Human case of Streptococcus suis serotype 16 infection.
Streptococcus suis infection is an emerging zoonosis Zoonosis Definition
Zoonosis, also called zoonotic disease refers to diseases that can be passed from animals, whether wild or domesticated, to humans. in Southeast Asia. We report a fatal case of S. suis serotype 16 infection in a Vietnamese man in 2001.
Streptococcus suis is a gram-positive, facultatively anerobic coccus coccus
Spherical bacterium. Many species have characteristic arrangements that are useful in identification. Pairs of cocci are called diplococci; rows or chains, streptococci (see streptococcus); grapelike clusters, staphylococci (see that may cause pneumonia, meningitis, septicemia septicemia (sĕptĭsē`mēə), invasion of the bloodstream by virulent bacteria that multiply and discharge their toxic products. The disorder, which is serious and sometimes fatal, is commonly known as blood poisoning. , and arthritis in pigs. The pig can also be a healthy carrier of S. suis in the upper respiratory tract (particularly the tonsils tonsils, name commonly referring to the palatine tonsils, two ovoid masses of lymphoid tissue situated on either side of the throat at the back of the tongue. and nasal cavities), the genital tract, and the alimentary tract (1,2). The first case of S. suis infection in humans was reported in Denmark in 1968. Since then, increasing numbers of cases have been reported in many countries, including the Netherlands; the United Kingdom; France; Hong Kong Special Administrative Region A special administrative region may be:
The Hospital for Tropical Diseases (HTD) in Ho Chi Minh City Ho Chi Minh City, formerly Saigon, city (1997 pop. 5,250,000), on the right bank of the Saigon River, a tributary of the Dong Nai, Vietnam. , Vietnam (N.T.H Mai et al., unpub, data). The number of cases is likely underreported and will likely increase further with increased awareness and enhanced capacity to culture and identify S. suis.
A 57-year-old unemployed man from Long An Province, southern Vietnam, who had a history of alcohol abuse, had a 10-day history of abdominal pain, jaundice, anorexia, and weight loss. At the time of admission to HTD in 2001, the patient was lethargic, his vital signs were stable, and his neck was not stiff. Physical examination showed cutaneous spider naevi, jaundice, hepatosplenomegaly, and ascites. Leukocyte count was 15.3 x 103 cells/[mu]L (70% neutrophils), blood urea nitrogen blood urea nitrogen
n. Abbr. BUN
Nitrogen in the form of urea in the blood or serum, used as a indicator of kidney function.
Blood urea nitrogen (BUN) 12.1 mmol/L (reference range 3.57-7.14 mmol/L), creatinine 150 gmol/L (< 115 mmol/L), sodium 127 mmol/L (135-145 mmol/L), potassium 6.67 mmol/L (3.5-5.1 mmol/L), serum aspartate aminotransferase 87 IU/L (12-30 IU/L), serum alamine aminotransferase 41 IU/L (13-40 IU/L), and albumin 20 g/L (35-52 g/L). An abdominal ultrasound examination showed hepatosplenomegaly and ascites. Ascitic fluid was cloudy and contained 5 g/L protein. Results of Gram stain and culture of ascitic fluid were negative. A diagnosis of spontaneous bacterial peritonitis spontaneous bacterial peritonitis Spontaneous peritonitis Critical care A severe acute infection of the peritoneum that accompanies end-stage liver disease and ascites Agents E coli, Klebsiella spp, S pneumoniae, Enterococcus faecalis associated with alcoholic liver cirrhosis was made, and the patient was treated with 2 g/day of ceftriaxone.
Twenty-four hours after admission, acute respiratory distress developed. The patient's family decided to take him home because they were unable to pay for further treatment; the patient died on the same day. The blood culture (BACTEC 9050 system; Becton Dickinson Microbiology Systems, Sparks, MD, USA), which was taken at the time of admission, grew S. suis 24 hours after collection. Further inquiries into potential pig exposure, after the blood culture results were reported, indicated that the patient kept pigs near his house and was known to regularly consume portions of the pig that had a high risk of being contaminated, such as the intestine.
