The Official Journal of the Turkish Society Of Clinical Microbiology and Infectious Diseases (KLİMİK)

Review Article

Infections Caused by Extended-Spectrum β-lactamase-Producing Enterobacteriaceae: Clinical and Molecular Epidemiology and Treatment Strategies

Abdullah Tarık Aslan
  • Department of Internal Medicine, Burdur Gölhisar Devlet Hastanesi, Burdur, Turkey
Murat Akova
  • Department of Infectious Diseases and Clinical Microbiology, Hacettepe University School of Medicine, Ankara, Turkey


Extended-spectrum beta-lactamases (ESBLs) are one of the most common defence mechanisms of gram-negative bacteria against beta-lactam antibiotics. Treatment options for infections with ESBL-producing Enterobacteriaceae are limited. Most of ESBL enzymes can be inhibited by clavulanate and tazobactam, in-vitro. In many clinical studies, beta-lactam beta-lactamase inhibitor (BLBLI) combinations have been compared with type-2 carbapenems (e.g. imipenem or meropenem), as gold standard antibiotics for the treatment of infections caused by ESBL-producing organisms. Nevertheless, the results of these trials have been somewhat conflicting.

Cefepime was another alternative for the treatment of these infections owing to its relative resistance to hydrolysis by ESBLs as compared with other cephalosporins. However, some ESBLs have high hydrolysing capabilities against cefepime (e.g. CTX-M-type) and BLBLI combinations (e.g. SHV-type). Additionally, microorganisms containing ESBLs can harbour other types of beta-lactamases (narrow spectrum oxacillinases [e.g. OXA-1] and AmpC-type beta-lactamases) and non-beta-lactamase resistance mechanisms (e.g. porin loss mutations, efflux pumps). Overall, bacteria can reduce their susceptibility or become fully resistant against cephalosporins, BLBLI combinations and even carbapenems when the simultaneous expression of these mechanisms exists. These bacteria can also have resistance genes on the same plasmid encoding ESBLs. They can become insusceptible to a variety of antibiotics, including fluoroquinolones, trimethoprim-sulfamethoxazole and aminoglycosides, thus further limiting therapeutic alternatives. Rapid dissemination of ESBL genes in the community and increasing prevalence of community-onset infections caused by ESBL-producing organisms have recently become a critical public health threat. A variety of infections, including urinary tract infections and bloodstream infections, can be seen in the community setting with these bacteria. International travel, urban wastewater, food animals, companion animals and contaminated drinking waters have been identified as possible sources for transmission of ESBL-producing organisms to humans in the community. Overall, these conditions result in a significant challenge to administer appropriate empirical antimicrobial therapy for patients in the community and hospital settings.


    Extended-spectrum beta-lactamases (ESBL) are widespread in enterobacteriaceae globally and contribute significantly to beta-lactam resistance in these bacteria.

    Bacteria harbouring ESBLs have usually multi-drug resistant phenotyes expressing resistance concomittantly to beta-lactams, aminoglycosides, quinolones and trimethoprim-sulfamethoxazole.

    ESBLs producers cause also a significant problem in the community setting, particularly in urinary tract infections.

    Therapeutic alternatives for these infections are limited and usually rely on carbapenems.

    Point-of-care tests are urgently needed for rapid diagnosis and for early targeted therapy.

Origins, characteristics and classification of extended-spectrum beta-lactamases (ESBLs)

Currently, beta-lactamase family includes more than 2800 unique proteins (1). Although varied types of beta-lactamases have been specified to date, they have common topographic structures consisting of alpha-helices and beta-plated sheets (2). They most probably originated from environmental sources and produced against naturally occurring beta-lactams. Although many classification systems have been proposed for beta-lactamases, the most commonly used ones are Ambler scheme and Bush-Medeiros-Jacoby system according to their amino acid homology and functional properties (substrate and inhibitor profiles), respectively (3,4). Both classification systems are illustrated and compared in Table 1. ESBLs include three major families, TEM, SHV, and CTX-M, with a large variety of other groups of enzymes. The first plasmid-mediated beta-lactamase was isolated in the early 1960s and named as TEM-1 with hydrolytic activity mainly against penicillins and first-generation cephalosporins. In the early 1980s, broad spectrum-cephalosporins (BSCs) were introduced into clinical practice. They were primarily used to treat infections with TEM-1- and SHV-1 penicillinase-producing organisms. The first ESBL-producing K. pneumoniae capable of hydrolysing BSCs was discovered in Germany in 1983. These enzymes mainly carried on plasmids and conferred resistance to penicillins, first, second and third-generation cephalosporins (3rdGCs) and aztreonam. However, carbapenems and cephamycins (e.g. cefoxitin) were stable (5,6). Over the years, ESBL enzymes have evolved via point mutations around the active site of TEM-1 or SHV-1 and gained the ability to hydrolyse different types of beta-lactam antibiotics (7). These mutations broadened the spectrum of activity of new ESBL derivatives by increasing affinity (lowering Km values) of these enzymes against a wide range of beta-lactam antibiotics (8). On the other hand, CTX-M (active on CefoTaXime, first isolated in Munich) type of ESBLs emerged through the mobilisation of chromosomal beta-lactamase (bla) genes from the Kluyvera spp. (9). The first CTX-M was reported from Japan in 1986 and initially named as TOHO-1 and later changed to CTX-M (10). These beta-lactamases hydrolyse cefotaxime and ceftriaxone better than they do ceftazidime. Presently, CTX-M group was classified into five different subgroups according to their amino acid identities and included the CTX-M-1, 2, 8, 9, 25 groups.

