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Chan YX, Cao H, Jiang S, Li X, Fung KK, Lee CH, Sridhar S, Chen JHK, Ho PL. Genomic investigation of Lactococcus formosensis, Lactococcus garvieae, and Lactococcus petauri reveals differences in species distribution by human and animal sources. Microbiol Spectr 2024; 12:e0054124. [PMID: 38687062 PMCID: PMC11237765 DOI: 10.1128/spectrum.00541-24] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2024] [Accepted: 04/16/2024] [Indexed: 05/02/2024] Open
Abstract
Lactococcus garvieae is a fish pathogen that can cause diseases in humans and cows. Two genetically related species, Lactococcus formosensis and Lactococcus petauri, may be misidentified as L. garvieae. It is unclear if these species differ in host specificity and virulence genes. This study analyzed the genomes of 120 L. petauri, 53 L. formosensis, and 39 L. garvieae isolates from various sources. The genetic diversity and virulence gene content of these isolates were compared. The results showed that 77 isolates previously reported as L. garvieae were actually L. formosensis or L. petauri. The distribution of the three species varied across different collection sources, with L. petauri being predominant in human infections, human fecal sources, and rainbow trout, while L. formosensis was more common in bovine isolates. The genetic diversity of isolates within each species was high and similar. Using a genomic clustering method, L. petauri, L. formosensis, and L. garvieae were divided into 45, 22, and 13 clusters, respectively. Most rainbow trout and human isolates of L. petauri belonged to different clusters, while L. formosensis isolates from bovine and human sources were also segregated into separate clusters. In L. garvieae, most human isolates were grouped into three clusters that also included isolates from food or other sources. Non-metric multidimensional scaling ordination revealed the differential association of 15 virulence genes, including 14 adherence genes and a bile salt hydrolase gene, with bacterial species and certain collection sources. In conclusion, this work provides evidence of host specificity among the three species. IMPORTANCE Lactococcus formosensis and Lactococcus petauri are two newly discovered bacteria, which are closely related to Lactococcus garvieae, a pathogen that affects farmed rainbow trout, as well as causes cow mastitis and human infections. It is unclear whether the three bacteria differ in their host preference and the presence of genes that contribute to the development of disease. This study shows that L. formosensis and L. petauri were commonly misidentified as L. garvieae. The three bacteria showed different distribution patterns across various sources. L. petauri was predominantly found in human infections and rainbow trout, while L. formosensis was more commonly detected in cow mastitis. Fifteen genes displayed a differential distribution among the three bacteria from certain sources, indicating a genetic basis for the observed host preference. This work indicates the importance of differentiating the three bacteria in diagnostic laboratories for surveillance and outbreak investigation purposes.
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Affiliation(s)
- You-Xiang Chan
- Department of Microbiology, University of Hong Kong, Hong Kong, China
| | - Huiluo Cao
- Department of Microbiology, University of Hong Kong, Hong Kong, China
| | - Shuo Jiang
- Department of Microbiology, University of Hong Kong, Hong Kong, China
| | - Xin Li
- Department of Microbiology, University of Hong Kong, Hong Kong, China
- Carol Yu Centre for Infection, University of Hong Kong, Hong Kong, China
- Department of Microbiology, Queen Mary Hospital, Hospital Authority, Hong Kong, China
| | - Ka-Kin Fung
- Department of Clinical Pathology, Pamela Youde Nethersole Eastern Hospital, Hospital Authority, Hong Kong, China
| | - Chung-Ho Lee
- Department of Clinical Pathology, Kwong Wah Hospital, Hospital Authority, Hong Kong, China
| | - Siddharth Sridhar
- Department of Microbiology, University of Hong Kong, Hong Kong, China
- Carol Yu Centre for Infection, University of Hong Kong, Hong Kong, China
- Department of Microbiology, Queen Mary Hospital, Hospital Authority, Hong Kong, China
| | | | - Pak-Leung Ho
- Department of Microbiology, University of Hong Kong, Hong Kong, China
- Carol Yu Centre for Infection, University of Hong Kong, Hong Kong, China
- Department of Microbiology, Queen Mary Hospital, Hospital Authority, Hong Kong, China
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Heckman TI, Yazdi Z, Older CE, Griffin MJ, Waldbieser GC, Chow AM, Medina Silva I, Anenson KM, García JC, LaFrentz BR, Slavic D, Toohey-Kurth KL, Yant P, Fritz HM, Henderson EE, McDowall R, Cai H, Adkison M, Soto E. Redefining piscine lactococcosis. Appl Environ Microbiol 2024; 90:e0234923. [PMID: 38597602 PMCID: PMC11107168 DOI: 10.1128/aem.02349-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2023] [Accepted: 03/10/2024] [Indexed: 04/11/2024] Open
