Comparative assessment of inoculum effects on the antimicrobial activity of amoxycillin-clavulanate and piperacillin-tazobactam with extended-spectrum β-lactamase-producing and extended-spectrum β-lactamase-non-producing Escherichia coli isolates.

A significant inoculum-size effect has been observed with piperacillin-tazobactam, and has been associated with β-lactamase production in extended-spectrum β-lactamase (ESBL) producers. This association has not been previously studied in the case of amoxycillin-clavulanate. Piperacillin-tazobactam and amoxycillin-clavulanate were compared, using high inocula of susceptible strains either harbouring ESBLs or not. Two non-ESBL-producing and 15 amoxycillin-clavulanate-susceptible and piperacillin-tazobactam-susceptible ESBL-producing Escherichia coli isolates, and their respective transconjugants, were tested in dilution susceptibility tests using standard and 100-fold higher inocula. Three ESBL-producing strains and E. coli ATCC 25922 were selected for time-kill studies using standard and high initial inocula. At high inocula, MICs of piperacillin increased >eight-fold for non-ESBL-producing strains, and MICs of piperacillin-tazobactam (8 : 1 ratio or with tazobactam fixed at 4 mg/L) increased>eight-fold for all ESBL-producing strains. However, amoxycillin MICs were not affected by a high inoculum with non-ESBL-producing strains, whereas the MICs of amoxycillin-clavulanate (2 : 1 and 4 : 1) increased ≤four-fold for ESBL producers, using the broth and agar dilution methods. In kinetic studies at a high inoculum, amoxycillin and amoxycillin-clavulanate were bactericidal against E. coli ATCC 25922, whereas piperacillin and piperacillin-tazobactam yielded decreases of <1 log₁₀ CFU/mL. Similarly, at a high inoculum, only amoxycillin-clavulanate was able to maintain bactericidal rates of killing over 24 h against the ESBL-positive E. coli isolates. The stability of amoxycillin-clavulanate and the contrasting results obtained with piperacillin-tazobactam against high inocula of ESBL-non-producing and ESBL-producing E. coli strains appear to be related to aspects other than the amount of β-lactamase production.     

Epidemiology and clinical features of community-onset bacteremia caused by extended-spectrum β-lactamase-producing Klebsiella pneumoniae

There is limited clinical information regarding community-onset bacteremia caused by extended-spectrum β-lactamase (ESBL)-producing Klebsiella pneumoniae. This study was performed to evaluate risk factors and clinical outcomes of community-onset bacteremia caused by ESBL-producing K. pneumoniae. A total of 435 patients with community-onset K. pneumoniae bacteremia were included and data from patients with ESBL-producing K. pneumoniae bacteremia were compared to those with non-ESBL-producing bacteremia. Isolates with ESBLs were microbiologically characterized. Of 435 patients with community-onset K. pneumoniae bacteremia, 33 (7.6%) were infected with ESBL producers, of which 25 were further classified as healthcare-associated infections. The most common underlying diseases were solid tumors (n?=?20, 60.6%) and diabetes mellitus (n?=?10, 30.3%), and the most common infection was intra-abdominal infection (n?=?20, 60.6%). Multivariate analysis showed that corticosteroid use (odds ratio [OR]?=?13.73, 95% confidence interval [CI]?=?1.93-97.6, p?=?0.009), percutaneous tubes (OR?=?7.30, 95% CI?=?2.41-22.12, p?相似文献   

Virulence characteristics of translocating Escherichia coli and the interleukin-8 response to infection

