Repetitive sequence element cloned from Leptospira interrogans serovar hardjo type hardjo-bovis provides a sensitive diagnostic probe for bovine leptospirosis

Leptospirosis in Ruminants in Yogyakarta, Indonesia: A Serological Survey with Mixed Methods to Identify Risk Factors

Leptospirosis is a zoonotic disease occurring worldwide with reproductive symptoms and production losses in livestock, while humans can suffer fatal renal failure. In Yogyakarta Special Province, Indonesia, there have been several outbreaks with high case fatality, demonstrating the public health importance, but there is limited understanding of the epidemiology. This study used an EcoHealth approach to ensure transdisciplinarity and community participation. Seroprevalence of Leptospira in animals was studied between October 2011 and May 2013 in 15 villages. Serum samples from 1404 cattle and 60 small ruminants were screened by a Microscopic Agglutination Test (MAT), first in pools, and then the individual positive samples were identified. Focus group discussions including farmers, village officials, and official stakeholders were used to explore knowledge and behavior of zoonotic diseases, particularly leptospirosis. Two small ruminants were seropositive for Leptospira icterohemorrhagiae. From the cattle, 3.7% were seropositive, and the most common serovars were Leptospira hardjo, followed by L. icterohemorrhagiae. Out of all farms, 5.6% had at least one positive cattle. Risk factor analyses showed that the risk of the farm being seropositive increased if the farmer used water from an open source, or if farming was not the main occupation. This study showed the presence of Leptospira spp. in ruminants in Yogyakarta and identified use of open water as a risk factor for the livestock. We also observed that the knowledge related to leptospirosis was low, and risky farm management practices were commonly employed.

Meta-analysis to estimate the load of Leptospira excreted in urine: beyond rats as important sources of transmission in low-income rural communities

BACKGROUND

Leptospirosis is a major zoonotic disease with widespread distribution and a large impact on human health. Carrier animals excrete pathogenic Leptospira primarily in their urine. Infection occurs when the pathogen enters a host through mucosa or small skin abrasions. Humans and other animals are exposed to the pathogen by direct contact with urine, contaminated soil or water. While many factors influence environmental cycling and the transmission of Leptospira to humans, the load of pathogenic Leptospira in the environment is likely to play a major role. Peridomestic rats are often implicated as a potential source of human disease; however exposure to other animals is a risk factor as well. The aim of this report is to highlight the importance of various carrier animals in terms of the quantity of Leptospira shed into the environment. For this, we performed a systematic literature review and a meta-analysis of the amount of pathogen that various animal species shed in their urine.

RESULTS

The quantity of pathogen has been reported for cows, deer, dogs, humans, mice, and rats, in a total of 14 research articles. We estimated the average Leptospira per unit volume shed by each animal species, and the daily environmental contribution by considering the total volume of urine excreted by each carrier animal. Rats excrete the highest quantity of Leptospira per millilitre of urine (median = 5.7 × 10⁶ cells), but large mammals excrete much more urine and thus shed significantly more Leptospira per day (5.1 × 10⁸ to 1.3 × 10⁹ cells).

CONCLUSIONS

Here we illustrate how, in a low-income rural Ecuadorian community, host population demographics, and prevalence of Leptospira infection can be integrated with estimates of shed Leptospira to suggest that peridomestic cattle may be more important than rats in environmental cycling and ultimately, transmission to humans.

Rapid diagnosis of leptospirosis in patients with different clinical manifestations by 16S rRNA gene based nested PCR

Leptospirosis, a zoonosis of global importance and it is underreported in India and more than 50,000 severe cases are reported each year. Here we present the evaluation of 16S rRNA based nested PCR assay for the rapid identification of human leptospires using serum and urine samples. The study includes 261 suspected cases for leptospirosis with different clinical manifestations. 16S rRNA based nested PCR assay was compared and evaluated against the conventional serological methods such as MAT and ELISA. The technique enabled amplification of a 289 bp product with notable percentage of positivity in all sample groups including 94.8 in pediatric cases, 93 in pregnant women, 94.2 in renal failure, 87.8 in jaundice and 94.6 in common febrile cases. The sensitivity and specificity was 94.4% and 100%, respectively. The technique proved to be prompt and effective for the diagnosis of leptospiral infection at the acute phase of the disease. PCR based approach detects leptospiral DNA from the clinical samples both at the acute and leptospiruria phase on comparison with its counter parts where detection is made possible only after 7 days or 7-30 days post-infection. In this regard PCR based diagnosis of leptospirosis should be made available for clinicians for the early diagnosis and prompt treatment of the disease.

Evaluation of LSSP-PCR for identification of Leptospira spp. in urine samples of cattle with clinical suspicion of leptospirosis

We evaluated the use of low-stringency single specific primer PCR (LSSP-PCR) for genetically typing Leptospira directly from urine samples of cattle with clinical suspicion of leptospirosis. Urine samples obtained from 40 cattle with clinical suspicion of leptospirosis were amplified by specific PCR using the following primers: Internal 1/Internal 2 and G1/G2. The internal primers were designed from the gene sequence of the outer membrane lipoprotein Lip32 from Leptospira kirschneri, strain RM52. The PCR products were amplified with these two pairs of primers, which had approximately 497 and 285bp, respectively, and were subsequently used as a template for LSSP-PCR analysis. The genetic signatures from the leptospires which were present in the urine samples allowed us to make a preliminary identification of the leptospires by comparing the LSSP-PCR profiles obtained directly from urine samples with those from reference leptospires. The LSSP-PCR profiles obtained with the Internal 1 primer or with the G1 primer allowed the grouping of the leptospires into serogroups. LSSP-PCR was found to be a useful and sensitive approach capable of identifying leptospires directly from biological samples without the need for prior bacterial isolation. In conclusion, the LSSP-PCR technique may still be helpful in discriminating serogroups of Leptospira from different animal reservoirs, since the early identification of carrier animals and information on the shedding state are crucial to prevent the spread of leptospiral infection to other animals and humans.

