Population Pharmacokinetic Analyses for Ertapenem in Subjects with a Wide Range of Body Sizes

Despite a number of studies reporting that ertapenem pharmacokinetic parameters differ considerably in obese patients from those in healthy volunteers, functions describing the relationships between this agent's pharmacokinetics and indicators of body size have not been developed. The aim of this analysis was to develop an ertapenem population pharmacokinetic model using data from a previously described study in normal-weight, obese, and morbidly obese healthy volunteers. A single ertapenem 1-g dose administered intravenously was evaluated in 30 subjects within different body mass index (BMI) categories. The population pharmacokinetic model was developed using the first-order conditional estimation method with interaction (FOCE-I) algorithm within NONMEM. The ability of age, sex, renal function, and various body size measures (total body weight, height, body mass index, ideal body weight, fat-free mass, and body surface area [BSA]) to explain a portion of the interindividual variability on select pharmacokinetic parameters was explored using stepwise forward selection (α = 0.01) and backward elimination (α = 0.001). The data were best described using a linear three-compartment model with total body weight as a covariate on clearance (CL = 1.79 · [weight/95.90]^0.278) and BSA as a covariate on central volume (Vc = 4.76 · [BSA/2.06]^1.86). After accounting for fixed effects, the estimated interindividual variability was very low (<10% for all clearance and volume terms). Goodness-of-fit diagnostics indicated a precise and unbiased fit to the data. Using the developed population pharmacokinetic model and simulation, reliable estimates of ertapenem serum exposures, which can be utilized to evaluate various dosing regimens in subjects with a wide range of body sizes, are expected.

Whole genome analyses of CMY-2-producing Escherichia coli isolates from humans, animals and food in Germany

Background

Resistance to 3rd-generation cephalosporins in Escherichia coli is mostly mediated by extended-spectrum beta-lactamases (ESBLs) or AmpC beta-lactamases. Besides overexpression of the species-specific chromosomal ampC gene, acquisition of plasmid-encoded ampC genes, e.g. bla_CMY-2, has been described worldwide in E. coli from humans and animals. To investigate a possible transmission of bla_CMY-2 along the food production chain, we conducted a next-generation sequencing (NGS)-based analysis of 164 CMY-2-producing E. coli isolates from humans, livestock animals and foodstuff from Germany.

Results

The data of the 164 sequenced isolates revealed 59 different sequence types (STs); the most prevalent ones were ST38 (n = 19), ST131 (n = 16) and ST117 (n = 13). Two STs were present in all reservoirs: ST131 (human n = 8; food n = 2; animal n = 6) and ST38 (human n = 3; animal n = 9; food n = 7). All but one CMY-2-producing ST131 isolates belonged to the clade B (fimH22) that differed substantially from the worldwide dominant CTX-M-15-producing clonal lineage ST131-O25b clade C (fimH30). Plasmid replicon types IncI1 (n = 61) and IncK (n = 72) were identified for the majority of bla_CMY-2-carrying plasmids. Plasmid sequence comparisons showed a remarkable sequence identity, especially for IncK plasmids. Associations of replicon types and distinct STs were shown for IncK and ST57, ST429 and ST38 as well as for IncI1 and ST58. Additional β-lactamase genes (bla_TEM, bla_CTX-M, bla_OXA, bla_SHV) were detected in 50% of the isolates, and twelve E. coli from chicken and retail chicken meat carried the colistin resistance gene mcr-1.

Conclusion

We found isolates of distinct E. coli clonal lineages (ST131 and ST38) in all three reservoirs. However, a direct clonal relationship of isolates from food animals and humans was only noticeable for a few cases. The CMY-2-producing E. coli-ST131 represents a clonal lineage different from the CTX-M-15-producing ST131-O25b cluster. Apart from the ST-driven spread, plasmid-mediated spread, especially via IncI1 and IncK plasmids, likely plays an important role for emergence and transmission of bla_CMY-2 between animals and humans.

Electronic supplementary material

The online version of this article (10.1186/s12864-018-4976-3) contains supplementary material, which is available to authorized users.

Virulence potential of commensal multidrug resistant Escherichia coli isolated from poultry in Brazil

There is an increasing number of reports worldwide about multidrug resistance (MDR) with potential of ExPEC in commensal E. coli. The present study evaluated the potential ExPEC in selected 44 MDR E.coli isolates, collected from livestock. ExPEC isolates were characterized by analysis of five main groups of virulence genes (papA and/or papC, sfa and/or foc, afa and/or dra, kpsMT II and iutA). We also determined the increased virulence potential analyzing other 29 virulence genes, the epidemiology of these isolates. Additionally, fifteen ExPEC isolates were selected to evaluate the adhesion and invasion capacity in vitro using Caco-2 cells. Based on the analysis of the five main virulence genes, 72.7% (32/44) strains were classified as ExPEC. The presence of each gene was iutA 88.6%, KpsMT II 70.4%, papC 25%, sfa/focDE 4.5%; afa/draBC genes were not found. All E. coli isolates were classified into: phylogenetic groups A (34%), B1 (10%), B2 (20%), and D (36%). MLST revealed 7 different STs among isolates, including a new ST identified (ST5687). The in vitro assay in Caco-2 cells showed that all isolates were capable to adhere or invade the epithelial cells, although this occurred at variable levels. The ExPEC isolate LO122 reached similar levels of invasion to the positive control strain Salmonella Typhimurium LT2. These results showed that the apparently commensal microbiota of poultry harbors MDR ExPEC isolates with high adhesion and invasion potential.

Determination of antimicrobial resistance to extended-spectrum cephalosporin, quinolones, and vancomycin in selected human enteric pathogens from Prince Edward Island, Canada

The aim of this study was to determine the frequency of fecal carriage of vancomycin-resistant Enterococcus spp. and Escherichia coli with reduced susceptibilities to extended-spectrum cephalosporins (ESCs) and quinolones in humans on Prince Edward Island, Canada. Convenience fecal samples from individuals on Prince Edward Island were screened phenotypically using selective culture and genotypically using multiplex polymerase chain reactions to detect E. coli and Enterococcus spp. resistant to critically important antimicrobials. Twenty-six (5.3%) of 489 individuals had E. coli with reduced susceptibility to ESCs. Twenty-five (96.2%) of the 26 isolates harbored blaTEM, 18 (69.2%) harbored blaCMY-2, 16 (61.5%) harbored blaCTX-M groups, 2 (7.7%) harbored blaSHV genes. None of the ESC-resistant E. coli was positive for carbapenem resistance. Twenty-one (8.3%) of 253 individuals had E. coli isolates with reduced quinolone susceptibility. All 21 isolates were positive for at least 1 qnr gene, with 3 (14.3%) isolates positive for qnrB, 5 (23.8%) positive for qnrS, and 13 (61.9%) positive for both qnrB and qnrS genes. All the enterococci isolates were vancomycin-susceptible. Higher susceptibility to the critically important antimicrobials was found in this study. This study can serve as a baseline for future antimicrobial resistance surveillance within this region.

Intravenous Fosfomycin: An Assessment of Its Potential for Use in the Treatment of Systemic Infections in Canada

Fosfomycin is a bactericidal agent that inhibits cell wall synthesis using a mechanism of action distinct from β-lactams or other antimicrobial agents. It is a broad-spectrum agent that is frequently active against antimicrobial-resistant bacterial pathogens including methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant enterococci (VRE), multidrug-resistant (MDR) Enterobacteriaceae, and some isolates of MDR Pseudomonas aeruginosa. Intravenous fosfomycin has been prescribed for a wide variety of infections in many countries for >40 years. It is most frequently used in combination with other antimicrobial agents (e.g., β-lactams, carbapenems, and aminoglycosides) and has an excellent safety profile, including in neonates and children, even with long-term administration (weeks). Fosfomycin achieves extensive tissue distribution including difficult to reach compartments such as aqueous humor, vitreous humor, abscess fluid, and CSF. Available data, to date, suggest no clinically relevant pharmacological interactions between fosfomycin and other agents, including drugs, stimulants, or food. Intravenous fosfomycin's role in therapy in Canada is likely as an agent used alone or in combination for complicated urinary tract infections in hospitalized patients as well as hospitalized patients with MDR infections who have not responded to first-, and potentially, second-line antimicrobials or in patients who cannot tolerate (due to adverse effects) first- and second-line antimicrobials.

