Hematogenous Osteomyelitis by Acinetobacter Baumannii: Case Report and Literature Review

doi:10.4236/wja.2011.12004

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World Journal of AIDS, 2011, 1, 23-27

doi:10.4236/wja.2011.12004 Published Online June 2011 (http://www.SciRP.org/journal/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.

Email: [email protected]

Received March 24th, 2011; Revised April 10th, 2011; Accepted 21st, 2011.

ABSTRACT

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

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-

isms.

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

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.

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