Is Escherichia coli ATCC 25922 a colicin producing strain? (a note).

The well-characterized strain of Escherichia coli ATCC 25922 recommended and widely used as a control Gram-negative bacterium for various laboratory experiments, especially for antibiotic susceptibility assays, was found to be antagonistic against another E. coli strain which is uniquely susceptible to fusidic acid, an antibiotic mainly active against Gram-positive bacteria. This antagonistic property appears to be selective, since it was not found against other E. coli or Staphylococcus aureus strains.

Antibacterial antagonism between fusidic acid and ciprofloxacin.

A routine laboratory disk susceptibility testing of a resistant Staphylococcus aureus strain showed that around the ciprofloxacin disk, placed by chance in proximity to a fusidic acid disk, the inhibition zone was truncated. Follow-up of this observation by a planned disk approximation method showed that there is a real antagonism between these two antibacterial agents. The antagonism was observed while testing S. aureus isolates including the standard ATCC 25923 strain, with Bacillus subtilis ATCC 6633 spores and also with a mutant Escherichia coli made fusidic acid susceptible. The antagonistic property was found structure-specific, only associated with those fluoroquinolones containing the cyclopropyl substituent at the N1-position: ciprofloxacin, enrofloxacin, sparfloxacin and WIN 57273. Fluoroquinolones without this substituent such as enoxacin, norfloxacin, pefloxacin and ofloxacin were not antagonized by fusidic acid, the steroidal Gram-positive active antibiotic.

Diazald, a newly recognized antimicrobial agent and its spectrophotometric determination.

Diazald, a chemical intermediate for the synthesis of biologically active compounds, was found to be a potent in vitro antimicrobial agent against yeasts, yeast-like and filamentous fungi as well as Gram-positive and Gram-negative bacterial strains. Its activity is not inhibited by either para-aminobenzoic acid (PABA) or the nitroso group-specific 2-aminothiazole-methoxyimino acetic acid (ATMAA). This suggests that the molecule as such is responsible for the antimicrobial activity. For its quick measurement a sensitive spectrophotometric method has been developed.

A comparison of cefonicid with other beta-lactams regarding the effect of human and mouse sera on antibacterial activity.

The effect of the addition of 50% human or mouse serum on the antibacterial activity of cefonicid, three first generation cephalosporins and ampicillin was studied. Human serum added to the test system considerably reduced the activity of cefonicid against Staphylococcus aureus and Staphylococcus epidermidis strains, and to a lesser degree against Proteus mirabilis, Escherichia coli and Klebsiella pneumoniae strains. Human serum also reduced, albeit to a lesser extent, the activities of cephalothin, cefazolin, and ampicillin, whereas it increased the activity of cephaloridine. In contrast, mouse serum did not or only insignificantly reduced the activity of cefonicid against some of the bacterial isolates; this is reflected in the excellent protective effect of cefonicid in experimental mouse infections.

Colorimetric detection and spectrophotometric determination of the aminothiazolyl-alkoxyimino beta-lactams.

The 2-aminothiazolyl-4-yl-2-alkoxyiminoacetamido substituent-containing beta-lactam antibiotics (cephalosporins and monobactams) develop a stable, concentration-dependent purple or cherry-red color after reaction with sodium nitrite in acidic condition. The color-formation is highly specific; it requires certain defined structural features such as the simultaneous presence of the intact aminothiazole-ring and an alkoxyimino substituent in the syn configuration. Other substituents on the beta-lactam nucleus have effect only on the intensity of the color. This simple and fast colorimetric procedure was found to be useful not only for the detection of this class of beta-lactam antibiotics but also for their quantitative spectrophotometric determination (lambda max 500 nm). A linear relationship exists between the intensity of the color plotted on a logarithmic scale and the concentration (12.5-200 micrograms/ml) of the compounds on an arithmetic scale. The beta-lactams studied in this class with definitely positive purple-red color reaction are; cefotaxime, ceftizoxime, ceftazidime, ceftriaxone, cefmenoxime, cefodizime, ceftiolene, cefpirome, aztreonam, HR 109, FK 027 (cefixime), FR 19346, SK&F 88070, FR 13300, carumonam, YM 13115, BMY 28142, DN 9550, deacetylcefotaxime, deacetoxycefotaxime and deacetylcefotaxime lactone.

