Scholarly article on topic 'Laboratory diagnosis, clinical management and infection control of the infections caused by extensively drug resistant gram-negative bacilli: A Chinese consensus statement'

Laboratory diagnosis, clinical management and infection control of the infections caused by extensively drug resistant gram-negative bacilli: A Chinese consensus statement Academic research paper on "Clinical medicine"

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Clinical Microbiology and Infection
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{" Enterobacteriaceae infection" / "multidrug resistant (MDR)" / "pandrug resistant (PDR)" / XDR / "XDR Acinetobacter infection" / "XDR Pseudomonas aeruginosa infection"}

Abstract of research paper on Clinical medicine, author of scientific article — Xiangdong Guan, Lixian He, Bijie Hu, Jianda Hu, Xiaojun Huang, et al.

Abstract Extensively drug-resistant (XDR) Gram-negative bacilli (GNB) are defined as bacterial isolates susceptible to two or fewer antimicrobial categories. XDR-GNB mainly occur in Enterobacteriaceae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Stenotrophomonas maltophilia. The prevalence of XDR-GNB is on the rise in China and in other countries, and it poses a major public health threat as a result of the lack of adequate therapeutic options. A group of Chinese clinical experts, microbiologists and pharmacologists came together to discuss and draft a consensus on the laboratory diagnosis, clinical management and infection control of XDR-GNB infections. Lists of antimicrobial categories proposed for antimicrobial susceptibility testing were created according to documents from the Clinical Laboratory Standards Institute (CLSI), the European Committee on Antimicrobial Susceptibility Testing (EUCAST) and the United States Food and Drug Administration (FDA). Multiple risk factors of XDR-GNB infections are analyzed, with long-term exposure to extended-spectrum antimicrobials being the most important one. Combination therapeutic regimens are summarized for treatment of XDR-GNB infections caused by different bacteria based on limited clinical studies and/or laboratory data. Most frequently used antimicrobials used for the combination therapies include aminoglycosides, carbapenems, colistin, fosfomycin and tigecycline. Strict infection control measures including hand hygiene, contact isolation, active screening, environmental surface disinfections, decolonization and restrictive antibiotic stewardship are recommended to curb the XDR-GNB spread.

Academic research paper on topic "Laboratory diagnosis, clinical management and infection control of the infections caused by extensively drug resistant gram-negative bacilli: A Chinese consensus statement"

Accepted Manuscript

Laboratory diagnosis, clinical management and infection control of the infections caused by extensively drug resistant gram-negative bacilli: A Chinese consensus statement

Xiangdong Guan, Lixian He, Bijie Hu, Jianda Hu, Xiaojun Huang, Guoxiang Lai, Yimin Li, Youning Liu, Yuxing Ni, Haibo Qiu, Zonghong Shao, Yi Shi, Minggui Wang, Rui Wang, Depei Wu, Canmao Xie, Yingchun Xu, Fan Yang, Kaijiang Yu, Yunsong Yu, Jing Zhang, Chao Zhuo

PII: S1198-743X(15)00986-6

DOI: 10.1016/j.cmi.2015.11.004

Reference: CMI 442

To appear in: Clinical Microbiology and Infection

Received Date: 1 June 2015

Revised Date: 6 November 2015

Accepted Date: 6 November 2015

Please cite this article as: Chinese XDR Consensus Working Group, Guan X, He L, Hu B, Hu J, Huang X, Lai G, Li Y, Liu Y, Ni Y, Qiu H, Shao Z, Shi Y, Wang M, Wang R, Wu D, Xie C, Xu Y, Yang F, Yu K, Yu Y, Zhang J, Zhuo C, Laboratory diagnosis, clinical management and infection control of the infections caused by extensively drug resistant gram-negative bacilli: A Chinese consensus statement, Clinical Microbiology and Infection (2015), doi: 10.1016/j.cmi.2015.11.004.

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Laboratory diagnosis, clinical management and infection control of the infections caused by extensively drug resistant Gram-negative bacilli: A

Chinese consensus statement

Chinese XDR Consensus Working Group

1 2 2 3

Members of working group: Xiangdong Guan , Lixian He , Bijie Hu , Jianda Hu , Xiaojun Huang4, Guoxiang Lai5, Yimin Li6, Youning Liu7, Yuxing Ni8, Haibo Qiu9, Zonghong Shao10, Yi Shi11, Minggui Wang12, Rui Wang7, Depei Wu13, Canmao Xie1, Yingchun Xu14, Fan Yang12, Kaijiang Yu15, Yunsong Yu16, Jing Zhang12, Chao Zhuo6

1) Department of Critical Care Medicine, The First Affiliated Hospital, Sun Yat-sen University, Guangzhou 510080, China,

2) Department of Respiratory (BH), Institute of Respiratory Disease (LH), Zhongshan Hospital, Fudan University, Shanghai 200032, China,

3) Department of Hematology, Union Hospital, Fujian Medical University, Fuzhou 350001, China,

4) Department of Hematology, People's Hospital, Peking University, Beijing 100044, China,

5) Department of Respiratory and Critical Care Medicine, Fuzhou General Hospital of Nanjing Military Command, Fuzhou 350025, China,

6) Department of Critical care medicine (LY), Guangzhou Institute of Respiratory Disease (CZ), The First Affiliated Hospital of Guangzhou Medical University, Guangzhou 510120, China,

7) Department of Respiratory (YL), Department of Clinical Pharmacology (RW), Chinese PLA General Hospital, Beijing 100853, China,

