Differentiation of Leptospira interrogans isolates by IS1500 hybridization and PCR assays

Genetic basis underlying the serological affinity of leptospiral serovars from serogroups Sejroe, Mini and Hebdomadis

Leptospirosis is a widely distributed zoonosis caused by pathogenic strains of bacteria of the genus Leptospira (Phylum Spirochaetes). Its agents are commonly classified based on their antigenic characteristics into serogroups and serovars, which are relevant for epidemiologic studies and vaccine development. Serological tests are considered laborious and require a specialized infrastructure. Some molecular methods have been proposed to accelerate these procedures, but they still can not replace the immunological tests, thus requiring a further understanding of the genetic basis underlying the serological classification. In this work, we focused on elucidating the genetic factors determinant for the serogroup Sejroe, which is one of the most prevalent serogroups in livestock. For this, we conducted a comparative analysis using >700 leptospiral genomic samples available in the public database. The analysis showed that the genes comprising the rfb locus are the main genetic factors associated with the serological classification. Samples from the serogroup Sejroe have an rfb locus with a conserved gene composition that differs from most other serogroups. Hebdomadis and Mini were the only serogroups whose samples have an rfb locus with similar gene composition to those from serogroup Sejroe, corroborating with the serological affinity shared by them. Finally, we could determine a small region in the rfb locus in which each of those three serogroups can be distinguished by its gene composition. This is the first work that uses an extensive repertoire of genomic data of leptospiral samples to elucidate the molecular basis of the serological classification and open the road to more reliable strategies based on molecular methods for serodiagnosis.

Selected Endemic Zoonoses in Pigs Presenting for Slaughter in Kampala, Uganda

Leptospirosis, brucellosis, and Q fever (coxiellosis) are bacterial zoonoses that cause acute febrile illness in people as well as reproductive losses in pigs. Pig keeping is an increasingly important livelihood to millions of smallholder farmers in Uganda because of exponential increases in demand for pork. The prevalence of leptospirosis and Q fever in pigs is unknown, and the few studies of porcine brucellosis have estimated a range of seroprevalence. Therefore, we undertook a prevalence survey of leptospirosis, brucellosis, and Q fever in pigs using quantitative real-time PCR to determine the potential importance of these zoonoses to the growing pig sector in Uganda. Six hundred forty-nine pigs were sampled in 2015–2016 at an urban pork slaughterhouse. Ten percent of pigs (n = 68) had leptospiral DNA in either their kidney or reproductive tissue. In adjusted analyses, variables predictive of leptospiral status included female sex (odds ratio [OR]: 2.37, P < 0.01) and pigs sampled in March 2016 (OR: 2.23, P = 0.02) and October 2016 (OR: 0.30, P = 0.04). DNA fingerprinting revealed circulation of at least four distinct serovars in these pigs. Brucella spp. and Coxiella burnetii DNA were not detected in any sampled pig. This is the first report of widespread circulation of pathogenic Leptospira spp. in pigs in Uganda, suggesting that leptospirosis likely has a greater impact on the health of pigs than was previously recognized. Pig farmers, pig traders, and slaughterhouse workers may be at greatest occupational risk because of their direct contact with infective leptospires in aborted fetuses, bodily fluids, and other tissues.

Leptospirosis in an asplenic patient -case report

Background

The presentation of clinical leptospirosis has been historically associated with animal workers, slaughterhouse workers and medical veterinarians. This association has shifted to be related to flooding events and outdoor activities; few cases are related to high-risk factors found in immunosuppressed patients. Scarcely a handful of cases have serological evidence of immune response against Leptospira serovar Bratislava representing serogroup Australis, a serovar associated with poor reproductive performance in swine and horses, and recently with cats.

Case presentation

Herein, we describe a rare clinical presentation of disseminated Leptospira infection in an immunosuppressed 65-year-old woman. She was admitted to the emergency room with fever, bacteraemia, bilateral uveitis and pulmonary involvement. The patient denied outdoor activities; she only had wide exposure to faeces and urine from cats living in her home. Her medical history included idiopathic thrombocytopenic purpura (ITP) diagnosed at the age of 18. She did not respond to medical treatment, and a splenectomy was performed. At age 60, she was diagnosed with Chronic Myeloid Leukemia (CML), and was treated with a tyrosine kinase inhibitor (TKI) –Imatinib. The patient voluntarily discontinued the treatment for the last 6 months. After extensive workup, no microorganisms were identified by the commonly used stains in microbiology. The diagnosis was performed through dark-field microscopy, microagglutination test (MAT), Leptospira genus-specific PCR, the IS1500 PCR for identification of pathogenic species, and 16S based sequencing for the genus identification.

Conclusion

Immunosuppressed patients may acquire uncommon infections from ubiquitous microorganisms. In this case, serology evidence of exposure to Leptospira serovar Bratislava by MAT and the presence of the Leptospira genus were identified. It should be on mind for the diagnosis in otherwise healthy patients, and thoroughly search on splenectomised patients exposed to animals. Additionally, this report highlights the usefulness of PCR for diagnosis of this potentially life-threatening illness.

Leptospira spp., a genus in the stage of diversity and genomic data expansion

Leptospirosis is a widespread global zoonotic bacterial disease with a noteworthy human-animal-ecosystem interface. The disease presents different clinical manifestations and a high mortality and morbidity rates in humans and animals throughout the world. Characterization and correct classification of Leptospira isolates is essential for a better understanding the epidemiological properties of the disease. In the last ten years, molecular typing tools have been developed and applied to this field. These methods together with the availability of hundreds of new whole genome sequences that belong to known and new described species are shaping the understanding and structure of the entire genus.

