World Journal of AIDS, 2011, 1, 23-27
doi:10.4236/wja.2011.12004 Published Online June 2011 (
Copyright © 2011 SciRes. WJA
Hematogenous Osteomyelitis by Acinetobacter
Baumannii: Case Report and Literature Review
Rajendrakumar Chimanlal Patel1, Sumir Prakash Sahgal1,2, Shervin Mortazavi1,2,3,
Yagnang Kaushikkumar Vyas 1, Richard Joseph Adam4, Vera Salim Antonios1
1Essen Medical Associates, New York, USA; 2Department of Internal Medicine, Albert Einstein College of Medicine, New York,
USA; 3Department of Internal Medicine, Bronx Lebanon Hospital Center, New York, USA; 4Department of Radiology, Bronx
Lebanon Hospital Center, New York, USA.
Received March 24th, 2011; Revised April 10th, 2011; Accepted 21st, 2011.
Background: Skeletal infection with Acinetobacter baumannii is a rare condition and found mainly among soldiers
injured in war. Multidrug resistant (MDR) Aci netobacte r baum annii (A. baumannii) osteomyelitis is difficult to treat and
requires long course of in travenous antibiotics. Most of reported cases in the literature are the consequences of direct
inoculation of the pathogen. Here in, we report the first case of A. Baumannii osteomyelitis disseminated through he-
matogenous route and the therapeutic approach for this rare infection. Clinical Presentation: A 46 year old Afri-
can-American male patient with human immunodeficiency virus (HIV) and end-stage renal disease on hemodialysis, who
developed persistent MDR A. baumannii bac teremia in t he h os pi ta l, t hought to be secondary to the hemodialysis catheter,
necessitating replacement of the catheter. Three months after his discharge to a skilled nursing facility (SNF), he de-
veloped left leg swelling without noticeable pain or fever. MRI revealed findings consistent with chronic osteomyelitis of
left tibia and intra op erative bone culture grew MDR A. baumannii. The patient had good outcome after three surgical
debridements and prolonged period (7 Months) of dual antimicrobial therapy. Discussion: While in most documented
cases of A. baumannii osteomyelitis, entry appears to require direct inoculation; our case suggests that this pathogen
can seed into bone hematogenously in the setting of immunosuppression, persistent bacteremia and possibly in the
presence of underlying bone infarcts. Clinicians need to be aware of this rare possible consequence of A. baumannii
bacteremia. In conclusion, combination of multiple surgical debridements and dual antimicrobial therapy for a long
period may result in a good outcome.
Keywords: Osteomyelitis, Hematogenous, Acinetobacter Baumannii, Risk Factors, Bacteremia
1. Introduction
A 46 year old African American male patient with
HIV/Acquired immunodeficiency syndrome (CD4 = 6,
Viral load > 60,000), non compliant with antiretroviral
medications, hypertension, chronic kidney disease and
history of anal squamous cell carcinoma in remission
was admitted to a community hospital with fever, re-
duced oral intake, and diarrhea. During his hospital stay,
he was admitted in Intensive Care Unit (ICU) due to res-
piratory distress requiring intubation and mechanical
ventilation. He was diagnosed with acute on chronic re-
nal failure which required urgent dialysis, and right lower
lobe pneumonia which was treated empirically with
vancomycin, piperacillin-tazobactam and azithromycin.
Permacath was placed for future hemodialysis. Blood
cultures remained negative. On this antibiotic regimen,
he improved, was extubated and later discharged to SNF.
Two weeks later, he was transferred back to the hospital
with fever and hematuria, treated in ICU with ciproflox-
acin for presumed urosepsis, and received blood transfu-
sion secondary to a significant drop in hematocrit. His
blood and urine cultures were negative. He was stabilized
and discharged back to SNF, only to come back 48 hours
later with fever and no obvious source of infection. He
was empirically started on vancomycin and piperacil-
lin-tazobactam. Blood cultures collected on admission
grew multidrug resistant Acinetobacter baumannii (sen-
sitive to polymyxin and ampicillin-sulbactam) with one
set growing vancomycin-resistant Enterococcus faecium
as well. He was placed on contact isolation and antibiot-
ics were changed to linezolid, gentamicin and ampicil-
Hematogenous Osteomyelitis by Acinetobacter Baumannii: Case Report and Literature Review
lin-sulbactam. On day six, repeated blood cultures con-
tinued to grow E. faecium and A. baumannii, so treat-
ment was again adjusted to daptomycin, gentamicin and
polymyxin. The hemodialysis catheter was suspected to
be the source of bacteremia, necessitating its removal,
with a placement of a temporary Shiley catheter for
hemodialysis. Repeated blood cultures continued to grow
A. baumannii intermittently, with positive cultures re-
ported on day 7, day 13, and day 16 and a strain that be-
came intermediately sensitive to ampicillin-sulbactam.
