Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0348321 (Haemophilus)
 15,372 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The incidence and mechanisms of ampicillin resistance (MIC greater than 1 mg/l) were investigated in 105 clinical isolates of Haemophilus influenzae collected in Edinburgh during 1983/4. Fifteen (14.3%) ampicillin-resistant strains were identified and these were non-serotypable and comprised six biotypes. Isoelectric focusing and beta-lactamase-inhibition studies demonstrated that production of the TEM-1 beta-lactamase was the principal mechanism of resistance in nine (60%) strains. Radiolabelling revealed that one beta-lactamase-positive strain also had an unusual penicillin-binding protein (PBP) profit. No beta-lactamase activity was detected in the other six (40%) ampicillin-resistant strains. Two beta-lactamase-negative ampicillin-resistant strains had atypical PBP profiles. SDS-PAGE analysis showed that four beta-lactamase-negative ampicillin-resistant strains, including one with altered PBPs, exhibited outer membrane protein profiles which differed from those of sensitive strains of the same biotype. The ampicillin-resistance mechanism of the remaining strain could not be determined. Thus, several resistance mechanisms, either acting individually or in combination, are implicated in ampicillin resistance in H. influenzae.
 ...
PMID:Ampicillin resistance in Haemophilus influenzae: identification of resistance mechanisms. 350 21

The in vitro activity of CGP 31523A, an aminothiazolyl cephem, was compared to that of other cephalosporins--imipenem, aztreonam, carbenicillin, and gentamicin. CGP 31523A inhibited E. coli, K. pneumoniae, P. mirabilis, C. diversus, K. oxytoca, P. stuartii, Salmonella and Shigella at less than or equal to 0.25 micrograms/ml. It was equal or 2-fold more active than cefotaxime and ceftazidime, and 4-fold more active than imipenem against these organisms. It inhibited all carbenicillin and gentamicin-resistant isolates of these species. Neisseria and Haemophilus were inhibited by less than or equal to 0.12 micrograms/ml. Some C. freundii, E. cloacae, E. aerogenes, P. vulgaris, and P. penneri had MICs greater than or equal to 16 micrograms/ml similar to cefotaxime, ceftazidime and aztreonam. Pseudomonas were resistant, MIC 128 micrograms/ml. CGP 31523A inhibited streptococci at less than or equal to 0.25 micrograms/ml with the exception of S. faecalis, and staphylococci were inhibited by 0.5 micrograms/ml but methicillin-resistant isolates were resistant. Bacteroides and some Clostridium had MICs greater than or equal to 16 micrograms/ml. CGP 31523A was less stable than cefotaxime and ceftazidime to the plasmid TEM/SHV/PSE-4 beta-lactamases. Like cefotaxime it was hydrolyzed by the P. vulgaris type Ic beta-lactamase but not by the type Ia enzymes. CGP 31523A was not an effective beta-lactamase inhibitor nor did it induce beta-lactamases. It had overall activity comparable to available extended spectrum cephalosporins.
 ...
PMID:Comparative in vitro activity and beta-lactamase stability of CGP 31523A, a new aminothiazolyl cephalosporin. 351 67

The plasmid-mediated Branhamella catarrhalis beta-lactamase BRO-1, also found in Moraxella nonliquefaciens, was characterized as regards substrate profile, isoelectric point and relative substrate affinity index (RSAI) to various substrates and compared in these aspects with the TEM-1 enzyme of Haemophilus influenzae. As measured by a biological assay and with high performance liquid chromatography (HPLC), BRO-1 was found to hydrolyse carbenicillin, mecillinam, methicillin and cefaclor with a higher rate than TEM-1. The only substrates having a relative rate of hydrolysis higher for TEM-1 than for BRO-1 were ampicillin and cephaloridine. The rates of hydrolysis registered with these two methods were comparable for all but 2 of 13 tested substrates. Isoelectric focusing yielded a main band at pH 5.6 and several satellite bands consistent with those reported by other authors for Branhamella enzymes having a substrate profile similar to that of BRO-1. A tenfold or higher difference in RSAI between BRO-1 and TEM-1 was recorded for five of the 15 compounds tested. BRO-1 seems to be the most common beta-lactamase in Bran. catarrhalis, irrespective of geographic origin. Its substrate profile, isoelectric pattern and RSAI differ from those of other known plasmid-mediated beta-lactamases described, thus justifying a specific designation.
 ...
PMID:Characterization of the plasmid-mediated beta-lactamase in Branhamella catarrhalis, with special reference to substrate affinity. 387 94

