Laboratory Studies
Perform diagnostic tests for Mycoplasma and Ureaplasma species when a patient presents with a clinical condition known to be caused by or associated with these organisms and when more common etiologies are excluded. The correct microbiological diagnosis takes on greater importance in patients who are immunosuppressed and at greater risk for disseminated infection and a poor outcome.
Examination of slides prepared from urethral exudate in male patients can be useful to quantitate neutrophils in order to document the presence of urethritis. Gram stains are useful in males to detect Neisseria gonorrhoeae, but they are not useful for detection of ureaplasmas or M genitalium since their lack of a cell wall precludes use of a Gram stain for detection. Likewise, examination of a Gram stain of CSF in a neonate with meningitis for the presence of inflammatory cells and to exclude the presence of other bacteria is valuable before proceeding to tests for detection of the genital mycoplasmas.
Culture
Obtain culture results.
M hominis and Ureaplasma species can be detected in culture using specialized media and techniques within 2-5 days. These organisms can also be detected by PCR assays. M genitalium requires a molecular-based assay due to its slow growth and fastidious nature.
Specialized culture media and growth conditions are necessary, and most hospital-based laboratories do not offer these services on site, except for some of the larger tertiary care university hospitals. Regional or national microbiology reference laboratories usually offer these cultures. Routine bacterial cultures are not sufficient to recover M hominis and cannot detect Ureaplasma species. Detailed laboratory procedures for detection and characterization of genital Mycoplasma and Ureaplasma infections can be found in reference texts. [27]
Specimens can be collected in a specialized liquid transport system, a growth medium designed for mycoplasmal organisms (eg, 10-B broth), or some of the common transport systems for Chlamydia species or other bacteria and viruses and shipped to a reference laboratory for testing if necessary. Preventing desiccation and protecting the specimen from adverse temperature extremes is essential if the organisms are to remain viable.
In men, urethral swabs are preferred over urine samples for detection of genital mycoplasmal infections because the organisms are cell associated. Use Dacron polyester swabs with plastic shafts, not wooden cotton-tipped swabs, because the latter may inhibit growth of Mycoplasma and Ureaplasma organisms. Prostatic secretions, semen, and urinary calculi can also be cultured.
For females, urine, cervical swabs, or vaginal swabs are acceptable. Avoid specimens contaminated by lubricants or antiseptics. Urine samples from females are most useful when obtained by catheter or suprapubic aspiration. Endometrial tissue, tubal samples, or pouch of Douglas fluid can be obtained to confirm a mycoplasmal etiology for pelvic inflammatory disease or postpartum fever. For women with clinical amnionitis, culture amniotic fluid, blood, and placenta.
Culture of nasopharyngeal, throat, and endotracheal secretions from neonates is appropriate, especially if their birth weight is less than 1500 g and they have clinical, radiographic, laboratory, or other evidence of pneumonia.
Extragenital or extrapulmonary specimens submitted for culture should reflect the site of infection and disease process. Sterile fluids, including synovial fluid, peritoneal fluid, pericardial fluid, CSF, and blood, are suitable for culture. Bone chips from patients with chronic osteomyelitis without a proven bacterial etiology are also appropriate for culture, as are wound aspirates and tissue collected after biopsy or autopsy. Successful isolation of M hominis and Ureaplasma species from blood can be achieved by inoculating 5-10 mL directly into liquid mycoplasmal growth medium in at least a 1:10 ratio. Smaller volumes can be used for neonates or children.
The recommended specimens for testing for the presence of M genitalium by molecular methods are first void urine for men and vaginal swabs for women. [26]
Proper specimen collection and handling
Proper specimen collection and handling are of utmost importance in detecting these fastidious organisms. Inquiring about the services of a suitable reference laboratory and maintaining the appropriate specimen transport medium in clinical facilities is worthwhile if Mycoplasma or Ureaplasma infections are frequently encountered. Numerous references describe the optimum conditions for specimen collection, handling, and detecting these organisms in culture. [27] Obtain specific instructions from the laboratory when testing is performed. If commercial molecular-based testing is available, the manufacturer of the test kit to be used will have specific instructions that must be followed.
Serologic studies
Serologic studies are not useful for evaluating genital mycoplasmal infections and none is commercially available in the United States.
Molecular techniques
Molecular techniques such as the PCR assay are available from research or reference laboratories using published methods or their own internally developed protocols. Three FDA-approved molecular tests are commercially available for detection of M genitalium, but not for M hominis or Ureaplasma species. Therefore, the availability of molecular testing is quite limited for these organisms.
Molecular techniques such as PCR are not required when culture is available for M hominis and Ureaplasma species, although it should be acknowledged that PCR assays may be inherently more sensitive for detection of small numbers of organisms in clinical material. Fastidious slow-growing mycoplasmal species, such as M genitalium and M fermentans, may cause clinically significant illnesses in the respiratory tract, urogenital tract, or other sites. The presence of M genitalium can be reliably detected only by molecular techniques such as the PCR assay or transcription mediated amplification. [28]
Imaging Studies
Imaging studies are not usually performed as part of a workup for uncomplicated infections due to Mycoplasma or Ureaplasma. Exceptions include persons who are immunosuppressed and have apparent septic arthritis or suspected pulmonary infection and neonates with clinical evidence of pneumonitis or chronic lung disease of prematurity. In each of these instances, genital Mycoplasma species may be involved.
CT scanning
Case reports describe neonates with congenital infections in whom intracranial calcifications and necrosis consistent with congenital cytomegalovirus infection were observed, yet the only infectious organism detected was M hominis; thus, in neonates with unexplained neurologic abnormalities and CSF pleocytosis, CT scanning of the head may be useful to further characterize the intracranial pathologic effects.
Radiography
Radiographic features typical of neonatal pneumonitis caused by chlamydiae and other pathogens are associated with congenital Ureaplasma infection. Infants who are culture-positive in the lower respiratory tract for Ureaplasma species develop radiographic lung findings consistent with bronchopulmonary dysplasia more rapidly than neonates with negative cultures.
Procedures
Specimen collection
Collection of adequate culture specimens from the infected site is of utmost importance if the microbiological diagnosis of an infection due to Mycoplasma or Ureaplasma species is to be determined because none of the clinical manifestations or other laboratory tests is definitive.
Collection techniques include the following:
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Lumbar puncture to obtain CSF
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Arthrocentesis to obtain synovial fluid
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Tracheal aspiration to obtain lower respiratory tract secretions or tissues
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Lung biopsy to obtain lower respiratory tract secretions or tissues
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Bronchoalveolar lavage to obtain lower respiratory tract secretions or tissues
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Nasopharyngeal aspiration to obtain respiratory secretions in neonates who are not intubated
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Blood collection to detect bacteremia
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Urethral or cervicovaginal swabs to detect urethritis or pelvic inflammatory disease.
The nature of the procedure reflects the infection suspected.
Severity of illness dictates the extent to which invasive procedures (eg, lumbar puncture, bronchoalveolar lavage, lung biopsy) are necessary.
Histologic Findings
Biopsies and examination of histopathology are not usually performed in the workup of suspected infections caused by genital mycoplasmas. These organisms do elicit an acute inflammatory response in immunocompetent hosts.
