High prevalence of extended-spectrum beta-lactamases and plasmid-mediated AmpC beta-lactamases in Enterobacteriaceae isolated from long-term care facilities in Korea

Prevalence and genetic characterization of clinically relevant extended-spectrum β-lactamase-producing Enterobacterales in the Gulf Cooperation Council countries

Introduction

Among Gram-negative bacteria (GNB), Enterobacterales (Enterobacterales), such as Escherichia coli (E. coli) and Klebsiella pneumoniae (K. pneumoniae), are the most clinically relevant pathogens in healthcare settings. Infections secondary to these pathogens are widely common but multidrug resistance (MDR) in Enterobacterales has become a significant challenge with increased morbidity, mortality, and cost of management. The escalating global prevalence of MDR in Enterobacterales has led to limited treatment options, raising an urgent need for novel antimicrobial therapy(s) and detailed studies exploring underlying resistance mechanisms. In Enterobacterales, the prime antimicrobial resistance mechanism against β-lactam antibiotics is mainly the production of β-lactamases, particularly extended-spectrum β-lactamases (ESBLs). Although the Gulf region is witnessing major challenges from infections secondary to MDR GNB, the extent of the problem has not been fully evaluated. Therefore, this review aims to address the prevalence and genetic characterization of ESBL-producing Enterobacterales in the Gulf Cooperation Council (GCC) countries.

Methods

PubMed® (National Library of Medicine, Bethesda, MD, USA) search was conducted, which looked for academic articles discussing the epidemiology of MDR Enterobacterales in the GCC countries, published in the last 5 years.

Results and conclusions

In GCC countries there is a high prevalence rate of MDR Enterobacterales, particularly ESBLs. Prevalence rates of ESBL-producing Enterobacterales among the Enterobacterales in general clinical samples in the GCC region is 21.6%-29.3%, with a slightly higher prevalence rate in intensive care unit patients (17.3-31.3%) and in patients with urinary tract infections (25.2%-31.7%). ESBL carriers have also been noted in the general community. ESBL-producing Enterobacterales from the GCC region show high levels of resistance to ampicillin, aztreonam, third-/fourth-generation cephalosporins, fluoroquinolones, and trimethoprim-sulfamethoxazole. Intermediate resistance rates are observed against nitrofurantoin, piperacillin/tazobactam, and gentamicin, with increasing resistance observed against tigecycline. The isolates demonstrate low-level resistance to carbapenems, fosfomycin, colistin, and amikacin. Enterobacterales isolates that are concomitant ESBL producers and are carbapenem resistant have been increasingly reported and demonstrate alarmingly increased antibiotic resistance patterns compared with ESBL Enterobacterales. The most prevalent genes for ESBL resistance in the Enterobacterales isolates in the GCC region are: bla CTX-M (subtype group 1) followed by/co-dominated by bla TEM and bla SHV, whereas the most common carbapenem-resistant genes are bla OXA-48 and bla NDM-1.

Prevalence and Characterization of Extended-Spectrum β-Lactamase-Producing Escherichia coli Isolated from Dogs and Cats in South Korea

Overall, 836 Escherichia coli isolates (695 isolates from dogs and 141 from cats) were recovered from the diarrhea, skin/ear, urine, and genitals of dogs and cats between 2018 and 2019. Cefovecin and enrofloxacin resistance were noted in 17.1% and 21.2% of E. coli isolates, respectively. The cefovecin and enrofloxacin resistance rates were higher in dog isolates (18.1% and 22.9%) compared with the rates in cat isolates (12.1%, 12.8%). Interestingly, resistance to both antimicrobials was noted in 10.8% (90/836) of the isolates, predominantly in isolates from dogs. bla_CTX-M-14, bla_CTX-M-15, and bla_CMY-2 were the most frequent extended-spectrum β-lactamase/plasmid-mediated AmpC β-lactamase (ESBL/AmpC)- gene types. The co-existence of bla_{CTX-M and}bla_CMY-2 was noted in six E. coli isolates from dogs. Sequencing analysis demonstrated that S83L and D87N in gyrA and S80I in parC were the most frequent point mutations in the quinolone resistance-determining regions of the cefovecin and enrofloxacin-resistant isolates. A total of 11 isolates from dogs carried the plasmid-mediated quinolone resistance genes (six aac(6')-Ib-cr, four qnrS, and one qnrB), while only two cat isolates carried the qnrS gene. Multilocus sequence typing of the cefovecin and enrofloxacin-resistant isolates revealed that sequence type (ST)131 E. coli carrying bla_CTX-M-14 and bla_CTX-M-15 genes and ST405 E. coli carrying bla_CMY-2 gene were predominant among the isolated E. coli strains. The majority of the ESBL/AmpC-producing isolates displayed diverse pulsed-field gel electrophoresis profiles. This study demonstrated that third-generation cephalosporin- and fluoroquinolone-resistant E. coli were widely distributed in companion animals. The detection of the pandemic ST131 clone carrying bla_CTX-M-_14/15 in companion animals presented a public health threat.

Antibiogram of Multidrug-Resistant Bacteria Based on Sepsis Onset Location in Korea: A Multicenter Cohort Study

BACKGROUND

Administration of adequate antibiotics is crucial for better outcomes in sepsis. Because no uniform tool can accurately assess the risk of multidrug-resistant (MDR) pathogens, a local antibiogram is necessary. We aimed to describe the antibiogram of MDR bacteria based on locations of sepsis onset in South Korea.

METHODS

We performed a prospective observational study of adult patients diagnosed with sepsis according to Sepsis-3 from 19 institutions (13 tertiary referral and 6 university-affiliated general hospitals) in South Korea. Patients were divided into four groups based on the respective location of sepsis onset: community, nursing home, long-term-care hospital, and hospital. Along with the antibiogram, risk factors of MDR bacteria and drug-bug match of empirical antibiotics were analyzed.

RESULTS

MDR bacteria were detected in 1,596 (22.7%) of 7,024 patients with gram-negative predominance. MDR gram-negative bacteria were more commonly detected in long-term-care hospital- (30.4%) and nursing home-acquired (26.3%) sepsis, whereas MDR gram-positive bacteria were more prevalent in hospital-acquired (10.9%) sepsis. Such findings were consistent regardless of the location and tier of hospitals throughout South Korea. Patients with long-term-care hospital-acquired sepsis had the highest risk of MDR pathogen, which was even higher than those with hospital-acquired sepsis (adjusted odds ratio, 1.42; 95% confidence interval, 1.15-1.75) after adjustment of risk factors. The drug-bug match was lowest in patients with long-term-care hospital-acquired sepsis (66.8%).

CONCLUSION

Gram-negative MDR bacteria were more common in nursing home- and long-term-care hospital-acquired sepsis, whereas gram-positive MDR bacteria were more common in hospital-acquired settings in South Korea. Patients with long-term-care hospital-acquired sepsis had the highest the risk of MDR bacteria but lowest drug-bug match of initial antibiotics. We suggest that initial antibiotics be carefully selected according to the onset location in each patient.