Bacteremia finally cleared with the continuation of same
antibiotic regimen for four weeks, and a new permacath
was placed on day 35. Patient was started on antiretrovi-
ral therapy and then disch a rged back to SNF.
Three months later, he developed left leg swelling
without pain or fever. On examination, mild, non-pitting
edema and a non-tender bony prominence was noted on
proximal part of anterior aspect of left lower leg. Venous
duplex ruled out deep venous thrombosis and x-rays
showed ill-defined large lytic lesion with periosteal reac-
tion in proximal left tibia (Figure 1). Non contrast com-
puted tomography (CT) scan showed periosteal irregular-
ity, a cortical defect in the antero-medial aspect of the
tibia consistent with cloaca, and an expanded medullary
cavity with a lobulated 3.3 x 1.8 x 11.6 cm lesion, sug-
gestive of sequestrum (Figure 2). These findings were
consistent with chronic osteomyelitis. Magnetic reso-
nance imaging (MRI) without gadolinium showed sub-
cutaneous tissue abscess, prominent surrounding marrow
edema and periostitis of proximal left tibia (Figure 1).
Osteonecrosis was noted in the left distal femur. Tibial
biopsy and culture from initial therapeutic debridement
confirmed the diagnosis of osteomyelitis; no acid-fast
bacilli or fungal elements found and no evidence of ma-
lignancy noted. Cultures grew MDR A. baumannii with
similar susceptibility pattern as the strain causing bac-
teremia during prior hospitalization.
Intravenous polymyxin B and vancomycin were
started and continued for 6 weeks. However, purulent
discharge from the let anterior leg was noted during the
5th week of antibiotic co urse. The patient then underwen t
extensive debridement of left anterior tibia. Intra-
operative bone culture grew A. baumannii and methicil-
lin sensitive staphylococcu s aureus (MSSA). Hence, van-
comycin was discontinued and cefazolin was added
while polymyxin B was continued for another 6 weeks.
After completion of treatment, purulent drainage stopped
and left leg wound was healed. Three weeks later, puru-
lent drainage was again noted with prominence of the
bony mass in the proximal left tibia. MRI without gado-
linium was performed showing similar findings as in the
prior study. Patient und erwent 3rd exten sive debridement
of the left anterior tibia. He was started on polymyxin B
Figure 1. Radiology images of the left leg. A-X-ray AP and
Lateral view. 1. Lytic lesion and periosteal reaction.B-Axial
T2 weighted MRI, 2. Subcutaneous abscess, 3. Marrow
edema and periostealreaction .C MRI (Coronal T1), 4. Se-
questrum and Irregularity in periosteum.
Figure 2. CT scan images of the left leg. A-Axial CT scan, 1.
Subcutaneous abscess, 2. Cloaca, 3. Calcified in marrow
cavity, 4. Irregular new bone formation (Periosteal reac-
tion); B-Sagittal reformation, 5. Sequestrum of 8.5 cm.
and ampicillin-sulbactam, which were continued for 3
months, resulting in total healing of the left leg wound.
After one year of follow-up period, patient remains in
full recovery in regards to his diagnosis of osteomyelitis.
2. Discussion
Over the last two decades, Acinetobacter baumannii has
emerged as a major nosocomial pathogen, especially in
ICU setting and in immunocompromised patients [1].
