CTX-M Type Research Articles

High prevalence of blaCTX-M extended-spectrum β-lactamase genes in Escherichia coli isolates from pets and emergence of CTX-M-64 in China

As a cause of community-acquired infections, extended-spectrum β-lactamase (ESBL)-producing Escherichia coli constitute an emerging public-health concern. Few data on the molecular epidemiology of ESBL-producing E. coli isolates from pets are available in China. Detection and characterization of ESBL genes (blaCTX-M, blaSHV and blaTEM) was conducted among 240 E. coli isolates recovered from healthy and sick pets in South China from 2007 to 2008. The clonal relatedness of ESBL-producing E. coli isolates was assessed by pulsed field gel electrophoresis. ESBL-encoding genes were identified in 97 (40.4%) of the 240 isolates and 96 (40.0%) of them harbored CTX-M. The most common CTX-M types were CTX-M-14 (n = 45) and CTX-M-55 (n = 24). The recently reported CTX-M-64 was identified in three isolates. Isolates producing CTX-M-27, -15, -65, -24, -3 and -9 were also identified. Ten isolates carried two or three CTX-M types, with the combination of CTX-M-14 and CTX-M-55 being the most frequent (n = 6). ISEcp1 was identified in the upstream region of 93 out of the 107 blaCTX-M genes (86.9%). The sequence of the spacer region (45 bp) between ISEcp1 and the start codon of all blaCTX-M-55 genes (except four) was identical to that of blaCTX-M-64. No major clonal relatedness was observed among these CTX-M producers. It is suggested that the horizontal transfer of blaCTX-M genes, mediated by mobile elements, contributes to their dissemination among E. coli isolates from pets. Our finding of high prevalence of ESBL in E. coli of companion animal origin illustrates the importance of molecular surveillance in tracking CTX-M-producing E. coli strains in pets.

CTX-M–Type Fluoroquinolone-Resistant Escherichia coli: Analysis of the Colonization of Residents and Inanimate Surfaces 1 Year after a First Case of Urinary Tract Infection at a Nursing Home in France

At a nursing home in France, 1 year after a first case of a cluster of urinary tract infections caused by an extended-spectrum beta-lactamase-producing strain of Escherichia coli, 9 (22%) of 49 residents were colonized with the outbreak strain. Colonization was associated with poor state of health (P = .04), incontinence (P = .007), and recent treatment with fluoroquinolones and/or cephalosporins (P = .003).

Prevalence of antimicrobial-resistant pathogens in Canadian hospitals: results of the Canadian Ward Surveillance Study (CANWARD 2008).

A total of 5,282 bacterial isolates obtained between 1 January and 31 December 31 2008, inclusive, from patients in 10 hospitals across Canada as part of the Canadian Ward Surveillance Study (CANWARD 2008) underwent susceptibility testing. The 10 most common organisms, representing 78.8% of all clinical specimens, were as follows: Escherichia coli (21.4%), methicillin-susceptible Staphylococcus aureus (MSSA; 13.9%), Streptococcus pneumoniae (10.3%), Pseudomonas aeruginosa (7.1%), Klebsiella pneumoniae (6.0%), coagulase-negative staphylococci/Staphylococcus epidermidis (5.4%), methicillin-resistant S. aureus (MRSA; 5.1%), Haemophilus influenzae (4.1%), Enterococcus spp. (3.3%), Enterobacter cloacae (2.2%). MRSA comprised 27.0% (272/1,007) of all S. aureus isolates (genotypically, 68.8% of MRSA were health care associated [HA-MRSA] and 27.6% were community associated [CA-MRSA]). Extended-spectrum β-lactamase (ESBL)-producing E. coli occurred in 4.9% of E. coli isolates. The CTX-M type was the predominant ESBL, with CTX-M-15 the most prevalent genotype. MRSA demonstrated no resistance to ceftobiprole, daptomycin, linezolid, telavancin, tigecycline, or vancomycin (0.4% intermediate intermediate resistance). E. coli demonstrated no resistance to ertapenem, meropenem, or tigecycline. Resistance rates with P. aeruginosa were as follows: colistin (polymyxin E), 0.8%; amikacin, 3.5%; cefepime, 7.2%; gentamicin, 12.3%; fluoroquinolones, 19.0 to 24.1%; meropenem, 5.6%; piperacillin-tazobactam, 8.0%. A multidrug-resistant (MDR) phenotype occurred frequently in P. aeruginosa (5.9%) but uncommonly in E. coli (1.2%) and K. pneumoniae (0.9%). In conclusion, E. coli, S. aureus (MSSA and MRSA), P. aeruginosa, S. pneumoniae, K. pneumoniae, H. influenzae, and Enterococcus spp. are the most common isolates recovered from clinical specimens in Canadian hospitals. The prevalence of MRSA was 27.0% (of which genotypically 27.6% were CA-MRSA), while ESBL-producing E. coli occurred in 4.9% of isolates. An MDR phenotype was common in P. aeruginosa.