Systematic Review of Plasmid AmpC Type Resistances in Escherichia coli and Klebsiella pneumoniae and Preliminary Proposal of a Simplified Screening Method for ampC

Beta-lactamase (BL) production is a major public health problem. Although not the most frequent AmpC type, AmpC-BL is increasingly isolated, especially plasmid AmpC-BL (pAmpC-BL). The objective of this study was to review information published to date on pAmpC-BL in Escherichia coli and Klebsiella pneumoniae, and on the epidemiology and detection methods used by clinical microbiology laboratories, by performing a systematic review using the MEDLINE PubMed database. The predictive capacity of a screening method to detect AmpC-BL using disks with cloxacillin (CLX) was also evaluated by studying 102 Enterobacteriaceae clinical isolates grown in CHROMID ESBL medium with the addition of cefepime (FEP), cefoxitin (FOX), ertapenem (ETP), CLX, and oxacillin with CLX. The review, which included 149 publications, suggests that certain risk factors (prolonged hospitalization and previous use of cephalosporins) are associated with infections by pAmpC-BL-producing microorganisms. The worldwide prevalence has increased over the past 10 years, with a positivity rate ranging between 0.1 and 40%, although AmpC was only detected when sought in a targeted manner. CMY-2 type has been the most prevalent pAmpC-BL-producing microorganism. The most frequently used phenotypic method has been the double-disk synergy test (using CLX disks or phenyl-boronic acid and cefotaxime [CTX] and ceftazidime) and the disk method combined with these inhibitors. In regard to screening methods, a 1-µg oxacillin disk with CLX showed 88.9% sensitivity, 100% specificity, 100% positive predictive value (PPV), 98.9% negative predictive value (NPV), and 98.9% validity index (VI). This predictive capacity is reduced with the addition of extended-spectrum beta-lactamases, showing 62.5% sensitivity, 100% specificity, 100% PPV, 93.5% NPV, and 94.1% VI. In conclusion, there has been a worldwide increase in the number of isolates with pAmpC-BL, especially in Asia, with CMY-2 being the most frequently detected pAmpC-BL-producing type of microorganism. Reduction in its spread requires routine screening with a combination of phenotypic methods (with AmpC inhibitors) and genotypic methods (multiplex PCR). In conclusion, the proposed screening technique is an easy-to-apply and inexpensive test for the detection of AmpC-producing isolates in the routine screening of multidrug-resistant microorganisms.

Risk Factors for Extended-Spectrum-β-Lactamase-Producing Escherichia coli in Community-Onset Bloodstream Infection: Impact on Long-Term Care Hospitals in Korea

Background

The prevalence of extended-spectrum β-lactamase-producing Escherichia coli (ESBL-EC) in the community has increased worldwide due to multifactorial reasons. ESBL-EC bloodstream infection (BSI) complicates the decision for proper antimicrobial administration. In this multicenter study, we investigated the prevalence, risk factors, and molecular background of community-onset (CO) ESBL-EC BSI.

Methods

We included data for all episodes of ESBL-EC BSI of community origin from May 2016 to April 2017 obtained from the Korean national antimicrobial resistance surveillance system, which comprises six sentinel hospitals. Data, including previous history of admission and use of antimicrobials and medical devices before BSI, were collected, along with microbiological analysis results.

Results

Among 1,189 patients with CO BSI caused by E. coli, 316 (27%) were identified as ESBL producers. History of admission, especially to a long-term care hospital (LTCH), and previous use of β-lactams/β-lactamase inhibitors, carbapenem, lincosamide, aminoglycoside, and extended-spectrum cephalosporin were independent risk factors for CO ESBL-EC BSI; admission to an LTCH showed the highest odds ratio (3.8, 95% confidence interval 2.3-6.1). The most common genotype was CTX-M-15 (N=131, 41%), followed by CTX-M-14 (N=86, 27%). ST131 was the most common sequence type among ESBL-EC groups (57%).

Conclusions

In Korea, 27% of CO E. coli BSI were caused by ESBL producers. From perspectives of empirical treatment and infection control, history of admission to an LTCH and antimicrobial use should be noted.

Determination of genetic relationship between environmental Escherichia coli with PFGE and investigation of IS element in blaCTX-M gene of these isolates

INTRODUCTION

ESBL producing Escherichia coli (E. coli) have spread in the hospital settings. The aims of this study determination of genetic relationship between Environmental E. coli with PFGE typing and investigation of IS element in bla_CTX-M gene of these isolates.

MATERIALS AND METHODS

A total of 50 E. coli isolates were collected from hospital environmental. The bla_CTX-M producing E. coli and IS element of this gene with phylogenetic typing were detected by PCR. The PFGE was performed to detect genetic relationships between this strains.

RESULTS

Most of the isolates were from urology wards, other samples were isolated from ICU, surgery and orthopedic ward. The majority of isolates were resistant to cefotaxime and ceftazidime antibiotics and also phosphomycin antibiotic resistant were detected in 10% of isolates. CTX-M gene was detected in 72% of isolates. Moreover, ISEcp1, IS26a, and IS26b were detected upstream of CTX-M in 24%, 8% and 16 of isolates. A phylogroup was the most frequent and PFGE analysis exhibited a diverse distribution of E. coli isolates.

CONCLUSIONS

The results demonstrated the existence of CTX-M-producing E. coli in a hospital environment which is a source for drug-resistant strains. In the most of strains, ISEcp1 was located in the upstream of CTX-M gene and Orf477 was found in the downstream. However, in some strains, IS26 was inserted within the ISEcp1element. Our results show that despite the fact that antibiotics of phosphomycin are not used in this hospital, resistance to phosphomycin was observed in the environmental E. coli.

Prevalence, Characteristics and Clonal Distribution of Extended-Spectrum β-Lactamase- and AmpC β-Lactamase-Producing Escherichia coli Following the Swine Production Stages, and Potential Risks to Humans