Four efficiently translocating Escherichia coli (TEC) strains isolated from the blood of humans (HMLN-1), pigs (PC-1) and rats (KIC-1 and KIC-2) were tested for their ability to adhere and translocate across human gut epithelial Caco-2 and HT-29 cells, to elicit a proinflammatory response and for the presence of 47 pathogenic E. coli virulence genes. HMLN-1 and PC-1 were more efficient in adhesion and translocation than rat strains, had identical biochemical phenotype (BPT) and serotype (O77:H18) and phylogenetic group (D). KIC-2 adhered more than KIC-1, belonged to different BPT and serotype but the same phylogenetic group as KIC-1. TEC strains elicited significantly higher IL-8 response in both cell lines (P < 0.05) and monocytic THP-1 (P < 0.0001) cells than non-TEC strains. KIC-2 induced the highest IL-8 response which may be associated with its immunostimulatory flagellin. Apart from adhesin genes fimH and bmaE that were carried by all strains, HMLN-1 and PC-1 carried capsule synthesis gene kpsMT III and KIC-2 carried the EAST1 toxin gene. The lack of known virulence genes and the ability of TEC to efficiently adhere and translocate whilst causing proinflammatory response suggests that these strains may carry as yet unidentified genes that enable their translocating ability.     

A novel flow cytometric assay for rapid detection of extended-spectrum beta-lactamases

The rapid detection of extended-spectrum beta-lactamases (ESBLs) is a challenge for most clinical microbiology laboratories because inaccurate identification of ESBL producers has important clinical implications for both antibiotic treatment and infection control. The aim of our study was to develop a rapid detection assay of ESBL producers based upon flow cytometric analysis. Antimicrobial susceptibility testing followed by molecular characterization of bla_TEM, bla_SHV or bla_CTX-M genes was performed on clinical isolates (41 ESBL positive and 20 ESBL negative) and isolates expressing well-characterized beta-lactamases, including ESBLs (n = 13), plasmid AmpCs (n = 3), oxacillinases (n = 5) and carbapenemases (n = 3). Additionally, two ATCC strains recommended by CLSI for susceptibility testing were used as controls. The flow cytometry analysis protocol involved an incubation of bacterial cells with different concentrations of ceftazidime (1, 2 and 4 mg/L) and cefotaxime (4, 8 and 16 mg/L) for 1 and 2 hours, in the presence and absence of clavulanic acid; subsequently, cells were stained with the fluorescent dye Bis-(1,3-dibutylbarbituric acid) trimethine oxonol [DiBAC₄(3)], a lipophilic anion able to diffuse across depolarized membranes. Additionally, CFU counts were performed. Susceptible isolates displayed increased fluorescence after 1 hour of incubation; conversely, the increase of the depolarized population was only observed after incubation with clavulanic acid associated with ceftazidime or cefotaxime in ESBL producers. An excellent correlation was obtained between the number of non-depolarized bacteria quantified by flow cytometry and by conventional CFU assays. A novel, accurate and fast flow cytometric assay is available to detect the presence of ESBLs.     

Ceftibuten-induced filamentation of extended spectrum beta lactamase (ESBL)-producing uropathogenic Escherichia coli alters host cell responses during an in vitro infection

Inadequate and delayed antibiotic treatment of extended spectrum beta-lactamase (ESBL)-producing isolates have been associated with increased mortality of affected patients. The purpose of this study was to compare the host response of human renal epithelial cells and polymorphonuclear leucocyte (PMN) cells when infected by ESBL-producing uropathogenic Escherichia coli (UPEC) isolates in the presence or absence of ineffective antibiotics.The renal epithelial cell line A498 and PMN cells were stimulated with ESBL-producing UPEC isolates in the presence or absence of three different antibiotics (trimetoprim, ceftibuten and ciprofloxacin). Host cell responses were evaluated as release of cytokines (IL-6, IL-8), reactive oxygen species (ROS), ATP and endotoxins. Bacterial morphology and PMN phagocytosis were evaluated by microscopy.In the presence of ceftibuten, 2 out of 3 examined ESBL-isolates changed their morphology into a filamentous form. The presence of ceftibuten enhanced IL-6, IL-8 and ROS-production from host cells, but only from cells stimulated by the filamentous isolates. The bacterial supernatant and not the filamentous bacteria per se was responsible for the increased release of IL-6, IL-8 and ROS. Increased endotoxin and ATP levels were found in the bacterial supernatants from filamentous isolates. Apyrase decreased IL-6 secretion from A498 cells and polymyxin B abolished the increased ROS-production from PMN cells. PMN were able to inhibit the bacterial growth of some ESBL-isolates in the presence of ceftibuten.In conclusion, antibiotic-induced filamentation of ESBL-producing UPEC isolates and the associated release of ATP and endotoxins can alter the host cell response in the urinary tract.     

