Prevalence of CTX-M beta-lactamases in Philadelphia, Pennsylvania

Carriage of ESBL-producing Klebsiella pneumoniae and Escherichia coli among children in rural Ghana: a cross-sectional study

BACKGROUND

Extended-spectrum beta-lactamase (ESBL)-producing Klebsiella pneumoniae (ESBL-KP) and Escherichia coli (ESBL-EC) present a high burden in both communities and healthcare sectors, leading to difficult-to-treat infections. Data on intestinal carriage of ESBL-KP and ESBL-EC in children is scarce, especially in sub-Saharan African countries. We provide data on faecal carriage, phenotypic resistance patterns, and gene variation of ESBL-EC and ESBL-KP among children in the Agogo region of Ghana.

METHODS

From July to December 2019, fresh stool samples were collected within 24 h from children < 5 years with and without diarrhoea attending the study hospital. The samples were screened for ESBL-EC and ESBL-KP on ESBL agar and confirmed using double-disk synergy testing. Bacterial identification and an antibiotic susceptibility profile were performed using the Vitek 2 compact system (bioMérieux, Inc.). ESBL genes, blaSHV, blaCTX-M, and blaTEM were identified by PCR and further sequencing.

RESULTS

Of the 435 children recruited, stool carriage of ESBL-EC and ESBL-KP was 40.9% (n/N = 178/435) with no significant difference in prevalence between children with diarrhoea and non-diarrhoea. No association between ESBL carriage and the age of the children was found. All isolates were resistant to ampicillin and susceptible to meropenem and imipenem. Both ESBL-EC and ESBL-KP isolates showed over 70% resistance to tetracycline and sulfamethoxazole-trimethoprim. Multidrug resistance was observed in over 70% in both ESBL-EC and ESBL-KP isolates. The blaCTX-M-15 was the most prevalent ESBL gene detected. blaCTX-M-27, blaCTX-M-14, and blaCTX-M-14b were found in non-diarrhoea stools of children, whereas blaCTX-M-28 was found in both the diarrhoea and non-diarrhoea patient groups.

CONCLUSIONS

The carriage of ESBL-EC and ESBL-KP among children with and without diarrhoea in the Agogo community with a high prevalence of blaCTX-M-15 is noteworthy, highlighting the importance of both the population as a possible reservoir. This study reports for the first time the ESBL gene blaCTX-M-28 among the studied populations in Ghana.

Diversity of β-lactamase-encoding genes in wastewater: bacteriophages as reporters

A reservoir of antibiotic resistance genes (ARGs) is present in pathogenic, commensal, and environmental bacteria as well as in mobile genetic elements, including bacteriophages. Wastewater treatment plants (WWTPs) are considered hotspots for the spread of ARGs. The aim of this work was to analyze the diversity of the highly prevalent ARGs bla_CTX-M and bla_TEM in bacterial and bacteriophage fractions associated with human and animal environments through the study of urban waste and animal residues discharged into WWTPs to provide information about the composition and maintenance of the current resistome in Buenos Aires, Argentina. The results showed that a putative extended-spectrum variant of the bla_TEM gene was the most frequently detected, with bla_TEM-116 being the most prevalent, while a recently described type, bla_TEM-229, was also found. In the bacteriophage fraction, we detected bla_CTX-M genes from four out of the five clusters described. The detection of bla_{CTX- M-9}-like and bla_CTX-M-25-like genes was unexpected based on surveys of the ARGs from clinical pathogens circulating regionally. The finding of divergent bla_CTX-M sequences associated with previously reported environmental genes argues in favor of the natural environment as a reservoir of resistance genes. ARGs were detected in bacteriophages as frequently as in bacterial communities, and furthermore, the bla_CTX-M genes were more diverse in the bacteriophage fraction. Bacteriophages might therefore play a role in the spread of ARGs in the environment, but they might also be used as "reporters" for monitoring circulating ARGs.

Prevalence and Molecular Characterization of Antimicrobial Resistance in Escherichia coli Isolated from Raw Milk and Raw Milk Cheese in Egypt

