Clotrimazole (Bay b 5097): In Vitro and Clinical Pharmacological Studies

Clotrimazole (Bay b 5097) is a new synthetic antifungal drug with in vitro activity against Candida spp., Torulopsis glabrata, and Saccharomyces spp. Pharmacological studies in man after the oral administration of 1.5 and 3 g of clotrimazole produced mean peak concentrations in the serum of 1.16 and 1.29 mug/ml, respectively, 2 hr after administration. In six patients taking 1.5 g of clotrimazole every 6 hr, there was a progressive decline in the serum concentrations after administration of a dose on days 1, 4, and 8. Nine other patients begun on a similar schedule manifested gastrointestinal symptoms attributed to the clotrimazole and were unable to complete the study. Concentrations of active drug in the urine were less than 1% of the administered dose.     

Effects of Azithromycin,Metronidazole, Amoxicillin,and Metronidazole plus Amoxicillin on an In Vitro Polymicrobial Subgingival Biofilm Model

Chronic periodontitis is one of the most prevalent human diseases and is caused by dysbiosis of the subgingival microbiota. Treatment involves primarily mechanical disruption of subgingival biofilms and, in certain cases, adjunctive use of systemic antibiotic therapy. In vitro biofilm models have been developed to study antimicrobial agents targeting subgingival species. However, these models accommodate a limited number of taxa, lack reproducibility, and have low throughput. We aimed to develop an in vitro multispecies biofilm model that mimics subgingival plaque, to test antimicrobial agents. Biofilms were cultivated using the Calgary Biofilm Device and were exposed to amoxicillin (AMX), metronidazole (MTZ), azithromycin (AZM), and AMX-MTZ at four different concentrations for 12, 24, or 36 h. Chlorhexidine (CHX) (0.12%) was used as the positive control. The compositions of the biofilms were analyzed by checkerboard DNA-DNA hybridization, and the percent reduction in biofilm metabolic activity was determined using 2,3,5-triphenyltetrazolium chloride and spectrophotometry. Thirty-five of the 40 species used in the inoculum were consistently recovered from the resulting in vitro biofilms. After 36 h of exposure at the 1:27 dilution, AMX-MTZ reduced metabolic activity 11% less than CHX (q = 0.0207) but 54% more than AMX (q = 0.0031), 72% more than MTZ (q = 0.0031), and 67% more than AZM (q = 0.0008). Preliminary evidence of a synergistic interaction between AMX and MTZ was also observed. In summary, we developed reproducible biofilms with 35 subgingival bacterial species, and our results suggested that the combination of AMX and MTZ had greater antimicrobial effects on these in vitro multispecies biofilms than expected on the basis of the independent effects of the drugs.     

In Vitro Studies with Cephanone

A new parenteral cephalosporin, cephanone, was studied in vitro.     

In Vitro Studies of Cefamandole

Cefamandole is a new cephalosporin antibiotic that was tested in vitro against 540 clinical isolates of gram-positive cocci and gram-negative bacilli. A concentration of 0.39 μg/ml inhibited 95% of the isolates of Staphylococcus aureus. A concentration of 6.25 μg/ml inhibited over 90% of the isolates of Proteus mirabilis and Escherichia coli, 69% of the isolates of Klebsiella pneumoniae, and 31% of the isolates of indole-positive Proteus spp. and Enterobacter spp. It was active against most cephalothin-resistant isolates of E. coli but not of K. pneumoniae.     

In Vitro Studies of Tobramycin

The in vitro activity of tobramycin was studied against 457 clinical isolates of gram-negative bacilli and 151 clinical isolates of gram-positive cocci. The vast majority of the gram-negative bacilli was inhibited by tobramycin at a concentration of 1.56 μg or less per ml. Only a few isolates of Staphylococcus aureus and no isolates of Streptococcus pyogenes or Diplococcus pneumoniae were susceptible to this drug. Tobramycin was generally more active than gentamicin sulfate against gram-negative bacilli, although organisms resistant to gentamicin sulfate were also resistant to tobramycin. The major difference between the two drugs was the greater activity of tobramycin against Pseudomonas aeruginosa.     