Prevalence and resistance patterns of extended‐spectrum and AmpC β‐lactamase in Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis, and Salmonella serovar Stanley in a Korean tertiary hospital

A total of 100 clinical isolates of Escherichia coli (n = 35), Klebsiella pneumoniae (n = 63), Proteus mirabilis (n = 1), and Salmonella serovar Stanley (n = 1), showing resistance to cefoxitin, or returning positive in extended-spectrum β-lactamase (ESBL) by Clinical and Laboratory Standards Institute (CLSI) ESBL confirmatory method, were studied. The isolates were examined by the boronic acid (BA) disk test, polymerase chain reaction, and pulsed-field gel electrophoresis (PFGE) to investigate genetic similarities. The concurrence rates for ESBLs by the CLSI and the BA disk test were 97% for E. coli and 96.7% for K. pneumoniae. A total of 41 isolates showing cefoxitin resistance yielded all positive by the BA disk test. All the 33 K. pneumoniae isolates, which showed positive by the BA disk test, were carrying AmpC genes. The TEM and CTX-M types were predominant in E. coli and the SHV and the CIT and/or DHA types were predominant in K. pneumoniae. PFGE analysis showed almost 75% of genetic similarities among K. pneumoniae isolates producing ESBLs and/or AmpC β-lactamases (AmpCs) as each K. pneumoniae carried variable genes and showed variable antibiotic patterns. Clearly, the BA disk test was a useful method for the detection of ESBLs and AmpCs. In particular, cefoxitin resistance and BA-positive trait of K. pneumoniae do reflect the presence of AmpC genes in the organism.

Emergence and Dissemination of Extended‐Spectrum β‐Lactamase–ProducingEscherichia coliin the Community: Lessons from the Study of a Remote and Controlled Population

Intestinal carriage is a key factor in extended-spectrum beta-lactamase (ESBL) infection epidemiology but is difficult to study in open communities. To overcome this problem, we studied a highly stable group of Amerindians for whom we reported an ESBL carriage prevalence of 3.2% in 2001. In 2006, ESBL carriage was assessed among 163 healthy volunteer adults. ESBL isolates were identified, and their molecular resistance mechanisms were characterized. Antibiotic use in the year before sampling and the epidemiological characteristics of the population were analyzed. Results were compared to those obtained in 2001. In 2006, the ESBL carriage prevalence, exclusively comprising Escherichia coli, was 8.0%. It mainly consisted of CTX-M-type ESBL. The strains and plasmids carrying ESBL were heterogeneous, but 1 CTX-M-2-producing strain was found in 4.3% of the subjects analyzed. No individual risk factor was identified. However, overall antibiotic use had almost doubled since 2001. A 3-fold increase was noted for beta-lactams. In this population, the frequency of ESBL increased with time because of the appearance of CTX-M ESBL, mimicking what occurs in the developed world. This resulted from the probable repeated introduction of new strains and plasmids and from interindividual dissemination. During the same period, antibiotic use substantially increased.

