碳青霉烯类与其他抗菌药物联合对鲍曼不动杆菌的协同效应

International Journal of Antimicrobial Agents36 (2010) 243–246

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Synergistic activities between carbapenems and other antimicrobial agents against Acinetobacter baumannii including multidrug-resistant and extensively drug-resistant isolates

Pattarachai Kiratisin a,?,Anucha Apisarnthanarak b,Srirumpa Kaewdaeng a

a Department of Microbiology,Faculty of Medicine Siriraj Hospital,Mahidol University,2Prannok Road,Bangkok-Noi,Bangkok10700,Thailand

b Division of Infectious Diseases,Faculty of Medicine,Thammasat University Hospital,Pratumthani12120,Thailand

a r t i c l e i n f o

Article history:

Received19February2010

Accepted29April2010

Keywords:

Carbapenems

Combination therapy

Synergy

Acinetobacter baumannii

a b s t r a c t

Treatment options for multidrug-resistant(MDR)and extensively drug-resistant(XDR)Acinetobacter bau-

mannii have been seriously limited and may require combination antimicrobial therapy.In this study,

we searched for synergistic activity between carbapenems(doripenem,imipenem and meropenem)and

various non-traditional agents(cefoperazone/sulbactam,doxycycline,rifampicin,netilmicin and moxi-

?oxacin)against40A.baumannii clinical isolates,including MDR and XDR isolates.The results showed

that combination of each carbapenem with cefoperazone/sulbactam,based on the Etest method,demon-

strated synergy more frequently(17.5–32.5%)than the other tested agents,which may suggest a role in

combination therapy against highly resistant A.baumannii.

? 2010 Elsevier B.V. and the International Society of Chemotherapy. All rights reserved.

1.Introduction

Multidrug-resistant(MDR)and extensively drug-resistant

(XDR)Acinetobacter baumannii have become a serious widespread

threat for nosocomial infections,which often result in higher mor-

tality[1].The prevalence of MDR and XDR A.baumannii,including

carbapenem-resistant A.baumannii,has been increasing in several

regions including Asia-Paci?c[2].Empirical combination therapy

is a common practice in areas where highly resistant A.bauman-

nii is endemic in order to achieve a possible synergistic effect

or at least to reduce selective pressure for the emergence of a

resistant phenotype[3].Although colistin,a polymyxin E,has

been shown to be effective against this resistant bacterium,its

toxicity is recognisable whilst little is known regarding its phar-

macokinetics/pharmacodynamics to achieve the optimal dosage.

As an alternative to colistin therapy,a few in vitro studies demon-

strated that carbapenems could be candidates for combination

therapy,such as imipenem plus tigecycline[4],meropenem plus

cipro?oxacin[5],and meropenem plus sulbactam[6].However,

there are very little data regarding doripenem,a newer car-

bapenem,with respect to its use alone or in combination against

A.baumannii.In this study,we evaluated the role of carbapen-

ems,including doripenem,imipenem and meropenem,when used

in combination with an antimicrobial agent of different classes

?Corresponding author.Tel.:+6624197058;fax:+6624113106.

E-mail address:sipkr@mahidol.ac.th(P.Kiratisin).

(cefoperazone/sulbactam,doxycycline,rifampicin,netilmicin and

moxi?oxacin)against A.baumannii,including MDR and XDR iso-

lates,recovered from patients in Thailand.These agents were

selected based on their potential use,including in combination

therapy,for the treatment of infection due to A.baumannii[7–9].

Synergistic activity was determined based on the Etest,a less

laborious and time-consuming method used practically in clinical

laboratories[10].

