Monoclonal antibodies specific for Campylobacter fetus lipopolysaccharides

A comparison of fourteen fully characterized mammalian-associated Campylobacter fetus isolates suggests that loss of defense mechanisms contribute to high genomic plasticity and subspecies evolution

Campylobacter fetus is currently classified into three main subspecies, but only two of these, C. fetus subspecies fetus and C. fetus subsp. venerealis originate principally from ruminants where they inhabit different niches and cause distinct pathogenicity. Their importance as pathogens in international trade and reporting is also different yet the criteria defining these properties have never been fully substantiated nor understood. The situation is further compromised because the ability to differentiate between these two closely related C. fetus subspecies has traditionally been performed by phenotypic characterisation of isolates, methods which are limited in scope, time-consuming, tedious, and often yield inconsistent results, thereby leading to isolate misidentification. The development of robust genetic markers that could enable rapid discrimination between C. fetus subsp. fetus and subsp. venerealis has also been challenging due to limited differences in the gene complement of their genomes, high levels of sequence repetition, the small number of closed genome sequences available and the lack of standardisation of the discriminatory biochemical tests employed for comparative purposes. To yield a better understanding of the genomic differences that define these C. fetus strains, seven isolates were exhaustively characterised phenotypically and genetically and compared with seven previously well characterised isolates. Analysis of these 14 C. fetus samples clearly illustrated that adaption by C. fetus subsp. venerealis to the bovine reproductive tract correlated with increasing genome length and plasticity due to the acquisition and propagation of several mobile elements including prophages, transposons and plasmids harbouring virulence factors. Significant differences in the repertoire of the CRISPR (clustered regularly interspersed short palindromic repeats)-cas system of all C. fetus strains was also found. We therefore suggest that a deficiency in this adaptive immune system may have permitted the emergence of extensive genome plasticity and led to changes in host tropism through gene disruption and/or changes in gene expression. Notable differences in the sub-species complement of DNA adenine methylase genes may also have an impact. These data will facilitate future studies to better understand the precise genetic differences that underlie the phenotypic and virulence differences between these animal pathogens and may identify additional markers useful for diagnosis and sub-typing.

Genotyping and antibiotic resistance patterns of Campylobacter fetus subsp.venerealis from cattle farms in India

Bovine genital campylobacteriosis caused by Campylobacter fetus subsp. venerealis (Cfv) is of considerable economic importance to the cattle industry worldwide. Cfv causes syndrome of temporary infertility in female cattle, early embryonic mortality, aberrant oestrus cycles, delayed conception, abortions and poor calving rates. In the present study, a total of 200 samples obtained from vaginal swabs, cervicovaginal mucous (CVM), preputial washes and semen straws were investigated that were obtained from organized cattle farm of MLRI, Manasbal and unorganized sectors. Out of a total of 200 samples, 49 (47·57%) vaginal swabs, 1 (3·33%) preputial wash and 8 (25%) carried out CVM samples were positive for Cfv, whereas none of the semen straws were positive for Cfv. A total of eleven isolates of Cfv were recovered. PFGE (Pulse field gel electrophoresis) analysis revealed four different pulsotypes (I-IV) circulating in the screened farms. A common pulsotype circulating among farms could not be established. Insertion element (ISCfe1), a 233 bp amplicon of Cfv, was sequenced and the sequence was deposited in GenBank (accession no: MK475662).

Effects of Campylobacter fetus on bull sperm quality

Campylobacter fetus is a gram-negative, motile, spiral or S-shaped bacterium, which induces campylobacteriosis. This disease causes decrease productivity of cattle. Although considerable research has been done on the role of C. fetus on female fertility, little is known about the effect on bulls. The aim of this work was to evaluate the effect of C. fetus subsp. fetus (Cff) and C. fetus subsp. venerealis (Cfv) on bull sperm quality. Samples of frozen semen (n = 29 straws) were each distributed into three groups: two of them incubated with the microorganism (Cff, Cfv) and a control group. The proportions of live spermatozoa, with functional membrane and true acrosomal reaction in control group were significantly (P < 0.01) greater than those observed in Cff and Cfv groups. However, no significant differences (P > 0.05) were found in sperm chromatin structure among treatments. In adhesion assay, proportions of spermatozoa with adhered Campylobacter were similar for both subspecies. Results confirm that Cff and Cfv have the same ability to bind in an irreversible way to bull spermatozoa and to affect sperm quality. It is proposed that adherence could be considered as the main cause of sperm alterations, and also an important step of pathogenesis and venereal transmission.

New molecular microbiology approaches in the study of Campylobacter fetus

Campylobacter fetus infection is a substantial problem in herds of domestic cattle worldwide and a rising threat in human disease. Application of comparative and functional genomics approaches will be essential to understand the molecular basis of this pathogen's interactions with various hosts. Here we report recent progress in genome analyses of C. fetus ssp. fetus and C. fetus ssp. venerealis, and the development of molecular tools to determine the genetic basis of niche‐specific adaptations. Campylobacter research has been strengthened by the rapid advancements in imaging technology occurring throughout microbiology. To move forward in understanding the mechanisms underlying C. fetus virulence, current efforts focus on developing suitable in vitro models to reflect host‐ and tissue‐specific aspects of infection.

