Mycobacterium neoaurum causing prosthetic valve endocarditis: a case report and review of the literature

braz j infect dis.2014;18(2):235–237

The

Brazilian

Journal

of

INFECTIOUS

DISEASES

w w w . e l s e v i e r . c o m / l o c a t e / b j i d

Case

report

Mycobacterium

neoaurum

causing

prosthetic

valve

endocarditis:

a

case

report

and

review

of

the

literature

Anupam

Kumar

_,

_George

_S.

_Pazhayattil

_,

_Aparna

_Das

_,

_Harry

_A.

_Conte

a_{DepartmentofInternalMedicine,UniversityofConnecticutSchoolofMedicine,Farmington,USA} b_{DepartmentofInternalMedicine,StFrancisHospital,114WoodlandStreet,Hartford,USA} c_{DepartmentofInfectiousDiseases,StFrancisHospital,114WoodlandStreet,Hartford,USA}

a

r

t

i

c

l

e

i

n

f

o

Articlehistory:

Received27December2012 Accepted28May2013

Availableonline25September2013

Keywords:

Mycobacteriumneoaurum

Prostheticvalve Endocarditis

a

b

s

t

r

a

c

t

Mycobacteriumneoaurumisararecauseofbacteremia,andinfectionusuallyoccursinan immunocompromisedhostinthesettingofanindwellingcatheter.Prostheticvalve endo-carditisduetonon-tuberculousmycobacteriatypicallycarriesadismalprognosis;wereport acaseofM.neoaurumprostheticvalveendocarditiswithfavorableresponsetoantimicrobial therapywithoutsurgicalintervention.

©2013 ElsevierEditoraLtda.Allrightsreserved.

Case

presentation

A30-year old Caucasian male presentedtothe emergency departmentwithshortnessofbreathandpalpitationsoftwo weeksdurationassociatedwithfeverandchills.Hispast med-icalhistory was significant for multiple episodes of MRSA (methicillinresistantStaphylococcusaureus)endocarditisinthe settingofintravenousdruguse,forwhichhehadundergone bovinemitralvalvereplacementayearprior.Headmittedto continuedintravenousdruguse.Hisvitalsignsonadmission were temperatureof101.4◦F, pulserate of106per minute, bloodpressureof98/58mmHgandrespiratoryrateof20per minute.Agrade3/6holosystolicmurmurwasheardbestatthe mitralareaandradiatedtotheaxilla.Thelowerextremities werewarmtotouch.Distalpulseswereintactandsymmetric. Adetailedneurologicalexamwasunremarkable.Admission

∗ _{Correspondingauthorat:24ParkPlace,Apt8C,Hartford,CT06106,USA.}

E-mailaddress:drkumar83@gmail.com(A.Kumar).

1 _{Currentaddress:SreeGokulamMedicalCollege,Trivandrum695607,India.}

laboratorytestsshowedaWBCcountof16.8K/mm3with neu-trophilpredominance (84%).Serumelectrolytes,blood urea nitrogen,creatinine,creatinekinase(CK)andliverfunction tests were within the normal range. Chest X-ray showed noabnormality,andelectrocardiogramshowednormalsinus rhythmwithmildleftatrialenlargement.

Bloodculturesweredrawnandthepatientwasstartedon empiricantibiotictherapywithvancomycin,ceftriaxoneand rifampin forprovisionaldiagnosis ofprostheticvalve endo-carditis.Atransthoracicechocardiogram revealedextensive vegetationsontheprostheticmitralvalvewithmild obstruc-tion tomitralinflowandanormalejectionfraction(Fig.1). The Gram stain ofthe blood smearwas reported as clus-tersofrodswithGram positivecharacteristicsand theacid faststain(Kinyoun)waspositiveforacid-fastbacteria.Three blood culture bottles (aerobic) grew yellow shiny colonies suggestive of Mycobacteria in 10 days. The organism was

1413-8670/$–seefrontmatter©2013 ElsevierEditoraLtda.Allrightsreserved.