2.Materials and methods

Forty non-duplicate A.baumannii isolates recovered from vari-

ous clinical specimens at Siriraj Hospital,a2400-bed tertiary-care

university hospital in Bangkok(Thailand),during January and

June2009were randomly selected for this study.All isolates

were cultivated and identi?ed according to standard microbio-

logical procedures.MDR and XDR phenotypes were de?ned as

isolates resistant to at least three different antimicrobial classes or

resistant to all but one or two antimicrobial agents,respectively

[11].Susceptibility testing was performed by the disk diffusion

method according to Clinical and Laboratory Standards Institute

(CLSI)recommendations[12].Minimal inhibitory concentrations

(MICs)of each agent used in the combination study(doripenem,

imipenem,meropenem,cefoperazone/sulbactam,doxycycline,

rifampicin,netilmicin and moxi?oxacin)were determined by Etest

(AB BIODISK,Solna,Sweden)and were interpreted based on CLSI

breakpoints.No CLSI breakpoint was available for doripenem,thus

a breakpoint of1mg/L was adopted according to the US Food and

0924-8579/$–see front matter? 2010 Elsevier B.V. and the International Society of Chemotherapy. All rights reserved.

doi:10.1016/j.ijantimicag.2010.04.011

244P.Kiratisin et al./International Journal of Antimicrobial Agents36 (2010) 243–246

Table1

Sources,antibiogram pro?les and minimal inhibitory concentrations(MICs)of Acinetobacter baumannii isolates.

No.Source Antibiogram pro?le a Carbapenem MIC(mg/L)Non-carbapenem MIC(mg/L)

DOR IMI MEM CPS DOX RIF NET MXF

MDR or XDR A.baumannii

1Sputum RRRRRRRR>32>32>3264643>25612 2Sputum RRRRRRRR>32>32>3248643>25612 3Sputum RRRRRRRR12>32>322448 1.5>2564 4Sputum RRRRRRRR>32>32>3264483>25612 5Sputum RRRRRRRR>32>32>32>256963>256>32 6Urine RRRRRRRR>32>32>32>256242>256>32 7Sputum RRRRRRRR>32>32>32192643>25612 8Sputum RRRRRRRR>32>32>3296644>25624 9Sputum RRRRRRRR24>32>321921284>256>32 10Urine RRRRRRRR>32>32>32>256963>25616 11Sputum RRRRRRRR24>32>32>256643>25612 12Pus RRRRRRRR12>322432963>25616 13Sputum RRRRRRRR>32>32>32128643>25612 14Sputum RRRRRRRR24>32>3264643>25612 15Sputum RRRRRRRR>32>32>32>256322>2568 16Sputum RRRRRRRR>32>32>3296963>25616 17Sputum RRRRRRRR>32>32>32961283>256>32 18Sputum RRRRRRRR12241632644>25612 19Blood RRRRRRRR24>32>3264642>25616 20Sputum RRRRRRRR32>32>3264963>256>32 21Blood IRIIRSSR>32>32>32192483>25612 22Blood IRIIRSSR6 1.53640.5>32>256>32 23Sputum IRRSSRRR312 1.536240.19 24Urine SRSSRRRR0.750.380.7526449612 25Urine RRIRRRRR12 1.53124>25612

Non-MDR A.baumannii

26Sputum SISSSSSS0.1250.250.19 1.50.194 1.50.032 27Sputum SISSSSSS0.1250.250.1920.125410.023 28Sputum SISSSSSS0.1250.250.25 1.50.094310.023 29Sputum SISSSSSS0.190.380.1910.19 1.520.047 30Sputum SRSIRSSS0.50.380.530.758 1.56 31Sputum SISSRSSS0.250.50.2520.256 1.50.047 32Sputum SISSSSSS0.190.380.2510.1253 1.50.023 33Sputum SISSSSSS0.1250.250.1910.125 1.520.032 34Sputum SISSSSSS0.190.380.190.7521 1.50.016 35Sputum SISSSSSS0.190.380.2520.38210.064 36Sputum SISSSSSS0.190.380.2520.19620.064 37Sputum SISSSSSS0.380.380.3830.19320.047 38Sputum SISSSSSS0.250.50.3830.125320.032 39Blood IRSISSSS0.50.380.38960.19630.047 40Sputum SISSSSSS0.50.250.190.750.047420.047

DOR,doripenem;IMI,imipenem;MEM,meropenem;CPS,cefoperazone/sulbactam;DOX,doxycycline;RIF,rifampicin;NET,netilmicin;MXF,moxi?oxacin;S,susceptible;I, intermediate;and R,resistant.

a The antibiogram pro?le is the susceptibility results for ceftazidime,ceftriaxone,cefepime,piperacillin/tazobactam,cipro?oxacin,gentamicin,amikacin and trimetho-prim/sulfamethoxazole,respectively.

