Nationwide surveillance of antimicrobial resistance among Enterobacteriaceae in intensive care units in Taiwan

BRIEF REPORT

Nationwide surveillance of antimicrobial resistance

among

Enterobacteriaceae in intensive care units in Taiwan

S.-S. Jean

P.-R. Hsueh

W.-S. Lee

H.-T. Chang

M.-Y. Chou

I.-S. Chen

J.-H. Wang

C.-F. Lin

J.-M. Shyr

W.-C. Ko

J.-J. Wu

Y.-C. Liu

W.-K. Huang

L.-J. Teng

C.-Y. Liu

Received: 30 April 2008 / Accepted: 25 July 2008 / Published online: 21 August 2008 # Springer-Verlag 2008

Abstract To determine the antimicrobial resistance profiles

among clinical isolates of Enterobacteriaceae in Taiwanese

intensive care units (ICUs), a national surveillance of

antibiotic resistance among important Enterobacteriaceae

was conducted from September 2005 through November

2005 at the ICUs of ten major teaching hospitals in Taiwan.

A total of 574 Enterobacteriaceae isolates recovered from

various clinical samples of our ICU patients were submitted

for in vitro test. Minimum inhibitory concentrations (MICs)

of these isolates to 18 antimicrobial agents were determined

by the broth microdilution method. The prevalences of

Enterobacteriaceae isolates with phenotypic

extended-spectrum

β-lactamase (ESBL) production were 26% in

Klebsiella pneumoniae, 16% in Serratia marcescens, 14%

in Escherichia coli, and 13% in Proteus mirabilis, in which

a significantly rising prevalence of ESBL production

among K. pneumoniae was noted (p=0.002) when

com-pared with a previous Taiwanese survey in 2000.

Hetero-S.-S. Jean

Departments of Intensive Care Units and Internal Medicine, Min-Sheng General Hospital,

Taoyuan County, Taiwan P.-R. Hsueh (*)

Departments of Laboratory Medicine and Internal Medicine, National Taiwan University Hospital,

National Taiwan University Medical College, 7 Chung-Shan South Road,

100 Taipei, Taiwan e-mail: [email protected] W.-S. Lee

Department of Internal Medicine, Taipei Municipal WanFang Hospital, Taipei, Taiwan

H.-T. Chang

Department of Internal Medicine, Far Eastern Memorial Hospital, Taipei County, Taiwan

M.-Y. Chou

Department of Internal Medicine, Cheng Hsin Rehabilitation Medical Center, Taipei, Taiwan

I.-S. Chen

Department of Internal Medicine, Cardinal Tien Hospital, Taipei County, Taiwan

J.-H. Wang

Department of Internal Medicine, China Medical College Hospital, Taichung, Taiwan

C.-F. Lin

Department of Internal Medicine, Taichung Veterans General Hospital, Taichung, Taiwan

J.-M. Shyr

Department of Clinical Pathology, Taichung Veterans General Hospital, Taichung, Taiwan

W.-C. Ko

Departments of Internal Medicine, National Cheng-Kung University Hospital, Tainan, Taiwan

J.-J. Wu

School of Medical Technology,

National Cheng-Kung University College of Medicine, Tainan, Taiwan

Y.-C. Liu

Department of Clinical Pathology, Kaohsiung Veterans General Hospital, Kaohsiung, Taiwan

geneous resistance to various fluoroquinolones was found

among our Enterobacteriaceae isolates, except for

Ente-trobacter cloacae. Emergence of ertapenem-resistant

iso-lates of E. coli, K. pneumoniae, E. cloacae, and S.

marcescens was noted. Gradually increasing rates of

drug-resistant Enterobacteriaceae were noted in Taiwanese

ICUs. Periodic surveillance of the evolutionary trend of

antimicrobial resistance among ICU isolates is crucial for

starting appropriately empirical antimicrobial therapy in the

future.

