-2 but can be "re-acquired" by Salmonella , allowing the pathogen to evade nutritional immunity. As the host and pathogen have been the focus of studies of nutritional immunity, this work adds commensal iron metabolism as a previously unrecognized mechanism modulating the interactions between pathogen and host nutritional immunity.

Respire or expire-precision killing of Helicobacter pylori by targeting complex I respiration

In this issue of Cell Chemical Biology, Lettl et al.1 identify complex I as a suitable target for selective killing of Helicobacter pylori. The unique composition of complex I in H. pylori enables precision targeting of the carcinogenic pathogen while sparing representative species of the gut microbiota.

Taxonomic and Metagenomic Analyses Define the Development of the Microbiota in the Chick

Chicks are ideal to follow the development of the intestinal microbiota and to understand how a pathogen perturbs this developing population. Taxonomic/metagenomic analyses captured the development of the chick microbiota in unperturbed chicks and in chicks infected with Salmonella enterica serotype Typhimurium (STm) during development. Taxonomic analysis suggests that colonization by the chicken microbiota takes place in several waves. The cecal microbiota stabilizes at day 12 posthatch with prominent Gammaproteobacteria and Clostridiales. Introduction of S. Typhimurium at day 4 posthatch disrupted the expected waves of intestinal colonization. Taxonomic and metagenomic shotgun sequencing analyses allowed us to identify species present in uninfected chicks. Untargeted metabolomics suggested different metabolic activities in infected chick microbiota. This analysis and gas chromatography-mass spectrometry on ingesta confirmed that lactic acid in cecal content coincides with the stable presence of enterococci in STm-infected chicks. Unique metabolites, including 2-isopropylmalic acid, an intermediate in the biosynthesis of leucine, were present only in the cecal content of STm-infected chicks. The metagenomic data suggested that the microbiota in STm-infected chicks contained a higher abundance of genes, from STm itself, involved in branched-chain amino acid synthesis. We generated an ilvC deletion mutant (STM3909) encoding ketol-acid-reductoisomerase, a gene required for the production of l-isoleucine and l-valine. ΔilvC mutants are disadvantaged for growth during competitive infection with the wild type. Providing the ilvC gene in trans restored the growth of the ΔilvC mutant. Our integrative approach identified biochemical pathways used by STm to establish a colonization niche in the chick intestine during development. IMPORTANCE Chicks are an ideal model to follow the development of the intestinal microbiota and to understand how a pathogen perturbs this developing population. Using taxonomic and metagenomic analyses, we captured the development of chick microbiota to 19 days posthatch in unperturbed chicks and in chicks infected with Salmonella enterica serotype Typhimurium (STm). We show that normal development of the microbiota takes place in waves and is altered in the presence of a pathogen. Metagenomics and metabolomics suggested that branched-chain amino acid biosynthesis is especially important for Salmonella growth in the infected chick intestine. Salmonella mutants unable to make l-isoleucine and l-valine colonize the chick intestine poorly. Restoration of the pathway for biosynthesis of these amino acids restored the colonizing ability of Salmonella. Integration of multiple analyses allowed us to correctly identify biochemical pathways used by Salmonella to establish a niche for colonization in the chick intestine during development.

Colonocyte-derived lactate promotes E. coli fitness in the context of inflammation-associated gut microbiota dysbiosis

BACKGROUND

Intestinal inflammation disrupts the microbiota composition leading to an expansion of Enterobacteriaceae family members (dysbiosis). Associated with this shift in microbiota composition is a profound change in the metabolic landscape of the intestine. It is unclear how changes in metabolite availability during gut inflammation impact microbial and host physiology.

RESULTS

We investigated microbial and host lactate metabolism in murine models of infectious and non-infectious colitis. During inflammation-associated dysbiosis, lactate levels in the gut lumen increased. The disease-associated spike in lactate availability was significantly reduced in mice lacking the lactate dehydrogenase A subunit in intestinal epithelial cells. Commensal E. coli and pathogenic Salmonella, representative Enterobacteriaceae family members, utilized lactate via the respiratory L-lactate dehydrogenase LldD to increase fitness. Furthermore, mice lacking the lactate dehydrogenase A subunit in intestinal epithelial cells exhibited lower levels of inflammation in a model of non-infectious colitis.

