Event Abstract

Back to Event

Of Fish and Men: Interspecies transmission of Streptococcus agalactiae?

Nguyen N. Phuoc1, Christian Delannoy2 and Ruth N. Zadoks3, 4*
  • 1 Hue University of Agriculture and Forestry, Viet Nam
  • 2 Skretting, Norway
  • 3 Moredun Research Institute, United Kingdom
  • 4 University of Glasgow, United Kingdom

Streptococcus agalactiae is an important pathogen of aquaculture and marine fishes. Particularly in South-East Asia, efficacy of current vaccines against S. agalactiae in tilapia is limited, which may be due in part to presence of multiple strains. Two biotypes are commonly recognized in aquatic S. agalactiae, with biotype 2 predominating in most continents. However, molecular serotyping and multilocus sequence typing of Southeast Asian isolates have demonstrated strain heterogeneity within biotypes as well as the existence of additional biotypes (Delannoy et al., 2013). Streptococcus agalactiae is also an important pathogen of humans, primarily as a cause of neonatal infectious disease with death or permanent disability as possible outcomes. In addition, it is an emerging pathogen in adults in Asia, Europe and the Americas (Crespo-Ortiz Mdel et al., 2014; Flores et al., 2015; Louthrenoo et al., 2014). To date, only a few human-derived strains are known to be infectious to fishes, whilst other human strains do not infect fishes and vice versa. Mechanisms underpinning streptococcal host adaptation are thought to be encoded, at least in part, on mobile genetic elements (Richards et al., 2011; Delannoy et al., 2016). This implies that lateral gene transfer between strains may be possible, and hence additional strains may acquire the ability to infect multiple host species. We conducted comparisons, including MLST, virulence gene typing and molecular serotyping (Jones et al., 2003; Sun et al., 2005) of S. agalactiae isolates from tilapia and humans from southern Vietnam, where there is intimate contact between host species in the Mekong Delta’s aquaculture industry. Fish isolates were collected from multiple tilapia farms across 3 provinces, whilst human isolates were obtained by the Hospital for Tropical Diseases in Ho Chi Minh City from patients with septicaemia. Preliminary results suggest that serotype III is more common in tilapia than previously reported and that strains hitherto only found in humans have acquired the ability to infect fish. This would have serious implications, both for vaccine development and for the risk of interspecies transmission. Antimicrobials are used widely in aquaculture and selection for antimicrobial resistance in major human pathogenic strains could affect consumer confidence and pose a risk to public health. Increasingly, the occurrence of S. agalactiae in fishes and men is a One Health problem.

Acknowledgements

We would like to thank Prof. Stephen Baker, Oxford Clinical Research Unit, Ho Chi Minh City, for providing DNA from human isolates, and fish farmers, students and officials in the Mekong Delta for help with collection of fish isolates.

References

Crespo-Ortiz Mdel et al. 2014 Emerging trends in invasive and noninvasive isolates of Streptococcus agalactiae in a Latin American hospital: a 17-year study. BMC Infect Dis. 14:428.

Delannoy et al. 2016. Genomic comparison of virulent and non-virulent Streptococcus agalactiae in fish. J Fish Dis. 39(1):13-29.

Delannoy et al. 2013. Human Streptococcus agalactiae strains in aquatic mammals and fish. BMC Microbiol. 13:41.
Flores et al. 2015. Sequence type 1 group B Streptococcus, an emerging cause of invasive disease in adults, evolves by small genetic changes. Proc Natl Acad Sci U S A. 112(20):6431-6

Jones et al. 2003. Multilocus sequence typing system for group B streptococcus. J Clin Microbiol. 41(6):2530-6.

Louthrenoo W, Kasitanon N, Wangkaew S, Hongsongkiat S, Sukitawut W, Wichainun R. 2014. Streptococcus agalactiae: an emerging cause of septic arthritis. J Clin Rheumatol. 20(2):74-8.

Richards et al. 2011. Comparative genomics and the role of lateral gene transfer in the evolution of bovine adapted Streptococcus agalactiae. Infect Genet Evol. 11(6):1263-75.

Sun et al. 2005. Comparison of a 3-set genotyping system with multilocus sequence typing for Streptococcus agalactiae (Group B Streptococcus). J Clin Microbiol. 43(9):4704-7.

Keywords: Tilapia, One Health, emerging infectious disease, Streptococcus agalactiae, Bloodstream infection

Conference: AquaEpi I - 2016, Oslo, Norway, 20 Sep - 22 Sep, 2016.

Presentation Type: Oral

Topic: Aquatic Animal Epidemiology

Citation: Phuoc NN, Delannoy C and Zadoks RN (2016). Of Fish and Men: Interspecies transmission of Streptococcus agalactiae?. Front. Vet. Sci. Conference Abstract: AquaEpi I - 2016. doi: 10.3389/conf.FVETS.2016.02.00058

Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters.

The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated.

Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed.

For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions.

Received: 30 May 2016; Published Online: 14 Sep 2016.

* Correspondence: DVM, PhD. Ruth N Zadoks, Moredun Research Institute, Penicuik, United Kingdom, ruth.zadoks@sydney.edu.au