Variability in LPS composition, antigenicity and reactogenicity of phase variants of Bordetella pertussis

Comparison of lipopolysaccharides (LPS) from phase variants of different strains of Bordetella phase variants of different strains of Bordetella pertussis has shown a difference in their composition, antigenicity and reactogenicity. Phase I variants of B. pertussis, with the exception of strain 134, contain a preponderance of LPS I whereas the major component of LPS of phase IV variants is LPS II. Sera raised to LPSs of phase I strains, other than 134, cross-react with each other but not with phase IV LPSs; and similarly all sera raised to phase IV LPSs cross-react with each other and with LPS from 134 phase I. The LPSs of all phase I variants, including that of 134, are approximately ten-fold or more reactive in the limulus amoebocyte lysate assay (LAL) than phase IV LPSs. In the human mononuclear cell pyrogen assay phase IV LPSs also stimulated a lower response than phase I LPSs. The B. pertussis phase I LPSs are 10-times more reactive than Escherichia coli standard endotoxin in the LAL assay but 100-times less reactive than E. coli LPS in the monocyte test for pyrogen. The SDS-PAGE profiles of B. pertussis LPSs are quite different from those of B. parapertussis and B. bronchiseptica strains. B. pertussis LPSs produced a typical lipo-oligosaccharide (LOS) pattern. B. bronchiseptica LPS produced a similar pattern but was antigenically distinct from B. pertussis LPSs I and II. B. parapertussis in contrast produced a ladder pattern typical of smooth type LPS.     

Differentiation of Coxiella burnetii by Sequence Analysis of the Gene (com1) Encoding a 27-kDa Outer Membrane Protein

The gene (com1) encoding a 27-kDa outer membrane protein in 21 strains of Coxiella burnetii from a variety of clinical and geographical sources was sequenced for strain differentiation. The com1 gene was highly conserved among all the strains tested but there were several differences in nucleotide and deduced amino acid sequences. Based on the com1 gene-specific nucleotides and deduced amino acids, the 21 strains were divided into four groups. Group 1 contained 14 strains originating from ticks, cattle and human cases of acute Q fever. Groups 2 and 3 included 2 and 3 strains, respectively, originating from human cases of chronic Q fever. Group 4 contained 2 strains originating from a human case of acute Q fever and a goat with abortion. The results indicated that the strains originating from ticks, cattle and human cases of acute Q fever differed at the molecular level from those of human chronic Q fever. This study suggests that a sequence analysis of the com1 gene can be used for strain differentiation of C. burnetii.     

Characterization of Escherichia coli O157:H7 from Downer and Healthy Dairy Cattle in the Upper Midwest Region of the United States

While cattle in general have been identified as a reservoir of Escherichia coli O157:H7, there are limited data regarding the prevalence and clonality of this pathogen in downer dairy cattle and the potential impact to human health that may occur following consumption of meat derived from downer dairy cattle. In the present study, conducted at two slaughter facilities in Wisconsin between May and October of 2001, we established a higher prevalence of E. coli O157:H7 in fecal and/or tissue samples obtained aseptically from intact colons of downer dairy cattle (10 of 203, 4.9%) than in those from healthy dairy cattle (3 of 201, 1.5%). Analyses of 57 isolates, representing these 13 positive samples (one to five isolates per sample), by pulsed-field gel electrophoresis, revealed 13 distinct XbaI restriction endonuclease digestion profiles (REDP). Typically, isolates from different animals displayed distinct REDP and isolates from the same fecal or colon sample displayed indistinguishable REDP. However, in one sample, two different, but highly related, REDP were displayed by the isolates recovered. Antimicrobial susceptibility testing indicated that 10 of the 57 isolates, recovered from 2 (1 downer and 1 healthy animal) of the 13 positive samples, were resistant to at least 1 of 18 antimicrobials tested. However, there was no appreciable difference in the frequency of resistance of isolates recovered from downer and healthy dairy cattle, and not all isolates with the same REDP displayed the same antimicrobial susceptibility profile. Lastly, it was not possible to distinguish between isolates recovered from downer and healthy cattle based on their XbaI REDP or antimicrobial susceptibility. These results indicate that downer cattle had a 3.3-fold-higher prevalence of E. coli O157:H7 than healthy cattle within the time frame and geographic scope of this study.     

