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At least 721 records · Page 40Linked to original sources
PubMed1985

Comprehensive evaluation of ciprofloxacin-aminoglycoside combinations against Enterobacteriaceae and Pseudomonas aeruginosa strains.

The in vitro activities of antibiotic combinations containing ciprofloxacin and either gentamicin, sisomicin, netilmicin, amikacin, or tobramycin were evaluated by checkerboard assay (agar dilution method). A total of 220 strains of Enterobacteriaceae and Pseudomonas aeruginosa (11 species, 20 strains each) were tested. Synergistic or antagonistic effects were observed in less than 1% of the tests performed; they appeared to represent method-dependent fluctuations rather than true antibiotic interactions. No significant differences among the five aminoglycosides tested were seen. Time-kill experiments performed with three representative strains of Escherichia coli and Serratia marcescens showed additive combination effects with respect to the kill rates and inhibition of bacterial regrowth. Exposure of Serratia strains to either ciprofloxacin or gentamicin before the addition of the second drug had little influence on the combination effects observed. No antagonistic drug interactions were seen in vivo when combination therapy with ciprofloxacin and gentamicin was evaluated in a model of E. coli thigh muscle infection in neutropenic mice. Comparable therapeutic effects were obtained, regardless of whether the two compounds were administered simultaneously or sequentially at 1- or 2-h intervals.

Aminoglycosides↗
PubMed1986

Antigenic relationships among penicillin-binding proteins 1 from members of the families Pasteurellaceae and Enterobacteriaceae.

Penicillin-binding proteins (PBPs) from Haemophilus influenzae RD purified by a combination of affinity chromatography, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and electroelution were used to immunize rabbits to obtain specific antisera. Antisera directed against PBP 1 (1b) of H. influenzae cross-reacted with representative organisms of the family Pasteurellaceae and with many members of the family Enterobacteriaceae but not with other gram-negative organisms. Immunization with purified PBP 3 of H. influenzae produced antisera that reacted with PBP 1 (1b) of H. influenzae and showed the same cross-reactive pattern with other species as the anti-PBP 1 antiserum. A 24,000-molecular-weight polypeptide of H. influenzae, not radiolabeled by [35S]penicillin, reacted with antisera against purified PBPs 1 (1a, 1b), 2, and 3. The results suggest that antigenic epitopes are shared among similar PBPs from related species and even among different PBPs within the same species.

Acyltransferases↗
PubMed1987

Acquisition by a Campylobacter-like strain of aphA-1, a kanamycin resistance determinant from members of the family Enterobacteriaceae.

A Campylobacter-like organism, BM2196, resistant to kanamycin and streptomycin-spectinomycin was isolated from the feces of a patient with acute enteritis. The kanamycin and streptomycin-spectinomycin resistances were not transferable to Camplylobacter sp. or to Escherichia coli, and no plasmid DNA was detected in this strain. The resistance genes were therefore tentatively assigned to a chromosomal locality. Analysis by the phosphocellulose paper-binding assay of extracts from BM2196 indicated that resistance to kanamycin and structurally related antibiotics was due to the synthesis of 3'-aminoglycoside phosphotransferase type I [APH(3')-I], an enzyme specific for gram-negative bacteria, and that resistance to streptomycin-spectinomycin was secondary to the presence of a 3",9-aminoglycoside adenylyltransferase. Homology between BM2196 and an APH(3')-I probe was detected by DNA-DNA hybridization. A 2.2-kilobase BM2196 DNA fragment conferring resistance to kanamycin was cloned in E. coli and was sequenced partially. The resistance gene appeared nearly identical to that of Tn903 from E. coli and was adjacent to IS15-delta, an insertion sequence widespread in gram-negative bacteria, thus indicating that Campylobacter species can act as a recipient for genes originating in members of the family Enterobacteriaceae.

Base Composition↗
PubMed1988

Resistance to ticarcillin-potassium clavulanate among clinical isolates of the family Enterobacteriaceae: role of PSE-1 beta-lactamase and high levels of TEM-1 and SHV-1 and problems with false susceptibility in disk diffusion tests.

