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PubMed1988

Ribosomal-RNA patterns of Escherichia coli, Salmonella typhimurium and related Enterobacteriaceae.

rRNA sequences are usually highly conserved among species. In Enterobacteriaceae we have shown that Salmonella typhimurium does not have an equivalent to the 23S rRNA of Escherichia coli but its 23S rRNA is cleaved in vivo into two smaller species. This cleavage appears to be a result of a difference between the S. typhimurium and E. coli rRNA sequences rather than to differences in ribonuclease activity. We have surveyed a wide range of Enterobacteriaceae for the presence or absence of 23S rRNA and found this rRNA species to be present in all strains of E. coli, Shigella and Citrobacter and all salmonellae examined except S. typhimurium. All S. typhimurium cultures, isolated at different times and from several different countries, lack an intact 23S rRNA. Thus, the presence or absence of this rRNA species is an excellent diagnostic characteristic for S. typhimurium.

Animals↗

PubMed2005

Phylogeny of the Enterobacteriaceae based on genes encoding elongation factor Tu and F-ATPase beta-subunit.

The phylogeny of enterobacterial species commonly found in clinical samples was analysed by comparing partial sequences of their elongation factor Tu gene (tuf) and of their F-ATPase beta-subunit gene (atpD). An 884 bp fragment for tuf and an 884 or 871 bp fragment for atpD were sequenced for 96 strains representing 78 species from 31 enterobacterial genera. The atpD sequence analysis exhibited an indel specific to Pantoea and Tatumella species, showing, for the first time, a tight phylogenetic affiliation between these two genera. Comprehensive tuf and atpD phylogenetic trees were constructed and are in agreement with each other. Monophyletic genera are Cedecea, Edwardsiella, Proteus, Providencia, Salmonella, Serratia, Raoultella and Yersinia. Analogous trees based on 16S rRNA gene sequences available from databases were also reconstructed. The tuf and atpD phylogenies are in agreement with the 16S rRNA gene sequence analysis, and distance comparisons revealed that the tuf and atpD genes provide better discrimination for pairs of species belonging to the family Enterobacteriaceae. In conclusion, phylogeny based on tuf and atpD conserved genes allows discrimination between species of the Enterobacteriaceae.

Amino Acid Sequence↗

PubMed2005

Quantitative microarray-based DNA-DNA hybridization assay for measuring genetic distances among bacterial species and its application to the identification of family Enterobacteriaceae.

Quantitative DNA-DNA hybridization to measure the genetic distances among bacterial species is indispensable for taxonomical determination. In the current studies, we developed a method to determine bacterial DNA relatedness on a glass microarray. Reference DNAs representing a total 93 species of Enterobacteriaceae were arrayed on a glass microplate, and signal intensities were measured after 2 hr of hybridization with Cy3-labeled bacterial DNAs. All immobilized DNAs from members of the family Enterobacteriaceae were identified by this method except for DNAs from Yersinia pseudotuberculosis and Y. pestis. These results suggest that quantitative microarray hybridization could be an alternative to conventional DNA-DNA hybridization for measuring chromosome relatedness among bacterial species.

DNA, Bacterial↗

PubMed1987

Enterobacteriaceae, coliforms, faecal coliforms and salmonellas in raw ewes' milk.

Thirty-nine samples of freshly drawn ewes' milk collected at 13 farms, and 120 samples of raw ewes' milk collected on arrival at a dairy were examined. Farm samples had geometric mean counts of 4.4 X 10(2) Enterobacteriaceae/ml, 3.9 X 10(2) coliforms/ml and 2.0 X 10(2) faecal coliforms/ml, whereas the respective mean counts were 6.2 X 10(3)/ml, 5.4 X 10(3)/ml and 1.3 X 10(3)/ml for dairy samples. Salmonellas were not detected by enrichment procedures in any of the 159 samples examined. Escherichia coli (47.5% strains), Enterobacter cloacae (17.7%), Ent. agglomerans (11.3%), Hafnia alvei (6.5%) and Klebsiella oxytoca (6.0%) were the predominant species in 434 Enterobacteriaceae strains isolated from farm samples. Levels and species of Enterobacteriaceae found in the present work in raw ewes' milk imply a considerable risk of early blowing in cheese-making from unpasteurized milk.