First Report of SHV-148-Type ESBL and CMY-42-Type AmpC β-Lactamase in Klebsiella pneumoniae Clinical Isolates in Tunisia

Extended-spectrum beta-lactamase producing Enterobacteriaceae present a real problem worldwide. We aimed to investigate the molecular mechanisms of resistance to antibiotics among Klebsiella pneumoniae clinical isolates collected from a Hospital in the southeast of Tunisia. Eighteen cephalosporin-resistant K. pneumoniae were recovered between April 2015 and August 2016. Molecular characterization of antimicrobial resistance encoding genes was performed by PCR and sequencing. Results revealed several types of Ambler class A β-lactamase encoding genes among our isolates: [blaCTXM-15 (15), blaSHV-28 (6), blaSHV-1 (2), blaSHV-148 (1), blaSHV-61 (1), blaSHV-76 (1), blaSHV-186 (1), blaTEM-1 (8)]. The association of blaOXA-1 was observed in nine isolates. However, the class C β-lactamase encoding genes were detected in four isolates [blaCMY-4 (2), blaCMY-42 (1), blaACT-35 (1)]. Molecular typing of K. pneumoniae isolates by pulsed-field gel electrophoresis showed 16 unrelated pulsotypes proving a high diversity among our isolates. Our study provides new epidemiological information showing a huge diversity of β-lactamase encoding genes among our isolates. In fact, this is the first report of SHV-76, SHV-148, and SHV-186 in Tunisia. This is also the first report of CMY-42 and ACT-35 producing K. pneumoniae in our country.

High prevalence of sequence type 131 isolates producing CTX-M-15 among extended-spectrum β-lactamase-producing Escherichia coli strains in northeast Iran

OBJECTIVES

The recent expansion of extended-spectrum β-lactamase (ESBL)-producing Escherichia coli is a worldwide problem. The purpose of this study was to investigate the molecular characteristics of ESBL-producing E. coli strains in Mashhad, located in the northeast of Iran.

METHODS

A total of 455 clinical E. coli isolates were collected at three hospitals in Mashhad between April-September 2015. Antimicrobial susceptibility was determined by the Kirby-Bauer disk diffusion test. The combination disk test was performed for phenotypic detection of ESBLs. PCR was used to screen isolates for ESBL typing. Phylogenetic groups and sequence type 131 (ST131) were determined by multiplex PCR.

RESULTS

The prevalence of ESBL-producing E. coli among the collected strains was 51.6% (235/455). Among the 235 ESBL-producing strains, 222 (94.5%) tested positive for CTX-M type, whilst 115 (48.9%), 92 (39.1%) and 21 (8.9%) were positive for TEM, OXA and SHV, respectively. Moreover, CTX-M-15 (94.1%; 209/222) was the most common ESBL among E. coli. Based on multiplex PCR, phylogenetic group B2 was predominant (169/235; 71.9%), followed by D (32/235; 13.6%), A (21/235; 8.9%) and B1 (13/235; 5.5%). ST131 was the predominant clonal group among the phylogenetic group B2 isolates (151/169; 89.3%).

CONCLUSION

The results revealed that an urgent investigation of the source and transmission pathways of the CTX-M-15-B2-ST131 E. coli clone is needed to mitigate this emergent public-health problem.

Plasmid-Mediated AmpC β-Lactamase and Underestimation of Extended-Spectrum β-Lactamase in Cefepime-Susceptible Elevated-Ceftazidime-MIC Enterobacteriaceae Isolates

Phenotypic detection of extended-spectrum β-lactamase (ESBL) is important for public health and infection control; however, plasmid-mediated AmpC β-lactamases (pAmpCs) can interfere with the ESBL phenotyping. We focused on Enterobacteriaceae strains that were susceptible to cefepime but had a mildly elevated minimum inhibitory concentration (MIC) of ceftazidime and studied the effect of pAmpC on the ESBL phenotyping in this population. Genotyping of ESBL and pAmpC was performed on 528 clinical isolates of Escherichia coli, Klebsiella spp., and Proteus spp. with a ceftazidime MIC of ≥2 μg/mL and cefepime MIC≤8 μg/mL; these isolates were collected at Nagasaki University Hospital from January 2005 to March 2011. In this sample, 145 isolates (27.5%) tested positive for pAmpC (pAmpC group). The concordance rates of phenotypic and genotypic detection of ESBLs were 69.2% in the pAmpC group and 88.8% in the non-pAmpC group (P=0.04). pAmpC was more commonly detected in isolates with non-CTX-M genes (5/53, 9.4%) than in isolates with CTX-M genes (8/121, 6.6%). Our data suggest that the presence of pAmpC increases the false negative detection of ESBL. When ESBL phenotyping is used, the underestimation of the prevalence of ESBL producers should be taken into account.

Rapid rise of the ESBL and mcr-1 genes in Escherichia coli of chicken origin in China, 2008-2014

Extended-spectrum beta-lactamase-producing Escherichia coli (ESBL-EC) strains are emerging around the world as a source of resistance to β-lactam antibiotics such as ampicillin, cefotaxime, and ceftazidime. mcr-1 is a novel plasmid-mediated gene conferring resistance to colistin. The aim of this study was to investigate the prevalence of ESBL-EC mcr-1 of chicken origin in the different provinces of China during 2008–2014. Overall, 341 of 821 isolates were determined to be ESBL-EC strains, and the proportion of ESBL-positive strains almost doubled from 2008 to 2014. The findings of our study revealed regional differences, with significantly more ESBL-EC isolates from stockbreeding in concentrated poultry industry areas in Shandong than from the other four provinces. The ESBL type analysis showed that bla_CTX-M was the most prevalent ESBL-encoding gene (92.7%). In total, twelve subtypes of CTX-M genes were detected, among which, bla_CTX-M-55 (34.3%) and bla_CTX-M-65 (17.9%) were the major identified genotypes. In addition, bla_TEM and pAmpC genes were carried by 86.0% and 8.5% of isolates, respectively. In this study, we also observed 44 E. coli isolates with multiple ST types (ST46, ST1286, ST10, ST29, ST101, and ST354) carrying mcr-1, and the majority of mcr-1–carrying plasmids were IncI2. The whole-genome sequencing analysis indicated the co-existence of bla_CTX-M and mcr-1 in ESBL-EC of both animal and human origin, and phylogenetic analysis further revealed their close relationship, especially several isolates sharing a small number of SNPs, which suggested the increasing trend of co-existence and transmission of ESBL and mcr-1 in both clinical medicine and veterinary medicine.

Management of infections caused by extended-spectrum β-lactamase-producing Enterobacteriaceae: current evidence and future prospects

INTRODUCTION

The spread of extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae has become a major public health threat worldwide. Area covered: A thorough systematic literature review describing the current evidence and future prospects of therapeutic options for infections caused by ESBL-producing Enterobacteriaceae. Expert commentary: The methods of detecting ESBLs have been evolving. The Clinical and Laboratory Standards Institute and the European Committee on Antimicrobial Susceptibility Testing lowered the MIC breakpoints of cephalosporins against ESBL-producing Enterobacteriaceae in 2010. Phenotypic testing for ESBLs is no longer recommended. Instead, the selection of appropriate antimicrobial agents largely depends on the report of minimum inhibitory concentrations (MICs). To date, therapeutic options for these multidrug-resistant organisms remain limited. The clinical efficacy of piperacillin/tazobactam and cefepime on in vitro-susceptible ESBL-producing Enterobacteriaceae remains a concern. Many studies found an in vitro-in vivo discordance based on current breakpoints. Carbapenems are the most reliable antibiotics for severe infections caused by ESBL-producing Enterobacteriaceae. However, their overuse has led to a serious problem of increasing drug resistance. Recently, ceftolozane/tazobactam and ceftazidime/avibactam have been approved for the treatment of complicated urinary tract infections and complicated intra-abdominal infections. The introduction of these new β-lactam/β-lactamase inhibitor combinations offers new carbapenem-sparing options for the treatment of ESBL infections.

