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A series of fluorinated arylsulfonylthiosemicarbazides and arylsulfonylhydrazones has been synthesized. A representative number of the synthesized compounds have been screened for their antibacterial activity but none of the compounds showed significant activity.
A series of new fluorine-containing 3,5-disubstituted aryl/alkylisoxazoles has been synthesized by the condensation of hydroxylamine with appropriate beta-diketones in the presence of pyridine and characterized by IR and 1H NMR spectral studies. These isoxazoles have been screened for their antibacterial activity against the gram positive bacteria, Staphylococcus albus, Streptococcus nonhemolyticus and the gram negative bacterium Escherichia coli.
Although recent studies have suggested that some antibacterial agents have good activity against the rapidly growing mycobacteria Mycobacterium fortuitum and Mycobacterium chelonei, an easily applicable method for susceptibility testing of clinical isolates is not yet available. We evaluated a disk diffusion method with Mueller-Hinton agar and 48-h readings with 59 strains of M. fortuitum and 11 strains of M. chelonei and compared the results to agar dilution susceptibilities for nine antimicrobial agents. All isolates were susceptible to 16 micrograms of amikacin or kanamycin per ml with minimum zone diameters of 14 and 18 mm, respectively. Amikacin inhibited 100% of isolates of M. fortuitum at 2 micrograms/ml, whereas 10 of 11 (91%) of M. chelonei strains had minimum inhibitory concentrations of 4.0 micrograms/ml or greater. Doxycycline and minocycline had almost identical activities, inhibiting 44% of strains at 4.0 micrograms/ml, and both allowed easy differentiation between susceptible and resistant strains by disk diffusion. Although most isolates of M. chelonei grew better on 7H10 agar, this media gave two- to eight-fold higher minimum inhibitory concentrations than were obtained with Mueller-Hinton agar. Disk diffusion susceptibility testing appears to be a simple and reliable means of predicting susceptibility results for M. fortuitum and most isolates of M. chelonei by the agar dilution method.
In contrast with other antibacterial agents produced by bacteria, the bacteriocins of Gram -- bacteria (briefly: cins G--) are characterized by their primary lethal action, their inactivation by trypsin, their resistance to pH 2 (in the crude state) and insensitivity to DNase I after treatment with 7 M urea. Only 4 among 26 studied cins G + have the 4 above-cited properties and share most properties of cines G--.
A method is proposed to induce chemically the incorporation of bacterial agents inot enamel and thus rende this tissue resistant to bacterial colonization. It consists of promoting a slight initial dissolution of enamel, followed immediately by tis reprecipitation. During this latter phase, antibacterial agents included in the test formulations would become trapped in the reprecipitating enamel. That this happens is proved by the chemical detection of antibacterial agents in treated enamel, as well as by the development of a remarkable resistance of treated specimens to grow in vitro plaque.
Developments in the measurement of interstitial tissue fluid using the tissue cage model are described. The design and physical characteristics of tissue cages are examined and evidence is presented to show that the fluid contained within these cages is representative of interstitial tissue fluid. The distribution of a variety of antibacterial agents into tissue cage fluid is examined and shows that this technique is a reliable experimental model for the study of drug distribution. The results also show that some antibacterial agents may never, normally, distribute into the tissue fluid and that the use of tissue homogenates, especially the kidney, is unreliable as a guide to the tissue concentration of a drug.
