Ppx1 putative exopolyphosphatase is essential for polyphosphate accumulation in Lacticaseibacillus paracasei.

The linear polymer polyphosphate (poly-P) is present across all three domains of life and serves diverse physiological functions. The enzyme polyphosphate kinase (Ppk) is responsible for poly-P synthesis, whereas poly-P degradation is carried out by the enzyme exopolyphosphatase (Ppx). In many Lactobacillaceae, the Ppk-encoding gene (ppk) is found clustered together with two genes encoding putative exopolyphosphatases (ppx1 and ppx2) each having different domain compositions, with the gene order ppx1-ppk-ppx2. However, the specific function of these ppx genes remains unexplored. An in-frame deletion of ppx1 in Lacticaseibacillus paracasei BL23 resulted in bacteria unable to accumulate poly-P, whereas the disruption of ppx2 did not affect poly-P synthesis. The expression of ppk was not altered in the Δppx1 strain, and poly-P synthesis in this strain was only restored by expressing ppx1 in trans. Moreover, no poly-P synthesis was observed when ppk was expressed from a plasmid in the Δppx1 strain. Purified Ppx2 exhibited in vitro exopolyphosphatase activity, whereas no in vitro enzymatic activity could be demonstrated for Ppx1. This observation corresponds with the absence in Ppx1 of conserved motifs essential for catalysis found in characterized exopolyphosphatases. Furthermore, assays with purified Ppk and Ppx1 evidenced that Ppx1 enhanced Ppk activity. These results demonstrate that Ppx1 is essential for poly-P synthesis in Lc. paracasei and have unveiled, for the first time, an unexpected role of Ppx1 exopolyphosphatase in poly-P synthesis.IMPORTANCEPoly-P is a pivotal molecular player in bacteria, participating in a diverse array of processes ranging from stress resilience to pathogenesis while also serving as a functional component in probiotic bacteria. The synthesis of poly-P is tightly regulated, but the underlying mechanisms remain incompletely elucidated. Our study sheds light on the distinctive role played by the two exopolyphosphatases (Ppx) found in the Lactobacillaceae bacterial group, of relevance in food and health. This particular group is noteworthy for possessing two Ppx enzymes, supposedly involved in poly-P degradation. Remarkably, our investigation uncovers an unprecedented function of Ppx1 in Lacticaseibacillus paracasei, where its absence leads to the total cessation of poly-P synthesis, paralleling the impact observed upon eliminating the poly-P forming enzyme, poly-P kinase. Unlike the anticipated role as a conventional exopolyphosphatase, Ppx1 demonstrates an unexpected function. Our results added a layer of complexity to our understanding of poly-P dynamics in bacteria.

Phosphate Uptake and Its Relation to Arsenic Toxicity in Lactobacilli.

The use of probiotic lactobacilli has been proposed as a strategy to mitigate damage associated with exposure to toxic metals. Their protective effect against cationic metal ions, such as those of mercury or lead, is believed to stem from their chelating and accumulating potential. However, their retention of anionic toxic metalloids, such as inorganic arsenic, is generally low. Through the construction of mutants in phosphate transporter genes (pst) in Lactiplantibacillus plantarum and Lacticaseibacillus paracasei strains, coupled with arsenate [As(V)] uptake and toxicity assays, we determined that the incorporation of As(V), which structurally resembles phosphate, is likely facilitated by phosphate transporters. Surprisingly, inactivation in Lc. paracasei of PhoP, the transcriptional regulator of the two-component system PhoPR, a signal transducer involved in phosphate sensing, led to an increased resistance to arsenite [As(III)]. In comparison to the wild type, the phoP strain exhibited no differences in the ability to retain As(III), and there were no observed changes in the oxidation of As(III) to the less toxic As(V). These results reinforce the idea that specific transport, and not unspecific cell retention, plays a role in As(V) biosorption by lactobacilli, while they reveal an unexpected phenotype for the lack of the pleiotropic regulator PhoP.

Is EEG Entropy a Useful Measure for Alzheimer's Disease?

