摘要:

Six murine monoclonal antibodies (MAbs) against staphylococcal enterotoxin A (SEA) and enterotoxin E (SEE) were prepared by fusion of myeloma cells with mouse spleen cells immunized with SEA and SEE. Of five MAbs to SEA tested, two MAbs were reactive with only SEA, whereas three were specific for both SEA and SEE. On the other hand, one MAb to SEE was found to be specific for only SEE. To study specificities of the combining sites of these MAbs, competitive binding assays with either SEA or SEE and horseradish peroxidase conjugated MAbs were performed using unconjugated MAbs as inhibitors. The results obtained in the assays suggest that different epitopes may be located on SEA and that some of them may be cross-reacting epitopes between SEA and SEE.Key words: enterotoxins, monoclonal antibodies,Staphylococcus aureus.

ISSN:0008-4166    

DOI:10.1139/m91-098

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

Eight murine monoclonal antibodies (MAbs) against staphylococcal enterotoxin D (SED) were obtained by fusion of myeloma cells with mouse spleen cells immunized with SED only or a combination of SED and either enterotoxin A (SEA) or enterotoxin E (SEE). When only SED was used as an immunogen, six MAbs were specific for SED only, whereas one MAb was reactive with both SED and SEE when both SEs were used as immunogens. One MAb reacted with SEA, SED, and SEE when both SEA and SED were used as immunogens. A MAb with the highest reactivity to SED was used to prepare an immunosorbent for purification of SED by immunoaffinity chromatography. Approximately 70% of the partially purified SED was recovered in the eluate. The purified SED was electrophoretically and antigenically pure. Immunoaffinity chromatography proved useful in the purification of SED in terms of ease of purification, percent enterotoxin, and enterotoxin purity.Key words: enterotoxin D, monoclonal antibodies,Staphylococcus aureus.

ISSN:0008-4166    

DOI:10.1139/m91-099

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

The convalescent sera from a patient recovered form whooping cough were used to identify the surface-exposed antibody-accessible outer membrane proteins (OMPs) ofBordetella pertussis. The results indicated that the 69 000 OMP, the 40 000 porin, agglutinogens 2 and 3, and a number of presently unknown OMPs were exposed on the surface. The importance of these surface-exposed antigens in the protection against whooping cough is discussed.Key words:Bordetella pertussis, whooping cough, immune response, surface antigens, outer membrane protein.

ISSN:0008-4166    

DOI:10.1139/m91-100

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

Experiments were designed to elucidate a possible physiological mechanism for stimulated growth ofListeria monocytogenesbyPseudomonas fluorescensin milk. The ability ofL.monocytogenesto grow in milk under aerobic and microaerophilic environments was compared. Neither environment favored the growth of the organism at 10 °C. Autoclaved whole milk was inoculated withP.fluorescensP26 and preincubated for 3 days at 10 °C followed by inoculation withL.monocytogenesScott A and further incubation for 8 days at 10 °C. Changes in selected milk components were monitored over the 8-day period. The amount of lactose in the milk was determined, as well as the extent of proteolysis and lipolysis. BothL.monocytogenesandP.fluorescenswere able to hydrolyze milk fat but were unable to use lactose. Milk protein was hydrolyzed byP.fluorescensbut not byL.monocytogenes. Whole milk partially proteolyzed by treatment with purified protease was inoculated withL.monocytogenes. Results indicated that the growth ofL.monocytogeneswas stimulated in proteolyzed milk. This is the first report to provide evidence describing a likely mechanism for commensalism betweenL.monocytogenesandPseudomonasspp.Key words:Listeria monocytogenes,Pseudomonas fluorescens, milk proteolysis.