Animals↗

PubMed1993

Study of Enterobacteriaceae throughout the manufacturing and ripening of hard goats' cheese.

The evolution of the counts and the species of Enterobacteriaceae as well as some physico-chemical parameters (pH, aw and NaCl and moisture contents) during manufacturing and ripening of a hard Spanish goats' cheese of the Armada-Sobado variety were studied. Enterobacteriaceae (mean log counts 4.45 g-1 in milk) increased 0.71-2.18 log units in curd and afterwards decreased until they disappeared after 2-4 weeks of ripening. This premature disappearance seems to be due to the decrease in aw values and in moisture contents. However, the low pH values, reached from the beginning of the ripening process, could also contribute to this phenomenon. The most abundant species in milk was Serratia liquefaciens (57.5% of isolates), followed by Morganella morganii (27.5%), Hafnia alvei (5%), Klebsiella oxytoca (5%) and Yersinia enterocolitica (5%). Yersinia enterocolitica was not subsequently isolated from either curd or in cheese. Hafnia alvei numbers increased in curd and in 1-week-old cheese where this micro-organism was the most abundant (47.5% and 75% of the isolates respectively). Escherichia coli, which was not isolated from milk, curd or 1-week-old cheese, was the predominant organism in 2-week-old cheese (57.8% of isolates). This confirms the finding of other authors who have shown that it is one of the most resistant species in ripening cheeses.

Animals↗

PubMed1999

Metabolism of L(-)-carnitine by Enterobacteriaceae under aerobic conditions.

Different Enterobacteriaceae, such as Escherichia coli, Proteus vulgaris and Proteus mirabilis, are able to convert L(-)-carnitine, via crotonobetaine, into gamma-butyrobetaine in the presence of carbon and nitrogen sources under aerobic conditions. Intermediates of L(-)-carnitine metabolism (crotonobetaine, gamma-butyrobetaine) could be detected by thin-layer chromatography. In parallel, L(-)-carnitine dehydratase, carnitine racemasing system and crotonobetaine reductase activities were determined enzymatically. Monoclonal antibodies against purified CaiB and CaiA from E. coli O44K74 were used to screen cell-free extracts of different Enterobacteriaceae (E. coli ATCC 25922, P. vulgaris, P. mirabilis, Citrobacter freundii, Enterobacter cloacae and Klebsiella pneumoniae) grown under aerobic conditions in the presence of L(-)-carnitine.

Acyltransferases↗

PubMed2000

The Yersinia high-pathogenicity island is present in different members of the family Enterobacteriaceae.

A pathogenicity island termed high-pathogenicity island (HPI) is present in pathogenic Yersinia. This 35 to 45 kb island carries genes involved in synthesis, regulation and transport of the siderophore yersiniabactin. Recently, the HPI was also detected in various strains of Escherichia coli. In this study, the distribution of the HPI in the family Enterobacteriaceae was investigated. Among the 67 isolates pertaining to 18 genera and 52 species tested, nine (13.4%) harbored the island. These isolates were three E. coli, one Citrobacter diversus and five Klebsiella of various species (Klebsiella pneumoniae, Klebsiella rhinoscleromatis, Klebsiella ozaenae, Klebsiella planticola, and Klebsiella oxytoca). As in Yersinia sp., all nine isolates synthesized the HPI-encoded iron-repressible proteins HMWP1 and HMWP2. In the K. oxytoca strain, the right-end portion of the HPI was deleted, whereas the entire core region of the island was present in the eight other enterobacteria strains analyzed. In most of these isolates, the HPI was bordered by an asn tRNA locus, as in Yersinia sp. This report thus demonstrates the spread of the HPI among various members of the family Enterobacteriaceae.