BACKGROUND: The number of individuals diagnosed with Alzheimer's disease (AD) has increased, and it is estimated to continue rising in the coming years. The diagnosis of this disease is challenging due to variations in onset and course, its diverse clinical manifestations, and the indications for measuring deposit biomarkers. Hence, there is a need to develop more precise and less invasive diagnostic tools. Multiple studies have considered using electroencephalography (EEG) entropy measures as an indicator of the onset and course of AD. Entropy is deemed suitable as a potential indicator based on the discovery that variations in its complexity can be associated with specific pathologies such as AD. METHODOLOGY: Following PRISMA guidelines, a literature search was conducted in 4 scientific databases, and 40 articles were analyzed after discarding and filtering. RESULTS: There is a diversity in entropy measures; however, Sample Entropy (SampEn) and Multiscale Entropy (MSE) are the most widely used (21/40). In general, it is found that when comparing patients with controls, patients exhibit lower entropy (20/40) in various areas. Findings of correlation with the level of cognitive decline are less consistent, and with neuropsychiatric symptoms (2/40) or treatment response less explored (2/40), although most studies show lower entropy with greater severity. Machine learning-based studies show good discrimination capacity. CONCLUSIONS: There is significant difficulty in comparing multiple studies due to their heterogeneity; however, changes in Multiscale Entropy (MSE) scales or a decrease in entropy levels are considered useful for determining the presence of AD and measuring its severity.

Impact of Chronic Exposure to Arsenate through Drinking Water on the Intestinal Barrier.

Chronic exposure to inorganic arsenic (As) [As(III) + As(V)], which affects millions of people, increases the incidence of some kinds of cancer and other noncarcinogenic pathologies. Although the oral pathway is the main source of exposure, in vivo studies conducted to verify the intestinal toxicity of this metalloid are scarce and are mainly focused on evaluating the toxicity of As(III). The aim of this study was to evaluate the effect of chronic exposure (6 months) of BALB/c mice to As(V) (15-60 mg/L) via drinking water on the different components of the intestinal barrier and to determine the possible mechanisms involved. The results show that chronic exposure to As(V) generates a situation of oxidative stress (increased lipid peroxidation and reactive species) and inflammation (increased contents of several proinflammatory cytokines and neutrophil infiltrations) in the intestinal tissues. There is also evidence of an altered expression of constituent proteins of the intercellular junctions (Cldn1, Cldn3, and Ocln) and the mucus layer (Muc2) and changes in the composition of the gut microbiota and the metabolism of short-chain fatty acids. All of these toxic effects eventually may lead to the disruption of the intestinal barrier, which shows an increased paracellular permeability. Moreover, signs of endotoxemia are observed in the serum of As(V)-treated animals (increases in lipopolysaccharide-binding protein LBP and the proinflammatory cytokine IL-1ß). The data obtained suggest that chronic exposure to As(V) via drinking water affects the intestinal environment.

ABC Transporter DerAB of Lactobacillus casei Mediates Resistance against Insect-Derived Defensins.

Bce-like systems mediate resistance against antimicrobial peptides in Firmicutes bacteria. Lactobacillus casei BL23 encodes an "orphan" ABC transporter that, based on homology to BceAB-like systems, was proposed to contribute to antimicrobial peptide resistance. A mutant lacking the permease subunit was tested for sensitivity against a collection of peptides derived from bacteria, fungi, insects, and humans. Our results show that the transporter specifically conferred resistance against insect-derived cysteine-stabilized αß defensins, and it was therefore renamed DerAB for defensin resistance ABC transporter. Surprisingly, cells lacking DerAB showed a marked increase in resistance against the lantibiotic nisin. This could be explained by significantly increased expression of the antimicrobial peptide resistance determinants regulated by the Bce-like systems PsdRSAB (formerly module 09) and ApsRSAB (formerly module 12). Bacterial two-hybrid studies in Escherichia coli showed that DerB could interact with proteins of the sensory complex in the Psd resistance system. We therefore propose that interaction of DerAB with this complex in the cell creates signaling interference and reduces the cell's potential to mount an effective nisin resistance response. In the absence of DerB, this negative interference is relieved, leading to the observed hyperactivation of the Psd module and thus increased resistance to nisin. Our results unravel the function of a previously uncharacterized Bce-like orphan resistance transporter with pleiotropic biological effects on the cell.IMPORTANCE Antimicrobial peptides (AMPs) play an important role in suppressing the growth of microorganisms. They can be produced by bacteria themselves-to inhibit competitors-but are also widely distributed in higher eukaryotes, including insects and mammals, where they form an important component of innate immunity. In low-GC-content Gram-positive bacteria, BceAB-like transporters play a crucial role in AMP resistance but have so far been primarily associated with interbacterial competition. Here, we show that the orphan transporter DerAB from the lactic acid bacterium Lactobacillus casei is crucial for high-level resistance against insect-derived AMPs. It therefore represents an important mechanism for interkingdom defense. Furthermore, our results support a signaling interference from DerAB on the PsdRSAB module that might prevent the activation of a full nisin response. The Bce modules from L. casei BL23 illustrate a biological paradox in which the intrinsic nisin detoxification potential only arises in the absence of a defensin-specific ABC transporter.