ISSN:0008-4166    

DOI:10.1139/m91-101

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

One hundred and twenty-fiveRhizobium melilotiisolates nodulating field-grownMedicago sativacv. Europe were evaluated for plasmid content and for symbiotic effectiveness with this host. Relative to the strain used commercially in France (RCR2011), isolates showed a comparable level of symbiotic effectiveness, although two isolates were poorly effective. Twenty-four distinct plasmid profiles were observed among these isolates, with a plasmid number varying between one and five per isolate. All isolates but one harboured a plasmid equivalent in size to that of theR.meliloti41 megaplasmid. Sizes of the other plasmids varied from 45 to >600 kb. The major plasmid group (representing 30% of the whole population) consisted of isolates carrying a megaplasmid plus a large plasmid with an average size of 230 kb. To assess the validity of plasmid grouping, 32 isolates representative of 12 plasmid groups were further characterized on the basis of their genomic DNA restriction patterns and their insertion sequence (IS) fingerprints, using the indigenous insertion sequence ISRm1as a probe. The DNA restriction patterns and IS fingerprints were highly distinctive among the 32 isolates examined since 20 and 16 types, respectively, were observed. These two characteristics are strongly correlated with the plasmid profiles of the strains, confirming the validity of plasmid grouping in assessing diversity of natural populations ofR.meliloti. Plasmid profile analysis, although less discriminating than DNA restriction patterns or IS fingerprinting, is the method of choice when many isolates need to be typed.Key words:Rhizobium meliloti, ecology, diversity, field population, symbiotic effectiveness.

ISSN:0008-4166    

DOI:10.1139/m91-102

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

The heat resistance of nine strains ofStreptococcus faeciumisolated from frankfurters was determined at 63 and 68 °C in brain heart infusion broth. Exponential-phase cultures (approximately 107colonies/mL) were used as inoculants. The heat resistance ofS.faeciumDP2181, a moderately resistant isolate, was further examined in broth (55, 63, and 68 °C) and frankfurter emulsion (63 and 68 °C). The decimal reduction times (Dvalues) were determined by regression. In broth, both time–temperature combinations resulted in a 3–4 log decline in bacterial numbers for the nineS.faeciumstrains tested. ForS.faeciumDP2181, the survivor curves deviated from the logarithmic order of death at all three heating temperatures. An initial slow period of death was evident at 55 °C and a resistant tail of organisms was observed at 55, 63, and 68 °C. TheD55D63, and,D68values for the logarithmic portion of the corresponding survivor curves were 105.6, 9.36, and 3.34 min, respectively. The survival of DP2181 was enhanced by the frankfurter emulsion. The results indicate that populations ofS.faeciumexisted that were very heat resistant and could survive normal frankfurter processing if initially present in high numbers.Key words: heat resistance, enterococci,Dvalue, resistant tail.

ISSN:0008-4166    

DOI:10.1139/m91-103

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

Typing ofNeisseria meningitidisserogroup B disease isolates was carried out using a panel of serotype- and subtype-specific monoclonal antibodies (MAbs) in enzyme-linked immunosorbent assays (ELISA). Three hundred and sixty-two strains isolated from 1977 to 1986 were typed using five serotyping and seven subtyping reagents and outer membrane vesicles as antigens. Serotype 2b accounted for 30% of the disease isolates. The most common subtype was P1.2, which occurred on 18.5% of all strains or 48.6% of the serotype 2b strains. Of the 362 strains typed, 135 (37.3%) were serotyped and 122 (33.7%) were subtyped. Overall, 185 (51.1%) of the strains could be assigned a serotype and (or) subtype. Strains (221) isolated during the years 1987–1989 were typed using a panel of 6 serotyping and 12 subtyping reagents by whole-cellELISA. Strains of serotypes 4 (21.7%) and 15 (20.8%) were the most common and carried a wide variety of subtypes. The most common subtypes were P1.2 (11.8%) and P1.16 (9.5%). Of the 221 strains analyzed, 132 (59.7%) were assigned a serotype and 123 (55.7%) a subtype and with all 18 MAbs, 192 (86.9%) of the strains were serotyped and (or) subtyped. Two different MAbs to the four epitopes 2a, 15, P1.2, and P1.16 gave discordant reactions of 0.3, 6.6, 2.6, and 2.2%, respectively, when used to analyze over 300 strains ofN.meningitidis.Key words: meningococcal serotypes, subtypes.

