Risk factors for multidrug resistance in nosocomial bacteremia caused by extended-spectrum β-lactamase-producing Escherichia coli and Klebsiella pneumoniae

The clinical impact of early detection of ESBL-producing Enterobacterales with PCR-based blood culture assays

BACKGROUND

Starting January 4, 2021, our health system core microbiology laboratory changed blood culture identification (BCID) platforms to ePlex BCID from BioFire BCID1 with the additional capability to detect the blaCTX-M-Type gene of ESBL-producing organisms. Clinical outcomes of ESBL bloodstream infections (BSI) after implementing ePlex BCID were unknown.

METHODS

Patients with ESBL BSI were compared pre and postimplementation of ePlex BCID in this 11-hospital retrospective analysis (BioFire BCID1 in 2019 vs ePlex BCID in 2021). The primary outcome was time from the Gram stain result to escalation to a carbapenem. Secondary outcomes included in-hospital mortality, 30-day readmission rate, length of stay (LOS), and the duration of antimicrobial therapy.

RESULTS

A total of 275 patients were analyzed. The median time of Gram stain result to escalation to carbapenem was reduced from 44.5 hours with BioFire BCID1 to 7.9 hours with ePlex BCID (P < .001). There were no significant differences in mortality, 30-day readmission, or LOS. The duration of antimicrobial therapy for ESBL BSI was lower in the ePlex BCID group (from 14.4 days to 12.7 days, P = .014).

CONCLUSIONS

Timely detection of the blaCTX-M-Type gene by BCID provides valuable information for the early initiation of appropriate and effective antimicrobial therapy. Although it was not associated with lower mortality, 30-day readmission, or LOS, it may have benefits such as decreasing antimicrobial exposure to patients.

Risk factors in acquiring multidrug-resistant Klebsiella pneumoniae infections in a hospital setting in Saudi Arabia

Over the last decades, the prevalence of multidrug-resistant (MDR) Klebsiella pneumoniae in clinical settings has increased progressively. This study determined the prevalence and risk factors associated with MDR K. pneumoniae infection among hospitalized patients in a referral hospital located in southern Saudi Arabia. A prospective cross-sectional study was conducted in King Abdullah Hospital from April 2021 to March 2022. K. pneumoniae (n = 211) bacteria were recovered from clinical samples of adult patients and examined for antibiotic susceptibility. Univariate and multivariate logistic regressions were applied to determine the factors associated with MDR K. pneumoniae infection. MDR K. pneumoniae strains was found in 66.8% (142/211) of the patients. Among MDR K. pneumoniae, the highest resistance rate was determined for ampicillin (100%), cefuroxime (97.9%), ceftriaxone (94.3%), and aztreonam (92.2%). The lowest resistance rate was determined for colistin (16.3%), and tigecycline (6.4%). Further, the patients' gender, age group, intensive care unit (ICU) admission, invasive medical devices, and chronic illness were found to be significantly associated with MDR K. pneumoniae infection. The independent risk factors associated with MDR K. pneumoniae infection were the male gender (adjusted odds ratio [AOR] 2.107, 95% confidence interval CI 1.125‒3.945, p = 0.02), patients ≥ 65 years of age (AOR 1.905; CI 1.003‒3.616, p = 0.049), ICU admission (AOR 1.963; CI 1.033‒3.732, p = 0.04), diabetes (AOR 1.95; CI 1.02‒3.727, p = 0.043) and chronic obstructive pulmonary disease (AOR 7.172; CI 1.557‒33.032, p = 0.011). The study offered a vision of MDR K. pneumoniae infection in our setting and provided essential indications for further studies that may lead to the prevention and reduction of MDR bacteria.

In Vitro Activities of Ceftazidime-Avibactam and Aztreonam-Avibactam at Different Inoculum Sizes of Extended-Spectrum β-Lactam-Resistant Enterobacterales Blood Isolates

