Emergence of extended-spectrum beta-lactamase (CTX-M-15 and CTX-M-14)-producing nontyphoid Salmonella with reduced susceptibility to ciprofloxacin among food animals and humans in Korea

Twenty of 1,279 nontyphoid Salmonella strains isolated from food animals and humans produced CTX-M-type extended-spectrum β-lactamase. All expressed CTX-M-15, except two which coexpressed CTX-M-14 and TEM-1. Insertion sequence ISEcp1 was identified upstream of bla(CTX-M) genes. The bla(CTX-M-15) and bla(CTX-M-14) genes were disseminated by large conjugative IncFIIs and IncI1-Iγ plasmids, respectively.     

Antibiotic resistance in orthopaedic surgery: acute knee prosthetic joint infections due to extended-spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae

The aim of this study was to describe the prevalence and characteristics of knee prosthetic joint infections due to extended-spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae. From 2000 to 2007, 132 infections out of 5,076 arthroplasties (2.6%) were registered. Seven out of 132 infections (5.3%) were due to ESBL-producing Enterobacteriaceae, Escherichia coli in six cases and Klebsiella pneumoniae in one. Open debridement and retention of the implant was the first surgical approach and all patients received intravenous carbapenems. Relapse was documented in four cases and remission in three. Therefore, debridement without prosthesis removal was associated with a high failure rate.     

The first major extended-spectrum beta-lactamase outbreak in Scandinavia was caused by clonal spread of a multiresistant Klebsiella pneumoniae producing CTX-M-15

Between May and December 2005, 64 multidrug-resistant isolates of Klebsiella pneumoniae were detected from patients admitted to Uppsala University Hospital. This represented a dramatic increase in ESBL-producing K. pneumoniae compared to previous years. To investigate the epidemiology and to characterize the resistance mechanisms of the isolates, a study was initiated. Antibiotic susceptibility was determined by means of the Etest and the disc diffusion method. Extended-spectrum beta-lactamase (ESBL) production was identified by clavulanic acid synergy test and confirmed with PCR amplification followed by DNA sequencing. DNA profiles of the isolates were examined with pulsed-field gel electrophoresis (PFGE). All isolates were resistant or exhibited reduced susceptibility to cefadroxil, cefuroxime, cefotaxime, ceftazidime, aztreonam, piperacillin/tazobactam, ciprofloxacin, tobramycin, and trimethoprim-sulfamethoxazole. They produced ESBL of the CTX-M-15 type, and the involvement of a single K. pneumoniae clone was shown. This is the first major clonal outbreak of multiresistant ESBL-producing K. pneumoniae in Scandinavia. The outbreak demonstrates the epidemic potential of enterobacteria containing ESBLs of the CTX-M type, even in a country with a relatively low selective pressure and a low prevalence of multiresistant bacteria.     

Detection of extended-spectrum beta-lactamase (ESBL)-producing strains by the Etest ESBL screen.

Resistance to contemporary broad-spectrum beta-lactams, mediated by extended-spectrum beta-lactamase (ESBL) enzymes, is an increasing problem worldwide. The Etest (AB Biodisk, Solna, Sweden) ESBL screen uses stable gradient technology to evaluate the MIC of ceftazidime alone compared with the MIC of ceftazidime with clavulanic acid (2 micrograms/ml) to facilitate the recognition of strains expressing inhibitable enzymes. In the present study, ESBL-producing strains (17 Escherichia coli transconjugants) were studied to define "sensitive" interpretive criteria for the Etest ESBL screen. These criteria (reduction of the ceftazidime MIC by > 2 log2 dilution steps in the presence of clavulanic acid) defined a group of 92 probable ESBL-positive organisms among the 225 tested strains of Klebsiella species and E. coli having suspicious antibiogram phenotypes. With a subset of 82 clinical strains, the Etest ESBL screen was more sensitive (100%) than the disk approximation test (87%) and was more convenient. The MICs of ciprofloxacin, gentamicin, and tobramycin at which 50% of isolates are inhibited were 16- to 128-fold higher (coresistance) for the ESBL screen-positive group of strains than for the ESBL screen-negative group of strains. Some strains for which cephalosporin MICs were elevated and which were Etest ESBL screen negative were also cefoxitin resistant, i.e., consistent with a chromosomally mediated AmpC resistance phenotype. The Etest ESBL screen test with the ceftazidime substrate appears to be a useful method for detecting or validating the presence of enteric bacilli potentially producing this type of beta-lactamase.     

