Detection of free and plankton-associated Helicobacter pylori in seawater

AIMS: To detect both free and plankton-associated Helicobacter pylori in seawater samples collected on the Italian coast of the Adriatic Sea using a nested-PCR. METHODS AND RESULTS: Dissolved oxygen, pH, salinity and chlorophyll 'a' were the parameters recorded together with the characterization of zooplanktonic organisms. Plankton-associated H. pylori DNA was searched for in water samples filtered through 200 and 64 microm nylon nets whereas free bacteria were retained with the subsequent filtration through 0.22 microm pore-size membranes. Nested-PCR using primers for the glmM (ureC) gene was performed to reveal the presence of H. pylori. The DNA sequencing of amplified products confirmed the specificity of the assay. The sensitivity of the nested-PCR assay for H. pylori detection was 62 CFU per 100 ml in spiked water samples. Helicobacter pylori either free or bound to planktonic organisms was found in seven of 12 monthly samples. In particular, free bacteria were detected during the summer sampling and in November, December and March associated to planktonic cells. CONCLUSIONS: The presence of free and plankton-associated H. pylori in seawater suggests that it can be a significant reservoir and a potential route of transmission for the microorganism. SIGNIFICANCE AND IMPACT OF THE STUDY: Our study seems to provide a promising background to define new and effective strategies for surveillance of this human pathogen.     

Occurrence, diversity and pathogenicity of mesophilic Aeromonas in estuarine waters of the Italian coast of the Adriatic Sea

A total of 208 strains of Aeromonas were isolated by monthly sampling from two estuaries (one provided with, and the other devoid of a waste-water treatment system) on the Italian coast of the Adriatic sea between September 1994 and August 1995. Biotyping at the species level allowed the identification of 96 strains (46%) as Aer. caviae , 46 (22%) as Aer. sobria , 33 (16%) as Aer. hydrophila and 25 (12%) as Aer. veronii . Eight strains (4%) were regarded as unnamed aeromonads. Aeromonas caviae was the most prevalent species in water with a high degree of pollution, while Aer. hydrophila strains were more commonly isolated from cleaner water. Aeromonas sobria and Aer. veronii were equally distributed in both estuaries. There was no correlation between temperature and numbers of aeromonads in either estuary. Using a biochemical fingerprinting method, strains were divided into similarity groups (PhP-types) based on their biochemical phenotypes. Several different PhP-types were found in each estuary, yielding a high diversity for these strains. However, some identical PhP-types were also found in both estuaries and at different times of the year, indicating that certain Aeromonas strains can survive more widely varying physico-chemical conditions. The production of toxins capable of causing cytoskeletal-dependent changes in the morphology of Chinese hamster ovary (CHO) cells was detected in 14 strains and appeared to be dependent on the season.     

Activation of c-myb expression by phytohemagglutinin stimulation in normal human T lymphocytes.

The expression of c-myb in normal human T lymphocytes directly derived from a normal subject and not adapted to continuous growth in culture was found to be markedly increased after phytohemagglutinin stimulation. In the same cells, the expression of c-myc mRNA is a much earlier event compared with the appearance of c-myb mRNA, which takes place soon after that of histone H3 mRNA. The increase in c-myb expression was not due to a particular T-lymphocyte subset, as shown by in situ hybridization assays.     

Structure and physico-chemical properties of bacteriophage G: III. A homogeneous DNA of molecular weight 5 × 108

The physico-chemical properties of the DNA released from bacteriophage G (active on Bacillus megatherium) are described. Phage G, an unusually large bacteriophage, has a nucleic acid content of 4 to 6 × 10⁸ daltons.Sedimentation velocity analysis at low angular speed and examination by electron microscopy, indicate that a single DNA molecule, sedimenting with s_{20, w}⁰ = 125 ± 1.5 S and at least 200 ± 20 μm long, is released upon thermal or osmotic shock. Melting temperature data and chromatographic analysis indicate a mean base composition of 70% A + T. CsCl and Cs₂SO₄ buoyant density data, circular dichroism spectra and sensitivity to specific nucleases indicate that phage G DNA is similar to the DNAs from T-even phages and is more glucosylated than phage T6 DNA. Direct glucose determination indicates a 185% molar ratio of glucose to cytosine. Linear density extrapolated from literature data and contour length measurement yield a lower limit for the molecular weight of phage G DNA of 4.9 × 10⁸. Comparison of this value with the s_20,w⁰ measured with the analytical ultracentrifuge seems to confirm the validity of the empirical relationship proposed by Freifelder (1970), between s_{20, w}⁰ and molecular weight, over a larger range than that previously known. A possible systematic error in defect in length determination, however, prevents a discrimination between this and other empirical formulae proposed by various authors, which predict a molecular weight that is 20 to 25% higher.     