The genus Acinetobacter consists of ubiquitous Gram
negative, non-fermentative, non-spore forming, aerobic,
oxidase negative coccobacilli. A. baumannii has been
Copyright © 2011 SciRes. WJA
Hematogenous Osteomyelitis by Acinetobacter Baumannii: Case Report and Literature Review25
isolated from several sources including environment (soil,
water, vegetables, and variety of food products), human
skin and throat and respiratory tract of hospitalized pa-
tients [2]. Acinetobacter can survive on dry particles up
to ten days, and more than four months on some surfaces
like PVC (polyvinyl chlorid e), rubber and ceramics [3,4].
The ability to withstand harsh environmental conditions
(including disinfectant solutions and desiccation), and to
acquire wide antimicrobial resistance contribute to its
propensity for causing outbreaks. In a report by Wilsp-
linghoff et al. in 49 United States hospitals (24,179 pa-
tients) between 1995 and 2002, A. baumannii has ac-
counted for 1.3% of nosocomial blood stream infection
(BSI) and 1.6% of all nosocomial BSI in ICU settings.
Nonetheless, despite its low incidence (0.6/10,000 ad-
missions), overall mortality, and mortality in ICU setting
were 34% and 43% respectively [1]. The most common
sources of Acinetobacter bacteremia are respiratory tract
and intravenous catheters [1]. Risk factors include pro-
longed hospitalization, ICU stay, mechanical ventilation,
recent invasive procedure or surgery, indwelling cathe-
ters, broad-spectrum antimicrobial therapy and prior
colonization with the org anism [2,5-9].
Acinetobacter osteomyelitis has been rarely reported
in the literature, mainly in war injury settings. In one
report, it was the most frequently found Gram negative
isolate from war wounds [10]. Isolated cases of Acineto-
bacter osteomyelitis were also reported: (1) an 8-year-old
boy after hamster bite, treated with parenteral dual an-
timicrobial therapy (gentamicin and carbenecillin) for 6
weeks [11], (2) a previously injured patient from an ar-
mory fragment, causing an open fracture of right femur
and treated with parenteral monoth erapy (g entamic in) for
6 weeks [12], and (3) a 55-year-old soldier injured by a
grenade with osteomyelitis of left proximal femur,
treated with parenteral monotherapy (tigecycline) for 43
days [13]. The largest case series reported is by Davis et
al. on 23 soldiers wounded in Iraq war who had wound
cultures positive for MDR Acinetobacter species [14].
Osteomyelitis was diagnosed in 18 patients who were
treated with a combination of antimicrobials and multiple
surgical debridements. Dual antimicrobial therapy (ami-
kacin and imipenem) was administered in 10 cases for
6-8 weeks. There was no mortality or recurrence of in-
fection reported within 9 months of foll ow-up period [14] .
A recent pilot study using a rat model suggested that
MDR A. baumannii did not appear to cause or contribute
to osteomyelitis [15]. However, in our patient, isolation
of A. baumannii from several bone specimens, including
the ones collected intraoperatively, implies a significant
role. Furthermore, the role of MDR A. baumannii in os-
teomyelitis may be dependent on strains [16]. While the
pilot study and the previously reported cases in the lit-
erature involved normal hosts, our patient had severe
immunosuppression which could be a key factor in the
pathogenesis of A. baumannii osteomyelitis. The low
virulence of the organism suggested by the study could
explain the chronic nature of osteomyelitis in this case.
In the experimental rat model, inoculation of S. aureus
and A. baumannii was associated with osteolysis,
whereas A. baumannii alone lead to osteoblastic activity
[15]. The initial bone cu ltu re in our patien t failed to show
S. aureus; however the intraoperative culture grew both S.
aureus and A. baumannii. It is unclear if S. aureus bac-
teremia has preceded the development of A. baumannii
infection in this hemodialysis p atient. However, it is pos-
sible that in the presence of S. aureus, A. baumannii
could persist in the bone, leading to a clinically signifi-
cant osteomyelitis. More studies may be needed to de-
termine the possible synergism between the two organ-
While in all cases reported in the literature, Acineto-
bacter osteomyelitis was the result of a direct inocu lation,
we report the first case of Acinetobacter osteomyelitis
resulting from hematogenous spread. Our patient had
several risk factors for acquiring nosocomial Acineto-
bacter infection including immunocompromised status,
ICU stay, multiple hospitalizations requiring antimicro-
bial therapy, and presence of a hemodialysis catheter.