Clonal dissemination of extended-spectrum beta-lactamase (ESBL)-producing Klebsiella pneumoniae isolates in a Korean hospital

In this study, we investigated the molecular characteristics of extended-spectrum beta-lactamase (ESBL)-producing Klebsiella pneumoniae isolates that were recovered from an outbreak in a Korean hospital. A new multilocus sequence typing (MLST) scheme for K. pneumoniae based on five housekeeping genes was developed and was evaluated for 43 ESBL-producing isolates from an outbreak as well as 38 surveillance isolates from Korea and also a reference strain. Overall, a total of 37 sequence types (STs) and six clonal complexes (CCs) were identified among the 82 K. pneumoniae isolates. The result of MLST analysis was concordant with that of pulsedfield gel electrophoresis. Most of the outbreak isolates belonged to a certain clone (ST2), and they produced SHV-1 and CTX-M14 enzymes, which was a different feature from that of the K. pneumoniae isolates from other Korean hospitals (ST20 and SHV-12). We also found a different distribution of CCs between ESBL-producing and -nonproducing K. pneumoniae isolates. The MLST method we developed in this study could provide unambiguous and well-resolved data for the epidemiologic study of K. pneumoniae. The outbreak isolates showed different molecular characteristics from the other K. pneumoniae isolates from other Korean hospitals.     

Prevalence and characterisation of extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli isolates in healthy volunteers in Tunisia

The objective of this investigation was to analyse the carriage rate of extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli in faecal samples of healthy humans in Tunisia and to characterise the recovered isolates. One hundred and fifty samples were inoculated on MacConkey agar plates supplemented with cefotaxime (2 μg/ml) for ESBL-positive E. coli recovery. The characterisation of ESBL genes and their genetic environments, detection of associated resistance genes, multilocus sequence typing (MLST) and phylogroup typing were performed by polymerase chain reaction (PCR) and sequencing. The presence and characterisation of integrons and virulence factors were studied by PCR and sequencing. ESBL-positive E. coli isolates were detected in 11 of 150 faecal samples (7.3%) and one isolate/sample was further characterised. These isolates contained the blaCTX-M-1 (ten isolates) and blaTEM-52c genes (one isolate). The ISEcp1 (truncated by IS10 in four strains) and orf477 sequences were found upstream and downstream, respectively, of all bla (CTX-M-1) genes. Seven different sequence types (STs) and three phylogroups were identified among CTX-M-1-producing isolates [ST/phylogroup (number of isolates)]: ST58/B1 (3), ST57/D (2), ST165/A (1), ST155/B1 (1), ST10/A (1), ST398/A (1) and ST48/B1 (1). The TEM-52-producing isolate was typed as ST219 and phylogroup B2. Six ESBL isolates contained class 1 integrons with the gene cassettes dfrA17-aadA5 (five isolates) and dfrA1-aadA1 (one). Healthy humans in the studied country could be a reservoir of CTX-M-1-producing E. coli.     

Clonal emergence of extended-spectrum beta-lactamase (CTX-M-2)-producing Salmonella enterica serovar Virchow isolates with reduced susceptibilities to ciprofloxacin among poultry and humans in Belgium and France (2000 to 2003)