The worldwide spread of extended spectrum β-lactamase (ESBL)- and AmpC β-lactamase (AmpC)-producing Escherichia coli poses serious threats to public health. Swine farms have been regarded as important reservoirs of ESBL/AmpC-EC. This study aimed to determine the prevalence, ESBL/AmpC types, and clonal distribution of ESBL/AmpC-EC from swine farms and analyze the difference according to the swine production stages. In addition, we evaluated the potential risks of swine ESBL/AmpC-EC clones to humans. Individual fecal samples (n = 292) were collected from weaning, growing, finishing, and pregnant pigs in nine swine farms of South Korea between July 2017 and March 2020. In total, 161 ESBL/AmpC-EC isolates were identified (55.1%), with the highest prevalence detected in the weaning stage (86.3%). The dominant ESBL and AmpC types were CTX-M-55 (69.6%) and CMY-2 (4.3%), respectively. CTX-M found in all production stages, while CMY was only found in growing and finishing stages. In the conjugation assay, the high transferability of CTX-M gene (55.8%) was identified, while the transfer of CMY gene was not identified. The major clonal complexes (CCs) were CC101-B1 (26.8%), CC10-A (8.7%), and CC648-F (2.9%). There was similarity in clonal distribution between different swine production stages within swine farms, estimated using the k-means analysis, which suggested a clonal transmission between the different swine stages. Among swine ESBL/AmpC-EC sequence types (STs), seven STs (ST101, ST10, ST648, ST457, ST410, ST617, and ST744) were common with the human ESBL/AmpC-EC, which registered in National Center for Biotechnology Information database. The clonal population structure analysis based on the virulence factor (VF) presented that swine ESBL/AmpC-EC clones, especially ST101-B1, harbored a highly virulent profile. In conclusion, ESBL/AmpC-EC was distributed throughout the swine production stages, with the highest prevalence in the weaning stage. The CTX-M was present in all stages, while CMY was mostly found in growing-finishing stages. The swine ESBL/AmpC-EC was identified to harbor shared clone types with human ESBL/AmpC-EC and a virulent profile posing potential risk to humans. Considering the possibility of genetic and clonal distribution of ESBL/AmpC-EC among swine production stages, this study suggests the need for strategies considering the production system to control the prevalence of ESBL/AmpC-EC in swine farms.

2003-2019: explosive spread of enterobacteria producing extended-spectrum beta-lactamases in Bangui Central African Republic

Introduction

the spread of enterobacteria producing extended-broad-spectrum beta-lactamases (ESBL) is a global public health-problem. In a study carried in 2003-2005 at the Pasteur Institute in Bangui, 450 enterobacteria were identified in clinical isolates, of which 17 were ESBL (prevalence: 3.78%). The aim of this study was to update this data.

Methods

from May 2018 to April 2019, a total of 941 enterobacteria were isolated and identified under identical conditions of recruitment and with the same techniques used in the previous study: phenotypic identification using Api 20E strips (bioMérieux SA, Marcy-l'Etoile, France) and antimicrobial drug susceptibility using the disk diffusion method (Bio-Rad antibiotic discs, Marnes la Coquette, France). Resistance genes were identified by polymerase chain reaction (PCR) and sequencing.

Results

from May 2018 to April 2019, a total of 941 enterobacteria were isolated of which 478 were ESBL, thus amounting to a prevalence of 50.80%. The genetic profiles of the bla CTX-M resistance genes exhibited the emergence of the CTX-M28 variant (CTX-M1 group) and variants of the M2 and M9 groups. There was also a notable increase, from 35 to 64%, in the ESBL with a bla SHV gene.

Conclusion

this study documents a 13 fold increase in the prevalence of ESBL derived from clinical isolates of the bacteriology laboratory of the Institute Pasteur in Bangui, by comparing its data with that of the publication by Frank et al. 2006. Together with this increase a significant diversification of the circulating CTX-M resistance genes was noticed.

Resistance Profiling and Molecular Characterization of Extended-Spectrum/Plasmid-Mediated AmpC β-Lactamase-Producing Escherichia coli Isolated from Healthy Broiler Chickens in South Korea

We aimed to identify and characterize extended-spectrum β-lactamase (ESBL)-and/or plasmid-mediated AmpC β-lactamase (pAmpC)-producing Escherichia coli isolated from healthy broiler chickens slaughtered for human consumption in Korea. A total of 332 E. coli isolates were identified from 339 cloacal swabs in 2019. More than 90% of the isolates were resistant to multiple antimicrobials. ESBL/pAmpC-production was noted in 14% (46/332) of the isolates. Six of the CTX-M-β-lactamase-producing isolates were found to co-harbor at least one plasmid-mediated quinolone resistance gene. We observed the co-existence of blaCMY-2 and mcr-1 genes in the same isolate for the first time in Korea. Phylogenetic analysis demonstrated that the majority of blaCMY-2-carrying isolates belonged to subgroup D. Conjugation confirmed the transferability of blaCTX-M and blaCMY-2 genes, as well as non-β-lactam resistance traits from 60.9% (28/46) of the ESBL/pAmpC-producing isolates to a recipient E. coli J53. The ISECP, IS903, and orf477 elements were detected in the upstream or downstream regions. The blaCTX-M and blaCMY-2 genes mainly belonged to the IncI1, IncHI2, and/or IncFII plasmids. Additionally, the majority of ESBL/pAmpC-producing isolates exhibited heterogeneous PFGE profiles. This study showed that healthy chickens act as reservoirs of ESBL/pAmpC-producing E. coli that can potentially be transmitted to humans.

The first report of Enterobacter gergoviae carrying bla NDM-1 in Iran

OBJECTIVES

Prompt detection of extended-spectrum β-lactamases (ESBL) and carbapenemase-producing enterobacteriaceae is crucial for infection prevention and control strategies. The present study aimed to characterize the ESBL and carbapenemase genes among Enterobacter isolates from an Iranian inpatient population.

MATERIALS AND METHODS

A total of 96 Enterobacter isolates obtained from inpatients between June 2016 and March 2017, were identified by the conventional microbiological methods and diagnostic kits. Antimicrobial susceptibility pattern was performed using the disk diffusion method. The ESBL and carbapenemase genes were screened using polymerase chain reaction (PCR).

RESULTS

All clinical isolates of Enterobacter were classified as E. gergoviae (52, 54.2%), E. aerogenes (34, 35.4%), E. cloacae (7, 7.3%), Cronobacter (E). sakazakii (3, 3.1%). The highest and lowest antimicrobial resistance rates were observed against ampicillin (93.8%) and imipenem (21.9%). High prevalence of multi-drug resistance (MDR=96.9%) was substantial. Of the 96 Enterobacter isolates, 35 (36.5%) and 28 (29.2%) were phenotypically ESBL-positive and non-susceptible carbapenem, respectively. Overall, the frequency of evaluated genes was as follows: blaCTX-M =25 (26%), blaTEM =30 (31.3%), blaSHV =12 (12.5%), blaIMP =3 (3.1%), blaVIM =0 (0%), blaNDM =8 (8.3%), and blaKPC =0 (0%).

CONCLUSION

In this study, we report for the first time the presence of E. gergoviae harboring blaNDM from an Iranian population. Regarding the increase of MDR Enterobacter spp. in our region, strict hygiene rules will be needed to control the quick spread of ESBL and carbapenemase-producing Enterobacter isolates in healthcare facilities of developing countries.