Thirty-four clinical isolates of the family Enterobacteriaceae from the University of Texas M. D. Anderson Cancer Center appeared resistant to ticarcillin-potassium clavulanate in agar dilution and broth macrodilution tests. Among those isolates producing a single non-class I beta-lactamase, resistance was due to production of high levels of TEM-1, SHV-1, or class IV enzymes. In five Escherichia coli isolates, production of low levels of PSE-1 was responsible for resistance which seemed due to rapid hydrolysis of ticarcillin rather than diminished susceptibility of PSE-1 to inhibition by potassium clavulanate. Comparisons of dilution and disk diffusion tests revealed major discrepancies, with 65% false susceptibility in the disk test. Revision of the interpretive criteria used for disk diffusion tests from less than or equal to 11 to less than or equal to 18 mm for resistance is proposed to resolve these discrepancies until clinical data are obtained which can be used to determine which in vitro test is most predictive of therapeutic outcome. These new criteria would diminish false susceptibility without introducing false resistance.

Clavulanic Acid↗
PubMed1990

Development of "oligotyping" for characterization and molecular epidemiology of TEM beta-lactamases in members of the family Enterobacteriaceae.

Based on the DNA sequences of blaTEM-1 and blaTEM-2, which encode parental penicillinases TEM-1 and TEM-2, respectively, and blaTEM-3, blaTEM-4, blaTEM-5, blaTEM-6, and blaTEM-7, which encode extended-spectrum beta-lactamases, we designed heptadecanucleotides to discriminate point mutations in five loci. Determination of the hybridization profiles by colony hybridization with this selection of probes, termed "oligotyping," allowed characterization of the TEM variants present in 265 clinical isolates of the family Enterobacteriaceae that exhibit synergism between a penicillinase inhibitor and broad-spectrum cephaslosporins. Among the 222 strains harboring TEM enzymes, Klebsiella pneumoniae (48%) and Escherichia coli (21%) were predominant, and TEM-3 was the most common enzyme (60%). Penicillinases TEM-1 and TEM-2 were detected alone (15 and 1%, respectively), combined (1%), or associated with another TEM beta-lactamase (17 and 6%, respectively). Fourteen variants, including seven new enzymes, were detected. One, TEM-13, was a new penicillinase with the same isoelectric point and substrate range as TEM-2 but differed by a single amino acid substitution, whereas the others, TEM-14 to TEM-19, were extended-spectrum beta-lactamases that consisted of novel combinations of known amino acid substitutions. Different TEM variants were found to coexist within the same cells. A patient could harbor two or three different strains that encoded the same enzyme or two indistinguishable isolates that produced distinct TEM beta-lactamases.

Amino Acids↗
PubMed1991

Comparison of the inoculum effects of members of the family Enterobacteriaceae on cefoxitin and other cephalosporins, beta-lactamase inhibitor combinations, and the penicillin-derived components of these combinations.

We compared the inoculum effects of 105 recent clinical isolates of the family Enterobacteriaceae on cefoxitin, other cephalosporins, aztreonam, and three beta-lactamase inhibitors (clavulanic acid, sulbactam, and tazobactam) and their penicillin-derived components. Piperacillin and aztreonam showed the largest inoculum effect, and cefoxitin showed the smallest. The other cephalosporins tested (cefotetan, ceftizoxime, and ceftriaxone) showed an intermediate inoculum effect. In general, the inoculum effect was of greater magnitude for the penicillin and beta-lactamase inhibitor combinations than for the cephalosporins tested. Bactericidal activity was assayed and morphologic changes were monitored for selected strains exhibiting a large inoculum effect. MICs correlated with bactericidal activity at an inoculum level of 10(5) CFU/ml, while activity at 10(8) CFU/ml was variable. Cefoxitin demonstrated the least filamentous transformation and the most rapid bactericidal activity. Aztreonam showed the most marked filamentous transformation and was no longer bactericidal at 10(8) CFU/ml. The beta-lactamase inhibitor combinations showed variable bactericidal activity, and regrowth occurred with a number of strains with all three agents tested.

Anti-Bacterial Agents↗
PubMed1992

In vitro activities of Ro 40-6890 against 164 predominantly intestinal members of the families Enterobacteriaceae and Vibrionaceae.