CONCLUSIONS

The release of lactate by intestinal epithelial cells during gut inflammation impacts the metabolism of gut-associated microbial communities. These findings suggest that during intestinal inflammation and dysbiosis, changes in metabolite availability can perpetuate colitis-associated disturbances of microbiota composition. Video Abstract.

How microbiological tests reflect bacterial pathogenesis and host adaptation

Historically, clinical microbiological laboratories have often relied on isolation of pure cultures and phenotypic testing to identify microorganisms. These clinical tests are often based on specific biochemical reactions, growth characteristics, colony morphology, and other physiological aspects. The features used for identification in clinical laboratories are highly conserved and specific for a given group of microbes. We speculate that these features might be the result of evolutionary selection and thus may reflect aspects of the life cycle of the organism and pathogenesis. Indeed, several of the metabolic pathways targeted by diagnostic tests in some cases may represent mechanisms for host colonization or pathogenesis. Examples include, but are not restricted to, Staphylococcus aureus, Pseudomonas aeruginosa, Klebsiella pneumoniae, Salmonella enterica, Shigella spp., and enteroinvasive Escherichia coli (EIEC). Here, we provide an overview of how some common tests reflect molecular mechanisms of bacterial pathogenesis.

Reshaping of bacterial molecular hydrogen metabolism contributes to the outgrowth of commensal E. coli during gut inflammation

The composition of gut-associated microbial communities changes during intestinal inflammation, including an expansion of Enterobacteriaceae populations. The mechanisms underlying microbiota changes during inflammation are incompletely understood. Here, we analyzed previously published metagenomic datasets with a focus on microbial hydrogen metabolism. The bacterial genomes in the inflamed murine gut and in patients with inflammatory bowel disease contained more genes encoding predicted hydrogen-utilizing hydrogenases compared to communities found under non-inflamed conditions. To validate these findings, we investigated hydrogen metabolism of Escherichia coli, a representative Enterobacteriaceae, in mouse models of colitis. E. coli mutants lacking hydrogenase-1 and hydrogenase-2 displayed decreased fitness during colonization of the inflamed cecum and colon. Utilization of molecular hydrogen was in part dependent on respiration of inflammation-derived electron acceptors. This work highlights the contribution of hydrogenases to alterations of the gut microbiota in the context of non-infectious colitis.

Epithelial-Derived Reactive Oxygen Species Enable AppBCX-Mediated Aerobic Respiration of Escherichia coli during Intestinal Inflammation

The intestinal epithelium separates host tissue and gut-associated microbial communities. During inflammation, the host releases reactive oxygen and nitrogen species as an antimicrobial response. The impact of these radicals on gut microbes is incompletely understood. We discovered that the cryptic appBCX genes, predicted to encode a cytochrome bd-II oxidase, conferred a fitness advantage for E. coli in chemical and genetic models of non-infectious colitis. This fitness advantage was absent in mice that lacked epithelial NADPH oxidase 1 (NOX1) activity. In laboratory growth experiments, supplementation with exogenous hydrogen peroxide enhanced E. coli growth through AppBCX-mediated respiration in a catalase-dependent manner. We conclude that epithelial-derived reactive oxygen species are degraded in the gut lumen, which gives rise to molecular oxygen that supports the aerobic respiration of E. coli. This work illustrates how epithelial host responses intersect with gut microbial metabolism in the context of gut inflammation.

Xenosiderophore Utilization Promotes Bacteroides thetaiotaomicron Resilience during Colitis

During short-lived perturbations, such as inflammation, the gut microbiota exhibits resilience and reverts to its original configuration. Although microbial access to the micronutrient iron is decreased during colitis, pathogens can scavenge iron by using siderophores. How commensal bacteria acquire iron during gut inflammation is incompletely understood. Curiously, the human commensal Bacteroides thetaiotaomicron does not produce siderophores but grows under iron-limiting conditions using enterobacterial siderophores. Using RNA-seq, we identify B. thetaiotaomicron genes that were upregulated during Salmonella-induced gut inflammation and were predicted to be involved in iron uptake. Mutants in the xusABC locus (BT2063-2065) were defective for xenosiderophore-mediated iron uptake in vitro. In the normal mouse gut, the XusABC system was dispensable, while a xusA mutant colonized poorly during colitis. This work identifies xenosiderophore utilization as a critical mechanism for B. thetaiotaomicron to sustain colonization during inflammation and suggests a mechanism of how interphylum iron metabolism contributes to gut microbiota resilience.