8) Department of Clinical Microbiology, Ruijin Hospital, Shanghai Jiaotong University School of Medicine, Shanghai 200025, China,

9) Department of ICU, Zhongda Hospital, Southeast University, Nanjing 210009, China,

1 10) Department of Hematology, General Hospital, Tianjin Medical University,

2 Tianjin 300052, China,

3 11) Department of Respiratory, Nanjing General Hospital of Nanjing Military

4 Command, Nanj ing 210002, China,

5 12) Institute of Antibiotics, Huashan Hospital, Fudan University, Shanghai 200040,

6 China,

7 13) Department of Hematology, The First Affiliated Hospital of Soochow University,

8 Suzhou 215006, China,

9 14) Clinical Laboratory, Peking Union Medical College Hospital, Bejing 100032,

10 China,

11 15) Department of ICU, Cancer Hospital of Harbin Medical University, Harbin

12 150081, China,

13 16) Division of Infectious Diseases, Sir Run Shaw Hospital, School of Medicine

14 Zhejiang University, Hangzhou 310016, China.

16 Corresponding: Minggui Wang,, Tel: 86-21-52888195

1 Abstract

2 Extensively drug-resistant gram-negative bacilli (XDR-GNB) are defined as

3 bacterial isolates susceptible to two or fewer antimicrobial categories. XDR-GNB

4 mainly occur in Enterobacteriaceae, Acinetobacter baumannii, Pseudomonas

5 aeruginosa, and Stenotrophomonas maltophilia. The prevalence of XDR-GNB is on

6 the rise either in China and other countries, posing a major public health threat due

7 to the lack of adequate therapeutic options. A group of Chinese clinical experts,

8 microbiologists and pharmacologists came together to discuss and draft a consensus

9 on the laboratory diagnosis, clinical management and infection control of

10 XDR-GNB infections. Lists of antimicrobial categories proposed for antimicrobial

11 susceptibility testing are created according to documents from the Clinical

12 Laboratory Standards Institute (CLSI), the European Committee on Antimicrobial

13 Susceptibility Testing (EUCAST) and the United States Food and Drug

14 Administration (FDA). Multiple risk factors of XDR-GNB infections are analyzed

15 with long-term exposure to extended-spectrum antimicrobials being the most

16 important one. Combination therapeutic regimens are summarized for treatment of

17 XDR-GNB infections caused by different bacteria based on limited clinical studies

18 and/or laboratory data. Most frequently used antimicrobials used for the combination

19 therapies include aminoglycosides, carbapenems, colistin, fosfomycin and

20 tigecycline. Strict infection control measures including hand hygiene, contact

21 isolation, active screening, environmental surface disinfections, decolonization and

22 restrict antibiotic stewardship are recommended to curb the XDR-GNB spread.


Bacterial resistance to antibiotics has become one of the major threats of human health[l]. Extensively drug resistance (XDR) refers to the phenomenon in some bacteria that shows resistance to nearly all antimicrobial agents available except one or two. XDR emerges primarily in gram-negative bacilli (herein after referred to as XDR-GNB), especially Enterobacteriaceae, Acinetobacter baumannii, Pseudomonas aeruginosa and Stenotrophomonas maltophilia. For the infections caused by XDR bacteria, efficacious treatment is limited and no data are available from large series of randomized clinical studies at present time. Antimicrobial monotherapy, including the old drug polymyxin and the newer antibiotic tigecycline, usually cannot provide satisfactory efficacy. Combination antimicrobial therapy is used in most cases. XDR infection mostly develops in the patients with severe underlying disease, immunodeficiency and/or repeated long-term use of broad-spectrum antimicrobial agents, and associated with poor clinical outcome. As a consequence, XDR has become one of the most troublesome issues in current management of bacterial infections. This consensus statement is formulated after back and forth discussion and consultation with the relevant clinical experts, microbiologists, and pharmacologists who are working in the field of infectious diseases in China, which may be helpful for improving clinical management of XDR bacterial infections.

Definitions for MDR, XDR and PDR

An expert consensus on multidrug-resistant (MDR), XDR and pandrug-resistant (PDR) bacteria was proposed in 2012 via a joint initiative of the European Centre for Disease Prevention and Control (ECDC) and the Center for Disease Control and Prevention (CDC), involving the relevant experts from the United States and many European countries[2]. This expert consensus is now widely referenced in China and other countries to define the bacterial resistance.

Multidrug-resistant (MDR): The isolate is non-susceptible to at least three

antimicrobial categories within its susceptibility spectrum (including resistant and intermediate). Resistance to one antimicrobial category is defined when the isolate is non-susceptible to at least one agent in the recommended list for susceptibility testing of the corresponding category.

Extensively drug-resistant (XDR): The isolate is non-susceptible to all but two or fewer antimicrobial categories (mainly refer to polymyxin and tigecycline). The determination of resistance to one antimicrobial category is the same as for MDR.

Pandrug-resistant (PDR): The isolate is non-susceptible to all agents in all the antimicrobial categories in current clinical use.

The concepts of PDR and XDR are dynamic and changing due to the available antimicrobial categories vary with time and country. For example, after tigecycline was launched for clinical use, the previous PDR strains of A. baumannii could become XDR if susceptible to tigecycline.