The goal of this study was to examine antimicrobial resistance and characterize the implicated genes in 222 isolates of Escherichia coli from 187 samples of raw milk and the two most popular cheeses in Egypt. E. coli isolates were tested for susceptibility to 12 antimicrobials by a disk diffusion method. Among the 222 E. coli isolates, 66 (29.7%) were resistant to one or more antimicrobials, and half of these resistant isolates showed a multidrug resistance phenotype (resistance to at least three different drug classes). The resistance traits were observed to tetracycline (27.5%), ampicillin (18.9%), streptomycin (18.5%), sulfamethoxazole-trimethoprim (11.3%), cefotaxime (4.5%), kanamycin (4.1%), ceftazidime (3.6%), chloramphenicol (2.3%), nalidixic acid (1.8%), and ciprofloxacin (1.4%). No resistance to fosfomycin and imipenem was observed. Tetracycline resistance genes tetA, tetB, and tetD were detected in 53 isolates, 9 isolates, and 1 isolate, respectively, but tetC was not detected. Aminoglycoside resistance genes strA, strB, aadA, and aphA1 were detected in 41, 41, 11, and 9 isolates, respectively. Sulfonamide resistance genes sul1, sul2, and sul3 were detected in 7, 25, and 3 isolates, respectively. Of 42 ampicillin-resistant isolates, bla_TEM, bla_CTX-M, and bla_SHV were detected in 40, 9, and 3 isolates, respectively, and 10 (23.8%) ampicillin-resistant isolates were found to produce extended-spectrum β-lactamase. Each bla gene of extended-spectrum β-lactamase-producing E. coli was further subtyped to be bla_CTX-M-15, bla_CTX-M-104, bla_TEM-1, and bla_SHV-12. The class 1 integron was also detected in 28 resistant isolates, and three different patterns were obtained by PCR-restriction fragment length polymorphism. Sequencing analysis of the variable region revealed that four isolates had dfrA12/orfF/aadA2, two had aadA22, and one had dfrA1/aadA1. These data suggest that antimicrobial-resistant E. coli are widely distributed in the milk production and processing environment in Egypt and may play a role in dissemination of antimicrobial resistance to other pathogenic and commensal bacteria.

The occurrence of CTX-M-25-producing Enterobacteriaceae in day-old broiler chicks in Japan

Day-old chicks from 3 hatcheries were placed on bedding paper and brought to a commercial broiler farm between January and July 2016. Sixty-six samples of the paper, which were stained with meconium droppings of the chicks, were collected and examined for isolation of cephalosporin-resistant Enterobacteriaceae. Cefotaxime (CTX)-resistant Klebsiella pneumoniae (1 isolate) and Enterobacter cloacae (4 isolates) were isolated from 5 (7.58%) of the 66 samples. Conjugation experiments revealed that the bla_CTX-M-25 gene conferring CTX resistance was transferred from the K. pneumoniae isolate and 2 of the 4 E. cloacae isolates to Escherichia coli DH5α via IncA/C plasmids carrying the gene. Our results suggested that the bla_CTX-M-25 gene originating from chicks may be spread among commercial broiler farms.

Prevalence of MDR pathogens of bacterial meningitis in Egypt and new synergistic antibiotic combinations

The aim of this study was identifying bacterial pathogens involved in meningitis, studying their antibiotic resistance profiles, investigating the antibiotic resistance genes as well as evaluating the use of various antibiotic combinations. Antibiotic susceptibility tests were evaluated according to CLSI guidelines. Antibiotic combinations were evaluated by calculating the Fractional Inhibitory Concentration (FIC) index. A total of 71 bacterial isolates were recovered from 68 culture positive CSF specimens. Sixty five of these isolates (91.5%) were recovered from single infection specimens, while 6 isolates (8.4%) were recovered from mixed infection specimens. Out of the 71 recovered isolates, 48 (67.6%) were Gram-positive, and 23 (32.4%) were Gram-negative. Thirty one of the Gram positive isolates were S. pneumoniae (64.6%, n = 48). Out of the recovered 71 isolates; 26 (36.6%) were multidrug-resistant (MDR) isolates of which, 18 (69.2%) were Gram-negative and 8 (30.8%) were Gram-positive. All MDR isolates (100%) showed resistance to penicillin and ampicillin, however, they showed lower resistance to meropenem (50%), levofloxacin (50%), amikacin (48%), pipercillin-tazobactam (45.8%). Most common antibiotic resistance genes were investigated including: tem (21.1%), shv (15.8%), ctx-m (15.8%) coding for TEM-, SHV, CTX-M extended-spectrum beta-lactamases (ESBLs), respectively; aac(6')-I b(26.3%) coding for aminoglycoside 6'-N-acetyltransferase type Ib ciprofloxacin resistant variant; and qnrA (5.3%) gene coding for quinolone resistance. The DNA sequences of the respective resistance genes of some selected isolates were PCR amplified, analyzed and submitted to the GenBank database under the accession numbers, KX214665, KX214664, KX214663, KX214662, respectively. The FIC values for ampicillin/sulbactam plus cefepime showed either additive or synergistic effect against ten tested Gram-negative MDR isolates, while doxycycline plus levofloxacin combination revealed synergism against two MDR Gram-positive isolates. The results indicate high prevalence of antibiotic resistance among MDR isolates. Therefore, new guidelines should be implemented in Egypt to rationalize the use and avoid the misuse and abuse of antimicrobial agents.