Antibiotic treatment is not required in cases of Salmonella enterica gastroenteritis but is essential in cases of enteric fever or invasive salmonellosis or in immunocompromised patients. Although fluoroquinolones and extended-spectrum cephalosporins are the drugs of choice to treat invasive Salmonella, resistance to these antibiotics is increasing worldwide. During the period 2000 to 2003, 90 Salmonella enterica serovar Virchow poultry and poultry product isolates and 11 serovar Virchow human isolates were found to produce an extended-spectrum beta-lactamase, CTX-M-2, concomitantly with a TEM-1 beta-lactamase. The bla(CTX-M-2) gene was located on a large conjugative plasmid (>100 kb). Pulsed-field gel electrophoresis indicated a clonal relationship between the poultry and human isolates. All these isolates displayed additional resistance to trimethoprim-sulfamethoxazole and tetracycline as well as a reduced susceptibility to ciprofloxacin (MICs of between 0.5 and 1 mug/ml). CTX-M-2-producing Salmonella with a reduced susceptibility to fluoroquinolones constitutes a major concern, since such strains could disseminate on a large scale and jeopardize classical antibiotic therapy in immunocompromised patients.     

Nosocomial outbreak of CTX-M-15-producing E. coli in Norway

Seven E. coli isolates expressing resistance to 3rd generation cephalosporins were recovered from blood (n=2), kidney and lung tissue (n=1), and urinary tract (n=4) samples from seven patients hospitalised or recently discharged from the Divisions of Geriatrics and Pulmonary Medicine, Central Hospital of Rogaland, between July and September 2004. All isolates expressed a typical ESBL-cefotaximase profile (cefotaxime MIC>ceftazidime MIC) with clavulanic acid synergy. A bla(CTX-M-15) genotype was confirmed in six strains that were coresistant to gentamicin, nitrofurantoin, trimethoprim-sulfamethoxazole and ciprofloxacin. A bla(CTX-M-3) genotype was detected in the last strain. XbaI-PFGE patterns of the six bla(CTX-M-15) isolates revealed a clonal relationship. Bla(CTX-M-15) strains were also positive for the ISEcp1-like insertion sequences that have been shown to be involved in the mobilization of bla(CTX-M.) Further analyses revealed two bla(CTX-M-15)-positive E. coli urinary isolates clonally related to the outbreak strain from two different patients at the same divisions in January and February 2004. These patients were later re-hospitalised and one had E. coli with an ESBL-cefotaximase profile in sputum and nasopharyngeal specimen during the outbreak period. Clinical evaluation suggests that the CTX-M-producing E. coli strains contributed to death in three patients due to delayed efficient antimicrobial therapy. The outbreak emphasises the epidemic potential of multiple-antibiotic-resistant CTX-M-15-producing E. coli also in a country with low antibiotic usage and low prevalence of antimicrobial resistance.     

Clinical importance of extended-spectrum beta-lactamase (PER-1-type)-producing Acinetobacter spp. and Pseudomonas aeruginosa strains.

Recently, an extended-spectrum beta-lactamase (PER-1) was found to be disseminated among Acinetobacter spp. and Pseudomonasaeruginosa isolates in Turkey. A population-based cohort study was conducted to elucidate predictive mortality factors in patients with nosocomial infections caused by Acinetobacter spp. and P. aeruginosa, with particular reference to PER-1-type extended-spectrum beta-lactamase (ESBL) production. The study group comprised 16 and 21 non-survivors and 82 and 126 survivors in cohorts infected with Acinetobacter and P. aeruginosa, respectively. In the Acinetobacter-infected cohort, nosocomial pneumonia, hypotension and infection with a PER-positive isolate were independent predictors of mortality. In the P. aeruginosa-infected cohort, impaired consciousness, a PER-positive isolate, male sex and (with a negative relative risk) urinary tract infection were independent predictors of death. This study demonstrated the relationship of PER-1-type ESBL-producing Acinetobacter spp. and P. aeruginosa with poor clinical outcome.     

Raman spectroscopic analysis of the clonal and horizontal spread of CTX-M-15-producing Klebsiella pneumoniae in a neonatal intensive care unit

