Investigation and hypothesis
Review of laboratory results showed that the culture of the
allograft performed immediately prior to bypass procedure
was positive for M. hominis, i.e. before the graft had any
contact with the patient. Although cultures on standard
medium were negative after 48 h, the patient’s clinical presentation
prompted to prolong the culture period and small
colonies of non-Gram stained bacteria slowly grew a few
days later. Both traditional method of identification and
Polymerase Chain Reaction (PCR) revealed M. hominis.
Prior to the allograft bypass procedure, the recipient did
not present any symptom that suggested a M. hominis infection.
Urethral culture test, performed 3 weeks after onset
of antibiotherapy, was negative. Furthermore, a PCR
performed on the initial S. aureus abscess immediately
before the allograft bypass procedure was negative for
M. hominis.
Our investigation suggests that the contamination of the
allograft is unlikely to have occurred during its preparation.
The allograft was performed by the surgeon under strict
sterile conditions before being grafted. The delay that
elapsed between handling and culture of the graft was not
sufficient to enable these particular intracellular bacteria
to grow. Therefore, our hypothesis was that the allograft
was contaminated at the time of recovery due to a M. hominis
infection or a carriage by the donor.
Based on our hospital procedure, the vessel is routinely
immersed in an antibiotic solution containing cefoxitin,
gentamicin, colymicin and vancomycin just after recovery
and kept for at least 24 h. The tissue sample, received from
the operating theatre, is routinely opened under a laminar
airflow hood, in a clean room, and the contents are placed
in sterile packaging. This specific packaging is sealed after
a microbiological control, and placed in the nitrogen container,
where it is preserved before being grafted. In our
case, the culture performed during processing by the tissue
bank did not grow any bacteria, but the culture, performed
on standard bacteriological medium, was not preserved
more than 48 h. However, M. hominis needs specific culture
media to grow or a delay of at least 72 h if the culture is
performed on a standard culture media.5 Furthermore,
our investigation showed that the antibiotic solution used
for conditioning of the graft is not active on M. hominis.6
The donor was a 22-year-old man, brain dead due to
a toxic suicide with paracetamol and dextropropoxyphene.
The patient had no previous history of sexual disease or
M. hominis infection, however, 4e13% of men have been
reported to be colonized by M. hominis. These bacteria
are also frequently discovered in young, sexually active individuals.
7 The donor also had a previous medical history of