Differential Trends in Extended-Spectrum Beta-Lactamase-Producing Escherichia coli Infections in Four Health Care Facilities in a Single Metropolitan Area: A Retrospective Analysis

Background: Prevalence of extended-spectrum beta-lactamase-producing Escherichia coli (ESBL-E. coli) is increasing worldwide, but greatly varies geographically. We compared the prevalence of ESBL-E. coli infections at four distinct health care facilities in San Francisco, California. Methods: Antimicrobial susceptibility reports were obtained for E. coli isolates from (1) a county hospital, (2) a public skilled nursing facility, (3) a university hospital, and (4) a Veterans Affairs (VA) Medical Center. We compared change in frequency of ESBL-E. coli and antimicrobial resistance to trimethoprim-sulfamethoxazole between 2012 and 2018. Results: From 2012 to 2018, frequency of ESBL-E. coli increased in urine and nonurine isolates from the county hospital (urine: 1.1% per year, 95% confidence interval [CI]: 0.5-1.6, p < 0.01; nonurine: 1.9% per year, 95% CI: 0.9-2.9, p < 0.01) and in urine isolates from the VA hospital (0.9% per year, 95% CI: 0.3-1.4, p < 0.01). The frequency of trimethoprim-sulfamethoxazole resistance fluctuated in all facilities. Conclusions: At the skilled nursing facility, the prevalence of ESBL-E. coli was highest, but remained stable over time, while the prevalence of ESBL-E. coli increased among urine and nonurine isolates at the county hospital and urine isolates at the VA hospital. The temporal trend of ESBL-E. coli infections, even within one city, varied by health care facility.

Molecular Characteristics of GES-Type Carbapenemase-Producing Pseudomonas aeruginosa Clinical Isolates from Long-Term Care Facilities and General Hospitals in South Korea

Since carbapenems have been used for the treatment of infections in medical settings, multidrug-resistant Pseudomonas aeruginosa containing resistance for carbapenems has become a major cause of nosocomial infections worldwide. Information on carbapenemase-producing P. aeruginosa isolates at community hospitals, including long-term care facilities and general hospitals, has rarely been reported in South Korea. The aims of this study were to describe the characteristics of seven carbapenemase-producing P. aeruginosa isolates recovered from two long-term care facilities in South Korea. The carbapenemase genes were identified by PCR and sequencing. Strain typing was assessed by pulsed field gel electrophoresis and multilocus sequence typing (MLST) analysis. Isolates with a genomic island and class I integron surrounding bla_GES-type were confirmed by the PCR mapping method. Of seven GES-type carbapenemase-producing P. aeruginosa isolates, the bla_GES-24 gene was detected in six isolates, and the bla_GES-5 gene was detected in one isolate. The epidemiological relatedness of the seven isolates carrying bla_GES-24 and bla_GES-5 showed >81% similarity. Five isolates carrying bla_GES-24 were sequence type 155 (ST155) by MLST, followed by one ST244 isolate carrying bla_GES-24 and one ST308 isolate carrying bla_GES-5. bla_GES-type genes were embedded in two different class I integrons in a genomic island-15-like region. Our results indicate the possible spread of carbapenemase-producing P. aeruginosa and present a current threat of antimicrobial resistance in community hospitals.

Acquisition of plasmid-mediated cephalosporinase producing Enterobacteriaceae after a travel to the tropics

Travelers are at high risk of acquiring multi-drug resistant Enterobacteriaceae (MRE) while traveling abroad. Acquisition of extended spectrum beta-lactamase producing Enterobacteriaceae (ESBL-E) while traveling has been extensively described, but not that of plasmid-mediated cephalosporinase producing Enterobacteriaceae (pAmpC-E). Here, we characterized the pAmpC-E acquired in 574 French travelers to tropical areas enrolled in the VOYAG-R study. Among the 526 MRE isolated at return, 57 (10.8%) from 49 travelers were pAmpC-E. The acquisition rate of pAmpC-E was 8.5% (49/574) ranging from 12.8% (25/195) in Asia, 7.6% (14/184) in Latin America to 5.1% (10/195) in Africa. The highest acquisition rates were observed in Peru (21.9%), India (21.4%) and Vietnam (20%). The carriage of pAmpC-E decreased quickly after return with 92.5% of colonized travelers being negative at one month. Most enzymes were CMY types (96.5%, n = 55, only met in Escherichia coli), including 40 CMY-2 (70.2%), 12 CMY-42 (21.1%), 1 CMY-6 and two new CMY-2 variants. The remaining were two DHA observed in Klebsiella pneumoniae. CMY-2 producing strains were acquired worldwide whereas CMY-42, except for one, were all acquired in Asia. Bla_CMY-2 genes were associated with different plasmid types, including IncI1 (45. 2%), IncF (10%), IncF-IncI (7.5%), IncA/C (5%) and IncR (2.5%) whereas bla_CMY-42 were all associated with IncI1 plasmids. Even though the pAmpC-E acquisition rate was much lower than that of ESBL-E, it was significant, especially in Asia, showing that pAmpC-E, especially CMY-type producing E. coli have spread in the community settings of tropical regions.

Impact of Inducible blaDHA-1 on Susceptibility of Klebsiella pneumoniae Clinical Isolates to LYS228 and Identification of Chromosomal mpl and ampD Mutations Mediating Upregulation of Plasmid-Borne blaDHA-1 Expression

Twenty-three Klebsiella pneumoniae (blaDHA-1) clinical isolates exhibited a range of susceptibilities to LYS228, with MICs of ≥8 μg/ml for 9 of these. Mutants with decreased susceptibility to LYS228 and upregulated expression of blaDHA-1 were selected from representative isolates. These had mutations in the chromosomal peptidoglycan recycling gene mpl or ampD Preexisting mpl mutations were also found in some of the clinical isolates examined, and these had strongly upregulated expression of blaDHA-1.

Colonization of long-term care facility residents in three Italian Provinces by multidrug-resistant bacteria

Background

Rationale and aims of the study were to compare colonization frequencies with MDR bacteria isolated from LTCF residents in three different Northern Italian regions, to investigate risk factors for colonization and the genotypic characteristics of isolates. The screening included Enterobacteriaceae expressing extended-spectrum β-lactamases (ESβLs) and high-level AmpC cephalosporinases, carbapenemase-producing Enterobacteriaceae, Pseudomonas aeruginosa or Acinetobacter baumannii, methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant enterococci (VRE).

Methods

Urine samples and rectal, inguinal, oropharyngeal and nasal swabs were plated on selective agar; resistance genes were sought by PCR and sequencing. Demographic and clinical data were collected.

Results

Among the LTCF residents, 75.0% (78/104), 69.4% (84/121) and 66.1% (76/115) were colonized with at least one of the target organisms in LTCFs located in Milan, Piacenza and Bolzano, respectively. ESβL producers (60.5, 66.1 and 53.0%) were highly predominant, mainly belonging to Escherichia coli expressing CTX-M group-1 enzymes. Carbapenemase-producing enterobacteria were found in 7.6, 0.0 and 1.6% of residents; carbapemenase-producing P. aeruginosa and A. baumannii were also detected. Colonization by MRSA (24.0, 5.7 and 14.8%) and VRE (20.2, 0.8 and 0.8%) was highly variable. Several risk factors for colonization by ESβL-producing Enterobacteriaceae and MRSA were found and compared among LTCFs in the three Provinces. Colonization differences among the enrolled LTCFs can be partially explained by variation in risk factors, resident populations and staff/resident ratios, applied hygiene measures and especially the local antibiotic resistance epidemiology.