Genetic Characterization of Extended-Spectrum Beta-Lactamases inEscherichia coliIsolates of Pigs from a Portuguese Intensive Swine Farm

There is a great concern by the emergence and the wide dissemination of extended-spectrum beta-lactamases (ESBLs) among animal Escherichia coli isolates. We intended to determinate the carriage level and type of ESBLs in E. coli obtained from fecal samples from pigs raised on an intensive pig farm in Portugal; further to characterize other associated resistance genes and their plasmid content, the phylogenetic groups, and the clonal relationship of ESBL-positive isolates. Sixty-five fecal samples were seeded in Levine media supplemented with cefotaxime for E. coli recovery. Susceptibility to 16 antimicrobial agents was performed by disk diffusion agar. ESBL-phenotypic detection was carried out by double-disk test; and the presence of the genes encoding TEM, OXA, SHV, and CTX-M type beta-lactamases was studied by polymerase chain reaction and sequencing. Other mechanisms of antimicrobial resistance and phylogenetic groups were also determined. Clonal relationship was performed by pulsed-field gel electrophoresis. ESBL-producing E. coli isolates were detected in 16 fecal samples, and one isolate per sample was studied. The CTX-M-1 type ESBL was detected in the 16 isolates. The gene encoding TEM-1 was identified to be associated with eight CTX-M-1-positive isolates. The tet(A) gene was found in 12 of 14 tetracycline-resistant isolates, and the aadA or strA-strB genes were found in the streptomycin-resistant isolates. Fourteen and two ESBL-containing isolates belonged to A and B1 phylogenetic groups, respectively. Clonal relationship of ESBL-containing isolates identified seven unrelated patterns. Swine represent an important reservoir of ESBL-containing E. coli isolates, especially of the CTX-M-1 type.

Characterization, and comparison, of human clinical and black-headed gull (Larus ridibundus) extended-spectrum -lactamase-producing bacterial isolates from Kalmar, on the southeast coast of Sweden

Antibiotic resistance is one of the great challenges for modern healthcare. In Gram-negative bacteria, CTX-M-type extended-spectrum beta-lactamases (ESBLs) have been rapidly spreading through Europe since the early 2000s. In Sweden, ESBL-producing Escherichia coli are still rare, but a 3-fold increase has been seen from 2004 to 2007. Enterobacteria and normal flora of wild animals, with or without antibiotic resistance traits, constitute a potential source of human infection and colonization. We studied wild birds with the aim to understand the environmental dissemination of antibiotic resistance and, focusing on clinically relevant resistance types, we made comparisons with human clinical samples. In this study, ESBL-producing human clinical isolates and isolates from juvenile black-headed gulls from Kalmar County hospital and the city of Kalmar, respectively, on the southeast coast of Sweden, were characterized and compared. Despite a low frequency of antibiotic resistance among the isolates from gulls, ESBL-producing E. coli isolates were found, two with bla(CTX-M-14) and one with bla(CTX-M-15). The same CTX-M types were dominant among human ESBL isolates. In addition, gull isolates were dispersed among the human samples in the PhenePlate clustering system, indicating that they neither differ from the human isolates nor form any separate clonal clustering. The finding of CTX-M-type ESBLs in E. coli isolated from black-headed gulls in Sweden, where 'background resistance' is low, is consistent with an ongoing environmental spread of these plasmid-borne resistance genes. The results indicate that a potential for transfer between the human population and environment exists even in countries with a low level of antibiotic resistance.

Evaluation of a DNA Microarray, the Check-Points ESBL/KPC Array, for Rapid Detection of TEM, SHV, and CTX-M Extended-Spectrum β-Lactamases and KPC Carbapenemases

Extended-spectrum beta-lactamases (ESBLs) and Klebsiella pneumoniae carbapenemases (KPC carbepenemases) have rapidly emerged worldwide and require rapid identification. The Check-Points ESBL/KPC array, a new commercial system based on genetic profiling for the direct identification of ESBL producers (SHV, TEM, and CTX-M) and of KPC producers, was evaluated. Well-characterized Gram-negative rods (Enterobacteriaceae, Pseudomonas aeruginosa, Acinetobacter baumannii) expressing various ss-lactamases (KPC-2, SHV, TEM, and CTX-M types) were used as well as wild-type reference strains and isolates harboring ss-lactamase genes not detected by the assay. In addition, phenotypically confirmed ESBL producers isolated in clinical samples over a 3-month period at the Bicetre hospital were analyzed using the Check-Points ESBL/KPC array and by standard PCR. The Check-Points ESBL/KPC array allowed fast detection of all TEM, SHV, and CTX-M ESBL genes and of the KPC-2 gene. The assay allowed easy differentiation between non-ESBL TEM and SHV and their ESBL derivatives. None of the other tested ss-lactamase genes were detected, underlining its high specificity. The technique is suited for Enterobacteriaceae but also for P. aeruginosa and A. baumannii. However, for nonfermenters, especially P. aeruginosa, a 1:10 dilution of the total DNA was necessary to detect KPC-2 and SHV-2a genes reliably. The Check-Points ESBL/KPC array is a powerful high-throughput tool for rapid identification of ESBLs and KPC producers in cultures. It provided definitive results within the same working day, allowing rapid implementation of isolation measures and appropriate antibiotic treatment. It showed an interesting potential for routine laboratory testing.

