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S Shadomy

Publications and source records attributed to S Shadomy.

At least 91 records · Page 5Linked to original sources
PubMed1972

In vitro susceptibility testing with tobramycin.

Tobramycin (nebramycin factor 6) is an aminoglycoside antibiotic active in vitro against many gram-negative species and Staphylococcus aureus. The susceptibility of 191 recently isolated pathogenic bacteria to tobramycin was measured by both a routine broth dilution procedure and the FDA standardized disc technique using a 10-mug disc. Twenty-five isolates each of Escherichia, Enterobacter, Klebsiella, indole-negative Proteus, Pseudomonas, Serratia, and S. aureus, and 16 isolates of group D enterococci were tested. The greatest activity was seen with S. aureus and Pseudomonas species; nearly all isolates of both were inhibited by 0.20 mug or less per ml. Tobramycin was slightly less active against Klebsiella and Enterobacter and moderately active against Escherichia and Proteus, with most isolates of these genera being inhibited by 1.56 mug/ml. Neither Serratia nor the enterococci were particularly susceptible. Correlations between zones of inhibition around the 10-mug disc and minimal inhibitory concentrations were determined, and a zone diameter of 16 mm was recommended as the critical point for prediction of susceptibility.

Aminoglycosides↗
PubMed1971

In vitro antifungal activity of clotrimazole (Bay b 5097).

The in vitro antifungal activity of clotrimazole (Bay b 5097) was compared with those of amphotericin B, griseofulvin, nystatin, and pyrrolnitrin. The inhibitory activity of clotrimazole against most systemic pathogens was comparable to that of amphotericin B; minimal inhibitory concentrations of the two drugs for Blastomyces dermatitidis, Histoplasma capsulatum, Sporothrix schenckii, Cryptococcus neoformans, and Coccidioides immitis were in the range of 0.20 to 3.13 and 0.10 to 6.25 mug/ml, respectively. One isolate of Allescheria boydii was resistant to 100 mug of amphotericin B per ml but was inhibited by 6.25 mug of clotrimazole per ml. Clotrimazole was less active than amphotericin B against Candida albicans and Aspergillus fumigatus. The activity of clotrimazole against dermatophytes was comparable to that of pyrrolnitrin; 0.78 mug of either compound per ml was fungicidal for most isolates of Trichophyton sp., Microsporum sp. and Epidermophyton floccosum. Both griseofulvin and nystatin were less active than clotrimazole. The size of inoculum was shown to have a significant effect on the results of in vitro susceptibility testing with clotrimazole.

Amphotericin B↗
PubMed1970

In Vivo Susceptibility of Cryptococcus neoformans to Hamycin, Amphotericin B, and 5-Fluorocytosine.

Previous investigations have shown that hamycin is 5 to 10 times more active in vitro than amphotericin B against Cryptococcus neoformans, whereas 5-fluorocytosine is approximately 15 times less active. Present studies are concerned with a comparison of these drugs in vivo. Three strains of C. neoformans which varied in both their virulence for mice and their susceptibilities to the antifungal agents were studied. Acute experimental infections were established in mice by using inocula containing approximately 4 x 10(6) cells. The mice were treated by gastric intubation for 28 days; daily dosages of the three drugs ranged from 12.5 to 250 mg/kg. The polyenes were suspended in 5% dimethyl sulfoxide, whereas 5-fluorocytosine was suspended in saline. Amphotericin B was the most effective drug, with almost complete absence of toxic deaths in control mice and increased survival in mice infected with two of the three strains and treated with 25 mg/kg per day or more. 5-Fluorocytosine was nontoxic but provided protection against only one strain. Hamycin was both the least effective and the most toxic compound, providing only slight protection at doses of 12.5 or 25 mg/kg per day and causing toxic deaths in over 50% of uninfected mice at doses above 25 mg/kg per day.

Journal Article↗
PubMed1970

Further in vitro studies with 5-fluorocytosine.

Susceptibilities of 53 isolates of Cryptococcus neoformans and of 15 isolates identified as either Candida albicans or Candida species to 5-fluorocytosine (5-FC) were measured. Thirteen, or 24.5%, of all isolates of C. neoformans were resistant to 5-FC. Eight of these isolates were recovered from patients treated with 100 mg of 5-FC per kg per day, whereas only one was from a patient receiving 150 mg per kg per day. Only one isolate of C. neoformans recovered before treatment was resistant. In 14 cases of cryptococcosis treated with 5-FC at one institution, therapeutic failures associated with resistant isolates of C. neoformans occurred in 6 of 10 cases receiving 100 mg per kg per day but in only one of 4 cases treated with 150 mg per kg per day. Mean concentrations of 5-FC in serum and cerebrospinal fluid were twofold higher in those patients receiving the larger dose. Of 15 isolates of Candida, 5 were susceptible to clinically meaningful concentrations of 5-FC and 8 were totally resistant. Seven of the resistant Candida isolates were isolated before treatment, and selection of resistant isolates during treatment was not observed. Resistant isolates were associated with three of five therapeutic failures. Treatment with 5-FC at 100 mg per kg per day was successful in four of nine patients with systemic candidiasis.