Oral Fosfomycin for the Treatment of Acute and Chronic Bacterial Prostatitis Caused by Multidrug-Resistant Escherichia coli

Acute and chronic bacterial prostatitis in outpatients is commonly treated with oral fluoroquinolones; however, the worldwide dissemination of multidrug-resistant (MDR) Escherichia coli has resulted in therapeutic failures with fluoroquinolones. We reviewed the literature regarding the use of oral fosfomycin in the treatment of acute and chronic prostatitis caused by MDR E. coli. All English-language references on PubMed from 1986 to June 2017, inclusive, were reviewed from the search “fosfomycin prostatitis.” Fosfomycin demonstrates potent in vitro activity against a variety of antimicrobial-resistant E. coli genotypes/phenotypes including ciprofloxacin-resistant, trimethoprim-sulfamethoxazole-resistant, extended-spectrum β-lactamase- (ESBL-) producing, and MDR isolates. Fosfomycin attains therapeutic concentrations (≥4 μg/g) in uninflamed prostatic tissue and maintains a high prostate/plasma ratio up to 17 hours after oral administration. Oral fosfomycin's clinical cure rates in the treatment of bacterial prostatitis caused by antimicrobial-resistant E. coli ranged from 50 to 77% with microbiological eradication rates of >50%. An oral regimen of fosfomycin tromethamine of 3 g·q 24 h for one week followed by 3 g·q 48 h for a total treatment duration of 6–12 weeks appeared to be effective. Oral fosfomycin may represent an efficacious and safe treatment for acute and chronic prostatitis caused by MDR E. coli.

Global epidemiology of CTX-M β-lactamases: temporal and geographical shifts in genotype

Globally, rates of ESBL-producing Enterobacteriaceae are rising. We undertook a literature review, and present the temporal trends in blaCTX-M epidemiology, showing that blaCTX-M-15 and blaCTX-M-14 have displaced other genotypes in many parts of the world. Explanations for these changes can be attributed to: (i) horizontal gene transfer (HGT) of plasmids; (ii) successful Escherichia coli clones; (iii) ESBLs in food animals; (iv) the natural environment; and (v) human migration and access to basic sanitation. We also provide explanations for the changing epidemiology of blaCTX-M-2 and blaCTX-M-27. Modifiable anthropogenic factors, such as poor access to basic sanitary facilities, encourage the spread of blaCTX-M and other antimicrobial resistance (AMR) genes, such as blaNDM, blaKPC and mcr-1. We provide further justification for novel preventative and interventional strategies to reduce transmission of these AMR genes.

Escherichia coli: an old friend with new tidings

Escherichia coli is one of the most-studied microorganisms worldwide but its characteristics are continually changing. Extraintestinal E. coli infections, such as urinary tract infections and neonatal sepsis, represent a huge public health problem. They are caused mainly by specialized extraintestinal pathogenic E. coli (ExPEC) strains that can innocuously colonize human hosts but can also cause disease upon entering a normally sterile body site. The virulence capability of such strains is determined by a combination of distinctive accessory traits, called virulence factors, in conjunction with their distinctive phylogenetic background. It is conceivable that by developing interventions against the most successful ExPEC lineages or their key virulence/colonization factors the associated burden of disease and health care costs could foreseeably be reduced in the future. On the other hand, one important problem worldwide is the increase of antimicrobial resistance shown by bacteria. As underscored in the last WHO global report, within a wide range of infectious agents including E. coli, antimicrobial resistance has reached an extremely worrisome situation that ‘threatens the achievements of modern medicine’. In the present review, an update of the knowledge about the pathogenicity, antimicrobial resistance and clinical aspects of this ‘old friend’ was presented.

Optimization of novel monobactams with activity against carbapenem-resistant Enterobacteriaceae - Identification of LYS228

Metallo-β-lactamases (MBLs), such as New Delhi metallo-β-lactamase (NDM-1) have spread world-wide and present a serious threat. Expression of MBLs confers resistance in Gram-negative bacteria to all classes of β-lactam antibiotics, with the exception of monobactams, which are intrinsically stable to MBLs. However, existing first generation monobactam drugs like aztreonam have limited clinical utility against MBL-expressing strains because they are impacted by serine β-lactamases (SBLs), which are often co-expressed in clinical isolates. Here, we optimized novel monobactams for stability against SBLs, which led to the identification of LYS228 (compound 31). LYS228 is potent in the presence of all classes of β-lactamases and shows potent activity against carbapenem-resistant isolates of Enterobacteriaceae (CRE).

Recombinant Endolysins as Potential Therapeutics against Antibiotic-Resistant Staphylococcus aureus: Current Status of Research and Novel Delivery Strategies

Staphylococcus aureus is one of the most common pathogens of humans and animals, where it frequently colonizes skin and mucosal membranes. It is of major clinical importance as a nosocomial pathogen and causative agent of a wide array of diseases. Multidrug-resistant strains have become increasingly prevalent and represent a leading cause of morbidity and mortality. For this reason, novel strategies to combat multidrug-resistant pathogens are urgently needed. Bacteriophage-derived enzymes, so-called endolysins, and other peptidoglycan hydrolases with the ability to disrupt cell walls represent possible alternatives to conventional antibiotics. These lytic enzymes confer a high degree of host specificity and could potentially replace or be utilized in combination with antibiotics, with the aim to specifically treat infections caused by Gram-positive drug-resistant bacterial pathogens such as methicillin-resistant S. aureus. LysK is one of the best-characterized endolysins with activity against multiple staphylococcal species. Various approaches to further enhance the antibacterial efficacy and applicability of endolysins have been demonstrated. These approaches include the construction of recombinant endolysin derivatives and the development of novel delivery strategies for various applications, such as the production of endolysins in lactic acid bacteria and their conjugation to nanoparticles. These novel strategies are a major focus of this review.

In vitro activity of eravacycline against 2213 Gram-negative and 2424 Gram-positive bacterial pathogens isolated in Canadian hospital laboratories: CANWARD surveillance study 2014-2015

Gram-negative (n=2213) and Gram-positive (n=2424) pathogens isolated from patients in 13 Canadian hospitals in 2014 and 2015 were tested for in vitro susceptibility to eravacycline and comparators using the Clinical and Laboratory Standards Institute broth microdilution method. The concentration of eravacycline inhibiting 90% of isolates (MIC₉₀) ranged from 0.5 to 2μg/mL for 9 species of Enterobacteriaceae tested (n=2067). Eravacycline activity was largely unaffected by extended-spectrum β-lactamase phenotypes in Escherichia coli (n=141) and Klebsiella pneumoniae (n=21). Eravacycline was active against Acinetobacter baumannii (n=28; MIC₉₀, 0.5μg/mL) and Stenotrophomonas maltophilia (n=118; MIC₉₀, 4μg/mL). Eravacycline MIC₉₀ for staphylococci (n=1653), enterococci (n=289), and streptococci (n=482) ranged from 0.12 to 0.25, 0.06 to 0.12, and 0.015 to 0.06μg/mL, respectively. Eravacycline's potency was equivalent to or 2- to 4-fold greater than tigecycline against Enterobacteriaceae and Gram-positive cocci tested. Eravacycline demonstrates promising activity against recent clinical Gram-negative and Gram-positive bacteria, including multidrug-resistant pathogens.

The Molecular and Clinical Epidemiology of Extended-Spectrum Cephalosporin- and Carbapenem-Resistant Enterobacteriaceae at 4 US Pediatric Hospitals

OBJECTIVE

In this report, we aim to describe the epidemiology of extended-spectrum cephalosporin-resistant (ESC-R) and carbapenem-resistant (CR) Enterobacteriaceae infections in children.

METHODS

ESC-R and CR Enterobacteriaceae isolates from normally sterile sites of patients aged <22 years from 4 freestanding pediatric medical centers were collected along with the associated clinical data.

RESULTS

The overall frequencies of ESC-R and CR isolates according to hospital over the 4-year study period ranged from 0.7% to 2.8%. Rates of ESC-R or CR Escherichia coli and Klebsiella pneumoniae varied according to hospital and ranged from 0.75 to 3.41 resistant isolates per 100 isolates (P < .001 for any differences). E coli accounted for 272 (77%) of the resistant isolates; however, a higher rate of resistance was observed in K pneumoniae isolates (1.78 vs 1.27 resistant isolates per 100 same-species isolates, respectively; P = .005). One-third of the infections caused by ESC-R or CR E coli were community-associated. In contrast, infections caused by ESC-R or CR K pneumoniae were more likely than those caused by resistant E coli to be healthcare- or hospital-associated and to occur in patients with an indwelling device (P ≤ .003 for any differences, multivariable logistic regression). Nonsusceptibility to 3 common non-β-lactam agents (ciprofloxacin, gentamicin, and trimethoprim-sulfamethoxazole) occurred in 23% of the ESC-R isolates. The sequence type 131-associated fumC/fimH-type 40-30 was the most prevalent sequence type among all resistant E coli isolates (30%), and the clonal group 258-associated allele tonB79 was the most prevalent allele among all resistant K pneumoniae isolates (10%).