Editing of the gut microbiota reduces carcinogenesis in mouse models of colitis-associated colorectal cancer

Enterobacteriaceae family members such as E. coli exacerbate development of intestinal malignancy. Zhu et al. report that targeting the metabolism of protumoral Enterobacteriaceae by tungstate prevents tumor development in murine models of colitis-associated colorectal cancer.

Chronic inflammation and gut microbiota dysbiosis, in particular the bloom of genotoxin-producing E. coli strains, are risk factors for the development of colorectal cancer. Here, we sought to determine whether precision editing of gut microbiota metabolism and composition could decrease the risk for tumor development in mouse models of colitis-associated colorectal cancer (CAC). Expansion of experimentally introduced E. coli strains in the azoxymethane/dextran sulfate sodium colitis model was driven by molybdoenzyme-dependent metabolic pathways. Oral administration of sodium tungstate inhibited E. coli molybdoenzymes and selectively decreased gut colonization with genotoxin-producing E. coli and other Enterobacteriaceae. Restricting the bloom of Enterobacteriaceae decreased intestinal inflammation and reduced the incidence of colonic tumors in two models of CAC, the azoxymethane/dextran sulfate sodium colitis model and azoxymethane-treated, Il10-deficient mice. We conclude that metabolic targeting of protumoral Enterobacteriaceae during chronic inflammation is a suitable strategy to prevent the development of malignancies arising from gut microbiota dysbiosis.

Precision editing of the gut microbiota ameliorates colitis

Inflammatory diseases of the gastrointestinal tract are frequently associated with dysbiosis, characterized by changes in gut microbial communities that include an expansion of facultative anaerobic bacteria of the Enterobacteriaceae family (phylum Proteobacteria). Here we show that a dysbiotic expansion of Enterobacteriaceae during gut inflammation could be prevented by tungstate treatment, which selectively inhibited molybdenum-cofactor-dependent microbial respiratory pathways that are operational only during episodes of inflammation. By contrast, we found that tungstate treatment caused minimal changes in the microbiota composition under homeostatic conditions. Notably, tungstate-mediated microbiota editing reduced the severity of intestinal inflammation in mouse models of colitis. We conclude that precision editing of the microbiota composition by tungstate treatment ameliorates the adverse effects of dysbiosis in the inflamed gut.

Dysbiosis-Associated Change in Host Metabolism Generates Lactate to Support Salmonella Growth

During Salmonella-induced gastroenteritis, mucosal inflammation creates a niche that favors the expansion of the pathogen population over the microbiota. Here, we show that Salmonella Typhimurium infection was accompanied by dysbiosis, decreased butyrate levels, and substantially elevated lactate levels in the gut lumen. Administration of a lactate dehydrogenase inhibitor blunted lactate production in germ-free mice, suggesting that lactate was predominantly of host origin. Depletion of butyrate-producing Clostridia, either through oral antibiotic treatment or as part of the pathogen-induced dysbiosis, triggered a switch in host cells from oxidative metabolism to lactate fermentation, increasing both lactate levels and Salmonella lactate utilization. Administration of tributyrin or a PPARγ agonist diminished host lactate production and abrogated the fitness advantage conferred on Salmonella by lactate utilization. We conclude that alterations of the gut microbiota, specifically a depletion of Clostridia, reprogram host metabolism to perform lactate fermentation, thus supporting Salmonella infection.

Microbial Respiration and Formate Oxidation as Metabolic Signatures of Inflammation-Associated Dysbiosis

Intestinal inflammation is frequently associated with an alteration of the gut microbiota, termed dysbiosis, which is characterized by a reduced abundance of obligate anaerobic bacteria and an expansion of facultative Proteobacteria such as commensal E. coli. The mechanisms enabling the outgrowth of Proteobacteria during inflammation are incompletely understood. Metagenomic sequencing revealed bacterial formate oxidation and aerobic respiration to be overrepresented metabolic pathways in a chemically induced murine model of colitis. Dysbiosis was accompanied by increased formate levels in the gut lumen. Formate was of microbial origin since no formate was detected in germ-free mice. Complementary studies using commensal E. coli strains as model organisms indicated that formate dehydrogenase and terminal oxidase genes provided a fitness advantage in murine models of colitis. In vivo, formate served as electron donor in conjunction with oxygen as the terminal electron acceptor. This work identifies bacterial formate oxidation and oxygen respiration as metabolic signatures for inflammation-associated dysbiosis.

