Campylobacter diarrhea in an adult mouse model.

An adult mouse (18-20 g) model was developed for studying the pathogenesis of Campylobacter isolates. Iron-loaded BALB/c mice given 10(8)-10(9) Campylobacter colony forming units by intraperitoneal injection developed a severe mucoid diarrhea within 4 h. Severe diarrhea, consisting of unformed stools containing blood, mucus, and fecal leukocytes, persisted for 24 h. Diarrheal symptoms in surviving mice resolved gradually; no diarrhea was observed 5 days after inoculation. Mice not pretreated with iron developed no diarrheal symptoms, and no severe diarrhea was produced in mice inoculated orally. A transient (less than 24 h) bacteremia occurred in mice inoculated either orally or intraperitoneally. Liver, spleen, and kidney were positive for Campylobacter for 48 h; intestinal contents were positive for 5-7 days. Mice given greater than or equal to 10(10) colony forming units showed symptoms of endotoxemia (ruffled fur, inactivity, shaking, tearing, and hypothermia) and died without diarrheal symptoms. Mice given nonpathogenic Escherichia coli strain HB101, heat-killed C. jejuni cells (greater than 10(10)), C. jejuni lipopolysaccharide extract, or purified lipopolysaccharide from either Vibrio cholerae 569B or Salmonella typhimurium showed no diarrheal symptoms.

Effect of iron concentration on toxin production in Campylobacter jejuni and Campylobacter coli.

The effect of iron concentrations in culture media on supernatant yields of campylobacter cytotonic toxin (CCT) was studied. Of the 118 Campylobacter spp. strains surveyed, 78.8% produced toxin in brucella broth or in casamino acids--yeast extract (CYE) broth. When the iron concentration of CYE was increased from 0.44 microgram/mL (7.9 microM) to 0.65 microgram/mL (11.6 microM) by the addition of ferric chloride, 94.9% of the strains were positive for toxin in a ganglioside GM1 based, enzyme-linked immunosorbent assay, using antibody to affinity-purified CCT. The addition of iron as ferrous sulfate was less effective. When four toxin-positive strains were grown in a deferrated medium of conalbumin-treated CYE with 0.04-0.08 microgram iron/mL (0.72-1.43 microM), two of the culture supernatants became negative (absorbance at 410 nm, less than 0.1 and less than 10 ng CCT/mL), and two produced about 90% less CCT but were still classified as positive (absorbance, greater than or equal to 0.1 and greater than or equal to 10 ng CCT/mL). It was therefore concluded that the production of CCT by Campylobacter spp. is influenced by iron concentration.

Evaluation of virulence factor testing and characteristics of pathogenicity in Yersinia enterocolitica.

The virulence of 10 strains of Yersinia enterocolitica containing 42- to 44-megadalton plasmids (serogroups O:3; O:4,32; O:8; O:9; O:13,7; and O:21) was compared in mice and guinea pigs. Adult mice were more responsive than guinea pigs to the Sereny-like conjunctivitis test. In tests on suckling mice, all Yersinia strains harboring plasmids were lethal, whereas all strains without plasmids were nonlethal. All strains of serogroups O:4,32; O:8; O:13,7; or O:21 which harbored a plasmid gave positive results in the mouse Sereny, peroral, and intraperitoneal tests. A positive reaction in these tests was correlated with the ability of the strains to elaborate lipase. Because the Sereny, peroral, and intraperitoneal tests measured the same virulence factor(s), the findings in any of these three tests would accurately predict the results of the other two tests. Mice which survived the Sereny and peroral tests were subsequently challenged intraperitoneally with 1,000 mouse lethal doses of the virulent WA (O:8) strain. Those inoculated with plasmid-harboring strains were protected, whereas those inoculated with plasmid-free strains were not.

Binding of cholera toxin to Giardia lamblia.

Binding of cholera toxin to Giardia lamblia was demonstrated by two slightly different methods: an immunofluorescence technique using antibody to cholera toxin and anti-rabbit immunoglobulin G conjugated to fluorescein isothiocyanate, and a one-step fluorescence method in which G. lamblia was incubated with the B subunit of cholera toxin conjugated to fluorescein isothiocyanate.