Use of lactic acid bacteria and yeasts to reduce exposure to chemical food contaminants and toxicity.

Chemical contaminants that are present in food pose a health problem and their levels are controlled by national and international food safety organizations. Despite increasing regulation, foods that exceed legal limits reach the market. In Europe, the number of notifications of chemical contamination due to pesticide residues, mycotoxins and metals is particularly high. Moreover, in many parts of the world, drinking water contains high levels of chemical contaminants owing to geogenic or anthropogenic causes. Elimination of chemical contaminants from water and especially from food is quite complex. Drastic treatments are usually required, which can modify the food matrix or involve changes in the forms of cultivation and production of the food products. These modifications often make these treatments unfeasible. In recent years, efforts have been made to develop strategies based on the use of components of natural origin to reduce the quantity of contaminants in foods and drinking water, and to reduce the quantity that reaches the bloodstream after ingestion, and thus, their toxicity. This review provides a summary of the existing literature on strategies based on the use of lactic acid bacteria or yeasts belonging to the genus Saccharomyces that are employed in food industry or for dietary purposes.

In vivo evaluation of the effect of arsenite on the intestinal epithelium and associated microbiota in mice.

Chronic exposure to inorganic arsenic (As) [As(III) + As(V)], which affects millions of people, increases the incidence of some kinds of cancer and other non-carcinogenic pathologies. Although the oral pathway is the main form of exposure, in vivo studies have not been conducted to verify the intestinal toxicity of this metalloid. The aim of this study is to perform an in vivo evaluation of the intestinal toxicity of inorganic As, using female BALB/c mice exposed through drinking water to various concentrations of As(III) (20, 50, and 80 mg/L) for 2 months. An increase was observed in oxygen and/or nitrogen reactive species, and in gene and protein expression of pro-inflammatory cytokines (IL-1ß, IL-2, IL-6) at concentrations equal to or greater than 50 mg/L. These changes were accompanied by a profound remodeling of the intestinal microbial profile in terms of diversity and global composition, which could be at the basis or exacerbate As(III) toxic effects. The histological study showed that there was moderate inflammation of the mucosa and submucosa, accompanied by hyperplasia of crypts at the highest administered dose. In addition, all the treatments with As(III) resulted in a decreased expression of Muc2, which encodes one of the main components of the intestinal layer of mucus. The effects described are compatible with the increased intestinal permeability observed at concentrations equal to or greater than 50 mg/L, indicative of loss of barrier function.

Peptide and amino acid metabolism is controlled by an OmpR-family response regulator in Lactobacillus casei.

A Lactobacillus casei BL23 strain defective in an OmpR-family response regulator encoded by LCABL_18980 (PrcR, RR11), showed enhanced proteolytic activity caused by overexpression of the gene encoding the proteinase PrtP. Transcriptomic analysis revealed that, in addition to prtP expression, PrcR regulates genes encoding peptide and amino acid transporters, intracellular peptidases and amino acid biosynthetic pathways, among others. Binding of PrcR to twelve promoter regions of both upregulated and downregulated genes, including its own promoter, was demonstrated by electrophoretic mobility shift assays showing that PrcR can act as a transcriptional repressor or activator. Phosphorylation of PrcR increased its DNA binding activity and this effect was abolished after replacement of the phosphorylatable residue Asp-52 by alanine. Comparison of the transcript levels in cells grown in the presence or absence of tryptone in the growth medium revealed that PrcR activity responded to the presence of a complex amino acid source in the growth medium. We conclude that the PrcR plays a major role in the control of the peptide and amino acid metabolism in L. casei BL23. Orthologous prcR genes are present in most members of the Lactobacillaceae and Leuconostocaceae families. We hypothesize that they play a similar role in these bacterial groups.