The in vitro activities of Ro 40-6890, the active metabolite of a novel orally absorbable cephalosporin ester, Ro 41-3399, against 164 nonfastidious aerobic gram-negative rods of predominantly intestinal origin from patients with diarrhea were evaluated by the agar dilution method recommended by the National Committee for Clinical Laboratory Standards. Ro 40-6890 was inhibitory (MIC for 90% of isolates [MIC90], 0.12 micrograms/ml) against the majority of intestinal members of the families Enterobacteriaceae and Vibrionaceae (Vibrio spp., Aeromonas spp., and Plesiomonas shigelloides). The potency of Ro 40-6890 was very similar to that of cefotaxime (MIC90, 0.12 micrograms/ml) and distinctly higher than those of cefadroxil (MIC90, > or = 128 micrograms/ml) and amoxicillin-clavulanic acid (MIC90, 32 micrograms/ml-2 micrograms/ml).

Amoxicillin↗
PubMed1994

Postantibiotic effect of meropenem on members of the family Enterobacteriaceae determined by five methods.

The postantibiotic effect (PAE) of meropenem was determined for 11 strains, both clinical isolates and reference strains of members of the family Enterobacteriaceae. The study compares PAE results obtained by five methods used to monitor bacterial regrowth, including viable counting, alone and in combination with impedance; bioluminescence, alone and in combination with impedance; and a morphological technique. After exposure of the test organisms to meropenem (0.1 x to 100 x MIC) for 2 h, concentration-dependent differences in counts by bioluminescence and viable counts were observed, the latter always being lower. The differences varied with the test organism. For example, after exposure of Providentia stuartii NCTC 10318 to 0.1 x MIC, the counts were 5.5 x 10(5) and 2.0 x 10(5) whereas after exposure of Citrobacter freundii MR76 to 0.1 x MIC of meropenem the counts were 2.3 x 10(6) and 6.8 x 10(3) by bioluminescence and viable counting, respectively. The discrepancies were probably due to the relative inability of the viable counting procedure to detect fragile aberrant morphologies and resulted in differences in the calculated PAE values. With methods which do not detect fragile morphologies, the PAE may be underestimated. A general trend was observed for the order of magnitude of the PAEs by the following methods (in order of decreasing magnitude of PAE): (i) morphological technique, (ii) bioluminescence technique alone, (iii) bioluminescence in combination with impedance, (iv) viable counting in combination with impedance, and (v) viable counting alone. It is our opinion that of the methods examined in this study, bioluminescence in combination with impedance best reflects the true values for PAEs, and these results were examined more closely.

Bacteriological Techniques↗
PubMed1973

Bactericidal effect of combinations of nalidixic acid and various antibiotics on Enterobacteriaceae.

The activity of nalidixic acid combined with each of 10 other antimicrobial agents on 95 strains of Enterobacteriaceae was studied. Synergism was found less often than antagonism, and the commonest outcome was indifference. Combinations of nalidixic acid with kanamycin, gentamicin, or colistin were more often synergistic than antagonistic, whereas with the other antibiotics the combination was more often antagonistic than synergistic. Synergistic effects were more common with Shigella than with other genera. In vitro examination for synergism or antagonism appears to be advisable before nalidixic acid is used therapeutically in combination with other antimicrobial agents.

Anti-Bacterial Agents↗
PubMed1997

Survey and molecular genetics of SHV beta-lactamases in Enterobacteriaceae in Switzerland: two novel enzymes, SHV-11 and SHV-12.

Sixty isolates of Enterobacteriaceae resistant to beta-lactam antibiotics were collected over a period of 2 years in Switzerland and screened by hybridization for the carriage of SHV genes. Thirty-four positive strains were found, and their SHV genes were amplified and sequenced. SHV extended-spectrum beta-lactamases (ESBLs) were found: 13 strains contained SHV-2a, 12 harbored SHV-2, and SHV-5 was found twice. Four strains were shown to contain SHV-1. In addition, we report two new SHV variants, termed SHV-11 (non-ESBL) and SHV-12 (ESBL). In spite of the carriage of SHV ESBLs, many strains showed only low resistance to one or more third-generation cephalosporins. In addition, 26 did not transfer the blaSHV gene in mating experiments.

Anti-Bacterial Agents↗
PubMed1999

Many class I integrons comprise distinct stable structures occurring in different species of Enterobacteriaceae isolated from widespread geographic regions in Europe.

