Investigation of the Infected Allograft Recipient
Apreviously healthy seventeen-year-old boy underwent anterior cruciate
ligament repair with implantation of a hemi patellar tendon allograft. The
following day, pain and erythema developed at the surgical site and the
patient had a fever of as much as 39°C. Six days after the procedure, he
underwent surgical exploration with arthrotomy of the knee and fasciotomy of
the thigh. The allograft tissue was removed. Cultures of the wound aspirate,
blood, and explanted tissue demonstrated growth of group-A streptococci.
The postoperative course of the patient was complicated by fluid collection
in the affected thigh and knee and persistent fever. Six days after allograft
explantation, needle aspiration of the knee yielded fluid which, when sent for
culture, demonstrated group-A streptococci, despite a week of treatment with
clindamycin and cefazolin. The patient received intravenous antibiotics in the
hospital for seventeen days and was discharged with an indwelling venous
catheter for continued antibiotic treatment at home.
Investigation of the Allograft Donor
We reviewed the medical records and the autopsy report of the allograft
donor, which stated that he had been a healthy man in his thirties who had
died three weeks after undergoing elective cervical spinal fusion for
degenerative disc disease. Three days before his death, the donor had
presented to an emergency department with a diffuse pruritic rash, which was
diagnosed as an allergic reaction to medications. The donor then returned to
the emergency department three days later because of back pain, nausea, and
vomiting, and he died soon after that. The autopsy findings included a
generalized rash and potentially toxic levels of a muscle relaxant and an
analgesic medication. In the report made by the medical examiner, death had
been attributed to the toxic effects of the drugs. No cultures had been
performed.
After the growth of group-A streptococci was demonstrated in the tissue
cultures from the allograft recipient, autopsy specimens from the donor were
sent to the United States Centers for Disease Control and Prevention (CDC).
Immunohistochemical testing was performed with use of a two-step indirect
immuno-alkaline phosphatase technique with an antibody against group-A
streptococci and with appropriate
controls8,9,
and bacterial cultures were performed on a stored blood specimen from the
donor.
The evaluation performed by the CDC demonstrated Gram-positive cocci in
dermal blood vessels. Immunohistochemical studies revealed the intracellular
and extracellular presence of group-A streptococci in these vessels as well as
in the lungs. In addition, group-A streptococci were isolated from a culture
of blood from the donor. On the basis of these findings along with the
previously noted rash, the cause of death of the donor was amended to
streptococcal toxic shock-like syndrome. The source of the group-A
streptococcal infection in the donor could not be identified.
Tissue Traceback and Testing
We reviewed files from the tissue-recovery organization and from the two
tissue processors (referred to in this paper as tissue-processor A and
tissue-processor B) that had received tissues from the donor.
Donor allografts were recovered by a single organization that, at the time
of recovery, placed twelve specimens from the allografts into culture medium.
All twelve cultures demonstrated growth of group-A streptococci. The recovery
organization distributed twenty musculoskeletal allografts from the donor to
tissue-processor A and ten to tissue-processor B.
Six of the allografts were rejected by tissue-processor A because they did
not meet physical specifications (e.g., the blood-vessel diameter was too
small or the allograft was damaged). Tissue-processor A placed specimens from
the remaining fourteen allografts into culture medium before processing, and
group-A streptococci grew on all cultures. The donor allografts were then
processed with a proprietary antimicrobial solution (but not subjected to
high-temperature or high-pressure disinfection methods), and tissue specimens
were again taken from the donor allografts and placed in culture medium. These
cultures demonstrated no growth, and the allografts were released for
transplantation. Tissue-processor B did not process or distribute any
allografts from the donor because the donor did not meet eligibility
requirements due to past foreign travel.
After receiving notification of the infection in the allograft recipient,
tissue-processor A recalled all non-implanted processed allografts from that
particular donor. The recalled tissues were immersed in thioglycolate broth,
which was incubated for twenty-one days. No organisms were recovered following
the twenty-one-day incubation. Tissue-processor B, which had not processed any
tissues from the donor, provided the unprocessed tissues to the CDC. Tissue
samples from tissue-processor B were ground in Todd-Hewitt broth and dispensed
in test tubes containing Todd-Hewitt broth with defibrinated sheep blood.
Samples were streaked onto blood-agar plates with and without gentamicin (2.5
mg/L). Group-A streptococci were recovered by the CDC from multiple samples of
the recalled allograft tissue provided to them by tissue-processor B.
Molecular Typing
PathoDx strep grouping latex agglutination tests (Remel, Lenexa, Kansas)
were used to evaluate the organisms that were recovered from tissues provided
by tissue-processor B, and the same tests were used to evaluate the organisms
that were recovered from the blood and explanted tissues of the infected
recipient and that had demonstrated beta-hemolysis on blood-agar plates.
Specimens identified as group-A streptococcal bacteria underwent T-protein
serotyping (T-typing) and emm-gene sequence typing (emm
typing). T-typing is an antigen-antibody agglutination reaction that is
visualized with use of suspensions of group-A streptococcal
cells10, and
emm typing involves sequencing the 150-base variable region of the
emm gene, which encodes the M protein, a major virulence
factor11. With use
of a database maintained by the Streptococcal Genetics Laboratory of the CDC,
we compared sequences from group-A streptococcal isolates obtained during our
investigation to more than 400 emm gene sequences, representing more
than 1000 invasive group-A streptococcal
isolates12.