Drug Administration(FDA).Synergy was evaluated by the Etest method according to previous studies that have validated this method as practical for antimicrobial combination testing includ-ing for A.baumannii[10,13].Brie?y,Etest strips of two agents were placed at a90?angle crossing at the MIC of each agent when tested alone.The fractional inhibitory concentration index(FICI)was used to determine synergistic activity.The FICI was derived from a sum-mation of the fractional inhibitory concentration(FIC)of the two agents used in the combination.The FIC of each agent was calcu-lated as a ratio of the MIC when used in combination and the MIC when used alone.FICIs were interpreted as previously de?ned:syn-ergy at a FICI≤0.5;additivity at a FICI>0.5–4;and antagonism at a FICI>4[14].

3.Results and discussion

Sources,antibiograms and MIC values of the study isolates are shown in Table1.Isolates were classi?ed as MDR or XDR A.bau-mannii(n=25)and non-MDR A.baumannii(n=15).Of the MDR and XDR A.baumannii isolates,23(92%)were carbapenem-resistant.All carbapenems were highly effective against non-MDR A.baumannii,with MICs not exceeding0.5mg/L.According to CLSI guidelines [12],all MDR and XDR A.baumannii were resistant to netilmicin, whilst non-MDR A.baumannii were all susceptible to netilmicin.For doxycycline,all XDR A.baumannii were resistant whilst some MDR A.baumannii and all non-MDR A.baumannii remained susceptible. There were no CLSI interpretations with respect to A.baumannii for cefoperazone/sulbactam,rifampicin and moxi?oxacin.None the less,MDR and XDR A.baumannii demonstrated higher MIC ranges for cefoperazone/sulbactam(1.5to>256mg/L),rifampicin(1.5to >32mg/L)and moxi?oxacin(0.19to>32mg/L)compared with non-MDR A.baumannii(0.75–96mg/L,1–8mg/L and0.016–6mg/L, respectively).

FICIs of the combinations between each carbapenem and the other agents are shown in Table2.Synergy was demonstrated more frequently when cefoperazone/sulbactam was combined with a carbapenem:doripenem(n=7;17.5%);imipenem(n=13;32.5%); or meropenem(n=12;30%).Only a single non-MDR A.baumannii isolate(2.5%)revealed synergistic activity with doxycycline plus any of the carbapenems.Both imipenem and meropenem also showed synergistic combinations with rifampicin in a non-MDR A.baumannii isolate,whilst doripenem showed no synergy with

P.Kiratisin et al./International Journal of Antimicrobial Agents36 (2010) 243–246245

Table2

Fractional inhibitory concentration indices(FICIs)of various carbapenem combinations a.

No.DOR combination with:IMI combination with:MEM combination with:

