Efficacy of acoustic waves in preventing Streptococcus mutans adhesion on dental unit water line.

BACKGROUND: The quality and health safety of water used for refrigeration and flushing of the handpieces, water-syringes and other components of dental units is of considerable importance. Water crosses these devices by a system of intersected small plastic tubes (about 2 mm of diameter), named dental unit water lines (DUWLs). DUWLs may be heavily colonized by many bacterial species in a planktonic phase, adherent or in biofilm lifestyle, resulting in a potential risk of infection, not only for all professionals who routinely use these devices, but also for occasional-patients, especially immunocompromised patients. Contamination of DUWLs can be prevented or reduced with the use of disinfectants, but the eradication of microorganisms, especially which those are adherent or living in biofilm lifestyle on the inner surfaces of DUWLs is challenging and often, the normal methods of water disinfection are not effective. Moreover, disinfectants routinely used to disinfect DUWLs may alter the bond strength of the dentine bonding agent used for restorative practice in dentistry. STUDY DESIGN: To identify an innovative and alternative strategy, able to prevent bacterial adhesion to DUWL surfaces through a physical approach, which is more effective in overcoming the problem of DUWL contamination and the risk of infection compared to the standard methods already in use. In this pilot study we tested a member of the oral streptococci family, that is not a component of the biofilm detected on the walls of DUWL, but is frequently detected in water samples from DUWL, due to human fluid retraction during dental therapy. Namely, the pathogenic bacterial species Streptococcus mutans. METHODS: We employ elastic acoustic waves at high-energy in preventing S. mutans adhesion to the inner walls of an experimental water circuit reproducing a DUWLs. To stress the capability of acoustic waves to interfere with bacterial adhesion also in extreme conditions, a high S. mutans contamination load was adopted. RESULTS: We observe a significant decrease of adherent bacteria exposed to acoustic waves treatment respect to control. CONCLUSION: This study demonstrates the effectiveness of acoustic waves in counteracting the adhesion of S. mutans to the inner walls of an experimental water circuit reproducing a DUWL, opening up new prospects for future practical applications. The interesting results, so far obtained, require an in-depth analysis of the methods regarding both the various bacterial species involved and the infective charges to be used.

Bacterial ratchet motors.

Self-propelling bacteria are a nanotechnology dream. These unicellular organisms are not just capable of living and reproducing, but they can swim very efficiently, sense the environment, and look for food, all packaged in a body measuring a few microns. Before such perfect machines can be artificially assembled, researchers are beginning to explore new ways to harness bacteria as propelling units for microdevices. Proposed strategies require the careful task of aligning and binding bacterial cells on synthetic surfaces in order to have them work cooperatively. Here we show that asymmetric environments can produce a spontaneous and unidirectional rotation of nanofabricated objects immersed in an active bacterial bath. The propulsion mechanism is provided by the self-assembly of motile Escherichia coli cells along the rotor boundaries. Our results highlight the technological implications of active matter's ability to overcome the restrictions imposed by the second law of thermodynamics on equilibrium passive fluids.

Plasmid-mediated fluoroquinolone resistance determinants in Escherichia coli from community uncomplicated urinary tract infection in an area of high prevalence of quinolone resistance.

In Italy fluoroquinolones (FQs) are extensively prescribed in empirical therapy of uncomplicated urinary tract infection (UTI) despite recommendations in national guidelines and widespread antibiotic resistance in community. To survey the dissemination of plasmid-mediated quinolone resistance in a peak area of FQs consumption, E. coli strains from 154 community and 41 local hospital patients were collected; low level ciprofloxacin resistance qnrA, qnrB, qnrS, and aac(6)'-Ib-cr genes were screened by PCR and patterns of transferable resistances were determined. Clinical ciprofloxacin resistance in hospital doubled community value, while overall rates of FQ resistance genes were similar (31.6% and 27.8%). Prevalence of aac(6')-Ib-cr gene was 11% in outpatients (21%, inpatients) and risk of harbouring this variant was significantly associated with gentamicin resistance; linkage to ceftazidime resistance was significant (P=0.001) and six out of eight strains produced CTX-M-15 and TEM-1 beta lactamases. In transconjugants, the unique pattern ampicillin/kanamycin-gentamicin/ ESBL + was associated with aac(6')-Ib-cr gene presence and with an increase of ciprofloxacin MIC value. Data highlight the need to monitor the resistance risk factors in the local community to provide clinicians with well-grounded guidelines for UTI therapy.

