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PubMed1977

Interaction of blood with enterobacteriaceae: hemolysis, hemagglutination, fibrinolysis.

One thousand eighty enterobacteriaceae, isolated during a period of three months, were tested for the presence of hemolysis, hemagglutination and fibrinolysis on human erythrocytes and plasma. The fibrinolysis on human erythrocytes and plasma. The Escherichia coli have the greatest diversity of action on the blood. Of 481 strains, 32.9% were hemolytic, 21.9% fibrinolytic, and 10.5% hemagglutinating. Of 190 strains of Klebsiella, 95.2% were fibrinolytic. Of 53 strains of Enterobacter, 90.6% were fibrinolytic, and of 53 strains of Enterobacter hafniae, 66% were fibrinolytic. Of seven strains of Serratia, 28.5% were hemolytic and 14.3% fibrinolytic. The Proteae were mostly fibrinolytic: 60.5% of 141 strains, with three strains being hemolytic and fibrinolytic. Of 19 strains of Citrobacter, 52.6% were fibrinolytic only. Providenica, Salmonella and Shigella did not interact with human blood. The patterns of blood interactions with the different species of Enterobacteriaceae are of value in the evaluation of the pathogenesis of the infections and septicemias they cause. Their study is an essential step in the understanding of the sequence of events leading to severe disturbances of the blood-clotting mechanism.

Enterobacteriaceae↗
PubMed2004

The effect of fixed orthodontic appliances on the oral carriage of Candida species and Enterobacteriaceae.

The aim of this investigation was to evaluate the prevalence of Candida and Enterobacteriaceae in a group of adolescents during fixed orthodontic appliance (FOA) therapy. The experimental group was recruited from a larger sample of orthodontic patients who were clinically examined once to obtain baseline data before active treatment. The group comprised 27 subjects; 13 males, 14 females (mean age 15.5 +/- 2.3 years). Thereafter, the experimental group was examined three times during a 3 month follow-up period after insertion of the FOA. The whole mouth plaque score was obtained, and the oral cavity was then sampled for Candida species and Enterobacteriaceae using three different microbiological culture techniques, namely the oral rinse, pooled plaque and the imprint culture.A significant increase in candidal numbers was observed after FOA insertion when the imprint technique was used (P < 0.001), although the overall candidal prevalence rates obtained using the oral rinse and pooled plaque techniques did not demonstrate such a change. The predominant Candida species isolated was C. albicans and the number of coliform carriers significantly increased after the insertion of a FOA, as detected by the oral rinse (P < 0.05) and the pooled plaque (P < 0.05) techniques. In total, eight coliform species were isolated following FOA therapy compared with the three species isolated before insertion of the appliance. The results also revealed a significant increase in plaque index due to the introduction of a FOA. Taken together, these data imply that insertion of a FOA is likely to promote oral carriage of Candida and coliform species. Furthermore, it appears that routine oral hygiene instruction and information on appliance hygiene given to these patients may not necessarily reduce plaque accumulation and possible attendant effects. Further work with a larger cohort is required to confirm these findings.

Adolescent↗
PubMed1979

Selection of small-colony variants of Enterobacteriaceae by in vitro exposure to aminoglycosides: pathogenicity for experimental animals.

Small-colony variants of gram-negative genera of Enterobacteriaceae were selected by in vitro exposure to gentamicin. These variants were shown to have decreased susceptibility in vitro to aminoglycosides. They were lethal for mice following intraperitoneal injection, with the LD50 (50% lethal dose) being the same as, or slightly less than, that for the parent organism. Variants of strain no. 2401 of Proteus mirabilis caused urinary tract infection in mice after implantation into their bladders. Although the variants grew somewhat less rapidly than did parent organisms, both parent and variant colonies alkalinized urine at the same rate. Electron microscopic study showed no differences between colonies of parents and variants. These studies indicated that small-colony variants of Enterobacteriaceae are pathogenic for experimental animals. Further, they may cause disease in humans and should not necessarily be regarded as only laboratory curiosities.

Aminoglycosides↗
PubMed1985

Resistance to beta-lactamase-stable cephalosporin antibiotics in strains of Enterobacteriaceae and Pseudomonas aeruginosa isolated from blood cultures.

