Antimicrobial resistance of Campylobacter: prevalence and trends in Japan.

Campylobacter is one of the most frequently diagnosed bacterial causes of human gastroenteritis in Japan and throughout the world. Resistance to quinolones in Campylobacter jejuni and C. coli isolated from humans has emerged in many countries during the past 15 years because fluoroquinolones are the drug of choice for the treatment of suspected bacterial gastroenteritis. Food contaminated with Campylobacter is the usual source of human infection; therefore, the presence of antimicrobial resistance strains in the food chain has raised concerns that the treatment of human infections will be compromised. The use of antimicrobial agents for food animals and in veterinary medicine is suspected to be correlated with an increase in quinolone-resistant strains of Campylobacter in food animals, especially in poultry products. In contrast to macrolide resistance in C. jejuni and C. coli isolated from humans showing a stable low rate, resistant Campylobacter spp. to quinolones have emerged in Japan. The paper summarizes food-borne Campylobacter infection in Japan, and the prevalence and trends of antimicrobial resistance of Campylobacter from the authors' data and other Japanese papers which reported the antimicrobial resistance of Campylobacter.

The lipopolysaccharide of recipient cells is a specific receptor for PilV proteins, selected by shufflon DNA rearrangement, in liquid matings with donors bearing the R64 plasmid.

Shufflon DNA rearrangement selects one of seven PilV proteins with different C-terminal segments, which then becomes a minor component of the thin pili of Escherichia coli strains bearing the plasmid R64. The PilV proteins determine the recipient specificity in liquid matings. A recipient Escherichia coli K-12 strain was specifically recognized by the PilVA', -C, and -C' proteins, while E. coli B was recognized only by the PilVA' protein. To identify specific PilV receptors in the recipient bacterial cells, R64 liquid matings were performed using various E. coli K-12 waa (rfa) mutants and E. coli B transformants as recipient cells. E. coli K-12 waa mutants lack receptors for specific PilV proteins. E. coli B cells carrying waaJ or waaJKL genes of E. coli K-12 were recognized by donors expressing the PilVC' protein or the PilVC and -C' proteins, respectively, in addition to the PilVA' protein. Addition of E. coli K-12 or B lipopolysaccharide (LPS) specifically inhibited liquid matings. We conclude that the PilV proteins of the thin pili of R64-bearing donors recognize LPS molecules located on the surface of various recipient bacterial cells in liquid matings.