Angela Barberi

Cryptosporidium infection: diagnostic techniques

The aim of this study was to compare a rapid immunological test and a PCR method with the conventional morphological technique for the identification of Cryptosporidium in faecal samples. Cryptosporidium was found in five samples by Kinyoun acid-fast stain. Five samples yielded positive results on immunoassay, three of which yielded negative results on microscopy. Thus, only two patients were positive for Cryptosporidium according to both methods. PCR analysis confirmed only one sample as positive. Non-homogeneous distribution of parasites in stool samples, lack of oocysts in the tested sample and antigenic diversity among Cryptosporidium species may explain the poor agreement among the three tests. Based on our experience, microscopy test with Kinyoun stain is the best and cheapest way to detect Cryptosporidium spp. in faecal samples. With this method, we have found a 5.4% prevalence of Cryptosporidium infection in our area, similar to those reported for other regions of Italy and Europe.

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].

Rubella in teenagers: epidemiology and prophylaxis in Siena, Italy

Six hundred and fifty-three teenagers (aged 11-13 year) living in Siena and its surroundings (Tuscany, Italy) were the sample for serological screening intended to ascertain immunity to rubella. It was found that 324 of the teenagers (49.62%) lacked antibodies and, hence, were unprotected against the infection. Out of the 324 girls, 196 (around 3/5) were vaccinated using live vaccine. Post-vaccinal complications, with clinical signs of rubella infection, were recorded in almost one third of the vaccinees. Virus isolation from the blood was, in every case, not possible after either 10 or 30 days from vaccination. The serological findings, expressed in hemagglutination inhibition antibodies, could be summarized in the following way: (i) antibodies at low titre were found in only eight out of 184 girls (4.35%) ten days after vaccination; (ii) serological conversion was recorded in 187 out of 188 girls (99.47%) 30 days after vaccination; (iii) the titres were moderately high but much lower than those recorded for the natural infection. The results are discussed in the context of their implications for the strategies of rubella vaccination as far as the safety and the effectiveness of the vaccine are concerned, with emphasis on the duration of the protective immunity.

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).