Clinical and Molecular Characterization of Community-Onset Urinary Tract Infections Due to Extended-Spectrum Cephalosporin-Resistant Enterobacteriaceae

OBJECTIVE To evaluate risk factors for and molecular characteristics of community-onset extended-spectrum cephalosporin-resistant (ESC-R) Enterobacteriaceae (EB) urinary tract infections (UTIs) in a US health system. DESIGN Case-control study. PARTICIPANTS All patients presenting to the emergency department or outpatient practices with EB UTIs from December 21, 2010, through April 22, 2013, were included. Case patients had ESC-R EB UTIs. Control patients had ESC-susceptible EB UTIs and were matched 1:1 on study year. METHODS Risk factors for ESC-R EB UTI were assessed using multivariable conditional logistic regression. A subset of case isolates was evaluated for extended-spectrum beta-lactamases. RESULTS A total of 302 patients with community-onset EB UTI were included, of which 151 were cases. On multivariable analysis, risk factors for ESC-R EB UTI included trimethoprim-sulfamethoxazole use in the prior 6 months (odds ratio, 2.40 [95% CI, 1.22-4.70]; P=.01), older age (1.03 [1.01-1.04]; P<.001), diabetes (2.91 [1.32-6.41]; P=.008), and presentation to the emergency department ( 2.42 [1.31-4.46]; P=.005). The prevalence of extended-spectrum beta-lactamases among 120 case isolates was 52% CTX-M, 29% TEM, 20% OXA, and 13% SHV. The prevalence of AmpC was 25%. Pulsed-field gel electrophoresis of the CTX-M Escherichia coli isolates showed no distinct clusters. CONCLUSIONS Use of trimethoprim-sulfamethoxazole, older age, diabetes, and presentation to the emergency department were associated with community-onset ESC-R EB UTI. There was a high prevalence of CTX-M among our community isolates. Further studies are needed to determine strategies to limit emergence of these organisms in the community. Infect Control Hosp Epidemiol 2016;1433-1439.

bla CTX-M-152, a Novel Variant of CTX-M-group-25, Identified in a Study Performed on the Prevalence of Multidrug Resistance among Natural Inhabitants of River Yamuna, India

Natural environment influenced by anthropogenic activities creates selective pressure for acquisition and spread of resistance genes. In this study, we determined the prevalence of Extended Spectrum β-Lactamases producing gram negative bacteria from the River Yamuna, India, and report the identification and characterization of a novel CTX-M gene variant bla_CTX-M-152. Of the total 230 non-duplicate isolates obtained from collected water samples, 40 isolates were found positive for ESBL production through Inhibitor-Potentiation Disc Diffusion test. Based on their resistance profile, 3% were found exhibiting pandrug resistance (PDR), 47% extensively drug resistance (XDR), and remaining 50% showing multidrug resistant (MDR). Following screening and antimicrobial profiling, characterization of ESBLs (bla_TEMand bla_CTX-M), and mercury tolerance determinants (merP, merT, and merB) were performed. In addition to abundance of bla_TEM-116 (57.5%) and bla_CTX-M-15 (37.5%), bacteria were also found to harbor other variants of ESBLs like bla_CTX-M-71 (5%), bla_CTX-M-3 (7.5%), bla_CTX-M-32 (2.5%), bla_CTX-M-152 (7.5%), bla_CTX-M-55 (2.5%), along with some non-ESBLs; bla_TEM-1 (25%) and bla_OXY (5%). Additionally, co-occurrence of mercury tolerance genes were observed among 40% of isolates. In silico studies of the new variant, bla_CTX-M-152were conducted through modeling for the generation of structure followed by docking to determine its catalytic profile. CTX-M-152 was found to be an out-member of CTX-M-group-25 due to Q26H, T154A, G89D, P99S, and D146G substitutions. Five residues Ser70, Asn132, Ser237, Gly238, and Arg273 were found responsible for positioning of cefotaxime into the active site through seven H-bonds with binding energy of -7.6 Kcal/mol. Despite small active site, co-operative interactions of Ser237 and Arg276 were found actively contributing to its high catalytic efficiency. To the best of our knowledge, this is the first report of bla_CTX-M-152 of CTX-M-group-25 from Indian subcontinent. Taking a note of bacteria harboring such high proportion of multidrug and mercury resistance determinants, their presence in natural water resources employed for human consumption increases the chances of potential risk to human health. Hence, deeper insights into mechanisms pertaining to resistance development are required to frame out strategies to tackle the situation and prevent acquisition and dissemination of resistance determinants so as to combat the escalating burden of infectious diseases.

Phylogenetic groups, extended-spectrum β-lactamases and metallo-β-lactamase in Escherichia coli isolated from fecal samples of patients with diarrhea in Iran

AIM

The aims of this study were to investigate the phenotypic and genotypic of extended-spectrum β-lactamase (ESBL) and metallo-β-lactamases (MBLs) and determine phylogenetic background E. coli isolates from fecal samples of patients with diarrhea in Kerman, southeast of Iran.

BACKGROUND

The emergence of ESBLs and MBLs-producing E. coli caused problems in antibiotic treatments. E. coli strains can be assigned to four main phylog-groups, including: A, B1, B2 and D.

PATIENTS AND METHODS

E. coli isolates (n=216) were obtained from fecal samples of patients with diarrhea between June and December 2013. ESBLs and MBLs were confirmed by disk-diffusion and broth micro-dilution methods. Using PCR, the ESBL-positive isolates were screened to determine the phylo-groups and the presence of bla CTX-M-15, bla OXA-1, bla PER-1, bla VIM and bla IMP genes.