β-lactam–avibactam combinations have been proposed as carbapenem-sparing therapies, but little data exist on their in vitro activities in infections with high bacterial inocula. We investigated the in vitro efficacies and the inoculum effects of ceftazidime–avibactam and aztreonam–avibactam against extended-spectrum β-lactam-resistant Enterobacterales blood isolates. A total of 228 non-repetitive extended-spectrum β-lactam-resistant Escherichia coli and Klebsiella pneumoniae blood isolates were prospectively collected in a tertiary center. In vitro susceptibilities to ceftazidime, aztreonam, meropenem, ceftazidime–avibactam, and aztreonam–avibactam were evaluated by broth microdilution method using standard and high inocula. An inoculum effect was defined as an eightfold or greater increase in MIC when tested with the high inoculum. Of the 228 isolates, 99% were susceptible to ceftazidime–avibactam and 99% had low aztreonam–avibactam MICs (≤8 mg/L). Ceftazidime–avibactam and aztreonam–avibactam exhibited good in vitro activities; MIC₅₀/MIC₉₀ values were 0.5/2 mg/L, 0.125/0.5 mg/L, and ≤0.03/0.25 mg/L, respectively, and aztreonam–avibactam was more active than ceftazidime–avibactam. The frequencies of the inoculum effect with ceftazidime–avibactam and aztreonam–avibactam were lower than with meropenem (14% vs. 38%, p < 0.001 and 30% vs. 38%, p = 0.03, respectively). The β-lactam-avibactam combinations could be useful as carbapenem-sparing strategies, and aztreonam–avibactam has the better in vitro activity but is more subject to the inoculum effect than ceftazidime–avibactam.

Repeated point prevalence survey on antimicrobial use in a university hospital: what have we learned?

OBJECTIVES

To evaluate the quality of antimicrobial prescribing, at the Department of Internal Medicine University Hospital Centre Rijeka, by assessing the necessity for antimicrobial treatment and adherence to the local Guidelines for hospital antimicrobial drug use and to compare results with previously conducted point prevalence surveys (PPSs).

METHODS

A PPS was conducted on 7th May 2019. Demographic and relevant clinical data of each patient receiving systemic antimicrobials were recorded anonymously in a patient-specific form. The appropriateness of antibiotic prescribing was assessed as adherence to the fourth edition of the Guidelines for hospital antimicrobial drug use.

KEY FINDINGS

One hundred and seventy-one patients were hospitalized at the Department of Internal Medicine; 37.4% (n = 64) of patients received 102 prescriptions for an antimicrobial drug [62.8% (n = 64) of prescriptions were for intravenous and 37.2% (n = 38) for oral administration]. Of these, 52 were treated for an identified existing infection, 5 were treated for an unknown indication and 7 received antibiotics as prophylaxis. The necessity for antimicrobial treatment was unclear in 19.3% (n = 11) of cases. The antimicrobials were prescribed according to the Guidelines in 65.4% (n = 34) of cases. Adherence to the Guidelines when treating lower respiratory tract infections, urinary tract infections and gastrointestinal tract infections was 47.8%, 55.6% and 92.9%, respectively.

CONCLUSIONS

Our study revealed antibiotic prescription frequency similar to EU/EEA average and high percentage of unjustified antimicrobial treatment introduction. The rate of adherence to the Guidelines was lower than those observed in western countries. The results lay a basis for tailoring antimicrobial stewardship programs/activities.

Does Fluoroquinolones and Third-Generation Cephalosporins Restriction Reverse Extended-Spectrum β-Lactamases Klebsiella pneumoniae Resistance Rates?

Aim: To decrease the incidence and resistance rates of extended-spectrum β-lactamases (ESBL) Klebsiella pneumoniae (KP) by restriction of the use of third-generation cephalosporins (3GCs) and fluoroquinolones. Methods: Consumption of 3GCs, fluoroquinolones, and carbapenems in association with ertapenem and fluoroquinolone-resistant KP isolates, were analyzed in 21 months by autoregressive integrated moving average models. A follow-up analysis was performed 5 years later. Results: Consumption of 3GCs decreased significantly during the postintervention period. Their restriction was associated with a decrease in ertapenem-resistant KP isolates by 17.5%. Fluoroquinolone, 3GCs, and carbapenem use did not significantly predict the percentage of ertapenem-resistant KP isolates. Fluoroquinolone, but not cephalosporin use, significantly predicted the percentage of fluoroquinolone-resistant isolates, with an increase of 1 defined daily dose (DDD) of fluoroquinolone/100 occupied bed-days (OBDs) corresponding to a 0.32% increase of fluoroquinolone-resistant isolates (p = 0.008). A decrease of 1 DDD of carbapenem/100 OBD was associated with a 16.94% increase of fluoroquinolone-resistant isolates (p = 0.007). Five years later, the consumption of all three antimicrobial classes increased significantly compared with the 2011-2013 period, whereas ertapenem-resistant KP rates significantly decreased. Conclusion: This study may bring a valuable contribution to the understanding of the intricate association between antibiotic consumption and bacterial resistance. Reporting a spectrum of different results could present a useful basis for more profound research of various interventions' effects.