VanA-type enterococci from humans, animals, and food: species distribution, population structure, Tn1546 typing and location, and virulence determinants

VanA-type human (n=69), animal (n=49), and food (n=36) glycopeptide-resistant enterococci (GRE) from different geographic areas were investigated to study their possible reservoirs and transmission routes. Pulsed-field gel electrophoresis (PFGE) revealed two small genetically related clusters, M39 (n=4) and M49 (n=13), representing Enterococcus faecium isolates from animal and human feces and from clinical and fecal human samples. Multilocus sequence typing showed that both belonged to the epidemic lineage of CC17. purK allele analysis of 28 selected isolates revealed that type 1 was prevalent in human strains (8/11) and types 6 and 3 (14/15) were prevalent in poultry (animals and meat). One hundred and five of the 154 VanA GRE isolates, encompassing different species, origins, and PFGE types, were examined for Tn1546 type and location (plasmid or chromosome) and the incidence of virulence determinants. Hybridization of S1- and I-CeuI-digested total DNA revealed a plasmid location in 98% of the isolates. Human intestinal and animal E. faecium isolates bore large (>150 kb) vanA plasmids. Results of PCR-restriction fragment length polymorphism and sequencing showed the presence of prototype Tn1546 in 80% of strains and the G-to-T mutation at position 8234 in three human intestinal and two pork E. faecium isolates. There were no significant associations (P>0.5) between Tn1546 type and GRE source or enterococcal species. Virulence determinants were detected in all reservoirs but were significantly more frequent (P<0.02) among clinical strains. Multiple determinants were found in clinical and meat Enterococcus faecalis isolates. The presence of indistinguishable vanA elements (mostly plasmid borne) and virulence determinants in different species and PFGE-diverse populations in the presence of host-specific purK housekeeping genes suggested that all GRE might be potential reservoirs of resistance determinants and virulence traits transferable to human-adapted clusters.     

VanA-Type Enterococci from Humans, Animals, and Food: Species Distribution, Population Structure, Tn1546 Typing and Location, and Virulence Determinants

VanA-type human (n = 69), animal (n = 49), and food (n = 36) glycopeptide-resistant enterococci (GRE) from different geographic areas were investigated to study their possible reservoirs and transmission routes. Pulsed-field gel electrophoresis (PFGE) revealed two small genetically related clusters, M39 (n = 4) and M49 (n = 13), representing Enterococcus faecium isolates from animal and human feces and from clinical and fecal human samples. Multilocus sequence typing showed that both belonged to the epidemic lineage of CC17. purK allele analysis of 28 selected isolates revealed that type 1 was prevalent in human strains (8/11) and types 6 and 3 (14/15) were prevalent in poultry (animals and meat). One hundred and five of the 154 VanA GRE isolates, encompassing different species, origins, and PFGE types, were examined for Tn1546 type and location (plasmid or chromosome) and the incidence of virulence determinants. Hybridization of S1- and I-CeuI-digested total DNA revealed a plasmid location in 98% of the isolates. Human intestinal and animal E. faecium isolates bore large (>150 kb) vanA plasmids. Results of PCR-restriction fragment length polymorphism and sequencing showed the presence of prototype Tn1546 in 80% of strains and the G-to-T mutation at position 8234 in three human intestinal and two pork E. faecium isolates. There were no significant associations (P > 0.5) between Tn1546 type and GRE source or enterococcal species. Virulence determinants were detected in all reservoirs but were significantly more frequent (P < 0.02) among clinical strains. Multiple determinants were found in clinical and meat Enterococcus faecalis isolates. The presence of indistinguishable vanA elements (mostly plasmid borne) and virulence determinants in different species and PFGE-diverse populations in the presence of host-specific purK housekeeping genes suggested that all GRE might be potential reservoirs of resistance determinants and virulence traits transferable to human-adapted clusters.