Determination of antimicrobial-resistant phenotypes

Disk diffusion, agar dilution, broth microdilution susceptibility testing methods and other commercial testing systems are used in clinical microbiology laboratories to determine the antimicrobial-resistant phenotypes of clinical isolates so as to identify it as MDR, XDR or PDR strain. The minimum inhibitory concentration (MIC) values of antimicrobial agents or the diameter of inhibition zone in disk diffusion testing should be determined for XDR strains if possible to provide the basis for selection of antimicrobial agents and the dosage in combination antimicrobial therapy.

Lists of antimicrobial categories proposed for antimicrobial susceptibility testing of various bacterial types and the corresponding breakpoints for interpretation of susceptibility testing results usually follow the guidelines of the Clinical Laboratory Standards Institute (CLSI) [3], the European Committee on Antimicrobial Susceptibility Testing (EUCAST) [4] and the United States Food and Drug Administration (FDA). Cefoperazone-sulbactam is one of the most commonly

1 used antimicrobials for the treatment of Acinetobacter spp. infections and routinely

2 tested in China. The breakpoints of cefoperazone-sulbactam usually follow the

3 recommendation of Jones RN [5]: S, <16/8 mg/L, I, 32/16 mg/L and R, >64/32

4 mg/L.

5 The recommended antimicrobial categories and agents for testing various

6 common XDR gram-negative bacteria are presented in Table 1 [3-4].

Table 1. Antimicrobial categories and agents for testing XDR gram-negative bacteria

Antimicrobial category Antimicrobial agent Enterobact eriaceae P. aeruginosa A. baumannii S. maltophilia

Penicillins Ampicillin +a b - -

Amoxicillin-clavulanate + - - -

ß-lactam/beta-lac Ampicillin-sulbactam + - + -

tamase inhibitor Cefoperazone-sulbactam + + + +

combinations Ticarcillin-clavulanate + + + +

Piperacillin-tazobactam + + + -

Third and fourth generation cephalosporins Cefotaxime or ceftriaxone + - + -

Ceftazidime + + + +

Cefepime + + + -

Monobactams Aztreonam + + - -

Cephamycins Cefoxitin + - - -

Cefmetazole + - - -

Ertapenem + - - -

Carbapenems Imipenem + + + -

Meropenem + + + -

Aminoglycosides Gentamicin + + + -

Amikacin + + + -

Fluoroquinolones Ciprofloxacin + + + -

Levofloxacin + + + +

Sulfonamides Trimethoprim-sulphamet hoxazole + - + +

Chloramphenicol Chloramphenicol + - - +

Polymyxins Polymyxin E + + + -

Polymyxin B + + + -

Tetracyclines Doxycycline + - + -

Minocycline + - + +

Glycylcyclines Tigecycline + - + +

Others Fosfomycin + + - -

a +, antimicrobial suggested for susceptibility testing; b-, antimicrobial not suggested for susceptibility testing.

Some of the special mechanisms underlying bacterial resistance are predictive of the possibility of XDR. For example, production of carbapenemase is the main mechanism of carbapenem resistance in Enterobacteriaceae. At present, carbapenemase production is primarily detected by phenotype testing and molecular biological methods. Phenotype testing methods include modified Hodge test, inhibitor-based method, and double-disk synergy test. Phenotype testing methods are simple to operate, practical and cost-effective, and convenient for routine testing, but the results cannot be available quickly due to longer time is required for bacterial growth. Additionally, such methods cannot provide the specific type of carbapenemase and related information. Polymerase chain reaction (PCR) based sequence analysis of carbapenemase gene is now the recognized "golden standard" test of carbapenemase. In addition, the commercial microarray chips or matrix assisted laser desorption ionisation - time of flight (MALDI-TOF) mass spectrometry can also be used to detect carbapenemases.

Mechanisms of antibiotic resistance in XDR-GNB

The XDR phenotype of Enterobacteriaceae is primarily due to production of carbapenemase[6,7,8]. Such XDR strains may have other mechanisms of resistance to antibiotics such as production of extended spectrum beta-lactamases (ESBLs) [7], AmpC beta-lactamase, or expressing efflux pump[8], or porin mutation[9]. In China, the common types of carbapenemase produced by Enterobacteriaceae strains are class A carbapenemase KPC (KPC-2), and metalloenzyme IMP, VIM and NDM-1 enzymes are reported sporadically.

The mechanisms of the antibiotic resistance in A. baumannii are also very complex, usually involving multiple mechanisms simultaneously, including production of multiple beta-lactamases, reduced membrane permeability and increased expression of efflux pump[10]. Its XDR phenotype is primarily attributed to expressing various carbapenemases. Studies on the clinical strains isolated in our country have found that the carbapenemases produced by A. baumannii mainly

includes OXA type enzymes (predominately OXA-23-like), metalloenzymes (IMP, VIM and NDM) and Ambler class A beta-lactamases (KPC and GES)[11], as well as increased expression of efflux pump (AdeABC).

The extensive drug resistance of P. aeruginosa usually results from the joint effects of multiple mechanisms of resistance[12,13], including production of multiple beta-lactamases (especially carbapenemases), high-level expression of efflux pumps, target modification and alteration of outer membrane proteins. The formation of biofilm also has an important effect on the in vivo susceptibility to antimicrobial agents. In China, resistance of P aeruginosa strains to carbapenems is primarily due to the loss of porin (OprD2), and high expression of efflux pump (Mex-Opr), as well as production of metalloenzymes (IMP, VIM, NDM, etc.).

