Evaluation of passive immunotherapeutic efficacy of hyperimmunized egg yolk powder against intestinal colonization of Campylobacter jejuni in chickens

Campylobacter jejuni is a leading cause of foodborne bacterial gastroenteritis in human. Chickens are the reservoir host of C. jejuni, and contaminated chicken meat is an important source of human infection. Therefore, control of C. jejuni in chickens can have direct effect on human health. In this study we tested the passive immunotherapeutic efficacy of the chicken egg-yolk-derived antibodies, in the form of hyperimmunized egg yolk powder (HEYP), against 7 colonization-associated proteins of C. jejuni, namely, CadF (Campylobacter adhesion to fibronectin), FlaA (flagellar proteins), MOMP (major outer membrane protein), FlpA (fibronectin binding protein A), CmeC (Campylobacter multidrug efflux C), Peb1A (Campylobacter putative adhesion), and JlpA (Jejuni lipoprotein A). Three chicken experiments were performed. In each experiment, chickens were treated orally via feed supplemented with 10% (wt/wt) egg yolk powder. In experiment 1, chicken groups were experimentally infected with C. jejuni (10(8) cfu) followed by treatment with 5 HEYP (CadF, FlaA, MOMP, FlpA, CmeC) for 4 d either individually or as a cocktail containing equal parts of each HEYP. In experiment 2, chickens were treated for 21 d with cocktail containing equal parts of 7 HEYP before and after experimental infection with C. jejuni (10(8) cfu). In experiment 3, chickens were treated with feed containing a cocktail of 7 HEYP before and after (prophylaxis), and after (treatment) experimental infection with C. jejuni (10(5) cfu). Intestinal colonization of C. jejuni was monitored by culturing cecal samples from chickens euthanized at the end of each experiment. The results showed that there were no differences in the cecal colonization of C. jejuni between HEYP treated and nontreated control chickens, suggesting that use of HEYP at the dose and the regimens used in the current study is not efficacious in reducing C. jejuni colonization in chickens.

Transcriptome analysis of Vibrio parahaemolyticus in type III secretion system 1 inducing conditions

Vibrio parahaemolyticus is an emerging bacterial pathogen capable of causing inflammatory gastroenteritis, wound infections, and septicemia. As a food-borne illness, infection is most frequently associated with the consumption of raw or undercooked seafood, particularly shellfish. It is the primary cause of Vibrio-associated food-borne illness in the United States and the leading cause of food-borne illness in Japan. The larger of its two chromosomes harbors a set of genes encoding type III section system 1 (T3SS1), a virulence factor present in all V. parahaemolyticus strains that is similar to the Yersinia ysc T3SS. T3SS1 translocates effector proteins into eukaryotic cells where they induce changes to cellular physiology and modulate host-pathogen interactions. T3SS1 is also responsible for cytotoxicity toward several different cultured cell lines as well as mortality in a mouse model. Herein we used RNA-seq to obtain global transcriptome patterns of V. parahaemolyticus under conditions that either induce [growth in Dulbecco's Modified Eagle Medium (DMEM) media, in trans expression of transcriptional regulator exsA] or repress T3SS1 expression (growth in LB-S media, in trans exsD expression) and during infection of HeLa cells over time. Comparative transcriptomic analysis demonstrated notable differences in the expression patterns under inducing conditions and was also used to generate an expression profile of V. parahaemolyticus during infection of HeLa cells. In addition, we identified several new genes that are associated with T3SS1 expression and may warrant further study.

Outbreak of Listeria monocytogenes in an urban poultry flock

Background

Listeria monocytogenes infection is most commonly recognized in ruminants, including cattle, sheep, and goats; but it is rarely diagnosed in poultry. This report describes an outbreak of L. monocytogenes in a backyard poultry flock. Also, it points out the importance of collaboration between veterinarians and public health departments and the possible implications of zoonotic diseases.