Prevalence of and risk factor for community-onset third-generation cephalosporin-resistant Escherichia coli bacteremia at a medical center in Taiwan

Background

Increased resistance to third-generation cephalosporin (3GC) is a serious concern for community-onset Escherichia coli infection because this resistance easily delays effective treatment. This study surveyed the current antimicrobial resistance pattern among E. coli isolates that cause community-onset bacteremia, with a special focus on the prevalence of and the risk factors for 3GC resistance, and determined factors for poor outcomes among patients with community-onset E. coli bacteremia.

Methods

This retrospective study was conducted at a tertiary-care teaching hospital in Taiwan. All adult patients with community-onset E. coli bacteremia between January 1, 2015, and December 31, 2015 were enrolled and were divided into two groups depending on whether the E. coli isolate was susceptible to 3GCs. Risk factors for 3GC resistance, 14-day all-cause mortality, and length of hospital stay were analyzed.

Results

The overall rate of 3GC resistance among E. coli isolates causing community-onset bacteremia was 19.7%, whereas it was 9.6% if only isolates causing community-acquired bacteremia were considered. Independent risk factors for 3GC-resistant community-onset E. coli bacteremia were hospitalization within the past 1 year (odds ratio: 2.4, 95% confidence interval: 1.6–3.7, P < 0.001), exposure to antibiotics within the past 15 days (2.6, 1.4–4.9, P = 0.002), residence in nursing home or long-term care facility (3.6, 1.0–12.3, P = 0.044), presence of underlying genitourinary disease (1.9, 1.2–2.9, P = 0.005), and presence of indwelling implantable intravenous port (2.2, 1.1–4.1, P = 0.021). 3GC resistance was independently associated with increased length of hospital stays (P < 0.001).

Conclusion

In this study, the prevalence of 3GC resistance was high among both patients with community-onset and those with community-acquired E. coli bacteremia. 3GC resistance is a strong independent risk factor for length of hospital stay. The effectiveness of empirical antibiotic treatment would partially explain the impact of 3GC resistance, but more evidence is needed. The choice of appropriate empirical antibiotics for community-onset E. coli bacteremia might impact outcomes in terms of the length of hospital stay and need to be individualized according to the patient-specific risk for acquiring drug-resistant pathogens.

Risk factors and molecular epidemiology of community-onset, multidrug resistance extended-spectrum β-lactamase-producing Escherichia coli infections

BACKGROUND/AIMS

Although multidrug resistance (MDR) among extended-spectrum β-lactamase-producing Escherichia coli (ESBL-EC) poses significant therapeutic challenges, little is known regarding the risk factors and epidemiology of community-onset MDR-ESBL-EC infections. We performed this study to investigate risk factors and the molecular epidemiology of community-onset MDR-ESBL-EC infections.

METHODS

We conducted a case-control-control study of community-onset infections. MDR-ESBL-EC was defined as ESBL-EC that demonstrated in vitro resistance to trimethoprim-sulfamethoxazole, fluoroquinolones (FQs), and gentamicin. Patients with MDR-ESBL-EC infections were designated as case patients. A control group I (CG I) patient was defined as a person whose clinical sample yielded ESBL-EC that did not meet the criteria for MDR. A control group II (CG II) patient was defined as a patient with a non-ESBL-EC infection.

RESULTS

Of 108 patients with ESBL-EC infections, 30 cases (27.8%) were due to MDR-ESBL-EC. Compared with CG I, prior use of FQs (odds ratio [OR], 3.16; 95% confidence interval [CI], 1.11 to 8.98) and immunosuppressant use (OR, 10.47; 95% CI, 1.07 to 102.57) were significantly associated with MDR-ESBL-EC. Compared with CG II, prior use of FQs (OR, 15.53; 95% CI, 2.86 to 84.27) and healthcare-associated infection (OR, 5.98; 95% CI, 2.26 to 15.86) were significantly associated with MDR-ESBL-EC. CTX-M-15 was the most common in MDR-ESBL-EC infections (59.1% [13/22]), while CTX-M-14 was the most common in non-MDR-ESBL-EC infections (41.6% [32/77]). CTX-M-15 was significantly associated with MDR-ESBL-EC (59.1% vs. 32.5%, p = 0.028). Pulsed-field gel electrophoresis showed clonal diversity of MDR-ESBL-EC isolates.

CONCLUSIONS

The emergence of strains of MDR-ESBL-EC in the community poses an important new public health threat. More information on the emergence and transmission of these strains will be necessary in order to prevent their spread.