S. maltophilia strains show intrinsic resistance to multiple antimicrobial categories including carbapenems. These strains also have multiple other mechanisms of acquired resistance mediated by chromosomes, plasmids, transposons, or integrons, including production of multiple beta-lactamases, multidrug efflux pumps, class I integron and ISCR elements associated with resistance to trimethoprim-sulfamethoxazole, phosphoglucomutase (SpgM) associated with resistance to multiple antimicrobial agents, reduction in outer membrane permeability, SmQnr determinants associated with resistance to quinolones, and mutations of bacterial gyrase genes[14,15].

Epidemiology of XDR-GNB

The data of CHINET, a bacterial resistance surveillance network in China, showed that XDR-GNB strains in China are mainly found in A. baumannii, Klebsiella pneumoniae and P aeruginosa. During 2008 to 2014, the prevalence of XDR strains in A. baumannii and K. pneumoniae increase from 10.9% to 19.7% and from 0.3% to 3.2%, respectively, whereas XDR P. aeruginosa decrease slightly from 2.1% to 1.6% [16]. During 2005-2014, the imipenem-resistance rates in K. pneumoniae increase from 2.4% to 10.5%, while in E. coli, the resistance rates are stable (around 1%).

1 The imipenem-resistance rates in A. baumannii increase from 31% to 62.4%,

2 whereas, imipenem-resistance rate in P. aeruginosa decrease from 31% to 26.6%

3 during this period of time [17]. The prevalence and phenotypic characteristics of

4 carbapenem-resistant E. coli and K. pneumoniae, and XDR P. aeruginosa and A.

5 baumannii, isolated from blood cultures in China see another paper published in this

6 issue [18].

7 Risk factors and clinical characteristics of XDR-GNB infections

8 The single most important risk factor for extensive resistance in gram negative

9 bacilli is long-term exposure to antimicrobial agents, especially use of

10 extended-spectrum antimicrobial agents[19]. Cephalosporins and other antimicrobial

11 agents are supplemented to animal feed stuff in some regions, which increases the

12 resistance of the colonizing bacteria in animals, especially Enterobacteriaceae,

13 which may facilitate the spread of resistant bacteria[20]. The other risk factors

14 leading to emergence of resistance are explained below, with specific

15 microorganisms.

16 XDR Enterobacteriaceae infection

17 The most common species of XDR Enterobacteriaceae is K. pneumoniae, followed

18 by E. coli. These strains usually cause infections of lungs, urinary tract, bloodstream,

19 as well as skin and soft tissue. The risk factors for XDR Enterobacteriaceae

20 infections include critical underlying diseases, prior use of antimicrobial agents, stay

21 in ICU, solid organ or blood transplantation, surgical operation and catheterization,

22 and indwelling drainage tube. XDR Enterobacteriaceae strains may colonize the

23 intestinal tract for a long time (up to several months), and result in spread of the

24 resistant strain in the hospital. Some of the colonizing bacteria may finally evolve to

25 clinical infection[21,22].

26 XDR Acinetobacter infection

27 XDR Acinetobacter strains are mostly found in hospital-acquired pneumonia (HAP),

28 mainly in ICU patients under mechanical ventilation. Recently, an epidemiological

29 survey on HAP conducted in China showed that Acinetobacter spp. was the most

common pathogen of HAP and 76.8% of the Acinetobacter strains causing HAP were resistant to carbapenems[23]. Acinetobacter strains isolated from sputum should be differentiated to infection or colonization. A. baumannii-related bloodstream infection is usually secondary to pulmonary or abdominal infection, or device-related infections. Efforts should be made to identify the primary source of infection and possible secondary sites of infection. Skin and soft tissue infections caused by A. baumannii mainly occur in the patients with diabetes mellitus or other underlying diseases, history of surgery or trauma, especially those with a history of trauma and water contact. A study suggested that XDRA. baumannii-related infection of central nervous system may be acquired via the respiratory tract, especially with ventilators, in addition to invasive procedures such as surgical operation[24]. Risk factors for XDR A. baumannii infection include general anesthesia, stay in ICU, prior hospitalization, and prior use of multiple classes of antimicrobial agents[24]. XDR P. aeruginosa infection

Infections caused by P. aeruginosa are mostly pulmonary, bloodstream, skin and soft tissue, abdominal or urinary tract infections. The predisposing factors for XDR P. aeruginosa infections include chronic obstructive pulmonary disease (COPD), long hospital stay before infection, mechanical ventilation, critical disease (APACHE II score >16), and inappropriate antimicrobial monotherapy[25,26]. A study indicated that prior use of fluoroquinolones was one of the independent risk factors for emergence of XDR P. aeruginosa infection[26]. XDR S. maltophilia infection

In 2004, 17 PDR strains of S. maltophilia were isolated from a hospital in Taiwan. The MIC ranges of tigecycline, trimethoprim-sulfamethoxazole and levofloxacin against these strains were 4-32, 8-32 and 16-64 mg/L, respectively. Seven strains were isolated from patients with infections (6 from pneumonia,1 from bile tract infection), and the remaining 10 strains were from colonized patients. For 12 of the 17 PDR S. maltophilia strains, non-PDR S. maltophilia strains had been isolated before the emergence of pandrug resistance, which suggests that the antimicrobial

1 resistance was selected by antimicrobial therapy. Mortality of the patients with

2 PDR-strain infection was higher than that of the patients with PDR-strain

3 colonization (86% vs. 10%)[27]. Risk factors for S. maltophilia infection include

4 long time stay in ICU, mechanical ventilation >7 days, tracheotomy, and use of

5 broad spectrum antimicrobial agents (e.g., carbapenems, broad spectrum

6 cephalosporins and fluoroquinolones). S. maltophilia strains are intrinsically

7 resistant to carbapenems. Furthermore, carbapenem therapy may promote the growth

8 of S. maltophilia strains [28]. Prior use of fluoroquinolones, piperacillin-tazobactam,

9 carbapenems will increase resistance of such bacteria to fluoroquinolones and

10 trimethoprim-sulfamethoxazole. Severe underlying disease is also considered as one

11 of the risk factors for the emergence of XDRS. maltophilia[29].