An Oxidative Central Metabolism Enables Salmonella to Utilize Microbiota-Derived Succinate

The mucosal inflammatory response induced by Salmonella serovar Typhimurium creates a favorable niche for this gut pathogen. Conventional wisdom holds that S. Typhimurium undergoes an incomplete tricarboxylic acid (TCA) cycle in the anaerobic mammalian gut. One change during S. Typhimurium-induced inflammation is the production of oxidized compounds by infiltrating neutrophils. We show that inflammation-derived electron acceptors induce a complete, oxidative TCA cycle in S. Typhimurium, allowing the bacteria to compete with the microbiota for colonization. A complete TCA cycle facilitates utilization of the microbiota-derived fermentation product succinate as a carbon source. S. Typhimurium succinate utilization genes contribute to efficient colonization in conventionally raised mice, but provide no growth advantage in germ-free mice. Mono-association of gnotobiotic mice with Bacteroides, a major succinate producer, restores succinate utilization in S. Typhimurium. Thus, oxidative central metabolism enables S. Typhimurium to utilize a variety of carbon sources, including microbiota-derived succinate.

Respiration of Microbiota-Derived 1,2-propanediol Drives Salmonella Expansion during Colitis

Intestinal inflammation caused by Salmonella enterica serovar Typhimurium increases the availability of electron acceptors that fuel a respiratory growth of the pathogen in the intestinal lumen. Here we show that one of the carbon sources driving this respiratory expansion in the mouse model is 1,2-propanediol, a microbial fermentation product. 1,2-propanediol utilization required intestinal inflammation induced by virulence factors of the pathogen. S. Typhimurium used both aerobic and anaerobic respiration to consume 1,2-propanediol and expand in the murine large intestine. 1,2-propanediol-utilization did not confer a benefit in germ-free mice, but the pdu genes conferred a fitness advantage upon S. Typhimurium in mice mono-associated with Bacteroides fragilis or Bacteroides thetaiotaomicron. Collectively, our data suggest that intestinal inflammation enables S. Typhimurium to sidestep nutritional competition by respiring a microbiota-derived fermentation product.

Salmonella enterica serovar Typhimurium induces intestinal inflammation to induce the generation of host-derived respiratory electron acceptors, thereby driving a respiratory pathogen expansion, which aids infectious transmission by the fecal oral route. However, the identity of nutrients serving as electron donors to enable S. Typhimurium to edge out competing microbes in the competitive environment of the gut are just beginning to be worked out. Here we demonstrate that aerobic and anaerobic respiratory pathways cooperate to promote growth of Salmonella on the microbial fermentation product 1,2-propanediol. We propose that pathogen-induced intestinal inflammation enables Salmonella to sidestep nutritional competition with the largely anaerobic microbiota by respiring a microbe-derived metabolite that cannot be consumed by fermentation.

Staphylococcus aureus and Staphylococcus epidermidis Virulence Strains as Causative Agents of Persistent Infections in Breast Implants

Staphylococcus epidermidis and Staphylococcus aureus are currently considered two of the most important pathogens in nosocomial infections associated with catheters and other medical implants and are also the main contaminants of medical instruments. However because these species of Staphylococcus are part of the normal bacterial flora of human skin and mucosal surfaces, it is difficult to discern when a microbial isolate is the cause of infection or is detected on samples as a consequence of contamination. Rapid identification of invasive strains of Staphylococcus infections is crucial for correctly diagnosing and treating infections. The aim of the present study was to identify specific genes to distinguish between invasive and contaminating S. epidermidis and S. aureus strains isolated on medical devices; the majority of our samples were collected from breast prostheses. As a first step, we compared the adhesion ability of these samples with their efficacy in forming biofilms; second, we explored whether it is possible to determine if isolated pathogens were more virulent compared with international controls. In addition, this work may provide additional information on these pathogens, which are traditionally considered harmful bacteria in humans, and may increase our knowledge of virulence factors for these types of infections.

