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M C Martino

Publications and source records attributed to M C Martino.

6 recordsLinked to original sources
PubMed2001

Helicobacter pylori pore-forming cytolysin orthologue TlyA possesses in vitro hemolytic activity and has a role in colonization of the gastric mucosa.

Hemolysins have been found to possess a variety of functions in bacteria, including a role in virulence. Helicobacter pylori demonstrates hemolytic activity when cultured on unlysed blood agar plates which is increased under iron-limiting conditions. However, the role of an H. pylori hemolysin in virulence is unclear. Scrutiny of the H. pylori 26695 genome sequence suggests the presence of at least two distinct hemolysins, HP1086 and HP1490, in this strain. Previous studies have shown that the in vitro hemolytic activity of H. pylori is reduced when it is coincubated with dextran 5000, suggesting the presence of a pore-forming cytolysin. HP1086 has homology to pore-forming cytolysins (TlyA) from other bacterial species, and the introduction of the cloned H. pylori tlyA gene into a nonhemolytic Escherichia coli strain conferred hemolytic activity. An H. pylori tlyA defined mutant showed reduced in vitro hemolytic activity, which appears to be due to pore formation, as the hemolytic activity of the wild-type strain is reduced to the same level as the tlyA mutant by the addition of dextran 5000. The mutant also showed reduced adhesion to human gastric adenocarcinoma cells and failed to colonize the gastric mucosa of mice. These data clearly suggest a role in virulence for H. pylori TlyA, contrary to the suggestion that hemolytic activity is an in vitro phenomenon for this pathogen.

Animals↗
PubMed2000

Phase variation in H type I and Lewis a epitopes of Helicobacter pylori lipopolysaccharide.

Helicobacter pylori NCTC 11637 lipopolysaccharide (LPS) expresses the human blood group antigens Lewis x (Le(x)), Le(y), and H type I. In this report, we demonstrate that the H type I epitope displays high-frequency phase variation. One variant expressed Le(x) and Le(y) and no H type I as determined by serology; this switch was reversible. Insertional mutagenesis in NCTC 11637 of JHP563 (a poly(C) tract containing an open reading frame homologous to glycosyltransferases) yielded a transformant with a serotype similar to the phase variant. Structural analysis of the NCTC 11637 LPS confirmed the loss of the H type I epitope. Sequencing of JHP563 in strains NCTC 11637, an H type I-negative variant, and an H type I-positive switchback variant showed a C14 (gene on), C13 (gene off), and C14 tract, respectively. Inactivation of strain G27, which expresses Le(x), Le(y), H type I, and Le(a), yielded a transformant that expressed Le(x) and Le(y). We conclude that JHP563 encodes a beta3-galactosyltransferase involved in the biosynthesis of H type I and Le(a) and that phase variation in H type I is due to C-tract changes in this gene. A second H type I-negative variant (variant 3a) expressed Le(x) and Le(a) and had lost both H type I and Le(y) expression. Inactivation of HP093-HP094 resulted in a transformant expressing Le(x) and lacking Le(y) and H type I. Structural analysis of a mutant LPS confirmed the serological data. We conclude that the HP093-HP094 alpha2-fucosyltransferase (alpha2-FucT) gene product is involved in the biosynthesis of both Le(y) and Le(x). Finally, we inactivated HP0379 in strain 3a. The transformant had lost both Le(x) and Le(a) expression, which demonstrates that the HP0379 gene product is both an alpha3- and an alpha4-FucT. Our data provide understanding at the molecular level of how H. pylori is able to diversify in the host, a requirement likely essential for successful colonization and transmission.

Antibodies, Monoclonal↗
PubMed1999

Characterization of Helicobacter pylori PldA, a phospholipase with a role in colonization of the gastric mucosa.

BACKGROUND & AIMS: Phospholipase activity may play a role in the pathogenicity of Helicobacter pylori. Furthermore, some drugs that are effective against H. pylori infection are phospholipase inhibitors. Scrutiny of the H. pylori 26695 genome sequence revealed the presence of a putative protein with homology to Esherichia coli outer membrane phospholipase A (PldA). The aim of this study was to investigate the role of this putative PldA in the pathogenicity of H. pylori. METHODS: An isogenic pldA mutant was constructed and analyzed for in vitro phospholipase A(2) and hemolytic activity. Adherence of the mutant to human gastric adenocarcinoma cells and the ability to colonize mice were also investigated. RESULTS: The pldA mutant showed a marked reduction in phospholipase A(2) and hemolytic activity compared with the wild-type strain. The mutant was unable to colonize mice at 2 and 8 weeks, but it did induce a significant immune response. In contrast, the ability of the mutant to adhere to human gastric adenocarcinoma cells was unaffected. CONCLUSIONS: The results suggest a role for PldA in colonization of the gastric mucosa and possibly tissue damage after colonization.

Animals↗
PubMed1996

Laparoscopic compared with open appendicectomy for acute appendicitis: a prospective study.

OBJECTIVE: To assess the benefits of laparoscopic appendicectomy over open appendicectomy and to evaluate the impact of the severity of appendicitis and of peritonitis on the advantages of the laparoscopic approach. DESIGN: Prospective unrandomised study. SETTING: University hospital, Italy. SUBJECTS: 137 consecutive patients with acute appendicitis, 60 of whom were treated by open and 77 by laparoscopic appendicectomy. Patients were subdivided according to the severity of appendicitis and the presence of peritonitis. MAIN OUTCOME MEASURES: Duration of operation, consumption of analgesics, duration of hospital stay, overall complications, wound infection. RESULTS: Hospital stay (median 2.5 days, range 1-18 compared with 4, range 2-22 p < 0.0001). and wound infection (3/77 (4%) compared with 13/60 (22%), p 0.02) were significantly lower after laparoscopic operation. The incidence of wound infection was significantly lower when subgroups were analysed separately. CONCLUSIONS: Hospital stay and wound infection rates were significantly lower after laparoscopic appendicectomy. With the exception of the wound infection rate, the variables studied may differ depending on the severity of the appendicitis and the presence of peritonitis. Result of comparative studies should be carefully interpreted when the two groups are not stratified for these features.

Acute Disease↗
PubMed1992

[The prevention of postoperative deep venous thrombosis with heparan sulfate per os. A controlled clinical study vs. heparin calcium].

The paper reports the results of a randomised study carried out on a pool of 100 patients undergoing surgery in order to assess the efficacy and tolerability of orally administered heparan sulfate versus heparin calcium in the prevention of postoperative deep-vein thrombosis. Despite the limits of oral administration, heparan sulfate is indicated in the pharmacological prevention of postoperative deep-vein thrombosis.

Administration, Oral↗