A total of 224 strains of Enterobacteriaceae and Pseudomonas aeruginosa isolated from blood cultures were screened for resistance to cefuroxime and cefotaxime. Seven of 200 strains of Enterobacteriaceae were resistant to either cefuroxime or cefotaxime, while five of 24 strains of Ps. aeruginosa were resistant to cefotaxime. A further 32 resistant variants were isolated by use of a single step selection procedure, without prior mutagenesis, from strains which were sensitive on initial screening. From the total of 44 resistant strains and variants isolated, 31 were found to produce elevated levels of chromosomal beta-lactamases. Of these 31, five strains of Proteus sp. produced significant amounts of beta-lactamase only when induced in the presence of cefuroxime or cefotaxime, while the remaining 26 strains also produced high levels of beta-lactamase in the absence of an inducer. Thirteen resistant strains and variants (9 Ps. aeruginosa, 3 P. mirabilis, 1 K. aerogenes) did not produce detectable levels of beta-lactamase in either the presence or absence of induction and presumably owed their resistance to another mechanism.

Cephalosporins↗
PubMed1987

In-vitro antimicrobial activity of enoxacin in combination with eight other antibiotics against Pseudomonas aeruginosa, Enterobacteriaceae and Staphylococcus aureus.

Susceptibilities of 28 strains of Pseudomonas aeruginosa, 32 strains of Enterobacteriaceae and 24 strains of Staphylococcus aureus were tested against combinations of enoxacin with either cefsulodin, piperacillin, or amikacin, enoxacin with either aztreonam, latamoxef or amikacin, and enoxacin with either oxacillin, clindamycin or vancomycin, respectively. Synergy was detected by the agar dilution technique and was defined as a four-fold decrease in the inhibitory concentration of both drugs (sigma FIC less than or equal to 0.5). Against Ps. aeruginosa, synergy occurred in 28.5% of the strains for enoxacin plus cefsulodin, 17.6% for enoxacin plus piperacillin, and 3.7% for enoxacin plus amikacin. Against the Enterobacteriaceae, synergy was detected with enoxacin plus aztreonam, latamoxef or amikacin in 9.3%, 3.1% and 0% of strains, respectively. Against Staph. aureus, no synergy was demonstrable with enoxacin plus oxacillin, clindamycin or vancomycin. No antagonism was detected for any combination tested. Selected strains demonstrating synergy by the agar dilution method for enoxacin plus cefsulodin or piperacillin failed to show synergy in kinetic studies.

Amikacin↗
PubMed1988

The differential expression of genes for the PSE-4 beta-lactamase in Pseudomonas aeruginosa and the Enterobacteriaceae.

The PSE-4 beta-lactamase has been identified, for the first time, in two non-pseudomonal strains. The gene in Klebsiella pneumoniae 241 (dal1) was located on a plasmid (pUK700) and was freely transferable to other enterobacterial strains and Pseudomonas aeruginosa. On the other hand, the gene in Enterobacter cloacae A113 (dal2) could only be transferred in the presence of a mobilizing plasmid. When both these genes were transferred within the Enterobacteriaceae, the beta-lactamase produced was slightly different from the prototype 'Dalgleish' PSE-4 enzyme. However, when dal1 and dal2 were transferred to P. aeruginosa the enzyme expressed was identical to this prototype enzyme. In addition, both these genes expressed higher levels of PSE-4 beta-lactamase production in P. aeruginosa than found in the Enterobacteriaceae. Thus it appears that the biochemical properties of the PSE-4 gene products from dal1 and dal2 are host-modified.

Enterobacteriaceae↗
PubMed1993

Antibiotic resistance of faecal Enterobacteriaceae isolated from healthy volunteers, a 15-week follow-up study.

