streptococcus suis is a zoonotic pathogen that can be transferred from pigs to humans , including humans ( with or without wounds ) who handle raw pork or have close contact with infected pigs ( e.g. , pig farmers ) . serotypes 2 and 14 are prevalent among patients with s. suis infections , although other serotypes ( 1 , 4 , 5 , 16 , and 24 ) have been detected in rare human cases . screened among 179 human s. suis strains isolated from clinical specimens in thailand ( 20062008 ) and reported that 165 ( 92.2% ) and 12 ( 6.7% ) strains were of serotype 2 and 14 , respectively , whereas only one ( 0.6% ) each was of serotype 5 and 24 . we herein report a human case of uncomplicated bacteremia due to s. suis serotype 5 in japan . furthermore , we provide the review of literature concerning clinical and microbiological characteristics of 4 human cases of infection due to s. suis serotype 5 . a 48-year - old man was admitted to our hospital with fever , rigors , and swelling of the right forefinger . the patient was a heavy user of alcohol without the underlying liver disease who had been working for a kushiyaki ( meat skewer restaurant ) , a job that included handling raw pork with his bare hands and occasional accidental stabbing of a finger with a skewer . two days before visiting our hospital , this individual had deeply stabbed his right forefinger with a skewer . on arrival in the emergency room , the patient had a body temperature of 39.4  c , and exhibited no neck stiffness or meningism , nor peripheral stigmata of infective endocarditis ; precordial examination revealed no audible cardiac murmur . leukocyte cell count and c - reactive protein were 8200/l and 0.40  mg / dl , respectively . after admission , blood culture by duplicate bottles revealed the presence of gram - positive cocci . given the patient s routine handling of raw pork , infection by s. suis was suspected ; this species identification was confirmed based on percent probability ( 98.9% ) match to biochemical parameters obtained using rapid i d 32 strep api ( sysmex biomrieux co. , ltd . , tokyo , japan ) . a transesophageal echocardiography , a computed tomography of the chest - abdomen - pelvis , and a magnetic resonance imaging of the brain failed to reveal evidence of infective foci . therefore , the patient was diagnosed with uncomplicated bacteremia due to s. suis , and was treated with a 2-week course of penicillin g ( 8 million units , three times per day , daily dose 24 million units ) . treatment was successful ; the patient remained well , with no recurrence of bacteremia , during 12 months of follow up . this speciation was further confirmed based on 99.86% ( 1415/1417  bp ) sequence identity to s. suis s735 ( t ) , in addition to amplification of species - specific glutamate dehydrogenase gene from the patient isolate . polymerase chain reaction ( pcr)-based capsular typing demonstrated that the isolate was of serotype 5 . multilocus sequence typing ( mlst ) was performed by sequencing 7 housekeeping genes ( aroa - cpn60-dpr - gki - muts - reca - thra ) according to the website for s. suis ( http://pubmlst.org/ssuis/ ) ; our results revealed the presence of a novel sequence type ( st ) 752 [ allelic profile , 8 - 21 - 5 - 264(new allele)-44 - 22 - 23 ] for this strain . virulence - associated gene ( vag ) profiling was performed as previously described ; both sly ( encoding the hemolysin suilysin ) and mrp ( encoding a muramidase - released protein ) were detected without amplification of epf ( encoding the extracellular factor ) . furthermore , antimicrobial testing suggested that the isolate would be classified as resistance to tetracycline ( tc ) and macrolide / lincosamide ( ml ) ( clarithromycin and clindamycin ) . note , however , that these classifications employed the breakpoints for viridans group streptococci , since the clinical and laboratory standards institute guidelines do not provide breakpoints for s. suis . our pcr - based results indicated that this isolate possessed both tet(o ) , the tc - resistance determinant , and erm(b ) , the ml - resistance determinant , . strains of serotype 5 are routinely isolated from diseased pigs . according to the mlst database , the porcine - linked serotype 5 isolates have been reported from uk , denmark , china , vietnam , and poland . clinical and microbiological features of four human cases of s. suis serotype 5 infections are shown in table 1 , table 2 . three previous patients infected with the serotype 5 strains have been documented : a patient eating raw pork who developed spontaneous bacterial peritonitis in thailand , a pig farmer with the wound who developed septic arthritis in sweden , and a pig farmer without the wound who developed arthroplasty infection and streptococcal toxic shock - like syndrome in the us . spontaneous bacterial peritonitis due to the other serotypes ,   as well as the arthritis and the streptococcal toxic shock syndrome are already documented . on the other hand , to our knowledge , this is the first report on the arthroplasty infection associated with the serotype 5 . we should further clarify the relationship between the arthroplasty infection and this serotype , based on the collection of human cases and the literature review . to the best of our knowledge , the present patient handling with raw pork is the first human case of uncomplicated bacteremia due to serotype 5 in japan . because most of human s. suis infections are associated with clonal complex ( cc ) 1 strains including st1 strains , cc1 strains are considered to be the most hazardous ones for humans . interestingly , we confirmed the new sequence type , st752 , of this isolate . the single locus variant ( allelic profile , 8 - 21 - 5 - 45 - 44 - 22 - 23 ) was found to match that of an st108 strain isolated from the heart and lung of pigs in japan , suggesting domestic distribution of the pigs harboring strains of st108 as well as cc1 with potential pathogenicity in humans . however , future work will need to evaluate serotype 5 strains for the presence of other virulence - associated factors . resistance of s. suis to antimicrobials ( macrolide / lincosamide , sulphonamides , and tetracycline ) commonly used in pigs is documented worldwide , with resistance in up to 85% of strains . bojarska and the colleagues   have reported that five isolates ( 24% ) of 21 invasive human infections were non - susceptible to ml and tc , and harbored the tet(o ) and erm(b ) genes . therefore , resistance should be considered when any of these classes are not effective in human clinical settings . in conclusion , clinicians should be aware of this microorganism when examining and treating patients with fever , who are handling raw pork or having close contact with infected pigs even if they are immunocompetent .
highlightsthis is the first document concerning human case of bacteremia due to streptococcus suis serotype 5 in japan.we confirmed the novel sequence type 752 of this isolate.both sly ( encoding the hemolysin suilysin ) and mrp ( encoding a muramidase - released protein ) were detected with no amplification of epf ( encoding the extracellular factor ) , showing the virulence - associated gene profiling.this isolate had both tet(o ) and erm(b ) as the antimicrobial resistance genes .