Differentiation of leptospires of the serogroup Pomona by monoclonal antibodies, pulsed-field gel electrophoresis and arbitrarily primed polymerase chain reaction

All reference strains described as representing separate serovars belonging to the serogroup Pomona and a clinical leptospiral isolate (LP2) from this serogroup were analyzed using a battery of 9 monoclonal antibodies, pulsed-field gel electrophoresis (PFGE) and arbitrarily primed polymerase chain reaction (AP-PCR). Monoclonal antibody analysis provided taxonomic results which were in agreement with the current classification of the serogroup Pomona into six serovars and allowed the classification of the isolate LP2 in the serovar pomona. PFGE and AP-PCR, although in general agreement with monoclonal antibody analysis, also were able to demonstrate some differences in the restriction patterns of strains Pomona, Monjakov and CB. These results indicate that these strains, grouped within serovar pomona after the introduction of bacterial restriction endonuclease analysis as the typing method, but formerly described as representing separate serovars (pomona, monjakov and cornelli, respectively), are similar but not identical to one another. This was also the case with strains 5621, the serovar mozdok reference strain, and K1, formerly described as serovar dania reference strain, but currently recognized to be a mozdok-like strain. These findings suggest that the deletion of some serovars within the serogroup Pomona, namely mozdok, cornelli, and dania, should be reconsidered. Thus, PFGE appears to be a useful tool for the serovar identification of leptospires belonging to the serogroup Pomona and for shedding light on the problem of their classification.

Use of a monovalent leptospiral vaccine to prevent renal colonization and urinary shedding in cattle exposed to Leptospira borgpetersenii serovar hardjo

OBJECTIVE

To determine whether a monovalent Leptospira borgpetersenii serovar hardjo (type hardjobovis) vaccine commercially available in Australia, New Zealand, Ireland, and the United Kingdom would protect cattle from renal colonization and urinary shedding when exposed to a US strain of Leptospira borgpetersenii serovar hardjo.

ANIMALS

24 Hereford heifers that lacked detectable antibodies against serovar hardjo.

PROCEDURE

Heifers received 2 doses, 4 weeks apart, of the commercial hardjo vaccine (n = 8) or a monovalent US reference hardjo vaccine (8) or were not vaccinated (controls; 8). Heifers were challenged 16 weeks later by intraperitoneal inoculation or conjunctival instillation. Serum antibody titers were measured weekly, and urine samples were examined for leptospires. Heifers were euthanatized 11 to 14 weeks after challenge, and kidney tissue was examined for evidence of colonization.

RESULTS

All 8 heifers vaccinated with the reference vaccine were found to be shedding leptospires in their urine and had evidence of renal colonization. All 4 control heifers challenged by conjunctival instillation and 2 of 4 control heifers challenged by intraperitoneal inoculation shed leptospires in their urine, and all 8 had evidence of renal colonization. In contrast, leptospires were not detected in the urine or tissues of any of the 8 heifers that received the commercial hardjo vaccine. Heifers that received the commercial hardjo vaccine had significantly higher antibody titers than did heifers that received the reference vaccine.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggest that cattle that received 2 doses of the commercial hardjo vaccine were protected against renal colonization and urinary shedding when challenged with L borgpetersenii serovar hardjo strain 203 four months after vaccination.

Leptospirosis

Leptospirosis is a worldwide zoonotic infection with a much greater incidence in tropical regions and has now been identified as one of the emerging infectious diseases. The epidemiology of leptospirosis has been modified by changes in animal husbandry, climate, and human behavior. Resurgent interest in leptospirosis has resulted from large outbreaks that have received significant publicity. The development of simpler, rapid assays for diagnosis has been based largely on the recognition that early initiation of antibiotic therapy is important in acute disease but also on the need for assays which can be used more widely. In this review, the complex taxonomy of leptospires, previously based on serology and recently modified by a genotypic classification, is discussed, and the clinical and epidemiological value of molecular diagnosis and typing is also evaluated.

Comparison of polymerase chain reaction assays with bacteriologic culture, immunofluorescence, and nucleic acid hybridization for detection of Leptospira borgpetersenii serovar hardjo in urine of cattle

OBJECTIVE

To compare sensitivity and specificity of various polymerase chain reaction (PCR) assays for detection of Leptospira borgpetersenii serovar hardjo in bovine urine and to compare results of the optimal PCR assay with results of immunofluorescence, nucleic acid hybridization, and bacteriologic culture.

ANIMALS

6 heifers.

PROCEDURE

Heifers were exposed to serovar hardjo type hardjo-bovis by conjunctival instillation of 10(6) leptospires on 3 successive days. Urine samples were collected before and after infection. Sensitivity and specificity of 5 PCR assays were compared, to determine the optimal assay for use with bovine urine samples. The optimal PCR assay was then compared with results of bacteriologic culture, nucleic acid hybridization, and immunofluorescence.

RESULTS

A PCR assay with the best combination of specificity (100%) and sensitivity (91%) was selected for comparison with the other diagnostic tests. Sensitivity for nucleic acid hybridization was 55%, whereas sensitivity for bacteriologic culture and immunofluorescence was 89 to 93%.

CONCLUSIONS AND CLINICAL RELEVANCE

Bacteriologic culture, PCR, and immunofluorescence were sensitive for detection of L borgpetersenii serovar hardjo type hardjo-bovis in urine specimens of cattle, but a single technique was not the most sensitive for each animal tested. Therefore, the use of 2 techniques in combination is warranted for maximal sensitivity for diagnosis.

Repetitive sequence of Leptospira interrogans serovar icterohaemorrhagiae strain Ictero No. 1: a sensitive probe for demonstration of Leptospira interrogans strains

A 4.8-kilobase (kb) repetitive sequence element generated with KpnI digestion was cloned from the Leptospira interrogans serovar icterohaemorrhagiae strain Ictero No. 1. The sequence, repeated in tandem, was located on the 280-kb fragment between the FseI and AscI sites on the chromosome by hybridization using the 4.8-kb fragment as a probe. We cloned the fragment containing the element for the Ictero No. 1 strain in a lambda EMBL3 bacteriophage DNA, and one out of 5 clones was sequenced. Within the sequenced 9-kb segment that partially repeated, 9 putative open-reading frames and 2 transfer RNA genes, for alanine and isoleucine, were identified. A similarity search for the products deduced from the sequenced data revealed that the repeated sequence includes both beta-oxidation enzymes, acyl-CoA dehydrogenase and enoyl-CoA hydratase, and hydroxythiazole kinase protein homologues. Hybridization experiments against different leptospiral strains using the element as a probe showed a similar sequence in the strains of L. interrogans and L. kirschneri, but not in any strains of L. borgpetersenii, L. weillii, L. meyeri or L. biflexa. Results indicated that the highly repeated element in the Ictero No. 1 strain exists as a well conserved sequence, though at a moderate level of repetition, in certain strains of L. interrogans and L. kirschneri. PCR amplification targeting the repetitive element was successful and indicated that the procedure provides a sensitive and specific probe to detect leptospires.