Antibacterial Resistance in Patients with Hematopoietic Stem Cell Transplantation

Recipients of hematopoietic stem cell transplantation (HSCT) are at substantial risk of bacterial, fungal, viral, and parasitic infections depending on the time elapsed since transplantation, presence of graft-versus-host disease (GVHD), and the degree of immunosuppression. Infectious complications in HSCT recipients are associated with high morbidity and mortality. Bacterial infections constitute the major cause of infectious complications, especially in the early post-transplant period. The emergence of antibacterial resistance complicates the management of bacterial infections in this patient group. Multidrug-resistant bacterial infections in this group of patients have attracted considerable interest and may lead to significant morbidity and mortality. Empirical antibacterial therapy in patients with HSCT and febrile neutropenia has a critical role for survival and should be based on local epidemiology. This review attempts to provide an overview of risk factors and epidemiology of emerging resistant bacterial infections and their management in HSCT recipients.

Multidrug-Resistant Escherichia coli and Klebsiella pneumoniae Isolated From Patients in Kashan, Iran

BACKGROUND

Escherichia coli and Klebsiella pneumoniae are common human pathogens that cause a wide spectrum of infections. Antimicrobial resistance is a basic obstacle in the management of these infections which has different patterns in various regions.

OBJECTIVES

In this study, the antibiotic resistance patterns and risk factors for multidrug-resistant (MDR) E. coli and K. pneumoniae were determined.

PATIENTS AND METHODS

In this cross-sectional study, a total of 250 isolates (134 E. coli and 116 K. pneumoniae) were collected and antimicrobial resistances to ampicillin, amoxicillin-clavulanic acid, amikacin, gentamycin, ceftriaxone, ceftazidime, ciprofloxacin and imipenem were evaluated by disc diffusion method and confirmed by E-test. Moreover, risk factors for MDR E. coli and K. pneumoniae were also detected.

RESULTS

The mean ages of the culture-positive cases of E. coli and K. pneumoniae were 33.39 ± 24.42 and 36.54 ± 24.66 years, respectively (P = 0.31); 137 (54.8%) cases were male and 113 (45.2%) were female (P = 0.53). Nineteen (14.2%) isolates of E. coli and 12 (10.3%) isolates of K. pneumoniae were sensitive to all the evaluated antibiotics. The prevalence of MDR E. coli and MDR K. pneumoniae was 50% and 46.6%, respectively (P = 0.59). The highest resistance for both strains was to ampicillin and no imipenem resistance was seen. The risk factors for MDR E. coli were admission history during the recent three months (P = 0.043) and antibiotic use in the previous month (P = 0.03); for MDR K. pneumoniae, they were admission in the pediatric ward (P = 0.016), surgical ward (P = 0.019), or gynecology ward (P = 0.12), admission duration of > seven days, and antibiotic use during the past month (P = 0.04).

CONCLUSIONS

The prevalence of multidrug resistance was high compared with developed countries, and history of admission, antibiotic use, admission duration and admission wards were the risk factors for multidrug resistance.

Differences in risk-factor profiles between patients with ESBL-producing Escherichia coli and Klebsiella pneumoniae: a multicentre case-case comparison study

Background

Generic epidemiological differences between extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli (ESBL-EC) and Klebsiella pneumoniae (ESBL-KP), are poorly defined. Nonetheless, defining such differences and understanding their basis could have strategic implications for infection control policy and practice.

Methods

Between 2009 and 2011 patients with bacteraemia due to ESBL-EC or ESBL-KP across all three acute hospitals in the city of Auckland, New Zealand, were eligible for inclusion. Recognised risk factors for ESBL bacteraemia were compared between species in a retrospective case-case study design using multivariate logistic regression. Representative isolates underwent ESBL gene characterisation and molecular typing.

Results

170 patients and 176 isolates were included in the study (92 patients with ESBL-EC, 78 with ESBL-KP). 92.6% had CTX-Ms. 39% of EC were ST131 while 51% of KP belonged to 3 different STs (i.e. ST20, ST48 & ST1087). Specific sequence types were associated with specific hospitals for ESBL-KP but not ESBL-EC. Variables positively associated with ESBL-EC on multivariate analysis were: community acquired infection (odds ratio [OR] 7.9; 95% CI: 2.6-23.9); chronic pulmonary disease (OR 5.5; 95% CI: 1.5-20.1); and high prevalence country of origin (OR 4.3; 95% CI: 1.6-11.6). Variables negatively associated with ESBL-EC were previous transplant (OR 0.06; 95% CI: 0.007-0.6); Hospital 2 (OR 0.3; 95% CI: 0.1-0.7) and recent ICU admission (OR 0.3; 95% CI: 0.07-0.9).

