Rapid tests for detection of carbapenemase producers in P. aeruginosa; what do we really need?

Rapid

tests

for

detection

of

carbapenemase

producers

in

P.

aeruginosa;

what

do

we

really

need?

Pruebas

rápidas

para

la

detección

de

Pseudomonas

aeruginosa

productora

de

carbapenemasas.

¿Qué

necesitamos

realmente?

Laurent

Poirel

_,

_Patrice

_Nordmann

a_{INSERMU914“EmergingResistancetoAntibiotics”,France}

b_{MedicalandMolecularMicrobiology,DepartmentofMedicine,FacultyofScience,UniversityofFribourg,Switzerland}

c_{CentreNationalAssocié-CentredeRéférencedesRésistancesauxAntibiotiques,LeKremlin-Bicêtre,France}

d_{HopitalFribourgeois-hôpitalCantonal,Fribourg,Switzerland}

Resistance to carbapenems in Pseudomonas aeruginosa is a majorissue sincethat species is intrinsicallyresistant tomany antibiotics and therefore, as soon as some acquired resistance traitsoccur,carbapenemsbecomerapidlytheultimate therapeu-tic options.1 _{Carbapenem resistancein P.aeruginosamay occur} throughthelossofanouter-membraneproteinnamedOprDthat resultsfrommutationsortruncationsinthecorrespondinggene.2 InEurope,thatmechanismaccountsfor15–20%ofthe imipenem-resistantP.aeruginosa isolates.Itis nottransmissiblesinceit is chromosomally-encodedandinterfereswithimipenem suscepti-bilityonly,meropenemanddoripenemaswellasbroad-spectrum cephalosporinsremainingeffectiveagainstOprD-deficientstrains (ifnoadditionalacquiredmechanism).However,theacquisitionof carbapenemasegenesisanothermechanismofcarbapenem resis-tanceinP.aeruginosathatis increasinglyidentified wordwide.3 That resistance trait is more worrisome since it corresponds to genes acquired through horizontal gene transfers that may disseminate, and impacts all carbapenem molecules that are all hydrolyzed by those enzymes. In P. aeruginosa, carbapene-mases are mainly metallo-␤-lactamases (MBLs) that hydrolyze allcarbapenems very efficiently.4 _{They arenot inhibited by} ␤-lactamaseinhibitorssuchasclavulanicacidandtazobactamand alsoconferresistancetoother␤-lactamssuchasbroad-spectrum cephalosporins.

Therefore,anaccurateandrapiddetectionofcarbapenemase production in P. aeruginosa is extremely important. Such rapid detectionmaycontributetofacilitatetheantibioticstewardship andtreatmentofinfectedpatientsandtopreventthefurtherspread ofthosecarbapenem-resistantisolates.

Therefore,inorder tooptimizeinfectioncontroland antimi-crobialtherapy, advancesindetection methodsare crucial.Use

∗ Correspondingauthor.

E-mailaddress:laurent.poirel@unifr.ch(L.Poirel).

of molecularbiology and in particular PCR-based techniquesis beingthe key-approachfor rapidand accurateidentificationof those resistancetraits.Themain advantagesof molecular tech-niquesaresensitivity,specificity,andtherelativerapidityofthese methods.Without moleculartechniquesin routinelaboratories, identification of resistance mechanisms is often fastidious and time-consuming.

However,therearesomedrawbackswiththosemolecular tech-niques,themainonesare:(i)theyareexpensive,(ii)theydorequire somesignificantexpertise,(iii)theydonotfullyreplacethe antibi-ogramsincetheyonlytargetsomespecificmoleculardeterminants butdonotevaluatetherealsusceptibilityoftheisolatetoalarge varietyofdrugs,(iv)thecorrelationbetweengeneidentification andresistanceisnotalwaysobserved(geneexpressionand mod-ulation),and(v)bydefinitiontheydonotidentifythenoveland emergingresistancegenes.

Thatisthereasonwhybiochemicalandphenotypicalmethods havestilltobeconsideredasinterestingtools.Inthestudy per-formedbyLucenaetal.inthisissue,5_{phenotypictestsfordetection} ofMBLproductionhavebeencomparedwithanimpressive collec-tionofmetallo-␤-lactamaseproducers,mostlyoftheSPMtype.The double-disksynergytest(DDST),theCombined-Disk(CD)assay, andtheMBLE-testhavebeencompared.Theyallshowsome advan-tagesanddisadvantages,butonemainshortcomingisthelackof clearcut-offtoaccuratelyinterprettheobtainedresults. Depend-ingonthestrainbackground(additionalresistancemechanismsor not),andontheuser’stechnicalskills,variableresultsand inter-pretationsmaybeobserved.

