Bloodstream Infection Combined with Thoracic Infection Caused by Mycoplasma hominis: A Case Report and Review of the Literature

Abstract

Objective: Mycoplasma hominis is usually found in urogenital tract infections and is associated with several extra-genitourinary infections, including septic arthritis, bacteremia, and meningitis. Here, we report a rare case of M. hominis induced bloodstream infection with thoracic inflammation in a surgical patient.

Methods: A 56-year-old male who underwent surgery for multiple pelvic and rib fractures developed fever, pleural effusion, and wound exudation despite receiving prophylactic anti-infection treatment with cefotiam. Then, replacing the broad-spectrum antimicrobial drugs such as biapenem, imipenem, linezolid still had no obvious curative effect. Meanwhile, a total of 4 groups of blood cultures were collected from patients, of which 2 groups reported positive results 2 to 3 days after specimen collection. At the same time, the patient's pleural effusion and wound pus were also cultured, and transparent needle-like small colonies grew on Columbia blood agar plates within 2 to 3 days after inoculation.

Results: The cultured transparent pinpoint-like small colonies were identified as M. hominis by matrix-assisted laser desorption-ionization time-of-flight mass spectrometry (MALDI-TOF MS) and 16SrRNA sequencing. The results of antibiotic susceptibility testing (AST) showed that M. hominis was susceptible to doxycycline, minocycline, josamycin, sparfloxacin, and spectinomycin but resistant to azithromycin, clarithromycin, norfloxacin, roxithromycin, and ofloxacin. According to the AST results and clinical symptoms, moxifloxacin was selected as targeted therapy for M. hominis infection, and cefoperazone/sulbactam was combined to prevent the infection of other gram-negative bacteria. Finally, the patient was cured successfully.

Conclusion: Although M. hominis bloodstream and thoracic infections are rare, they cannot be ignored. M. hominis is intrinsically resistant to agents that work on bacterial cell wall synthesis used. Fluoroquinolones could be kept as potential active and thus a likely curative factor. When routine empirical anti-infection treatment is ineffective, the pathogen should be identified as early as possible. If necessary, gene sequencing technology should be used for diagnosis and sensitive anti-infection drug treatment should be promptly administered to reduce the risk of bloodstream infections.

Keywords: 16SrRNA sequencing; Mycoplasma hominis; critical illness; infection.

Figure 1

Representative results of sample culture (A) Tiny, non-hemolytic, and transparent colonies grew on the Columbia blood agar plate of blood-positive cultures three days after inoculation. (B) Tiny, non-hemolytic, and transparent colonies grew on the Columbia blood agar plate of pleural fluid sample cultures three days after inoculation. (C) On day 5, transparent and tiny colonies were observed on the blood agar plates with blood cultures. (D) Fried egg-type colonies were observed on mycoplasma medium after 5 days of incubation.

Figure 2

Peaks information of M. hominis using MALDI-TOF MS.

Figure 3

The results of antibiotic susceptibility testing of M. hominis..

Figure 4

The diagnosis and treatment process of the patient.