Conclusions

Differences in risk profiles between patients with ESBL-EC and ESBL-KP suggest fundamental differences in transmission dynamics. Understanding the biological basis for these differences could have implications for infection control practice. Tailoring of infection control measures according to ESBL species may be indicated in some instances.

Management of febrile neutropenia in the era of bacterial resistance

Managing cancer patients with fever and neutropenia must be considered as a medical emergency since any delay in initiating appropriate empirical antibacterial therapy may result in high rates of mortality and morbidity. Emerging antibacterial resistance in bacterial pathogens infecting febrile neutropenic patients complicates management, and choosing the type of empirical antimicrobial therapy has become a challenge. To further complicate the decision process, not all neutropenic patients are in same category of susceptibility to develop severe infection. While low-risk patients may be treated with oral antibiotics in the outpatient setting, high-risk patients usually need to be admitted to hospital and receive parenteral broad-spectrum antibiotics until the neutrophil levels recover. These strategies have recently been addressed in two international guidelines from the Infectious Diseases Society of America (IDSA) and the European Conference on Infections in Leukaemia (ECIL). This review gives a brief overview of current antimicrobial resistance problems and their effects in febrile neutropenic cancer patients by summarizing the suggestions from the IDSA and ECIL guidelines.

European guidelines for empirical antibacterial therapy for febrile neutropenic patients in the era of growing resistance: summary of the 2011 4th European Conference on Infections in Leukemia

Owing to increasing resistance and the limited arsenal of new antibiotics, especially against Gram-negative pathogens, carefully designed antibiotic regimens are obligatory for febrile neutropenic patients, along with effective infection control. The Expert Group of the 4(th) European Conference on Infections in Leukemia has developed guidelines for initial empirical therapy in febrile neutropenic patients, based on: i) the local resistance epidemiology; and ii) the patient's risk factors for resistant bacteria and for a complicated clinical course. An 'escalation' approach, avoiding empirical carbapenems and combinations, should be employed in patients without particular risk factors. A 'de-escalation' approach, with initial broad-spectrum antibiotics or combinations, should be used only in those patients with: i) known prior colonization or infection with resistant pathogens; or ii) complicated presentation; or iii) in centers where resistant pathogens are prevalent at the onset of febrile neutropenia. In the latter case, infection control and antibiotic stewardship also need urgent review. Modification of the initial regimen at 72-96 h should be based on the patient's clinical course and the microbiological results. Discontinuation of antibiotics after 72 h or later should be considered in neutropenic patients with fever of unknown origin who are hemodynamically stable since presentation and afebrile for at least 48 h, irrespective of neutrophil count and expected duration of neutropenia. This strategy aims to minimize the collateral damage associated with antibiotic overuse, and the further selection of resistance.

Frequency of occurrence and antimicrobial susceptibility of Gram-negative bacteremia isolates in patients with urinary tract infection: results from United States and European hospitals (2009-2011)

We evaluated the frequency of occurrence and antimicrobial susceptibility patterns of Gram-negative bacteria isolated from bacteremic patients with UTI from European (EU) and United States (USA) hospitals during a 3-year period (2009-2011). Susceptibility testing was performed by the reference broth microdilution method on 2071 Gram-negative bacilli. The most frequently isolated pathogens were Escherichia coli (63·3/71·3% in USA/EU), Klebsiella spp. (16·7/11·2%) and Proteus mirabilis (6·4/5·0%). Escherichia coli susceptibility rates were generally similar in the USA and EU, with extended-spectrum beta-lactamase (ESBL)-phenotype rates at 8·1% in both regions. Among Klebsiella spp., ESBL rates varied from 11·4/17·1% in 2009 to 16·1/40·4% in 2011 in USA/EU, and susceptibility rates were generally lower in EU compared to the USA. Pseudomonas aeruginosa exhibited lower susceptibility rates to ceftazidime, meropenem and piperacillin/tazobactam in EU (78·4, 78·4 and 76·5%, respectively) compared to USA (91·2, 88·2 and 91·2%, respectively). In summary, very few antimicrobials provided satisfactory coverage (>90%) when tested against Klebsiella spp. and P. aeruginosa isolates in EU.