<b>Table 1.</b> Classification of beta-lactamases (3, 4).

Table 1. Classification of beta-lactamases (3, 4).

ESBLs are usually inhibited by clavulanate and tazobactam. This property discriminates them from AmpC-type beta-lactamases (11). However, insufficient inhibition by tazobactam or clavulanate can be observed in some clinical ESBL-producing isolates. SHV-type ESBLs are generally more resistant to beta-lactamase inhibitors (BLIs) than CTX-M type (12). CTX-M type ESBLs are more efficiently inhibited by tazobactam compared with clavulanate.

Institutions setting standards for in vitro antibiotic susceptibility testing both from Europe and United States (i.e. EUCAST and CLSI) do not recommend routine detection of ESBLs in the microbiology laboratory, claiming ESBL expression is less important than the MIC values in determining the optimal therapy for ESBL-producing Enterobacteriaceae infections. Also, phenotypic detection methods for ESBLs are somewhat cumbersome for microbiology laboratories and require one additional day to obtain results. ESBL detection methods can give false results for pathogens expressing AmpC- or Metallo-beta-lactamases combined with ESBLs and Klebsiella oxytoca which shows ESBL phenotype by a chromosomal enzyme called K 1 that hydrolyses some cephalosporins but not others (13). However, in some cases, reporting the presence of ESBLs may be essential to avoid making significant errors in treatment. Pitout et al. (14) demonstrated that the Vitek-2 microdilution method might fail to detect piperacillin-tazobactam (PTZ) resistance, especially in CTX-M-15 and OXA-1 co-producing isolates. ESBL expression may also compromise clinical outcomes of some antibiotic therapies, although MIC values of these antibiotics are in susceptibility ranges. To that end, reduction of MIC values is not a panacea since phenotypic ESBL detection methods may be more sensitive and specific than CLSI and EUCAST breakpoints to identify the presence of ESBLs. From a clinical standpoint, performing ESBL detection tests routinely in countries having high ESBL prevalence may also be reconsidered for purposes of infection control and epidemiological investigations.

Antibiotic co-resistance mechanisms among ESBL-producing Enterobacteriaceae

The plasmids containing genes expressing ESBLs frequently carry genes conferring resistance to aminoglycosides (AGs), fluoroquinolones (FQs) and trimethoprim-sulfamethoxazole (TMP-SMX) (15, 16). Furthermore, hyperproduction of beta-lactamases, porin mutations, co-production of narrow-spectrum oxacillinases (e.g. OXA-1) and AmpC diminish susceptibility to several antibiotics involving BSCs, beta-lactam/beta-lactamase inhibitor (BLBLI) combinations, and even carbapenems (17). AmpC is usually encoded by chromosomal genes; however, plasmid-mediated AmpC acquisition is not uncommon (18). ESBLs expressed with AmpC may not be reliably detected by routine laboratory methods since >8 fold reduction in MIC values of third-generation cephalosporins cannot be detected with clavulanate when concomitant AmpC expression is present. AmpC-producing pathogens are resistant to BSCs, BLBLIs, and cephamycins, but spare cefepime. The activity of beta-lactam antibiotics can also be substantially impaired by overexpression of parent enzymes (TEM-1 or SHV-1) (19). Furthermore, the simultaneous production of multiple ESBL genes in a given isolate can reduce the effectiveness of BLBLIs (7).

OXA-1/30 (mainly OXA-1) and CTX-M genes can be carried on the same plasmid and may render pathogens resistant against amoxicillin-clavulanate (AMC) and piperacillin-tazobactam (PTZ) (20). OXA 1/30 is frequently associated with CTX-M-15 in both E. coli (particularly in ST131) and K. pneumoniae (21, 22). Additionally, OXA-1 may be carried with aac (6’)-Ib-cr gene which compromises the activities of amikacin and tobramycin. Rapid diagnostic methods revealing clinically significant resistance mechanisms in a short time can prove very useful in such settings.