Case presentation

Depression, lack of appetite, labored breathing, and increased mortality were noted for 5 months in several affected birds within the flock. The pathologic changes in the internal organs of infected birds included severe myocarditis, pericarditis, pneumonia, hepatitis, and splenitis. No lesions were noted in the brain. Gram-positive organisms were seen in histologic sections of the heart and spleen. Listeria monocytogenes was detected by real time PCR from formalin fixed heart and spleen, and was isolated from fresh lung, spleen, and liver. This isolate was identified as L. monocytogenes serotype 4b by 16S rDNA sequencing and by PCR-based serotyping assay.

Conclusions

This is the first report describing outbreak of L. monocytogenes in backyard poultry flock in Washington State and use of molecular methods to confirm L. monocytogenes infection from formalin fixed tissues.

Production and evaluation of chicken egg-yolk-derived antibodies against Campylobacter jejuni colonization-associated proteins

Campylobacter jejuni is one of the most important causes of foodborne gastroenteritis. Chickens are considered a reservoir host of C. jejuni, and epidemiological studies have shown that contaminated chicken meat is a primary source of human infection. The objective of this study was to produce chicken egg-yolk-derived antibody (IgY) against the five C. jejuni colonization-associated proteins or CAPs (CadF, FlaA, MOMP, FlpA, and CmeC). Recombinant C. jejuni CAPs were expressed in Escherichia coli and were purified by affinity chromatography. Specific-pathogen-free laying hens were hyperimmunized with each recombinant CAP to induce production of α-CAP-specific IgY. Egg yolks were collected from immunized and nonimmunized hens and were lyophilized to obtain egg-yolk powder (EYP) with or without α-C. jejuni CAP-specific IgY. IgY was purified from EYP, and the antibody response in serum and egg yolk was tested by indirect enzyme-linked immunosorbent assay. The α-C. jejuni CAP-specific IgY levels were significantly (p<0.05) higher in both serum and EYP obtained from immunized hens as compared with the nonimmunized hens. Each α-C. jejuni CAP-specific IgY reacted with the C. jejuni cells and recombinant CAPs as detected by immunofluorescence microscopy and Western blot assays, respectively. We also show that α-CadF, α-MOMP, and α-CmeC IgY significantly reduced adherence of C. jejuni to the chicken hepatocellular carcinoma (LMH) cells, suggesting that these α-C. jejuni CAP-specific IgY may be useful as a passive immunotherapeutic to reduce C. jejuni colonization in chickens.

Urine from treated cattle drives selection for cephalosporin resistant Escherichia coli in soil

The U.S. Food and Drug Administration recently issued new rules for using ceftiofur in food animals in part because of an increasing prevalence of enteric bacteria that are resistant to 3^rd-generation cephalosporins. Parenteral ceftiofur treatment, however, has limited effects on enteric bacteria so we tested the hypothesis that excreted ceftiofur metabolites exert significant selection pressure for ceftiofur-resistant Escherichia coli in soil. Test matrices were prepared by mixing soil with bovine feces and adding urine containing ceftiofur metabolites (CFM) (0 ppm, ∼50 ppm and ∼100 ppm). Matrices were incubated at 23°C or 4°C for variable periods of time after which residual CFM was quantified using a bioassay. Bla_CMY-2 plasmid-bearing ceftiofur resistant (cef^R) E. coli and one-month old calves were used to study the selection effects of CFM and transmission of cef^R bacteria from the environment back to animals. Our studies showed that urinary CFM (∼13 ppm final concentration) is biologically degraded in soil within 2.7 days at 23°C, but persists up to 23.3 days at 4°C. Even short-term persistence in soil provides a >1 log₁₀ advantage to resistant E. coli populations, resulting in significantly prolonged persistence of these bacteria in the soil (∼two months). We further show that resistant strains readily colonize calves by contact with contaminated bedding and without antibiotic selection pressure. Ceftiofur metabolites in urine amplify resistant E. coli populations and, if applicable to field conditions, this effect is far more compelling than reported selection in vivo after parenteral administration of ceftiofur. Because ceftiofur degradation is temperature dependent, these compounds may accumulate during colder months and this could further enhance selection as seasonal temperatures increase. If cost-effective engineered solutions can be developed to limit ex vivo selection, this may limit proliferation for ceftiofur resistant enteric bacteria while preserving the ability to use this important antibiotic in food animal production.