A rapid latex agglutination test for detection of leptospiral antibodies

A rapid semi-quantitative latex agglutination test (LAT) has been standardized for the detection of leptospiral antibodies in serum samples of man and animals. The efficacy of the LAT was compared with the plate enzyme linked immunosorbent assay (ELISA). A total of 276 human serum samples were analyzed by both LAT and ELISA and percentage positives were 84.8 and 85.9%, respectively. Similarly, of 65 animal samples tested, 63.1 and 69.2% positivity were observed in LAT and ELISA, respectively. Even though the ELISA test was slightly more sensitive than LAT, the rapidity, simplicity and economics of the LAT were found to fulfill the requirements of a screening test for leptospiral antibodies.

Development of an immunomagnetic antigen capture system for detecting leptospires in bovine urine

A magnetic bead antigen capture system which combined the use of two evolving techniques - immunomagnetic separation (IMS) and time-resolved fluoroimmunoassay (TR-FIA) - was developed to detect Leptospira borgpetersenii serovar hardjo in bovine urine. The assay utilised monoclonal antibody coated magnetic beads to capture leptospiral antigen which was in turn detected using another monoclonal antibody (Indicator) labelled with biotin. Signal was generated by the binding of europium labelled streptavidin to indicator antibody. The sensitivity of the assay was improved from 10(3) to 10(2) leptospires per ml by using an ethanol precipitation procedure to treat each sample. The assay detected only 31 of 56 (55 per cent) urine specimens culture-positive for hardjo, but seven of 24 urine samples culture-negative for hardjo were identified as positive by the assay. These seven samples were from animals which were culture positive on at least one other occasion. These results suggest that this system should be further investigated as a complementary test to culture for the identification of hardjo carrier animals.

Differentiation of Leptospira interrogans isolates by IS1500 hybridization and PCR assays

Genetic variability among Leptospira interrogans (sensu stricto) serovars was assessed by Southern blot hybridization and PCR analyses. The experiments used probes directed to sequences in a recently described insertion element, IS1500. Hybridization analysis showed that IS1500 was present on polymorphic fragments and that differences in these patterns could be used to identify serovars. Hybridization analysis was also useful in discriminating between serovar pomona type kennewicki isolates, making possible the identification of 15 previously unrecognized genetic groups. A PCR assay was developed in which the primers are positioned near the terminal inverted repeats of the element and directed outward. This assay yielded characteristic amplification patterns from isolates, allowing them to be identified. We applied these assays to several new animal isolates of L. interrogans from Nicaragua, which recently had an outbreak of human leptospirosis. Three groups of isolates were identified: one strain of serovar pomona type kennewicki and two genetically distinct groups of isolates which may be genetic intermediates between serovars canicola and portlandvere. The IS-based typing assays described should be useful for epidemiological analysis of leptospirosis.

Magnetic immuno capture PCR assay (MIPA): detection of Leptospira borgpetersenii serovar hardjo

Magnetic immuno PCR assay (MIPA) was developed for the rapid detection of leptospires excreted in urine samples (n = 59) collected from 35 experimentally infected cattle. The immunomagnetic separation of leptospires from inhibitors in frozen formalin fixed bovine urine prior to PCR detection resulted in a marked improvement on previous detection methods. MIPA is a rapid 5 step protocol requiring 70 mins preparation time prior to amplification, which consistently detects 10(1) organisms. MIPA detected 76% (38/50) of culture positive urines and in addition three urines that were culture negative were shown to be positive by this method of detection. Consequently we conclude that whilst MIPA is an improvement on previously published PCR detection methods, the culture of the organism is still the standard against which other detection methods have to be compared.

The development of a ligase mediated PCR with potential for the differentiation of serovars within Leptospira interrogans

A ligase mediated polymerase chain reaction (LMPCR) was developed to amplify between the repetitive element, IS1533, of Leptospira and adjacent chromosomally located Bg/II restriction endonuclease enzyme sites. To do this, complimentary oligonucleotide linkers designed to anneal together with an overhanging Bg/II end were ligated to Bg/II digested DNA from 35 leptospiral reference strains and field isolates. This ligated DNA was used as template for PCR with oligonucleotide primers specific for the linker and for the repetitive element IS1533. The resultant amplicon profile hybridised a 102 bp region derived from the terminus of IS1533 thus confirming that amplicons generated by LMPCR contained part of IS1533. The number of fragments generated containing IS1533 was significantly fewer than that generated by RFLP but the LMPCR method has the potential to use far less template DNA and be quicker than standard RFLP. Obvious and reproducible interserovar differences were demonstrated by LMPCR whereas for 20 of 21 L. hardjo-bovis isolates tested no intraserovar differences were observed. Of those serovars known to possess IS1533 homologues and tested here by LMPCR, each produced a unique amplicon profile which hybridised the IS1533 terminus probe. The limited heterogeneity amongst hardjo-bovis isolates is discussed as is the potential contribution of this method to diagnosis, differentiation and the phylogenetics of the Leptospires.

Leptospirosis - An Emerging Pathogen in Travel Medicine: A Review of its Clinical Manifestations and Management

Leptospirosis is a zoonosis caused by a spirochete, Leptospira interrogans. The disease has a wide range of clinical manifestations, ranging from a mild febrile illness to classic Weil's disease, which presents with jaundice, myalgia, acute renal failure, and tissue hemorrhage. Transmission usually occurs from contact with infected water surfaces. Recently, recreational activities such as hiking, swimming in lakes, biking through infected water, and hunting have been associated with the acquisition of this disease. This review describes the epidemiology, clinical manifestations, diagnostic methods, management, and prevention of this disease.

