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University of Wollongong University of Wollongong

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Faculty of Science, Medicine and Health - Papers: part A Faculty of Science, Medicine and Health

1-1-2008

Acinetobacter baumannii mediastinitis after cardiopulmonary bypass: case Acinetobacter baumannii mediastinitis after cardiopulmonary bypass: case

report and literature review report and literature review

Elias Lachanas University of Athens

Periklis Tomos University of Athens

Nicolaos Sfyras Ippokrateion Hospital

Spiros Miyakis University of Athens, [email protected]

Alkiviadis Kostakis University of Athens

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Recommended Citation Recommended Citation Lachanas, Elias; Tomos, Periklis; Sfyras, Nicolaos; Miyakis, Spiros; and Kostakis, Alkiviadis, "Acinetobacter baumannii mediastinitis after cardiopulmonary bypass: case report and literature review" (2008). Faculty of Science, Medicine and Health - Papers: part A. 222. https://ro.uow.edu.au/smhpapers/222

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Acinetobacter baumannii mediastinitis after cardiopulmonary bypass: case Acinetobacter baumannii mediastinitis after cardiopulmonary bypass: case report and literature review report and literature review

Abstract Abstract Background: Mediastinitis resulting from surgical site infection may occur in 1% of patients undergoing median sternotomy. Methods: Case report and review of the pertinent English-language literature. Results: We report a case of mediastinitis caused by Acinetobacter baumannii, in a patient with multiple comorbidities who underwent cardiopulmonary bypass. Successful treatment consisted of surgical debridement, reconstruction, and ampicillin-sulbactam. Conclusions: Acinetobacter baumannii should be recognized as a potential causative agent of severe postoperative mediastinitis.

Disciplines Disciplines Medicine and Health Sciences | Social and Behavioral Sciences

Publication Details Publication Details Lachanas, E., Tomos, P., Sfyras, N., Miyakis, S. & Kostakis, A. (2008). Acinetobacter baumannii mediastinitis after cardiopulmonary bypass: case report and literature review. Surgical Infections, 9 (2), 201-204.

This journal article is available at Research Online: https://ro.uow.edu.au/smhpapers/222

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ACINETOBACTER SPP. are recognized increas-ingly as pathogens causing nosocomial in-

fections, associated with considerable morbid-ity [1,2]. We report a patient with multiple riskfactors who developed sternal osteomyelitiscaused by Acinetobacter baumannii after cardiacsurgery. Successful treatment consisted of sur-gical debridement, followed by reconstructionusing the pectoralis muscles as flaps, combinedwith administration of ampicillin-sulbactam.We discuss the limited number of cases of me-diastinitis caused by Acinetobacter spp. reportedin the English-language literature. To the bestof our knowledge, this is the first report of A. baumannii mediastinitis complicating cardio-pulmonary bypass, underlying the idea thatthis nosocomial organism should be consid-ered in the differential diagnosis of pathogenscausing severe postoperative infections.

CASE REPORT

A 60-year-old obese (body mass index 34.6),diabetic, hypertensive female smoker under-went complete myocardial revascularizationusing the left internal mammary artery via me-dian sternotomy. An intra-aortic balloon pump(IABP) inserted via the left femoral artery-sup-ported her low cardiac index for 24 h postop-eratively. The postoperative course was com-plicated by lower-extremity compartmentsyndrome, resulting in common peronealnerve injury despite fasciotomy. The patientwas discharged on postoperative day 20, oth-erwise well.

The patient was re-admitted two weeks post-discharge complaining of fever, sternal pain,and purulent discharge from the sternotomyscar. The admission temperature was 38.5°C,

SURGICAL INFECTIONSVolume 9, Number 2, 2008© Mary Ann Liebert, Inc.DOI: 10.1089/sur.2006.097

Acinetobacter baumannii Mediastinitis after Cardiopulmonary Bypass: Case Report

and Literature Review

ELIAS LACHANAS,1 PERIKLIS TOMOS,1 NICOLAOS SFYRAS,2SPIROS MIYAKIS,3 and ALKIVIADIS KOSTAKIS1

ABSTRACT

Background: Mediastinitis resulting from surgical site infection may occur in 1% of patientsundergoing median sternotomy.

