Streptococcus suis: an emerging zoonotic pathogen

doi:10.1016/S1473-3099(07)70001-4

The Lancet Infectious Diseases

Volume 7, Issue 3, March 2007, Pages 201-209

https://doi.org/10.1016/S1473-3099(07)70001-4 Get rights and content

Summary

Streptococcus suis is a major porcine pathogen worldwide, and can be transmitted to human beings by close contact with sick or carrier pigs. S suis causes meningitis, septicaemia, endocarditis, arthritis, and septic shock in both pigs and human beings, and mortality is high. Human infection with S suis occurs mainly among certain risk groups that have frequent exposure to pigs or pork. Outbreaks of human S suis infection are uncommon, although several outbreaks have occurred in China in recent years. In July, 2005, the largest outbreak of human S suis infection occurred in Sichuan province, China, where 204 people were infected and 38 of them died. There have been 409 cases of human S suis infection worldwide, most of which have occurred in China, Thailand, and the Netherlands, and these infections have led to 73 deaths. This review provides background information on the biology and molecular characteristics of this Gram-positive bacterium, and describes the clinical signs, pathology, epidemiology, diagnosis, and treatment of human infection with S suis.

Introduction

Streptococcus suis is an important pathogen associated with a wide range of diseases in pigs, including meningitis, septicaemia, pneumonia, endocarditis, and arthritis.¹ S suis can be transmitted to human beings by direct contact. The first human case of S suis was reported in Denmark in 1968.² Human infection with S suis has become a serious zoonosis and has been reported in many countries with intensive swine production. More than 200 cases were reported worldwide before 2005, most of them from European and Asian countries and regions.³

In July, 2005, a large outbreak of human S suis infection occurred in Sichuan province, China, accompanied by several sporadic cases in other provinces. This was the third reported outbreak of human S suis infections that has occurred in China, with two earlier outbreaks occurring in Jiangsu province in 1998 and 1999. In the past 8 years in China, at least 237 people have been infected with S suis and 53 of them died.4, 5, 6 The repeated intensive outbreaks of human S suis infection have raised great public concern worldwide regarding S suis as an emerging zoonotic agent.

Section snippets

Biological features

S suis is a Gram-positive facultative anaerobe, is coccoid or ovoid, and occurs as single cells, in pairs, or in short chains.⁷ Based on the capsular polysaccharides, 35 serotypes have been identified (types 1–34 and 1/2),7, 8, 9, 10, 11 but serotypes 32 and 34 have since been proven to be Streptococcus orisratti.¹² Serotype 2 is most commonly associated with diseases in pigs and human beings, and is the most frequently reported serotype worldwide.13, 14, 15 Except for two human S suis

Identification

S suis is able to grow in anaerobic or aerobic conditions, but is unable to grow in 6·5% NaCl solution.⁴⁷ Colonies of S suis are small (0·5–1·0 mm diameter), greyish or transparent, and slightly mucoid.¹ Most S suis strains produce narrow zones of α-haemolysis on sheep blood agar plates. S suis type 2 colonies produce α-haemolysis on sheep blood agar plates and β-haemolysis on horse blood agar plates.¹ Presumptive identification based on four biochemical tests (Voges-Proskauer, salicin,

Clinical signs in human infection

Human infections with S suis are most frequently manifested as purulent meningitis, but reports of septic shock with multiple organ failure, endocarditis, pneumonia, arthritis, and peritonitis have also been reported (table 1). Differences in clinical signs among patients infected with S suis have been observed. In the acute form of meningitis, symptoms include high fever, headache, chills, nausea, vomiting, and vertigo, followed by one or more of the following: hearing loss, walking ataxia,

Pathology

There are many descriptions of the pathological and histopathological lesions in pigs infected with S suis.¹ The most common gross lesions are congestion of the meninges, lymph nodes, and lungs, and the most common histopathological finding is within the choroidal plexus. Evidence of encephalitis, oedema, and congestion of the brain may be present. In the central nervous system, lesions associated with meningitis and choroiditis may be observed, including oedema of the leptomeninges and the

Epidemiology

S suis is distributed worldwide and is most adapted to domesticated pigs, but is also occasionally recovered from wild boars, horses, dogs, and cats.1, 120 S suis type 2 colonises the palatine tonsils of clinically ill and apparently healthy pigs.²⁰ The symptomless carrier therefore represents a potential source of infection to herds or to human beings. Piglets are most susceptible, but infection can occur at any age.¹ Predisposing factors are found in pigs raised in suboptimum conditions (eg,