Circular and linear plasmids of Lyme disease spirochetes have extensive homology: characterization of a repeated DNA element

We have cloned three copies of a repeated DNA segment from Borrelia burgdorferi sensu stricto strain B31, present on both circular and linear plasmids of this and other B. burgdorferi sensu lato strains. The DNA sequences are characterized by a highly homologous segment containing two open reading frames (ORFs), ORF-A and ORF-B. Five additional ORFs can be found on the slightly less homologous flanking sequences: ORF-G on the opposite strand upstream of ORF-A, and ORF-C, ORF-D, ORF-E, and ORF-F downstream of ORF-B. The 4.6-kb-long element containing ORF-A through ORF-E is flanked by approximately 180-bp-long imperfect inverted repeats (IRs). The putative gene product of ORF-C displays homology to proteins involved in plasmid maintenance in a number of gram-positive and gram-negative bacteria. ORF-E features several short, highly homologous direct repeats. ORF-A, ORF-B, and ORF-D are homologous to three ORFs on a recently described 8.3-kb circular plasmid of Borrelia afzelii Ip21 that are flanked by similar IRs (J. J. Dunn, S. R. Buchstein, L.-L. Butler, S. Fisenne, D. S. Polin, B. N. Lade, and B. J. Luft, J. Bacteriol. 176:2706-2717,1994). ORF-C and ORF-E, however, are missing from this region on the Ip21 plasmid. Furthermore, the repeated DNA element as defined by the IRs is present in opposite orientations relative to the flanking sequences on the B31 and Ip21 plasmids.

The repetitive element Rep MP 1 of Mycoplasma pneumoniae exists as a core element within a larger, variable repetitive mosaic

The repetitive element Rep MP 1 has been previously described as a 300-bp element present within the chromosome of Mycoplasma pneumoniae in at least 10 copies. Sequence found flanking Rep MP 1 in lambda clone 5B52 has been demonstrated to exist in multiple copies within the genome of M. pneumoniae. A HindIII M. pneumoniae fragment containing the lambda MP 5B52 insert and its flanking sequences was cloned into pBluescript. Sequence comparisons of this clone, designated pMPH 624-20, with nucleotide database entries showed that in addition to the 300-bp Rep MP 1 element, flanking sequence blocks were conserved within several other cloned sequences. These short repeated sequences, approximately 80, 56, and 71 nucleotides long, are termed sRep A, sRep B, and sRep C, respectively. These sRep regions were used as probes in the selection of cloned sequences containing these repetitive flanking regions. Comparison of these sequences demonstrated that the 300-bp Rep MP 1 elements is actually the core element within a larger, variable repetitive mosaic. The repetitive regions surrounding the core element are found in various combinations, arrangements, and distances from the core in a mosaic pattern. These newly identified portions of the mosaic do not exist independently of the core element. The core appears to be the only invariant portion of this repetitive mosaic.

IS1533-based PCR assay for identification of Leptospira interrogans sensu lato serovars

A PCR-based assay was developed for typing L. interrogans sensu lato serovars. The assay is designed to exploit the presence of many copies of the leptospiral insertion sequence IS1533 and IS1533-like sequences present in the genomes of most leptospiral serovars. The PCR primers were designed to amplify DNA of unknown sequence between closely placed IS1533 or IS1533-like sequences. Amplification reactions primed with IS1533-based primers generated products of different sizes. When few copies of IS1533 were present in the genome, amplification of a few products was still detected. These results suggest that IS1533 elements may be found close together. Analysis of DNA amplified from different serovars showed the presence of differently sized products, thus enabling the serovars to be identified. Genetic variation among isolates within the same serovar was also demonstrated with the IS1533-based primers. Amplification reactions using DNA extracted from the urine of infected animals generated specific products which were similar to the products generated from purified bacterial DNA. These results demonstrate that this assay is selective enough to be used for typing leptospiral serovars from clinical material and thus allows leptospiral typing without isolation of the bacteria in pure culture.

Leptospirosis as a cause of reproductive failure

Leptospirosis is a zoonotic disease caused by members of the genus Leptospira. Veterinarians' perceptions of leptospirosis as a disease of domestic animals has undergone considerable modification in the past decade or so because they have increasingly appreciated the role of the host-maintained leptospires as causes of reproductive wastage in their respective host species kept under modern intensive management systems.

Special tests for the diagnosis of infectious causes of reproductive failure in ruminants

The detection of many infectious disease agents, including those of importance in ruminant reproductive failure, increasingly will be achieved through means other than the laborious and time-consuming traditional isolation and culture procedures. New diagnostic methodologies are designed both to enhance the rapidity with which results are obtained and to increase specificity and sensitivity of identification of the causative agent. Immunoenzyme histochemical staining of formalin-fixed paraffin-embedded tissues offers, especially in cases of abortions in which necropsy material routinely is examined histologically, an efficient and timely means of identifying many important pathogens. Antemortem serologic diagnostics will continue to be dominated by ELISA technologies. In the past decade, the specificity of serodiagnosis has been enhanced greatly by the use of monoclonal antibody-based competitive ELISA systems and further improvements in such methods will result from the use of defined antigens derived by recombinant DNA techniques. Although DNA hybridization technology has been applied successfully to detect many important veterinary pathogens and has been shown to have merit for improved diagnosis of some fastidious agents, those methods, because of their technical complexity, in general, have not been shown to be applicable for routine diagnostic uses. In contrast, methods using the PCR for specific gene amplification offer exceptional promise. Although the PCR presently is too technically exacting for routine use, its broad applicability and exquisite sensitivity and specificity suggest that it will play an ever-increasing role in future veterinary diagnostic techniques.