Virulence markers and serotypes of Shiga toxin-producing Escherichia coli, isolated from cattle in Rio Grande do Sul, Brazil

AIMS: To determine the prevalence of Shiga toxin-producing Escherichia coli (STEC) and serotypes and virulence markers of the STEC isolates from beef and dairy cattle in Rio Grande do Sul, Brazil. METHODS AND RESULTS: Faecal samples from beef cattle were collected at slaughterhouses. The isolates were submitted to colony hybridization assay with specific DNA probes for stx1, stx2 and eae genes, and serotyped for the identification of O and H antigens. Thirty-nine per cent of beef cattle surveyed harboured at least one STEC strain. Among the distinct serotypes identified, 10 were shared by both beef and dairy cattle. Most of the strains isolated harboured stx2. Genotypic and phenotypic profiles allowed the identification of 34 and 31 STEC strains, isolated from beef and dairy cattle, respectively. Serotypes O10:H14, O15:H21, O96:H21, O119:H4, O124:H11, O128:H21, O137:H-, O141:H19, O159:H42, O160:H2 and O177:H11, identified in this study, have not been previously reported as STEC isolated from cattle. CONCLUSIONS: Cattle are an important reservoir of STEC strains associated with human diseases in South America. SIGNIFICANCE AND IMPACT OF THE STUDY: Determining the prevalence, genotypic profile and serotypes of STEC strains isolated from cattle enables the prediction of possible risk for public health.     

A Comparative Study of the Sugar Composition of O-antigenic Lipopolysaccharides Isolated from Vibrio alginolyticus and Vibrio parahaemolyticus

A comparative study of the sugar composition of O-antigenic lipopolysaccharides (LPS) isolated from Vibrio alginolyticus and those from V. parahaemolyticus was carried out. 3-Deoxy-d-mannooctulosonic acid, 2-keto-3-deoxy octonate (KDO), a regular sugar constituent of gram-negative bacterial LPS, was totally absent from LPS of all V. alginolyticus strains examined as it was from those of V. parahaemolyticus. Furthermore, a KDO-like thiobarbituric acid test-positive substance, identical with that of either V. parahaemolyticus 07 or 012, was also found in LPS from three strains, 505–78, 905–78, and 1013–79 (designated tentatively as group I), out of the five strains of V. alginolyticus tested. LPS from the members of group I contained, as component sugars, glucose, galactose, l-glycero-d-manno-heptose, glucosamine, galactosamine, the KDO-like substance, and an unidentified amino sugar P1. Thus, LPS of the members of group I possessed a similar sugar composition which is similar to that of LPS from either V. parahaemolyticus 07 or 012. LPS of strain 1027–79, one of the other two strains (designated tentatively as gorup II), contained as component sugars, glucose, l-glycero-d-mannoheptose, glucosamine, galactosamine, and the other unidentified amino sugar P2, while LPS of strain 53–79, the other member of group II, contained galactose as an additional component. The results indicate that LPS of strain 1027–79 has a sugar composition similar to that of V. parahaemolyticus 09 LPS.     

Characterization of Aeromonas hydrophila Strains of Clinical,Animal, and Environmental Origin Expressing the O:34 Antigen