Antimicrobial resistance is an increasing threat in

hospital-ized patients experiencing sepsis caused by

Enterobacter-iaceae, and it has resulted in increased illnesses, mortality,

and healthcare costs, particularly in patients admitted to

intensive care units (ICUs) [

1

,

2

]. National programs about

monitoring the trends of endemic resistance and comparing

the data with those of other countries are warranted to

guide optimal empirical antibiotics for selected infections.

Surveillance of Multicenter Antimicrobial Resistance in

Taiwan (SMART), initiated in 2000, is a nationwide

programme in Taiwan designed to monitor antimicrobial

resistance among clinically important bacteria.

From September 2005 through November 2005, the ICU

wards of ten major teaching hospitals in different regions of

Taiwan were involved in this study. A total of 574

non-duplicated isolates (one isolate per patient) of

Enterobac-teriaceae were collected. Identification of species was

performed with conventional biochemical methods and the

Vitek system (bioMérieux Vitek, St Louis, MO, USA). The

isolates that were recovered from various clinical specimens

included Escherichia coli (160 isolates), Klebsiella

pneu-moniae (162 isolates), Enterobacter cloacae (75 isolates),

Serratia marcescens (68 isolates), Citrobacter freundii (12

isolates), Morganella morganii (33 isolates), and Proteus

mirabilis (64 isolates). Antimicrobial susceptibility testing

was performed using the broth microdilution method

according to Clinical and Laboratory Standards Institute

(CLSI) recommendations [

3

]. A total of 18 antimicrobial

agents (Table

1

) were tested. Reference strains E. coli

ATCC 25922, K. pneumoniae ATCC 700603, and

Pseudo-monas aeruginosa ATCC 27853 were used as quality

control strains for each batch of MIC tests. Susceptibility

categories of these isolates were determined based upon

CLSI MIC breakpoints, except for moxifloxacin,

isepami-cin, and tigecycline in that their MIC breakpoints are not

available [

4

].

For phenotypic identification of extended-spectrum

β-lactamase (ESBL) production for E. coli, K. pneumoniae,

and P. mirabilis, CLSI guidelines using the confirmatory

disk diffusion methods were applied [

4

]. For other

Enter-obacteriaceae species, ESBL production was defined based

on the MICs of ceftazidime, ceftriaxone, or cefepime that

were equal to or greater than 2

μg/ml. If the MIC of

cefepime in the presence of clavulanic acid (10

μg) was at

least eight-fold less than that of cefepime, the isolate was

regarded to have ESBL production as previously described

[

5

].

Among these Enterobacteriaceae isolates, the most

common source (45.1%) was respiratory tract, 14.6% were

from patients with bloodstream infection, and 7.8% from

other sterile sites (pleural effusion, ascites, cerebrospinal

fluid, and synovial fluid). E. coli (27.9%) and K.

pneumo-niae (28.2%) were the two predominant bacteria of all

Enterobacteriaceae.

The results of antimicrobial susceptibilities for the

isolates are shown in Table

1

. With the exception of E.

cloacae and C. freundii, cefmetazole retained acceptable in

vitro activities (>75% susceptibilities) against the other

isolates. Ceftazidime and ceftriaxone exhibited good

activ-ities against Enterobacteriaceae isolates tested except E.

cloacae and C. freundii. Cefepime had rather low resistant

rates (<10%) for all isolates tested. Piperacillin-tazobactam

displayed fair (60–80%) susceptibility against E. cloacae,

C. freundii, and S. marcescens. In contrast, all carbapenems

exhibited excellent activities against all isolates tested.

However, eight K. pneumoniae isolates, two E. cloacae

isolates, and two S. marcescens isolates were not

suscep-tible to ertapenem. Additionally, one isolate of K.

pneumo-niae with intermediate susceptibility to imipenem and

meropenem was noted. Of note, levofloxacin has better in

vitro activity than ciprofloxacin against all these isolates.

The MIC

levels of moxifloxacin was two-fold higher than

those of levofloxacin for most of our enterobacterial

isolates. Netilmicin and isepamicin showed similar in vitro

susceptibilities to amikacin, and these three agents had

remarkably better in vitro activity than gentamicin. All of

the isolates tested, except the P. mirabilis isolates (MIC

,

32

μg/ml), were inhibited by 2 μg/ml of tigecycline.