Production of organic acids by probiotic lactobacilli can be used to reduce pathogen load in poultry

Probiotic Lactobacillus can be used to reduce the colonization of pathogenic bacteria in food animals, and therefore reduce the risk of foodborne illness to consumers. As a model system, we examined the mechanism of protection conferred by Lactobacillus species to inhibit C. jejuni growth in vitro and reduce colonization in broiler chickens. Possible mechanisms for the reduction of pathogens by lactobacilli include: 1) stimulation of adaptive immunity; 2) alteration of the cecal microbiome; and, 3) production of inhibitory metabolites, such as organic acids. The Lactobacillus species produced lactic acid at concentrations sufficient to kill C. jejuni in vitro. We determined that lactic acid produced by Lactobacillus disrupted the membrane of C. jejuni, as judged by biophotonics. The spectral features obtained using Fourier-transform infrared (FT-IR) and Raman spectroscopy techniques were used to accurately predict bacterial viability and differentiate C. jejuni samples according to lactic acid treatment. FT-IR spectral features of C. jejuni and Lactobacillus grown in co-culture revealed that the metabolism was dominated by Lactobacillus prior to the killing of C. jejuni. Based on our results, the development of future competitive exclusion strategies should include the evaluation of organic acid production.

Salmonella Enteritidis strains from poultry exhibit differential responses to acid stress, oxidative stress, and survival in the egg albumen

Salmonella Enteritidis is the major foodborne pathogen that is primarily transmitted by contaminated chicken meat and eggs. We recently demonstrated that Salmonella Enteritidis strains from poultry differ in their ability to invade human intestinal cells and cause disease in orally challenged mice. Here we hypothesized that the differential virulence of Salmonella Enteritidis strains is due to the differential fitness in the adverse environments that may be encountered during infection in the host. The responses of a panel of six Salmonella Enteritidis strains to acid stress, oxidative stress, survival in egg albumen, and the ability to cause infection in chickens were analyzed. This analysis allowed classification of strains into two categories, stress-sensitive and stress-resistant, with the former showing significantly (p<0.05) reduced survival in acidic (gastric phase of infection) and oxidative (intestinal and systemic phase of infection) stress. Stress-sensitive strains also showed impaired intestinal colonization and systemic dissemination in orally inoculated chickens and failed to survive/grow in egg albumen. Comparative genomic hybridization microarray analysis revealed no differences at the discriminatory level of the whole gene content between stress-sensitive and stress-resistant strains. However, sequencing of rpoS, a stress-regulatory gene, revealed that one of the three stress-sensitive strains carried an insertion mutation in the rpoS resulting in truncation of σ(S). Finding that one of the stress-sensitive strains carried an easily identifiable small polymorphism within a stress-response gene suggests that the other strains may also have small polymorphisms elsewhere in the genome, which likely impact regulation of stress or virulence associated genes in some manner.

Cell invasion of poultry-associated Salmonella enterica serovar Enteritidis isolates is associated with pathogenicity, motility and proteins secreted by the type III secretion system