Conclusions

The widespread diffusion of MDR bacteria in LTCFs within three Italian Provinces confirms that LTCFs are an important reservoir of MDR organisms in Italy and suggests that future efforts should focus on MDR screening, improved implementation of infection control strategies and antibiotic stewardship programs targeting the complex aspects of LTCFs.

First Report of blaCTX-M-28 in Enterobacteriaceae Isolates in the United Arab Emirates

Background

The CTX-M family of extended-spectrum beta lactamase (ESBL) enzymes is comprised of over 60 bla_CTX-M gene variants with the predominance of bla_CTX-M-15 in many regions. In this report, we present the first description of bla_CTX-M-28 in the United Arab Emirates.

Methods

Forty-five non-duplicate ESBL producing isolates identified in a secondary care facility in the United Arab Emirates from June to July 2016 were studied. Gene sequencing was performed and DNA sequences were annotated using the BLAST program to identify the gene subtypes.

Results

The majority of the ESBL positive isolates were E. coli (n/N = 39/45; 86.6%) followed by K. pneumoniae (n = 5) and K. oxytoca (n = 1). All isolates harboured bla_CTX-M and bla_TEM genes, 18 had bla_SHV, and 2 were bla_VIM positive. Thirty-seven isolates (82.2%) were positive for bla_CTX-M-28. Other bla_CTX-M genes identified include bla_CTX-M-167 (n = 2; isolates #1 and 26) and one each for bla_CTX-M-38, bla_CTX-M-163, and bla_CTX-M-198. No bla_CTX-M-15 was identified. The predominant bla_TEM subtype was bla_TEM-171 (n = 8) followed by one of each of bla_TEM-120, bla_TEM-163, and bla_TEM-206. The bla_SHV subtypes were bla_SHV-148 and bla_SHV-187.

Conclusion

The findings indicate the first description of bla_CTX-M-28 in a setting where bla_CTX-M-15 was previously predominant.

Comparison of rates of fecal colonization with extended-spectrum beta-lactamase-producing enterobacteria among patients in different wards, outpatients and medical students

Because asymptomatic carriage of extended-spectrum beta-lactamase (ESBL) producers is a risk factor for infection, data on colonization dynamics are important when planning infection control. This study investigated fecal colonization with ESBL producers among inpatients, outpatients and medical students and compares the characteristics of ESBL producers among these groups. Carriage rates were investigated in 5581 fecal samples; 4343 from inpatients (330, 1397, 619 and 1864 from adult ICUs [intensive care units], adult non-ICUs, pediatric ICUs and pediatric non-ICUs, respectively), 814 from outpatients and 424 from screening of medical students. ESBL producers were characterized by co-resistance, integrons carried, and aminoglycoside resistance and ESBL genes. Dynamic regression models were built to identify relationships between combinations of time series of monthly antibiotic consumption, prevalence of carriers and infected subjects. Inpatients, ICU patients and adults showed higher prevalence than outpatients, non-ICU patients or children (7.4%, 9.3% and 12.0% vs. 3.1%, 6.1% and 4.1%, respectively). Klebsiella pneumoniae was more frequent in ICU patients; dominance of CTX-M-15 producers was more marked in adult than in pediatric inpatients. ESBL carriage was shown to be a consequence of infection in adults in the time-series analysis; antibiotic consumption had little effect. The epidemiology of colonization with ESBL producers differed between pediatric ICU, adult ICU and adult non-ICU patients. In adults, carriage of ESBL producers seems to be the consequence of infection, especially in ICU patients; the main source of colonization is nosocomial acquisition. In contrast, children are less likely to acquire colonizer strains in hospitals; importation of ESBL producers by colonized children seems to be significant.

Role of piperacillin/tazobactam as a carbapenem-sparing antibiotic for treatment of acute pyelonephritis due to extended-spectrum β-lactamase-producing Escherichia coli

Extended-spectrum β-lactamase-producing Escherichia coli (ESBL-Ec) is a frequent cause of acute pyelonephritis (APN), requiring carbapenem therapy. However, alternatives to carbapenems are needed due to the emergence of carbapenemase-producing micro-organisms. The purpose of this study was to compare the clinical efficacy of piperacillin/tazobactam (TZP) versus ertapenem in the treatment of adult patients with APN caused by ESBL-Ec. A retrospective observational study of APN caused by ESBL-Ec susceptible to TZP was performed at a university-affiliated hospital in the Republic of Korea between February 2011 and June 2013. All adult patients initially treated with in vitro-active TZP were compared with those treated with ertapenem to evaluate antibiotic clinical efficacy. The primary endpoint was treatment failure, defined as a composite of in-hospital mortality, change of initial antibiotic regimen and microbiological eradication failure. During the study period, 68 patients prescribed TZP and 82 patients prescribed ertapenem were eligible for inclusion in the study. There was no significant difference between the two treatment groups in the occurrence of in-hospital mortality, change of initial antibiotic regimen or microbiological eradication failure. In the multivariate analyses, predictors associated with treatment failure included septic shock [odds ratio (OR) = 4.27, 95% confidence interval (CI) 1.66-10.99] and recent administration of immunosuppressive agents (OR = 2.84, 95% CI 1.02-7.91). However, the type of antibiotic was not associated with treatment failure. TZP could be an effective alternative to ertapenem for the treatment of APN caused by ESBL-Ec, sparing carbapenem consumption in the multidrug-resistant era.

Distribution of ESBLs, AmpC β-lactamases and carbapenemases among Enterobacteriaceae isolates causing intra-abdominal and urinary tract infections in the Asia-Pacific region during 2008-14: results from the Study for Monitoring Antimicrobial Resistance Trends (SMART)

OBJECTIVES

To investigate the antimicrobial resistance and assess the molecular characteristics of β-lactamases (ESBLs, AmpC β-lactamases and carbapenemases) among Enterobacteriaceae isolates that caused intra-abdominal infections (IAIs) in patients hospitalized in the Asia-Pacific region during 2008-14.

METHODS

Multiplex PCR was used to detect the specific types of β-lactamase in 2893 isolates with MICs of ertapenem >0.5 mg/L. In-hospital acquisition times for most isolates were also delineated.

