Iatrogenic Ventriculitis Due to Mycoplasma Hominis: A Case Report and Review of the Literature

Background

Mycoplasma hominis is a small free-living organism belonging to the genus Mycoplasma [1]. Mycoplasma lacks a rigid cell wall and therefore cannot be visualized by routine light microscopy [1]. Moreover, the lack of a cell wall prevents visualization of Mycoplasma species by Gram staining and makes the organism resistant to cell wall inhibitors such as beta-lactam antibiotics [1–3]. It is very challenging and resource- and time-consuming to diagnose infections caused by this organism because of the requirement for special selective medium and specific incubation conditions for culturing M. hominis [4]. Furthermore, there are few biochemical traits that are valuable for diagnosis [4]. Accordingly, matrix-assisted laser desorption ionization-time-of-flight mass spectrometry (MALDI-TOF MS) has been adopted as a cost-effective, rapid, reliable method for the diagnosis of M. hominis [5].

M. hominis generally colonizes the urogenital tracts of sexually active adults and is a causative organism of urogenital tract infections [1]. Central nervous system (CNS) infections due to M. hominis are rare. To best of our knowledge, only 21 cases of CNS infection caused by M. hominis, including our current case, have been reported in the literature.

Here, we present a successfully treated case of M. hominis ventriculitis secondary to extraventricular drain. This is the first case of M. hominis causing CNS infection reported in a country in the Middle East.

Case Report

MICROBIOLOGY LABORATORY FINDINGS:

Yellowish clear CSF samples from EVD were inoculated on sheep blood agar, MacConkey agar, chocolate agar, anaerobic blood agar, and thioglycolate broth, incubated at 37°C according to the internal policies and procedures of the microbiology laboratory at King Fahd Hospital of the University. CSF analysis revealed a white blood cell count of 1430/cu mm, with 82% segmented cells, a protein value of 316 mg/dL, and a glucose level of 3.0 mg/dL. Direct Gram stain smears from samples showed few pus cells and no organisms. After 48 h of incubation, there was growth of nonhemolytic, translucent, pinpoint colonies on anaerobic blood agar only (Figure 2). Gram stain smears from colonies showed no evidence of bacteria. The isolate was identified as M. hominis using MALDI-TOFMS (VITEK MS; bioMérieux) and Knowledge Base database (version 3.0), with a confidence value of 99.9. Subsequent CSF samples also grew colonies of M. hominis. Table 1 summarizes CSF laboratory results for the patient during admission.

Discussion

M. hominis primarily colonizes the respiratory tract and genitourinary tract. This organism is mainly transmitted to humans through obstruction of the urinary tract, sexual contact, and vertical transmission in utero or intrapartum [1,3]. Surface antigenic variation of M. hominis may be related to the persistence of these organisms at invasive sites [1]. Most infections caused by M. hominis are primarily related to genital tract colonization.

The infections caused by this organism include acute pyelonephritis, cervicitis, endometritis, tubal factor infertility, postabortion bacteremia, bacterial vaginosis, and other genital tract infections. Other reportable clinical conditions caused by M. hominis include bacteremia after renal transplantation, trauma, and genitourinary manipulations; osteomyelitis; septic arthritis; aspiration associated-empyema; peritonitis; intra-abdominal abscesses; and wound infections [1,3]. In the early 1980s, M. hominis infections were also reported following organ transplantation and immunosuppressive therapy. These infections most likely originated from the patient’s normal flora [4].

M. hominis has also been reported from brain abscesses and meningitis. Several cases of CNS infection by M. hominis have been described in premature infants with prolonged rupture of the membranes, probably owing to genital colonization of pregnant women. These neonates usually present with mild, subclinical meningitis without sequelae or neurological damage with permanent handicaps [1,3]. In adults, rare cases of M. hominis meningitis have been described mainly following neurosurgery manipulations [3,6,7]. Moreover, few cases of M. hominis infection following ventriculoperitoneal shunt insertion with central nervous system involvement have been reported [7,8]. In general, CNS infections with M. hominis usually resolve spontaneously [3]. Existing literature on patients with CNS infection caused by M. hominis is summarized in Table 2.

Isolation of M. hominis in any quantity from sterile body fluids is significantly associated with disease, and identification at the species level is necessary [1]. The optimal temperature for M. hominis growth is between 35 and 37°C, and these organisms grow best under anaerobic conditions, usually within 1–5 days of incubation [3]. M. hominis can be detected routinely in bacteriologic culture medium, such as chocolate agar or blood agar; accordingly, there have been many instances of incidental discovery when Mycoplasma species were not specifically sought [3]. MALDI-TOF MS is a rapid, reliable, cost-effective method and has been shown to accurately identify most Mycoplasma species, particularly M. hominis [1,5].

Mycoplasma species are innately resistant to all beta-lactams, sulfonamides, trimethoprim, and rifampin. M. hominis is usually susceptible to tetracycline, fluoroquinolone, clindamycin, chloramphenicol, streptomycin, and gentamicin [1,3]. Some strains of M. hominis have been reported to be resistant erythromycin, fluoroquinolone, and tetracycline. The extent to which tetracycline resistance occurs in M. hominis varies geographically and may reach 40–50% in some locations. Agar dilution is considered the reference method for antimicrobial testing for Mycoplasma [1].

Conclusions

The findings of this case report, coupled with a thorough review of the literature, demonstrated the pathogenic potential of M. hominis. Particularly in developing countries, in which laboratories may have limited access to advanced technologies, such rare infectious diseases remain major diagnostic challenges.