Biomedical subjects

R Shawar

Publications and source records attributed to R Shawar.

9 recordsLinked to original sources

PubMed1998

Antitubercular natural products: berberine from the roots of commercial Hydrastis canadensis powder. Isolation of inactive 8-oxotetrahydrothalifendine, canadine, beta-hydrastine, and two new quinic acid esters, hycandinic acid esters-1 and -2.

Berberine (4) is responsible for the activity of an extract of a commercial root sample of Hydrastis canadensis against multiply drug resistant Mycobacterium tuberculosis. Two new quinic acid feruloyl esters, compounds 2 and 3, have been isolated from the same source along with canadine (1c), 8-oxotetrahydrothalifendine (1), and beta-hydrastine (5). These were found to be inactive. The structures of the new compounds were elucidated from spectral (1H, 13C, HMQC, HMBC, and H-H COSY) and chemical evidences.

Alkaloids↗

PubMed1998

A simple, inexpensive apparatus for performance of preparative scale solution phase multiple parallel synthesis of drug analogs. II. Biological evaluation of a retrospective library of quinolone antiinfective agents.

A series of pure fluoroquinolone antiinfective agents was prepared by multiple parallel synthesis using a simple new apparatus. These compounds were evaluated biologically against Gram-positive and Gram-negative microorganisms and against a BCG strain transfected with luciferase in a fluorescence-based antitubercular assay. Activity against relatively fast growing, acid-fast Mycobacterium smegmatis was determined in part by agar-dilution streak assays. Data obtained against Escherichia coli-derived DNA gyrase does not correlate well with whole cell assays against E. coli. These compounds were assayed by a convenient glass-fiber filter binding method modified for high throughput screening. In these analogs, the results with a N-1 cyclopropyl substituent were often inferior to those obtained with a N-1 2',4'-difluorophenyl substituent. None of the new compounds prepared was superior in its antimycobacterial potency to ciprofloxacin or temafloxacin.

Anti-Infective Agents↗

PubMed1993

In vitro antimicrobial susceptibilities of Nocardia species.

The in vitro activities of various quinolones, two new aminoglycosides, a new cephamycin analog (cefmetazole) and a new spectinomycin analog (trospectomycin), imipenem, and trimethoprim-sulfamethoxazole against 26 isolates of Nocardia asteroides, 7 isolates of N. brasiliensis, and 6 isolates of N. caviae were determined by a broth microdilution method. The three new quinolones, PD 117558, PD 117596 and PD 112739, inhibited 90% of N. asteroides at 1 to 2 micrograms/ml, and two new aminoglycosides, SCH 21420 and SCH 22591, inhibited 90% of N. asteroides at 2 to 4 micrograms/ml. Among the beta-lactams, cefmetazole was more active than imipenem. N. brasiliensis and N. caviae isolates were also very susceptible to the three quinolones (MICs for 50% of the isolates, 0.25 to 1 microgram/ml) and the two aminoglycosides (MICs for 50% of the isolates, 1 to 2 micrograms/ml). Cefmetazole was moderately active against N. brasiliensis, whereas imipenem showed poor activity against both of these species.

4-Quinolones↗

PubMed1993

Two-site comparison of broth microdilution and semisolid agar dilution methods for susceptibility testing of Cryptococcus neoformans in three media.

This study evaluated the inter- and intralaboratory agreement between results of the semisolid agar dilution and broth microdilution methods of antifungal susceptibility testing of Cryptococcus neoformans. Three media were tested in two laboratories. The drugs tested were amphotericin B, flucytosine, itraconazole, fluconazole, and Schering 39304. Analysis by kappa statistics revealed good agreement between the laboratories for the two methods. The highest level of inter- and intralaboratory agreement was observed in RPMI 1640 with L-glutamine followed by Eagle's minimum essential medium and yeast nitrogen broth. The broth microdilution method appears more suitable than the semisolid agar dilution method for testing cryptococci because of its ease in performance, cost, and simplicity.

Agar↗

PubMed1992

Collaborative investigation of broth microdilution and semisolid agar dilution for in vitro susceptibility testing of Candida albicans.

A study was performed in two laboratories to evaluate the effect of growth medium and test methodology on inter- and intralaboratory variations in the MICs of amphotericin B (AMB), flucytosine (5FC), fluconazole (FLU), itraconazole (ITRA), and the triazole Sch 39304 (SCH) against 14 isolates of Candida albicans. Testing was performed by broth microdilution and semisolid agar dilution with the following media, buffered to pH 7.0 with morpholinepropanesulfonic acid (MOPS): buffered yeast nitrogen base (BYNB), Eagle's minimal essential medium (EMEM), RPMI 1640 medium (RPMI), and synthetic amino acid medium for fungi (SAAMF). Inocula were standardized spectrophotometrically, and endpoints were defined by the complete absence of growth for AMB and by no more than 25% of the growth in the drug-free control for all other agents. Comparative analyses of median MICs, as determined by each test method, were made for all drug-medium combinations. Both methods yielded similar (+/- 1 twofold dilution) median MICs for AMB in EMEM and RPMI, 5FC in all media, and FLU in EMEM, RPMI, and SAAMF. In contrast, substantial between-method variations in median MICs were seen for AMB in BYNB and SAAMF, FLU In BYNB, and ITRA and SCH in all media. Interlaboratory concordance of median MICs was good for AMB, 5FC, and FLU but poor for ITRA and SCH in all media. Endpoint determinations were analyzed by use of kappa statistical analyses for evaluating the strength of observer agreement. Moderate to almost perfect interlaboratory agreement occurred with AMB and 5FC in all media and with FLU in EMEM, RPMI, and SAAMF, irrespective of the test method. Slight to almost perfect interlaboratory agreement occurred with ITRA and SCH in EMEM, RPMI, and SAAMF when tested by semisolid agar dilution but not broth microdilution. Kappa values assessing intralaboratory agreement between methods were high for 5FC in all media, for AMB in BYNB, ENEM, and RPMI, and for FLU in EMEM, RPMI, and SAAMF. One laboratory, but not the other, reported substantial to almost perfect agreement between methods for ITRA, and SCH in EMEM, RPMI, and SAAMF. Both laboratories reported poor agreement between methods for the azoles in BYNB. Discrepancies noted in azole-BYNB combinations were largely due to the greater inhibitory effect of these agents in BYNB than in other media. These results indicate that the semisolid agar dilution and broth microdilution methods with EMEM or RPMI yield equivalent and reproducible MICs for AMB, 5FC, and FLU but not ITRA and SCH.

