Genetic and pathogenic difference between Streptococcus agalactiae serotype Ia fish and human isolates

Chishih Chu,I-An Tsai,Ying-Hsiang Wang,Che-Chun Chen,Pei-Yu Huang,Hung-Ming Chen,Chih-Cheng Lu

doi:10.1186/s12866-016-0794-4

Chishih Chu, I-An Tsai + Show 5 more

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https://doi.org/10.1186/s12866-016-0794-4

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Abstract

BackgroundStreptococcus agalactiae (GBS) is a common pathogen to infect newborn, woman, the elderly, and immuno-compromised human and fish. 37 fish isolates and 554 human isolates of the GBS in 2007–2012 were investigated in serotypes, antibiotic susceptibility, genetic difference and pathogenicity to tilapia.ResultsPCR serotyping determined serotype Ia for all fish GBS isolates and only in 3.2 % (3–4.2 %) human isolates. For fish isolates, all consisted a plasmid less than 6 kb and belonged to ST7 type, which includes mainly pulsotypes I and Ia, with a difference in a deletion at the largest DNA fragment. These fish isolates were susceptible to all antimicrobials tested in 2007 and increased in non-susceptibility to penicillin, and resistance to clindamycin and ceftriaxone in 2011. Differing in pulsotype and lacking plasmid from fish isolates, human serotype Ia isolates were separated into eight pulsotypes II–IX. Main clone ST23 included pulsotypes II and IIa (50 %) and ST483 consisted of pulsotype III. Human serotype Ia isolates were all susceptible to ceftriaxone and penicillin and few were resistant to erythromycin, azithromycin, clindamycin, levofloxacin and moxifloxacine with the resistant rate of 20 % or less. Using tilapia to analyze the pathogenesis, fish isolates could cause more severe symptoms, including hemorrhage of the pectoral fin, hemorrhage of the gill, and viscous black and common scites, and mortality (>95 % for pulsotype I) than the human isolates (<30 %); however, the fish pulostype Ia isolate 912 with deletion caused less symptoms and the lowest mortality (<50 %) than pulsotype I isolates.ConclusionGenetic, pathogenic, and antimicrobial differences demonstrate diverse origin of human and fish serotype Ia isolates. The pulsotype Ia of fish serotype Ia isolates may be used as vaccine strains to prevent the GBS infection in fish.Electronic supplementary materialThe online version of this article (doi:10.1186/s12866-016-0794-4) contains supplementary material, which is available to authorized users.

Highlights

Streptococcus agalactiae (GBS) is a common pathogen to infect newborn, woman, the elderly, and immuno-compromised human and fish. 37 fish isolates and 554 human isolates of the group B Streptococcus (GBS) in 2007–2012 were investigated in serotypes, antibiotic susceptibility, genetic difference and pathogenicity to tilapia
PCR identification of bacterial species and serotypes of GBS Single colony was taken into Brian Heart Infusion (BHI) broth and total DNA was purified from overnight bacterial cultures using the Genomic DNA purification kit (Quality Systems Inc., Taiwan)
We analyzed genetic and pathogenic differences of the GBS isolates from a hospital and nearby cultured fish farms to investigate the possible zoonotic transmission of GBS between fish and human

Summary

Introduction

Streptococcus agalactiae (GBS) is a common pathogen to infect newborn, woman, the elderly, and immuno-compromised human and fish. 37 fish isolates and 554 human isolates of the GBS in 2007–2012 were investigated in serotypes, antibiotic susceptibility, genetic difference and pathogenicity to tilapia. Streptococcus agalactiae (GBS) is a common pathogen to infect newborn, woman, the elderly, and immuno-compromised human and fish. 37 fish isolates and 554 human isolates of the GBS in 2007–2012 were investigated in serotypes, antibiotic susceptibility, genetic difference and pathogenicity to tilapia. Streptococcus are pathogenic to cause streptococcal disease for humans and animals. Streptococcal infection has been reported in rainbow trout in 1957 [7] and later on in various fishes, including O. aura × O. nilotica hybrid fish [8], Mugil cephalus L. Using antibiotics to treat streptococcal infection in fish, resistance rate to erythromycin, clarithromycin, and azithromycin was less than 15 % for fish isolates [15]. Human GBS has gradually become resistant to clindamycin and erythromycin and differed in resistance rate among countries and sources [16, 17]

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