A collection of Aeromonas strains of different origins were characterized for isolates expressing the O:34 somatic antigen. Of over 200 strains tested, approximately 14% belonged to serogroup O:34 with >85% of these strains identified as A. hydrophila regardless of source. A subset of 14 A. hydrophila O:34 strains were further analyzed for a number of structural and pathogenic features. Most O:34 strains expressed similar whole-cell protein profiles with regards to minor bands, but major band differences were noted in outer membrane proteins (OMPs) migrating between the 31K and 58K region. OMP profiles could be subdivided into three distinct patterns. All O:34 strains expressed a heterogeneous O polysaccharide side chain profile in their lipopolysaccharide (LPS), although some variation in the electrophoretic migration of lower and higher molecular weight LPS bands was noted. Polyclonal antisera raised against a 45-K OMP-associated protein of one O:34 strain (AH-195) reacted in immunoblot assays with a major 43 to 46-K OMP in 11 of 14 (79%) O:34 strains tested. Most O:34 strains (69%) were found to be pathogenic in mice with LD-50 values (i.p.) of <1.0 × 10⁷ CFU; pathogenicity appeared to correlate best with elevated protease activity. The collective results suggest significant differences in both structural and pathogenic properties between some members of the O:34 group originating from human and nonhuman (fish, water) sources. Received: 14 December 1995 / Accepted: 22 January 1996     

Antimicrobial resistance and toxin gene profiles of Staphylococcus aureus strains from Holstein milk

Isolation of Staphylococcus aureus (Staph. aureus) from Holstein milk samples with mastitis and nonmastitis was conducted to estimate its prevalence, antimicrobial resistance and toxin genes. A total of 353 milk samples were collected from three Chinese Holstein herds. Fifty‐three Staph. aureus isolates collected from 29 Staph. aureus‐positive samples were characterized via antimicrobial susceptibility, toxin genes and Pulsed‐field Gel Electrophoresis (PFGE) profiles. The prevalence of Staph. aureus was 4·0–9·5% in mastitic and 7·3–11·5% in nonmastitic samples in the analysed herds. Approximately 61·0% of Staph. aureus strains isolated from mastitis cows were resistant to ≥10 antimicrobials compared with 0% of isolates with nonmastitis. The most frequently observed super antigenic toxin gene was pvl (41·5%) followed by seh + pvl (13·2%). We did not find mecA‐positive methicillin‐resistant Staph. aureus (MRSA) strains, while mecA‐negative MRSA strains were identified in the three herds. PFGE results suggested potential transmission of Staph. aureus strains in different farms. These results open new insights into Staph. aureus transmission and antimicrobial resistance of Holstein dairy cows and into developing strategies for udder health improvement of dairy cattle.     

Lipopolysaccharide changes in smooth-type avirulent Shigella in comparison with initial virulent strains]

The comparative study of the lipopolysaccharides (LPS) of virulent and avirulent strains of S. sonnei, phase I (smooth colonies), has been made. Electrophoresis of LPS and subsequent densitometry of electrophoregrams have revealed the increase of the fraction of long 0-chains with a considerable number of recurring elements in 2 out of 3 LPS preparations obtained from avirulent shigellae. In mice immunized with these LPS preparations a considerably greater number of antibody-producing cells can be detected in Jerne's test on sheep red blood cells (SRBC) sensitized with the LPS of a virulent strain than on those sensitized with the above LPS preparations. Long 0-specific chains supposedly inhibit the fixation of individual complement components on the corresponding sensitized SRBC. The LPS of the third avirulent strain of S. sonnei, phase I, with transposon integrated into its genome, which has led to the formation of the avirulent variant of a previously virulent strain, seems to contain fine structural differences from the initial virulent strain. The immunogenicity of the LPS of this avirulent strain is greatly (3-4 times) decreased, which is manifested by the number of antibody-producing cells detected in Jerne's test on SRBC sensitized with LPS preparations obtained from these two strains.     

Grouping by plasmid profiles of atypical Aeromonas salmonicida isolated from fish, with special reference to salmonid fish