From 25 March to 1 July 1991 faecal samples from healthy volunteers of two cities and their rural surroundings, Weert (n = 91) and Roermond (n = 96) were collected weekly and analysed for the presence of Enterobacteriaceae, resistant to ampicillin, ciprofloxacin, nalidixic acid, neomycin, nitrofurantoin, oxytetracycline, sulphamethoxazole or trimethoprim. In total, 682 and 690 samples from Weert and Roermond, respectively, were analysed for the prevalence and the degree of resistance to each antimicrobial agent. The mean prevalence of resistance of the samples from Weert varied from 28% +/- 12 (mean +/- S.D.) for ampicillin to 0.1% +/- 1 (range 0-2%) for ciprofloxacin. For Roermond the prevalence of resistance varied from 41% +/- 7% for sulphamethoxazole to 0% for ciprofloxacin. The high degree of resistance (i.e. > 50% of the faecal flora of one particular individual) varied from 8% +/- 4 for sulphamethoxazole to 2% +/- 2 for trimethoprim for Weert. For Roermond the figures varied from 14% +/- 4 for sulphamethoxazole to 0.3% +/- 1 (range 0-2%) for nalidixic acid. High degrees of resistance were not found for ciprofloxacin and nitrofurantoin in either city. In Weert ampicillin-resistant Enterobacteriaceae were isolated from 69/91 individuals.

Adult↗
PubMed1997

Bactericidal activity of cefodizime on Enterobacteriaceae in an in-vitro model simulating plasma pharmacokinetics in humans.

An in-vitro dialysis model was employed to assess the feasibility of once-daily dosing of cefodizime in the treatment of infections caused by various Enterobacteriaceae: Escherichia coli, Klebsiella pneumoniae, Morganella morganii, Serratia marcescens, Providencia stuartii and Enterobacter cloacae. This model simulated the concentrations of cefodizime detected in human blood after an intravenous (i.v.) bolus injection of 1 g or 2 g of the antibiotic. Validation of the model was undertaken to confirm its utility. Based on the data obtained with this model, once-daily dosing with 1 g cefodizime (i.v.) should be effective against infections due to the commonest Gram-negative bacteria (E. coli, K. pneumoniae, M. morganii). For infections caused by Enterobacteriaceae strains that produce large quantities of Class I beta-lactamases, twice-daily (P. stuartii or S. marcescens) or four times daily (E. cloacae) administration of 1 g cefodizime may be required.

Cefotaxime↗
PubMed1999

Antimicrobial susceptibility of Enterobacteriaceae isolated from vegetables.

There is potential for the normal faecal flora of humans to be augmented by resistant strains of bacteria, acquired from food. The frequency of resistance in the aerobic Gram-negative faecal flora is often very high. The purpose of this study was to find out whether food strains contribute to this resistance. One hundred and thirty-seven vegetable samples were studied, 48 of Finnish origin, and 89 imported. From these samples, 535 different strains of bacteria belonging to the family Enterobacteriaceae were isolated. Enterobacter spp. were most frequent, Escherichia coli was rare. Sensitivity testing was undertaken only for isolates with different biotypes and antibiograms. No resistance was found to cefotaxime, aztreonam, imipenem, gentamicin, nalidixic acid or ciprofloxacin. The frequency of trimethoprim resistance was 0.2%, sulphamethoxazole resistance 1.3%, and tetracycline resistance 5.5%. These frequencies were much lower than those found in faecal flora. Chloramphenicol and cefuroxime resistance was found in 12% and 14% of isolates, respectively. The only statistically significant differences between the Finnish and imported strains were for these two; the Finnish isolates were more resistant to cefuroxime, whereas the imported ones were more resistant to chloramphenicol. Consequently, bacteria from vegetables are not responsible for the high prevalence of resistant Enterobacteriaceae in faecal flora in Finland; they are in fact unusually susceptible to the antibiotics studied. Multiresistance profiles, typical of strains associated with human activities, were not identified in these isolates.

Anti-Bacterial Agents↗
PubMed2002

Metallo-beta-lactamase-producing Enterobacteriaceae isolates in a university hospital in Taiwan: prevalence of IMP-8 in Enterobacter cloacae and first identification of VIM-2 in Citrobacter freundii.

A total of 9082 clinical isolates of Enterobacteriaceae other than Klebsiella spp. collected in 1999 and 2000 at a university hospital in Taiwan were investigated for the production of metallo- beta-lactamases (MBLs). Thirty-six (2.9%) of the 1261 Enterobacter cloacae isolates and one (0.3%) of the 340 Citrobacter freundii isolates were found to carry bla(IMP-8) and bla(VIM-2), respectively, by colony hybridization, PCR and sequence analysis. The IMP-8 producers were recovered from 20 patients and four of them had recently transferred from other hospitals, implying spread of IMP-8-producing E. cloacae among different healthcare settings. Of the 20 non-repetitive IMP-8 producers, 17 (85%) isolates also harboured bla(SHV-12), which was on the same transferable plasmids with bla(IMP-8). The bla(VIM-2)-positive isolate and all non-repetitive bla(IMP-8)-positive isolates appeared susceptible to imipenem (MICs < 8 mg/L) and meropenem (MICs < 4 mg/L), indicating the difficulty in detection of MBLs in Enterobacteriaceae by routine susceptibility testing. Ribotyping of the IMP-8-producing E. cloacae isolates indicated that the dissemination of bla(IMP-8) was due largely to the spread of an epidemic clone, but horizontal transfer among unrelated strains also occurred.