Risk factors for hospital-acquired bloodstream infections caused by extended-spectrum β-lactamase Klebsiella pneumoniae among cancer patients

BACKGROUND

Incidence of infection due to extended-spectrum β-lactamase producing Klebsiella pneumoniae (ESBL-KP) has increased rapidly in recent years. However, its prevalence in cancer patients is seldom reported.

AIMS

This study was designed to identify the risk factors for bloodstream infections (BSIs) with ESBL-KP, and to understand its susceptibility among cancer patients on antibiotics.

METHODS

We conducted a retrospective study with a total of 118 cancer patients between 2009 and 2011 with BSIs, among which 88 were infected with non-ESBL-KP and 30 with ESBL-KP. Patterns of susceptibility, clinical characteristics and mortality were investigated. Multivariate logistic regression model was used to unveil independent risk factors.

RESULTS

On multivariate analysis, length of stay (LOS) (p = 0.025), and prior exposure to cephalosporins (p = 0.006), fluoroquinolones (p = 0.011), macrolides (p = 0.007) and aminoglycosides (p = 0.008) were independent risk factors for BSIs of ESBL-KP. For mortality, there was no significant difference between ESBL-KP and non-ESBL-KP groups (p = 0.431). Moreover, compared with non-ESBL-KP, ESBL-KP displayed reduced sensitivity to aminoglycosides (p < 0.001, except amikacin), fluoroquinolones (p < 0.001), piperacillin-tazobactam (p = 0.005) and trimethoprim-sulfamethoxazole (p < 0.001), respectively.

CONCLUSIONS

ESBL-KP exhibited less susceptibility to various non-β-lactamase antibiotics, and infections due to these organisms were related to LOS and preexisting use of antibiotics. Thus, judicious use of all antibiotics should be underscored to reduce the infections caused by ESBL-KP.

Trends of mortality due to septicemia in Greece: an 8-year analysis

BACKGROUND

Infectious diseases are among the major causes of death worldwide. We evaluated the trends of mortality due to septicemia in Greece and compared it with mortality due to other infections.

METHODS

Data on mortality stratified by cause of death during 2003-2010 was obtained from the Hellenic Statistical Authority. Deaths caused by infectious diseases were grouped by site of infection and analyzed using SPSS 17.0 software.

RESULTS

45,451 deaths due to infections were recorded in Greece during the 8-year period of time, among which 12.2% were due to septicemia, 69.7% pneumonia, 1.5% pulmonary tuberculosis, 0.2% influenza, 0.5% other infections of the respiratory tract, 7.9% intra-abdominal infections (IAIs), 2.5% urinary tract infections (UTIs), 2.2% endocarditis or pericarditis or myocarditis, 1.6% hepatitis, 1% infections of the central nervous system, and 0.7% other infections. A percentage of 99.4% of deaths due to septicemia were caused by bacteria that were not reported on the death certificate (noted as indeterminate septicemia). More deaths due to indeterminate septicemia were observed during 2007-2010 compared to 2003-2006 (3,558 versus 1,966; p<0.05).

CONCLUSION

Despite the limitations related to the quality of death certificates, this study shows that the mortality rate due to septicemia has almost doubled after 2007 in Greece. Proportionally, septicemia accounted for a greater increase in the mortality rate within the infectious causes of death for the same period of time. The emergence of resistance could partially explain this alarming phenomenon. Therefore, stricter infection control measures should be urgently applied in all Greek healthcare facilities.

CTX-M-type β-lactamases: a successful story of antibiotic resistance

Production of extended-spectrum β-lactamases (ESBLs) is the principal mechanism of resistance to oxyimino-cephalosporins evolved by members of the family Enterobacteriaceae. Among the several ESBLs emerged among clinical pathogens, the CTX-M-type enzymes have proved the most successful in terms of promiscuity and diffusion in different epidemiological settings, where they have largely replaced and outnumbered other types of ESBLs. Originated by the capture and mobilization of chromosomal β-lactamase genes of strains of Kluyvera species, the blaCTX-M genes have become associated with a variety of mobile genetic elements that have mediated rapid and efficient inter-replicon and cell-to-cell dissemination involving highly successful enterobacterial lineages (e.g. Escherichia coli ST131 and ST405, or Klebsiella pneumoniae CC11 and ST147) to yield high-risk multiresistant clones that have spread on a global scale. The CTX-Mβ-lactamase lineage exhibits a striking plasticity, with a large number of allelic variants belonging in several sublineages, which can be associated with functional heterogeneity of clinical relevance. This review article provides an update on CTX-M-type ESBLs, with focus on structural and functional diversity, epidemiology and clinical significance.