RESULTS

ESBL-positive isolates (n= 56) were detected. Among ESBL-positive isolates, 51 isolates were positive for bla CTX-M15 and one isolate was positive for both bla CTX-M-15 and bla OXA-1 genes. None of the isolates were positive for bla PER-1, bla VIM and bla IMP genes. PCR assay for phylotyping of isolates indicated that the isolates were belonged to groups A (54.16%), B1 (11.11%), B2 (12.96%) and D (21.75%). The isolates possessed bla CTX-M-15 gene were belonged to A (35 isolates), B1 (5), B2 (3) and D (8) phylo-groups.

CONCLUSION

Our results indicate that bla CTX-M-15 gene is widespread among diarrheagenic E. coli isolates. ESBL-producing E. coli isolates were disseminated among a diversity of phylo-groups. Further studies are necessary to identify the ESBL genes in relation to phylogenetic groups.

Development and evaluation of a novel universal β-lactamase gene subtyping assay for blaSHV, blaTEM and blaCTX-M using clinical and livestock-associated Escherichia coli

OBJECTIVES

Antibiotic resistance among Escherichia coli is globally an increasing problem in public healthcare. Understanding the spread of plasmid-mediated ESBL genes is of great importance in elucidating their molecular epidemiology. However, differentiation of subtypes and alleles is frequently hampered by the lack of comprehensive diagnostic tools. We therefore developed a novel universal blaSHV, blaTEM and blaCTX-M subtyping assay based on PCR and Sanger sequencing that results in large amplicons of >700 bp, enabling differentiation of bla alleles as precisely as possible.

METHODS

The assay was established using 10 reference strains with known bla genotypes that represent all examined primer groups and 101 uncharacterized ESBL-producing E. coli of clinical and livestock-associated origins from different German regions. All isolates were tested in parallel with established blaSHV, blaTEM and blaCTX-M subtyping assays for the respective β-lactamases and their alleles.

RESULTS

The novel assay yielded equal (n = 92) or better (n = 47) subtyping results compared with established subtyping methods and reliably detected all expected enzymes in the reference strains. Overall, the occurring enzymes could be differentiated into groups representing one (n = 9), two (n = 5) or three (n = 4) highly similar alleles. Moreover, ESBL and non-ESBL allelic variants of blaSHV and blaTEM occurring in the same isolate were distinguished reliably.

CONCLUSIONS

We established a highly discriminatory assay for the subtyping of clinically important ESBL genes that can easily be used in epidemiological analyses.

CTX-M β-lactamase-producing Klebsiella pneumoniae in suburban New York City, New York, USA

CTX-M extended-spectrum β-lactamase (ESBL)–producing Klebsiella pneumoniae isolates are infrequently reported in the United States. In this study, we analyzed nonduplicate ESBL-producing K. pneumoniae and Escherichia coli clinical isolates collected during 2005–2012 at a tertiary care medical center in suburban New York City, USA, for the presence of bla_CTX-M, bla_SHV, bla_TEM, and bla_KPC genes. Despite a high prevalence of bla_CTX-M genes in ESBL-producing E. coli since 2005, bla_CTX-M genes were not detected in K. pneumoniae until 2009. The prevalence of CTX-M–producing K. pneumoniae increased significantly over time from 1.7% during 2005–2009 to 26.4% during 2010–2012 (p<0.0001). CTX-M-15 was the dominant CTX-M genotype. Pulsed-field gel electrophoresis and multilocus sequence typing revealed high genetic heterogeneities in CTX-M–producing K. pneumoniae isolates. This study demonstrates the recent emergence and polyclonal spread of multidrug resistant CTX-M–producing K. pneumoniae isolates among patients in a hospital setting in the United States.

Pediatric multicenter evaluation of the Verigene gram-negative blood culture test for rapid detection of inpatient bacteremia involving gram-negative organisms, extended-spectrum beta-lactamases, and carbapenemases

We evaluated the investigational use only (IUO) version of the rapid Verigene Gram-negative blood culture test (BC-GN), a microarray that detects 9 genus/species targets (Acinetobacter spp., Citrobacter spp., Enterobacter spp., Escherichia coli/Shigella spp., Klebsiella oxytoca, Klebsiella pneumoniae, Proteus spp., Pseudomonas aeruginosa, and Serratia marcescens) and 6 antimicrobial resistance determinants (blaCTX-M, blaKPC, blaNDM, blaVIM, blaIMP, and blaOXA) directly from positive blood cultures. BC-GN was performed on positive BacT/Alert Pediatric FAN and Bactec Peds Plus blood cultures with Gram-negative organisms at two tertiary pediatric centers. Vitek MS (bioMérieux, Durham, NC) was used to assign gold standard organism identification. The Check MDR CT-102 microarray (Check Points B.V., Wageningen, Netherlands) was used as an alternative method for detecting resistance determinants. In total, 104 organisms were isolated from 97 clinical blood cultures. BC-GN correctly detected 26/26 cultures with Acinetobacter spp., P. aeruginosa, and S. marcescens, 5/6 with Citrobacter spp., 13/14 with Enterobacter spp., 23/24 with E. coli, 2/3 with K. oxytoca, 16/17 with K. pneumoniae, and 0/1 with Proteus spp. BC-GN appropriately reported negative BC-GN results in 8/13 blood cultures that grew organisms that were not represented on the microarray but failed to detect targets in 3/5 cultures that grew multiple Gram-negative organisms. BC-GN detected 5/5 and 1/1 clinical blood cultures with blaCTX-M and blaVIM. All 6 results were corroborated by Check MDR CT-102 microarray testing. The Verigene BC-GN test has the potential to expedite therapeutic decision making in pediatric patients with Gram-negative bacteremia. Sensitivity was satisfactory but may be suboptimal in mixed Gram-negative blood cultures.