CONCLUSIONS

The epidemiology of ESC-R and CR Enterobacteriaceae varied according to hospital and species (E coli vs K pneumoniae). Both community and hospital settings should be considered in future research addressing pediatric ESC-R Enterobacteriaceae infection.

Co-Occurrence of Plasmid-Mediated AmpC β-Lactamase Activity Among Klebsiella pneumoniae and Escherichia Coli

Introduction:

Extended-spectrum β-lactamases (ESBLs), including the AmpC type, are important mechanisms of resistance among Klebsiella pneumoniae and Escherichia coli isolates.

Objective:

The aim of the study was to investigate the occurrence of AmpC-type β-lactamase producers isolated from two hospitals in Tripoli, Libya.

Methods:

All clinical isolates (76 K. pneumoniae and 75 E. coli) collected over two years (2013-2014) were evaluated for susceptibility to a panel of antimicrobials and were analyzed phenotypically for the ESBL and AmpC phenotype using E-test and ESBL and AmpC screen disc test. Both ESBL and AmpC-positive isolates were then screened for the presence of genes encoding plasmid-mediated AmpC β-lactamases by polymerase chain reaction (PCR).

Results:

Of the K. pneumoniae and E. coli tested, 75% and 16% were resistant to gentamicin, 74% and 1.3% to imipenem, 71% and 12% to cefoxitin, 80% and 12% to cefepime, 69% and 22.6% to ciprofloxacin, respectively. None of the E. coli isolates were multidrug resistant compared with K. pneumoniae (65.8%). K. pneumoniae ESBL producers were significantly higher (85.5%) compared with (17.3%) E. coli isolates (P <0.0001, OR=4.93). Plasmid-mediated AmpC genes were detected in 7.9% of K. pneumoniae, and 4% E. coli isolates. There was low agreement between phenotypic and genotypic methods, phenotypic testing underestimated detection of AmpC enzyme and did not correlate well with molecular results. The gene encoding CMY enzyme was the most prevalent (66.6%) of AmpC positive isolates followed by MOX, DHA and EBC. Only one AmpC gene was detected in 5/9 isolates, i.e, bla_CMY (n=3), bla_MOX (n=1), bla_DHA (n=1). However, co-occurrence of AmpC genes were evident in 3/9 isolates with the following distribution: bla_CMY and bla_EBC (n=1), and bla_CMY and bla_MOX (n=2). Neither bla_FOX nor bla_ACC was detected in all tested isolates. All AmpC positive strains were resistant to cefoxitin and isolated from patients admitted to intensive care units.

Conclusion:

Further studies are needed for detection of other AmpC variant enzyme production among such isolates. Continued surveillance and judicious antibiotic usage together with the implementation of efficient infection control measures are absolutely required.

Complete sequences of two novel bla NDM-1-harbouring plasmids from two Acinetobacter towneri isolates in China associated with the acquisition of Tn125

Two novel New Delhi metallo-β-lactamase-1 (NDM-1)-positive plasmids containing a complete composite transposon, Tn125, from two respective Acinetobacter towneri isolates were characterized. Plasmid pNDM-GJ01 (30,293 bp) isolated from A. towneri G165 did not show homology to any known plasmid structure, except for the transposon Tn125 containing bla_NDM-1. A novel repB gene and two XRE-type transcriptional regulators were found in pNDM-GJ01. Plasmid pNDM-GJ02 (62,011 bp) isolated from A. towneri G295 showed the highest homology to pBJAB0715 (41% coverage, 99% nucleotide identity). In addition to the bla_NDM-1-harbouring transposon Tn125, pNDM-GJ02 also had an IS26-composite transposon, which contains ISCR1 and two class 1 integrons carrying different cassette arrays. Both clinical isolates were highly resistant to β-lactams and susceptible to tigecycline and colistin. Ten other resistance genes were detected in G295, and one other resistance gene was detected in G165. No transconjugant was obtained from any of the donors by broth and filter mating. The emergence of these two novel plasmids carrying NDM-1 in Acinetobacter spp., pNDM-GJ01 and pNDM-GJ02, suggests Tn125 mobile integration.

The ecology of extended-spectrum β-lactamases (ESBLs) in the developed world

BACKGROUND

Since the initial appearance in the 1980s, Enterobacteriaceae producing extended-spectrum β-lactamase (ESBL) have increased in prevalence and emerged as a major antimicrobial-resistant pathogen. The source of these antimicrobial-resistant bacteria in the developed world is an area of active investigation.

METHODS

A standard internet search was conducted with a focus on the epidemiology and potential sources of ESBL-producing Enterobacteriaceae in the developed world.

RESULTS

The last decade has witnessed several major changes in the epidemiology of these bacteria: replacement of TEM and SHV-type ESBLs by CTX-M-family ESBLs, emergence of Escherichia coli ST131 as a prevalent vehicle of ESBL, and spread of ESBL-producing E. coli in the community. The most studied potential sources of ESBL-producing Enterobacteriaceae in humans in the community include food and companion animals, the environment and person-to-person transmission, though definitive links are yet to be established. Evidence is emerging that international travel may serve as a major source of introduction of ESBL-producing Enterobacteriaceae into the developed world.

CONCLUSIONS

ESBL-producing Enterobacteriaceae has become a major multidrug-resistant pathogen in the last two decades, especially in the community settings. The multifactorial nature of its expansion poses a major challenge in the efforts to control them.

Carbapenem-Resistant Enterobacteriaceae: A Strategic Roadmap for Infection Control

The incidence of carbapenem-resistant Enterobacteriaceae (CRE) has increased worldwide with great regional variability. Infections caused by these organisms are associated with crude mortality rates of up to 70%. The spread of CRE in healthcare settings is both an important medical problem and a major global public health threat. All countries are at risk of falling victim to the emergence of CRE; therefore, a preparedness plan is required to avoid the catastrophic natural course of this epidemic. Proactive and adequate preventive measures locally, regionally, and nationally are required to contain the spread of these bacteria. The keys to success in preventing the establishment of CRE endemicity in a region are early detection through targeted laboratory protocols and containment of spread through comprehensive infection control measures. This guideline provides a strategic roadmap for infection control measures based on the best available evidence and expert opinion, to enable preparation of a multifaceted preparedness plan to abort epidemics of CRE. Infect Control Hosp Epidemiol 2017;38:580-594.

Fecal carriage of MDROs in a population of Lebanese elderly: Dynamics and impact on bacterial fitness

Muti-Drug Resistant Organisms (MDROs) are problematic all over the world, especially in Lebanon. High fecal carriage rates of MDR Enterobacteriaceae were reported from Lebanese nursing homes. Some studies show that MDROs have a fitness cost as compared to sensitive isolates. In this study, the competitive growth of MDR Escherichia coli obtained from fecal samples from elderly is assessed. Fecal swabs from ten elderly patients from a Lebanese nursing home were obtained between June and December, 2015. Isolates were identified by API 20E and antimicrobial susceptibilities were determined. Production of ESBL (extended spectrum β lactamase), MBL (metallo β lactamse), AmpC and KPC (Klebsiella pneumonia carbapenemase) was detected phenotypically by the use of EDTA, PBA, cloxacillin, and DDSTs. In-vitro competition assays were performed using E. coli isolates with different combinations of bacterial resistance. A total of 117 isolates was obtained with 71.8% E. coli, 7.7% of which were ESBL and 5.1% AmpC producers. Sensitive E. coli isolates out-competed all other isolates when in competition, followed sequentially by ESBL, AmpC, and OXA-48 (oxacillin) producers. This study shows an advantage of sensitive E. coli strains obtained from fecal samples to out-compete resistant strains in specific in-vitro conditions. This ability could be exploited in the elimination of MDR organisms from the gut flora, after further investigation.