Influence of Campylobacter fetus subsp. fetus on ram sperm cell quality

Campylobacter fetus subsp. fetus infection can occur in female sheep, causing infertility or abortion. Despite extensive research on the effect of these bacteria on female fertility, little research has been done on the influence of C. fetus subsp. fetus on the male factor. Our objective was to examine the influence of C. fetus subsp. fetus on ram sperm. Motility index, percentage of live spermatozoa, mean αt value (an indication of the chromatin stability of the sperm cell) and percentage of sperm cells expressing the FAS receptor were measured in sperm incubated in the presence or absence of C. fetus subsp. fetus. The motility index and viability of sperm incubated with the bacteria were lower than those of untreated sperm samples after 5 h. In bacteria-incubated sperm cells, the percentage expressing FAS receptor was already significantly elevated at 15 min. Bacteria-incubated sperm showed a greater prevalence of morphological damage. The bacteria were attached to tail and acrosome regions, and the sperm damage was concentrated in both the motility and chromatin regions. Bacteria-infected sperm cells showed a decrease in motility, increase in early acrosome reaction and chromatin damage. Similar effects were induced by incubation of the sperm with supernatants from C. fetus subsp. fetus cultures. Thus this study demonstrates that C. fetus subsp. fetus has a detrimental effect on the quality of ram sperm.

Structural characterization and serological specificities of lipopolysaccharides from Salmonella enterica serovar Gallinarum biovar Pullorum standard, intermediate and variant antigenic type strains

The structure and serological specificities of the lipopolysaccharides (LPSs) from Salmonella enterica serovar Gallinarum biovar Pullorum were studied to provide an improved basis for the distinction between antigenic types and the development of improved diagnostic tests. The structure of the LPS O-polysaccharide (O-PS) from S. Pullorum standard, intermediate and variant antigenic type strains was determined by mass spectrometry, nuclear magnetic resonance spectroscopy and chemical analysis. The LPS of the three strains shared a common structural repeating oligosaccharide unit containing d-mannose, l-rhamnose, d-galactose and d-tyvelose (1:1:1:1). The O-PS of the variant type LPS contained an additional d-glucose residue linked to the O-4 position of the d-galactose residue. The O-PS of the intermediate type LPS was partially the same as that of the variant LPS, however, the molar ratio of the d-glucose component was lower with respect to the other glycose components. Serological specificities of the three antigenic type LPSs were examined with anti-S. Pullorum LPS monoclonal antibodies (Mabs). On immunoblots, Mabs to the standard type O-PS reacted with high molecular mass (HMM) and low molecular mass (LMM) LPS from the standard strain, and with LMM but not HMM LPS from the variant strain. Monoclonal antibodies to the variant type O-PS reacted with HMM but not LMM LPS from the variant strain, and did not react with HMM or LMM LPS from the standard strain. On ELISA, the standard, intermediate and variant antigenic type strains were differentiated by the relative reactivity with the anti-LPS O-PS Mabs. Several of the anti-LPS O-PS Mabs were specific for S. Pullorum and other serogroup D1 Salmonella, and are potentially useful for the development of improved diagnostic tests for these organisms.

Escherichia coliGenosensor Based on Polyaniline

Avidin-modified polyaniline (PANI) electrochemically deposited onto a Pt disk electrode has been utilized for direct detection of Escherichia coli by immobilizing a 5'-biotin-labeled E. coli probe (BdE) using a differential pulse voltammetric technique in the presence of methylene blue as a DNA hybridization indicator. Depending on the target sample and the sonication time, this BdE-avidin-PANI bioelectrode can be utilized to electrochemically detect a complementary target probe (0.009 ng/microL), E. coli genomic DNA (0.01 ng/microL) and 11 E. coli cells/mL in 60 s to 14 min (hybridization time) without using PCR and can be used 5-7 times at temperatures of 30-45 degrees C.