Citrobacter freundii↗
PubMed2004

Analysis of AmpC beta-lactamase expression and sequence in biochemically atypical ceftazidime-resistant Enterobacteriaceae from paediatric patients.

OBJECTIVES: To analyse the variation of ampC beta-lactamase gene sequence and expression in biochemically atypical Enterobacteriaceae isolates, and to identify them definitively. METHODS: beta-Lactamase gene-containing recombinant plasmids transformed into Escherichia coli were selected using ampicillin. PCR analysis was used to locate specific ampC and 16S rRNA genes, and the amplicons were sequenced. Random amplified polymorphic DNA PCR was used to group isolates and API 20E biochemical profiling was used to identify them putatively. RESULTS: Of 50 ceftazidime-resistant clinical Enterobacteriaceae isolates, 36 were identified (>95% confidence)-using API 20E test strips-as being organisms known to express inducible class C beta-lactamases (Citrobacter freundii, Enterobacter cloacae, Morganella morganii or Hafnia alvei). The rest were biochemically atypical. Of these, isolate I113, putatively identified as E. coli, possesses a chromosomally encoded ampC which differs by 15% from C. freundii OS60 ampC and by >30% from E. coli ampC. A related ampC gene was found in another seven of the atypical isolates. The use of various identification methods, including ampC sequence analysis, revealed that these I113-like ampC-positive isolates represent Citrobacter murliniae and Citrobacter youngae. CONCLUSIONS: We report sequences for two new Citrobacter spp. ampC genes, and provide evidence that ampC sequencing is a discriminatory method for identifying atypical Citrobacter spp. isolates.

Bacterial Proteins↗
PubMed2005

Phenotypic detection of beta-lactamase-mediated resistance to oxyimino-cephalosporins in Enterobacteriaceae: evaluation of the Mastascan Elite Expert System.

OBJECTIVES: The aim of this study was to evaluate phenotypic detection of beta-lactamase-mediated resistance to oxyimino-cephalosporins in Enterobacteriaceae using the Mastascan Elite Expert System challenged with a battery of genotypically characterized organisms. METHODS: Isolates (n = 120) were identified to species level and antimicrobial susceptibilities were determined using agar incorporation methods and Mastascan Elite. Phenotypes were examined using an Expert System (ES) and putative genotypes were suggested using interpretative reading. RESULTS: Identification was correct in 119 of 120 isolates. The ES was able to identify the correct beta-lactam phenotype (as deduced from molecular methods) in a single choice in 98 of 120 (81.7%) isolates. In an additional 15 (12.5%) cases, the ES identified the correct beta-lactam phenotype within two or more choices. The detected phenotype was incorrect in seven (5.8%) isolates, but three of these were not inherent to the ES. CONCLUSIONS: The Mastascan Elite ES is relatively inexpensive and flexible and can identify the mechanism of resistance to oxyimino-cephalosporins in the majority of Enterobacteriaceae without recourse to molecular methods.

Cephalosporins↗
PubMed2006

Efficacy of practised screening methods for detection of cephalosporin-resistant Enterobacteriaceae.