Resistance of bacteria to beta-lactam antibiotics has become a serious problem in the past several decades. Virtually all Staphylococcus aureus, many Haemophilus influenzae, Branhamella catarrhalis, Neisseria gonorrhoeae, many Enterobacteriaceae, many Pseudomonas aeruginosa and Bacteroides species possess beta-lactamases which hydrolyze to varying degree penems, penams, carbapenems, cephems, cephamycins and monobactams. The most common plasmid-mediated beta-lactamase is the so-called TEM beta-lactamase (Richmond Sykes type IIIa) which exists in Haemophilus, Neisseria and many of the Enterobacteriaceae. Techniques to overcome this resistance have been the development of beta-lactamase stable compounds and of beta-lactamase inhibitors. However, inducible chromosomally mediated beta-lactamases in species such as Enterobacter, Pseudomonas, Citrobacter and some Serratia have become an increasing problem with more widespread use of beta-lactamase stable cephalosporins.
 ...
PMID:A perspective on the present contribution of beta-lactamases to bacterial resistance with particular reference to induction of beta-lactamase and its clinical significance. 387 25

The in vitro activity of cefotetan was assessed against beta-lactamase producing clinical isolates. The majority of Enterobacteriaceae were inhibited by less than or equal to 8 micrograms/ml with 50% of isolates inhibited by less than or equal to 1 microgram/ml. Cefotetan inhibited organisms resistant to cefazolin, cefonicid and cefoperazone, but not isolates of Enterobacter, Citrobacter or Serratia resistant to ceftizoxime. Cefotetan inhibited beta-lactamase producing Haemophilus influenzae and Neisseria gonorrhoeae at less than or equal to 1 microgram/ml, but it did not inhibit Acinetobacter or Pseudomonas aeruginosa. Cefotetan was as active as cefoxitin against anaerobic species such as Bacteroides fragilis and Clostridium. Cefotetan was not hydrolyzed by Richmond-Sykes plasmid beta-lactamases of type III such as TEM and SHV, nor by the OXA or PSE beta-lactamases. It also was not hydrolyzed by cephalosporinases of Richmond-Sykes type Ia or Id. Cefotetan inhibited beta-lactamases of the type Ia and Id, but it also induced these beta-lactamases in P. aeruginosa, E. cloacae and C. freundii.
 ...
PMID:The activity and beta-lactamase stability of cefotetan compared to other beta-lactam antibiotics. 387 87

Interpretive zone-size standards currently used for cephalothin and cefamandole disk tests also may be applied to tests with disks containing 30 micrograms of cefaclor or cefazolin. Against 627 representative isolates, susceptibility to cefaclor and cefazolin could be predicted by testing cephalothin. However, cefazolin is more active than cephalothin against isolates of Escherichia coli with a TEM beta-lactamase plasmid. The expanded spectrum of cefamandole continues to necessitate separate testing. Against methicillin-resistant staphylococci, cefaclor disks were more reliable than cephalothin or cefamandole, but false-susceptible results were seen with all four disks. For testing Haemophilus influenzae, the cefazolin disks were not reliable; cephalothin or cefaclor disks could predict susceptibility to either drug.
 ...
PMID:Reliability of cefaclor, cefazolin, cefamandole, and cephalothin disks to predict susceptibility of Enterobacteriaceae, Staphylococcus species, and Haemophilus influenzae. 387 52

Resistance of bacteria to beta-lactam antibiotics has become a serious problem in the past several decades. Virtually all Staphylococcus aureus, and many Hemophilus influenzae, Branhamella catarrhalis, Neisseria gonorrhoeae, Enterobacteriaceae, and Bacteroides species possess beta-lactamases that hydrolyze penicillins and cephalosporins. The most common plasmid-mediated beta-lactamase is the TEM enzyme (Richmond-Sykes type IIIa), which is present in Hemophilus, Neisseria, and Enterobacteriaceae. One technique to overcome bacterial resistance has been the development of beta-lactamase inhibitors. Clavulanic acid is a beta-lactamase inhibitor that inhibits the beta-lactamases of S. aureus, Hemophilus, Neisseria, Branhamella, Eschericia coli, Klebsiella, and Bacteroides. Clavulanate acts as a "suicide" inhibitor, forming a stable enzyme complex that binds to serine at the active site of the enzyme. Clavulanate readily crosses the outer cell wall of most Enterobacteriaceae to interact with beta-lactamases in the periplasmic space. Clavulanate does not inhibit beta-lactamases such as the Richmond-Sykes type I enzymes found in Pseudomonas aeruginosa, Enterobacter, and Citrobacter species, which are inducible enzymes that function primarily as cephalosporinases.
 ...
PMID:Contribution of beta-lactamases to bacterial resistance and mechanisms to inhibit beta-lactamases. 390 41