Clinical and molecular epidemiology of ESBLs

According to the 2017 EARS-Net surveillance; resistance rates to the 3rdGCs were 14.9% and 31.2% in invasive isolates of E. coli and K. penumoniae, respectively, in the European Union (EU). More than 80% of isolates in both species were ESBL producers. The resistance rates were highest in Eastern and Southern European countries as compared with Northern and Western Europe (23). In the US, the incidence of infections with ESBL-producing organisms has increased from 1997 to 2011, slightly more frequent for infections with ESBL-producing Klebsiella spp. compared with ESBL-producing E. coli infections. The ESBL phenotype was identified in 7% of the 2,768 Klebsiella isolates tested in 1997–2000 at 30 US hospitals (24). This figure increased to 15% among isolates collected from 79 US hospitals between 2011 and 2013 (25). For E. coli, two surveillance programs in the US reported a proportion of ESBL phenotype 1% and 8% of isolates in 1997–2000, while in 2011–2013 this proportion raised to 12% (26). In Southeast and East Asia, the nosocomial detection rates of ESBL E. coli were 20–40%, and it has reached 60–70% in China (27). In a recent meta-analysis, the ESBL detection rates in long-term care facilities were reported to be 10–60% in European countries and ~50% in China (28). In another meta-analysis (including 66 studies) concerning with the ESBL faecal colonization prevalence in the community, the pooled prevalence rate was 14% (95% confidence interval, 9.0–20.0%) and the authors predicted that this figure was likely to increase by 5.38% annually (29). The colonization rates were ~4% in Europe, ~2% in North America and ~46% in West Pacific regions.

Molecular epidemiology of ESBLs has changed considerably in the last decade. Currently, blaCTX- M-15 genes are the most prevalent ESBL genes in most regions of the world (30). The blaCTX-M-14 genes are also frequently detected in some parts of Europe, such as Spain, and East and Southeast Asia. Nevertheless, in Southeast Asia, including India, blaCTX- M-15 is more frequent than blaCTX-M-14 (30, 31).

Most of the infections caused by community-onset ESBL-producing Enterobacteriaceae involve urinary tract infections (UTIs). Moreover, some life-threating infections, such as bloodstream infections (BSIs) and intra-abdominal infections (IAIs), have been encountered with increasing frequency (32-34). In the mid to late 1990s, some anecdotal studies reported that ESBL-producing Enterobacteriaceae had started to disseminate from inpatient to outpatient settings (35, 36). One possible reason for this dissemination was the gradual increase of medical care in long-term care facilities (LTCFs) where severely ill patients including those with central lines, urinary catheter, other invasive devices and those are mechanically ventilated were managed for long-term periods (37). Since many of LTCFs are ’for-profit’ organizations, they were initially reluctant to apply infection control and antimicrobial stewardship measures (38). Therefore, LTCFs soon became an essential source of ESBL-producing Enterobacteriaceae, along with other multi-drug resistant organisms (MDROs) (39, 40). Those patients with complicated medical conditions were continually transferred back and forth between health care facilities, and they served as “Trojan horses” for MDROs, including ESBL-producers (41). This evolution of medical care facilitated the spread of formerly pure nosocomial ESBLs into non-hospital settings (32). Recently, Pulcini et al. (42) conducted a large-scale study to identify the differences of antibiotic resistance for microorganisms isolated from urinary samples between community dwellers and nursing home residents. The frequencies of ESBL-producing E. coli were 4.6% and 7.7% (p=<0.0001) in outpatient and inpatient settings, respectively.

Currently, the primary pathogens causing community-onset infections are CTX-M type ESBL-producing E. coli (32). The patients who colonized with these pathogens are often previously treated with FQs and 3rdGCs, are exposed to invasive interventions and nosocomial environments (7). In addition to the selective pressure effect of antibiotic overuse in humans, uncontrolled use of antibiotics in veterinary medicine and food-producing animals has led to the rapid dissemination of ESBLs in the community (43). Additionally, environmental sources such as urban wastewaters, contaminated drinking water, and spreading via international travel have been proposed as possible acquisition means of ESBL-genes in the community (44). However, relative contributions of the factors mentioned above on widespread dissemination of CTX-Ms in the world are still debated.

Horizontal gene transfer is one of the most strong forces in bacterial evolution. When virulent bacterial clones acquire resistance determinant genes, they can emerge as a dominant pathogen through clonal expansion within local or global population such as ST131 as the dominant extra-intestinal pathogenic E. coli worldwide (45). ST131, highly virulent strain of E. coli, has been isolated in various infections including meningitis, osteomyelitis, peritonitis (46, 47), UTIs and urosepsis (48).