Diagnosis and treatment

Presumptive diagnosis of human S suis infection is based on clinical signs and microscopic lesions. Confirmation of infection is achieved by isolation of the infectious agents and the recognition of microscopic lesions in tissues. Epidemiology history, such as information about direct contact with sick pigs, is very useful for final confirmation. The detailed clinical signs and microscopic lesions have been discussed in previous sections. In addition to clinical information, the initial routine

Prevention and control

Because the main infectious sources are sick pigs, prevention of transmission to human beings depends on the control of sick animals. Various types of vaccines have been developed for pigs, with varied protective efficacy. Vaccination with purified capsule vaccine failed to protect swine from S suis type 2.¹⁴⁵ Mice immunised with purified suilysin vaccine from S suis type 2 were completely protected against challenge with the virulent S suis type 2 strain from which the vaccine originated.⁴²

Conclusions

S suis is an increasingly important pathogen, causing meningitis, septicaemia, arthritis, and endocarditis in both pigs and human beings. S suis can naturally colonise the respiratory tract, especially the tonsils, of pigs. Carriers play an important role in the transmission of S suis within herds and sometimes to human beings. Although the virulence factors of S suis are yet to be firmly established, various methods for identification of strains of S suis have been developed, comprising

Search strategy and selection criteria

Literature searches were done predominantly using the following databases: Medline (PubMed; http://www.ncbi.nlm.nih.gov), CNKI (http://www.cnki.net), Wanfang Data (http://www.wangan.calis.edu.cn), WHO (http://www.who.int/en), and ScienceDirect (http://www.sciencedirect.com). Search terms included were “Streptococcus suis”, “Streptococcus suis infection”, “human Streptococcus suis infection”, “human Streptococcus suis infection and epidemiology”, and “Zhulianqiujun”. Relevant articles or

References (146)

JE Hill et al.
Biochemical analysis, cpn60 and 16S rDNA sequence data indicate that Streptococcus suis serotypes 32 and 34, isolated from pigs, are Streptococcus orisratti
Vet Microbiol
(2005)
HJ Wisselink et al.
Distribution of capsular types and production of muramidase-released protein (MRP) and extracellular factor (EF) of Streptococcus suis strains isolated from diseased pigs in seven European countries
Vet Microbiol
(2000)
EJ Watkins et al.
Septicaemia in a pig-farm worker
Lancet
(2001)
M Gottschalk et al.
The pathogenesis of the meningitis caused by Streptococcus suis: the unresolved questions
Vet Microbiol
(2000)
FM Aarestrup et al.
Serological characterization and antimicrobial susceptibility of Streptococcus suis isolates from diagnostic samples in Denmark during 1995 and 1996
Vet Microbiol
(1998)
HE Smith et al.
The cps locus of Streptococcus suis serotype 2: genetic determinant for the synthesis of sialic acid
Microb Pathog
(2000)
PM Norton et al.
Epithelial invasion and cell lysis by virulent strains of Streptococcus suis is enhanced by the presence of suilysin
FEMS Immunol Med Microbiol
(1999)
S Lun et al.
Role of suilysin in pathogenesis of Streptococcus suis capsular serotype 2
Microb Pathog
(2003)
S Quessy et al.
Description of an albumin binding activity for Streptococcus suis serotype 2
FEMS Microbiol Lett
(1997)
O Okwumabua et al.
A polymerase chain reaction (PCR) assay specific for Streptococcus suis based on the gene encoding the glutamate dehydrogenase
FEMS Microbiol Lett
(2003)

PR Davies et al.

Evaluation of methods used for detecting Streptococcus suis type 2 in tonsils, and investigation of the carrier state in pigs

Res Vet Sci

(1991)

N Chanter et al.

Meningitis in pigs caused by Streptococcus suis—a speculative review

Vet Microbiol

(1993)

AC Hui et al.

Bacterial meningitis in Hong Kong: 10-years' experience

Clin Neurol Neurosurg

(2005)

C Lopreto et al.

Primary Streptococcus suis meningitis: first case in humans described in Latin America

Enferm Infecc Microbiol Clin

(2005)

P Perseghin et al.

Streptococcus suis meningitis in an Italian blood donor

Lancet

(1995)

J Woo

Streptococcus suis meningitis in man in Hong Kong

Trans R Soc Trop Med Hyg

(1986)

JJ Staats et al.