Wild-type strains of the bacterial phytopathogen Erwinia amylovora (the cause of fire blight disease of apples and pears) are markedly susceptible to novobiocin, deoxycholate, and sodium dodecyl (= lauryl) sulfate. The inhibitory concentration, expressed as the concentration causing a 99% inhibition of growth, of these three antibacterial agents were 15 to 100, 40 to 800, and 50 to 800 mug/ml, respectively, depending on the E. amylovora strain. Growth of strains of other Erwinia spp. and Salmonella typhimurium is not affected at all, or is only slightly affected, at these concentrations. Introduction of the F'lac(+), RP1, and R100drd-56 (but not E-lac(+)) plasmids into an E. amylovora strain results in enhanced susceptibility to novobiocin and sodium dodecyl sulfate but not to deoxycholate. E. amylovora wild-type strains spontaneously release a periplasmic enzyme, cyclic phosphodiesterase, but not a cytoplasmic enzyme, glucose-6-phosphate dehydrogenase, into the growth medium. Addition of MgCl(2) (20 mM) and NaCl (84 mM) to tryptone broth stimulates the growth of wild-type E. amylovora strains and reduces or eliminates leakage of the periplasmic enzyme. Mutant strains of E. amylovora, selected for resistance to each separate antibacterial agent (or to all three of them), showed a direct correlation (in all but the novobiocin-resistant mutant) between drug resistance and reduced periplasmic leakiness. The relatively low maximum growth temperature (<37 degrees C) of E. amylovora seems unrelated to periplasmic leakage, as judged from the inability of added MgCl(2) to raise the maximum growth temperature, although the generation time at 30 degrees C is reduced from 108 to 54 min upon the addition of 20 mM MgCl(2). The extensive leakage of periplasmic enzyme and unusual drug susceptibility of E. amylovora strains might stem from some defect(s) in some cell envelope component(s) other than the lipopolysaccharide of these bacteria (which contain the usual liposaccharide constituents).
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Antibacterial activity of ticarcillin was determined in comparison with that of sulbenicillin, amoxicillin, cefuroxime, clindamycin and metronidazole against anaerobic bacteria which have been isolated from various clinical materials in this hospital. Growth of more than 90% of Gram-negative anaerobic rod bacteria was inhibited by ticarcillin at its concentration of 100 micrograms/ml. Strains resistant to ticarcillin showed cross resistance against both sulbenicillin and amoxicillin. Antibacterial activity of ticarcillin against Gram-positive anaerobic bacteria was found almost equal to sulbenicillin but slightly inferior to amoxicillin. Cefuroxime was found most inferior among the tested six antibiotics when an inoculation level of 10(8)/ml was utilized, but it showed similar activity to ticarcillin when they were tested with 10(6)/ml inoculation. Approximately 10% of bacteroides strains was resistant to clindamycin while all the strains were sensitive to metronidazole.
Reproducible experimental surgical-wound infections in mice for use in the evaluation of topical antibacterial agents are described. The experimental would was created on the backs of mice by means of a midline incision and was infected by means of cotton sutures monocontaminated with Staphylococcus aureus or Pseudomonas aeruginosa. The course of these wound infections was followed by quantitation of surface bacteria through use of a surface rinse technique. Surface wound counts of the infecting organisms thus obtained appeared to reflect the dynamics of the total wound count, as determined by homogenization of biopsied tissue. Treatment of infected wounds with a placebo cream had only a slight effect on surface wound counts and on mortality in the case of the S. aureus infection but enhanced markedly the lethality of the P. aeruginosa infection.
The effect of 8 antibacterial agents on the elimination of 32P-labelled Escherichia coli from rat polymorphonuclear cells was studied. None of the drugs tested had a detectable influence on the expulsion of labelled products from the cells being exposed to the various drugs during the elimination phase.
Enamel specimens treated with systems containing enamel conditioners and antibacterial agents have previously been shown to incorporate the latter into the enamel. It has now been demonstrated that enamel blocks treated with these systems become highly resistant to bacterial colonization, that this effect is rather long lasting, and that the treated specimens prevent acid formation when incubated with Streptococcus mutans in a sugar-containing medium.
Using 32P-labelled Escherichia coli, the effect of 8 antibacterial agents on the ability of rat polymorphonuclear cells to ingest the labelled bacteria was studied with and without serum present during the ingestion phase. No impairment of ingestion was observed when testing gentamicin, cephalothin and trimethoprim. High doses of oxytetracycline, doxycycline, colistin, erythromycin and chloramphenicol seemed to impair ingestion. The effect was most pronounced when applying 100 mug/ml of doxycycline: the ingestive capability was reduced to 25% without serum and 24% with serum present compared to untreated controls. 83 mug/ml of colistin reduced theingestion to 39% without serum present, this effect being totally eliminated when serum was present during the ingestion phase.