Evidence of interspecies transmission of pathogenic Leptospira between livestock and a domestic cat dwelling in a dairy cattle farm

A domestic cat dwelling in a dairy cattle farm with haematuria was referred for a physical examination. The examination showed no abnormalities therefore complementary exams were performed. Leukocytosis with neutrophilia, monocytosis and hyperproteinaemia were detected. The urine analysis showed a bacterial infection without ultrasound findings. Serological titers to Leptospira interrogans serovar Pomona and Autumnalis were detected. Molecular analysis demonstrated the presence of Leptospira spp. in urine. The findings were consistent with subclinical leptospirosis. The cattle herd had evidence of Leptospira infection. The microbiological exams confirmed the presence of the Leptospira spp. in urine and serum. According to the evidence presented in this study, cats that dwell within a dairy farm could play a role in the Leptospira infection epidemiologically. The importance of feline leptospirosis must be evaluated with leptospirosis control in livestock.

Molecular typing of Leptospira interrogans serovar Hardjo isolates from leptospirosis outbreaks in Brazilian livestock

Background

Leptospirosis is caused by pathogenic spirochetes of the genus Leptospira spp. This zoonotic disease is distributed globally and affects domestic animals, including cattle. Leptospira interrogans serogroup Sejroe serovar Hardjo and Leptospira borgpetersenii serogroup Sejroe serovar Hardjo remain important species associated with this reproductive disease in livestock production. Previous studies on Brazilian livestock have reported that L. interrogans serovar Hardjo is the most prevalent leptospiral agent in this country and is related to clinical signs of leptospirosis, which lead to economic losses in production. Here, we described the isolation of three clinical strains (Norma, Lagoa and Bolivia) obtained from leptospirosis outbreaks that occurred in Minas Gerais state in 1994 and 2008.

Results

Serological and molecular typing using housekeeping (secY and 16SrRNA) and rfb locus (ORF22 and ORF36) genes were applied for the identification and comparative analysis of Leptospira spp. Our results identified the three isolates as L. interrogans serogroup Sejroe serovar Hardjo and confirmed the occurrence of this bacterial strain in Brazilian livestock. Genetic analysis using ORF22 and ORF36 grouped the Leptospira into serogroup Sejroe and subtype Hardjoprajitno. Genetic approaches were also applied to compare distinct serovars of L. interrogans strains by verifying the copy numbers of the IS1500 and IS1533 insertion sequences (ISs). The IS1500 copy number varied among the analyzed L. interrogans strains.

Conclusion

This study provides evidence that L. interrogans serogroup Sejroe serovar Hardjo subtype Hardjoprajitno causes bovine leptospirosis in Brazilian production. The molecular results suggested that rfb locus (ORF22 and ORF36) could improve epidemiological studies by allowing the identification of Leptospira spp. at the serogroup level. Additionally, the IS1500 and IS1533 IS copy number analysis suggested distinct genomic features among closely related leptospiral strains.

Electronic supplementary material

The online version of this article (doi:10.1186/s12917-017-1081-9) contains supplementary material, which is available to authorized users.

PATHOGENIC LEPTOSPIRA SEROVARS IN FREE-LIVING SEA LIONS IN THE GULF OF CALIFORNIA AND ALONG THE BAJA CALIFORNIA COAST OF MEXICO

The California sea lion ( Zalophus californianus ), a permanent inhabitant of the Gulf of California in Mexico, is susceptible to pathogenic Leptospira spp. infection, which can result in hepatic and renal damage and may lead to renal failure and death. During summer 2013, we used the microscopic agglutination test (MAT) to investigate the prevalence of anti-Leptospira antibodies in blood of clinically healthy sea lion pups from seven rookery islands on the Pacific Coast of Baja California (Pacific Ocean) and in the Gulf of California. We also used PCR to examine blood for Leptospira DNA. Isolation of Leptospira in liquid media was unsuccessful. We found higher antibody prevalence in sea lions from the rookery islands in the gulf than in those from the Pacific Coast. Antibodies against 11 serovars were identified in the Gulf of California population; the most frequent reactions were against serovars Bataviae (90%), Pyrogenes (86%), Wolffi (86%), Celledoni (71%), and Pomona (65%). In the Pacific Ocean population, MAT was positive against eight serovars, where Wolffi (88%), Pomona (75%), and Bataviae (70%) were the most frequent. Serum samples agglutinated with more than one Leptospira serovar. The maximum titer was 3,200. Each island had a different serology profile, and islands combined showed a distinct profile for each region. We detected pathogenic Leptospira DNA in 63% of blood samples, but we found no saprophytic Leptospira. Positive PCR results were obtained in blood samples with high and low MAT titers. Together, these two methods enhance the diagnosis and interpretation of sea lion leptospirosis. Our results may be related to human activities or the presence of other reservoirs with which sea lions interact, and they may also be related to sea lion stranding.

Leptospira Serovars for Diagnosis of Leptospirosis in Humans and Animals in Africa: Common Leptospira Isolates and Reservoir Hosts

The burden of leptospirosis in humans and animals in Africa is higher than that reported from other parts of the world. However, the disease is not routinely diagnosed in the continent. One of major factors limiting diagnosis is the poor availability of live isolates of locally circulating Leptospira serovars for inclusion in the antigen panel of the gold standard microscopic agglutination test (MAT) for detecting antibodies against leptospirosis. To gain insight in Leptospira serovars and their natural hosts occurring in Tanzania, concomitantly enabling the improvement of the MAT by inclusion of fresh local isolates, a total of 52 Leptospira isolates were obtained from fresh urine and kidney homogenates, collected between 1996 and 2006 from small mammals, cattle and pigs. Isolates were identified by serogrouping, cross agglutination absorption test (CAAT), and molecular typing. Common Leptospira serovars with their respective animal hosts were: Sokoine (cattle and rodents); Kenya (rodents and shrews); Mwogolo (rodents); Lora (rodents); Qunjian (rodent); serogroup Grippotyphosa (cattle); and an unknown serogroup from pigs. Inclusion of local serovars particularly serovar Sokoine in MAT revealed a 10-fold increase in leptospirosis prevalence in Tanzania from 1.9% to 16.9% in rodents and 0.26% to 10.75% in humans. This indicates that local serovars are useful for diagnosis of human and animal leptospirosis in Tanzania and other African countries.