Impact of initial inadequate empirical antimicrobial therapy on clinical outcomes

Infections caused by ESBL-producing organisms are associated with a higher rate of mortality (49-51), prolonged infection-related hospital stay (52, 53) and higher healthcare-associated costs (54-56). Therefore, initially selecting appropriate empirical antibiotic therapy is very important, but also a challenge with the rising incidence of antimicrobial resistance. Although some studies asserted no significant impact of inappropriate initial empirical antimicrobial therapy on mortality (57, 58), many other studies consistently demonstrated otherwise (59, 60). This contradiction can be explained by resistance profile of the causative pathogen, source and severity of infections, achieving appropriate source control, baseline comorbidities and place of acquisition of infection (e.g. community-onset vs hospital-acquired). Tumbarello et al. (61) investigated the determinants of inappropriate empiric antibiotic therapy in bacteremia with ESBL-producing E. coli. They concluded that unknown source of bacteremia, resistance to more than three antimicrobials, previous hospitalization and antibiotic exposure were risk factors for receiving inappropriate empiric antibiotic therapy.

Early prediction methods for bloodstream infections with ESBL-producing Enterobacteriaceae and impact of de-escalation on clinical outcomes

The World Health Organization (WHO) published a global priority pathogens list to focus attention on the most hazardous pathogens for public health. Enterobacteriaceae resistant to the 3rdGCs (which includes ESBL-producing Enterobacteriaceae) were included within the critical category (first priority) of this list because of a rapid increase in prevalence particularly in community, the easy transmission of ESBL genes via plasmids and limitations in antibiotic choices for treatment of infections caused by these pathogens. However, timely identification of ESBL-producing bacterial infections can improve relevant outcomes. Incorporation of ESBL-prediction scores may improve the appropriateness of empirical antimicrobial therapy and reduce carbapenem use. To that end, Goodman and colleagues (62) developed a decision tree algorithm to estimate the likelihood of a bacteremic patient being infected with an ESBL-producing E. coli or Klebsiella spp. The final tree that stratifies bacteremia with Enterobacteriaceae according to the risk of ESBL production contained five predictors: the history of prior ESBL colonization and infection, chronic indwelling vascular hardware, age ≥43 years, recent hospitalization in an ESBL high burden region and ³6 days of antibiotic exposure in the prior six months. The positive and negative predictive values of this decision tree were 90.8% and 91.9%, respectively. Sensitivity rate was 51.0%, and specificity rate was 99.1%. In another study, multiple logistic regression analysis was used to identify independent risk factors for BSIs with ESBL-producing Enterobacteriaceae (63). Prior colonization/infection with ESBL-producing Enterobacteriaceae, outpatient gastrointestinal or genitourinary procedures within one month and the number of prior courses of beta-lactams and FQs used within the previous three months were independent risk factors for BSIs with Enterobacteriaceae. However, these decision tree analysis and early prediction risk score models need to be validated in large scale studies.

Early prediction of ESBL-producing organisms as a causative pathogen via prediction scores or machine learning may enable us to give appropriate early therapy (64). After antimicrobial susceptibility results, the initial therapy may be streamlined and narrowed, if possible. Two different research groups investigated the impact of this practice, so-called “de-escalation or step-down therapy” on clinically relevant outcomes in BSIs with Enterobacteriaceae. They found that both oral step-down therapy and early de-escalation of therapy were not associated with higher 30-day mortality rates and clinical failure rates in BSIs with Enterobacteriaceae. Furthermore, switch to oral therapy shortened the duration of hospitalization significantly (65, 66).


ESBL-producing Enterobacteriaceae species are one of the most frequently encountered pathogens in both hospital-acquired and community-onset infections. Their widespread dissemination, particularly in the community, has threatened public health for the last two decades. Several high-risk clones and successful plasmid types have played a significant role, particularly in the dissemination of ESBL-producing E. coli worldwide. The wide array of co-resistance mechanisms has also rendered many different classes of antibiotics useless. Therefore, delayed initiation of appropriate antimicrobial therapy was frequently reported in previous studies concerning infections caused by ESBL-producing Enterobacteriaceae. In order to resolve this issue, rapid diagnostic methods should be explored to shorten interval time between taking a sample for culture and identification of species, in-vitro susceptibilities and resistance determinants. Rapid diagnostics will provide relevant information not only for the determination of appropriate therapy much earlier but also for implementing the appropriate infection control measures and epidemiological investigations. To that end, affordable, user-friendly and accurate rapid diagnostics are urgently needed in routine practice. Also, prediction score models or decision tree algorithms may be useful for early prediction of infections caused by ESBL-producing organisms and prescribing appropriate antimicrobial therapy for infections caused by these pathogens. Similarly, machine learning may be an appealing tool in the near future for this purpose.