Human Wharton’s Jelly Stem Cell Conditioned Medium Enhances Freeze-Thaw Survival and Expansion of Cryopreserved CD34+ Cells

Hematopoietic stem cells (HSCs) from umbilical cord blood have been successfully used to treat blood disorders but one major hurdle is the relatively low cell dose available. Double cord blood unit transplantation results in elevated engraftment failure because one unit predominates over the other. Various approaches are thus being undertaken to expand HSCs ex vivo from single cord blood units. We report here a protocol involving slow freezing (?1 °C per minute to ?120 °C) + freezing medium containing DMSO + FBS + 24 h-50 % hWJSC-CM that enhances thaw-survival of CD34+ cells. Post-thawing, the fold, percentage and colony forming unit numbers of CD34+ cells were significantly increased (2.08?±?0.3; 102?±?1.17 %; 1.07?±?0.02 respectively) while the percentages of apoptotic, necrotic, dead and sub-G1 phase cells (91.06?±?3.63 %; 91.80?±?5.01 %; 95.6?±?3.61 %; 86.1?±?16.26 % respectively) were significantly decreased compared to controls. Post-thaw culture in 24 h-50 % hWJSC-CM+FBS for 72 h showed further significant increases in CD34+ cells (fold: 2.28?±?0.17; percentage: 153.3?±?21.99 %, CFU: 1.6?±?0.19) and significant decreases in apoptotic, necrotic, dead and sub-G1 cells (49.2?±?3.59 %; 62.0?±?4.30 %; 56.6?±?5.06 %; 28.6?±?5.74 % respectively) compared to controls. We hypothesize that these improvements are probably related to the high levels of cytokines, cell adhesion molecules and growth factors in hWJSC-CM that help to preserve cell membrane integrity during freezing and stimulate mitosis post-thaw. A 24 h-50 % hJWSC-CM may be a useful supplement for freezing CD34+ cells in cord blood banks.     

Antibiotic Resistance Patterns and Plasmid Profiles of Salmonella typhimurium Isolates in Turkey

 To understand the resistance mechanisms present in 75 isolates of Salmonella typhimurium derived from clinical infections in Turkey, antimicrobial resistance patterns and associated plasmids were investigated. Among the 22 strains that produced extended-spectrum β-lactamase (ESBL), 20 were resistant to aminoglycosides and 12 to trimethoprim-sulfamethoxazole. Strains that did not produce ESBL did not express aminoglycoside or trimethoprim-sulfamethoxazole resistance, although 27 of them were ampicillin resistant. None of the strains were resistant to imipenem or fluoroquinolones. Nineteen strains producing ESBL carried a plasmid of >100 MDa. Seven ESBL-producing strains conjugally transferred their ESBLs and trimethoprim-sulfamethoxazole resistance. No correlation was found between the resistance patterns and plasmids in non-ESBL-producing strains.     