In Vitro Studies with Cefazolin

Susceptibilities of 259 isolates of pathogenic bacteria to cefazolin were measured by broth and agar dilution procedures. Beta-hemolytic streptococci were inhibited by 0.25 mug/ml, whereas Staphylococcus aureus and alphahemolytic streptococci were inhibited by 2.0 mug/ml. Enterococci were resistant to less than 32 mug/ml. Wide variation was seen with gram-negative species. Most isolates of Klebsiella species and Proteus mirabilis were inhibited by 4.0 or 8.0 mug/ml. Escherichia coli were less susceptible, and most isolates of Pseudomonas aeruginosa, Serratia species, and Enterobacter species were resistant to 128 mug/ml.     

Photodynamic and Sonodynamic Therapy with Protoporphyrin IX: In Vitro and In Vivo Studies

Sono-photodynamic therapy is a promising anticancer technique based on the combination of sonodynamic and photodynamic therapy to improve the cancer treatment effectiveness. This study was aimed at analyzing the effects of the sono-photodynamic (SPD) activity on protoporphyrin IX (PpIX) solution and PpIX-loaded rat liver. In vitro, PpIX 5 μM solutions were irradiated with light (635 nm, 30–50 mW/cm²), ultrasound (1 MHz, 1–2 W/cm²) and both. The PpIX absorption spectra recorded over exposure time revealed that the PpIX decay rate induced by SPD activity (combined irradiation) was approximately the sum of those induced by photodynamic and sonodynamic activity. In vivo, rats were intraperitoneally injected with 5-aminolevulinic acid at the dose of 500 mg/kg weight. After 3 h of injection, the PpIX-loaded livers were irradiated with light (635 nm, 180 ± 9 J/cm²), ultrasound (1.0 MHz, 770 ± 40 J/cm²) and both using a single probe capable of illuminating and sonicating the liver simultaneously. After 30 h, the liver damage induced by each protocol was analyzed histologically. It was found that a greater necrosis depth was induced by the SPD activity. These results suggest that the SPD activity could improve the PpIX decay rate and have greater scope than photodynamic or sonodynamic activity. Further studies should be performed to gain a better understanding of this protocol.     

In Vitro Susceptibility Studies with Cefaclor and Cephalexin

The in vitro activity of cefaclor and cephalexin against clinical isolates of four bacterial genera was compared. Both agents had a similar range of activity, but cefaclor was significantly more active by weight than cephalexin for most isolates tested.     

In Vitro Susceptibility Studies with Josamycin and Erythromycin

The in vitro activity of josamycin and erythromycin against five bacterial species was compared. In general, erythromycin was slightly more active by weight than josamycin, although both agents had a similar range of activity.     

Azlocillin: In Vitro Studies of a New Semisynthetic Penicillin

The activity of azlocillin, a new semisynthetic penicillin, was determined against 582 clinical isolates of gram-negative bacilli and gram-positive cocci. Over 75% of the isolates of Pseudomonas aeruginosa were inhibited at a concentration of 12.5 mug or less per ml. Azlocillin is also active against indole-negative and -positive Proteus spp., inhibiting 98 and 71%, respectively, at a concentration of 12.5 mug or less per ml. Isolates of Klebsiella spp. and Enterobacter spp. showed less susceptibility than isolates of Escherichia coli and Serratia spp. Gram-positive cocci except penicillin G-resistant Staphylococcus aureus were susceptible to azlocillin. Azlocillin failed to inhibit the growth of gram-negative bacilli when large inocula were used. It was more active in alkaline pH, but the type of medium used had little effect on its activity. Azlocillin was more active than mezlocillin, ticarcillin, and carbenicillin and as active as BLP-1654 against isolates of P. aeruginosa. It was not as active as mezlocillin against the majority of the other gram-negative bacilli.     

Mezlocillin: In Vitro Studies of a New Broad-Spectrum Penicillin

Mezlocillin is a new semisynthetic penicillin that inhibited 71% of the isolates of Serratia marcescens, 67% of Escherichia coli, 50% of Enterobacter spp., and 49% of Klebsiella spp. at a concentration of 12.5 μg/ml. It is also active against both indole-positive and -negative Proteus spp. and gram-positive cocci, except penicillin G-resistant Staphylococcus aureus. At a concentration of 100 μg/ml, it inhibited 94% of the isolates of Pseudomonas aeruginosa. It is more active than ampicillin, carbenicillin, and cephalothin against some gram-negative bacilli.     