ISSN:0008-4166    

DOI:10.1139/m91-104

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

Total bacterial counts and the number of the fish pathogenic bacteriumVibrio salmonicidahave been studied in water samples collected twice a month in 12 Norwegian fish farms from October 1988 to June 1989. Total counts were determined by staining with 4′,6-diamidino-2-phenylindole followed by epifluorescence microscopy. Cells ofV.salmonicidawere enumerated with a fluorescent antibody technique using highly specific monoclonal antibodies. Despite the fact that no outbreak of cold-water vibriosis was reported,V.salmonicidawas detected in all 12 farms, in numbers ranging from 12 to 43 bacteria/mL. The number of farms whereV.salmonicidawas detected was generally highest during the winter. Total bacterial counts in the water samples varied between 4 × 104and 9 × 105bacteria/mL and the lowest numbers occurred during the winter period. The total bacterial counts were comparable with counts in water uninfluenced by fish farming. On the basis of our results, and additional information available about cold-water vibriosis caused by the bacteriumV.salmonicida, an asymptomatic carrier state of the disease is proposed.Key words: cold-water vibriosis, asymptomatic carrier, fluorescent antibody, fish pathogen.

ISSN:0008-4166    

DOI:10.1139/m91-105

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

Deletion mutant analysis of the mercury-resistant determinant (meroperon) from theStaphylococcus aureusplasmid pI258 was used to verify the location of themerAandmerBgenes and to show the existence of mercuric ion transport gene(s). ORF5 was confirmed to be a transport gene and has an amino acid product sequence homologous to themerTgene products from several gram-negative bacteria and aBacillusspecies. Deletion analysis established that inactivation ofmerAon a broad-spectrummerresistance determinant resulted in a mercury-hypersensitive phenotype. Gene dosage had no apparent effect on the level of resistance conferred by the intactmeroperon or on the expression of an inducible phenotype, except that when the intact pI258meroperon was on a high copy number plasmid, uninduced cells possessed a volatilization rate that was at most only 3.5-fold less than that observed for induced cells. There was no need for mercury ion transport proteins for full resistance when themeroperon was expressed in a high copy number plasmid.Key words: mercury resistance,Staphylococcus aureusplasmid.

ISSN:0008-4166    

DOI:10.1139/m91-106

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

A series of greenhouse and field experiments were conducted to evaluate aqueous in-furrow spray techniques for inoculating crop plants with cell suspensions of rhizosphere-competent root-colonizing bacteria. Maximum root colonization of soybean or canola roots by strains ofSerratia,Pseudomonas, andBradyrhizobiumoccurred using log 8 colony-forming units (cfu)/mL in the spray in greenhouse conditions. Field experiments evaluating a dose reponse demonstrated that maximum soybean root colonization by strains ofSerratiaorPseudomonaswas achieved between log 7 and 8 cfu/mL, while root colonization by aBacillusstrain was not related to cell concentration in the spray suspension. Root colonization greater than log 4.5 cfu/g root fresh weight was achieved for most strains by in-furrow spray application of a suspension of log 8 cfu/mL at a rate of 10 mL/m for canola, soybean, and wheat, while root colonization of corn ranged from a maximum of log 3.4 to no recovery. In-furrow spray may be a useful method for inoculating plants with rhizosphere-competent bacteria for experimental purposes, thereby avoiding interactions of formulation. It may also have some value for commercial delivery of bacteria to agricultural crops when it is compatible with accepted agronomic practices.Key words: rhizosphere, plant growth promoting rhizobacteria, formulation,Pseudomonas, root colonization.

ISSN:0008-4166    

DOI:10.1139/m91-107

出版商:NRC Research Press    

年代:1991

数据来源: NRC