Physiological Role of Two-Component Signal Transduction Systems in Food-Associated Lactic Acid Bacteria.

Two-component systems (TCSs) are widespread signal transduction pathways mainly found in bacteria where they play a major role in adaptation to changing environmental conditions. TCSs generally consist of sensor histidine kinases that autophosphorylate in response to a specific stimulus and subsequently transfer the phosphate group to their cognate response regulators thus modulating their activity, usually as transcriptional regulators. In this review we present the current knowledge on the physiological role of TCSs in species of the families Lactobacillaceae and Leuconostocaceae of the group of lactic acid bacteria (LAB). LAB are microorganisms of great relevance for health and food production as the group spans from starter organisms to pathogens. Whereas the role of TCSs in pathogenic LAB (most of them belonging to the family Streptococcaceae) has focused the attention, the roles of TCSs in commensal LAB, such as most species of Lactobacillaceae and Leuconostocaceae, have been somewhat neglected. However, evidence available indicates that TCSs are key players in the regulation of the physiology of these bacteria. The first studies in food-associated LAB showed the involvement of some TCSs in quorum sensing and production of bacteriocins, but subsequent studies have shown that TCSs participate in other physiological processes, such as stress response, regulation of nitrogen metabolism, regulation of malate metabolism, and resistance to antimicrobial peptides, among others.

Characterization of the binding capacity of mercurial species in Lactobacillus strains.

BACKGROUND: Metal sequestration by bacteria has been proposed as a strategy to counteract metal contamination in foodstuffs. Lactobacilli can interact with metals, although studies with important foodborne metals such as inorganic [Hg(II)] or organic (CH3 Hg) mercury are lacking. Lactobacilli were evaluated for their potential to bind these contaminants and the nature of the interaction was assessed by the use of metal competitors, chemical and enzymatical treatments, and mutants affected in the cell wall structure. RESULTS: Lactobacillus strains efficiently bound Hg(II) and CH3 Hg. Mercury binding by Lactobacillus casei BL23 was independent of cell viability. In BL23, both forms of mercury were cell wall bound. Their interaction was not inhibited by cations and it was resistant to chelating agents and protein digestion. Lactobacillus casei mutants affected in genes involved in the modulation of the negative charge of the cell wall anionic polymer lipoteichoic acid showed increased mercury biosorption. In these mutants, mercury toxicity was enhanced compared to wild-type bacteria. These data suggest that lipoteichoic acid itself or the physicochemical characteristics that it confers to the cell wall play a major role in mercury complexation. CONCLUSION: This is the first example of the biosorption of Hg(II) and CH3 Hg in lactobacilli and it represents a first step towards their possible use as agents for diminishing mercury bioaccessibility from food at the gastrointestinal tract. © 2017 Society of Chemical Industry.

Viruses in pulp and periapical inflammation: a review.

The presence of viruses in endodontic disease has been studied in the last decade. Their presence is associated with periapical radiolucency and with clinical findings, such as pain. The aim of this review is to analyze the scientific evidence currently published about viruses in pulp and periapical inflammation, and its possible clinical implications. A literature review was carried out using the Medline/Pubmed database. The search was performed, in English and Spanish, using the following keyword combinations: virus AND endodontic; virus AND periapical; virus AND pulpitis; herpesvirus AND periapical; papillomavirus AND periapical. We subsequently selected the most relevant studies, which complied with the search criterion. A total of 21 articles were included, of which 18 detected the present of viruses in the samples. In 3 of the studies, viral presence was not found in the samples studied. The Epstein-Barr virus was found in about 41 % of cases compared to controls, in which it was present in about 2 %. The main association between viruses and endodontic pathosis is between Cytomegalovirus and Epstein-Barr virus; these are found in 114 of the 406 samples of different endodontic pathosis. Some evidence supports that the Epstein-Barr virus is present in a significant number of endodontic diseases, without exact knowledge of their action in these diseases.

Emergence of an outbreak-associated Clostridium difficile variant with increased virulence.