CPS DOX RIF NET MXF CPS DOX RIF NET MXF CPS DOX RIF NET MXF

MDR or XDR Acinetobacter baumannii

10.690.94 1.04 1.00 1.380.75 1.50 1.50 1.00 1.500.75 1.38 1.50 1.00 1.50

20.92 1.00 1.500.88 1.500.75 1.50 1.50 1.00 1.500.75 1.13 1.50 1.00 1.50

3 1.33 1.0

4 2.00 1.50 2.00 1.04 1.13 1.50 1.00 1.500.7

5 1.00 1.50 1.00 1.50

4 1.13 1.50 1.500.88 1.50 1.13 1.50 1.50 1.00 1.50 1.13 1.50 1.50 1.00 1.50

50.63 1.50 1.500.69 1.000.63 1.50 1.50 1.00 1.000.38 1.50 1.50 1.000.63

60.310.88 1.13 1.00 1.000.19 1.04 1.130.750.750.25 1.25 1.130.750.75

70.710.88 1.50 1.00 1.500.75 1.50 1.50 1.00 1.500.44 1.50 1.50 1.00 1.50

80.850.88 1.00 1.00 1.50 1.04 1.50 1.13 1.00 1.500.880.88 1.50 1.00 1.17

90.40 1.50 1.42 1.50 1.500.44 1.13 1.13 1.00 1.000.44 1.50 1.13 1.00 1.00 100.63 1.04 1.50 1.00 1.500.50 1.50 1.50 1.00 1.500.50 1.50 1.50 1.00 1.50 110.63 1.50 2.00 1.50 2.000.38 1.13 1.50 1.00 1.500.38 1.00 1.040.75 1.25 12 1.42 2.00 2.00 1.50 2.000.440.75 1.040.75 1.250.71 1.00 1.670.88 1.42 130.75 1.00 1.50 1.00 1.500.440.88 1.170.75 1.500.44 1.00 1.500.75 1.50 140.50 1.75 1.75 1.00 1.750.75 1.13 1.50 1.00 1.500.75 1.00 1.170.75 1.50 150.44 1.00 1.50 1.00 1.500.22 1.13 1.50 1.00 1.500.310.75 1.25 1.00 1.13 160.88 1.500.88 1.00 1.500.42 1.50 1.04 1.00 1.500.44 1.04 1.040.75 1.50

17 1.38 1.00 1.50 1.000.630.75 1.50 1.50 1.00 1.000.75 1.00 1.04 1.00 1.00

18 1.25 1.17 1.17 1.50 1.670.71 2.00 1.42 1.50 2.00 1.00 1.50 1.50 1.50 2.00

19 1.17 1.42 2.00 1.50 2.00 1.13 1.50 1.50 1.00 1.250.75 1.13 1.50 1.00 1.50

20 1.25 1.75 1.42 1.50 1.500.690.88 1.50 1.000.420.69 1.04 1.50 1.00 1.00 210.69 1.38 1.04 1.00 1.500.44 1.50 1.25 1.00 1.500.38 1.38 1.04 1.00 1.50 220.25 1.430.880.75 1.040.22 1.76 1.04 1.38 1.500.22 1.170.75 1.04 1.04 23 1.000.830.830.500.670.88 1.00 1.25 1.25 1.410.88 1.00 1.420.71 1.41 240.88 1.42 1.420.42 1.01 1.00 1.16 1.160.45 1.67 1.42 2.00 1.750.76 1.33 25 1.00 2.00 1.50 1.50 2.000.880.83 1.50 1.50 2.00 1.00 2.00 1.75 1.50 2.00

Non-MDR A.baumannii

260.88 1.660.890.85 1.720.71 1.250.63 1.09 1.260.67 1.150.990.99 1.38 270.88 2.00 1.25 2.00 1.750.88 1.51 1.26 2.00 2.000.99 2.000.99 2.00 2.00 28 1.01 1.43 1.01 1.13 1.45 1.43 1.44 1.00 2.00 2.00 1.26 1.44 1.26 1.26 2.00 290.84 2.000.670.710.68 1.00 1.320.66 1.16 1.340.72 1.660.99 1.16 1.15 300.42 1.270.630.830.820.66 1.160.69 1.67 1.670.88 1.430.75 1.26 1.76 310.75 1.52 1.00 1.000.840.440.880.710.830.990.63 1.520.83 1.26 1.44

32 1.41 2.00 1.16 1.32 1.70 1.00 1.750.99 1.16 1.35 1.51 2.00 1.26 1.26 1.46

33 2.00 1.50 1.09 1.25 1.500.88 1.27 1.43 1.76 2.000.84 2.00 1.32 1.75 2.00

34 2.000.460.870.83 1.660.660.390.88 1.16 1.16 1.000.340.990.99 1.41 350.71 1.32 1.16 1.04 1.390.70 1.16 1.03 1.04 1.000.88 1.66 1.51 1.14 1.26 36 1.24 2.000.99 1.75 2.000.88 1.15 1.00 1.16 1.50 1.00 2.000.83 1.51 1.73 270.83 1.32 1.16 1.03 1.15 1.00 1.150.99 1.75 1.15 1.00 1.32 1.16 1.16 1.15 38 1.00 2.00 1.26 1.51 1.480.42 1.010.830.88 1.26 1.00 1.75 1.16 1.00 1.16 390.140.840.71 1.00 1.250.19 1.150.41 1.00 1.150.250.990.50 1.000.99 400.69 1.380.880.880.39 1.17 2.00 1.14 1.51 1.68 1.00 2.00 1.50 1.41 1.68

a FICI interpretation:≤0.5,synergy(underlined);>0.5–4,additivity;>4,antagonism[14].