After sustaining persistent bacteremia, the catheter was
removed and antimicrobial therapy was given for 4
weeks. However, this treatment did not seem to prevent
the hematogenous seeding of bacteria in the tibia.
Hematogenous osteomyelitis is primarily a disease of
children but can also occur among adults [17]. Involve-
ment of long bones is typically seen in children, while
vertebral seeding is common in adu lts [17]. The risk fac-
tors predispose to persistent bacteremia, such as our pa-
tient presented with, also favor the development of he-
matogenous osteomyelitis. It is possible in this case that
an underlying condition su ch as osteonecrosis could have
predated the infection and rendered the bone more sus-
ceptible to metastatic infection. The large area of seques-
tration supports this hypothesis. Furthermore, osteone-
crosis was noted in the left distal femur on MRI. Poten-
tial risk factors in our patient for acquiring osteonecrosis
include HIV and renal disease. The radiological appear-
ance in our case is otherwise classical for chronic osteo-
myelitis, with a cloaca and bony sequestrum.
It is not surprising that multiple surgical debridements
were required, with the presence of sequestrum in the
setting of chronic osteomyelitis. The typical 6 weeks
course of antimicrobials was not sufficient to control the
infection. However, failure to eliminate infection could
have been associated with the need for further surgical
debridements. Polymyxin B has become an important
Copyright © 2011 SciRes. WJA
Hematogenous Osteomyelitis by Acinetobacter Baumannii: Case Report and Literature Review
antimicrobial agent in the treatment of MDR Acineto-
bacter species. Nephrotoxicity associated with polymy-
xin B was not a concern in our case since the patient was
already receiving hemodialysis. None of the cases of
Acinetobacter osteomyelitis reported in the literature was
treated with polymyxin B. The addition of ampicillin-
sulbactam was beneficial in this case, and dual antim-
icrobial therapy may have contributed to good outcome.
It would be difficult to determine if one factor has made
the difference (surgical interventions, duration of antim-
icrobials, dual therapy) or a combination of all. Nonethe-
less, our patient responded well with this multifaceted
treatment approach.
3. Conclusions
In conclusion, this is the first reported case of MDR A.
baumannii hematogenous osteomyelitis. While in most
documented cases of A. baumannii osteomyelitis, entry
appears to require direct inoculation; our case suggests
that this pathogen can seed into bone hematogenously in
the setting of immunosuppression, persistent bacteremia
and possibly in the presence of underlying bone infarcts.
The ability of Acinetobacter to cause metastatic bone
infections has not been previously reported and further
studies may be warranted. Clinicians need to be aware of
this rare possible consequence of A. baumannii bactere-
mia. In addition, increasing prevalence of this organism
worldwide may warrant the need for newer antimicrobi-
als with activity against these organ isms. Combination of
multiple surgical debridements and dual antimicrobial
therapy for a long period may result in a good outcome.
4. Acknowledgements
First of all, we like to thank our patient for giving us
permission and written consent to collect all the relevant
information. We are very thankful to Dr. Alfonso Ortiz
for his help throughout the project and Dr. Catherine
Maldjian to guide us in selecting appropriate radiological
images for this report. We could not have completed this
case report without the support from all the administra-
tive staff of medical record and radiological departments
of Bronx Lebanon Hospital Center and Montefiore Med-
ical Center.
[1] H. Wisplinghoff, T. Bischoff, M. T. Sandra, et al., “No-
socomial Bloodstream Infections in US Hospitals: Analy-
sis of 24,179 Cases from Prospective Nationwide Sur-
veillance Study,” Clinical Infectious Diseases, Vol. 39,
No. 3, 2004, pp. 309-317. doi:10.1086/421946
[2] P. E. Fournier, “The Epidemiology and Control of Aci-
netobacter Baumannii in Health Care Facilities,” Clinical
Infectious Diseases, Vol. 42, No. 5, 2006, pp. 692-699.
[3] C. Webster, K. Towner and H. Humphreys, “Survival of
Acinetobacter on Three Clinically Related Inanimate
Surfaces,” Infect Control Hosp Epidemiol, Vol. 21, No. 4,
2000, p. 246. doi:10.1086/503214
[4] C. Wendt, B. Dietz, E. Dietz, et al., “Survival of Acine-
tobacter Baumannii on Dry Surfaces,” Journal of Clinical
Microbiology, Vol. 35, No. 6, 1997, pp. 1394-1397.
