Culture, Serotyping, and Whole-Genome Sequencing: Strengthening Leptospirosis Surveillance in Veterinary Practice

Routine diagnostic tests are essential for confirming leptospirosis in individual animals, but they do not always provide the detailed information needed to understand how the disease is circulating within animal populations. For surveillance, outbreak investigations, and vaccine planning, identifying the infecting Leptospira strain becomes equally important. Culture, serotyping, and whole-genome sequencing (WGS) provide this deeper level of characterization, helping veterinarians and diagnostic laboratories monitor disease trends, identify emerging strains, and support long-term control strategies. 

Why Culture Remains Important 

Although culture is not routinely used for rapid clinical diagnosis, it remains the definitive method for confirming infection because it allows recovery of viable Leptospira organisms^1,2,3,4. Unlike molecular or serological tests, culture produces isolates that can undergo further characterization, making it an indispensable tool for epidemiological investigations. 

Historically, successful isolation has been limited by the organism's fastidious growth requirements, prolonged incubation periods, and the risk of contamination. Improvements in selective media and laboratory techniques have increased the likelihood of recovering pathogenic leptospires, expanding the role of culture in veterinary surveillance¹. 

The value of culture extends beyond confirming infection. Recovered isolates contribute to a better understanding of circulating strains, support the development and validation of diagnostic assays, and provide information that can guide disease monitoring programs^1,4. 

Obtaining Quality Samples for Culture 

Successful isolation begins with appropriate specimen collection and handling. 

During acute infection, whole blood collected in sodium heparin is considered an appropriate specimen for culture. During later stages of infection, aseptically collected urine may also be submitted, although prior antimicrobial treatment can reduce the likelihood of recovering viable organisms¹. 

Animal kidneys, particularly from wildlife reservoir hosts, are valuable specimens because renal colonization is common in persistent infection. Prompt inoculation into suitable culture media is essential, as leptospiral viability declines rapidly in urine and autolysed tissues^1,5,6. 

The development of improved media formulations, including HAN media, has enhanced the recovery of fastidious pathogenic leptospires that are difficult to isolate using conventional culture methods^1,4. 

Serotyping: Identifying Circulating Serovars 

Once isolates have been recovered, serotyping provides critical epidemiological information. 

Serotyping classifies Leptospira based on differences in surface lipopolysaccharide (LPS), the principal antigen responsible for serovar identity and an important component of bacterin vaccines¹. Identifying circulating serovars helps determine which strains are present within a region and supports decisions regarding vaccine composition and surveillance priorities. 

Reference antisera remain the basis of serotyping, while monoclonal antibody panels provide more detailed differentiation between closely related serovars¹. 

Importantly, serotype and genotype are not always directly related. The same serovar may occur in different Leptospira species, highlighting the importance of combining serotyping with molecular characterization for accurate epidemiological interpretation [58,59]. 

Whole-Genome Sequencing Expands Epidemiological Insights 

Whole-genome sequencing has become an important tool for characterizing cultured isolates at a much higher resolution than traditional typing methods. 

WGS provides detailed information on phylogeny, genetic diversity, and evolutionary relationships among pathogenic leptospires¹. By comparing genomic data across isolates, diagnostic laboratories can better understand strain distribution, identify genetic relationships between outbreaks, and monitor changes in circulating populations over time. 

The availability of standardized core genome databases also facilitates comparison of isolates across different laboratories and geographic regions, strengthening both national and international surveillance efforts¹. 

Practical Clinical Insights 

For practicing veterinarians, culture and advanced strain characterization are particularly valuable when: 

• Investigating disease outbreaks within herds or companion animal populations. 

• Monitoring changes in circulating serovars within a region. 

• Supporting surveillance programs designed to inform vaccine selection. 

• Submitting isolates for epidemiological investigations when unusual disease patterns are observed. 

• Collaborating with diagnostic laboratories to improve understanding of local disease trends. 

Although these techniques are not intended for rapid clinical decision-making, they generate information that supports long-term disease control and surveillance. 

Conclusion 

Culture, serotyping, and whole-genome sequencing provide essential information that extends well beyond confirming individual cases of leptospirosis. By identifying circulating strains, improving epidemiological understanding, and supporting surveillance and vaccine planning, these laboratory approaches strengthen veterinary disease control programs. Incorporating isolate characterization into surveillance activities enables veterinarians and diagnostic laboratories to better monitor changing patterns of leptospiral infection and respond more effectively to emerging challenges. 

References 

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2. Hornsby RL, Alt DP, Nally JE. Isolation and propagation of leptospires at 37 C directly from the mammalian host. Scientific reports. 2020 Jun 15;10(1):9620. https://www.nature.com/articles/s41598-020-66526-4.pdf 

3. Narkkul U, Thaipadungpanit J, Srilohasin P, Singkhaimuk P, Thongdee M, Chaiwattanarungruengpaisan S, Krairojananan P, Pan-Ngum W. Optimization of culture protocols to isolate Leptospira spp. from environmental water, field investigation, and identification of factors associated with the presence of Leptospira spp. in the environment. Tropical medicine and infectious disease. 2020 Jun 5;5(2):94. https://www.mdpi.com/2414-6366/5/2/94 

4. Cranford HM, Browne AS, LeCount K, Anderson T, Hamond C, Schlater L, Stuber T, Burke-France VJ, Taylor M, Harrison CJ, Matias KY. Mongooses (Urva auropunctata) as reservoir hosts of Leptospira species in the United States Virgin Islands, 2019–2020. PLoS neglected tropical diseases. 2021 Nov 15;15(11):e0009859. https://journals.plos.org/plosntds/article/file?id=10.1371/journal.pntd.0009859&type=printable 

5. Zarantonelli L, Suanes A, Meny P, Buroni F, Nieves C, Salaberry X, Briano C, Ashfield N, Da Silva Silveira C, Dutra F, Easton C. Isolation of pathogenic Leptospira strains from naturally infected cattle in Uruguay reveals high serovar diversity, and uncovers a relevant risk for human leptospirosis. PLoS neglected tropical diseases. 2018 Sep 13;12(9):e0006694. https://journals.plos.org/plosntds/article/file?id=10.1371/journal.pntd.0006694&type=printable 

6. Guedes IB, de Souza Rocha K, Negrão MP, de Souza GO, de Paula Castro JF, Cavalini MB, de Souza Filho AF, Neto MS, Aizawa J, de Moraes CC, Heinemann MB. Leptospira transport medium (LTM): A practical tool for leptospires isolation. Journal of microbiological methods. 2020 Aug 1;175:105995. https://www.sciencedirect.com/science/article/pii/S0167701220303390