Salmonella enterica serovar Enteritidis (S. Enteritidis) is a major cause of food-borne gastroenteritis in humans worldwide. Poultry and poultry products are considered the major vehicles of transmission to humans. Using cell invasiveness as a surrogate marker for pathogenicity, we tested the invasiveness of 53 poultry-associated isolates of S. Enteritidis in a well-differentiated intestinal epithelial cell model (Caco-2). The method allowed classification of the isolates into low (n = 7), medium (n = 18) and high (n = 30) invasiveness categories. Cell invasiveness of the isolates did not correlate with the presence of the virulence-associated gene spvB or the ability of the isolates to form biofilms. Testing of representative isolates with high and low invasiveness in a mouse model revealed that the former were more invasive in vivo and caused more and earlier mortalities, whereas the latter were significantly less invasive in vivo, causing few or no mortalities. Further characterization of representative isolates with low and high invasiveness showed that most of the isolates with low invasiveness had impaired motility and impaired secretion of either flagella-associated proteins (FlgK, FljB and FlgL) or type III secretion system (TTSS)-secreted proteins (SipA and SipD) encoded on Salmonella pathogenicity island-1. In addition, isolates with low invasiveness had impaired ability to invade and/or survive within chicken macrophages. These data suggest that not all isolates of S. Enteritidis recovered from poultry may be equally pathogenic, and that the pathogenicity of S. Enteritidis isolates is associated, in part, with both motility and secretion of TTSS effector proteins.

Challenges associated with heterologous expression of Flavobacterium psychrophilum proteins in Escherichia coli

A two-parameter statistical model was used to predict the solubility of 96 putative virulence-associated proteins of Flavobacterium psychrophilum (CSF259-93) upon over expression in Escherichia coli. This analysis indicated that 88.5% of the F. psychrophilum proteins would be expressed as insoluble aggregates (inclusion bodies). These solubility predictions were verified experimentally by colony filtration blot for six different F. psychrophilum proteins. A comprehensive analysis of codon usage identified over a dozen codons that are used frequently in F. psychrophilum, but that are rarely used in E. coli. Expression of F. psychrophilum proteins in E. coli was often associated with production of minor molecular weight products, presumably because of the codon usage bias between these two organisms. Expression of recombinant protein in the presence of rare tRNA genes resulted in marginal improvements in the expressed products. Consequently, Vibrio parahaemolyticus was developed as an alternative expression host because its codon usage is similar to F. psychrophilum. A full-length recombinant F. psychrophilum hemolysin was successfully expressed and purified from V. parahaemolyticus in soluble form, whereas this protein was insoluble upon expression in E. coli. We show that V. parahaemolyticus can be used as an alternate heterologous expression system that can remedy challenges associated with expression and production of F. psychrophilum recombinant proteins.

Type III secretion system 1 genes in Vibrio parahaemolyticus are positively regulated by ExsA and negatively regulated by ExsD

Vibrio parahaemolyticus harbours two distinct type III secretion systems (T3SS1 and T3SS2). A subset of 10 T3SS1 genes are transcribed when V. parahaemolyticus is grown in tissue culture medium [Dulbecco's modified Eagle's medium (DMEM)], while transcription of these genes (except exsD) is minimal upon growth in Luria-Bertani-Salt (LB-S). Transcription of T3SS1 genes and cytotoxicity towards HeLa cells was prevented by deletion of exsA while complementation with exsA restored these traits. Overexpression of ExsA in the wild-type strain, NY-4, activated the transcription of T3SS1 genes when bacteria were grown in LB-S. Thus, ExsA is necessary and sufficient to induce the transcription of T3SS1 genes. Deletion of the exsD permitted the transcription of T3SS1 genes when bacteria were grown in the LB-S medium and complementation with the wild-type exsD gene-blocked transcription of T3SS1 genes. Overexpression of ExsD in NY-4 prevented the transcription of T3SS1 gene when bacteria were grown in DMEM. A gel mobility shift assay demonstrated that purified ExsA protein binds a novel motif in the upstream region of vp1668 and vp1687, indicating that ExsA interacts directly with the promoter sequences of T3SS1 genes. ExsA positively regulates the expression and secretion of Vp1656 while ExsD negatively regulates the expression and secretion of Vp1656.