13 Antimicrobial therapy for XDR-GNB infection

14 Principals for antimicrobial therapy of XDR-GNB infection

15 1. When a strain of XDR-GNB is isolated from clinical specimens, especially XDR

16 A. baumannii or S. maltophilia, a distinction should be made between infection or

17 colonization.

18 2. Appropriate effective antimicrobial agents should be selected according to the

19 results of susceptibility testing. When the strain is non-susceptible to all the

20 antimicrobial agents tested, the agents showing intermediate or inhibition zone or

21 MIC value closer to the breakpoints of susceptibility (or intermediate) for that strain

22 may be selected for combination therapy at a higher dosage.

23 3. Combination therapy is usually used to manage XDR-GNB infections.

24 4. The dosing regimen should be designed according to pharmacokinetic and

25 pharmacodynamic (PK/PD) profiles, e.g., higher dose and/or longer duration of

26 intravenous infusion for beta-lactams such as carbapenems, high Cmax and/or

27 AUC/MIC or Cmax/MIC values for quinolones and aminoglycosides.

28 5. The dose of antimicrobial therapy should be adjusted appropriately in patients

29 with hepatic or renal impairment and elderly patients.

1 6. Every effort should be made to eliminate the risk factors of infection and control

2 of infection source, and actively address the primary disease.

3 Selection of antimicrobial agents for XDR-GNB infections

4 A limited number of antimicrobial agents are now available for XDR-GNB

5 infections. Considering the in vitro susceptibility, tigecycline and polymyxins are

6 the most active for XDR-GNB, however, limited clinical studies indicate that high

7 rate of clinical failure is observed with tigecycline or polymyxin monotherapy.

8 Combined antimicrobial therapy (two- or three-drug combinations) is usually used to

9 manage XDR-GNB infections largely based on case reports, case series or small

10 cohort studies, solid evidence are needed to justify the advantage of combination

11 therapy [30](Table 2).

Table 2. Combination antimicrobial therapies described for XDR-GNB infections

Two-drug combination Three-drug combination

XDR Enterobacteriaceae [21, 35, 42, 61, 62,] Tigecycline-based combinations: Tigecycline + aminoglycosides'1 Tigecycline + carbapenemsb Tigecycline + fosfomycin Tigecycline + polymyxin Polymyxin-based combinations: Polymyxin + carbapenems Polymyxin + tigecycline Polymyxin + fosfomycin Other combinations: Fosfomycin + aminoglycosidesa (ceftazidime or cefepime) + amoxicillin-clavulanic acid Aztreonam + aminoglycosides"1 Tigecycline + polymyxin + carbapenemsb

XDR A. baumannii [, 44, 51, 56, 57, 66] Combinations based on sulbactam or its fixed-dose combination: (cefoperazone-sulbactam or ampicillin-sulbactam) + tigecycline (cefoperazone-sulbactam or ampicillin-sulbactam) + doxycycline Sulbactam + carbapenemsb Tigecycline-based combinations: Tigecycline + (cefoperazone-sulbactam or ampicillin-sulbactam) Tigecycline + carbapenemsb Tigecycline + polymyxin Polymyxin-based combinations: Polymyxin + carbapenemsb Polymyxin + tigecycline Cefoperazone-sulbactam + tigecycline + carbapenemsb Cefoperazone-sulbactam + doxycycline + carbapenemsb Imipenem + rifampicin + (polymyxin or tobramycin)

XDR P. aeruginosac [31, 32, 42, 45] Polymyxin-based combinations: Polymyxin + anti-pseudomonal beta-lactamsd Polymyxin + ciprofloxacin Polymyxin + fosfomycin Polymyxin + rifampicin Anti-pseudomonal beta-lactams-based combinations: Anti-pseudomonal beta-lactamsd + aminoglycosides3 Anti-pseudomonal beta-lactamsd + ciprofloxacin Anti-pseudomonal beta-lactamsd + fosfomycin Ciprofloxacin-based combinations: Ciprofloxacin + anti-pseudomonal beta-lactamsd Ciprofloxacin + aminoglycosides2 Combination of two beta-lactams: (ceftazidime or aztreonam) + piperacillin-tazobactam Ceftazidime + cefoperazone-sulbactam Aztreonam + ceftazidime Polymyxin + anti-pseudomonal beta-lactamsd + ciprofloxacin Polymyxin + anti-pseudomonal beta-lactamsd + fosfomycin Polymyxin IV infusion + carbapenems + polymyxin aerosol inhalation Aztreonam + ceftazidime + amikacin

XDR S. maltophilia" [47, 48, 54] Trimethoprim-sulphamethoxazole-based combinations: Trimethoprim-sulphamethoxazole + (ticarcillin-clavulanic acid or cefoperazone-sulbactam) Trimethoprim-sulphamethoxazole + fluoroquinolonesf Trimethoprim-sulphamethoxazole + minocycline Trimethoprim-sulphamethoxazole + ceftazidime Trimethoprim-sulphamethoxazole + polymyxin Quinolones-based combinations: Fluoroquinolonesf + trimethoprim-sulphamethoxazole Fluoroquinolonesf + (ticarcillin-clavulanic acid or