Peer-review: Externally peer-reviewed

Author Contributions:
Concept – A.T.A., M.A.; Design – A.T.A, M.A.; Supervision – A.T.A., M.A.; Data Collection and/or Processing – A.T.A.; Analysis and/or Interpretation – A.T.A.; Literature Review – A.T.A.; Writer – A.T.A, M.A.; Critical Reviews – A.T.A, M.A.

Conflict of Interest: The authors have no conflict of interest to declare.

Acknowledgements: We would like to thank to the members of SCARE (Study group for Carbapenem Resistance) for their encouragements and supports.

Financial Disclosure: The authors have no relevant affiliations or financial involvement with any organization or entitiy with a financial interest in or financial conflict with the subject matter or materials discussed in manuscript. This includes employment, consultancies, honoraria, stock ownership, expert testimony, grants or patents received or pending, or royalties.

Show References


  1. Bush K. Past and present perspectives on β-lactamases. Antimicrob Agents Chemother 2018; 62: e01076-18.
  2. Knox JR. Extended-spectrum and inhibitor-resistant TEM-type beta-lactamases: mutations, specificity, and three- dimensional structure. Antimicrob Agents Chemother 1995; 39: 2593-2601.
  3. Ambler RP. The structure of beta-lactamases. Philos Trans R Soc Lond B Biol Sci 1980; 289: 321-31.
  4. Bush K. and Jacoby GA. Updated functional classification of β-lactamases. Antimicrob Agents Chemother 2010; 54: 969-76.
  5. Tamma P and Rodríguez-Baño J. The use of noncarbapenem β-lactams for the treatment of extended-spectrum β-lactamase infections. Clin Infect Dis 2017; 64: 972–80.
  6. Lee JH, Bae IK, Lee SH. New definitions of extended-spectrum β-lactamase conferring worldwide emerging antibiotic resistance. Med Res Rev 2012; 32: 216–32.
  7. Paterson DL and Bonomo RA. Extended-spectrum β-lactamases: a clinical update. Clin Microbiol Rev 2005; 18: 657–86.
  8. Knott-Hunziker V, Petursson S, Waley SG, Jaurin B, Grundström T. The acyl-enzyme mechanism of beta-lactamase action. The evidence for class C beta-lactamases. Biochemical Journal. 1982; 207: 315–22.
  9. Cantón R, Novais A, Valverde A, Machado E, Peixe L, Baquero F, et al. Prevalence and spread of extended-spectrum beta- lactamase-producing enterobacteriaceae in Europe. Clin Microbiol Infect 2008; 14: 144 –53.
  10. Peirano G, Pitout JD. Molecular epidemiology of Escherichia coli producing CTX-M beta-lactamases: the worldwide emergence of clone ST131 O25:H4. Int J Antimicrob Agents 2010; 35: 316-21.
  11. Harris PNA. Clinical management of infections caused by Enterobacteriaceae that express extended- spectrum β-lactamase and AmpC enzymes. Semin Respir Crit Care Med 2015; 36: 56–73.
  12. Drawz SM, Bonomo RA. Three decades of beta-lactamase inhibitors. Clin Microbiol Rev 2010; 23: 160–01.
  13. Gheorghiu R, Yuan M, Hall LM, Livermore DM. Bases of variation in resistance to beta-lactams inKlebsiella oxytoca isolates hyperproducing K1 beta-lactamase. J Antimicrob Chemother 1997; 40: 533–41.
  14. Pitout JD, Le P, Church DL, Gregson DB, Laupland KB. Antimicrobial susceptibility of well-characterised multiresistant CTX- M-producing Escherichia coli: failure of automated systems to detect resistance to piperacillin/tazobactam. Int J Antimicrob Agents 2008; 32: 333–38.
  15. Ben-Ami R, Schwaber MJ, Navon-Venezia S, Schwartz D, Giladi M, Chmelnitsky I, et al. Influx of extended-spectrum beta-lactamase-producing enterobacteriaceae into the hospital. Clin Infect Dis 2006; 42: 925–34.
  16. Pitout JD, Laupland KB. Extended-spectrum beta-lactamase-producing enterobacteriaceae: an emerging public-health concern. Lancet Infect Dis 2008; 8: 159–66.
  17. Harris PNA, Tambyah PA, Paterson DL. β-lactam and β-lactamase inhibitor combinations in the treatment of extended-spectrum β-lactamase producing enterobacteriaceae: time for a reappraisal in the era of few antibiotic options? Lancet Infect Dis 2015; 15: 475-85.