The prevalence of Clostridium difficile infections has increased due to the emergence of epidemic variants from diverse genetic lineages. Here we describe the emergence of a novel variant during an outbreak in a Costa Rican hospital that was associated with severe clinical presentations. This C. difficile variant elicited higher white blood cell counts and caused disease in younger patients than did other strains isolated during the outbreak. Furthermore, it had a recurrence rate, a 30-day attributable disease rate, and disease severity as great as those of the epidemic strain NAP1. Pulsed-field gel electrophoresis genotyping indicated that the outbreak strains belong to a previously undescribed variant, designated NAPCR1. Whole-genome sequencing and ribotyping indicated that the NAPCR1 variant belongs to C. difficile ribotype 012 and sequence type 54, as does the reference strain 630. NAPCR1 strains are resistant to fluoroquinolones due to a mutation in gyrA, and they possess an 18-bp deletion in tcdC that is characteristic of the epidemic, evolutionarily distinct, C. difficile NAP1 variant. NAPCR1 genomes contain 10% more predicted genes than strain 630, most of which are of hypothetical function and are present on phages and other mobile genetic elements. The increased virulence of NAPCR1 was confirmed by mortality rates in the hamster model and strong inflammatory responses induced by bacteria-free supernatants in the murine ligated loop model. However, NAPCR1 strains do not synthesize toxin A and toxin B at levels comparable to those in NAP1 strains. Our results suggest that the pathogenic potential of this emerging C. difficile variant is due to the acquisition of hypothetical functions associated with laterally acquired DNA.

Defence against antimicrobial peptides: different strategies in Firmicutes.

The Firmicutes constitute a phylum of bacteria that can be found in a wide variety of habitats, from soil to the gastrointestinal tract of animals, where they have to thrive in complex communities. Competition in these communities usually involves the production of compounds such as antimicrobial peptides (AMPs) to eliminate competitor organisms. Animals and plants also produce AMPs to control their associated microbiota. In turn, defence mechanisms have evolved to prevent the action of these compounds. The close association of some Firmicutes with humans as prominent pathogens or commensal organisms has driven a considerable research effort on defence mechanisms used by these bacteria against antimicrobial compounds. This review focuses on the most recent advances on two well-characterized defence mechanisms against AMPs: the modification of the cell wall by D-alanylation and the role of peptide antibiotic-specific adenosine triphosphate-binding cassette transporters.

Accumulation of polyphosphate in Lactobacillus spp. and its involvement in stress resistance.

Polyphosphate (poly-P) is a polymer of phosphate residues synthesized and in some cases accumulated by microorganisms, where it plays crucial physiological roles such as the participation in the response to nutritional stringencies and environmental stresses. Poly-P metabolism has received little attention in Lactobacillus, a genus of lactic acid bacteria of relevance for food production and health of humans and animals. We show that among 34 strains of Lactobacillus, 18 of them accumulated intracellular poly-P granules, as revealed by specific staining and electron microscopy. Poly-P accumulation was generally dependent on the presence of elevated phosphate concentrations in the culture medium, and it correlated with the presence of polyphosphate kinase (ppk) genes in the genomes. The ppk gene from Lactobacillus displayed a genetic arrangement in which it was flanked by two genes encoding exopolyphosphatases of the Ppx-GppA family. The ppk functionality was corroborated by its disruption (LCABL_27820 gene) in Lactobacillus casei BL23 strain. The constructed ppk mutant showed a lack of intracellular poly-P granules and a drastic reduction in poly-P synthesis. Resistance to several stresses was tested in the ppk-disrupted strain, showing that it presented a diminished growth under high-salt or low-pH conditions and an increased sensitivity to oxidative stress. These results show that poly-P accumulation is a characteristic of some strains of lactobacilli and may thus play important roles in the physiology of these microorganisms.

Cross-regulation of Aps-promoters in Lacticaseibacillus paracasei by the PsdR response regulator in response to lantibiotics.