[Efficacy of bronchoscopic Nd:YAG laser therapy for laryngotracheal stenoses after long-term intubation]

From 1987 to 1993, 38 patients with laryngotracheal stenosis due to prolonged intubation were treated with the Nd:YAG-laser. A total of 45 stenoses were identified and classified according to endoscopic assessment. Patients who had an asymptomatic airway for at least 8 months and did not require further intervention were considered treatment successes. The best results were found in the diaphragmas and granulomas (86% and 65%), in stenoses less than 1 cm in length (61%) and in cases with less than 70% obstruction of the tracheal lumen (61%).

Bronchoalveolar lavage in the diagnosis of disseminated lung tumors

We report our experience with bronchoalveolar lavage (BAL) and its value in the diagnosis of malignant lung infiltrates. A total of 162 patients with biopsy- or autopsy-proven cancer had an analysis of BAL fluid performed. Cytologic examination showed malignant cells in 123 (76%) patients. The diagnostic accuracy varied depending on the neoplastic nature and growth pattern of the disease. BAL disclosed cancer cells in 93% of 44 bronchioloalveolar carcinomas. Carcinomatous lymphangitis due to metastatic cancer was diagnosed in 83% of 69 cases. Hematogenous metastases (with sharply circumscribed nodules on chest radiography) were diagnosed in 45% of 22 such cases. We recognized 67% of 15 non-Hodgkin's lymphomas and 3 of 9 cases of Hodgkin's disease with pulmonary involvement. Immunocytochemistry using monoclonal and/or polyclonal antibodies was of value in the identification and classification of cells in non-Hodgkin's lymphoma.

Acute lung inflammation: neutrophil elastase versus neutrophils in the bronchoalveolar lavage--neutrophil elastase reflects better inflammatory intensity

OBJECTIVE

To test the hypothesis whether PMN-Elastase in bronchoalveolar lavage fluid (BALF) could reflect neutrophil activity in the lower respiratory tract.

DESIGN

Prospectively, morphologic findings of acute and chronic inflammation in the transbronchial lung biopsy specimens were compared with the numbers of neutrophils in the BALF and the concentration of PMN-Elastase in the same.

SETTING

Ambulatory outpatient service of bronchology and respiratory physiopathology and intensive care unit of a communal hospital.

PATIENTS

50 ambulatory outpatients and 10 critically ill patients of the ICU, presenting infiltrative lung diseases.

INTERVENTIONS

Transbronchial lung biopsies and bronchoalveolar lavage were performed through a fiberoptic bronchoscope. Venous blood samples were obtained after bronchoscopy.

MEASUREMENTS AND RESULTS

Biopsy specimens and cell count in the BALF were examined by light microscopy. PMN-Elastase and albumin were measured in the BALF-supernatant and in the plasma. C-reactive protein (CRP) and a1 proteinase inhibitor (a1-PI) were measured in the plasma. Intrapulmonary originating PMN-Elastase was calculated with reference to albumin. The results concerning acute inflammation obtained by transbronchial lung biopsy (TBLB) (n = 16) correlated better with the levels of PMN-Elastase in the BALF (n = 21) than with the neutrophil count (n = 28) (p < 0.5 versus p < 0.025 for chi 2). The sensitivities and specificities of the above methods were respectively 76.9%, 100%, 100% and 100%, 95.2%, 63.1%. The intrapulmonary originating PMN-Elastase was about 99.7% of the measured BALF-Elastase.

CONCLUSION

The PMN-Elastase concentration in the BALF is a more accurate indicator of the inflammatory intensity in the alveolar structures than in the number of neutrophils. It may therefore be useful to the clinician in his attempt to detect acute inflammation in the lower respiratory tract.

[Unilateral gynecomastia induced by the use of anabolic steroids. A clinical case report]

The authors studied a case of left unilateral gynecomastia occurring in a 26-year-old body-builder after anabolic steroids assumption. The mammal features were found by echography and mammography and they showed the presence of a 3 cm diameter retroareolar area of gland tissue surrounded by fibrotic tissue. After excluding every likely cause giving gynecomastia through laboratory tests, it was clear a relationship with the assumption of high doses of anabolic hormones, with particular regard to methyltestosterone. Therefore, also this substance which on its own is not aromatized by extrasplanchnic tissues, can be responsible for man's mammal hypertrophy, if joined to a slight iatrogenic liver cytolysis.