  18. Alvarez M, Tran JH, Chow N, Jacoby GA. Epidemiology of conjugative plasmid-mediated AmpC β-lactamases in the United States. Antimicrob Agents Chemother 2004; 48: 533–37.
  19. Akhan S, Coskunkan F, Tansel O, Vahaboglu H. Conjugative resistance to tazobactam plus piperacillin among extended-spectrum β-lactamase-producing nosocomial Klebsiella pneumoniae. Scand J Infect Dis 2001; 33: 512–15.
  20. Woodford N, Carattoli A, Karisik E, Underwood A, Ellington MJ, Livermore DM. Complete nucleotide sequences of plasmids pEK204, pEK499, and pEK516, encoding CTX-M enzymes in three major Escherichia coli lineages from the United Kingdom, all belonging to the international O25:H4-ST131 clone. Antimicrob Agents Chemother 2009; 53: 4472–82.
  21. Castanheira M, Farrell SE, Deshpande LM, Mendes RE, Jones RN. Prevalence of beta-lactamase-encoding genes among Enterobacteriaceae bacteremia isolates collected in 26 U. S. hospitals: report from the SENTRY Antimicrobial Surveillance Program (2010). Antimicrob Agents Chemother 2013; 57: 3012–20.
  22. Rodríguez-Baño J, Mingorance J, Fernandez- Romero N, Serrano L, Lopez-Cerero L, Pascual A, et al. Virulence profiles of bacteremic extended-spectrum beta-lactamase-producing Escherichia coli: association with epidemiological and clinical features. PloS One 2012; 7: e44238.
  23. European Centre for Disease Prevention and Control (ECDC). Surveillance of antimicrobial resistance in Europe 2017. Annual report of the European Antimicrobial Resistance Surveillance Network (EARS-Net). Stockholm, Sweden: ECDC; 2018.
  24. Jones RN, Biedenbach DJ, Gales AC. Sustained activity and spectrum of selected extended-spectrum β-lactams (carbapenems and cefepime) against Enterobacter spp. and ESBL-producing Klebsiella spp.: report from the SENTRY antimicrobial surveillance program (USA, 1997–2000). Int J Antimicrob Agents 2003; 21: 1–7.
  25. Castanheira M, Mills JC, Costello SE, Jones RN, Sader HS. Ceftazidime-avibactam activity tested against Enterobacteriaceae isolates from US hospitals (2011 to 2013) and characterization of β-lactamase-producing strains. Antimicrob Agents Chemother 2015; 59: 3509–17.
  26. McDanel J, Schweizer M, Crabb V, Nelson R, Samore M, Kahder K, et al. Incidence of extended-spectrum β-lactamase (ESBL)-producing Escherichia coli and Klebsiella infections in the United States: A systematic literature review. Infect Control Hosp Epidemiol 2017; 38: 1209-15.
  27. Jean SS, Hsueh PR, SMART Asia-Pacific Group. Distribution of ESBLs, AmpC β-lactamases and carbapenemases among Enterobacteriaceae isolates causing intra-abdominal and urinary tract infections in the Asia-Pacific region during 2008-14: results from the study for monitoring antimicrobial resistance trends (SMART). J Antimicrob Chemother 2017; 72: 166–71.
  28. Flokas ME, Alevizakos M, Shehadeh F, Andreatos N, Mylonakis E. Extended- spectrum β-lactamase-producing Enterobacteriaceae colonisation in long-term care facilities: a systematic review and meta-analysis. Int J Antimicrob Agents 2017; 50: 649–56.
  29. Karanika S, Karantanos T, Arvanitis M, Grigoras C, Mylonakis E. Fecal colonization with extended-spectrum beta-lactamase- producing enterobacteriaceae and risk factors among healthy individuals: a systematic review and metaanalysis. Clin Infect Dis 2016; 63: 310-18.
  30. Bevan ER, Jones AM, Hawkey PM. Global epidemiology of CTX-M β-lactamases: temporal and geographical shifts in genotype. J Antimicrob Chemother 2017; 72: 2145-55.
  31. Rodríguez-Baño J, Navarro MD. Extended-spectrum β-lactamases in ambulatory care: a clinical perspective. Clin Microbiol Infect 2008; 14: 104–10.
  32. Rodríguez-Baño J, Paterson DL. A change in the epidemiology of infections due to extended-spectrum β-lactamase-producing organisms. Clin Infect Dis 2006; 42: 935–37.
  33. Quan J, Zhao D, Liu L, Chen Y, Zhou J, Jiang Y, et al. High prevalence of ESBL-producing Escherichia coli and Klebsiella pneumoniae in community-onset bloodstream infections in China. J Antimicrob Chemother 2017; 72: 273–80.
