Streptococcal Infections in Marine Mammals

Abstract

Marine mammals are sentinels for the marine ecosystem and threatened by numerous factors including infectious diseases. One of the most frequently isolated bacteria are beta-hemolytic streptococci. However, knowledge on ecology and epidemiology of streptococcal species in marine mammals is very limited. This review summarizes published reports on streptococcal species, which have been detected in marine mammals. Furthermore, we discuss streptococcal transmission between and adaptation to their marine mammalian hosts. We conclude that streptococci colonize and/or infect marine mammals very frequently, but in many cases, streptococci isolated from marine mammals have not been further identified. How these bacteria disseminate and adapt to their specific niches can only be speculated due to the lack of respective research. Considering the relevance of pathogenic streptococci for marine mammals as part of the marine ecosystem, it seems that they have been neglected and should receive scientific interest in the future.

First report of a severe nasopulmonary acariasis caused by Orthohalarachne diminuata Doetschman, 1944 (Acari: Halarachnidae) in a captive South American sea lion (Otaria flavescens Shaw, 1800)

“…Likewise, Seguel et al (2018a) suspected O. diminuata to act as a vector for beta-hemolytic streptococci in South American fur seals. Generally, beta-hemolytic streptococci constitute one of the most frequently isolated bacterial pathogens in marine mammals ( Numberger et al, 2021 ). Interestingly, in the current case, Streptococcus dysgalactiae equisimilis was diagnosed in trachea and bronchi by bacteriological analyses.…”

Streptococcus vicugnae sp. nov., isolated from faeces of alpacas (Vicugna pacos) and cattle (Bos taurus), Streptococcus zalophi sp. nov., and Streptococcus pacificus sp. nov., isolated from respiratory tract of California sea lions (Zalophus californianus)

“…The species within the genus Streptococcus , the family Streptococcaceae , order Lactobacillales , are facultatively anaerobic, catalase-negative, non-sporulating and non-motile Gram-positive spherical or ovoid bacterial cells, occurring in pairs or in short or long chains [1]. The Streptococcus species typically colonize the human or animal oropharynx, respiratory, urogenital and gastrointestinal tracts [1, 2]. The majority of Streptococcus are known to be either commensals or parasites of humans and animals; however, some species are highly pathogenic for their hosts, e.g.…”

“…S. pyogenes, S. pneumoniae, S. equi ) [1]. Many Streptococcus species of veterinary importance have been described [1–7]. Some Streptococcus species have been reported as infectious agents in free-ranging and captive wildlife species, including marine mammals [2], e.g.…”

“…Strains SL1232 T and KCJ4950 were able to grow in this broth supplemented with up to 4.5% NaCl, but the seal strains CSL7591 T and CSL7508 T were able to tolerate up to 6.5–7.5% NaCl in the tested conditions. A salt concentration of the Pacific Ocean in the regions of natural distribution of California sea lions is approximately 3.4–3.5% [24, 25], therefore, the potential ability of these two novel species to survive in the upper respiratory tract (nasal or oropharyngeal cavities) of the seals, which would be regularly exposed to sea water [2], might explain their tolerance to higher salt concentrations in this experiment.…”

“… zooepidemicus , i.e. in other Streptococcus species, which are regularly found in marine mammals [2]. The conserved signature indels (CSIs) in twelve amino acid sequences of uroporphyrinogen decarboxylase (WP_199543697.1; 1 aa deletion), excinuclease ABC subunit UvrC (WP_199544234.1; 1 aa insertion), dihydroorotate dehydrogenase electron transfer subunit (WP_199544189.1; 2 aa insertion), DNA polymerase III subunit gamma/tau (WP_199544329.1; 1 aa insertion), DHH family phosphoesterase (WP_199544874.1; 1 aa insertion), sigma-70 family RNA polymerase sigma factor (WP_199544946.1; 1 aa insertion), insulinase family protein (WP_199544890.1; 3 aa insertion), copper homeostasis protein CutC (WP_199542895.1; 1 aa deletion), UDP-N-acetylglucosamine 1-carboxyvinyltransferase (WP_074481986.1; 1 aa insertion), dTMP kinase (WP_199542903.1; 1 aa deletion), DNA helicase PcrA (WP_199543824.1; 2 aa insertion), and phosphoribosylamine-glycine ligase (WP_199545122.1; 1 aa deletion), which were recently found to be specific for members of the Equinus subclade [36], were also identified in strains SL1232 T and KCJ4950, and therefore, clearly demonstrates that these two novel strains belong to the Equinus subclade.…”