Diffuse panbronchiolitis observed in an Italian male

We describe a case of a 43 year old man who presented with productive cough, dyspnea, severe obstructive ventilatory failure and diffuse micronodular shadows on chest roentgenogram. Bronchoalveolar lavage fluid analysis showed an increased total cellularity sustained by a huge neutrophilia. Sweat test was negative. Transbronchial lung biopsy and autopsy showed unit lesion of diffuse panbronchiolitis. This report represents, to the best of our knowledge, the first case of diffuse panbronchiolitis observed in Europe.

Prognostic significance of the evaluation of bronchoalveolar lavage cell populations in patients with HIV-1 infection and pulmonary involvement

To investigate the prognostic utility of the morphologic and immunologic evaluation of BAL cell populations in determining mortality risk, we analyzed BAL data obtained from 115 patients infected with HIV-1. Forty fatal outcomes occurred within 73 patients with OI. The OI patients who died showed a significant increase in neutrophils with respect to surviving patients. Furthermore, the finding of a BAL neutrophilia in HIV-1-infected patients with OI strongly correlated with a high risk of death. Among 42 cases without OI, 11 patients died. Patients without OI who had a fatal outcome showed an increase in CD3+ and CD8+ BAL lymphocytes with respect to the survivors. The presence of a lymphocytic alveolitis was associated with a significant increase in the mortality rate. Taken together our data suggest that the evaluation of the BAL cell populations might be useful in predicting the risk of fatal outcome in patients with HIV-1 infection.

Alveolar macrophages from patients with AIDS and AIDS-related complex constitutively synthesize and release tumor necrosis factor alpha

To verify the hypothesis that alveolar macrophages (AMs) from patients infected with HIV-1 could synthesize and release TNF alpha, AMs recovered from the BAL fluid of 11 patients with seropositive HIV-1 (six with AIDS and five with ARC) were tested in vitro for their ability to destroy TNF alpha-susceptible targets. Furthermore, the presence of TNF alpha was assessed in AM-conditioned supernatants on the basis of their cytotoxic activity and by using an immunoenzymatic test and immunoblotting. Transcription of the TNF alpha gene in AMs was also studied by means of the Northern blot analysis. AMs freshly recovered from patients infected with HIV-1 exhibited high levels of cell-mediated cytotoxicity against U937 targets, and the addition of a polyclonal anti-TNF alpha antibody resulted in a significant inhibition of the target lysis. Cell-free supernatants conditioned by unstimulated AMs exerted high levels of cytotoxic activity against TNF alpha-sensitive targets, whereas duplicate, neutralization experiments performed in the presence of an anti-TNF alpha antibody proved that the observed cytotoxic activity was mostly mediated by TNF alpha. The presence of high amounts of TNF alpha in the conditioned media was confirmed by the immunoenzymatic test. In addition, the immunoblot analysis showed that the TNF alpha released by AMs has a Mr 17,000 band, identical to a standard preparation of recombinant TNF alpha. The Northern blot demonstrated that unstimulated AMs express detectable levels of mRNA transcripts for TNF alpha. Taken together, our data support the concept that AMs from patients with HIV-1 infection constitutively release TNF alpha.(ABSTRACT TRUNCATED AT 250 WORDS)

Cytotoxic events taking place in the lung of patients with HIV-1 infection. Evidence of an intrinsic defect of the major histocompatibility complex-unrestricted killing partially restored by the incubation with rIL-2

To characterize the cytotoxic events taking place in the lung of patients with HIV-1 infection, we studied the cells recovered from the bronchoalveolar lavage (BAL) of nine patients with AIDS, seven patients with AIDS-related complex, and two patients with lymphadenopathy. Phenotypic analysis was coupled to a series of functional evaluations of nonspecific cytotoxic abilities performed on lung effectors, including their property to bind K-562 targets, to release natural killer cytotoxic factor (NKCF), and to become cytotoxic following in vitro activation with rIL-2. Our results demonstrated that lung cells bearing the NK-related CD16, CD56, and CD57 antigens were quantitatively increased, irrespective of the disease stage. The majority of the cells also coexpressed the CD3 molecule and the alpha/beta T cell receptor (TCR), notably the phenotype characterizing MHC-unrestricted cytotoxic T cells. From a functional point of view, a severe impairment of the spontaneous cytotoxic ability was demonstrated in most patients. Evaluation at the single cell level showed a normal percentage of the effector/target conjugates formed by HIV-1 lymphocytes. The release of NKCF was undetectable in patients with AIDS even following lectin stimulation, whereas BAL cells from patients with earlier infection produced and/or could be triggered to release discrete amounts of NKCF by incubation with PHA. Studies designed to activate lung cytotoxic cells with rIL-2 showed that in most patients the stimulation of effector cells with rIL-2 enhanced the spontaneous killing and elicited a lymphokine-activated killer (LAK) phenomenon.(ABSTRACT TRUNCATED AT 250 WORDS)