Group-A streptococcal isolates from the blood and tissue of the donor as
well as the recipient were T-type 3-13 and M protein gene type 3
(emm3). These isolates were indistinguishable by emm typing
and represented a novel subtype, emm3.17.
Investigation of Other Allograft Recipients
A total of six musculoskeletal allografts processed by tissue-processor A
had been implanted, including the allograft received by the patient presented
in this report. We reviewed the medical and surgical records and interviewed
the health-care providers of the five other allograft recipients. The tissues
that had been implanted included other hemi patellar tendons, tibialis
tendons, and a peroneus tendon. No adverse outcomes were detected in the other
five recipients.
Our investigation demonstrated an infection with a novel strain of group-A
streptococci due to transplanted musculoskeletal allograft tissues recovered
from a cadaveric donor. This is the first laboratory-confirmed report of
group-A streptococcal transmission from implanted allograft tissues. In our
investigation, isolation of a novel subtype of these bacteria in both the
allograft donor and the allograft recipient confirmed transmission. The
recovery of the rare subtype emm3.17 from normally sterile specimens
of both the tissue donor and the tissue recipient provides very strong
evidence that the isolates were linked. The Streptococcus Genetics Laboratory
at the CDC has performed sequence analysis of more than 800 type emm3
clinical isolates (invasive and noninvasive) since the year 2000 and has
documented forty-one different emm3 subtypes from its surveillance
and from sequences submitted to it from multiple countries. The isolates
described in this report were the only subtype emm3.17 isolates that
the CDC has encountered.
Invasive group-A streptococcal disease is associated most commonly with
skin and other soft-tissue infections as well as bacteremia without an
identified
source13. It is a
rare cause of surgical-site infections, accounting for less than 0.4% of such
infections reported between 1998 and 2002 to the National Nosocomial
Infections Surveillance System at the CDC (unpublished data).
Two key events led to the transmission of infection in this patient. First,
the donor's death initially was not attributed to infection. United States
Food and Drug Administration (FDA) donor-screening guidelines recommend
rejection of tissue donors who have known or suspected sepsis at the time of
death14. However,
infections in tissue donors may not be recognized. Infection in this donor was
not detected by clinical evaluation or initial autopsy. The availability of
autopsy specimens was particularly important in this investigation, as it
allowed for testing which ultimately led to identification of the cause of
death of the donor.
Second, evidence of group-A streptococci in the allograft tissue at the
preprocessing stage did not prompt tissue-processor A to reject the
allografts, as repeat cultures performed after processing showed no evidence
of the organism. However, previous reports of allograft-associated infections
have highlighted problems with regard to tissue-processing with antimicrobial
solutions and with regard to the culturing methods used to detect bacterial
contamination after processing. In one case, antimicrobial treatment did not
eradicate Clostridium sordellii from allograft tissues and
post-processing cultures failed to detect the contamination because residual
antimicrobial agents interfered with the culture
results7.
Two measures might help address the events that led to this case and
improve the overall safety of allograft tissues. First, because some organisms
are particularly virulent or difficult to eradicate, their presence in donor
tissues should prompt consideration of rejecting those tissues unless a
validated sterilizing method can be applied. In January 2005, the American
Association of Tissue Banks specified several "high-virulence
organisms" which, when detected in pre-processing cultures, necessitate
rejection or sterilization of individual tissues. Group-A streptococci are
included on this list when isolated from cardiac, vascular, musculoskeletal,
and osteoarticular
tissues15. In
consideration of the fact that, at the preprocessing stage, cultures of blood
and musculoskeletal tissues from more than 1200 donors at one tissue bank
demonstrated growth of this organism in only 0.02% of
cultures16, the
rejection of tissues with positive cultures for group-A streptococci will have
little impact on the supply of tissues.
Second, to identify infections in potential donors, assessment of donor
eligibility should continue throughout the recovery and processing phases of
allograft preparation. Findings of a common organism in multiple cultures at
the preprocessing stage should prompt reevaluation of the clinical history of
the donor, as these findings may be consistent with systemic infection. In
this case, additional review might have led to an increased suspicion of
group-A streptococcal sepsis in the donor.
Findings from this investigation and others have contributed to the
development of new procedures at tissue-processor A and to the implementation
of new industry standards and FDA regulations and guidance for the tissue
industry. Tissue-processor A now routinely reevaluates the medical history of
a donor when there are any positive culture results at the preprocessing
stage. At a national level, in May 2005, the FDA finalized the last of three
rules that were developed to improve the safety of human-tissue
transplants17.
The guidelines set by the CDC with regard to the prevention of group-A
streptococcal disease identify the occurrence of postsurgical infection with
this organism as a sentinel event that should prompt investigation and
enhanced
surveillance18.
Some postsurgical group-A streptococcal infections reflect transmission from
asymptomatic but colonized healthcare workers. However, given the findings in
this case, contaminated allografts should also be considered potential sources
of this organism when postsurgical infections are recognized. Because many
allografts can be harvested from each donor, it is important that clinicians
immediately report possible allograft-associated infection to the tissue
processor, local health department, FDA, and CDC so that the potential problem
can be promptly investigated. ?