Three sizes of inserted regions of DNA (800, 1,000, and 1,500 bp) were shown to be common among class I integrons in unrelated clinical isolates of Enterobacteriaceae from different European hospitals. Sequencing showed that 800-bp inserted regions comprised identical sequences including aacA4, that 1,000-bp inserted regions included aadA, and that 1,500-bp inserted regions included dfrI and aadA1, irrespective of host species and geographic origin. In addition promoter sequences were mostly identical for each size class. These data suggest that inserted gene cassettes and promoter regions of integrons are conserved and stable, with resistance genes transferred more often as part of the entire integron structure than as individual gene cassettes.

Base Sequence↗
PubMed1999

TEM-24 produced by four different species of Enterobacteriaceae, including Providencia rettgeri, in a single patient.

Four species of members of the family Enterobacteriaceae harboring extended-spectrum beta-lactamase (ESBL) were recovered in a single patient hospitalized in an intensive care unit. Among these isolates, we describe for the first time an ESBL-producing Providencia rettgeri strain. Bacteria from the same species were shown to be genetically related by pulsed-field gel electrophoresis analysis. These strains produced the same TEM derivative ESBL, characterized as TEM-24. This enzyme had the peculiarity of being encoded by a large conjugative plasmid of 180 kb, never previously described for such an ESBL.

Anti-Bacterial Agents↗
PubMed2000

A 1998 survey of extended-spectrum beta-lactamases in Enterobacteriaceae in France. The French Study Group.

In a 3-month period in 1998, 79 consecutive isolates of Enterobacteriaceae producing an extended-spectrum beta-lactamase (ESBL) were collected. ESBLs were predominantly TEM derivatives (74 of 79): TEM-24-like (40 isolates), TEM-3-like (29 isolates), TEM-21 (3 isolates), and TEM-4 and TEM-52 (1 isolate each). Four isolates produced SHV derivatives SHV-4 (three isolates) and SHV-5 (one isolate), and one strain produced a CTX-M-3 enzyme. The high proportion of TEM-24-like-producing Enterobacter aerogenes isolates (36 of 79) suggests the occurrence of an epidemic strain in France.

Data Collection↗
PubMed2000

A novel CTX-M beta-lactamase (CTX-M-8) in cefotaxime-resistant Enterobacteriaceae isolated in Brazil.

To estimate the diversity of extended-spectrum beta-lactamases in Brazil, 18 strains from different species of the family Enterobacteriaceae exhibiting a positive double-disk synergy test were collected by a clinical laboratory from several hospitals in Rio de Janeiro, Brazil, in 1996 and 1997. Four strains (Proteus mirabilis, Enterobacter cloacae, Enterobacter aerogenes, and Citrobacter amalonaticus) hybridized with a 550-bp CTX-M probe. The P. mirabilis strain produced a CTX-M-2 enzyme. The E. cloacae, E. aerogenes, and C. amalonaticus isolates harbored a bla gene which was identified by cloning and sequencing as a bla(CTX-M) gene. E. coli HB101 transconjugants and the E. coli DH5alpha transformant harboring a recombinant plasmid produced a CTX-M beta-lactamase with an isoelectric point of 7.6 conferring a resistance phenotype characterized by a higher level of resistance to cefotaxime than to ceftazidime, as observed with the other CTX-M enzymes. The deduced protein sequence showed a novel Ambler class A CTX-M enzyme, named CTX-M-8, which had 83 to 88% identity with the previously described CTX-M enzymes. The phylogenic study of the CTX-M family including CTX-M-8 revealed four CTX-M types, CTX-M-8 being the first member of a new phylum of CTX-M enzymes. The evolutionary distances between the four types of CTX-M were large, suggesting that the four clusters branched off early from a distant unknown enzyme and that intermediate enzymes probably existed.

Amino Acid Sequence↗
PubMed2001

Activity of ertapenem (MK-0826) versus Enterobacteriaceae with potent beta-lactamases.