High prevalence of ESBL-producing Enterobacteriaceae carriage in Dutch community patients with gastrointestinal complaints

The aim of this study was to determine the rate of carriage of ESBL-producing Enterobacteriaceae (ESBL-E) in the community in the Netherlands and to gain understanding of the epidemiology of these resistant strains. Faecal samples from 720 consecutive patients presenting to their general practitioner, obtained in May 2010, and between December 2010 and January 2011, were analysed for presence of ESBL-E. Species identification and antibiotic susceptibility testing were performed according to the Dutch national guidelines. PCR, sequencing and microarray were used to characterize the genes encoding for ESBL. Strain typing was performed with amplified fragment length polymorphism (AFLP) and multilocus sequence typing (MLST). Seventy-three of 720 (10.1%) samples yielded ESBL-producing organisms, predominantly E. coli. No carbapenemases were detected. The most frequent ESBL was CTX-M-15 (34/73, 47%). Co-resistance to gentamicin, ciprofloxacin and cotrimoxazole was found in (9/73) 12% of the ESBL-E strains. AFLP did not show any clusters, and MLST revealed that CTX-M-15-producing E. coli belonged to various clonal complexes. Clonal complex ST10 was predominant. This study showed a high prevalence of ESBL-producing Enterobacteriaceae in Dutch primary care patients with presumed gastrointestinal discomfort. Hence, also in the Netherlands, a country with a low rate of consumption of antibiotics in humans, resistance due to the expansion of CTX-M ESBLs, in particular CTX-M-15, is emerging. The majority of ESBL-producing strains do not appear to be related to the international clonal complex ST131.     

Effects of inoculum and beta-lactamase activity in AmpC- and extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli and Klebsiella pneumoniae clinical isolates tested by using NCCLS ESBL methodology

Escherichia coli and Klebsiella pneumoniae isolates with extended-spectrum beta-lactamases (ESBLs) or AmpC cephalosporinases generally respond as predicted to NCCLS tests for ESBL production. However, inoculum size may affect MICs. The effect of inoculum level in clinical isolates expressing beta-lactamases were studied at inocula within 0.5 log unit of the standard inoculum, using broth microdilution methodology with ceftazidime, cefotaxime, cefepime, cefpodoxime, and aztreonam. Strains with TEM-1 or no beta-lactamases gave consistent MIC results with inocula of 10(5) and 10(6) CFU/ml. When the bacteria were screened for ESBL production and the lower inoculum was used, several strains with ESBLs, including CTX-M-10, TEM-3, TEM-10, TEM-12, TEM-6, SHV-18, and K1, gave false-negative results for one or more antimicrobial agents (MICs below the NCCLS screening concentration for detecting suspected ESBLs). When the higher inoculum was used, MICs of at least one antimicrobial agent increased at least fourfold in strains producing TEM-3, TEM-10, TEM-28, TEM-43, SHV-5, SHV-18, and K1. All antimicrobial agents showed an inoculum effect with at least one ESBL producer. Confirmatory clavulanate effects were seen for both inocula for all ESBL-producing strains with all antimicrobial agents tested, except for the CTX-M-10-producing E. coli with ceftazidime and the SHV-18-producing K. pneumoniae with cefotaxime. In kinetic studies, cefpodoxime and cefepime were hydrolyzed by ESBLs in a manner similar to that of cefotaxime. When total beta-lactamase activity and hydrolysis parameters were evaluated, however, no single factor was predictive of inoculum effects. These results indicate that the NCCLS screening and confirmation tests are generally predictive of ESBL production, but false-negative results can arise when a lower inoculum is used in testing.     

Extended-spectrum beta-lactamase-producing Escherichia coli infections in children: Are community-acquired strains different from nosocomial strains?