Isolation of Leptospira interrogans serovar Hardjoprajitno from a calf with clinical leptospirosis in Chile

BACKGROUND

Although Leptospira isolation has been reported in Chilean cattle, only serological evidence of serovar Hardjo bovis infection has been routinely reported. The present report provides characterization of the pathological presentation and etiology of a clinical case of leptospirosis in a calf from the Los Rios Region in Chile.

CASE PRESENTATION

In a dairy herd in southern Chile, 11 of 130 calves died after presenting signs such as depression and red-tinged urine. One of these calves, a female of eight months, was necropsied, and all the pathological findings were consistent with Leptospira infection. A urine sample was submitted to conventional bacteriological analysis together with highly specific molecular biology typing tools, in order to unravel the specific Leptospira specie and serovar associated with this clinical case. A significant finding of this study was that the obtained isolate was confirmed by PCR as L. interrogans, its VNTR profile properly matching with L. interrogans Hardjoprajitno as well as its specific genomic identity revealed by secY gen.

CONCLUSION

Leptospira interrogans serovar Hardjoprajitno was associated with the investigated calf clinical case. This information adds to the value of serologic results commonly reported, which encourage vaccination improvements to match circulating strains. In addition, this finding represents the first case report of this serovar in Chilean cattle.

Detection of asymptomatic renal Leptospira infection in abattoir slaughtered cattle in southeastern Georgia, United States

Objectives:

Leptospirosis is one of the most widespread zoonotic infectious diseases affecting humans and animals. Several animal species, including cattle, can act as potential asymptomatic carriers facilitating zoonotic transmission of Leptospira. This study was conducted to assess the occurrence of asymptomatic renal Leptospira carriers among cattle slaughtered in southeastern Georgia, United States.

Methods:

A battery of diagnostic tests, including dark field microscopy, direct fluorescent antibody staining, polymerase chain reaction, and culture, were performed on a set of bovine kidneys (n = 37) collected from an abattoir in southeastern Georgia, United States. Virulence of a field isolate obtained from this study was tested in a hamster experimental model.

Results:

Motile spirochete-like structures were observed by dark field microscopy in 23 (59%) out of 37 kidney samples tested. In all, 29 samples (78%) were positive by direct fluorescent antibody staining. Only 11 (29.7%) samples by polymerase chain reaction and 3 (8.1%) by culture were positive for Leptospira sp. The isolates obtained by culture were confirmed as Leptospira borgpetersenii. Hamsters experimentally infected with one of the Leptospira field isolates obtained from this study did not show clinical signs but developed renal infection with interstitial nephritis and tubular necrosis.

Conclusions:

This study confirms that asymptomatic Leptospira renal infection is present among cattle in the region. Our findings underscore the need for future studies to assess the potential environmental contamination and transmission to humans in contact with infected cattle.

Analysis of multilocus sequence typing for identification of Leptospira isolates in Brazil

A collection of 101 Leptospira isolates was tested by multilocus sequence typing (MLST) and by traditional serotyping. MLST divided the isolates into 4 sequence types (STs), while serotyping classified them into 6 serogroups. Two isolates failed to generate products for some genes by MLST. MLST was less discriminatory than serotyping for uncommonly occurring isolates from humans in Brazil.

Insertion sequences as highly resolutive genomic markers for sequence type 1 Legionella pneumophila Paris

The causative agent of legionellosis, Legionella pneumophila, colonizes all natural and human-made water networks, thus constituting the source of contaminated aerosols responsible for airborne human infections. Efficient control of infections, especially during epidemics, necessitates the fastest and most resolutive identification possible of the bacterial source for subsequent disinfection of reservoirs. We thus compared recognized typing approaches for Legionella with a method based on characterization of insertion sequence (IS) content. A total of 86 clinical or environmental isolates of L. pneumophila, including 84 Paris isolates, sampled from 25 clinical investigations in France between 2001 and 2007, were obtained from the Legionella National Reference Center. All strains were typed by monoclonal antibody subgrouping, sequence-based typing, pulsed-field gel electrophoresis, and restriction fragment length polymorphism based on the presence or absence of IS elements. We identified six different types of IS elements in L. pneumophila Paris and used them as genomic markers in hybridization experiments. One IS type, ISLpn11, revealed a high discriminatory power. Simpson's index of discrimination, calculated from the distribution of IS elements, was higher than that obtained with the other typing methods used for L. pneumophila Paris. Moreover, specific ISLpn11 copies were found only in strains isolated from particular cities. In more than half of the cases, each clinical isolate had an ISLpn11 profile that was recovered in at least one environmental isolate from the same geographical location, suggesting that our method could identify the infection source. Phylogenetic analysis suggests a clonal expansion for the L. pneumophila Paris strain.

Development of O-antigen gene cluster-specific PCRs for rapid typing six epidemic serogroups of Leptospira in China

Background

Leptospira is the causative agent of leptospirosis. The O-antigen is the distal part of the lipopolysaccharide, which is a key component of outer membrane of Gram-negative bacteria and confers serological specificity. The epidemiology and clinical characteristics of leptospirosis are relative to the serology based taxonomic unit. Identification of Leptospira strains by serotyping is laborious and has several drawbacks.

Results

In this study, the O-antigen gene clusters of four epidemic Leptospira serogroups (serogroup Canicola, Autumnalis, Grippotyphosa and Hebdomadis) in China were sequenced and all genes were predicted in silico. Adding published sequences of two serogroups, Icterohaemorrhagiae (strain Lai and Fiocruz L1-130) and Sejroe (strain JB197 and L550), we identified six O-antigen-specific genes for six epidemic serogroups in China. PCR assays using these genes were developed and tested on 75 reference strains and 40 clinical isolates.