Validation of a monoclonal antibody-based capture enzyme-linked immunosorbent assay for detection of Campylobacter fetus

A monoclonal antibody (MAb)-based antigen capture enzyme-linked immunosorbent assay (ELISA) was compared with the routine culture methodology for the detection of Campylobacter fetus subspecies from bovine and ovine field samples inoculated into Clark's transport enrichment medium (TEM). The work was a collaboration between two different diagnostic laboratories, one in Canada and the other in England. In both labs, TEM samples were incubated for 4 days at 35 degrees C and then tested by culture and ELISA. The ELISA consisted of initial screening with MAb M1825 against C. fetus subspecies core lipopolysaccharide (LPS). All samples positive on ELISA screening were then retested by ELISA with MAb M1825 and MAbs M1177, M1183, and M1194, which recognize serotype A- and/or serotype B-specific C. fetus subspecies LPS epitopes. The Canadian samples consisted of 1,060 preputial washings from 529 bulls, of which 18 were positive by both culture and ELISA and 1,042 were negative by both methods. The English samples consisted of 321 tissue specimens, mostly stomach contents and placentas, from 190 aborted ovine and bovine fetuses. A total of 262 samples were negative by culture and ELISA, 52 samples were positive by culture and ELISA, and 7 samples were culture negative but ELISA positive. The results for all 70 culture-positive isolates were confirmed by conventional biochemical methods as C. fetus subsp. fetus, with 39 presumptively identified by the ELISA as serotype A and 30 presumptively identified as serotype B and with one sample containing isolates presumptively identified as serotype A and serotype B. A receiver operating characteristic analysis of the combined ELISA data from both countries resulted in an area under the curve of 0.997, with a sensitivity of 100% and a specificity of 99.5% relative to the results of culture. The data confirm that this ELISA method can be used as an excellent test for the screening of field samples in TEM for the presence of C. fetus subspecies.

Recent developments in bio-molecular electronics techniques for food pathogens

Food borne illnesses contribute to the majority of infections caused by pathogenic microorganisms. Detection of these pathogens originating from different sources has led to increased interest of researchers. New bio-molecular techniques for food pathogen detection are being developed to improve the sensor characteristics such as sensitivity, reusability, simplicity and economic viability. Present article deals with the various methods of food pathogen detection with special emphasis on bio-molecular electronics techniques such as biosensors, microarrays, electronic nose, and nano-materials based methods.

Bilateral prosthetic knee infection by Campylobacter fetus

We present the first documented case of a bilateral prosthetic knee joint infection with Campylobacter fetus. Our patient's risk factors included age, the presence of prosthetic joints, and potential exposure through his contact with farm animals. It is important to be aware of the possibility of C fetus joint infections in high-risk patients who present with pain after total joint arthroplasty.

Evaluation of a monoclonal antibody-based enzyme-linked immunosorbent assay for detection of Campylobacter fetus in bovine preputial washing and vaginal mucus samples

A monoclonal antibody-based enzyme-linked immunosorbent assay (ELISA) was described and evaluated for use as a presumptive screening test for detection of Campylobacter fetus in bovine preputial washing and vaginal mucus samples. A total of 725 diagnostic samples collected in the field and submitted in Clark's transport enrichment medium (TEM) were analyzed. Cultural isolation of C. fetus was used as the standard for comparison. After incubation of the TEM vials for 4-5 days, fluid was removed for culture and ELISA testing. A sandwich ELISA format was used and the target antigen was C. fetus lipopolysaccharides (LPS). A rabbit anti-C. fetus polyclonal antiserum was used as the capture antibody. Murine monoclonal antibodies (MAbs) to C. fetus serotype A and B LPS core and O-polysaccharides and a goat anti-mouse horseradish peroxidase conjugate were used as detection antibodies. ELISA and culture results for the diagnostic samples were in complete agreement. Seven hundred and eight samples were negative by both tests. All 17 culture positive samples were positive by ELISA with a MAb to LPS core. The ELISA with MAbs to LPS O-polysaccharides detected all culture positive samples with the homologous C. fetus serotype. Sixty-six preputial wash samples from three known C. fetus culture positive bulls were also analyzed. Forty-nine of these samples were positive by both ELISA and culture, 16 were positive by ELISA only, and one was negative by both ELISA and culture. The results indicate that this ELISA is useful as a screening test for the detection of C. fetus in diagnostic samples.

Identification and serological specificity of a polysaccharide component from Mycoplasma bovis

Whole-cell lysate and proteinase K digest preparations of the Mycoplasma bovis type strain (American Type Culture Collection 25523) were compared using sodium dodecyl sulfate polyacrylamide gel electrophoresis. Coomassie blue staining for protein revealed approximately 50 bands for the lysate but only a single band for the digest. Silver staining for polysaccharide revealed at least 19 bands for the digest. Fourteen monoclonal antibodies (MAbs) were produced using a screening procedure with an M. bovis digest. On immunoblots of digests of four M. bovis strains, an almost identical profile was seen with each strain for all 14 MAbs but differences were evident between strains. One MAb, M1557, was used to analyse 17 M. bovis strains on immunoblots. Ten to 20 bands were observed with 16 of the 17 strains, and differences were apparent among all 16 strains. In an enzyme-linked immunosorbent assay, M1557 reacted with 16 of the 17 M. bovis strains, but did not react with any of 41 non-M. bovis organisms tested. Strong reactions were observed with the MAbs and M. bovis colonies in immunofluorescence. The M. boris polysaccharide and MAbs to this component may be useful for the development of diagnostic assays for this organism.