236

Fig.1–Echocardiogramshowingvegetationsonthe prostheticmitralvalvewithmildobstructiontomitral inflow.

identifiedasMycobacteriumneoaurumusinghigh-pressure liq-uidchromatography.Thepatientwastreatedwithintravenous tobramycin, oralazithromycin and oralmoxifloxacinbased on susceptibility testing results. On day 10 ofhis hospital stay he developed severe abdominal pain. CT scan of the abdomenrevealedasplenicandleftrenalinfarct.Magnetic Resonance Imaging(MRI) ofbrain revealed onecentimeter brainabscess.Surgicalinterventionwasdiscouragedgivenhis ongoingdruguse.Thepatient’sconditionimproved remark-ablywithinthenextfewdays.Hisrepeatbloodcultureswere negativeonday 4andhissymptoms resolved.Althoughit wasadvised thathecontinue the same antimicrobial regi-menforanextendedperiodoftime,hewasunwillingtodo so.Hewasfinallydischargedonday39onaregimenoforal azithromycin,ethambutolandmoxifloxacin.Thepatientdid notfollowupwithhisphysicians,andhewasreadmitteda yearlaterforprostheticvalveendocarditisduetocoagulase negativestaphylococcalspecies.His AFBculturesdrawn at thistimewerenegative.Herespondedtointravenous antibi-oticsandsurgicalmanagementwasonceagainnotpursued givenhisongoingintravenousdruguse.

Discussion

Infective endocarditis due to mycobacterium species is an unusual but established clinical entity. Nontuberculous mycobacteria(NTM)havebeenreportedmorefrequentlyas a cause of infectiveendocarditis than Mycobacterium tuber-culosis, especially of prosthetic valves.1,2 _{The commonly}

identifiedNTMspeciescausingendocarditishaveincludedthe followingrapidlygrowingmycobacteria:Mycobacterium fortu-itum,Mycobacteriumabscessus, andMycobacteriumchelonae.2,3

NTMPVE hasbeen described in bothmechanical and bio-logic valvular prostheses. M. neoaurum has been reported rarely as a cause of bloodstream infections in immuno-compromisedhosts,suchaspatients withmalignanciesor transplantrecipients.4M.neoaurumhasalsobeenimplicated

inpulmonaryinfections,5_{meningoencephalitis,}6_urinarytract

infection,7_{andcatheterrelatedinfections.}4,8 _vanDuinetal.

reportedthefirstcaseofPVEduetoM.neoaurumwithgood out-comein2010.9_{Inourpatient,thesourceofM.neoaurumwas}

likelycontaminationduringillicitintravenousdruginjection.

M.neoaurumcanbedetectedonroutineaerobicblood cul-turesandisarapidlygrowingorganismonLowenstein–Jensen agar. Theorganismgrowsattemperaturesbetween25 and 35◦C, usually within five days. M. neoaurum colonies also have a characteristic yellowish-orange smooth appearance that is distinct from the colony characteristics of non-chromogenicmycobacteriumspecies.Inmanyofthereported cases ofendocarditis due toNTM the blood cultures were negative and the identification of the NTM was done by culturing the removed prosthetic valve, or by histopath-ology analysis in conjunction with molecular assays. The advancedmethodsfororganismidentificationinclude high-pressureliquidchromatographyandgenotypicmethodslike sequencingofunique16S rRNA.4_{The16SrRNAutilizesthe}

hypervariablenucleotidesequencesthatlendspecies-specific variabilitywithinmembersofthesamegenus.Therefore,if blood culturesare negativein a patient suspectedof hav-ingPVE,definitivediagnosiscanbemadebyremovalofthe infectedprostheticvalveandperformanceofthe aforemen-tionedstudies.Inanimmunocompromisedpatient,however, unexplainedfeverandsymptomsofinfectionalongwith iso-lation of M. neoaurum, particularly in multiple specimens, shouldbeconsideredhighlysuggestiveofinfectionwiththis organism.

Susceptibility testing of rapidly growing mycobacteria has several limitations: it is not standardized; results are often delayed well into empiric therapy, and most impor-tantly there is a lack of data linking clinical response to in vitro test results. Presently, the minimum recom-mendations for antibiotic susceptibility testing of rapidly growing NTM include clarithromycin, amikacin, cefoxitin, imipenem(thecarbapenempreferredovermeropenem and ertapenem),tobramycin,doxycycline,linezolid,ciprofloxacin, andsulfonamides.10 _{M.neoaurumdisplaysexcellent}

suscep-tibility tociprofloxacinwhileresistancetoit isnowwidely encountered amongstotherrapidly growingNTM.Arecent study,however,diddemonstratehighresistanceforM. neoau-rumtoclarithromycin.11_{Combination antimicrobialtherapy}

includingmacrolides,fluoroquinolonesandaminoglycosides isabettertherapeuticapproachthanmonotherapyowingto diagnosticdelayinorganismidentificationandvarying sus-ceptibilityandresistancepatternsfordifferentmycobacteria species.EndocarditisduetoNTM,particularlyinvolvingthe prosthetic valves, carries a dismal prognosis and requires prolonged antibiotictherapy (rangingbetween47days and 187days).3_{PreviouslyreportedcatheterrelatedM.neoaurum}

