Microbiology Case Study: A 64 Year Old Post-Chemotherapy Female

Case History

A 64 year old female with metastatic left breast cancer, status-post chemotherapy, presented for erythema, discomfort, and oozing from her port site for approximately one month. At presentation she was afebrile. Her port site exhibited erythema and fluctuance. Her most recent absolute neutrophil count was 1910/cmm. Her port was removed, and a tissue specimen was sent for microbiologic examination.

Laboratory Identification

Gram stain showed neutrophils without bacteria. Aerobic cultures grew a beaded gram positive rod on blood agar at 36 hours. Kinyoun stain was positive for acid fast bacilli. Matrix assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF) at that time identified Mycobacterium fortuitum group.

Image 1. Growth on 7H10 agar.
Image 2. Kinyoun stain showing acid fast bacilli.

Discussion

M. fortuitum is a group of rapid growing mycobacteria. Within the group is M. conceptionense, M. houstonense, and M. senegalense. The group comprises the second most-commonly isolated rapidly growing mycobacterial respiratory isolates in patients (after M. abscessus), generally those with underlying lung disease. Progressive pulmonary disease is generally not seen.  It has also been associated with skin and soft tissue infections (SSTIs), surgical wound infections, lymphadenitis, and catheter-related infections. It is seen in the environment and represents a common contaminant. Identification is by culture and molecular techniques. It is susceptible to many antibiotics (typically aminoglycoside, cefoxitin, imipenem, or levofloxacin). Therapy includes two agents based on susceptibility testing for 6 to 12 months. This is somewhat controversial in pulmonary disease as the clinical significance is not clear.

This patient is being treated through a peripheral IV. The chest port site at two weeks showed dehiscence of the wound with drainage. Susceptibilities are pending.

References

  1. Park S, Suh GY, Chung MP, Kim H, Kwon OJ, Lee KS, Lee NY, and Koh WJ. Clinical significance of Mycobacterium fortuitum isolated from respiratory specimens. Respiratory Medicine. March 2008;102(3):437-442.
  2. Sethi S, Arora S, Gupta V, Kumar S. Cutaneous Mycobacterium fortuitum Infection: Successfully Treated with Amikacin and Ofloxacin Combination. Indian J Dermatol. 2014;59(4):383–384.

-Jonathan Wilcock, MD is a 1st year anatomic and clinical pathology resident at the University of Vermont Medical Center.

-Christi Wojewoda, MD, is the Director of Clinical Microbiology at the University of Vermont Medical Center and an Associate Professor at the University of Vermont.

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