It is noteworthy that in this survey K. pneumoniae

(26%), S. marcescens (16%), E. coli (14%), and P. mirabilis

Department of Internal Medicine, Kaohsiung Veterans General Hospital, Kaohsiung, Taiwan

L.-J. Teng

School of Medical Technology, National Taiwan University Hospital,

National Taiwan University College of Medicine, Taipei, Taiwan

C.-Y. Liu

Department of Internal Medicine, Taipei Veterans General Hospital, Taipei, Taiwan

Table 1 Antimicrobial susceptibilities of 574 clinical Enterobacteriaceae isolates recovered from patients treated at ICUs of ten major teaching hospitals in Taiwan in 2005

Antimicrobial agent MIC (μg/ml) % for indicated agent

Range MIC50 MIC90 S I R

Escherichia coli (160) Cefazolin 1– >128 4 >128 66 3 31 Cefmetazole 0.25– >128 1 64 86 3 11 Ceftriaxone <0.03– >128 0.06 64 78 7 15 Ceftazidime <0.03– >128 0.12 32 83 2 15 Cefepime <0.03– 128 0.06 4 94 1 5 Piperacillin-tazobactam <0.03– >128 2 32 89 5 6 Cefoperazone-sulbactam ≤0.03– >64 1 32 –a _{– –} Imipenem <0.03–4 0.25 0.25 100 0 0 Meropenem <0.03–8 0.03 0.06 99 1 0 Ertapenem <0.03– >32 0.03 0.25 98 0 2 Ciprofloxacin <0.03– >128 0.25 64 68 1 31 Levofloxacin <0.03– >32 0.25 16 71 2 27 Moxifloxacin <0.03– >32 0.5 32 – – – Gentamicin 0.25– >128 1 64 64 4 32 Amikacin 0.5– >128 2 4 98 0 2 Netilmicin 0.25– >128 1 4 99 0 1 Isepamicin 0.5– >128 1 2 – – – Tigecycline 0.12–4 0.25 0.5 – – – Klebsiella pneumoniae (162) Cefazolin 0.5– >128 2 >128 68 1 31 Cefmetazole 0.12– >128 1 128 85 1 14 Ceftriaxone <0.03– >128 0.06 128 78 5 17 Ceftazidime <0.03– >128 0.25 128 79 3 18 Cefepime <0.03– >128 0.06 16 88 2 10 Piperacillin–tazobactam <0.03– >128 4 >128 80 4 16 Cefoperazone–sulbactam 0.06– >64 0.5 64 – – – Imipenem 0.12–8 0.25 0.5 99 1 0 Meropenem <0.03–8 0.03 0.06 99 1 0 Ertapenem <0.03– >32 0.03 1 95 0 5 Ciprofloxacin <0.03– >128 0.06 128 73 2 25 Levofloxacin <0.03– >32 0.06 32 79 2 19 Moxifloxacin <0.03– >32 0.12 32 – – – Gentamicin 0.06– >128 0.5 >128 73 4 23 Amikacin 0.25– >128 1 >128 86 2 12 Netilmicin 0.5– >128 1 >128 85 3 12 Isepamicin 0.06– >128 0.5 >128 – – – Tigecycline 0.12–16 1 2 – – – Enterobacter cloacae (75) Cefazolin 2– >128 >128 >128 1 4 95 Cefmetazole 16– >128 >128 >128 1 4 95 Ceftriaxone <0.03– >128 4 128 58 19 23 Ceftazidime 0.06– >128 2 >128 53 0 47 Cefepime <0.03–16 0.12 4 96 4 0 Piperacillin–tazobactam 0.5– >128 4 128 74 13 13 Cefoperazone–sulbactam <0.03– >64 4 64 – – – Imipenem 0.25–0.5 0.5 0.5 100 0 0 Meropenem <0.03–0.25 0.06 0.12 100 0 0 Ertapenem <0.03–4 0.12 2 97 3 0 Ciprofloxacin <0.03–128 0.06 4 84 3 13 Levofloxacin <0.03– >32 0.06 4 89 3 8 Moxifloxacin <0.03– >32 0.12 8 – – – Gentamicin 0.12– >128 0.5 128 68 0 32