RESULTS

Among 2728 (94.3%) isolates proven with β-lactamase production, the rates of non-susceptibility to imipenem were low (average = 7.9%) among IAI Enterobacteriaceae isolates from all Asia-Pacific countries except Vietnam (17.7%) and the Philippines (10.2%). A stepwise and significant increase in annual rates of carbapenemase production among these isolates was noted. CTX-M-15 and CTX-M-14 were the dominant ESBL variants in most IAI Enterobacteriaceae species. The most abundant AmpC β-lactamase variants were bla_CMY-2 among isolates of Escherichia coli and bla_DHA-1 among isolates of Klebsiella pneumoniae. In addition, the IAI Enterobacteriaceae isolates harbouring a bla_CMY-2 or bla_DHA-1 allele were associated with high community-acquired rates (38.0% and 42.6%, respectively). AmpC ACT and MIR variants were mostly detected in Enterobacter species. The bla_NDM-1,4,5,7-harbouring isolates of E. coli, K. pneumoniae and Enterobacter cloacae were most commonly identified among IAI isolates from Vietnam and the Philippines. Also of note, bla_OXA-48-harbouring IAI Enterobacteriaceae isolates were detected exclusively in Vietnam.

CONCLUSIONS

The high resistance burden in Vietnam and the Philippines warrants aggressive control policies to combat the worsening trend in antimicrobial resistance among Enterobacteriaceae species causing IAIs.

Long-Term Care Facilities Are Reservoirs for Antimicrobial-Resistant Sequence Type 131 Escherichia coli

In this cross sectional study, one-fourth of LTCF residents were colonized intestinally with ST131 E. coli. The most dependent residents were at highest risk. Strain transmission occurred within and between LTCFs. Molecular typing showed similarities to clinical isolates.

Background. Emerging data implicate long-term care facilities (LTCFs) as reservoirs of fluoroquinolone-resistant (FQ-R) Escherichia coli of sequence type 131 (ST131). We screened for ST131 among LTCF residents, characterized isolates molecularly, and identified risk factors for colonization.

Methods. We conducted a cross-sectional study using a single perianal swab or stool sample per resident in 2 LTCFs in Olmsted County, Minnesota, from April to July 2013. Confirmed FQ-R E. coli isolates underwent polymerase chain reaction-based phylotyping, detection of ST131 and its H30 and H30-Rx subclones, extended virulence genotyping, and pulsed-field gel electrophoresis (PFGE) analysis. Epidemiological data were collected from medical records.

Results. Of 133 fecal samples, 33 (25%) yielded FQ-R E. coli, 32 (97%) of which were ST131. The overall proportion with ST131 intestinal colonization was 32 of 133 (24%), which differed by facility: 17 of 41 (42%) in facility 1 vs 15 of 92 (16%) in facility 2 (P = .002). All ST131 isolates represented the H30 subclone, with virulence gene and PFGE profiles resembling those of previously described ST131 clinical isolates. By PFGE, certain isolates clustered both within and across LTCFs. Multivariable predictors of ST131 colonization included inability to sign consent (odds ratio [OR], 4.16 [P = .005]), decubitus ulcer (OR, 4.87 [ P = .04]), and fecal incontinence (OR, 2.59 [P = .06]).

Conclusions. Approximately one fourth of LTCF residents carried FQ-R ST131 E. coli resembling ST131 clinical isolates. Pulsed-field gel electrophoresis suggested intra- and interfacility transmission. The identified risk factors suggest that LTCF residents who require increased nursing care are at greatest risk for ST131 colonization, possibly due to healthcare-associated transmission.

[Prevalence and risk factors of multi-drug resistant organism colonization among long-term care facilities in Gran Canaria (Spain)]

INTRODUCTION

Multidrug resistant organisms (MDRO) are an important cause of nosocomial infections, with complicated clinical-therapeutic management and elevated morbidity-mortality, and an increase in healthcare costs. In long term care facilities (LTCFs) colonization/infection by MDRO among residents is increasing, and they may act as reservoirs and vehicles for the dissemination and production of outbreaks by resistant strains in acute hospitals. This study aimed at determining the prevalence of carriers of some common MDRO, and identifying factors associated with carrier state.

MATERIAL AND METHODS

A cross-sectional prevalence study was conducted on 235 residents in two LTCFs in the province of Las Palmas de Gran Canaria (Canary Islands, Spain) between October and November of 2012. The presence of MMR was investigated in nasal, pharyngeal and rectal swabs using selective media. Risk factors associated with carrier state were calculated using univariate and multivariate analysis.

RESULTS

More than one-third (36.2%) of residents were found to be carriers of ≥ 1 distinct MDROs. More than one-quarter (26.6%) were carriers of ESBL producing Enterobacteriaceae, and 10.2% were MRSA carriers. Factors found to be associated with colonization by any MDRO were: prior colonization or infection by MDRO, hospitalization in the past 3 months, recurrent infections of the urinary tract, and peripheral arterial disease.

CONCLUSIONS

The prevalence of MDRO in the LTCFs settings studied is greater than that found in the literature, and in particular ESBL producing Enterobacteriaceae. Due to the high prevalence of infection/colonization by MDRO, it is possible that residents of LTCFs could act as important reservoirs of MDRO, and facilitate their spread into the acute care setting.

Plasmid-mediated AmpC β-lactamase (CMY-2) gene in Salmonella typhimurium isolated from diarrheic pigs in South Korea

Abstracts

Risk factors for colonization with extended-spectrum beta-lactamase-producing enterobacteriaceae on admission to rehabilitation centres

Patients newly admitted to rehabilitation centres are at high risk of colonization with multidrug-resistant bacteria because many of them have experienced prolonged stays in other healthcare settings and have had high exposure to antibiotics. We conducted a prospective study to determine the prevalence of and risk factors for colonization with extended-spectrum beta-lactamase-producing Enterobacteriaceae (ESBL-PE) in this population. Subjects were screened by rectal swab for ESBL-PE within 2 days of admission. Swabs were plated on chromagar ESBL plates and the presence of ESBL was verified by a central laboratory. A multilevel mixed effects model was used to identify risk factors for ESBL-PE colonization. Of 2873 patients screened, 748 (26.0%) were positive for ESBL-PE. The variables identified as independently associated with ESBL-PE colonization were: recent stay in an acute-care hospital for over 2 weeks (OR=1.34; 95% CI, 1.12, 1.6), history of colonization with ESBL-PE (OR=2.97; 95% CI, 1.99, 4.43), unconsciousness on admission (OR=2.59; 95% CI, 1.55, 4.34), surgery or invasive procedure in the past year (OR=1.49; 95% CI, 1.2, 1.86) and antibiotic treatment in the past month (OR=1.80; 95% CI, 1.45, 2.22). The predictive accuracy of the model was low (area under the ROC curve 0.656). These results indicate that ESBL-PE colonization is common upon admission to rehabilitation centres. Some risk factors for ESBL-PE colonization are similar to those described previously; however, newly identified factors may be specific to rehabilitation populations. The high prevalence and low ability to stratify by risk factors may guide infection control and empirical treatment strategies in rehabilitation settings.

Detection of plasmid-mediated AmpC β-lactamase in Escherichia coli and Klebsiella pneumoniae

BACKGROUND

Detecting plasmid-mediated AmpC (pAmpC) β-lactamase-producing organism is important for optimal infection control and providing accurate and effective treatment option for physicians.