Nosocomial outbreaks of extended-spectrum β-lactamase (ESBL)-producing Klebsiella pneumoniae are an increasing concern in neonatal intensive care units (NICUs). We describe an outbreak of ESBL-producing K. pneumoniae that lasted 5?months and affected 23 neonates in our NICU. Proton pump inhibitor and extended-spectrum cephalosporin exposure were significantly associated with the risk of ESBL-producing K. pneumoniae colonisation and/or infection. Thirty isolates recovered from clinical, screening and environmental samples in the NICU were studied by means of Raman spectroscopy, pulsed-field gel electrophoresis and repetitive extragenic palindromic polymerase chain reaction (rep-PCR). The Raman clustering was in good agreement with the results of the other two molecular methods. Fourteen isolates belonged to the Raman clone 1 and 16 to the Raman clone 3. Molecular analysis showed that all the strains expressed SHV-1 chromosomal resistance, plasmid-encoded TEM-1 and CTX-M-15 β-lactamases. Incompatibility groups of plasmid content identified by PCR-based replicon typing indicated that resistance dissemination was due to the clonal spread of K. pneumoniae and horizontal CTX-M-15 gene transfer between the two clones.     

Nosocomial outbreak of infections by Proteus mirabilis that produces extended-spectrum CTX-M-2 type beta-lactamase

Nineteen multidrug-resistant Proteus mirabilis strains were isolated from 19 patients suffering from infections probably caused by P. mirabilis. These strains were recovered from urine or other urogenital specimens of 16 inpatients and three outpatients with a hospitalization history in a urology ward of Funabashi Medical Center, from July 2001 to August 2002. These strains demonstrated resistance to cefotaxime, ceftriaxone, cefpodoxime, and aztreonam, while they were highly susceptible to ceftazidime (MIC, 相似文献   

Characterization of extended-spectrum beta-lactamase (TEM-52)-producing strains of Salmonella enterica serovar typhimurium with diverse resistance phenotypes

Two Salmonella enterica serovar Typhimurium strains from different clonal origins, both producing an extended-spectrum beta-lactamase (TEM-52), were isolated from a patient. This enzyme was encoded on a single plasmid and was found at very low levels in one strain, while being encoded on multiple plasmids and in multiple different EcoRI fragments in the other strain.     

CTX-M-3 and CTX-M-15 extended-spectrum beta-lactamases in isolates of Escherichia coli from a hospital in Algiers, Algeria

Sixteen strains of Escherichia coli isolated between January and June 2005 in a hospital in Algiers carry the ISEcp1 element and the TEM and either CTX-M-3 (n=3) or CTX-M-15 (n=13) beta-lactamases. Fourteen of the isolates are multidrug resistant. Five isolates from the neonatal ward were indistinguishable by pulsed-field gel electrophoresis.     

Comparison of nine phenotypic methods for detection of extended-spectrum beta-lactamase production by Enterobacteriaceae

The detection of extended-spectrum β-lactamase-producing (ESBL) bacteria is of importance for infection control and epidemiological surveillance. We aimed to compare phenotypic methods available in the routine laboratory and to evaluate two-step strategies using these methods for the detection of ESBL-positive Enterobacteriaceae. Two methods used for routine susceptibility testing (Vitek2 and disk diffusion methods) and seven methods designed for the detection of ESBL production (ESBL Etests, combination disks, double-disk synergy [DDS] methods on Mueller-Hinton [MH] agar and cloxacillin-containing MH agar, and the Cica-Beta test) were tested against 107 strains of Enterobacteriaceae not susceptible to extended-spectrum cephalosporins. All strains were screened for the presence of acquired ESBL-encoding genes by PCR, and the PCR result was considered the gold standard for evaluation of the other test methods. Among the 107 strains, 52 (49%) were ESBL positive. With Vitek2, sensitivities were the highest when using extended cards (73% to 79%), but 25% to 31% of the strains yielded indeterminate results. For the disk diffusion method, sensitivities were the highest (96%) when testing at least cefotaxime, cefepime, and a third compound (ceftazidime, cefpodoxime, or aztreonam). For the specific methods, specificities ranged from 62% (ceftazidime ESBL Etest) to 100% (DDS using a disk spacing of 20 mm). When a method designed for ESBL detection was used on strains considered ESBL negative or with an indeterminate result by a first routine susceptibility method, sensitivities reached 100% for a majority of combinations. In conclusion, two-step strategies using phenotypic methods available in most clinical laboratories may reach a sensitivity of 100% for ESBL detection among a large panel of species, including AmpC producers, providing a sensible choice of tests.