The molecular characteristics of cefepime-susceptible Escherichia coli and Klebsiella spp. isolates with a positive β-lactamase screening test result but negative confirmation

A negative extended-spectrum β-lactamase (ESBL) phenotypic confirmation test result obtained after a positive ESBL screening test result but which was cefepime-susceptible (NCPSCS) using the Clinical and Laboratory Standards Institute (CLSI) methods has been observed among isolates of Escherichia coli and Klebsiella spp. in the antimicrobial surveillance program in Shanghai, China. Among isolates collected from Huashan Hospital in 2005, NCPSCS strains were observed in 2.5% of 433 E. coli isolates and in 1.2% of 562 Klebsiella spp. isolates. We then selected 11 E. coli isolates and seven Klebsiella spp. NCPSCS isolates. Transmission electron microscopy (TEM), SHV, plasmid-borne AmpC, and CTX-M type ESBL genes were detected by the polymerase chain reaction (PCR) method. We found that all except two K. pneumoniae strains of NCPSCS isolates producing ESBL and AmpC harbored a plasmid-borne CMY-2 or DHA-1 type AmpC enzyme. The majority of NCPSCS E. coli and K. pneumoniae strains from Shanghai harbor plasmid-borne AmpC enzyme, and we recommend that, when NCPSCS strains are identified, further work such as the PCR detection of ESBL genes is necessary to determine whether they will produce ESBLs. The ESBL-positive strains should be reported as resistant to cefepime according to the CLSI guidelines.

Diversity of Escherichia coli Strains Producing Extended-Spectrum β-Lactamases in Spain: Second Nationwide Study

The prevalence of extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli (ESBLEC) in Spain increased 8-fold from 2000 to 2006. ESBL type, clonal relationship, antimicrobial susceptibility, and clinical data about infections caused by ESBLEC are evaluated in a second nationwide study developed in 2006. From 1008 clinical isolates obtained over 2 months from 44 hospitals, 254 were used for further analysis. ESBL production was evaluated by synergy testing, PCR, and sequencing. Antimicrobial activity was evaluated by microdilution. The clonal relationship was evaluated by repetitive extragenic palindromic-PCR (REP-PCR). The O25b subtype and the new afa operon FM955459 were determined by triplex PCR in isolates producing CTX-M-15. Multilocus sequence typing was performed on these isolates. A total of 72% of all ESBLs were of the CTX-M type, 26.8% were of the SHV type, and 1.2% were of the TEM type. The most prevalent ESBLs were CTX-M-14 (119 isolates), SHV-12 (68 isolates), CTX-M-15 (37 isolates), and CTX-M-9 (21 isolates). By REP-PCR, 214 clones were detected. All but five CTX-M-15 ESBLEC isolates corresponded to the international O25b/ST131 clone. This clone had not been detected in the first study (published in 2000). Epidemiological and clinical features were studied in 304 representative patients. A total of 60% of the patients were older than 60 and had nonfatal underlying diseases, and 55% had recently received antibiotics. Urinary tract infections accounted for 71% of cases, and 9% were bacteremic. There has been a significant increase in the prevalence of ESBLEC in Spain, with most of these strains being CTX-M-producing isolates, including the pandemic O25b-ST131. SHV-12-producing E. coli remains an important cause of community-acquired infection.