Agar↗

PubMed1992

Why patients fail antibiotic prophylaxis at cesarean delivery: histologic evidence for incipient infection.

A prospective, blinded study was conducted to test the hypothesis that antimicrobial prophylaxis failure after cesarean delivery is associated with incipient infection of the uterus, as determined by histologic evaluation of bacterial invasion and acute inflammatory cell response. One hundred nineteen patients undergoing cesarean delivery and receiving antibiotic prophylaxis were included in this study. At the time of the operation, a hysterotomy biopsy was obtained for hematoxylin and eosin staining. Marked histologic differences were noted in decidual inflammation, myometrial inflammation, and myometrial polymorphonuclear cell invasion in those patients who subsequently developed endometritis (N = 7) compared with subjects without postpartum endometritis. Using two techniques for in situ identification of bacteria within myometrial tissue (acridine orange and fluorescein DNA probe to bacterial ribosomal RNA), all clinically infected parturients demonstrated large numbers of organisms in the myometrial layer of the biopsy specimen, compared with few organisms seen in a matched subset of noninfected controls. These data support the concept that incipient infection at the time of cesarean delivery may limit the effectiveness of antimicrobial prophylaxis. Use of rapid-diagnosis methodologies may allow timely identification of these at-risk patients so that therapeutic antibiotics can be initiated.

Anti-Bacterial Agents↗

PubMed1990

Comparative kinetics of hematoporphyrin derivative uptake and susceptibility of Bacillus subtilis and Streptococcus faecalis to photodynamic action.

Hematoporphyrin derivative (HpD) is widely used in photoradiation therapy of tumors and other diseases, and has been shown to affect the viability of gram positive bacteria. This investigation assessed the efficiency of binding of HpD to Bacillus subtilis and Streptococcus faecalis when HpD-treated organisms were exposed to red light. Kinetic studies indicated that the amount of HpD bound increased with increasing external concentration of HpD until saturation of binding sites was reached. S. faecalis had a higher affinity for HpD and was more susceptible to photoinactivation than B. subtilis. The data from this study suggest that differences in susceptibility of microorganisms to photoinactivation are directly related to the affinity of each strain for HpD.

Bacillus subtilis↗

PubMed1990

Use of the RapID-ANA system and sodium polyanetholesulfonate disk susceptibility testing in identifying Haemophilus ducreyi.

Haemophilus ducreyi has traditionally been difficult to identify. We have utilized simple test methods to identify 19 fresh isolates obtained during a recent outbreak of chancroid in Houston and six strains of H. ducreyi from other outbreaks. Tests were performed from growth on chocolate agar after 48 h of incubation at 35 degrees C with increased humidity and CO2. All isolates exhibited typical colonial morphology and Gram stain. Isolates were catalase negative and oxidase and nitrate positive (in enriched broth). The RapID NH system failed to identify these strains because of negative reactions with alkaline phosphatase and nitrate reductase. However, by using the RapID-ANA system, all strains were positive for alkaline phosphatase and arginine, glycine, and serine aminopeptidases. Their biochemical profiles were distinct from those obtained with 66 strains representing 13 species similar to H. ducreyi. We also investigated the use of sodium polyanetholesulfonate (SPS) disk susceptibility to identify and differentiate H. ducreyi from other species. All H. ducreyi isolates were susceptible, as evidenced by the presence of a zone of inhibition with an average size of 15 mm around the SPS disk. With the exceptions of Neisseria gonorrhoeae, Gardnerella vaginalis, and Capnocytophaga spp., no other strain showed any evidence of inhibition. The latter three organisms can be easily differentiated from H. ducreyi by various features including reactions in the RapID-ANA. We conclude that, by considering simple growth and biochemical characteristics, SPS susceptibilities, and reactions in RapID-ANA, it is possible for more clinical laboratories to definitively identify this organism.

Bacteriological Techniques↗

PubMed1989

Comparative in vitro activity of ceftibuten (Sch 39720) against bacterial enteropathogens.

Ceftibuten is a new orally active cephalosporin with significant bioavailability. Its in vitro activity was compared with those of other agents against 383 strains of enteric pathogens derived from clinical specimens. Ceftibuten was very active against the strains of the family Enterobacteriaceae tested (overall MIC for 90% of strains tested, 0.25 microgram/ml) but was less active against Campylobacter jejuni (MIC for 90% of strains, 16 micrograms/ml). The MBC was one to two dilutions higher than the corresponding MICs for most pathogens tested.

Anti-Bacterial Agents↗