Fluoroquinolonesf + ceftazidime

Polymyxin-based combinations:

Polymyxin + ticarcillin-clavulanic acid

Polymyxin + trimethoprim-sulphamethoxazole

aAminoglycosides include amikacin, isepamicin, etc. bCarbapenems include meropenem, imipenem, etc (not ertapenem).

cMost data are from the in vitro studies or case reports of MDR or XDR P. aeruginosa. The data from clinical studies are limited for combination therapies. dAnti-pseudomonal beta-lactams refer to the beta-lactams active against P. aeruginosa, such as carbapenems (meropenem, imipenem), ceftazidime, aztreonam, piperacillin-tazobactam, and cefoperazone-sulbactam.

eMost data are from the in vitro studies or case reports of MDR S. maltophilia. The data from clinical studies are limited for combination therapies. fluoroquinolones include ciprofloxacin, levofloxacin and moxifloxacin.

Common antimicrobial agents for the treatment of XDR-GNB infections Aminoglycosides: Studies indicate that aminoglycosides alone have achieved favorable efficacy in treating carbapenem-resistant K. pneumoniae infections, 80% of which are bloodstream infections [21]. The antibiotics of this category are usually combined with other antimicrobial agents to treat infections caused by XDR Enterobacteriaceae, P. aeruginosa or A. baumannii[31, 32, 33]. A dose of 15 mg/kg per day is recommended for amikacin or isepamicin in many countries, but in China the dose is lower because therapeutic drug monitoring (TDM) for aminoglycosides has not yet been implemented. For patients with severe infection and normal renal function, 0.8g/day is recommended, once daily. Considering the increasing use of aminoglycosides in the treatment of MDR, XDR bacterial infections and relatively high dose is recommended, the establishment of aminoglycoside TDM methods and implementation in clinical are needed in countries where aminoglycoside TDM have not yet been used. Carbapenems:

Time-kill assays revealed antimicrobial synergism for imipenem in combination with colistin (75%), tigecycline (50%), ampicillin/sulbactam (42%), and amikacin (42%) for carbapenem-resistant A. baumannii [34]. Several clinical studies have suggested that carbapenems in combination with other antimicrobial agents such as polymyxins are associated with better efficacy for CRE infections than carbapenem monotherapy or other antimicrobial combinations [21,35, 36, 37]. Studies indicate that carbapenems can be used in a high-dose (e.g., meropenem 2g q8h), prolonged-infusion (2-3 h) regimen to treat infections caused by carbapenem-resistant K. pneumoniae strains with MICs of <8 mg/L[21,36, 38]. If possible, exact carbapenem MIC value or inhibition zone are welcome to be reported for XDR or PDR gram-negative bacilli for determining whether carbapenems can be used in combination therapy. Meropenem and imipenem are the commonly used carbapenems, but not ertapenem because it is not active against A. baumannii and P. aeruginosa, and the low recommended dose of 1g once a day. They are usually used in combination with polymyxins, tigecycline, fosfomycin, or rifampicin[34,39].

1 Fosfomycin: The majority (95%) of the carbapenemase-producing

2 Enterobacteriaceae strains are susceptible to fosfomycin. Most (83%) of the

3 metalloenzyme-producing strains are also susceptible to fosfomycin [40]. In China,

4 about 40% of the CRE isolates were sensitive to fosfomycin [41]. Intravenous

5 fosfomycin can be used in combination with polymyxin, tigecycline, carbapenems,

6 and aminoglycosides to treat carbapenemase-producing XDR or PDR K.

7 pneumoniae and P. aeruginosa infections, with a clinical success rate of 54.2% and

8 bacterial eradication rate of 56.3% in 48 ICU patients. The main adverse event was

9 reversible hypokalaemia [42]. Fosfomycin-resistance can develop during therapy,

10 supporting the idea of using this agent in combination [42, 43]. The dosing regimen

11 of fosfomycin is 8g q8h or 6g q6h, intravenous infusion. Clinical studies are

12 currently limited in this respect. Both oral and intravenous fosfomycin are available

13 in China and intravenous preparation is commonly used for the treatment of MRSA

14 and Enterococcus infections in combination with vancomycin, however it is now

15 having an increasing use of fosfomycin in XDR gram-negative bacterial infections.

16 Polymyxins: This category of antibiotic includes polymyxin B and polymyxin E

17 (colistin). Polymyxins have good in vitro activity against various highly resistant

18 gram-negative clinical isolates. Synergistic antimicrobial effect is observed when it

19 is combined with carbapenems, quinolones, piperacillin-tazobactam, tigecycline, or

20 doxycycline [31,32,44,45,46]. About 68%-79% of the S. maltophilia isolates were

21 susceptible to polymyxins [46,47]. However, only 37.5% of the multi-drug resistant

22 strains were susceptible [48]. Polymyxin is mainly used to treat various XDR

23 gram-negative bacterial infections. There is apparent heterogeneous resistance to

24 polymyxins in these gram-negative strains [49]. The mutation prevention

25 concentration (MPC) of polymyxins is high for A. baumannii[50]. Polymyxins are

26 usually used in combination with carbapenems, tigecycline, or fosfomycin[49]. For

27 the elderly and the patients with reduced renal function, special attention should be

28 taken to monitor renal function.