Conclusion

The results show that the PCR-based assays can be reliable and alternative means for rapid typing of these six serogroups of Leptospira.

Variable nucleotide tandem-repeat analysis revealing a unique group of Leptospira interrogans serovar Pomona isolates associated with California sea lions

Leptospira interrogans serovar Pomona isolates were compared by variable nucleotide tandem-repeat typing. Most cattle isolates grouped together, while isolates from pigs and wildlife were distributed across several groups. Significantly, California sea lion isolates formed a unique group, providing evidence that these animals are maintenance hosts of serovar Pomona.

Geographical dissemination of Leptospira interrogans serovar Pomona during seasonal migration of California sea lions

Leptospirosis is one of the most widespread bacterial zoonoses in the world and affects most mammalian species. Although leptospirosis is well documented and characterized in terrestrial species, less information is available regarding the distribution and impact of leptospirosis in marine mammals. Additionally, the role of animal migrations on the geographical spread of leptospirosis has not been reported. Periodic epizootic outbreaks of acute leptospirosis among California sea lions (Zalophus californianus) have been reported since 1971. In this study, we collected samples from California sea lions stranded along the Pacific coast of North America during the most recent epidemic in 2004, and maintained leptospirosis surveillance of the California sea lion population along the California coast through 2007. Several isolates of Leptospira interrogans serovar Pomona were obtained from kidney and urine samples collected during this study, a finding consistent with serological evidence that California sea lions are persistently exposed to this leptospiral serovar. Combined, these data support a model whereby California sea lions are maintenance hosts for L. interrogans serovar Pomona, yet periodically undergo outbreaks of acute infection. During the 2004 outbreak, the incidence of new leptospirosis cases among California sea lions coincided with the seasonal movement of male sea lions from rookeries along the coast of central and southern California north as far as British Columbia. These data show that seasonal animal movement contributes to the distribution of leptospirosis across a large geographical region.

Detection of pathogenic Leptospira bacteria in pinniped populations via PCR and identification of a source of transmission for zoonotic leptospirosis in the marine environment

Leptospirosis, caused by the spirochete Leptospira, is a geographically widespread disease that affects a broad range of mammals, including marine mammals. Among pinniped populations, periodic epizootics of leptospirosis are responsible for significant die-offs. Along the west coast of North America, the most recent leptospirosis epizootic occurred in 2004, during which samples were collected from cases ranging from California to British Columbia. The primary objective of this study was to use this well-defined sample set to determine the feasibility of using PCR techniques to diagnose Leptospira infection among pinniped populations in comparison with diagnostic methodologies commonly used for marine mammals. Successful amplification was achieved from a variety of samples, including freshly collected urine, urine stored at -80 degrees C for less than 6 months, and kidney (freshly collected, frozen, and decomposed), as well as feces- and urine-contaminated sand collected in the vicinity of a live-stranded animal. Pathological examination of tissue collected from Leptospira-infected animals revealed the presence of leptospiral antigen in the kidneys. The use of species-specific primer pairs revealed a pattern of host specificity for Leptospira interrogans in sea lions and Leptospira kirschneri in elephant seals. These studies indicate PCR is a sensitive and specific diagnostic tool for the detection of Leptospira infection in pinnipeds and reveal a potential source for epizootic, enzootic, and zoonotic spread of leptospirosis in a marine environment.

Multiple-locus variable-number tandem repeat analysis (MLVA) of Leptospira interrogans serovar Pomona from Argentina reveals four new genotypes

Outbreaks of leptospirosis occur regularly in Argentina, but little is known about their epidemiological relationships. We have analyzed the genetic diversity of a collection of 16 strains of Leptospira interrogans serovar Pomona isolated from animals and humans in Argentina during the past 45 years. Genotyping was performed by multiple-locus variable-number tandem repeat analysis (MLVA) using the loci VNTR4, VNTR7, VNTR9, VNTR10, VNTR19, VNTR23 and VNTR31, as described by Majed et al. [Identification of variable-number tandem-repeat loci in Leptospira interrogans sensu stricto. J Clin Microbiol 2005;43:539-45]. Clustering analysis revealed four new distinct MLVA genotypes, with a dominant one. Strains with this genotype were consistently isolated since 1960 to the present, mainly from cows and pigs, but also from humans, representing 75% of the total strains studied. These strains coexisted temporally and geographically with isolates presenting the other new genotypes. VNTR4 locus, with four different alleles, presented the highest diversity between the VNTR loci analyzed. MLVA patterns obtained will be useful for future diagnostic and epidemiological tracing analysis.

Assessment of Southern blot ribotyping for differentiation of Leptospira strains isolated from field rats

A Southern blot ribotyping based on EcoRV and HindIII digestion with two 16S and 23S rDNA probes for differentiating 27 Leptospira serovars was developed. The results between ribotyping and serotyping among 40 leptospiral strains isolated from field rats trapped in the northeastern region of Thailand during 1999-2000, were compared. A combination of Southern blot ribotyping, using EcoRV or HindIII digestion with both 16S and 23S rDNA as the probes, successfully typed 27 Leptospira serovars into 24 ribotypes with the discriminatory index (D) values of 0.99. The 16S- and 23S-EcoRV ribopatterns produced 17 and 9 profiles, respectively, with D values of 0.95 and 0.63, respectively. Ribopatterns of HindIII from both specific probes yielded 17 patterns. The D values of 16S- and 23S-HindIII ribopatterns were 0.94 and 0.93, respectively. With EcoRV digestion, the 16S rDNA probe was more discriminative than the 23S rDNA probe for differentiating Leptospira serovars. Moreover, the 16S-EcoRV (11 profiles), 16S-HindIII (11 profiles), and 23S-HindIII (10 profiles) ribopatterns produced higher numbers of distinct and unique profiles than the 23S-EcoRV (5 profiles). The results showed 100% concordance between ribotyping and serotyping, leading to all 40 isolates being successfully typed. The current study revealed that ribotyping as a quick and powerful tool for differentiating Leptospira serovars, has potential value in epidemiological studies.