Bacterial Outer Membrane Proteins↗

PubMed1985

Population analysis of susceptibility to cefotaxime and desacetyl-cefotaxime in Staphylococcus and Enterobacteriaceae.

Population analyses of susceptibility to cefotaxime (CTX) and desacetyl-cefotaxime (DCTX) of strains of Staphylococcus and some genera of Enterobacteriaceae were carried out. DCTX, which is the main metabolite of CTX, has antimicrobial activity. The penicillinase-producing strains of S. aureus and S. epidermidis were homogeneous as regards susceptibility to both agents. CTX was about 4-8 times more active than DCTX. The methicillin-resistant strains contained a sub-population of resistant bacteria with both CTX and DCTX. The frequency of resistant bacteria was 10(-6) - 10(-5). The E. coli strain was homogeneous to both agents. The strains of Enterobacter cloacae and Citrobacter freundii had a sub-population of resistant bacteria with both agents. The frequency of resistant bacteria was 10(-7) - 10(-4.5). In Klebsiella pneumoniae no resistant sub-population was found. CTX was about four times more active than DCTX with the strains of the Enterobacteriaceae. DCTX had no advantage over CTX as regards homogeneity of susceptibility of the populations examined. CTX seems applicable for treatment of infections with E. coli, Klebsiella pneumoniae, and penicillinase-producing, methicillin-susceptible Staphylococcus, but should not be used alone in treatments of infections with Enterobacter cloacae or Citrobacter freundii.

Cefotaxime↗

PubMed1986

Population analysis of susceptibility to ciprofloxacin and nalidixic acid in Staphylococcus, Pseudomonas aeruginosa, and Enterobacteriaceae.

Susceptibility to ciprofloxacin (Cfl) and nalidixic acid (Nal) was tested in vitro by means of the population analysis technique against six strains of Staphylococcus, one strain of Pseudomonas aeruginosa, and seven strains from five genera of Enterobacteriaceae. All strains of Staphylococcus were uniformly resistant to Nal as was the Pseudomonas aeruginosa strain, all bacteria being resistant to 250- less than 500 micrograms/ml. The Enterobacteriaceae were heterogeneous as regards susceptibility to Nal. With some strains minority populations of highly-resistant bacteria could be detected with frequencies of about 10(-6.3). The MIC for Cfl for the staphylococci varied between 0.25 and 0.50 microgram/ml. There were no differences in MIC of penicillinase-producing and penicillin-susceptible strains, either in Staphylococcus aureus or in Staphylococcus epidermidis. The MIC for Cfl in the enterobacteria varied between 0.004 and 0.03 microgram/ml. The MIC for Cfl in the Pseudomonas aeruginosa was 0.25 microgram/ml. MIC for Cfl increased in all strains when the parental strains were compared to bacteria selected from the plates with the highest concentration permitting growth, indicating heterogeneity against Cfl. But while the MIC of the selected enterobacteria were lower than one fourth of the level obtainable in serum, the MIC of the selected staphylococci and Pseudomonas aeruginosa were either exceeding the level obtainable in serum or were only a little lower than this level. While Cfl thus seems to be a promising antimicrobial agent in the treatment of infections caused by enterobacteria, the suitability for infections caused by staphylococci and Pseudomonas aeruginosa should be further explored.

Ciprofloxacin↗

PubMed2000

[Detection of extended spectrum beta-lactamases producing Enterobacteriaceae in feces].

A study was made of 366 feces for detection of extended spectrum beta-lactamases producing Enterobacteriaceae from feces. The selective agar was used for modified drigalski agar (Eiken Chemical Co., LTD) with 2 micrograms/ml cefotaxime (ESBL screen agar). 92 strains of Enterobacteriaceae, 41 Escherichia coli, 15 Citrobacter freundii, 13 Enterobacter cloacae, 11 Klebsiella pneumoniae, and other 12, were isolated from ESBL screen agar. And, R-plasmid that were selected by 2 micrograms/ml cefotaxime were transferred by conjugation from two of the 92 strains. These strain were E. coli TH9809927 and Proteus mirabilis TH9808262 that were amplified by "Toho-1 type" primer. The clude enzyme from two strains (donor) and transconjugants were especially hydrolysed cepharoridine and cefotaxime. Accordingly, two strains (0.5%) were detected as ESBL producers. We think that the result of our survey suggests the increase of ESBLs producing bacterial infection in Japan, and believe that there is a trend of infection of its by surveilance of the feces.

