The use of natural compounds as inhibitory agents for virulence factor production is a new approach to overcome increased antimicrobial resistance in

Cholix toxin (ChxA) is a recently discovered exotoxin inVibrio choleraewhich has been characterized as a third member of the eukaryotic elongation factor 2-specific ADP-ribosyltransferase toxins, in addition to exotoxin A ofPseudomonas aeruginosaand diphtheria toxin ofCorynebacterium diphtheriae. These toxins consist of three characteristic domains for receptor binding, translocation, and catalysis. However, there is little information about the prevalence ofchxAand its genetic variations and pathogenic mechanisms. In this study, we screened thechxAgene in a large number (n= 765) ofV. choleraestrains and observed its presence exclusively in non-O1/non-O139 strains (27.0%; 53 of 196) and not in O1 (n= 485) or O139 (n= 84). Sequencing of these 53chxAgenes generated 29 subtypes which were grouped into three clusters designatedchxAI,chxAII, andchxAIII.chxAI belongs to the prototype, whilechxAII andchxAIII are newly discovered variants. ChxA II and ChxA III had unique receptor binding and catalytic domains, respectively, in comparison to ChxA I. Recombinant ChxA I (rChxA I) and rChxA II but not rChxA III showed variable cytotoxic effects on different eukaryotic cells. Although rChxA II was more lethal to mice than rChxA I when injected intravenously, no enterotoxicity of any rChxA was observed in a rabbit ileal loop test. Hepatocytes showed coagulation necrosis in rChxA I- or rChxA II-treated mice, seemingly the major target for ChxA. The present study illustrates the potential of ChxA as an important virulence factor in non-O1/non-O139V. cholerae, which may be associated with extraintestinal infections rather than enterotoxicity.

Effect of different cryoprotectants on acid/bile tolerance, β-galactosidase activity, and cholesterol assimilation properties of freeze dried Pediococcus acidilactici, Lactobacillus plantarum, and Lactobacillus salivarius were evaluated. The retention of probiotic properties and viability of the above three cultures freeze dried with lactose, skimmed milk, and maltodextrin were found to be significant (P ≤ 0.05). In another approach, lactic acid bacteria (LAB) were subjected to cold shock first and then freeze dried. Effect of cold shock treatment on retention of probiotic properties of freeze dried LAB cultures was also investigated. The cold shock treatment resulted in an increase of 6–8%, both in viability and probiotic properties, compared with LAB freeze dried without cold shock treatment. The survival of freeze dried L. plantarum, L. salivarius, and P. acidilactici was investigated over a period of 60 d storage at 4°C. The above three cultures freeze dried with maltodextrin exhibited 83%, 68%, and 60% retention in survival percentage, respectively, in comparison with initial values.

To investigate the virulence of the Vp_PirAB-like genes in Vibrio parahaemolyticus-AHPND causing strain and factors that associate with the virulence level. The virulence of Vp_PirAB-like were examined using a non-virulent strain FP11 of V. parahaemolyticus transformed with a plasmid harboring Vp_PirAB-like genes and then used it to challenge shrimp Litopenaeus vannamei and Marsupenaeus japonicus. Both species experienced 100% mortality 10 days post-infection. Analysis of a mutant strain (E1M), that was originally identified as virulent strain (E1) but lost its virulence to L. vannamei, revealed that it lacked a part of the Vp_PirA-like gene and all of Vp_PirB-like gene. The copy numbers of Vp_PirA-like and Vp_PirB-like genes varied among virulent strains and were not correlated with their virulence. In Western blotting, Vp_PirA-like and Vp_PirB-like proteins were detected in both cell lysate and culture supernatant. The strongest intensity of detecting band in culture supernatant could be observed in the strain that caused the highest mortality. V. parahaemolyticus AHPND-causing strain, unlike the human tdh-positive strain, did not show any enterotoxicity. V. parahaemolyticus AHPND-causing strains secret the Vp_PirA-like and Vp_PirB-like proteins during growing phase. The amount of secreted proteins affects the shrimp mortality. The secreted proteins of Vp_PirAB-like are key factors of virulence in V. parahaemolyticus AHPND-causing strain, but not gene copy.

The purpose of this study was to investigate the prevalence of extended-spectrum β-lactamase (ESBL)-producing Escherichia coli (ESBL-Ec) in retail chicken meats in Japan. Fifty-six domestic and 50 imported (Brazil, n=36; United States, n=8; Thailand, n=6) chicken meat samples were analyzed. The 162 ESBL-Ec included 111 from 43 (77%) domestic samples and 51 from 26 (52%) Brazilian samples. Fifty-three and 30 of 111 and 51 ESBL-Ec from domestic and Brazilian chickens, respectively, were selected for ESBL genotyping. The blaCTX-M (91%), blaTEM (36%) and blaSHV (15%) genes were detected in ESBL-Ec isolated from domestic chickens, whereas blaCTX-M (100%) and blaTEM (20%) were detected in ESBL-Ec isolated from imported chickens. Among the blaCTX-M group, blaCTX-M-2 (45%) and blaCTX-M-1 (34%) were prevalent in domestic chicken isolates, whereas blaCTX-M-2 (53%) and blaCTX-M-8 (43%) were prevalent in imported chicken isolates. Domestic chicken isolates were mostly resistant to tetracycline (83%), followed by streptomycin (70%) and nalidixic acid (62%). Imported chicken isolates were resistant to streptomycin (77%), followed by nalidixic acid (63%) and tetracycline (57%). Notably, extensive multidrug resistance was detected in 60% (32/53) and 70% (21/30) ESBL-Ec from domestic and imported chickens, respectively. Virulence genes associated with diarrheagenic and extra-intestinal pathogenic E. coli were detected in ESBL-Ec isolated from domestic and imported chickens. These data suggest that ESBL-Ec in retail chicken meats could be a potential reservoir for antimicrobial resistance determinants and that some are potentially harmful to humans.