Microbiology Case Study: A 22 Year Old Female with Wound Infection

 

Case History

22 year old female with a past medical history of scoliosis presents for routine follow-up after hospital discharge for post-op wound infection following a spinal fusion surgery. Patient had an anterior and posterior spinal fusion with allograft and hardware on 1/18/18. She had a laminectomy and irrigation for post-op epidural hematoma on 1/19/18. Subsequently, she developed a lumbar spine abscess and underwent irrigation and debridement of the abscess on 3/1/18. Two operative cultures of the left paraspinal musculature grew only tiny clear colonies on the anaerobic blood plates. Gram stain of these colonies did not show any organism. MALDI-ToF MS identified these colonies as Mycoplasma hominis which was confirmed at a reference laboratory by PCR. The patient was given daptomycin plus levofloxacin. Since discharge from the hospital, she had wound healing with intermittent discharge.

Lab Identification

Mycoplasma hominis requires a specific rich and complex agar medium for growth and grows tiny colonies on standard media such as Columbia agar. In a patient with urogenital disease, Mycoplasma hominis is diagnosed with a urogenital specimen culture and confirmed by PCR. In a patient with spinal hardware infection, Mycoplasma hominis is diagnosed by a culture of infected tissue with PCR confirmation.

Discussion

Mycoplasma is a bacteria that lacks a cell wall and contains the smallest bacterial genome totally sequenced. Due to its lack of cell wall, Mycoplasma cannot be visualized with a Gram stain, and it is innately resistant to b-lactams.1 Due to its small bacterial genome, 580 kpb, it cannot be detected by light microscopy and requires complex nutrients for growth1.

Mycoplasmas are frequently part of the oropharyngeal and genital tract flora among healthy subjects.1 There are more than 200 Mycoplasma species, of which 13 have been isolated from humans. Only 6 species, among which 5 are pathogens, live in the urogenital tract.2 As one of the Mycoplasma species detected in the genitourinary tract, M. hominis can be either a pathogen or part of the normal flora.1 Colonization with M. hominis is associated with younger age, lower socioeconomic status, multiple sexual partners, African American ethnicity, and hormonal status.1 Infection with M. hominis is more common among pregnant women.1

Mycoplasma hominis is associated with genital infections in females but not in males. Examples of infections include pelvic inflammatory disease and bacterial vaginosis.1 In addition, it is responsible for pregnancy-related infections such as chorioamnionitis and post-partum fever secondary to endometritis.1 Moreover, M. hominis is associated with infections of the newborns, meningitis among premature babies, and low birth weight among neonates.1 Lastly, M. hominis can lead to extragenital infections including spinal hardware infections, septic arthritis, retroperitoneal abscess, hematoma infection, and osteitis.1

Infections by Mycoplasma hominis are infrequent and difficult to confirm prior to the start of empiric therapy.2 Urogenital and systemic infections due to Mycoplasma hominis are treated with oral tetracycline.1 For organisms resistant to tetracycline, fluoroquinolones are recommended.1 For wound infections or abscesses, doxycycline, clindamycin, or fluoroquinolones are recommended for at least 2 weeks.1 Drainage and debridement may be necessary.1

References

  1. Pereyre S. et Mycoplasma hominis, M. genitalium and Ureaplasma spp.  Antimicrobe http://www.antimicrobe.org/m06.asp
  1. Baum S. Mycoplasma hominis and ureaplasma urealyticum infections. (2017, Dec. 7th).  Last retrieved on March 27, 2018 from https://www.uptodate.com/contents/mycoplasma-hominis-and-ureaplasma-urealyticum-infections

 

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

Wojewoda-small

-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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