Molecular Characteristics and Antibiotic Resistance Profiles of Klebsiella Isolates in Mthatha, Eastern Cape Province, South Africa

The increase in the incidence of extended-spectrum β-lactamase- (ESBL-) producing Klebsiella species has become a serious problem worldwide, because of their incrimination in antibiotic resistance. The objective of this study is to investigate the resistance genes responsible for ESBL-producing Klebsiella species and carbapenemase-producing Klebsiella (CRE) isolated in Mthatha and to study their epidemiology. A prospective, descriptive study of 202 nonrepetitive samples from patients was obtained from Nelson Mandela Academic Hospital. The cultured Klebsiella isolates were subjected to antimicrobial susceptibility tests and the polymerase chain reaction of bla_CTX-M, bla_TEM, bla_SHV, bla_KPC, and bla_NDM genes. Overall K. pneumoniae were the majority with 169 (83.7%) species isolates, followed by K. oxytoca with 29 (14.4%), while K. ozaenae and Raoultella ornithinolytica were 2 (0.9%) each. The prevalence of ESBL production in all Klebsiella species was 117 (57.9%). ESBL-genotypic resistance is driven in Mthatha by bla_SHV 121 (77.1%) followed by bla_TEM 105 (66.9%) and bla_CTX-M at 89 (56.7%). The most common ESBL genotype combination among the Klebsiella was bla_TEM + bla_SHV + bla_CTX-M at 79 (50.3%). There is a steady increase in the rate of ESBL genes in the last five years.

Updates in the Management of Cephalosporin-Resistant Gram-Negative Bacteria

Resistance to cephalosporins is now common among Gram-negative bacterial infections, including those caused by the Enterobacteriaceae and Pseudomonas aeruginosa, posing a major threat to public health. As resistance to the traditional drugs of choice for these infections, carbapenems, has also become increasingly common, interest in cefepime and piperacillin-tazobactam as carbapenem-sparing alternatives has increased. Additionally, the availability of the novel β-lactam-β-lactamase inhibitor combinations ceftolozane-tazobactam and ceftazidime-avibactam has added to the antimicrobial armamentarium available to treat these multidrug-resistant infections. Here, we review the recent literature on the use of carbapenem-sparing alternatives and highlight the potential utility of novel antimicrobials.

Emergence of serotype K1 Klebsiella pneumoniae ST23 strains co-producing the plasmid-mediated AmpC beta-lactamase DHA-1 and an extended-spectrum beta-lactamase in Korea

BACKGROUND

Serotype K1 Klebsiella pneumoniae has emerged as an important community pathogen causing various infections, including liver abscesses. Although serotype K1 K. pneumoniae community isolates have been reported as susceptible to most classes of antimicrobial agents, a few cases of infection caused by extended-spectrum beta-lactamase (ESBL)-producing serotype K1 K. pneumoniae have recently been reported in Asian countries. We identified three ESBL-producing strains of serotype K1 K. pneumoniae and conducted a molecular characterization of their drug resistance.

METHODS

Three ESBL-producing serotype K1 K. pneumoniae ST23 strains were identified from strains in the Asian Bacterial Bank. Antimicrobial susceptibility testing was performed using the broth microdilution method, and ESBL production was tested by the double-disk synergy test and a confirmatory test. PCR was performed to detect the genes for plasmid-mediated ESBL and AmpC beta-lactamases.

RESULTS

All three strains were resistant to cefotaxime, ceftazidime, and piperacillin/tazobactam, and all were determined to be ESBL-producers. No known ESBL genes, including bla_SHV, bla_TEM, bla_CTX-M, bla_GES, bla_PER, and bla_VEB, were detected among the three strains. Of all plasmid-mediated AmpC beta-lactamase (PAB) genes, including bla_DHA-1, bla_CMY, bla_FOX, and bla_MOX, the bla_DHA-1 gene was detected in two of the strains. The PFGE patterns revealed that the two isolates carrying bla_DHA-1 were closely related (84% similarity).

CONCLUSIONS

No ESBL genes were detected among three ESBL-producing serotype K1 K. pneumoniae ST23 strains. Two strains contained the PAB gene bla_DHA-1. The emergence of resistant strains of community-origin serotype K1 K. pneumoniae has important implications for effective treatment and infection control practices.

High Prevalence of ESBL-Producing Klebsiella pneumoniae Causing Community-Onset Infections in China

The aim of this work was to investigate the epidemiological and genetic characteristics of ESBL-producing Klebsiella pneumoniae (ESBL-Kp) causing community-onset infections. K. pneumoniae isolates were collected from 31 Chinese secondary hospitals between August 2010 and 2011. Genes encoding ESBL and AmpC beta-lactamases were detected by PCR. The isolates were assigned to sequence types (STs) using multi-locus sequence typing (MLST). Eleven ESBL-Kp strains were selected for whole-genome sequencing (WGS) for investigating the genetic environment and plasmids encoding ESBL genes. A total of 578 K. pneumoniae isolates were collected, and 184 (31.8%) carried ESBL genes. The prevalence of ESBL-Kp varied from different geographical areas of China (10.2–50.3%). The three most prevalent ESBL genes were bla_CTX-M-14 (n = 74), bla_CTX-M-15 (n = 60), and bla_CTX-M-3 (n = 40). MLST assigned 127 CTX-M-14 and CTX-M-15 producers to 54 STs, and CC17 was the most prevalent population (12.6%). STs (23, 37, and 86) that were known frequently associated with hypervirulent K. pneumoniae (hvKP) account for 14.1% (18/127). Phylogenetic analysis by concatenating the seven loci of MLST revealed the existence of ESBL-producing K. quasipneumoniae (two strains) and K. varricola (one strain), which was further confirmed by WGS. This study highlights the challenge of community-onset infections caused by ESBL-Kp in China. The prevalence of STs frequently associating with hvKP should be of concern. Surveillance of ESBL-KP causing community-onset infections now appears imperative.

The Antimicrobial Susceptibility of Klebsiella pneumoniae from Community Settings in Taiwan, a Trend Analysis

Drug-resistant Klebsiella pneumoniae, especially extended-spectrum β-lactamase (ESBL)- and/or AmpC β-lactamase-producing strains, is an emerging problem worldwide. However, few data focusing on drug susceptibility of K. pneumoniae from community is available. In this study, we analyzed 1016 K. pneumoniae isolates from outpatients or those visiting emergency rooms collected during 2002–2012 from Taiwan Surveillance of Antimicrobial Resistance program. Significantly decreased susceptibilities to 3^rd generation cephalosporins and ciprofloxacin were found during the study period. By 2012, susceptibility to cefotaxime and ciprofloxacin was 83.6% and 81.6%, respectively. The prevalence of ESBL-producers increased from 4.8% in 2002 to 11.9% in 2012 (P = 0.012), while that of AmpC β-lactamase-producers increased from 0% to 9.5% in the same period (P < 0.001). Phylogenic analysis of the ESBL and AmpC-β-lactamase-producers by pulsed-field gel electrophoresis and multi-locus sequence typing revealed wide genetic diversity even among the most common sequence type 11 isolates (33.0%). By multivariate analysis, later study year, elderly, and urine isolates were associated with carriage of ESBL genes, while only urine isolates were associated with carriage of AmpC β-lactamase genes. Further studies are needed to determine which antibiotics are reasonable empirical therapy options for patients presenting with severe sepsis that might be caused by K. pneumoniae.

An update on the management of urinary tract infections in the era of antimicrobial resistance

Urinary tract infections (UTIs) caused by antibiotic-resistant Gram-negative bacteria are a growing concern due to limited therapeutic options. Gram-negative bacteria, specifically Enterobacteriaceae, are common causes of both community-acquired and hospital acquired UTIs. These organisms can acquire genes that encode for multiple antibiotic resistance mechanisms, including extended-spectrum-lactamases (ESBLs), AmpC- β -lactamase, and carbapenemases. The assessment of suspected UTI includes identification of characteristic symptoms or signs, urinalysis, dipstick or microscopic tests, and urine culture if indicated. UTIs are categorized according to location (upper versus lower urinary tract) and severity (uncomplicated versus complicated). Increasing rates of antibiotic resistance necessitate judicious use of antibiotics through the application of antimicrobial stewardship principles. Knowledge of the common causative pathogens of UTIs including local susceptibility patterns are essential in determining appropriate empiric therapy. The recommended first-line empiric therapies for acute uncomplicated bacterial cystitis in otherwise healthy adult nonpregnant females is a 5-day course of nitrofurantion or a 3-g single dose of fosfomycin tromethamine. Second-line options include fluoroquinolones and β-lactams, such as amoxicillin-clavulanate. Current treatment options for UTIs due to AmpC- β -lactamase-producing organisms include fosfomycin, nitrofurantion, fluoroquinolones, cefepime, piperacillin-tazobactam and carbapenems. In addition, treatment options for UTIs due to ESBLs-producing Enterobacteriaceae include nitrofurantion, fosfomycin, fluoroquinolones, cefoxitin, piperacillin-tazobactam, carbapenems, ceftazidime-avibactam, ceftolozane-tazobactam, and aminoglycosides. Based on identification and susceptibility results, alternatives to carbapenems may be used to treat mild-moderate UTIs caused by ESBL-producing Enterobacteriaceae. Ceftazidime-avibactam, colistin, polymixin B, fosfomycin, aztreonam, aminoglycosides, and tigecycline are treatment options for UTIs caused by carbapenem-resistant Enterobacteriaceae (CRE). Treatment options for UTIs caused by multidrug resistant (MDR)-Pseudomonas spp. include fluoroquinolones, ceftazidime, cefepime, piperacillin-tazobactam, carbapenems, aminoglycosides, colistin, ceftazidime-avibactam, and ceftolozane-tazobactam. The use of fluoroquinolones for empiric treatment of UTIs should be restricted due to increased rates of resistance. Aminoglycosides, colistin, and tigecycline are considered alternatives in the setting of MDR Gram-negative infections in patients with limited therapeutic options.