Gut microbiota and the immune system: an intimate partnership in health and disease.

In recent years there have been increased rates of autoimmune diseases, possibly associated to altered intestinal microflora. In this brief review article, after a description of the structure and function of the gut microbiota organ and its cross-talk with the human host, we give a report on findings indicating how the host immune system responds to bacterial colonization of the gastrointestinal tract. The disturbances in the bacterial microbiota will result in the deregulation of adaptive immune cells, which may underlie autoimmune disorders. The mammalian immune system, which seems to be designed to control microorganisms, could be instead influenced by microorganisms, as suggested in recent literature. Alterations in both the structure and function of intestinal microbiota could be one of the common causative triggers of autoimmune and/or autoinflammatory disorders.

JC Viral reactivation in a pediatric patient with Crohn's disease.

This is a report concerning human polyomavirus JC (JCV) reactivation in a pediatric patient with Crohn's disease (CD) during the treatment with 5-aminosalicylic acid (5-ASA), a non-steroidal anti-inflammatory drug (NSAID). We examined 9 bioptic samples from three different bowel districts (ileum, cecum, rectum) of this child. These samples were analyzed by Quantitative PCR (Q-PCR) to investigate the presence of JCV DNA. JCV DNA was detected in one rectum biopsy taken two months after 5-ASA treatment. Although our result must be validated in a larger group of subjects and with a longer follow-up period, it underlines the importance of JVC monitoring in CD patients.

Virulence traits in Escherichia coli strains isolated from outpatients with urinary tract infections.

This study aims to characterize phenotypic and genotypic virulence traits in Escherichia coli strains, isolated from outpatients with urinary tract infections, comparing with those obtained from inpatients. Information on the pathogenic behavior of the uropathogenic strains was obtained by monitoring different biological properties, such as autoagglutination, hemagglutination, adhesiveness to and invasion of human bladder (HT1376) cells, biofilm formation, phylogenetic grouping, and virulence-related genes. The results show similar behavior in the two groups concerning autoagglutination, hemagglutination, and biofilm formation. None of the strains examined was invasive. However, in strains from outpatients there was an increased adhesion to HT1376 cells compared with clinical strains, a significant higher presence of genes codifying for adhesins and cell protection factors, and a lower proportion of strains belonging to B1 group. These findings add further information on the pathogenic traits of community E. coli, since strains isolated from the outpatients' group were differently "armed" in comparison with those of clinical cases, and more suitable to infect healthy individuals.

Listeria monocytogenes in a young patient with non Hodgkins lymphoma: case report.

Listeria monocytogenes is an intracellular food-borne pathogen, widely distributed in the environment, which rarely causes clinical infection in healthy people, but may cause severe disease in immunocompromised patients. A case of listeriosis is certified in an immunocompromised patient, thus confirming this microorganism to be an opportunistic human pathogen.

Encrusted cystitis in an immunocompromised patient: possible coinfection by Corynebacterium urealyticum and E. coli.

Encrusted cystitis is a severe chronic inflammatory disease of the bladder characterized by excessively alkaline urine and calcifications within the bladder wall. A case of a 60 year-old man affected by systemic lupus erythematosus (SLE), which developed encrusted cystitis due to Corynebacterium urealyticum with E. coli co-infection, shows that the treatment of encrusted cystitis with a endoscopic debulking of the encrusted stones and an antimicrobial therapy specific for C. urealyticum often is not sufficient for the complete resolution of symptoms.

Conserved sequence motifs among bacterial, eukaryotic, and archaeal phosphatases that define a new phosphohydrolase superfamily.

