Summary. Broth-culture filtrates of Campylobacterpylori induced non-lethal cytopathic effects in vitro in 7 of 9 mammalian cell lines tested. Transmission electronmicroscopy revealed that the response consisted of intracellular vacuolisation. Intestine 407 cells were among the most responsive and were used for routine assay. About 55% of isolates of C. pylori tested, originating from four geographic regions worldwide, produced cytotoxic activity. The activity was neutralisable by specific antisera to broth-culture filtrates or to sonicated bacteria but not by antisera to other bacterial preparations. Cytotoxic activity was heat-labile (70°C for 30 min), was proteasesensitive and ammonium-sulphate precipitable. It did not pass through an ultrafiltration membrane with a nominal mo1.-wt limit of 100 x lo3. It was concluded that C. pylori can produce a factor that alters cultured cells in vitro. The relevance of this factor to the pathogenesis of gastritis associated with C. pylori remains to be determined.

There is no ideal method for detecting Helicobacter pylori. The 'standard' 13Carbon urea breath test (13C-UBT), which involves collecting eight to 15 breath samples and subsequent costly analysis, was modified by pooling 2 1 samples of expired breath taken at five minute intervals for 40 minutes into a collecting bag, from which a single 20 ml aliqt ot was taken and analysed by mass spectrometry. This test was evaluated on 50 patients after routine upper gastrointestinal endoscopy, and results were compared with those from the standard 13C-UBT, bacteriology, ELISA serology, and histology -the latter being taken as the gold standard. Hpylori were seen in 34 of 50 (68%) patients (in three it was detected in biopsy specimens from the corpus alone). The modified 13C-UBT was positive (pooled excretion 613CO2>5 per mil) in 31 patients and negative in 19 (three false negative results), specificity was 100% (standard 13C-UBT 94%) and sensitivity 92% (standard 13C-UBT 93%). The modified '3C-UBT had a coefficient ofvariation within subjects of 3.7%. For the ELISA serology and culture the specificities were both 100%, but the sensitivities were 82% and 68% respectively. The '3C-UBT results correlated with the grade of histological gastritis. The modified 1 C-UBT is simpler, cheaper, more reproducible, and provides an easy non-invasive method for the detection of H pylon. subject (helpful for the serial monitoring of treatment), and makes it ideal for epidemiological studies, particularly as it can be used in children and women of child bearing age and because no radiation is involved, a licence is not required.Since the initial report of the 13C-UBT,' however, the technique has not been further refined; little is known of its reproducibility and as multiple samples are required to produce an excretion curve, interpretation of results may be difficult and the test costly. Therefore, the test has so far remained essentially a research tool.We describe a modified protocol for the '3C-UBT and results of reproducibility studies, which together should make this test for H pylori easier to use in routine clinical practice.Patients and methods Fifty patients attending for routine upper gastrointestinal endoscopy were invited to enter the study, which had Parkside District Health Authority ethical committee approval. The patients gave written informed consent. Height, weight, and respiratory function (measured by peak flow, forced vital capacity, and forced expiratory volume in one second) were recorded. Exclusion criteria were recent (within two months) use of bismuth containing compounds, antibiotics known to be active in vivo against H pylori, or previous resective gastric surgery.

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Since a model of staphylococcal skin infection adequately reflecting human disease was unavailable, a self-limiting animal infection model specific for virulent Staphylococcus species was developed. A virulent strain of S. aureus, NCTC 9789 (ATCC 27700), was used to develop an infection model in adult, male CF-1 mice treated with 0 to 150 mg of cyclophosphamide (CY) per kg 4 days before challenge. Bacteria were inoculated onto the dorsal side of shaved mice at 0 to 10(6) CFU per mouse. Simultaneously, the skin was gently scraped to remove the superficial layers without drawing blood. The wound was occluded with impermeable film secured with surgical tape. At a CY dose of 50 mg/kg and an inoculum of 10(5) CFU, 89% of the mice (96 of 108) developed large abscesses (approximately 15-mm diameter). Mice which were not immunocompromised developed fewer abscesses (20 of 68). Generally, no abscesses formed when the mice were not wounded (1 of 62), occluded (0 of 89), or inoculated (11 of 50). The abscesses developed 24 to 48 h after challenge and persisted for 2 to 3 weeks. The challenge organism was isolated from the abscesses. The rates of abscess formation of three additional S. aureus strains varied widely in normal and CY-treated mice. Three strains of S. epidermidis, one of Micrococcus varians, and one of S. saprophyticus failed to cause abscesses. Bacterial proliferation studies demonstrated that a strain of S. aureus and a strain of S. epidermidis proliferated to the same levels 48 h after challenge. Immunosuppression and wounding had little effect on the levels of proliferation of S. aureus (P greater than 0.2). Without occlusion, however, S. aureus proliferated to significantly lower levels (P less than 0.005). This model may be be useful for screening topical anti-infective agents or studying the mechanisms of bacterial pathogenesis and host response.