Rapid increase in resistance to third generation cephalosporins, imipenem and co-resistance in Klebsiella pneumoniae from isolated from 7,140 blood-cultures (2010-2014) using EARS-Net data in Spain

INTRODUCTION

An analysis was made about the evolution of resistance to 3rd generation cephalosporins, imipenem, and other antibiotics in invasive isolates of Klebsiella pneumoniae (K. pneumoniae) according to the Spanish EARS-Net database (2010-2014).

METHODS

Forty-two hospitals from 16 Autonomous Communities with an approximate population coverage of 33% participated.

RESULTS

A total 7,140 pneumoniae corresponding to the same number of patients were studied. Overall resistance percentages (I+R) were: cefotaxime 15.8%, ceftazidime 13.7%, imipenem 1.7%, ciprofloxacin 20.1%, tobramycin 14.1%, gentamicin 10.4%, and amikacin 1.9%. Resistance to 3rd generation cephalosporins increased from 9.8% (2010) to 19% (2014); to ciprofloxacin from 15.4% (2010) to 19.6% (2014); to gentamicin from 6.2% (2010) to 10.3% (2014) and to tobramycin from 7.1% (2010) to 14.2% (2014) (p<.001 in all cases). Combined resistance to 3rd generation cephalosporins, ciprofloxacin, and aminoglycosides increased from 3.3% (2010) to 9.7% (2014) (p<.001). Resistance to imipenem also increased from 0.27% (2010) to 3.46% (2014) (p<.001). A total of 121 isolates were resistant to imipenem, of which 104 (86%) produced carbapenemases: 74 OXA-48, 14 VIM, 9 KPC (6 KPC-2 and 3 KPC-3), 6 IMP, and 1 GES.

CONCLUSIONS

Over the 5 year period (2010-2014), resistance to 3rd generation cephalosporins in invasive K. pneumoniae in Spain has doubled. The combined resistance to 3rd generation cephalosporins, ciprofloxacin, and aminoglycosides has tripled, and imipenem resistance has increased almost 13 times, mostly due to the spread of carbapenemase-producing isolates.

Isolation and Characterization of Escherichia coli Sequence Type 131 and Other Antimicrobial-Resistant Gram-Negative Bacilli from Clinical Stool Samples from Veterans

Emerging multidrug-resistant (MDR) Gram-negative bacilli (GNB), including Escherichia coli sequence type 131 (ST131) and its resistance-associated H30 subclone, constitute an ever-growing public health threat. Their reservoirs and transmission pathways are incompletely defined. To assess diarrheal stools as a potential reservoir for ST131-H30 and other MDR GNB, we cultured 100 clinical stool samples from a Veterans Affairs Medical Center clinical laboratory (October to December 2011) for fluoroquinolone- and extended-spectrum cephalosporin (ESC)-resistant E. coli and other GNB, plus total E. coli We then characterized selected resistant and susceptible E. coli isolates by clonal group, phylogenetic group, virulence genotype, and pulsotype and screened all isolates for antimicrobial resistance. Overall, 79 of 100 stool samples yielded GNB (52 E. coli; 48 other GNB). Fifteen samples yielded fluoroquinolone-resistant E. coli (10 were ST131, of which 9 were H30), 6 yielded ESC-resistant E. coli (2 were ST131, both non-H30), and 31 yielded susceptible E. coli (1 was ST131, non-H30), for 13 total ST131-positive samples. Fourteen non-E. coli GNB were ESC resistant, and three were fluoroquinolone resistant. Regardless of species, almost half (46%) of the fluoroquinolone-resistant and/or ESC-resistant non-E. coli GNB were resistant to at least three drug classes. Fecal ST131 isolates closely resembled reference clinical ST131 isolates according to virulence genotypes and pulsed-field gel electrophoresis (PFGE) profiles. Thus, a substantial minority (30%) of veterans with diarrhea who undergo stool testing excrete antibiotic-resistant GNB, including E. coli ST131. Consequently, diarrhea may pose transmission risks for more than just diarrheal pathogens and may help disseminate clinically relevant ST131 strains and other MDR GNB within hospitals and the community.

Host-Specific Patterns of Genetic Diversity among IncI1-Iγ and IncK Plasmids Encoding CMY-2 β-Lactamase in Escherichia coli Isolates from Humans, Poultry Meat, Poultry, and Dogs in Denmark

CMY-2 is the most common plasmid-mediated AmpC β-lactamase in Escherichia coli isolates of human and animal origin. The aim of this study was to elucidate the epidemiology of CMY-2-producing E. coli in Denmark. Strain and plasmid relatedness was studied in 93 CMY-2-producing clinical and commensal E. coli isolates collected from 2006 to 2012 from humans, retail poultry meat, broilers, and dogs. Multilocus sequence typing (MLST), antimicrobial susceptibility testing, and conjugation were performed in conjunction with plasmid replicon typing, plasmid multilocus sequence typing (pMLST), restriction fragment length polymorphism (RFLP), and sequencing of selected blaCMY-2-harboring plasmids. MLST revealed high strain diversity, with few E. coli lineages occurring in multiple host species and sample types. blaCMY-2 was detected on plasmids in 83 (89%) isolates. Most (75%) of the plasmids were conjugative and did not (96%) cotransfer resistance to antimicrobials other than cephalosporins. The main replicon types identified were IncI1-Iγ (55%) and IncK (39%). Isolates from different host species mainly carried distinct plasmid subtypes. Seven of the 18 human isolates harbored IncI1-Iγ/sequence type 2 (ST2), IncI1-Iγ/ST12, or IncK plasmids highly similar to those found among animal isolates, even though highly related human and animal plasmids differed by nonsynonymous single nucleotide polymorphisms (SNPs) or insertion sequence elements. This study clearly demonstrates that the epidemiology of CMY-2 can be understood only by thorough plasmid characterization. To date, the spread of this β-lactam resistance determinant in Denmark is mainly associated with IncK and IncI1-Iγ plasmids that are generally distributed according to host-specific patterns. These baseline data will be useful to assess the consequences of the increasing human exposure to CMY-2-producing E. coli via animal sources.

IMPORTANCE

CMY-2 is the most common plasmid-mediated AmpC β-lactamase in Escherichia coli This β-lactamase is poorly inhibited by clavulanic acid and confers resistance to cephamycins, third-generation cephalosporins, and aztreonam. Furthermore, resistance to carbapenems has been reported in E. coli as a result of production of plasmid-encoded CMY-2 β-lactamase in combination with decreased outer membrane permeability. The gene encoding CMY-2 generally resides on transferable plasmids belonging to different incompatibility groups. The prevalence of CMY-2-mediated cephalosporin resistance in E. coli varies significantly depending on the geographical region and host. This study demonstrates that the epidemiology of CMY-2 can be understood only by thorough plasmid characterization. To date, the spread of this β-lactam resistance determinant in Denmark is mainly associated with IncK and IncI1-Iγ plasmids, which are generally distributed according to host-specific patterns. These data will be useful to assess the consequences of the increasing human exposure to CMY-2-producing E. coli via animal sources.

Susceptibility patterns and ESBL rates of Escherichia coli from urinary tract infections in Canada and the United States, SMART 2010-2014

Increasing antimicrobial resistance in urinary tract infections (UTI) is a concern. To evaluate resistance trends, 3498 Escherichia coli UTI isolates were collected from 2010 to 2014 in the Study for Monitoring Antimicrobial Resistance Trends (SMART) in Canada and United States (US). ESBL phenotype and susceptibility were determined using CLSI microdilution and breakpoints. US ESBL rates increased in 2010-2014 (7.8-18.3%, P < 0.0001), especially among hospital-associated (HA) infections, males, and older patients (≥65 years). Overall, ESBL rates in Canada showed no significant trend (10.4-13.0%. P = 0.079), and were lower than US rates in recent years, but increased significantly among community-associated (CA) infections, females, and older patients. In the US, but not Canada, susceptibility to cephalosporins and fluoroquinolones among 2013-2014 isolates was significantly lower in isolates from HA than CA UTI, males than females, and ≥65- than <65-year-olds. These observations confirm increasing resistance in E. coli. Subgroup analyses like these may help direct empirical therapy.