  34. Blot S, Antonelli M, Arvaniti K, Bloth K, Creagh-Brown B, De Lange D, et al. Epidemiology of intra-abdominal infection and sepsis in critically ill patients: “AbSeS”, a multinational observational cohort study and ESICM Trials Group Project. Intens Care Med 2019; 45: 1703-17.
  35. Goldstein FW, Pean Y, Gertner J. Resistance to ceftriaxone and other beta- lactams in bacteria isolated in the community. The vigil’roc study group. Antimicrob Agents Chemother 1995; 39: 2516–19.
  36. Pitout JD, Hanson ND, Church DL, Laupland KB. Population-based laboratory surveillance for Escherichia coli-producing extended-spectrum beta-lactamases: importance of community isolates with blactx-m genes. Clin Infect Dis 2004; 38: 1736–41.
  37. Munoz-Price LS. Long-term acute care hospitals. Clin Infect Dis 2009; 49: 438–43.
  38. Denman SJ, Burton JR. Fluid intake and urinary tract infection in the elderly. JAMA 1992; 267: 2245–59.
  39. De Medina T, Carmeli Y. The pivotal role of long-term care facilities in the epidemiology of Acinetobacter baumannii: another brick in the wall. Clin Infect Dis 2010; 50: 1617–28.
  40. Marchaim D, Chopra T, Bogan C, Bheemreddy S, Sengstock D, Jagarlamudi R, et al. The burden of multidrug-resistant organisms on tertiary hospitals posed by patients with recent stays in long-term acute care facilities. Am J Infect Control 2012; 40: 760–65.
  41. Sengstock DM, Thyagarajan R, Apalara J, Mira A, Chopra T, Kaye KS. Multidrug-resistant Acinetobacter baumannii: an emerging pathogen among older adults in community hospitals and nursing homes. Clin Infect Dis 2010; 50: 1611–16.
  42. Pulcini C, Urmes IC, Attinsounon CA, Fougnot S, Thilly N. Antibiotic resistance of enterobacteriaceae causing urinary tract infections in elderly patients living in the community and in the nursing home: a retrospective observational study. J Antimicrob Chemother 2019; 74: 775–81.
  43. Singer RS, Finch R, Wegener HC, Bywater R, Walters J, Lipsitch M. Antibiotic resistance-the interplay between antibiotic use in animals and human beings. Lancet Infect Dis 2003; 3: 47–51.
  44. Chong Y, Shimoda S, Shimono N. Current epidemiology, genetic evolution and clinical impact of extended- spectrum β-lactamase-producing Escherichia coli and Klebsiella pneumoniae. Infect Genet Evol 2018; 61: 185–88.
  45. Johnson JR, Johnston B, Clabots C, Kuskowski MA, Castanheira M. Escherichia coli sequence type ST131 as the major cause of serious multidrug-resistant E. coli infections in the United States. Clin Infect Dis 2010; 51: 286 –94.
  46. Assimacopoulos A, Johnston B, Clabots C, Johnson JR. Post- prostate biopsy infection with Escherichia coli ST131 leading to epididymo-orchitis and meningitis caused by Gram-negative bacilli. J Clin Microbiol 2012; 50: 4157–59.
  47. Bert F, Johnson JR, Ouattara B, Leflon-Guibout V, Johnston B, Marcon E, et al. Genetic diversity and virulence profiles of Escherichia coli isolates causing spontaneous bacterial peritonitis and bacteremia in patients with cirrhosis. J Clin Microbiol 2010; 48: 2709 –14.
  48. Courpon-Claudinon A, Lefort A, Panhard X, Clermont O, Dornic Q, Fantin B, et al. Bacteraemia caused by third-generation cephalosporin- resistant Escherichia coli in France: prevalence, molecular epidemiology and clinical features. Clin Microbiol Infect 2011; 17: 557–65.
  49. Kim YK, Pai H, Lee HJ, Park SE, Choi EH, Kim J, et al. Bloodstream infections by extended-spectrum beta-lactamase-producing Escherichia coli and Klebsiella pneumoniae in children: epidemiology and clinical outcome. Antimicrob Agents Chemother 2002; 46: 1481-91.
  50. Ha YE, Kang CI, Cha MK, Park SY, Wi YM, Chung DR, et al. Epidemiology and clinical outcomes of bloodstream infections caused by extended-spectrum β-lactamase-producing Escherichia coli in patients with cancer. Int J Antimicrob Agents 2013; 42: 403-09.
  51. Kang CI, Chung DR, Ko KS, Peck KR, Song JH. Korean Network for Study of Infectious Diseases. Risk factors for infection and treatment outcome of extended-spectrum β-lactamase-producing Escherichia coli and Klebsiella pneumoniae bacteremia in patients with hematologic malignancy. Ann Hematol 2012; 91: 115-21.
