Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:2.3.1.28 (chloramphenicol acetyltransferase)
5,100 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A Haemophilus influenzae b (Hib) membrane protein with a molecular mass of 28 kDa bound polyclonal antisera raised against a highly purified Hib fimbrial subunit. We cloned the gene encoding this protein and found that the gene was expressed in Escherichia coli. DNA sequence analysis identified an 843-bp open reading frame which predicted a 26.78-kDa protein with an amino-terminal signal sequence and a mature protein with 70% similarity to the 28-kDa lipoprotein of E. coli (F. Yu, S. Inouye, and M. Inouye, J. Biol. Chem. 261:2284, 1986). Colony blot hybridization analysis with an intergenic probe of the cloned gene demonstrated that 29 of 32 H. influenzae strains hybridize with this gene. Insertion of a chloramphenicol acetyltransferase gene into the open reading frame inactivated expression of the 28-kDa protein in E. coli. Isogenic Hib strains were derived by marker exchange mutagenesis to generate mutants which no longer expressed the 28-kDa protein as recognized with Western immunoblot analysis. There was no difference in the rate of nasopharyngeal colonization of infant rats or monkeys by the isogenic mutants which lacked the 28-kDa protein compared with colonization by the wild-type strain. In contrast, the frequency of invasion and density of bacteremia in infant rats caused by the isogenic mutants were reduced relative to those caused by the wild-type Hib strain. We conclude that this 28-kDa outer membrane protein aids transepithelial invasion of type b strains but is not essential.
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PMID:Contribution of a 28-kilodalton membrane protein to the virulence of Haemophilus influenzae. 198 77

Seven clinical isolates of chloramphenicol-resistant Haemophilus influenzae were studied. The products of chloramphenicol inactivation by chloramphenicol acetyltransferase (CAT) were identified by high performance liquid chromatography. The sole product in H. influenzae is a single monoacetyl compound, whereas variants of CAT isolated from other chloramphenicol-resistant bacteria usually produce both monoacetyl and diacetyl chloramphenicol metabolites. The chloramphenicol resistance gene was found to reside on a 65-kb plasmid which, in five of the six cases studied, appeared to be integrated into the host cell chromosome.
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PMID:Demonstration of a functional variant of chloramphenicol acetyltransferase in Haemophilus influenzae. 266 28

A total of 2,811 clinical isolates of Haemophilus influenzae were obtained during 1986 from 30 medical centers and one nationwide private independent laboratory in the United States. Among these, 757 (26.9%) were type b strains. The overall rate of beta-lactamase-mediated ampicillin resistance was 20.0%. Type b strains were approximately twice as likely as non-type b strains to produce beta-lactamase (31.7 versus 15.6%). The MICs of 12 antimicrobial agents were determined for all isolates. Ampicillin resistance among strains that lacked beta-lactamase activity was extremely uncommon (0.1%). Percentages of study isolates susceptible to cefamandole, cefaclor, cephalothin, and cephalexin were 98.7, 94.5, 87.3, and 43.3%, respectively. For 14 strains (0.5% of the total), chloramphenicol MICs were greater than or equal to 8.0 micrograms, and thus the strains were considered resistant. All of these resistant strains produced chloramphenicol acetyltransferase. In addition, all 14 strains were resistant to tetracycline; 11 produced beta-lactamase. The percentage of isolates susceptible to tetracycline was 97.7%. In contrast, erythromycin and sulfisoxazole were relatively inactive. The combination of erythromycin-sulfisoxazole (1/64) was more active than erythromycin alone but essentially equivalent in activity to sulfisoxazole alone. Finally, small numbers of clinical isolates of H. influenzae were resistant to trimethoprim-sulfamethoxazole and rifampin.
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PMID:National collaborative study of the prevalence of antimicrobial resistance among clinical isolates of Haemophilus influenzae. 325 21