The PsdRSAB and ApsRSAB detoxification modules, together with the antimicrobial peptides (AMPs)-resistance determinants Dlt system and MprF protein, play major roles in the response to AMPs in Lacticaseibacillus paracasei BL23. Sensitivity assays with a collection of mutants showed that the PsdAB ABC transporter and the Dlt system are the main subtilin resistance determinants. Quantification of the transcriptional response to subtilin indicate that this response is exclusively regulated by the two paralogous systems PsdRSAB and ApsRSAB. Remarkably, a cross-regulation of the derAB, mprF and dlt-operon genes-usually under control of ApsR-by PsdR in response to subtilin was unveiled. The high similarity of the predicted structures of both response regulators (RR), and of the RR-binding sites support this possibility, which we experimentally verified by protein-DNA binding studies. ApsR-P shows a preferential binding in the order PderA > Pdlt > PmprF > PpsdA. However, PsdR-P bound with similar apparent affinity constants to the four promoters. This supports the cross-regulation of derAB, mprF and the dlt-operon by PsdR. The possibility of cross-regulation at the level of RR-promoter interaction allows some regulatory overlap with two RRs controlling the expression of systems involved in maintenance of critical cell membrane functions in response to lantibiotics.

Protective effects of oral administration of lactic acid bacteria strains against methylmercury-induced intestinal toxicity in a murine model.

The utilization of lactic acid bacteria has been proposed to mitigate the burden of heavy metal exposure through processes probably involving chelation and reduced metal bioaccessibility. We evaluated the effects of daily intake of two strains of lactobacilli (Lactobacillus intestinalis LE1 or Lactobacillus johnsonii LE2) on intestinal toxicity during methylmercury (MeHg) exposure through drinking water (5 mg/L) for two months in mice. MeHg exposure resulted in inflammation and oxidative stress at the colon, as well as an increase in intestinal permeability accompanied by decreased fecal short-chain fatty acids (SCFA). The administration of the strains resulted in a differential protective effect that, based on their chelation capacity, supported the existence of additional mechanisms of action besides chelation. Both strains reduced IL-1ß levels and oxidative stress, while LE1 lowered TNF-α, diminished MeHg-induced mucus over-secretion triggered by the IL-4/IL-13/STAT6 pathway, reduced intestinal permeability, and ameliorated inflammation and oxidative stress, probably by acting on the Keap1/Nrf2/ARE pathway. Administration of LE1 partially restored SCFA contents, which could be partly responsible for the positive effects of this strain in alleviating MeHg toxicity. These results demonstrate that lactobacilli strains can be useful tools in reducing the intestinal toxicity of MeHg, the main mercurial form conveyed by food.

Malic enzyme and malolactic enzyme pathways are functionally linked but independently regulated in Lactobacillus casei BL23.

Lactobacillus casei is the only lactic acid bacterium in which two pathways for l-malate degradation have been described: the malolactic enzyme (MLE) and the malic enzyme (ME) pathways. Whereas the ME pathway enables L. casei to grow on l-malate, MLE does not support growth. The mle gene cluster consists of three genes encoding MLE (mleS), the putative l-malate transporter MleT, and the putative regulator MleR. The mae gene cluster consists of four genes encoding ME (maeE), the putative transporter MaeP, and the two-component system MaeKR. Since both pathways compete for the same substrate, we sought to determine whether they are coordinately regulated and their role in l-malate utilization as a carbon source. Transcriptional analyses revealed that the mle and mae genes are independently regulated and showed that MleR acts as an activator and requires internalization of l-malate to induce the expression of mle genes. Notwithstanding, both l-malate transporters were required for maximal l-malate uptake, although only an mleT mutation caused a growth defect on l-malate, indicating its crucial role in l-malate metabolism. However, inactivation of MLE resulted in higher growth rates and higher final optical densities on l-malate. The limited growth on l-malate of the wild-type strain was correlated to a rapid degradation of the available l-malate to l-lactate, which cannot be further metabolized. Taken together, our results indicate that L. casei l-malate metabolism is not optimized for utilization of l-malate as a carbon source but for deacidification of the medium by conversion of l-malate into l-lactate via MLE.

Characterization of a regulatory network of peptide antibiotic detoxification modules in Lactobacillus casei BL23.

