Two chicken houses and an attached egg-processing facility in a laying farm were sampled between 1994 and 1998 to investigate Salmonella contamination. Each of the houses was environmentally controlled and fitted with egg belts that transported eggs from the houses to the egg-processing facility. Four hundred twenty-eight Salmonella isolates were obtained from 904 environmental samples collected from the houses. Two hundred fifty-two of the 428 (58.9%) isolates yielded five serotypes as follows: Salmonella enterica subsp. enterica serovar Livingstone, Salmonella serovar Cerro, Salmonella serovar Montevideo, Salmonella serovar Mbandaka, and Salmonella serovar Corvallis. The remaining (41.1%, 176 of 428) isolates included four other serotypes and isolates that were untypeable. Salmonella isolates obtained from the drain water collected after the washing of the eggs in the egg-processing facility yielded the same serotypes as those found in the chicken houses. Strains having an identical pulsed-field gel electrophoresis (PFGE) pattern were continually recovered from a house for more than 1 year. Several strains of Salmonella Cerro, Salmonella Mbandaka, and Salmonella Montevideo obtained from both the houses and from the egg-processing facility were indistinguishable by PFGE, respectively. These results suggest that Salmonella organisms originating from a single clone colonized the chicken houses and that the egg belts are likely to be one of the means by which Salmonella organisms are spread from one house to the others.
SUMMARY: Subtypes of stx1 and stx2 in 45 Shiga toxin-producing Escherichia coli (STEC) strains isolated from cattle were investigated by PCR. Only subtype stx1a was detected among all the stx1-positive strains. The major stx2 subtype was stx2a followed by stx2d, stx2c, stx2b, and stx2g in decreasing order of frequency. stx2c was found in strains of serotypes O157 and O174. stx2d was found in 11 strains. These strains were confirmed by DNA sequencing to carry both the activatable tail and the END motif; all were eae-negative, and 3 contained stx2d as the only stx. stx2g was found in 2 strains in association with stx2a, estA1, and astA. In addition, 7 hybrid strains of shigatoxigenic and enterotoxigenic E. coli (STEC/ETEC) were found to harbor one or both of stx1a and stx2a (stx1a/stx2a ) and estA1. Among 27 serotypes of STEC strains isolated from cattle, O157:H7 and O109:H-strains were eae-positive. Other putative adhesin genes, such as saa, iha, espP, and lpfA O113 were detected in more than 12 serotypes.
Pathogenic genes such as stx1, stx2, STh gene, STp gene, LT gene, invE, eae, aggR, afaD, astA, cdt and cnf were investigated in Escherichia coli isolated from cattle during Nov. 2012 and Aug. 2013. Plural pathogenic genes were concurrently detected by multiplex PCR, and screen-positive genes were confirmed and sub-classified by PCR. Among 100 cattle investigated, 180 E. coli strains with diarrheic genes (DEC) were detected in 79 cattle, and 45 of them, isolated from 32 cattle, were Shiga toxin-producing E. coli (STEC). More than 30 of cattle carried astA, cdt, cnf and stx2 in descending order. STh gene, LT gene, invE, aggR and afaD were not detected in this study. Both stx1 and stx2 were concurrently detected from 6 of 45 STEC strains and stx2 alone was detected from 19. Seventeen STEC strains carried STp gene, astA, or cdt along with stx1 or stx2. Additionally, 135 remaining DEC were classified into 18 enterotoxigenic E. coli with STp gene, 25 enteropathogenic E. coli with eae, and 92 other DEC with astA, cdt and cnf. Both O and H serotypes were identified in 48 strains, including O157 : H7, O1H7 and so on. O157 : H7 were identified in 3 strains that carried stx2 and eae together, as found in human pathogenic strains isolated from patients with gastroenteritis and hemolytic-uremic syndrome.
A small plaque mutant with reduced neurovirulence in newborn mice was obtained from Edmonston strain measles virus after propagation for 5 months in NIH3T3 cells. It retained the antigenicity of the parental virus and tended to induce higher neutralizing antibody titers in the adult BALB/c mice. The intracerebral (but not intraperitoneal) inoculation of the live mutant virus one day before prevented the newborn BALB/c mice from encephalitis caused by the intracerebral challenge with the parental strain at a dose of 10-20 LD50. The intracerebral inoculation with the mutant virus whose replication capacity was inactivated by UV-irradiation was ineffective. The protection was not attributed to interferons nor to viral interference. The mechanism remains unknown.
An L cell clone developing cytopathic plaques upon infection with measles virus (Edmonston strain) was obtained. The sensitivity as measured by the newly devised UV-Vero assay was not significantly different between plaque-forming and non-plaque-forming L cell clones. Cytopathogenicity and sensitivity to the virus infection appear to be under different host cell regulations.
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