Effect of metC mutation on Salmonella Gallinarum virulence and invasiveness in 1-day-old White Leghorn chickens

Salmonella enterica serotype Gallinarum (S. Gallinarum) is the causative agent of fowl typhoid (FT) in chickens. FT is a severe systemic disease of chickens causing heavy economic losses to the poultry industry through mortality, reduced egg production and culling of precious breeding stocks. In this study, a metC (encoding cystathionine beta lyase) mutant was produced from a virulent strain of S. Gallinarum by Mini-Tn5 insertional inactivation. The mutant was significantly attenuated in virulence for 1-day-old White Leghorn chickens. Inactivation of metC resulted in 10(4)-fold increase in the LD50 when compared with the wild type parent. The metC mutant showed an in vivo competitiveness defect in the challenged chickens and significantly lower (P < 0.01) bacterial burden in the reticuloendothelial organs when compared with the wild-type parent. These results indicate that metC gene is important for virulence of S. Gallinarum in chickens.

An allele-specific PCR assay for the rapid and serotype-specific detection of Salmonella pullorum

Salmonella serovar Pullorum is a causative agent of pullorum disease (PD) in poultry and is responsible for severe economic losses to the poultry industry in many parts of the world. A definitive detection of Pullorum requires culture followed by serotyping and biochemical identification, a process that is tedious and takes several weeks to accomplish. We have developed a rapid allele-specific polymerase chain reaction (PCR) method based on the nucleotide polymorphism in rfbS gene sequence for the serotype-specific detection of Pullorum and its differentiation from the closely related Gallinarum. The specificity of this PCR assay was tested using DNA samples from Pullorum (n = 13), Salmonella serotypes other than Pullorum (n = 19), and closely related non-Salmonella organisms (n = 5). The PCR assay was highly serotype-specific as the PCR amplicon of 147 base pairs was observed only in the case of Pullorum, while all the other DNA samples tested PCR negative. A definitive identification of Pullorum cultures was possible in less than 3 hr. As little as 100 pg of SP DNA was detected. This allele-specific PCR method is highly specific as well as sensitive and may be an effective molecular tool in the rapid and serotype-specific detection of Pullorum and differentiation from other Salmonella species.

Cloning and expression of 51-kDa antigenic protein of Neorickettsia risticii NR-JA1

Neorickettsia (Ehrlichia) risticii is a causative agent of acute diarrheal syndrome in horses, commonly known as Potomac horse fever. Korean isolate of N. risticii NR-JA1 was cultivated in mouse macrophage cell line P388D1. A complete ORF of p51 antigenic protein gene was amplified and cloned into pQE32 and pcDNA3.1 vectors and the resultant clones were named as pQE32/Nr-51 and pcDNA3.1/Nr-51, respectively. Recombinant p51 (rp51) protein antigen was expressed in E. coli (pQE32/Nr-51) and cos-7 cell line (pcDNA3.1/Nr-51). The rp51 protein showed immunoreactivity with anti- mouse p51 antibodies. BALB/c mice were inoculated with recombinant plasmid DNA (pcDNA3.1/Nr-51). The serum samples collected from these BALB/c mice showed IgG ELISA titers of 1:128. In a Western immunoblot assay, these serum samples showed a strong reactivity to rp51 expressed in cos-7 cell line transfected with pcDNA3.1/Nr-51. The results of this preliminary indicate that N. risticii p51 protein is an immmuno-dominant antigen and may be a good target for the development of serological or a molecular diagnostic test and possibly an improved recombinant DNA based vaccine against Potomac horse fever.