Of 2458 isolates of Haemophilus influenzae examined in a recent British survey, 42 were resistant to chloramphenicol. Two resistant isolates were of type b and 40 were non-capsulate. Spectrophotometric assay showed that all the resistant isolates produced chloramphenicol acetyltransferase (CAT). CAT activity did not increase following growth on heated blood agar containing chloramphenicol 2 mg/L but was reduced by 84-98% when extracts were treated for 30 min with 5', 5'-dithiobis-2-nitrobenzoate. These data suggest that H. influenzae CATs resemble the Type-II CATs produced by enterobacteria. Extrachromosomal DNA was detected in five only of the 42 resistant isolates and cured derivatives of two plasmid-containing strains retained their chloramphenicol resistance. These results suggest that the CAT gene is located on the chromosome.
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PMID:Mechanisms of chloramphenicol resistance in Haemophilus influenzae in the United Kingdom. 326 60

Haemophilus influenzae, Streptococcus pneumoniae, and Aerococcus species were tested for susceptibility to chloramphenicol by standard broth microdilution and disk-diffusion methods. MICs and zone diameter breakpoints were correlated with production of chloramphenicol acetyltransferase (CAT). A comparison of MICs and zone diameters indicated that the interpretative criteria for H. influenzae and S. pneumoniae should be an MIC of less than or equal to 4 micrograms/ml or a zone diameter greater than or equal to 25 mm for susceptible strains and an MIC of greater than or equal to 8 micrograms/ml or a zone diameter of less than or equal to 20 mm for resistant strains; for Aerococcus species, interpretative criteria should be an MIC of less than or equal to 8 micrograms/ml or a zone diameter of greater than or equal to 20 mm for susceptible strains and an MIC of greater than or equal to 32 micrograms/ml or a zone diameter of less than or equal to 12 mm for resistant strains. All but four strains of H. influenzae and one strain of S. pneumoniae that were resistant to chloramphenicol by these criteria produced CAT. For Aerococcus species, however, chloramphenicol-resistant strains were negative for CAT as determined by a commercially available disk test. When comparing susceptibility results with CAT production, thiamphenicol was a better indicator of the presence of the enzyme than chloramphenicol and may be useful in assaying resistance to chloramphenicol.
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PMID:Relationship between in vitro susceptibility test results for chloramphenicol and production of chloramphenicol acetyltransferase by Haemophilus influenzae, Streptococcus pneumoniae, and Aerococcus species. 326 21

The activity of chloramphenicol against 100 different strains of Haemophilus influenzae was assessed by a macrotube broth dilution technique and by a standardized disk diffusion method using both enriched chocolate agar (CHOC) and Mueller-Hinton agar containing 1.0% hemoglobin and 1.0% IsoVitaleX (BBL Microbiology Systems, Cockeysville, Md.) supplement (CHOC-MHA). Filter disks containing 30 micrograms of chloramphenicol were used with the disk diffusion procedure. The following zone diameter interpretive criteria were defined: CHOC-MHA, less than or equal to 25 mm = resistant [corrected] and greater than or equal to 26 mm = susceptible [corrected]; CHOC, less than or equal to 28 mm = resistant [corrected] and greater than or equal to 29 mm = susceptible [corrected]. all of the H. influenzae strains examined were also characterized by using two rapid assays for chloramphenicol acetyltransferase (CAT) activity: a 1-h tube method (t-CAT) and a 30-min procedure which used commercially available reagent-impregnated disks (d-CAT). The t-CAT procedure was found to be significantly more accurate than the d-CAT procedure as a means for demonstrating production of CAT.
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PMID:In vitro chloramphenicol susceptibility testing of Haemophilus influenzae: disk diffusion procedures and assays for chloramphenicol acetyltransferase. 349 44