OBJECTIVES

The aim of this study was to investigate the prevalence of pAmpC β-lactamase and compare the results of boronic acid (BA) disk test with other phenotypic tests detecting AmpC positive isolates.

MATERIALS AND METHODS

A total of 273 clinical isolates of Klebsiella pneumoniae (n: 82) and Escherichia coli (n: 191) were analysed. The presence of pAmpC β-lactamase was determined by BA disk test, cefoxitin (FOX) screening test, modified three dimensional test (M3DT), and multiplex polymerase chain reaction (PCR). Pulsed-field gel electrophoresis was performed to evaluate the genetic similarities between isolates. To detect extended spectrum β-lactamases (ESBL) in the presence of AmpC β-lactamase, ESBL confirmation test was carried out with and without BA solution.

RESULTS

Of the 273 strains tested, 127 strains were found FOX resistant, 114 were positive by M3DT, 108 were positive in BA disk test, and the multiplex PCR detected 24 pAmpC β-lactamase-positive isolate. The prevalence of AmpC-producing strains was 10.9% in E. coli and 3.6% in K. pneumoniae in the tested population by PCR. CIT and MOX group genes were predominant type in these strains.

CONCLUSION

These results emphasize that clinical laboratories should consider testing the presence of pAmpC enzymes particularly in FOX-resistant isolates, and BA disk test will improve detection of this emerging resistance phenotype.

Detection of clonal KPC-2-producing Klebsiella pneumoniae ST258 in Korea during nationwide surveillance in 2011

This study analysed the characteristics and genetic similarity of recent Klebsiella pneumoniae carbapenemase (KPC-2)-producing Klebsiella pneumoniae isolates from Korea. Recent laboratory surveillance detected an increase in carbapenemase-producing Enterobacteriaceae in Korea. A total of 6 KPC-2-producing K. pneumoniae were identified from 277 Enterobacteriaceae clinical isolates. All were sequence type (ST) 258 and they had the same pulsotype. They had high MICs for carbapenems and multi-drug resistance. TEM-1, SHV-11 and OXA type β-lactamases were detected in all isolates, whereas CTX-M type β-lactamases and plasmid-mediated AmpC β-lactamase (PABL) were not present. A conjugation experiment failed, but blaKPC-2-harbouring plasmids from the six isolates were used to transform Escherichia coli DH5-α by electroporation. Each of the transformants harboured a blaKPC-2-positive approximately 95 kb plasmid, which was typed in the IncFII incompatibility group and co-harboured TEM-1 and OXA-9 β-lactamases. They shared the same restriction profile. This study confirms the emergence of clonal ST258 KPC-2-producing K. pneumoniae in some regions of Korea.

Prevalence of urinary colonization by extended spectrum-beta-lactamase Enterobacteriaceae among catheterised inpatients in Italian long term care facilities

Background

Long Term Care Facilities (LTCFs) play a key role in guaranteeing care to patients in developed countries. Many patients, mostly elderly, access LTCFs at some time in their lives, and their healthcare pathways often require them to move back and forth between hospital and outpatient settings. These patterns bring about new challenges regarding infection control, especially healthcare associated infections.

Methods

A point prevalence study was conducted in 23 Italian LTCFs, to identify colonization in patients with urinary catheter (>24 hours). Species identification, susceptibility tests and extended spectrum beta lactamase (ESBL) production screenings were performed using Vitek 2 System. Enterobacteria identified by Vitek 2 System as ESBL-producers or suspected AmpC hyperproducers on the basis of cephamycin resistance, were sent to a research laboratory where they underwent a double-disk synergy test. Finally, ESBL-producers were screened for bla resistance genes by PCR assay.

Results

211 patients with catheter were screened, 185 out of 211 patients showed positive samples for the presence of Enterobacteriaceae, 114 of these 185 patients were colonized by extended spectrum cephalosporins resistant microorganisms. We identified a total of 257 Gram negative pathogens, of which 51.8% (133/257) were extended spectrum cephalosporins resistant. 7 out of 133 cephamycin not susceptible strains proved to be AmpC-type beta-lactamases and 125/133 ESBL-producers; 1 was not further characterized. 43 out of 257 (16.7%) E. coli, 37/257 (14.4%) P. mirabilis, 20/257 (7.8%), P. stuartii, 14/257 (5.4%) M. morganii, 7/257 (2.7%), K. pneumoniae, 4/257 (1.6%) C. koseri proved to be overall ESBL-producers by double-disk synergy test. Third and fourth generation cephalosporin resistant P. mirabilis, P. stuartii and M. morganii strains mainly harboured a blaTEM gene (95.9%), while 89.1% of E. coli were positive for the blaCTX-M determinant by PCR and sequencing. Patients with decubitus had a higher risk of colonization by at least one resistant isolate (p < 0.01). Samples of patients undergoing antibiotic therapy and patients with decubitus showed a higher risk (p < 0.05) of colonization by beta-lactam resistant microorganisms.

Conclusions

These data confirm the presence of high percentages of ESBL-positive Enterobacteria in Italian LTCFs and the predominance of CTX-M type ESBL in E. coli. The alarming presence of ESBL-producing Enterobacteriaceae in Italian LTCFs can seriously compromise the effectiveness of antibiotic therapy.acilities (LTCFs), Antimicrobial resistance.

Evidence for recent acquisition and successful transmission of bla(CTX-M-15) in Salmonella enterica in South Korea

We identified two distinct bla(CTX-M)-bearing and five distinct bla(CMY-2)-bearing genetic structures located on plasmids from Salmonella enterica and Escherichia coli isolates (n = 35) collected from chickens in South Korea. All Salmonella plasmids shared a common replicon, bla(CTX-M-15) transposon, and core resistance phenotype, while E. coli bla(CTX-M-15) plasmids included four distinct replicons.

Escherichia coli sequence type 131 is a dominant, antimicrobial-resistant clonal group associated with healthcare and elderly hosts

OBJECTIVE

To determine prevalence, predictors, and outcomes of infection due to Escherichia coli sequence type ST131.

DESIGN

Retrospective cohort.

SETTING

All healthcare settings in Olmsted County, Minnesota (eg, community hospital, tertiary care center, long-term care facilities, and ambulatory clinics).

PATIENTS

Ambulatory and hospitalized children and adults with extraintestinal E. coli isolates.

METHODS

We analyzed 299 consecutive, nonduplicate extraintestinal E. coli isolates submitted to Olmsted County laboratories in February and March 2011. ST131 was identified using single-nucleotide polymorphism polymerase chain reaction and further evaluated through pulsed-field gel electrophoresis. Associated clinical data were abstracted through medical record review.