Detection of Bartonella species from ticks, mites and small mammals in Korea

We investigated the prevalence of Bartonella infections in ticks, mites and small mammals (rodents, insectivores and weasels) collected during 2001 through 2004, from various military installations and training sites in Korea, using PCR and sequence analysis of 16S rRNA, 23S rRNA and groEL heat shock protein genes. The prevalence of Bartonella spp. was 5.2% (n = 1,305 sample pools) in ticks, 19.1% (n = 21) in mesostigmatid mites and 13.7% (n = 424 individuals) in small mammals. The prevalence within the family Ixodidae was, 4.4% (n = 1,173) in Haemaphysalis longicornis (scrub tick), 2.7% (n = 74) in H. flava, 5.0% (n = 20) in Ixodes nipponensis, 11.1% (n = 9) in I. turdus, 33.3% (n = 3) in I. persulcatus and 42.3% (n = 26) in Ixodes spp. ticks. In rodents, the prevalence rate was, 6.7% (n = 373) in Apodemus agrarius (striped field mouse) and 11.1% (n = 9) in Eothenomys regulus (Korean red-backed vole) and in an insectivore,Crocidura lasiura, 12.1% (n = 33). Neither of the two weasels were positive for Bartonella spp. Phylogenetic analysis based on amino acid sequence of a portion of the groEL gene amplified from one A. agrarius spleen was identical to B. elizabethae species. We demonstrated the presence of Bartonella DNA in H. longicornis, H. flava and I. nipponensis ticks, indicating that these ticks should be added to the growing list of potential tick vectors and warrants further detailed investigations to disclose their possible roles in Bartonella infection cycles.

Identification of Salmonella gallinarum virulence genes in a chicken infection model using PCR-based signature-tagged mutagenesis

Salmonella gallinarum (SG) is a non-motile host-adapted salmonella that causes fowl typhoid, a severe systemic disease responsible for significant economic losses to the poultry industry worldwide. This study describes the application of a PCR-based signature-tagged mutagenesis system to identify in vivo-essential genes of SG. Ninety-six pools representing 1152 SG mutants were screened in a natural-host chicken infection model. Twenty presumptive attenuated mutants were identified and examined further. The identity of the disrupted gene in each mutant was determined by cloning of the DNA sequences adjacent to the transposon, followed by sequencing and comparison with the bacterial genome database. In vitro and in vivo competition indices were determined for each identified mutant and a total of 18 unique, attenuating gene disruptions were identified. These mutations represented six broad genomic classes: Salmonella pathogenicity island-1 (SPI-1), SPI-2, SPI-10, SPI-13, SPI-14 and non-SPI-encoded virulence genes. SPI-13 and SPI-14 are newly identified and designated in this study. Most of the genes identified in this study were not previously believed or known to play a role in the pathogenesis of SG infection in chickens. Each STM identified mutant showed competitiveness and/or virulence defects, confirmed by in vitro and in vivo assays, and challenge tests. This study should contribute to a better understanding of the pathogenic mechanisms involved in progression of disease caused by SG, and identification of novel live vaccine candidates and new potential antibiotic targets.

Rapid differentiation of Mycobacterium bovis and Mycobacterium tuberculosis based on a 12.7-kb fragment by a single tube multiplex-PCR

The aim of this work was the design and validation of a rapid and easy single tube multiplex-PCR (m-PCR) assay for the unequivocal differential detection of Mycobacterium bovis and Mycobacterium tuberculosis. Oligonucleotide primers were based on the uninterrupted 229-bp sequence in the M. bovis genome and a unique 12.7-kb insertion sequence from the M. tuberculosis genome, which is responsible for species-specific genomic polymorphism between these two closely related pathogens. The m-PCR assay was optimized and validated using 22 M. bovis and 36 M. tuberculosis clinical strains isolated from diverse host species and 9 other non-tuberculous mycobacterial (NTM) strains. The designed primers invariably amplified a unique 168-bp (M. bovis-specific) and 337-bp (M. tuberculosis-specific) amplicon from M. bovis and M. tuberculosis strains, respectively. The accuracy of the assay, in terms of specificity, was 100%, as none of the NTM strains tested revealed any amplification product. As little as 20 pg of genomic DNA could be detected, justifying the sensitivity of the method. The m-PCR assay is an extremely useful, simple, reliable and rapid method for routine differential identification of cultures of M. bovis and M. tuberculosis. This m-PCR may be a valuable diagnostic tool in areas of endemicity, where bovine and human tuberculosis coexist, and the distinction of M. bovis from M. tuberculosis is required for monitoring the spread of M. bovis to humans.