Cefepime-resistant Gram-negative bacteremia in febrile neutropenic patients with hematological malignancies

This study was performed to determine the local etiologic pattern of blood culture isolates and antibiotic resistance in febrile neutropenic patients with hematological malignancies. A total of 142 blood culture isolates from febrile neutropenic patients admitted to our hematology unit were examined, particularly for the detection of cefepime resistance, because cefepime, a fourth-generation cephalosporin, has been used in our unit as initial therapy for febrile neutropenia. Among all isolates, 67 (47.2%) were Gram-positive bacteria, the majority of which were fully sensitive to vancomycin. Gram-negative bacteria accounted for 68 (47.9%) of the isolates. Cefepime resistance was seen in 24 (35.3%) of the Gram-negative isolates, and had significantly increased in 2007. The cefepime-resistant isolates primarily consisted of Escherichia coli, Pseudomonas aeruginosa, and Klebsiella pneumoniae. Approximately 60% of the cefepime-resistant isolates were extended-spectrum β-lactamase (ESBL)-producing organisms. Molecular analysis showed the predominant emergence of CTX-M types. Most of the cefepime-resistant isolates were resistant to third- and various fourth-generation cephalosporins, while having a high susceptibility to carbapenems, particularly meropenem. Cefepime resistance was often detected in the blood culture isolates from febrile neutropenic patients. This result suggests that therapeutic strategies for febrile neutropenia should be modified based on the local antibiotic resistance patterns.

A novel IS26 structure surrounds bla CTX-M genes in different plasmids from German clinical Escherichia coli isolates

This report focuses on the molecular characterization of 22 extended-spectrum β-lactamase-producing Escherichia coli isolates collected in a German university hospital during a period of 9 months in 2006. Relationship analysis of clinical isolates was done via PFGE, multilocus sequence typing, plasmid profiling and additionally PCR for bla ESBL detection and determination of phylogroups. After conjugal transfer, plasmid isolation and subsequent PCR for bla ESBL detection and determination of incompatibility groups were performed. Using one-primer walking, up to 3600 bp upstream and downstream of different bla CTX-M genes could be sequenced. β-Lactamases found were TEM-1 (n=14), SHV-5 (n=1) and a wide variety of CTX-M types (n=21), i.e. CTX-M-15 (n=12), CTX-M-1 (n=4), CTX-M-14 (n=2), CTX-M-9 (n=1), CTX-M-3 (n=1) and one new type, CTX-M-65 (n=1). In 18 isolates, bla ESBL genes were located on conjugative plasmids of sizes between 40 and 180 kbp belonging to incompatibility groups FII (n=9), N (n=5) and I1 (n=4). bla CTX-M was found to be associated with the common elements ISEcp1, IS26 and IS903-D, but with unusual spacer sequences for ISEcp1 in two isolates. These insertion sequences, connected to bla CTX-M as well as other genes, were located between two IS26 elements in a configuration that has not yet been described. The results reveal the emergence of bla ESBL, predominantly bla CTX-M, located on different plasmids harboured by genotypically different E. coli strains. The identical gene arrangement in the bla CTX-M neighbourhood in plasmids of different incompatibility groups indicates a main role of IS26 in distribution of mobile resistance elements between different plasmids.

CTX-M Type Extended Spectrum β-Lactamases in Escherichia coli Isolates From Community Acquired Upper Urinary Tract Infections at a University in the European Part of Turkey

Extended spectrum beta-lactamase (ESBL) producing Escherichia coli has been an emerging etiologic agent in the community acquired infections. We investigated the occurrence of ESBL producing E. coli isolated from patients admitted with community acquired urinary tract infection (UTI) to the hospital of the Trakya University, Turkey during 2006. Eleven single patient isolates of E. coli harboring ESBL were identified among 30 E. coli isolated from patients admitted with symptoms corresponding to upper UTI. CTX-M type ESBLs were detected in all 11 ESBL-producers by isoelectric focusing and polymerase chain reaction screening. Sequence analysis revealed CTX-M-1 in one isolate, CTX-M-3 in three isolates and CTX-M-15 in seven isolates. ESBL-producing E. coli isolated from community acquired UTIs are widespread in the European part of Turkey.

Changing prevalence of Escherichia coli with CTX-M–type extended-spectrum β-lactamases in outpatient urinary E. coli between 2003 and 2008

One hundred ninety-three single-patient isolates of Escherichia coli harboring extended-spectrum β-lactamases (ESBL) were identified among 11 407 E. coli urine isolates recovered from single-patient outpatient urine cultures from 2003 to 2008. The percentage of ESBL-producing E. coli among community-onset E. coli urine isolates increased from 0.21% in 2003 to 2.99% in 2008. One hundred seven of the ESBL producers were positive for the presence of bla CTX-M genes. The percentage of CTX-M–producing E. coli rose from 0.07% in 2003 to 1.66% in 2008. The annual percentage of ESBL E. coli producing CTX-Ms changed from 35% in 2003 to 64% in 2008. Genes belonging to 3 bla CTX-M groups: bla CTX-M-1 group, bla CTX-M-2 group, and bla CTX-M -9 group, were detected. In addition, resistance to commonly used antimicrobial agents for community-acquired urinary tract infections was found common among CTX-M–producing E. coli isolates. Ertapenem and nitrofurantoin showed good in vitro activity against CTX-M producers.