Plasmid profile analyses were performed for 113 strains of atypical Aeromonas salmonicida and the reference strain A. salmonicida subsp. salmonicida ATCC 14174. The atypical A. salmonicida strains comprised 98 strains obtained from fish originating from 54 farms and 2 lakes in Norway, 10 strains from Canada (2), Denmark (2), Finland (1), Iceland (1) and Sweden (4), the reference strains NCMB 1109 and ATCC 15711 (Haemophilus piscium) of A. salmonicida subsp. achromogenes, and the type cultures A. salmonicida subsp. achromogenes NCMB 1110, A. salmonicida subsp. masoucida ATCC 27013 and A. salmonicida subsp. smithia CCM 4103. A total of 95 strains of atypical A. salmonicida were separated into 7 groups (I to VII) based on the plasmid profiles. Eighteen strains of atypical A. salmonicida had no common plasmid profile. The type strain NCMB 1110 and the reference strain NCMB 1109 were included in group IV, and the type strain ATCC 27013 in group V, but the other reference and type strains had plasmid profiles different from all the other strains. An epidemiological link was documented between strains collected from different farms/localities in each of groups I, III, V and VII. Physiological and biochemical characterizations were performed for 93 of the strains to investigate phenotypic differences between the plasmid groups. Group VII strains and 3 strains with no common plasmid profile differed from the other groups in being catalase-negative. Differences in phenotypic characteristics were shown between the plasmid groups. However, significant variations in reactions for several phenotypic characteristics also occurred within each of the groups I to VII. The present study indicates that plasmid profiling may give useful epidemiological information during outbreaks of atypical A. salmonicida infections in fish. Additional comprehensive phenotypic characterisation is of limited value since the phenotypic characteristics in each plasmid group are not uniform.     

Chromosome sizes and phylogenetic relationships between serotypes of Actinobacillus pleuropneumoniae

The genome size of Actinobacillus pleuropneumoniae was determined by pulsed field gel electrophoresis of AscI and ApaI digested chromosomal DNA. The genome size of the type strain 4074^T (serotype 1) was determined to be 2404±40 kb. The chromosome sizes for the reference strains of the other serotypes range between 2.3 and 2.4 Mb. The restriction pattern profiles of AscI, ApaI and NheI digested chromosomes showed a high degree of polymorphism among the different serotype reference strains and allowed their discrimination. The analysis of the macrorestriction pattern polymorphism revealed phylogenetic relationships between the different serotype reference strains which reflect to some extent groups of serotypes known to cross-react serologically. In addition, different pulsed fields gel electrophoresis patterns also revealed heterogeneity in the chromosomal structure among different field strains of serotypes 1, 5a, and 5b, while strains of serotype 9 originating from most distant geographical places showed homogeneous ApaI patterns in pulsed field gel electrophoresis.     

Phage specificity and lipopolysaccarides of stem- and root-nodulating bacteria (Azorhizobium caulinodans, Sinorhizobium spp., and Rhizobium spp.) of Sesbania spp

Phage susceptibility pattern and its correlation with lipopolysaccharide (LPS) and plasmid profiles may help in understanding the phenotypic and genotypic diversity among highly promiscuous group of rhizobia nodulating Sesbania spp.; 43 phages were from two stem-nodulating bacteria of S. rostrata and 16 phages were from root-nodulating bacteria of S. sesban, S. aegyptica and S. rostrata. Phage susceptibility pattern of 38 Sesbania nodulating bacteria was correlated with their LPS rather than plasmid profiles. Different species of bacteria (A. caulinodans- ORS571, SRS1-3 and Sinorhizobium saheli- SRR907, SRR912) showing distinct LPS subtypes were susceptible to different group of phages. Phages could also discriminate the strains of Si. saheli (SSR312, SAR610) possessing distinct LPS subtypes. Phages of Si. meliloti (SSR302) were strain-specific. All the strains of R. huautlense having incomplete LPS (insignificant O-chain) were phage-resistant. In in vitro assay, 100% of the phages were adsorbed to LPS of indicator bacterium or its closely related strain(s) only. These observations suggest the significance of LPS in phage specificity of Sesbania nodulating rhizobia. Highly specific phages may serve as biological marker for monitoring the susceptible bacterial strains in culture collections and environment.     