Molecular characterization of Leptospira sp. strains isolated from human subjects in São Paulo, Brazil using a polymerase chain reaction-based assay: a public health tool

A polymerase chain reaction (PCR)-based assay which amplifies repetitive DNA elements present within bacterial genomes was used to characterize and differentiate Leptospira sp. Thirty-five strains from a reference culture collection and 18 clinical isolates which had been previously analyzed by cross agglutinin absorption test (CAAT) were evaluated by this technique. PCR results from analysis of the reference culture collection showed no bands corresponding to serogroups Australis, Autumnalis, Bataviae, Celledoni, Cynopteri, Djasiman, Panama, Pomona, Pyrogenes, and Tarassovi. However, the PCR method was able to clearly discriminate the serogroups Andamana, Ballum, Canicola, Grippotyphosa, Hebdomadis, Icterohaemorrhagiae, Javanica, Sejroe, Semaranga, and Shermani. Clinical isolates previously characterized by CAAT as serovar Copenhageni, serovar Castellonis, and as serovar Canicola were in agreement with PCR results. The clinical isolate previously characterized as serovar Pomona was not differentiated by PCR. Forty additional clinical isolates from patients with leptospirosis obtained in São Paulo, Brazil were also evaluated by this PCR method. Thirty-nine of these were determined to belong to serogroup Icterohaemorrhagiae (97.5%) and one to serogroup Sejroe (2.5%). These results demonstrate that the PCR method described in this study has utility for rapid typing of Leptospira sp. at the serogroup level and can be used in epidemiological survey.

Serological evidence of the persistence of infection with Leptospira interrogans serovar Hardjo in cattle in Mongolia

Serum samples were collected randomly from Mongol breed cattle in three geographically distinct provinces of Mongolia. Antibodies specific to Leptospira interrogans serovar Hardjo were detected by microscopic agglutination test (MAT) at titres of 100 or more in 80.4% (86/107) of the samples from Dornod Province, but in only 28.9% (13/45) in Arkhangai and 23.5% (12/51) in Khuvsgul Provinces, respectively. Treatment of 9 serum samples from Dornod, positive to serovar Hardjo in MAT and negative in the homologous immunoglobulin G (IgG) enzyme-linked immunosorbent assay (ELISA), with 2-mercaptoethanol (2-ME) indicated that those animals were recently infected.

New Leptospira serovar Sokoine of serogroup Icterohaemorrhagiae from cattle in Tanzania

The prevalence of leptospirosis is generally high in domestic animals and rodents in Tanzania. Identification of Leptospira isolates from cattle was carried out to establish prevalent Leptospira serovars. Serological typing was done based on monoclonal antibodies and the standard cross-agglutination absorption test. Molecular typing involved pathogenic- and saprophytic-specific PCRs and a PCR specifically amplifying DNA from the species Leptospira kirschneri. DNA fingerprinting with primers derived from sequences of insertion elements IS1500 and IS1533 was carried out. Both serological and molecular characterization indicated that one of the Leptospira isolates, coded RM1, represents a new serovar of the species L. kirschneri of serogroup Icterohaemorrhagiae. The serovar name Sokoine is proposed for this new Leptospira isolate.

A clone of Leptospira interrogans sensu stricto is the major cause of leptospirosis in the archipelago of Andaman and Nicobar Islands, India

AIMS

Andaman and Nicobar Islands in India has a century long history of human leptospirosis. Several isolates have been recovered over the years from different locations. The present study was undertaken to understand the clonal relationship between all these pathogenic leptospires recovered from these islands.

METHODS AND RESULTS

Arbitrarily primed polymerase chain reaction (AP-PCR) was employed to genetically characterize 40 isolates recovered during 1995--2001 and their fingerprints were compared with those of 26 reference strains of known genetic and serological affinities. Sequences of PCR-amplified products from representative isolates were compared with those of different strains belonging to seven genospecies. AP-PCR fingerprints revealed that 32 of the 40 isolates were clonal in nature and fingerprints of all the isolates matched with known reference strains of pathogenic Leptospira interrogans sensu stricto. Comparison of sequence data of PCR amplified products of reference strains and isolates also corroborated these findings.

CONCLUSIONS

The study revealed that 80% of the isolates recovered from these islands were clonal in nature and all the isolates taken in the study belonged to Leptospira interrogans sensu stricto.

SIGNIFICANCE AND IMPACT OF THE STUDY

An extension of the study in animal population would help in understanding the transmission dynamics of this commonly circulating clone in these islands, which in turn might help in effective control of this public health problem.

Experimental canine leptospirosis caused byLeptospira interrogansserovars pomona and bratislava

OBJECTIVE

To evaluate gross, histopathologic, and serum biochemical findings caused by Leptospira interrogans serovars pomona and bratislava inoculated in dogs.

ANIMALS

Twenty-seven 8-week-old female Beagles.

PROCEDURE

Dogs were randomly assigned to challenge or control groups. Challenge groups were conjunctivally inoculated on 3 successive days with 5 x 10(7) L interrogans serovar pomona (n = 12) or serovar bratislava (11). Clinical signs were recorded throughout the experiment, and clinical pathology assays, bacteriologic culture, and necropsies (6 or 7 dogs necropsied at each time point) were done on postinoculation day (PID) 7, 10, 14, and 20.