Citrobacterspp. Simultaneously HarboringblaCTX-M,blaTEM,blaSHV,blaampC, and Insertion Sequences IS26andorf513: an Evolutionary Phenomenon of Recent Concern for Antibiotic Resistance

A collection of 40 confirmed isolates of Citrobacter spp., obtained from the culture of 5,732 clinical samples during 2006 to 2008, was studied for the presence of blaCTX-M, blaTEM, blaSHV, and blaampC by monoplex and multiplex PCRs. These isolates were also looked at for the presence of insertion elements IS26 and orf513, which play an important role in the resistance gene pool. blaCTX-M, blaTEM, blaSHV, and blaampC were noticed in 67.5%, 40%, 25%, and 40% of isolates, respectively. Sequencing for the specific CTX-M type revealed the presence of CTX-M-15-type extended-spectrum beta-lactamases (ESBL). sul1-type integrons were detected in 32.5% (13/40) of isolates, and a single plasmid of ca. approximately 22 kb was also noticed in all the isolates harboring bla genes. A total of 48.2% (13/27) of isolates harboring blaCTX-M alleles were found to carry IS26 elements and 53.4% (7/13) of isolates harboring the sul1-type integrons were found to carry orf513. Alarmingly, a few isolates simultaneously carried IS26 and orf513, reflecting the occurrence of complex evolution. All the Citrobacter isolates were noticed to produce an amplicon of 400 bp in an IS26 PCR, similar to that of the predominant UK CTX-M-15-producing Escherichia coli clone (clone A) and suggesting a probable genetic relatedness between the two, which could not be proved with British and Indian E. coli isolates in our earlier studies. Here, a first report is being presented describing the occurrence of blaCTX-M-15 in Indian Citrobacter spp. This is also the first report describing the simultaneous occurrence of blaTEM, blaSHV, and blaampC along with blaCTX-M in class 1 integrons. The recent findings indicate that the genetic environment of blaCTX-M-15 has changed through the insertion of IS26 and orf513, although the consequences of these events remain uncertain. It perhaps also suggests a "turnover" of these mobile elements in the population over time.

Antimicrobial Susceptibility Patterns of KPC-Producing or CTX-M-Producing Enterobacteriaceae

Enterobacteriaceae clinical isolates harboring KPC-(178 strains) or CTX-M-encoding (67 strains) genes were collected during surveillance programs in the 2000-2007 period; and susceptibility was tested by broth microdilution methods. Organisms were dominantly collected in U.S. hospitals (93%). CTX-M-15 and -14 were the most prevalent CTX-M types (97%), all collected from the United States. KPC producers were isolated in the United States (160/178), Israel, China, and Argentina. bla(CTX-M)-carrying isolates were 95.5 and 98.5%, susceptible to Imipenem and meropenem respectively, and were all susceptible to tigecycline, whereas KPC-producing isolates were highly resistant to all antimicrobials tested except polymyxin B and tigecycline (90.6% and 99.4% susceptibility, respectively). The occurrence of KPC-producing and CTX-M-producing isolates has rapidly increased especially in U.S. hospitals, and expanded therapeutic options are needed to treat infections caused by these emerging organisms.

