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Human Streptococcus agalactiae strains in aquatic mammals and fish.

Delannoy CM, Crumlish M, Fontaine MC, Pollock J, Foster G, Dagleish MP, Turnbull JF, Zadoks RN - BMC Microbiol. (2013)

Bottom Line: ST23 serotype Ia, a subpopulation that is normally associated with human carriage, was found in all grey seals, suggesting that human effluent may contribute to microbial pollution of surface water and exposure of sea mammals to human pathogens.The final subpopulation consisted of non-haemolytic ST260 and ST261 serotype Ib isolates, which belong to a fish-associated clonal complex that has never been reported from humans.Furthermore, it provides a rational framework for exploration of pathogenesis and host-associated genome content of S. agalactiae strains.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute of Aquaculture, School of Natural Sciences, University of Stirling, Stirling, UK.

ABSTRACT

Background: In humans, Streptococcus agalactiae or group B streptococcus (GBS) is a frequent coloniser of the rectovaginal tract, a major cause of neonatal infectious disease and an emerging cause of disease in non-pregnant adults. In addition, Streptococcus agalactiae causes invasive disease in fish, compromising food security and posing a zoonotic hazard. We studied the molecular epidemiology of S. agalactiae in fish and other aquatic species to assess potential for pathogen transmission between aquatic species and humans.

Methods: Isolates from fish (n = 26), seals (n = 6), a dolphin and a frog were characterized by pulsed-field gel electrophoresis, multilocus sequence typing and standardized 3-set genotyping, i.e. molecular serotyping and profiling of surface protein genes and mobile genetic elements.

Results: Four subpopulations of S. agalactiae were identified among aquatic isolates. Sequence type (ST) 283 serotype III-4 and its novel single locus variant ST491 were detected in fish from Southeast Asia and shared a 3-set genotype identical to that of an emerging ST283 clone associated with invasive disease of adult humans in Asia. The human pathogenic strain ST7 serotype Ia was also detected in fish from Asia. ST23 serotype Ia, a subpopulation that is normally associated with human carriage, was found in all grey seals, suggesting that human effluent may contribute to microbial pollution of surface water and exposure of sea mammals to human pathogens. The final subpopulation consisted of non-haemolytic ST260 and ST261 serotype Ib isolates, which belong to a fish-associated clonal complex that has never been reported from humans.

Conclusions: The apparent association of the four subpopulations of S. agalactiae with specific groups of host species suggests that some strains of aquatic S. agalactiae may present a zoonotic or anthroponotic hazard. Furthermore, it provides a rational framework for exploration of pathogenesis and host-associated genome content of S. agalactiae strains.

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Population snapshot of S. agalactiae constructed in eBURST. In addition to the 9 eBURST groups that are shown, 36 singletons were present in the database (last accessed 7 November 2012). Founders of major clonal complexes (ST1, ST17, ST19, all of which form part of eBURST group 1, and ST23, which is the founder of eBURST group 2) and sequence types (ST) identified in the current study are labelled. Italics indicate STs isolated from fish, bold italics indicate the ST from fish and a frog, and shaded labels indicate STs from sea mammals. All β-haemolytic S. agalactiae isolates from fish belonged to a single branch of eBURST group 1, all seal isolates (n=6) belonged to eBURST group 2 and all non-haemolytic isolates belonged to two small eBURST groups that included ST260 and ST261.
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Figure 2: Population snapshot of S. agalactiae constructed in eBURST. In addition to the 9 eBURST groups that are shown, 36 singletons were present in the database (last accessed 7 November 2012). Founders of major clonal complexes (ST1, ST17, ST19, all of which form part of eBURST group 1, and ST23, which is the founder of eBURST group 2) and sequence types (ST) identified in the current study are labelled. Italics indicate STs isolated from fish, bold italics indicate the ST from fish and a frog, and shaded labels indicate STs from sea mammals. All β-haemolytic S. agalactiae isolates from fish belonged to a single branch of eBURST group 1, all seal isolates (n=6) belonged to eBURST group 2 and all non-haemolytic isolates belonged to two small eBURST groups that included ST260 and ST261.

Mentions: E-burst analysis (Figure 2) showed that all piscine isolates from Asia and the Middle-East and the frog isolate from Asia (ST7 and its SLV ST500; ST283 and its SLV ST491) belonged to 2 related subgroups, both of which are part of eBURST group 1. The bottlenose dolphin isolate from the UK (ST399) also belonged to eBURST group 1. This large eBURST group includes a number of major subgroups that used to be separate eBURST groups or clonal complexes (CCs). For ease of reference and comparison with the literature, such subgroups or subCCs are indicated in the figure and subsequent text by their founding ST. All grey seal isolates from the UK belonged to ST23, which is the founder of eBURST group 2 or CC23 and not related to ST7 or ST283. Piscine isolates from Latin America (ST260) were part of a small eBURST group that also includes ST257, ST259, ST552 and ST553 (Figure 2). The most likely founder of this eBURST group is ST552 and the group is also referred to as CC552. Based on additional analysis of DLVs, ST261 and ST246 may also be related to CC552 whilst ST258 is a TLV of CC552 (Figure 3).