Table 1 (continued)

Antimicrobial agent MIC (μg/ml) % for indicated agent

Range MIC50 MIC90 S I R

Amikacin 0.5– >128 1 8 97 0 3 Netilmicin 0.25– >128 1 4 98 0 2 Isepamicin 0.5– >128 1 2 – – – Tigecycline 0.5–8 1 1 – – – Serratia marcescens (68) Cefazolin 32– >128 >128 >128 0 0 100 Cefmetazole 4– >128 16 128 76 9 15 Ceftriaxone 0.06– >128 4 >128 70 9 21 Ceftazidime 0.12– >128 1 8 90 1 9 Cefepime 0.04–64 0.25 16 84 13 3 Piperacillin-tazobactam 1– >128 8 64 63 34 3 Cefoperazone–sulbactam 0.25– >64 8 >64 – – – Imipenem 0.12–2 0.5 0.5 100 0 0 Meropenem <0.03–2 0.03 0.12 100 0 0 Ertapenem <0.03–16 0.12 0.5 97 0 3 Ciprofloxacin 0.06–128 2 32 43 16 41 Levofloxacin 0.06– 32 1 8 66 9 25 Moxifloxacin 0.06– >32 2 16 – – – Gentamicin 0.5– >128 8 >128 47 10 43 Amikacin 1– >128 2 >128 87 0 13 Netilmicin 0.5– >128 2 >128 85 0 15 Isepamicin 0.5– >128 2 >128 – – – Tigecycline 1–8 2 2 – – – Citrobacter freundii (12) Cefazolin 2– >128 128 >128 33 0 67 Cefmetazole 0.5–128 32 128 25 25 50 Ceftriaxone 0.06–64 0.25 32 59 33 8 Ceftazidime 0.25–128 0.5 128 50 0 50 Cefepime <0.03–1 0.06 1 100 0 0 Piperacillin–tazobactam 2– >128 4 >128 67 0 33 Cefoperazone–sulbactam 0.5– >64 1 >64 – – – Imipenem 0.12–0.5 0.25 0.5 100 0 0 Meropenem <0.03–0.06 0.03 0.06 100 0 0 Ertapenem <0.03–1 0.03 1 100 0 0 Ciprofloxacin <0.03–8 0.25 4 75 0 25 Levofloxacin <0.03–2 0.25 2 100 0 0 Moxifloxacin 0.12–8 0.5 4 – – – Gentamicin 0.12– >128 0.5 128 67 0 33 Amikacin 0.5–8 1 4 100 0 0 Netilmicin 0.5–8 1 4 100 0 0 Isepamicin 0.5–1 1 1 – – – Tigecycline 0.5–1 0.5 1 – – – Morganella morganii (33) Cefazolin >128 >128 >128 0 0 100 Cefmetazole 4–64 8 16 97 0 3 Ceftriaxone <0.03–128 0.03 4 94 0 6 Ceftazidime 0.12– >128 0.25 4 91 0 9 Cefepime <0.03–2 0.03 0.25 100 0 0 Piperacillin–tazobactam 0.12– >128 0.5 2 97 0 3 Cefoperazone–sulbactam 1–64 2 8 – – – Imipenem 0.06–0.25 0.25 0.25 100 0 0 Meropenem 0.06–0.12 0.12 0.12 100 0 0 Ertapenem <0.03–0.25 0.03 0.06 100 0 0 Ciprofloxacin <0.03–32 1 8 55 24 21

(13%) were the four leading pathogens with the highest

rates of ESBL production. None of our C. freundii isolates

exhibited ESBL-producing phenotype.