  52. Lautenbach E, Patel JB, Bilker WB, Edelstein PH, Fishman NO. Extended-spectrum beta-lactamase-producing Escherichia coli and Klebsiella pneumoniae: risk factors for infection and impact of resistance on outcomes. Clin Infect Dis 2001; 32: 1162–71.
  53. Stewardson A, Fankhauser C, De Angelis G, Rohner P, Safran E, Schrenzel J, et al. Burden of bloodstream infection caused by extended- spectrum β-lactamase-producing enterobacteriaceae determined using multistate modeling at a Swiss University Hospital and a nationwide predictive model. Infect Control Hosp Epidemiol 2013; 34: 133-43.
  54. Nieminen O, Korppi M, Helminen M. Healthcare costs doubled when children had urinary tract infections caused by extended-spectrum β-lactamase-producing bacteria. Acta Paediatr 2017; 106: 327-33.
  55. Tumbarello M, Spanu T, Di Bidino R, Marchetti M, Ruggeri M, Trecarichi EM, et al. Costs of bloodstream infections caused by Escherichia coli and influence of extended-spectrum-beta-lactamase production and inadequate initial antibiotic therapy. Antimicrob Agents Chemother 2010; 54: 4085–91.
  56. MacVane SH, Tuttle LO, Nicolau DP. Impact of extended-spectrum β-lactamase-producing organisms on clinical and economic outcomes in patients with urinary tract infection. J Hosp Med 2014; 9: 232-38.
  57. De Rosa FG, Pagani N, Fossati L, Raviolo S, Cometto C, Cavallerio P, et al. The effect of inappropriate therapy on bacteremia by ESBL-producing bacteria. Infection 2011; 39: 555–61.
  58. Tsai HY, Chen YH, Tang HJ, Huang CC, Liao CH, Chu FY, et al. Carbapenems and piperacillin/tazobactam for the treatment of bacteremia caused by extended-spectrum β-lactamase-producing Proteus mirabilis. Diagn Microb and Infect Dis 2014; 80: 222-26.
  59. Tumbarello M, Sanguinetti M, Montuori E, Trecarichi EM, Posteraro B, Fiori B, et al. Predictors of mortality in patients with bloodstream infections caused by extended-spectrum-beta-lactamase-producing Enterobacteriaceae: importance of inadequate initial antimicrobial treatment. Antimicrob Agents Chemother 2007; 51: 1987–94.
  60. Endimiani A, Luzzaro F, Brigante G, Perilli M, Lombardi G, Amicosante G, et al. Proteus mirabilis bloodstream infections: risk factors and treatment outcome related to the expression of extended-spectrum beta-lactamases. Antimicrob Agents Chemother 2005; 49: 2598-05.
  61. Tumbarello M, Sali M, Trecarichi EM, Leone F, Rossi M, Fiori B, et al. Bloodstream infections caused by extended-spectrum-beta-lactamase- producing Escherichia coli: risk factors for inadequate initial antimicrobial therapy. Antimicrob Agents Chemother 2008; 52: 3244-52.
  62. Goodman KE, Lessler J, Cosgrove SE, Harris AD, Lautenbach E, Han JH, et al. A clinical decision tree to predict whether a bacteremic patient Is infected with an extended-spectrum β-lactamase-producing organism. Clin Infect Dis. 2016; 63: 896-03.
  63. Augustine MR, Testerman TL, Justo JA, Bookstaver PB, Kohn J, Albrecht H, et al. Clinical risk ccore for prediction of extended-spectrum b- lactamase-producing Enterobacteriaceae in bloodstream isolates. Infect Control Hosp Epidemiol 2017; 38: 266- 72.
  64. Aslan AT, Akova M. Extended spectrum β-lactamase producing enterobacteriaceae: carbapenem sparing options. Expert Rev Anti Infect Ther. 2019 Nov 20. DOI: 10.1080/14787210.2019.1693258 [Epub ahead of print].
  65. Palacios-Baena ZR, Delgado-Valverde M, Valiente Méndez A, Almirante B, Gomez-Zorrilla S, Borrell N, et al. Impact of de-escalation on prognosis of patients with bacteraemia due to enterobacteriaceae: a post-hoc analysis from a multicenter prospective cohort. Clin Infect Dis 2019; 69: 956-19.
  66. Tamma PD, Conley AT, Cosgrove SE, Harris AD, Lautenbach E, Amoah J, et al. Association of 30-day mortality with oral step-down vs continued intravenous therapy in patients hospitalized with enterobacteriaceae bacteremia. JAMA Intern Med 2019; 179: 316-23.