RESULTS

Most isolates were from urine specimens (90%), outpatients (68%), and community-associated infections (61%). ST131 accounted for 27% of isolates overall and for a larger proportion of those isolates resistant to fluoroquinolones (81%), trimethoprim-sulfamethoxazole (42%), gentamicin (79%), and ceftriaxone (50%). The prevalence of ST131 increased with age (accounting for 5% of isolates from those 11-20 years of age, 26% of isolates from those 51-60 years of age, and 50% of isolates from those 91-100 years of age). ST131 accounted for a greater proportion of healthcare-associated isolates (49%) than community-associated isolates (15%) and for fully 76% of E. coli isolates from long-term care facility (LTCF) residents. Multivariable predictors of ST131 carriage included older age, LTCF residence, previous urinary tract infection, high-complexity infection, and previous use of fluoroquinolones, macrolides, and extended-spectrum cephalosporins. With multivariable adjustment, ST131-associated infection outcomes included receipt of more than 1 antibiotic (odds ratio [OR], 2.54 [95% confidence interval (CI), 1.25-5.17]) and persistent or recurrent symptoms (OR, 2.53 [95% CI, 1.08-5.96]). Two globally predominant ST131 pulsotypes accounted for 45% of ST131 isolates.

CONCLUSIONS

ST131 is a dominant, antimicrobial-resistant clonal group associated with healthcare settings, elderly hosts, and persistent or recurrent symptoms.

Molecular characterization of extended-spectrum-β-lactamase-producing and plasmid-mediated AmpC β-lactamase-producing Escherichia coli isolated from stray dogs in South Korea

A total of 47 extended-spectrum-cephalosporin-resistant Escherichia coli strains isolated from stray dogs in 2006 and 2007 in the Republic of Korea were investigated using molecular methods. Extended-spectrum β-lactamase (ESBL) and AmpC β-lactamase phenotypes were identified in 12 and 23 E. coli isolates, respectively. All 12 ESBL-producing isolates carried bla(CTX-M) genes. The most common CTX-M types were CTX-M-14 (n = 5) and CTX-M-24 (n = 3). Isolates producing CTX-M-3, CTX-M-55, CTX-M-27, and CTX-M-65 were also identified. Twenty-one of 23 AmpC β-lactamase-producing isolates were found to carry bla(CMY-2) genes. TEM-1 was associated with CTX-M and CMY-2 β-lactamases in 4 and 15 isolates, respectively. In addition to bla(TEM-1), two isolates carried bla(DHA-1), and one of them cocarried bla(CMY-2). Both CTX-M and CMY-2 genes were located on large (40 to 170 kb) conjugative plasmids that contained the insertion sequence ISEcp1 upstream of the bla genes. Only in the case of CTX-M genes was there an IS903 sequence downstream of the gene. The spread of ESBLs and AmpC β-lactamases occurred via both horizontal gene transfer, accounting for much of the CTX-M gene dissemination, and clonal spread, accounting for CMY-2 gene dissemination. The horizontal dissemination of bla(CTX-M) and bla(CMY-2) genes was mediated by IncF and IncI1-Iγ plasmids, respectively. The clonal spread of bla(CMY-2) was driven mainly by E. coli strains of virulent phylogroup D lineage ST648. To our knowledge, this is the first report of bla(DHA-1) in E. coli strains isolated from companion animals. This study also represents the first report of CMY-2 β-lactamase-producing E. coli isolates from dogs in the Republic of Korea.

Characterization of carbapenem-nonsusceptible Klebsiella pneumoniae bloodstream isolates at a Taiwanese hospital: clinical impacts of lowered breakpoints for carbapenems

This study was conducted in order to characterize carbapenem-nonsusceptible Klebsiella pneumoniae isolates and to evaluate the impacts of recently lowered interpretative breakpoints for carbapenems for Enterobacteriaceae. Among 152 K. pneumoniae bloodstream isolates suspected as AmpC or extended-spectrum β-lactamase (ESBL) producers, 58 (38.2%) isolates were currently interpreted as nonsusceptible to ertapenem, imipenem, or meropenem, and 42 (72.4%) of them were categorized as carbapenem-susceptible by the previous criteria. The high revision rate was associated with the predominance (79.3%) of DHA-1 among the carbapenem-nonsusceptible isolates due to both polyclonal and clonal spread. ESBLs were common (~57%) in both ertapenem-susceptible and -nonsusceptible isolates; however, 84.8% of the carbapenem-nonsusceptible isolates were also AmpC producers. The IMP-8 metallo-β-lactamase was detected in three isolates. Polyacrylamide gel electrophoresis suggested decreased OmpK35 expression in all but one ertapenem-nonsusceptible isolate, and genetic disruptions of ompK35 and ompK36 were detected in 30 and six ertapenem-nonsusceptible isolates, respectively. A comparison between patients infected by AmpC- or ESBL-producing ertapenem-susceptible (n=62) isolates and those with isolates revised as ertapenem-nonsusceptible (n=41) revealed more cases of malignancies (36.6% versus 14.5%; p=0.01) and higher Charlson score (p=0.033) among the patients with ertapenem-nonsusceptible isolates; however, the acquisition of an isolate revised as carbapenem-nonsusceptible was not identified as an independent mortality risk factor.

Colonization with extended-spectrum β-lactamase-producing Escherichia coli and Klebsiella species in long-term care facility residents

We describe the prevalence of and risk factors for colonization with extended-spectrum β-lactamase-producing Enterobacteriaceae (ESBL-EB) in the long-term care facility (LTCF) setting. Colonization prevalence differed significantly across the 3 LTCFs evaluated in the study, with recent use of levofloxacin and fecal incontinence demonstrating borderline significant associations with ESBL-EB colonization.

Influx of multidrug resistant, Gram-negative bacteria (MDRGNB) in a public hospital among elderly patients from long-term care facilities: a single-center pilot study

Residence at a long-term care facility (LTCF) and older age are both recognized as significant risk factors for harboring MDRGNB. However, well designed prospective observational studies are few on the prevalence and risk factors of MDRGNB influx to hospital due to elderly patients arriving from LTCFs. Between November 1 and December 31, 2009, at a 500-bed, public teaching hospital in Seoul, Republic of Korea, all clinical cultures within 48 h of hospitalization from elderly patients at least 50 years of age arriving from LTCFs were collected prospectively. During these periods, the prevalence of MDRGNB influx among elderly patients from LTCFs was higher than that among other hospitalized patients (14.5% vs. 2.5%, odds ratio [OR] 8.1, 95% confidence interval [CI] 3.5-18.8, P<0.001). Of a total of 55 elderly hospitalized subjects from 6 LTCFs, clinical cultures were performed in 37. MDRGNB were found in 8 patients (6 of whom were infected). There was no difference between patients with and without MDRGNB regarding previously reported clinical characteristics associated with harboring MDRGNB. However, the mortality within one month of hospitalization was higher in patients with MDRGNB than without MDRGNB, regardless of the appropriateness of the antibiotics they received (OR, 15.91; 95% CI, 1.01-251.36; P=0.049). In conclusion, the prevalence of MDRGNB influx among elderly patients from LTCFs is significant in Korean public hospital. They require specific remedies in order to reduce the risk of early mortality.