Journal Article↗
PubMed1969

Bioassay for hamycin and amphotericin B in serum and other biological fluids.

A bioassay suitable for measuring concentrations of the polyene antifungal agents hamycin and amphotericin B in biological fluids is described. By using Paecilomyces varioti as the indicator organism, sensitivity of the bioassay was found to be in the range of 0.01 to 0.02 mug/ml. A linear dose-response curve was obtained with amphotericin B; the curve for hamycin was curvilinear. In a series of assays, hamycin serum levels in the range of 0.01 to 3.5 mug/ml were measured; with amphotericin B, serum levels in the range of 0.015 to 0.175 mug/ml were measured in patients receiving orthodox intravenous medication and as high as 9.0 mug/ml in one patient treated with extraordinarily high doses of the drug.

Amphotericin B↗
PubMed1969

In vitro studies with 5-fluorocytosine.

5-Fluorocytosine, an antifungal agent with potential value as a chemotherapeutic agent, is being evaluated in the treatment of human cryptococcosis. In vitro studies with this agent have been hindered by the fact that it is inhibited significantly in the presence of partially degraded biological substances. This loss of activity is presumed to result from a competitive inhibition between the agent and its natural analogues. Procedures are described for in vitro studies with 5-fluorocytosine. These include methods for susceptibility testing and a bioassay for 5-fluorocytosine in biological fluids. Minimal inhibitory and minimal fungicidal concentrations of 5-fluorocytosine for Cryptococcus neoformans were usually in the range of 0.46 to 3.9 mug/ml and 3.9 to 15.6 mug/ml, respectively. Corresponding values for Candida albicans were 0.46 to 3.9 mug/ml and 15.6 mug/ml or greater, respectively. Strains of C. neoformans and C. albicans resistant to greater than 1,000 mug/ml were encountered both after exposure to the drug and in the absence of any known exposure. Bioassays of specimens from patients treated with 5-fluorocytosine indicated that serum and cerebrospinal fluid concentrations of 10 to 30 mug/ml and 8 to 20 mug/ml, respectively were readily achieved with a dosage of 100 mg per kg per day.

Antifungal Agents↗
PubMed1969

In vitro and in vivo activity of hamycin against Blastomyces dermatitidis.

Clinical responses of patients with blastomycosis to treatment with hamycin have been variable. An explanation for this was sought in a series of studies in which in vitro and in vivo susceptibilities to hamycin of five strains of Blastomyces dermatitidis were compared. Minimal inhibitory concentrations of hamycin for the five strains indicated uniformly high levels of in vitro susceptibility (0.008 to 0.016 mug/ml). In vivo activity was measured in infected mice treated intraperitoneally for a period of 28 days with doses of the drug ranging from 0.001 to 0.030 mg per mouse. Significant differences in response to treatment among the five strains were noted (P < 0.001), and protective doses were found to vary from 0.001 to >0.030 mg per mouse per day. Further observations of infected mice after treatment revealed marked rates of relapsing infection, and several strains caused death. Persistent inapparent infections were also detected on culture of selected organs. Toxicity due to hamycin alone was not observed. These results suggest that variations in clinical responses to hamycin therapy in treatment of blastomycosis reflect differences in pathogenesis and host response in vivo to the infecting organism rather than differences in susceptibility of B. dermatitidis to hamycin.

Amphotericin B↗
PubMed1968

Effect of inoculum size on in vitro susceptibility testing with lincomycin.

There is disagreement in the literature as to whether lincomycin is primarily a bacteriostatic or a bactericidal agent against gram-positive cocci and also regarding the levels of activity of this agent against susceptible microorganisms. These questions were examined in a study of the effect of inoculum size on the results of tube dilution susceptibility determinations with lincomycin against 49 clinical isolates of Staphylococcus aureus and 25 strains of streptococci and pneumococci. Lincomycin was both highly active and bactericidal when tested against 40 strains of S. aureus with inocula containing a maximum of 10(4) cells per ml [median minimal inhibitory concentration (MIC), 0.78 mug/ml; median minimal bactericidal concentration (MBC), 1.56 mug/ml]. With inocula of 10(5) cells per ml, lincomycin was primarily bacteriostatic (median MIC, 1.56 mug/ml; median MBC, 12.5 mug/ml). There were further decreases in inhibitory levels and significant losses of bactericidal activity when inocula containing more than 10(7) cells were tested (median MIC, 3.13 mug/ml; median MBC > 100 mug/ml). Similar measurements with streptococci and pneumococci revealed a lesser effect of inoculum size. The mean MBC value for alpha-hemolytic streptococci increased from 0.40 to 1.05 mug/ml with an increase in inocula from 10(4) to 10(6) cells per ml, but without a marked increase in MIC values. Similar results were obtained for beta-hemolytic streptococci and pneumococci.

Bacteriological Techniques↗