Evaluation of methods for recognising strains of the Bacillus cereus group with food poisoning potential among industrial and environmental contaminants

Toxin production, biochemical properties and ribotypes of Bacillus cereus group (B. cereus, B. thuringiensis, B. mycoides) strains originating from industrial and environmental sources (n = 64), from food poisoning incidents (n = 22) and from reference sources (n = 7) were analysed. Forty ribotypes were found among the 93 strains. Eleven strains from food poisoning incidents produced emetic (mitochondrio) toxin, as determined by the boar spermatozoa toxicity test. These strains possessed closely similar ribotypes which were rare among strains of other origins. Sperm toxin producing (cereulide positive) strains did not hydrolyse starch and did not produce haemolysin BL, as determined by the reverse passive latex agglutination test. Sixteen different ribotypes were found among B. cereus strains from board machines (n = 16) and from packaging board (n = 16), indicating many different sources of B. cereus contamination in board mills. Strains originating from packaging board had predominantly different ribotypes from those of dairy and dairy product originating strains. Nine (53%) out of 17 strains from a single dairy process shared the same ribotype whereas strains from milk and milk products from different dairies had different ribotypes indicating that B. cereus group populations were dairy specific. Twenty-two percent of strains isolated from the paperboard industry on non-selective medium were lecithinase negative, including enterotoxin producing strains. This stresses the importance of other detection methods not based on a positive lecithinase reaction.     

Characterization of Escherichia coli O157:H7 from downer and healthy dairy cattle in the upper Midwest region of the United States

While cattle in general have been identified as a reservoir of Escherichia coli O157:H7, there are limited data regarding the prevalence and clonality of this pathogen in downer dairy cattle and the potential impact to human health that may occur following consumption of meat derived from downer dairy cattle. In the present study, conducted at two slaughter facilities in Wisconsin between May and October of 2001, we established a higher prevalence of E. coli O157:H7 in fecal and/or tissue samples obtained aseptically from intact colons of downer dairy cattle (10 of 203, 4.9%) than in those from healthy dairy cattle (3 of 201, 1.5%). Analyses of 57 isolates, representing these 13 positive samples (one to five isolates per sample), by pulsed-field gel electrophoresis, revealed 13 distinct XbaI restriction endonuclease digestion profiles (REDP). Typically, isolates from different animals displayed distinct REDP and isolates from the same fecal or colon sample displayed indistinguishable REDP. However, in one sample, two different, but highly related, REDP were displayed by the isolates recovered. Antimicrobial susceptibility testing indicated that 10 of the 57 isolates, recovered from 2 (1 downer and 1 healthy animal) of the 13 positive samples, were resistant to at least 1 of 18 antimicrobials tested. However, there was no appreciable difference in the frequency of resistance of isolates recovered from downer and healthy dairy cattle, and not all isolates with the same REDP displayed the same antimicrobial susceptibility profile. Lastly, it was not possible to distinguish between isolates recovered from downer and healthy cattle based on their XbaI REDP or antimicrobial susceptibility. These results indicate that downer cattle had a 3.3-fold-higher prevalence of E. coli O157:H7 than healthy cattle within the time frame and geographic scope of this study.     

Effect of BMP15 and/or AMH during in vitro maturation of oocytes from involuntarily culled dairy cows

The high metabolic activity to which the dairy cattle are exposed to maintain milk production altered steroid metabolism that affects reproductive physiology and reduce oocyte competence. Our aims were (a) to characterize the competence of immature oocytes collected from dairy cattle based on the expression of genes in cumulus cells (CCs) and (b) to improve oocyte competence to support preimplantation embryo development by the supplementation of maturation medium with bone morphogenetic protein 15 (BMP15) and/or anti‐mullerian hormone (AMH). Oocyte donors were identified at the moment of ovary collection and grouped by involuntarily culled dairy cows (Holstein breed) or beef cattle. The embryo development speed to blastocyst of the cull dairy cattle versus beef cattle (control group) was lower. Besides, <10% of oocytes (with CC biopsies) derived from dairy cattle were able to develop to the blastocyst stage. In addition, a higher level of expression and a positive correlation were observed in the expression of most of the genes evaluated (LUM, KRT18, KRT8, CLIC3, BMPR1B, and SLC38A3) in the cumulus–oocyte complexes that produced blastocysts versus those which did not develop correctly (arrested development). Further, use of BMP15 in the maturation of oocytes from dairy cattle seems to increase competence, modulating the expression of OCT4, SOX2, CDX2, GATA6, and TP1 in resulting blastocysts.     