Bacteriological Techniques↗

PubMed1976

Comparison of the antibacterial activity of nine cephalosporins against Enterobacteriaceae and nonfermentative gram-negative bacilli.

The in vitro antibacterial activity of nine cephalosporins (cephalothin, cephaloridine, cephalexin, cefazolin, cefamandole, cefuroxime, cefatrizine, cefoxitin, and cefazaflur) was determined against 344 strains of Enterobacteriaceae and 99 nonfermentative gram-negative bacilli. Cefamandole, cefazaflur, and cefuroxime were the most active cephalosporins against the Enterobacteriaceae (with the exception of Serratia marcescens). However, cefoxitin was the only cephalosporin that inhibited all 30 S. marcescens strains in a concentration of 16 mug/ml and was by far the most active compound against selected cephalothin-resistant strains of Escherichia coli, Klebsiella, and Proteus mirabilis. Acinetobacter spp. were inhibited best by cefuroxime, but none of the cephalosporins had appreciable activity against the Pseudomonas spp.

Bacteria↗

PubMed1984

Early synergistic interactions between amikacin and six beta-lactam antibiotics against multiply resistant members of the family Enterobacteriaceae.

An in vitro comparison of the early synergistic interaction between amikacin and each of six beta-lactam antibiotics was made by using time-kill curves against 48 multiply resistant members of the family Enterobacteriaceae. Overall, these six combinations demonstrated early synergism (greater than or equal to 2 logs of increased kill after 7 h of incubation) against the 48 strains on 74% (range, 67 to 85%) of occasions; cefotaxime-amikacin and piperacillin-amikacin were the most efficacious combinations. Antagonism was not observed with any of the combinations against any of the 48 Enterobacteriaceae strains tested.

Amikacin↗

PubMed1973

Comparison of five aminocyclitol antibiotics in vitro against Enterobacteriaceae and Pseudomonas.

The in vitro susceptibility of 163 strains of Enterobacteriaceae and 23 isolates of Pseudomonas aeruginosa to various concentrations of gentamicin, kanamycin, spectinomycin, tobramycin, and BB-K8, a new semisynthetic aminoglycoside antibiotic, was determined. Studies were performed in Mueller-Hinton agar and broth, and two different sizes of bacterial inocula were used. On a weight basis, gentamicin and tobramycin demonstrated comparable activity in vitro and were the most active of the five drugs tested against Escherichia coli, Klebsiella, Enterobacter, and Proteus species. All of these organisms were inhibited by gentamicin or tobramycin at concentrations of 5.0 mug or less/ml in agar with both inocula of bacterial cells. In addition, tobramycin was the most active drug against isolates of P. aeruginosa and gentamicin was the most active against Salmonella and Shigella species. Although kanamycin and BB-K8 demonstrated a high degree of activity against most Enterobacteriaceae, they were not the most active agents tested for any genus. Spectinomycin was the least active compound, and many isolates grew in concentrations higher than those readily attainable in serum.

Aminobutyrates↗

PubMed1986

Novel plasmid-mediated beta-lactamase in members of the family Enterobacteriaceae from Ohio.

