1. 1. The concentrations of echinochrome-A in coelomic fluid from healthy specimens of the sea urchin Echinus esculentus (L.) ranged from 3 to 60 μg/ml, with a geometric mean of 14 μg/ml. 2. 2. Echinochrome-A (50 μg/ml) dissolved in sea water, with the aid of mammalian proteins as dispersants, was bactericidal or bacteriostatic towards six out of seven strains of marine gram-negative and gram-positive bacteria. 3. 3. Echinochrome-A is suggested as a major factor in the bactericidal activity of coelomic fluid from E. esculentus.

Echinochrome-A as a bactericidal substance in the coelomic fluid of Echinus esculentus (L.)

Bactericidal activity of coelomic fluid from the sea urchin Echinus Esculentus

The polymerase chain reaction (PCR) was used to amplify a 522-bp region of the adenylate cyclase toxin (cyaA) gene of Bordetella pertussis. As few as 100 cfu from a suspension of B. pertussis could be detected by this procedure when the amplified PCR product was detected by ethidium bromide staining of agarose gels. However, simulated clinical specimens, prepared from swabs impregnated with known numbers of B. pertussis cells, only yielded a positive reaction with > or = 10(4) cfu. Hybridisation of a Southern blot of the PCR products from the swab samples with a cya-specific probe gave a positive reaction with as few as 8 cfu, but the hybridisation signal was uniformly weak with fewer than 10(4) cfu. Nevertheless, three of 13 nasopharyngeal swabs, taken from suspected clinically defined cases of whooping cough and stored frozen for up to 18 months, gave a positive PCR reaction.

Identification of Bordetella pertussis in nasopharyngeal swabs by PCR amplification of a region of the adenylate cyclase gene

SUMMARY. Twelve selected strains of Bordetella pertussis were compared quantitatively for their ability to produce heat-labile toxin (HLT); all proved to be active producers, with only a three-fold range between the highest and the lowest. Bordet-Gengou agar, charcoal agar, modified Hornibrook medium and Stainer and Scholte (12G) medium differed little in their ability to support toxin production by three B. pertussis strains. However, cells grown on the solid media for 24 h were slightly more toxic than their counterparts grown for 72 h whereas in the liquid media the opposite was true. The concentration of iron in the medium did not influence HLT production, but high concentrations of nicotinic acid significantly reduced the HLT content of the cells. Crude preparations of toxin underwent only a 10% loss of toxicity per annum at—20°C and were stable for up to 2 weeks at 4°C. At 37°C, toxicity was lost within a few days. The toxin was partially purified by a series of mild procedures and had a mol. wt by gel filtration of 89 000 ±10%. HLT was toxoided by treatment with formaldehyde to give a product which was immunogenic in rabbits but not in mice. Because anti-HLT could be absorbed out of the rabbit antisera by treatment with intact B. pertussis, it was concluded that some of the HLT in the bacteria is surface-exposed even though the main part may have a cytoplasmic location.

F.T. Perkins

Papers

An international collaborative study on the measurement of the opacity of bacterial suspensions