Streptococcus suis: past and present

Vet Res Commun

(1997)

JP Arends et al.

Meningitis caused by Streptococcus suis in humans

Rev Infect Dis

(1988)

DE Geffner Sclarsky et al.

Streptococcus suis meningitis

An Med Interna

(2001)

YH Wang et al.

Analysis of infectious syndrome caused by Streptococcus suis type 2

Jiangsu Med J

(2005)

(1984)

M Gottschalk et al.

Susceptibility of Streptococcus suis to penicillin

J Vet Diagn Invest

(1991)

C Prieto et al.

Biochemical traits and antimicrobial susceptibility of Streptococcus suis isolated from slaughtered pigs

Zentralbl Veterinarmed B

(1994)

(1994)

Cited by (429)

Genomic characterisation of bioaerosols within livestock facilities: A systematic review
2024, Science of the Total Environment
Livestock facilities are widely regarded as reservoirs of infectious disease, owing to their abundance in particulate matter (PM) and microbial bioaerosols. Over the past decade, bioaerosol studies have increasingly utilised high throughput sequencing (HTS) to achieve superior throughput, taxonomic resolution, and the detection of unculturable organisms. However, the prevailing focus on amplicon sequencing has limited the identification of viruses and microbial taxa at the species-level. Herein, a literature search was conducted to identify methods capable of overcoming the aforementioned limitations. Screening 1531 international publications resulted in 29 eligible for review. Metagenomics capable of providing rich insights were identified in only three instances. Notably, long-read sequencing was not utilised for metagenomics. This review also identified that sample collection methods lack a uniform approach, highlighted by the differences in sampling equipment, flow rates and durations. Further heterogeneity was introduced by the unique sampling conditions, which makes it challenging to ground new findings within the established literature. For instance, winter was associated with increased microbial abundance and antimicrobial resistance, yet less alpha diversity. Researchers implementing metagenomics into the livestock environment should consider season, the microclimate, and livestock growth stage as influential upon their findings. Considering the increasing accessibility of long-read sequencing, future research should explore its viability within a novel uniform testing protocol for bioaerosol emissions.
Essential oils improve nursery pigs' performance and appetite via modulation of intestinal health and microbiota
2024, Animal Nutrition
Optimal intestinal health and functionality are essential for animal health and performance, and simultaneously intestinal nutrient transporters and intestinal peptides are also involved in appetite and feed intake control mechanisms. Given the potential of essential oil (EO) in improving animal performance and improving feed palatability, we hypothesized that dietary supplementation of cinnamaldehyde and carvacrol could improve performance and appetite of nursery pigs by modulating intestinal health and microbiota. Cinnamaldehyde (100 mg/kg), carvacrol (100 mg/kg), and their mixtures (including 50 mg/kg cinnamaldehyde and 50 mg/kg carvacrol) were supplemented into the diets of 240 nursery pigs for 42 d, and data related to performance were measured. Thereafter, the influence of EO on intestinal health, appetite and gut microbiota and their correlations were explored. EO supplementation increased (P < 0.05) the body weight, average daily gain (ADG) and average daily feed intake (ADFI) of piglets, and reduced (P < 0.05) diarrhea rates in nursery pigs. Furthermore, EO increased (P < 0.05) the intestinal absorption area and the abundance of tight junction proteins, and decreased (P < 0.05) intestinal permeability and local inflammation. In terms of intestinal development and the mucus barrier, EO promoted intestinal development and increased (P < 0.05) the number of goblet cells. Additionally, we found that piglets in the EO-supplemented group had upregulated (P < 0.05) levels of transporters and digestive enzymes in the intestine, which were significantly associated with daily gain and feed utilization. In addition, EO supplementation somewhat improved appetite in nursery pigs, increased the diversity of the gut microbiome and the abundance of beneficial bacteria, and there was a correlation between altered bacterial structure and appetite-related hormones. These findings indicate that EO is effective in promoting growth performance and nutrient absorption as well as in regulating appetite by improving intestinal health and bacterial structure.
Contribution of nadR to the cell growth and virulence of Streptococcus suis serotype 2
2024, Veterinary Microbiology