Epidemiologic studies of plasmid-mediated resistance at the Cleveland Veterans Administration Medical Center revealed that related plasmids had disseminated among members of the family Enterobacteriaceae. We studied the beta-lactamases encoded by these plasmids in Escherichia coli C600 transformants or transconjugants. Substrate and inhibition profiles of the enzymes determined by two of these plasmids suggested an activity resembling TEM-1; however, isoelectric focusing revealed a pI of 7.0. These two plasmids were originally found in a Serratia marcescens (pDS076) and an Enterobacter cloacae (pDS075) strain isolated from the same sink in the medical intensive care unit and later, in an Enterobacter cloacae (pDS142 identical to pDS076) isolate colonizing a patient in the same unit. The plasmids also carried the aminoglycoside resistance determinant, 2"-aminoglycoside nucleotidyl transferase. A 2-kilobase AvaI restriction endonuclease digestion fragment of pSD075 known to carry the beta-lactamase determinant was used as a molecular probe. This probe did not recognize sequences of any plasmid-mediated beta-lactamase tested including the recently described determinants ROB-1, TLE-1, and OXA-4-7. A TEM-1 probe derived from the 0.7-kilobase PstI-EcoRI fragment of pBR322 failed to recognize the new beta-lactamase gene. Four additional Enterobacter cloacae and two Enterobacter aerogenes strains isolated in Columbus, Ohio, have been shown to produce a pI 7.0 beta-lactamase and to carry plasmids recognized by the 2-kilobase probe. These data suggest dissemination of a novel plasmid-mediated beta-lactamase among members of the family Enterobacteriaceae in Ohio and demonstrate the development and utility of a molecular probe for the new determinant. We suggest that the novel beta-lactamase be named OHIO-1.

DNA, Bacterial↗

PubMed1988

Susceptibilities to antibiotics and antiseptics of new species of the family Enterobacteriaceae.

One hundred and sixty-nine strains of new species of the family Enterobacteriaceae, isolated mainly from the environment, were tested to determine their susceptibilities to 13 antibiotics and 4 antiseptics or disinfectants. All the species were susceptible to aminoglycosides, doxycycline, and trimethoprim but were resistant to chloramphenicol. Susceptibility to beta-lactams varied more among the strains. However, all the strains were cefotaxime susceptible, apart from some Buttiauxella agrestis strains for which MICs were greater than 256 micrograms/ml. The antiseptic MBCs were similar to those published elsewhere for species of the Enterobacteriaceae of clinical origin. No resistance to chlorhexidine was observed. On the other hand, the environmental strains presented a greater resistance to active chlorine than did the reference strains.

Anti-Bacterial Agents↗

PubMed1990

In vitro activities of cefoperazone and sulbactam singly and in combination against cefoperazone-resistant members of the family Enterobacteriaceae and nonfermenters.

Among 28,000 isolates of the family Enterobacteriaceae and nonfermenters isolated at multiple medical centers, 1,084 (4%) were resistant to cefoperazone (MIC, greater than or equal to 64 micrograms/ml) and 1,711 (6%) exhibited cefoperazone MICs of 2 to 32 micrograms/ml. Ninety-six percent of these 2,795 isolates produced beta-lactamase, as determined by the nitrocefin test. Sulbactam alone (8 micrograms/ml) was inactive against 99.6% of the isolates other than Acinetobacter calcoaceticus and Pseudomonas cepacia. Sulbactam enhanced the activity of cefoperazone against 56% of the isolates of the family Enterobacteriaceae and 44% of the nonfermenters. In the presence of sulbactam concentrations of less than or equal to 8 micrograms/ml, 65% of the cefoperazone-resistant isolates had reductions in cefoperazone MICs of greater than or equal to 2 log2 dilution steps and were susceptible to less than or equal to 32 micrograms/ml. Antagonism was not observed.

Bacteria↗

PubMed1994

In vitro activity of SCE-2787, a new cephalosporin with potent activity against Pseudomonas aeruginosa and members of the family Enterobacteriaceae.