Two-component systems (TCS) are major signal transduction pathways that allow bacteria to detect and respond to environmental and intracellular changes. A group of TCS has been shown to be involved in the response against antimicrobial peptides (AMPs). These TCS are characterized by the possession of intramembrane-sensing histidine kinases, and they are usually associated with ABC transporters of the peptide-7 exporter family (Pep7E). Lactobacillus casei BL23 encodes two TCS belonging to this group (TCS09 and TCS12) that are located next to two ABC transporters (ABC09 and ABC12), as well as a third Pep7E ABC transporter not genetically associated with any TCS (orphan ABC). This study addressed the involvement of modules TCS09/ABC09 and TCS12/ABC12 in AMP resistance. Results showed that both systems contribute to L. casei resistance to AMPs, and that each TCS constitutes a functional unit with its corresponding ABC transporter. Analysis of transcriptional levels showed that module 09 is required for the induction of ABC09 expression in response to nisin. In contrast, module 12 controls a wider regulon that encompasses the orphan ABC, the dlt operon (d-alanylation of teichoid acids), and the mprF gene (l-lysinylation of phospholipids), thereby controlling properties of the cell envelope. Furthermore, the characterization of a dltA mutant showed that Dlt plays a major role in AMP resistance in L. casei. This is the first report on the regulation of the response of L. casei to AMPs, giving insight into its ability to adapt to the challenging environments that it encounters as a probiotic microorganism.

Paediatric oral pathology in a Chilean population: a 15-year review.

BACKGROUND: There is only limited information available in Chile regarding the frequency of biopsied oral lesions in paediatric patients. AIM: To determine the frequency of histologically diagnosed lesions in oral pathology specimens from paediatric patients in a Chilean population over a 15-year period. DESIGN: Oral and maxillofacial biopsy records of patients aged 16 years or under were retrieved by visual inspection from the archives of public and private Oral Pathology Health Services in Valdivia, Chile, during the period 1995-2010. Records that contained anatomical site and histopathological diagnoses of the specimen were included. The study population was divided into three age groups according to dentition stage. Oral lesions were classified as inflammatory/reactive, cystic, or tumour/tumour-like. RESULTS: A total of 542 biopsy specimens from children were found. These represented 20.6% of all oral biopsies. The average age was 11.1 years, with female predilection. The most common category of oral lesions was inflammatory/reactive (75.8%), followed by tumour/tumour-like (16.8%) and cystic (7.4%) lesions. The mucocele was the most commonly found lesion, followed by pyogenic granuloma and irritation fibroma, which taken together accounted for 63.8% of all paediatric oral biopsies. The most common localisation for lesions was the lower lip (50.3%). CONCLUSIONS: The vast majority of oral lesions found were predominantly inflammatory/reactive and benign types, although malignant lesions can present themselves in children.

Infectious Endocarditis by Pseudomonas aeruginosa in an Immunocompetent Adult.

In the following case review, we present a 49-year-old male without a history of injection drug (IDU) use nor any known structural heart disease, who developed left-sided pseudomonal infectious endocarditis. The only known risk factors were urinary tract infection (UTI) with secondary bacteremia and prolonged healthcare contact with admission to the intensive care unit. Infectious endocarditis (IE) is the infection of the endocardium. The official diagnosis can only be established after histological and microbiological studies confirm microorganism-colonized vegetations in the heart valves, but a clinical suspicion with high sensitivity and specificity can be approached with modified Duke's criteria. Even though structural heart disease is the major predisposing factor for IE, healthcare-associated IE has risen with the new therapeutic interventions. Transient bacteremia, which might result after various procedures, forms part of the factors causing healthcare-associated IE. Although both, community-acquired and hospital-acquired infections by Pseudomonas aeruginosa have been reported, pure community-acquired infections without previous exposure to the hospital or healthcare environment are extremely rare. Intensive care unit (ICU) patients are at special risk for this microbe. It is considered an important causative agent in ventilator/associated pneumonia, catheter-associated urinary tract infection (UTI), and catheter-associated bloodstream infections. IE by P. aeruginosa remains a rare form of IE. Though 95% of cases are associated with injection drug use (IDU), healthcare contact is becoming more important each day as the primary risk factor. The most common complications include abscesses in the ring and annulus, congestive heart failure (CHF), embolisms, inability to sterilize valves, splenic abscesses, recurrent bacteremia, and neurologic complications. This condition is highly fatal, with a mortality rate of over 73% for patients older than 30 years. Recommended antibiotic treatment for IE caused by P. aeruginosa consists of high-dose tobramycin in combination with antipseudomonal penicillin or high-dose ceftazidime, cefepime, or imipenem.