Human Streptococcus agalactiae strains in aquatic mammals and fish.

Delannoy CM, Crumlish M, Fontaine MC, Pollock J, Foster G, Dagleish MP, Turnbull JF, Zadoks RN - BMC Microbiol. (2013)

Population snapshot of S. agalactiae constructed in eBURST. In addition to the 9 eBURST groups that are shown, 36 singletons were present in the database (last accessed 7 November 2012). Founders of major clonal complexes (ST1, ST17, ST19, all of which form part of eBURST group 1, and ST23, which is the founder of eBURST group 2) and sequence types (ST) identified in the current study are labelled. Italics indicate STs isolated from fish, bold italics indicate the ST from fish and a frog, and shaded labels indicate STs from sea mammals. All β-haemolytic S. agalactiae isolates from fish belonged to a single branch of eBURST group 1, all seal isolates (n=6) belonged to eBURST group 2 and all non-haemolytic isolates belonged to two small eBURST groups that included ST260 and ST261.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3585737&req=5

Figure 2: Population snapshot of S. agalactiae constructed in eBURST. In addition to the 9 eBURST groups that are shown, 36 singletons were present in the database (last accessed 7 November 2012). Founders of major clonal complexes (ST1, ST17, ST19, all of which form part of eBURST group 1, and ST23, which is the founder of eBURST group 2) and sequence types (ST) identified in the current study are labelled. Italics indicate STs isolated from fish, bold italics indicate the ST from fish and a frog, and shaded labels indicate STs from sea mammals. All β-haemolytic S. agalactiae isolates from fish belonged to a single branch of eBURST group 1, all seal isolates (n=6) belonged to eBURST group 2 and all non-haemolytic isolates belonged to two small eBURST groups that included ST260 and ST261.
Mentions: E-burst analysis (Figure 2) showed that all piscine isolates from Asia and the Middle-East and the frog isolate from Asia (ST7 and its SLV ST500; ST283 and its SLV ST491) belonged to 2 related subgroups, both of which are part of eBURST group 1. The bottlenose dolphin isolate from the UK (ST399) also belonged to eBURST group 1. This large eBURST group includes a number of major subgroups that used to be separate eBURST groups or clonal complexes (CCs). For ease of reference and comparison with the literature, such subgroups or subCCs are indicated in the figure and subsequent text by their founding ST. All grey seal isolates from the UK belonged to ST23, which is the founder of eBURST group 2 or CC23 and not related to ST7 or ST283. Piscine isolates from Latin America (ST260) were part of a small eBURST group that also includes ST257, ST259, ST552 and ST553 (Figure 2). The most likely founder of this eBURST group is ST552 and the group is also referred to as CC552. Based on additional analysis of DLVs, ST261 and ST246 may also be related to CC552 whilst ST258 is a TLV of CC552 (Figure 3).

Bottom Line: ST23 serotype Ia, a subpopulation that is normally associated with human carriage, was found in all grey seals, suggesting that human effluent may contribute to microbial pollution of surface water and exposure of sea mammals to human pathogens.The final subpopulation consisted of non-haemolytic ST260 and ST261 serotype Ib isolates, which belong to a fish-associated clonal complex that has never been reported from humans.Furthermore, it provides a rational framework for exploration of pathogenesis and host-associated genome content of S. agalactiae strains.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute of Aquaculture, School of Natural Sciences, University of Stirling, Stirling, UK.

ABSTRACT

Background: In humans, Streptococcus agalactiae or group B streptococcus (GBS) is a frequent coloniser of the rectovaginal tract, a major cause of neonatal infectious disease and an emerging cause of disease in non-pregnant adults. In addition, Streptococcus agalactiae causes invasive disease in fish, compromising food security and posing a zoonotic hazard. We studied the molecular epidemiology of S. agalactiae in fish and other aquatic species to assess potential for pathogen transmission between aquatic species and humans.

Methods: Isolates from fish (n = 26), seals (n = 6), a dolphin and a frog were characterized by pulsed-field gel electrophoresis, multilocus sequence typing and standardized 3-set genotyping, i.e. molecular serotyping and profiling of surface protein genes and mobile genetic elements.

Results: Four subpopulations of S. agalactiae were identified among aquatic isolates. Sequence type (ST) 283 serotype III-4 and its novel single locus variant ST491 were detected in fish from Southeast Asia and shared a 3-set genotype identical to that of an emerging ST283 clone associated with invasive disease of adult humans in Asia. The human pathogenic strain ST7 serotype Ia was also detected in fish from Asia. ST23 serotype Ia, a subpopulation that is normally associated with human carriage, was found in all grey seals, suggesting that human effluent may contribute to microbial pollution of surface water and exposure of sea mammals to human pathogens. The final subpopulation consisted of non-haemolytic ST260 and ST261 serotype Ib isolates, which belong to a fish-associated clonal complex that has never been reported from humans.

Conclusions: The apparent association of the four subpopulations of S. agalactiae with specific groups of host species suggests that some strains of aquatic S. agalactiae may present a zoonotic or anthroponotic hazard. Furthermore, it provides a rational framework for exploration of pathogenesis and host-associated genome content of S. agalactiae strains.

Show MeSH
Related in: MedlinePlus