Infections caused by extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli are an important cause of morbidity and mortality, especially in children. We compared 58 epidemiologically unrelated ESBL-producing E. coli strains that caused infections. They were isolated between 2008 and 2012 in two Parisian pediatric hospitals and grouped according to their origin into either community-acquired (CA) (n = 37) or nosocomially acquired (NA) (n = 21) strains. Molecular characteristics of the ESBLs, phylogenetic traits of the strains including their belonging to clone O25b-ST131, prevalence of associated virulence genes, growth capacities in different media, metabolic phenotype and biofilm formation abilities were studied. ESBL type, associated resistance and distribution of phylogenetic groups were similar in the CA and NA groups. More than 60% of the B2 phylogroup strains in both groups belonged to the ST131 clone. Interestingly, CA strains possessed more genes encoding virulence factors and the distribution of these genes differed significantly between the two groups: fyuA, hlyC, papC and papGII were more frequent in the CA group, whereas iroN was more frequent in the NA group. CA strains also showed enhanced growth capacities in Luria Bertani rich medium. They tended to produce more biofilm but the difference was not significant. This study confirms the wide spread of clone ST131 among infected children, regardless of whether their infections were community- or nosocomially acquired. It highlights genotypic and phenotypic differences according to the origin of the strains that could indicate adaptability of these multi-resistant bacteria to specific environmental and host factors.     

Activity of ethanol and daptomycin lock on biofilm generated by an in vitro dynamic model using real subcutaneous injection ports

Vancomycin lock solution (LS) is recommended for the conservative treatment of subcutaneous injection port (SIP)-related infections, but may be associated with failure. We used an in vitro dynamic model of biofilm formation in an SIP, based on a continuous flow circulating via a real SIP, to assess the effectiveness of vancomycin (5 mg/ml), daptomycin (5 mg/ml) and ethanol 40 % LS in eradicating a pre-established Staphylococcus epidermidis biofilm. Heparin, Ringer’s lactate and enoxaparin sodium LS were used as controls. The logarithmic reductions of colony-forming units (CFU) were compared by Student’s t-test. After 24 h of exposure, the vancomycin LS did not exert a greater bactericidal effect than the heparin LS control (mean logarithmic reduction: 2.27?±?0.58 vs. 1.34?±?0.22, respectively, p?=?0.3). The mean logarithmic reduction was greater with daptomycin LS (5.45?±?0.14 vs. 0.39?±?0.12, p?<?0.01) and ethanol LS (6.79?±?1.03 vs. 1.43?±?0.54, p?=?0.02). Bacterial revival after exposure to 24 h of LS was assessed. The mean viable bacteria count was significantly higher for vancomycin LS (9.36?±?0.10 log₁₀CFU) and daptomycin LS (9.16?±?0.02 log₁₀CFU) than for ethanol LS (2.95?±?1.65 log₁₀CFU). Ethanol appeared to be the most attractive option to treat SIP-related infection, but its poor ability to entirely disrupt the biofilm structure may require its use in association with a dispersal agent to avoid renewal of the biofilm.     

The use of antibiotic-containing agars for the isolation of extended-spectrum β-lactamase-producing organisms in intensive care units

MacConkey agar containing either cefotaxime 1.0 mg/L or ceftazidime 1.0 mg/L was evaluated for use in screening for extended-spectrum beta-lactamase (ESBL)-producing organisms. The media were evaluated using known ESBL-positive and -negative strains and 630 clinical specimens over a 6-month period. All Enterobacteriaceae isolated were identified and screened for ESBL production by phenotypic methods. In total, 14 ESBL-producing organisms were detected in the clinical samples. All known ESBL-positive strains were also detected. The use of both screening plates was required to detect all ESBLs.     

Detection and clinical significance of extended-spectrum beta-lactamases in a tertiary-care medical center.

The prevalence of extended-spectrum beta-lactamase (ESBL)-mediated resistance remains unknown for most hospitals, and national guidelines for testing and reporting ESBL-mediated resistance have not yet been developed. We undertook a study to determine the prevalence of ESBLs and the clinical need for testing in our tertiary-care medical center. Members of the family Enterobacteriaceae isolated over a 6-month period for which ceftazidime or ceftriaxone MICs were greater than 1 microg/ml were tested for production of ESBLs by the double-disk synergy method. Approximately 1.5% of isolates of the family Enterobacteriaceae (50 of 3,273), which were isolated from 1.2% of patients (23 of 1,844), were found to express ESBLs. ESBL-producing strains included eight different species and were isolated from patients located throughout the hospital, including outpatient clinics. By using the interpretive guidelines of the National Committee for Clinical Laboratory Standards, 26 to 39% of the isolates would have been reported to be susceptible to ceftazidime, depending upon the routine susceptibility method used. However, tests with cefpodoxime found all of the ESBL-producing strains to be resistant or intermediate. Nine patients infected with ESBL-producing isolates were treated with therapy which included an expanded-spectrum cephalosporin. Seven were cured. The deaths of the other two patients were not attributed to bacterial resistance missed by routine susceptibility testing. These observations suggest that in our tertiary-care medical center, it may not be clinically necessary or cost-effective at this time to institute additional testing on a routine basis to detect ESBL production in all clinical isolates of the family Enterobacteriaceae.     