Stability of cefatrizine in aqueous solution and in sera.

Cefatrizine (SK & F 60771; BL--S640), like most other phenylglycine-type cephalosporins, has a tendency to lose potency in aqueous solutions and in normal sera even at low temperatures. Cefatrizine can be stabilized during storage by sodium metabisulphite (Na2S2O5), a reducing agent partially in tap water, better in deionized water, and to a lesser degree in citric acid-phosphate buffer (pH 6). Although this partial stabilizing effect of sodium metabisulphite is temperature-dependent, storage at 4 degrees C gives better results than storage in the frozen state (-20 degrees C). In these aqueous solutions and in sera, the potency of cefatrizine can be preserved even at room temperature for up to four weeks by the addition of 0.1 ml of 2 N hydrochloric acid to each 2 ml of aqueous solutions or sera.

Novel fermentation procedures for the production and the isolation of antibiotics.

Novel procedures for the production, in shaken and/or air-agitated fermentations, and the isolation of antibiotics were developed by which active crystalline flavofungin by Streptomyces flavofungini and an antibiotic produced by Streptomyces SK&F, BC-1652 were obtained.

Comparative laboratory studies on alpha-methoxyimino furyl- and phenylacetamido cephalosporins: structure-activity relationships.

Eleven new cephalosporins (three phenylacetamido and eight furylacetamido) containing a methoxyimino group on the 7 beta-acyl side chain and having various substituents at their 3-positions, exhibited similar qualitative, but differing quantitative in vitro antibacterial spectra compared to that of cefuroxime, the first therapeutically used alpha-methoxyimino cephalosporin. The syn-isomers and the alpha-acyl substituted compounds are more active than either the anti-isomer or the beta-acyl substituted compounds. Compounds containing substituted tetrazole rings at the 3-position are likewise more active than those containing other types of substituents in this position. In vivo (mouse) the heterocyclic furylacetamido compounds are more efficacious (protective) than the aromatic phenylacetamido compounds. The furylacetamido alpha-methoxyimino cephalosporins containing at the 3-position the tetrazole group carrying an acidic function possess favorable pharmacokinetic properties, i.e., higher serum levels and prolonged biological half-lives in mouse and squirrel monkey and extensive binding to serum proteins.

Antibacterial activity of primycin against multiple strains of gram-positive bacteria.

Crystalline primycin was found to be very active in broth dilution assay against Staphylococcus aureus (50 strains), Staphylococcus epidermidis (77 strains), Streptococcus faecalis (76 strains) and one strain of Listeria monocytogenes with minimal inhibitory concentrations (MIC) of 0.12-0.5 microgram/ml. The activity was influenced by the pH of the liquid medium with greater activity (lower MICs) at pH 8 against the majority of strains, than at pH 6 or 7.3. In disc agar diffusion assay Bacillus subtilis ATCC 6633 proved more sensitive than staphylococcus strains.

Detection of beta-lactamase activity with nitrocefin of multiple strains of various microbial genera.

The production or presence of beta-lactamase(s) was studied by the rapid method utilizing the chromogenic cephalosporin compound nitrocefin in cultures of multiple strains belonging to the same genus as well as groups of microorganisms. The genera were: Staphylococcus spp., Streptococcus faecalis, Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis, indole-positive Proteus spp., Enterobacter spp., Serratia marcescens, rare Enterobacteriaceae, Pseudomonas aeruginosa, Haemophilus influenzae and Neisseria gonorrhoeae. With this sensitive and rapid assay for beta-lactamase, it was possible to verify and separate the beta-lactamase producing cultures from the non-producers and include the useful strains to on-going research, such as beta-lactam screen, beta-lactamase inhibitory study and lytic properties of beta-lactams. The data also provide evidence for the possible role of beta-lactamase(s) in the physiology, biochemistry and pathogenicity of bacterial strains. The nitrocefin method was found a very specific and extremely useful procedure for the detection and estimation of beta-lactamase activity.

Enoxacin: a potent inducer of filamentous Escherichia coli cells (a note).

Enoxacin (CI-919; AT-2266), a new naphthyridine derivative was found to induce morphologic changes at very low concentrations in Escherichia coli but not in Staphylococcus aureus and Pseudomonas aeruginosa cells. The development of the long filamentous forms observed with nalidixic acid is most probably a consequence of inhibition of DNA synthesis. The phenomenon may, however, not be the sole mechanism of the broad-spectrum antimicrobial activity of enoxacin.