Methods: Case report and review of the pertinent English-language literature.Results: We report a case of mediastinitis caused by Acinetobacter baumannii, in a patient

with multiple comorbidities who underwent cardiopulmonary bypass. Successful treatmentconsisted of surgical debridement, reconstruction, and ampicillin-sulbactam.

Conclusions: Acinetobacter baumannii should be recognized as a potential causative agentof severe postoperative mediastinitis.

12nd Propedeutic Department of Surgery, Athens University, Laikon Hospital, Athens, Greece.2Department of Cardiac Surgery, Ippokrateion Hospital, Athens, Greece.33rd Department of Medicine, Athens University, Sotiria Hospital for Chest Diseases, Athens, Greece.

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LACHANAS ET AL.

white blood cell count was 3,900/mm3 (89%neutrophils), C-reactive protein (CRP) concen-tration was 170 mg/L (normal � 5 mg/L), anderythrocyte sedimentation rate (ESR) was 57mm/h. The chest radiograph was normal.Computed tomography (CT) of the chest withthree-dimensional reconstruction revealed ex-tensive necrosis of the sternum (Fig. 1). Therewas no evidence of retrosternal space involve-ment. The patient was treated empirically withvancomycin for four days (until culture resultswere available) without improvement. Bloodcultures were negative. Gram stain of pus fromthe sternal wound revealed non-motile gram-negative coccobacilli. The organisms werestrictly aerobic, catalase-positive, and oxidase-negative. On culture (API 20NE system; Bio-Merieux API, Marcy l’Etoile, France), the iso-late was identified as Acinetobacter baumannii,following the simplified identification schemeproposed [3]. Susceptibility testing with a broth

microdilution method performed and inter-preted according to standard guidelines [4] re-vealed the following minimum inhibitory con-centrations (MICs) (mcg/mL): ampicillin 16;ampicillin-sulbactam 1; piperacillin 16; ticar-cillin-clavulanic acid 8; cefuroxime 32; cefo-taxime 8; ceftazidime 2; cefepime 1; imipenem-cilastatin 0.5; gentamicin 1; amikacin 1; andciprofloxacin 32.

The diagnosis was postoperative infectiousmediastinitis type IIIB [5] caused by Acinetobac-ter baumannii, and ampicillin-sulbactam (3 gevery 6 h) was administered intravenously. Thepatient underwent pulmonary function tests anddobutamine stress echocardiography, which re-vealed small airways disease, no signs of my-ocardial ischemia, and a left ventricular ejectionfraction of 60%. Therefore, surgical debridementand sternum reconstruction was undertaken.

During the operation, wires and necroticbone, cartilage, and soft tissue were removed,

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FIG. 1. Preoperative computed tomography scans of chest with three-dimensional reconstruction. (A) Thoracic cage.(B) Selected location in sternum, showing necrotic (dark) areas.

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ACINETOBACTER BAUMANNII MEDIASTINITIS

and the sternal defect was reconstructed usingpectoral muscles as flaps [6]. Recovery was un-eventful, and the patient was discharged onoral ampicillin-sulbactam on the tenth postop-erative day in excellent physical condition,with a normal hematologic profile and sternalstability. Acinetobacter baumannii grew fromculture of the necrotic bone, with an identicalsusceptibility pattern.

At follow-up three months later, the patientwas free of symptoms, CRP and ESR were nor-mal, and the surgical site was evaluated witha repeat three-dimensional CT scan and a three-phase 99technetium methylene-diphosphonatescintigram, revealing normal healing and os-teoblastic activity, respectively. Antibiotictreatment was then discontinued. The patientremains well; she ceased smoking, and her di-abetes control is optimal.