29 The recommended dosages of polymyxin E (colistimethate sodium, CMS) are

30 2.5-5.0 mg/kg per day of colistin-base activity (CBA) given by intravenous infusion

in 2-4 divided doses[51]. One million IU CMS is approximately equivalent to 30 mg CBA and to 80 mg CMS. Because the two possible ways of expressing a colistin dose in mg (ie, as mg of CBA or as mg of CMS) can lead to medication errors that threaten patient safety, the Prato polymyxin consensus suggests that the expression of dose as mg of CMS in the dose section of product information should cease[52]. The daily dose of CMS should not exceed 9 million units (Europe) or 300mg (5mg/kg) of CBA (USA). Colistimethate 30-60 mg of CBA can be used by aerosol inhalation two times a day to treat the pulmonary infections caused by XDR bacteria. At least one of polymyxins (colistin or polymyxin B) should be maintained a supply as the last-line antibiotics for the treatment of XDR bacterial infections in countries where the products are not currently registered such as in China. Quinolones: Quinolone antibiotics have good antimicrobial activity against P. aeruginosa and S. maltophilia. Newer quinolone antibacterials such as moxifloxacin are more active against S. maltophilia than ciprofloxacin and levofloxacin [47, 54]. In 2014, 12.9% and 8.25% of the P. aeruginosa and S. maltophilia isolates were resistant to ciprofloxacin, respectively [16]. Quinolones can be used in combination with beta-lactams, aminoglycosides, or polymyxins for treatment of the infections caused by XDR P. aeruginosa[53] or S. maltophilia [47,54]. The daily dose of ciprofloxacin is generally 0.6-1.2g for adults in 2-3 divided oral doses. The recommended dose of levofloxacin for adults is usually 0.5g or 0.75g, once daily, oral or intravenous infusion. The recommended dose of moxifloxacin for adults is 400 mg intravenous infusion, once daily.

Sulbactam and sulbactam-containing combinations: Beta-lactamase inhibitor sulbactam is active against Acinetobacter spp., thus, sulbactam-based fixed dose combinations have shown good antimicrobial activity for Acinetobacter strains. Ampicillin-sulbactam is usually used in many countries, but cefoperazone-sulbactam is used more frequently to treat MDR A. baumannii infections in China, the latter shows lower resistant rate than the former (12% vs 34%)[55]. In general, the recommended upper limit of sulbactam dose is 4.0g/day, but can be increased to 6.0g/day or even 8.0g/day for MDR and XDR A. baumannii infections [51]. The

1 dose should be adjusted for the patients with reduced renal function. It can be

2 combined with other antimicrobial agents such as carbapenems [56] to treat the

3 infections caused by XDR A. baumannii.

4 Cefoperazone-sulbactam: The usual dosing regimen is 3.0 g (cefoperazone

5 2.0gplus sulbactam 1.0g) intravenous infusion, q8h or q6h. Cefoperazone-sulbactam

6 is usually used in combination with tigecycline, minocycline [57,58], carbapenems

7 or aminoglycosides to treat XDR A. baumannii infections in China.

8 Tetracyclines: Minocycline is one of the few recommended antimicrobial agents for

9 treating S. maltophilia infections. The US FDA has approved minocycline injection

10 for treatment of A. baumannii infections. The dosing regimen of minocycline is

11 100mg intravenous infusion, q12h. Clinical data are lacking in this respect. Currently,

12 minocycline injection is not available in China. Minocycline tablets or doxycycline

13 injection (equivalent dose of minocycline) can be used to combine with other

14 antimicrobial agents for treatment of the infections caused by XDR A. baumannii[44,

15 57, 58]or S. maltophilia [47, 48, 54].

16 Tigecycline: As the first antibiotic of glycylcyclines, it remains active for CRE and

17 XDR A. baumannii. Tigecycline susceptibility rates were 98% and 90% for

18 carbapenem-resistant Klebsiella spp and Acinetobacter spp., respectively. And 92%

19 of the S. maltophilia isolates were susceptible to tigecycline [59]. Recent reports on

20 the susceptibility of A. baumannii to tigecycline vary greatly [60]. Therefore, it

21 should be used according to the results of susceptibility testing. Tigecycline is

22 inactive against P. aeruginosa. Tigecycline is distributed extensively in body tissues

23 and associated with low blood concentration[21]. It is therefore inappropriate to use

24 tigecycline alone for managing bloodstream infection. Since its launch in China in

25 2012, tigecycline has been used primarily to treat the respiratory tract, skin and soft

26 tissue, and abdominal infections caused by XDR A. baumannii, or

27 Enterobacteriaceae. It is usually used in combination with cefoperazone-sulbactam,

28 carbapenems, or aminoglycosides. Tigecycline is also used in combination with

29 polymyxin[61]. Clinical data are still lacking for tigecycline in the treatment of S.

30 maltophilia infections[47, 54]. The usual dosing regimen of tigecycline is 100mg,

followed by 50mg q12h by intravenous infusion. Preliminary studies indicate that increasing tigecycline dose may improve the efficacy in treating severe bacterial infections, especially complicated intra-abdominal infection[62], HAP[63] and VAP[64]. But this finding requires confirmation. The main adverse reactions of tigecycline are gastrointestinal reactions.

Trimethoprim-sulphamethoxazole: Trimethoprim-sulphamethoxazole (TMP-SMX) has good antimicrobial activity against S. maltophilia with the resistance rates lower than 10%[16,46, 47]. About 87% of the MDR S. maltophilia strains are still susceptible to this drug. TMP-SMX combined with minocycline or ceftazidime has shown good in vitro antimicrobial activity (partially synergistic) against MDR S. maltophilia strains[48]. TMP-SMX is the first choice for treating S. maltophilia infections [47, 54]. TMP-SMX is also active against a few XDR A. baumannii and CRE strains.