OBJECTIVES: Enterobacteriaceae with extended-spectrum beta-lactamases (ESBLs) are now widespread and simple phenotypic tests are required to detect them in diagnostic laboratories. We investigated the performance of screening methods at 16 hospitals in South-East England. METHODS: Sixteen laboratories in South-East England submitted 1195 consecutive Enterobacteriaceae isolates found to be resistant, by their routine methods, to any or all of cefpodoxime, ceftazidime and cefotaxime. These isolates were re-tested centrally with various cephalosporin/clavulanate combinations and with multiplex PCR for bla(CTX-M) and bla(AmpC) alleles. RESULTS: Screening methods among the laboratories were the following: cefpodoxime discs alone (1 site); cefpodoxime, cefotaxime and ceftazidime discs (9 sites) or agar dilution (1 site); Phoenix (2 sites), Vitek 1 (1 site) and Vitek 2 (2 sites). A total of 8% of isolates submitted based on disc tests proved fully cephalosporin-susceptible, compared with 3% sent based on tests with automated systems and none of those sent based on agar dilution tests. Among isolates submitted solely on cefpodoxime resistance 256/372 (69%) proved cephalosporin-susceptible or had only borderline resistance with no clear mechanism demonstrable; this proportion decreased to 28/160 (18%) for those submitted on the basis of resistance to ceftazidime, 18/122 (15%) for those resistant to cefotaxime and 26/496 (5%) for those resistant to both cefotaxime and ceftazidime. The inference of ESBL production by Vitek 2 had the best agreement with reference laboratory results. CONCLUSIONS: Many isolates found resistant only to cefpodoxime at the source sites proved not to have ESBLs or AmpC; screening with cefotaxime and ceftazidime allowed better specificity for identification of mechanism-based resistance, as did the automated systems. Cefpodoxime disc tests nevertheless remain a useful primary screen for laboratories prepared only to test one agent.

Cephalosporins↗
PubMed1976

A heterophile system in human renal transplantation. V. Relationship of heterophile transplantation antigen and common antigen of Enterobacteriaceae.

Heterophile transplantation antigen and common antigen of Enterobacteriaceae appear serologically to be separate specificities. However, both antigens are common to Enterobacteriaceae, rat erythrocytes, and some human kidneys. Both antigens are obtained from various tissues by the same chemical procedure. Immunity to each antigen is frequently produced by renal transplantation. We suggest that the antigens are either separate molecules which are similar in chemical structure in the region of the antigenic determinant as well as in tissue distribution or separate reactive sites located on the same molecule. The possibility that common antigen may be a human alloantigen raises theoretical possibilities relative to susceptibility to infection and pyelonephritis, as well as to its relationship to histocompatibility.

Animals↗
PubMed2003

Multicenter evaluation of a human monoclonal antibody to Enterobacteriaceae common antigen in patients with Gram-negative sepsis.

OBJECTIVE: To evaluate in Gram-negative sepsis patients the human monoclonal immunoglobulin M antibody (MAB-T88) directed at the enterobacterial common antigen which is a specific surface antigen closely linked to lipopolysaccharide and shared by all members of the Enterobacteriaceae family of Gram-negative bacteria. DESIGN: Prospective, randomized, double-blinded, placebo-controlled, multicenter trial. SETTING: Thirty-three academic medical centers in the United States. PATIENTS: Patients were entered with a clinical diagnosis of sepsis, the presence of either shock or multiple organ dysfunction, and presumptive evidence for Gram-negative infection. INTERVENTIONS: Patients received a single intravenous infusion, over 30 mins, of either 300 mg of MAB-T88 formulated in albumin, or placebo (albumin). MEASUREMENTS AND MAIN RESULTS: The primary analysis group was prospectively identified as those patients with documented evidence of an infection with bacteria of the family Enterobacteriaceae at any site. The primary end point was survival within the first 28 days. A total of 826 patients were enrolled with 55% (n = 455) in the primary analysis group. There were no significant differences between the intervention and control primary analysis group study groups for sites of infection, severity of illness, underlying medical conditions, adequacy of antibiotic or surgical treatment, or other baseline variables except for a higher frequency of chronic renal failure in the MAB-T88 group (4.4% vs. 1.3%, p=.051). The average Acute Physiology and Chronic Health Evaluation II scores were 26.8 +/- 8.6 (mean +/- sd) in the MAB-T88-treated group and 26.5 +/- 8.3 in the placebo-treated group (p =.72). There was no significant difference between MAB-T88- and placebo-treated groups during the first 28-day all-cause mortality in the primary analysis group (34.2% vs. 30.8%, p=.44) or in all 826 patients enrolled (37.0% vs. 34.0%, p=.36). On subset analysis, the use of MAB-T88 was not associated with significant mortality trends. More adverse events were seen with the use of MAB-T88 in the bacteremic enterobacterial common antigen group (p <.05). CONCLUSIONS: Use of the human monoclonal antibody, MAB-T88, did not improve the mortality in patients with presumed Gram-negative sepsis or in those patients with proven enterobacterial common antigen infections. No subset trends were identified that would support further investigation of this agent in sepsis.