The prevalence of antibiotic resistance in Haemophilus influenzae is increasing. The encapsulated strains of group b are the strains that are most important in the pathogenesis of severe systemic infections, and it is in this group that the incidence of resistance is highest. Strains simultaneously resistant to ampicillin, chloramphenicol, and tetracycline are rare but have been isolated in several parts of the world. Transferable antibiotic resistance is well documented, and both small (3.6 megadaltons) and large (38-42 megadaltons) plasmids mediating beta-lactamase and chloramphenicol acetyltransferase production and tetracycline resistance have been detected in H. influenzae. The possibilities for treatment of infections due to such organisms include the use of the newer cephalosporins, of a combination of a beta-lactamase inhibitor and ampicillin, and of alternate agents such as minocycline and trimethoprim. Sporadic strains resistant to these agents have also been reported.
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PMID:Antibiotic resistance in Haemophilus influenzae: epidemiology, mechanisms, and therapeutic possibilities. 354 Nov 36

Chloramphenicol resistance in Haemophilus influenzae occurs most frequently via plasmid-mediated chloramphenicol acetyltransferase production. We studied four strains with high-level chloramphenicol resistance (MIC greater than 20 micrograms/ml) which did not have detectable chloramphenicol acetyltransferase activity. The chloramphenicol resistance determinant was transformed into a chloramphenicol-susceptible laboratory H. influenzae strain from each of the four wild-type strains, enabling isogenic comparisons. By thin-layer chromatography and a bioassay, there was no evidence of non-chloramphenicol acetyltransferase modification of chloramphenicol. In vitro protein synthesis in the presence of chloramphenicol was equivalently inhibited in the chloramphenicol-resistant transformants and in the susceptible recipient. Chloramphenicol uptake by these strains during logarithmic growth was compared by high-pressure liquid chromatographic quantitation; at chloramphenicol concentrations of 5, 10, and 20 micrograms/ml the four transformants showed a decreased rate of uptake of chloramphenicol compared with the isogenic chloramphenicol-susceptible recipient. Sodium dodecyl sulfate-polyacrylamide gel electrophoretic analysis of outer membrane proteins revealed a markedly diminished 40-kilodalton protein in the resistant transformants. We propose that the mechanism of chloramphenicol resistance in these strains is a relative permeability barrier due to the loss of an outer membrane protein.
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PMID:A permeability barrier as a mechanism of chloramphenicol resistance in Haemophilus influenzae. 387 25

We examined chloramphenicol-resistant Haemophilus parainfluenzae and Haemophilus ducreyi strains isolated in various parts of the world. The antibiotic resistance determinants were located on conjugative plasmids in H. ducreyi, but were chromosomally located in H. parainfluenzae. Both species produced chloramphenicol acetyltransferases (CATs) that were sensitive to 5,5'-dithiobis(2-nitrobenzoic acid) like the enteric type II and Haemophilus influenzae CAT enzymes, but differed from these enzymes in elution patterns and subunit molecular weight. Southern blot analysis showed the H. parainfluenzae and H. ducreyi CAT genes were molecularly related to the enteric type II class as well as the H. influenzae CAT. Heterogeneity of the physiochemical properties of the CATs was observed; however, the data suggested that all three Haemophilus spp. have a common ancestral source for the CATs.
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PMID:Molecular characterization of chloramphenicol-resistant Haemophilus parainfluenzae and Haemophilus ducreyi. 387 58

We examined nine chloramphenicol-resistant (minimal inhibitory concentration, greater than or equal to 15 micrograms/ml) Haemophilus influenzae strains isolated in various parts of the world to characterize the genetic and biochemical bases of the resistance; four were type b. All nine contained conjugative plasmids, ranging in molecular weight from 34 x 10(6) to 46 x 10(6), which encoded for resistance to chloramphenicol and tetracycline or chloramphenicol, tetracycline, and ampicillin. Deoxyribonucleic acid homology studies showed that these plasmids were closely related to a previously described ampicillin-resistant plasmid, RSF007, and to each other. All nine isolates and their chloramphenicol-resistant transconjugants produced chloramphenicol acetyltransferase. We conclude that chloramphenicol resistance in these strains of H. influenzae is via plasmid-mediated production of chloramphenicol acetyltransferase.
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PMID:Characterization of chloramphenicol-resistant Haemophilus influenzae. 696 77


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