Population Pharmacokinetic Assessment and Pharmacodynamic Implications of Pediatric Cefepime Dosing for Susceptible-Dose-Dependent Organisms

The Clinical and Laboratory Standards Institute (CLSI) revised cefepime (CFP) breakpoints forEnterobacteriaceaein 2014, and MICs of 4 and 8 μg/ml were reclassified as susceptible-dose dependent (SDD). Pediatric dosing to provide therapeutic concentrations against SDD organisms has not been defined. CFP pharmacokinetics (PK) data from published pediatric studies were analyzed. Population PK parameters were determined using NONMEM, and Monte Carlo simulation was performed to determine an appropriate CFP dosage regimen for SDD organisms in children. A total of 664 CFP plasma concentrations from 91 neonates, infants, and children were included in this analysis. The median patient age was 1.0 month (interquartile range [IQR], 0.2 to 11.2 months). Serum creatinine (SCR) and postmenstrual age (PMA) were covariates in the final PK model. Simulations indicated that CFP dosing at 50 mg/kg every 8 h (q8h) (as 0.5-h intravenous [i.v.] infusions) will maintain free-CFP concentrations in serum of >4 and 8 μg/ml for >60% of the dose interval in 87.1% and 68.6% of pediatric patients (age, ≥30 days), respectively, and extending the i.v. infusion duration to 3 h results in 92.3% of patients with free-CFP levels above 8 μg/ml for >60% of the dose interval. CFP clearance (CL) is significantly correlated with PMA and SCR. A dose of 50 mg/kg of CFP every 8 to 12 h does not achieve adequate serum exposure for older children with serious infections caused by Gram-negative bacilli with a MIC of 8 μg/ml. Prolonged i.v. infusions may be useful for this population.

Epidemic potential of Escherichia coli ST131 and Klebsiella pneumoniae ST258: a systematic review and meta-analysis

OBJECTIVES

Observational studies have suggested that Escherichia coli sequence type (ST) 131 and Klebsiella pneumoniae ST258 have hyperendemic properties. This would be obvious from continuously high incidence and/or prevalence of carriage or infection with these bacteria in specific patient populations. Hyperendemicity could result from increased transmissibility, longer duration of infectiousness, and/or higher pathogenic potential as compared with other lineages of the same species. The aim of our research is to quantitatively estimate these critical parameters for E. coli ST131 and K. pneumoniae ST258, in order to investigate whether E. coli ST131 and K. pneumoniae ST258 are truly hyperendemic clones.

PRIMARY OUTCOME MEASURES

A systematic literature search was performed to assess the evidence of transmissibility, duration of infectiousness, and pathogenicity for E. coli ST131 and K. pneumoniae ST258. Meta-regression was performed to quantify these characteristics.

RESULTS

The systematic literature search yielded 639 articles, of which 19 data sources provided information on transmissibility (E. coli ST131 n=9; K. pneumoniae ST258 n=10)), 2 on duration of infectiousness (E. coli ST131 n=2), and 324 on pathogenicity (E. coli ST131 n=285; K. pneumoniae ST258 n=39). Available data on duration of carriage and on transmissibility were insufficient for quantitative assessment. In multivariable meta-regression E. coli isolates causing infection were associated with ST131, compared to isolates only causing colonisation, suggesting that E. coli ST131 can be considered more pathogenic than non-ST131 isolates. Date of isolation, location and resistance mechanism also influenced the prevalence of ST131. E. coli ST131 was 3.2 (95% CI 2.0 to 5.0) times more pathogenic than non-ST131. For K. pneumoniae ST258 there were not enough data for meta-regression assessing the influence of colonisation versus infection on ST258 prevalence.

CONCLUSIONS

With the currently available data, it cannot be confirmed nor rejected, that E. coli ST131 or K. pneumoniae ST258 are hyperendemic clones.

Kisameet Clay Isolated from the Central Coast of British Columbia, Canada, Demonstrates Broad-Spectrum Antimicrobial Activity

Clay minerals are naturally occurring layered phyllosilicates which consist of fine particles and possess antimicrobial activity. In a recent article, Behroozian et al. obtained Kisameet clay (KC) from Kisameet, from the central coast of British Columbia, Canada, northwest of Vancouver and assessed its antimicrobial activity versus 16 selected ESKAPE pathogens (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter spp.) possessing a variety of different resistance profiles [S. Behroozian, S. L. Svensson, and J. Davies, mBio 7(1):e01842-15, 2016, http://dx.doi.org/10.1128/mBio.01842-15]. KC demonstrated complete bacterial eradication of Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Staphylococcus aureus within 24 h. For Enterobacter spp., the organisms were eradicated with 1% KC within 5 h, while for Enterococcus faecium, it took 48 h to kill all organisms. Although many questions need to be answered, these exciting findings highlight the importance of testing natural substances/products from around the globe to assess whether they possess antimicrobial activity and potential for usage as topical, oral, or systemic agents for the treatment of multidrug-resistant pathogens.

Frequency of Plasmid-Mediated AmpC β-Lactamases in Escherichia coli Isolates from Urine Samples in São Paulo, Brazil

Plasmid-mediated AmpC β-lactamases (PMACBLs) in Enterobacteriaceae encode resistance to third-generation cephalosporins, and these can mediate carbapenem resistance when associated with porin loss. However, no standardized phenotypic method is available for detecting these enzymes in the clinical microbiology laboratory. Limited data are available concerning the frequency of PMACBLs in Enterobacteriaceae in Brazil. This study was conducted in response to an increased cefoxitin (CFO) resistance rate of 3.7% in Escherichia coli isolates from urine samples from patients with suspected urinary tract infections during 2010. We collected 2,266 E. coli isolates prospectively during January 2012. A total of 109 (4.8%) isolates were nonsusceptible to CFO. These strains were further examined using multiplex PCR for the presence of genes encoding PMACBLs and using inhibitor assays with CFO and ceftazidime (CAZ) disks with and without phenylboronic acid. Pulsed-field gel electrophoresis was used to evaluate clonal dissemination. Genes encoding PMACBLs were detected in 1.8% of the isolates from inpatients and 0.46% of isolates from outpatients. The most prevalent gene was blaCMY-2 and blaCMY-4 was also detected. The phenotypic analysis showed 100% sensitivity and specificity for CMY-2 and CMY-4 when CFO-resistant isolates with a minimum zone diameter difference of 5 mm for CAZ or CAZ and CFO were considered positive. Although most of the isolates were nonclonal, one clonal group with two isolates was observed. Thus, the most frequent PMACBL in E. coli from São Paulo, Brazil is CMY-2, and both clonal and plasmid-mediated dissemination occur.

In vitro activities and detection performances of cefmetazole and flomoxef for extended-spectrum β-lactamase and plasmid-mediated AmpC β-lactamase-producing Enterobacteriaceae

To investigate the in vitro activities of cephamycins (cefmetazole and flomoxef) for extended-spectrum β-lactamase (ESBL)- and plasmid-mediated AmpC β-lactamase (pAmpC)-producing Enterobacteriaceae, a total of 574 third-generation cephalosporin-resistant clinical isolates were collected at a Japanese multicenter study. PCR and sequencing identified 394 isolates with only ESBL genes, 63 isolates with only pAmpC genes, and 6 isolates with both ESBL and pAmpC genes. blaCTX-M types predominated 95.5% of the ESBL genes, and blaCMY-2 predominated 91.3% of the pAmpC genes. The MIC50/90 values of cefmetazole and flomoxef were ≤ 1/4 and ≤ 1/≤ 1 μg/mL for isolates with only ESBL genes, respectively, and 16/>16 and 8/16 μg/mL for isolates with only pAmpC genes, respectively. Flomoxef ≥ 4 μg/mL had the best screening performance for the detection of isolates with pAmpC genes. Flomoxef had better in vitro activities against ESBL-producing Enterobacteriaceae and provided a clearer distinction between ESBL and pAmpC-producing Enterobacteriaceae compared to cefmetazole.