A review of laboratory techniques and their use in the diagnosis of Leptospira interrogans serovar hardjo infection in cattle

This paper reviews the laboratory diagnosis of Leptospira hardjo infection in cattle. Two genotypes of L hardjo, Hardjoprajitno and Hardjobovis, have been identified in cattle, but only Hardjobovis has been isolated in Australia. There are problems with diagnosis and control of bovine leptospirosis. Infection is usually subclinical and the serological titres vary greatly in peak and duration. Leptospires may be excreted in urine for up to 18 months. Low microscopic agglutination test titres may be significant in unvaccinated herds as indicators of endemic infection. Vaccines differ in their composition, and their efficacy is difficult to evaluate. The serological response after vaccination is difficult to differentiate from the response after infection. Pregnant cows that become infected may abort, but this is usually after the serological response has peaked. Therefore, paired serum samples are of little use in diagnosing abortion caused by L hardjo. Fluorescent antibody techniques are more sensitive than dark field microscopy for detection of leptospires in urine and tissue samples. Techniques for culture have improved but are still difficult to perform and take 3 months or longer for results to be known. DNA probes and polymerase chain reaction tests are very sensitive and specific, quick to perform, and can be used on fluid and tissue samples.

Characterization of Leptospira isolates from serovar hardjo by ribotyping, arbitrarily primed PCR, and mapped restriction site polymorphisms

Leptospira serovar hardjo isolates of the hardjoprajitno and hardjobovis genotypes were characterized by ribotyping, arbitrarily primed PCR (AP-PCR) fingerprinting, and the study of mapped restriction site polymorphisms (MRSPs) in rrs and rrl genes. After restriction of chromosomal DNA with BglII, EcoRI, or HindIII, each genotype was individualized with a distinct ribotype. The fingerprints produced by AP-PCR with seven primers clearly separated the two groups; primers KF and RSP produced species-specific products which assigned hardjoprajitno and hardjobovis isolates to the species L. interrogans sensu stricto and L. borgpetersenii, respectively. Furthermore, AP-PCR fingerprints gave evidence of a considerable genomic heterogeneity at the strain level among the hardjobovis group. Conversely, the hardjoprajitno group was homogeneous. MRSP profiles in ribosomal genes indicated that hardjoprajitno and hardjobovis isolates belonged to L. interrogans MRSP group B and L. borgpetersenii group C, respectively. AP-PCR and determination of MRSPs in ribosomal genes proved to be quick and reliable methods for typing Leptospira strains and for studying intraspecific population structures.

Rapid and specific detection of pathogenic Leptospira species by amplification of ribosomal sequences

We have developed an assay for the detection of pathogenic Leptospira that is based on the polymerase chain reaction. With the combination of agarose gel electrophoresis and blotting, pathogenic Leptospira can be discriminated specifically from nonpathogenic Leptospira and other bacterial species. This method, based on the amplification of 16S ribosomal RNA sequences, is able to detect 10 leptospiral cells/mL in cattle urine samples and 100 leptospiral cells/mL in pig urine samples. Using this assay leptospires were detected in urine samples from cattle that were experimentally infected with Leptospira interrogans serovar hardjo type hardjobovis.

Detection of leptospiral DNA by PCR

An EcoRI fragment (1.2 kb) which is highly conserved among Leptospira interrogans isolated in Korea was cloned into pBluescript vector from L. interrogans serovar lai WH20. The EcoRI fragment was sequenced, and a pair of primers (LP1 and LP2) was designed for PCR assay. PCR amplification of target DNA obtained from cultured L. interrogans showed that 274 bp could be detected when as little as 100 fg of leptospiral genomic DNA was used in the reaction mixture. No amplification of DNA was detected from DNA of Leptospira biflexa serovars patoc and sau paulo, Borrelia burgdorferi, Staphylococcus aureus, Escherichia coli, and Salmonella typhimurium. Amplification of 274-bp target DNA could be detected in DNA samples purified from 500 microliters of blood collected from experimentally infected gerbils 2 days after infection, while antibodies to L. interrogans could be detected by the microscopic agglutination test 7 days after infection. The specificity and high sensitivity of the test provided valuable tools for the early diagnosis of leptospirosis.

Detection and identification of Leptospira interrogans serovars by PCR coupled with restriction endonuclease analysis of amplified DNA

Primers for PCR were selected from a sequenced fragment of clone pL590, which contains a repetitive element present in the genome of Leptospira interrogans serovar hardjo type hardjoprajitno (M. L. Pacciarini, M. L. Savio, S. Tagliabue, and C. Rossi, J. Clin. Microbiol. 30:1243-1249, 1992). A specific DNA fragment was amplified from the genomic DNAs of serovar hardjo type hardjoprajitno and nine serovars also belonging to L. interrogans as a consequence of the spread of the same or a closely related repetitive element within this species (Pacciarini et al., J. Clin. Microbiol. 30:1243-1249, 1992). In addition, specific amplification was obtained from two Leptospira borgpetersenii serovars (tarassovi and hardjo type hardjobovis). Negative PCR results were observed with all of the other Leptospira serovars tested, including nonpathogenic ones (serovars patoc and andamana), another spirochete (Borrelia burgdorferi), bacteria commonly found in biological samples, and swine and bovine cell lines. Direct PCR on biological samples such as kidney samples demonstrated that preliminary isolation and culture of Leptospira cells are not required for efficient detection. Furthermore, digestion of the amplified DNA with the enzymes HinfI and DdeI yielded specific polymorphic patterns, allowing discrimination among the majority of the serovars. These methods were applied to 25 field isolates of serovar pomona, leading to the conclusion that they were suitable for the simple and rapid detection of L. interrogans and for serovar identification.

Physical and genetic map of the Serpulina hyodysenteriae B78T chromosome

A combined physical and genetic map of the Serpulina hyodysenteriae B78T genome was constructed by using pulsed-field gel electrophoresis and DNA blot hybridizations. The S. hyodysenteriae genome is a single circular chromosome about 3.2 Mb in size. The physical map of the chromosome was constructed with the restriction enzymes BssHII, EclXI, NotI, SalI, and SmaI. The physical map was used to constructed a linkage map for genes encoding rRNA, flagellum subunit proteins, DNA gyrase, NADH oxidase, and three distinct hemolysins. Several flaB2-related loci, encoding core flagellum subunit proteins, were detected and are dispersed around the chromosome. The rRNA gene organization in S. hyodysenteriae is unusual. S. hyodysenteriae has one gene each for 5S (rrf), 16S (rrs), and 23S (rrl) rRNAs. The rrf and rrl genes are closely linked (within 5 kb), while the rrs gene is about 860 kb from the other two rRNA genes. Using a probe for the S. hyodysenteriae gyrA gene, we identified a possible location for the chromosomal replication origin. The size and genetic organization of the S. hyodysenteriae chromosome are different from those of previously characterized spirochetes.

