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Title : 69 year-old Female w/ right knee pain
Date : October 18, 2011
Contributed by

Min Hee Lim  M.D. Samsung Medical Center

Patient History
Age/Sex 69/Female
Chief complaint Right knee pain
Present illness

A 69-year-old women presents with one day history of right knee pain.

Past medical history

She was admitted to the orthopedic department and underwent right total knee replacement arthroplasty for degenerative arthritis 6 years ago. She was being treated for right knee pain with acupuncture in right knee for 5 weeks before 6 months.

Physical examination

The patient was seen acute looking appearance. Her temperature was 38.1; pulse, beats 112 per minute; blood pressure 101/60 mmHg; and respiratiorn rate, 20 per minute. Her right knee was swollen.

Initial laboratory findings

The CBC revealed 9730 (Neutrophil segmented 91.6%) >11.4<124K. The ESR was 95 mm/h and CRP was 29.88 mg/dL. The level of AST/ALT was 53/41 IU/L and BUN/Cr was 29.9/1.35 mg/dL.

Radiologic findings
Hospital course

The right knee joint fluid aspiration was done. The joint fluid was turbid and fluid analysis results revealed infected arthritis (RBC 500/uL, WBC 105,000/uL; poly 73%, lympho 7%). She received vancomycin, and underwent urgent debridement of the right knee. Intraoperative findings revealed very turbid yellowish joint fluid at intraarticular space and periarticular soft tissue was infected. The existing prostheses were removed and repeated debridement was done. On the third hospital day, closed pus and blood cultures drawn on admission grew gram positive cocci arranged in chain. She complained for her progressive lower back pain. She also had history of surgery of lumbar spine for spinal stenosis. Lumbar spine MRI was done.

Question - ID Case of the Week ( October 18, 2011 )
The patient has developed prosthetic knee joint infection and bacteremia with concomitant infectious spondylitis at the same time. What do you think the most likely causative organism is?
Correct Answer

Group B hemolytic streptococci


The most serious complication of joint prosthesis is infection with an incidence of 1.5-2.5% for primary interventions and up to 20% for revision procedures. Staphylococci are the most frequently isolated organism at all time points: early, delayed and late. CoNS account for most of these (30%-41%) with S. aureus as the second most common (12%-39%). Late infections ar presumed to be of haematogenous aetiology and S. aureus seems to predominate at this point. Streptococci, enterococci and diphtheroids each account for around 10% of cases. Gram-negative organisms are much less common than Gram-positive, causing around 8% of cases. Little is known about group B streptococcus (GBS) in periprosthetic joint infections. Recently, however, the incidence of invasive GBS infections in non-pregnant adults is increasing. The median frequency of GBS prosthetic joint infection was around 3%. GBS prosthetic joint infections commonly occurs in patients with several comorbidities and often presents with acute symptoms and damaged periprosthetic soft tissue. Also, infection frequently presents ≥3 months after implantation, indicating a predominantly haematogenous route. The most common clinical presentation of invasive GBS infections reported was bacteremia without focus, followed by skin and/or soft tissue infection and pneumonia. Outcome of GBS prosthetic joint infections is good. The optimal treatment strategy for GBS prosthetic joint infection is unknown. Penicillin is the antimicrobial agent of choice of GBS infection. Debridement with retention of the implant can be successfully performed if the duration of symptoms is short, the implant stable, and the tissue damage minor.



1.      Prosthetic joint infections: microbiology, diagnosis, management and prevention. International Journal of Antimicrobial Agents. 2008;32:287-293

2.      The diagnosis and management of prosthetic joint infections. Journal of Antimicrobial Chemotherapy. 2010;65 suppl 3:iii45-54

3.      Increasing Burden of Invasive Group B Streptococcal Disease in Nonpregnant Adults, 1990-2007. Clinical Infectious Diseases. 2009;49:85-92

4.      Invasive Group B streptococcal Disease in the Elderly, Minnesota, USA, 2003-2007. Emerging Infectious Diseases. 2009;15:1279-1281

5.      Group B streptococcus in prosthetic hip and knee joint-associated infections. Journal of Hospital Infection. 2011;79:64-69


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