Others: Rifampicin has shown certain antimicrobial activity against A. baumannii. It can be used in combination with carbapenems for treatment of the infections caused by XDR A. baumannii[65]. However, a recent randomized clinical trial indicated that 30-day mortality is not reduced by addition of rifampicin to colistin in serious XDR A. baumannii infections [66]. A few XDR-GNB strains including NDM-1-producing Enterobacteriaceae strains are susceptible to aztreonam[67], which might be used in the combination therapy for such strains.

New antimicrobial agents: Two P-lactamase inhibitor combinations, ceftazidime-avibactam and ceftolozane-tazobactam, had been approved by FDA for the treatment of complicated intraabdomial infections and complicated urinary tract infections in the US in Feb. 2015 and Dec. 2014, respectively. Avibactam is a synthetic non-P-lactam, P-lactamase inhibitor that inhibits the activities of Ambler class A (including ESBL), class C (especially AmpC), class D (such as OXA-48) P-lactamases as well as KPC carbapenemases. The addition of avibactam greatly improves the activity of ceftazidime versus most species of Enterobacteriaceae and P. aeruginosa as well. Limited data suggest that the addition of avibactam does not improve the activity of ceftazidime versus Acinetobacter species [68]. A randomized

1 active-controlled, double-blind, phase II trial proved that ceftazidime-avibactam plus

2 metronidazole was as effective and well tolerated in patients with complicated

3 intra-abdominal infections as meropenem [69].

4 Ceftolozane is a novel cephalosporin, with the similar structure of ceftazidime,

5 distinguished from other cephalosporins by improved activity against P. aeruginosa,

6 including various drug-resistant phenotypes such as carbapenem-,

7 piperacillin-tazobactam-, and ceftazidime-resistant isolates, as well as strains that are

8 multidrug-resistant isolates [70]. Phase II and phase III clinical trials of ceftolozane-

9 tazobactam have been completed. In a phase II Trial, ceftolozane-tazobactam plus

10 metronidazole was resulted in the similar clinical and microbiological success rates

11 as meropenem in the treatment of complicated intra-abdominal infections[71].

13 Control of XDR-GNB hospital infections

14 The increase of XDR-GNB infections results from the combined effect of

15 antibiotic selection pressure and spread of resistant clones. Infection control

16 measures must be appropriately integrated with antimicrobial stewardship to

17 effectively curb, prevent the spread of XDR-GNB and reduce infections caused by

18 resistant bacteria[21,72,73].

19 Hand hygiene

20 Hand hygiene is the most fundamental, effective and cost-effective strategy for

21 reducing cross infections, and avoiding the spread of resistant bacteria through the

22 hands of healthcare staff [73].

23 Contact precaution

24 The microbiology laboratory should notify clinicians in a timely and reliable way

25 when a XDR-GNB strain is identified. Clinicians may implement contact precaution

26 measures such as single room, partial separation of at least 1m between beds, for

27 patients infected with XDR-GNB and reduce the practice of sharing devices.

28 Sphygmomanometer, stethoscope, thermometer, infusion pump and other relevant

29 devices should be provided specifically for patients with XDR-GNB infection[72].

1 When a patient infected with XDR-GNB is transferred to another department or

2 hospital, or leaves the ward for examination, handover procedures and warning tips

3 are required[74].

4 Active screening

5 In ICU and other wards with highly prevalent XDR-GNB strains, patients should be

6 screened with samples of perianal and rectal swabs for CRE, wound secretion and

7 nasopharyngeal region for XDR non-fermenters to promptly identify resistant

8 bacteria by way of conventional or rapid diagnostic methods[73]. The patients

9 should be isolated appropriately. Molecular epidemiological measures may be

10 adopted to track the route of transmission if necessary, by which to provide rationale

11 for blocking the transmission of the resistant bacteria [75].

12 Environmental surface disinfection

13 The surface of the objects frequently contacted by healthcare staff and patients in the

14 hospital environment should be disinfected regularly and completely [73,76].

15 Fluorescence labeling or ATP Hygiene Monitoring System can be used to monitor

16 the effectiveness of disinfection, and so ensure that the transmission of resistant

17 strain is effectively blocked.

18 Decolonization

19 The patients colonized with XDR-GNB may have a whole body sponge bath with

20 chlorhexidine, which is helpful for reducing catheter-related bloodstream

21 infections[77].

22 Management of antimicrobial agent use in clinical setting

23 We recommend to strictly adhere to the indications for clinical use of antimicrobial

24 agents; limit antimicrobial use through specific agents restriction ( carbarpenems,

25 tigecycline, polymyxin, et al); formulate evidence-based treatment guidelines or

26 dosing regimens according to the local profile of resistant bacteria to guide and

27 standardize the use of antimicrobial agents.

28 Rational and appropriate formulary should be developed to ensure the supply of

29 the antimicrobial agents which are necessary for clinical treatment, including newer

30 antimicrobial agents. The available evidence for the effect of antimicrobial rotation

1 or cycling on curbing the increasing antimicrobial resistance is contradictory[78].

2 Furthermore, in the hospitals or specific wards with highly prevalent XDR-GNB,

3 some GNB species are highly resistant to nearly all the antimicrobial agents

4 available. Therefore, caution must be exercised when considering exclusion of a

5 specific category of antimicrobial agents in a medical institution or specific wards


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