[Epidemiological, clinical, biological and developmental aspects of leptospirosis: apropos of 30 cases in Aquitaine]

We have studied retrospectively 30 cases of leptospirosis observed in Aquitaine (South West France) from 1980 till 1992. This review was made in three internal and a nephrology department in Bordeaux hospital. Most cases occurred by indirect contact with infected animals or by occupational exposures. Onset was brutal with fever often associated with painful syndrome and sometimes conjunctival suffusion. Jaundice (70%), acute renal failure (67%), meningitis (50%) and hemorrhagic signs (50%) were among the major visceral manifestations. Diagnosis was always confirmed by micro-agglutination test. Leptospira ictero-hemorrhage was the predominant serogroup found. The outcome was favorable in 22 patients; reversible complications were seen in six cases (five acute renal failure with hemodialysis myocarditis and pulmonary edema in two hemodialysed patients, polyradiculoneuritis). Two patients died (acute respiratory failure and meningo-encephalitis with diffuse hemorrhagic syndrome). The characteristic of our series is the high frequency of hepatorenal syndrome due to the importance of our nephrologist recruitment. Furthermore our study confirm the vital prognostic characters of the pulmonary, renal, hemorrhagic and neurologic complications. No absolute relationship was found between the clinical and laboratory findings and the serotype of leptospira. Penicillin remains the treatment of choice and should be started as soon as possible the avoid the life threatening visceral complications.

Effect of streptomycin treatment on the shedding of and the serologic responses to Leptospira interrogans serovar hardjo subtype hardjobovis in experimentally infected cows

Shedding patterns of and serologic responses to Leptospira interrogans serovar hardjo subtype hardjobovis (L. hardjobovis) have been studied in experimentally infected cows treated with streptomycin in comparison to experimentally infected cows receiving no such treatment. Fourteen cows were experimentally infected with L. hardjobovis, and blood and urine samples were collected weekly for 24 weeks. The microscopic agglutination test (MAT) and enzyme-linked immunosorbent assay (ELISA) were used to determine serologic responses. The polymerase chain reaction (PCR) was used to determine bacterial shedding in urine. Six weeks after infection six cows were treated with the antibiotic streptomycin (25 mg/kg body weight/day); three cows were treated only once, and the remaining three were treated for five consecutive days. After treatment all six cows had lower serologic responses compared to the untreated cows. The treated cows became also PCR-negative two days after the first treatment, whereas the eight untreated cows remained PCR-positive for at least 70 days. Cows that stopped shedding did not resume shedding within the observation period. Since streptomycin treatment reduces the period of shedding, transmission of leptospira via contaminated urine might be prevented by a single treatment of an infected herd.

Comparison of genetic maps for two Leptospira interrogans serovars provides evidence for two chromosomes and intraspecies heterogeneity

Genetic maps were constructed for Leptospira interrogans serovars icterohaemorrhagiae and pomona. Previously we independently constructed physical maps of the genomes for these two serovars. The genomes of both serovars consist of a large replicon (4.4 to 4.6 Mb) and a small replicon (350 kb). Genes were localized on the physical maps by using Southern blot analysis with specific probes. Among the probes used were genes encoding a variety of essential enzymes and genes usually found near bacterial chromosomal replication origins. Most of the essential genes are on the larger replicon of each serovar. However, the smaller replicons of both serovars contain the asd gene. The asd gene encodes aspartate beta-semialdehyde dehydrogenase, an enzyme essential in amino acid and cell wall biosyntheses. The finding that both L. interrogans replicons contain essential genes suggests that both replicons are chromosomes. Comparison of the genetic maps of the larger replicons of the two serovars showed evidence of large rearrangements. These data show that there is considerable intraspecies heterogeneity in L. interrogans.

Characterization of two DNA probes specific for Serpulina hyodysenteriae

Two DNA probes, one 1.1- and one 0.75-kb probe, specific for Serpulina hyodysenteriae were isolated from a genomic library generated from virulent S. hyodysenteriae 5380. These probes are highly specific and react with all S. hyodysenteriae strains tested. Under stringent conditions, the DNA probes did not react with the nonpathogenic species Serpulina innocens or with other species of enteric bacteria, including Escherichia coli. Both probes are able to detect S. hyodysenteriae in colony blot hybridizations, and when applied to fecal specimens, they can detect 10(4) S. hyodysenteriae cells in 0.1 g of seeded fecal matter. Both probes can detect S. hyodysenteriae in fecal specimens from swine with clinical signs of swine dysentery after experimental challenge and from swine from a herd with an acute outbreak of swine dysentery. These probes have application as a diagnostic tool in veterinary microbiology.

Restriction fragment length polymorphisms distinguish Leptospira borgpetersenii serovar hardjo type hardjo-bovis isolates from different geographical locations

Genetic variability among Leptospira borgpetersenii serovar hardjo type hardjo-bovis isolates representing several geographical regions was determined by restriction endonuclease analysis. Five previously unidentified EcoRI digestion patterns and one previously unidentified HhaI digestion pattern were seen with the various isolates. The copy number and genomic distribution of an L. borgpetersenii insertion sequence (IS1533) was determined. Hardjo-bovis isolate 033 (the type strain for hardjo-bovis) contained 40 well dispersed copies of IS1533. IS1533 probes were used to compare hardjo-bovis isolates by DNA blot hybridization analysis. Use of these probes showed the presence of additional genetic heterogeneity among hardjo-bovis isolates, which restriction endonuclease analysis did not show. Pulsed-field gel electrophoretic analysis of DNAs from several isolates suggested that some polymorphisms arose by genomic rearrangements. All hardjo-bovis isolates were categorized into 14 distinct groups on the basis of common hybridization and endonuclease digestion patterns. Most of these groups were isolated from distinct geographical regions, suggesting that several different clonal populations of hardjo-bovis exist.