[5] B. Kurcik-Trajkovska, “Acinetobacter Spp.—A Serious
Enemy Threatening Hospitals Worldwide,” Macedonian
Journal of Medical Sciences, Vol. 2, No. 2, 2009.
[6] J. M. Cisneros and J. Rodriguez-Bano, “Nosocomial
Bacteremia due to Acinetobacter Baumannii: Epide-
miology, Clinical Features, and Treatment,” Clinical Mi-
crobiology and Infection, Vol. 8, No. 7, 2002, pp.
687-693. doi:10.1046/j.1469-0691.2002.00487.x
[7] E. Playford, J. Craig and J. Iredell, “Carbapenem-
Resistant Acinetobacter Baumannii in Intensive Care Unit
Patients: Risk Factors for Acquisition, Infection and Their
Consequences,” The Journal of Hospital Infection, Vol.
65, No. 3, 2007, pp. 204-211. doi:10.1086/503214
[8] P. A. Tiley and F. J. Roberts, “Bacteremia with Acineto-
bacter Species: Risk Factors and Prognosis in Different
Clinical Settings,” Clinical Infectious Diseases, Vol. 18,
No. 6, 1994, pp. 896-900. doi:10.1093/clinids/18.6.896
[9] J. L. Garcia-Garmendia, C. Ortiz-Leyba, J. Garnacho-
Montero, et al., “Risk Factors for Acinetobacter Bauman-
nii Nosocomial Bacteremia in Critically Ill Patients: A
Cohort Study,” Clinical Infectious Diseases, Vol. 33, No.
7, 2001, pp. 933-939. doi:10.1086/322584
[10] M. J. Tong, “Septic Complications of War Wounds,” The
Journal of the American Medical Association, Vol. 305,
No. 24, 1972, pp. 1044-1047.
[11] R. Martin, D. Martin and C. Levy, “Acinetobacter Os-
teomyelitis from a Hamster Bite,” The Pediatric Infec-
tious Disease Journal, Vol. 7, No. 5, 1988, pp. 364-365.
[12] G. Volpin, N. Krivoy and H. Stein, “Acinetobacter Sp.
Osteomyelitis of the Femur: A Late Sequel of Unrecog-
nized Foreign Body Implantation,” Injury, Vol. 24, No. 5,
1993, pp. 345-346.
[13] J. Schafer and J. Mangino, “Multidrug Resistant Acine-
tobacter Osteomyelitis from Iraq,” Emerging Infectious
Diseases, Vol. 14, No. 3, 2005, pp. 512-514.
[14] K. Davis, K. Moran, C. McAllister and P. Gray, “Multi-
drug-Resistant Acinetobacter Infections in Soldiers,”
Emerging Infectious Diseases, Vol. 11, No. 8, 2005, pp.
[15] S. C. Collinet-Adler, C. A. Castro, C. G. Ledonio, et al.,
“Acinetobacter Baumannii Is Not Associated with Os-
teomyelitis in a Rat Model,” Clinical Orthopaedics and
Related Research, Vol. 469, No. 1, 2011, pp. 274-282.
Copyright © 2011 SciRes. WJA
Hematogenous Osteomyelitis by Acinetobacter Baumannii: Case Report and Literature Review
Copyright © 2011 SciRes. WJA
[16] D. P. Crane, K. Gromov, D. Li, et al., “Efficacy of Col-
listin-Impregnated Beads to Prevent Multidrug-Resistant
A. Baumannii Implant-Associated Osteomyelitis,” Jour-
nal of Orthopaedic Research, Vol. 27, No. 8, 2009, pp.
1008-1005. doi:10.1002/jor.20847
[17] J. T. Mader, M. Shirtliff and J. H. Calhoun, “The Host
and the Skeletal Infection: Classification and Pathogene-
sis of Acute Bacterial Bone and Joint Sepsis,” Best Prac-
tice & Research Clinical Rheumatology, Vol. 13, No. 1,
1999, pp. 1-20. doi:10.1053/berh.1999.0003