Investigation of oxacillin-hydrolyzing beta-lactamase in borderline methicillin-resistant clinical isolates of Staphylococcus aureus.

Background: Mechanisms of borderline resistance of Staphylococcus aureus to penicillinase-resistant penicillins (PRPs) may include hyperproduction of classical penicillinase and/or production of beta-lactamase hydrolyzing also PRPs.

Methods: beta-Lactamase activity of whole cells and purified enzymes was estimated spectrophotometrically and in isolated cytoplasmic membranes by bioassay with Bacillus subtilis as test strain.

Results: Out of 53 clinical isolates of S.

beta-Lactam susceptibility patterns and investigation of cephalosporin hydrolysing beta-lactamases of Gram-negative extraintestinal clinical isolates.

Of more than 3500 isolates of enterobacteriaceae, 48-69% were resistant to aminopenicillins and 11-45% to amoxycillin+clavulanic acid. Resistance to second and third generation cephalosporins was present in 11-17 and 3-8% of Escherichia coli, 47-56 and 15-52% of Klebsiella-Enterobacter, 36-57 and 16-27% of Proteus, Providencia and Morganella isolates. Pseudomonas aeruginosa strains varied in their resistance to antipseudomonal beta-lactams.

A synthetic gamma-lactone group with beta-lactamase inhibitory and sporulation initiation effects.

Previous studies showed that some lactones have beta-lactamase inhibitory or antibacterial effects, others--like A-factor (a gamma-butyrolactone) and its derivatives--stimulate sporulation in Streptomyces griseus strains. Our experiments were aimed at exploring whether synthetic gamma-lactones had such effects. None of the seven gamma-lactones studied showed antibacterial activity, but two of them inhibited beta-lactamases isolated from various bacteria.

Beta-lactam antibiotics functionalized with gem-bisphosphonates.

Acylation of amoxycillin and cephalexin with acids III, V and VII, and with isocyanate VIII furnished the corresponding beta-lactam antibiotics (X and XIII-XV, respectively). The antibacterial activity of these new antibiotic analogues against Helicobacter pylori was found to be identical with those of amoxycillin, Augmentin, erythromycin and ciprofloxacin.

Comparison of the toxicity of fluconazole and other azole antifungal drugs to murine and human granulocyte-macrophage progenitor cells in vitro.

We studied the inhibitory effects on colony formation by granulocyte-macrophage colony forming units (cfu-gm) of eight azole antifungal agents in vitro. All agents, except fluconazole, inhibited colony formation dose-dependently with 50% inhibitory concentrations (IC50) in the range of 0.78-49 micromol/L in cultures of murine and human bone marrow.

[Effect of imidazole antifungal agents on colony formation by murine bone marrow CFUc (colony forming units in culture].

In spite of modern antifungal therapy, the prognosis of systemic mycoses in neutropenic patients is usually poor without recovery of neutrophil counts. So, even a minor myelotoxicity might be a significant disadvantage of any drug used for the treatment of neutropenic patients with fungal infections. Since "Colony Forming Units in culture" (CFUc), the common progenitors of granulocytes and macrophages, are supposed to be a major target of agents damaging bone marrow, we studied the inhibitory effect of four imidazole antifungal drugs to colony formation by murine CFUc in vitro.

Use of chromatofocusing for separation of beta-lactamases. IX. Analytical chromatofocusing for the separation of a chromosomal cephalosporinase from Proteus vulgaris 1028.

Simultaneous purification and isoelectric point (pI) determination was carried out at analytical scale of the chromosomal cephalosporinase from the Proteus vulgaris 1028 strain. Comparison of the enzyme to the purification results with m-aminophenylboronic acid-agarose affinity chromatography with sodium dodecyl sulphate-polyacrylamide gel electrophoresis revealed that minute amounts of accompanying proteins having identical pI values but different molecular masses were found in the chromatofocused preparation. The molecular mass of the enzyme was 24,000 dalton.

Purification and some properties of Candida albicans DNA polymerases.

DNA polymerases of Candida albicans were purified to near homogeneity. Three well distinguished peaks of DNA polymerase activity (Enzyme I, II and III respectively) were obtained by DEAE-Sephacel chromatography. This purification step was followed by column chromatographies on Sepharose 6B and denatured DNA-cellulose.

In vitro investigation of BK-218, a new oral and parenteral cephalosporin.

The antibacterial activity of BK-218 was similar to that of cefamandole when it was tested against several laboratory strains. The inhibiting effect of BK-218 was greater than that of cephalexin and cefoxitin on penicillin-binding proteins of Escherichia coli HB101. This result was in close correlation with the relative inhibition of radiolabeled glucosamine incorporation (greatest with BK-218) and with the lytic effect (most intensive with BK-218).

Modified general affinity adsorbent for large-scale purification of penicillinases.

N-Acetyl-D-(-)-penicillamine as a stable second-generation biospecific affinity ligand has previously been suggested for purification of Bacillus cereus 569/H beta-lactamase I. A complex spacer arm is coupled with the matrix by using epichlorohydrin and phloroglucinol doubly activated with divinyl sulphone in the meta position. Coupling of D-(-)-penicillamine ligand resulted in an active affigel.

Curing of 60Co gamma-resistance inducing effect of R46 R-factor by 5-fluorouracil.

The 60Co gamma-resistance inducing effect of R46 factor, and its elimination by 5-fluorouracil were studied. R46 increased the survival of the wild-type strain and its rec- mutants. After treatment with 5-fluorouracil (1 g/liter) the clones lost not only antibiotic resistance, but the 60Co gamma-radioresistance as well, encoded by R46 R-factor.

Use of chromatofocusing for separation of beta-lactamases. VIII. Analytical chromatofocusing of chromosomal cephalosporinases from four Klebsiella strains.

Although still there are Klebsiella strains which do not harbour plasmids and produce constitutive chromosomal beta-lactamases, recently clinical isolates were found in ever increasing numbers carrying mainly TEM-, CARB- and OXA type R-factors. We selected four chromosomal cephalosporinase producing Klebsiella strains to study the pI values of the enzymes and their simultaneous separability from accompanying proteins by chromatofocusing techniques. We compared pI values of the pure and the crude preparations: K.

Elimination of UV-resistance inducing effect of R46 R factor by 5-fluorouracil.

R-factor curing capacity of 5-fluorouracil (5-FU) was studied. Well detectable increase in UV-resistance was found in E. coli K12 AB1157 strain and its recB-, recC-, recF- mutants harbouring R46 R-factor.

Effect of the pKM101 plasmid on the repair of single-strand breaks in DNA induced by ionizing irradiation in Escherichia coli.

The effect of pKM101 plasmid on repair of single-strand breaks in DNA induced by 60Co-gamma irradiation in E. coli K12 AB1157 (wild type) and in its recA- and recB- mutant cells was studied by alkaline sucrose gradient sedimentation method. For quantitative analysis of sedimentation profiles we calculated the S1/2 values described by Veatch and Okada.

R46 and pKM101 plasmid-mediated resistance to ionizing radiation in Escherichia coli.

The ability of the R46 R factor and its derivative pKM101 to modify sensitivity to 60Co gamma radiation was studied. In Escherichia coli K12 both plasmids enhanced bacterial survival after 60Co gamma irradiation. This effect was dependent on recA+ genotype but not on recB+, recB+ recC+, and recF+ genotypes.