Twenty-six strains belonging to the five main species of the genus Listeria were examined for production of thiol-dependent exotoxins. All strains of L. monocytogenes cultured in charcoal-treated broth secreted a haemolytic factor at a level ranging from 200 to 800 haemolytic units (HU) ml-1, except for the strain EGD (1500 HU ml-1) and the type strain CIP 82110T (10 HU ml-1). The haemolytic activity reached a maximum level by 8-10 h and then rapidly declined as soon as bacterial exponential growth ceased. The titres of haemolytic activity were markedly reduced when bacteria were grown in charcoal-untreated broth. The haemolytic factor produced by L. monocytogenes strains was characterized as listeriolysin O (Mr about 60,000), a member of the group of thiol-dependent exotoxins. Strains of Listeria ivanovii also produced high levels of thiol-dependent exotoxin (about 2500 HU ml-1), in both charcoal-treated and untreated broth. Small amounts of haemolytic factor (about 9-30 HU ml-1) were also produced by Listeria seeligeri in charcoal-treated broth. The haemolysin produced by L. seeligeri was identified for the first time as a thiol-dependent exotoxin of Mr about 60,000, antigenically related to listeriolysin O. As expected, we failed to detect thiol-dependent exotoxin in the two nonhaemolytic species, Listeria innocua and Listeria welshimeri.

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An evaluation of patients with meconium peritonitis shows that, apart from the fibro-adhesive type, the (Pseudo) cystic and the generalized type, a fourth type can be distinguished. In a case of this fourth type, the "microscopic" type of meconium peritonitis, no signs of a peritonitis are found on macroscopic examination of the abdominal cavity. Conversely, microscopic examination will reveal meconium components focally outside the bowel. The clinical and histological data of 14 patients are discussed. It is pointed out that a significantly large number of patients with meconium peritonitis also have atresia of the small bowel. Based on the patient evaluation, a hypothesis is brought forward concerning the pathogenesis of these atresias.

The serum bactericidal test has been used for many years for optimal assessment of the efficacy of antibiotic therapy in patients with infective endocarditis and other bacterial infections. Its capacity to predict the bacteriological outcome of acute pulmonary exacerbations in patients with cystic fibrosis was evaluated. A total of 54 courses of intravenous antibiotic therapy were analyzed in 22 patients, whose ages ranged from 4 months to 24 years (mean age: 10 years). The serum bactericidal activity of blood samples, taken at expected peak and trough antibiotic levels on day 4 of therapy, were determined against the potentially pathogenic strains isolated in sputum at the time of admission. For 104 isolates (64 Pseudomonas aeruginosa, 28 Staphulococcus aureus, and 12 Haemophilus influenzae strains), the peak and trough bactericidal titers were compared to bacteriological outcome. Bacteriological success was defined as a decrease of 2 log10 units or more in the bacterial density in sputum between days 0 and 7 of therapy. At peak antibiotic levels, serum bactericidal titers of 1:128 or more were 96% (all isolates) and 89% (P aeruginosa isolates), predictive of cure, whereas serum bactericidal titers of less than 1:16 were 100% predictive of failure for all infecting bacteria. In patients aged less than 18 years, the best peak titer for predicting success was 1:64, with a predictive value of 96% for titers of 1:64 or greater The peak titer that best predicted success in patients aged 18 years or more was 1:128, with a predictive value of only 83% for titers of 1:128 or greater. No trough serum bactericidal titer achieved statistical significance as a predictor of bacteriological outcome in the two patient age groups. Peak serum bactericidal titers of 1:64 or more (patients aged less than 18 years) and of 1:128 or more (patients aged 18 years or more) are recommended to provide optimal treatment of acute pulmonary exacerbations of cystic fibrosis.