This 2005 multicenter study regarding the antimicrobial

susceptibilities of Enterobacteriaceae disclosed three

im-portant points. First, persistently high rates of ESBL

phenotype were found among our K. pneumoniae and E.

coli isolates. In comparison with the data in 2000 [

1

], a

2.4-fold increase in the prevalence rate of ESBL phenotype was

found among K. pneumoniae isolates (p=0.002, by

chi-square test). Second, high percentages (>10%) of ESBL

phenotype were also found in our S. marcescens and P.

mirabilis isolates. Third, carbapenem-resistant

Enterobac-teriaceae isolates have emerged in ICUs in Taiwan.

In this study, the prevalence rates of ESBL-producing K.

pneumoniae and E. coli isolates resembled those of ICU

pathogens in North America [

6

]. Fortunately, these rates

remained lower than those from Latin America and several

Asian countries [

5

,

7

]. Higher prevalence of ESBL

production among our S. marcescens isolates than two

common AmpC producers (E. cloacae and C. freundii)

might be partially responsible for the higher non-susceptible

rate of S. marcescens to cefepime.

Carbapenems are often considered as the last resort for

the management of serious infections in ICUs. However,

ertapenem was considered as the most vulnerably affected

carbapenem agent against K. pneumoniae (with plasmid

encoding AmpC or ESBLs or in porin-deficient isolates)

[

8

], E. coli (AmpC

β- lactamase production, associated

with loss of both OmpC and OmpF porins) [

9

], and E.

cloacae (with enhanced efflux of ertapenem) isolates [

10

],

which was consistent with our data in terms of higher

non-susceptibilities of ertapenem than others. Concerning the

susceptibilities of fluoroquinolones in our study, with the

exception of E. cloacae, the other Enterobacteriaceae

showed heterogeneous susceptible rates to these agents.

However, levofloxacin was significantly more active

against important enteric GNBs than ciprofloxacin in our

ICU survey results. Finally, except for Proteus isolates,

tigecycline possessed excellent in vitro activity against

Antimicrobial agent MIC (μg/ml) % for indicated agent

Range MIC50 MIC90 S I R

Levofloxacin <0.03–8 0.5 8 82 3 15 Moxifloxacin 0.06–32 2 16 – – – Gentamicin 0.05– >128 2 128 61 0 39 Amikacin 0.5–4 1 2 100 0 0 Netilmicin 0.25– 8 1 4 100 0 0 Isepamicin 0.5–8 1 4 – – – Tigecycline 1–8 2 2 – – – Proteus mirabilis (64) Cefazolin 4– >128 8 >128 59 13 28 Cefmetazole 1–16 2 4 100 0 0 Ceftriaxone <0.03–128 <0.03 8 95 2 3 Ceftazidime <0.03–32 0.12 0.5 97 0 3 Cefepime 0.06–16 0.12 4 98 2 0 Piperacillin–tazobactam 0.25–16 0.5 1 100 0 0 Cefoperazone–sulbactam 0.5–32 2 16 – – – Imipenem <0.03–0.12 0.06 0.12 100 0 0 Meropenem <0.03–0.12 0.06 0.06 100 0 0 Ertapenem <0.03–0.12 <0.03 0.03 100 0 0 Ciprofloxacin <0.03–64 0.5 32 60 6 34 Levofloxacin 0.06– >32 0.5 16 64 11 25 Moxifloxacin 0.25– >32 4 32 – – – Gentamicin 0.5– >128 16 >128 42 3 55 Amikacin 1– >128 4 8 91 0 9 Netilmicin 0. 5– >128 4 16 90 6 4 Isepamicin 2– >128 8 16 – – – Tigecycline 2–>32 16 32 – – –

S susceptible, I intermediate, R resistant

Enterobacteriaceae isolates, including phenotypic

ESBL-and AmpC-producing organisms. However, because of its

bacteriostatic mechanism, close monitoring of future

changes in the values of tigecycline MIC for

Enterobacter-iaceae isolates is warranted.

In conclusion, the emergence of ESBL-producing

Enter-obacteriaceae other than E. coli and K. pneumoniae was

found. Resistance to carbapenems is emerging, and

resis-tance to fluoroquinolones continues to be a worrisome

problem. Periodic surveillance of antimicrobial resistances

among isolates from ICUs is crucial for initiation of

appropriate empirical antimicrobial therapy.

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