Antimicrobial Susceptibility Patterns Among Extended-Spectrum β-Lactamase-Producing Enterobacteriaceae in a Large Pediatric Hospital in the United Kingdom

Of the 551 extended spectrum β-lactamase-producing isolates characterized, the MIC90 for Escherichia coli, Klebsiella spp., and Enterobacter spp. were in the susceptible range when tested against meropenem, but were in the resistant range for all other antimicrobials tested excluding E coli and Klebsiella spp. against ertapenem and ciprofloxacin, and for Enterobacter spp. against ciprofloxacin.

Epidemiologic and Genotypic Review of Carbapenemase-Producing Organisms in British Columbia, Canada, between 2008 and 2014

Carbapenemase-producing organisms (CPOs) are a serious emerging problem for health care facilities worldwide. Owing to their resistance to most antimicrobial therapies, CPOs are difficult to treat and pose a challenge for infection prevention and control. Since 2010, lab-based surveillance for CPOs and PCR-based testing were implemented in British Columbia (BC), Canada. A review of CPOs in BC from 2008 to March 2014 was done to characterize the resistance mechanisms and possible clonal strain transmission and to compare pulsed-field gel electrophoresis (PFGE), multilocus sequence typing (MLST), and plasmid restriction fragment length polymorphism (RFLP) as molecular typing tools. During this study period, a total of 177 CPO cases were identified. Patient demographics and travel history were reviewed, and a descriptive analysis was carried out. PFGE profiles, MLST, and plasmid RFLP analysis for a subset of Escherichia coli, Klebsiella pneumoniae, and Enterobacter species isolates were obtained and analyzed. Our findings demonstrate that CPOs have been increasing in number in BC over time, from 1 isolate/year retrospectively identified in 2008 and 2009 to 82 isolates in 2013 and 30 isolates in the first quarter of 2014. Overall, K. pneumoniae isolates lack clonality, although some seemingly related clusters have been found. Plasmid analysis showed evidence of the spread of plasmids carrying carbapenemase-encoding genes between the examined isolates. Analysis of Enterobacter cloacae isolates revealed a more clonal nature of these CPOs in BC. The presence of related clusters provides evidence of interpatient organism transmission both within and between institutions. Although in our study, NDM-harboring E. cloacae isolates appeared to spread clonally, the spread of carbapenem resistance in K. pneumoniae seems to be plasmid mediated.

Molecular characterisation of acquired and overproduced chromosomal blaAmpC in Escherichia coli clinical isolates

Escherichia coli recovered from three hospitals in Barcelona (Spain) were studied to determine the prevalence of isolates with acquired AmpC (ac-AmpC) and/or overproduced chromosomal AmpC (c-AmpC). Mechanisms involved in blac-AmpC overexpression, blaac-AmpC and the plasmids associated with their distribution as well as the prevalence of plasmid-mediated quinolone resistance (PMQR) in AmpC-producing isolates were also determined. Isolates were selected according to their resistance phenotype. blaac-AmpC, alterations in the blac-AmpC promoter/attenuator, and PMQR genes [qnrA, qnrB, qnrS, aac(6')-Ib-cr and qepA] were characterised by PCR and sequencing. blac-AmpC expression was determined by qRT-PCR. Population structure analysis was performed using PFGE, MLST and phylogenetic group PCR. Plasmids carrying blaac-AmpC were characterised by PCR-based replicon typing and S1-PFGE. IncI1 and IncF plasmids were also analysed by plasmid MLST and replicon sequence typing, respectively. Among 21563 E. coli isolates, 240 (1.1%) overproduced AmpC β-lactamases, including 180 (75.0%) harbouring ac-AmpC (132 CMY-2 variants and 48 DHA-1) and 60 (25.0%) c-AmpC enzymes. Three mutation profiles in the blac-AmpC promoter/attenuator were associated with a 72.5-, 19.9- and 5.8-fold increased expression, respectively. Moreover, 63.3% of ac-AmpC and 43.3% of c-AmpC isolates belonged to B2, D, E or F phylogenetic groups. PMQR was found in 31% of ac-AmpC isolates [38 qnrB4, 8 aac(6')-Ib-cr, 6 qnrS1 and 3 qnrB19] and in 10% of c-AmpC isolates [5 aac(6')-Ib-cr and 1 qnrS1]. IncI1-ST12 and IncF were associated with blaCMY-2 and blaDHA-1, respectively. These results suggest that ac-AmpC β-lactamases were the main mechanism of AmpC production. Isolates and plasmids both showed high genetic diversity.

Cooccurrence of Multiple AmpC β-Lactamases in Escherichia coli, Klebsiella pneumoniae, and Proteus mirabilis in Tunisia

Over a period of 40 months, plasmid-mediated AmpC β-lactamases were detected in Tunis, Tunisia, in 78 isolates (0.59%) of Escherichia coli, Klebsiella pneumoniae, and Proteus mirabilis. In 67 isolates, only one ampC gene was detected, i.e., blaCMY-2-type (n = 33), blaACC (n = 23), blaDHA (n = 6) or blaEBC (n = 5). Multiple ampC genes were detected in 11 isolates, with the following distribution: blaMOX-2, blaFOX-3, and blaCMY-4/16 (n = 6), blaFOX-3 and blaMOX-2 (n = 3), and blaCMY-4 and blaMOX-2 (n = 2). A great variety of plasmids carrying these genes was found, independently of the species and the bla gene. If the genetic context of blaCMY-2-type is variable, that of blaMOX-2, reported in part previously, is unique and that of blaFOX-3 is unique and new.

The changing epidemiology of hospital outbreaks due to ESBL-producing Klebsiella pneumoniae: the CTX-M-15 type consolidation

ABSTRACT 

Klebsiella pneumoniae is responsible for a large number of hospital outbreaks. In the 1990s, there were clonal epidemics, affecting mostly intensive care patients, which carried SHV and TEM enzyme types. With the advent of CTX-M-15 enzymes in the 2000, plasmids encoding multiple extended-spectrum β-lactamase (ESBL) types were described and, frequently, nosocomial outbreaks reported polyclonal dissemination and involved multiple Enterobacteriaceae. Worryingly, the interface between community and hospital is becoming blurred, and there is increasing evidence for the presence of ESBL-producing K. pneumoniae in the community. Furthermore, carbapenem resistance is increasingly reported in ESBL-producing K. pneumoniae strains. Infection control measures and stewardship programs are vital weapons in controlling the pandemic evolution of multidrug-resistant K. pneumoniae.

Resistance Rates of Intra-Abdominal Isolates from Intensive Care Units and Non-Intensive Care Units in the United States: The Study for Monitoring Antimicrobial Resistance Trends 2010-2012

BACKGROUND

Enterobacteriaceae (3,235 isolates), Pseudomonas aeruginosa (476 isolates), and Acinetobacter baumannii (106 isolates) from inpatient intra-abdominal infections (IAIs) were collected for the 2010-2012 Study for Monitoring Antimicrobial Resistance Trends (SMART) program in the United States. This report evaluates the in vitro activity of several antimicrobial agents recommended for treatment of IAIs and compares profiles of isolates from intensive care units (ICUs) and non-intensive care units (non-ICUs).

METHODS

Gram-negative bacilli from hospitalized patients with IAIs were obtained each year from 2010-2012 from hospitals in the United States and tested for susceptibility to 12 antibiotics according to 2012 Clinical and Laboratory Standards Institute (CLSI) guidelines.

RESULTS

The most active agents against members of the Enterobacteriaceae family from both ICUs and non-ICUs were amikacin, ertapenem, and imipenem-cilastatin, whereas the least active agent was ampicillin-sulbactam. Amikacin was the only agent with good activity against P. aeruginosa, whereas none of the agents tested exhibited substantial activity against A. baumannii. Amikacin, ceftazidime, ceftriaxone, ciprofloxacin, levofloxacin, and imipenem-cilastatin were significantly less active against Enterobacteriaceae from ICU patients, whereas cefepime and ceftazidime were significantly less active against P. aeruginosa from ICU patients. Intensive care unit isolates were more likely to be multi-drug-resistant than non-ICU isolates, although there was no difference in extended-spectrum β-lactamase (ESBL) production rates between the two patient groups.

CONCLUSIONS

Despite increasing resistance trends, in this study amikacin, ertapenem, and imipenem-cilastatin were shown to have good in vitro activity against the most frequently isolated gram-negative bacilli from IAIs in ICU and non-ICU settings.