The Occurrence of blaCTX-M, blaSHV, and blaTEM Genes in Extended-Spectrum β-Lactamase-Positive Strains of Klebsiella pneumoniae, Escherichia coli, and Proteus mirabilis in Poland

Bacteria belonging to the Enterobacteriaceae family that produce extended-spectrum β-lactamase (ESBL) enzymes are important pathogens of infections. Increasing numbers of ESBL-producing bacterial strains exhibiting multidrug resistance have been observed. The aim of the study was to evaluate the prevalence of blaCTX-M, blaSHV, and blaTEM genes among ESBL-producing Klebsiella pneumoniae, Escherichia coli, and Proteus mirabilis strains and to examine susceptibility to antibiotics of tested strains. In our study, thirty-six of the tested strains exhibited blaCTX-M genes (blaCTX-M-15, blaCTX-M-3, blaCTX-M-91, and blaCTX-M-89). Moreover, twelve ESBL-positive strains harbored blaSHV genes (blaSHV-18, blaSHV-7, blaSHV-2, and blaSHV-5), and the presence of a blaTEM gene (blaTEM-1) in twenty-five ESBL-positive strains was revealed. Among K. pneumoniae the multiple ESBL genotype composed of blaCTX-M-15, blaCTX-M-3, blaSHV-18, blaSHV-7, blaSHV-2, and blaSHV-5 genes encoding particular ESBL variants was observed. Analysis of bacterial susceptibility to antibiotics revealed that, among β-lactam antibiotics, the most effective against E. coli strains was meropenem (100%), whereas K. pneumoniae were completely susceptible to ertapenem and meropenem (100%), and P. mirabilis strains were susceptible to ertapenem (91.7%). Moreover, among non-β-lactam antibiotics, gentamicin showed the highest activity to E. coli (91.7%) and ciprofloxacin the highest to K. pneumoniae (83.3%). P. mirabilis revealed the highest susceptibility to amikacin (66.7%).

Epidemiology and risk factors for isolation of Escherichia coli producing CTX-M-type extended-spectrum β-lactamase in a large U.S. Medical Center

A case-case-control study was conducted to identify independent risk factors for recovery of Escherichia coli strains producing CTX-M-type extended-spectrum β-lactamases (CTX-M E. coli) within a large Southeastern Michigan medical center. Unique cases with isolation of ESBL-producing E. coli from February 2010 through July 2011 were analyzed by PCR for blaCTX-M, blaTEM, and blaSHV genes. Patients with CTX-M E. coli were compared to patients with E. coli strains not producing CTX-M-type ESBLs (non-CTX-M E. coli) and uninfected controls. Of 575 patients with ESBL-producing E. coli, 491 (85.4%) isolates contained a CTX-M ESBL gene. A total of 319 (84.6%) patients with CTX-M E. coli (282 [74.8%] CTX-M-15 type) were compared to 58 (15.4%) non-CTX-M E. coli patients and to uninfected controls. Independent risk factors for CTX-M E. coli isolation compared to non-CTX-M E. coli included male gender, impaired consciousness, H2 blocker use, immunosuppression, and exposure to penicillins and/or trimethoprim-sulfamethoxazole. Compared to uninfected controls, independent risk factors for isolation of CTX-M E. coli included presence of a urinary catheter, previous urinary tract infection, exposure to oxyimino-cephalosporins, dependent functional status, non-home residence, and multiple comorbid conditions. Within 48 h of admission, community-acquired CTX-M E. coli (n = 51 [16%]) and non-CTX-M E coli (n = 11 [19%]) strains were isolated from patients with no recent health care contacts. CTX-M E. coli strains were more resistant to multiple antibiotics than non-CTX-M E. coli strains. CTX-M-encoding genes, especially bla(CTX-M-15) type, represented the most common ESBL determinants from ESBL-producing E. coli, the majority of which were present upon admission. Septic patients with risk factors for isolation of CTX-M E. coli should be empirically treated with appropriate agents. Regional infection control efforts and judicious antibiotic use are needed to control the spread of these organisms.

Risk factors for gastrointestinal tract colonization with extended-spectrum β-lactamase (ESBL)-producing Escherichia coli and Klebsiella species in hospitalized patients

We describe the prevalence of and risk factors for colonization with extended-spectrum β-lactamase (ESBL)-producing Escherichia coli and Klebsiella species (ESBL-EK) in hospitalized patients. The prevalence of colonization with ESBL-EK was 2.6%. Colonization was associated with cirrhosis, longer duration of hospital stay prior to surveillance, and prior exposure to clindamycin or meropenem.

Characterization of two new CTX-M-25-group extended-spectrum β-lactamase variants identified in Escherichia coli isolates from Israel

Objectives

We characterized two new CTX-M-type extended-spectrum β-lactamase (ESBL) variants in Escherichia coli isolates from stool samples of two elderly patients admitted at the Tel Aviv Sourasky Medical Center, Israel. Both patients underwent treatment with cephalosporins prior to isolation of the E. coli strains.

Methods

ESBLs were detected by the double-disk synergy test and PCR-sequencing of β-lactamase genes. The bla_CTX-M genes were cloned into the pCR-BluntII-TOPO vector in E. coli TOP10. The role of amino-acid substitutions V77A and D240G was analyzed by site-directed mutagenesis of the bla_CTX-M-94 and bla_CTX-M-100 genes and comparative characterization of the resulting E. coli recombinants. MICs of β-lactams were determined by Etest. Plasmid profiling, mating experiments, replicon typing and sequencing of bla_CTX-M flanking regions were performed to identify the genetic background of the new CTX-M variants.

Results

The novel CTX-M β-lactamases, CTX-M-94 and -100, belonged to the CTX-M-25-group. Both variants differed from CTX-M-25 by the substitution V77A, and from CTX-M-39 by D240G. CTX-M-94 differed from all CTX-M-25-group enzymes by the substitution F119L. Glycine-240 was associated with reduced susceptibility to ceftazidime and leucine-119 with increased resistance to ceftriaxone. bla_CTX-M-94 and bla_CTX-M-100 were located within ISEcp1 transposition units inserted into ∼93 kb non-conjugative IncFI and ∼130 kb conjugative IncA/C plasmids, respectively. The plasmids carried also different class 1 integrons.

Conclusions

This is the first report on CTX-M-94 and -100 ESBLs, novel members of the CTX-M-25-group.

Risk factors for infection or colonization with CTX-M extended-spectrum-β-lactamase-positive Escherichia coli

There has been a significant increase in the prevalence of Enterobacteriaceae that produce CTX-M-type extended-spectrum β-lactamases. The objective of this study was to evaluate risk factors for infection or colonization with CTX-M-positive Escherichia coli. A case-control study was conducted within a university system from 1 January 2007 to 31 December 2008. All patients with clinical cultures with E. coli demonstrating resistance to extended-spectrum cephalosporins were included. Case patients were designated as those with cultures positive for CTX-M-positive E. coli, and control patients were designated as those with non-CTX-M-producing E. coli. Multivariable logistic regression analyses were performed to evaluate risk factors for CTX-M-positive isolates. A total of 83 (56.8%) of a total of 146 patients had cultures with CTX-M-positive E. coli. On multivariable analyses, there was a significant association between infection or colonization with CTX-M-type β-lactamase-positive E. coli and receipt of piperacillin-tazobactam in the 30 days prior to the culture date (odds ratio [OR], 7.36; 95% confidence interval [CI], 1.61 to 33.8; P = 0.01) and a urinary culture source (OR, 0.36; 95% CI, 0.17 to 0.77; P = 0.008). The rates of resistance to fluoroquinolones were significantly higher in isolates from case patients than in isolates from control patients (90.4 and 50.8%, respectively; P < 0.001). We found that nonurinary sources of clinical cultures and the recent use of piperacillin-tazobactam conferred an increased risk of colonization or infection with CTX-M-positive E. coli. Future studies will need to focus on outcomes associated with infections due to CTX-M-positive E. coli, as well as infection control strategies to limit the spread of these increasingly common organisms.

Epidemiology and genetics of CTX-M extended-spectrum β-lactamases in Gram-negative bacteria

CTX-M enzymes, the plasmid-mediated cefotaximases, constitute a rapidly growing family of extended-spectrum β-lactamases (ESBLs) with significant clinical impact. CTX-Ms are found in at least 26 bacterial species, particularly in Escherichia coli, Klebsiella pneumoniae and Proteus mirabilis. At least 109 members in CTX-M family are identified and can be divided into seven clusters based on their phylogeny. CTX-M-15 and CTX-M-14 are the most dominant variants. Chromosome-encoded intrinsic cefotaximases in Kluyvera spp. are proposed to be the progenitors of CTX-Ms, while ISEcp1, ISCR1 and plasmid are closely associated with their mobilization and dissemination.

Molecular epidemiological analysis of Escherichia coli sequence type ST131 (O25:H4) and blaCTX-M-15 among extended-spectrum-β-lactamase-producing E. coli from the United States, 2000 to 2009

Escherichia coli sequence type ST131 (from phylogenetic group B2), often carrying the extended-spectrum-β-lactamase (ESBL) gene bla(CTX-M-15), is an emerging globally disseminated pathogen that has received comparatively little attention in the United States. Accordingly, a convenience sample of 351 ESBL-producing E. coli isolates from 15 U.S. centers (collected in 2000 to 2009) underwent PCR-based phylotyping and detection of ST131 and bla(CTX-M-15). A total of 200 isolates, comprising 4 groups of 50 isolates each that were (i) bla(CTX-M-15) negative non-ST131, (ii) bla(CTX-M-15) positive non-ST131, (iii) bla(CTX-M-15) negative ST131, or (iv) bla(CTX-M-15) positive ST131, also underwent virulence genotyping, antimicrobial susceptibility testing, and pulsed-field gel electrophoresis (PFGE). Overall, 201 (57%) isolates exhibited bla(CTX-M-15), whereas 165 (47%) were ST131. ST131 accounted for 56% of bla(CTX-M-15)-positive- versus 35% of bla(CTX-M-15)-negative isolates (P < 0.001). Whereas ST131 accounted for 94% of the 175 total group B2 isolates, non-ST131 isolates were phylogenetically distributed by bla(CTX-M-15) status, with groups A (bla(CTX-M-15)-positive isolates) and D (bla(CTX-M-15)-negative isolates) predominating. Both bla(CTX-M-15) and ST131 occurred at all participating centers, were recovered from children and adults, increased significantly in prevalence post-2003, and were associated with molecularly inferred virulence. Compared with non-ST131 isolates, ST131 isolates had higher virulence scores, distinctive virulence profiles, and more-homogeneous PFGE profiles. bla(CTX-M-15) was associated with extensive antimicrobial resistance and ST131 with fluoroquinolone resistance. Thus, E. coli ST131 and bla(CTX-M-15) are emergent, widely distributed, and predominant among ESBL-positive E. coli strains in the United States, among children and adults alike. Enhanced virulence and antimicrobial resistance have likely promoted the epidemiological success of these emerging public health threats.

Clinical characteristics of bacteraemia caused by extended-spectrum β-lactamase-producing Enterobacteriaceae in the era of CTX-M-type and KPC-type β-lactamases

Clin Microbiol Infect 2012; 18: 887-893 ABSTRACT: A multicentre, case-control study was conducted to assess risk factors and patient outcomes of bacteraemia caused by Enterobacteriaceae producing extended-spectrum β-lactamases (ESBLs) and Klebsiella pneumoniae carbapenemases (KPCs). One hundred and five and 20 patients with bacteraemia caused by ESBL-producing and KPC-producing organisms were matched to controls who had bacteraemia caused by non-ESBL/KPC-producing organisms, respectively. Independent risk factors for ESBL production included admission from a nursing home (OR 4.64; 95% CI 2.64-8.16), chronic renal failure (OR 2.09; 95% CI 1.11-3.92), the presence of a gastrostomy tube (OR 3.36; 95% CI 1.38-8.18), length of hospital stay before infection (OR 1.02; 95% CI 1.01-1.03), transplant receipt (OR 2.48; 95% CI 1.24-4.95), and receipt of antibiotics with Gram-negative activity in the preceding 30 days (OR 1.76; 95% CI 1.00-3.08). Twenty-eight-day crude mortality rates for patients infected with ESBL-producing or KPC-producing organisms and controls were 29.1% (34/117) and 19.5% (53/272), respectively (OR 1.70; 95% CI 1.04-2.80). On multivariate analysis, inadequate empirical therapy (OR 2.26; 95% CI 1.18-4.34), onset of bacteraemia while in the intensive-care unit (OR 2.74; 95% CI 1.47-5.11), Apache II score (OR 1.17; 95% CI 1.12-1.23) and malignancy (OR 2.66; 95% CI 1.31-5.41) were independent risk factors for mortality. CTX-M was the most common ESBL type in Escherichia coli, whereas SHV predominated in Klebsiella spp. and Enterobacter spp.

High rates of susceptibility to ceftazidime among globally prevalent CTX-M-producing Escherichia coli: potential clinical implications of the revised CLSI interpretive criteria

The CTX-M family of extended-spectrum β-lactamases (ESBLs) is a significant global public health threat. The prevalence of specific bla (CTX-M) genes varies geographically, but bla (CTX-M-15) and bla (CTX-M-14) dominate in most countries. We applied the latest Clinical Laboratory Standards Institute (CLSI) interpretive criteria (M100-S20) to a diverse collection of ESBL-producing Escherichia coli strains obtained from clinical specimens in our laboratory. Whereas under previous CLSI recommendations all isolates in this strain collection would have been reported as ceftazidime-resistant, under the new recommendations, approximately 11% of CTX-M-15-producing E. coli and 93% of CTX-M-14-producing E. coli respectively tested as ceftazidime-susceptible. We also found that, whilst many CTX-M-14-producers had minimum inhibitory concentrations (MICs) less than the breakpoint of 4 mg/L, the MIC distribution for these strains was higher than that of wild-type E. coli, with one CTX-M-14-producing isolate having an MIC of >64 mg/L. Although the new CLSI recommendations imply that ceftazidime can be safely used to treat serious infections due to CTX-M-producing E. coli, clinical outcome data are lacking. Consequently, the widespread use of ceftazidime in this setting could have profound clinical implications.

CTX-M-producing non-Typhi Salmonella spp. isolated from humans, United States

CTX-M-type beta-lactamases are increasing among US Enterobacteriaceae isolates. Of 2,165 non-Typhi Salmonella isolates submitted in 2007 to the National Antimicrobial Resistance Monitoring System, 100 (4.6%) displayed elevated MICs (≥2 mg/L) of ceftriaxone or ceftiofur. Three isolates (serotypes Typhimurium, Concord, and I 4,5,12:i:-) contained bla(CTX-M-5), bla(CTX-M-15), and bla(CTX-M-55/57), respectively.

Molecular characteristics of extended-spectrum beta-lactamase-producing Escherichia coli from the Chicago area: high prevalence of ST131 producing CTX-M-15 in community hospitals

This study was designed to characterise 30 non-duplicate extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli clinical isolates from the community in the Chicago metropolitan area collected during 2008. The majority of isolates (n=28) were recovered from urine and 2 isolates were from blood. Molecular characterisation was done using the following techniques: isoelectric focusing; polymerase chain reaction (PCR) and sequencing of bla(ESBL); PCR for plasmid-mediated quinolone resistance determinants; identification of ST131; phylogenetic grouping; and replicon typing. Genetic relatedness was determined by pulsed-field gel electrophoresis (PFGE) with XbaI and repetitive sequence-based PCR (rep-PCR) typing. Twenty-six (87%) of the ESBL-producing E. coli were positive for bla(CTX-M) genes (22 CTX-M-15 and 4 CTX-M-14), whilst the remaining 4 isolates produced SHV-2. Twenty-eight isolates (93%) were non-susceptible to ciprofloxacin and 16 (53%) were positive for aac(6')-Ib-cr. Overall, 16 (53%) of the ESBL-producers belonged to clonal complex ST131 that produced CTX-M-15 or CTX-M-14. Molecular characteristics of ST131 showed that it belonged to three distinct but related PFGE clones, was derived from phylogenetic group B2 and contained IncFII type plasmids. These results illustrate that E. coli clonal complex ST131 producing CTX-M-15, CTX-M-14, OXA-1, TEM-1 and aac(6')-Ib-cr has emerged as an important cause of community-onset urinary tract infections caused by ESBL-producing E. coli isolates in the Chicago area.

Molecular epidemiology of CTX-M-producing Escherichia coli isolates at a tertiary medical center in western Pennsylvania

A combination of phenotypic and genotypic methods was used to investigate 70 unique Escherichia coli clinical isolates identified as producing extended-spectrum beta-lactamases (ESBLs) at a medical center in Pittsburgh, PA, between 2007 and 2008. Fifty-seven isolates (81%) produced CTX-M-type ESBLs, among which CTX-M-15 was predominant (n = 46). Isolates producing CTX-M-2, -9, -14, and -65 were also identified. One CTX-M-producing isolate coproduced CMY-2 cephalosporinase. Ten isolates (14%) produced SHV-type ESBLs, either SHV-5 or SHV-7. Two isolates produced only CMY-2 or -32. Pulsed-field gel electrophoresis revealed the presence of two major clusters of CTX-M-15-producing E. coli isolates, one in phylotype B2 (n = 15) and the other in phylotype A (n = 19). Of four phylotype B2 isolates that were able to transfer the bla(CTX-M-15)-carrying plasmids, three showed fingerprints related (>60%) to those of plasmids from phylotype A isolates. In phylotype B2, all CTX-M-15-producing isolates, as well as three isolates producing CTX-M-14, two producing SHV-5, and one producing SHV-7, belonged to the international epidemic clone defined by serotype O25:H4 and sequence type 131. The plasmids from eight of nine CTX-M-15-producing E. coli isolates of phylotype A that were examined were highly related to each other and were also found in two isolates belonging to phylotype D, suggesting horizontal transfer of this bla(CTX-M-15)-carrying plasmid between phylotypes. Our findings underscore the need to further investigate the epidemiology and virulence of CTX-M-producing E. coli in the United States.

Prevalence and clonality of extended-spectrum beta-lactamases in Asia

Asia is almost certainly a part of the world in which extended-spectrum beta-lactamases (ESBLs) have emerged de novo, with some early antimicrobial resistance studies showing high levels of the ESBL phenotype, particularly among Klebsiella, and most notably in China, Korea, Japan and India. There is a lack of genotyping studies but work from the late 1990s suggests that SHV-5 and SHV-12 were most common then, with only very rare reports of TEM-related ESBL genes. As in other parts of the world, quite marked differences have since been seen in the pattern of ESBL genes, particularly in relation to the CTX-M family. The early emergence of TOHO CTX-M-2 in Japan contrasted with CTX-M-3 and -14 in China and many other parts of the Far East, suggesting the separate transfer of genes from the genome of Kluyvera spp. to mobile genetic elements in human-associated Enterobacteriaceae. ESBL production rates are now very high compared with Europe. In most countries, there are mixtures of CTX-M types, with VEB appearing significantly in Vietnam and Thailand, and ESBL isolates from India being completely dominated by the presence of bla(CTX-M-15) alone, with no other CTX-M types reported. With the total population of India and China being c. 2.4 billion and with faecal carriage rates of, probably, c. 10%, these countries represent major reservoirs of bla(CTX-M) genes. Increasing international travel and trade will lead to the movement of many of these ESBL genes. The high prevalence of ESBL genes in Asia means that the empirical treatment of serious infections with beta-lactam antibiotics, except carbapenems, is seriously compromised.