Ertapenem (MK-0826; L-749,345), a new carbapenem with a long serum half-life, was tested, in vitro, against beta-lactamase-producing bacteria. The new compound had a MIC at which 90% of the isolates were inhibited of 0.06 microg/ml for extended-spectrum beta-lactamase (ESBL)-producing klebsiellas, compared with 0.5 microg/ml for imipenem, 16 microg/ml for cefepime, and >128 microg/ml for ceftazidime and piperacillin-tazobactam. MICs of ertapenem for AmpC-derepressed mutant Enterobacteriaceae were 0.015 to 0.5 microg/ml, whereas imipenem MICs were 0.25 to 1 microg/ml and those of cefepime were 0.5 to 4 microg/ml, and resistance to ceftazidime and piperacillin-tazobactam was generalized. Despite this good activity, the MICs of ertapenem for ESBL-positive klebsiellas mostly were two- to fourfold above those for ESBL-negative strains, and the MICs for AmpC-hyperproducing Enterobacter cloacae and Citrobacter freundii mutants exceeded those for the corresponding AmpC-basal mutants. These differentials did not increase when the inoculum was raised from 10(4) to 10(6) CFU/spot, contraindicating significant lability. Carbapenemase producers were also tested. The IMP-1 metallo-beta-lactamase conferred substantial ertapenem resistance (MIC, 128 microg/ml) in a porin-deficient Klebsiella pneumoniae strain, whereas a MIC of 6 microg/ml was recorded for its porin-expressing revertant. SME-1 carbapenemase was associated with an ertapenem MIC of 2 microg/ml for Serratia marcescens S6, compared with <0.03 microg/ml for Serratia strains lacking this enzyme. In summary, ertapenem had good activity against strains with potent beta-lactamases, except for those with known carbapenemases.

Bacterial Proteins↗
PubMed2001

Integrons and gene cassettes in the enterobacteriaceae.

Integrons were detected in 59 of 120 (49%) urinary isolates of Enterobacteriaceae by PCR using degenerate primers targeted to conserved regions of class 1, 2, and 3 integrase genes. PCR sequencing analysis of the cassette arrays revealed a predominance of cassettes that confer resistance to the aminoglycosides and trimethoprim.

Aminoglycosides↗
PubMed2002

Countrywide spread of CTX-M-3 extended-spectrum beta-lactamase-producing microorganisms of the family Enterobacteriaceae in Poland.

Eighty-four clinical isolates of the family Enterobacteriaceae, recovered from 1998 to 2000 in 15 hospitals in 10 Polish cities, were analyzed. All the isolates produced beta-lactamases with pIs of 8.4 and 5.4, and the pI 8.4 enzymes were demonstrated to hydrolyze cefotaxime but not ceftazidime in the in vitro bioassay. PCR analysis and DNA sequencing have revealed that in all cases the pI 8.4 beta-lactamase was probably the CTX-M-3 extended-spectrum beta-lactamase (ESBL) variant, which was originally identified in 1996 in Praski Hospital in Warsaw. In the majority of isolates, bla(CTX-M-3) genes resided within large conjugative plasmids with similar fingerprints, which, in the context of the high degree of diversity of the randomly amplified polymorphic DNA types of the isolates, suggested that horizontal transfer of plasmids was likely the main mechanism of CTX-M-3 spread. The dissemination of plasmids was probably preceded by the center-to-center transmission of several strains, as indicated by the identification by pulsed-field gel electrophoresis of closely related or possibly related Klebsiella pneumoniae, Escherichia coli, and Citrobacter freundii isolates in five different hospitals. CTX-M-3-producing organisms revealed a very high degree of diversity in beta-lactam resistance levels and patterns. This was attributed to several factors, such as the production of other beta-lactamases including additional ESBLs, possible quantitative variations in CTX-M-3 expression, segregation of AmpC derepressed mutants, and permeability alterations.

Conjugation, Genetic↗
PubMed2002

CTX-M-1, CTX-M-3, and CTX-M-14 beta-lactamases from Enterobacteriaceae isolated in France.

Six clinical CTX-M-producing isolates of the family Enterobacteriaceae were detected between 1999 and 2000 in different French hospitals. Two strains produced CTX-M-1 and CTX-M-3 and four strains produced CTX-M-14, a mutant Ala-231-->Val of CTX-M-9. A putative transposable element, ISEcp-1, was located 43 bp upstream of all the bla(CTX-M) genes. Two CTX-M-14-encoding plasmids exhibited similar restriction patterns. The CTX-M-1- and CTX-M-3-encoding plasmids were related to the CTX-M-1- and CTX-M-3-encoding plasmids previously reported in 1990 in France and in 1998 in Poland, respectively.

DNA Transposable Elements↗