DISCUSSION

Postoperative mediastinitis (surgical site in-fection associated with sternal osteomyelitis,with [organ/space] or without [deep inci-sional] infection of the retrosternal space) oc-curs in approximately 1% of patients undergo-ing median sternotomy for cardiopulmonarybypass [5]. The mortality rate is high (14%–48%), and the cost of hospitalization is in-creased [7,8]. Diabetes mellitus, obesity, to-bacco smoking, airways disease, the use of theleft internal mammal artery as a graft for car-diopulmonary bypass, and the use of an IABPare among the risk factors for mediastinitis af-ter sternotomy [9]; all these risk factors werepresent in our patient.

Staphylococci (Staphylococcus aureus, S. epider-midis) are isolated in more than 70% of post-operative mediastinitis cases having an identifi-able pathogen [10]. Mixed infections, includinganaerobic species, may account for as many as40% of cases [11]. The extent of the involvementof anaerobes in mediastinal infections still is de-bated; growth of these organisms in vitro is of-ten laborious, whereas distinguishing anaerobesas true pathogens from commensal organisms issometimes problematic [12]. Gram-negative or-ganisms and fungi are infrequent isolates in me-diastinal surgical site infections [10,11].

Acinetobacter baumannii is one of at least 21Acinetobacter species. In clinical practice,genospecies 1 (A. calcoaceticus), 2 (A. bauman-nii), 3, and 13 are called Acinetobacter bauman-nii-calcoaceticus complex, representing approx-imately 80% of isolates from clinical infections[13]. In contrast with earlier beliefs (that A. bau-mannii opportunistically affected patients athigh mortality risk), this organism is now anestablished pathogen of hospital infections, as-sociated independently with a higher mortal-ity rate [1,2]. Acinetobacter spp. most often causeventilator-associated pneumonia, but may alsocause blood stream infections, as well as otherinfections, such as intra-abdominal abscess,keratitis, and meningitis [1,14]. Acinetobactermediastinitis is rare. A case of postoperativemediastinal infection caused by A. calcoaceticushas been reported in a patient with esophago-tracheal fistula [15], and a case of A. baumannii(then termed A. anitratus) sternoclavicular sep-tic arthritis has been associated with intra-venous drug abuse [16]. To our knowledge, thecase described here is the first reported in theEnglish-language literature of mediastinalwound infection caused by A. baumannii aftercardiopulmonary bypass. Interestingly, thefirst case of multi-drug-resistant A. baumanniimediastinitis after heart transplantation hasbeen described recently [17], identifying thisorganism as an emerging pathogen for post-operative infections.

Hospital-acquired infections caused byAcinetobacter spp. resistant to most broad-spec-trum agents (with the usual exception of car-bapenems and polymyxins) are encounteredfrequently worldwide [14], including our coun-try [18]. The frequency of isolation and the sus-ceptibility pattern of resistant isolates dependson local factors, such as infection control mea-sures and local antibiotic use policies [14]. An-tibiotic combinations have been given formulti-drug-resistant strains, with inconsistentoutcomes [13]. The strain isolated from the pre-sent case was not multi-drug-resistant, andampicillin-sulbactam was used. Sulbactam isactive against Acinetobacter (i.e., in comparisonwith clavulanate and tazobactam), presumablybecause of the selective affinity to its penicillinbinding proteins and more favorable pharma-cokinetics [19]. Ampicillin-sulbactam in high

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doses may be considered for the treatment ofmulti-drug-resistant strains if imipenem-cilas-tatin cannot be used or is contraindicated[13,19].

The optimal surgical treatment of mediasti-nal infections is debatable, and depends largelyon the extent of tissue damage at the time ofdiagnosis [5,10]. When the diagnosis of sternalinfection is delayed more than 20 days, optimalsurgical treatment consists of prompt debride-ment followed by muscle flaps [10]; the latterprocedure can be performed using the pec-toralis muscles [5,6]. In addition to surgery, an-tibiotics should be administered; in cases withunidentified pathogens or in mixed infections,the drugs are directed against a broad spec-trum of suspected pathogens, taking into ac-count local patterns of resistance of the mostcommon pathogens.

