Mycoplasma is NOT Recovered in Routine Aerobic Bacterial Cultures
Mycoplasma species will not be detected by standard aerobic blood culture systems used in routine clinical practice, and special culture methods or molecular testing are required for their diagnosis.
Why Routine Cultures Miss Mycoplasma
The 2018 IDSA/ASM guideline 1 notably excludes Mycoplasma from the table of organisms recovered by conventional blood culture methods, which is highly significant. The guideline explicitly lists organisms that grow in standard blood cultures (including historically fastidious organisms like HACEK bacteria and Brucella), but Mycoplasma is conspicuously absent from this comprehensive table.
The Technical Problem
While research shows that Mycoplasma hominis can grow in both aerobic and anaerobic blood culture media 2, there are critical limitations:
- Cultures appear falsely negative - The organism grows but bottles don't signal positive visually
- Special detection required - Acridine orange staining and subculture on Columbia sheep blood agar are necessary to detect growth 2
- Sodium polyanetholesulfonate (SPS) inhibition - This standard anticoagulant used in most blood culture bottles inhibits Mycoplasma growth 2, 3
- Atmospheric requirements - Mycoplasma species have specific oxygen requirements (often microaerophilic conditions with 5% O₂) that differ from standard aerobic incubation 4
Clinical Implications
In practical terms, if you suspect Mycoplasma infection (particularly M. hominis septicemia in postpartum/post-abortion fever, or M. pneumoniae in respiratory infections), you must:
- Request specific Mycoplasma cultures using specialized media without SPS
- Consider molecular testing (NAAT) as the preferred diagnostic method
- Use serology for M. pneumoniae when appropriate
- Do not rely on routine aerobic cultures - they will miss the diagnosis
This is why Mycoplasma septicemia may be underdiagnosed in clinical practice 2, 3 - laboratories using standard blood culture systems without special protocols will fail to detect these organisms even when present.