Members of a new molecular family of bacterial nonspecific acid phosphatases (NSAPs), indicated as class C, were found to share significant sequence similarities to bacterial class B NSAPs and to some plant acid phosphatases, representing the first example of a family of bacterial NSAPs that has a relatively close eukaryotic counterpart. Despite the lack of an overall similarity, conserved sequence motifs were also identified among the above enzyme families (class B and class C bacterial NSAPs, and related plant phosphatases) and several other families of phosphohydrolases, including bacterial phosphoglycolate phosphatases, histidinol-phosphatase domains of the bacterial bifunctional enzymes imidazole-glycerolphosphate dehydratases, and bacterial, eukaryotic, and archaeal phosphoserine phosphatases and threalose-6-phosphatases. These conserved motifs are clustered within two domains, separated by a variable spacer region, according to the pattern [FILMAVT]-D-[ILFRMVY]-D-[GSNDE]-[TV]-[ILVAM]-[AT S VILMC]-X-¿YFWHKR)-X-¿YFWHNQ¿-X( 102,191)-¿KRHNQ¿-G-D-¿FYWHILVMC¿-¿QNH¿-¿FWYGP¿-D -¿PSNQYW¿. The dephosphorylating activity common to all these proteins supports the definition of this phosphatase motif and the inclusion of these enzymes into a superfamily of phosphohydrolases that we propose to indicate as "DDDD" after the presence of the four invariant aspartate residues. Database searches retrieved various hypothetical proteins of unknown function containing this or similar motifs, for which a phosphohydrolase activity could be hypothesized.

Identification of the gene (aphA) encoding the class B acid phosphatase/phosphotransferase of Escherichia coli MG1655 and characterization of its product.

An open reading frame located in the tyrB-uvrA intergenic region of the Escherichia coli MG1655 chromosome was identified as encoding the class B acid phosphatase of this species on the basis of cloning and expression experiments. A protocol for purification of the enzyme (named AphA) was developed, and its properties were analyzed. The enzyme is a 100-kDa homotetrameric protein which apparently requires a metal co-factor for activity. Similarly to other bacterial class B acid phosphatases, it is able to dephosphorylate several organic phosphomonoesters as well as to catalyze the transfer of low-energy phosphate groups from phosphomonoesters to hydroxyl groups of various organic compounds.

Genetic rearrangements in the tyrB-uvrA region of the enterobacterial chromosome: a potential cause for different class B acid phosphatase regulation in Salmonella enterica and Escherichia coli.

Unlike in Escherichia coli, in Salmonella enterica production of class B acid phosphatase (AphA) was detectable also in cells growing in the presence of glucose. Characterization of the aphA locus from a S. enterica ser. typhi strain showed that the aphA determinant is very similar to the E. coli homolog, and that its chromosomal location between the highly conserved tyrB and uvrA genes is retained. However, the aphA flanking regions were found to be markedly different in the two species, either between tyrB and aphA or between aphA and uvrA. The differences in the aphA 5'-flanking region, which in S. enterica is considerably shorter than in E. coli (183 vs. 1121 bp) and includes potential promoter sequences not present in E. coli, could be responsible for the different regulation of class B acid phosphatase observed in the two species.

Bacterial acid phosphatase gene fusions useful as targets for cloning-dependent insertional inactivation.

The Morganella morganii phoC gene, encoding a class A acid phosphatase, was used to generate gene fusions with modified amino-terminal moieties of the Escherichia coli lacZ gene carrying a multiple-cloning site flanked by phage-specific promoters and recognition sites for universal sequencing primers. The corresponding hybrid proteins retained a PhoC-like enzymatic activity which is easily detectable by a plate histochemical assay, rendering similar gene fusions potentially useful as targets for cloning-dependent insertional inactivation. Cloning experiments performed in plasmids carrying similar lacZ-phoC fusions confirmed their usefulness as cloning vectors for direct screening of recombinants. As compared to conventional lacZ alpha-complementation-based vectors, which can only be used in E. coli hosts carrying specific lacZ mutations, the lacZ-phoC fusion-based vectors can be used in combination with any E. coli host and require a less expensive histochemical assay for screening of recombinants, while retaining all the advantageous features that made the former so popular as general purpose cloning vehicles.

Violacein and biofilm production in Janthinobacterium lividum.