RESULTS

Infection could not be confirmed in any serovar bratislava-inoculated dog, and control dogs remained healthy throughout the experiment. Positive culture and fluorescent antibody test results were confirmed in 11 of 12 serovar pomona-inoculated dogs. Fever and lethargy starting at PID 7 were the most common clinical signs in serovar pomona-infected dogs. On day 10, gross lesions included multifocal renal and pulmonary hemorrhage and perirenal edema. Serovar pomona-inoculated dogs had histopathologic lesions including hepatitis, interstitial nephritis, and pneumonia at PID 7, 10, 14, and 20. Increases in BUN, anion gap, and bilirubin concentration occurred on PID 10, 14, and 20. Platelet counts in dogs with positive results of bacteriologic culture were decreased from baseline values on PID 10, 12, and 14.

CONCLUSIONS AND CLINICAL RELEVANCE

Conjunctival inoculation with L interrogans serovar pomona resulted in a high rate of infection with concomitant hemorrhagic and inflammatory lesions of the kidneys, liver, and lungs.

Characterization of IS1501 mutants of Leptospira interrogans serovar pomona

Leptospira interrogans is a diverse species in which individual serovars have distinctive restriction fragment length polymorphisms that are useful in strain identification. Many of these polymorphisms can be detected using hybridization probes derived from insertion sequences; an observation that suggests these IS elements are active and can transpose in L. interrogans. Two spontaneous mutants of L. interrogans serovar Pomona strain RZ11 were isolated by immune selection and characterized. Changes in the size and antigenicity of LPS from these mutants were detected. Genetic analysis showed that both mutants have additional copies of an IS3-like element, designated IS1501, that are not present in the parental strain. One mutant, GT211, has a single additional copy of IS1501, whereas the other mutant, GT210 has three additional copies of IS1501 relative to strain RZ11. IS1501 transposition generated 3-bp direct repeats from target sequences flanking the insertion site. RT-PCR analysis of transcripts at altered loci showed IS1501 transcripts extended into adjacent sequences. These data are the first to show spontaneous transposition of an endogenous Leptospira insertion sequence, and suggest that IS1501 may be capable of gene activation.

FREQÜÊNCIA SOROLÓGICA ANTILEPTOSPÍRICA EM CÃES: SUA CORRELAÇÃO COM ROEDORES E FATORES AMBIENTAIS, EM ÁREA TERRITORIAL URBANA

RESUMO Com o objetivo de conhecer-se a freqüência sorológica antileptospírica em cães e sua correlação com roedores e fatores ambientais, na área territorial urbana de 32 km2 do Município de Botucatu, SP, colheram-se 1.000 amostras de sangue de cães, em 20 postos homogeneamente distribuídos. A prova diagnóstica utilizada foi a de soroaglutinação microscópica (SAM), com 24 sorovares de Leptospira spp. Das 1.000 amostras submetidas à prova, 17,9% foram reagentes. Os cães reagentes que tiveram contato com roedores (23,68%) mostraram-se significativos (p < 0,05) em relação aos reagentes que não tiveram contato (15,37%). Na correlação entre animais de residências ligadas (18,10%) ou não ligadas (13,63%) à rede pública de esgoto e a soropositividade, não se observou significância estatística (p > 0,05). Ocorreram reações para 20 sorovares, com maior importância para: castellonis (28,68%), autumnalis (19,12%), pyrogenes (17,65%), icterohaemorrhagiae (11,03%) e canicol (9,56%).

Enzyme-linked immunosorbent assay for the detection of canine Leptospira antibodies using recombinant OmpL1 protein

OmpL1 is a 31-kDa outer membrane protein characterized in 1993 and known to be expressed only in pathogenic Leptospira spp. Recombinant OmpL1 (GST-rOmpL1) was expressed for use as an ELISA antigen for the detection of anti-Leptospira antibodies. In immunoblot analysis, the protein reacted with sera of dogs infected with three different serotypes of Leptospira interrogans, while did not react with sera of dogs both uninfected negative controls and infected with Borrelia burgdorferi, which is closely related to Leptospira spp. Moreover, in ELISA using GST-rOmpL1, the optical density (O.D.) values from the positive controls were very high (1.125 +/- 0.549). In contrast, the O.D. values from clinically healthy dogs and dogs with diseases other than leptospirosis were very low (0.109 +/- 0.046 and 0.089 +/- 0.046, respectively). These data suggest that the detection of anti-Leptospira antibodies by ELISA using the GST-rOmpL1 protein can be applied for diagnosis of canine leptospirosis.

A 22-mer primer enhances discriminatory power of AP-PCR fingerprinting technique in characterization of leptospires

OBJECTIVES

To evaluate the discriminatory power and usefulness of arbitrarily primed-polymerase chain reaction (AP-PCR) characterization of leptospires with M16 primer.

METHODS

AP-PCR fingerprints of 20 reference strains of Leptospira representing 20 different serovars belonging to seven genospecies (Leptospira interrogans, 11; L. noguchii, 2; L. borgpetersenii, 1; L. santarosai, 2; L. biflexa, 2; L. kirschneri, 1; L. weilii, 1) were generated by employing M16 primer. Fingerprints generated with this primer were compared with those generated with two other commonly used primers PB1, and L10. An attempt was also made to type 20 leptospiral isolates with the M16 primer.

RESULTS AND CONCLUSION

Fingerprints with M16 primer could not only differentiate between strains of different genospecies, but also between strains of the same genospecies belonging to different serovars. While two commonly used primers (PB1 and L10) failed to discriminate between some of the different serovars belonging to the same genospecies, this primer was able to generate discriminatory fingerprints for all strains tested. All 20 Leptospira isolates, recovered from patients in Andaman Islands, could also be typed by fingerprints generated with the M16 primer. The discriminatory power of M16 primer adds more specificity to the rapidity of this system of characterization and can be used as an excellent tool in epidemiological studies on Leptospira.