Fecal carriage of CTXM type extended-spectrum beta-lactamase-producing organisms by children and their household contacts

To investigate the epidemiology of fecal carriage of CTX-M type extended-spectrum beta-lactamases (ESBL)-producing organisms among children and their household contacts. Fecal carriage with CTX-M-producing organisms was studied in 53 children and 172 household members. Molecular methods were used to characterize the isolates. The children were mostly healthy and hospitalized for relatively mild febrile illnesses. Overall, the prevalence of fecal carriage of CTX-M-producing bacteria was 43.5% (admission children, 37.7%; household children, 20.7% and household adults, 50.3%). Household colonization index (defined by number of household carriers/total number of members) was significantly higher among families with at least one individual having a history of prolonged (>3 months) out-of-town residence in the previous year (mean+/-standard deviation; yes group, 0.67+/-0.36 vs. no group, 0.39+/-0.28, P=0.009) and was inversely correlated with the living space per person (R-square=0.139, P=0.006). Among 29 households with at least two carriers of CTX-M-producing enterobacteria, six clusters of clonally related strains were shared by 15 individuals from seven households; with both intra- and inter-household transmission. CTX-M beta-lactamases may spread extensively amongst family members in the home.

Extended-spectrum beta-lactamase-producing Escherichia coli in patients with travellers’ diarrhoea

The identification of patients carrying extended-spectrum beta-lactamase (ESBL)-producing bacteria is important, since these patients are at risk of receiving inappropriate empirical therapy if they become infected. The purpose of this study was to investigate the occurrence of ESBL-producing bacteria in patients with travellers' diarrhoea. Patients with travellers' diarrhoea (N = 242) having delivered stool samples for the diagnosis of Salmonella, Shigella, Yersinia or Campylobacter, were also examined for ESBL-producing Escherichia coli, Klebsiella pneumoniae and Proteus mirabilis. The overall prevalence of faecal carriage of ESBL-producing bacteria was 24% (58/242). Of the patients who had travelled in Europe, 3% (2/63) were found to be ESBL carriers in comparison to 36% (50/138) of those who had travelled outside Europe. ESBL-producing E. coli was especially common among patients returning from India (11/14), Egypt (19/38; 50%) and Thailand (8/38; 22%). In total, 90% of the genes of the ESBL-positive samples were of CTX-M type. The CTX-M-1 group dominated, followed by the CTX-M-9 group. The repetitive sequence-based PCR fingerprint pattern showed that there was no similarity between the ESBL strains found. Patients who have travelled outside Europe are at high risk of being colonized with ESBL-producing Enterobacteriaceae, and, if infected, are also at risk of receiving inappropriate empirical antibiotic therapy.

Integrated Detection of Extended-Spectrum-Beta-Lactam Resistance by DNA Microarray-Based Genotyping of TEM, SHV, and CTX-M Genes

Extended-spectrum beta-lactamases (ESBL) of the TEM, SHV, or CTX-M type confer resistance to beta-lactam antibiotics in gram-negative bacteria. The activity of these enzymes against beta-lactam antibiotics and their resistance against inhibitors can be influenced by genetic variation at the single-nucleotide level. Here, we describe the development and validation of an oligonucleotide microarray for the rapid identification of ESBLs in gram-negative bacteria by simultaneously genotyping bla(TEM), bla(SHV), and bla(CTX-M). The array consists of 618 probes that cover mutations responsible for 156 amino acid substitutions. As this comprises unprecedented genotyping coverage, the ESBL array has a high potential for epidemiological studies and infection control. With an assay time of 5 h, the ESBL microarray also could be an attractive option for the development of rapid antimicrobial resistance tests in the future. The validity of the DNA microarray was demonstrated with 60 blinded clinical isolates, which were collected during clinical routines. Fifty-eight of them were characterized phenotypically as ESBL producers. The chip was characterized with regard to its resolution, phenotype-genotype correlation, and ability to resolve mixed genotypes. ESBL phenotypes could be correctly ascribed to ESBL variants of bla(CTX-M) (76%), bla(SHV) (22%), or both (2%), whereas no ESBL variant of bla(TEM) was found. The most prevalent ESBLs identified were CTX-M-15 (57%) and SHV-12 (18%).

Prévalence des souches de Escherichia coli et de Klebsiella pneumoniae productrices de β-lactamases à spectre étendu de type CTX-M à l’hôpital Bretonneau (CHRU de Tours)

The CTX-M type extended spectrum β-lactamases constitute a rapidly growing cluster of enzymes that have disseminated geographically. This study evaluates the prevalence of these enzymes in the university hospital in Tours, in 2007. Twenty-eight strains were studied: 21 Escherichia coli and seven Klebsiella pneumoniae. The gene bla CTX-M was detected by real-time PCR for 27 strains. The CTX-M-1 group, including CTX-M-15, was the most frequent CTX-M-type enzyme.