S. suis was identified on the basis of colony morphology, negative katalase reaction, optochin resistance, and APlStrep (bioM6rieux, Marcy l'Etoile, France). Serotyping was performed by slide agglutination agglutination, in biochemistry
agglutination, in biochemistry: see immunity.
agglutination, in linguistics
agglutination, in linguistics: see inflection. using specific antisera (Statens Serum Institute, Copenhagen, Denmark) and was positive for serotype 16. Confirmation of the serotype was performed at the International Reference Laboratory for S. suis Serotyping, Quebec City, Quebec, Canada (M. Gottschalk). This strain was susceptible to penicillin (MIC 0.032 mg/L), ceftriaxone (0.064 mg/L), rifampin (0.032 mg/L), chloramphenicol chloramphenicol (klōr'ămfĕn`əkŏl'), antibiotic effective against a wide range of gram-negative and gram-positive bacteria (see Gram's stain). It was originally isolated from a species of Streptomyces bacteria. (2 mg/L), erythromycin erythromycin (ĭrĭth'rōmī`sĭn), any of several related antibiotic drugs produced by bacteria of the genus Streptomyces (see antibiotic). (0.064 mg/L), levofloxacin (0.38 mg/L), and vancomycin (0.5 mg/L) but resistant to tetracycline (64 mg/L) by E-test (AB-Biodisk, Solna, Sweden) when Clinical Laboratory Standard Institute breakpoints were used. On pulsed-field gel electrophoresis (PFGE) that used restriction enzyme SmaI, this strain showed little similarity with a representative set of serotype 2 isolates from Vietnam (Figure). Multilocus sequence typing Multilocus sequence typing (MLST) is a technique in molecular biology for the typing of multiple loci. The procedure characterizes isolates of bacterial species using the DNA sequences of internal fragments of multiple (usually seven) housekeeping genes. (MLST) (www.mlst.net) showed that the sequence of 5 of 7 alleles of the included housekeeping genes had not been previously described. Thus, this strain was assigned the new sequence type 106. On eBURST analysis (www.mlst.net), this sequence type does not belong to any of the clonal complexes but is a singleton. PCR PCR polymerase chain reaction.
polymerase chain reaction
Polymerase chain reaction (PCR) for detection of the genes encoding the putative virulence factors extracellular protein factor (EF) and suilysin were negative. Results of Western blot for detection of muramidase-released protein (MRP) and EF, using rabbit polyclonal antibody against MRP and EF (provided by H. Smith, the Netherlands), were also negative. S. suis serotype 2 strains 31533 and 89-1591 (provided by M. Gottschalk, Canada) were used as positive and negative controls respectively.
The total number of human S. suis infections reported until August 2006 was [approximately equal to] 400, and nearly 90% of these cases occurred in China, Thailand, Hong Kong, Taiwan, and the Netherlands (4). These data did not include at least 200 cases of S. suis infection in Vietnam (C. Schultsz, unpub. data). At present, 33 capsular serotypes of S. suis have been recognized (1,4). S. suis serotype 2 is considered to be the most pathogenic to pigs and humans. All human cases of S. suis infection for which serotyping was available were caused by S. suis serotype 2, except for 1 case of serotype 1 (9), l case of serotype 4 (3), and 1 case of serotype 14 (6). Among 116 cases of S. suis meningitis seen at HTD from 1997 through 2005, 115 were caused by serotype 2 and 1 by serotype 14.