Three cases of leptospirosis requiring intensive care

Presented here are three cases of severe leptospirosis, one icteric and two pulmonary hemorrhagic, that occurred in patients in Styria, Austria. Leptospirosis presents with protean and nonspecific manifestations. Thus, as these three cases emphasize, the key to diagnosis may be maintaining a high index of suspicion for the disease in previously healthy febrile patients with septic shock, acute renal and hepatic dysfunction and respiratory failure requiring intensive care.

Serological and molecular characterization of leptospira serovar Kenya from captive African giant pouched rats (Cricetomys gambianus) from Morogoro Tanzania

Two identical leptospiral isolates coded Sh9 and Sh25 obtained from the urine of captive African giant pouched rats (Cricetomys gambianus), destined for use as biodetector of antipersonnel landmines were typed as serovar Kenya using cross-agglutination absorption test and DNA fingerprinting with the insertion element sequences IS1533 and IS1500 derived primers. The two isolates were previously characterized using cultural and serological-microagglutination test as pathogenic leptospires of the serogroup Ballum, closely related to serovars Kenya and Peru. To our knowledge, this is the first reported in-depth characterization of leptospira isolates from Tanzania.

Molecular evolution and mosaicism of leptospiral outer membrane proteins involves horizontal DNA transfer

Leptospires belong to a genus of parasitic bacterial spirochetes that have adapted to a broad range of mammalian hosts. Mechanisms of leptospiral molecular evolution were explored by sequence analysis of four genes shared by 38 strains belonging to the core group of pathogenic Leptospira species: L. interrogans, L. kirschneri, L. noguchii, L. borgpetersenii, L. santarosai, and L. weilii. The 16S rRNA and lipL32 genes were highly conserved, and the lipL41 and ompL1 genes were significantly more variable. Synonymous substitutions are distributed throughout the ompL1 gene, whereas nonsynonymous substitutions are clustered in four variable regions encoding surface loops. While phylogenetic trees for the 16S, lipL32, and lipL41 genes were relatively stable, 8 of 38 (20%) ompL1 sequences had mosaic compositions consistent with horizontal transfer of DNA between related bacterial species. A novel Bayesian multiple change point model was used to identify the most likely sites of recombination and to determine the phylogenetic relatedness of the segments of the mosaic ompL1 genes. Segments of the mosaic ompL1 genes encoding two of the surface-exposed loops were likely acquired by horizontal transfer from a peregrine allele of unknown ancestry. Identification of the most likely sites of recombination with the Bayesian multiple change point model, an approach which has not previously been applied to prokaryotic gene sequence analysis, serves as a model for future studies of recombination in molecular evolution of genes.

Leptospira interrogans serovar Valbuzzi: a cause of severe pulmonary haemorrhages in the Andaman Islands

Outbreaks of leptospirosis that present with predominant pulmonary signs and symptoms have been occurring in the Andaman Islands since the late 1980s. Before this, pulmonary haemorrhage had not been observed as a common complication of leptospirosis in India. During an outbreak on North Andaman in 1997, four leptospire isolates were obtained from blood of a fatal case and three other patients who recovered. These isolates were characterized using serological and molecular techniques. Cross-agglutination absorption tests and microscopic agglutination tests using mAbs were used for serological characterization. Genetic typing was done using DNA sequencing of PCR products. Serologically, the isolates were closely related to strain Valbuzzi serovar Valbuzzi of serogroup Grippotyphosa. The sequences of PCR products from these isolates were compared with those of 45 strains belonging to seven species. The isolates showed 97.5-100 % sequence similarity to reference strains belonging to Leptospira interrogans, indicating that the isolates belong to L. interrogans. Serogroups Icterohaemorrhagiae and Australis have been incriminated as the cause of pulmonary haemorrhage in China, Korea and Australia. The four isolates characterized in the present study were obtained from patients with similar symptoms. However, they belonged to serovar Valbuzzi of serogroup Grippotyphosa, indicating that serogroups other than Icterohaemorrhagiae and Australis can also cause pulmonary haemorrhage.

Update on molecular techniques for diagnostic testing of infectious disease

The era of diagnostic molecular biology has arrived for small animal clinicians, and it is a near certainty that assays such as the PCR and RT-PCR will become more widely available for a wider array of infectious agents. Already there is an extensive list of infectious diseases of dogs and cats that have been investigated with molecular tools. A partial list is included in box 1. An understanding of the advantages and disadvantages of the molecular techniques and some of the questions these techniques can answer for clinicians can serve practitioners well in their approach to the diagnosis of infectious diseases in dogs and cats. It is likely that additional applications of these tools to small animal medicine will become apparent as investigators use and refine them for their research purposes, or as new uses emerge from human medical applications. Clinicians also are likely to reap the benefits of this knowledge. Because samples often are acquired easily from clinical patients in most practice settings, access to these tools puts all clinicians in the group of discoverers of new, or variations of, infectious diseases and their clinical manifestations.

Comparison of polymerase chain reaction assay, bacteriologic culture, and serologic testing in assessment of prevalence of urinary shedding of leptospires in dogs

OBJECTIVE

To compare results of polymerase chain reaction (PCR) testing of urine samples, serologic testing, and bacteriologic culture of urine to determine prevalence of urinary shedding of leptospires in dogs.

DESIGN

Serial case study.

ANIMALS

500 dogs evaluated serially without regard to health status.

PROCEDURE

Urine samples were examined via PCR assay and bacteriologic culture for leptospires. Blood samples were analyzed for antibodies against serovars canicola, bratislava, pomona, icterohemorrhagiae, grippotyphosa, and hardjo.

