Faculty Bibliography

Se estudio la respuesta a los antimicrobianos en 546 cepas de Salmonella enteritidis, y 260 cepas de Shigella en el periodo de enero de 1979 a diciembre de 1980. Se encontro que mas del 50% de las cepas analizadas presentaron resistencia a tetraciclina, estreptomicina, gentamicina y kanamicina. Se observo um incremento en la resistencia a varios de los antimicrobianos en este estudio en comparacion a trabajos realizados en anos anteriores. La multirresistencia fue mayor para el genero Salmonella que para el genero Shigella y para confirmarla, se determino la concentracion minima inhibitoria a los mismos antimicrobianos. El patron de resistencia mas frecuente fue a la ampicilina, cloranfenicol, estreptomicina, tetraciclina, cefalotina, gentamicina y kanamicina para Salmonella. Mientras que en el caso de Shigella, la resistencia a tetraciclina y estreptomicina fue el patron mas frecuente (AU).

The lipopolysaccharide (LPS) structure of Campylobacter spp. can be visualized with polyacrylamide gel electrophoresis by examining proteinase K-treated whole cell lysates. Polyacrylamide gel electrophoresis LPS profiles of C. jejuni strains are rough type with low concentrations of low-molecular-weight polysaccharide side chains, serum-resistant C. fetus strains have smooth-type LPS, and serum-sensitive C. fetus strains have rough-type LPS. We electroblotted the proteinase K-treated whole cell lysates of 17 C. jejuni and 9 C. fetus strains from polyacrylamide gel electrophoresis to nitrocellulose paper to examine antigenicity to immune rabbit sera. There was virtually no antigenic cross-reactivity of C. jejuni and C. fetus LPS. Among C. jejuni strains, core LPS structures were cross-reactive, but the O-polysaccharide side chains were best recognized by homologous antisera. Antisera to several serum-resistant C. fetus strains recognized only the polysaccharide side-chain regions of serum-resistant strains and no part of the LPS from the sensitive strain. Antiserum raised against a serum-sensitive C. fetus strain but not homologous antisera recognized the core region of the LPS of the serum-resistant C. fetus strains. These findings suggest that core LPS antigens are widely shared within C. fetus subsp. fetus strains but that in the serum-resistant strains this core region is not surface exposed and therefore not immunogenic to rabbits infected with whole cells

Most Campylobacter jejuni strains are sensitive and most Campylobacter fetus strains are resistant to the bactericidal activity in normal human serum. We purified lipopolysaccharides from Campylobacter strains to determine whether their composition and structure relate to serum susceptibility. The lipopolysaccharide of two serum-sensitive strains was best isolated by the Galanos procedure, but for two serum-resistant strains a cold-ethanol extraction was optimal. For each lipopolysaccharide preparation, the ratio of 2-keto-3-deoxyoctonate to protein was increased by 100 to 1,000-fold over that of whole cells. For serum-resistant strains, total carbohydrates was a high proportion of lipopolysaccharide weight; for serum-sensitive strains, 2-keto-3-deoxyoctanate was a high proportion of total carbohydrates. By polyacrylamide gel electrophoresis, the lipopolysaccharide of serum-sensitive strains appeared rough, but for serum-resistant strains a smooth-type ladder was seen, with a minimal core region and several high-molecular-weight complexes. Proteinase K-treated whole-cell lysates showed polyacrylamide gel electrophoresis profiles similar to that of pure lipopolysaccharide. Proteinase K-treated whole-cell lysates from seven serum-sensitive C. jejuni strains all had rough profiles, and five serum-resistant C. fetus strains all had smooth profiles. These studies indicate that lipopolysaccharide composition may be an important determinant of serum susceptibility among Campylobacter species and that serum resistance is usually associated with a smooth-type lipopolysaccharide