Scattering of the rRNA genes on the physical map of the circular chromosome of Leptospira interrogans serovar icterohaemorrhagiae

Leptospira interrogans is a pathogenic bacterium with a low G+C content (34 to 39%). The restriction enzymes NotI, AscI, and SrfI cut the chromosome of L. interrogans serovar icterohaemorrhagiae into 13, 3, and 5 fragments separable by one- and two-dimensional pulsed-field gel electrophoresis (PFGE). The genome is composed of a circular 4.6-Mbp chromosome and a 0.35-Mbp extrachromosomal element. A physical map of the chromosome was constructed for NotI, AscI, and SrfI by using single and double digests, or partial NotI digests obtained at random or by cross-protection of NotI sites by FnuDII methylase, and linking clones. rRNA genes were found to be widely scattered on the chromosome.

Pulsed-field gel electrophoresis of NotI digests of leptospiral DNA: a new rapid method of serovar identification

Fingerprints for 72 reference serovar strains of pathogenic Leptospira spp. were obtained by pulsed-field gel electrophoresis (PFGE) following NotI restriction digests of the chromosome. These strains included the serovar reference strains of serogroups Australis, Ballum, Bataviae, Grippotyphosa, Panama, Pomona, and Pyrogenes. Sixty-four serovars could be identified by a unique NotI restriction profile. The remaining serovars were differentiated by chromosomal digestion with SgrAI. These included four serovars from serogroup Australis, two serovars from serogroup Ballum, and two serovars from serogroup Bataviae. Thirteen of 18 recent clinical isolates identified by microagglutination test and cross-adsorption procedure were correctly typed by PFGE. The results indicate that PFGE, which is considerably more rapid than serology, should be useful for identification and epidemiological studies.

Repetitive sequences cloned from Leptospira interrogans serovar hardjo genotype hardjoprajitno and their application to serovar identification

We selected, from a genomic library of Leptospira interrogans serovar hardjo genotype hardjoprajitno, two probes containing repetitive sequences (pL1 and pL590). The hybridization patterns of these probes to DNA isolated from a variety of Leptospira serovars were examined and their ability to detect subtle differences at the genomic organization level was established. We identified the DNA fragments within pL1 and pL590 which are sufficient to yield polymorphic hybridization patterns; these results define the upper size limit of two novel repetitive elements in the Leptospira genome. The pattern and degree of hybridization observed for the serovars tested in this work were used to divide Leptospira spp. into groups which share genetic relatedness; our conclusions are consistent with previous classifications by other authors.

Presence of putative sphingomyelinase genes among members of the family Leptospiraceae

The presence of multiple DNA elements in pathogenic members of the family Leptospiraceae, similar to the sphA sphingomyelinase gene from Leptospira borgpetersenii, was demonstrated by low-stringency hybridization experiments. These DNA elements were designated putative sphingomyelinase genes. Grouping of strains by similarity of hybridization patterns corresponds to the species subdivision of the family Leptospiraceae on the basis of genetic characteristics. Therefore, hybridization with the sphA gene can be used as a taxonomic tool. These hybridization experiments indicate the presence of two groups of genetically related pathogenic Leptospira species.

Molecular cloning and characterization of DNA from human intestinal spirochetes

HindIII cleaved human intestinal spirochete genomic DNA was cloned into the plasmid vector pBluescript. The inserts from three of these clones (pRB.C33, pRB.C47 and pRB.F11) successfully hybridized with DNA from the nine human intestinal spirochetes used in this study. The fourth insert (from clone pRB.A8) failed to hybridize with DNA from two of these isolates (HRM4 and HRM9), and, all four of the inserts hybridized with the M1 strain of swine intestinal spirochete Treponema innocens. Hybridization with DNA from the P18 strain of Treponema hyodysenteriae was observed only for the probe pRB.F11. No hybridization was detected with the human strain of Borrelia burgdorferi. With these probes we were thus able to demonstrate, in southern blot experiments, a restriction site polymorphism among the isolates of the human intestinal spirochetes we tested.

Genome conservation in isolates of Leptospira interrogans

Reference strains for each of the 23 serogroups of Leptospira interrogans yielded different pulsed-field gel electrophoresis patterns of NotI digestion products. This was also the case for the 14 serovars belonging to serogroup Icterohaemorrhagiae (with one exception). The NotI restriction patterns of 45 clinical leptospiral isolates belonging to serovar icterohaemorrhagiae were analyzed and compared with those of type strains. No differences were observed between isolates from countries of different continents, namely, France, French Guiana, New Caledonia, and Tahiti. The pattern was indistinguishable from that of the reference strain of serovar icterohaemorrhagiae.

Physical map of chromosomal and plasmid DNA comprising the genome of Leptospira interrogans

The size and physical structure of the Leptospira interrogans genome was characterized using contour-clamped homogenous electric field (CHEF) gel electrophoresis. The L. interrogans genome is approximately 4750 kb in size and is composed of two molecular species of DNA: a 4400 kb chromosome; and a 350 kb plasmid, pLIN1. A physical map of the chromosome was constructed with the restriction enzymes NotI and SfiI. A physical map of pLIN1 was constructed with ApaI, NotI, Sse83871, SgrAI, and SmaI. Both the L. interrogans chromosome and pLIN1 are circular.

Detection and characterization of leptospiral antigens using a biotin/avidin double-antibody sandwich enzyme-linked immunosorbent assay and immunoblot

A biotin/avidin double-antibody sandwich enzyme-linked immunosorbent assay (ELISA) for the detection of antigens of Leptospira interrogans serovars in experimentally inoculated bovine urine samples was evaluated. Immunoglobulin G (IgG) from rabbits immunized with L. interrogans serovar hardjo type hardjobovis sonicated, whole cell, and formalinized-heated antigen preparations were purified by a protein A-superose column coupled to fast protein liquid chromatography, and evaluated for species specificity in the ELISA. The ELISA using each specific IgG detected as few as 10(4) leptospires of the homologous serovar hardjo diluted in phosphate-buffered saline solution with Tween 20 (PBSS-Tween 20). On immunoblot analysis of proteinase-K-digested whole cell leptospiral preparations, each IgG revealed the presence of bands specific to serovar hardjo, suggesting the presence of serovar-specific epitopes on the lipopolysaccharide molecules. The minimum number of cells of heterologous serovars pomona, grippotyphosa, bratislava, icterohaemorrhagiae and copenhageni detected by each ELISA was greater, ranging from 10(6) to 10(7). The common antigenic determinants observed on immunoblot analysis were different for each specific IgG, except for a major cross-reacting, possibly flagellar, protein doublet at approximately 36-36.5 kDa. Leptospires were equally well detected by the ELISA in both bovine urine and PBSS-Tween 20.