Streptococcus suis serotype 2 (SS2) has been reported to be a highly invasive pathogen in swine and a zoonotic agent for humans. Although many bacterial virulence factors have been identified, our an insightful understanding of SS2 pathogenicity is lacking. The gene nadR, encoding nicotinamide-nucleotide adenylyltransferase, was first reported as a regulator and transporter of the intracellular NAD synthesis pathway in Salmonella typhimurium. In this study, we constructed a mutant strain of nadR (ΔnadR) to test the phenotypic and virulence variations between the deletion mutant and the wild-type strain ZY05719. The phenotypic experimental results showed that ΔnadR obviously inhibited cell growth and exhibited shorter chains than WT. The growth defect of ΔnadR was caused by the loss of the function of nadR for transporting the substrates nicotinamide mononucleotide and nicotinamide riboside in the intracellular NAD synthesis pathway. In the process of interaction with the host, ΔnadR participated in adherence and invasion to the host cells, and it was more easily cleared by RAW264.7 macrophages. More importantly, both zebrafish and BALB/c mice in vivo virulence experimental results showed that ΔnadR dramatically attenuated the virulence of SS2, and the ability of ΔnadR to colonize tissues was notably reduced in comparison with that of WT in the BALB/c mice infection model. To the best of our knowledge, this is the first time to demonstrate that nadR not only plays an important role in bacterial growth, but also in connection with the virulence of SS2 as a global transcriptional regulator.
Prevalence of Streptococcus suis in pigs in China during 2000–2021: A systematic review and meta-analysis
2023, One Health
Streptococcus suis (S. suis) is one of the most important pathogens affecting pig production worldwide. It can be also transmitted to human through the behaviors of eating undercooked pork or slaughtering sick pigs. A meta-analysis was conducted to estimate the prevalence across different geographical areas in China. Forty-three articles were included and distributed in 22 provinces of China. The prevalence of S. suis infection in pigs varied from 4.2% to 93.7%, with a summary estimate of 40.8% (95%CI, 32.9–48.6%). Six provinces, classified as frequent outbreaks in human cases, had a higher prevalence (52.7%, 95%CI: 43.7–61.6%) than other provinces (36.0%, 95%CI: 27.0–44.9%). Jiangsu province had the highest prevalence with 73.1% (95%CI: 70.42–75.68%), followed by Hunan (59.64%, 95%CI: 55.83–63.37%), Shanxi (55.56%, 95%CI: 47.05–63.83%), and Guangxi (50.55%, 95%CI: 49.45–51.64%). The prevalence has been decreasing gradually, from 47.6% (95%CI: 38.1–57.1%) before 2010, then dropped to 39.1% (95%CI: 25.5–52.8%) during 2011–2015, and reached the lowest in recent five years (2016–2020), with 34.3% (95%CI: 23.1–45.4%). The study findings showed that S. suis was presented in pig populations of most provinces of China, which indicated that effective control measures in pigs should be implemented. Our results also provided solid evidence for the early warning and prevention of human S. suis infection in China, which would mitigate the risk to humans.
Fulminant Streptococcus suis infection detected on peripheral blood smear: A case report
2023, Journal of Infection and Chemotherapy
Streptococcus suis, a gram-positive coccus, is recognized as an emerging zoonotic pathogen that causes serious infections in humans, such as bacterial meningitis and sepsis, with poor outcomes. The pathogen is known to be transmitted through the consumption of raw pork or occupational exposure to pigs. A previously healthy 38-year-old woman with occupational exposure to raw pork was presented to our emergency department with a clinical diagnosis of rapidly progressive septic shock. Peripheral blood smears detected chains of cocci inside granulocytes, which led to the early recognition of gram-positive cocci in short chains before the blood culture test results. Blood cultures later tested positive for S. suis serotype 2. The patient's condition deteriorated despite aggressive resuscitative measures including antibiotics, vasopressors, multiple blood transfusions, mechanical ventilation, and renal replacement therapy. Initiation of veno-arterial extracorporeal membrane oxygenation was ineffective, and the patient died 16 h after admission. The identification of bacteria in the peripheral blood smear indicated an overwhelming infection and led to the rapid recognition of bacteremia. Our report aims to raise awareness about fatal zoonotic pathogens and to promote the unique role of peripheral blood smears that could provide preliminary diagnostic information before blood culture results.
Streptococcus suis meningoencephalitis diagnosed with metagenomic next-generation sequencing: A case report with literature review
2023, Journal of Infection and Chemotherapy
Streptococcus suis is a pathogen of emerging zoonotic diseases and meningoencephalitis is the most frequent clinical symptom of S. suis infection in humans. Rapid diagnosis of S. suis meningoencephalitis is critical for the treatment of the disease. While the current routine microbiological tests including bacterial culture and gram staining are poorly sensitive, diagnosis of S. suis meningoencephalitis by metagenomic next-generation sequencing (mNGS) has been rarely reported. Here, we report a 52-year-old female pork food producer with a broken finger developed S. suis meningoencephalitis. After her admission, no pathogenic bacteria were detected through bacterial culture and Gram staining microscopy in the cerebrospinal fluid obtained via lumbar puncture. However, mNGS identified the presence of S. suis in the sample. mNGS is a promising diagnostic tool for rapid diagnosis of rare infectious diseases in the central nervous system.