Heterogeneity in Expression of Lipopolysaccharide and Major Outer-Membrane Proteins by Strains of Escherichia coli O157 with Different H-Serotypyes

A total of 11 strains of Escherichia coli (E. coli) belonging to serogroup O157 were examined for the expression of long-chain lipopolysaccharide (LPS) and major outer-membrane proteins (OMPs) by means of SDS-PAGE. The strains belonged to either one of four different flagellar (H) types or did not express flagella. Four of the eleven strains carried genes encoding Shiga-like toxins (SLTs). All the strains exhibited one of four LPS profiles, designated A, B, C or D. Electron microscopic analysis with the freeze-substitution technique demonstrated the differences in the cell surface structures of strains with each LPS profile. Strains with LPS profile A, B or C had layers of thin fibers 10, 20 and 20 nm long, respectively, on the outer membrane but strains with LPS profile D had no such structure. An analysis of the OMPs showed that all the strains had one of four OMP profiles, designated I, II, III or IV. Both LPS and OMP profiles were dependent on H-serotypes, and the combination pattern of LPS and OMP profiles of the strains was unique for each H-serotype. These data support the existence of heterogeneous groups of O157 strains.     

Lipopolysaccharide heterogeneity in strains ofSerratia marcescens agglutinated by O14 antiserum

Lipopolysaccharides (LPS) from 71 strains ofSerratia marcescens that were agglutinated by O14 antiserum were examined by SDS-PAGE. Four major profiles were found, designated LPS1 to LPS4. These groups accounted for 51, 7, 5, and 3 strains respectively. Five strains were unclassified. Immunoblotting showed that O14 antibodies bound only to LPS1 and not to LPS2, 3, or 4. LPS1 also bound antibodies in O1, O4, O12, and O23 antisera. LPS2 reacted specifically with O8 antiserum, LPS3 with O6, and LPS4 with O2, O3, O6, O12, and O21 antisera. These reactions were not found in agglutination tests with boiled, whole-cell antigens. However, tests with autoclaved antigens (45 min at 121°C) corroborated the immunoblotting classifications; LPS1 strains belonged to serotype O14, LPS2 to serotype O8, LPS3 to serotype O6, and LPS4 to serotype O21. We conclude that there is a heat-stable antigen on many clinical strains ofS. marcescens that masks the expression of O-specific LPS antigens and which binds with nonspecific antibody in serum O14. We propose that O-antigens should be prepared from autoclaved cultures and that the H-reference strain O14H9 CDC 1783-57 (LPS2) should be reclassified as serotype O8.     

Characterization of Yersinia enterocolitica 4/O:3 isolates from tonsils of Bavarian slaughter pigs

Aims: Yersinia enterocolitica 4/O:3 isolates of slaughter pigs originating from different farms were characterized to study the distribution of different genotypes at farm. A correlation between the genotypes and the resistance patterns was also examined. Methods and Results: Hundred and eighty‐seven ail‐positive Y. enterocolitica 4/O:3 isolates recovered from pigs originating from 31 Bavarian farms in 2000, 2003 and 2004 were characterized. PFGE using NotI, ApaI and XhoI enzymes revealed 31 genotypes. The most common genotype was found in 13% of the pigs. From most farms (71%), only one genotype was found. Some genotypes were found during different years. Low resistance was noted to streptomycin (9%), sulphamethoxazole (9%), amoxicillin/clavulanic acid (5%) and tetracycline (1%) by agar disc diffusion method. Conclusions: Several genotypes were found. Some genotypes were widely distributed and persisted for years. Farm‐specific genotypes may exist. No clear relation between the genotypes and antimicrobial patterns was found. Significance and Impact of the Study: This study provides data on the genetic diversity of Bavarian pig strains and antimicrobial resistance. It may be of interest for other countries where Y. enterocolitica strains are genotyped to get more information about the strain distribution of this pathogen.     