rifampicin.Two XDR A.baumannii isolates(5%)demonstrated syn-ergy between doripenem and netilmicin,one of which was the only isolate that showed synergy between imipenem and netilmicin. One of each XDR A.baumannii and non-MDR A.baumannii showed synergy of imipenem+moxi?oxacin and doripenem+moxi?oxacin combinations,respectively.No synergy was observed for combinations of meropenem+netilmicin and meropenem +moxi?oxacin.In addition,none of the combinations demon-strated antagonism.

In critically ill patients,infection due to MDR or XDR A.bau-mannii is a signi?cant predictor of mortality and requires high-cost https://www.360docs.net/doc/473860064.html,bination antimicrobial therapy may be consid-ered to improve the chance of survival.However,limited data are available on effective combinations against A.baumannii.We looked for combination activity between various carbapenems plus other non-traditional agents.Synergy was observed more often between cefoperazone/sulbactam and a carbapenem.MICs of doripenem,imipenem and meropenem were reduced3.18-, 3.78-and3.65-fold,respectively,when combined with cefopera-zone/sulbactam(data not shown).Synergy of a carbapenem and sulbactam against A.baumannii has also been shown in a few studies[3,6].For other agents(doxycycline,rifampicin,netilmicin and moxi?oxacin),synergistic activity with a carbapenem was less effective.Generally,doripenem and imipenem demonstrated comparable potential for synergy with other agents and were slightly better than meropenem with respect to synergistic activ-ities.It is noteworthy that antagonism was not detectable in any combination.Most FICIs were also<2.00,suggesting that MICs of the combined agents were decreased,albeit with no synergism. Particularly for patients with serious infections due to highly resis-tant A.baumannii,this study has demonstrated the potential clinical value of combination treatment between a carbapenem and other non-traditional agents.The activity of carbapenems,at least,may be enhanced when used in combination with some of these agents. However,in vitro synergistic activity could be dependent on strains and methods and thus results should be used with extreme caution in empirical therapy.Although time-kill and checkerboard methods are considered to be standard testing for antimicrobial combina-tion studies,they are time consuming and labour intensive.The Etest method is more feasible for testing in general clinical lab-oratories.It was determined that results of combination activity based on the Etest method were ca.63–75%in agreement with the time-kill method compared with44–88%for the checkerboard method[10].Therefore,the Etest technique may be used as an alternative and convenient method for synergy testing although further evaluation is warranted.It should also be mentioned that,

246P.Kiratisin et al./International Journal of Antimicrobial Agents36 (2010) 243–246

as a limitation,antagonism may be less detected by the Etest combination study because the inhibition zone may be con?ned under the crossed strips[10].For isolates with very high MIC levels, it is unlikely to achieve clinical plasma concentrations of the indi-vidual drug.Therefore,time-kill study using the steady-state con-centration according to the pharmacokinetic/pharmacodynamic model of each antibiotic as well as additional clinical trials based on in vitro data should be carried out to validate the value of these combination regimens.Furthermore,advances in knowledge of underlying resistance mechanisms among these strains would be important to provide a better understanding of how combination therapy could bene?t clinical outcomes.

Acknowledgments

The authors thank the Department of Microbiology,Faculty of Medicine Siriraj Hospital(Bangkok,Thailand)for providing iso-lates used in this study.They also thank Janssen(Thailand),MSD (Thailand)and Astra Zeneca(Thailand)for their support of study reagents.

Funding:PK was a recipient of the Siriraj Research Development Fund during this study.

Competing interests:None declared.

Ethical approval:Not required.

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