AIMS: To analyse the environmental stimuli modulating violacein and biofilm production in Janthinobacterium lividum. METHODS AND RESULTS: Violacein and biofilm production by J. lividum DSM1522(T) was assayed in different growth conditions. Our data suggest that violacein and biofilm production is controlled by the carbon source, being inhibited by glucose and enhanced by glycerol. J. lividum produced violacein also in the presence of different sub-inhibitory concentrations of ampicillin. As opposite, the production of N-acylhomoserine lactone(s), quorum sensing regulators was shown to be positively regulated by glucose. Moreover, violacein-producing cultures of J. lividum showed higher CFU counts than violacein-nonproducing ones. CONCLUSIONS: Taken together, our results suggest that violacein and biofilm production could be regulated by a common metabolic pathway and that violacein as well as biofilm could represent a response to environmental stresses and a key factor in the survival mechanisms of J. lividum. SIGNIFICANCE AND IMPACT OF THE STUDY: Although several recent studies disclosed a number of interesting biological properties of violacein, few data are reported on the physiologic function of violacein in J. lividum. This paper adds new information on the complex mechanisms allowing and regulating bacterial life in hostile environments.

Gut-associated bacterial microbiota in paediatric patients with inflammatory bowel disease.

BACKGROUND: Clinical and experimental observations in animal models indicate that intestinal commensal bacteria are involved in the initiation and amplification of inflammatory bowel disease (IBD). No paediatric reports are available on intestinal endogenous microflora in IBD. AIMS: To investigate and characterise the predominant composition of the mucosa-associated intestinal microflora in colonoscopic biopsy specimens of paediatric patients with newly diagnosed IBD. METHODS: Mucosa-associated bacteria were quantified and isolated from biopsy specimens of the ileum, caecum and rectum obtained at colonoscopy in 12 patients with Crohn's disease, 7 with ulcerative colitis, 6 with indeterminate colitis, 10 with lymphonodular hyperplasia of the distal ileum and in 7 controls. Isolation and characterisation were carried out by conventional culture techniques for aerobic and facultative-anaerobic microorganisms, and molecular analysis (16S rRNA-based amplification and real-time polymerase chain reaction assays) for the detection of anaerobic bacterial groups or species. RESULTS: A higher number of mucosa-associated aerobic and facultative-anaerobic bacteria were found in biopsy specimens of children with IBD than in controls. An overall decrease in some bacterial species or groups belonging to the normal anaerobic intestinal flora was suggested by molecular approaches; in particular, occurrence of Bacteroides vulgatus was low in Crohn's disease, ulcerative colitis and indeterminate colitis specimens. CONCLUSION: This is the first paediatric report investigating the intestinal mucosa-associated microflora in patients of the IBD spectrum. These results, although limited by the sample size, allow a better understanding of changes in mucosa-associated bacterial flora in these patients, showing either a predominance of some potentially harmful bacterial groups or a decrease in beneficial bacterial species. These data underline the central role of mucosa-adherent bacteria in IBD.

Cloning and characterization of the NapA acid phosphatase/phosphotransferase of Morganella morganii: identification of a new family of bacterial acid-phosphatase-encoding genes.

The gene encoding a minor phosphate-irrepressible acid phosphatase (named NapA) of Morganella morganii was cloned and sequenced, and its product characterized. NapA is a secreted acid phosphatase composed of four 27 kDa polypeptide subunits. The enzyme is active on several organic phosphate monoesters but not on diesters, and is also endowed with transphosphorylating activity from organic phosphoric acid esters to nucleosides and other compounds with free hydroxyl groups. Its activity is inhibited by EDTA, inorganic phosphate, nucleosides and Ca2+, but not by fluoride or tartrate, and is enhanced by Mg2+, Co2+ and Zn2+. At the sequence level, the NapA enzyme did not show similarities to any other sequenced bacterial phosphatases. However, a search for homologous genes in sequence databases allowed identification of two open reading frames located within sequenced regions of the Escherichia coli and Proteus mirabilis genomes respectively, encoding proteins of unknown function which are highly homologous to the Morganella enzyme. Moreover, the properties of the NapA enzyme are very similar to those reported for the periplasmic nonspecific acid phosphatase II of Salmonella typhimurium (for which no sequence data are available). These data point to the existence of a new family of bacterial acid phosphatases, which we propose designating class B bacterial acid phosphatases.

Characterization and sequence of PhoC, the principal phosphate-irrepressible acid phosphatase of Morganella morganii.