Mechanisms of Action of Rabbit CAP18 on Monolayers and Liposomes Made from Endotoxins or Phospholipids

We have investigated the mechanism of action of the cationic antimicrobial protein (18 kDa) CAP18 on liposomes and monolayers made from phospholipids and enterobacterial lipopolysaccharides (LPS). CAP18 intercalates into lipid matrices composed of LPS from sensitive strains, weaker into those made of LPS from a resistant strain (Proteus mirabilis strain R45) or negatively charged phospholipids, but not into those composed of neutral phosphatidylcholine. From the combination of data obtained with fluorescence resonance energy transfer and Fourier-transform infrared spectroscopy and film balance measurements, it can be concluded that structural differences in the LPS determine the depth of intercalation of CAP18 into the respective lipid matrices. Thus, we identified the L-Arap4N linked to the first Kdo of the LPS of P. mirabilis strain R45 to be responsible for the CAP18 resistance of this strain. These data provide insight into CAP18-mediated effects on the integrity of the outer membrane of Gram-negative bacteria and led to an improved model for rabbit CAP18 membrane interaction. Received: 14 January 2000/Revised: 20 April 2000     

Comparative Characterization of the Lipopolysaccharides of Different Pseudomonas fluorescensBiovar I Strains

From the biomass of five Pseudomonas fluorescensbiovar I strains, including the P. fluorescenstype strain IMV 4125 (ATCC 13525), lipopolysaccharides (LPS) were isolated (by extraction with a phenol–water mixture followed by repeated ultracentrifugation), as well as individual structural components of the LPS macromolecule: lipid A, the core oligosaccharide, and O-specific polysaccharide (O-PS). 3-Hydroxydecanoic, 2-hydroxydodecanoic, 3-hydroxydodecanoic, dodecanoic, hexadecanoic, octadecanoic, hexadecenoic, and octadecenoic fatty acids were present in lipid A of the LPS of all the strains studied. Glucosamine, ethanolamine, and phosphoethanolamine were revealed in the lipid A hydrophilic part of all of the strains. Glucose, rhamnose, mannoze, glucosamine, galactosamine, KDO, a trace amount of heptoses, ethanolamine, phosphoethanolamine, alanine, and phosphorus were identified as the main core components. Interstrain differences in the core oligosaccharide composition were revealed. Structural analysis showed that the O-PS of the type strain, as distinct from that of other strains, is heterogeneous and contains two types of repetitive units, including (1) three L-rhamnose residues (L-Rha), one 3-acetamide-3,6-dideoxy-D-galactose residue (D-Fuc3NAc) as a branching substitute of the L-rhamnan chain and (2) three L-Rha residues and two branching D-Fuc3NAc residues. The type strain is also serologically distinct from other biovar I strains due to the LPS O-chain structure, which is similar to those of the strains of the species Pseudomonas syringae, including the type strain. The data of structural analysis agree well with the results of immunochemical studies of LPS.     

Seroprevalence of Neospora caninum infection in dairy cattle of Southern China

A seroepidemiological survey of Neospora caninum infection in dairy cattle was carried out in China's southern Guangdong Province between July 2009 and March 2010. A total of 370 serum samples of dairy cattle was collected from 5 farms and examined for antibodies to N. caninum by enzyme-linked immunosorbent assay. The overall seroprevalence of N. caninum in dairy cattle was 18.9% (70/370). The seroprevalence of N. caninum in aborting cows (22.7%) was higher than that in nonaborting cows (16.3%), but the difference was not statistically significant (P > 0.05). Five-yr-old dairy cattle had the highest seroprevalence (27.8%), followed by those that were 6-yr-old (20.4%). Dairy cattle with 4 pregnancies had the highest seroprevalence (29.2%). There was no apparent association of N. caninum seropositivity with age or number of pregnancies (P > 0.05). The results of the present survey indicated that the infection with N. caninum is prevalent in dairy cattle of all ages in southern China, which may be one of the causes of bovine abortion. This is the first report of seroprevalence of N. caninum in dairy cattle in southern China.