Adolescent↗
PubMed2002

Evolution of the gyrB gene and the molecular phylogeny of Enterobacteriaceae: a model molecule for molecular systematic studies.

Phylogenetic trees showing the evolutionary relatedness of Enterobacteriaceae based upon gyrB and 16S rRNA genes were compared. Congruence among trees of these molecules indicates that the genomes of these species are not completely mosaic and that molecular systematic studies can be carried out. Phylogenetic trees based on gyrB sequences appeared to be more reliable at determining relationships among Serratia species than trees based on 16S rRNA gene sequences. gyrB sequences from Serratia species formed a monophyletic group validated by significant bootstrap values. Serratia fonticola had the most deeply branching gyrB sequence in the Serratia monophyletic group, which was consistent with its atypical phenotypic characteristics. Klebsiella and Enterobacter genera seemed to be polyphyletic, but the branching patterns of gyrB and 16S rRNA gene trees were not congruent. Enterobacter aerogenes was grouped with Klebsiella pneumoniae on the gyrB phylogenetic tree, which supports that this species could be transferred to the Klebsiella genus. Unfortunately, 16S rRNA and gyrB phylogenetic trees gave conflicting evolutionary relationships for Citrobacter freundii because of its unusual gyrB evolutionary process. gyrB lateral gene transfer was suspected for Hafnia alvei. Saturation of gyrB genes was observed by the pairwise comparison of Proteus spp., Providencia alcalifaciens and Morganella morganii sequences. Depending on their level of variability, 16S rRNA gene sequences were useful for describing phylogenetic relationships between distantly related Enterobacteriaceae, whereas gyrB sequence comparison was useful for inferring intra- and some intergeneric relationships.

DNA Gyrase↗
PubMed2002

The inner-core lipopolysaccharide biosynthetic waaE gene: function and genetic distribution among some Enterobacteriaceae.

To determine the function of the waaE gene in the biosynthesis of the inner-core LPS of Klebsiella pneumoniae, a waaE non-polar mutant has been constructed. Data obtained from the comparative chemical analysis of LPS samples obtained from the wild-type, the mutant strain and the complemented mutant demonstrated that the waaE gene is involved in substitution of alpha-L-glycero-D-manno-heptopyranose I (L,D-HeppI) at the O-4 position by a beta-D-glucopyranose (beta-D-Glcp) residue. In addition, DNA amplification and nucleotide sequence determination studies revealed that waaE homologues located between the waaA and coaD genes are present in clinical isolates of Enterobacteriaceae containing the structure beta-D-Glcp-(1-->4)-alpha-L,D-HeppI (K. pneumoniae, Proteus mirabilis and Yersinia enterocolitica), as well as in strains of Serratia marcescens and Enterobacter aerogenes of unknown LPS-core structures. Complementation studies using non-polar waaE mutants prove that all the waaE homologues perform the same function. Furthermore, K. pneumoniae, Ser. marcescens and P. mirabilis non-polar waaE mutants showed reduced adhesion and pathogenicity. In addition, the Ser. marcescens and P. murabilis waaE mutants showed reduced swarming motility and ability to form biofilms in vitro. All these characteristics were rescued by reintroduction of the waaE gene independently of its origin. An easy DNA amplification method to detect this gene was established, which also helps in finding the potential presence of this structural feature [beta-D-Glcp-(1-->4)-alpha-L,D-HeppI] in the inner-core LPS of Enterobacteriaceae members with unknown LPS-core structures.

Bacterial Proteins↗
PubMed1985

Antigenic relationships among type-3 fimbriae of Enterobacteriaceae revealed by immunoelectronmicroscopy.

Antigenic relationships among type-3 fimbriae of 31 strains, representing 19 species and eight genera of Enterobacteriaceae, were investigated by immunoelectronmicroscopy in tests with 17 different type-3 fimbrial antisera. At least nine antigenically distinct groups among type-3 fimbriae were distinguished. The constituent membership of some groupings did not conform with current views on the taxonomy of Enterobacteriaceae.

Antigens, Bacterial↗