S. suis serotype 2 can cause meningitis, septicemia and septic shock, arthritis, endocarditis endocarditis (ĕn'dōkärdī`tĭs), bacterial or fungal infection of the endocardium (inner lining of the heart) that can be either acute or subacute. , pneumonia, endophthalmitis, and cellulitis Cellulitis Definition
Cellulitis is a spreading bacterial infection just below the skin surface. It is most commonly caused by Streptococcus pyogenes or Staphylococcus aureus. in humans (3,5,8). The mortality rate for S. suis serotype 2 meningitis is <10% (10), but it can reach 70% among patients with septicemia and septic shock (11). The exact route of infection for humans is not known. Cases have been linked to accidental inoculation through skin injuries, for example, during occupational exposure to pigs and pork, but inhalation of aerosols and ingestion of contaminated food have also been suggested (3,9,11,12). Preexisting pre·ex·ist or pre-ex·ist
v. pre·ex·ist·ed, pre·ex·ist·ing, pre·ex·ists
To exist before (something); precede: Dinosaurs preexisted humans.
v.intr. medical conditions, such as alcoholism and liver cirrhosis, as was present in our patient, or a prior splenectomy Splenectomy Definition
Splenectomy is the surgical removal of the spleen, which is an organ that is part of the lymphatic system. The spleen is a dark-purple, bean-shaped organ located in the upper left side of the abdomen, just behind the bottom of the may predispose to severe infection.
Serotype 16 has never been isolated from humans and, to our knowledge, has also rarely been reported as a cause of invasive disease in pigs. One isolate of S. suis serotype 16 was reported from a diseased pig in Germany and 4 isolates from slaughter pigs in South Korea (13,14). The S. suis serotype 16 strain was sensitive to all antimicrobial agents tested except tetracycline, as has been reported for serotype 2 isolates (5). PFGE results showed that this human serotype 16 isolate was unrelated to human serotype 2 isolates. On MLST, this isolate had a new sequence type that did not belong to any of the clonal complexes. In contrast, most serotype 2 isolates reported so far belong to clonal complex 1 (www.mlst.net). Taken together, these results suggest that capsule switch, such as has been observed for S. pneumoniae, does not explain the emergence of invasive isolates of a different serotype. In addition, the PCR and Western blot analyses indicate that the serotype 2 capsule, EF, MRP, or suilysin is not required for virulence or S. suis in humans, as has also been shown in pigs.
S. suis infection is an emerging zoonosis in Asia. Strains with serotype 16 are among those capable of infecting humans.
This study was supported by The Wellcome Trust.
Dr Nghia is an infectious disease specialist. His research interests include the epidemiology, diagnosis, clinical manifestations, and treatment of Streptococcus suis infection in Vietnam.
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A disease which can be spread from animals to humans.
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an infection of the blood which develops in a wound [Greek sēptos decayed + haima blood]
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Pertaining to any of the Streptococcus bacteria. toxic shock syndrome toxic shock syndrome (TSS). acute, sometimes fatal, disease characterized by high fever, nausea, diarrhea, lethargy, blotchy rash, and sudden drop in blood pressure. It is caused by Staphylococcus aureus, an exotoxin-producing bacteria (see toxin). caused by Streptococcus suis serotype 2. PLoS Med. 2006;3:e151.
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Ho Dang Trung Nghia, * Ngo Thi Hoa, * Le Dieu Linh, * James Campbell, * To Song Diep, ([dagger]) Nguyen Van Vinh Chau, ([dagger]) Nguyen Thi Hoang Mai, * Tran Tinh Hien, ([dagger]) Brian Spratt, ([double dagger]) Jeremy Farrar, * and Constance Schultsz *
* Oxford University Clinical Research Unit, Ho Chi Minh City, Vietnam; ([dagger]) Hospital for Tropical Diseases, Ho Chi Minh City, Vietnam; and ([double dagger]) Imperial College London History
Imperial College was founded in 1907, with the merger of the City and Guilds College, the Royal School of Mines and the Royal College of Science (all of which had been founded between 1845 and 1878) with these entities continuing to exist as "constituent colleges". , London, United Kingdom
Address for correspondence: Constance Schultsz, Oxford University Clinical Research Unit, The Hospital for Tropical Diseases, 190 Ben Ham Tu, Quan 5, Ho Chi Minh City Vietnam; email: email@example.com