In this study the disc sensitivities of five organisms growing in pure cultures (Staphylococcus aureus, beta-hemolytic Streptococcus, Proteus mirabilis, Pseudomonas aeruginosa, and Candida albicans) were first determined against each of seven antibacterial agents (penicillin, streptomycin, gentamicin, kanamycin, silver nitrate, Sulfamylon, and Betadine). Then the sensitivity of each organism growing in combination with one of the others (10 combinations) was tested against each of the same antibacterials. Significantly increased and decreased sensitivities were found in 30 percent of the cultures with decreases largely predominating. Total obliteration of all sensitivity occurred 10 percent of the time. The changes in sensitivity were not distributed randomly but rather were associated more with particular agents and organisms. Sulfamylon, was associated with decreases 70 percent of the time with sensitivity obliteration in 50 percent of the tests. Streptococcus led all the organisms, being associated with decreases in half of the tests. It is possible that mixed-culture sensitivities could provide the most valid information when mixed infections exist, since they more closely simulate the real clinical situation. Therefore it is suggested that both mixed and pure culture sensitivity testing be done for all mixed infections.
The disc agar-diffusion-test using Bacillus subtilis ATCC 6051 as test organism is a simple and rapid method for routine testing of antibacterial agents in urine specimens. The test records urine levels which are expected under medium dosage, and in many cases even lower concentrations of renal excreted antibiotics. Out of 5655 analysed urine samples 22% contain antibacterial substances. In urine specimens over which information was volunteered that either no chemotherapy had been administered or that more than a three day's interval free of therapy existed, inhibitory substances are found in 8% and 27% respectively. Urine specimens which are supposedly collected from patients under current chemotherapy do not show therapeutic relevant antibiotic levels in 26%. Between urine specimens with and without antibacterial activity there is no significant difference in the incidence of viable counts of 10-4-10-5/ml and 10-5/ml. From urine samples with antibacterial content increases in the numbers of multiple resistant strains of E. coli, Proteus spp., Pseudom. aerug. and Enterobacter spp. together with high numbers of Candida spp. are observed.
A 1:1 water-paste slurry of a placebo and several experimental dentifrices was swabbed daily for six weeks on the teeth of albino rats, and the plaque collected on the teeth was measured in vivo first before the treatments began and one, two, three, and six weeks after. The results indicate that adding a suitable antimicrobial agent to a placebo dentifrice markedly reduced plaque accumulations on the teeth brushed with that product. When an enamel-conditioning vehicle was used instead of the placebo, the antiplaque effectiveness increased severalfold. It was concluded from the two first articles of this series 1,2 that adding antibacterial agents to enamel-conditioning systems resulted in the incorporation of the antimicrobial compound into enamel treated with these systems, and that enamel treated in such a fashion acquired marked antibacterial properties of its own. The data reported in this article support a third conclusion, namely, that the enamel-conditioning-antibacterial systems have a considerable antiplaque effect in laboratory rats.
The novel antibacterial peptide mimetic alaphosphin (l-alanyl-l-1-aminoethylphosphonic acid) selectively inhibited peptidoglycan biosynthesis in both gram-negative and gram-positive bacteria. It induced accumulation of uridine diphosphate-N-acetyl-muramyl-tripeptide in gram-positive organisms and significantly reduced the intracellular pool levels of d-alanine. Alaphosphin was actively transported into bacterial cells by stereospecific peptide permeases and was subsequently hydrolyzed by intracellular aminopeptidases to yield l-1-aminoethylphosphonic acid. This alanine mimetic rapidly accumulated inside susceptible cells to yield a concentration which was 100- to 1,000-fold in excess of that of the precursor peptide in the surrounding medium. In the case of susceptible gram-negative organisms, it was shown that 1-aminoethylphosphonic acid was incorporated into a metabolite which was tentatively identified as uridine diphosphate-N-acetylmuramyl-aminoethylphosphonate. The primary intracellular target site of 1-aminoethylphosphonic acid was alanine racemase (EC 5.1.1.1), which was reversibly and competitively inhibited in the gram-negative organisms Escherichia coli and Pseudomonas aeruginosa and irreversibly inhibited in a time-dependent manner in the gram-positive organisms Staphylococcus aureus and Streptococcus faecalis. A secondary target site could be uridine diphosphate-N-acetylmuramyl-l-alanine synthetase [EC 6.3.2.8(b)]. The mechanism of action of alaphosphin may be regarded as involving at least three stages: (i) active transport by peptide permeases; (ii) intracellular peptidase cleavage; and (iii) action of l-1-aminoethylphosphonate on alanine racemase.