We believe that those diagnostic techniques,in order to be used,mustnotonlybeaffordableandrapid,butoverallmustbe easy toperformand interpret. Routinelaboratoriescannotrely oncomplicatedscreeningstrategiesthat,inaddition,mayprovide difficult-to-interpretresults.Effortsmustbeplacedindeveloping thoseteststhatmaybeusedinanyclinicallaboratory,andnotonly inthosewithadvancedtechnologiesorhighlyqualifiedpersonal.

1

Published in (QIHUPHGDGHV,QIHFFLRVDV\0LFURELRORJtD&OtQLFD

±

which should be cited to refer to this work.

One recently developed technique aiming to rapidly iden-tifycarbapenemaseproducers,eitherinPseudomonasspp.andin Enterobacteriaceae, is theCarba NP test that corresponds to an efficient and reliable diagnostic tool for identification of those enzymes.6_{Themainadvantagesofthistestarethatitisextremely} rapidandcostless,bycontrasttomostoftheotherknown tech-niques. It actually represents a breakthrough for detection of carbapenemaseproducerswithresultsobtainedinlessthantwo hours,eitherdirectlyfromcoloniesbutalsofromclinicalsamples suchasbloodculturesandurines.7,8_{Anothermajoradvantageof} thistestisthatitcanbeimplementedinanyclinicallaboratories due toitssimplicity.Itistherefore welladapted tothecurrent needs, i.e. improvingthehygiene controland theantimicrobial therapy.InacountrysuchasBrazilwherethestudyfromLucena etal.hasbeenperformed,5_{itmightreallyprovideanadded-value} since notonlyitslowpriceandlow-expertiserequirementwill surelyfittotheexpectations,butalsothecurrentandvery worri-someepidemiology(withhugedisseminationofSPM-1-producing P.aeruginosastrainsalloverthecountry9,10_{)willmakeitan} essen-tialtool.

Public healthauthorities aroundtheworldpromptto estab-lishguidelinesrecommendingstrictandaccuratemonitoringof antimicrobialresistanceshouldfacilitatethedevelopmentand dis-seminationofthosekindsofmethodsthatcorrespondtotheneeds inthe“real”dailylife.

References

1.NordmannP,NaasT,FortineauN,PoirelL.Superbugsinthecomingnewdecade; multidrugresistanceandprospectsfortreatmentofStaphylococcusaureus, Enterococcusspp.andPseudomonasaeruginosain2010.CurrOpinMicrobiol. 2007;10:436–40.

2.NordmannP.Gram-negativebacteriawithresistancetocarbapenems.MedSci (Paris).2010;26:950–9.

3.PoirelL,PitoutJD,NordmannP.Carbapenemases:moleculardiversityand clin-icalconsequences.FutureMicrobiol.2007;2:501–12.

4.WalshTR,TolemanMA,PoirelL,NordmannP.Metallo-␤-lactamases:thequiet beforethestorm?ClinMicrobiolRev.2005;18:306–25.

5.LucenaA,DallaCostaLM,DaSilvaNogueiraK,MatosAP,GalesAC,Raboni SM.Comparisonofphenotypictestsforthedetectionofmetallo-␤-lactamases inclinicalisolatesofPseudomonasaeruginosa.EnfermInfectMicrobiolClin. 2014;32:625–30.

6.NordmannP,PoirelL,DortetL.Rapiddetectionofcarbapenemase-producing Enterobacteriaceae.EmergInfectDis.2012;18:1503–7.

7.DortetL, Bréchard L, Cuzon G, PoirelL, Nordmann P.Strategy for rapid detectionofcarbapenemase-producingEnterobacteriaceae.AntimicrobAgents Chemother.2014;58:2441–5.

8.DortetL,BréchardL,PoirelL,NordmannP.Rapiddetectionof carbapenemase-producing Enterobacteriaceae from blood cultures. Clin Microbiol Infect. 2014;20:340–4.

9.GalesAC,MenezesLC,SilbertS,SaderHS.Disseminationindistinct Brazil-ian regionsof an epidemic carbapenem-resistant Pseudomonas aeruginosa producing SPM metallo-␤-lactamase. J Antimicrob Chemother. 2003;52: 699–702.

10.Poirel L, Magalhaes M, Lopes M, Nordmann P. Molecular analysis of metallo-␤-lactamasegeneblaSPM-1-surroundingsequencesfromdisseminated

PseudomonasaeruginosaisolatesinRecife,Brazil.AntimicrobAgentsChemother. 2004;48:1406–9.

2