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↗

PubMed1988

Cephaloridine resistance in gram-negative bacteria isolated in Scotland.

The incidence of cephaloridine resistance (minimum inhibitory concentration, MIC greater than 8 mg L-1) in isolates from urinary tract infections was 45.1% in Glasgow, 22.6% in Dundee and 25.9% in Edinburgh. The incidence of ampicillin resistance (MIC greater than 8 mg L-1) was even higher:- being 45.2% in Dundee and 48.5% in Edinburgh. In Glasgow, the incidence was 71.9% which is the highest proportion of ampicillin resistance reported in the United Kingdom. The cephaloridine resistant strains were examined for beta-lactamase production. Amongst these strains 50.8% produced only a chromosomal beta-lactamase, whereas 47.9% produced beta-lactamases which were potentially plasmid-mediated on the basis of biochemical tests. Only 1% of the resistant strains produced no detectable beta-lactamase.

Ampicillin Resistance↗

PubMed1987

Selection of enhanced cefotaxime resistance in Enterobacter spp.

Four strains of Enterobacter spp. with different chromosomal beta-lactamase expression (inducible, constitutive or negligible) were grown in broth containing either cefoxitin or cefotaxime, then plated on to agar containing 20 mg cefotaxime per litre to quantitate the cefotaxime-resistant mutants present in the population. Spontaneous resistant mutants were initially isolated from each strain at frequencies of 10(-4) to 10(-5). These high frequencies of spontaneous mutation suggested that more than one type of mutational event could yield cefotaxime resistance. Induction of a high level of beta-lactamase in broth cultures was not in itself sufficient to confer a high level of cefotaxime resistance on the population, and increased resistance following selection of resistant mutants did not necessarily correlate with any significant increase in beta-lactamase activity.

Cefotaxime↗

PubMed1987

Ampicillin resistance in Haemophilus influenzae: identification of resistance mechanisms.

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.

Ampicillin↗

PubMed1987

Cephalosporin assays.

Explore the source record for details and available documents.

Bacteria↗

PubMed1986

Qualitative and quantitative aspects of beta-lactamase production as mechanisms of beta-lactam resistance in a survey of clinical isolates from faecal samples.

A study has been conducted to identify the beta-lactamases most likely to contribute to beta-lactam resistance in clinical populations and to investigate their interactions with cefuroxime and newer cephalosporins. A total of 217 ampicillin-resistant, Gram-negative isolates from faecal samples of healthy volunteers in Germany, South America and Amman were investigated. Such strains represent the 'gene pool' from which infections might arise. Escherichia coli was the prevalent species (59.9%) followed by Klebsiella spp. (20.3%) and Enterobacter cloacae (12.0%). At least 56.7% and possibly as high as 64.5% of strains owed their principal beta-lactamase activity to enzymes mediated by R-plasmids. The most prevalent R-plasmid mediated beta-lactamase was TEM-1 which was produced by 109 strains. The beta-lactamase activity of strains producing only a chromosomal enzyme was often markedly higher than that of strains also producing an R-plasmid mediated enzyme. The qualitative and quantitative aspects of beta-lactamase production were investigated in cell free and whole cell tests and this confirmed the superior broad spectrum beta-lactamase resistance of ceftazidime over other new cephalosporins.

Anti-Bacterial Agents↗

PubMed1984

In vitro properties of ceftazidime, a highly active broad-spectrum cephalosporin with antipseudomonal activity.

Ceftazidime is an aminothiazolyl cephalosporin that exhibits a high level of broad-spectrum activity, with particularly good activity against Pseudomonas sp. Although activity in vitro against staphylococci is moderate, the majority of enterobacteria are susceptible, with MIC50 values in the range from 0.06 to 4 micrograms/ml. This cephalosporin is also highly active against indole-positive Proteus sp, Providencia sp, Citrobacter sp, and Serratia sp, with MIC50 values ranging from less than or equal to 0.06 to 0.13 microgram/ml. Good activity against Pseudomonas sp is a notable feature, with MIC90 values in the range of 4 to 8 micrograms/ml. Ceftazidime is bactericidal at concentrations identical or close to the MIC. Antibiotic performance in vitro appears to be unaffected by the presence of body fluids. Good stability to hydrolysis by a range of the prevalent beta-lactamases, good penetration into the intact bacterium, and a high affinity for the essential penicillin-binding proteins combine to account for the broad spectrum and high activity of ceftazidime. Comparative in vitro studies have shown ceftazidime to be as active and sometimes more active than available aminoglycoside antibiotics. Since the mode of action of ceftazidime differs fundamentally from that of the aminoglycosides, high activity is maintained against the majority of aminoglycoside-resistant isolates. Ceftazidime should therefore represent a viable and potentially safer alternative to aminoglycoside antibiotics.

Anti-Bacterial Agents↗