Comparison of Three Biochemical Tests for Rapid Detection of Extended-Spectrum-β-Lactamase-Producing Enterobacteriaceae

Enterobacterial isolates producing clavulanic-inhibited extended-spectrum β-lactamases (ESBLs) are increasingly spreading in the community and are often responsible for nosocomial infections. Rapid biochemical tests have been developed recently for their detection. Three tests, namely, the Rapid ESBL NDP test, the β-Lacta test, and the Rapid ESBL Screen, have been evaluated with a collection of 108 well-characterized strains, including wild-type strains, strains producing ESBLs, overexpressed cephalosporinases, and carbapenemases. The ESBL NDP test and the Rapid ESBL Screen (a copy of the ESBL NDP test) are aimed at detecting ESBL producers, while the β-Lacta test is aimed at detecting not only ESBL producers but also cephalosporinase and carbapenemase producers. The sensitivity and specificity for detecting ESBL producers (n = 60) were 95% and 100% for the Rapid ESBL NDP test, 80% and 87% (after 30 min) and 92% and 83% (after 2 h) for the Rapid ESBL Screen, and 88% and 71% for the β-Lacta test, respectively. Varied and time-consuming detection (up to 2 h) of ESBLs by the Rapid ESBL Screen and concomitant and varied detection of producers of AmpC and several types of carbapenemases correspond to significant shortcomings of using the Rapid Screen ESBL and β-Lacta tests, respectively.     

Effects of phenotype and genotype on methods for detection of extended-spectrum-beta-lactamase-producing clinical isolates of Escherichia coli and Klebsiella pneumoniae in Norway

Consecutive clinical isolates of Escherichia coli (n = 87) and Klebsiella pneumoniae (n = 25) with reduced susceptibilities to oxyimino-cephalosporins (MICs > 1 mg/liter) from 18 Norwegian laboratories during March through October 2003 were examined for bla(TEM/SHV/CTX-M) extended-spectrum-beta-lactamase (ESBL) genes, oxyimino-cephalosporin MIC profiles, ESBL phenotypes (determined by the ESBL Etest and the combined disk and double-disk synergy [DDS] methods), and susceptibility to non-beta-lactam antibiotics. Multidrug-resistant CTX-M-15-like (n = 23) and CTX-M-9-like (n = 15) ESBLs dominated among the 50 ESBL-positive E. coli isolates. SHV-5-like (n = 9) and SHV-2-like (n = 4) ESBLs were the most prevalent in 19 ESBL-positive K. pneumoniae isolates. Discrepant ESBL phenotype test results were observed for one major (CTX-M-9) and several minor (TEM-128 and SHV-2/-28) ESBL groups and in SHV-1/-11-hyperproducing isolates. Negative or borderline ESBL results were observed when low-MIC oxyimino-cephalosporin substrates were used to detect clavulanic acid (CLA) synergy. CLA synergy was detected by the ESBL Etest and the DDS method but not by the combined disk method in SHV-1/-11-hyperproducing strains. The DDS method revealed unexplained CLA synergy in combination with aztreonam and cefpirome in three E. coli strains. The relatively high proportion of ESBL-producing E. coli organisms with a low ceftazidime MIC in Norway emphasizes that cefpodoxime alone or both cefotaxime and ceftazidime should be used as substrates for ESBL detection.     