View all citing articles on Scopus

View full text

ReviewStreptococcus suis: an emerging zoonotic pathogen

Summary

Introduction

Section snippets

Biological features

Identification

Clinical signs in human infection

Pathology

Epidemiology

Diagnosis and treatment

Prevention and control

Conclusions

Search strategy and selection criteria

Vet Microbiol

Vet Microbiol

Lancet

Vet Microbiol

Vet Microbiol

Microb Pathog

FEMS Immunol Med Microbiol

Microb Pathog

FEMS Microbiol Lett

FEMS Microbiol Lett

Res Vet Sci

Vet Microbiol

Clin Neurol Neurosurg

Enferm Infecc Microbiol Clin

Lancet

Trans R Soc Trop Med Hyg

Streptococcus suis: past and present

Vet Res Commun

Meningitis caused by Streptococcus suis in humans

Rev Infect Dis

Streptococcus suis meningitis

An Med Interna

Analysis of infectious syndrome caused by Streptococcus suis type 2

Jiangsu Med J

Ministry of Health of People's Republic of China. Report of human Streptococcus suis in Sichuan (in Chinese)

Investigation on 8 human cases with meningitis caused by Streptococcus suis type 2

Chin J Prev Med

Description of 14 new capsular types of Streptococcus suis

J Clin Microbiol

Characterization of six new capsular types (23 through 28) of Streptococcus suis

J Clin Microbiol

Immunomagnetic isolation of Streptococcus suis serotypes 2 and 1/2 from swine tonsils

J Clin Microbiol

Isolation and characterization of Streptococcus suis capsular types 9–22

J Vet Diagn Invest

Description of six new capsular types (29–34) of Streptococcus suis

J Vet Diagn Invest

Serotyping and evaluation of the virulence in mice of Streptococcus suis strains isolated from diseased pigs

Rev Inst Med Trop Sao Paulo

Streptococcus suis infection in swine. A sixteen month study

Can J Vet Res

Streptococcus suis infection as a cause of severe illness: 2 cases from Croatia

Scand J Infect Dis

Prevalence of Streptococcus suis types 1 and 2 in domestic pigs in Australia and New Zealand

Vet Rec

Carrier rate of Streptococcus suis capsular type 2 in palatine tonsils of slaughtered pigs

J Clin Microbiol

Factors affecting the survival of Streptococcus suis type 2

Vet Rec

Susceptibility of Streptococcus suis to penicillin

J Vet Diagn Invest

Biochemical traits and antimicrobial susceptibility of Streptococcus suis isolated from slaughtered pigs

Zentralbl Veterinarmed B

Streptococcus suis

Virulence markers of Streptococcus suis type 1 and 2

Adv Exp Med Biol

Purification and characterization of a 52-kilodalton immunoglobulin G-binding protein from Streptococcus suis capsular type 2

J Bacteriol

Identification and characterization of the cps locus of Streptococcus suis serotype 2: the capsule protects against phagocytosis and is an important virulence factor

Infect Immun

Environmentally regulated genes of Streptococcus suis: identification by the use of iron-restricted conditions in vitro and by experimental infection of piglets

Microbiology

Structure, regulation, and putative function of the arginine deiminase system of Streptococcus suis

J Bacteriol

Identification and characterization of two temperature-induced surface-associated proteins of Streptococcus suis with high homologies to members of the arginine deiminase system of Streptococcus pyogenes

J Bacteriol

Cloning and nucleotide sequence of the gene encoding the 136-kilodalton surface protein (muramidase-released protein) of Streptococcus suis type 2

Review
Streptococcus suis: an emerging zoonotic pathogen