ACKNOWLEDGMENT

The authors thank Ms. Danielle Bowler forediting the manuscript.

REFERENCES

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2. Robenshtok E, Paul M, Leibovici L, et al. The signifi-cance of Acinetobacter baumannii bacteraemia com-pared with Klebsiella pneumoniae bacteraemia: Riskfactors and outcomes. J Hosp Infect 2006;64:282–287.

3. Bouvet PJ, Grimont PA. Identification and biotypingof clinical isolates of Acinetobacter. Ann Inst PasteurMicrobiol 1987;138:569–578.

4. National Committee for Clinical Laboratory Stan-dards. Methods for dilution antimicrobial suscepti-bility tests for bacteria that grow aerobically. Fourthedition. Approved Standard M7-A4. Wayne, PA.1997.

5. El Oakley RM, Wright JE. Postoperative mediastini-tis: Classification and management. Ann Thorac Surg1996;61:1030–1036.

6. Tomos P, Lachanas E, Michail PO, et al. Alternativebi-pectoral muscle flaps for postoperative sternotomymediastinitis. Ann Thorac Surg 2006;81:754–755.

7. Loop FD, Lytle BW, Cosgrove DM, et al. Sternalwound complications after isolated coronary artery

bypass grafting: Early and late mortality, morbidityand cost of care. Ann Surg 1990;49:179–187.

8. Nelson RM, Dries DJ. The economic implications ofinfection in cardiac surgery. Ann Thorac Surg 1986;42:240–242.

9. Demmy TL, Park SB, Liebler GA, et al. Recent expe-rience with major sternal wound complications. AnnThorac Surg 1990;49:458–462.

10. Grossi EA, Culliford AT, Krieger KH, et al. A surveyof 77 major infectious complications of median ster-notomy: A review of 7,949 consecutive operative pro-cedures. Ann Thorac Surg 1985;40:214–223.

11. Sarr MG, Gott VL, Townsend TR. Mediastinal infec-tion after cardiac surgery. Ann Thorac Surg 1984;38:415–426.

12. Citron DM. Specimen collection and transport, anaer-obic culture techniques, and identification of anaer-obes. Rev Infect Dis 1984;6 Suppl 1:S51–S58.

13. Murray CK, Hospenthal DR. Treatment of multidrugresistant Acinetobacter. Curr Opin Infect Dis 2005;18:502–506.

14. Bergogne-Berezin E, Towner KJ. Acinetobacter spp. asnosocomial pathogens: Microbiological, clinical, andepidemiological features. Clin Microbiol Rev 1996;9:148–165.

15. Stoutenbeek CP, van Saene HK, Miranda DR, et al.Acinetobacter mediastinitis and pneumonia in a thoro-trastoma patient: The oropharyngeal flora as sourceof infection. Intensive Care Med 1983;9:139–141.

16. Bayer AS, Chow AW, Louie JS, et al. Sternoarticualrpyoarthrosis due to gram-negative bacilli: Report ofeight cases. Arch Intern Med 1977;137:1036–1040.

17. George RS, Birks EJ, Haj-Yahia S, et al. Acinetobactermediastinitis in a heart transplant patient. Ann Tho-rac Surg 2006;82:715–716.

18. Maniatis AN, Pournaras S, Orkopoulou S, et al. Mul-tiresistant Acinetobacter baumannii isolates in intensivecare units in Greece. Clin Microbiol Infect 2003;9:547–553.

19. Marques MB, Brookings ES, Moser SA, et al. Com-parative in vitro antimicrobial susceptibilities of noso-comial isolates of Acinetobacter baumannii and syner-gistic activities of nine antimicrobial combinations.Antimicrob Agents Chemother 1997;41:881–885.

Address reprint requests to:Dr. Spiros Miyakis

3rd Department of MedicineAthens University

Sotiria Hospital for Chest DiseasesMesogeion 152

11527, Athens, Greece

E-mail: [email protected]

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