R. A. Musmanno

Comparisons between degree of histological gastritis and DNA fingerprints, cytotoxicity and adhesivity of Helicobacter pylori from different gastric sites.

Thirty-six isolates of H. pylori from up to three gastric biopsy sites (antrum, corpus and fundus) from 13 patients in Italy with different degrees of histological gastritis were investigated. All strains were tested for motility, cytotoxicity and degree of adhesion, and were typed by analysis of ribosomal RNA gene patterns (ribopatterns). Seventeen different DNA types (ribotypes) were identified, with each patient possessing H. pylori of one or more unique types. Only two patients had identical H. pylori at three sites. Most patients had H. pylori with different ribotypes or subtypes, but nine strains were not typable. Five patients had the same strain colonizing two of the three sites and atypical strains were mostly from the antrum. A complex pattern of H. pylori colonization in the stomach of some individuals was evident and suggested multiple sources of infection. No consistent associations were detected between degree of gastritis and adherence, cytotoxicity and motility but a 2.56Kb rRNA gene fragment that had a higher frequency in strains associated with severe gastritis than mild gastritis, may provide a useful molecular marker for future pathogenicity studies.

Studies on strong and weak killer phenotypes of wine yeasts: production, activity of toxin in must, and its effect in mixed culture fermentation

R.A. MUSMANNO, T. DI MAGGIO and G. CORATZA.1999.Two different killer phenotypes were detected among K+ (killer) yeasts isolated from spontaneous wine fermentations using a plate bioassay. The two phenotypes differed in their degree of killer activity, and were designated as SK+(strong killer) and WK+(weak killer). Strains showing either phenotype were assayed for expression of killer activity under different growth conditions. Growth in must negatively affected expression of the killer activity of both phenotypes. The supernatant fluids from must cultures showed a lower killing effect than those from yeast phosphate dextrose broth (YPDB) cultures. The ability of the two K+ phenotypes to prevail on K‐sensitive yeasts was studied in mixed‐culture fermentation experiments. Under these conditions, only strains showing SK+ phenotype were able to prevail on the K‐sensitive yeasts. These results suggest that the K+ phenotype could play a relevant role in spontaneous fermentations provided that the strain exhibits an SK+ phenotype, and that the latter phenotype should be preferred when selected K + strains are to be used as fermentation starters.

Pathogenic Mechanisms of Helicobacter pylori: Production of Cytotoxin

Bacteria associated with mucosal infections of the digestive system generally produce toxins, especially when they cause inflammatory lesions. Illnesses due to thermotolerant campylobacters, to enterohemorrhagic Escherichia coli, and to Clostridium difficileare only some examples. It would be surprising if Helicobacter pylori (HP) did not produce any toxic substances. The difficulty consists in attributing a pathogenic meaning to the toxin, since the range is quite wide of clinical and histological presentation of gastroduodenal inflammatory diseases linked to the presence in the stomach of H. pylori organisms [1]. Johnson and Lior [2] firstly reported the production of heat-labile cytotoxin by 80.6% of 36 HP strains they tested. However, most of our knowledge of the cytotoxigenicity of HP is from Leunk et al. [3] whose work has inspired us in part. They found that about 55% of 201 HP strains isolated in four different parts of the world produced a substance which caused intracellular vacuolization in cells of several lines in vitro, not only in lines generally employed in toxigenicity tests, like Chinese hamster ovary (CHO) cells, Vero cells, and Y-1 cells, but also in human tumoral cells like HeLa, KATO III, and HEp-2, as well as in human embryonic intestinal cells which were the most responsive. They also inferred that the toxin was proteinaceous in nature being heat labile (destroyed at 70 °C for 30 min), protease sensitive, and ammonium-sulfate precipitable. Its molecular weight ought to be higher than 100 kDa since cytotoxic activity could be found only in the retentate of a concentrated broth culture filtrate (CBCF) passed through 100 kDa molecular weight limit ultrafiltration membrane.

Antibodies to Vacuolating Toxin of Helicobacter pylori in Dyspeptic Patients

Certain Helicobacter pylori (HP) strains are capable of inducing a cytopathic effect in mammalian cells in vitro consisting in the formation of intracytoplasmic vacuoles [1, 2]. In vitro cells exposed to broth culture filtrate (BCF) of vacuolating HP (VHP) strains die more rapidly than do cells exposed to BCF of non-VHP ones and to uninoculated broth. In addition, VHP causes a strong reduction of the proliferation index of Epstein-Bass Virus (EBV) -transformed B lymphocytes [2].

Production of serum-opacity factor by Streptococcus pyogenes strains isolated from pharyngitis in children prevalence of ≪rheumatogenic≫ M types among of-negative strains

Two hundred ten S. pyogenes strains isolated in 1979, 1980 and 1984 from children with pharyngitis were here examined for properties which might be relevant to their rheumatogenic potential. Strains were first tested for the production of streptococcal serum-opacity factor and, among those scored as OF-negative, the presence was then verified of M types which have been epidemiologically related to rheumatic fever. Members of ≪rheumatogenic≫ M types are present among strains causing pharyngitis in children; which, however, also include a considerable proportion of OF-positive, probably non-rheumatogenic, strains. The results are discussed in the light of the low incidence of rheumatic fever in this country.

Serum Antibodies to the Vacuolating Toxin Produced by Helicobacter pylori

Cytotoxin is one of the candidate factors of virulence of Helicobacter pylori (HP) [1]. Toxigenicity occurs frequently in strains isolated from patients with peptic ulceration [2], and there is serological evidence that cytotoxin production also occurs in vivo. In fact, in immunoblotting tests we saw that all the 31 individuals infected by cytotoxic (CT+) HP strains tested and 14 of 20 patients (70%) infected by noncytotoxic (CT−) organisms had serum immunoglobulin G (IgG) which recognized HP cytotoxin-associated proteins (CAP). IgA to CAP were hardly detected, mostly in patients infected by CT+ strains, while IgM were not detected at all (N. Figura et al., in preparation).