RESULTS

Titers > or = 1:100 against at least 1 serovar were detected in 104 (20.8%) dogs, and titers > or = 1:400 were detected in 41 (8.2%) dogs. High titers were detected most commonly to serovar grippotyphosa, followed by icterohemorrhagiae, canicola, pomona, bratislava, and hardjo. High titers to > 1 serovar were detected in 14 dogs. A positive PCR assay result was obtained in 41 (8.2%) dogs, only 9 of which had a titer > or = 1:100. Leptospires were not cultured from the urine of any dog. Only 4 dogs had clinical leptospirosis. Overall disease prevalence was 0.8% for the 6-month evaluation period. Compared with PCR assay, serologic testing for predicting shedding had a sensitivity of 22%, specificity of 79%, positive predictive value of 9%, and negative predictive value of 92%.

CONCLUSIONS AND CLINICAL RELEVANCE

Irrespective of health status, 8.2% of dogs were shedding pathogenic leptospires. Serologic testing was a poor predictor of urinary shedding. Clinically normal dogs that shed leptospires may pose a zoonotic risk to their owners.

Clinical application of a polymerase chain reaction assay for diagnosis of leptospirosis in dogs

OBJECTIVE

To evaluate the use of a polymerase chain reaction (PCR) assay on urine samples for diagnosis of leptospirosis in dogs.

DESIGN

Prospective case study.

ANIMALS

132 dogs with clinical signs suggestive of leptospirosis and 13 healthy dogs.

PROCEDURE

PCR testing was performed on urine samples to detect leptospiral DNA; results were compared with results of conventional criteria for the diagnosis of leptospirosis.

RESULTS

Leptospirosis was diagnosed in 8 dogs via established criteria; all these dogs had positive results of PCR assay, including 1 dog with positive results before seroconversion developed. A positive PCR assay result was also obtained in 16 dogs that did not have a confirmed diagnosis of leptospirosis. In the 8 dogs that had a confirmed diagnosis of leptospirosis, serovars pomona (n = 3 dogs), grippotyphosa (2), canicola (2), and bratislava (1) were identified serologically. The remaining 121 dogs all had a diagnosis other than leptospirosis or were healthy. For PCR testing on urine, sensitivity was 100%, specificity was 88.3%, positive predictive value was 33%, and negative predictive value was 100%.

CONCLUSIONS AND CLINICAL RELEVANCE

Positive PCR test results prior to seroconversion may have value in establishing an early diagnosis. Positive results in dogs that had signs consistent with leptospirosis despite failing to meet established criteria for leptospirosis raise questions regarding the sensitivity of serologic testing in diagnosis of leptospirosis. Serovars pomona, grippotyphosa, and canicola were most common.

Pulmonary complications of leptospirosis

Leptospirosis is a worldwide disease. In this time of globalization knowledge about leptospirosis is important. Although pulmonary involvement has an incidence varying from 20% to 70% and its exteriorization may vary from mild to severe, The severe form appears to be becoming more prevalent (at least in Brazil) and may be associated with higher mortality.

Leptospirosis

Leptospirosis is a globally important zoonotic disease that affects humans on all continents, in both urban and rural contexts, and in temperate and tropical climes. Leptospirosis is a disease of the environment; transmission depends on interactions between humans and mammalian reservoir hosts. A variety of infectious diseases that present as undifferentiated febrile syndromes, such as malaria, dengue and influenza, as well as viral hemorrhagic fevers can mimic leptospirosis. The importance of pulmonary hemorrhage as a lethal complication of leptospirosis has become more widely recognized. In contrast to textbook dogma, population-based studies indicate that there is a poor correlation between infecting leptospiral strain and clinical expression of disease. Genetic transformation of a Leptospira sp. has now been reported, which should allow for detailed analysis of a variety of leptospiral genes. Publication of the whole Leptospira genome is eagerly awaited. Following recent reports of a new, highly effective conjugate typhoid vaccine, new efforts to find leptospirosis vaccines should include the manufacture and testing of conjugate leptospiral lipopolysaccharide vaccines. Recent advances, particularly in epidemiology, molecular genetics and pathogenesis, are placing leptospirosis at the cutting edge of biomedical science.

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.

Identification of new repetitive element in Leptospira interrogans serovar copenhageni and its application to PCR-based differentiation of Leptospira serogroups

A new repetitive DNA element was identified in an isolate of Leptospira interrogans serovar copenhageni from a patient in Salvador, Brazil. A Sau3A genomic library from this strain was constructed and screened for repetitive DNA elements. An insert of 438 bp (Rep1) from one library clone hybridized to multiple chromosomal DNA fragments resolved electrophoretically after digestion with BamHI, HindIII, and MfeI. A single oligonucleotide primer, designated iRepl, was designed to generate multiple PCR amplicons of various electrophoretic mobilities in a PCR typing method. The method distinguished strains belonging to the eight pathogenic and three saprophytic species of the genus Leptospira. Clinical isolates obtained during urban epidemics between 1996 and 1998 in Salvador, Brazil, were analyzed by this PCR method. Although the iRep1 primer was unable to discriminate strains among L. interrogans serovar copenhageni isolates, it was able to differentiate strains belonging to different species and serogroups of Leptospira identified in Salvador. This PCR-based method may provide a faster and less expensive alternative to serologic tests used in reference laboratories.

Leptospirosis in Latin America

Leptospirosis is a common disease in Latin America. Transmission to humans occurs by contact with water or soil contaminated with the urine of rodents, dogs, or livestock. Pathogenesis is still poorly understood, and bacterial toxin or virulence factors are probably responsible for many features of the disease. The anicteric form is the most frequent presentation, and its clinical picture resembles influenza or other acute febrile diseases. Icterohemorrhagic leptospirosis, or Weil's syndrome, represents the severe form of the disease. Its clinical picture is similar to bacterial sepsis and multiple organ involvement occurs, mainly in kidneys and lungs, and causes great morbidity and mortality. Death is often related to multiple organ failure and pulmonary hemorrhages. Diagnosis is based on serology or blood, cerebrospinal fluid and urine cultures in specific media. Treatment involves a combination of antibiotics and supportive measures.

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.