Phosphatase activities were investigated in Morganella morganii, which is one of the few enterobacterial species producing high-level phosphate-irrepressible acid phosphatase activity (HPAP phenotype), and the gene encoding the major phosphate-irrepressible acid phosphatase was cloned, sequenced, and its product characterized. Using p-nitrophenyl phosphate as substrate, Morganella produced a major phosphate-irrepressible acid phosphatase (named PhoC) which is associated with the HPAP phenotype, a minor phosphate-irrepressible acid phosphatase, and a phosphate-repressible alkaline phosphatase. The presence of the PhoC activity prevented induction of alkaline phosphatase when a PhoC-hydrolysable organic phosphate ester, such as glycerol 2-phosphate, was the sole phosphate source. PhoC is a secreted nonspecific acid phosphatase apparently composed of four 25 kDa polypeptide subunits. The enzyme is resistant to EDTA, P(i), fluoride and tartrate. The M. morganii PhoC showed 84.6% amino acid sequence identity to the PhoN nonspecific acid phosphatase of Providencia stuartii, 45.3% to the PhoN nonspecific acid phosphatase of Salmonella typhimurium, and 37.8% to the principal acid phosphatase (PhoC) of Zymomonas mobilis. Comparison of sequence data and of regulation of these enzymes suggested a different phylogeny of members of this gene family within the Enterobacteriaceae.

Use of glucose starvation to limit growth and induce protein production in Escherichia coli.

The use of glucose starvation to uncouple the production of recombinant beta-galactosidase from cell growth in Escherichia coli was investigated. A lacZ operon fusion to the carbon starvation-inducible cst-1 locus was used to control beta-galactosidase synthesis. beta-Galactosidase induction was observed only under aerobic starvation conditions, and its expression continued for 6 h following the onset of glucose starvation. The cessation of beta-galactosidase expression closely correlated with the exhaustion of acetate, an overflow metabolite of glucose, from the culture medium. Our results suggest the primary role of acetate in cst-1-controlled protein expression is that of an energy source. Using this information, we metered acetate to a glucose-starved culture and produced a metabolically sluggish state, where growth was limited to a low linear rate and production of recombinant beta-galactosidase occurred continuously throughout the experiment. The cst-1 controlled beta-galactosidase synthesis was also induced at low dilution rates in a glucose-limited chemostat, suggesting possible applications to high-density cell systems such as glucose-limited recycle reactors. This work demonstrates that by using an appropriate promoter system and nutrient limitation, growth can be restrained while recombinant protein production is induced and maintained.

Plasmid "curing" by some recently synthetized 4-quinolone compounds.

Nalidixic acid and two recently synthetized 4-quinolones eliminated F'lac and R-plasmids from E. coli at concentrations of one half or one quarter of the minimum inhibitory concentration (MIC). Two of the three plasmids tested were cured by all derivatives, although with different frequencies. Pefloxacin was the most effective compound compared with the other quinolones and nalidixic acid the least active.

Inhibition of plasmid conjugation by some recently synthetized 4-quinolone compounds.

Four fluoroquinolones (norfloxacin, ciprofloxacin, ofloxacin, and pefloxacin) were compared with nalidixic acid for their inhibitory effect on conjugal plasmid transfer. The inhibition was observed in mating experiments using various combinations of drugs at subinhibitory concentrations and 3 different plasmids in the E. coli k12 genetic background. Fluoroquinolones inhibited plasmid transfer to a greater extent than nalidixic acid. Ofloxacin and pefloxacin were consistently the most active agents, causing 90 to 100% inhibition of plasmid transfer in all mating systems studied.

Double sugar-tyrosine medium improves O-1 phage Salmonella screening.

A modification of the procedure for O-1 phage Salmonella screening is presented. The novel method is based on the use of two media, i.e., a new medium (double sugar-tyrosine [DST]), which permits the combination of adonitol and sucrose fermentation and tyrosine clearing tests, and the previously described o-nitrophenyl-beta-D-galactopyranoside urease indole medium. In comparative trials, the new procedure and the conventional one were used to screen for Salmonella isolates from 553 lactose-negative strains of members of the family Enterobacteriaceae. The O-1 phage test, performed on DST medium, recognized the same number of phage-susceptible Salmonella strains as did the standardized method; however, it permitted the correct identification of a greater number of phage-resistant strains for discard (95.6 versus 85.3%). In particular, DST medium presented a higher efficacy than triple sugar iron agar (which is the corresponding medium in the reference procedure) in correctly identifying phage-negative cultures for discard (69.1 versus 28.5%).