Abstract
Piscine lactococcosis is a significant threat to cultured and wild fish populations worldwide. The disease typically presents as a per-acute to acute hemorrhagic septicemia causing high morbidity and mortality, recalcitrant to antimicrobial treatment or management interventions. Historically, the disease was attributed to the gram-positive pathogen Lactococcus garvieae. However, recent work has revealed three distinct lactococcosis-causing bacteria (LCB)-L. garvieae, L. petauri, and L. formosensis-which are phenotypically and genetically similar, leading to widespread misidentification. An update on our understanding of lactococcosis and improved methods for identification are urgently needed. To this end, we used representative isolates from each of the three LCB species to compare currently available and recently developed molecular and phenotypic typing assays, including whole-genome sequencing (WGS), end-point and quantitative PCR (qPCR) assays, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS), API 20 Strep and Biolog systems, fatty acid methyl ester analysis (FAME), and Sensititre antimicrobial profiling. Apart from WGS, sequencing of the gyrB gene was the only method capable of consistent and accurate identification to the species and strain level. A qPCR assay based on a putative glycosyltransferase gene was also able to distinguish L. petauri from L. garvieae/formosensis. Biochemical tests and MALDI-TOF MS showed some species-specific patterns in sugar and fatty acid metabolism or protein profiles but should be complemented by additional analyses. The LCB demonstrated overlap in host and geographic range, but there were relevant differences in host specificity, regional prevalence, and antimicrobial susceptibility impacting disease treatment and prevention. IMPORTANCE Lactococcosis affects a broad range of host species, including fish from cold, temperate, and warm freshwater or marine environments, as well as several terrestrial animals, including humans. As such, lactococcosis is a disease of concern for animal and ecosystem health. The disease is endemic in European and Asian aquaculture but is rapidly encroaching on ecologically and economically important fish populations across the Americas. Piscine lactococcosis is difficult to manage, with issues of vaccine escape, ineffective antimicrobial treatment, and the development of carrier fish or biofilms leading to recurrent outbreaks. Our understanding of the disease is also widely outdated. The accepted etiologic agent of lactococcosis is Lactococcus garvieae. However, historical misidentification has masked contributions from two additional species, L. petauri and L. formosensis, which are indistinguishable from L. garvieae by common diagnostic methods. This work is the first comprehensive characterization of all three agents and provides direct recommendations for species-specific diagnosis and management.
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Affiliation(s)
- Taylor I. Heckman
- Department of Medicine & Epidemiology, School of Veterinary Medicine, University of California, Davis, California, USA
| | - Zeinab Yazdi
- Department of Medicine & Epidemiology, School of Veterinary Medicine, University of California, Davis, California, USA
| | - Caitlin E. Older
- USDA-ARS, Warmwater Aquaculture Research Unit, Stoneville, Mississippi, USA
| | - Matt J. Griffin
- College of Veterinary Medicine, Mississippi State University, Stoneville, Mississippi, USA
| | | | - Alexander M. Chow
- Department of Medicine & Epidemiology, School of Veterinary Medicine, University of California, Davis, California, USA
| | - Isabella Medina Silva
- Department of Medicine & Epidemiology, School of Veterinary Medicine, University of California, Davis, California, USA
| | - Kelsey M. Anenson
- Department of Medicine & Epidemiology, School of Veterinary Medicine, University of California, Davis, California, USA
| | - Julio C. García
- USDA-ARS, Aquatic Animal Health Research Unit, Auburn, Alabama, USA
| | | | - Durda Slavic
- Animal Health Laboratory, University of Guelph, Ontario, Canada
| | - Kathy L. Toohey-Kurth
- California Animal Health and Food Safety Laboratory, University of California, Davis, California, USA
| | - Paula Yant
- California Animal Health and Food Safety Laboratory, University of California, Davis, California, USA
| | - Heather M. Fritz
- California Animal Health and Food Safety Laboratory, University of California, Davis, California, USA
| | - Eileen E. Henderson
- California Animal Health and Food Safety Laboratory, University of California, Davis, California, USA
| | | | - Hugh Cai
- Animal Health Laboratory, University of Guelph, Ontario, Canada
| | - Mark Adkison
- California Department of Fish and Wildlife, Rancho Cordova, California, USA
| | - Esteban Soto
- Department of Medicine & Epidemiology, School of Veterinary Medicine, University of California, Davis, California, USA
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