I appreciate Dr Kotaska’s comments on the amniotic fluid infection/inflammation (AFII) autopsy quality assurance study recently published in the journal [BCMJ 2021;63:383-387]. The practice at BC Children’s and BC Women’s Hospitals is to sample for bacteria from areas that are unlikely to be artifactually contaminated at or after delivery, such as the lung and stomach contents. This study was not intended to assess the sensitivity and specificity of bacterial culture in the setting of AFII and as such a non-AFII cohort was not included for comparison; anecdotally, however, bacterial cultures from non-AFII cases at BC Children’s and BC Women’s Hospitals are mostly negative, which demonstrates the low level of detectable delivery and tissue sampling–related contamination.
Dr Kotaska makes the excellent point that the relationship between microbes, inflammation, and delivery continues to be poorly understood. A robust relationship between intra-amniotic microbes and AFII has been established; however, the recent application of highly sensitive molecular techniques for bacterial detection has failed to demonstrate detectable microbial DNA in all AFII cases; conversely, the presence of intra-amniotic microbes (particularly Mycoplasma and Ureaplasma) without any appreciable maternal inflammatory response has been convincingly shown. Thus, bacterial culture by itself is a poor diagnostic test for AFII but can be diagnostically useful in the context of histological AFII where bacteria are not seen microscopically. Dr Kotaska also makes the important practical point that bacterial culture presently has no predictive value as there is no robust data to support treatment to decrease preterm birth, although this is also not well studied.
Testing for Mycoplasma and Ureaplasma is difficult as these obligate intracellular microorganisms are fastidious and require special handling, as Dr Kotaska points out. Mycoplasma and Ureaplasma culture is presently not performed in British Columbia and the only locally available Mycoplasma/Ureaplasma testing is molecular based and not validated on placental tissue, so testing for Mycoplasma and Ureaplasma in the setting of AFII, or pregnancy loss in general, is not routinely done at our centre. If I were to test a clinical sample for Mycoplasma or Ureaplasma I would submit lung and stomach contents for culture-based studies or lung and stomach contents and tissue for molecular testing. The genomes of Mycoplasma and Ureaplasma may also be visualized fluorescently in the cytoplasm of infected cells, although this approach is more suitable to a research environment.
—Jefferson Terry, MD, PhD, FRCPC
This letter was submitted in response to “Re: The value of ancillary testing in amniotic fluid infection/inflammation-related early pregnancy loss and perinatal death in British Columbia.”
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