[A comparative evaluation of computerized diagnostic decisional support in gastroenterology in relation to typical clinical pictures]

On the basis of the results obtained in a previous perspective comparative study aimed to compare the diagnostic accuracy of a computerized diagnostic decisional support in gastroenterology with that of non-specialist physicians, the Authors have carried out a retrospective study, based on the same series and on the same results, but disaggregating the global comparisons according to the feature of the clinical presentations. The latter were therefore classified by independent gastroenterologists as "typical", "atypical", or "borderline", and for each group the difference of diagnostic accuracy between program and physicians was again evaluated. Even if the program proved more accurate in all groups, the greatest difference was observed in the "borderline" group which the Authors claim to include the kind of presentation which more than any other needs a decisional aid. This should suggest a possible useful implementation of the system in daily clinical practice.

[Endobronchial administration of netilmicin in patients with bronchopulmonary infections seen in the neurosurgical intensive care unit]

The Authors report the results obtained in the treatment of bronchopulmonary infections in patients hospitalized in the Neurosurgical Intensive Care Unit. Netilmicin was administered by systemic and endobronchial routes. The cleaning of the bronchial tree was always performed. Twenty-six patients (16 males and 10 females) were enrolled and assigned to one of the following groups. Group A: 16 patients with confirmed pneumonia; Group B: 10 patients without bronchopulmonary infections, as controls for serum pharmacokinetic study. In the majority of the cases pneumonia was caused by Staphylococcus aureus and Pseudomonas aeruginosa. The results obtained were positive: pneumonia resolution was observed in 10 patients (67%), improvement in 4 (27%) and failure in one case (6%). A pharmacokinetic study has confirmed bacteriologically active serum levels of netilmicin and also the availability of netilmicin within the bronchial secretions. Endobronchial plus systemic netilmicin administration was active and well tolerated in these critical patients.

Phenotypical and functional analysis of bronchoalveolar lavage lymphocytes in patients with HIV infection

The lungs of patients with acquired immunodeficiency syndrome (AIDS) are frequently affected by opportunistic and nonopportunistic infections and pulmonary localizations of Kaposi's sarcoma. The aim of this study was to verify whether, in patients with human immunodeficiency virus (HIV) infections, immunologic pulmonary abnormalities set the stage for the lung complications. For this purpose, a phenotypic and functional characterization of lymphocytes recovered from the bronchoalveolar lavage (BAL) fluid of 24 patients with clinical symptoms and signs of HIV infections was performed (six patients with constitutional disease, five patients with neurologic manifestations, and 13 patients with full-blown AIDS). Our data showed that (1) in patients with HIV, the percentage and absolute number of pulmonary CD8 cells were significantly increased over those in control subjects (in 25% of these patients, mostly with full-blown AIDS, CD8 cells sustained an alveolitis); (2) lung CD4 cells were reduced in percentage but not in absolute number, with the exception of patients with AIDS in whom a significant decrease of the absolute number of BAL CD4 cells has been found (further phenotypic analysis of CD4 lymphocytes showed a reduction of the expression of T4A, B, and E with respect to the T4, T4C, T4D, and T4F epitopes); (3) although the number of BAL cells bearing NK-related determinants was increased, we were unable to demonstrate any in vitro natural killer cell activity. We suggest that the impairment of a proper NK activity in the lungs of these patients might be central to the mechanisms leading to the in situ immunodeficiency state and to the pulmonary complications characterizing AIDS.

Transbronchial lung biopsy in infiltrative lung disease. The importance of the pathologic approach

Infiltrative diffuse lung diseases represent a heterogenous group of lesions with overlapping clinical and roentgenological features. Their diagnosis frequently needs a pathologic approach. We report our experience (671 patients with lung infiltrates) with transbronchial lung biopsy (TBB) procedure. The results of morphologic investigation were subdivided into three groups: 1) A specific morphologic diagnosis was made in 192 cases (29%) 2) Histopathologic changes well consistent with the clinical pattern were present in 258 patients (38%) 3) Non-specific lesions were found in 221 cases (33%). The diagnosis yield of the method was of 67%. UIP, DIP, Pulmonary Angiitis and Granulomatosis, Bronchiolitis Obliterans-Organizing Pneumonia and other rarer lung diseases may not be diagnosed on the basis of lesions present in TBB specimens.