Allele-specific PCR method based on rfbS sequence for distinguishing Salmonella gallinarum from Salmonella pullorum: serotype-specific rfbS sequence polymorphism

Cloning and sequence analysis of rfbS gene identified two polymorphic nucleotides, one at position 598 (Salmonella gallinarum-specific) and other at position 237 (Salmonella pullorum-specific). Based on S. gallinarum-specific nucleotide found at position 598, an allele-specific PCR method was developed for serotype-specific detection of S. gallinarum. This PCR method was able to discriminate pure cultures of S. gallinarum from S. pullorum and other Salmonella serotypes from serogroup D in less than 3 h. Serotype-specific detection of S. gallinarum was possible in less than 24 h when the PCR was applied on the presumptive Salmonella colonies obtained after overnight incubation of selective media plates streaked with the clinical material from diseased chickens. As little as 100 pg of genomic DNA could be detected with S. gallinarum-specific primers; no PCR product was detected in non-S. gallinarum serotypes of serogroup D and other closely related non-salmonella organisms. This rfbS allele-specific amplification assay is specific, reproducible and less time consuming than the standard bacteriological methods used to detect S. gallinarum and could be an effective molecular tool for rapid definitive diagnosis of fowl typhoid in the areas of endemicity where fowl typhoid infection exists.

Molecular fingerprinting of clinical isolates of Mycobacterium bovis and Mycobacterium tuberculosis from India by restriction fragment length polymorphism (RFLP)

Forty mycobacterial strains comprising clinical Indian isolates of Mycobacterium tuberculosis (28 field isolates +1H37 Rv) and Mycobacterium bovis (10 field isolates +1 AN5) were subjected to restriction fragment length polymorphism analysis (RFLP) using IS6110 and IS1081 probes. Most of these strains originated from dairy cattle herd and human patients from Indian Veterinary research Institute (IVRI) campus isolated from the period of 1986 to 2000. Our study showed presence of 8 copies of IS6110 in most of the M.tuberculosis (96.6%) strains irrespective of their origin with the exception of one M.tuberculosis strain with presence of an extra copy (3.4%). All M.bovis strains showed a single copy of IS6110 on the characteristic 1.9 kb restriction fragment. RFLP analysis with IS1081 invariably showed the presence of 5 copies in all isolates of M.bovis and M.tuberculosis at the same chromosomal location. Similarity of IS6110 RFLP fingerprints of M.tuberculosis strains from animals and human suggested the possibility of dissemination of single M.tuberculosis strain among animals as well as human. It was not possible to discriminate within the isolates of either M.tuberculosis or M.bovis, when IS1081 was used as target sequence. The IS6110 RFLP is a valuable tool for disclosing transmission chain of M. tuberculosis and M. bovis among humans as well as animals.

A multiplex-PCR for the differentiation of Mycobacterium bovis and Mycobacterium tuberculosis

A multiplex-polymerase chain reaction (PCR) assay based on one-step amplification and detection of two different mycobacterial genomic fragments was designed for differentiation of Mycobacterium bovis and Mycobacterium tuberculosis. The oligonucleotide primers were chosen from a 500-bp genomic fragment which is well conserved in M. bovis and the pncA gene (based on M. tuberculosis-specific nucleotide polymorphism, a cytosine residue at position 169), specific for M. tuberculosis. The multiplex-PCR allowed detection of a single product of 500 bp in M. bovis isolates while M. tuberculosis isolates generated a single product of 185 bp, with or without an additional product of 500 bp. None of the atypical mycobacterial isolates revealed any amplification products. The method was found to be highly specific and could detect as little as 20 pg of pure DNA. This multiplex-PCR assay, based on the 500-bp fragment and the pncA gene, may be very useful for the rapid and specific differentiation of these two closely related mycobacteria and easy to use in medical and veterinary microbiological laboratories.