infections required a minimum ofthree weeksof antimi-crobialtherapy,withrecoveryaugmentedbyremovalofthe infectedcatheter.4_{Whileprosthesisremovalwouldhavebeen}

ideal, the good therapeutic response in our patient could be duetothe indolentnature andlow pathogenicityofM. neoaurum and theexcellent susceptibility profileit displays incontrast tootherNTM.12 _{Thisisfurthercorroboratedby}

theremarkableresponsetotherapyforthepatientreported byvanDuinetal.andformajorityofthepatientswhohad

brazj infect dis.2014;18(2):235–237

237

infectionsofindwellingcathetersduetoM.neoaurum.4,9_Since

there is lack of considerable treatment experience for M. neoaurumendocarditisinvolvingtheprostheticvalves,we rec-ommendseveralweeksofcombinationantimicrobialtherapy andremovaloftheinfectedprosthesiswhenpossible.

Inconclusion, NTMPVE isawell-defined clinical entity thatshouldbeconsideredinpatientswithprostheticvalves who present withsymptoms ofendocarditiswith negative bloodcultures.M.neoaurumisarapidlygrowingNTMthatcan causeinfectiveendocarditisinimmunocompromised individ-uals.NTMPVEduetoM.neoaurum,incontrasttoPVEdueto other NTM,may beamenabletolong term antibiotic ther-apy,especiallyifcombined withprosthesisremoval.Inthe absence ofdefinitive regimens and substantial experience, physicianscanrelyonantibioticsusceptibilitydataand previ-ouscasereportstoguidetheirantibioticchoiceanddurationof therapy.Ingeneral,however,endocarditissecondarytoNTM, particularly involving the prosthetic valves, carries a poor prognosis.

Conflict

of

interest

Theauthorsdeclarenoconflictsofinterest.

r

e

f

e

r

e

n

c

e

s

1. Corrales-MedinaV,ConchaR,SimkinsJ,SanchezM,Baracco G.Nativevalveendocarditiscausedbyrapidlygrowing mycobacteria:casereportandreviewoftheliterature.ScandJ InfectDis.2007;39:639–41.

2.OlallaJ,PomboM,AguadoJM,etal.Mycobacteriumfortuitum

complexendocarditis–casereportandliteraturereview.Clin MicrobiolInfect.2002;8:125–9.

3.StrabelliTM,SicilianoRF,CastelliJB,etal.Mycobacterium chelonaevalveendocarditisresultingfromcontaminated biologicalprostheses.JInfect.2010;60:467–73.

4.WasherLL,RiddellJ,RiderJ,ChenowethCE.Mycobacterium neoaurumbloodstreaminfection:reportof4casesandreview oftheliterature.ClinInfectDis.2007;45:e10–3.

5.MorimotoY,ChanED,HeifetsL,RoutesJM.Pulmonary infectionwithMycobacteriumneoaurumidentifiedby16S ribosomalDNAsequence.JInfect.2007;54:e227–31.

6.HeckmanGA,HawkinsC,MorrisA,BurrowsLL,BergeronC. RapidlyprogressivedementiaduetoMycobacteriumneoaurum

meningoencephalitis.EmergInfectDis.2004;10:924–7.

7.ZanettiS,FaeddaR,FaddaG,etal.Isolationandidentification ofMycobacteriumneoaurumfromapatientwithurinary infection.NewMicrobiol.2001;24:189–92.

8.HollandDJ,ChenSC,ChewWW,GilbertGL.Mycobacterium neoauruminfectionofahickmancatheterinan

immunosuppressedpatient.ClinInfectDis.1994;18:1002–3.

9.vanDuinD,GoldfarbJ,SchmittSK,TomfordJW,TuohyMJ, HallGS.Nontuberculousmycobacterialbloodstreamand cardiacinfectionsinpatientswithoutHIVinfection.Diagn MicrobiolInfectDis.2010;67:286–90.

10.GriffithDE,AksamitT,Brown-ElliottBA,etal.Anofficial ATS/IDSAstatement:diagnosis,treatment,andpreventionof nontuberculousmycobacterialdiseases.AmJRespirCritCare Med.2007;175:367–416.

11.Brown-ElliottBA,WallaceJrRJ,PettiCA,etal.Mycobacterium neoaurumandMycobacteriumbacteremicumsp.nov.ascauses ofmycobacteremia.JClinMicrobiol.2010;48:4377–85.

12.ElHelouG,ViolaGM,HachemR,HanXY,RaadII.Rapidly growingmycobacterialbloodstreaminfections.LancetInfect Dis.2013;13:166–74,