The in vitro activity of cefpirome, a new cyclopyridinium cephalosporin, was evaluated against 947 aerobic and anaerobic bacteria. Cefpirome inhibited 90% of Escherichia coli, Klebsiella spp., Citrobacter diversus, Morganella morganii, Proteus vulgaris, Proteus mirabilis, Aeromonas spp., Salmonella spp., Shigella spp. and Haemophilus and Neisseria species at less than or equal to 0.4 mg/l. It had activity comparable to that of cefotaxime, ceftizoxime, ceftazidime, aztreonam, and moxalactam against these species. Only a few Citrobacter freundii, Enterobacter spp. and Serratia marcescens had MICs above 3.1 mg/l. The activity of cefpirome against Pseudomonas aeruginosa, 90% MIC of 12.5 mg/l, was superior to piperacillin, moxalactam, cefotaxime and cefoperazone. The 90% MIC against Staphylococcus aureus was 0.8 mg/l, but methicillin-resistant staphylococci were not inhibited. Cefpirome was not significantly hydrolyzed by most plasmid beta-lactamases (TEM, SHV-1, PSE, OXA) nor by chromosomal enzymes (P99, Branhamella catarrhalis, K1). Cefpirome did not inhibit chromosomal or plasmid beta-lactamases. Mice systemically infected with E. coli, Klebsiella pneumoniae, P. aeruginosa and S. aureus were protected by concentrations of cefpirome ranging from 0.85 mg/kg for K. pneumoniae to 4.467 mg/kg for P. aeruginosa.
 ...
PMID:The in vitro activity and beta-lactamase stability of cefpirome (HR 810), a pyridine cephalosporin agent active against staphylococci, Enterobacteriaceae and Pseudomonas aeruginosa. 392 97

Documented ampicillin treatment failures of systemic Haemophilus influenzae type b infections have been associated with synthesis of a TEM-1 beta-lactamase. A patient with H. influenzae type b meningitis in whom ampicillin treatment failed is described; the isolate was beta-lactamase-negative according to the cell suspension chromogenic cephalosporin assay. The false-negative result occurred in a strain which elaborated a novel, plasmid-mediated beta-lactamase with characteristics which distinguish it from TEM-1 beta-lactamase. Clinically important ampicillin resistance in H. influenzae type b occurs by mechanisms other than by synthesis of TEM-1 beta-lactamase. Diagnostic microbiology laboratories should perform antibiotic susceptibility tests in addition to tests for beta-lactamase production.
 ...
PMID:Ampicillin treatment failure of apparently beta-lactamase-negative Haemophilus influenzae type b meningitis due to novel beta-lactamase. 611 76

The emergence of beta-lactamase producing strains of Haemophilus influenzae and Neisseria gonorrhoeae has required fundamental changes in the antimicrobial therapy of disease caused by these organisms. Ampicillin resistance in both organisms is caused by plasmid mediated production of TEM beta-lactamase. This enzyme is specified by a sequence of mol. wt 3.2 X 10(6) which is capable of inserting itself at multiple sites in DNA replicons without the requirement for significant base sequence homology between donor and recipient replicon. Further, it does so without requirement for conventional recombination enzymes. Analysis of beta-lactamase specifying plasmids of H. influenzae show that they generally have a molecular mass in the order of 30 X 10(6) and contain the complete TnA sequence. They are conjugative but are incapable of mobilizing smaller beta-lactamase plasmids. Previous studies have presented evidence suggesting that these plasmids may have evolved by insertion of the TnA sequence (perhaps introduced from enteric bacteria) into a phenotypically cryptic plasmid of mol. wt 27 X 10(6) resident in rare strains of H. influenzae. In this study, we review data showing a high degree of homology between the small (3--7 X 10(6) mol. wt), nonconjugative beta-lactamase specifying plasmids of N. gonorrhoeae, H. parainfluenzae and H. ducreyl and present new evidence that cryptic plasmids highly homologous to the beta-lactamase plasmids are present in many strains of H. parainfluenzae. This suggests that the small beta-lactamase specifying plasmids of H. parainfluenzae, H. ducreyi and N. gonorrhoeae may have arisen by insertion of TnA into phenotypically cryptic plasmids present in H. parainfluenzae.
 ...
PMID:Evolution of antibiotic resistance plasmids in Neisseria gonorrhoeae and Haemophilus species. 631 45


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>