Annalisa Cavallero

A New Simple Immunoassay for Detecting Helicobacter pylori Infection: Antigen in Stool Specimens

Background/Aim: Several diagnostic tests are available for evaluating Helicobacter pylori (Hp) infection: histological examination, culture of gastric biopsy specimens, rapid urease test, urea breath test and serology. A recently marketed direct enzyme immunoassay (HpSA) detects Hp antigen in stool samples. The aim of our study was to evaluate overall diagnostic sensitivity, specificity and positive and negative predictive values of this new diagnostic test. Methods: We included in the study 84 patients (39 males and 45 females; mean age 49.57 years) with dyspeptic symptoms who were examined by upper gastrointestinal endoscopy. Exclusion criteria were previous treatment with proton pump inhibitors, bismuth compounds or antibiotics. During the endoscopic examination biopsies were taken from antrum and corpus for Hp culture and histological examination, and stool specimens were submitted to the laboratory to be stored until the HpSA test. Hp was judged to be present when culture or histology and culture were positive. The 13C-urea breath test was done only in culture-negative patients in whom either histology or immunoassay or both were positive. Results: Hp was found in 55 patients by both culture and histology. Stool antigen has been detected in 54 of the 55 Hp-positive patients, giving a sensitivity of 98.2% and a negative predictive value of 96.4%. In 2 out of 29 patients HpSA gave a positive result, but the biopsy-based methods were negative, resulting in a low rate of false-positives, with 93.1% specificity and 96.4% positive predictive value; the 13C-urea breath test confirmed these results as negative. Conclusion: Our results show that this new test is highly sensitive and specific for the detection of Hp infection, and it is satisfactorily reproducible.

Isolation and genotyping of Acanthamoeba strains from corneal infections in Italy

Acanthamoeba keratitis (AK) is a corneal disease caused by members of a genus of free-living amoebae and is associated predominantly with contact lens (CL) use. This study reports 16 cases of culture-proven AK diagnosed in northern Italy. Genotype identification was carried out with a PCR assay based on sequence analysis of the 18S rRNA gene, and sensitivity and specificity were evaluated in comparison with traditional parasitological techniques. A 405 bp region of the 18S rRNA gene (ASA.S1) including diagnostic fragment 3 (DF3) was amplified using the genus-specific primers JDP1 and JDP2. Genotype assignment was based on phenetic analysis of the ASA.S1 subset of the nuclear small-subunit rRNA gene sequence excluding the highly variable DF3 region. Phylogenetic analysis was also performed on the sequences obtained. All patients complained of monolateral infection; 11 (68.75%) admitted improper CL disinfection. In 14/16 (87.5 %) subjects, corneal scrapings were stained with calcofluor white and haematoxylin and eosin and, in ten cases (62.5 %), microscopy was positive for Acanthamoeba cysts. In vitro culture on 3 % non-nutrient agar plates was obtained in all cases (100 %), whereas cloning and axenic growth were positive for 14 amoebic stocks (87.5 %). PCR analysis had 100 % sensitivity and specificity compared with in vitro axenic culture, showing positive amplification from 15 isolates. All Acanthamoeba strains belonged to the T4 genotype, the main AK-related genotype worldwide. These results confirmed the importance of a complete diagnostic protocol, including a PCR assay, for the clinical diagnosis of AK on biological samples. Genotyping allowed inclusion of all isolates in the T4 group, thus demonstrating the prevalence of this genotype in northern Italy.

Direct Detection of Helicobacter pylori Mutations Associated with Macrolide Resistance in Gastric Biopsy Material Taken from Human Immunodeficiency Virus-Infected Subjects

ABSTRACT One hundred forty gastric biopsies were tested by microbiological methods and by amplifying a sequence of 23S rRNA and identifying mutations associated to clarithromycin resistance. Seventy-six specimens were positive for Helicobacter pylori. Mutational analysis revealed alterations in 18 (39.1%) of 46 and 2 (8.7%) of 23 samples from human immunodeficiency virus-seropositive and -seronegative persons, respectively. The results of the mutational analysis fully correlated with those of the susceptibility tests.

Nocardia keratitis : A case report

Purpose To describe a case of Nocardia keratitis resistant to 2% amikacin, with a toxic-allergic reaction to fortified topical 5% amikacin, and recurrence of the infection with topical corticosteroids. Methods Nocardia was diagnosed from a smear and positive culture and identified as Nocardia asteroides by gas chromatography and quantitative fatty acid analysis using the Microbial Identification System. Treatment was started with topical 2% amikacin, which was subsequently raised to 5% because of clinical resistance. Results A toxic-allergic reaction was observed after 5% amikacin so the drug was discontinued and commercially available drugs combining 1% chloramphenicol, 0.5% tetracycline, and 18 mil IU colistin with 0.3% ofloxacin were given. These were well tolerated and the infection improved quickly. After 1 month the antibiotics were discontinued and topical 0.1% clobetasone was given to reduce scar formation. The infection recurred after 1 week but responded to 3 months of the previous antibiotic combination and its sensitivity was checked with the Epsilometer test. Conclusions Nocardia keratitis may not respond to 2% topical amikacin and fortified topical 5% amikacin may cause a strong toxic-allergic reaction. A commercially available combination of chloramphenicol, tetracycline, and colistin, with ofloxacin, may be effective but the treatment must be continued for several months. Topical steroids should only be used with considerable caution since they can lead to relapse of the infection.

Announcement and Erratum

On Saturday, April 29, 2000, the EASL will host a joint meeting with the European Liver Transplantation Association. The 2000 postgraduate course will be on ‘Adult and paediatric cholestasis’ and the President’s meeting will be on ‘Combination therapy in liver disease: What is the additional effect of the 2nd therapy? What is the basic mechanism?’ The two single topic symposia will focus on ‘Liver regeneration’ and on ‘Prognosis in liver disease’. The two state of the art lectures will discuss ‘Microchips and microarrays in biomedicine’ and ‘Herbal medicine and the liver’. The President of the 2000 meeting is Prof. Solko Schalm, Rotterdam, The Netherlands. The EASL will offer 120 travel bursaries to selected young investigators and 30 to Eastern Europeans, pending on submission of an abstract. In addition, first authors under 35 years of age who submit abstracts will have free registration. This part of the EASL’s policy to encourage young investigators to attend and present at its scientific meetings. For further information, please contact: