The Novel CTX-M-116 β-Lactamase Gene Discovered in Proteus mirabilis Is Composed of Parts of the CTX-M-22 and CTX-M-23 Genes

The novel β-lactamase gene bla_CTX-M-116 was identified in a Proteus mirabilis nosocomial isolate recovered from the urine of a patient in Moscow in 2005. DNA sequence analysis showed bla_CTX-M-116 to be a hybrid gene consisting of 5′ bla_CTX-M-23 (nucleotides 1 to 278) and 3′ bla_CTX-M-22 (nucleotides 286 to 876) moieties separated by an intervening putative site of recombination (GTTAAAT). A retrospective analysis of available bla_CTX-M genes in the GenBank database revealed 19 bla_CTX-M genes that display the same hybrid structure.     

CTX-M-123, a Novel Hybrid of the CTX-M-1 and CTX-M-9 Group β-Lactamases Recovered from Escherichia coli Isolates in China

The chimeric bla_CTX-M-123 gene was identified in two ceftazidime-resistant Escherichia coli isolates from animals in different Chinese provinces. Like other CTX-M-1/9 group hybrids (CTX-M-64 and CTX-M-132), the ends (amino acids 1 to 135 and 234 to 291) of CTX-M-123 match CTX-M-15 while the central part (122 to 241) matches CTX-M-14. bla_CTX-M-123 is carried on related, but not identical, ∼90-kb IncI1 plasmids in the two isolates, and one isolate simultaneously carries the group 1 bla_CTX-M-55 gene on an additional IncI2 plasmid.     

High Prevalence of ST131 Isolates Producing CTX-M-15 and CTX-M-14 among Extended-Spectrum-β-Lactamase-Producing Escherichia coli Isolates from Canada

Phenotypic and genotypic methods were used to characterize extended-spectrum-β-lactamase (ESBL)-producing Escherichia coli isolated in 2007 from 11 different Canadian medical centers. Of the 209 ESBL-producing E. coli isolates tested, 148 (71%) produced CTX-M-15, 17 (8%) produced CTX-M-14, 5 (2%) produced CTX-M-3, and 1 produced CTX-M-27. Overall, 96 (46%) of the ESBL producers belonged to clonal complex ST131, with the highest prevalence in Brampton, Calgary, and Winnipeg. ST131 is an important cause of community onset urinary tract infections due to ESBL-producing E. coli across Canada.Since 2000, Escherichia coli producing CTX-M enzymes has emerged worldwide as an important cause of community onset urinary tract infections (UTIs), and this has been called “the CTX-M pandemic” (3). This phenomenon accelerated rapidly, especially during the past 5 years, and today organisms producing these enzymes are the most common type of extended-spectrum β-lactamase (ESBL) producers found in most areas of the world (24). Although several members of the family Enterobacteriaceae that produce CTX-M β-lactamases have been involved in hospital-acquired infections, E. coli producing these enzymes is more likely to be responsible for community onset infections (21).Currently, the most widely distributed CTX-M enzyme is CTX-M-15, which was first detected in E. coli from India in 2001 (10). Multidrug-resistant, CTX-M-15-producing E. coli is emerging worldwide, especially since 2003, as an important pathogen causing both community onset and hospital-acquired infections (6, 14, 20).Two recent studies using multilocus sequencing typing (MLST) identified a single clone of CTX-M-15-producing E. coli, named ST131, in isolates from several countries, including Spain, France, Canada, Portugal, Switzerland, Lebanon, India, Kuwait, and Korea (6, 14). This clone is associated with serogroup O25, belongs to highly virulent phylogenetic group B2, and harbors multidrug-resistant IncFII plasmids. Since those initial studies, isolates of clonal complex ST131 that produce CTX-M-15 have also been reported in several countries, including the United Kingdom (11), Italy (2), Turkey (27), Croatia (12), Japan (25), the United States (8), and Norway (13). Isolates of clonal complex ST131 have also been associated with other types of β-lactamases, as well as ciprofloxacin-resistant E. coli isolates that do not have ESBLs (4, 9, 12, 15).Due to the worldwide emergence of clone ST131 isolates that produce CTX-M β-lactamases, we designed a study to investigate the prevalence and characteristics of this clone in ESBL-producing E. coli isolated from community and hospital settings during 2007 from 11 different Canadian medical centers.(This study was presented at the 26th International Congress of Chemotherapy and Infection in Toronto, Ontario, Canada, 2009 [abstract P179].)Nonrepeat ESBL-producing E. coli was collected over a 1-month period in 2007 from different Canadian medical centers representing 11 cities in six provinces (Table ​(Table1).1). ESBL production was confirmed phenotypically by using the Clinical and Laboratory Standards Institute [CLSI] criteria for ESBL screening and disk confirmation tests (5).

TABLE 1.

ESBL-producing E. coli isolated at various medical centers in Canada

产CTX-M-14和CTX-M-15大肠埃希菌毒力基因分布差异

目的分析尿培养产CTX-M-14和产CTX-M-15大肠埃希菌毒力基因分布的差异。方法收集南京鼓楼医院2012年临床尿培养分离大肠埃希菌162株,双环协同试验检测超广谱β内酰胺酶(ESBLs);采用PCR和DNA测序对blaCTX-M编码基因及毒力基因iut A、omp T、fyu A、fde C、fim H、tra T、cva C、pap、kps MT、PAIs、usp、aer、hly A、cnf和chu A进行分析;用脉冲场凝胶电泳(PFGE)分析产CTX-M-14和产CTX-M-15大肠埃希菌遗传相关性;将细菌分为产CTX-M-14和产CTX-M-15大肠埃希菌2组,统计学分析毒力基因在这2组之间的分布差异。结果 162株大肠埃希菌中,126株产ESBLs,91株产CTX-M酶,其中bla_(CTX-M-14)和bla_(CTX-M-15)编码基因分别检出49株和36株。PFGE分析显示,产CTX-M酶大肠埃希菌具有遗传多样性。毒力基因iut A、fyu A、fim H、tra T及chu A在2组中的检出率均较高(65%);pap、kps MT、omp T在2组中的检出率约为20%~60%;cva C和PAIs在2组中的检出率较低(20%);毒力基因fed C在产CTX-M-14大肠埃希菌组中分布高于产CTX-M-15大肠埃希菌组(P=0.017);未检出aer、hly A和cnf毒力基因。结论在尿培养大肠埃希菌中,产CTX-M-14菌株fed C毒力基因分布较产CTX-M-15菌株更高。     

Novel Plasmid-Encoded Ceftazidime-Hydrolyzing CTX-M-53 Extended-Spectrum β-Lactamase from Salmonella enterica Serotypes Westhampton and Senftenberg

We describe the characterization of a novel CTX-M β-lactamase from Salmonella enterica. Four S. enterica isolates (three of serotype Westhampton and one of serotype Senftenberg) resistant to extended-spectrum cephalosporins (cefotaxime and ceftazidime) were recovered in 2004 from living cockles in three supermarkets located in distant geographic areas in France, which got their supplies from the same fishery. The isolates were found to produce a novel extended-spectrum β-lactamase (ESBL) belonging to the CTX-M-1 phylogenetic group and named CTX-M-53. The CTX-M-53 β-lactamase harbored the substitution Asp240Gly, like the CTX-M-15 enzyme, which is specifically implicated in a higher catalytic efficiency against ceftazidime. The bla_CTX-M-53 gene was located on a mobilizable 11-kb plasmid, pWES-1. The complete sequence of pWES-1 revealed the presence of a novel insertion sequence, ISSen2, and an IS26 element upstream and downstream of the bla_CTX-M-53 gene, respectively; however, transposition assays of the bla_CTX-M-53 gene were unsuccessful. IS26 elements may have contributed to the acquisition of the bla_CTX-M-53 gene. Interestingly, the mobilization module of the pWES-1 plasmid was similar to that of quinolone resistance plasmids (carrying the qnrS2 gene) from aquatic sources. Although belonging to two serotypes differentiated on the basis of the O-antigen structure (E1 or E4 groups), the isolates were found to be genetically indistinguishable by pulsed-field gel electrophoresis. Multilocus sequence typing showed that the isolates of serotype Westhampton had a sequence type, ST14, common among isolates of serotype Senftenberg. This is the first characterization of the CTX-M-53 ESBL, which represents an additional ceftazidime-hydrolyzing CTX-M enzyme.Salmonella enterica is a frequent pathogen of animals and humans. Food-borne diseases caused by this species represent an important public health problem worldwide. Extended-spectrum cephalosporins (ESC) and fluoroquinolones are often used in the treatment of invasive cases of salmonellosis. However, the emergence of extended-spectrum β-lactamases (ESBLs) in Enterobacteriaceae is an increasing problem worldwide, compromising the utilization of these drugs in the treatment of complicated Salmonella infections. Moreover, there is an increasing number of reports of ESBL-producing S. enterica strains throughout the world (3, 36). These strains, isolated mostly in hospitalized patients, produced plasmid-mediated class A ESBLs belonging to the TEM, SHV, cefotaximase (CTX-M), or PER families (3).CTX-M ESBLs are class A ESBLs that in general possess a higher level of hydrolytic activity against cefotaxime (and ceftriaxone) than against ceftazidime but that are inhibited by clavulanic acid, sulbactam, and tazobactam (5, 9, 26). On the basis of their amino acid sequences, the CTX-M enzymes have been classified into five major phylogenetic branches, namely the CTX-M-1, -2, -8, -9, and -25 groups (5, 9, 26; http://www.lahey.org/Studies/other.asp). CTX-M ESBLs are a rapidly growing group, which contains ESBLs encoded by more than 80 identified CTX-M genes (http://www.lahey.org/Studies/other.asp). In the genus Salmonella, 14 different CTX-M β-lactamases have been reported in several serotypes and over wide geographic areas (3, 5, 20, 21, 36-38). We report here the characterization of the novel CTX-M-53 ESBL in S. enterica serotypes Westhampton and Senftenberg in France. The S. enterica strains showing an ESBL phenotype were recovered from cockles from the Etel River (Morbihan, France) in August 2004. A molecular characterization of the β-lactamase gene was done by PCR, cloning, and sequencing. The genomic diversity of the isolates was determined by pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST). The novel CTX-M enzyme was characterized by MIC determination of the β-lactams, isoelectric focusing (IEF), and kinetic parameters. The CTX-M-carrying plasmid was fully sequenced, and bla_CTX-M mobilization experiments were performed.     

Cefoxitin as an alternative to carbapenems in a murine model of urinary tract infection due to Escherichia coli harboring CTX-M-15-type extended-spectrum β-lactamase

We investigated the efficiency of the cephamycin cefoxitin as an alternative to carbapenems for the treatment of urinary tract infections (UTIs) due to Escherichia coli producing CTX-M-type extended-spectrum β-lactamases. The susceptible, UTI-inducing E. coli CFT073-RR strain and its transconjugant CFT073-RR Tc (pbla(CTX-M-15)), harboring a bla(CTX-M-15) carrying-plasmid, were used for all experiments. MICs of cefoxitin (FOX), ceftriaxone (CRO), imipenem (IMP), and ertapenem (ETP) for CFT073-RR and CFT073-RR Tc (pbla(CTX-M-15)) were 4 and 4, 0.125 and 512, 0.5 and 0.5, and 0.016 and 0.032 μg/ml, respectively. Bactericidal activity was similarly achieved in vitro against the two strains after 3 h of exposure to concentrations of FOX, IMI, and ETP that were 2 times the MIC, whereas CRO was not bactericidal against CFT073-RR Tc (pbla(CTX-M-15)). The frequencies of spontaneous mutants of the 2 strains were not higher for FOX than for IMP or ETP. In the murine model of UTIs, mice infected for 5 days were treated over 24 h. Therapeutic regimens in mice (200 mg/kg of body weight every 3 h or 4 h for FOX, 70 mg/kg every 6 h for CRO, 100 mg/kg every 2 h for IMP, and 100 mg/kg every 4 h for ETP) were chosen in order to reproduce the percentage of time that free-drug concentrations above the MIC are obtained in humans with standard regimens. All antibiotic regimens produced a significant reduction in bacterial counts (greater than 2 log(10) CFU) in kidneys and bladders for both strains (P < 0.001) without selecting resistant mutants in vivo, but the reduction obtained with CRO against CFT073-RR Tc (pbla(CTX-M-15)) in kidneys was significantly lower than that obtained with FOX. In conclusion, FOX appears to be an effective therapeutic alternative to carbapenems for the treatment of UTIs due to CTX-M-producing E. coli.     

志贺菌属中鉴别出产CTX-M-55型菌株

在革兰阴性肠杆菌中,国内有关大肠埃希菌、肺炎克雷伯菌和阴沟肠杆菌B内酰胺酶耐药基因已有较多报道[1-5],但志贺菌属产β内酰胺酶耐药基因的报道鲜见[6].我们对20株志贺菌属进行9种β内酰胺酶基因(TEM、SHV、CARB、LAP、GES、PER、VEB、CTX-M-1群、OXA-1群)检测,经测序和BLASTn比对发现CTX-M-55型,报告如下.     

广州地区肺炎克雷伯菌携带CTX-M-14质粒同源性分析

目的研究广州肺炎克雷伯菌(Klebsiella pneumonia,Kp)CTX-M-14型超广谱β-内酰胺酶(ESBLs)的质粒同源性特征。方法收集2007～2008年广州地区9家医院临床分离的产ESBLs肺炎克雷伯菌,PCR检测ESBLs分子表型;用肠杆菌科基因间重复序列PCR(Enterobacteriaceae repetive intergenic consensus-PCR,ERIC-PCR)分析产CTX-M-14型ESBLs菌株的分子同源性;取产CTX-M-14型ESBLs的Kp的所有非克隆株,通过结合试验、质粒图谱、PCR分析blaCTX-M-14基因环境。结果产ESBLsKp共181株,69.1%(125/181)的产ESBLs株为CTX-M表型;其中产CTX-M-14型ESBLs株的检出率为28.2%(51/181),经ERIC-PCR分析,共分为33个基因型;基因环境显示,75.7%(25/33)blaCTX-M-14位于90 kb的可接合质粒上,其他耐药基因blaSHV、blaDHA-1、blaOXA-1、qnr、aac(6’)-Ib-cr等均未检到;有28株菌的blaCTX-M-14位于ISEcp1-like插入序列下游,ISEcp1-like末端与blaCTX-M-14间距均为42 bp,有2株菌ISEcp1末端与blaCTX-M-14起始区间距也为42 bp;但在ISECP1中间有一个S10插入序列。结论广州地区ESBLs主要分子表型为CTX-M型,主要流行为CTX-M-14型,携blaCTX-M-14质粒的传播,可能是本地区CTX-M型ESBLs高发生率的主要原因。     

Detection and Molecular Characterization of Escherichia coli CTX-M-15 and Klebsiella pneumoniae SHV-12 β-Lactamases from Bovine Mastitis Isolates in the United Kingdom

Recent reports raised concerns about the role that farm stock may play in the dissemination of extended-spectrum β-lactamase (ESBL)-producing bacteria. This study characterized the ESBLs in two Escherichia coli and three Klebsiella pneumoniae subsp. pneumoniae isolates from cases of clinical bovine mastitis in the United Kingdom. Bacterial culture and sensitivity testing of bovine mastitic milk samples identified Gram-negative cefpodoxime-resistant isolates, which were assessed for their ESBL phenotypes. Conjugation experiments and PCR-based replicon typing (PBRT) were used for characterization of transferable plasmids. E. coli isolates belonged to sequence type 88 (ST88; determined by multilocus sequence typing) and carried bla_CTX-M-15 and bla_TEM-1, while K. pneumoniae subsp. pneumoniae isolates carried bla_SHV-12 and bla_TEM-1. Conjugation experiments demonstrated that bla_CTX-M-15 and bla_TEM-1 were carried on a conjugative plasmid in E. coli, and PBRT identified this to be an IncI1 plasmid. The resistance genes were nontransferable in K. pneumoniae subsp. pneumoniae isolates. Moreover, in the E. coli isolates, an association of ISEcp1 and IS26 with bla_CTX-M-15 was found where the IS26 element was inserted upstream of both ISEcp1 and the bla_CTX-M promoter, a genetic arrangement highly similar to that described in some United Kingdom human isolates. We report the first cases in Europe of bovine mastitis due to E. coli CTX-M-15 and also of bovine mastitis due to K. pneumoniae subsp. pneumoniae SHV-12 β-lactamases in the United Kingdom. We also describe the genetic environment of bla_CTX-M-15 and highlight the role that IncI1 plasmids may play in the spread and dissemination of ESBL genes, which have been described in both human and cattle isolates.     

Dietary supplements and herbal medicine toxicities—when to anticipate them and how to manage them

Background

Dietary supplements and herbal medicines are gaining popularity in many developed countries.

Aims

Although most can be used without any problem, serious toxicities do occur.

Methods

Problems can be anticipated when they are used for non-traditional indications, at excessive dose, for prolonged duration, or by patients who are also on multiple modern pharmaceuticals. Problems should also be anticipated when these products claim to be able to relieve symptoms rapidly or when herbs with pronounced pharmacological effects or toxic components are used.

Results

Resuscitation, symptomatic and supportive care are the most important aspects of management of toxicities from these products.

Conclusion

This article reviews when problems with these products can be anticipated and outlines a practical approach to management.     

Molecular and Biochemical Characterization of CTX-M-131, a Natural Asp240Gly Variant Derived from CTX-M-2, Produced by a Providencia rettgeri Clinical Strain in S?o Paulo,Brazil

CTX-M-131 is a natural Asp240Gly variant from the CTX-M-2 group detected in a Providencia rettgeri clinical strain from Brazil. Molecular analysis showed that bla_CTX-M-131 was inserted in a complex class 1 integron harbored by a 112-kb plasmid, which has not been previously described as a platform for CTX-M-encoding genes with the Asp240Gly mutation. Steady-state kinetic parameters showed that the enzyme has a typical cefotaximase catalytic profile and an enhanced activity against ceftazidime.     

Widespread Dissemination of CTX-M-15 Genotype Extended-Spectrum-β-Lactamase-Producing Enterobacteriaceae among Patients Presenting to Community Hospitals in the Southeastern United States

Extended-spectrum-β-lactamase (ESBL)-producing organisms are increasingly prevalent. We determined the characteristics of 66 consecutive ESBL-producing isolates from six community hospitals in North Carolina and Virginia from 2010 to 2012. Fifty-three (80%) ESBL-producing isolates contained CTX-M enzymes; CTX-M-15 was found in 68% of Escherichia coli and 73% of Klebsiella isolates. Sequence type 131 (ST131) was the commonest type of E. coli, accounting for 48% of CTX-M-15-producing and 66% of CTX-M-14-producing isolates. In conclusion, the CTX-M genotype and ST131 E. coli were common among ESBL isolates from U.S. community hospitals.     

Unruptured brain aneurysms: when to screen and when to treat?

The detection rate of intracranial aneurysms has increased with the improved availability of non-invasive imaging methods. Moreover, persons who have relatives with intracranial aneurysms increasingly demand imaging to rule out aneurysms. To deal with these problems, radiologists require basic knowledge regarding the detection and treatment of unruptured intracranial aneurysms. The prevalence of aneurysms in the normal population is 2?-?3?%. It increases to 4?-?10?% in persons with one relative with an aneurysm and to about 20?% in persons with two relatives with an aneurysm. The average natural rupture risk is estimated to be 5?% within 5 years of detection. In the individual case it depends on several variables that are discussed here. According to the literature, the risk of endovascular aneurysm treatment is about 5?%. On the basis of these data, the benefit of MRA screening needs to be discussed individually with the patient.