Molecular Epidemiology of Extended-Spectrum β-Lactamase-Producing Klebsiella pneumoniae Isolates in a District Hospital in Taiwan

Thirty-one of 104 clinical isolates of Klebsiella pneumoniae collected over a period of 8 months were found to be putative extended-spectrum β-lactamase (ESBL) producers. Isoelectric focusing and an iodine overlay agar method were used for preliminary identification of the ESBLs. They were further identified by DNA sequencing. Seventy-one percent of the isolates were found to produce SHV-5. The variation in the ESBL patterns of these isolates was slight, with only five patterns being identified. The strains were typed by pulsed-field gel electrophoresis (PFGE), and 16 different genotypes were identified. When the PFGE patterns were analyzed by the algorithmic clustering method called the unweighted-pair group method using arithmetic averages, five clusters were found. However, significant genetic variations were found among 11 isolates and between each cluster. A plasmid of 36 kb was found in all clinical isolates and in the transconjugants. Our results indicate that the increase in the number of ESBL-producing K. pneumoniae isolates in this hospital is due mainly to the dissemination of a resistance plasmid rather than to the clonal spread of a few epidemic strains.     

The F-actin and adherence-dependent mechanical differentiation of normal epithelial cells after TGF-β1-induced EMT (tEMT) using a microplate measurement system

The epithelial to mesenchymal transition (EMT) is known to involve several physiological and pathological phenomena. In this study, we utilized a microplate measurement system (MMS) approach based on the deflection of a flexible micro-cantilever to measure cell stiffness (in Pa) and adhesion force (in nN) of a single cell during EMT with nN resolution. Our results demonstrated that after transforming growth factor-β1 (TGF-β1) induced EMT (tEMT), NMuMG cells became stiffer due to thicker and more abundant F-actin and displayed stronger vinculin accumulation after long-term cell-substrate adhesion. The MMS could distinguish differences in compressive stiffness (219?±?10 and 287?±?14 Pa), tensile stiffness (114?±?14 and 132?±?12 Pa), and adhesion force (150?±?42 and 192?±?31 nN) between cells before and after tEMT. However, without proper development of the F-actin structure and adequate adherent time, the mechanical differences were diminished. After tEMT, the cells with increased stiffness and a cell-substrate adhesion force benefited by migrating more rapidly and had more invasiveness. Thus, this technology has the potential to benefit research focused on cancer diagnosis, drug development, and cell-substrate interactions.     

Nosocomial outbreak due to extended-spectrum-beta-lactamase- producing Enterobacter cloacae in a cardiothoracic intensive care unit

Enterobacter cloacae has been associated with several outbreaks, usually involving strains that overproduce chromosomal beta-lactamase or, uncommonly, strains expressing extended-spectrum beta-lactamases (ESBL). Only sporadic cases of ESBL-producing E. cloacae have been identified in our hospital in recent years. We describe the epidemiology and clinical and microbiological characteristics of an outbreak caused by ESBL-producing E. cloacae in a cardiothoracic intensive care unit (CT-ICU). Prospective surveillance of patients with infection or colonization by ESBL-producing E. cloacae among patients admitted to the CT-ICU was performed during the outbreak. Production of ESBL was determined by decreased susceptibility to expanded-spectrum cephalosporins and a positive double-disk test result. Clone relatedness was determined by pulsed-field gel electrophoresis (PFGE). From July to September 2005, seven patients in the CT-ICU with ESBL-producing E. cloacae were identified (four males; median age, 73 years; range, 45 to 76 years); six patients had cardiac surgery. Four patients developed infections; three had primary bacteremia, one had ventilator-associated pneumonia, and one had tracheobronchitis. ESBL-producing E. cloacae showed resistance to quinolones and aminoglycosides. PFGE revealed two patterns. Five isolates belonged to clone A; two carried a single ESBL (pI 8.2 and a positive PCR result for the SHV type), and three carried two ESBLs (pIs 8.1 and 8.2 and positive PCR results for the SHV and CTX-M-9 types). Isolates belonging to clone B carried a single ESBL (pI 5.4 and a positive PCR result for the TEM type). Review of antibiotic consumption showed increased use of cefepime and quinolones during June and July 2005. The outbreak was stopped by the implementation of barrier measures and cephalosporin restriction. ESBL production could be increasingly common in nosocomial pathogens other than Escherichia coli or Klebsiella pneumoniae.     