Characterization of serovars of the genus Leptospira by DNA hybridization with hardjobovis and icterohaemorrhagiae recombinant probes with special attention to serogroup sejroe

Recombinant DNA probes derived from genomic libraries of serovars hardjobovis and icterohaemorrhagiae were applied for the characterization of leptospires. Differences in hybridization signals in combination with the banding pattern appear to provide good characteristics for strain typing. The banding patterns were easy to distinguish, since the recombinant DNA probes hybridized with a limited number of fragments. They were also indicative of genomic relationships between serovars. The probes suggested the existence of four subgroups with extensive genomic homology within the serogroup Sejroe. A number of serovars outside the serogroup Sejroe showed genomic homology with these subgroups. Amplification with the polymerase chain reaction showed a correlation with the genomic homologies demonstrated by Southern analysis. Knowledge about genomic relationships between leptospiral strains, as revealed by Southern analysis, may lead to a more rational approach for primer selection for polymerase chain reaction or cloning of particular genes.

Nucleic acid probe characterizes Leptospira interrogans serovars by restriction fragment length polymorphisms

Restriction endonuclease analysis (REA) of genomic DNA can discriminate between many Leptospira interrogans serovars. However, several serovars have similar restriction endonuclease digestion patterns which prohibits accurate identification. This investigation expands previous REA studies of L. interrogans to include serovars in serogroup Tarassovi. Most serovars in this serogroup had characteristic digestion patterns by which they could be identified. However, four of the serovars in this serogroup had similar digestion patterns, thus preventing serovar identification by REA alone. To discriminate between these serovars REA was supplemented with Southern blot analysis. The DNA from each serovar showed similar but unique patterns when hybridized with a probe synthesized from a repetitive sequence element cloned from L. interrogans serovar hardjo type hardjo-bovis. The applicability of this technique to characterize other serogroups was assessed. One hundred sixty six of 190 serovars screened by Southern blot analysis contained sequences which hybridized with the repetitive element probe under conditions of relaxed stringency. These results suggest that Southern blot analysis using this probe will be a valuable supplement for typing L. interrogans.

Borrelia burgdorferi contains repeated DNA sequences that are species specific and plasmid associated

Borrelia burgdorferi, the causative agent of Lyme borreliosis, contains linear and supercoiled circular (SC) plasmids. Because SC plasmids are present in multiple copies, these plasmids were examined for species-specific sequences that could serve as high-copy-number target DNAs for a diagnostic probe. Three EcoRI fragments (4.3, 4.2, and 3.5 kilobase pairs [kb]) that hybridized with multiple DNA fragments from B. burgdorferi were identified and cloned from a SC plasmid-enriched fraction. The 4.2- and 3.5-kb fragments were similar in that they hybridized with each other and with similar-sized EcoRI fragments from two unrelated strains of B. burgdorferi. The 4.3-kb fragment did not hybridize with the other two cloned sequences. Both types of sequences hybridized with most of the SC plasmids in seven B. burgdorferi isolates, whereas only a single 49-kb linear plasmid, found in two of the seven strains tested, hybridized with the cloned sequences. None of the cloned sequences hybridized with chromosomal DNA from B. burgdorferi or with total DNA or SC plasmids from Borrelia hermsii, B. turicatae, B. coriaceae, B. parkeri, or B. anserina. These data indicate that the repeated DNA sequences described in this study appear to be plasmid associated and specific to B. burgdorferi. Heteroduplexes formed from the 4.2- and 3.5-kb fragments showed that hybridizing regions in each fragment comprise a 1.8-kb conserved region that is adjacent to a 1.5-kb region that exhibits greater sequence variability. The sequence divergence seen in the variable region is likely the result of genetic drift and may mean that these regions represent closely related genes that encode functionally similar but antigenically distinct proteins.

Relationship among selected Leptospira interrogans serogroups as determined by nucleic acid hybridization

Leptospiral DNAs from a variety of Leptospira interrogans serogroups of veterinary significance, as well as a nonpathogenic leptospira, were compared by Southern blot hybridization of EcoRI-digested genomic DNA. The serogroups examined could be assigned to one of three groups on the basis of the degree of cross-hybridization between genomic DNAs. Only a few restriction fragments hybridized between the three groups, and most of these were shown to contain ribosomal DNA. The restriction fragment length polymorphism observed among the intergroup hybridizations allowed differentiation among serogroups and, in some cases, serovars. Under the hybridization conditions used, no hybridization was observed between leptospiral DNA and Leptonema, Escherichia coli, or porcine DNA.

Detection of leptospires in urine by polymerase chain reaction

Primers for polymerase chain reaction (PCR) were synthesized from clones derived from a Leptospira hardjo (type hardjobovis) library. One pair of synthetic oligonucleotide primers was selected for further analysis. Under experimental conditions an amplification was obtained with DNA of Leptospira interrogans of some serovars belonging to serogroup sejroe. However, very little or no amplification was observed with DNA from other serovars of this group. No amplification was observed with DNA from other serogroups, other bacteria, or eucaryotic organisms. Cattle urine, seeded with hardjobovis, was processed in several ways and subsequently subjected to PCR. Boiling of the samples or treatment with detergents appeared to be most effective. Urine samples containing fewer than 10 leptospires gave a positive result in the PCR assay. Twenty urine samples obtained from a slaughterhouse or farm cows were investigated using the PCR assay, culture isolation, dot and quick blot hybridization, and serological tests. This comparative study suggests that amplification by PCR may be a valuable method for the detection of leptospires in cattle urine.