Cefazaflur, a New Parenteral Cephalosporin: In Vitro Studies

Cefazaflur was tested in vitro against 262 strains of bacteria. Inhibitory and bactericidal concentrations were determined with two inoculum sizes of bacterial cells in Mueller-Hinton broth and nutrient broth. Agar dilution studies also were performed. When tested in agar, 5.0 mug or less of cefazaflur per ml inhibited almost all strains of Staphylococcus aureus, Escherichia coli, Klebsiella, and Proteus mirabilis. The drug was less active against Enterobacter and indole-positive Proteus, and 7.5 mug of antibiotic per ml inhibited approximately two-thirds to one-fourth of the strains. A concentration of 50 mug of cefazaflur per ml was required for inhibition of the enterococci. There was negligible activity against Pseudomonas. The drug demonstrated less activity in broth than in agar, and a major inoculum effect was seen with some strains. For example, with a lower inoculum, 2.5 mug of cefazaflur per ml killed all strains of E. coli, whereas with the higher inoculum, 7.5 mug of cefazaflur per ml, inhibited 64% and killed only 8% of strains. The activity of the drug for some strains was greater in Mueller-Hinton broth; for others, it was greater in nutrient broth. There were considerable differences in the results of the broth and agar studies for some species when the same medium was employed. Because of differences in activity found with different media, inocula, and method of testing, an evaluation of the eventual usefulness of cefazaflur must await the results of in vivo studies.     

Risk of Development of In Vitro Resistance to Amoxicillin, Clarithromycin, and Metronidazole in Helicobacter pylori

We have studied initial killing, morphological alterations, the frequency of occurrence, and the selective growth of resistant subpopulations of Helicobacter pylori during exposure to amoxicillin, clarithromycin, or metronidazole by bioluminescence assay of intracellular ATP levels, microscopy, and a viable count assay. We found an induction of spheroplasts and a decrease in intracellular ATP levels after 21 h of exposure to high concentrations of amoxicillin. During clarithromycin exposure the onset of a decrease in intracellular ATP levels started after prolonged incubation, and with the highest concentration of clarithromycin an induction of coccoid forms was seen after 68 h. Metronidazole exposure resulted in the strongest initial decrease in intracellular ATP levels, and coccoid forms were seen after 21 h of exposure to high concentrations of metronidazole. Amoxicillin caused a low-level increase in resistant subpopulations, which indicates a need for surveillance of the amoxicillin susceptibility of H. pylori in order to detect decreasing susceptibility. No increase in the numbers of resistant subpopulations was demonstrated during clarithromycin exposure. Metronidazole selected resistant subpopulations, which caused high-level resistance in H. pylori.     

In Vivo and In Vitro Studies of a Chronic Oxygen Saturation Sensor

An oxygen saturation sensor, for the purpose of chronically controlling the heart rhythm produced by a pacemaker, should be specific to oxygen saturation and should be minimally affected by the harsh blood environment. For the sensor type we tested we found: (1) one sensor failure in 205.5 canine-months of chronic implantation (n = 11, range 4 to 50 months); (2) hematocrit-induced error of less than 5 percentage points of SvO2 over the range of 50% to 80% SvO2 and 15% to 45% hematocrit; (3) carboxyhemoglobin (HbCO)-induced error of less than 4 percentage points of SvO2 with HbCO up to 20%; (4) a fibrotic sheath-induced error of less than 3 percentage points of SvO2 in the range of 50% to 80% SvO2 due to fibrotic sheath thicknesses up to 0.22 mm; (5) no significant error induced by velocity variations local to the sensor; (6) no significant error due to temperature in the range of 30 degrees to 42 degrees C; and (7) that the sensor could be as close as 0.3mm to the ventricular wall and still only produce an error of 5% SvO2.     