Transbronchial lung biopsy and bronchoalveolar lavage in diagnosis of diffuse infiltrative lung diseases

We investigated 801 patients with lung infiltrates who underwent transbronchial lung biopsy (TBB) and performed cytologic studies of lavage fluid of 491 patients who also underwent bronchoalveolar lavage (BAL). A specific histopathological diagnosis was made in 232 cases (29%). Histopathological changes consistent with the clinical pattern were present in 296 cases (37%). The diagnostic yield of TBB was 66%. Routine evaluation of BAL fluid allowed us to make a specific diagnosis in 49 cases. The role of the pulmonary pathologist in the interpretation of TBB and BAL specimens is discussed.

Transbronchial lung biopsy in pulmonary sarcoidosis. Is it an evaluable method in detection of disease activity?

To assess the value of transbronchial lung biopsy in the evaluation of disease activity in pulmonary sarcoidosis, lung biopsy specimens obtained from 37 patients with this disease and their cellular patterns of bronchoalveolar lavage were studied. Morphologic analysis has showed peculiar lesions: predominant interstitial alveolitis consisting of mononuclear cells and scattered neutrophils, and eosinophils, diffuse in 13 cases and focal in 11 cases, interstitial nodular clusterings of mononuclear cells (five cases), diffuse intraalveolar infiltration of macrophages (one case), granulomas (27 cases), hyaline membranes (one case), intraalveolar (two cases) and interstitial (six cases) fibrosis, and finally cuboidal metaplasia of alveolar lining cells (eight cases). Hyaline membranes were always combined to a diffuse alveolitis consisting of some neutrophils. Only diffuse alveolitis was significantly associated with a high lymphocytosis in BAL (p less than 0.05).

[Evaluation of the diagnostic role of the carcinoembryonic antigen in ascitic fluid]

The diagnostic role of carcinoembryonic antigen (CEA) in ascitic fluid was evaluated in order to assess whether or not ascitic haemorrhage is related to cancer. A total of 30 patients with ascitic haemorrhage were analysed (17 had cirrhosis, 5 non-metastasised cancers and 8 metastasised cancers). CEA radioimmunoassay was performed in serum and ascitic fluid. The results showed that CEA in the ascitic fluid highlighted a clear distinction between the average values of the 3 groups examined serum assay did not. Results were respectively: cirrhotic patients 6.11, non-metastasised cancers 38 and metastasised cancers 204.12. Ascitic fluid measurement revealed considerable variation, especially between the first and third groups examined (p = .00000004). Although CEA must be regarded as an aspecific laboratory test for malignancy, these results suggest that CEA determination in the ascitic fluid may be useful for screening patients with ascitic haemorrhage.

The systemic effect of cancers on human sera proton NMR relaxation times

In animal models of cancer, an elevation of T1 and T2 in uninvolved tissues and in the blood of tumor bearing animals has been termed "the systemic effect." This study reports T1 values in sera of human patients from Genoa, Italy, with several types of cancer and non-cancerous diseases. T1 values were significantly elevated over normal controls (1628 +/- 113 ms) in colorectal cancers (1725 +/- 149 ms) and stomach cancers (1817 +/- 219 ms). However a systemic effect was not demonstrated in acute myeloid leukemia, chronic lymphatic leukemia, chronic myeloid leukemia, or plasma cell myeloma, or in pancreatic and lung cancers. Noncancerous states of cirrhosis, chronic hepatitis, and monoclonal gammapathies did not show a T1 elevation. In general, T1 values of sera correlated with protein content of the sera; however, a disproportionate contribution of gamma-globulin protein on water proton relaxation times was observed in several cases.

[Current potential of fiberscopy in the diagnosis of bronchopulmonary lesions]

The Authors relate the results of their casuistics of bronchial endoscopies. Out of 3438 endoscopies, 1237 were bronchial biopsies and 496 lung biopsies. According to the results obtained the Authors have concluded that this method represents an important progress in thoracic endoscopy. It can be also widely applied for the diagnosis of bronchopulmonary diseases.