Infection after knee arthroplasty in an immunosuppressive patient caused by Mycobacterium senegalense: a case report and literature review

Background The infection caused by nontuberculous Mycobacterium (NTM) is gradually increasing in both hospital-acquired infection and community-acquired infection. The most common NTM mainly includes Mycobacterium fortuitum group, the M. chelonae/abscessus group and the M. smegmatis group. The infection caused by the third biological variety in M. fortuitum group is rarely reported worldwide. Case presentation A 33-year-old female patient with 8-year history of rheumatoid arthritis underwent a right knee arthroplasty and developed postoperative infection. In hospital A, debridement was carried out to preserve the prosthesis joint. M. fortunatum was cultured in biopsy tissue taken out during operation and puncture fluid. Unfortunately, it is impossible to carry out the drug sensitivity test of Mycobacterium in hospital A. Local doctors used amikacin and levofloxacin to treat the patient empirically. In order to treat the infection accurately, the patient went to hospital B (a specialized hospital of tuberculosis) for drug sensitivity test. According to the results of drug sensitivity, cefoxitin, clarithromycin, amikacin and moxifloxacin were used in combination treatment. After two weeks of treatment, there was no significant remission, so the patient went to hospital C (a large teaching hospital) for joint prosthesis removal and bone cement frame transfer operation, and anti-infection treatment was carried out according to the drug sensitivity test results. One month later, the patient's condition improved significantly and the wound healed. Conclusions NTM should be considered as main pathogens in immunosuppressive patients when the wound did not heal due to infection. Simple antibiotic treatment is not good for deep abscess, but treatment combined with surgical debridement and appropriate antibiotics is obviously effective.


Case Presentation
A 33-year-old female patient developed incision pain accompanied by exudation of yellow purulent secretion after right knee replacement ( fig 1). The patient had a history of rheumatoid arthritis for more than 8 years. She took methotrexate and leflunomide for a long time. The patient first went to hospital A and found that the right knee joint was swollen and the skin temperature was slightly high.
The incision of the operation was interrupted, which could be seen to pass through the superficial subcutaneous sinus about the size of mung bean all the time, and the yellow brown purulent secretion could be seen to flow out ( fig 1). The main laboratory test positive indexes were C-reactive protein 32.97mg/l, rheumatoid factor 78.7u/ml, ESR 120mm / h, hemoglobin 85g / L, albumin 27g / L, blood potassium 3.36mmol/l, blood calcium 1.72mmol/l. The swollen right knee joint was punctured, and a large number of leukocytes were found in the puncture fluid and M. fortunatum was detected in the puncture fluid culture. The surgeons performed surgical debridement while preserving the prosthesis joint. M. fortuitum was detected in the tissues taken during operation and the culture of puncture fluid. Because in hospital A the drug sensitivity test of M. fortuitum is unable to be carried out, amikacin 0.4g per day, levofloxacin 0.6g per day intravenous drip were used to treat the patients. In order to accurately use antibiotics for treatment, the patient went to hospital B (a special hospital of tuberculosis) to carry out the drug sensitivity test of M. fortuitum. According to the results of drug sensitivity, the doctors adjusted the treatment drug, and changed it into intravenous drip of cefoxitin 4.0 g twice a day, intravenous drip of amikacin 0.5 g once a day, intravenous drip of moxifloxacin 0.4 g once a day, and oral administration of clarithromycin 0.5 g twice a day. However, after two weeks of treatment, the patient's condition did not improve significantly. In order to relieve the pain as soon as possible, the patient went to hospital C (a large teaching hospital). In the hospital C, doctors carried out a systematic test on the patient. The detection results of rheumatoid factor and autoantibody of patient were detailed in Table 1. The analysis of the immune function of the patients, including the lymphocyte classification count and its function analysis, were detailed in Table 2 products were performed using primers described previously [3].  Table 3. According to the drug sensitivity results, doctors found that the antibiotics selected in hospital B did not contradict the drug sensitivity results, so they continued to treat according to this plan. After one month of treatment, the wound healed and the patient's condition improved significantly.

Literature review
We searched PubMed for cases of M. fortuitum group infection and found 10 case reports in addition to ours (Table 4). We found that the previous case reports showed that the M. fortuitum group mainly The study protocol was approved by the Tongji Hospital ethics committee for research in health.
Informed written consent was obtained from the patient.

Consent to publish
The patient provided written consent for the case details to be published.

Availability of data and materials
All data is contained within the manuscript. Clinical isolates will be made available upon requests from Dr. Ziyong Sun.

Competing interests
The authors declare that they have no competing interest.

This work was supported by research grants from the National Mega Project on Major Infectious
Disease Prevention (2017ZX10103005-007) and Provincial Natural Science Foundation (2019CFB666).
The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Authors' contributions
LT drafted the manuscript.     Imaging showed that the prosthesis tissue had been removed and implanted into the cement frame for fixation.

Figure 4
The result of IVD-MALDIBIOTYPER showed that the strain was Mycobacterium senegalense.