The in vitro activity of SCE-2787, 7-[(Z)-2-(5-amino-1,2,4-thiadiazol-3- yl)-2-methoxyiminoacetamido]-3-(1-imidazo[1,2-b]pyridazinium)methy l-3- cephem-4-carboxylate, was compared with those of ceftazidime, ceftriaxone, and imipenem against recent clinical isolates. SCE-2787 inhibited 50% of tested isolates of the family Enterobacteriaceae at < or = 0.25 micrograms/ml. SCE-2787 was equally active as or more active than ceftazidime and ceftriaxone against members of the Enterobacteriaceae, with the exception of Proteus vulgaris. The MIC of SCE-2787 at which 90% of the isolates of Pseudomonas aeruginosa were inhibited was 2 micrograms/ml, two- to fourfold lower than those of imipenem and ceftazidime, respectively. SCE-2787, like ceftazidime and imipenem, did not inhibit the majority of strains of Pseudomonas cepacia and Xanthomonas maltophilia. SCE-2787 inhibited beta-hemolytic streptococci at < or = 0.12 micrograms/ml, but it did not inhibit Enterococcus faecalis, Listeria monocytogenes, or the anaerobic species tested. Methicillin-resistant staphylococci required SCE-2787 MICs of > or = 16 micrograms/ml, whereas methicillin-susceptible staphylococci were inhibited by 2 micrograms/ml. No difference between the MICs and MBCs was noted, except for P. aeruginosa, for which there was a fourfold difference. SCE-2787 was active over a pH range of 6 to 8. The inoculum size of 10(5) to 10(7) CFU caused only a twofold change in the MIC for Escherichia coli and Staphylococcus aureus but a 4- to 16-fold change in Enterobacter cloacae and P. aeruginosa. beta-Lactamases from Bush groups 1, 2a, and 2b did not hydrolyze SCE-2787. There was significant hydrolysis of SCE-2787 by the beta-lactamases designated 2b', i.e., TEM-3, TEM-5, TEM-7, and TEM-9, and by the group 2d beta-lactamases. SCE-2787 had poor affinity for group 1 and group 2b enzymes and constitutively produced chromosomal beta-lactamases such as P-99 of Enterobacter cloacae and plasmid-mediated TEM-1 of E. coli. SCE-2787 has in vitro activity comparable to that of current parenteral cephalosporin and is more active against P. aeruginosa and S. aureus.

Cephalosporins↗

PubMed1999

Use of an isogenic Escherichia coli panel to design tests for discrimination of beta-lactamase functional groups of Enterobacteriaceae.

A study was designed to determine if an isogenic panel of Escherichia coli strains containing many different beta-lactamases could be used for the preliminary screening of a large number of beta-lactam agents to identify which might be most useful in the development of a definitive test for specific beta-lactamases found among the members of family Enterobacteriaceae. The susceptibilities of 46 strains, comprising the isogenic panel, to expanded-spectrum cephalosporins, cephamycins, and aztreonam were determined in the presence and absence of beta-lactamase inhibitors in broth microdilution tests. The results indicated that strains producing extended-spectrum beta-lactamases (ESBLs) could be distinguished from strains producing other Bush-Jacoby-Medeiros functional group 2 or group 1 beta-lactamases. For strains producing group 1 beta-lactamases, cefpodoxime and ceftazidime MICs were > or = 4 micrograms/ml and addition of clavulanate did not reduce the MICs more than fourfold. For strains producing group 2 enzymes other than ESBLs, cefpodoxime and ceftazidime MICs were < or = 2 micrograms/ml. With a single exception (ceftazidime for the strain producing SHV-3), among strains producing ESBLs, cefpodoxime and ceftazidime MICs were > or = 4 micrograms/ml and addition of clavulanate reduced the MICs by more than eightfold. Cephamycins could also be used to discriminate between strains producing group 1 beta-lactamases and ESBLs, since only the former required cefotetan concentrations as high as 8 micrograms/ml or cefoxitin concentrations of > 16 micrograms/ml for inhibition. Other cephalosporins provided some discrimination between the various beta-lactamase producers, although they were not as reliable as either cefpodoxime or ceftazidime. These results indicate the utility of an isogenic panel for identification of candidate drugs among many for further testing with clinical isolates of the family Enterobacteriaceae to determine the best agents for detection of specific beta-lactamases in this family.

Anti-Infective Agents↗