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Title : A 54 year-old female w/ both knee pain
Date : Aug. 1, 2010
Contributed by

Sang Taek Heo MD PhD
Gyeongsang National University Hospital, Korea

Patient History
Age/Sex A 54 yr-old / Woman
Chief complaint both knee pain
Present illness

A 54-year-old, previously healthy woman with a five-month history of both knee pains was referred to our hospital. Two months ago, she was took the arthroscopic synobectomy on the left knee at the local clinics. On one week after operation, she had a pain and swelling on the left knee and took the antibiotics. Before one week on the admission, she got an incision and debridement for suspicious infectious arthritis on the both knees. She was referred to our hospital because of continuous knees pain and fever after operation.

Past medical history

  The patient had been healthy without any specific medical problem before this episode.

Physical examination

Initial chest x-ray was normal.  The lower extremities CT was checked (Figure). The fluid collections of peri-articular area were aspirated.

On the third day of hospitalization, Results from fluid aspirations were obtained 2 positive of AFB stain and negative of TB-PCR. We started antibiotics and anti-Tb medication (HREZ). But, she kept feeling febrile sense.

Radiologic findings

 
Question - ID Case of the Week ( Aug. 1, 2010 )
What is the most likely causative microorganism in this patient?
 
Correct Answer

NTM (Mybacterium abscessus) periarticular abscess

 

 
Review

Nontuberculous mycobacterial (NTM) species are generally free-living organisms that are ubiquitous in the environment. There have been more than 140 NTM species identified. Disseminated disease in severely immunocompromised patients (most commonly caused by MAC and less commonly by the rapidly growing mycobacteria [RGM], eg, M. abscessus, M. fortuitum, and M. chelonae).

Rapidly growing mycobacteria (RGM) include three clinically relevant species: M. fortuitum, M. chelonae, and M. abscessus. The RGM are environmental organisms found worldwide that usually grow in culture in less than one week following initial isolation, and may sometimes grow on standard microbiologic media (rather than requiring special mycobacterial media).

Skin and soft tissue infection — RGM are an uncommon cause of soft tissue infection. A high index of suspicion is necessary for diagnosis. Signs and symptoms include nodules (frequently with purple discoloration), recurrent abscesses, or chronic discharging sinuses.

In a retrospective case series of 63 patients with skin and soft tissue infections due to RGM, the following findings were noted:

  • M. fortuituminfections were more likely to present as a single lesion (89 percent)
  • M. chelonaeand M. abscessus were more likely to present as multiple lesions (62 percent)
  • Patients with multiple lesions were more likely to be immunosuppressed (67 percent)

Musculoskeletal infection — Infection of the musculoskeletal system with RGM usually involves tenosynovitis and occurs from either percutaneous inoculation (eg, trauma or surgery) or hematogenous seeding. The clinical course is indolent, slowly progressive, and destructive, in part because of a delay in diagnosis.

Treatment- For serious skin, soft tissue, and bone infections caused by M. abscessus, clarithromycin 1,000 g/day or azithromycin 250 mg/day should be combined with parenteral medications (amikacin, cefoxitin, or imipenem). Intravenous amikacin is given at a dose of 10 to 15 mg/kg daily to adult patients with normal renal function to provide peak serum levels in the low 20 mg/ml range.

The lower dose (10 mg/kg) should be used in patients older than 50 years and/or in patients in whom long-term therapy (3 wk) is anticipated. The three times-weekly amikacin dosing at 25 mg/kg is also reasonable, but may be difficult to tolerate over periods longer than 3 months. The amikacin combined with high-dose cefoxitin (up to 12 g/d given intravenously in divided doses) is recommended for initial therapy (minimum, 2 wk) until clinical improvement is evident. Limited cefoxitin availability may necessitate the choice of an alternative agent such as imipenem (500 mg two to four times daily), which is a reasonable alternative to cefoxitin (175, 359, 360). For serious disease, a minimum of 4 months of therapy is necessary to provide a high likelihood of cure. For bone infections, 6 months of therapy is recommended. Surgery is generally indicated with extensive disease, abscess formation, or where drug therapy is difficult.  We treated our patient with clarithromycin single therapy. She's been in good clinical status so far.

 


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