Structure-related effect of pH on the bioassay sensitivity of five thiadiazole cephalosporins (a note).

Using the buffered disc agar-diffusion method with Bacillus subtilis as test organism' a direct relationship was found between the pH, incubation temperature and the structure-dependent activity of five thiadiazole cephalosporins. This appears to be related to the ionizable group(s) of the molecules.

Staphylococcus aureus Tour, a selectively mouse-pathogenic strain for experimental chemotherapeutic study (a note).

Staphylococcus aureus Tour is a unique strain. It is highly pathogenic to mice but not to other laboratory animals and primates. This selective pathogenicity makes it useful for experimental chemotherapeutic studies. Since it is highly specialized for mice, it imitates the natural course of infection and produces death after intraperitoneal infection of a relatively few cells even when suspended in isotonic saline. This strain has been found to be very sensitive (MIC's) to various beta-lactams and gentamicin as well as useful for infection-protection studies in mice (ED50's) with a series of cephalosporins.

Hydroxylamine inactivation of cephalosporins: nucleophilic attack on beta-lactam structures.

Cephalosporins are not degraded by hydroxylamine (NH2OH) in neutral and acidic solutions. Their reaction with NH2OH in slightly alkaline solutions leads to microbiological inactivation which seems to be a structure dependent phenomenon. In these experiments the mandelic acid-type compounds appear to be quite stable to the effect of NH2OH, whereas, cefazolin is gradually degraded and the straight chain-containing cephalosporins are variably inactivated. The phenylglycine-type oral cephalosporins were generally sensitive to the alkaline conditions used in these tests and apparently are not inactivated by NH2OH. On the contrary, the phenylglycine-type cephalosporins seem to be somewhat stabilized in the presence of NH2OH.

Ceftizoxime treatment of cutaneous and subcutaneous tissue infections.

Forty-seven adults with infected cutaneous lesions including decubitus ulcers, leg ulcers, cellulitis, pyoderma, and infected dermatitis were treated in a randomized single-blind study with ceftizoxime (2 gm/day, administered intravenously) or cefamandole (4 gm/day, administered intravenously). The duration of treatment ranged from five to 17 days with ceftizoxime and from six to 14 days with cefamandole. Both gram-positive cocci (mostly Staphylococcus sp) and gram-negative bacilli were cultured from the infected areas before treatment. Clinical and bacteriological responses to both drugs were excellent. Ceftizoxime at a dosage of 1 gm twice daily proved to be at least as effective as 1 gm of cefamandole given four times daily. Both drugs were well tolerated, effective, and safe in the treatment of skin and skin-structure infections. Neither drug therapy had to be discontinued because of adverse effects.

Effect of pH on the activity of ceftizoxime.

The in vitro antibacterial activity of ceftizoxime (Cefizox) is influenced by the ambient pH of the medium. This pH-dependent activity was observed when either the assay discs or the assay medium were buffered. For the conventional disc agar-diffusion assay, using Bacillus subtilis ATCC 6633, the medium buffered to pH 6 had definite advantage for measuring potency and activity. In serial dilution assay, the acidic (pH 6) medium gives better MIC values with Staphylococcus aureus strains. In the case of Escherichia coli strains, the pH of the medium (6, 7.3 and 8) appears to be of less significance.

Disulfiram-like reaction to certain cephalosporins.

Semisynthetic cephalosporins, containing the methyltetrazolethiol substituent at the 3-position of the fused beta-lactam dihydrothiazine nucleus, can clearly produce disulfiram-like reactions in certain subjects who consume ethanol after treatment with these cephalosporins. So far, cefamandole, cefoperazone, and moxalactam have been repeatedly reported to produce this reaction, which is strictly related to the chemical structure of the cephalosporin. Similar to the characteristic symptoms and signs observed with disulfiram and these cephalosporins, increased acetaldehyde concentrations in blood were also measured. The phenomenon can be studied in an animal (rat) model. Patients experiencing these often frightening disulfiram-type reactions seldom need specific treatment; however, it is mandatory to strongly caution patients not to consume alcoholic beverages for a few days after treatment with these cephalosporins. Other aspects and ramifications of this phenomenon are also reviewed.