The Effect of Dextran on Platelet Factor 3 Activity: In Vitro and In Vivo Studies

Intravenous infusions of one liter of low molecular weight and standard clinical dextran in normal adult subjects resulted in a significant alteration of platelet function as characterized by marked depression of platelet factor 3 (PF 3) activity. Disruption of the abnormal platelets by sonic oscillation corrected the defect, indicating that dextran coating of the platelets inhibited the release of PF 3 activity. These findings were confirmed by in vitro studies.
Infusions of serum albumin failed to produce a significant alteration in PF 3 activity.
The PF 3 depression could not be related to hemodilution or the total platelet count. Clot retraction, platelet adhesiveness, and the platelet thromboplastin test were normal. Serum prothrombin time was abnormal in some subjects.
The platelet abnormality was related to the plasma dextran concentration and the retention of large dextran molecules in the circulation. Clinical dextran had a more deleterious effect on PF 3 activity than low molecular weight dextran.
Since the majority of subjects had normal bleeding times associated with their reduced levels of PF 3 activity, the clinical significance of these studies is not clear. Nevertheless, the results of these experiments indicate that dextran coating of platelets interferes with the release of PF 3 activity, and suggest that alteration of the platelet surface may modify other platelet functions involved in maintaining a normal bleeding time.     

In Vitro Studies of Tobramycin, an Aminoglycoside Antibiotic

Tobramycin is an aminoglycoside antibiotic which has excellent antibacterial activity against Pseudomonas, Staphylococcus aureus, and many members of the Enterobacteriaceae. Most strains of Serratia, Providence, Streptococcus, and Diplococcus pneumoniae were resistant to concentrations of tobramycin which could be achieved in man. Tobramycin was effective against certain Pseudomonas strains resistant to gentamicin. The growth medium used to determine the inhibitory level of tobramycin had a significant effect upon the minimal inhibitory concentration. Calcium and magnesium ions inhibited the bactericidal effect of tobramycin. Tobramycin and carbenicillin acted in a synergistic manner. Ethylenediaminetetraacetic acid did not act in a synergistic manner with tobramycin. Broth-dilution susceptibility tests and disc-diffusion tests in agar (10-μg discs) showed excellent correlation except with Proteus strains.     

Bartter's Syndrome: Physiological and Pharmacological Studies

Six siblings with Bartter's syndrome were studied. Increasedurinary Immunoreactlve prostaglandin E (iPgE) was correctedby administration of the prostaglandin synthetase inhibitors,Indomethacin, ibuprofen and meclofenamate. In addition, plasmapotassium rose, plasma renln activity and angiotensin resistancedecreased, and the exaggerated natriuresis following salineloading was abolished. Increased urinary iPgE also became normalfollowing the phospholipase inhibitor, mepacrine, but the otherabnormalities remained unaltered. The kallikrein inhibitor,aprotlnin, did not alter urinary iPgE, plasma potassium or electrolytebalance. During hypotonic saline infusion, proximal tubularsodium reabsorption was normal or increased. Free water clearanceand the percentage of distaliy delivered sodium which was reabsorbedwere, however, significantly decreased. The results suggestthat neither the increased renal PgE production nor the hyper-bradykinlnemiaseen in Bartter's syndrome play a major role in its pathogenesis,or manifestations, and that the effects of the prostaglandinsynthetase inhibitors on the syndrome are non-specific. Theresults and relevant literature are analysed in an attempt toidentify the initial defect in the interrelated sequence ofevents. The data are compatible with an intrarenal defect insodium transport, leading to increased sodium delivery to thedistal tubule, with secondary hyperreninemia, hypokalemia andelevated iPgE excretion.     

In Vitro Studies with Combinations of 5-Fluorocytosine and Amphotericin B

Synergistic antifungal activity of 5-fluorocytosine (5-FC) and amphotericin B was studied using an abbreviated checkerboard titration scheme. 5-FC was titrated in twofold increments (100 to 0.05 μg/ml) in the absence and presence of graded increments of amphotericin B (1.0. 0.5, 0.1, 0.05, and 0.01 μg/ml) in buffered yeast nitrogen base. A limited number of experiments were performed using expanded dual titration checkerboard schemes and growth curve studies. Forty-eight isolates of yeastlike organisms were tested; two were inhibited by the buffer system. Evidence of synergy, as indicated by a fourfold or greater reduction of the minimal inhibitory concentration of 5-FC in the presence of subinhibitory concentrations of amphotericin B, was seen with 11 of 46 isolates, or 24%, at the fungistatic level and with three isolates, or 7% at the fungicidal level. Indifferent results were obtained for 44 and 74% of the isolates, respectively, at the fungistatic and fungicidal levels. Antagonism was observed with three isolates.