Extended-spectrum β-lactamase-producing Enterobacteriaceae in Cameroonian hospitals

Extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae have been described worldwide, but there are few reports on the carriage of these bacteria in Cameroon. In order to investigate the types of ESBLs and to analyse some risk factors associated with ESBL carriage, faecal samples were collected between 3 January and 3 April 2009 from hospitalised patients at Yaounde Central Hospital and at two hospitals in Ngaoundere, Cameroon. Enterobacterial isolates resistant to third-generation cephalosporins were screened for ESBL production using the double-disk synergy test. Polymerase chain reaction (PCR) and DNA sequencing were performed in order to find out the different types of ESBL genes in presumptive ESBL-positive isolates. During the study period, a total of 121 different patients were screened for ESBL carriage. The prevalence among these patients whose faecal samples were found to contain ESBL-producers was 55.3 % (67/121). According to a univariate analysis, hospitalisation during the previous year was found to be associated with ESBL carriage. Of the 71 bacteria isolated, Escherichia coli was predominant and represented 48 % of all isolates. ESBL characterisation revealed two types of ESBLs, CTX-M-15 (96 %) and SHV-12 (4 %). The present study emphasises the importance of screening for ESBLs in laboratories in African countries. The monitoring and detection of ESBL-producing bacteria are important in the setting up of appropriate treatment of patients and to ensure effective infection control efforts.     

Prevalence and risk factors of extended-spectrum beta-lactamase-producing Escherichia coli and Klebsiella pneumoniae in an Israeli long-term care facility

The purpose of this study was to ascertain the prevalence of extended-spectrum beta-lactamases (ESBLs) among Escherichia coli and Klebsiella pneumoniae strains obtained from urine samples of residents of a long-term care facility and to determine the risk factors for acquisition of ESBL-producing strains. All urine samples collected from January 2003 to October 2003 that were positive for E. coli or K. pneumoniae were tested for the presence of ESBL. Records of patients with ESBL-positive (ESBL-P) samples were analyzed for clinical and demographic data. The records of a matched control group of patients whose urine samples were positive for E. coli or K. pneumoniae but were ESBL-negative (ESBL-N) were also analyzed. The overall rate of ESBLs among the E. coli and K. pneumoniae samples was 25.6%. Of 350 urine samples that grew E. coli, 77 (22%) were positive for ESBL; 34 of 84 (40.5%) samples that grew K. pneumoniae were ESBL-P. Male sex, treatment in the subacute care unit, recent antimicrobial treatment, pressure sores, (percutaneous endoscopic gastrostomy) PEG tube, anemia, hypoalbuminemia, permanent urinary catheter, and any recent invasive procedure were all associated with ESBL-P bacteria in the univariate analysis. The multivariate analysis revealed three independent risk factors for the presence of an ESBL-producing strain: anemia, permanent urinary catheter, and previous antibiotic use. Fluoroquinolones were most strongly associated with the development of ESBL-producing bacteria. The prevalence of ESBL-producing E. coli and K. pneumoniae in the long-term care facility investigated was unexpectedly high and corroborates the notion that long-term care facilities could be important reservoirs of resistant bacteria. Identification of the risk factors for ESBLs is the first step in formulating an effective strategy to curtail the spread of ESBL resistance in long-term care facilities.